A 38KHz IR LED

Hi,

Been working on a lap timer project and I've made a system with an IR sensor.

Unfortunately my attempts at making a IR emitter have not gone as well as I hoped.

Is there a 38KHz IR emitter that's already on the market? I'm looking for an item that requires a power source and then starts emitting IR which could be picked up by the sensor as the driver passes.

Cheers Atrixa

No nothing Avaliable like that. If you want just an IR beam with no modulation then simply set the PWM frequency to 38KHz, select 50% duty cycle with an analogWrite of 128 and connect your IR LED to that pin, with a resistor. For more power then use a transistor.

There's one issue to consider, though.

Grumpy_Mike is right in that by tinkering with the timers, you can get a very clean 38KHz square wave for IR transmission. However, the IR receivers I know have automatic gain control, which means that if they get a constant signal for too long, they start to give false results; and they need some recuperation time following a long signal.

You could transmit 010101... , each lasting the minimum 6 or 10 cycles (see the receiver's datasheet), and test for sequences of two or more 0's - I believe even a fast car is not fast enough to escape that.

igendel: Grumpy_Mike is right in that by tinkering with the timers, you can get a very clean 38KHz square wave for IR transmission. However, the IR receivers I know have automatic gain control, which means that if they get a constant signal for too long, they start to give false results; and they need some recuperation time following a long signal.

http://www.vishay.com/ir-receiver-modules/presence-sensor/

TSSP4038 or TSSP58038 would be the parts to use.

Chagrin: http://www.vishay.com/ir-receiver-modules/presence-sensor/

TSSP4038 or TSSP58038 would be the parts to use.

Thanks, I wasn't aware of this kind!

TSSP4038 or TSSP58038 would be the parts to use.

+1

The TSSP58038 is more directional and probably better for this application.

You can also put the emmitter in a directional pipe (or just heat shrink tubing to create a narrower beam.