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Knex 4wd w/ steering

I'm building my own 4wd truck with knex, and I want it to have steering. I found my own weird and not-always-reliable way, but I want to see if there is an easier way to build it, like using joints and axles. I can find 4wd cars and cars with steering, but none with both. Suggestions must be MOTORIZED, and WITHOUT MODIFYING PIECES. Thanks for the help!

Topic by Mr._Rodgers    |  last reply


I need a help on fixing the OBD II codes P0452 and P0410 for a 2001 s10 4wd blazer 4 door?

I was told that the vacuum lines could have a problem with this if they are cracked or there is a leak 

Question by gadget613    |  last reply


4x4 Issues Nissan Pathfinder, '93

4WD acts like it isn't 4WD, but only rear wheel drive.  Not good on snow and ice. Sometimes 2WD on dry pavement feels like 4WD when taking sharp turns. I've tried the trick of reversing for a few feet when switching back n forth.  Sometimes seems to work, sometimes not. Suggestions?  Appraisals?  Guesses?

Topic by Toga_Dan    |  last reply


does any 1 know how to make a sensor to detect cornering in a car and road moisture?

Im thinking an Infared diode that reflects on the road into an infared phototransistor for the road mositure (water) sensor. ( i have one problem with this its going to be placed under a car how will it keep clean?) i guess i just gotta to find a good spot. Also for the cornering sensor ( more like a G sensor but it has to be sensitive.) how will it be sensitive enough ? Its for a justy 4wd traction control system im thinking off ( note to all justy enthusiast i dont have it yet)

Question by josh1001    |  last reply


Rc car modding help?

My dad had (broken) a rc car from a old friend that was sitting in the garage. He said that I could have it. It is a Nikko Super Dictator. When we were trying to fix it the curcuit board went poof and clouds of smoke came out of it, I don't want to fix the board but was thinking about buying a cheap RC kit and using arduino to decode and to control it. Another way I thought of controlinng it was to get an rc kit and use a speed controler. The servo in it has 6 wires and has no markings on it to tell me what it is. If anyone has done this project before please send me a link to an instructable. Also Please tell me the easyst way to control it and if I could just use a prebuilt rc kit with a speed controler, the type of servo and the motor. IF ANYONE HAS ONE THEY WOULD LIKE TO SELL THAT WOULD BE GREAT TOO, JUST SEND ME A MESSAGE. Any help, tips and/or links would be appresated. PS: Do a google search to find out stats. thanks, David.

Question by David97    |  last reply


i need a knex cv shaft, who can figure one out???

Okay for you knex ppl i need to figure out a way to make a cv shaft for knex, i got 4wd already i just want stearing now, i can post pics and stuff if someone can make the cv shaft?? :D :D

Question by aaronj    |  last reply


Wheelchair mountain bike

Hi guys, I have an idea for a go anywhere buggy that I can use on mountain bike trails instead of my wheelchair. I have a very basic design of my idea and need advice on where to go from here. I have a very rough sketch of my idea. But I have no idea of how to use AutoCAD or do anything else with this fantastic little device. So I thought I would ask all of you guys for your input. In the attached sketch. The pink represents a rigid frame. The green is suspension. The black is bicycle tires appropriate for your needs. The blue is an adjustable net seating. And the gray is batteries and motors. However my son informs me that it is possible to put the motor in the hub of the wheel. Which sounds like an excellent idea to me! My idea is to hang the frame from the suspension above the wheels.  And balance the weight of the occupant(s) and the batteries. I think that this has potential for many other applications, but I just want to go play in the woods and the beach again!

Topic by Mmjmama    |  last reply


Anyone know why a 99 Chevy blazer would engage 4-Hi 4wd but not 4-Low?

2-Hi and 4-Hi work just fine but the 4-low just won't engage. Trying to figure out if  can DIY fix it if it's something simple, rather than pay an exorbitant amount to a mechanic. Thanks.

Question by A.J.B.    |  last reply


anyone have an idea for a good knex solid axle suspension?

K so i have ideas for everything else, can someone come up with a good solid axle suspension for a rock crawler out of knex, i also came up with a torsion bar ifs set up...if you can make a SMALL cv shaft i could make 4wd steering and indipendant as well, but for now i want solid axle! lol i just want to see how many ppl can do all this, steering idea would be good too!

Question by aaronj    |  last reply


The New Knex Innovationists Tournament - T.N.K.I.T (Round 1 Results)

The results for the first round of the contest. Good luck to the people who moved on! -Viccie.B1993- 1st: Kairah --- Kairah's K'nex Train V01 --- 770/800 points. 2nd: Jollex --- K'nex Snowmobile --- 640/800 --- points. 3rd: (Atlas) --- Knex Pickup Truck With Suspension --- 620/800 points. 4th: Silentassasin21 --- Willy's Jeep --- 610/800 points. 5th: Knexguy --- FN-SCAR-H --- 600/800 points. 5th: ZakS95 --- K'nex Car --- 600/800 points. 6th: Serial-Cricket --- Horse Drawn Carriage --- 590/800 points. 7th: 222222222539 ---- Every Terrain Tank With Fully Automatic Turret - 580/800 points. 8th: K'nex Mad --- Knex 4WD Truck --- 550/800 points. 9th: DJ Radio --- 4WD Tank - 540/800 points. 10th: Killer~SafeCracker --- K'nex Racer --- 530/800 points. 11th: The Jamalam --- T.N.K.I.T I-Think-Entry --- 510/800 points. 12th: Owen-Mon-82397 --- K'nex Car (TNKIT Entry) --- 490/800 points. 13th: Heat-Seeker --- "Gypsy" Caravan --- 480/800 points. 14th: Cj81499 --- The New K'nex Innovations Tournement Car --- 400/800 points. 15th: AJLeece --- Random Car For TNKIT --- 360/800 points. 16th: Millawi Legend --- K'nex Tunes Puller --- 310/800 points. The people who aren't listed did not move on because they were too late. Link to round 2: https://www.instructables.com/community/The-New-Knex-Innovationists-Tournament-TNKIT-2/

Topic by Skreetsha    |  last reply


using 2 x adafruit motor shield v2 in MATLAB

Hi, I set up an Arduino + adafruit motor shield v2 to control 4 x DC motors in a robot arm via MATLAB, which work fantastic. I mounted the robot arm on a 4WD base (each wheel has a separate DC motor), so now I have additional 4 more DC motors to control. I know the adafruit motor shield v2 is stackable, as long as you solder the I2C part on the second shield. I don't know if MATLAB supports 2 x adafruit motor shield v2 on top of Aurduino (2nd shield via I2c), to control 8 DC motors in total any advise or experience is highly appreciated

Question by Begginer2017    |  last reply


Belarus Tractors-cold weather starting information?

Thank you for taking my question.  I purchased a Belarus tractor model 525 (65 hp. 4wd) new in 1990.  Although the tractor came equipped with glow plugs, they burned out shortly after I purchased the tractor.  I replaced the glow plugs again and they also didn't last long.  I then installed a block heater which heats the water and also a small heater from Wolverine company which actually glues on externally to the bottom of the oil pan.  Now although these products help somewhat, I was wondering if any of my good Instructable friends have had similar problems with these types of tractors and how they eliminated the problem.  The two heater items while they help, require several hours if not overnight to work.  Other than the cold weather starting problem this has been a good solid tractor.  In closing, I know these tractors are made in Belarus/Russia where the temps are far more severe than here in Southeast Missouri so I know there must be a solution.  One last thought, cold weather for these tractors is defined as any temp. below 60 degrees F.  Thanks, Debra Kay  

Question by Debra kay    |  last reply


what do you think

Every one is going "green" these days and I myself am planning on going head on the opposite direction this is what I have, let me know what you think. I am building a GMC 3/4 ton 4wd. my first priority was what motor to use. so I asked around and a family friend said he had a 2 ton grain truck that has been sitting for years and was looking to get rid of it, he said it had a big block in it. so I took it because it was a big block. it is a 366 cubic inch big block tall deck (NOT A BORED OUT 350) I figured if its good enough for a two ton truck its good enough for my 3/4 ton. I also pulled out the transmission and it is the sm 465great transmission, and my dad gave me the transfer case its the np 205 the king of transfer cases. now I need better axels all i have are the factory 12 and 14 bolt. I am sure they will do but I am looking at getting the Rockwell 2 and 1/2 ton planetary gear set. you know the axels in the duce and a halves .I have a predicted fuel mileage of three to five miles to the gallon. but I could challenge anyone to try to out pull me because I have the gearing and the power

Topic by vince 09    |  last reply


Low Powered Air Conditioner

I live in a converted bus made into a mobile home in Outback Australia. I'm currently building a 'Solar System'  so I can go anywhere without relying on hooking up to mains power. The biggest problem I'm having is finding an 'Inverter' that will handle power consumption to run my 'Fridge' and ''Air Conditioner', I have a 2500w Inverter but this can only run an 'Aircon' up to 300w, so tell me where you can get one that runs at this power level !! I have an idea that may get over both problems (Fridge and Aircon). I was looking through 'ebay' and found a 80L Fridge/Freezer that runs on 12v, mainly used for 4WDs and RVs. I'm just wondering if I could somehow carefully drill a hole into the freezer cabinet and coil copper or aluminum small bore pipe around the internal walls of this, then have a small 12v DC Pump circulating 'Antifreeze' or similar through a external radiator with fan blowing through this into my living area. I know this will be a drain on batteries as the freezer will be constantly running due to the warmer return fluid circling around inside the cabinet, but I'm not really worried about this as I will have 4 Solar Panels totaling around 500w production at 7-8amps and  4 Deep Cycle Batteries rated at 100ah each, total 400ah. Will this setup be efficient as a air cooling system without effecting the frozen food in my freezer too much. Would love to here any comments on this and also any suggestions will be gratefully accepted. Regards Keith

Question by Keefe    |  last reply


The New Knex Innovationists Tournament - T.N.K.I.T (Round 1)

The category is "K'nex Vehicles".Only one thing to remember, 2-16 wheels on your vehicle needed!You can show it in a Forum Topic, a Slideshow, or a Video.The things where your vehicle will be judged on:- Originality- Looks- Added Functions Such As: Suspension, Engine Model, Etc- ReliabilityIf you have made something, post a link here, and i'll judge it as soon as i see it.Enter it before 1 September 2009, or you'll be disqualified.Contestants:- St J - Entry:- Millawi Legend - Entry: https://www.instructables.com/id/Knex-Tunes-Puller/- Kairah - Entry: https://www.instructables.com/community/Kairahs-Knex-Train-V01-TNKIT-Entry/- Shadowninja31 - Entry:- Silentassasin21 - Entry: https://www.instructables.com/id/Knex-willys-jeep/- DarthVader - Has been banned sadly enough, so he can't enter anything.- (Atlas) - Entry:- Jollex - Entry: https://www.instructables.com/id/Knex-Snowmobile-TNKIT-Entry/- ZakS95 - Entry: https://www.instructables.com/community/Knex-Car/- Knexguy - Entry: https://www.instructables.com/community/TKNIT-entry-and-FN-SCAR-H/- 222222222539 - Entry: https://www.instructables.com/id/TKIT-Round-1-Entry-Every-Terrain-Tank-with-Fu/- Killer SafeCracker - Entry: https://www.instructables.com/id/Knex-Racer-TNKIT-Entry/- LordSnipe - Entry:- Owen-mon-82397 - Entry: https://www.instructables.com/community/Knex-Car-TNKIT-Entry/- Cj81499 - Entry: https://www.instructables.com/id/the-new-knex-innovations-tournement/- Dj Radio - Entry: https://www.instructables.com/id/Knex-tank-1/- KillerPanda - Entry:- Heat-Seeker - Entry: https://www.instructables.com/community/knex-gypsy-caravan-TNKIT/- Serial-Cricket - Entry: https://www.instructables.com/community/Knex-Horse-Drawn-Carridge-TNKIT/- Yannyboy - Entry:- Katarukito - Entry:- Ajleece - Entry:- Knex Mad - Entry: https://www.instructables.com/id/KNEX-4WD-TRUCK/- Knexmaster7000 - Entry:- Darth Gecko Man - Entry:- The Jamalam - Entry: https://www.instructables.com/community/TNKIT-I-think-entry/Do your thing, guys!UPDATE:THE RESULTS ARE HERE:https://www.instructables.com/community/The-New-Knex-Innovationists-Tournament-TNKIT-1/

Topic by Skreetsha    |  last reply


How to design and build a belt driven generator for a small tractor?

The storm that swept through Ohio last Friday (seems like an eternity ago) took out our power. It may not be restored until sometime next week (ah, life in the country). We are used to this sort of thing in the winter and are prepared for it. However, we are not prepared to deal with it when it is this hot. I have a small generator that can run a fan and a few lights and am prepared to sacrifice the contents of the fridge. My generator doesn't put out enough power to run a window AC unit much less our central AC unit. My neighbor has a gas powered generator that is big enough to do the trick but he is pouring so much money into the tank that he might as well stay at a hotel. So anyhow I looked into getting a PTO driven generator to run off my Kubota BX1500 (think diesel engined, 4wd lawn mower on steroids rather than tractor-it's a tiny little thing). It really doesn't burn all that much fuel and it offers the option of using home brewed biodiesel (damn the Tax Man-full speed ahead!). Here's the rub though: you need about 2 hp/kw to run a generator off the PTO. My Kubota has about 12.5 hp. The smallest PTO driven generator I can find (Norther Tool) is a 10 KW unit. That won't work out very well. However, they also have a 2900 watt belt driven generator head that would be large enough to do the job. I suppose I could mig together an angle iron frame that will hook to the three point hitch and mount the generator head and the driven jack shaft but I don't have any experience in building belt drive units. Soooo, anybody out there have any experience in cobbling together belt drive units from scratch? The tractor's PTO shaft turns at 540 rpm but the generator really won't work right unless it turns at least 3600 rpm (interestingly the ratio works out to be 6.66 to 1, possibly not a good omen). Grainger has a large (if over priced) selection of pulleys that will get me in the ballpark. This still leaves a lot of questions though, probably more that I can think of since I have no experience in belt drive systems. I am specifically worried about how to set up the necessary bearings to support the jack shaft that connects the PTO shaft to the drive pulley. For that matter I don't know where to get a shaft that has PTO splines on one end and a keyway on the other. In any case, one of you guys have probably already done this or something pretty close to it. So how about letting the rest of us in on all the necessary tricks? Thanks!

Question by Ogg1    |  last reply


Im will create the 4wdrobot with lcd that show the obstacle and the distance cm help please the code?

/* 2011-10-03 robot4wd_06.pde Eric Pavey - www.akeric.com This software is released to the wild, free to be used and modified. If you use it, I just ask for some credit ;) Program to drive the 4wd robot chasis using an arduino paired up with a ping))) sensor and a servo for collision detection. Hardware: Arduino Duemilanove (but I'm sure any others will work) http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove Arduino is powered off a 5xAA producing 7.5v, sitting in the belly of the chassis. Main chassis is the "4wd mobile platform" from DF Robot http://www.dfrobot.com/index.php?route=product/product&path=37&product_id=97 http://www.makershed.com/ProductDetails.asp?ProductCode=MKSEEED8 http://www.rugcommunity.org/page/dfrobot-4wd-arduino-mobile Motor control using the Adafruit motorshield: http://www.ladyada.net/make/mshield/index.html There doesn't seem to be API docs, but there is this header file: https://github.com/adafruit/Adafruit-Motor-Shield-library/blob/master/AFMotor.h Motor shield is powered off 4xC batteries (6v). Paralax ping))) : http://www.parallax.com/tabid/768/ProductID/92/Default.aspx http://www.arduino.cc/en/Tutorial/Ping Notes: I had to rewire the ribon connecting the ping to the motorshield: The ping's ribon is ground\+5v\signal, but the motorshield's input pins order are +5v\ground\signal. It works from 2cm to 3m. Paralax (Fubata) "standard servo": This is found in the "PING))) Mounting Bracket Kit": http://www.parallax.com/Store/Robots/RoboticAccessories/tabid/145/CategoryID/22/List/0/SortField/0/Level/a/ProductID/248/Default.aspx This is plugged into the 'servo2' port on the motorshield. It uses the servo library: http://arduino.cc/en/Reference/Servo Much of the ping code at the bottom is taken straight from the Arduino examples. */ //-------------------------------------------------------------------------- // Library include stuff: #include // needed for the motorshield. #include // motorshield needs this for running servos. #include LiquidCrystal lcd(3, 4, 5, 6, 11, 12); //-------------------------------------------------------------------------- // globals: // ping))) stuff: int g_pingPin = 19; // this is actually analog pin 5, pretending to be digital, on the motorshield. long g_collideDist = 50; // in cm, how far before collision mode kicks in? long g_cm = 300; // the current ping reading, just ana initial default. boolean g_checkLeft = false; // used for collision detection boolean g_checkRight = false; // used for collision detection boolean g_checkCenter = false; // used for collision detection int g_leftDist = 0; // used for collision detection int g_rightDist = 0; // used for collision detection // motor stuff: AF_DCMotor g_motor1(1, MOTOR12_8KHZ); // back left AF_DCMotor g_motor2(2, MOTOR12_8KHZ); // back right AF_DCMotor g_motor3(3, MOTOR12_8KHZ); // front right AF_DCMotor g_motor4(4, MOTOR12_8KHZ); // front left byte g_motorSpeed = 255; // max is 255 // Mode (state) stuff: byte g_mode = 1; // 1 = drive, 2 = proximity check, 3 = turning byte g_driveDir = -1; // 0 = stop, 1 = straight, 2 = right, 3 = left // servo stuff: Servo g_servo2; int g_servo2pin = 9; // servo2 uses digital pin 9, even though the docs say pin 10... int g_servoCenter = 98; // in degrees. 98 is straight ahead based on how I mounted the servo (it must be // a little inaccurate). full left is 180, full right is 0. // Servo is flipped upside down, fyi int g_servoRight = 135; // how far right? Max is 180, full right. int g_servoLeft = 45; // how far left? Min is 0, full left. // time stuff unsigned long g_time; // global time tracker unsigned long g_ptime; // global previous time tracker unsigned long g_elapsed = 0; // helps keeping track of framerate. unsigned long g_interval = 33; // in ms (about 30fps). This slows down the processing allowing the // multiple systems to play nicely together. Make this number smaller and it won't have enough // time for each state to run properly: The servo won't do a full sweep when scanning. unsigned long g_turnlength = 750; // in ms, how long to turn for. Since we don't know how far // it turns, we just guess on how long it should. The type of terrain turing on has a great // effect on what this should be. This value works well for my hardwood floors. unsigned long g_turnUntil; // used to track how long to turn. //-------------------------------------------------------------------------- // setup \ loop : void setup() { // Attach & center the servo: g_servo2.attach(g_servo2pin); g_servo2.write(g_servoCenter); // center it by default // Setup our framerate stuff g_time = millis(); g_ptime = g_time; } void loop() { // Main program entry point. // Need to keep the aiming and the piging at a fixed rate, or the closer the object gets // to the ping the faster it will aim, and do bad stuff. g_ptime = g_time; g_time = millis(); g_elapsed += g_time - g_ptime; // Wait for the proper amount of time to pass before we do anything: if(g_elapsed < g_interval){ return; } else{ g_elapsed = 0; } // Do stuff, based on the current mode: if(g_mode == 1){ g_cm = ping(); // sometimes the sensor returns a 0 value that can foul up things :( if(g_cm > g_collideDist || g_cm == 0){ // If there is nothing in our way, drive! if(g_driveDir != 1){ g_driveDir = 1; move(g_driveDir); } } else{ // if we're too close to something, stop the motors and switch to 'proximity check' mode: if(g_driveDir != 0){ g_driveDir = 0; move(g_driveDir); } // initialize the proximity check stuff: g_checkLeft = false; g_checkRight = false; g_checkCenter = false; g_leftDist = 0; g_rightDist = 0; // switch to mode 2: g_mode = 2; } } else if(g_mode == 2){ // Do proximity check! boolean checked = proximityCheck(); if(checked){ // Define which direction to turn. // If the right distance is greater than the left distance, turn that direction, // otherwise go the other way: if(g_rightDist >= g_leftDist){ g_driveDir = 2; } else{ g_driveDir = 3; } // now that we've set which direction to turn, start timing how long the turn // has taken, and switch to mode 3. g_turnUntil = millis() + g_turnlength; g_mode = 3; } } else if(g_mode == 3){ // We must be turning! The logic for switching to other modes is in that function. turn(); } } //-------------------------------------------------------------------------- // Helper functions: void turn(){ // Executed when g_mode == 3 // Used to turn the robot. if (millis() < g_turnUntil){ // keep'on turning... move(g_driveDir); } else{ // If we're done turning, see if there is anything still in our way: g_cm = ping(); // sometimes the sensor returns a 0 value that can foul up things :( if(g_cm > g_collideDist || g_cm == 0){ // If there is nothing in our way go back to mode 1: g_mode = 1; } else{ // If stuff is still in our way, turn more in the same direction until // not blocked: g_turnUntil = millis() + g_turnlength; } } } boolean proximityCheck(){ // Used when mode == 2: Swing the ping left and right taking readings to // find which way is safe to go. Returns false when in the middle of the check // operation, returns true when entire check process is complete. // Current angle of the servo: float angle = g_servo2.read(); // check left first: ( full left is 0 deg) if(g_checkLeft == false){ if(angle > g_servoLeft){ g_servo2.write(angle-10) ; return false; } else{ g_checkLeft = true; g_leftDist = ping(); return false; } } // check right second: ( full right is 180 deg) if(g_checkLeft == true && g_checkRight == false){ if(angle < g_servoRight){ g_servo2.write(angle+10) ; return false; } else{ g_checkRight = true; g_rightDist = ping(); return false; } } // Go to center position third: if(g_checkLeft == true && g_checkRight == true && g_checkCenter == false){ if(angle != g_servoCenter){ g_servo2.write(angle-10) ; return false; } else{ g_checkCenter = true; return false; } } // Finally if we've checked left, right, and got back to center, return true // to tell the later code that the full check is complete: if(g_checkLeft == true && g_checkRight == true && g_checkCenter == true){ return true; } else{ return false; } } void move(byte mode){ // This function moves the wheels. Can be called to when mode == 1 (driving) or 3 (turning). if(mode == 0){ // all stop! g_motor1.setSpeed(0); g_motor2.setSpeed(0); g_motor3.setSpeed(0); g_motor4.setSpeed(0); } else{ // full speed! g_motor1.setSpeed(g_motorSpeed); g_motor2.setSpeed(g_motorSpeed); g_motor3.setSpeed(g_motorSpeed); g_motor4.setSpeed(g_motorSpeed); // full speed, but which direction? if(mode == 1){ // go straight g_motor1.run(FORWARD); g_motor2.run(FORWARD); g_motor3.run(FORWARD); g_motor4.run(FORWARD); } else if(mode == 2){ // turn right g_motor1.run(FORWARD); g_motor2.run(BACKWARD); g_motor3.run(BACKWARD); g_motor4.run(FORWARD); } else if (mode == 3){ // turn left g_motor1.run(BACKWARD); g_motor2.run(FORWARD); g_motor3.run(FORWARD); g_motor4.run(BACKWARD); } } } float ping(){ // Returns the distance in cm from the ping sensor. Pulled from // Arduino docs. // The PING))) is triggered by a HIGH pulse of 2 or more microseconds. // Give a short LOW pulse beforehand to ensure a clean HIGH pulse: pinMode(g_pingPin, OUTPUT); digitalWrite(g_pingPin, LOW); delayMicroseconds(2); digitalWrite(g_pingPin, HIGH); delayMicroseconds(5); digitalWrite(g_pingPin, LOW); // The same pin is used to read the signal from the PING))): a HIGH // pulse whose duration is the time (in microseconds) from the sending // of the ping to the reception of its echo off of an object. pinMode(g_pingPin, INPUT); long duration = pulseIn(g_pingPin, HIGH); float cm = microsecondsToCentimeters(duration); return cm; } long microsecondsToCentimeters(long microseconds){ // Simple conversion setp, kept as a function simply to illustrate // how it works. Pulled from Arduino docs. // The speed of sound is 340 m/s or 29 microseconds per centimeter. // The ping travels out and back, so to find the distance of the // object we take half of the distance travelled. //return microseconds / 29 / 2; return microseconds / 58; } // while(val == HIGH) { // Loop until pin reads a high value //val = digitalRead(ultraSoundSignal); //timecount = timecount +1; // Count echo pulse time} //ultrasoundValue = timecount; // Append echo pulse time to ultrasoundValue //lcd.clear(); //lcd.setCursor(0,0); //lcd.print("OBSTAKEL cm "); //lcd.print(timecount/10); //delay(200); //if(timecount > 0){ //digitalWrite(ledPin, HIGH);}

Question by pe2hlc    |  last reply


i will the 4wdrobot with lcd that show the obstacle and the distance cm help please the code?

/*  2011-10-03  robot4wd_06.pde  Eric Pavey - www.akeric.com  This software is released to the wild, free to be used and modified.  If you use it,  I just ask for some credit ;)    Program to drive the 4wd robot chasis using an arduino paired up with a ping))) sensor  and a servo for collision detection.    Hardware:    Arduino Duemilanove (but I'm sure any others will work)  http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove  Arduino is powered off a 5xAA producing 7.5v, sitting in the belly of the chassis.    Main chassis is the "4wd mobile platform" from DF Robot  http://www.dfrobot.com/index.php?route=product/product&path;=37&product;_id=97  http://www.makershed.com/ProductDetails.asp?ProductCode=MKSEEED8  http://www.rugcommunity.org/page/dfrobot-4wd-arduino-mobile    Motor control using the Adafruit motorshield:  http://www.ladyada.net/make/mshield/index.html  There doesn't seem to be API docs, but there is this header file:  https://github.com/adafruit/Adafruit-Motor-Shield-library/blob/master/AFMotor.h  Motor shield is powered off 4xC batteries (6v).    Paralax ping))) :   http://www.parallax.com/tabid/768/ProductID/92/Default.aspx  http://www.arduino.cc/en/Tutorial/Ping  Notes:  I had to rewire the ribon connecting the ping to the motorshield:  The  ping's ribon is ground\+5v\signal, but the motorshield's input pins order are +5v\ground\signal.  It works from 2cm to 3m.    Paralax (Fubata) "standard servo":  This is found in the "PING))) Mounting Bracket Kit":  http://www.parallax.com/Store/Robots/RoboticAccessories/tabid/145/CategoryID/22/List/0/SortField/0/Level/a/ProductID/248/Default.aspx  This is plugged into the 'servo2' port on the motorshield.  It uses the servo library:  http://arduino.cc/en/Reference/Servo    Much of the ping code at the bottom is taken straight from the Arduino examples.  */ //-------------------------------------------------------------------------- // Library include stuff: #include   // needed for the motorshield. #include   // motorshield needs this for running servos. #include LiquidCrystal lcd(3, 4, 5, 6, 11, 12); //-------------------------------------------------------------------------- // globals: // ping))) stuff: int g_pingPin = 19; // this is actually analog pin 5, pretending to be digital, on the motorshield. long g_collideDist = 50; // in cm, how far before collision mode kicks in? long g_cm = 300; // the current ping reading, just ana initial default. boolean g_checkLeft = false; // used for collision detection boolean g_checkRight = false; // used for collision detection boolean g_checkCenter = false; // used for collision detection int g_leftDist = 0;  // used for collision detection int g_rightDist = 0;  // used for collision detection // motor stuff: AF_DCMotor g_motor1(1, MOTOR12_8KHZ); // back left AF_DCMotor g_motor2(2, MOTOR12_8KHZ); // back right AF_DCMotor g_motor3(3, MOTOR12_8KHZ); // front right AF_DCMotor g_motor4(4, MOTOR12_8KHZ); // front left byte g_motorSpeed = 255; // max is 255 // Mode (state) stuff: byte g_mode = 1; // 1 = drive, 2 = proximity check, 3 = turning byte g_driveDir = -1; // 0 = stop, 1 = straight, 2 = right, 3 = left // servo stuff: Servo g_servo2; int g_servo2pin = 9; // servo2 uses digital pin 9, even though the docs say pin 10... int g_servoCenter = 98; // in degrees.  98 is straight ahead based on how I mounted the servo (it must be     // a little inaccurate).  full left is 180, full right is 0.     // Servo is flipped upside down, fyi int g_servoRight = 135; // how far right?  Max is 180, full right. int g_servoLeft = 45; // how far left?  Min is 0, full left. // time stuff unsigned long g_time;  // global time tracker unsigned long g_ptime;  // global previous time tracker unsigned long g_elapsed = 0;  // helps keeping track of framerate. unsigned long g_interval = 33; // in ms (about 30fps).  This slows down the processing allowing the     // multiple systems to play nicely together.  Make this number smaller and it won't have enough     // time for each state to run properly:  The servo won't do a full sweep when scanning. unsigned long g_turnlength = 750; // in ms, how long to turn for.  Since we don't know how far     // it turns, we just guess on how long it should.  The type of terrain turing on has a great     // effect on what this should be.  This value works well for my hardwood floors. unsigned long g_turnUntil; // used to track how long to turn. //-------------------------------------------------------------------------- // setup \ loop : void setup() {   // Attach & center the servo:   g_servo2.attach(g_servo2pin);   g_servo2.write(g_servoCenter);  // center it by default   // Setup our framerate stuff   g_time = millis();   g_ptime = g_time; } void loop() {   // Main program entry point.     // Need to keep the aiming and the piging at a fixed rate, or the closer the object gets   // to the ping the faster it will aim, and do bad stuff.   g_ptime = g_time;   g_time = millis();   g_elapsed += g_time - g_ptime;   // Wait for the proper amount of time to pass before we do anything:   if(g_elapsed < g_interval){     return;   }   else{     g_elapsed = 0;   }   //  Do stuff, based on the current mode:   if(g_mode == 1){     g_cm = ping();     // sometimes the sensor returns a 0 value that can foul up things :(     if(g_cm > g_collideDist || g_cm == 0){       // If there is nothing in our way, drive!       if(g_driveDir != 1){         g_driveDir = 1;         move(g_driveDir);       }     }     else{       // if we're too close to something, stop the motors and switch to 'proximity check' mode:       if(g_driveDir != 0){         g_driveDir = 0;         move(g_driveDir);       }       // initialize the proximity check stuff:       g_checkLeft = false;       g_checkRight = false;       g_checkCenter = false;       g_leftDist = 0;       g_rightDist = 0;        // switch to mode 2:       g_mode = 2;        }   }   else if(g_mode == 2){     // Do proximity check!     boolean checked = proximityCheck();      if(checked){       // Define which direction to turn.       // If the right distance is greater than the left distance, turn that direction,       // otherwise go the other way:       if(g_rightDist >= g_leftDist){         g_driveDir = 2;       }       else{         g_driveDir = 3;       }       // now that we've set which direction to turn, start timing how long the turn       // has taken, and switch to mode 3.       g_turnUntil = millis() + g_turnlength;       g_mode = 3;     }   }   else if(g_mode == 3){     // We must be turning!  The logic for switching to other modes is in that function.     turn();   } } //-------------------------------------------------------------------------- // Helper functions: void turn(){   // Executed when g_mode == 3   // Used to turn the robot.     if (millis() < g_turnUntil){     // keep'on turning...     move(g_driveDir);   }    else{     // If we're done turning, see if there is anything still in our way:     g_cm = ping();     // sometimes the sensor returns a 0 value that can foul up things :(     if(g_cm > g_collideDist || g_cm == 0){       // If there is nothing in our way go back to mode 1:       g_mode = 1;     }     else{       // If stuff is still in our way, turn more in the same direction until       // not blocked:       g_turnUntil = millis() + g_turnlength;     }   } } boolean proximityCheck(){   // Used when mode == 2:  Swing the ping left and right taking readings to   // find which way is safe to go.  Returns false when in the middle of the check   // operation, returns true when entire check process is complete.     // Current angle of the servo:   float angle = g_servo2.read();     // check left first: ( full left is 0 deg)   if(g_checkLeft == false){     if(angle > g_servoLeft){       g_servo2.write(angle-10) ;       return false;        }     else{       g_checkLeft = true;       g_leftDist = ping();       return false;       }   }   // check right second: ( full right is 180 deg)   if(g_checkLeft == true && g_checkRight == false){     if(angle < g_servoRight){       g_servo2.write(angle+10) ;       return false;          }        else{       g_checkRight = true;       g_rightDist = ping();       return false;     }   }   // Go to center position third:   if(g_checkLeft == true && g_checkRight == true && g_checkCenter == false){     if(angle != g_servoCenter){       g_servo2.write(angle-10) ;       return false;     }           else{       g_checkCenter = true;       return false;     }   }   // Finally if we've checked left, right, and got back to center, return true   // to tell the later code that the full check is complete:   if(g_checkLeft == true && g_checkRight == true && g_checkCenter == true){     return true;   }   else{     return false;   } } void move(byte mode){   // This function moves the wheels.  Can be called to when mode == 1 (driving) or 3 (turning).   if(mode == 0){     // all stop!     g_motor1.setSpeed(0);     g_motor2.setSpeed(0);     g_motor3.setSpeed(0);     g_motor4.setSpeed(0);   }   else{     // full speed!     g_motor1.setSpeed(g_motorSpeed);     g_motor2.setSpeed(g_motorSpeed);     g_motor3.setSpeed(g_motorSpeed);     g_motor4.setSpeed(g_motorSpeed);         // full speed, but which direction?     if(mode == 1){       // go straight       g_motor1.run(FORWARD);       g_motor2.run(FORWARD);       g_motor3.run(FORWARD);       g_motor4.run(FORWARD);     }     else if(mode == 2){       // turn right       g_motor1.run(FORWARD);       g_motor2.run(BACKWARD);       g_motor3.run(BACKWARD);       g_motor4.run(FORWARD);      }     else if (mode == 3){       // turn left       g_motor1.run(BACKWARD);       g_motor2.run(FORWARD);       g_motor3.run(FORWARD);       g_motor4.run(BACKWARD);     }   } } float ping(){   // Returns the distance in cm from the ping sensor.  Pulled from   // Arduino docs.     // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.   // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:   pinMode(g_pingPin, OUTPUT);   digitalWrite(g_pingPin, LOW);   delayMicroseconds(2);   digitalWrite(g_pingPin, HIGH);   delayMicroseconds(5);   digitalWrite(g_pingPin, LOW);   // The same pin is used to read the signal from the PING))): a HIGH   // pulse whose duration is the time (in microseconds) from the sending   // of the ping to the reception of its echo off of an object.   pinMode(g_pingPin, INPUT);   long duration = pulseIn(g_pingPin, HIGH);    float cm = microsecondsToCentimeters(duration);   return cm; } long microsecondsToCentimeters(long microseconds){   // Simple conversion setp, kept as a function simply to illustrate   // how it works.  Pulled from Arduino docs.     // The speed of sound is 340 m/s or 29 microseconds per centimeter.   // The ping travels out and back, so to find the distance of the   // object we take half of the distance travelled.   //return microseconds / 29 / 2;   return microseconds / 58; }          // while(val == HIGH) {                  // Loop until pin reads a high value //val = digitalRead(ultraSoundSignal); //timecount = timecount +1;             // Count echo pulse time} //ultrasoundValue = timecount;          // Append echo pulse time to ultrasoundValue //lcd.clear(); //lcd.setCursor(0,0); //lcd.print("OBSTAKEL  cm "); //lcd.print(timecount/10); //delay(200); //if(timecount > 0){ //digitalWrite(ledPin, HIGH);}    

Question by pe2hlc    |  last reply


"Secrets" about CB/UHF antennas on your car

Despite more and cellphone and internet coverage mobile radios are still a favourite of people in remote areas or just loving to explore by 4WD.And for most the complex task of starting with this great hobby ends by buying a radio and antenna.Of course the raio goes it fits best and that is fine but what about that antenna and while at it what type of antenna do you need?Let's start with the great myth that so called rugged or heavy duty antennas are really worth their money.Durability and stiffness is their main selling point or better was.At highway speeds they won't bend and flex around like your whip antenna.In the bush they won't swing all the way down onto the painted parts of your car either.But then again, a more solid steel whip on a spring base would do the same - but won't look as cool or proffessional...Inside those plastic or fibreglass rods is a dipole antenna, in rare case you get a 5/8 configuration or even a normal steel whip with a pipe around it...Means in terms of reception or transmission quality they are not a tiny better or worse than any other antenna out there.Come down to well it is tuned and where the radiating part is located.Location...There are often obvious choices to put an antenna, like that nice mount or your nudge- or bull-bar.Or the good old boot clamp in the back.I have even see 4WD's with the antenna mounted onto the rear bumper :(Why is it so important to place the antenna correctly?Place on the front corner of your car it is not only quite low but also partially covered by the metal parts of your car - limiting where the antenna can properly radiate.If you ever got some half decent training on a tiny handheld UHF radio then you remember to seek higher ground if you can't get anyone to hear you.The same is true for the antenna on your car.You want nothing obstructing it.People with a long spring base often think of it as just an elevated foot.Most of these however are "ground idependent", which means they actually form a dipole with the antenna you screw on the top.Having this "pole" below bonnet hight is quite bad for your reach and reception quality already.Mounting just a normal whip on a direct foot here means you might have better luck with a handhelp from inside the car...The best would be right in the center of your roof, the highest and most centered point.This provides not only the optimum radiation pattern but also give you that little edge in terms of higher ground.How much gain do I need and how long should my antenna be?Gain is quite relative if you ask me as it far more important to mount the antenna in the best possible place.A 3DB antenna on the roof will often provide better reception and range than a 9DB mounted on the bullbar.Assuming you have the best feasable location than to simplify it:The further you can see the higher DB you want if reaching far is the main objective.For general use a 4.5 - 6DB antenna is always good.In hilly terrain range does not matter that much, here you want the outgoing signal to be as strong as possible and with a shape that allows better coverage by being more like a sphere.For extreme cases it can mean on a 9DB antenna your friend that is just over that little bump ahead is not visible and with that can't hear you.On a 3DB antenna however the signal is strong enough to reach that blindspot at a short distance.The overall length of an antenna can be deceiving for UHF frequencies.What matters is where the antenna is radiating from.In most cases it will be the top 15 to 30 cm of your antenna.For a dipole or ground independent antenna you often need to include the entrire base mount.Antenna tuning....For the good old 27MHz bands we always had our SWR meter at hand and tried to get the best tuning.Since the big jump to UHF the commercial antennas come pre-tuned and are claimed to be good to go.That means that are within acceptable performance to fit almost all installation locations.In terms of SWR reading it means that 1 over 3 is still perfectly fine.Would have been an outcry on 27Mhz though in my times.What is true though that there is not that much real difference to notice between a near perfect 1 over 1.1 to 1 over 3.If you would bother to a distance test it might be less than 200m you gain on the near perfect antenna.For the reception it does not even matter all, so why bother anyway?On the much lower frequencies a really good SWR does not only mean you can get your signal much further out there but also that your transmitter is happy.Modern ones are now all digital and have ways to protect and compensate for bad antennas or cables.Together it means we could just forget about these few extra meters and move on.The stress on the transmitter in your UHF radio however is still there ;)The reflective energy from a badly tuned antenna has to go somewhere and that is usually back into the transmitter.The bit that lost directly to your antenna, as said, does not matter too much with the overall limited range of the UHF frequencies.I did quite a lot of experimenting with my own and commercail UHF antennas, so a network analyser and SWR meter was a requirement anyway.In terms of output power a good SWR reading means you get what your transmitter is capable of and set for.With an SRW reading between 2.5 and 3 however a 4W radio might only actually transmit 3-3.5W.With a bad mounting and an not so optimal cable it might go below 3W!Distance is not so much affected by this as we now know, but the loss in power on 3DB antenna in hilly terrain can make the difference between being heard and your signal getting lost in static on the other end.Repairing a blown transmitter often costs more than a simple SWR meter for UHF, so why not add it to the Xmas wish list? ;)Two antennas...In some case you want two antennas.Be it for two different DB ratings on the same radio or for totally different frequencies.High and centered is still best here but you should keep the antennas as far apart as possible, preferable at different heights as well.On a single radio it does not matter too much but right next to each other the unused anteanna is like these beams on your TV antenna on the roof.Unlike the directional and watned features in a Yagi antenna the unused element means we change the radiation pattern.In the worst case creating a blindspot from which direction we won't get any signals.As a rule of thumb let them be apart at least twisc as far as the wavelenght, so for UHF over 65cm.

Topic by Downunder35m  


Options to improve cooling and reduce consumption for portable coolers

I recently had to start learning how to service airconditioners on the fast and that learning got me thinking about my portable coolers.... Some of us like to go camping or on longer fishing trips, so there might be one of those 3-way fridges in use or a better cmpressor model. The one thing they all have in common is that they can only cool down to a difference in ambient temperatures. No matter which way we turn it the cooling produces heat and that needs to get away somehow. The other big thing is the cooling cycling - or the lack of it on a warm day. After some reading and thinking I came up with some ideas that might be applicable to your existing cooler if you are willing to mess around a bit. Let's start with the produced heat, shall we? Down here in Australia most people either have the fridge in their4WD or camper. In a car or small camper trailer there is often the problem of airflow, so the cooler might be doing overtime for no other reason than a lack of airflow. If you check online sites like Amozon and Ebay you quickly find fan systems meant to be installed inside the cooler to get lower temperatures and a quicker cooling of fresh goods. The thing is that the box is quite well insulated and the benefit of the airflow goes only as far as it can reach. And even if the box is quite empty and you would have a benefit of the cold air moving around it won't change the fact that "improved" cooling always comes with more heat in this case. But if we use one of these fan systems to actually improve the airflow on the hot side we not only get better cooling but also a reduce power consumption - something worth considering if you have no backup power generator.... This of course brings us to placement. As I have done the mistake myself you might be tempted to put a 3way cooler onto your seat. Opening it with the back free means the lid always gets stuck on the seat, do it the other way around and you block the airflow. If you do put it on the seat then make sure two things match: 1. The thing is secured properly. 2. The airflow from your aircon is able to reach the hot side of the cooler. Even permanent installations in a camper benefit from a good airflow. Often the fridge or freezer is built into some sort of bench and the airflow behind might be very limited. A simple solution here is to add a vent on top of the bench to allow the hot air to escape. A better one is to use a fan that is powered together with the heating element or compressor and drives the hot air to the outside. How to improve the cold side of the box or fridge? Well, to be honest there is not much that can be done unless you are prepared for some serious work. Depending on compartment size, contents and how full it is a little fan can help to keep the temperatures even but it won't help to get it cooler or reduce the cycling periods for the cooling. The only really working way that I found is to use a "battery" for the storage of the cold. The cooling works by checking the inside temp of the box and if above the set temp the cooling won't stop. This is all well and good while we have a constant supply of power but once we are on batteries it would be great to keep the active time to a minimum. A working solution is to build a container that fits around the cooling element. Smaller types often use an aluminium heatsink, bigger types might come with a compressor and an evaporator. In either case proper sealing is important! Most good models are fully waterproof, meaning even if you would fill them with water they would not leak in other areas than the door. But double check and if in doubt use a bit of silicone to make sure. Ok, but how do we "store" the cold coming from the device? Cold packs ;) These things contain a ready to use mix that holds cold temperatures quite well. Another really good alternative is alcohol or radiator coolant, although the last has limited capabilites in terms of holding capaity for the cold as it is desinged to exchange heat fast rather than to keep it. With a suitable sized and sealed box around the active cooling element we will need longer to actually see any cooling happen (with a warm "battery") but that can be compensated for by good planning or a frozen water bottle. If the cooling element is covered with a box of cooling gel then it has to cool this first before anything happens inside the box. But once it does the pack is already far below the normal temp it would have during normal operation. Remember the inside of the cold pack cools down first before the outside will get cold ;) So once the set temperature is reached the device will shut off. But since the cold pack is far below the set temp it will continue to cool our box until the core is warmer than the set temp. Quick thinkers will now say the benefit is lost as the time required to cool the "battery" down again is much longer than the normal cycle time - and they would be correct. But as we get much colder temps inside the gel box the overall running will still be less compared to normal operation. And since from the second cycle on the gel is only warming up to operating temp of the box it will be much faster than with a warm box. Another benefit might be the ease of cleaning and ice removal. Some peltier driven coolers have big cooling fins or a quite bad design for the heatsink allowing mould to grow where you can't remove it easy. If the box is made from stainless steel and flush with the back wall of the box we won't have that problem anymore. Ok, but how much is good or too much for the size and gel content? You got me there as it is bit tricky. You don't want to loose much usable space for starters and you don't want to wait hours for the gel to cool down if the box was not used. IMHO the size should fit the cooling element with about 20% to spare all around. If stainless steel is not an option than aluminium is the next best choice. Thin sheets can either be be cold formed with a hammer or "brazed" with a good torch and the right rods. Ok, before that route is there anything I should consider or do first? Depends ;) 3-way systems usually use a flame or heating elements to heat an ammoia solution. After years of neglect corrosion can form and reduce the amount of heat transfered into the system and reducing the efficiency this way. It might help to take the heating elements out once a year or so to clean them and the contact areas from any corrosion or dirt build up. With a fixed shedule for this you won't have the problem of never noticing a badly corroded heating element either - and this is the main failure on these systems.... Modifying your camper or making a few mods to your 4WD drawer system is not for the faint of heart and should be done with consideration. The last thing you want to do is rush things to find out it was not necessary. Before cutting holes check if you can't find the room for the fan in a different spot and use ducts to control the airflow - sometimes it is easier to blow air in than to get air out ;) When it comes to creating vents or connections for air to the outside always make sure it is waterproof and insect safe! If you can let the outlet go downwards so water won't run in, for 4WD trailers consider a flap to prevent water from going during a river crossing. Flyscreens will not only prevent insects from coming in but on the inside also prevent dust to go eerywhere - allow to the removal and cleaning! The salts used in these cold packs can be corrosive, so you have to make sure there are no leaks and that there is no steel to come into contact with gel - this includes screw ends hidden in through-holes. If in doubt use a coat of paint but keep it as thin as possible. Even on peltier systems it might be impossible to remove the heatsink without massive surgery on the internals. So before you take it all apart to gain access check if it is far easier to seal around the box opening and possible screw connections using silicone. The cooling battery can be screwed on and sealed with silicone as well as an easy escape route. Although for this to work you need to check if the material of the box allows for a proper bond with the silicone! Some materials just won't allow anything to stick at all, even after sanding them. So do a test first in an area where you would be able to cut the silicone away without causing damage. If you can rip or peel it off the surface you should not try to use a cooling battery screwed to the wall, only use a box that is fully sealed with the cooling element and has a seperate back - one complete unit around the cooling element. I have a 3-way system with a freezer compartment that does the cooling for the fridge too - what can I do? These units either provide good freezing with the fridge temps too low or good fridge cooling with no freezing capabilites - depending on the thermostat used. Our problem is that is next to impossible to add a cooling battery of the normal kind to these systems. The L-shaped freezer box can really only be added with a L-shaped cooling battery from underneath. Only if you don't need any freezing at all you could add a cooling battery to fit into the freezer box shape. In either case the benefit is somehow limited by the way the thermostat is used. If there is no temp control for freezing it should be fine. Warnings... Only peltier driven coolers are free from refrigerants. Every 3-way or compressor system uses refrigerant as evident by more or less piping and heating elements. Never attempt to screw anything into a cooling element containing refrigerant! Even if you think between the channels all will be fine it won't be! The material is just pressed to form the channels and any damage caould mean refrigerant leaking out! Use silicone instead and make sure all surfaces are properly cleaned before applying it, also wait until the silicone is really fully cured before putting any stress on it. As said, these cooling gels can be corrosive, especially if DC voltage is involved. Make sure that everything that is not aluminum or plastic is properly sealed before allowing ongoing contact with cooling gels. Do not attempt any of this if you have to ask yourself what tools you might need or how make a suitable container for the gel. If in doubt check Google on how to work with aluminium or stainless steel if there are not enough Instructables for it. The gel will expand a little bit if it freezes, this no problem in a metal container if you allow for a bit of flex or on the side added strength  - whatever suits you better. Another option is to get a few different cold packs (by the active ingredient) and to do a check in a little container. Freeze it and note whe level cold and warm. Little to no difference means nothing to worry in terms of expansion during freezing.

Topic by Downunder35m  


Tempered glass screen protectors - understand and beware!

I recently had the joy of needing a new screen protector for my mobile after being dumb enough to drop it on gravel. The hard cover took all the impact but the film protector on the screen was scratched badly. Was old and partially worn anyway so I decided to upgrade to a Tempered Glass screen protector. Being somewhere rural I had no chance to get one in a shop so I ordered online. With no intention of advertising for some sellers, I collected a few links so you can check what I am talking about: Item1 Item2 Item3 Item4 Item5 Item6 So, what is my concern with these? They all can be found on amazon and other online services as well as on local markets... As I said I ordered a glass screen protector. If you check these listings and even some of the packing you will notice they all have a thing in common - being shatter proof and of 9H hardness. I also love this video showing how to remove and fix a glass screen protector! The last time I checked glass had one very distinct feature: It is hard and before it really bends it breaks - unless you use fibre optics of fibre glass cloth... What is my concern and warning here? Pretty simple: Stay away from expensive scams! Some claim their screen protector is only 0.25mm thick, even the 0.2mm one I measured was over 0.5mm with the glue... The hardness of 9H refers to the so called Moh's hardness - look it up on Wikipedia if you like. That means these tempered glass protectors would have a similr hardness than a diamond, or at least close to it. Problem is that they are made from plastic to start with and not glass at all. They claims that the screen protector is flexible because it is so thin - again a fake! Even the thinnest tempered glass will shatter if you bend it enough, not so these plastic ones. If you think I am making all this up try to use a really sharp knife or deburring tool and cut the thin sides of one of these protectors. All the ones I tested could be cut quite easy - and I though glass can't be cut with a kinfe... A nice website showing that the scratch resistance is far from the claims can be found here. And a video showing how a real glass screen protector sounds and breaks can be found here. So is it really all bad and should I avoid getting one? Not really if it is only for the added protection. To be clear here, and without the intention to blame any of the above sellers, some protectors actually do have a top layer made from glass and you can hear it as in the above video - it sound solid and not like plastic if you tap it with something hard. Another factor is the simple fact that plastic absorbs impact much better than glass. So where a real glass screen protector might shatter and crack like in the above video, the fake ones might one get a nasty dint or scratch. But you should be aware and clear about what you get and what to expect from it. These glass imitations are made from a strong polycarbonate plastic, similar to the stuff used for bullet and explosion proof "glas" windows - if you every watched the Mythbusters you have seen the big sheets I mean. The top layer of these things is specially treated to repell water, oil and dirt, it also gives the surface the good scratch resistance. The technique is nothing new, camera lenses, plastic sheets and the clear covers you see over the timetable at your bus stop all use it. The new thing is to intentionally mislable a product to make the consumer think it is glass ;) What is the real difference for the user? Check this video. Here a guy performs a drop test with a real glass screen protector. Thing is once the protector breaks the screen itself is broken too but until then it was not too bad. Here it is demonstrated how a real glass screen protector reacts to certain types of abuse - one of the reason I decided on glass. Compared to the plastic counterfeits just the sound on the glass is worth it, but I think the hacksaw was best. Another video from XDA gives a bit more info on how the glass is made - if you can't seeing a phone being abused then don't watch the drop tests at the end ;) Glass with these hardness levels and types of surface protection will give the user a long and worry free use of the phone. The plastic fakes will perform at a similar level for some time but will show signs of wear long before even the top coat of the glass one fails. Both types have their uses and if the fakes would be labeled correctly the user would actually benefit from that. On bigger screens like a tablet I would actually prefer the plastic ones to prevent damage once it needs replacing. On a mobile used in less than perfect conditions I would also go for plastic as it usually is a bit thinner and will fit better within quality hard covers. But when it comes to real abuse like using with dirty fingers most of the time or mostly outdoors where a lot of dust and fine sand can be involved I always go for glass. If you paid attention to the surface treatment then you already realised that the plastic and the glass are in the same region, making them quite scratch resistant. Still fine sand or metal dust will scratch it.... The difference is in the hardness of the actual material that was covered with the oleophobic film. Glass will not give in any way, where plastic is much softer - so not to be confused with the surface hardness! This mean that sharp and point object will easier penetrate the plastic than the glass, something to be considered if you often ecounter harsh use. In terms of actual protection we need to differenciate between surface quality and actual screen damage. After all when badly scratched we can replace the protector but if the display got damaged we are back to square one. The surface hardness was already covered so let's move on to the screen itself. In some of the above videos you can see the abuse a screen might see in normal conditions, and if we would not drop our phones so often repair shops would not be at every corner LOL I have done quite a few screen repairs, mostly for friends and work mates that did not want to pay the hefty extras in a repair shop. From there I got the stories on how it happened and in almost all cases the screen cracked when the phone landed on the corners. In one case the screen and glass protector failed, including the actual display when the phone was dropped out of a 4WD and landed screen first onto a rock. A glass protector will spread the (direct onto the face) impact force onto a much larger area, where a plastic one will produce a dint onto the actual screen much sooner. So again glass wins in terms of actually protecting your expensive screen. But be aware that all this is useless if the phone lands on the corners!! Let me explain: Both the top glass on your screen and the screen protector have a thin layer of "glue". This acts like a shock absorber, so unless an impact goes deep enough so the pressure on the actual screen is too much only the protector should fail. But the screen itself is a tight fit into the frame of the phone, so all side and corner impacts go directly into the glass. As the rest of the glass has no way to give or go the stresses will crack the screen. How should I treat my phone with the new screen protector? Exactly the same way you would without it of course. But if you don't have a proper cover that offers protection of the corners you should invest in one. Having a quality protector and a good case does not mean your phone can be used as a football, see it as an added insurance in case something does go wrong. For obvious reason it can also pay off to have a spare at hand, if something bad happens that requires replacement of the protector you won't be left with an unprotected screen ;) Last but not least, double it up: For people that already know their screen will see a fair bit of abuse in term of scratches it is a good idea to put an extra film protector onto the glass one. Once it is too scratched you peel it off and replace it, while the glass protector gives you the actual protection for your screen. Corning Willow glass As time of wrinting Corning Willow glass is the only "flexible" glass on the market, unless stated with your flexible screen protector you can assume it will be just plastic. I did not list it above as this high tech material is mainly reserved for displays and at least to my knowledge is not available for screen protectors, although I will stand corrected as I have to assume some big players use it for their protectors. The material is actually a sandwich where an ultra thin sheet of glass stis bewteen two layers of durable coating, read it up on their website it is quite interesting. It won't reach the strength of their famous Gorilla glass so without an outer plastic that has the additional oleophobic coating it won't provide the strenght of real tempered glass protectors. Some phones like the Galaxy Round and the fleixble HTC phones use it for example.

Topic by Downunder35m    |  last reply


Heavy duty UHF CB radio antennas and why cheap can be much better....

If you not a fan of normal road cars then you might get some 4WD and go off road every now and then.There are even those doing trips to remote locations that take a few weeks.An essential piece of equippment these days is a UHF radio.In a convoy you might get away with a handheld one if the cars are not too far apart and the terrain suitable.Most peole however opt for a permanent installation in the dash or roof console.After that decision comes the hardest and often costly part: What antenna to use....If you trust certain online reviews and manufacturer claims then one thing becomes quickly obvious.If you need a sturdy and powerful antenna then you have to pay top dollar.Some come with heavy spring bases claiming to protect the heavy fibreglass rod if you hit a bush or trees branch.There is always a compromise between weight and stability.And trust me, on the right corrugations you prefer not to look at your antenna....So how are these expensive antennas made?As I don't have any own pictures and don't want to steal them from the net: Please search for the terms used if you don't know them already.To answer this let me go to the other types of antennas you can get for your UHF radio.There is the famous rubber ducky - a stubby antenna best suited for short range on difficult terrian.Then we have the fibreglass whip antennas that have more or less coils integrated or even consist of one single coil with different spacings in sections.Good for normal road use, not so much off road as they won't tolerate too much vibration, they often snap off the base screw.Most people now just ignore the short whip antennas of 15 to 30cm length as they usually only come with a gain of around 4.5-6db.I will explain later why that might be a misconception.The last ones are those steel whips with one or two "loading" coils.These coils electrically shorten the antenna.They also provide a matching to the 50 Ohm required for most transmitters and antenna cables.Usually they are designed to be 5/8 Lambda antennas.A good antenna for just receiving, like when using a scanner is not critical in length.Transmitting however means you need a proper Standing Wave Reflection or SWR ratio.For this the antenna needs to be tuned.To be of any good use your antenna needs to match the transmitting frequency.This works best if the antenna length is at 1/2, 1/4 or 5/8 of the corresponging frequencies wavelength.Also called Lambda if you look for antennas.In the good old 27-MHz days we were used to quite long antennas in our backyard, for the car we then opted for 1/4 of this - usually around 2m in length.For UHF however 1/4 wavelength already means you are down to about 16cm...Going for 1/2 is a good thing here as it is still quite short at about 34cm.Real difference when it comes to these Lambda factors is the radion angle produced.You can imagine a 1/4 to look like a huge donut with no hole, about 25° for the radiation angle.At 1/2 this will be flattened out to around 20°.A 5/8 Lambda ntenna can get as low as 16°.Imagine it like a flashligh that has adjustable focus.The light source is of fixed output as your transmitter.The lens does the job of the antenna.If you make the beam more narrow then the light intensity of a certain areas at a certain distance will increase.Means for the radio you get a longer distance your signal can travel with enough energy.This however comes at a price!Imagine you are at the bottom of quite stepp mountain and your mate is up on the top about 2km above you.A high gain antenna with a narrow radion pattern might not even reach up there, while a short stubbie with just 3db still has a chance due to the more spherical radiation.Also explain why low gain and with that short antennas work best in hilly terrain...Back to the thick ones...As you can see you can basically hide any type of whip antenna into a fibreglass rod.But most of the are as said "ground independent", means unlike your normal whip they don't need the spring or foot to be of low resistance to your car's body.How does that work?Well, exactly like these ground independent whip antennas with a spring base or metal pole base work.You know the earliest antenna was a dipol - look it up on Wiki ;)For our CB radios that means you have a metal rod or spring that is about 1/4 or in some cases 1/4 of the wavelenght long.This is connected to the shielding of the coax cable and provides the required ground for the mounted antenna.The big difference is that only too often a dirt cheap dipol is hiding in your expensive fibreglass rod ;)The complete antenna might bring over 2kg on a scale, but the actual thing allowing you to receive and transmit is a few grams of coax cable...HOLD ON A MINUTE!! Some will say now...My whip is 70cm long and my expensive heavy duty one with 9db is 2m long - how does that work with your wavelength theory??Well, it is not my theory, just a fact ;)Imagine a 1/4 Lambda dipol, then it would be all up around 35cm long.And funny enough, that is about the length of a $180 heavy duty stubby if you just tak the rod itself.Go 1/2 of Lambda and you get an overall length of the dipol of around 65cm - add the metal rod making the crew that holds the fibreglass rod and you have the common 70-75cm heavy duty antenna...Anything above this length usually is either just a long rod with noting above the 75cm mark or simple has the 75cm long dipol made from the coax cable at the top with the antenna cable going down the otherwise empty rod.Ok, I got it, either 1/2 of the wavelength or 1/4, so about 35 or 16cm long.Ground independent we add either 1/4 for the spring base and rod or 1/2 for the longer ones.And how again does it work with the gain of an antenna?If you trust Wiki then it comes down to the radiation pattern.These heavy duty antennas usually come with around 6 or 9db, the short ones with 3-4.5db.These values might give you an indication about the theoretically possible distance you can transmit but nothing about the terrain it is suited for.Common rules of thumb created by those selling antennas and radios is that you a high gain antenna on flat terrain and a low gain antenna in a hilly area.Around 4.5-6db seems to be the golden ratio here as these anteannas are equally bad for both extremes in terms of terrain options.What you really would need to know is the actual radiation patterns in a three dimensional plane.A straight whip or dipol as a more or less donut shapead radiation pattern.However, location affects this!Mounted in the middle of the roof it is closest to perfect, while at the corner of your bumper bar you will distord the donut and also block parts out with the body of your car.This is why for this type of mounting elevated antennas are prefered.Makes no sense to have a 16cm long stubbie mounted so the top is still lower than your bonnet...Any antenna with a loading coil (or several) or top load will have a distinctively different pattern.We speak of so called "lobes".If you see it in 2D then for example a 1/2 lambda straight whip will look a bit like the infinity symbol.A 1/4 Lambda of the same style looks more like two ping pong bats joined without the handles.Those with loading coils or linear arrays made from coax cable however can produce multiple, prefered lobes.Usually they are in the 4-6db range and claim to be "universal" or as "allrounder".Here you get a quite narrow main lobe of 12-16° with one or more but much shorter lobes going upwards at about 10-30° depending on the configuration.At short range, like in hilly terrain both lobes overlap while you get a dead area at greater distances.You can sometimes notice that when you are on a low level talking to someone up high.There are cases when with a bit more difference in angle to each other (in terms of height and distance) the signal jumps up a few numbers.You just went from the dead zone into the lobe ;)With just a db value for the anteanna but no details about the actual design, heavy duty antennas can fool you badly.In mayn cases a 1/2 Lambda straight whip on the roof will outperform a costly, heavy duty antenna mounted to your bullbar.This is the reason why the expensive ones are the biggest cheat - they just elevate a quite small antenna above your roof line.And since it is heavy it needs a big spring and you hope it will not break if you hit something on a narrow track.All while the thin stainless stell whip with the cheap magnetic base just flexes under all obstacles with no damage at all.Plus, if you really get into the thick jungle you can just take the magnet off until you are through LOLWhy is a SWR and power meter still an important tool to invest into?Those remembering or still using 27-MHz radios only know too well why you need a proper SWR and power meter.With the lenght of the antenna at these low frequencies and affecting factors new the antenna proper tuning is a must.The bandwidth of the channels also means you have to tune the lowest and highest channel so the are basically even, anything else and the old guys would scream "UNACCEPTABLE!" ;)Especially it you want to get the last out of your system without going illegal.For some reason we accepted the claims that an SWR reading of around 1:2 is fine and acceptable.Most of the radios lower the power output to protect the transmitter if the SWR goes to far out.Allows for simple mass production of antennas with fixed cable lengths that are usually well overpriced.The most expensive bit is the cable itself here...I had no time to build an analog SWR and pwoer meter that works properly on 27 and 470MHz, so I ordered cheap SW30 from China.With that I first checked my little collection of antennas then those of some of my friends.This includes everything from short rubber duckies over loaded and straight whips to heavy duty models.One thing that was obvious right away: most are far away from an SWR readin anyone with a 27MHz groundplane antenna on a long mast would accept.And only one heavy duty antenna had a SWR readin of below 1:1.6 for channel 1 AND channel 40!That one was relatively cheap noname brand.With that sorted I decided to tune at least my steel whip antennas.To my utter disappointment they were all just a tiny bit too short - a thing that would have caused a proper 27MHz antenna manufacturer to to keep a large stockpile of his antennas...I had one though that was longer than needed.And before you ask: Yes, I tested them on both my elevated bullbar mount AND a direct mount on the roof rack.Did not change much for the bad ones so I ignored the mounting position for the tuning.I checked the power once for both channels on my prefered antenna and got 4.4W.Mind you that one has a SWR reading of 1:2.2 and will no longer be used as I can't be bothered to make it longer.For some reason I thought I check the SWR and power everytime I cut a bit off the antenna instead of just watching the SWR reading.At original length I had a SWR of 1:1.9 on ch40 and 1:1.75 on ch1 with 4.6W.I kept trimming down by about 2mm increments until I got an even readin of 1:1.07 on both channels.And with every trim the power went up a little bit.I have a friend that is or better, was just at the brink of being unable to reach from my driveway when he is parked in front of his house.A radio check after the tuning revealed that instead of coming with a lot of static noise and sometimes cut out I got a solid reading of 2 on his end with a much more acceptable level of noise.However, I still struggles as badly to hear him...Funny thing is that test was with just a plain and straight whip of 1/2 Lambda, in my case the tuning resulted in a length of 38cm from the base of antenna screw to the tip.My fancy 9db high gain antenna that is just over 70cm long did not even reach him while I could hear him slightly better than on my tuned one.Changing the mounting to the roof rack gave me a clear reception and a signal strength of 4 at my friends end with no noise.Elevation and nothing around the antenna does matter...After all this, would I still bother to buy a ready to go antenna for 470MHz?Only if I had to.Getting some RG58 cable or re-using it from on old antenna is cheap enough.A standard screw mount with a grub screw to hold a steel whip sets you back less than 10 bucks, from China even cheaper.And most will find a soldered on connector on the other end of an old antenna to be salvaged if required.If you don't have any sring steel wire of about 40cm length then think out of the box ;)The packing of pillows and such often come with a sring steel wire to make the plasitc floil keep its shape, some old suitaces have thicker wire doing the same.And if you ask nicely you might get a bristle or two for free from a street sweeping machine at your councils depot ;)After all we only need a maximum of 40cm to have enough left to trim and tune down.What is left to do?Of course some distance tests to check how well such a simple antenna really really works in comparison to commercial models.I only have one 9db antenna and will check it first to see if on flat terrain there is much difference in distance for transmitting.Unless this difference is well above one kilometer I will not bother with a high gain antenna like this anymore and instead opt for a longer mast and 1/2 Lambda.Another thing on the to do list to try a ground plane antenna with topload to squeeze the radion lobe down to under 15°.The resulting antenna would be quite short here and using an elevated mast is a must have to get over roof level with at leat a few wavelengths of distance to the roof.I guesstimate that an optimised antenna of this style should result in a distance increase of about 10-15km of flat terrain while being utterly useless in a hilly areas.Plus, such a design is not really suited for a vehicle going fast on a freeway, so it will go on my house instead.

Topic by Downunder35m