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MetroMPG 09-30-2008 10:53 AM

MPGuino show 'n' tell at Ottawa EV meeting
I brought the guino to Ottawa last night and gave a brief presentation at the "round table" session. It was well received and more than a few members said they'd be looking into it after the meeting.

Why would I bring a guino to an EV club?

1) Most of the members are tinkerers by nature and I thought would find the project inherently interesting;

2) Many of the members who also own ICE vehicles are conscious of managing their fossil fuel consumption, so would be interested in a ScanGauge or MPGuino;

3) Since the Guino code & hardware is open source, I suggested the project has the potential to be modified into an open source energy monitor for EVs, showing Watt-hours per mile instead of MPG. I think several of the Ottawa members are capable of tackling that kind of thing.

The VSS could be used as-is in most conversions, and instead of monitoring a fuel injector, it would be a matter of adding a voltmeter function (to monitor pack voltage) and milivoltmeter function to measure voltage drop across a calibrated shunt to calculate current (most EV conversions have at least one shunt for an analog ammeter gauge).

I should probably mention it on the EVDL as well...

dcb 09-30-2008 01:02 PM

Cool :) Let me know how I can help.

Here's another idea, there aren't enough analog pins to monitor every battery, but certainly you could monitor the full pack and the half pack voltage. And if the half pack voltage isn't about half of the full pack voltage, then you know right away that you have a problem somewhere (battery/connection).

bennelson 10-21-2008 11:20 PM

I just ordered an MPGuino kit for my pre-OBDII S10 truck.

I love the idea of an E-Guino for the Electro-Metro. I also know another EV builder working on his own home-built battery pack monitor.

I will have to check with him to see how that's coming along.

Coyote X 10-22-2008 12:00 AM

An LM331 voltage to frequency converter could be used for the injector signal. It would take a bit of a rewrite to measure the frequency instead of pulse width but nothing bad hopefully.

Another possible option for dc use would be use a voltage to pwm circuit to feed the injector signal as is. The shunt resistor would have to have a filtering circuit to give a smooth signal to the converter circuit.

That is about all I can think of right off for using it as an ev monitor :)

dcb 10-22-2008 12:53 AM

Unless I'm missing something, I'd say make the atmega do all the work. It can read the shunt and battery pack (and half pack?) voltages directly on the analog pins. external circuitry is still a couple resistors and some zeners.

EV definitely merits some personal attention.

It will take a little more care in resistor selection though, you want to wind up with a voltage divider that peaks at close to 5 volts at the atmega for the battery pack monitors and the motor shunt (maybe just trim pots). Might be nice if it has an onboard charger to monitor the 120 input also, and vss of course.

analog connections so far:
1 battery discharge shunt
1 battery pack
1 onboard charger input shunt
1 *battery half pack (to detect gross battery problems)
1 *aux battery

digital connections:
1 vss
3 buttons

And, well, I think that takes up all the available pins except one analog and serial rx/tx :)

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