Post by rbturner on Feb 23, 2019 21:03:23 GMT -5
There about a million ways to do any particular job. This is one method for doing LED headlights. It is not the best way but is the cheapest.
This method is supposedly hard on the LED lights because we are using them as directional diode too. I have never lost an LED yet using this method though.
This loco was gifted to me by Hypoponera. He did the motor up grade and I decided to use it for the LED 'school'.
Under the hood;
Basic materials; el-cheapo 5mm LED's. LED's operate on about 3 volts so they need to have the input voltage lowered. The standard is to use 1000 ohm resistors. I am out of them so you can put resistors in series and they will add up. I am going to use a 680 and a 270 ohm for a total of 950 ohms. These are 1/4 watt capacity.
As a resistor passed current (amps) it can get warm or even hot enough to melt plastic. A LED draws about 20 milliamps. (ballpark) 1000 milliamps is 1 amp.
So, using our 'volts times amps equals watts formula; we arrive at 12 (volts) times .020 (amps) equals .24 watts or written as a fraction; 1/4 watt.
Applying the theory that only one LED at a time will be lit (when on DC track) the 2 LED's can share a resistor. If you were to run these on DCC (which is AC voltage) both LED's would light and you would be well over the 1/4 watt and closer to 1/2 watt.
Anyway, I soldered the 2 resistors together;
Here's the LED. Notice there is a long leg and a short leg. The long one is the anode or positive. The short one is the cathode or negative. The negative is also marked with a flat spot in the body.
Take a close look and notice the positive is smaller. Think of it as the pitcher and the big side as the catcher.
Next I bend the leads out to allow easy soldering; pictured is my bamboo skewer applicator tool.
I had a bunch of wire scraps left from a decoder install so I used them to extend the leads;
When Mike upgraded to a can motor he drilled and tapped the frame in a good spot. I'll use that screw for the ground connection;
The resistors mounted;
I use packing tape to mount the LED's in the shell.
(to be continued; I forgot to get a good picture of the LED's mounted)