myDAQ, Increase Digital Output?

[SNorrell]

Thanks y'all, I'll look into the driver circuit you're suggesting. 

Any thoughts on getting the analog-out to work? Or is that still too small of current anyway?

[Dennis_Knutson]

The analog output does not have enough current either though you can at least set it for the correct voltage. I don't understand why you are using a 3 volt part. Why was this specified for your project? Was it just something laying around your college lab? Did anyone consult with an electronics major?

[SNorrell]

The relays were recommended to us by the electrician in the department. The 3V coil seems to work fine with the constant 5V from the DAQ and, with Tom's suggestion, I was able to get the relay to switch by connecting 5 of the DOs to each relay (since we have 2 myDAQs to use, we have enough DOs to power three!)

[SNorrell]

I would rather get one DO for each relay, but, under our time crunch, I think the multiple DOs per relay might have to do. I'll be talking to our department's electrician today about the relay driver.

Thanks for all the help!

[RavensFan]

Does this electrician know anything about DAQ boards?  Or does he just know black to black, white to white, and don't cross them?

I think you are in danger of burning out those boards even if it seems like it is working now.  For 3V, coils, you need 120 mA which is 30! digital outputs per coil (at 4 mA per output).  Maybe with 5V applied, you need less current, but it is still more voltage on that coil than it is supposed to have.

[Dennis_Knutson]

The spec sheet clearly states that you can apply up to 130% of the rated voltage. You've already damaged them by applying 5 volts. It's just s matter of time before you'll see little puffs of smoke.

[crossrulz]

Something you could do is use something like a 2N2222 to switch between 3V and ground on the relay coil.  You will need a 3V power supply that can handle the current you need.  You will also need a 5V digital buffer since you will need more the 4mA to cause the transistor to turn on, meaning you will need a 5V power supply as well.

What are the relays switching?  I'm sure we can come up with a much better solution for you (ie a relay that works off of 5V coil).