#Ilda dac driver
#Ilda dac code

#Ilda dac driver

The Arduino runs a small library called OLSDВ - The Open Laser Show DAC driver project.

#Ilda dac code

This Arduino code links against a little library that talks to the Dual DAC chip over SPI. For now, I wrote a little class that spits out Arduino code for a given frame. IвЂ™m currently neatening up the project and generalising the code to make it possible to generate the ILDA data files from inputted data too. As a PHP guy, I used PHP and wrote a few helper classes called php-ilda to manage this, but you could do it any number of ways.

The first stage of the project was therefore to find a way to decode these files and feed the data into the galvanometer/amplifier setup. This standard is specified quite clearly in a document published by IDLA. These files contain вЂњframesвЂќ - sets of coordinates for the laser heads to draw and any associated colour information. One important standard is format of the files that store a show. ILDA, the International Laser Display Association defines a number of standards on the topic of laser shows.

IвЂ™ll go through the block diagram section-by-section and explain what part each component plays in generating awesome laser shows. IвЂ™ve put together a little system that works fairly well and I thought IвЂ™d blog about it so other people can have a go too! Here goesвЂ¦ Overview I paid around ВЈ70 for a pair of 25kpps galvos and the amplifiers for them, shipped from China of course.Д¬ontrolling these is where the real challenge comes. Price point really translates to scan speed, measured in kpps (thousands of points per second). HereвЂ™s what the test pattern should look like. Still not perfect, there are some tuning tweaks to be made to the galvo driver amplifiers.

Projecting the ILDA test pattern onto my wall. With two placed orthogonally (at right-angles), one pivoting a mirror on the X axis, and another on the Y axis, you can reflect the laser beam on both mirrors and produce a coordinate system on a surface such as a wall. The object can be a needle (in the case of gauges or meters) or as IвЂ™ll be using, mirrors. Effectively they move an object proportional to the amount of current flowing through them. A ballpoint pen spring with a tiny mirror glued to the top produces some fascinating oscillating patterns when you shine a simple laser pointer at it - imagine what you can do when you introduce digital control and high precisionвЂ¦ I love the colours, the power, sometimes the danger, but also the beautiful things you can do when you combine them with some simple optics and mechanics. The use of pots allow this to be scale for different DACs and output requirements.Lasers have always fascinated me. The upper left pot outputs that voltage into the upper op amp with a gain of 1. We need an offset of 10, so 10/3 requires 3.33V (blue trace). That is set with the 30k pot value on the upper right pot. The 5V range on the DAC needs to be a 20V range on the output, so we need a gain of 4. The output to the galvo is the output of the lower op amp (green trace). The DAC input is the lower voltage input (amber trace). The lower right op amp sets the gain and the upper left sets the offset. The rails on the op amps are -15V and 15V. A standard DAC on a micro controller has a range of 0-5V or 0-3.3V. Ideally that would be +5 to -5, but 0 to (+10 and -10) would have the same effect. A laser galvo typically used for laser light shows requires a 10V peak to peak differential voltage to move the galvo position.