How to add a Dimmer on a 12v AC power supply

[75RR]

The 2v steps in my transformer/power supply (the AC side which I use with the incandescent bulb) are a little too large.
Was wondering if it were possible to add a dimmer that would allow me to adjust the light intensity at each step.
Can anyone provide a diagram and parts list for this?
Instructions would also be helpful!



Will hopefully at some point get a working LED and dimmer with the DC half.
Would be very nice to have both options and be able to swop between one and the other as needed.

[billbillt]

Hello,
I bought and assembled this very easy and simple PWM kit for controlling an LED light setup I made..

http://www.ebay.com/itm/NEW-12V-60-WATT ... 540210c75b

It was super easy to do and works very well for me.. I am sure there less expensive solutions out there, but this was a quick fix for me..

[Crater Eddie]

Simplest would to be to find a "Variac" to plug your supply into. That would allow you to vary the input to the supply thus varying the output. This would not work if your supply is regulated, but if the schematic on the front is accurate then it is not regulated. An example of a Variac can be seen in my thread about my big Russian scope.
Failing that, you can get a switching supply that runs off the output of your supply and is then itself variable, such as this one:

http://www.amazon.com/gp/product/B00C46 ... UTF8&psc=1

Then you would have to run some tests to see if you get the dreaded "banding" artifacts that have plagued so many in the past.
CE

[75RR]

Thanks billbillt. The output is AC so not sure that will work.

Thanks Crater Eddie. Would a photo of the insides of the transformer help?

[Crater Eddie]

Oh, I was thinking about the DC side, I see now that you were talking about the AC output. No problem at all, a Variac would be just fine. That's what I would do.
CE

[billbillt]

Hi,
I see you also have DC outputs on the front of this unit.... You could use that... If you are going to use LED lighting at some stage, you will have to use DC anyway... LED's are a DC device....

[Crater Eddie]

Plugging the power supply into a variac would allow you to vary both the ac output and the dc output. This might be a bonus.
CE

[billbillt]

Adjusting the light output of an LED is not done by adjusting the voltage... They operate in a narrow range of voltage depending mainly on their color...

[Crater Eddie]

Yes I am aware of that. I was talking about controlling the brightness of the incandescent bulb.
The bulb could be run from either circuit, the ac or the dc, the bulb doesn't really care which. Running the bulb on the dc circuit would allow the use of a PWM type dimmer module to control the intensity. But the variac would allow the use of either.
CE

[billbillt]

To quote:
"Will hopefully at some point get a working LED and dimmer with the DC half.
Would be very nice to have both options and be able to swop between one and the other as needed."

Also posted about working LED.. I was posting about that only... A PMW unit works best for that...

[Crater Eddie]

And I agree. My apologies.

[billbillt]

Actually, you could use DC for both incandescent and LED lighting... You will have to use a resistor on the LED anyway....