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Electronics => Electronics => Topic started by: airman00 on May 27, 2009, 06:19:41 PM

Title: Extending Range of Infrared Detector
Post by: airman00 on May 27, 2009, 06:19:41 PM

SETUP:
standard T-1 3/4  IR LED with 220 ohm resistor connected to 5V power source
IR Phototransistor ( the QRB1134 ) in this circuit - http://www.superdroidrobots.com/product_info/qrb1134.htm (http://www.superdroidrobots.com/product_info/qrb1134.htm) - with a voltmeter monitoring the signal

QRB1134 - http://www.superdroidrobots.com/product_info/QRB113x.pdf (http://www.superdroidrobots.com/product_info/QRB113x.pdf)

Neither the LED nor the phototransistor use a modulate IR signal. They are just ON.

GOAL:
I want to be able to detect IR light that is emitted by an IR LED with a IR Phototransistor. I don't want to send any data, just need to be able to detect the light. I want to be able to detect the IR Light from 6 feet away.

TEST:
I am trying to see how far away I can move the phototransistor from the IR LED and still get a signal. I point the IR LED at the IR Phototransistor , use a cell phone camera to verify that the IR light is hitting the phototransistor, and then see if I get any signal at all from the phototransistor.

PROBLEM:
I do get a signal when they are 1 foot apart, but passed 1 foot I do not get any signal. What can I do to increase this range?
I know further range is possible because TV remotes have ranges farther than 6 feet!

Thanks

Title: Re: Extending Range of Infrared Detector
Post by: Razor Concepts on May 27, 2009, 06:58:46 PM

Look into higher power IR leds?
Also there are often those IR screens in front of the LEDs (red semi-transparent), maybe those have an impact on the IR signal - maybe mess around with those.

Title: Re: Extending Range of Infrared Detector
Post by: Rebelgium on May 28, 2009, 05:05:36 PM

It is certainly possible.

Try using a IR receiver from a TV/VCR/...
Use a voltmeter to measure the output of it, and when you know what kind of voltages to expect you can design firmware for a µC, or a circuit with opamps to convert it to TTL level.

Title: Re: Extending Range of Infrared Detector
Post by: airman00 on May 28, 2009, 05:46:56 PM

I figured it out - keep the IR LED's voltage at 5V and increase the IR phototransistors voltage to 12V. Works well now, especially with a comparator.

Title: Re: Extending Range of Infrared Detector
Post by: Admin on May 30, 2009, 12:14:45 PM

Reading your other post:
http://www.societyofrobots.com/robotforum/index.php?topic=8042.0 (http://www.societyofrobots.com/robotforum/index.php?topic=8042.0)

I suspect what you really want is a laser diode . . .
http://www.mouser.com/Search/Refine.aspx?Keyword=laser+diode (http://www.mouser.com/Search/Refine.aspx?Keyword=laser+diode)

You can also hack them out of old cd/dvd players. Don't forget eye protection!

If not that, would about modulation at 38KHz? And is there environmental noise?

Title: Re: Extending Range of Infrared Detector
Post by: airman00 on May 30, 2009, 01:28:01 PM

I'm using IR detectors to locate this IR ball - http://www.acroname.com/robotics/parts/R194-ROBO-BALL.jpg (http://www.acroname.com/robotics/parts/R194-ROBO-BALL.jpg)

Title: Re: Extending Range of Infrared Detector
Post by: Admin on May 30, 2009, 01:32:58 PM

OH! should have said that earlier :P

Quote

increase the IR phototransistors voltage to 12V. Works well now, especially with a comparator.

interesting . . . doing any amplification on it, by any chance? What range you now getting?