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[SOLVED] Digital variable resistor for AC power circuit

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Advanced Member level 1
Jan 24, 2006
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ac variable resistor


I am working on a 230Vac dimmer circuit,
and has encountered a question.

Is there a digital variable resistor for 230Vac.
I don't think a digital potential meter will
work on the variable resistor on a AC dimmer circuit.

I saw on a website where it recommend a
opto- LDR devices but I couldl not found any.

Another solution is to do switching for
the resistor value, but it will takes up too
much space.

I can't think of any other solution.
Is there anyone familiar with digital AC dimmer?

Thank you for your help.

Siong Boon


ac power control circuit using a triac

As far as i know there is no digital potentio meter working at high voltage.

Why dont you try simple ac dimmer with a triac.
Google for ac dimmer circuit you can find a lot from analog to digital


digital works resistor

Ya. The circuit I have now is
the ac dimmer with a triac.

The circuit involved a variable resistor,
and I am thinking of ways to digitised
the variable resistor.

I guess a digital pot would not be able to do the job.
The voltage across the pot would be too high, isn't it?

resistors in digital works

Well the circuit using the TRIAC the potenciometer only adjust the RC time for the gate of the TRIAC.
So, you could control with a uC the time of the gate of the TRIAC and then you have a "digital potencimeter" in you dimmer. You should use an optocoupler for isolating the uC from the AC dangerous voltage.

digitally control ac power

How do I take care of the zero crossing?
Or do I need to take care of the zero crossing?
I am thinking that if I don't operate in syn
the firing will not be uniform.
Isn't this the case?

Thank you very much.
Siong Boon

ac power circut

Simply assume, that sync to zero crossing is required for a phase angle controller. I noticed however, that didn't say anything about the load characteristic. Of course phase angle control is different from a variable resistor respectively a variable transformer, which would be actually the best way for power control of an arbitrary AC load. Some loads don't work with phase angle control, others (e.g. heaters) can use more simple full wave switching.

time space resistor circuit

Ok. I got what you mean.
Thank you very much.

Does dimming a fluorescent lamp works in the similar way?

Best Regards,
Siong Boon

variable resistor in ac circuit

Does dimming a fluorescent lamp works in the similar way?

No, it wont work with fluorescent lamps


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