how to control valve via PCI6023E and labview

[buddha]

I have a PCI6023 board and labview 5.1. I need to control the opening/closing of a gas valve via these two.The problem is that the power needed to operate the valve is 24 volts while the PCI6023E board has the power of only 5V. What can be done? Please help.

[Doug_Norman]

This is a very typical senario. PC DAQ boards cannot drive much in the way of output because they get their voltage and power from the PC. One solution would be some type of National Instruments relay module. In the past I have used the ER-8, SCC, and SCXI modules. Each has its own advantages depending on your complete system. You will typically have to provide your own 24 volt source. If you are looking for a more home grown solution, I have used a couple of approaches before. One is to connect directly to a relay - the key here is it has to have a coil that can be driven with 5V TTL. I don't know a part number of one off hand. The second approach is to use a slightly bigger relay and actually drive its coil via a simple transister(TIP-120) circuit. L
et me know if you need the circuit. Again, both of these approaches require external power sources.

Best Regards,

Doug Norman
doug.norman@ni.com

[Jonnie_5]

Run a secondary power supply to the valve via a transistor triggered by the DAQ board. You can get a cheap AC/DC wall plug in supply for a coupla bucks and transistors are a few cents.

/ <---- 24V2Collector
|
DAQ2Base----->|
|
\ -----> Emitter2valve

[buddha]

Yes please,I need the circuit.
Thanks .

[Doug_Norman]

Here is the circuit. You'll notice I originally did this for PWM (pulse width modulation). You will want to connect your digital output to where I show the analog output from the DAQ board. You will also want to replace the DC motor with your relay coil (or you could even directly power the valve coil). Whether you choose a TIP120 or TIP140 depends on the amount of current you need to drive. The TIP140 can handle more, but I don't have the specs off hand. This file is a PowerPoint slide. Let me know if you'd rather a Word document.

Regards,

Doug Norman