How do i build a digital voltmeter without using a programmable ic?

i want to build a digital voltmeter having 3 digit display.but i don't want to use a programmable ic. it is possible to build it or there is an alternative device to replace the programmable ic?

Asked by niok_sosa 7 years ago

Help finding an LED voltmeter? (or figuring out how to use a 3 wire one for this)

For my coilgun/railgun/whatever project I want to use one of those all In one LED voltmeters, however, all the ones I can find are either 2 wire and just measure the input voltage, or 3 wire, and require a neutral ground. That's where the problem lies. I want to use it to monitor the capacitor bank's charging, which goes up to 250 volts, I'd be fine splitting the voltage and using two meters, but to measure it the negative connection is high voltage positive, which means I can't measure the capacitor bank's charging. Is there an LED volt meter (that's not super expensive) that will accept power from a separate source and has negative and positive connections for measuring voltage? If not, how can I work around this neutral ground problem?

Asked by XOIIO 5 years ago

Is it possible to create a voltmeter to test car batteries with an arduino and 3 leds?

I am trying to figure out how to wire an arduino as a voltage meter to test the voltage on car batteries and lead acid batteries in other things. I want to output the readings in 3 different colors leds (green, yellow, red) that correspond to the voltage range. Im a n00b in this field and Id hate to fry any components trying to figure this out without guidance, my main concern is making the voltage and current safe for the arduino, so I need to know any additional components necessary to make this work. I know  I need to implement a voltage divider, etc to bring the voltage to a range the arduino can handle but do not know if the 1/4w resistors I have on hand will suffice. Id appreciate any feedback on how to hook this up and even more so anyone able to provide sample code and/or urls with hints to get this working.

Asked by cwbuckner84 8 years ago

can measuring power from an electric fence kill your voltmeter? Answered

I think I may have killed my digital multimeter by trying to test the voltage pulses from my electric fence.  The fence was powered by a small charger, a Zareba .05 joule pulsing model, but soon after testing the voltage, I started getting extremely low readings on anything I tested, from a car battery to wall current.  Clearly it didn't blow the fuses in my meter (an Ideal 61-360) since they still registered power inputs, but just as clearly, something is very wrong with the meter now.  Any clue as to what might have happened?

Asked by tomasaur 3 years ago

I'm making a voltmeter for household batteries, what resistor values should I use on the input? Answered

So I've made a voltmeter, a basic outline is it has a different amp as the input, this feeds into an ADC DCA feedback system to find the accurate value. It works fine as it is but the purpose of it is to find the voltage of household batteries. I have heard that for this I will need to use large input resistors on the difference amp so that the voltage measured is more accurate when the battery is near depletion or something like that. Is this true? If so could someone explain it to me or send me a link to somewhere that does because everything I've found so far seems to be vague. I link would be great regardless as I need to show evidence of what I've found. Thanks in advance.

Asked by TomV48 2 years ago

Wiring Digital Voltmeter Ammeter Without Shunt

I have this: They say is can it be used up to 10 amps without a shunt, but I can't find wiring diagram. I am trying to wire into 50 watt led light. I know the small red and black go to power source. I am not sure how to connect 3 thick wires( red, black, yellow) without a shunt. I am only trying to meter 1.5 amp circuit.  Here's what I am trying to wire. Thank you

Posted by flatfish 4 years ago

How can I use an Arduino to record the voltage of an RC circuit??

Complete noob here.  I would like to lay a simple RC circuit out on a breadboard, and use the Arduino's analog input to look at how the voltage changes across the capacitor as the capacitor charges.  I've studied the theory -- I know the graphs and the how to calculate theoretical results, but I want to see real data so I can work with my own numbers.  (I have already used the analog input to measure voltage from sensors so I feel as if I have a decent understanding of what is required for that)  Of course I could go buy a voltmeter, but where's the fun of that?  Thank you in advance for any help.

Asked by Slicklines 7 years ago

How do I to put an mA meter and V meter to my 12v 1.7A regulated power supply with loads that start at 1mA up to 15mA?

I have aregulated power supply 120VAC to 12VDC & 1.7A to operate small coreless motors that start rotating at 1-3mA operating up to 13mA and need to add a mAmeter, trim pot, rheostat and fuse. How?

Asked by SirDeClare 2 years ago

Modifications to LED Bar Graph Volt Meter for 12volt batteries(and Battery banks) Answered

Hi I found this LED bar graph voltmeter at want to understand how to build this voltmeter.But please read the solorb website page before posting, for more info.1. What is an offset resistor???2. What is a 'span'(see pic notes)2. For 12v operation,short J2 and J5,but what to do to all the other unconnectd 'J 'wires, just join the wires or what?3.To use without the Blue LEDs, just remove the two LEDs or any other connection/shorting is required????4.What is switch S1 used for ???, I do NOT want to manually push switches while the meter is in operation.5.How to stop the blink-LED mode, I want the constant display mode always.6.There is also two arrows shorting two pins on the IC with words 'Adjust for 12v'?????????7.How to calibrate the circuit accurately???PS:- If you want to know more about a larger part of this project,visit

Asked by mhkabir 8 years ago

Fluctuating voltage?

I am trying to build an ammeter using a 100:5A CT and a pic16F716 and display the value using 7segments. However, The voltage I get from the CT after rectifying it using an OPAMP still fluctuates between 4.8 and 5.4 .  I don't understand what is causing it to fluctuate that way. I will attach a picture of the circuit I am working on.

Asked by IndiraK2 1 year ago

Good voltmeter ICs? Answered

I would like to make a readout for my knob-controlled DC power supply so I don't always have to use the voltmeter with it.   Web search for "LSI DVM" did not produce useful results. What are some good ICs to use for something like that?

Asked by 8bit 8 years ago

Low voltage AC?

How can I make a simple circuit that will produce alternating current using 1.5 to 9v power supply? This is an experiment for using an AC voltmeter - that is, making the needle move.

Asked by brandegor 8 years ago

How do i make a coil? Answered

The might sound a bit childish but i want to know about a coil. I am currently making a voltmeter(analog).I need to make a coil for it. I have a magnetic wire(around1.5 meters).Every time I make a coil out of it and supply it with power the battery shorts. I get no responce from the coil(like it does not attracts or repels a magnet or nail).So how do make a correct coil for my voltmeter and how do i know weather it responces.

Asked by flyingdutchmen1659 5 years ago

voltmeter and ammeter

Hi guys, could someone help me with this thing,

Posted by mammotz 6 years ago

Arduino 5x9 led display and 0-10V voltmeter. Answered

Arduino Duemilanove ATmega328 I want to make a 5x9 led display that monitors a 0-9.99VDC source for a huge motor. I would like to display up to a hundredth of a volt. I would like to do this all using 1 board. I plan on having it display the 3 digits using the 5x9 led display. Can I do this with the limited pins I have without using a shift register? (I think thats what it is called) Do I have all that I need? I have some knowledge of electronics but am in the learning stage but this project will help me a lot in my everyday life. This will be used to monitor a DC water turbine for my pool. I have: -tons of LEDS -Arduino -tons of resistors

Asked by newrev426 7 years ago

How to build a joule thief? Answered

      I'm building a voltaic cell and a joule thief. I searched on some instructables and followed the one on youtube by MAKE:. When I hook up a 9V for a few seconds (To not burn the LED out), it works. However, a AA doesn't work. Not even a brand new one. So, I presume that I haven't wrapped the toroid around enough to create more voltage and lessen the amperage (If that's what joule thieves do)? I posted some pictures below. Also, I'm looking to buy a voltmeter, I'm around basic level and just need to measure if the joule thief is even increasing voltage (For now at least). Here are some cheap ones I'm looking at on amazon: Some of those have autoranging, is this to automatically find the voltage/amperage? Thanks, please reply

Asked by knexpert1700 4 years ago

How do I create/buy a 0-9v LED Voltmeter?

I am doing a school science fair project and I need to create/buy a LED Voltmeter. It will be hooked up to a DC motor that is connected to my bike. This DC motor is producing about 0-9v. This LED Voltmeter will be used to display how much power is going to be made.

Asked by 7Chris Crash 9 years ago

HP 3400a True RMS Voltmeter?

I have had one of these for the longest time and I really know very little of what it is used for.  It seems to work, but it does not appear to measure like a normal voltmeter, you can't just set it to the 30v range and hold the leads against a 9v battery, you seem to have to pulse it.  Does anyone know about them?  How much are they work because I was thinking of selling it and I have everything for it, the unit, the power cord, test leads, a manual etc. Any info on it or how it works would be appreciated! Thanks

Asked by Electric Spectre1 5 years ago

How can i make a 4 to 9v voltmeter using lm3914 and how to compute the resistors?


Asked by JmM1 2 years ago

How do I use the LM3914H bargraph voltmeter circuit to switch 2 amp, 12 VDC loads instead of LED's?

I'm thinking either power transistors or relays instead of the LED's, but designing the actual circuit is a little beyond me. I'd actually like to build two of these and use the second to measure DC current of 0 - 20 amps, I'm thinking measuring the voltage drop across a shunt resistor...

Asked by stevekrawcheck 5 years ago

Adding a volt meter? Answered

Is there an easy way to add a voltmeter to this project so you can tell how much charge is in the battery?

Asked by ddibling 7 months ago

Any cheaper way to find out voltage Answered

Other than a voltmeter. They are like $200 and I don't want one that bad.

Asked by Chromatica 8 years ago

Overvolted multimeter?

Hi.  Simple question. (or maybe not) I have a digital multimeter I bought a while ago that I think I accidentally put too much voltage through. The voltmeter function on it is now broken. Whenever it's turned on, it reads "156 VDC" even though no voltage is being applied. (however, when I do apply voltage, the meter does detect it.) All other functions seem to be working correctly, but I'm bummed because the voltmeter is what I use the most. Is there any way to "reset" a multimeter? if not, is there anything I could try to fix it? Thanks in advance.

Asked by tylervitale 5 years ago

bulding a generator?

I have a 5sme22nj028a general electric motor and wanted to buld a generator.  It is 10 pin (not including earth). I have used a voltmeter to see what generate but there are many combonations and they all seem to generate. Also it is brushless. Please help.

Asked by David97 7 years ago

I cant find a voltmeter that detects minimal voltage to prove the success of a Baghdad battery Answered

I am using copper cylinder, iron rod, cork (to seal and stabilize), and an electrolyte - probably red wine vinegar. I am using a glazed vase to house it.  It all assembles well.  The model I am following, from a youtube video produced .4 volts.  I cannot find a tester that detects such low voltage. Can one be recommended, or, is there another way to demonstrate the voltage? any response to this question or in general would be greatly appreciated.  Helping my son with a science project.  thanks, brad

Asked by bradleestoller 6 years ago

I have continuity in both coils (AC-DC) but no power output?

I have a 12v 2A transformer without power outputI testes/checked with a voltmeter both coils (AC-DC) but no V+ output

Asked by MarcosM117 7 days ago

What to do with this 'mystery machine' to turn it into an sci-fi monitor/screen/prop that's alive? Ideally, stand-alone? Answered

You're looking at a photo of what I came to call the 'mystery machine', as I've no idea what it's real purpose is exactly. I suspect it's an old, big multi- or voltmeter. As I say in the question, I'm looking to turn it into an sci-fi monitor/screen/prop that's 'alive' somehow; continually generating interesting content. What I'm thinking of is replacing the big, central meter with a monitor/screen of somesort. But, what kind? Ideally, this'll be easy to make, stand-alone and cheap.

Asked by Hellwolve 5 years ago

I have continuity in both coils (AC-DC) but no power output?

I have a 12v 2A transformer without power outputI testes/checked with a voltmeter both coils (AC-DC) but no V+ output

Posted by MarcosM117 7 days ago

variable load DC volt meter?

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

Posted by Menthol 8 years ago

How to rewire from a three phase motor to a 240 volt single phase motor.

I am replacing a  40 year old three phase motor with a 240 volt single phase motor. The three wires are all black and not coded in any way. How do I measure with a voltmeter? I assume one wire is neutral, but which one? Thanks.

Asked by beachbum2006 8 years ago

Compaq Presario v2000 Laptop Doesn't Turn On?

Hi y'all! I need a little help. I'm trying to fix my uncle's laptop. It is a Compaq Presario v2000 Laptop. It will not turn on or show any lights on the front(e.g charging, power up, ect.). I have tried blowing out the motherboard, removing and inserting the battery, and testing the DC power jack with a voltmeter. Any help will be appreciated! 

Asked by joespicnictables 6 years ago

test a power wupply without a voltmeter

OK so yesterday i got this broken laptop from someone.  I knew the problem was the ac jack ( it would charge if the the jack was proped up in just the right way) but only if I used a power supply that did not come with the computer.  I have never soldered anything in my life but figured what the heck.  I took the laptop apart and located the AC jack.  Since I do not have the cash flow to buy a new AC jack I decided to experiment and just reflow the solder on each post of the jack. Well things went well.....I think.  The problem is this.  When I plug in the power supply the "charge" led comes on for just a second or two and shuts off right away.  But there is further information about this power supply.  It is putting out 3 volts less then the original power supply.  Could this be the cause?  The think the OEM power supply is dead because I have nver been able to get the computer to do anything with that one.  Is there a way I can test this power supply without a volt meter or any other product to plug it into?

Posted by jcaresheets 7 years ago

LED Strip connected to car 12v port and isn't lighting up?

So i bought an LED strip which was rated at 12V, i connected it to the wall and they lit up, i then got a car charger which was 12V and wired it up, and they don't light up. The car charger itself has its indicator LED glowing and i checked with a voltmeter that it was supplying the 12V. I cannot seem to figure out for the life of me why they aren't lighting up? Any ideas?

Asked by marcelrees 1 year ago

What is a good schematic for a multimeter with an attiny85v and some 7 segment leds?

I want to make a multimeter out of an attiny85v, and some 7segment leds for a 12volt power supply that I made, I would like it to measure from 0.0V to 12.0 volts, with an accuracy of .1 volts. Anyone know any good circuits? EDIT: This is what I am looking for, except the author has not included any code

Asked by Michael_Bell 5 years ago

SLA Battery Charging? Answered

Quick question about charging SLA Batteries, I haven't really dealt with battery charging too much in the past.  I have two 12v 5Ah SLA batteries, in series, and I have built an under/over voltage protection circuit for each of them, but while charging I noticed that testing voltages across each battery, they are different, however, as soon as I remove the charger and test them as is, they have the exact same voltage (+/-0.05 volts, they are very close).  Is this just because the charger is hooked up, or should I be worried at all about that? I am charging them to 14.75 volts each, or would like to, they say they should be charged to 14.5 to 15v right on the front of them.  While charging they both climb, but one climbs faster and stops once the voltmeter reads 15.2v across it.  0.2v over the rated value really doesn't seem to be of major concern, I just find it odd the different voltmeter readings across the batteries are different while the charger is connected and identical when its not.  Does it have something to do with charging them in series?  I did read that you really can't measure batteries while charging, you have to disconnect the charger first, but any insight would be appreciated.

Asked by Electric Spectre1 1 year ago

Problem with my variable regualted dc power supply.

I have a used variable voltage regulated power supply that does not work ; when i turn it on, the Volt meter tops, and if I switch to ammeter, it shows 0amp, if i plug a voltmeter on the female banana plugs there's no juice... I've checked the fuse, it is not damaged. i've also checked to potentiometer with my ohm-meter looks like it's working normally. I don't know what is wrong with it... Do anyone have any idea ?

Posted by lordofthedonuts 9 years ago

Audio signal help? Answered

I was going to build Amplifier with Gain = 20 Minimum Parts From this datasheet But I have no Idea how to put the signal on. I think that the signal is Vin (pin 3)  but that is one cable when a headphone has three cables. I know the red wire is right and the blue is left and the other is comm so I onley need 2. Because there is one input I need to make it one cable. Would this work (I will test what resistor I need with a voltmeter later). If I am wrong about there olny being one input can someone explane to me how to wire it.

Asked by David97 6 years ago

How many LEDs rated at 5V can I use on a 6 Watt Radio Amp?

I there, I have a 6 watt radio amp that if I used the Voltmeter correctly is only really using 1.3 watts at it's highest volume on the busiest song.  I want to add LED lights to the dial and I'm wondering how many can I use?  I purchased LED lights rated to a max of 6V and the engineer told me that they can be used for a 5V power supply.  I would like to use as many as I can in series and will like to learn how one comes up with that number.  Thanks

Asked by javierdiaz4 3 years ago

Really small analog gauge controlled by simple circuit

I'm looking to make a steampunk version of dr who's sonic screwdriver with some LEDs, a tiny recording module for the sound, and I also wanted a little analog gauge with a needle that would activate when the button was pushed. It doesn't have to actually measure anything, I just want the needle to move in some way. i found a little voltmeter on sparkfun that I could probably repurpose, but it's 2x2 inches which is a little bigger than I wanted.  I'm looking for something about half that size. Does anyone know of anything that would fit the description, or a way I could fake it?

Posted by sasham43 4 years ago

what does a #131 error mean on an Msntv 2 receiver?

Recently I picked up an Msntv 2 at a local goodwill, and when I took it home and tried to power it up, nothing happened. When I opened it up, I saw that two capacitors, both 470uf 16v low esr, had blown. After ordering the caps on ebay and waiting two weeks, they finally arrived. Today I attempted to replace the capacitors with my 40 watt soldering iron, which turned out to be quite a challenge, so I guess i need a more powerfull one in the future. I thought that I had totally destroyed the board connections on all four holes for both the capacitors by the time I had finished soldering, but nevertheless I plugged it in and this time it powered on but went to a green screen that said there was a problem with my receiver and gave me the error code #131. Because it powers on now, I kn ow that at least one of the capacitors works. I have a couiple of questions now to help determine my next move. First, can i check the capacitors by simply checking for voltage with a voltmeter? second, What does an error code 131 even mean? Third, could the error be because I dont have the msntv service? any help would be appreciated! Edit: I just checked the capacitors with a voltmeter, and they had a voltage on them so i dont think that that is the problem. Could it be a problem with the compact flash card where the files are stored?

Asked by danielemur 5 years ago

Please, help me with this 3_state switch !?

ANSWER : so, at the end, it was a switch. I had to do it the hard way :( have a look at the last picture. Hi, could someone help me with this 3-state switch ??? I would like to remove it from the PCB, solder some wires and make ARDUINO + MOSFETs to control it = instead of me, manipulating the switch, I want the arduino to do that for me. Unfortunately I'm not able to find out which PINs I have to connect together to simulate the switch. I did some measurements and make matrix - if it could help to find out which pins to put together. Thank you in advance. Zholy P.S. : The voltmeter was set to 2000mV, and the RED_positive probe was attached to the NUMBER pins

Asked by zholy 7 years ago

Can anyone please tell me how to wire my flyback tranformer up to make a high power source for a tesla coil. Answered

My flyback transformer has 9 pins at the bottem and is a "L40B02510 MSKK SANYO" I was hoping that i couuld just attach the + to one pin and the - to another pin (using one 9 volt battery) then add a ground to another pin.But im sure its not that easy if it is please tell what pins to use. I dont have a voltmeter to find the primary and secondary. I really need help and please dont send me link that will have me searching all over the internet i have spent weeks tyring to get this to work and nothing works.

Asked by talbayaty 6 years ago

Building a genertor? Answered

I have a 5sme22nj028a general electric motor and wanted to buld a generator. It is 10 pin (not including earth). I have used a voltmeter to see what generate but there are many combonations and they all seem to generate. Also it is brushless. I have posted this question before but fogort to include that the motor says varable speed on the side. I was thinking that connecting diffrent pins would make the motor go at diffrent speeds. In my other question someone said that it may need a mirco prosser before it. I think that this is probaly the case but wanted to see if anyone knew about this motor. So if it needs or doesnt need a micro prosessor before it, please tell me. I should be able to work it out from there. Thanks

Asked by David97 7 years ago

Charging capacitor from rectified mains? Answered

Recently my father brought 2 6400uf 400v phillips from his work. i want to charge it with rectiried mains. will be using them in paralell for coilgun  1) what is the voltage of 220v mains when rectified?(my voltmeter bunt) 2) when i try to charge them directly from a rectifier it melts my wire due to current. unfortunately i donot have a high power resistor to limit the current. How can i solve this without buying a high power resistor? 3) I want an led to light up when the voltage from the rectified mains is attained. 4)what will be the best. a 55 amp relay or a 75amp switch. i know that the switch can handle much more current but will the switching be quick  enough?   thanks in advance.

Asked by ARJOON 7 years ago

What am I doing wrong ??? Arduino - tachometer !? Answered

Hello ... I would like to ask, what am I doing wrong. I'm trying to create this instructable ... I downloaded the code, created the circuit (photo provided) ... and I'm using these components :  1. IR LED = SFH487-3 (code CY88)  2. Phototransistor = SFH300-3 (code NP64) Resistors are the same value, like in the instructable. Please, could you tell me, what am I doing wrong ??? Thank you very much. Zholy P.S. : IR LED is working, the PhotoTransistor is working as well

Asked by zholy 8 years ago

how can i find out which part of my charger is malfunctioning? Answered

Hello, I am desperate for help. I have a PWR+ charger for my laptop I purchased a few months ago, today it stopped working. What happened? well the charger still has some function, when I checked it with my voltmeter the output varied from 3 to 6 volts, the little LED on the charger was pulsating, not rapidly, but in short 1 second intervals. Could this be a problem with the voltage regulator? The required amount of power that a normal charger for my laptop outputs is a steady 14 volts, not sure about the current. Now my charger is useless and I don't want to spend another 30 bucks to get a new one, please help. Thanks in advance.

Asked by nahum45 6 years ago

Solar panel short reads 28v? yet charge controller reads 14v? Batteries?

I have a solar panel that I picked up on internet for free due to damaged glass(no biggie).  Placing a voltmeter across the output leads has 28.6volts.  I connected this to a PWM charge controller recycled from a junk yard.  I set the CC parameters to 24v and hooked up two 12v car batteries(13.2v good) in series to make my 24v circuit.  Now the CC digital panel reads 14v.  Checked all the connections and retested the panel, two batteries and CC. It checks out ok. But why does the CC readout at 14v in full sunlight? yet the panel reads 28.6v? The only thing is the two batteries are different in AH ratings. One is 96 Ah and the other 115Ah.

Asked by JuG2 1 year ago