Introduction: Laser Midi Controller - (Laser Triggered Midi Keyboard)

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About: Inspired by the 80's

Project goal:

"Construct a laser triggered midi controller, using standard electric components and a recycled midi keyboard."


Step 1.

Find a recycled midi keyboard / controller.

Step 2.

Construct a laser triggered switch.

Step 3.

Connect midi device, measure components (shorts), and test device.

You can now play instruments, beats, loops and samples by interrupting the laser.

- have fun


Components used:
1x Recycled midi keyboard/controller
1x Recycled network cable
3x 1.5V Battery
12x Red dot laser pointer diode (ebay)
12x Standard photo-resistor (ebay)
12x 10K resistor (0.6W used in this example)
12x NPN Transistor 2n3904 (ebay)
+ wood, screws and glue...

Let's begin...

Step 1: Step 1: Find a Recycled Midi Keyboard / Controller.

Remove electronics from midi keyboard.
Most cheap midi devices contain a midi controller board and a trigger circuit board.
The model used in this example is ESi Keycontrol 49.

Find key triggers on circuit board.
Connect the midi device to your computer and try to short the circuit until you discover where to attach trigger wires.
This may take some time, since most keyboards have velocity triggers.
(On this model we had to short circuit two connections first, and then find the corresponding base connection).

Hook up 5V power train on midi controller.
Attach a wire to the USB connector on the circuit board.
This is done to get a steady source of 5 Volts for the laser triggers.

Now let's do the laser triggers...

Step 2: Step 2: Construct a Laser Triggered Switch.

Build 12x light triggered switches.
The schematic is based on: Making an led light sensor.
(after testing the device we found the 100K resistor has to be ~1.6K to 10K).

Build wooden cases.
We build two simple wooden boxes to contain the lasers and the triggers.
Drill holes and mount the laser diodes, connected in parallel and attach to 4,5V / 5V power source.

*Note: Cheap lasers diodes are somewhat un-precise, please test lasers before you mount them.

After soldering laser diodes (in parallel), hook up the power source and match laser dots on your other wooden box.
Now drill holes for the photo resistors.

(we used a 24cm / 9.5inches, spacing between the two wooden boxes)

Construct triggering circuits.
Connect 5V power train (USB power) to photo diodes and resistors (see schematic).
Connect single wires to all transistors and the corresponding keys on the midi trigger board.
(We used an old network cable to get wires).

*Note: On the ESi Keycontrol 49, each 6 keys share a common base connection.

Next ...

Step 3: Step 3: Connect Midi Device, Measure Components (shorts), and Test Device.

Measure components.
Now we measure the wires for shorts and measure resistors / photo-resistors.


Rock and roll!

Congratulations! Your laser midi is ready to rock.


If there is no "rock and roll"?
If you connected everything properly the laser midi should work on first try, but please note we spend several days making and testing this device, so maybe you have to test / tinker at bit before it rocks.

P.S. You can use the laser switch to trigger just about any low voltage signal.
P.P.S. The device works best in a low light environment (you can use a ~100K variable-resistor to find a setting that works in daylight or use brighter lasers).

Merry Christmas...

The Laser MIDI Team