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I'm working on two arduino (one a dock, the other one on a robot) communicating through a IR to let the latter know about its location.

I 3D printed a piece which goal was to channel the 3 IR led lights, to prevent them from overlapsing (exactly in the same manner as the Kobuki.

For a reason I don't know, the IR signals seem to go through the 3D printed piece which doesn't seem to let visible light through.

I known that there is no 100% absorbant materials, and I know "black for visible lights" doesn't necessarily mean "black for IR lights".

I think my problem is more related to my lack of experience in the field. My question is : why do I get signals from a IR led channeled toward a location I am not in ?

Patently, it means my light channels are not channeling light.

Therefore, better : How can I make a better (and cheap) channel for IR light ?

The piece I 3D printed is grey (silvery like I guess)

edit : to prevent incomprehension, i would like to clarify "channel". What I mean is to block all light "not going" in the right direction, whatever happens to that light. I apologize if it is not the word I should have used.

Pierre-Antoine Guillaume
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    IR (infrared) is like heat, right? If you have a fire in your room, does it still get hot at the other end of the room, even if you have a chair between you and the fire? – Nick Gammon Dec 28 '16 at 08:40
  • We had this problem at a previous job - and it's surprisingly difficult. Long story short, we found that enclosing the devices inside cardboard boxes did NOT work, but wrapping the boxes entirely in aluminum foil, without a single gap, pretty much did work - although then it's difficult to get the cables in. Good luck. – Mark Smith Dec 28 '16 at 08:48
  • Well one is first and foremost an electromagnetic radiation I can deflect with a mirror while the other is a mechanical energy of shock between molecules, isn't it ? – Pierre-Antoine Guillaume Dec 28 '16 at 08:52
  • Oh, really ? I'm going to try and spread a little aluminum on the 3d printed thing, thank you – Pierre-Antoine Guillaume Dec 28 '16 at 08:54
  • I use aluminium tape for this kind of thing. It's used for sealing joints in heat ducting. Cheap and easily obtainable, and being self adhesive makes it easy to apply. – Majenko Dec 28 '16 at 09:59
  • Are you sure the signal isn't just reflecting of the walls. – Gerben Dec 28 '16 at 10:05
  • didn't know it existed as tape as well, i'll look for that (I've stuck it with glue for now). – Pierre-Antoine Guillaume Dec 28 '16 at 10:12
  • I don't think the signal is reflecting on walls, because I put a specific set up to try it ! – Pierre-Antoine Guillaume Dec 28 '16 at 10:13
  • You can also get reflective spray paint that is quite good. It's also used for EM shielding on the inside of plastic cases since it's conductive. – Majenko Dec 28 '16 at 10:30
  • Are you using ASK modulation? Are you using ASK IR receiver devices commonly found in remotely controlled entertainment equipment? – st2000 Dec 28 '16 at 14:01
  • It could still reflect of the 3D printed material. Try, and temporarily replace the IR leds with visible light leds, and see what you can still see. – Gerben Dec 28 '16 at 17:06

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You can not use common modulation remote control receivers as they contain an ACG feature which will likely "turn up the volume" until it detects even a weak reflected signal. Instead consider if this reflective sensor, which does not contain an AGC feature, is appropriate for your design.

Alternatively you might explore the response time of the AGC feature to see if you can defeat its intended purpose. That is to say, rapidly switch between IR transmitters in order to keep the AGC level at low gain. Essentially blinding it from weak reflected signals.

You might also transmit continuously on all IR sources and determine if the AGC will put the weak signals below the noise floor.

st2000
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  • I don't know if it will work but i've ordered some of these. Do you happen to know if they work with IRremote ( https://github.com/z3t0/Arduino-IRremote ) ? – Pierre-Antoine Guillaume Jan 04 '17 at 11:04
  • We are supposed to avoid making recommendations. However I could not find good technical information w/o referencing an actual part. – st2000 Jan 04 '17 at 14:34
  • When working beyond tried and tested Arduino projects, you need to take the extra effort to verify if components will do what you expect. In this case, most IR remote controls operate at about 38KHz. There are exceptions. Vishay makes several parts based on the linked to specifications. According to this specification, the last 2 digits of the Vishay part number indicate the operating frequency. At the bottom of page 1 two parts are listed in the parts table. There the TSSP4038 is listed as operating at or near 38KHz. – st2000 Jan 04 '17 at 14:34
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I realize this is old but I have had a similar challenge making an code wheel for an optical encoder. PLA material did not block the infrared. however, all of the codewheels that I have made with black PETG material have worked. Obviously you would want to fill in the shape as much as possible and assure that you do not have gaps between the layers. Personally I have not had to make any tweaks with the Prusa MK3 printer, black PETG material and the common 0.2 layer height.

Mark
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The best and cheapest way would be to use BLACK colored printing material as it would absorb the IR waves and would not let them pass! I did a similar thing when I was building an IR-based Robot so using a black reflector and painting the chassis black increased the efficiency!

Black for visible light is the same for IR too as light is just a small spectrum of electromagnetic radiation, just as IR.

Manav
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