Author: timmiclark, published on 2015-01-25
The second prototype out of the jRobot project, this little tank bot makes use of a number of simple parts to do a whole lot.
I have updated it to make it more versatile. The tracks are a little more grippy as well!
The jRobot project allows my students to dock their Raspberry Pi with any of the robots, plug it all in and program away.
The sample build shown makes use of the MCP3008 ADC to allow the RPi to access a range of analogue sensors including the Sharp 2Y0A02 Infrared distance sensor.
It has the same pin based docking system as the Apogee Robot (http://www.thingiverse.com/thing:648394)
You’ll need 26 tracks per side. The tracks are joined by 35mm long 2mm stainless steel pins. (The same pins are used to hold the RPi in place.
Each track assembly will need: 2 x Cogs; 2 x Inner Cog Brackets; 2 x Outer Cog Brackets; and 1 x Track Mid Frame (I am yet to test the improved inner frame)
The two track assemblies are then joined by 2 x body parts. The motors must be installed before the body parts are glued together.
I glue the whole thing together using 5 minute epoxy. Some one a tip of each stainless steel rod is also helpful to stop the tracks from falling apart.
The motors fit the cogs directly and are no-name yellow geared ones that you get on eBay (http://www.ebay.com.au/itm/1pcs-Anti-interference-f-Robot-Smart-Car-Chassis-DIY-DC3V-6V-DC-Geared-Motor-TT-/291314517942?pt=AU_B_I_Electrical_Test_Equipment&hash=item43d3b2c7b6)
The motor contoller in the same bot is an L298N board which fits perfectly in the bottom of the tank body. ( http://www.ebay.com.au/itm/1pcs-Anti-interference-f-Robot-Smart-Car-Chassis-DIY-DC3V-6V-DC-Geared-Motor-TT-/291314517942?pt=AU_B_I_Electrical_Test_Equipment&hash=item43d3b2c7b6
Their are 4 x 5mm holes for LEDs and a square hole that allows for a sensor bracket and cable access.
I use a Step Down Buck power regulator that has a USB output to power the Pi – while the motors run straight of the battery. This does mean that the Pi will restart when the batteries run low. I use 2 x 9V rechargbles (500mAh each) which allows for a good 30+ minutes of run time.
I use an Adafruit perma proto quarter size breaboard for the breakout board and use header pins so that my students can use jumper cables to wire it up.
The sensors are up to you, but I am using two sharp infrared sensors on the one shown that run through an MCP3008 ADC and interface with the RPi via the SPI bus. I also have a light sensitive resistor on it and plan to add a sensor at the rear and one facing down to stop the robot driving off cliffs.
I have plans to be able to extend the length of the track assembly adding a third cog … but I need to overcome some derailing issues.
Believe it or not, the one shown was printed on an Up! Mini as I did not have access to my school’s larger printer over the summer break.
Tags: adafruit, jRobot, raspberry, Raspberry_Pi, tank, tank_tracks