Poor performance of IR LED

I'm trying to control an Olympus camera (E500) with Arduino. I connected an IR LED to an output pin which is triggered from arduino once a button is pressed. The produced IR signal makes the camera to shoot a picture. The whole thing works fine but only within a range of 50cm circa and only when the camera faces the led - with small deviations from this position the camera will not see the IR. I guess this is because the light produced by my LED is too weak.

Would things go better if I connected multiple LEDs looking at different directions? Should I use external power supply of 12 Volt for my LED and trigger it from the base of a NPN transistor (common collector circuit)? Should I try some other type of LED? Any suggestions?

Well we could sure a link to the specific IR led you are using. Some require operating at more forward current then a normal 20ma type led, I had one in the past that ran at 100ma I believe. Also are you using a series current limiting resistor, is so what value and if not you may have damaged your arduino output pin.

Lefty

retrolefty: Well we could sure a link to the specific IR led you are using. Some require operating at more forward current then a normal 20ma type led, I had one in the past that ran at 100ma I believe. Also are you using a series current limiting resistor, is so what value and if not you may have damaged your arduino output pin. Lefty

I don't know the exact model of the LED I'm using. It's a standard IR-LED like that ones that most remote controllers have. Should I try to find some particular type of LED? I used a resistor of 220 Ohm in series with the LED. The output pin is fine - I just checked with a voltmeter while asking from Arduino to provide a constant (digital) output (It really gives 4.99V). However, even the internal resistance of my LED is zero, the current with the use of a 220 Ohm resistor, is 22.7mA. What is the maximum current an Arduino Uno can give safely? (I have an external power supply of 1A max.)

chung:

retrolefty: Well we could sure a link to the specific IR led you are using. Some require operating at more forward current then a normal 20ma type led, I had one in the past that ran at 100ma I believe. Also are you using a series current limiting resistor, is so what value and if not you may have damaged your arduino output pin. Lefty

I don't know the exact model of the LED I'm using. It's a standard IR-LED like that ones that most remote controllers have. Should I try to find some particular type of LED? I used a resistor of 220 Ohm in series with the LED. The output pin is fine - I just checked with a voltmeter while asking from Arduino to provide a constant (digital) output (It really gives 4.99V). However, even the internal resistance of my LED is zero, the current with the use of a 220 Ohm resistor, is 22.7mA. What is the maximum current an Arduino Uno can give safely? (I have an external power supply of 1A max.)

20-30ma is the recommended continuous output current for an output pin, with a 40ma absolute maximum or destroy the pin value. There are UV leds rated to run at 20ma, but again we don't know what your are dealing with. Running at more the 20-30ma requires you use a switching transistor between the output pin and the led/resistor combination. You could try using multiple led/resistors wired in parallel and switched with a transistor to try and get more range. UV leds might also not be optimized at the same UV frequency that your camera is using, but I don't know how to tell what your camera wants and again your not sure what led you are working with.

Lefty

Hi, Are you using the setup inside or outside, is there a lot of natural light around, maybe coming in through a window, if so try a shade around the camera sensor - without a shade my lap timer does not work at all, with a small matt black cardboard tube around the sensor it works flawlessly.

Also try driving the LED with more current, I am driving mine with 100ma - obviously not directly from an Arduino PIN. You mention that you are sending a signal, I assume that this is a 38Khz coded signal of some sort in which case the LED is off a lot of the time and can be driven harder.

To get a wider angle from a single LED, reflect it off something, try a quick experiment like pointing the LED up and reflecting if off your hand towards the camera, you will get a much wider viewing angle - a sheet of white paper or aluminium foil in a small housing for your transmitter will do the same but much more efficiently.

I am using IR Emitters and Detectors for an RC Car lap timing project here -

http://rcarduino.blogspot.com/2012/03/punk-consoles-and-ir-transmitters-555.html

EDIT: If you off load generating the 38Khz IR signal to a 555 timer, you can drive the LED harder and use a potentiometer to tune the frequency which will both help with range.

Duane B

rcarduino.blogspot.com

50cm is pretty bad. Even with a 20ma red LED I could easily get 2 meters (and as an aside most IR receivers aren't super sensitive to the wavelength of the light). Like Duane mentioned with the cardboard tube I'd suggest testing it a dark room or at night. If you have any other visible light LEDs test your circuit with it to see if you're getting some decent current. Also make sure you've got the right carrier frequency for the beam.

If you're looking for a stronger LED try a TSAL6200 (which is 100ma) or a red pen laser will work at even more extreme ranges.

Thank you all for your answers. Finally I figured out a solution:

In order to check the strength of my LED I used my laptop's camera. I compared its brightness when emitting some sort of signal with that of an LED from a TV remote control. I observed two things; first off, it was too directional and second it was too dim. For the second problem, I used a common collector NPN circuit and I provided 60mA to the LED. In order to make the light scatter a bit, I wrapped around some aluminum foil and it performed much better. I found using a web camera to test IR LEDs pretty helpful...

Research using higher current with short pulses for driving an IR led.

IE http://lifeproject.spacestudios.org.uk/?portfolio=arduino-ir-communication