Thanks, Bill!
A thought...
The timing errors (timer A re-triggering) always occur at the transition from timer A to timer B. Timer B is triggered by the relay controlled by timer A. Timer B controls another relay that opens the connection from the PIR's output to the base resistor of a Darlington, which disables the ability of the PIR to trigger timer A until timer B runs out.
Is there a chance that the errors are caused by the timer B relay switching? If so, I can remove the relay and substitute a PNP transistor, using the high output from timer B to open the PIR connection.
The existing traces on the board will work for this substitution. The only thing I don't know is what the value of the PNP base resistor should be. I would be using a 2N3906 PNP. The voltage to the base resistor would be ~10.3VDC (12VDC - ~1.7VDC from the 556). I'm not certain of the current delivered by the PIR output, but the voltage is a range from ~2VDC to 3.2VDC. The 2N3906 datasheet states the collector current limit is 200mA - does the PIR output current need to be less than this value for this to work? Is there a more suitable PNP for this application (higher collector current)? What do you think?
A thought...
The timing errors (timer A re-triggering) always occur at the transition from timer A to timer B. Timer B is triggered by the relay controlled by timer A. Timer B controls another relay that opens the connection from the PIR's output to the base resistor of a Darlington, which disables the ability of the PIR to trigger timer A until timer B runs out.
Is there a chance that the errors are caused by the timer B relay switching? If so, I can remove the relay and substitute a PNP transistor, using the high output from timer B to open the PIR connection.
The existing traces on the board will work for this substitution. The only thing I don't know is what the value of the PNP base resistor should be. I would be using a 2N3906 PNP. The voltage to the base resistor would be ~10.3VDC (12VDC - ~1.7VDC from the 556). I'm not certain of the current delivered by the PIR output, but the voltage is a range from ~2VDC to 3.2VDC. The 2N3906 datasheet states the collector current limit is 200mA - does the PIR output current need to be less than this value for this to work? Is there a more suitable PNP for this application (higher collector current)? What do you think?