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Discussion Starter · #1 ·
Hi again.

The other day I chipped two Scaley Porsche GT1s.

The lane changing still works, but:

Laps will no longer count (Arc Pro / Magic Arc).

I guess this is because both cars leds have ground down flat on the track! All other cars are OK.

1) Would 3mm, clear, 940nm, 1.2-1.7v approx. be correct a replacement?

2) How best to mount these in the cars to prevent further trouble?

(I have searched, but cant find this on the forum).

Thank you very much.

Keith
 

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I don't know of the specs for Scaley IR LED's but I do know from experience that filing down the lens on an LED usually increases the dispersion of the emitted light rather than narrowing it. So if you adjust the height a little higher into the chassis you might find that your worn down LED's still work fine. Maybe check that the plastic is clean, if it has been rubbing on the track it may have picked up some schrapnel.
 

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Hi K - what is the distance between the trailing edge of the guide blade and the position of the IR LED? remember with the ARC PRO there are stringent limits -could this be the problem?

c
 

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Discussion Starter · #4 ·
4cms exactly from the led to rear of braid. I believe the laps counted at least once earlier.

The counting is done on the ARC PRO single sensor principle (about which I know nothing).

The leds are actually slightly indented! Hence I would like to order some new ones and would be grateful for the spec.

Your help is appreciated guys.

Keith
 

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If the IR LED is several cm behind the trailing edge of the black plastic of the guide blade a standard ARC PRO will not read laps correctly. Is the IR LED so far back?

c
 

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Discussion Starter · #6 ·
Yes, the IR LED is 3.7cm behind the trailing edge of the black plastic of the guide blade.

I will reposition it and test. This should not be too much of a problem.

Cheers.
 

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LEDs wear down if they are pushed through a thin chassis. I always cut a small rectangle of 1-2mm plasticard and drill a 3mm hole in it - then glue it over the 3mm hole in the chassis that I drilled for the LED. This way the LED is flush with the chassis rather than sticking down and getting ground down by the rails. The LED is an interference fit so I dont glue it in, I simply hold it down into the hole with a small blob of blu tack.

Having the LED slightly higher also lengthens the time the sensor sees the LED when the car is passing.

940nm LEDs are hit and miss. 875nm IR LEDs work much better. Being slightly below operating wavelength is better than being over for technical reasons I dont quite understand but has something to do with range extending more over the nominal rating than under the nominal rating.

In laymans terms the 940 struggles to reach down to the required wavelength and the 875 has an easier time reaching up to the required wavelength even though the required wavelength is numerically nearer to the 940.

Voice of experience - I had unreliable results with 940 until the gurus recommended 875 and I now have superb reliability.
 

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Discussion Starter · #9 ·
Good morning and thanks for your informative reply Mr Modifier. I appreciate your time and trouble once again.

I will post a hopefully useful photo or so when this is complete.

K

:)
 
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