IR leds vers Halogen light bulbs

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Doug-in-the-woods
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IR leds vers Halogen light bulbs

Post by Doug-in-the-woods » Fri Jun 22, 2007 10:31 pm

been trying to make progress but keep getting smacked with glitches.
I wired up the Swantech timers w/ IR emitters in the track.
Worked great until I measured the current!! ouch!!!!
meter says 200ma.
added resistor to obtain 20 ma. now the timers won't reconize the leds. Not bright enought.]
changed out to Halogen light bulbs that draw 850ma but the timers reconize the light bulbs.
With 4 D cells the lights will work for about 4-5 hours drawing 850ma.
Each D cell = 4 amp hours
maybe adding a computer power supply to substitute for the batteries??
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Re: IR leds vers Halogen light bulbs

Post by Twitch » Sun Jun 24, 2007 4:10 pm

You can get wall-wart style power supplies at Radio Shack that'll source more than 200mA easily. I got one a while back for a piece of hardware that needed 12V at 800mA. No problem.

It'll mean a requirement for 110VAC, but it won't run low in the middle of a competition, either.

Tom



Doug-in-the-woods
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Re: IR leds vers Halogen light bulbs

Post by Doug-in-the-woods » Sun Jun 24, 2007 9:20 pm

If I get time I plan on adding a 110v power supply but running outta time.



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Re: IR leds vers Halogen light bulbs

Post by SuperDave » Fri Jun 29, 2007 9:13 am

Note to those who think IR is the solution for finish line detection. IR bulbs at 20 ma which is a relatively high current, though perhaps in this case not exciting the most efficient IR emitters, didn't work but VISIBLE light halogen bulbs did even though IR sensors are used. Caveat racer!


(Note: the author is a designer and vendor of tracks, timers and software. Comments by him or to him should take that into account as appropriate.)

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Re: IR leds vers Halogen light bulbs

Post by Doug-in-the-woods » Fri Jun 29, 2007 9:28 pm

Wouldn't IR be perfered over visiable light IF the IR is pulsed say 38meghertz?
Or DTMF?
I believe most ifnot all tv audio equiptment uses such?
An IR beam that caries the DTMF signal and the dectors hav a detection circuit which decodes ONLY the carried signal?
A greator distance could be utilized?



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Re: IR leds vers Halogen light bulbs

Post by SuperDave » Sat Jun 30, 2007 7:48 am

IR is preferred over visible light but visible light has LOTS of IR. IR is essentially just another name for heat. Fluorescents tend to have low IR (no heat), halogen have huge IR. They are after all just incandescents with a gas inside that helps them last longer. In addition IR sensors are not totally insensitive to visible light, just more sensitive to IR.

The TV stuff is pulsed at 38 kHz (not megahertz) and that's fast enough IF the detectors have consistent response times (not generally spec'd). DTMF is audible audio (you can hear the beeps) and thus below 3 khz (I don't recall the exact frequencies at this moment) so it isn't fast enough and won't have consistent response times. The DTMF standard as I recall looks for 100 mS tones and 40 mS off times so response consistency is not a concern for them, it is for you.

Absent a well thought out artificial 'dark room' for the detector, a longer distance implies more potential interfering sources. Pulsing helps filter steady interfering signals but momentary interference (flash bulb) can still blind a detector and make it appear as though the pulses went away.

All of the above issues and more can and have been fixed in some designs and not fixed in lots of others. Few are aware of the problems and fewer still have the knowledge and equipment to test for them. As I said, caveat racer.


(Note: the author is a designer and vendor of tracks, timers and software. Comments by him or to him should take that into account as appropriate.)

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Re: IR leds vers Halogen light bulbs

Post by Doug-in-the-woods » Sun Jul 01, 2007 6:43 am

Well the Race went off pretty well considering that the turn out of racers was low but the crowd was big.
Question 4 superdave-
the Halogen bulbs worked great in shop but get the finish line outside and one lane won't read correctly. Won't detect when car passes so the timer won't display time.
Same lane as before (Wednesday in front of supermarket)
Painted track flat black, but still won't detect. If I place my hand to interfer the beam then it detects.
Other lane o problems?
Lane Brain sensors seamed to work (placed directly behind the timer sensors.
Perhaps add another Halogen bulb or look at building a pulsing circuit?



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Re: IR leds vers Halogen light bulbs

Post by SuperDave » Sun Jul 01, 2007 8:40 am

"Outside" is one of the world's great IR sources. It's called the sun.

Brighter bulbs may work but probably won't since the most likely problem isn't light but dark. That is, the car blocks the halogen but other light keeps the sensor active. Choices include put the sensor in a dark room, reduce it's sensitivity or [moderator cut - no advertising]


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Re: IR leds vers Halogen light bulbs

Post by NealOnWheels » Mon Jul 02, 2007 10:50 pm

Do you have the detectors in the track or in the bridge?

If in the bridge then you must deal with reflected light from the sun or other sources.

Ideally they should be in the track where there will be less reflections to worry about.



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Re: IR leds vers Halogen light bulbs

Post by SlartyBartFast » Tue Jul 03, 2007 6:57 am

Another consideration:

Are the IR detectors and emitters tuned to the same wavelength?

Halogen bulbs emit broadband IR. IR leds are narrow band.

But here's a question: why did you add the resistors to the IR LEDs? Is 200ma outside the specification of the LEDs?



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Re: IR leds vers Halogen light bulbs

Post by Doug-in-the-woods » Tue Jul 03, 2007 8:19 am

The leds are / were rated at 20ma.
Could maybe get some higher rated leds perhaps.
Saw some on net just need to relocate.



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Re: IR leds vers Halogen light bulbs

Post by John Shreffler » Tue Aug 21, 2007 2:19 pm

The currents do seem a bit high. My timers use 12 ma. for the illuminators, and pairs of lanes are wired in series, so the total illuminator draws 6 ma per lane. This gives 20 continuous hours of operation from AA cells on a 6 lane track. Total saturation of the photo sensors is achieved at a separation distance of 7 inches, good for the tallest trucks. The amount of IR light you need to saturate a photo sensor depends on the value of the pullup resistor. For example, if the pullup resistor is 5 or 6 Kohms, you may have to go with a halogen source. But if you went up to 30 Kohm, you would have no problem with IR diodes. I recently found a super great diode in terms of efficiency and focus, plus it glows slightly red so you tell if it is working. I bought ten thousand, which should last the rest of my days. I will send a sample to the first 5 serious Pineheads who send me a SASE. Mailing address on www.newdirections.ws


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Re: IR leds vers Halogen light bulbs

Post by Pinewood Daddy » Wed Aug 22, 2007 10:23 am

3 years ago I built a timer using the Swantech modules. Used the Radio Shack IR emitters he suggested. 2 years ago I added a 110V power supply. I've never had a problem. There are pics around on here somewhere.



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