IR detector for marble track.

[fotoopa]

IR detector for marble track.
This detector can be inserted anywhere on the existing marble track. It has the dimensions for the Fischertechnik blocks. The detector works with an IR led and a photodiode as receiver. The 3D print housing is made in such a way that it shields the ambient light as much as possible. If necessary, an extra cover can be mounted afterwards on top. It has 5 mounting possibilities for optimal environmental suppression. The resistance values are given for 5V. If 9V is desired, the values can be increased slightly. The current values will also work at 9V but the current is higher. I use my regular 3 pin connection: output, VCC, GND. Because there is a pullup resistor you have to take into account that the output voltage will have the same value as the installed VCC. Therefore, do not use 9V where the output should be 5V max!


HD: https://www.flickr.com/photos/fotoopa_hs/49157990727




HD: https://www.flickr.com/photos/fotoopa_hs/49157280378


HD: https://www.flickr.com/photos/fotoopa_hs/49157990747

The 3D print files on Thingiverse: https://www.thingiverse.com/thing:4015962

On the picture the cover plate is still shown with 2x2 pins, but the .stl file now contains 2x4 pins. This gives you 5 possibilities to mount the shield. The shield is only needed when there is direct sunlight. You have to be a bit handy to solder the whole thing, but I'm 76 years old, I need strong glasses with extra light and then it works fine.

Frans.

[juh]

Very impressive once again, Frans! I just added the links to the list.

Is ambient light really a problem in your application? I'm asking as I've been using a similar (reflective) sensor, a TCRT5000, recently. Initially I used the delta method to cancel out ambient light, by comparing the input value before and after turning the IR-source on. However, I failed to produce conditions that would severely taint the measurements, so I conluded that if needed I could do without canceling ambient light.

Jan

[fotoopa]

Is ambient light really a problem in your application?
Jan

No, I haven't had a problem with that yet. The shielding is only a precaution in case there are problems with direct sunlight. For the time being, I don't mount the lids.
Some precautions have been taken:
- The IR photodiode contains an ambient filter (FA type).
- The IR led has a narrow radiation angle.
- The 3D print is printed in black.
The internal shape where the diode and the photo transistor are located has a narrow horizontal bore of 4 mm. This makes it difficult for external light to reach the photodiode. With all these precautions, I haven't discovered any problems.

I'll have another flex rail module ready in a few days. It is now on the test table ( with servo). I'll make a new topic for it.

Frans.

[NBGer]

Hello,

great job!
You are doing all your parts very thoroughly!

Actually I am not very interested in marble tracks. But I am sure, I could use this IR detector in other projects, too!