This past Tuesday, we completed the circuit assembly that converts the digital position signals sourced from our Arduino into dual analog voltages (+/- 5V) from the drawing pictured top middle to the 3x5 inch perf-board. These analog voltages are then fed into the galvanometer controller board, consequently driving the mirror's position steps required for creating the beam fan. On the bottom right the finished circuit board is pictured. The included components (from left to right) are as follows: 3-wire cable harness connection to galvo controller board, Arduino signal interface 4-pin Euro connector, two op-amps (in black/blue) with paired trimpots, 3-pin Euro connector for +/- 15VDC power rails, MCP4725 Digital-to-Analog Convertor (DAC). On the botoom right a view of the underside of the circuit board showing the connections made in between components of the board. 

I have moved on for now from testing the various components of my harp and begun the process of packaging the components. Pictured above is the rough layout of the different pieces and their power sources. I was able to arrange the components in such a way that they fit in the given space of the box. On the left is a power strip that the multiple power sources plug into. In the top left corner, the board is cut to make room for the fan that is going to be installed for cooling. The perforated circuit board in the top right will be populated with the circuit components that produce dual + ~ - 5 VDC signals required to drive the galvanometer's controller board.  The board below that is the Arduino. To the left of both of these boards are the relays that will be used to turn the laser power source on/off and drive some indicator lights together with the foot switches for my laser harp. The silver box with holes is the power supply for the galvanometer controller board, which is the component directly above the silver box.

The black wood board pictured in a previous blog will act as a shelf, covering this bottom layer of components. On top of that shelf, the galvanometer and laser source will be mounted.

This is the case that will package all of my laser harp components. The board rests on an inner ledge and is what will enclose the wiring. The galvo mirror, laser source, and photo sensor(s) will be mounted on top of the board. I spray-painted the wood board black to make it match the case. 

Today I soldered the header pins to the sockets of the MCP4725 Digital to Analog Converter (DAC) board. This board will generate analog drive signals in the range of 0-5 VDC from digital signals sent to it over a I2C communication link from the microcontroller board. The drive signals will further be fed to a bipolar amplifier circuit, serving as the final set of signals controlling the position of the galvonometer mirror. As a reminder, the galvonometer mirror is what creates the fan of beams from the original single laser source.

Today, we tested our Arduino microcontroller to see how the user interface worked on the computer. I watched a tutorial that explained some of the basics to writing the necessary code for relating the inputs and outputs of your Arduino board. I wrote a simple code that turned one of the Arduino's embedded LEDs on and off. Easy, I know, but this was the first code I had ever written so it was exciting!

Galvanometer in from Holland as pictured above. (Item that laser source is pointing into)

Things we tested with the galvo:
- maximum deflection angle
- maximum fan anlge
- voltage necessary to achieve desired fan width
- possible approaches to create equally +/- voltage