SCR Phase Angle control

[NCD]

Hi All,
I'm trying to produce a chopped sine wave to simulate an SCR controlling
mains voltage. The output
only needs to be a few volts with an positive offset.
I've thought of making a table of normalized values to represent the fixed
frequency sine wave(50Hz)
and to switch the output to a fixed level(offset) below a certain output
value. That way I can control
the trigger angle. Of course the trigger is reset when passing through the
offset value.
I'm I on the right track here or is there an easier way with a prebuilt VM?

TIA for you help

Nick

[chutla]

Greetings Nick:

You should be able to get good results with your technique. (You're essentially doing a poor-man's
Direct Digital Sythesis, when reading a pre-constructed table like you are doing) Another way to do this is generate a sine wave, using one of the sine generator vi's and then run it through a series of comparators (use comparison primitive) each with a different threshold. Add the values of each comparator output, and voila, this is your stepped wave. In this manner, you are simulating a "flash" A/D convertor.
Another way to do this, is to run a square wave generator (say at 400Hz) and MULTIPLY this by a sine wave at 50 Hz. This will give you a Sine wave modulated square wave, (or vice versa, since mathematically, they are identical!)


Eric

[NCD]

Hi Eric,
thank you for the ideas, I've been trying to get a square wave to chop the
sine wave but
I haven't had enough experience with LV as yet to figure it out. I'm going
to try to implement
you last suggestion, I'll let you know how I fair.

Thanks again

Nick

[chutla]

Try this lil' vi


Eric