I am currently trying to track rpm of a shaft that rotates up to 150,000 rpm using a DRV 5055 TI hall effect sensor and a teensy 4.1. I used the circuit down bellow to filter and turn the signal into a square wave, also shown. The problem is that the square wave has bouncing in the transitions causi…

[image] zwattenbarger_0123: The problem is that the square wave has bouncing in the transitions causing my rpm reading to be way higher then it should be. No it is not. See the noise is on both the high part of the trace on on the LOW part, which should be at ground level. Eliminate the nois…

Also, I believe that you have configured the hysteresis feed back resistor incorrectly for what appears to be an inverting comparator configuration. See: Comparator Hysteresis - Circuit Cellar but add some part numbers to that schematic and maybe redraw it so the ground tends to be towards the bott…

I assume you have one hall sensor on the part that is going 150000 RPM, or can. I don't understand why you are attempting to measure the pulse duration from leading edge to trailing edge. RPM would be proportional to the frequency, which would require measurement from rising edge to the next risin…

[image] alto777: I first calculated 2500 Hz and 400 us period . Then I did at again and got the same answer. Oops. My calculator added an extra zero. I guess that zero key could benefit from some debouncing! Maybe a solution appears in this thread ?

That looks pretty noisy out of your circuit: [image] I think the Teensy 4.1 has a selectable hysteresis setting. Do you actually need that circuit?

I will look into that, but this is just a prototype and for future iterations I don't want to be reliant on a teensy.

[image] zwattenbarger_0123: The problem is that the square wave has bouncing Quite likely to be related to using an analog sensor! You are detecting the magnetic field from your motor shaft. The magnetic field is NOT a uniform, point field, as you are seeing on your scope. How is your magn…

[image] zwattenbarger_0123: I am currently trying to track rpm of a shaft that rotates up to 150,000 rpm using a DRV 5055 TI hall effect sensor How is the magnetic field that the Hall device is supposed to sence actually generated? Do you have magnets on the motor shaft? What are those tria…

AVRs have built-in schmitt triggers, and the Teensy 4.x have configurable schmitt triggers. If the noise is smaller than the hysteresis in the schmitt triggers or the stick-built comparator circuit, then you shouldn't have bouncing. If the stick-built comparator ends up amplifing the noise, then a…

Debouncing Code For RPM Reading

Projects Programming

6v6gt February 3, 2025, 8:48pm 3

Maybe some of the discussion in this recent and similar thread are useful to you: Arduino reading frequency correctly in the real world

That is 25kHz or a period of 40uS !

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Debouncing Code For RPM Reading

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