Hey guys.
I've been searching for a while now for a beam-break sensor utilising a reflector panel instead of a sender/receiver-setup. My goal is to detect presence in the vicinity of the sensor and up to about 15m from it.
So far I've been using a sender/receiver setup with batteries and solar panels on one side. However even after upgrading the battery capacity and putting in another solar panel, there is not enough light during the daytime this time of year.
Can I build one myself with an Arduino without burning my retinas on an IR laser?
I'd rather not begin to construct advanced enclosures with lenses and such. The perfect setup could be a red(?) laser modulated to a frequency, installed right next to - but not interferring with - a sensor able to detect the reflected light.
Do you know if this could be possible and which components to use for this?
BlueSails:
Hey guys.
I've been searching for a while now for a beam-break sensor utilising a reflector panel instead of a sender/receiver-setup. My goal is to detect presence in the vicinity of the sensor and up to about 15m from it.
So far I've been using a sender/receiver setup with batteries and solar panels on one side. However even after upgrading the battery capacity and putting in another solar panel, there is not enough light during the daytime this time of year.
Can I build one myself with an Arduino without burning my retinas on an IR laser?
I'd rather not begin to construct advanced enclosures with lenses and such. The perfect setup could be a red(?) laser modulated to a frequency, installed right next to - but not interferring with - a sensor able to detect the reflected light.
Do you know if this could be possible and which components to use for this?
Cheers
Are you using lenses on both sides to capture and focus the light? If not, why not?
Reduce the field of view of the receiver so that all it can see is the transmitter (via the reflector).
The simplest way is to put it at one end of a long tube such as a PVC drain pipe or copper water pipe. The longer the better.
Use a synchronous pulse detection system. Measure the received signal with the transmitter off. Measure it again with the transmitter on. If the signal is higher then you know the beam isn't being blocked.
Increase the peak transmit power while also reducing the average power. If you pulse at 1 ms on and 100 ms off, then you can safely drive the LED at 10 times its normal current. It will look like a strobe light. Use a mosfet switch to get the required current.
Reflection sensors need a lot more IR power, or optics.
Tell us more about your working setup.
Direct links, with the right LEDs, need very little current.
I made a link where the whole transmiter uses 60mA from a single LiPo battery,
and it does more than 65 meters without optics.
15 meters would require a lot less current.
Leo..
BlueSails:
Can I build one myself with an Arduino without burning my retinas on an IR laser?
You don’t need modulation, so that really simplifies this.
Parts needed would not be much more than a cheap visible low power laser diode with driver, a mirror, and phototransistor.
Recess the phototransistor so that it only has a very narrow field of view. I would use a drinking straw about 4 inches long and wrapped in electrical tape to block light.
Whole setup could fit inside an altoid tin.
If you can find a laser diode that allows you to “adjust” the collimating lens, you can widen the spot to make alignment easier. At 45 feet a lot of the cheap pointers are already the size of a dime anyways though.
There is a lot of difference between a 'LASER Link' and a 'Beam Break Detector'. LD Link com utilizes beam scatter to simplify alignment over distance. Beam Break detection cannot function reliably if the scatter overwhelms the detector. for beam break to work reasonably well, you need close emitter/detector range, or well collimated beam over loner range with accurate alignment. You need optics for the latter. the soda straw 'solution' will only work for relatively short distances. simple collimation optics (lenses) on the emitter, freznell lense on the reflector, and maybe a short tunnel (not a soda straw, but something more like 2 inches (~50 mm?) of 3/4 inch (~15 mm?) white PVC thick wall pipe) on the detector will work for 15m reflected path. IR emitter preferred (30mW LASER Diode, with acrylic collimation lenses works best; High power IR LED, like those used in night vision illuminators works good too), Modulated emitter/demodulated recvr. required to eliminate ambient light interference issues. Your cell phone camera, or most cheap digital cameras, will detect the IR bream strike on the target (first, the reflector, and then , the detector) to aid in alignment. If you are gonna do it, do it right. And doing it right doesn't always mean expensively. the whole setup shouldn't run you over $20 USD, if you already have the arduino.
123Splat:
There is a lot of difference between a 'LASER Link' and a 'Beam Break Detector'. LD Link com utilizes beam scatter to simplify alignment over distance. Beam Break detection cannot function reliably if the scatter overwhelms the detector. for beam break to work reasonably well, you need close emitter/detector range, or well collimated beam over loner range with accurate alignment. You need optics for the latter. the soda straw 'solution' will only work for relatively short distances. simple collimation optics (lenses) on the emitter, freznell lense on the reflector, and maybe a short tunnel (not a soda straw, but something more like 2 inches (~50 mm?) of 3/4 inch (~15 mm?) white PVC thick wall pipe) on the detector will work for 15m reflected path. IR emitter preferred (30mW LASER Diode, with acrylic collimation lenses works best; High power IR LED, like those used in night vision illuminators works good too), Modulated emitter/demodulated recvr. required to eliminate ambient light interference issues. Your cell phone camera, or most cheap digital cameras, will detect the IR bream strike on the target (first, the reflector, and then , the detector) to aid in alignment. If you are gonna do it, do it right. And doing it right doesn't always mean expensively. the whole setup shouldn't run you over $20 USD, if you already have the arduino.
This is what I was hoping for.
I have the Arduino but I'm unable to figure out either:
1: How to modulate a powerful IR LED on the Arduino and simultaneously "decode" it on the same Arduino. Heck, I can't even figure it out on separate Arduinos.
2: Find a receiver (photoresistor?) that will detect a visible (red?) laser light during daytime conditions without modulation.
To take the best from both scenarios I was thinking of modulating a red laser to make alignment easier and at the same time have the receiver not being disturbed by ambient light. Would this be possible? Feasible? How?
Wawa:
Reflection sensors need a lot more IR power, or optics.
Tell us more about your working setup.
Direct links, with the right LEDs, need very little current.
I made a link where the whole transmiter uses 60mA from a single LiPo battery,
and it does more than 65 meters without optics.
15 meters would require a lot less current.
Leo..
A corner reflector (3D corner, like a corner cut off a box) will always return light in the direction it arrived but off to the side.
As long as the sensor views the reflector and not much else and the reflector is shaded from other light sources a phototransistor can be used to amplify what is received.
Laser.... if you can then don't use a laser. They make a lot less light per mA than leds. Collimate an IR led as able to be close to as small as the reflector and you won't be liable for blinding anyone even temporarily.
I assume you have mains power for one side.
Did you already try to use both units you have side-by-side, with a retroreflector on the oppositie side.
Leo..
I assume this is used outside.
Optics make the beam 'thicker" (the size of the lens), and a double beam further reduces false triggers from insects etc.
Leo..
Wawa:
I assume you have mains power for one side.
Did you already try to use both units you have side-by-side, with a retroreflector on the oppositie side.
Leo..
I haven't tried this yet. I'll give it a try before anything else.
However, being able to build a reliable setup with modulated, powerful IR leds and a reflector would be nice for upcoming projects
GoForSmoke:
or maybe how many leds could you illuminate the reflector with?
I'm not sure how to answer that. If using an arduino to modulate the leds I guess the limiting number of leds is determined by the max current draw from the arduino?
If I'm going to build a separate modulator I guess I can put in a lot of leds?
It seems I should work on how to modulate an IR led (or several) and how to have an Arduino receive the signal from these LEDs.
Can any of you point me in a specific direction as to how I could accomplish this?
I still need to find a receiver (photoresistor? which?) and to program everything (please help)
I know a 555 timer might work and I know that an Arduino is also capable of modulating to 38 kHz but I have not been able to find any tutorials on HOW. I know my way around the basics of the Arduino bu I cannot figure out where to start on this one.
So please be specific. Then I will build this and test it across the 15m distance and let you know.
Driving the LEDs on one Arduino and receiving on another is a possibility if it makes things easier. There's something about using the timer on the Arduino to modulate that makes using "interrupts" for decoding difficult. Am I right?
