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Old 08-25-2009, 11:28 AM   #2205 (permalink)
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Originally Posted by MPaulHolmes View Post
Hey Don, that's exactly what Fran had just suggested to me about the throttle. He also said that it is often a problem when it goes below 0v. Hmm... The throttle pot is far away from the rest, and the wires are really long that could be picking up noise.
This was a long time ago, but I finally got through the whole thread and don't think this has been fully addressed...

Is it just the atmega8 that has issues with locking up the processor if the voltage goes below 0v or above 5v? Or is it all the Atmel chips? Something that causes a lockup such that the watchdog doesn't even trip concerns me.

A solution/workaround and something I was thinking about regardless of the lockup issue: add an i2c bus. With that, we could put any number of adc's on the bus (should someone want to monitor many things, like each individual battery voltages perhaps). And we wouldn't have to worry if the inputs to those chips went outside the range of the processor. We could have simple error checking on the return values of those chips and there would be no possibility of a noisy throttle line or whatever causing a lock-up. And they'd most likely be more accurate than the built-in adc's of the atmega8.

I looked at prices a little. Looks like they're a couple of dollars a piece. So, it's probably not something the ultra-low-end builders will want. But I might like some on my version... And obviously the prices go down quite a bit when buying in bulk...

I did find the TI ADS7828, which is a 8 channel ADC for $6.66 from mouser. You can have up to four of these chips on an i2c bus, allowing a total of 32 ADC options. I think one of these chips is going to be much better bang-for-the-buck than several 1 channel ADC's.

Last edited by montgoss; 08-25-2009 at 02:11 PM.. Reason: Found an interesting i2c chip
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