Can the pressure of an input water source in a laminar flow setup be variable? Answered

I.e. Can I change the total ballistic traveling distance of the water stream by lowering/raising the water pressure into the laminar flow nozzle assembly? I can't seem to find any theory/equations regarding laminar water flow and how pressure fits into its creation. Thanks for any help everyone!

Question by kidiron   |  last reply


Unified power flow controller, matlab/simulink?

Please somebody should help me change the default port of UPFC to 2 input, 2 output matlab/simulink I need to do some simulation with 2 input, 2 output port, so anybody who can help should email me tchubabyboy@gmail.com to send my circuit diagram. i have attached files I am using matlab/simulink 2012a

Question by tchut 


Liquid dispenser wireless pour control

Hi guys, anyone knows the concept behind this https://www.youtube.com/watch?v=nAJvbFYtpIU. It is a wireless drink pourer, that can control the liquid flow. Can't find if something like this can be made with Arduino. Does some one have an idea if this can be done?

Topic by justforcavaliers   |  last reply


how can i control the current flow to the motor of a toy car using arduino?

I need the codes for arduino and its setup. i want the remote controlled toy car to have constant current in its motor  even after i dont push the control button. i am new and never used arduino before. thanks

Question by marufbillah   |  last reply


Valve that shuts off once a set pressure is reached?

For something I am in the process of designing, I need a valve that can be connected to a high pressure source and will allow the gas from the high pressure side to to flow into a sealed container on the other side until a pre-set pressure is reached. It should then shut off. The system used to do this should also be able to handle a very high pressure spike (possibly even the type of compressed pressure wave generated during a super-sonic combustion / detonation) on the sealed container side. If you can provide a diagram or the name of a type of valve or even just a description of how this could be done it would be appreciated. No computer controlled stuff please. ##################### The answer I have discovered is to use a regular diaphragm-type pressure regulator. ######################

Question by Jaycub   |  last reply


Help me in led different modes (led Flicker , led flow with timer set,etc.) control using mit app inventor

Help me in led different modes (led Flicker , led flow with timer set,etc.) control using mit app inventor and bluetooth.

Question by rutukesh 


how can i control the airflow coming from my airpump for a brine shrimp hatchery?

I think i want to make a valve of some type on the tubing itself. i have an airpump that doesnt come with any flow control, i put a tube on that and an airstone at the end, but my "aquarium" is really small (gallon and a half, tops) and the bubbles are causing havoc. I need to be able to divert some of the air somewhere along the tube. any help would be appreciated.

Question by parker92   |  last reply


How to automatically control the baffles in my HVAC?

I have three baffles in my HVAC duct lines that direct the air to either end of the first floor or upstairs.  I close the upstairs baffle in the winter forcing the heated air into the first floor.  The heated air naturally flows to the top floor, keeping both floors at a constant temp.  I reverse the process in the summer.  In the spring and the fall they need to be switch multiple times as we move from air conditioning to the furnace. I'd like to automatically control all three baffles with a winter or summer setting.  Switch to summer, they adjust, switch to winter, they adjust.  They aren't hard to change, but I'd like to learn more about servo's, electronics, etc.  I have installed X10 in my home and currently operate lights and motion detectors from a program called SMARTHOME. I'd like to use my X10 RF to communicate the controls, but I'm open on this one. Thanks in advance for any help! Tom

Question by swill01   |  last reply


Using Arduino to control circuit to LED strip

Hey guys! First forum post here.I am currently trying to design an LED light system where when I place my wallet onto an NFC reader the lights turn on in my room.I am using an Arduino Uno for this project and I am stumped on how I do it.I have a separate DC Controller and a 12v, 3A battery to power the LED strips. I just want to use the Uno and NFC reader to either open or close the circuit. I don't want to pass the amperage through the Uno as it will just fry the board.Is there any way I can control the flow of the circuit without having the power pass through the Uno? I want to keep the power the battery pack supplies and want to make sure I won't just fry my board.Any help will be appreciated! If you have further questions feel free to ask.

Question by MikoPico   |  last reply


What would a basic arduino controlling system for an underwater ROV be like?

I am working on an underwater ROV for a competition and have been considering using Arduino to control it. However. I have not actually ever used Arduino and therefore have no knowledge of the subject. So my question is this, what would the basic components be for controlling the ROV be? It would have to be able to control several (4-ish) medium sized motors as well as 2-3 small motors and i would LIKE to have either a joystick and a few buttons on the controlling side. I can imagine ALL the power would be unable to be run through the Arduino system so would it be that there would be some kind of second component for say each motor to control power flow? Also the motors are "double throw switch" motors so there would not need to be any kind or" throttle "

Question by shabaki 


How to control 100 bidirectional DC motors?

Hi,  I'm trying to control 100 DC motors using a microcontroller (Arduino Mega) The motors run on 1.5V and have a operational current of 40mA. 1) Each motor must be able to rotate clockwise and counter clockwise 2) The motors must be able to move independently     (though direction of the motors at any one time will be the same)      eg. at time = 0; motor 1,20, 30, 45 will rotate CW            at time = 10; motor 20, 35, 80 will rotate CCW 3) Using minimum amount of pins from the Arduino (Shift Register ?) How should i go about doing this ? I have tried using L293D H-Bridge, but in order to control 100 motors,  i will need 50 H-Bridges and 200 digital output pins I'm thinking of a simpler circuitry (image attached) to control the motors. Digital output pins from the Arduino will contol the relay switches, and the DPDT relay will change the polarity of the the voltage supply. Will this work ?  Are there any smaller alternatives to the mechanical relay (transistor ?)  Can a transistor allow current flow in both directions ? I would really appreciate if you could provide some inputs and ideas as to how you would go about controlling a large amount of motors. Cheers!

Question by fujiapple   |  last reply


I have a question about My ROV control system.

I am building an ROV and I need to know whether this control board will work. I planed on Running 1 Cat5 and 1 set of speaker wires to control and run systems on-board. When I flip a switch on the control panel, a 3v signal is sent down the Cat5 wire to the base of a transistor, which opens the flow of power between the Emitter and collector. My main question is, does a transistor work as a switch? Example. A signal enters the Base and opens the other two connections. Is this right? Oh, and the other two pictures are what i plan for it to look like. I am building it using the motors from one project (posted recently) , the frame another, and my own control. I will post an instructable as soon as it is done.

Topic by ry25920   |  last reply


I want to make and old school dial water meter using arduino and flow meter?

I need help making a old school dial meter like the ones used in electricity or auto richshaws. http://static.splashnology.com/articles/Examples_of_Skeuomorphism_in_Graphic_Design/Rickshaw_Meter_app_by_ranganath_krishnamani.png i want to flow water through a flowmeter and record data from arduino. i also want this arduino to control dial meter and show the appropriate numbers depending on the litres flown. i do not have any knowledge of coding , however im alright to prepare the hardware and solder etc! if i has a set of instructions

Question by ashishngupta   |  last reply


How to step down a 12v DMX LED Controller to 5v?

Hey i currently have an "Abstract MFD-10" DMX controller that i want to run 64 LEDs/2meters of "LPD8806 +5v Strips" off of. DMX Controller= http://www.abstractavr.com/products/dmx-led-drivers/60w-dmx-led-driver/ Led Strips= http://www.adafruit.com/products/306 How do i step down the 12v supply to 5v while maintaining the flow to keep the strips running effectively? If you give me the formula for it i can work it out myself and will post here with what i worked out as i enjoy doing my own workings but i am a bit lost with this. Also I am willing to simply change a component in the controller itself if this would be easier and cleaner (No external boards/components) Need anymore info just ask.

Question by Pathogenex   |  last reply


where do I find in the internet about the Swing-Mark automatic valve for resturants and bars.?

Swing-Mark valve is a automatic flow chemical dispensing mixing valve, that works with the flow of water going through the valve. dispensing detergent and sanitizer chemical to each sink at a pre mix of water and chemical controled by the valve. Depending on the type of metering valve it has. Resturant and bar owners real perfer these valves because they automaticly always have a E P A regulated mixture of sanitizer per water, to wash and sanitize glasses and cups. Or any info on similar valves.    THANK YOU

Question by f1cam   |  last reply


Can I have flowing liquid through multiple separated electrolysis cells, with those cells in series? Answered

Hi, my question is a curious one regarding electrochemistry. I have multiple electrolysis cells, with some separation between them but a constant flow of water passing through each of them in turn. Since electrolysis cells like this tend to require a current-limited power source and don't end up dropping much voltage per cell, I wanted to electrically connect the cells in series. This way, I could use a single power supply in current-control mode and not have multiple supplies fighting each other. My assumption that individual power supplies would end up fighting each other is based on the fact that the water is an additional electrical path that can allow current to bypass a given electrode. Using one power supply and having the cells in parallel would not be a problem as long as the current through each cell balances out on its own, however I feel that having one power supply across all cells in series would make current balance per cell a non-issue. My question is: Is it true that, with a power supply pushing a single current through multiple water electrolysis cells that have a torturous but admittedly connected water path, electrolysis efficiency will be the same as having separate power supplies on each cell?

Question by DavidB568   |  last reply


Hey everyone, I amworking on an HHO generator, have all of the specs, not sure how to procede, any suggestios?

I am not sure how or where to hook the generator into a car, and I have also heard that it is important to use a pulse generator into the unit to control power flow does anyone know where I can find more detailed concerning the installation into an engine, as well as information on how to build, or buy a pulse generator?

Question by Loki1978   |  last reply


Hall effect sensor to trigger relay

Hi! I have a project that needs to sense whether water is flowing through a pipe. I bought a water flow sensor on Amazon (https://www.amazon.com/gp/product/B01LVWHJP0/) thinking I could use it as a basic switch, however, it's got a hall effect sensor and I don't understand how to deal with the voltage output. Measuring from the pulse signal to ground, the sensor swaps the polarity each time it's triggered: With water running, I see a positive voltage. Turn the water off and back on, voltage goes negative. My control system can't deal with this. What I need is a simple circuit to turn the sensor's pulse output into a contact closure. Can anyone help? Thank you!

Topic by rpdubz   |  last reply


The Reactable - A collaborative electronic music instrument

I was watching current earlier on and found this pod:The reactable is a collaborative electronic music instrument with a tabletop tangible multi-touch interface. Several simultaneous performers share complete control over the instrument by moving and rotating physical objects on a luminous round table surface. By moving and relating these objects, representing components of a classic modular synthesizer, users can create complex and dynamic sonic topologies, with generators, filters and modulators, in a kind of tangible modular synthesizer or graspable flow-controlled programming language.The video won't embed, but it's pretty awesome: Current PodThe project's official website is here.The software is open source, although I can't see many details of the hardware.

Topic by whatsisface   |  last reply


K40 Chinese laser conversion to Arduino

After fixing most of the issues on cheap laser cutter I am about to do the next step and install an Arduino board to get rid of the dongle and crappy controller. I also would like to put this in the form of a nice Instructable so others can upgrade their machines as well. But during my research I noticed that several different versions of the controller, laser power supply and control panel exist. If you are interested in upgrading your machine so you can use Inkscape directly and no longer need a dongle and crappy software: Post a pic of your laser power supply (including a clear pic of the connection terminals), a pic of your control panel (both from the outside and the bottom), let me know if you already have safety switches for the lid and water flow. Everything posted here in time will be included in the Instructable if it is different from my machine. Once the Ible is finnished you will get detailed instructions on what you need, how to program the Arduino, get the plugins working in Inkscape and how to do your first real engravings and cuttings on the new setup after calibrating everything. Here is a video showing raster and vector engraving followed by cutting the piece out - what more can I ask for if only spare parts are used? ;) https://youtu.be/GqFTPMBchyQ  

Topic by Downunder35m   |  last reply


How to make methane compressor from bicycle pump? Answered

Methane (biogas) is a byproduct of a number of green alternatives such as a compost heap. This methane can be captured and processed usefully in small volumes. However it must be compressed to some level that will produce a controlled flow, let's say 14-20 pounds per square inch. In fact the methane could be captured and stored in a bicycle inner tube for later processing. Anybody got any thoughts on how a bicycle or small aquarium pump could be modified to compress small quantities of methane?

Question by egbertfitzwilly   |  last reply


Needle valve on the cheap?

I need a needle valve or similar to adjust some pressure with more or less precision. Problems I am facing with commercial solutions at the moment: Needs to withstand about 300psi max pressure, must survive contionous exposure to concentrated ammonia vapour. I already wasted too much money on stainless steel valves claiming to be chemical proof and capable of 6000psi only to find out they use seals that turn to goo in the ammonia vapour and fail. And since the stuff is not really healthy, not easy to get, I would prefer something safer. Real problem is also that the thing should be able to allow for good flow rates when opened fully. Modes of operation: During the active cycle ammonia vapour needs to pass through an opening as big as possible while after that the flow must be shut off. The reverse cycle needs to be adjustable from closed to fully open with great detail to control the flow rate. Current ways to compensate: With a ball valves and extra piping I could seperate the two cycles so I won't have to bother with tiny openings but I would prefer to use only a single connection. With a bypass around the needle valve this could be accomplished better but still looks ugly. Materials out of the question: Copper, brass, normal seals based on rubber, nitrile or similar. Questions: I know fully sealed in.line valves exist for LPG system and similar. Are any of these magnetic valves available for the use with ammonia? And if so: Can they be operated with a neodymium magnet instead of the coil? Even stainless steel valves rated for chemical use and high pressure fail quickly on the seals. Is there anything available that does not use soft seals but for example aluminium instead? Thinking spray pump here... One way ball valve systems like used in simple spray pumps are a great thing. With some aluminium tubing I was able to make a simple valve that with some more attention to detail might even work. But of course there no other way of moving the ball then to use a magnet and with sufficient back pressure even neodymium ones fail to get the ball in the open position and keep it there. Now getting this combine with a needle... If, instead of the ball, a magnet in a teflon shell is used on a spindle I could spin a magnet around the outside to turn the valve with great precision. Has anyone already designed such a thing or would I have to start from scratch here?

Question by Downunder35m   |  last reply


Why to use RF directional couplers in some measurements and control processes ?

I am an electronic engineer in the field of RF directional couplers, but I am puzzled about this question, why to use RF directional couplers in some measurements and control processes ? Today I come to this forum to turn to you to discuss my understandings are appropriate. Here are my personal understandings: RF radio frequency is referred to as RF current, it is a high frequency AC change electromagnetic wave short. Less than 1000 times per second changes in alternating current called low frequency current, more than 10000 times called high frequency current, and radio frequency is such a high frequency current. RF technology in the field of wireless communications with a wide range of irreplaceable role. In the electronics theory, the current flows through the conductor, the conductor will form a magnetic field around; alternating current through the conductor, the conductor will form an alternating electromagnetic field, known as electromagnetic waves. When the electromagnetic wave frequency is lower than 100khz, the electromagnetic wave will be absorbed by the surface, can not form an effective transmission, but the electromagnetic wave frequency is higher than 100khz, the electromagnetic wave can be spread in the air, and the outer edge of the ionospheric reflection, the formation of long-distance transmission capacity (Analog or digital) with high-frequency current modulation (amplitude modulation or FM), the formation of radio frequency signals, through the antenna to launch into the air, the radio frequency of the high-frequency electromagnetic waves.  Long-range radio frequency signal received after the anti-modulation, reduced to the electrical information source, this process is called wireless transmission. Wireless transmission developed for nearly two hundred years, forming a large number of users and product groups, but because of climate change and the impact of surface obstacles, can not transmit the perfect information. Modern human invention of the cheap high-frequency transmission cable (radio frequency line), in order to pursue the perfect quality of information transmission, taking into account the original wireless devices, wireless cable transmission began to pop. Resulting in the concept of radio frequency transmission. If your information source through the secondary modulation, with the cable to the opposite end, the opposite side with anti-modulation of the information source after the re-application, no matter how low frequency, but also radio frequency transmission, if there is no modulation anti-modulation process, The information source is transmitted directly to the opposite end of the cable, no matter how high the frequency, are the general cable transmission. SI --- Signal Integrity Signal Integrity PI --- Power Integrity Power Integrity emc --- electromagnetic compatibility Electromagnetic Compatibility rf - radio frequency RF emc = emi + ems EMI = Conduction + Radiation Emission SI: The Fourier transform shows that the higher the signal rises, the higher the amplitude of the higher harmonics. The MAXWELL equations see that these alternating harmonics produce alternating current at the adjacent line. And even through the space parasitic capacitance directly to another conductor, so these high harmonics is caused by radiation interference (emission) of the main factors; (that the simple point is that the signal rise faster, the more complete the signal, the better the signal quality, But for emi bad) . PI: PCB exists on the number \ \ analog area, high frequency \ 'low frequency region and other different areas and planes, if the partition is not easy to interfere with each other, that is, conduction conduction (conduction). Ps: Excuse me if I was wrong in words or expressions as I am a green hand in the field of RF directional couplers. I need continual learnings. What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated. May someone would like to help ? thanks in advance.

Topic by maryzhu   |  last reply


Portable Homemade TV Answered

I built a TV from an old laptop screen and one of those LCD control boards you can get from eBay but I’m curious how to go about adding a battery to it to make it portable. So, my question is, how do I go about battery safety and how do I control charging and isolation? For example, if I plug the TV in because the battery is dead, do I just have a charging board between the input and battery and let the charging board take care of the rest? And the same question is applied to when the battery is at peak charge but I don’t want to use the battery just simply plugged in. The battery is a 12v 2A lipo and I don’t want any fires. I’ve thought about adding a switch to simplify things but that’s inconvenient and armature I could make a circuit that would cut off the flow when the battery is at peak I suppose but I’m not sure of the schematics or if that is the right approach. I’m good at building just not figuring this stuff out….

Question by aniox   |  last reply


Is this solar setup flawed? Answered

I have a 12V 10W solar panel that I'd like to use to charge a smartphone and/or a battery pack (5000mAh-15000mAh). I realise it's not a large panel but smartphones aren't that greedy and my use would be moderate. I was hoping that I could just attach the panel I have to a car lighter receptacle and use a double USB plug that I already have. Is this a sensible arrangement? The advantages, to me, are that all I'd need is a $5-$10 receptacle and I'd have a very simple setup (no inverter or charge controller, well, I suppose the USB plug would be a controller, perhaps). Would this system work? Even if it did work would it be an efficient set-up? Would there be any danger of damage to smartphone or panel? Also: will I need to earth anything or are the devices I charge capable of earthing? Would I need a diode to stop charge flowing back to the panel when there was no sun? Thanks for reading, I'd really appreciate any input on these questions.

Question by faintingcabbage   |  last reply


Can I use a 10 amp 120 volt relay for more then 10 amps if the voltage is lower? Answered

I am currently working on a mini A/C with a TEC that draws 12V and 12 amps and the relays I want to control it with have a rating of 10 amps 120v. not sure if it is as simple as this but 10A*120V=1200 watts. While 12A*12V=144 watts so in my eyes this would work because there is much less power flowing through the relay but I would like to request advice from someone who is a bit more knowledgeable then I. Help would be greatly appreciated thanks a bunch. Harry

Question by harry88   |  last reply


P.M. D.C. Motor for Treadmill

Hi I am working on an Image 15.0 R Treadmill. As soon as you start it , it shuts down as if the circuit has been interrupted. I unhooked the drive belt so that there was no resistance to it and it does the same still. The speed sensor seems to be working okay so I pulled the controller (board) and tried re-flowing it. as I flip the treadmills switch on not starting the treadmill-just turning the power on the motor runs for about 3 seconds. Because the cover is off while I am working on it I can see that during that 3 second window the motor has a spark (bolt) from one of the bolts to the post (I think stater) the one that if the motor were disassembled the part spinning inside the copper wind. I don't remember what it's called (armature?) Anyway this arching does not re-occur unless I completely unhook the board once more and re-assemble. After re-flow the motor still just begins to load (start) bumps about 1/2 a rotation and stops. I read an article here that Iceng had commented about bringing his P.M. D.C. Motor model # c335483304 back to life......it is the exact motor....my girlfriend has been on me about fixing her treadmill so here I am. Anything would be of great interest and help to me. Thanks a million in advance. Troy

Topic by ill build u one   |  last reply


Smart amplifier design building blocks help? (making an amp w/ auto-volume adjust by controlling gain with running avg)

I am currently working on a simple headphone audio amp that automatically adjusts volume to my preference, regardless of what video I click on when it is plugged into a computer. I am tired of some video's being so quiet that I have to crank up the volume to overdrive to hear it, while other video's blast out sound and burst my eardrums. And of course when watching photonicinduction videos, he often can be hard to hear his voice at really low volume at like 12 at night when everyone is asleep, but then the sparks and hammers come into the picture, it is often too late to crank the volume back down, and thus makes your ears bleed or waking everyone up in the neighborhood! X-(. (Luckily he has included sound warnings, but I am lazy, and will engineer things that do the hard work of adjusting volume for me! :)   ) In a way, I understand that this will minimize the dynamic range, which I suppose hardcore "audiophiles" will go NUTS over me actually WANTING to do that, but none the less, That is what I want. My design currently is just a simple emitter follower with a NPN and PNP transistor is the class AB operation, and to minimize crossover distortion and give a definite gain, I have negative feedback op amp from the output of the totem pole transistor arrangement back to the inputs that feed the base of the low and high side transistor. (obviously, the transistors by themselves are low impedance output, (CV mode) and high impedance input, and have a gain of like 1.) Sorry, no schematics, but you capable of googling it if you want to see what I am describing. As it is, it works fine. HOWEVER, it does not do the automatic volume, or gain control. That is set in stone by a resistor divider network between the feedback and ground (the basic non inverting amp feedback config.) I do not want a fixed gain. I want a electrically adjustable gain. The thing I plan to use to do the automatic adjustment would be a peak detector on the input, which is probably going to be a simple diode and capacitor with a buffer, and a discharge resistor (or constant current drain) across the capacitor to gradually lower the max output, or possibly an integrating op amp that effectively takes a running average. The output of that needs to control GAIN of the primary amplifier, and I want to be able to control the PID of that thing, maybe by tuning the a LCR circuit, or what have you. It is all nice and analog, just the way I like it! :) If ONLY there was some magical (and common) component that I could control the resistance anywhere in the feedback loop, of with a given voltage w/ respect to ground... I was thinking of like a MOSFET, but I would have to deal with the non linearity of the input vs output impedance, which probably changes with respect to everything from the current flowing through the channel, the voltage relative to ground at the source, the temperature, the alignment of the planet's, what mood god is in, etc etc etc. That is too many factors for an open loop control on to model in discrete stuff! And digital potentiometers are out of the question since, well they are digital, I want an elegant simple solution, and the are $$ and difficult to deal with. They have so many requirements that need to be addressed.  I prefer a elegant discrete transistor circuit, but op amps and other basic building blocks are acceptable, (this thing I want to be built over a weekend with with jellybean parts from by junk bin.) if you happen to know of a specific audio chip that does this for me, please mention it, but I will probably not use it, but maybe analyze the internal circuitry and learn how it works.

Question by -max-   |  last reply


ben heck a/v selector, alternate chips

Hey guys, I am about to set out and create Ben Heck's A/V selector.  http://www.engadget.com/2007/03/13/how-to-make-a-solid-state-a-v-switcher/ He uses a bus switch, CBT3244A, Digi-Key part # 568-3619-5-ND (out of stock I believe).  While I could order a comparable bus switch, I have several lying around from hacking apart a kid's toy.  74hc374. I've looked at the datasheets and, I've never been very adept at understanding them, preferring the lazymans terms.  I understand that the original chip has 2 switches (to use for two separate a/v connections, or turning both on for a connection with more pins) while the chip I have has only one switch, allowing up to 8 channels to go through. What I'm confused about is the state of the "on" switch for the one I have, or maybe the clock.  From what I understand, they each need to be pulled LOW (connected to ground) in order for their respective inputs to flow through, can the clock, in my case, be ignored? For the arduino tags, I do plan to make this project remote controlled.  But I'm a serious beginner in this area.  Basically I plan to replicate this project for arduino.  http://www.tauntek.com/tinyir2-learning-ir-remote-control-receiver.htm  Would there be a point to that?  Or would it be simpler to just order the chip by itself already programmed.  I think that programmed tinyir2 PIC chip and arduino chips come out around the same price wise.  I have the other components lying around already.

Topic by stalledaction   |  last reply


How to 'load' a CIS solar panel to maximize power output and efficiency? Answered

I have 4 decent CIS solar panels that, in series and in bright sun, will give ~16V, and can offer ~ 200mA shorted. However, if shorted, the voltage obviously sags to almost 0V, so basicly no power is delivered based on the fact that V*I=P at the other extreme, there is almost 4V open circuit, but essentially no current flow. Again, 0W of power delivery. The voltage and current figures above are just memory and I did log the data at various resistances awhile ago. My intention is to charge 3 lithium batteries in series to 12.6V, that will then feed power to a modified car charger (basic buck circuit for downconverting 9V-18V to 5V) Since the current is so low, can I maximize efficiency by connecting the cells directly to the battery pack without any additional circuitry other than a blocking diode? Or in order to speed up the charging do I need to add some complex control circuit that will intelligently match the impedance? If the battery charging speed is based on current, does that mean a direct connection is best?

Question by -max-   |  last reply


How to find out a relay's "trigger" voltage

Hey there! I currently have several "old" (read: unused) relays laying around that I'd like to trigger using my Arduino Uno. The issue with all of them is that they've got no datasheets available or if they have, I can't tell from the sheets at what voltage the relay triggers. Since they're all quite small and perfectly fit on a standard breadboard, I don't assume they would consume more than the 5V my arduino could provide. I already checked the connections using my multimeter and there's definitely current flowing through the line it's supposed to run through when unenergized. The actual relay I'm talking about is an AZ8-1CH-24DE (http://www.digchip.com/datasheets/parts/datasheet/540/AZ81CH24DE-pdf.php). Attached is the wiring scheme that's printed onto the relay. And here's how I've wired the whole thing: 1 - +5V from Arduino (always on) 2 - LED1, which connects to arduino's GND 3 - LED2, which connects to arduino's GND 4 - arduino GND 5 - +5V from Arduino (control pulse) I've also tried switching 4 and 5 around, thinking I inverted the two pins, but whatever I do, I can't get the relay to switch from LED1 being on to LED2 being on. Would be glad if someone could help me out with this. I'm kinda new to the whole thing, but I though I understood how these things *should* work.. Also, if anyone comes to the conclusion that the relay will definitely need a higher (12V?) voltage to "trip", could you also tell me how I can control that relay from my arduino while only having my +5V pin from the arduino available? I thought about transistors, but maybe there's another way. Best regards, Philipp

Topic by Christoph680   |  last reply


Please suggest components for a water spray/vacuum system for cooling and dust collection while grinding. Answered

The grinding is being done in a tight area. A long handled grinding disc (please see picture) is being used. Only the grinding disk rotates, not the long handle.  It would be best if the water lines and vacuum lines could be attached along the handle, welded? cable ties?  The system needs to be portable but electricity will be available. The smaller the components, such as water reservoir, peristaltic pump, vacuum pump, vacuum holding tank, spray nozzle, tubing, the better. The material to be ground is heat sensitive so the water spray is needed for cooling.The water pump needs to be a peristaltic type pump so that the fluid is only in contact with the tubing.  I will also need a way to connect the flexible tubing of the pump to a more rigid, perhaps metal fluid line along the handle..  Due to the small grinding surface, water flow does not need to be great, perhaps 20 ml per minute.  The dust produced from grinding can obscure the view so a vacuum source is necessary.  I welcome any suggestions on:  how the system could be designed, what components I would need,  where components could be purchased,  how to keep costs down, etc.  I greatly appreciate any guidance you can give me.

Question by jadeway   |  last reply


The bernoullivator

So I was chatting away on an 'ible in comments and had an idea... Basically it's a replacement for elevators that works on bernoullis principle, the whole idea is just to make a nicer world for people in tall buildings... The idea is taking an elevator shaft, two massive fans and some people, so you get your two fans and alot of air blowing up the shaft, now on the inside handles are added beside the doors and buttons for opening from the inside of the shaft, the original doors are given rubber seals, to add efficiency and not deafen the people outside. The down one uses a slightly lower flow of air to create a controlled descent speed. The top and bottom floors have handles leading to the doors for those that made a woopsy, and big mesh grids to stop them... This would allow for more people to travel through one shaft than in a single box as noone stops at unneeded floors, also in smaller buildings with large elevator travel, there's the possibility of both better energy efficiency and faster travel between floors, in theory wheelchair users could use it too, I think, they may need to have a mini parachute... It wouldn't be super costly to do when you think of the cost represented by the highly complicated systems used in elevators... Also think jsut how cool everyone who used it would feel, the tech exists in parachute simulators, basically small scale productions of this...

Topic by killerjackalope   |  last reply


I'm willing to create a zvs induction heater but I have some questions Answered

Hello there! I want to create a ZVS induction heater but I don't fully understand yet how the coils need to be driven. I haven't started yet with building it, but I already wanted to check if the induction heating effect was working, so I connected a coil onto my high current DC blockwave generator and nothing really happens. it's a PWM controller which switches between 0V and the applied voltage. Is it because it sends DC signals to the coil, and the magnetic field goes into saturation? If so, I added a capacitor in series with the coil, to filter out the DC component but now nothing happens. There is nearly no current flowing trough the circuit. I'd also need some information on what influences the intensity of the heating? Is it the Amp*Turns that matters? because we're using high frequency here to lower the required current; but if it's amp*turns then we need the current to be as high as possible. So something's wrong there in the way I thought this works :/ I do know how the material gets heated. (by eddy currents that increase if the flux alternates at higher amplitudes) also, at what voltage should the coil be switched? does the voltage matter? Should I use something like 12v? 40v? or even 2v of I only need high current? I do know that the use of the high frequency is to increase skin effect in the material to be heated, but what other reasons are there for using such high frequency? Is it also because eddy currents will increase at higher frequency? If so, why would this happen? A lot of questions indeed :) but I'm not going to start copy-pasting the circuit, and then just being happy that it's working. I also need to know Why it works, and how! Thanks in advance, Electorials

Question by DELETED_Electorials   |  last reply


May 2019 site changes: my observations and thoughts

In early May 2019, Instructables' website has been radically reworked with a revamp. Changes I have observed include:Navigation: Many categories and subcategories have been eliminated and instead reworked under other folders as part of the changes (there is no "Play" category and subcategories such as "NERF" and "Paper Airplanes" no longer exist) "Recent" filtering is not directly available to people browsing the site--you must sift through the categories and get through at least two pages to find a way to filter the selected category for "recent" (i.e. Homepage -> Circuits -> Projects -> (Page at which you may select "recent")) There are no filters for searches On the front page and in the categories' main pages, featured projects are emphasizedThe Forum/"Community": Without manually typing in the URL, there is no direct way to access the "community" page Buttons to access the forum among in the category pages are tied to the community pages for that category (as a result. They do not allow you to see the general forum posts of the community without viewers manually deleting the category from the URL and going from thereThe way people navigate about sites controls what they can see and how they see if, so all of these things will change the flow and behavior of Instructables' viewers versus how it was before. Versus before, it is more cumbersome for viewers to get to recent content while featured content is more readily available. This will influence where people go and what they see.----------------------------------What do I believe this means for the future?Drawing on my decade of experience on this site, I suspect viewership of non-featured Instructables will drop. Thus, the viewership gap--between those projects that have been featured and those that have not--will then widen.Of these changes I think people will say you either "get featured or get buried."

Topic by OrigamiAirEnforcer   |  last reply


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 (https://www.instructables.com/id/Wire-a-Potentiometer-as-a-Variable-Resistor/), 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   |  last reply


Are high power resistors really neccessary on a benchtop PSU conversion?

Was looking through the site and I was just wondering--why all the huge resistors on the bench-top power supply conversions of PC Power supplies? From personal experience this seems like a waste of perfectly good electricity.I know that they require some current to just stay on however in designing a project for my school's Engineering Technology department I found that the heat generated by such a small resistance (Around 10 ohms) was unacceptably high. Originally I was looking at Instructables and this sitethis site for inspiration but all the cooling measures taken to prevent the high power resistor from becoming a hazard seemed rather silly. A few calculations and experiments later with the 250 watt power supply and I determined that 160 ohm1 watt resistors and 1K 1/2 watt resistors were perfectly acceptable for the purpose of keeping the PSU awake and functioning. I connected one of each between each voltage and ground. According to calculations I can get away with dissipating a grand total of two watts or less spread across multiple resistors.The current divider rule dictates that if you add resistances in parallel, the resulting resistance will be smaller meaning more current will flow through the overall circuit. However this increased current will divide itself across the parallel resistances according to the rule Ix= RtIT/(Rx+Rt). The current through and power dissipated by the resistor you've soldered into the PSU will not change enough to be significant no matter how large or small a resistance you attach in parallel with it--with the exception of an effective short and what in God's name are you doing intentionally shorting the terminals of your bench-top PSU? Now several months later, the PSU is still operating happily and powering multiple micro-controller projects on a display board. Therefore I can reliably conclude that the high-power 10 ohm resistors in many computer power supply conversions are probably a gratuitous waste of wattage. You can get away with using a higher resistance and a resistor that dissipates much less current.

Topic by Psickattus   |  last reply


Some advices on "self switcher circuit between battery & AC-DC ADAPTER power sources"

To put it shortly, I have small 12V 10A solar system (panels, car battery,  PWM charger, LEDs, car radio, car lighter (used for usb phone chargers etc) backed up with 12V 3A AC-DC adapter. They share common "ground" and outs connected in parallel but I dont want it to draw any power from AC adapter unless PWM controller shuts down power when battery gets empty. Anything below 500mah is neglible. I dont understand much about relays or microchips perhaps a relay design would be simpler and more efficient... So I tried to design a circuit with TIP33 transistor(because i found that it supports 10A continuous draw). but apparently it needs like 2V (max3) as Base-emitter voltage. if so, i need to add something between R1 and Adapter +12V and R4 and battery12V to reduce voltage to 2 volts... I have 3 questions 1st: is there any more efficient and relatively simple way to drop voltage withoutt leds? otherwise i will just use them as both indicators and voltage droppers since current will be lower than 20mah. 2nd: i am not sure if R2 and zener diode would be enough to let T2 draw all the current to keep TIP33 off while battery is on. perhaps i should remove R2 as well? 3rd: Since PWM and adapter both have reverse voltage and overload protection im planning to put a single diode to deny unnecessary current flow on R3 from battery.(i already removed the second one from design just before i write this here). i am thinking about putting resistor values to let only 30ma run there. Would that diode overheat while running on AC or drop voltage from adapter too much? R3=440 R1+R2=160 R4=anything depends on the T2(sth simple to handle 15-20mah C-E)

Question by sailorondatea   |  last reply


Will this circuit work out of curiosity?

I saw a question, https://www.instructables.com/answers/Need-help-with-the-wiring-diagram/ that asked about making a relay circuit that is capible of moving or rotating something to one extreme, then stop, and reverse direction to go the other way, but what intresting is that there is also supposed to be a delay in it, so it goes all the way in one direction, stops for a moment, and reverses direction and stops, then reverses... you get the idea. That question intrigued me, as I like really basic and elegant solutions that do not use a raspberry pi to do such a demeaningly simple task! I can see something like that being used for an automatic door w/ one button operation, and I decided to see what I can come up with on my own with a few relays on paper. Here was my solution. However, although I have traced it all out and it seems to be functional, can anyone else verify that? When I get the parts, I will actually try to build a scale model to and see how well it works (after all, thats the best way to discover problems! The physics engine of real-life is never wrong :) ). I may modify it so it just uses a "open" and "close" switch instead w/ the limit switches. (a bit more practical for that use.) But I wanted to challenge myself with those requirements instead. The idea here is that I have 2 DPDT switches, the 1st one will be a latch, and the second one will change the polarity of the motor. There is a giant RC circuit on the output of the 1st relay which delays the changing of polarity to the motor using the 2nd relay (as an H bridge), and the limiting switches control power to the motor in one or the other direction, (so when one limit is hit, the power cannot continue to flow through the into the motor, so it does not keep trying to push the switch off, but still must allow the polarity to be reversed and let the motor travel the other direction to the other side, so it does not freeze up right there. Thats needed because the same RC circuit which delays the polarity switching is 'laggy' and the capacitor takes time to discharge, and it will continue to try to press that motor into the switch until the capacitor has discharged fully though the relay coil. Just not good engineering practice.) 

Question by -max-   |  last reply


Help with capacitor basics? (the math part) [ANSWERED. Come here for the proof if you want it!] Answered

I understand the operation for capacitors, which make a lot of intuitive sense to me, and seems deceptively simple. I know that the derivative  of the voltage across a capacitor (the slew rate, if you will) is proportional to the current, for a given capacitance. So when the voltage is not changing much, like when it is connected across power supply rails, and the capacitor has little-to-no current flowing through it, and it appears as a high impedance. Fair enough. And when I am winding up the wick on the constant-voltage power supply, so that the slew rate is constant, and the voltage is changing at a constant rate, the current will be relative to how fast that voltage rising/falling. Again, that makes sense. I have proven that to myself time and time again. The technical math way of showing all that is this:          dV/dT * C = I or with units plugged in: d(volts)/d(seconds) * Farads = Amps (or something like that)   Likewise, I know that I can do things in reverse, and that forcing a controlled current through the capacitor, that the slew rate of the voltage across the capacitor will be proportional to that. In other words; the voltage will be integrated over time (as it steadily rises or falls). I do not like integrals in math (esp. when they require by parts or partial fractions!), but the concepts do come in handy in practical design! This is also my 2nd favorite way of imagining what an integral are! (My favorite is actually the water cup or well analogy, where a water faucet or hose is a function, and a the level of water in the cup, pool, well, etc. is the integrated result. That makes the function of integrals really clear and deceptively easy LOL!) So, I basicly have been trying to figure out how to take these simple, easy-to-understand relationships, and take ohms law, and have a super basic RC circuit, with 5V, 5 ohms, and 0.1F. I have so far figured out how to take ohms law, substitute I in the capacitor formula, and get a function. HOWEVER, this is where I get stuck. -------------------------------------------------------------------------------------------------------- Here is the circuit:            +5V---(V2)-----/\/\/\/\/\/----(V1)-----| |-------0v----(grd) So after having a bit of a think, I have figured out that I really need to account for 2 different V's. The 5V power supply, V2, and the voltage across the capacitor, V2. I know that the current flowing through everything in a series circuit is the same, so then I can easily figure out current by calculating the voltage drop across the resistor which is this:            I = (V2 - V1) / R  So now, lets plug that into the mysterious capacitor derivative thingy: (All I did was substitute the I in the capacitor formula with the that ohms law formula above.)           dV(1)/dT * C = (V(2) - V(1) ) / R. -------------------------------------------------- Now, I just plug in the values, and simplify as much as I can, to make it more friendly to my eyes. C = 0.1F, and R = 5 in my case, since I am using a 5 ohm resistor, 100mF capacitor, and I know V2 = 5V, since that is the output of a 7805 voltage reg.           d(V(1))/dT * 0.1F = (5V - V(1) ) / 5ohms. That dV/dT is a bit hard to look at, so I will use V prime, or V' to represent that instead:          V(1)' * 0.1 = (5 - V(1)) / 5 I do not know how to simplify that further though, to end up with that weird inverse exponential curve that is the time constant thingy, with that decaying charging curve. I have V on one side, and V' on the other side. :( So this is how far I got:        5 + (1/2 * V(1)') = V(1) EDIT: I HAVE ADDED THE PROOF HERE IF YOU WANT IT

Question by -max-   |  last reply


Arduino Uno Synth project - Audio output questions

Hi! I am developing a synth/sampler project based on the Arduino Uno r3. This is my first electronics project ever and because of that reason I have some questions which I can't find a definite answer for on internet. The synth has two function. It has a tone generator using the ToneAC library. With code I have mimicked LFO and VCO functions, using potmeters I can adjust the frequency and LFO speed realtime. The other function is that I can trigger samples stored on a SD card using the TMRpcm library. The device will be used in nightclubs on high end soundsystems and PA. I am afraid I will damage the equipment with my device because I do not send a pure audio (AC?) signal. Currently the flow is like this: PWM output (pin 9, 10) -> voltage divider to 2.5v -> RC Low Pass Filter 15Khz -> LM386 amp with volume control -> mono jack output -> mixing desk -> amplifier -> speakers (the TMRpcm and ToneAC library share the same pin (9), I have fixed this by disabling the TMRpcm when the ToneAC is playing and vice versa. The mono jack is wired as follow. pin 9 goes to plus side of mono jack output, pin 10 to negative side. The TMRpcm pin 9 also needs to go to plus side of mono jack output, and mono jack negative needs to go to ground. Because I disable the ToneAC at that time I consider port 10 grounded because it not generating any sound so there is no signal/voltage running out of it, aka the IO pin is set to LOW) I am hoping that using the voltage divider I am within range of the Audio Line levels of a default mixers Line-IN (like Pioneer, Behringer, etc). The RC Low Pass Filter is used to filter of inaudible frequencies and clean up the sound a bit, the LM386 audio amp is used to amplify the signal and (hopefully) make it a real audio signal. The lowest frequency you can play with the synth is 100hz and the highest frequency is 3100hz. Because I lack a lot of knowledge in this field and because I do not own a oscilloscoop I can't say for sure if my output signal is harmful for the equipment and was hoping to get some guidance on my project on this forum.

Topic by erik404 


K155ID1 chip showing low voltage between decimal pins and power supply. Is the chip bad? Answered

Hello, I turn to those who know probably a heck of a lot more about this than I do.  I've been trying to build myself a nixie tube clock, and everything has been going fairly well. I recently got the driver chips in the mail which convert BCD -> Decimal in order to hook the nixies up to a digital logic system like an arduino. I'm using a 12 V -> 180 V switching power supply for lighting the nixie tube. It is connected to ground on a computer power supply that I'm using to power the entire project. The 5 V rail on the computer power supply is connected to the Vcc pin of the K155ID1 chip as shown in the picture. I've connected the ground pin on the K155ID1 to the common ground of the computer power supply. I have nothing connected to the A, B, C, or D pins on the driver chip, which from what I understand should be the same as inputting the BCD number 0000 or just 0 in decimal. If I'm inputting a 0 as my number, the chip should output a 0 in decimal. From every single datasheet I've seen talking about this chip, that should mean that pin "0" (as shown in the picture) should become effectively grounded, and assuming that the "0" pin is connected to the 0 digit on the nixie tube, that should connect the nixie tube to ground, which should allow 180 volts to flow through the nixie tube, causing it to light up. Unfortunately, this is not what happens. In fact, nothing happens. Nothing happens no matter what pin on the driver the nixie tube is connected to. The only way I can get the nixie tube to light is if I connect it directly to ground, in which case, it lights up very nicely, but obviously that doesn't help with controlling it in any way. I took out my multimeter and measured the voltage between the 180 V supply line of the nixie tube and the pins of the driver chip, and every single pin (except A, B, C, and D) show a voltage of about 80 volts, which is not enough to light a nixie.  My question is, is there something I'm missing? I would think that the chip was bad or that I popped it or something. Heck, you could fill an electronics graveyard with all the chips I've popped over the years. But I've rebuilt this setup 4 times now, and I've attempted this following multiple schematics, and even switching the chip out for a brand new one 5 times. Each and every time the result is exactly the same. Either I'm overlooking something huge, or I just happened to buy 10 dead nixie driver chips. Thanks, in advance for any input!

Question by tylervitale   |  last reply