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anyone used a continuous rotation resistor for a dc motor for tracking position like this one from digikey:




manufacturer is Bourns. I need to track rotation of motor, to linear motion, like a lead screw. motor is 6v, ~1500rpm. only need to track about 20 revolutions in either direction. anyone have any other cheap suggestions, that are relatively small in size.

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- how about a linear potentiometer, also called a 'slider pot' from an audio system, with the wiper attached to the linear-motion portion of your solution.

- then you measure the analog voltage at the slider - this then tells you how much linear motion your actuator has undergone. then control the motor direction in your software.

- so, in the diagram below: linear actuator full left would give the highest AtoD value; full right would give the lowest value.



MOTOR  ----->    |   Linear actuator = Lead screw   |



                          --- (knob) -------------------------------

                          |          Slider potentiometer          |


                             |        |         |

                           V+         |        Gnd    


                                 To 430 AtoD






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if you can fix a magnet to the shaft a magnetic sensing IC will give you very good accuracy absolute position readings up to high RPM


I have used an AS5132  which gives 360 counts / revolution at speeds up to 72.9K RPM


but there are the

AS5140H (10 bit count per revolution = 1024 counts / revolution at speeds up to 10k RPM)

and AS5048B (14 bit counts per revolution = 16384 counts / revolution with a sample rate of 11kHz (doesn't list an RPM))

as well




AS5132 = $5.50

AS5140 = $10

AS5048 = $11

prices from mouser.

 the magnet is about a 40 cents or so link (diametrically magnetized)


at least with the AS5132 which i have used...  if you are talking to it serially, it has a 9 bit multi turn counter internally  (+- 256 turns) that you can read as well as the position within the current revolution to give you the full count of its position so you don't have to keep up with it yourself.


and the current position (within the current turn) can be read out as a pwm signal, as serial data, and or as a pulse train depending on what you are reading it with.

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