So I have this customer with an led setup I have not seen. They are using a 120v-12vac 5a transformer. They then have some kind of in-line converter changing the 12vac to 12vdc before it goes to the Plasto-led light strips. What is the purpose of this configuration? When you put just a dimmable 12vdc driver in its place the lights will not dim with the 600w incandescent dimmer. I have found a cheap 3a ac to dc converter on line at Super Bright Led and it worked for 4 months but now is burnt up. Any solutions or thoughts? Thanks.
LED dimming
- Thread starter blugrs77
- Start date
- Status
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Most likely the AC to DC converter also regulates the voltage and/or provides a regulated current at about 12VDC.
If you try to feed the transformer from an inline dimmer you will get very bad results unless the dimmer is rated for magnetic (transformer) use. Putting DC into the transformer is very bad.
If there is regulation in the converter, then reducing the transformer output voltage will not reduce the current to the LEDs until you get to the point where it can no longer regulate.
Have you tried measuring the DC current into the LED array with the unmodified transformer/converter configuration? your converter may not be large enough. Or it may not like the waveform of the dimmed input.
It is wired 120v to 600w dimmer incandescent. The load of the dimmer dims the voltage to the transformer which in turn lowers the output on the load side. 1/2 dim gives me roughly a 7vac output. The output only is ran through an ac to dc converter and my dc output is now 6vdc. The dc output is connected to the leds and they are about half bright. If the ac transformer is dimmable by an incandescent dimmer it was my thought process that this was their way to dim dc voltage with a standard dimmer. Am I wrong in that thinking?
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Yes and no.
Not all series (two wire) dimmers can drive a transformer. The inrush of a transformer can burn out the dimmer and if the two halves of the dimmed AC waveform are not symmetrical the resulting DC on the transformer can cause saturation and high current with loss output voltage at the same time.
A lot depends on the size of the transformer.
James L
Senior Member
- Location
- Kansas Cty, Mo, USA
- Occupation
- Electrician
I tried this wireless remote dimmer a few weeks back, pretty impressive. I could not install a wall dimmer
http://smile.amazon.com/gp/product/B004X4O1NG?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
Simple plug-in transformer to 12vdc. 2-wire into the dimming module, 2-wire out to led ribbon. On/off switch on wall.
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Or go with a magnetic transformer
http://smile.amazon.com/Ledwholesal...49&sr=8-1&keywords=Magnetic+transformer+12vdc
and pair it with compatible mag lo vo dimmer
http://smile.amazon.com/s/ref=nb_sb...dimmer&rh=i:aps,k:Magnetic+low+voltage+dimmer
http://smile.amazon.com/gp/product/B004X4O1NG?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
Simple plug-in transformer to 12vdc. 2-wire into the dimming module, 2-wire out to led ribbon. On/off switch on wall.
----------------------------
Or go with a magnetic transformer
http://smile.amazon.com/Ledwholesal...49&sr=8-1&keywords=Magnetic+transformer+12vdc
and pair it with compatible mag lo vo dimmer
http://smile.amazon.com/s/ref=nb_sb...dimmer&rh=i:aps,k:Magnetic+low+voltage+dimmer
Ravenvalor
Senior Member
- Location
- Triad region of NC
- Occupation
- Electrician
Good stuff James. Can't beat that price for that remote dimmer either.
Fulthrotl
~Autocorrect is My Worst Enema.~
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- E
don't buy one as cheap next time?
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