can i replace a linear 100k potentiometer with multi turn potentiometer 100k to get more resolution. The linear potentiometer 100k which i mentioned is used in pwm which i brought from ebay for controlling speed of a 12v 9a 500rpm dc motor but when i am using 100k linear pot i am not able to get proper resolution in speeds of dc motor eg:at 1,2,3,4….hz.so i wanted to replace linear pot with multi turn pot is it possible or not.Do i need to mention anything else
Electronic – can i replace a linear100k potentiometer with multi turn potentiometer 100k to get more resolution
potentiometer
Related Solutions
Well you can modify the linear pot to get an almost logarithmic response by adding a resistor from the CCW side to the wiper. Because of its simplicity this might be worth a try. Here's what the idea looks like: -
For the pedal circuit you need this might be ideal. It's not perfect of course but it reduces the risk of buying linear pots because these can be made "almost logarithmic by adding one resistor.
One thing to remember is that if the design calls for a 1M pot and you have a 1M resistor across wiper to CCW, the end to end pot value will change as the wiper advance towards CW. This would probably mean that you should use a 2M pot and 2M resistor.
Some experimentation is required and if you could post a circuit I'm sure better advise could be given. Pictures gleened from here
EDIT - picture of circuit attached with my best guess at log/lin: -
As @Brian Drummond suggested, when you set the pins to input mode, they have high impedance, so they're not going to sink much current no matter how the external resistors are set up. The data sheet suggests using 10k or less because if you use a higher value than that, you'll need to increase the sample time of the ADC. The ADC works by allowing current from the input to charge a capacitor, then holding the the charge in the capacitor and using it as the input to a comparator. The ADC repeatedly generates candidate values and compares them with the capacitor charge until it finds the closest match; that value becomes the ADC output. If the impedance of the analog source is greater than 10k, the capacitor won't fully charge, and you'll get incorrect readings. You can increase the sample time, but that will decrease your sampling resolution (you'll get fewer samples per second). I don't think there's much reason to use a 100k pot over a 10k unless 100k is all you have.
Best Answer
Allow me to be a dissenting voice. Maybe not. Multi-turn pots are not inherently higher resolution than single turn pots of the same element length (and type), many merely contain a mechanism that may make it easier to set the wiper to a given position. The mechanism may have effects such as backlash that are annoying.
Generally if you find yourself using only a small range of a pot, perhaps near one end, a better choice is to replace the unused part of the pot element with fixed resistors.
For example, if you had a 100K pot voltage divider with 5V applied and only used the first 1V of it you could add a series 80K resistor and shunt the element with 25K.
Some pots such as the 10-turn panel-mount Helipot wirewound style actually have a very long (helical) element and do give you greatly improved resolution, however it may still be worth considering limiting the range where appropriate.