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Old 01-22-2009, 11:47 PM   #15 (permalink)
Coyote X
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I was thinking worst case would be it needs an op amp to drive the input. But really a pull down/voltage divider resistor should work fine. I drove it home with the scope running the whole time and the voltages never changed, so once I get a balance point above/below 2.5V it should be fine long term I figure.

Having to divide the voltage between 14 and 11V should not be that hard though really. The zener can protect the AVR from over voltages and the two resistors as a voltage divider should be all that is needed. I will try out this weekend first with a 100k pot pulldown and a lcd scope I have that will be good enough to see the voltages now that we know what we are looking for.

                to AVR ---+------+---|___|-- Inj Input
                          |      |
                         .-.     |
                         | |     z
                      R2 | |     A 5.1V Zener
                         '-'     |
                          |      |

                         GND    GND
One of these days I will quit making you add stuff to the schematic

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