Input buffer

[jrt4fun]

Hi,

I'm creating an application that reads the state of 4 relays (NO contacts) to PortA0 - 3 of a Pic16F876A.
I was wondering whether I need to implement a buffer circuit to shape the input pulse or not.
Attached is an example of the buffer.

Thanks.

Best regards

[Acetronics2]

Hi, Jrt

Capacitors close to your inverter inputs would be much better for debouncing.
a 40106 or 4584 W/Schmitt trigger inputs instead ,one step better.

now, if your NO contacts are just used for reading relay state, debounce can be achieved by the PIC itself ...

Alain

[mister_e]

i agree with alain, everything can be done by the PIC. No adds, only by software.

Probably one resistor in serie will be enough if your your load at the relay output provide enough low impedance for the low level or OFF signal.

[jrt4fun]

Hi guys,

Thank you for the information !!!
Now I can finalize my PCB :-)

Best regards