Mark_R
Member
The circuit below is the digital input section of a commercial I/O board. Manufacturer says inputs will work from 400V down down to 24V (guaranteed) perhaps as low as 12V. I am perplexed as to how one can obtain that wide of a range from a fixed set of resistances. Could someone explain the function of the resistor in parallel with the opto diode (R15 for instance) My thought is that once the diode is forward biased, the 12K resistor ceases to have much impact on the circuit.
Am I missing something obvious here? it seems too simple.
PS, i believe the PIC is just a input stretcher to allow for AC signals .
Thanks.
Am I missing something obvious here? it seems too simple.
PS, i believe the PIC is just a input stretcher to allow for AC signals .
Thanks.