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Jester009 · 11th September 2007, 02:01 PM

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 · 12th September 2007, 03:14 AM

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 · 12th September 2007, 06:02 AM

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

Quote:

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.

Quote:

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

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

Quote:

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:
http://www.freefunfiles.com/software...generator.html

Jester009 · 12th September 2007, 09:35 AM

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...

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...

Code:

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

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

ericgibbs · 12th September 2007, 10:02 AM

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 · 12th September 2007, 08:39 PM

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,

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11th September 2007, 02:01 PM	(permalink)
Jester009	Need a place to start... 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

12th September 2007, 03:14 AM	(permalink)
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

12th September 2007, 09:35 AM	(permalink)
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... 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... Code: http://wiredworld.tripod.com/tronics/signal_source.html Please add comments... Will it be easy to follow the design with IGBT??

12th September 2007, 10:02 AM	(permalink)
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. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

12th September 2007, 08:39 PM	(permalink)
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, __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.