I'm having the toughest time finding DIY-type devices for laser distance measuring. The ultrasound ones seem pretty straightforward, but I need no overlap between sensors only about six inches apart, so lasers seem like the only option. I see there are some all-in-one units (e.g. from Stanley) that do the trick, but then I'd have to hack into them to get the values and I don't know what the heck I'm doing with that.
The other issue is that this is for measuring the distance up or down an actual laser beam (that also reacts when broken). So, for playback, the laser would also need to be pulsed (to play notes), which is simple with just the Arduino, but as a part of another unit... could be quite problematic.
I could have two lasers -- one for breaking and one for measuring, but one would be nicer.
Anyone know of how to get the parts to hack one of these together? I don't need much accuracy, it's just gestural over a couple meters.
I'm not sure if they work by firing a laser pulse and timing how long it takes to come back or not.
I have seen a webcam being used to 'see' the laser as well.
I'd surf around Wikipedia a bit to see how its done.
If you are building a laser harp then I can recommend you buy an optical bandpass filter tuned to your laser frequency, put it on a simple photocell and measure the resistance of the reflected light during the blanking pulse/beam on.
I've worked with a bunch of laser instruments and this was the only way I could get a true reflective trigger to work. The closer you break the beam to the sensor, the stronger the light and the lower the resistance.
It works pretty well, but no reflective harp is ever 100%. You have to be very careful to calibrate it properly in each venue. Even JMJ has been known to "fake" the harp during gigs. Manchester Main Rd comes to mind.
Oh yes, you will need a laser in the 200mw+ range - and be careful, these can burn you.
