144
« on: May 19, 2014, 10:39:49 PM »
A general list of items that you will need include:
0. Comprehension of laser safety and regulations for your area
You absolutely must understand the risks involved with using lasers and follow all regulations in your area. This is an obligation on your part.
1. Safety Glasses
You need safety glasses for the laser frequencies and intensities you will be working with. This is a 100% must. If you do not know how to select these you should consider taking a laser safety class in your area.
2. Laser Module
A laser module is a device that consists of all components necessary to drive a laser diode. Generally they will also contain optics to focus the laser beam and some other electronics/hardware to control the temperature of the diode (for some laser diodes, temperature differences can dramatically influence the power output).
Laser Modules are expected to be powered by an appropriate power supply/source and expect to receive an input signal from a controller board (I.e. a LaserShark). The type of signal they expect to receive can be either an analog signal (which allows the laser beam brightness to be varied) or TTL signal (which allows the laser beam to be turned on or off)
The LaserShark is capable of driving up to two analog (0-5v) laser modules and one TTL (0 or 5V) laser module at the same time.
LaserShark boards CANNOT drive laser diodes directly so be sure you purchase a laser module!
When selecting laser modules you will need to consider your application. The first question should be what color(s) your need. For diode lasers you can have direct drive (most red, blue, and now 520nm greens!) and dpss lasers (i.e 532nm green lasers). Preferably you want to stick with direct drive lasers as these can modulate faster which is important when drawing things such as text.
The next thing to consider is how fast the laser module driving circuit can actually modulate the laser output. This is frequently provided as a Khz rating and higher is better.
Another thing to consider is how powerful the laser must be for your application (and what you are qualified to operate safely!). This can be identified by the Watt rating of the laser. Will you be projecting at wall in the dark 5ft away... across a brightly lit room, etc? This will make a significant difference in the power requirement of the laser module.
If you have looked at the time-lapse images of my website, I used a ~20mW green 532nm laser module (which is especially bright to human eyes) in a dimly lit room with a throw of about 15ft.
And a final note about selecting laser modules... If you want multiple colors, you may want to consider purchasing a multi-color laser module vs purchasing multiple individual laser modules and combining them with optics.
Oh and two more gotchas! When selecting a laser module check the duty cycle.. ideally you want a 100% duty cycle module. Also, if you purchase a 532nm laser make sure it has an IR filter!
2. Power supply for laser module
If your laser module does not plug into the wall directly, you will need a power supply appropriate for the voltage and current requirements of your laser module. Note that it is fine if the current capacity of your power supply exceeds that of the laser module, it will only utilize what it needs.
Power supplies can be both of the linear type (generally larger, heavier, and less efficient but with better noise characteristics) or switching type (smaller, lighter, and more efficient, but generally with worse nose characteristics). Ebay has a plethora of switching shielded power supplies at great prices. Unless your laser module has specific power requirements these are probably your best bet for cost and size reasons.
3. Galvo kit
A galvo kit will consist of:
-2x galvos mounted at right angles to each other in a metal block.
Galvos are dc motors that have a limited rotation and position feedback circuitry built into them. They are not able to move a significant amount of mass but they are able to move extremely quickly! Each of these galvos has a mirror attached to them. These two "steer-able" mirrors are what allow the laser beam of a laser projector to be positioned anywhere in a 2d projection plane. And if you were wondering why you see lines/curves/etc instead of a fast moving dot, it's because of a phenomenon known as the "persistence of vision effect"
-2x Laser galvo amplifiers
Galvo amplifiers receive a differential signal from a controller board (i.e. a LaserShark) and according to this input control "drive" the galvos themselves. Your kit should come with that connect your laser galvo amplifiers to the lasershark. When selecting your galvo kit you should try to get one that uses 3-pin (+/GND/-) wires vs 4-pin (+/GND/GND/-). If you purchase the latter you will have to make an adapter that ties the two GND pins together (the LaserShark uses a 3-pin connector).
-1x Power supply
The galvo kit components will likely be tuned to this power supply. For this reason it is important to use this power supply and NOT attach anything else to it! If you attempt to power other devices using this power supply in addition to the galvo components you may find your laser lines become wobbly or dimension become distorted.
For lasershow devices, galvos are normally rated by their KPPS rates (kilo-points per second). As an example, a 20Kpps galvo system will be able to draw 20,000 points anywhere in the 2d projection plane. Clearly higher KPPS rates are better, but they also get expensive quick! If you are searching ebay for galvo kits, you will likely find 20-30kpps is the sweet spot for price/performance.
Another aspect to consider when purchasing a kit is the scan angle. Because the mirrors have to move less of a distance, it is possible to have higher KPPS rates with smaller scan angles. Sellers of these galvo kits will often try to "downplay" the scan angle when advertising higher KPPS kits so be sure to pay attention to this detail!
In the original youtube video I posted I used 30KPPS galvos. These have been fine for drawing the text segments seen.
4. Active cooling
Galvo amplifiers boards get hot quick! You may find that you need to actively cool them with fans. Ebay is a great source for these. I personally am a fan of hydro bearing fans due to their low noise level.
5. Mounting hardware and a case
You will want to aim your laser module(s) at the galvos by mounting them on a rigid piece of metal. I used a piece of aluminum for my build.
The case is important as it helps to keep dust off everything but more importantly it aids in preventing stray beams from exiting the unit at unexpected angles.
Show Posts
