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View Full Version : Pull up / pull down resistors for the propeller and other ICs ???



Zap-o
12-22-2009, 04:34 AM
When using a pull up / pull down resistor for the propeller how do you determine the right size? I know Ohms law but, I guess I am asking if there a specific place I need to look in a data sheet. Also, If I want to use other digital Ic's can I assume the process the same?

Thanks in advance

Leon
12-22-2009, 04:49 AM
It depends on the environment in which the system will be operating, and how much power you can spare. Large values will take less current but be more susceptible to noise.

Leon

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Amateur radio callsign: G1HSM

Zap-o
12-22-2009, 05:05 AM
Leon there has to be a value that I can calculate in the data sheets. Anyone know?

Leon
12-22-2009, 05:13 AM
There isn't, I checked in Horowitz and Hill to make sure. 10k is a good value for many applications.

Leon

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Amateur radio callsign: G1HSM

MikeK
12-22-2009, 07:05 AM
See the section on Bus Pull-up Resistors in Microchip's app note AN1028
ww1.microchip.com/downloads/en/AppNotes/01028B.pdf (http://ww1.microchip.com/downloads/en/AppNotes/01028B.pdf)

I haven't looked at it in a while, but it might be helpful.

Mike

Post Edited (MikeK) : 12/21/2009 11:19:02 PM GMT