This is a good discussion Jeff. Actually, the LED controlling device works very nicely with LEDs and incandecent bulbs. I have both LED and incandecent lights on mine in the Cub. I'll also be using a combination of both when I refit the lights on the KR this fall.
The power supply does not work by limiting voltage. Instead, it uses Pulse Width Modulation (PWM). That means it varies the duty cycle of the 12v being quickly switched on and off to it's output. As it turns out, the light intensity varies at the same rate with both the LED and incandecent bulbs. Using this unit also provides an easy avenue to upgrade your lighting to LED lighting in the future as you would already have the controller in place. And it really costs no more than a good quality rheostat. ($15) The biggest issue with the one I pointed to on ebay (which is the one I am using) is the 1 amp limitation. It doesn't take a lot of incandecent bulbs to add up to 1 amp, although most modern panels are far less than that. When this unit hits a 1 amp or higher draw, it crowbars and shuts off. You have to shut it off for 30 seconds for it to reset. However, you can also buy 8 amp units as well. I can't imagine anyone would be pulling that kind of current with their panel lights. The advantage to it is that it is a switching power supply, so does not have to dissipate heat like a resistive rheostat. Jeff Scott Los Alamos, NM ----- Original Message ----- Ok, It has been a long time since I was in Electrical Engineering 101. But, I believe this is a case where Ohms law needs to be applied to figure out the correct type of pot to use. In fact, I think you actually want to use a rheostat. Ohms law states that V = I X R or voltage equals I (amperage) times R (resistance) . Since you know your voltage is 12 VDC and you are trying to calculate the needed resistance then you can calculate Ohms law the following way. R = V / I If your calculations show that you are trying to dissipate much more then 1 watt, then as I recall you are going to have heat build up. So you may need to consider the value of R and have a heat sink. Remember, the more heat the greater the chance the pot or rheostat with heat up and eventually fail. The below item that Jose is recommending is for LED use which is different then calculating a pot for incandescent bulbs. I do not believe you could safely use a device designed for LED control on an incandescent bulb. But, it has been more years than I want to admit since I was an engineering student but, I am pretty sure I am right. An incandescent bulbs brightness is controlled by limiting the amperage to the bulb. A LED's brightness is controlled by the voltage to it. So as I recall for an LED you would want a variable power supply type of device with a voltage regulator at its core. By design it would be solid state and not be as big a heat source as say a pot or Rheostat. The ebay device in which Jose is pointing to is for LED use. Yes, the ad states at the bottom that it can be used for incandescent bulbs. I am not sure how well it would work because it is a voltage limiting device. My two cents worth and I qualified its been a while. Jeff York Georgetown Scott County airport 2010 KR Nationals Peoples Choice and best interior 2011 Air Fest Best Experimental and Best Instrument panel
