Monday, October 18, 2010

Dark Detecting LED Failure

Today was not so much of a good day that I would have hoped for.  I was able to find most of the parts locally for the dark detecting LED, but not the exact photo transistor LTR 4206E, not sure if I will be able to find that one locally to begin with.

Even still I decided to try my hand at making one of them.  I think the last time I tried to solder anything was up 15 years ago at least.  Not to mention that my room and table was probably not the best place to try and solder something.  I had everything connected correctly but even with the battery the LED still lit up even when the lights where on in the room.  Not sure what I did wrong in any event I found another one that looks to be from the same site and a little easier.

So tomorrow I will go out back to Radio Shack and pick up these extra parts, hopefully wont cost to much more to try and get at least one of these up and running.  Besides the new design is made for two LED perfect for a set of eyes.

On a side not I also melted plastic garbage bag when I was moving my soldering iron, cant stand the smell of that, but a little air freshener, fan on high and out of the room for a bit and it was cleared up.  Tomorrow I can worry about cleaning of the melted plastic from the iron.

If anyone has any idea of where to get the parts in the San Diego area please let me know.  (mainly the photo transistor)


Here's a list of parts for the basic design (with two LEDs):
  • A phototransistor (we use type LTR-3208E)
  • 2N3904 (or similar) transistor, QTY 2.
  • 5k ohm resistor
  • Yellow or red LEDs, QTY 2. (We used 10 mm diffused yellow LEDs)
  • 50 ohm resistors (one for each LED)
  • Battery holder with 2 AA-size alkaline batteries