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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    |  last reply

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    |  last reply

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    |  last reply

Finding the wattage rating of resistors and variable resistors? Answered

Is there a way to find the wattage rating of resistors and such mathematically? or is it something that has to be tested in real life? I have quite a few resistors that I'd like to use, but don't know the wattage rating of them. I only know their resistance, and I could calculate other values if I put voltage across them with a multimeter.  Also, what type of variable resistor would you recommend to control a 12 VDC device that draws 12 amps?

Question by tylervitale    |  last reply

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    |  last reply

Can we use variable resistor as a normal resistor? Answered

Like i want 4.7kohm constant can i do that som how

Question by TheGreatResistor    |  last reply

resistor id?

This might sound stupid, but being brand new to electronics i need to pose this question, i found a scematic with 3 resistors on, 1 is a variable rated as R1 100K, the second R2 1K, the third R3 270R, the problem is the third resistor, what does the "R" stand for?

Question by nicobotha12345    |  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 (, 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

Accurate adjustable resistor?

I need a simple, low cost, small device capable of 10 different resistance settings, and must be capable of mechanically reproducing them exactly, on command.  It cannot be a potentiometer, as it is innacurate without some sort of  measurement device (which I cannot use), nor a rotart switch or encoder (too big and expensive, cannot use digital).  Basically, is there some alternative <$2 that will do this.  Again, no digital stuff or measuring position, only going between several set resistance settings (but any incrament thereof is okay).   

Question by jduffy54    |  last reply

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    |  last reply

Help needed with custom variable resistor value/range?

I would like 0.4ohm to4ohm variable resistor to replace car IAT sensor, i looked online for pot and resistor combination couldn`t figure it out then i went up a level and was searching variable wemos resistor (it would be nice to see on a small display the original sensor value and the fake one that wemos outputs, just an idea) but no luck either, is there anyone who can point me in the right direction either analog or digital way?thnx alot

Question by turbiny  

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    |  last reply

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    |  last reply

Looking to control a motor position using a variable resistor and Arduino uno - it is not a servo?

I am a Radio ham and want to upgrade my rotator to electronic control instead of switches see as to what im trying to control - Need to create a c  programming type to make it simple

Question by m8    |  last reply

Anyone know of a resistor that is sensitve to sound vibrations?

Does anybody know of something like a photo cell, except instead of the light being the variable to determine the resistance of a circut, it would be sound and vibrations? If ya do, could ya give me a comment on what it would be called, what they're used in, and where ya could maybe buy one? Thanks! -xD

Question by ! xD !    |  last reply

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    |  last reply

Which resistors directly affect the frequency range?

I am currently working on an audio equalizer, and this is a link to the basic schematic I am using. If I am not mistaking, it would be the R1 and R2. I am also using Don Lancaster's book called the Active Filter Cookbook. I am confused on which equation I actually need to solve for the resistors using a certain frequency range. I am grateful for any help. Thank you.

Question by sound91  

Accurate Variable Current Sink? Differential Voltage Reference?

Some background: I have recently aquired a few really nice (and really heavy!!!) LAMBDA power supplies, The largest one supplies 24V, and up to 9A, but has annoying foldback current limiting, which causes the output shut off when even a short period overload (like inrush current) is detected. What I want: I would like to modify this power supply to give me (ideally) completly variable 0-15v dual rail voltages & 0-5A adjustable current limit, & I would like this to be controlled with arduino so that I can use a nice LCD display and control the supply remotely with a bluetooth or wifi app, and possibly do some data logging which could come in handy for energy measurements and stuff! My current PSU design: The schematic below is what I've currently built in LTspice. Both the voltage & current regulation work. The voltage across the (+) and (-) inputs of the current error amplifier should be the sum of the voltage drop across the shunt resistor and the voltage drop of a voltage reference, so when the voltage on the shunt resistor exceeds the voltage of that reference, the op amp will start to limit current by reducing the bias voltage on the pass transistor. This V_ref needs to be both variable and accurate, but since this V_ref is a differential voltage between the output of the pass transistor and the input of the error amp, I came up with the clever idea to use a resistor there and a variable constant current sink. That way the constant current through that resistor results in a fixed V_drop across it. With a bit of fudging around with it, I was able to make it work. However, I need to replace that "ideal" current sink with a real one. I tried using the classic NPN-based one, but it wasn't good enough. I then attempted to make the slightly improved version of that current sink with a spare op amp, although this worked, it would stop pulling current once the voltage fell below what was being maintained across the small resistor. The REAL question: Would anyone happen to know how to make a really accurate and variable current sink? Maybe if this is not such a great idea, what other methods can I use to generate a fixed differential voltage?

Question by -max-    |  last reply

What would be a good way to vary between 12V, 15 Amps and 0V, 0 Amps, gradually?

 The power is coming from a battery, and so is DC and has nothing built in to vary it. For example, what potentiometers or the like could reliably handle it?

Question by electrick    |  last reply

Why is my 555 timer metronome circuit so variable?

I constructed this metronome circuit using a IC555 timer chip (see image below) and it worked fine on the breadboard. I wanted 2 ticks a second (2Hz) so used a trimpot to set that but was getting wild fluctuations with either the tempo increasing or really fast ticks even with the trimpot at maximum resistance. So I changed out the trimpot to a 30KR resistor and that seemed to work, but after doing the circuit nine times, it has also proved highly variable and I don't know why. I'm running the circuit on 6V (2x CR2032) and my resistors are rated at 1% tolerance. Any help please?

Question by chiok    |  last reply

How do you choose a potentiometer? Answered

I'm trying to use a potentiometer as a variable resistor does, how do I determine the rating for the Pot?

Question by joeAMERICA    |  last reply

How are we able to know the variable of a Strain Gauge? Answered

Hi, for a school-project I need to measure the weight of an object. Therefore I am using an old weight-scale. The component wich includes 2 Strain Gauges has 2 seperated wires coming out and 1 other wire conected to the Ground. Because we can't find something changing when we measure differend kinds of things, (for example the changing resistor-value) we hope that you can help us. The two wires coming out of the Strain Gauges are connected to an Amplifier (TL081CP). The scale itself is a KRUPS TYP 841 ; 871-B Thanks!

Question by zupperzipper    |  last reply

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    |  last reply

Is there a way to change the value of a variable and keep it afterwards? Arduino Answered

Hello everyone, I don't really know if this is possible, I am using processing, arduino and a force sensitive resistor to control a servo and I want to change the value of a variable and then if I reset the arduino, it will kept the new value. Is there anyway to do this? This is the part of my code I want to change. void fsrMovement(){         int maxforce= 1023;  // THIS IS THE VARIABLE         if(Serial.available()){  // SERIAL AVAILABLE TO USE WITH PROCESSING         maxforce =;         }         force = analogRead(FSR);  // Reads the FSR               Serial.print("Force sensor reading = ");         Serial.println(force); // This will print the raw force value         int pos = map(force, 0, maxforce, 0, 175); // Scales the force reading to degrees for servo control         Serial.print("servomotor degrees = ");         Serial.println(pos); // This will print the adjusted servo reading (an angle)         myservo1.write(pos); // Write the new angle to the servo         delay(10); // Delay 10 milliseconds before taking another reading

Question by rojascan    |  last reply

Can I make a 15W+ 1-5Ohm resistor?

I'm making a yard sprayer with a 12V, 5amp pump.  It works great, but I'd like to add in a 2nd, slower speed setting for situations where I want less fluid going through the sprayer.  It needs to a be a simple fast/slow switch, not a variable resistor, since I need the flow rate to be repeatable and consistent.  Ideally, I'd like to make about a 2-ohm resistor, that would need to be able to handle about 15W.  Unfortunately, no local shops have anything like that, and I don't want to wait for an on-line order to get shipped. Is there any way to make a DIY resistor to roughly achieve these characteristics?  (Like I said, the important part is that it will be a consistent resistance value, not a specific resistance value, and not burn up with 2-4 amps going through it..)

Topic by SvdSinner    |  last reply

Model RR, LEDs on variable ac input voltage Answered

Led's for ac powered model railroading, to replace incandescent bulbs.  Voltage to track varies from 5 to 17 volts AC.  Leds will light up, but what is it doing to them. They do not pop like a flash bulb at top voltage. I've rectified some to dc voltage for lights in cars, the variable voltage seems to power them. Ideally a circuit that put out a constant 3.2 DC volts, with a variable 5 to 17 volt AC input.  Or maybe would a constant 3.2 volt AC out would function? I found that with HO DCC control, a white led with a 1k resistor will function, have not ran them for more than few hours though. Prewired rectified leds go for around $3.00  each, 5 passenger cars, 2 bulbs each, gets pricey with 4 sets of cars. Surly someone has gone through this.

Question by 31cssinc    |  last reply

is it needed to use a resistor in a circuit consisting of a 12 volt motor and a 12volt rechargable battery .

I' making a wheel chair run by a 12 volt rechargable  battery connected to a 12volt motor and also a switch.Is a resistor needed,if needed what resistor should be used?Can I use a variable resistor

Question by pvamsi    |  last reply

Small variable power supply from car charger?

A friend of mine gave me a bunch or car USB charger used in his company to charge the tablets and phones the delivery drivers use. His problem was that they ordered 10 exclusive for Apple products and 15 generic ones that have the standard 1amp/2.1amp USB outlets. I was asked to take a look and see if the problem is easy to fix. Long story short it was as apart from 2 blown fuses they all suffered from bad solder connections for the cigarette  lighter contacts that failed. Anyway I looked the chips up used to regulate it all and to my surprise the datasheet said they are "variable" from about 0.3V to the max supply voltage of 32V or even 40V. Checked two of mine and same story for one, the other is dirt cheap unregulated and only used to charge a flashlight. But it made me wonder... Since the output voltage is created with a simple resistor divider giving the right feedback voltage it is very easy to adjust them to whatever might be required. Could be a far better option than our standard adjustable voltage regulators and easier plus cheaper than building your own circuit. All the benefits of short circuit protection, under voltage shut off and self regulated max power to prevent overheating for 5 bucks from the next china shop. Give it a go one day before you power wasting old school regulators ;)

Topic by Downunder35m    |  last reply

How to decrease power, voltage, and amps coming from a wall socket in your house?

I am making a table top and would like to put LEDs in it. I want to be able to connect them to a variable resistor so it acts like a dimmer switch. I want to be able to run this off of wall power. I do not know how to drop the power, voltage, and amps coming from the wall to the ratings of a variable resistor? I know P=VI and V=IR, but I can't find a resistor with a high enough power rating to decrease wall power. what I would need help with is find a componet or something that greatly decreases the Power; thus decreasing voltage and amprage; to a level that I can run through a variable resistor and to the LEDs.   Yes I know LEDs are supposed to run off of DC, but they do work with AC; they just dont get as bright, which is fine by me.

Question by jkindred    |  last reply

Does any one know what this component is? - C521?

It is found in a variable temperature controlled soldering iron without feedback. It is about the size of an 1/8w resistor. The marking on the side says C53 or C531 (it's a bit smudged). The component symbol looks a bit like the pic below.

Question by Electronics111    |  last reply

Need help figuring things out in a very simple circuit!!!

I have an AC motor rated at 120 Volts, 60 Hertz and 4.5 Amps. I've already tried connecting this motor straight to a wall outlet, and it works fine. The problem is, I want to control how fast it spins. So, I plan on using a variable resistor connected in series. However, I seem to have already burnt out a 20k variable resistor and I want to know whats going on before I try anything else. I have a 1M and a 2M resistor waiting to be tested but I'm unsure whether or not they will burn out like the 20k! The confusing part is I don't know how to calculate anything because I don't know how much current is coming out of the outlet!

Question by Ke-Bob    |  last reply

joule thief: can i use a cellphone battery charger to power a joule thief? output 5v~ 400-600mah. Answered

What resistor should i use? a 1k resistor,220ohm or a variable resistor/potentiometer B50K is ok?  masters help pls.. im noob

Question by reopoop    |  last reply

What component should I use to modulate an heating pad ? Answered

Rheostat, variable resistor, potentiometer, pulse width modulator, or dimmer, to my understanding I can use any of them to control the heat in my heating wire. I have a 19V 3.16A ouput and my heating wires resistance is 6.6 Ω (1.27 Ω/m). Thanks in advance for your reply.

Question by ninazz    |  last reply

Treadmill Motor Controller

HI, I would like to make a very simple controller my treadmill's Motor. Its MoBo went bad and I dont wanna fork over $200 for a new one. The motor works fine. I just want to make a very basic DC Motor speed controller. I know just a simple Pot or other variable resistor wont do.Will it? I've been messing around with Electronics since I was 9 so I'm not afraid to solder up some circuits even if its a complicated one. Im looking to spend around $50. Thanks.

Topic by AlxMad    |  last reply

how to replace a potentiometer by a photocell ? ?

In the diagram, two pins of the pot are connected to resistors on each side and the third (variable) to the power source. That makes three connections and the photocell has only two!?

Question by marcia09    |  last reply

does anybody know how to overclock AND underclock your gameboy so you can make it variable?

I have a gameboy that I overclocked and I underclocked a game boy. with positive results and they work great! i also circuit bent my guitar effects pedaland I've seen a video on youtube of a guy who used a 555 timer to help the game not crashand a variable resistor. can't figure it out


HELP - Calculating base resistor value when using a transistor to control a relay

Hi, it is a very long time since I have done anything like this so bear with me.I want to make a simple circuit using a transistor to control a relay. I think a BC547 NPN transistor will do the job. I would like someone to confirm my logic or point out where I have gone wrong.The variables are given below.Vcc - 12VRc - resistance of the coil on the relay - 362 ohmsVin - 3V - to cause the transistor to saturate and then switch the relay onI will use a diode to protect the transistor when the relay switches off.I calculate Ic to be 33mA (12V/362ohms).Using a gain of 400 I have calculated Ib to be 82.5 micro amps. Therefore I need Ib to be greater than 82.5 microamps to saturate the transistor. If I used a 15k ohm resistor then...If Vin = 3V, Ib = (3-0.7)/15,000 = 153 micro amps.Is my logic correct? Vin will vary between 0-10V. I assume this transistor will cope with this.I have attached an image of the way I intent to arrange everything.I hope this makes sense to someone.Thanks in advance.Ed

Topic by denzil023    |  last reply

Need a 100v voltage regulator?

So what I am trying to do is make a variable power supply from a computer PSU, I've done thise before minus the variable part. I need a voltage regulator that will limit 200 or more volts to 100 volts DC. I also need different variable voltage regulator that will allow me to adjust this from 0 to 100 volts, they usually have a circuit in the datasheet that uses some resistors and a potentiometer. So, are there voltage regulators like this? If not what is another way to do it?

Question by XOIIO    |  last reply

Getting leds to light up in sync with wind?

Hi all, I would need your help with a project I have in mind...  I've been at it in my mind for a while, but I'm getting nowhere fast, as I'm rather a newbie in electronics!!  I did enlist a friend to help with that, though! ;) I would like to find a way to have the wind trigger the lighting/fading of a led, the same way one could do with a variable photo resistor (variable-resistor-wind-sensor-like, or could it be more slight-motion-based?). It needs to be compact and inexpensive, as I would need to make a whole lot of those. Ideally, it would be an analog sensor, but I am open to other ideas. No Arduino, though, please...  I'm not there yet.  Either one sensor for each led,  or one sensor for a few leds at a time. It could be powered by an external battery. Any ideas? Thanks!

Topic by lodoiska    |  last reply

555 oscillator?

How can I make a simple variable oscillator out of a 555 timer, loudspeaker, capacitors, transistor, potentiometer, and resistors? (and anything else I may need). I would ideally like it to go from about 10Hz-20KHz.

Topic by andy70707    |  last reply

Sentry Gun and PIR sensors

Hello, I have a question about PIR sensors for a robot I'm making. Most have a digital pin that goes high when movement is detected. The time that this pin stays high for (delay time) is often adjustable by a variable resistor on the sensor. My problem is that I need a sensor with no delay time - the digital pin should go low as soon as movement stops. If anyone could point me in the direction of a pir sensor with no delay time/one with a very short delay time (under 0.5s) I would be grateful. Or possibly, If I were to remove the variable resistor, would that remove the delay time? thanks.

Topic by SentryGunner  

How to make a graphite arduino piano?

Hey frnds! I got inspired by this project:      and a new project came in my mind which will use arduino but i'm not good at programming. As in the above mentioned project the graphite worked as a variable resistor. Is there a way to use this resistor with arduino to play different tones at different resistivity from the "pitches.h library". I know there can be. So plz if anyone know kindly give the program.

Question by SnehilSensei    |  last reply

Can anyone help me with this vocal canceller circuit diagram? Answered

1. I am a little bit blur with the Variable resistor part , must connect all three pin? 2. What about the left and right input's ground must connect to the ground in the circuit ?

Question by victordre95    |  last reply

Anyone Have experience with Adafruit Square FSR?

I am hoping to create a circuit that will variably control the speed of a motor through pressure. If I were to wire up one of these , simply as the switch between a small motor and a power source around 5v, would it work to simply turn the motor off at rest and vary the speed with pressure? Is there a way to use this resistor as a "switch" without using an Arduino or  other micro controller? Any help is appreciated. Thanks! 

Topic by Flashflint    |  last reply

Circuit Help Needed

Hello, i need help with a project for school due in 3 months. And i  need help with a circuit with some odd requests.  A variable resistor will change the voltage from 1-18v.   From voltages 1-10v will heat up a peltier tile  and from voltages 11-18v will change polarity around causing the peltier tile to then cool down but at a faster rate. This all needs to be done without a switch and only with the  variable voltage.  If 1-18v is not possible 1-12v may be even better.    So voltages 1-10v will heat up a peltier tile and from voltages 11-12v will change polarity around causing the peltier tile to then cool down but at a faster rate. And again without a switch and only with the variable voltage.  Thanks! -Jon-

Topic by MRCmegarallycar    |  last reply

LED Dimmer circuit needed

LED dimmer circuit please suggest me a good one,my LED is CREE XML LED voltage ratings is 3-3.5V and current ratings is 0.7-3A.Input should be 5Volts. It should have a variable resistor with switching function.ON/Off potentiometer. Your early response is welcomed!.?

Question by Faizan Hamayun    |  last reply

How to generate a fixed differential voltage dependant on a voltage relative to ground?

What methods can I use to generate an accurate & precise variable differential voltage that's dependant on the output of a +-10V DAC? I tried to use a resistor with a small variable current sink using the classic opamp+NPN design, but no design I made would sink current below 1V. I need it to continue sinking current down to 0V, I do have a negative supply rail avalible. (I think my last question was a bit TL;DR for some, so this is a shortened version of that.)

Question by -max-    |  last reply