I would like to dim 12vac landscape lights with a 50w max load. Will a 120v knob controlled dimmer work?

I see many 12vdc and 120vac dimmers. The only 12vac dimmer is >$100.

Thanks,

Michael

 

A mains voltage dimmer will dim low-voltage filament lamps supplied via a transformer. That's a proper copper-iron transformer not the so-called "electronic" transformer.

 

A mains voltage dimmer will dim low-voltage filament lamps supplied via a transformer. That's a proper copper-iron transformer not the so-called "electronic" transformer.

Yes, I'm using a copper-iron transformer.

 

Yes, I'm using a copper-iron transformer.

It might buzz, but otherwise it should work OK.

 

It might buzz, but otherwise it should work OK.

Thank you sir.

 

It is unlikely to work using a commercial because of one got-ya': All of them that I have seen use a diac that triggers the triac when there is 30 to 36 volts DC across the timing capacitor. With a 12 VAC (RMS) input voltage you cannot get enough voltage for the diac to avalanche and trigger the triac (or other thyristor).

With such a low AC voltage it would be difficult or more presicely impossible to find a diac or pair of transistors to substitute as a diac with a breakdown voltage low enough so that you would still have plenty of dimming range.

Last month a person in a developing country asked me to show how to make a lamp dimmer using the 12 volt VAC winding on a transformer to dim a 12 VAC tungsten bulb. The circuit generates a trigger pulse for the NE555. By adjusting R7 the fraction of each half cycle waveform can be adjusted. Yeah, this uses a lot of transistors and other discreet components because very few integrated circuits are available where he lives. When I checked back with him he said it works "perfectly". Electric power where he lives in 50 Hz. Just a thought.

 

It is unlikely to work using a commercial because of one got-ya': All of them that I have seen use a diac that triggers the triac when there is 30 to 36 volts DC across the timing capacitor. With a 12 VAC (RMS) input voltage you cannot get enough voltage for the diac to avalanche and trigger the triac (or other thyristor).

With such a low AC voltage it would be difficult or more presicely impossible to find a diac or pair of transistors to substitute as a diac with a breakdown voltage low enough so that you would still have plenty of dimming range.

Last month a person in a developing country asked me to show how to make a lamp dimmer using the 12 volt VAC winding on a transformer to dim a 12 VAC tungsten bulb. The circuit generates a trigger pulse for the NE555. By adjusting R7 the fraction of each half cycle waveform can be adjusted. Yeah, this uses a lot of transistors and other discreet components because very few integrated circuits are available where he lives. When I checked back with him he said it works "perfectly". Electric power where he lives in 50 Hz. Just a thought.

View attachment 265526

Thank you for the details. I am a novice when it comes to electricity but what I hear you say is a commercial dimmer won't work well because there is not enough power in the 12vac input to permit the dimming. Thanks for the reply.

 

Just to clarify what I said in post #2. You connect the primary of the transformer to the output of the dimmer and the lamps to the secondary. The dimmer is supplied by mains voltage.

 

Just to clarify what I said in post #2. You connect the primary of the transformer to the output of the dimmer and the lamps to the secondary. The dimmer is supplied by mains voltage.

I see... I didn't understand that. I'll have to think about it. That arrangement may not work since I have multiple 12v circuits on the low voltage side of the transformer.