Recently I took delivery of the parts needed to make the Sub$20 Bike light and a few other goodies.
However being right in the middle of my exams I haven’t had as much time to play around as I would like.
That said I still found time to put together a simple voltage Meter using a cheap 8 LED bar display and some Zener diodes.
The 8 LED Display with resisters and zeners on the right.
I put a youtube video of it in action as well.
In short, each LED in the display is connected to a reverse bias Zener Diode of a different voltage rating and is in series with a resistor. The resistor protects the LED from over current. If your not familiar with a Zener diode, it works by limiting current until a set voltage is reached, this is its break down voltage.
To think of this another way, imagine the Zener diodes as drinking glasses of different heights sitting in a kitchen sink, with their heights corresponding to their “break down voltage”. If you fill the sink with water one by one the level of water will rise above the rim of the glass’s and they will begin to fill. In this case the water level is the power supply voltage with the water flowing into the glasses being the current.
Once condensed down into a smaller size this simple and cheap display should work fine as a battery voltage meter in the work light project. This should let me know when the batters are going flat so I dont deep discharge them by mistake.
Anyway, enough with the procrastination for me..
