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AC Power source

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Sarac

New Member
hi,

Can anybody tell me how an AC power source ( variable ) can be designed.
the device should adjust the voltage from 0 to 220 ( or more ) volt and 1-2 A is OK too.

thank you
 

Chippie

Member
I use a variac for such things.........

You should consider the use of an isolating transformer when working with mains lectriccery.. 8)
 

Sarac

New Member
Chippie said:
I use a variac for such things.........
chippie thanks for the idea but i'm actualy looking for cheaper way. since i will use this one or two time for adjusting a device.

Do you think that i can manage the same with an 220volt dimmer made by triacs ??

thnks a lot
 

Chippie

Member
I s'pose you could do.....but again the dimmer should be fed from an isolated supply for safety's sake and your own! 8)
 

stevez

Active Member
A crude approach would be to use an appropriately sized power resistor that is adjustable (possibly a rheostat). Unless you were able to obtain a discard or surplus item the cost might equal that of a variac. There a probably electronic means to do this but the cost again would exceed the cost of a variac.
 

Nostrafus

New Member
Well, it may not be exactly what you want, but here is a schematic for a 12V Dc to 120V Ac Inverter, It's good for projects that require an Ac Power source, but you're not comfortable hooking up to your wall outlet, just in case the project backfires, the only thing you'll lose is a few diodes, a couple capacitors, and a battery.

http://www.aaroncake.net/circuits/inverter.htm

Now I'm not sure of how well it works, since I've never used it, but most of the stuff on this page can be scrapped from other projects or stuff people throw out (like old microwaves or tv's)

I don't think it will give you quite the same amperage as a wall outlet, but it should suffice.
 

Sarac

New Member
ok thnks for the suggestions,
first i will give a try to 220 volt dimmer ( with triac ) for adjusting the line voltage somewhere between 0v to 220 volt ( i guess 170 volt could do for me )

If its not work as want i will try the other suggestion.
Bcs it will not be under constant use, the cheaper is the better for me.

thnks guys,
 

stevez

Active Member
Be aware that your question about varying the voltage and some of the responses might or might not be in synch. When I looked at the question I presumed that you have a 50 or 60 Hz sine wave at 220 volts - and you'd like to vary that voltage from zero to 220 volts. I presumed you wanted to retain the sinewave without distorting it (don't know what you are doing with it). A variac or the resistor will accomplish that. Certainly there are electronic means to do that as well but they are likely to be more complex.

Unless I am mistaken (help me out guys) a simple "triac" light dimmer form of control will more or less cut off or truncate portions of the sinewave. In the strictest sense the RMS value of the voltage is reduced but you no longer have a sine wave. At about 50% the peak voltage will be the same as it is at 100% or anything betwee 50% and 100%. It's only when you start cutting off the other half of the sinewave that the peak voltage will drop.

A filament or electric heater responds well to this kind of control - motors and other circuits do not. This may or may not be significant but I thought it was worth mentioning.
 

pebe

Member
stevez said:
.........Unless I am mistaken (help me out guys) a simple "triac" light dimmer form of control will more or less cut off or truncate portions of the sinewave. In the strictest sense the RMS value of the voltage is reduced but you no longer have a sine wave. At about 50% the peak voltage will be the same as it is at 100% or anything betwee 50% and 100%. It's only when you start cutting off the other half of the sinewave that the peak voltage will drop.

A filament or electric heater responds well to this kind of control - motors and other circuits do not. This may or may not be significant but I thought it was worth mentioning.
You are quite right, stevez.
 

Chippie

Member
so until we find out exactly what our poster is doing with his supply, we cant comment on which is the most appropriate........but he is now aware that there are differences in the way a varied supply can be produced.
 

Sarac

New Member
thank you all,

i got enough info which supply should be produced for my application.
i should say wave form of the supply is not so much important ( i think )
then triac dimmer should be ok.

anyway now i'm aware of each application differences

thnks again
 

stevez

Active Member
Thanks for the support!

This is a perfect example of how, in my opinion, a forum like this works. Someone might start with a simple question and the various contributors (and the originator) build on it. This progression helps me learn or it reaffirms my learning. Non-contributors view it and hopefully they learn too. While not a substitute for a program of study (self directed, classroom, etc) is certainly helps. To the originators and moderators - nice job, thank you.
 

Sarac

New Member
stevez said:
Thanks for the support!

This is a perfect example of how, in my opinion, a forum like this works. Someone might start with a simple question and the various contributors (and the originator) build on it. This progression helps me learn or it reaffirms my learning. Non-contributors view it and hopefully they learn too. While not a substitute for a program of study (self directed, classroom, etc) is certainly helps. To the originators and moderators - nice job, thank you.
That's why i visit this forum everyday and read all posts regularly.
I think, no where else is more informative than this forum.

keep going friends
 
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