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Old 23rd March 2004, 05:54 PM   #1
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Bill Fitzpatrick's Avatar
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Location: Eugene, OR
Default Using a pot to control a digital pot

I'd like to forego the controller chip and use a single pot to control several digital pots. Does anyone have experience or info on this?
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Old 23rd March 2004, 06:36 PM   #2
macboy is offline macboy  Canada
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In theory, this should not be difficult.
Use the pot as voltage divider with stable voltage reference and suitable filter on the output (say 47K and .22 uF). The pot's output would feed into a microcontroller with an ADC. You might want to apply a digital filter of some kind to this input as well. The micro then calculates the appropriate value to write to the pots to give the desired attenuation. Same value to all pots. I'd use a PIC because they are easy to use and many include the ADC plus I2C and SPI peripherals needed to communicate with the digital pots.
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Old 23rd March 2004, 07:01 PM   #3
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You missed the point. I want to avoid controller chips. I just want to use a pot as a voltage divider to control a digital pot chip directly.
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Old 23rd March 2004, 08:10 PM   #4
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Doesn't use a pot as the control, but eliminates the microcontroller:

If you're really set on the analog pot as a control you'll need some sort of A/D converter plus some glue logic to convert the ADC output into the proper format for the digital pot. Unless you get really lucky and find an ADC with a serial output that is exactly the right format for the digital pot input...
"Never confuse motion with action." B. Franklin
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Old 23rd March 2004, 08:25 PM   #5
tool49 is offline tool49  Canada
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Check this one out, I've built it and it works! but I went back to the microcontroller to be able to use the better chips. (i.e. PGA2310)

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