Using a Transistor to Control an LED or anything

For my LCC project I decided to use a 2N4401 NPN transistor to control status LEDs and AC Switches. I did this so that the power draw from the Arduino chip would be as low as possible.

Below is a diagram of how this works. I used a 2N4401 NPN transistor that “turns on” when the gate goes high or positive. This essentially allows it to switch the negative or ground leg of the circuit. I did this because the Arduino can’t turn a digital IO line to ground- just 0v or 5v. Continue reading “Using a Transistor to Control an LED or anything”

LCC code

I haven’t published my code for this project yet. Mainly because it’s dangerous and not totally tested. Here’s what I mean:

This software controls the environment of a living thing. Failure of the software can cause death. I’m not ok with that. For example- last night I  had an over heat condition. Because of a badly written IF statement, the corrective actions never executed. Thankfully I was home!

I am in the process of re-writing the code to simplify the corrective actions and to provide more debug information.  Arduino doesn’t provide ANY error trapping/reporting so testing has been more difficult than I’d prefer.

I hope to have a viable and tested code base to publish this weekend.

I just hope my lizard doesn’t mind the flashing lights while I’m testing…. 😉

 

LCC Breadboard Visual

Below is the breadboard circuit diagram. It’s pretty final. I hope to clean it up a bit when the project is final.

The major additions in this rev is that I’m using transistors against the Arduino digital outs to control the AC relays and a corresponding LED indicator.  The on/off switches in those circuits provide a bypass to turn on the AC switches if necessary.