How to Output an Square Wave on a 1124?

[Scott S]

I am using an 1124 Module in conjuction with a 1325. I am new to Labview and I am still learning, however I have hit a huge bump in the road. I am trying to design this so that it will output a square wave, particullary a PWM Signal. However, everything I read said that there is no buffer on the 1124, only point by point...is this going to be a problem for generating this kind of signal. Thus far I have successfully gotten it to output a DC Voltage.

[Russell]

This is true. The 1124 will only output DC Voltages. By saying it will output only "point-by-point" this means you must continually use the software to change the output voltage. The voltage can change only as fast as your software can run. This is different from a buffered, hardware-timed output where an array of datapoints could be stored in hardware while a clock moves them out sequentially.

So I suppose you could still generate a PWM signal, but it would have to be at a very low frequency. However, you won't be able to use the 1124 if your program cannot perform point-by-point updates that keep up with the required rate.

We do have a solution as far as isolated analog waveform output. There is the NI SCC-CO20 isolated analog output signal conditioning module which you must use with an E-Series board, but you can only get up to two channels per board.

In your case, since you just want a square wave, I would use a PCI-6602 counter board and some optical isolators.

Russell

Applications Engineer
National Instruments
http://www.ni.com/support

[Scott S]

One last question. We are using a    
NI PCI-MIO-16XE-50 DAQ card. I understand that 4 of the D igital I/O lines are used by the SCXI, so that leaves 4 left I can use. Well if this is true, and I try to use those, will the output on those also be limited by the cpu. Thanks.

[Russell]

Yes, those digital I/O lines are also "point-by-point" which require software-timed updates.

Russell

[Scott S]

Thank you...