alec:
The comparitor interfaces to the swich input to the PCM. When it goes below 400 mV (the contact closure), it pulls down the input of the ELM411?
Note that te comparior is availabe with ref connected to - and ref connected to +.
Fast collapse is just as important as power up. The power supply cant have a long time constant.
The comparitor has to be chosen, so its open collector output is ON when the switch is pressed.
A DPST swich COULD be used to eliminate the comparitor AND isolate the indicator circuit.
I built an automotive circuit that happened to use the regulated ant pre amp supply as a trigger for a timer. Issues could occur in my case with the on/off while starting, ON behavior of the radio supply. He may not have that issue. During starts some accessories go off like radio and heater.
The comparitor interfaces to the swich input to the PCM. When it goes below 400 mV (the contact closure), it pulls down the input of the ELM411?
Note that te comparior is availabe with ref connected to - and ref connected to +.
Fast collapse is just as important as power up. The power supply cant have a long time constant.
The comparitor has to be chosen, so its open collector output is ON when the switch is pressed.
A DPST swich COULD be used to eliminate the comparitor AND isolate the indicator circuit.
I built an automotive circuit that happened to use the regulated ant pre amp supply as a trigger for a timer. Issues could occur in my case with the on/off while starting, ON behavior of the radio supply. He may not have that issue. During starts some accessories go off like radio and heater.