Either way, I got annoyed with not being able to see my analog clock at night and instead of choosing a sensible solution I decided to have a LED light it up.
At the same time that I have this low-current LED as light I don't want it to waste battery power by being on 24/7 so it needed some kind of on/off circuit.
First few ideas were based around the clock itself, to have it as a timer and manually set when to light and not, I quickly deemed this as unnecessarily complex for such a small project.
This lead me to the next, final, idea: Light control.
I'm using a phototransistor to 'measure' the light and then decide if the LED should be lit or not. The circuit got a draw of ~3mA(As far as I can measure with my budget multimeters) when lit and in the µA range when not lit, this should give quite a good battery life even on AAA batteries.
The entire circuit consists of 5 resistors, 2 transistors and a phototransistor and has so far been tested on breadboard and in Proteus. I'll solder this together whenever the mood strikes me.
Here's a schematic 'til I get it soldered together.
No comments:
Post a Comment