Make optical encoder using IR Receiver [closed]

Question

I want to make an optical encode to measure rpm of a motor. I have F429 optical encoder but it does not seems to be working above 2100 RPM. Also it is full of errors.

I have seen in this tutorial to make single channel optical encoder but the circuit diagram is not clear. Do i need to use 3 pin IR Receiver or 2 pin IR receiver. I think a 3 pin receiver is used in the video but the circuit diagram is not clear to me.

SPECIFICATION:

Encoder wheels slots: 20
Desired RPM to measure: 1000

QUESTION: Need a circuit diagram to create an optical encoder using 3 pin IR Receiver(phototransistor) and an IR LED.

Please edit your question and make it complete and independent of external sources. — devnull
– devnull, Commented Oct 30, 2024 at 16:26
How many slots does your encoder wheel have and what is the desired maximum RPM to measure? — Jens
– Jens, Commented Oct 30, 2024 at 17:40

Jens · Accepted Answer · 2024-10-30 18:30:31Z

The mentioned "3 pin IR receiver" is not just a phototransistor, it is a complex receiver circuit which decodes IR signals modulated with a fixed frequency and sent by a remote control.

It cannot be used in this application except at low RPM rates and only if the IR LED is driven by a generator with this frequency, typically 38 kHz.

The mentioned "2 pin IR receiver" is a fake, it is an IR transmitter LED used in IR remote controls. Not really useful as optical detector, but not absolutely impossible.

The F429 encoder seams to work at the desired 1000 RPM. With 20 slots at 1000 RPM you have a light interrupt frequency of below 400 Hz, this should be ok for this module.

You may have issues with ambient light there, so a cover may be useful. As jsotola mentioned, you should inspect the optical path. The light should only go through one slot at a time.

according to the data sheet, the 3 pin receiver has data rate of 1200 bits/pulse per second. MAX rpm = (data_rate/grid_hole)*60----------------= (1200/20)*60---------= 3600 RPM. I think it would be enough for my application. Your suggestion is to continue using F429? — Pratham
– Pratham, Commented Oct 31, 2024 at 7:03
Yes, stay with this F429, it is made for the job. There is no improvement in sight using the other componets, optical properties don't match. Better describe the errors you see, add a schematic and the software you use. The issue may be there. — Jens
– Jens, Commented Oct 31, 2024 at 17:05

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