InfraRed ramblings

[Demon]

Using this 940nm LED set on Amazon: https://www.amazon.ca/dp/B01HGIQ8NG

Can I have the transmitter LED on without any pulsing? (resistor values are temporary, did not do any calculations yet)



This circuit was inspired by this tutorial: https://www.instructables.com/Intro-to-IR-Circuits/

I just want to detect a hole in a disk; no communication.


Examples on google often use 38kHz or 56kHz, but their receiver has 3 pins; VDD, VSS and DAT. That leads to me to believe there's more going on in that receiver.

This guy has a really nice way to calculate the values:

[richard]

if there is any ambient light leakage a ir sensor like SEN-19018 would be better than a photo diode, with the bonus of making
led modulation unnecessary too.

if the distance between led and sensor is small [under 10mm] then you only need a small current through led 5 to 20 mA
would be heaps

[Demon]

There will be minimal light leakage. These will be on either side of a disk, as close as I can get them.

I plan on putting black heatshrink over the LEDs as close as I can to the rotating disk.

This will be used as a way to home a stepper (fuel gauge on a flight sim); I need to find 0 easily. I'm sure there as more precise techniques, but I'm looking for a simple low-cost solution that works.

I was planning on using these steppers: https://www.amazon.ca/dp/B0CPSLS944

[mark_s]

Search optical interrupter. These are used often for homing.

https://www.amazon.ca/s?k=optical+in...ref=nb_sb_noss

[Demon]

ARGH! That's what they're called. I knew these existed, I just didn't know their names.

[mark_s]

You can also use a hall effect IC and a small magnet. The hall effect ic's come in a 3 pin TO-92 package and are easy to interface to your micro.

For example

https://dronebotworkshop.com/stepper-motor-hall-effect/

[Demon]

Thanks Mark!

I was considering laying a limit switch flat along the outer edge of the disk, and use a notch to catch the limit switch roller. But I'm liking the hall sensor even more:
- no moving parts,
- impervious to dirt or light seepage,
- can sit directly on the PCB,
- lower cost,
- and waaaay less bulky.


Going to try this hall sensor:
https://www.digikey.ca/en/products/d...ULPGM/12165112

And these magnets:
https://www.digikey.ca/en/products/d...c/8189/5400498

[mark_s]

I bought some of those stepper motors you linked above. Really cheap, small with a gearbox, but be aware they are wired so you cannot use them with a standard stepper driver module. These have five leads (4 phases and a common) so your micro must generate four phases to make it run. It is easier to use a step and direction driver like the one in the hall effect video. I was able to modify the motors to run on a standard driver using this info.

https://forum.arduino.cc/t/howto-mod...-4wire/1132680

[Demon]

Yeah, these are unipolar steppers, not bipolar.

I'm using the ULN2003 as driver that came with them. I'll be switching to a ULN2803 for my use.