han_5583 Posted June 30, 2008 Report Share Posted June 30, 2008 Hi guys, I'm a moderate labview user and I have done a few project before. My current project is about generating PWM signals to control the rpm of an electric motor. When I simulate the signal I can see the generated PWM clearly on the virtual graph, but when I connect it with the DAQ assistant (analog output), the PWM signals suddenly run very slow. I suspect I dont provide enough buffer to the output, but I dont know how to increase the buffer size. Currently the PWM signals does not go through the DAQ device. Anyway, I'm using USB-6008. Please advice. Quote Link to comment
crelf Posted June 30, 2008 Report Share Posted June 30, 2008 QUOTE (han_5583 @ Jun 29 2008, 05:09 AM) the PWM signals suddenly run very slow. Show us your code. Quote Link to comment
Karissap Posted July 1, 2008 Report Share Posted July 1, 2008 What output speed do you need? The USB-6008 is a low cost USB-DAQ, it doesn't have buffered output and has a software timed output sample speed of only 150Hz. Other high performance USB Daqs will give you a high speed buffered output. For example the USB-6211 outputs at 250kHz with a buffer size of 8,191 samples. Quote Link to comment
han_5583 Posted July 1, 2008 Author Report Share Posted July 1, 2008 this was what i have done. Quote Link to comment
LAVA 1.0 Content Posted July 1, 2008 Report Share Posted July 1, 2008 QUOTE (han_5583 @ Jun 30 2008, 07:48 AM) this was what i have done. => you are using the analog output... QUOTE (han_5583 @ Jun 29 2008, 11:09 AM) USB-6008. Please advice. => Analog Output rate 150Hz... => your time target is 1 second so that's the reason why it runs with 1 Hz... => change the target time of the express function (add an input, to see what happens when you decrease the target time) => place a "wait" in your loop... => use the stop input from your express-daq vi => the express functions produce some "overhead" Quote Link to comment
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