I am creating a laser maze by reflecting a laser in mirrors across a room. I have built the laser tripwire from Robotix (thanks!) and can see that it works. The challenge is the implementation - when I set thresholds from "near dark" to "laser reflected 5-6 times before it hits the photoresistor" I run into low differential readings that are sometimes set off when the tripwire isn't tripped and/or slight variations in the laser's direction (e.g. vibrations due to walking across the floor).
Looking for ideas on how to either increase the strength of the laser beam or increase precision in mirrors and arduino (possibly physical/mechanical stuff) to make the setup more reliable.
I have already bought a stronger laser (green light, rifle scope) and larger mirrors. That photoresistor is so tiny, it seems like something I could address but I am not sure how to rig something up. And open to any other ideas.
Thanks,
Pete
p.s. Has anyone created a laser maze before? (Btw, I am loving it when it works - really cool!)
You should put the photo sensor in a small tube to limit ambient light to set it off. If using a simple photo resistor try using a photo transistor where you can adjust gain more precise. Another tip is to put a color filter to allow only the color (wavelength) of laser to pass through. Also look at resistance bridge type of measuring and using op amps.
Thanks for the ideas! They sound promising.
Be smart and get that laser out of there. If that beam reflects into an eye, you will end up in court on serious charges.
A phototransistor at the back of a tube restricts the view into a very narrow cone. If the view reflects or sources light into the detector and the some one or thing blocks it, there you have a tripwire.
I know that lasers are TV/movie fascinating. So is fire but I don't play with that, have people walk through it either.
You want to make a safe laser effect, look into interference patterns or onto the wall displays you can make reasonably safe.
Look up collimation, you can fake a laser beam using a led and optics that will be far brighter for the power used but not as full-power-retina-etch-focused as the laser.
Vibrations will remain an issue unless you are on a solid concrete floor. Especially with six mirrors, any change in angle by vibration is amplified and the end point of your laser will be all over the place.
A possible solution to this would be to use slightly divergent (or just a much wider) beam, and/or an array of sensors on the other end so that when the beam is a little off it simply activates another sensor.
A possible solution to interference is using modulated IR.
Look at how laser tag games work: they have a red beam that shows you where you're aiming, and an invisible IR beam right next to it that does the real work.
In optics, there are more to it that meets the eye. If safety is your concern, then a collimator (posted by GoForSmoke) is good but you might have to stay away from that somehow. A double collimation might suffice but still way off from real lazers. Also I don't know if there are ways for the particles to be seen but during my experiments, the light can only be seen on the object that might intersect the optical axis. Regarding that, using collimated LEDs defeats your purpose of the tripwire where light particles are seen. Also, you might want to also replace your mirrors with a high reflectance one, probably at around 93% reflectance, tested at 45° angle, passed endurance test at temperature same as your lazer light temperature.
To see a light beam from the side, crud needs to be in the air to reflect from, cough, cough.
If you just want tripwires, collimate the fricking detectors and light the room enough to cover the endpoints.
My buddy was swinging his cheap pointer around when he hit a wide-view curved mirror and got some of the dispersed reflect. He spent a bit over 2 hours wondering if that eye would ever see anything but red. Not black, red. If someone on your ground spends even 1 minute like that, guess what you lose?