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Infrared light activated switch

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jpoopdog

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Hi,

I am currently brainstorming ideas for a light effect to put into the spokes of my mountain bike wheels, essentially i want to be able to do something like those led pattern fans. I already got the pattern down and know all that, the only issue so far has been setting up a stable clock so to speak. for example its no good to have words displaying if they spin as fast as the wheels.

Anyway, just now it occured to me, i could put sensors along the spokes and have them detect for infrared light, to establish that that point in time the whole thing is upright, and i could have the pattern adjust to display upright based on when a sensor detects infrared light, no problems.

What im asing about is what would be the best way to do this?
Should i use a photoresistor with an infrared filter (to block out everything but infrared), or are there specially designed infrared sensitive resistors or cheap sensors that change resistance and so fourth, when exposed to infrared light? the aim is to situate a laser or infrared led to activate the LED's by triggering a sensor, and this would be done for like 10-15 sensors along the wheel. The intention here is to only use said effects at night.

ANyway, what would be the best way to trigger the sensor? laser? high powered LED? and what kind of sensor could i use? would a photoresistor work?
 
A Hall-effect sensor, plus a small magnet on a spoke, would probably be simplest/cheapest and would eliminate the need for optical-filters/pulse-decoders.
How will you get power to LEDs on the spokes?
 
Buy a 2 quid bike computer and use the sensor (reed switch) on the spokes and the magnet on the forks.
You'll need to debounce the contacts in software, but thats no hardship.
 
I've known the reeds of reed switches become permanently magnetised by a constantly passing magnet. The contacts then stay closed :(. Shouldn't happen with a high quality switch, of course. But at £2.........?
 
My pushbike has had one for over a 1000 miles, and still working ok.
I recently repaired a gyroscopic ball thingy for someone that has one operating at 250hz, I didnt think they went that quick either.
Simple ideas are often good ones.
I made the assumption that bike computers are reeds from the cost, I've checked mine with a meter and it read a few ohms with the magnet close to the sensor so it looks like a reed allright.
I prototyped something along the same lines but a lot simpler, wheel mounted lights, the front half of the front wheel lit up white and the rear half of the rear wheel red, the same half section of the wheel remaining lit over a minimum speed.
I got it to work, but for some reason it never got past a bench test, probably because of the praticalities of having batteries and leds etc on a bike wheel.
 
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My pushbike has had one for over a 1000 miles, and still working ok.
Good to hear it. My experience must have been with a dodgy switch of dubious provenance. It was used on an agricultural bale-wrapping machine but lasted only one season :(
 
I've seen those bale counter thingies, didnt know they used a reed switch.
 
Probably the commercial ones don't. Mine was a home-brew, built yonks ago before cheap Hall-effect sensors were readily available.
 
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