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Author Weird electronics problem
Steve
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Registered: 30th Mar 02
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20th Oct 14 at 09:26   View Garage View User's Profile U2U Member Reply With Quote

Basically I have a couple of lasertag guns, they have 3 what I believe are IR sensors on them to detect the hits, what Im trying to do is extend the sensors away from the gun.

the sensors themselves are black 2 pin IR receivers (I think)

Anyway I removed the sensors off the pcb no problem, then I attached a 12inch wire to each point where it was joined with the sensor then attached on the ends of these wires.

Tested it out and it received hits on the sensor perfectly, however the gun wouldn't fire properly, it was sometimes not firing at all, then sometimes it was taking a few seconds for it to fire after pulling the trigger. This is where it gets strange to me...

Removed the sensor and left the wires the same length but with no sensor or anything on the ends, same problem. However if I cut one of the wires down to about an inch, or remove it altogether the gun works fine!?!? What is this voodoo? why would it matter how long the wire is especially as there is nothing even on the other ends of the wires?

The only thing I can think is perhaps the wires are acting as some sort of aerial, or causing some sort of RF interference? in which case would using shielded wire help?
ed
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20th Oct 14 at 12:51   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by Steve
What is this voodoo?

Physics, I believe,
DaveyLC
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20th Oct 14 at 12:55   View User's Profile U2U Member Reply With Quote

You did wire up the IR LED's around EXACTLY the same way you removed them yes?
Steve
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20th Oct 14 at 12:57   View Garage View User's Profile U2U Member Reply With Quote

Yeah, but they aren't really part of the equation as the problem happens even with no detectors on the ends of the wire.

Basically 2 12 inch wires attached to the pcb with nothing on the ends, the gun wont fire properly.

If I just cut one of them down to about an inch it works fine
DaveyLC
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20th Oct 14 at 12:59   View User's Profile U2U Member Reply With Quote

The wire you are using might have quite a high natural resistance.. or maybe your soldering sucks? Have you tried testing the impedance with a meter?
Steve
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20th Oct 14 at 13:21   View Garage View User's Profile U2U Member Reply With Quote

Nope, the resistance thing has been mentioned to me today aswell, so will try some thicker wire later.

This was a guys reply on the electronic forum who seemed to think it could be related to the wires acting like antennas

quote:
Yes and Yes. The IR Rx circuitry will probably have a high gain amplifier of some kind which could pickup external noise. I don't know why the gun doesn't fire, maybe it does but it's just too fast for you to see and then it detects what it thinks is the return beam straight away. Or if it's receiving anything it just might not fire, that might be part of how it works.
Adam
Cavey
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20th Oct 14 at 15:17   View User's Profile U2U Member Reply With Quote

IR beams show up on phone cameras don't they? That would show if its firing at all I guess?
DaveyLC
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20th Oct 14 at 15:18   View User's Profile U2U Member Reply With Quote

BTW Steve, are you using shielded wire? If not, you should
Steve
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20th Oct 14 at 17:09   View Garage View User's Profile U2U Member Reply With Quote

no and plan too
Bart
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20th Oct 14 at 17:22   View User's Profile U2U Member Reply With Quote

Resistance shouldn't be an issue on such a short cable, assuming you've not wired it in something much smaller than the original cable. Volt drops normally only occur on really long cable runs.

Also, I can't see how a shielded cable would make any difference unless a data/analogue signal is being transmitted?
Again on such short distance and such a low voltage device I wouldn't expect it to pickup any interference.

quote:
Originally posted by Cavey
IR beams show up on phone cameras don't they? That would show if its firing at all I guess?


Tried this on a Siemens ultrasonic hand held programmer, it showed up on an old smartphone but not on my iPhone 5s..... odd

[Edited on 20-10-2014 by Bart]
DaveyLC
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20th Oct 14 at 17:31   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by Bart

Also, I can't see how a shielded cable would make any difference unless a data/analogue signal is being transmitted?




That's what IR LED's are for.. serial data
ed
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21st Oct 14 at 08:37   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by Cavey
IR beams show up on phone cameras don't they? That would show if its firing at all I guess?

They also travel at the speed of light
Balling
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21st Oct 14 at 09:17   View Garage View User's Profile U2U Member Reply With Quote

quote:
Originally posted by Cavey
IR beams show up on phone cameras don't they? That would show if its firing at all I guess?
They used to. Some newer phones have IR filters.

I discovered this after trying 4 different sets of batteries in a remote only to realise my new phone didn't show the IR light.

Ed, you look at the diode. The duration of the light output is typically slower than the speed of light.


Cavey
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21st Oct 14 at 11:25   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by ed
quote:
Originally posted by Cavey
IR beams show up on phone cameras don't they? That would show if its firing at all I guess?

They also travel at the speed of light


You know I didn't mean taking a photo of it

And I didn't know they'd filtered them nowadays, still show up on my Nexus

[Edited on 21-10-2014 by Cavey]

 
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