Need a place to start...

[Jester009]

Hi,

I need to come up with a circuit to generate alternating currents. (Range 0-5A sinusoidal) It needs to be controlled through a user interface in the computer. I'm clueless guys. Plz help...
Give me a place where can start. I should admit that I'm a NOOB

 

[Jester009]

Anybody have any idea??

I have got three suggestions so far...
1). Using a triac with a PIC to control its firing angle...
2). Generate PWM and drive a half bridge with IGBT's...
3). Use an audio amplifier controlled by audio signal source...

I don't have an in-depth knowledge about any of these designs. Can anybody please comment on these... I'm kinda lost

 

[kchriste]

Can you give us an idea of what frequency and voltage ranges you want in addition to the 0-5A capability?

1). Using a triac with a PIC to control its firing angle...

This will give you a fixed output frequency and not a very nice sinewave at all.

2). Generate PWM and drive a half bridge with IGBT's...

This will do what you want, but is somewhat complicated for a noob.

3). Use an audio amplifier controlled by audio signal source...

This is will also work over a limited frequency range determined by the audio amp's frequency response.
You could use something like this with the audio amp:
**broken link removed**

 

[Jester009]

Hi kchriste,

Thanks a lot for the reply. This is going to be used to test relays, i.e. apply a specified current and measure the tripping time. I don't have a clear idea about the voltage I have to generate a 50Hz sine wave of specified current ranging (0 - 5A)

I decided to take the amplifier option. So I guess the basic block diagram should be like this...

**broken link removed**

I still don't have an in-depth knowledge about the design.

I searched a bit and came up with a signal source. Hope I'll be able to use this...

http://wiredworld.tripod.com/tronics/signal_source.html

Please add comments... Will it be easy to follow the design with IGBT??

 

[ericgibbs]

hi,
If its 50Hz and sinusoidal, why not use a Variac Transformer to drive a 1:1 isolation transformer [ thats if the isolation is required] ?

The voltage isnt specified, so taking the worst case as mains ie; 250Vac then
250 * 5 = 1.25KVA rating for both transformers.

You can get motorised Variacs that the PIC/driver can control.

 

[Hero999]

Yes I agree, but It's better to have the isolation transformer as at low voltages the current will be 'lost' magnetising the isolation transformer,