Seeking a Freelancer to help create test board

Community Jobs and Paid Consultancy
1

Hi Arduino Community,

I have an informal background in software but know extremely little when it comes to electrical engineering/electronics. I am working on a project and was curious to see if there are experts/freelancers out there who do 'gig' work and would like to help me.

Essentially I am looking for someone to create a test board that enables me to do the following from an Arduino processor w/ USB connection (specific version/type doesn't matter to me but the more popular the better):

  • Control a true analog output voltage from 0-5v on a PIN (not PWM)
  • Include a wheatstone amplifier for a load cell so I can measure push/pull from a strain gauge

And that's it! I know it's so ridiculously simple you're wondering why I am asking for help. I went down the path of getting a Zero and an M0 and buying a wheatstone shield from a 3rd party website. What I've learned is:

  1. I can only find boards that have a DAC output running at 0-3.3v like the M0 (not to the 5v I require)
  2. The wheatstone shield I found is interfering/doing something with said analog outputs above causing them to not work

Anyone interested in helping? I am happy to pay for your time. I assume this is really "easy" for someone who knows what they are doing... :slight_smile:

-Blake

2

balke_macho:

  1. I can only find boards that have a DAC output running at 0-3.3v like the M0 (not to the 5v I require)

Then get a DAC that can do 0-5V. Can't believe they're not available.

  1. The wheatstone shield I found is interfering/doing something with said analog outputs above causing them to not work

That's too vague a description with far too little information for any sensible comment.

3

Hi Blake,

have you considered using a digital potentiometer across the 5V rail and using a transistor to give you more current if that is an issue.

try this reference

Cheers Pete.

4

wvmarle:
Then get a DAC that can do 0-5V. Can't believe they're not available.

That's too vague a description with far too little information for any sensible comment.

I'll look into an external DAC or digital pentiometer as Pete suggested (thanks Pete!).

As for the "problem" with the wheatstone bridge shield: So with an M0 board's built-in DAC, I can control A0's output voltage from 0-3.3v predictably. However, when I attempt to control it with the wheatstone bridge shield on I always get a constant ~1.8v from the A0 pin. I assume the shield is "doing" something causing it to not work.

You'll have to forgive just how green I am here!

-Blake

5

OK so break this down into its component parts.

First you take to OP from the bridge and turn it onto a value that you can send out of the serial port. Doing this you can test that that part works independently of the DAC or DIgipot part.

If you are getting reliable reading from the bridge then do the same for the DAC or Pot and see if you can control the voltage with a simple for/next loop.

If both parts are working independently then post the code and perhaps someone here can integrate them for you.

Cheers Pete.

6

Why don't you want to use a PWM DAC? You should probably address that so someone can offer appropriate help.

I designed an Arduino shield that, among other things, outputs a 12-bit +-10V bipolar signal. However, since it's meant for industrial use, it needs an 18-24VDC power supply.
You won't find it on my site since it was designed to address a specific problem but you can PM me if still interested though.