I request your help with an ADC conversion interface to digital readout display

[Sparks51]

Hello Gents,
I want to connect an ADC with an 8 bit output to a digital counter but am stuck trying to figure out the interface circuit between the two. The input to the ADC will be a range of zero to 3.27 volts which I would like to equate from zero to 100, (or actually 99), as indicated by the digital readout.

I've done allot of research but just can't seem to find the info I need. Any help will be very appreciated!

Thanks!

 

[Papabravo]

You need to give us more information. How about a part number for the A/D converter. When you say a digital counter, I picture a laboratoy instrument. Without using a microcontroller, such as a PIC, I think you will have an enormously difficult time accomplishing your task.

Sounds like you want a voltage to pulse train converter. For example if the ADC reds 47 you output 47 pulses. I don't know how you would clear the counter for the next reading, but there has to be a way.

 

[Sparks51]

RE: ADC interface

First, Thanks Papabravo for your help!

This is my first A/D project so please hang in here with me, thanks.

I do not have a specific numbered A/D converter picked out yet other than thinking I would like a flash type. I'm open to suggestion though.

By my calculations an 8 bit, being the most common, should be needed to accomodate the amount of voltage counts/steps that I need to read. That being 100.

About the digital counter, sorry I should have explained better. I indend to used the standard pulse train to bcd decoder to lcd driver type system. Here again I'm open to suggestion.

Yeah I was starting to think a micro-controller of some type might be the way to go. Along with project cost, ease of construction is a concern. It would be desirable if there could be some sort of reasonable balance.

You are right, some sort of pulse train converter.

Thanks again for your thoughts!

 

[Nigel Goodwin]

As you've already thought about, a micro-controller (PIC or other type) would make this a trivial project to do - requiring only the one PIC, and very little else.

Depending what you're trying to do (which you don't tell us), you may be able to use a simple LCD meter module?, these are freely available and just require a couple of resistors to set the range you want.

 

[Analog]

Well suppose you pick an 8 bit converter that has a Full Scale voltage of 5V. That means when you get all 1s, you're at 5V, or 255 binary = 5V. Since you want to get 3.7V = 100, a little math says you need to attenuate your input signal to scale it appropriately. i.e. the A/D's value of 100 counts represents 1.9608V. Therefore, if you build a simple resistor divider or op-amp attenuator to get you to this level, then it becomes a simple 8 bit output that you can interface via TTL, PLD or other glue logic to a display.