How to I display voltage on a 7 segment display?

Okay, I've never actually come across this before or needed to do this but now i come to it, i realise I am really lost to it. What i need to do is display a 3 digit (hundreds eg. 342) number on three 7 segment displays. So pretty much I just need a 3 digit voltage read-out to be incorporated into a portable design. I've been looking around and have come across the Analog to Digital converters, and understand how they work, but I'm not sure how to incorporate them or to put it to any use. So if anyone knows or has a schematic or any information I could work off, please help. :)


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funlw654 years ago
Well, you need to start from somewhere...
What about using microcontrollers? Many of them have ADC (analog to digital converters) and are easy to program in Pascal language if that is easy for you.

Look at this project, is in French but you can use Google Translate:

It use a PIC12F675 8 pin microcontroller and some other components as interface.

And here is a nice description/tutorial about PIC12F675:

Maybe this will get you started in the microcontroller world.

Anyway, if this is oto hard for you, try to find similar projects based on the Arduino board.

Best regards
DustinEE7 years ago
You can try a TC7107. It's a 40 pin IC chip that will split up the voltage between 4 7segment LEDs into 1's 10's and 100's and only displays a 1 on the thousands 7segment LED allowing you to have 1999 be displayed.
kelseymh8 years ago
Is this a homework problem in a double-E class? If not (or even if it is :-), you should look up "digital voltmeter schematic" in Google. If you didn't realize that "voltmeter" is what you're trying to build, that might explain why you didn't find anything when you searched Google before posting this question.
pyroten (author)  kelseymh8 years ago
haha no it's not a homework problem. And yes i know I'm trying to build a voltmeter from scratch, i probably should have put it in the question. Erm, so far i haven't found much, and the possible chips i could use like the 7107 and 7106 aren't available to me. I was looking for something dead simple, with readily available parts. I can use ic's, it's just a matter of whether or not i can get my hands on them.
:-) Good luck! The thing is, you need a voltage divider (with high-precision resistors) to get the 0-9 volts, 10-90 volts, and 100-900 volts separated, voltage-based ADCs (or high-precision resistors with current-based ADCs), then seven-segment drivers to convert the ADC's digital output to lines output for the digits. The schematics on Google detail all of this.
PKM kelseymh7 years ago
you need a voltage divider to get the 0-9 volts, 10-90 volts, and 100-900 volts separated

I'm not sure I understand this part- given a voltage between 0-1000V how can you separate out the digits? I would have thought this problem just needs a 10-bit or greater ADC, and then I'm not sure how I'd turn that into three decimal digits in a simple manner (unless there are multi-digit seven-segment drivers that take that many bits of input). Could always display it in octal :)
pyroten (author)  kelseymh8 years ago
Thanks. Right, so i need to get each unit separated as you said. Then i need any? 7 segment driver like this. Do i need a driver for each unit and do i need a ADC (this one is my main option, for each unit as well?

Oh yea so will my chosen ic's work?
Thanks Heaps :)
Buddy im confused, what is it that you are trying to measure? i know this isnt an answer, its more of a comment. sorry
pyroten (author)  evildoctorbluetooth8 years ago
yup, what kelseymh said. I need a voltmeter from scratch to be displayed on 3 7 segments
So you specificly want to build one, as opposed to buying one? Digital voltmeters are quite complicated, and it would need calibrating. hope that hasnt put you off. ak
pyroten (author)  evildoctorbluetooth7 years ago
well yea. It's going to be incorporated into a portable device so i don't need all the extra functions a multimeter has. (I already have a multimeter) i just need as simple as it gets. So i can design the board as well to allow it to fit into my space. (dw it didn't put me off) :)
He wants to design a digital voltmeter for himself, from scratch.