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.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.
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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.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.
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