I have an AC speed controller board and I would like to replace the 500K potentiometer on it with a potentiometer/switch combo to suit my application. However, the potentiometer I have is valued at 1M. It's a common type of speed controller from amazon.
Is there an easy way to reduce the overall resistance of the pot by half to make it 500K? A resistor in parallel to make some kind of a voltage divider?
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3\$\begingroup\$ We will need to see a schematic of the circuit surrounding the potentiometer. \$\endgroup\$– Spehro PefhanyCommented May 26, 2021 at 0:50
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\$\begingroup\$ see my revised question \$\endgroup\$– AwiringCameronCommented May 26, 2021 at 1:00
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6\$\begingroup\$ A photograph is not a schematic. \$\endgroup\$– HearthCommented May 26, 2021 at 1:01
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\$\begingroup\$ You can create one by tracing out the circuit. There are only seven components. \$\endgroup\$– TransistorCommented May 26, 2021 at 6:40
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2 Answers
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As we don't have a schematic, I'll take a guess.
Looks like a simple triac-diac "dimmer" type circuit. In such a case, the potentiometer is connected as a rheostat. In such a case, the center and the left pin (from the front, pins down) of the pot are either connected to each other or the left pin is unconnected.
So you can try the 1M pot with 1M 1/4-W resistor in parallel, connected as the original. The linearity will be affected but it should not be exceptionally worse than it is.
As always, keep in mind that working with mains voltage is inherently hazardous and be sure to get help or abandon the project if you are not thoroughly familiar with appropriate safety measures.
answered May 26, 2021 at 1:11
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This type of speed controller has a small trim POT for setting the minimum output (e.g. to keep motors from stalling). After bringing this resistance down, I was able to make the main POT behave like I was expecting. I appreciate the help.