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IR emitter woo's

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MrDEB

Well-Known Member
I have a IR dector on a brdge spanning across a pinewood derby track. The dectors are mounted to timmers.
My big mistake is I thoght it was working (IR emitter in track but pulling 200ma instead of 20ma.
Tried adding a small resistor to get to 20 ma but the dector wouldn't reconize.
I Guess overdriving an IR emitter really increases the output.
Well the IR leds didn't last very long.
Installing some 6v Halogen bulbs in track (seem to work) but running 4 D cell batteries and the bulbs draw .8 amps. Guess the 4 D batteries wouldn't last too
long.
My next tricjk is to use an old computer power supply (5v) and the magenitic switches that turn on the lights and the timmers will handle up to 3 amps.
Just have to worry that the Halogen bulbds don't stay on toooo long. Them bulbs get hot but boy are they bright!!!
This is getting old as far as trying to get something to run right.
 
If the detectors are IR, then you might have good luck running the halogen lamps in series (half the voltage). You don't have to see the light as long as the detector can.
 
Can't run in series

Good idea but each lane has a magnetic switch that turns on the timer and the light bulb for that lane.
Have a computer power supply which should work seeing how I only need 5v (4 D cells = 6v?)
hopfully the power supply wil take the place of the 2 D cell packs (1 pack = 4 D cells per lane)
Wonder how long the D cells would last at 850ma for 6-8 seconds per run?
 
found site that states that a D cell has 4 amp hour ratting.
At 850ma it should last 4-4.5 hours I assume??
maybe the power supply is not needed?
Boy them lights are bright.
 
You can probably power the IR emitters at 200mA but only for short periods.

Use a 555 timer with the LEDs connedted from the positive rail to pin three and set the current at 200mA for a duty cycle of 90% high at 30kHz. As the timer is acting as a current sink then the actual duty cycle for the LEDs will be 10%. Also and don't to allow for the saturation voltage on the 555's output when calculating the current.

Connect the detector to a missing pulse detector (use another 555, the circuit is on the datasheet).

You could use a 556 dual timer if you want to save space time and money.
 
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