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Author Topic: InfraRed Presence Detector/Switch malfunctioning  (Read 5261 times)

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kal00

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InfraRed Presence Detector/Switch malfunctioning
« on: April 17, 2011, 12:47:19 PM »
Good day everyone, hope you can help me.

I have a simple circuit controlling my bedroom light, a bistable, but the triggering is quite special. Its an IR LED right next to a phototransistor (with black coating), with some fancy electronics on the side. When you put your hand (or any other object) above the LED-Phototransistor pair, the IR light from the LED bounces off the object and lands on the phototransistor, triggering the bistable circuit.

The (big) problem here is that this circuit doesn't work very well under direct sunligh, or even indirect sunlight... damn, not even with light from other lamps (across the hallway lamps). It gets saturated, false positives, random triggering... etc, even with the black coating on the phototransistor. I thought of a solution, but I don't have many experience, this is where I need you help  :) .

I'm thinking of puting a TSOP IR receiver or something of the sort. From what I've read, this kind of receivers are only sensitive to a given frecuency, say 35kHz, and when they receive this frequency they trigger. My question is: Given that sunlight (or any other light for that matter) doesn't have a frequency (like IR remotes), would the TSOP be inmune to ambient light and sunlight?

If this isn't the case, what would be the best way to make a switch of this type? I don't want to touch it (like capacitance, where you need to touch the plastic o material above the plates), I just want to wave my hand in front of it.

Thanks in advance for your valuable time!

_pike

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #1 on: April 17, 2011, 13:06:32 PM »
take a look here.....
http://pcbheaven.com/circuitpages/IR_Short_Distance_Beam_Cut_Detector/
and here....
http://pcbheaven.com/circuitpages/Long_Range_IR_Beam_Break_Detector/
You will find VERY USEFUL INFO!!!!!

As Kam say....

"The receiver circuit is based on the TSOP1838 chip. It has an integrated PIN diode and a preamplifier circuit inside the chip. Moreover, the epoxy package is an IR filter by itself, that blocks other light sources beyond IR spectrum.

using tsop as you also said, you will see better results.....And something else...why don't you try to oscillate to another frequency so it wont be sensitive from ir remotes?

« Last Edit: April 17, 2011, 13:09:10 PM by _pike »

kal00

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #2 on: April 17, 2011, 22:18:02 PM »
Thanks for quick response _pike!

This "IR Filter" that the TSOP and other IR receivers have, is the "black coating" I mention with my phototransistor. It's not bulletproof against strong light, or sunlight, that's why it's such a hassle to work with IR outdoors or indoors with lots of ambient light.

The thing here is that if the frequency of operation would make a different result from what I have right now (saturation and false triggering due to ambient and sun light). I haven't tried it out because my local electronics shop doesn't sell the TSOP, I would have to order it and it takes some time.

Thanks!
« Last Edit: April 17, 2011, 22:19:46 PM by kal00 »

kam

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #3 on: April 18, 2011, 00:52:07 AM »
hello kal00. You can use capacitance sensor with a bigger touchpad, and covert it into proximity sensor. I built one quickly and got like 10-12 cm of range. You can have anything between 0 to 10 cm easy. Check this out:
Capacitance touch sensor with PIC

I think that this solution is best for you. Oh, and it is absolutely bullet proof against any sort of light whatsoever, no matter how strong.

kal00

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #4 on: April 18, 2011, 21:14:32 PM »
Hello kam, thanks for you kind response.

I think that the size of the aluminum sheet may be too big for a wall switch, you know the white plate that goes in the wall. Is there a way to make it more sensitive?

Something about this size would be perfect.



But I think if I reduce the size of the aluminum sheet of your project, the sensitivity or functioning may be affected.

Thanks for your time!

kam

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #5 on: April 18, 2011, 21:41:38 PM »
Sure you can use a smaller aluminum foil. Anything bigger than 6x6 cm can be used. use the biggest possible. The distance may be reduced of course, but it will be better than the IR pair. I'm sure you can get it work at 4-5 cm with a size of aluminum foil 8x8cm

kal00

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #6 on: April 21, 2011, 15:20:43 PM »
I will give it a try kam thanks! As soon as I get the PIC12F615 because this particular model is not available where I live. The only ones I have are PIC12F675 PIC12F629. Can I ask two more questions kam?

1.- I'm building another project, to detect direction of walking, I was thinking of putting two lasers with LDR's on the other side to detect the cut of light, but can I use IR sensors? Not in the same frequency , but on different frequencys so the 2 IR receivers are independent. Hope you understand me.

2.- Can your "IR Long Distance Detector" switch be used as a presence detector for sumos or other robots in general? Used in a pair, receiver next to transmitter.

Thanks for sharing your wisdom and experience.

kam

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #7 on: April 21, 2011, 21:20:00 PM »
1: yes you can use them. if you use the short-distance (which i recommend),  make sure you house them in a place where not much direct ambient light falls
2: hm, that would be difficult to answer, unless i really understand what you want to make

_pike

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #8 on: April 22, 2011, 01:09:13 AM »
Why don't you try trandusers?38-40Khz ??Transdusers are also used for these applications...... ;)   (mostly)

kal00

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Re: InfraRed Presence Detector/Switch malfunctioning
« Reply #9 on: April 22, 2011, 09:11:36 AM »
Thanks for your response guys, I will give it a try with all your advices. Thanks again for your valuable time, and keep doing a great job kam! your work is really inspiring.  :)