Mpguino schematic question ?

[user102]

Hi I have a question about the current schematic for the inputs from the vss and injectors on the mpguino schematic.


[from injectors or vss]->[50kohm resistor]->[5.1v zener(cathode]->[adcport of atmega]
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[Earth]

If the atmega program got corrupted and one of the two adc ports or both became an output and went to 5v Im assuming this would just take out the ports on the atmega ? Due to the short to gnd though the zener and nothing else?

Also what if the ports started to output a pwm signal by accident where the voltage was below the zener voltage is there potential that this could screw up the car electronics or engine?


Finally if a diode was in series with the 50 k ohm resistor to protect against reverse polarity how much would this effect the operation of the circuit?

Thanks

[TheTestPilot]

Hi
The 50k resistors limit the current to a very low value both ways , if the zener doesn't cause the micro to give up first ,my opinion is the car electronics has the upper hand.
I think the MPGuino would be displaying some really wierd things if it ever got to output pwm.
I have used a MPGuino for several years & it has never complained ,powered day & night.



Tp