Can I use a 120v AC to 12v AC electronic transformer to power 12v bulbs? I have a 150 watt transformer that I tried connecting to a single 10w incandescent bulb, but the bulb just flickers at a low frequency.

  • \$\begingroup\$ What does a 120v AC to 12v AC fluorescent light ballast look like? And what kind of bulb are you referring to? \$\endgroup\$ – jippie Sep 1 '14 at 18:06
  • \$\begingroup\$ Added clarification that I'm talking about an incandescent bulb -- the ballast looks like a rectangular box with two 120v input wires and two 12v output. \$\endgroup\$ – Ethereal Sep 2 '14 at 16:33
  • \$\begingroup\$ I have never seen a fluorescent light ballast with a 12V output. Do you have an image? \$\endgroup\$ – jippie Sep 2 '14 at 17:34
  • \$\begingroup\$ Sure, this is the model that I have -- perhaps it isn't for fluorescent lights, I just assumed... amazon.com/gp/product/B001CN6IWI/… \$\endgroup\$ – Ethereal Sep 2 '14 at 18:16
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    \$\begingroup\$ AHA!!! It's an electronic transformer with a 12V "secondary" which puts out 12VAC at 30 kHz and can supply between 50 and 150 watts into a halogen (incandescent) load. \$\endgroup\$ – EM Fields Sep 2 '14 at 19:02

In a word, "No."

A hot 12 volt, 10 watt incandescent lamp looks like about 14.4 ohms and, when it's cold, about 1.5 ohms.

The fluorescent ballast initially generates a high voltage to break over what looks like an infinite impedance in the lamp, and then once current starts to flow through the lamp and its impedance drops drastically, it limits the current through the lamp until the mains voltage goes through zero volts, extinguishing the lamp.

Once the voltage goes through zero, its amplitude starts to increase, starting the cycle anew.

So, with only the incandescent lamp resistance across it, the ballast can only go into current-limiting mode and won't be able to generate enough voltage to drive the incandescent lamp properly.


In a word, "Yes."

The device is an electronic transformer with a 12 volt, 30 kHz output, and is designed to feed a halogen (incandescent) load of from 50 to 150 watts.

The trouble you're having is because you're asking it to drive a 10 watt load.

  • \$\begingroup\$ I think I understand, but could I use a resistor in series with the lamps in order to provide a higher impedance? If so, what resistance would be necessary? I'll have qty. 8 of these lamps in series. \$\endgroup\$ – Ethereal Sep 2 '14 at 16:31
  • \$\begingroup\$ Belay my original post; see the edit. \$\endgroup\$ – EM Fields Sep 2 '14 at 19:12

The device shown in the link you provided in the comments is not a "fluorescent light ballast", it is an electronic transformer meant to power halogen light bulbs. The reason your lamp is blinking is that the device has a minimum load of 50W and you only load it with a 10W bulb.


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