So not going though the process of actually ordering a pcb fromBatchPCB, (proof of the design passing DRC can be foundhere )to satisfy this part of the course requirements i purchased a 12v battery monitor kit from jaycar... but i forgot to check that it worked for 6 volts!
it's built on the LM3914 led driver, so with a bit of luck and some help from the datasheet i managed to modify it for the dagu rover's 6v operation (with a switch to go back to 12v for when the real tank is operational)...
The basic idea of the hack is that there is an internal voltage regulator in the chip, and the ratio of a pair of resistors attached to this define the upper and lower voltage limits that light the led bar graph. Hmm. Simple, just got to find the resistors! the 1k variable resistor that comes in the kit is obviously one of the pair, and the other is the 1k at the top left of the chip socket. i substituted the 10k variable from the sparkfun kit and hooked up to 6v DC to test some values... once the correct value was established (2.8 k) it was a simple task to add a spdt switch to select either resistor value....
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