Sending a voltage from the DAQPad 6020E to a 5V relay

[auratech19]

I'm having some trouble with the DAQPad 6020E (the one with the 30 digital channels).  I'm trying to make the 6020E send a 5V signal to a relay.  When the relay recieves the 5V signal, it switches on and allows a 12V signal to pass from my power supply to a solenoid pinch valve.  When the pinch valve receives the 12V signal it opens up.  The problem is that  the DAQPad crashes after I switch off the 5V signal flowing to the relay.  The relay switch opens and cuts off the 12V signal to the solenoid valve.  Sometime I can open and close it a few times before the DAQPad crashes.  I know the problem is the DAQPad and not the circuit design for the pinch valves because I can send a 5V signal from a power supply and it works fine.  For some reason the DAQPad is crashing while connected to my circuit after I tell it to send a few of these 5V signals.  Also, the DAQPad will not crash if it is not connected to my circuit.  I tried sending some 5V signals to a multimeter to see if the DAQPad would crash and it did not.  So, I think there is a problem occuring between my circuit and the DAQPad.  Any help would be greatly appreciated!

[AnalogKid2DigitalMan]

Can you attach a sketch or schematic of how everything is wired up? What current does the 5V relay draw on the coil or input side? Im not familiar with the DADPad- what do you mean by 'crashing'?

Thanks

[Conseils]

Have you put some flyback diodes on the solenoids and relays....
Think about back emf's  http://en.wikipedia.org/wiki/Back_emf
Solenoid (http://en.wikipedia.org/wiki/Solenoid)

Make sure you put them in the right way round otherwise you will create a short circuit.
A couple of 1N4005 should do nicely.. and should stop the system crashing.

[auratech19]

okay, so here's a rough sketch of the circuit.  i'll try placing a IN4005 flyback diode between the solenoid and relay to see if that helps.  thanks for all the help.

[Dennis_Knutson]

ACROSS THE COIL!

You may already have damaged the daq board.

[AnalogKid2DigitalMan]

Would like to know make and model of the relay so we can figure out if the DAQ card even has enough current to drive the relay.

The common pole of the relay should also not be wired to ground!

[AnalogKid2DigitalMan]

Here is what I propose

[SteelStonehenge]

That's just what I was going to suggest.  Sounds like a spike is feeding back to the DAQ card

eric

[auratech19]

alright, I'll try setting up the circuit with the diodes the way you suggested.  thanks for the help Analog!  i don't think the board is damaged, the DAQPad still sends and receives digital signals fine when it's not connected to the circuit.  still, any suggestions you have are greatly appreciated.  i'll let you all know if the current solution solves the problem.  thanks again!

kyle

[Conseils]

You were asked some very pertinent questions by AnalogKid on the relay type you have connected to the 5v digital output line.
You would be well advised to consider responding to his kind offer, as it's likely that you are under driving the relay and at worst case potentially damaging the output line.

Note carefully the comments made by Dennis, you could already have caused some damage to the board.. watch out for early or random failures.

Finally a few stars would not go amis ..... see the bottom right of the messages.
Especially as AnalogKid  kindly offered to model the circuit for you and posted a nice diagram.

Finally what form does the power supply take for the 12v solenoid. Does it have enough current to handle the 'inrush' current as well as a continous rating for the operation required in your application.

Whilst the quality of the responses you will receive will be nothing short of superb, to a large extent they are limited by the information you can provide.