OK. this is what I'm up to.
I'm building an electric car. I need to moniter each battery something like this
http://home.earthlink.net/~evtkw/
Although I'd like to use the fusion brain and car pc so ultimately I have two screens, one for gauges, the other for MP3 player, radio, etc. The gauge screen will be behind the steering wheel, touch screen in the normal position.
More like the Holden Efigy
http://www.seriouswheels.com/2005/20...l-1280x960.htm
The 12 volt cells in the 280 volt battery need to be isolated from each other to be moniterd. So the plan is to build a voltage devider circuit that will drop 9 to 15 volts down to 1.4 to 3 and drive an LED. The LED is linked by 1000um fiber cable (aka 1mm light pipe) to an opticalresister datasheet;
http://pdf1.alldatasheet.com/datashe...OED-ST-8L.html
Use one for each analog port to display the voltage on the EQ looking bar meter I posted above.
I've built a breadboard circuit and it sort of works. The opticalresistor to analog port side works great and I can display full off to a bright light as a bar meter in fusion control with a flashlight or led pointed at it. The fiber or light pipe seems transparent in that it is working beautifully.
The trouble I'm having is the individual circuits for each battery. I'm currently playing with a red LED, a 2 resistor voltage divider driving the "adjust" pin on an LM317T voltage regulator. Vout goes to the LED, Vin direct to + of the battery.
It's sort of working. The display isn't linear, and it's more like 5 - 25 volts to dim the LED.
Anyone have any ideas? a more simple way? better? I'm not an engineer and am pushing the limits of my geekedness building this circuit.