Firing angle control of SCR using DAQ

[futboloholic]

Guys can i control firing angle of SCR using DAQ card and Labview?? If yes then how am i supposed to do the connection and how can i protect my DC (Low Voltage) DAQ card from High AC voltage so that it doesn't burn out. Is their any way to connect Labview and DAQ with an SCR of which i want to control firing angle using labview??
I am really sorry if my question seems stupid or isn't in the correct forum. I am new NI forums and i have just started out with Labview and Daq card. Please help me out people.

[johnsold]

This is probably the correct Board for your question.

You mentioned several key points, so the question itself is also appropriate.

Now the answers: Yes. and No. And Very Carefully.

Protection: A few DAQ devices have isolated inputs and outputs. Most do not. Use of an isolated DAQ can help with the protection issues. You need to evaluate the possible ground loops, periodic transients, and fault conditions to see whether the isolation is sufficient. There are two issues: Safety of personnel - that is, the person at the computer - and damage to equipment.  Also consider using pulse transformers rather than direct connections for triggering the SCR.

Performance: Do you need to adjust the firing angle on a cycle-by-cycle basis or is an average over half a second to a second acceptable? How much timing resolution do you need on the firing angle?  If you need things to happen reliably on timescales of less than a tenth of a second, you will probably need to go to a real-time operating system. The timing jitter introduced by any desktop OS will make fine control impossible.

Reliablity: What happens if the software fails while the power is applied to the high voltage part of the system? For example a DAQ device generating a continuous pulse train from a counter may see that pulse train continue even it the program quit unexpectedly. If this kind of scenario can create unsafe conditions, hardware safety controls (watchdog timers) may be required.

Can it be done with LabVIEW? Yes. Will it be easy or inexpensive? That depends on the answers to the kinds of questions above.

Lynn