For the most part, 10K will work fine.  As you can see on your EasyPIC7
development board (I have the same) 4K7 works just fine as well.  20K
resistors are too large.  I have never used anything larger than a 10K in m=
y
projects.  Of course there are always exceptions to any rule.

Randy Abernathy
CNC and Industrial Machinery=20
service, repair, installation and=20
design

4626 Old Stilesboro Rd NW
Acworth, GA 30101
Phone: 678-982-0235
Fax: 770-974-5295
E-mail: cnc002@bellsouth.net

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Allen Mulvey
Sent: Wednesday, April 03, 2013 1:47 PM
To: PIC List
Subject: [PIC] Pull Up Resistors

Sorry, this is my first post. I forgot to tag the subject
line.

=20

Is there a way to compute the optimum value of pull up (or

pull down) resistors on PIC digital inputs?

=20

Most example circuits I have seen seem to use 10k. My

EasyPIC7 board uses 4k7. I have been experimenting and 20k

resistors produce unreliable results. I don't see anything

in the data sheet to help with this.=20

=20

I am using a pic16f877a. The leakage current is one

micro-amp. Sampling the port must draw considerably more. My

current project is not battery operated but, if it were, I

would like to use the largest resistors possible.

=20

Thanks,

=20

Allen

=20

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