Switch

horizontech · Joined: 09 Nov 2003 Posts: 13

Hi !

I need to put a wired switch 300 foot from the pic.

To get minimum voltage drop i think to put 18vdc unreg

What is the best sulution (Opto, Transistor Etc..) to

put 18Vdc on the Pic pin to read the switch ?

Thanks for your help

Happy new year !!

Neutone · Joined: 08 Sep 2003 Posts: 839 Location: Houston

Run 18 volts to the switch
From the switch run to a 10K resistor
From the 10K resistor run to the input pin
From the input pin run to another resistor 100K
From the 100K run to ground

The pins are current limited and will clamp current to supply voltage.
When switched off the larger resistor will pull it to ground.
There are application notes on the microchip site showing this done with line power to monitor zero crossing.

LeranCCS · Joined: 13 Jan 2004 Posts: 5

300 feet is a long distance. i think the opto is the better selection.