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arunb
Joined: 08 Sep 2003 Posts: 492 Location: India
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MCP41100 (digital Pot) does not show correct value |
Posted: Fri Dec 07, 2007 1:35 am |
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PCM 3.169
MCU 16F628
Hi,
I am using a 16F628 mcu to control a MCP41100 (100 K digital pot).
After powering up the device, I checked the resistance between the PB0 and PA0 (resistor ends) and found that it was 72 Kohm instead of 100Kohm.
Kindly explain this anamoly.
thanks
arunb |
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dyeatman
Joined: 06 Sep 2003 Posts: 1924 Location: Norman, OK
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Posted: Fri Dec 07, 2007 8:00 am |
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I might suggest you read the device data sheet particularly paying attention to the section on the 100K version. I believe that will povide the explanation you require. |
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rnielsen
Joined: 23 Sep 2003 Posts: 852 Location: Utah
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Posted: Fri Dec 07, 2007 9:53 am |
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Every part that is manufactured has a 'tolerance' associated with it since nothing is perfect. There should always be a plus/minus associated with it. The spec. sheet states that, for the 100K version, the internal resistance is 100K plus/minus 30K. It's a rather wide window but it's what is spec'd out and your part falls, barely, within that specification. The only way to get a 100K part is to buy a bunch of them and measure each one until you find one that is close enough.
Ronald |
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Ttelmah Guest
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Posted: Fri Dec 07, 2007 4:48 pm |
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Also, remember that if there is any load on the wiper, this will affect the apparent resistance between the endpoints.
Best Wishes |
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arunb
Joined: 08 Sep 2003 Posts: 492 Location: India
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RE: |
Posted: Fri Dec 07, 2007 10:31 pm |
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Hi All,
Thanks for the help.
bye
arunb |
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