Wireless Laser Harp

The Concept:

Build a completely wireless laser harp generator controller using cheap marketplace modules

The system: A standard laser harp system contains: a laser harp generator connected to a projector with ilda connection, a wired footswitch for basic operations, a wired sensor to detect hands on beams, a wired connection with a keyboard or synth module or PC ( called MIDI or MIDI-USB).

The goal is to get rid of wires when possible: we start from the Footswitch. Let's cut the wire!

You need:

1 Kromalaser KL 3d-EVO board + Laser sensor module ( buy from www.kromalaser.com price for students: Euro 150 )

1 footswitch with 4 pushbuttons normally open type ( buy from Thomann: Eurolite LED KLS RGB Footswitch: Euro 40)

1 remote control 4ch based on PT2262 (buy on the bay, search "2262/2272 4CH Key 315MHZ Wireless Remote", Euro 5 both)

1 4 ch receiver based on PT2272 (as above) Some wires and soldering iron soldering skill :)

The Eurolite Footswitch: We start dismounting the footswitch and the remote controller. Just unscrew the covers on both of them.

We find 4 pairs of wires in the footswitch and 4 switches on the remote. they must be connected with 4 pair of wires. Take away the battery from the remote and solder 4 pairs of wires as shown in this picture, label them A,B,C,D, see pictures

Now, in the footswitch, remove the long black wire and cut the plug with all red wires connected, leaving all 4 pairs of wires (one per switch) and label them A,B,C,D

Solder each pair coming from the remote with the corresponding pair coming from the switch. There is no polarity, so it is enough to respect A,B,C,D sequence.

Check pressing each switch, the red Led on the remote must turn on.

Find a suitable place to put the remote inside the footswitch, fasten with adesive tape and put the cover back. The wireless footswitch is now ready.

Now it's time to connect the receiver

This module requires a supply voltage of at least 5V. We will take the 5Vcc supply form the EVO board.

We added an Led to the module as indicated in the schematics: The Led will lit when any switch will be pressed on the transmitter side.

The output pins d0,d1,d2,d3 are equivalent to A,B,C,D switches on transmitter side, as shown in this picture (image: h.jpg) Now let's have a look at the EVO board.

The board and sensor come with a manual and schematics, so it is very easy to understand how to connect our receiver. First we have to remove the DIN plugs on the panel. (This is not mandatory, we could solder wire on the back, but it made us comfortable to think that we will not use these connectors anymore since we are going wireless. If you want to leave connectors in place, remember that on the back all connections are specular :) )

Look at the picture of the back of the board: The "Ultrasensor"'s connector has 4 pins, and 2 of them are used to supply power to the sensor. We will use these pins to supply the footswitch receiver and the Ultrasensor receiver (later in this Instructable) The Footswitch connector has the 4 pins that must be connected to Footswitch receiver (Sw1 = A, Sw2 = b, Sw3 = c, Sw4 = d) This picture is taken from the front of the board: Take care to insulate the receiver board from when placing it near the Evo board.

Test: give supply to EVO board following its
manual's recommendation, and press a switch: the green led will lit. If it doesn't, something is wrong in power supply of the receiver. With a meter, check voltage on receiver pins d0,d1,d2,d3 (a,b,c,d) of the receiver.

Pressing the pedal A you should have voltage on pin d0 and so on.

If everything is ok, you can connect the ILDA cable between the EVO board and your laser projector and press switches 1 and 4 together (they must be pressed together in the same time): The laser harp should open, as described in the EVO manual.

We provide a ZIP with:

Kromalaser 3d-EVO manual

Updated firmware supporting these wireless modifications

Firmware upgrade software (read manual to upgrade)

Now we will cut the cable between the laser harp controller and the sensor detecting your hand on the laser.

The sensor has the purpose to detect the reflection of a laser harp beam when you touch it.

A bit of hacking has been required to understand how the Kromalaser's "Ultrasensor" works. Without going too deep in details, it is essentially a pulse amplifier. The input pulse comes from a BPW34 photodiode, and the amplifier gives on output two signals, one digital and one analog.

Our purpose is to send the digital pulse from the sensor to the EVO controller board wireless.

The pulse frequency depends on the scanning frequency: measuring we discover that the distance between a beam and the next one is a bit more than 1mS (millisecond) with a standard scanning rate. This means that our wireless rx/tx system must be able to send the pulse from the Ultrasensor to the controller in less than 1mS. Initially we thought to use the same system we used for the footswitch, but there was no chance to go that fast. The delay between the moment in which the button in the remote is pressed and the data is received and decoded on the receiver is far longer than 1mS. In other words, that solution didn't work at all The aim to solve this with cheap commercial modules led us to this solution:

You need:
The sensor (included in the price of the Kromalaser EVO controller, Euro 150 for students)

A pair of Arduino Nano board, chinese clone (Amazon or eBay, less than 4 Euro)

A pair of nRF24L01, a 2Mbps rx/tx module at 2.4GHz (Amazon or eBay, less than 4 Euro)

1 Battery backup with usb-to-MINIUSB cable (Amazon, less than 10 Euro)

Our firmware, open source and free to use (not for commercial products: you can't resell)

Soldering some wires required

Let's start : these are basic wires to connect:
First connect the A.Nano with the RTx module. Do this also for the second Arduino Nano + Nrf24l01 module (you need 2 of these because one is the transmitter and the other the receiver).

This wiring is common to both A.Nanos and nRf24L01s. In next pictures we will show only the Nano connections to the other devices and not the nRF24L01 which we suppose to be already correctly wired to the Nano.

We need now to use one digital input to connect to the digital out of the Ultrasensor on the Arduino Nano board.

Connect ultrasensor's pin D to the Nano's pin D2. Connect both GND together on Ultrasensor and Nano and do the same for both +5V. Look at pictures for the Nano's supply pins and the connection details.

The sensor+arduino+Rtx must be battery powered. To do that we simply buy a cheap 1-battery backup for cell phones and we use the MINIUSB plug on the arduino nano to supply everything.

Let's go now on the controller's side.
We need a digital output from the Nano to send the pulse to the digital input on the EVO controller board.

The Ultrasensor's plug we removed from the EVO board has everything we need.

We have to connect GND, +5V to the Nano GND and +5V to supply everything, and next we wire D+ on the Ultrasensor connector to the D2 on the Nano.

You have now to flash both Nanos, one with the firmware for the transmitter (the one connected to sensor) and the other with firmware for receiver (the one connected to Kromalaser Ultrasensor).

Complete schematics, PCB layout and firmware can be downloaded for free

Tools needed to DIY the PCB: Eagle Cad (there is a free version online)

In this Instructable we wanted to show how to cut the wires between a laser harp footswitch and the laser sensor.

This has been done on the Kromalaser hardware but with some small modification can be applied to any laser harp or to new projects, just remember that you can't use our firmware and designs for commercial products.

This project is still in progress, please follow us here, we will son publish how to cut the MIDI wire from the laser harp and the sound module.

http://www.laserharp.com/projects