# digital io variable

Discussion in 'General Electronics Chat' started by jismagic, Apr 28, 2014.

1. ### jismagic Thread Starter Member

Sep 7, 2013
77
0
Hello,
Do you guys know anything like variable voltage digital io.
Normally using a dio card gives an output 5v Or 0.. I will need all sorts of voltage 5v-24v.
Seen something like that?

Thanks
Jis

2. ### MrChips Moderator

Oct 2, 2009
12,636
3,454
There are a number of ways of achieving this. You need to tell us more of what you are attempting to do.

On way is to get a DAC (digital-to-analog converter) board.

3. ### jismagic Thread Starter Member

Sep 7, 2013
77
0
Thanks for reply..I am interested in generating finite number of digital output for a test equipment. Its easy to buy this from market. But I do get this only for digital voltage range. But I need voltage range 5 to 24v.
I should also be able to control individual output voltage..

4. ### MrChips Moderator

Oct 2, 2009
12,636
3,454
Hundreds of commercial boards are available or you can build your own. Google DAC board. How much current do you need to supply?

5. ### jismagic Thread Starter Member

Sep 7, 2013
77
0
The current will be max of 20ma per channel

Jan 3, 2012
26
4
7. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,505
512
The conventional approach to digital is that you have two values, On and Off. You can represent these two values in many ways, one example is that Off is 0 volts, On is 5 volts.

The fact that you want more than two values tells me that you don't want digital.

What you want is digital CONTROL. This is very normal. Normal people use Digital to Analog Converter (DAC) to accomplish this task.

8. ### jismagic Thread Starter Member

Sep 7, 2013
77
0
What I meant by "variable" is my digital ON can be 3V,5V,12V,13V,15V or even 24V.

Individually controlling mean , one digital output can be 0, other one can be 3V, third one can be 15V etc.

thanks
jis

9. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,505
512
That is what DAC does.

10. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
428
why not use a proper voltage rated open colletor output buffer? then all you need to do is feed the voltage you want to make the 1's to the pull up resistors.

11. ### ScottWang Moderator

Aug 23, 2012
4,933
777
The output of your DAC card adding a LM358 to amplifing the voltage from 0~5V to 0~30V, and the gain set to 6.

If you afraid of the current od op amp is not enough, then you can adding a bjt to amplifying the current.