Splitting up laser beams ?

Hey everyone,

I'm thinking of making a project similar to this: Laser Harp

First of all I wonder which laser should I use ? I don't care about the color, I want to see the laser traces.

Also, I can probably split one laser beam into 5 or what ever using a mirror mounted on a motor and switching the laser on/off at the right moment, right ?

Also, How can I sense which laser is blocked ? use multiple LDR's or photo transistors ?

Yeppers.

ItsMike said:

Hey everyone,

I'm thinking of making a project similar to this: Laser Harp

First of all I wonder which laser should I use ? I don't care about the color, I want to see the laser traces.

Click to expand...

You're going to need something more than the common "5 mW" laser modules you see everywhere; I have a "pre-ban" (USA) 250 mW green laser pointer, and the beam is only somewhat visible in the daytime, but at night it is very visible; you'll probably want to look into 100 mW or greater modules. Something to note - these are not "eye-safe" - they can easily blind you. Look into purchasing a pair of laser safety goggles to use for the wavelength of the laser involved (for instance, don't attempt to use a green laser wearing goggles meant for red lasers). Depending on the venue (smoke machines, etc) - you might be able to use a lower power module...

ItsMike said:

Also, I can probably split one laser beam into 5 or what ever using a mirror mounted on a motor and switching the laser on/off at the right moment, right ?

Click to expand...

Yes.

ItsMike said:

Also, How can I sense which laser is blocked ? use multiple LDR's or photo transistors ?

Click to expand...

You could - but it might be simpler to use one (or a few, positioned properly) LDR's or phototransistors, with possibly some optical lens setup - and detect the reflection of the laser off your hand. This will tell the system when the beam is blocked. Set up the motor so that you have some kind of pulse encoder/detector (slotted disc, hall effect sensor, or better perhaps a phototransistor/LDR that detects the laser just as the sweep is starting). Provided that the motor is fairly accurate, the amount of time for the sweep of the beam will tell you the position of the beam; when you detect the reflection of your hand, you'll also know the position of the beam from that reference point, and from there you can determine what "note" to play.