In the bill of materials you will find all the parts you need to build SPOT, as well suggested vendors and estimated prices. We also put together a zip-file that contains, amongst others: Adobe Illustrator files for the laser-cutter; an Arduino sketch to map the movements of the master to the slave platform; a Processing sketch to record and playback movements; schematics to make a power supply pcb; and a .3dm file that can be viewed with Rhinoceros or a .3dm viewer.
Here are a couple of things we feel we should explain:
We use M3 threaded steel rods, and ball joints and –ends for three reasons:
- M3 is a common size in the RC and Robotics world
- M3 is significantly stronger than M2 (which is also a common size)
- M3 threaded steel rods are significantly cheaper (!) than M2 threaded steel rods.
We use metal-geared hobby servos because of their robustness. However, you can lower the cost of your project a bit by using plastic-geared hobby servos, which will still deliver sufficient force for most uses. The power consumption for plastic-geared hobby servos is not significantly lower and we would still recommend using a computer power supply.
We use a computer power supply because of the current each servo can draw (up to 2A). The computer power supply is the most expensive part of this kit (although they can be bought for $14.99 at Amazon) but in our opinion it is a worthwhile investment, especially in combination with our custom printed circuit board*. The board will allow you to safely hook up any 3.3V, 5V or 12V project giving you more than enough current to work with (somewhere around 20A at 5V). You can lower the cost and the footprint of your project and avoid having to make your own printed circuit board by using an adjustable dc power supply ($9.99 at Amazon). This does require you to add 7 100μF electrolytic capacitors; one near the power supply and one near each of the servos.
The Adobe Illustrator files for laser cutting have not been adjusted for removed material thickness (as this varies from laser cutter to laser cutter) or variations in the actual material thickness (e.g. 4mm MDF is usually 4.1mm MDF). We found that with the laser cutter we used (Trotec Speedy 300™), adjustments were not necessary. The lines are cut in the following order:
- Black (engraving)
- Red (255, 0, 0)
- Blue (0, 0, 255)
- Desert Blue (51, 102, 153)
- Cyan (0, 255, 255)
For the arms that will be attached to the potentiometers we included four sets, adjusted with 0.05mm increments starting at 0.00mm, to find a tight fit. To make your own adjustments use the ‘Offset Path…’ function, which you can find under ‘Object>Path’. In the case of the arms for the potentiometers this is a negative offset. ‘Miter’ can be kept at default.
* The design file will be made available at http://www.eatelier.nl