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Replace Low Voltage Bi-Pin Halogens with LEDs

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Step 6: Test

Picture of Test
fixture_on.jpg
With the driver mounted, you are ready to test. You can do this at your bench or installed in the fixture or choice. If you see a lot of flicker then your fixture may not be low voltage DC but rather low voltage AC. You need to modify the circuit to handle the AC by using a full wave rectifier and some capacitors, not too bad but not ideal. Enjoy, and be safe!
peterlonz5 years ago
Something seems not to add up here: A typical halogen is about 50 watts & its efficiency is not hugely different to LED's as (I understand things), as for example a compact fluorescent is, being 3 to 4 times as efficient as a halogen. So how on earth can an array of three LED's, total 10 watts, be anywhere near the light output of the replaced halogen ?
Thanks, cool instructable. What is the color temperature in this setup, I gather its the bluish light , 6500? and if we wanted the warmer light it would throw off 2-3 times the heat? Can this be dimmed?
jmengel (author)  blazingpencilsdotcom5 years ago
This is a warm white LED, 3000K as noted by CameronSS. I would rate the light as similar to the halogen it replaced in terms of color. I have Rebel stars that put out much more light (100 lumens/watt) but these are the 6500K cool LEDs with bluish tint. The warmer LEDs are less efficient, so they will get hotter at the same luminous output as the cool white LEDs. For example, to get 1000 lumens using a 100 lumen/watt cool white LED would take 10W, most of which would end up as heat. Similarly, with a 60 lumen/Watt warm white LED would require 16.7W, most of which would end up as heat. The difference in heat output is basically the ratio of luminous efficiency, so 1.67 times more heat in the above example.

The driver circuit as shown does not support dimming. The drive IC can support dimming but uses a PWM approach that would not be compatible with the typical triac dimmers found in most residential applications. I am working on a triac dimmable driver circuit based on the LM3445 reference design provided by NSC.

LM3445