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Topic: 3/4 HP Motor encoder and Parts Compatibility (Read 185 times) previous topic - next topic


Jun 14, 2018, 06:25 am Last Edit: Jun 14, 2018, 06:36 am by BackFiire
I have a 3/4 HP motor that already has a programmed VFD to control it. I want to use Arduino to display the RPM on an LED screen and use a toggle switch to show angular position under a certain RPM for more accuracy. The arduino will be connected to an encoder, i have a Dynapar HS20 series(7Pin w/o index)[HS20-0180-8-1-3-3-6]. I will be running this motor at variable speeds up to 5000RPM.

(im also not sure the exact PPR of my encoder, on the manual all i see is 50 to 2540PPR, unsure how to find my exact PPR, or if this is determined in code?)

Ive done plenty of readings on the forms and different websites and im trying to determine the best parts to use and if they will be compatible.

  • I have been looking at LS7366R encoder chip because i have read that this frees up much of the process power from the Arduino board but im trying to determine if i need it and if it will work with my encoder. Are there better encoder chips i dont know about ?
  • Ive also been trying to determine which board to use. I have an Arduino Mega 2560 and a elegoo Uno R3 but i dont know which one is better or it doesnt matter or there something better i dont know about
  • Another thing is i have a MAX31885 Thermocouple working and on IC already, will this work with what im trying to display. This isnt too important so i can scrap this idea if it isnt compatible.
  • Last question i have is if the encoder i have is accurate enough. I have read that it has 2 signal outputs(A & B) but no Z. Will i need the Z for accuracy at higher speeds. As i understand it the Z sends a pulse for a full rotation as A&B does not so when you combine the 3 it is much more accurate.

i understand this is a multilayered question so if you can offer the smallest piece of help it would be appreciated. If its a better known part, if i need to scrap a part i already have, anything. Im a beginner and have been trying to do as much research im just not sure which pieces connect to which or how.


An Arduino can handle rotary encoders. The A and B channels tell the ticks and direction. The Z channel can indicate 0°, so that you can count the A/B pulses between two Z pulses, to find the resolution of your encoder.


Jun 14, 2018, 03:58 pm Last Edit: Jun 14, 2018, 04:00 pm by TomGeorge
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.

I want to use Arduino to display the RPM on an LED screen and use a toggle switch to show angular position under a certain RPM for more accuracy.
What RPM conditions, the angle position display will be updating continuously, and may not be readable if the RPM is not LOW enough.

The VFD should have an analog output that represents RPM.
If you are going to run the motor at LOW RPM you may need to fit a separate cooling fan as the integrated fan will not be spinning fast enough to ventilate the motor.

Can you please tell us your electronics, programming, Arduino, hardware experience?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....


After a rapid reading of the datasheet, from page 2:

Code 1 = Model = HS20
Code 2 = PPR = 180
Code 3 = bore size = 8 mm

180 PPR for a quadrature encoder = 180 * 4 edges per rotation. The microcontroller will have to deal with  180*4*5000/60 = 60000 edges per second, or 1 edge every 16 us.

I can't tell if a Mega can handle this load since it will depend on the parallel tasks to perfom, I just know that a DUE can handle more than 240000 edges per second.


For high RPM it's sufficient to count only one edge per pulse, with only 15000 interrupts per second. Since the value is for display only, an encoder with a much lower PPR could be chosen as well.

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