Resistor to trick 12v transformer

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SUMMARY

This discussion focuses on the challenge of using LED lights with a 12V electronic transformer, specifically one rated at 105 watts. Users report that the transformer requires a minimum load to function properly, as it only illuminates the LEDs when an incandescent bulb is present in the circuit. Recommendations include using two 15-ohm resistors in parallel to simulate the necessary load, as well as considerations regarding the transformer’s characteristics, such as its dimmable feature and potential self-biasing issues with LEDs.

PREREQUISITES
  • Understanding of electronic transformers and their load requirements
  • Basic knowledge of LED and incandescent bulb circuitry
  • Familiarity with electrical resistance and Ohm's Law
  • Experience with measuring AC voltage and using multimeters
NEXT STEPS
  • Research the specifications of electronic transformers, particularly those labeled for LED use
  • Learn about load balancing techniques in lighting circuits
  • Investigate the differences between AC and DC LED modules
  • Explore the use of resistors in parallel to achieve desired load resistance
USEFUL FOR

Electrical engineers, hobbyists working with LED lighting, and anyone troubleshooting electronic transformer issues will benefit from this discussion.

  • #31
Hi
I have an excellent test-equipment design I want to share with you because it will enable you to track down your fault.
It needs parts : 2 of 12v filament lamps; a mounting arrangement for the lamps, and a probe. Oh, and red and blue paint.

Connect the 2 lamps in series, and connect the series circuit to the battery which is supplying the circuit under test. Connect the probe to the joining between the 2 lamps.
The 2 lamps glow weakly as soon as they are connected. If the probe is touched to a part of the circuit at positive voltage, one of the lamps will glow. Paint this one red. Paint the other lamp blue.
Keep this test equipment forever! You will soon find faults like the one described in this thread using your 2-lamp tester!
 

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  • #32
Could it be that the leds are self-biasing themselves off in some way as charge is only flowing one way through the circuit? Foggy thinking on my part, here, but I seem to remember something of the sort happening in another context.
You could try connecting one of the led units the other way round which would stop this happening as current could then flow in both directions through the transformer.
If it works then I was right - otherwise I wasn't!
 
  • #33
Besides the fact that it is an "electronic transformer" (i.e. ballast), it also states:
Soft Start
Overload
Short Circuit Protection
Auto Reset
For 12V Halogen Lights Use Only

Correctly-biased LED's probably look like a short circuit to this device, therefore causing it to shut itself down.