Variable Relay?

 Hi Instructables!, I'm working on a project to control a robot from the web but before I build it I want to find a way to control 24v motors from a laptop parallel port using relays and another power source. My problem is controlling them variably like from a joystick without going either on or off. I do happen to have an arduino microcontroller I could use but I was hoping not to simply for ease and cost reasons. Thanks for your help :)

Question by cornboy3 9 years ago  |  last reply 9 years ago

Variable resistor problem..

Http:// ripped this out of a car audio system, i don't know the input volts, or whats what. I use to have it connected to a 3V battery to change a LED from 0 to 3V. Well, i pulled it out, wires gone. resolder wires as you can see. problem: WHAT IS WHAT?! All i know by the labels is it says RED on the lowest rail. the rest, dont know. If someone can please help me id love that. It switches on/off as well as changes volts. so i need 4 wires connected.

Topic by Killa-X 11 years ago  |  last reply 11 years ago

Variable frequency generator? Answered

I'm looking for a way to build a simple frequency generator that generates high and low frequencies. I was thinking of using a POT to control the frequency range. I looked for it all around but the search didn't help much.

Question by Misac-kun 6 years ago  |  last reply 6 years ago

Infinitely Variable Transmission?

Ok, so I have been looking at this thing called the D-drive and it inspired me to come up with my own IVT design which was solid gears for max torque handling and still could change speed and direction easily and smoothly. This is what I came up with and I would like to hear your opinions on it.  It starts with input to a differential, one side of which is inverted and the other isn't before returning to a second reverse powered differential.  The two sides are slowed using a fluid braking system which has a rotor powered by the side's drive-line, and a flow limiting valve to apply resistance.  As one side slows the other accelerates.  When there is no brake power on either side you have reached a powered neutral, and when the second side is braked the direction changes and accelerates. So, will it work? How practical is it? Are you going to say it sucks, then steal my idea?

Question by 7 years ago  |  last reply 4 years ago

Is this the right variable resistor? Answered

I found this schematic from Make Magazine and it gave in my eyes a vague description of a certain Resistor. They label it as a variable resistor, but I've narrowed it down to it probably being some sort of knob that turns. I was just wondering if is the right resistor? Any help would be great!   Here is the page for the 'Lie Detector'. To be honest this is my first ever schematic into circuit I have ever done, and I have done a lot of research. Hope it goes well.

Question by soapdude 8 years ago  |  last reply 8 years ago

Infrared Variable Output? Answered

I am trying to wire some infrared LEDs to an Arduino. Problem is, the signal from the infrared LEDs has to be able to change variably, like from a potentiometer. What I mean is, I am aware you can read an ouput from an IR LED, then use the Arduino to replicate this and consequently control things, but what if I wanted to ouput a signal that changed, like a potentiometer? Basically, I would like to be able to control some motors speed through PWM by a potentiometer, but wirelessly. I'm not sure if this is possible, and if it is, is there some information I could look into? Any help is greatly appreciated.

Question by Adum24 5 years ago  |  last reply 5 years ago

Variable Capacitor Replacement?

Do you think it would be possible to substitute a variable resistor and a normal capacitor for a variable capacitor? The way I figure it is that a variable capacitor is supposed to adjust how fast said capacitor charges and discharges, wouldn't a variable resistor and a normal capacitor also function like this? I'm working on an idea for a small am radio, and looking to substitute these parts. Could it work? Thanks

Question by transistorguy 6 years ago  |  last reply 6 years ago

Variable power supply? Answered

Is there a fairly simple circuit, method to making a desktop power supply running on 240v a.c mains supply with a user controlled variable output say 0-24v D.C with variable ampage upto say 1 amp. I may be over simplicating thing in my head but is it just a case of a transformer taking my mains input down to the upper most requirement ( 24v @ 1amp ) on the output, and the using some type of variable resitors on the output to further restrict the output to my requirement. I would be grateful for any guidance and information on this topic. Thanks to the community in advance.

Question by mickcaulton 10 years ago  |  last reply 9 years ago

Variable frequency drive

Hello there instructables, I have another question discussing maglev theory and i was directed that the true way to build this project was to use 3-phase power! So this question, although related, is also an entirely new project in its own right! Now to the point, i have been researching single to 3-phase conversion, and there are a few options available like rotary or static phase converters, but i have been intruiged by a device called a variable frequency drive! Okay so what i understand so far (i think) is that these convert ac to dc, run that dc through a H bridge rectifier using igbt's and then convert the 3 outputs back to ac...... okay assuming my analogy is correct so far, to my question, 1. How are the igbt's triggered in the h bridge? do they use a function generator with altering timesteps to create the seperate phases? 2. Also how are these kept in sequence with eachother? Many thanks in advance for any help you can provide!

Topic by Xmortx114145 6 years ago  |  last reply 6 years ago

Variables in a batch file?

Im working with Vista SP1 and experimenting with batch files, i came up with a problem so i'd see what you thought. This is the code i was using::top@echo offcolor 0aTitle Experiment by Meecho -------------------------------------echo Type a letter between a and d.echo -------------------------------------set /p letter=if %letter%=agoto a:aecho This is the result of entering Apause>nulWhat happens is that the box closes after you enter your letter and press enter, i dont have any more results (i.e. where it says :a) because i found it didnt work

Question by Pawn_of_Prophecy 10 years ago  |  last reply 6 years ago

Batch Code variables?

So, I have been making a "OS" in Batch recently, and i am working on the main menu. it all works fine on the first variable, but when i type in anything else, (anything on the keyboard) it comes up with just the first variable. Anyone got any ideas for fixes? here's the code: ========================= @echo off :MMlauncher title Main_Menu echo Welcome to DolphOS! echo What would you like to do? echo. echo 1 File Explorer echo 2 Games echo 3 Notepad echo 4 Clock echo 5 Close DolphOS set /p programs=Enter number here: if%programs%==1 goto FeLauncher if%programs%==2 goto GMSLauncher if%programs%==3 goto NtpdLauncher if%programs%==4 goto ClkLauncher if%programs%==5 goto ShtDwn :FeLauncher echo l ping localhost -n .15 >nul cls echo la ping localhost -n .15 >nul cls echo lau ping localhost -n .15 >nul cls echo laun ping localhost -n .15 >nul cls echo launc ping localhost -n .15 >nul cls echo launch ping localhost -n .15 >nul cls echo launchi ping localhost -n .15 >nul cls echo launchin ping localhost -n .15 >nul cls echo launching ping localhost -n .15 >nul cls echo launching ping localhost -n .15 >nul cls echo launching F ping localhost -n .15 >nul cls echo launching Fi ping localhost -n .15 >nul cls echo launching Fil ping localhost -n .15 >nul cls echo launching File ping localhost -n .15 >nul cls echo launching File ping localhost -n .15 >nul cls echo launching File e ping localhost -n .15 >nul cls echo launching File ex ping localhost -n .15 >nul cls echo launching File exp ping localhost -n .15 >nul cls echo launching File expl ping localhost -n .15 >nul cls echo launching File explo ping localhost -n .15 >nul cls echo launching File explor ping localhost -n .15 >nul cls echo launching File explore ping localhost -n .15 >nul cls echo launching File explorer ping localhost -n .15 >nul cls echo launching File explorer. ping localhost -n .15 >nul cls echo launching File explorer.. ping localhost -n .15 >nul cls echo launching File explorer... ping localhost -n .15 >nul cls echo launching File explorer... ping localhost -n 5 >nul cls echo launching File explorer... cls C:\users\Harrison\Documents\DolphOS\FeLauncher :GMSLauncher echo l ping localhost -n .15 >nul cls echo la ping localhost -n .15 >nul cls echo lau ping localhost -n .15 >nul cls echo laun ping localhost -n .15 >nul cls echo launc ping localhost -n .15 >nul cls echo launch ping localhost -n .15 >nul cls echo launchi ping localhost -n .15 >nul cls echo launchin ping localhost -n .15 >nul cls echo launching ping localhost -n .15 >nul cls echo launching ping localhost -n .15 >nul cls echo launching G ping localhost -n .15 >nul cls echo launching Ga ping localhost -n .15 >nul cls echo launching Gam ping localhost -n .15 >nul cls echo launching Game ping localhost -n .15 >nul cls echo launching Games ping localhost -n .15 >nul cls echo launching Games ping localhost -n .15 >nul cls echo launching Games. ping localhost -n .15 >nul cls echo launching Games.. ping localhost -n .15 >nul cls echo launching Games... ping localhost -n .15 >nul cls echo launching Games ping localhost -n 5 >nul cls :NtpdLauncher echo l ping localhost -n .15 >nul cls echo la ping localhost -n .15 >nul cls echo lau ping localhost -n .15 >nul cls echo laun ping localhost -n .15 >nul cls echo launc ping localhost -n .15 >nul cls echo launch ping localhost -n .15 >nul cls echo launchi ping localhost -n .15 >nul cls echo launchin ping localhost -n .15 >nul cls echo launching ping localhost -n .15 >nul cls echo launching ping localhost -n .15 >nul cls echo launching N ping localhost -n .15 >nul cls echo launching No ping localhost -n .15 >nul cls echo launching Not ping localhost -n .15 >nul cls echo launching Note ping localhost -n .15 >nul cls echo launching Notep ping localhost -n .15 >nul cls echo launching Notepa ping localhost -n .15 >nul cls echo launching Notepad ping localhost -n .15 >nul cls echo launching Notepad. ping localhost -n .15 >nul cls echo launching Notepad.. ping localhost -n .15 >nul cls echo launching Notepad... ping localhost -n 5 >nul cls ====================== thanks in advance,  -ThePuppet

Question by Fred the evil puppet 6 years ago  |  last reply 6 years ago

use an attribute as a variable in batch?

How can I use a file attribute as a variable in batch, something like this? IF 'attrib'=='+h' C:\Users\XOIIO\Desktop\foldername (echo yes) ELSE (echo no) is there any way to do this?

Question by XOIIO 8 years ago  |  last reply 8 years ago

Variable Speed Stepper Motor

Hello Everyone, I am looking for some help to make a controller to drive a stepper motor using a potensiometer. I want to be able to vary the speed from 0 to 100rpms or however fast the stepper motor will go.   I have a bi polar stepper motor that I am using.  If anyone could help with this it would be great!  Thanks

Topic by TWMCNANEY 6 years ago  |  last reply 4 years ago

ATX Variable power supply. Answered

In the various instructables on this subject, all the component values aren"t given. such as the  120ohm resistor required but no watt value is given. can anyone give me a detailed parts list so I can buy the components needed for this project?

Question by pollock9131 8 years ago  |  last reply 8 years ago

Variable capacitor and discharge question?

I don't have a variable capacitor of my own to test this so I am relying on the instructable community. What if you have a variable capacitor tuned so that it is at its maximum capacitance and then charge it in a circuit for 5 tau (essentially full charge). Then you completely removed it from any circuit so that you only had a variable capacitor with two (short) leads not connected to anything. Lastly, you turned the tuning knob so that the capacitor had less capacitance all the way to essentially 0 farads. What happens to the stored energy?

Question by seanroberts 8 years ago  |  last reply 7 years ago

Voltage controlled Variable Resistor??

I'm making a circuit in which a person spins a motor shaft, generating current. The faster the motor spins, the lower I want the resistance to be to a part of a separate circuit. I'm thinking of some sort of voltage controlled resistor I can make. Any instructions? Thanks. ~plmqaz

Question by plmqaz1243 7 years ago  |  last reply 7 years ago

ATX Variable power supply circuit problems? Answered

I finished putting together the variable power curcuit board I had asked about earlier. I am getting 0-18volts with no load applied just my meter. When I try to connect a small dc motor or anything to it , my voltage goes to 0. I used a 5k linear taper potentiometer and didn't notice untill after assembling that it is only rated for .5 watts. Could this be the problem? I also used a salvaged ceramic cap, and a salvaged 1uf cap, but dont know how to test them with a regular fluke multimeter. Could somebody please help! I'm a newbee, so I appologize for my electronics ignorance, but we all got to start somewhere.

Question by pollock9131 8 years ago  |  last reply 8 years ago

Variable AC Power Supply ?

I need for my experimental work , one Variable High Voltage AC power supply with Variable frequency ?Any body can help , it will be highly appreciated. thanks 

Question by fezanali1 7 years ago  |  last reply 7 years ago

How can I preform arithmetic with system variables in batch files?

Question by BatchMan 8 years ago  |  last reply 6 years ago

Variable USB Power Supply (5V 2A)

I was looking to either build, buy, put together (kit) a Variable USB Power Supply similar to the one that I saw on the EEVBlog ( I really liked the compact design of his version, but he never finished it, so I can't buy that kit ;-( Is there a simple way to put together something that is protected (so I don't kill the USB socket I get power from) and has a Variable Volt and Amp adjustments knobs/buttons. I've looked at getting a full size Bench Power Supply, but would love to just have one so that I can power from my laptop or any of my million Micro USB power adapters (5v 500ma through 5v 3A supplies). My first project is something I need to eventually run off of AA batteries, but I didn't wanna keep on re-charging the batteries while I test my circuit design. Would rather have a constant source of 1.25v-1.5v power during the prototype phase. I'm just now getting into Electronics, so please take it easy on my poor little brain. Hopefully this hasn't already been asked, didn't find anything in my quick search through the forums.

Topic by drofnasnhoj 3 years ago  |  last reply 3 years ago

Variable wave laser devices? Answered

Are there any lasers available to the general public capable of changing wavelength? If so, where can I get one? Is there an easy way to make one?

Question by DIY Emilio 8 years ago  |  last reply 8 years ago

Variable Speed on a DC motor

Hi everyone, Does anyone have any suggestions on how I can slow down the roatational speed of a 14.4V DC motor? Its come out of a cordless drill and I have another project to put it to use but it rotates too fast at the moment. I have 2 options: 1) Use a variable resistor to slow down the speed 2) Use a gearing system In an ideal world I would prefer to use the variable resistor, as then I could change the speed of the motor quickly and effortlessly. Mechanical circuits are not my best skill and Ive already burnt out a cheap potentiometer (presumably too much current?) so I need to think more inteligently about what the design should be rather than just bolting components on the side of it. If anyone has any ideas please feel free, im open to all suggestions at the moment. Thanks Mat.

Topic by mathewjenkinson 11 years ago  |  last reply 11 years ago

how to convert treadmill dc pulse moter to be used as variable speed moter on a bandsaw? Answered

I would like to have a variable speed  moter on a band saw or a turning lathe and i have a couple treadmill moters .Is there a way to make a power supply or buy one that will work. There's 3 wires on it -1's for a pulse from a hales sencer..

Question by tom slick 6 years ago  |  last reply 6 years ago

variable frequency drive construction?

Hello i am working on a go kart but instead it will be powered by a 1/3 horsepower split phase AC motor. it operates off 768 watts and i am curious in using a Microcontroller and a high power H bridge to control it. can anyone help me or give me an idea on how to step up 12v dc into 120v dc and then using the H bridge to generate the frequency and also where to find some NPN transistors that can handle it and how to possibly reverse the direction of the motor?

Question by luig 6 years ago  |  last reply 2 years ago

AVR, Variable resistors, USB

Hello everyone,What a great site this is, I've only seen like 50 projects so far and I know there are an incredible large amount still left to discover on the site.. for all of you who write the guides and articles, great job! =)So on to my questions..I'm trying to learn how to build and program a circuit with an AVR uC. Previously I've played with NE555 circuits and I've connected those normal HD44780 LCDs to the LPT port and so on..I've also worked with repairing TV sets earlier, replacing both normal components and SMBs..So I got some basic knowledge of soldering and reading schematics, so thats no problem.However the programming part is more problematic and also how to connect some components to the uC.. My wish to learn is how to connect variable resistors to the uC and connect the uC to a computer (via USB perhaps) and then read the values there and perhaps sending them further to another program.More simple, I want to be able to connect a variable resistor to a uC and then be able to read the value and use that value on the computer..In the long run, what I want to accomplish is a similar piece like the Aurora open source mixer. first I want to learn how to connect lets say 2-3 variable resistors, which I believe should be connected to the ADC channels on the uC, right? Together with a low value resistor between the variable resistor and the uC, I've got that info from somewhere so I hope I'm on the right track.Ok, so that's quite simple, I guess.. But then, how do I read the values on the uC? I think the uC should poll the ADC pins with a few milliseconds in between, or does it work in some other way? Before I connect it to a PC, a simple way to see if it works would be to send the "value" from the variable resistors to a led for each resistor and increasing or lowering the brightness of the led depending on the value from the resistor.That should be quite simple to rewrite when hooking up the uC to a computer, just forward the info the PC instead of to the led.. or to them both perhaps..What would the code be for doing such?My "problem" as most people think, is that I learn by examples, not by books or pages on the net with advanced explanations.. I need to have it quite simple, even though I have no problem learning new stuff..I've been working with PHP programming for a few years and even though I know its far from PHP in a uC, its still programming so I have some sort of basic thinking, which I hope will be handy somehow =)I've searched through the net, also searched AVR Freaks and I've even asked on the forums of AVR Freaks who tells me, sure you can do that, you just have to start programming.. But I really dont know where to start..I learned PHP by downloading examples, see what they do, change a bit and see what happens and so on.. Sure I can do that with the AVR as well, but there are no examples that even read just one pin with a variable resistor connected.. if I had that I would be able to duplicate and make it read on more pins and so on..I should be able to emulate the code somehow with the AVR developer software, so somehow I should probably be able to emulate a variable resistor and find out what values I get from it.. but I havent been able to get something like that working either..Finally, I'm now writing here cause this page hosts a great load of great guides, from "how to sew your own panties" to "building your own waterbottle rocket".. and because I didnt get that much help from AVR you guys are my last hope, I hope you could help me out..// Chrisps. if someone would be interested in making a guide on how to accomplish this and perhaps even connect the uC over USB to a computer, that would be the best thing ever ;) but I'm not gonna go that far, just some help would be enough.. hehe .ds

Topic by toffie 9 years ago  |  last reply 9 years ago

Unable to retrieve Rfid variable.

I am unable to retrieve string (RFID) from Arduino connected to Android app through Bluetooth . Arduino code #include #include #include #define SS_PIN 10 #define RST_PIN 9 char command; String string; MFRC522 rfid(SS_PIN, RST_PIN); // Instance of the class MFRC522::MIFARE_Key key; byte nuidPICC[3];// Init array that will store new NUID String RFID; void setup() {   Serial.begin(9600);   SPI.begin(); // Init SPI bus   rfid.PCD_Init(); // Init MFRC522 } void loop() {   if ( ! rfid.PICC_IsNewCardPresent())     return;   // Verify if the NUID has been readed   if ( ! rfid.PICC_ReadCardSerial())     return;        for (byte i = 0; i < 4; i++) {       nuidPICC[i] = rfid.uid.uidByte[i];       if(i==0)       {         RFID=String(nuidPICC[i],HEX);         //Serial.println(RFID);       }       else       {        String temp =String(nuidPICC[i],HEX);        RFID=String(RFID + temp);        }    }       //Serial.println("\n Rfid :-");    //Serial.println(RFID);      if (Serial.available() > 0)     {string = "";}         while(Serial.available() > 0)     {       command = ((byte);             if(command == ':')       {         break;       }             else       {         string += command;       }             delay(1);     }     if(string == "TO")     {        // ledOn();         //ledon = true;         //Serial.println(RFID);     }     rfid.PICC_HaltA();   // Stop encryption on PCD   rfid.PCD_StopCrypto1(); } Android Code rfid.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 readrfid();             }         });  --------------------------------------------------------------------------------------------     // This will be the Readfrom Rfid !     private void readrfid()     {         String tp;         if (btSocket!=null)         {             try             {                 btSocket.getOutputStream().write("TO".toString().getBytes());                 ins = btSocket.getInputStream();                     while(ins.available() > 0)                     {                         //Reading from serial input                         valor= Byte.toString((byte);                     }                 //Displaying readed value                 Toast.makeText(getApplicationContext(), valor , Toast.LENGTH_SHORT).show();             }             catch (IOException e)             {                 msg("Error");             }         }     } Thank You.

Question by HiteshP16 3 years ago

Simple/ and or cheap variable thermostat?

Well I have a friend who is looking into the purchase of a snake, and meanwhile picking out the snake and the heating element isn't the hard part for him (he's looking at a 23 watt 120vac heating pad for it). He was also looking at a thermostat designed for snake tanks, however they want close to $150 for it, and it doesn't even have many features, it's basically a black box with an 3 digit lcd and a programable timer. I know it wouldn't be hard to put something similar together from a pic and a few different parts, however it's been a long few years since I've designed a full schematic of something, let alone look at one. So I was wondering if someone so kind might aid me in making of a schematic so my friend can go order the parts he needs and I can build it for him (don't have a problem assembying circuits from raw schematics, I find it fun). However, there is a couple things he wants out of it. Number one most importantly, he wants it to be able to adjust the output voltage so he doesn't fry his snake (most simple thermostats simply turn on until temperature is reached, then off), no he wants something more dynamic than that. Second, he needs to have an external temperature probe so that he can keep the thermostat outside of the tank whilst keeping a handy eye on the temp and also obviously so that the thermostat knows when to come on (is there a limit to the length of wire you can put on a thermocouple?). Third and last, we need a simple timer circuit that keeps track of the time (what's that involve? a 13mhz crystal and a few other parts?) so that at night the thermostat can change it's "heating schedual", I assume so that it tries to maintain a temperature say 3-4C above the programmed temp. (night mode anyone?) However the thermostat he was looking at buying wanted you to buy a second cord, which connected to an external appliance timer (yes you heard me, a $9 wall timer) so that it knows what time it was. My friend really needs this as he's looking into getting this snake within the month. I appreciate anything anyone has to offer. Thanks guys! -Punkguyta

Topic by Punkguyta 10 years ago  |  last reply 10 years ago

Low Cost DC motor Controler?

I want to power a 90 Volt, 5amp Perment Brush type DC Gear Motor. The, "Variable speed controller", needs to be able to use 115v AC or 115v DC input power, which is selectable by the operator. I have used a Staco variable tranformer which uses 115v AC input and rectified the output to drive the motor. But also need the 115v DC input option.

Question by Realdann 6 years ago  |  last reply 6 years ago

36Vd.c. @ 8.3A Power Supply + Buck Converter

Hello Friends, I have a 36Vd.c. @ 8.3A Power Supply that I would like to convert into a Variable Bench Power Supply. After researching the topic, I have decided on choosing a Buck Converter as opposed to a Linear Regulator.  Shopping around online, I stumbled upon the LM2596 Converter:;=item462bb7a8a5                      Any thoughts and or suggestions? Beyond that, I do have a general question... I've read on a few power supply instructables that it's recommended that all rails be used (for example all yellow/12v cables) to insure a more steady current. Now being that the max output of the above mentioned power supply is 8.3A and (please correct me if I'm wrong) according to the supplied spec sheets, power is coming from 3 rails, would it be safe to assume it not necessary to feed all rails into a buck converter since its output is only 2A? Please put me in my place...

Topic by davidkiyan 4 years ago  |  last reply 4 years ago

Does anyone know how to make a dress with an adjustable hemline? Answered

I have a dress from a thrift store that is the basis for a fabulous costume for the fantasy convention. Only problem is the hemline is too boring. I came across these dresses in a catalog that seem to have exactly the feature I need to put on my dress, but I have no idea how it is done. I've scoured the internet so now I pass it on for your consideration... see below.,275&GEN1;=Outlet+&T1;=P85827+S&dispRow;=0&srccode;=#top The dress apparently has ties inside that you can cinch up to control the level of blousing. Thanks for your help!

Question by penumbra_ 8 years ago  |  last reply 8 years ago

how do you load a Java script Variable from a webpage into a VB program?

I would like to have the Visual Basic progam to load the user logged into Habbo via the variable habboName and make the title in the title bar (HabboName - HabbOS.)           Code: document.habboLoggedIn = true; var habboName = "Habboname"; var habboId = 25724911; var facebookUser = false; var habboReqPath = ""; var habboStaticFilePath = ""; var habboImagerUrl = "/habbo-imaging/"; var habboPartner = ""; var habboDefaultClientPopupUrl = ""; = "060fd7869028127ca5d9aa2f02167c8f4e70651d"; if (typeof HabboClient != "undefined") { HabboClient.windowName = "060fd7869028127ca5d9aa2f02167c8f4e70651d"; }  

Question by drmjj55 8 years ago

Homemade power supply problems

I am trying to build a variable power supply using a LM317 variable voltage regulator. When connected to no load, i can get a sweep from 1 volt to 15 volts. but when a load (small pager motor, laser diode) is connected, i can only get up to 4 volts, and about 12 milliamps of current. Help!

Question by wii552 8 years ago  |  last reply 8 years ago

How can I make a varible induction heater driver? Answered

So a few days ago I saw a slideshow on how to make an induction heater. I thought that was really cool. However the circuit the author used to drive the work coil only had two functions, on and off. The author claims the circuit can drive 24VAC at 180 kHz. I was wondering if anybody knows of a circuit that can drive 24VAC with a variable frequency, between 100 kHz and 200 kHz. Thanks in advance!

Question by junits15 9 years ago  |  last reply 9 years ago

Does this switch exist? Answered

It may just be my google-fu failing me, but I can't find switch I am sure must exist: A sliding switch with reversing (DC) polarity. At one end of the slider, power is full "forward".  Slide the controller, and power decreases.  Reach the centre, and power is zero/off.  Slide past the centre, and power increases again, but with reversed polarity, ie in reverse.

Question by Kiteman 6 years ago  |  last reply 6 years ago

Newbie needing help please

Hi everyone, I'm new here, and new to making circuits. I've been scrapping them for quite some time and feel terrible about how much goodies I've thrown out in the process :(  anywho, I saved a ton of it, And today I picked up a "Futura 100 color graphics at its finest" box, it has 5 knobs on the front for: Hue, saturation, contrast, black, and white, has a power on led and reset button, floppy drive. in the back it has a 3-25pin connectors (2female and 1male) for printers, a video in and video out, power switch and 3 prong plug, fan, keyboard connector, and a 9-pin male test port?  Inside it had a dark drive and has TONS of ic chips. ill quit blabbering and get on with it, does anyone have any ideas on what this can be turned into? One or multiple projects is fine, as long as this thing gets a good use. I'm hoping to make a variables power with led display for my atx.

Topic by Ryan53090 4 years ago  |  last reply 4 years ago

Heat gun mod question

I am not an electrician but I like to tinker. I am just getting started with DIY type electronics kits and I have decent soldering skills. I cant say I am an expert at reading prints, but I can usually build a simple schmatic. I wish to disassemble a heat gun for parts and add in a potentiometer to vary the heat, another potentiometer to control the airflow, and a digital temperature probe with temp display. I am attempting to build a heat generating device with precise control of the temperature and airflow. I dont really want to spend $150 on a fancy LED digital display heat gun with variable heat dial, so this is my next option and potentially a heck of a lot more fun. Initially I just want to get the variable heat and airflow control(potentiometers) hooked up, and if it will be easy enough I can later install the temp display. I could always just use a cheap "laser" temp probe to check the temp and ensure it is fairly stable. The heat gun I am looking at is a piece of junk and it only has 2 temp settings. How easy is it to install a potentiometer for varying the heat and one for the airflow? I assume I can just install the one for heat control inline after the circuit that sets the maximum heat level and dial in the temp I want. As for the airflow control I assume I could do the same thing, but instead put it before the power lead feeding the fan. I am not an electrical engineer so I want to make sure this will work first before I fry my cheapo $20 heat gun. Would it be bettter to just gut the entire thing and work with the naked parts and install my own circuit to control and display the temp or could I keep the basic unit intact and mod from there? Any ideas, or a basic schematic that would satisfy this requirement would be greatly appreciated.

Topic by RokGoblin 10 years ago  |  last reply 10 years ago

How to build a 0-36v, 0-10a, Regulated, AC/DC Power Supply? Answered

I'm looking for how to make a variable regulated power supply for DC electronics. I have wall warts and single range transformers for lots of different items ranging from battery chargers to toys to LED lights and am looking to combine them all down into one unit. I need to be able to adjust the voltage from ad little as 1.2v @ 200ma all the way up to 36v @ 10amps. I would normally take the easy way out and buy a power supply online that would handle it, but I am strapped for cash and this is more a luxury then a necessity. If possible I would like to be able to use LCD/LED panel meters that are powered by the input along with fine and coarse controls, along with dual outputs. Something along the lines of the Mastech HY5005E-2 that's pictured below. Maybe convert a cheap PC power supply with a digital multimeter? I can solder and work a basic circuit but I haven't done anything this complicated as yet.  I would appreciate any help offered. Thanks!

Question by Dochide 8 years ago  |  last reply 8 years ago

Such a thing as a variable voltage/current overcharge protection?

I've had a couple of bad transformers in battery chargers in the last couple of months and I am thinking of building my own variable voltage/current battery charger with an ST Microelectronics L200. Figure #23 But I would like to have overcharge protection so I don't have to monitor the batteries charging once I set the volts and current for that battery. Something that would just shut off or switch to a trickle charge when the battery reaches the voltages I want or set. Also, another question - I am intending to use a salvaged transformer from an old chamberlain garage door opener for this project and need to know the best method for lowering the voltage from it to something the L200 can handle. It's a 1:3 and takes my 125v main to roughly 42v and the L200 is rated at a maximum of 40v input. I was figuring on just using a resistor, but I don't know how to calculate what I need since the current and voltage will be changing the load on a per battery basis. Also I think the transformer might be a little small for this project, it only measures about 2"x2", while most of the chargers transformers were twice the size or more. So I'm wondering if it might not be able to handle the constant power or heat requirements for charging. *Added a pick of the transformer. And since I've asked this many questions, I might as well add another. I was looking through the "how to get free electronic parts" pages and I didn't see any on solar cells. Does anyone know if any company does samples for cells the way they do for electronic parts? I am capable of following simple to moderate schematics and can solder well. But when it comes to making new circuits and such, I tend to just hobble together something I've seen or used before that works. When it comes to programming and calculating circuit load and all that I become bogged down pretty fast. If I can see it and experiment with it till I get it right, I am better off and maybe learn something. So the simpler the better.

Question by Dochide 7 years ago  |  last reply 7 years ago

How could I make a variable interval buzzer/vibrating device? Answered

I would like to make a small device, perhaps the size of 3-4 stacked half-dollars, that could be programmed to vibrate lightly at various intervals (like every minute or two minutes or 3.5 min, etc).  Could anyone help me with how I could make something like this? The size could vary, but I want it to be a discrete device that would only draw the attention of its user for a brief moment every interval (depending on how long the interval is programmed to be).  I am very new to doing anything with electronics, so I'd greatly appreciate any advice or guidance.

Question by Kazbachris 8 years ago  |  last reply 8 years ago

Need a variable power supply... recommendations?

I think its time that I invested in a good desktop variable power supply for building circuits and such. I have one currently, but I'm borrowing it from our school because they have a few extra and don't mind it being gone. But as the school year closes, I am going to have to return it. So any recommendations for a variable desktop supply? My budget is around $100 USD. Thanks!!!

Topic by astroboy907 5 years ago  |  last reply 5 years ago

Voltage multiplier and magnetic force?

Does magnetic force affect how much energy is multiplied by per section in a voltage multiplier like the one in this instructables: ? I was thinking of making this multiplier and to make it a bit more variable to make a voltage multiplier (electro-magnets around the capacitors) like the ac voltage muliplier on

Question by pmk222 6 years ago  |  last reply 6 years ago

How do I regulate voltage on a multi-amp battery charger.

I know very little about electronics. I have a car battery charger that outputs in 12 voltsDC. It is also "switch" selectible for 2 or 10 or 50 Amps. Once I select one of these choices 2/10/50, I would like to vary the voltage up and down from 1v to 12v. How do I build something that will vary the voltage at each of these amperage levels. Thanks- Steve

Topic by st600r 1 year ago  |  last reply 1 year ago

variable load DC volt meter?

I would like to build my own one of these with more settings and variable load and input voltages. Maybe someone has a more elegant solution? Something that would fit in a small box or maybe even a something to put in between the DC source and my multimeter Voltmeters

Topic by Menthol 9 years ago  |  last reply 9 years ago

Variable speed on a 5v brushless fan

Hi everyone! I have a 5v DC (0,15A, 50mm x 15mm) computer brushless fan that I want to power with a battery pack (4x AA rechargeables= 4,8v) or the MightyMinty Boost. This small blower is meant to be a part of a woodgas stove, and will bring air to the fire through a small duct. I'm looking for a circuit that would allow me to control the speed of the fan and the airflow. Kinda like a dimmer switch. Is there a readily available switch or devices that I could plug between the batteries and the fan? I guess the RC guys out there know a few thing about variable speed controller. I'm a newbie at this; I don't what to build a circuit from scratch, unless it's really simple. Thanks

Topic by jemor143 7 years ago  |  last reply 7 years ago

Switched Mode Variable Power Supply

Curious, Monday or Tuesday of this last week I found an Instructable for a Switched Mode Variable Power Supply I found very interesting. I didn’t print the design out because I wasn’t sure how I was fixed for parts. I went back the next day and the Instructable was gone. All I get is; “404: We're sorry, things break sometimes” I really don’t have any other description other than it was built in a metal enclosure, blue, and used 2 V/A meters. Without the Instructable I can’t even tell you who made the Instructable. Has anyone seen and/or has the plans for this Instructables? The only thing I can add is a picture I've added from the internet.Any help would be greatly appreciated. Thanks, Dennis

Question by DennisB36 1 year ago  |  last reply 3 months ago

Variable Voltage Regulators with + and - 12v input? Answered

Hi, I have put one of these together for an ATX power supply and have come across something that I might be getting wrong.... In mocking up the LM317 circuit in breadboard (standar one found everywhere on line and on the LM317 pages), I have got the thing metering -11v to +11v??? I am using one of the black ground wires of the PSU on the black side of the volt meter, but cant figure out why I am not just getting positive voltages??? Could the diode be faulty? Or is this in fact correct? Any help appreciated...

Question by lone_viper 7 years ago  |  last reply 7 years ago

Potentiometer/Variable resistor with AC advice

I'm a computer store tech who knows how to solder some(but DC stuff only) and who also enjoys cooking, so my ? is: What's the best choice of pot. for use with US household current to actually control the cooking temp of my hotplate? End result is to eliminate the annoying "heat spikes" you get due to lack of a pot. in the design, IE literally everything sold these days turns on at full current/temp until it reaches X temp, basically it's just temporally defined by how far you turn the knob, and your pancakes wind up crispy black around the edges and gooey in the middle  instead of golden brown and amazing all over. I want it to turn on at X current until X temp (like electric frypans/burners did if you're old enough to remember.) All I need to do ( I think) is add a pot/VR into my burner's element  "line" the right way, it already shuts off at X temp just fine. Incidentally, that's the "click" you hear when any home electric cooking device (sold in North America, at least) hits temp or turns on, the temp. control switch thingee connecting. It's NOT a VR/pot, just a pair of electrodes JUST barely touching strapped very tightly to some ceramic discs. It uses thermal expansion of the discs/electrodes to make things just a tiny bit bigger and separate the tiny little electrode spoons  But all that boring geekspeek affects in this configuration as basically just temporal heating, IE no reduction of the amount of heat in my frypan, just the cooking time. Science says if I reduce the amount of electrons flowing thru it just slightly as well,  it'll be colder but still hot and still shut off when it's hot enough. A pot/VR wired in the right way will do exactly that, won't it? After some research I'm thinking something like a 30-50K "B"-taper pot. wired with 2 of 3 traces (, I'm looking for a "broad" response range while turning with a tight  "pinch" effect at low end for amazing banana-brown-sugar-pinch-of-nutmeg pancakes with coffee on the tiny balcony/fire escape in the morning but I have no idea how the numbers work for AC currents. Does 120vAC mean a different pot or a diff config/approach altogether? Or should I be looking into AC variable resistors, instead? I know an awful lot about "base" science, enough to get me this far, right, but AC throws me for a loop a lot, and there's a gap in my knowledge/experience, between the basic stuff and how it applies to stuff like my application, I don't get a lot of the numbers/formulas and how to use them.  A VR would the ideal tool here, but they are hard to get in the right form with the electrical qualities I need, whereas pots are usually "turning switches", right?

Topic by MattH68 2 years ago  |  last reply 2 years ago

Batch: How do you search for a variable(text) within another variable(text)? Answered

I want to use a batch file that based on user input, searches for a variable (already set) within the user input. eg. I figured that this would work: @echo off set var=A set /p var2=Choice:  (USER TYPES "A B C") findstr /i /c:"%var%" %var2% OR findstr /i /c:"%var%" ^ if %errorlevel% equ 0 echo.%var% is in %var2% pause >nul Exit

Question by HoeraufPrograms 6 years ago  |  last reply 6 years ago