The Smart, Stealth LED Blinkenlight

Step 8 Add LED's to the reflector.

In the reflector I selected, there is a white plastic backing behind the red-colored reflector lens. There is a gap between the two pieces so I drilled 3 holes for LED's which don't extend into the red plastic.

Then I did some experiments, wiring up an LED with clip leads and a resistor to supply around 20mA of current. What I found was the reflector material worked in reverse too, so most of the light from the LED was reflected back onto the white background. I didn't like this so I drilled further into the red plastic to remove the reflector pyramids and allow the LED light to get through. This worked great.

Then I went to wire them up. I determined that the flat on the LED shell indicated the wire on the LED that is the cathode or negative terminal. I carefully placed all the LED's in the 3 holes so the flat was on the same side then wired them in series. Between two of the LED's I needed a jumper so I decided to slip in the 100-ohm R4 current-limiting resistor instead. I tested the circuit but found it wouldn't light up. It turned out that one of the LED's had the flat on the anode, so one LED was installed backward. Once I corrected that, all 3 LED's lit up nice and bright.

I soldered on red and black wires to indicate positive and negative, respectively. I added some glue to seal the electronics from the weather and let it sit.