Photo Interrupter RPM Sensor

Hi all,
I’m looking for an RPM sensor to measure rotor head rpm, I have searched online, read the available topics and rpm wiki. I just need to confirm my understanding.
This type here has a Schmitt trigger output, which mean it does not require a pull up resistor, does it ?, and can be directly connected to the PWM port on Pixhawk !

Thanks in advance

I don’t think so.
The device you’ve selected creates essentially a frequency based on speed. → The higher the rpm the higher the output frequency.

However, PWM stands for Pulse Width Modulation which is essentially the space in between pulses that is being checked /changed. (Or used to control something like a servo).
So, whilst the frequency is essentially also changed, it is not proportional to the pulse itself. As such I doubt you would get a consistent and reliable reading if you connected such a device to a PWM port.

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Hi @Pasto,

For measuring RPM with the PX4, you can use our TFRPM01 sensor, which is a pulse counter. The TFRPM01 sensor connects to the autopilot via I2C, and the probe connects to it using a 3-pin header. The probe is sensing element itself - for example your optical gate from amazone link. The pinout of the sensor from Amazon seems to be compatible with the TFRPM01 probe input.

For more information, you can check here: TFRPM01 Documentation