I have my rotational light dimmer and am wondering the logic behind it.
If it is a potentiometer, when fully off, it should be wasting lets say 50V of power if not using a transistor. By logical design:
1) Should it have an extremely low voltage with a resistor and control a transistor to limit large power loss?
2) Is the dimmer a rheostat or a potentiometer?
If anybody has a answer, that would be great for my understanding. Thanks!
Electronic – How much power is wasted with a light dimmer
potentiometerrheostat
Related Solutions
I would suggest wiring both ends of the pot to port pins that can be configured not to burn quiescent current while sitting at half-rail (many processors have pins that can be configured to be either digital outputs or analog inputs) and float both ends of the pot while not taking readings. Connect the midpoint of the pot to an ADC input, with a significant-value cap to ground. If you have multiple pots and can't afford to use three processor pins for each one, you could e.g. use external chips to connect and disconnect the ends of the pots. Note that the ends of the various pots should not be tied together; when a pot is disconnected, it should not connect to anything else.
If you do things this way, the ADC input voltage, with its cap to ground, should remain roughly constant when the pot is connected and disconnected. When powering up the cap, take readings repeatedly until either they stabilize or it becomes clear they won't (because they go up and down, rather than asymptotically approaching some value). If there isn't too much leakage in the circuit, you shouldn't have to have the pot powered up very long if it isn't being moved, since the cap should start out at, and remain at, the proper voltage.
To search for the described part, use the keywords potentiometer with detents.
The specifics mentioned would suggest a potentiometer with 10 detents, such as this one on Amazon, or another on Jameco.
The detents can be low torque (a gentle click at each transition) or high torque (a firm click). The common / inexpensive ones are low-torque, but they seem to survive longer than a few high-torque pots with detents I have used.
More expensive such potentiometers allow individual mechanically adjustable detent torque, even to the extent of mixing high and low torque detents within a single pot (example).
At the high end of the spectrum, some manufacturers offer programmable detent torque: Internally these are essentially like stepper motors integrated with the potentiometer shaft, with the externally controlled coil current determining the holding torque at each detent position. I haven't seen this type available in retail, only through OEM sales by quotation.
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Best Answer
Dimmers traditionally involve a TRIAC that chops the ac waveform with a potentiometer controlling the duty cycle. These circuits cause highly distorted currents leading to a low power factor. Knowing this, you will easily find examples of such circuits online.
Varying current through an incandescent lamp with a series resistor (rheostat, potentiometer) wastes an unacceptable, even unmanageable, amount of power.
Note that this applies to incandescent lamps. There is no single standard solution to dimming LED lamps because of the varying drive methods used in the lamps.