IR Endurance

Projects General Guidance
1

Hi,
I am using an IR Led pulsed at <>70hz with a carrier of <> 40Khz. Its driven with 9v and a current limiting resistor of 470 Omhs, the carrier and pulse are generated through chained 555 Timers.

Assuming the circuit is active for hours at a time will the IR LED survive in the longer term ?

If not, can anyone suggest an alternative approach to providing a persistent IR Signal ?

Thanks for any help
Duane.

rcarduino.blogspot.com

2

Endurance of an LED depends upon heating, thus current. We don't yet know the forward voltage of your IR LED, hence its current. Assuming the forward voltage is 2V or so then the current will be (9V-2V)/470 = 15mA. This is not a particularly high current for LED's and unless the LED is in a very hot environment, it should last "in the longer term". Perhaps you can find some specifications on your LED's datasheet regarding aging, since LED's do age with time.

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3

As RuggedCircuits says, read the data sheet carefully.

IR LEDs can often cope with 100mA or more, and generally have quite a short range if you try and drive them with less.

4

Thanks for the responses. There is very little chance of finding a data sheet in the shops I have access to. Dubai may have the worlds tallest tower, but component shopping in 'Old Dubai' is quite literally an adventure.

I have just moved the circuit from bread board to strip board and dropped the current limiter to 330 in the process, on your advice I could still go lower, but will see how this works out for now.

Thanks

Duane B

rcarduino.blogspot.com