New build! An Arduino controlled laser rig
So for my 4, 5, and 6 th laser rig builds, I want to incorporate the following:
1. Cryogenically cool the six 638 reds LD modules with one bank at one set point temperature and another bank at another set point temperature. This is so I can replicate Planter’s wavelength division multiplexing technique and hopefully corral the multiple beams in the near field enough to fit on the scanner mirrors.
2. Water cool the entire rig, including the two NUBM07E diodes to keep them near ambient temperatures.
3. Employ the latest galvo scanners from Pangolin.
4. And finally, control the entire rig using an inexpensive Arduino, some power mosfet boards to drive the TEC’s using a PID algorithm and a wifi board for cloud reporting.
For those who are unfamiliar with Arduino boards—they are tiny microcontroller open-source computers that cost $20-25 and are great for adding intelligence to a device. Arduino senses the environment by receiving inputs from many sensors, in my case, temp and humidity probes, and affects its surroundings by controlling the TEC’s and the fans used to cool the red and blue LD modules.
Importantly, I want the laser rig to sense the current conditions that it has been placed—is it hot or cold, humid, freezing, raining—and adjust on the fly how cold it can get the TEC’s. I also want it to go to an emergency mode if things get too hot to preserve the LD’s and prevent the TEC’s from burning up.
As far as an interface goes, I am using a touch screen color LCD display from 4D systems. It a 3.2 inch unit with an onboard computer and 4 gigs of memory. I like it as it was easy to program and the display can be designed on your laptop and then transferred to the display. You then call the display and inputs with one line of code. Pretty sweet.
With a touch screen input, you can set the unit to boot into a security setting that will query you with an input passcode. You then choose an array of options: quick start, calibration, set RGB modulation levels—in essence everything you see at the back of laser rig, knobs and switches, controlled by a touch screen interface and software.
Ah yes the software. So I have a background in Perl, Python and R. I took a C class back in college—but that was 40 years ago. Arduino’s are programmed in C++, so there was somewhat of a learning curve there, but it was not too bad. With over 300,000 boards out there, and an active hacking community, you can find code that approximates what you want to do. Nonetheless, it was challenging to get thing working correctly and robustly. Substituting "||" for "&& "can make or break a particular conditional statement.
So now for some pictures:
I first started milling out the water cooler heat exchangers out of solid 1” billet aluminum using my homebrew CNC machine.
Next I milled out some Plexiglas spacers so that the dual stage TECs can be properly spaced on the water cooler.
Here is the rig in its current state showing the location of the green red and blue LD modules, the water cooling radiators: one long 3 fan radiator setup in the front of the rig and a single radiator with a VERY fast 6000 rpm PWM fan at the rear. The box with the blue light on is the water reservoir with built-in water pump. To the left is the touch-screen LCD and to the right is the Arduino reset button (very handy).
Here are some pics of the LCD and Arduino in action. The next pic shows the initial splash screen and the temp and calibration screens. Right now I’m seeing -30C on the front bank of LDs and -20C on the rear bank. That is when the outside temp is 20C.
This is the inside of the case with a maze of wires yet to be bundled. You can see the front radiator fans, the rear radiator fan and the tubing for the water coolers. The mosfets that drive the TEC’s are shown to the far left with a large radiator for each, as they can get quite hot at full power.
And finally this a pic from the top showing the placement of the red and blue LD's, The mosfet board with the heat sink and the Arduino board. The little square guy is the Dallas Temperature One-Wire probe. One of those temp probes are glued to the various LD modules, and another one is floating taking the case temp. You can have as many of these temp probes as you want, as they are all individually addressable, wired in series, and operate on one serial connection.
Now that I have the software figured out, I’m going to populate the LD holders with diodes and install the optics and post some laser light pics. Stay tuned!
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