It is an engineering challenge to build a power LED Light that works and is as efficient as fluorescent lights. Although LED lights are smaller, they generate a lot of heat in a small space that need to be dissipated. Another big problem is with the power supply. They work with DC voltage (10V or 32V), which means that the AC line voltage need to be converted.
Because of the two issues I mentioned above, it is not practical to have LED lights to replace very small incandescent lights like Candelabra based decorative lights. Unless of course the whole assembly is powered by a DC voltage.
We had two halogen torch lights (Torchiere) that I had already converted to fluorescent lights. Now I have converted both of them to 20 Watt power LED lights. In this post I will document this project.
Also a disclaimer is in order. I don’t consider this project to be finalized, it is just a stepping stone to a better version in the future.
Capacitive coupling is used to transfer power to the bridge rectifier. I tested the circuit with 5 uF, 10 uF, and 20 uF. This allowed me to transfer more power gradually during testing.
R1 is supposed to be a relatively small valued resistor. I used a car headlight as a resistor (R1), because I did not have a suitable resistor. About 14 Volt drops across it, and also at least some of the power loss is converted to light. Obviously this is not an efficient way to transfer power. This is one of the things that will need to be fixed in the future.
The part labelled M is the fan motor for the CPU cooler. The CPU heat sink is a standard Intel Socket 775 CPU cooler. I put a 150 ohm resistor (R2) to slow down the fan to reduce the fan noise. The fan needs to spin just enough to move the air a little bit.
J1 is a Peltier device and it is optional. I had it and so I used it. Only about 0.8 Volts drop across it at 0.6 Amps. The cold side is facing the power LED and the hot side is facing the CPU cooler.
One big problem I had was with the noise from the fan. Although rather quite normally, when placed on the torch lamp, the lamp acted as an amplifier and made the noise problem bigger. I had to use a foam to insulate the LED lamp from the torch lamp base so that the LED lamp is suspended on the foam base.
Overall, the LED lights are putting out at least as much light as the fluorescent lights did, if not more. One difference is that the LED lights come on instantly whereas the fluorescent lights took a few seconds and flickered when first turned on. So far both LED lights are working great!
CPU cooler, peltier device, and the power LED stacked up.
When the CPU cooler is attached to the prototyping board, it pushes on the power LED against the CPU cooler and keeps them in place. Heat sink compound is used to transfer heat.
Here is a picture showing the Power LED lamp in the torch lamp housing. Note that the torch lamp looks like a big loudspeaker. It does amplify any little sound produced in the LED lamp. I put two black foams on each side of the lamp to raise it so that the LED lamp does not touch the torch lamp base.
The second lamp is an exact copy of the first one (after the first one worked without any problems). Parts are on the other side.
This picture shows the other side of the circuit board.
Side view of the component side.
NOTE: the AC Capacitor C1 is pretty large and sits on the floor with two cables from it going up to the LED lamp. The large capacitor is not shown in any of the pictures above. This is one more thing that needs to be fixed in the future.