### Author Topic: irLed emmiter/Detector Schematic  (Read 2901 times)

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#### santiagoe

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##### irLed emmiter/Detector Schematic
« on: March 27, 2007, 10:03:08 PM »
Purpouse of project to improve detection with more than one led. Six is better than one.
I think.

I want to build a irled/detector but i want to build one that uses 6 irled and one detector.

I'am thinking of doing it this way:

put the irled in a circle (3 on one side and 3 on the other side forming a circle).

put the detector in the middle.

I have 2 questions concerning this project:

Question #1: Would it be possible to connect all this irleds together as one and so as to conected that one line to one pin of the microcontroller and not six? I yes go on to the next question.

Question #2: How would i need to connect the 6 irleds(-with - & + with+) and would i need resistors for all of them or would i just need to place one at the end of the connection ? Any schematics for this specific project?

Sorry that's more than 3 ?

Thanks for yas help.

#### dunk

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##### Re: irLed emmiter/Detector Schematic
« Reply #1 on: March 28, 2007, 03:35:25 AM »
hey santiagoe,
#1. sure, that should work.
#2. one resistor should be fine but you should check the maximum current output of your microcontrollers i/o pin (check the microcontrollers datasheet) and compair it to the current draw of your IR LEDs. (check the LEDs datasheet.) add up the current draw of all the LEDs you intend to drive from a single pin.
if the total current you want to draw from a pin is more than the microcontroller can supply you will need to drive the LEDs with a MOSFET.
try to find a MOSFET that is designed to be controlled from a TTL voltage (IE, 5Volts).
alternatively you could just controll each led using a separate I/O pin and switch them all on/off at the same time.

i really don't know how much more range multiple LEDs will give you.
keep us informed of your findings

something else you should check out is the brightness of the LEDs. the LED datasheet should give you a "brightness" value. buy the IR LED with the highest value.

dunk.

#### santiagoe

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##### Re: irLed emmiter/Detector Schematic
« Reply #2 on: March 28, 2007, 01:16:22 PM »
thanks for your response dunk!

#### Brandon121233

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##### Re: irLed emmiter/Detector Schematic
« Reply #3 on: March 28, 2007, 05:38:03 PM »
As I have never experimenting with doing this before I cant give any first hand knowledge on how well it would work... having said that I know the way that infrared remotes can work form over 20 feet away is that they are double and sometimes even triple the voltage or current that they are rated for, the way they can still do that with out having the LED blow out is by pulsing it relatively slow so it is on sending data for maybe 50 milliseconds and then it rests for say 400 milliseconds, by doing that it keeps the LED cool enough to not blow out, if you can implement some kinda system like that you might get a lot better results than just having 6 LED's. Also I don't know exactly what you are using this for but if you plan on using it to detect something over about 5-10 feet, an ultrasonic rangefinder would be a lot more accurate and easier to implement. If I said anything wrong above someone please correct me. Good luck with your project.
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