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The laser trigger hardware

The hardware for the laser setup is relatively simple. A basic PCB (printed circuit board) was developed for the various components plug in to. Prior to the PCB there were several prototyping stages, going from a breadboard to a slightly more permanent soldered strip board but these were too frustrating to work with. In the past I've created PCBs using both etching and milling but for this project the time seemed right to try some of the cheap PCB manufacturers based in China.

A bare PCB and a fully populated one.


The laser controller hardware is centered around an inexpensive Arduino Pro Mini board with some supporting components. The board has been laid out so it can be populated as a single, standalone unit but it could equally be housed in a dedicated case with the input and output jacks connected to the board via wires rather than soldered on directly. This is the approach I'm starting to favour so my next assembly might take advantage of this flexibility.

The lasers I've found to be the most reliable are these Quarton Laser Modules from Amazon. These are not inexpensive, but compared to cheap lasers you can pick up off ebay these seem to work flawlessly. They seem to be extremely reliable and ideal for my particular use case. The documentation with the laser states that it has a 650nm wavelength and this is a sufficiently common wavelength to make choosing sensors easy.

I went with these phototransistors for sensors and they work well in combination with the laser module. They do detect a reasonably wide spectrum range however  (450nm to 1100nm) so they do need to be shielded from ambient light. There will be more on the design of the laser and sensor housing design in another post.

The challenge with this board was trying to keep it as inexpensive as possible while still providing a decent choice of features. More user controlled options necessarily increases the user interface complexity so the challenge was to provide some degree of flexibility with minimal components. As I'm using the board more in real world setups though, I'm noticing that a single mode is sufficient so no user interaction is really required other than switching between setup mode and active mode. This simplifies everything greatly as it means there is less code to go wrong, less parts to solder on to the board and less remembering how things work. The option is always there though to provide more complex options.
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