PIC16F886 Pulldown inputs

[pescador]

Ok thanks - I'll connect the opto collector tied high to the PIC and drive the Opto to GND - easy - no need then for ground resistors...

Thanks for R values..REV.pdf

[Ioannis]

Maybe I was not very clear.

With your original design, you would change the 2K to 100 ohms.

But with the new design, the pullup will be around 10K. NOT 100 ohms. I am pretty sure you will destroy the optos.

Ioannis

[pescador]

- So just to be clear - I'm driving the optos using the 2k to the anode, the output is the "collector" tied hi to a resistor - to the PIC w 5V. I'm not sure 100 ohms to the PIC would damage the PIC, but I dont think the opto would care?

In any case - I'll use 10K like you suggest.. no real reason to use 100.

[Ioannis]

With 100 ohms from +5 to the collector of opto, you will force 50mA through opto. This is the absolute max according to the data sheet. It will lead sooner or later to the destruction of the opto.

Please do use 10K from +5 to the collector of the opto and drive from the collector the PIC port. The emitter of the opto will be earthed.

Everytime you feed current to the LED of the opto, the PIC port will be low and when the LED is off, port will be high.

Ioannis