RoboTank #1 / The base

This is the first post about this new project using the TAMIYA Tracked Vehicle Kit as a base for building a robotic tank vehicle.  This will be an ongoing project and you should expect many posts about this subject.  Here's a video where I'm building one of the two kits I got:

Since the kit comes with  a single motor assembly allowing the tank to only go straight forward or backward,  I also bought the Double Gearbox from TAMIYA.  It can be assemble with 4 different ratios: 12.7:1, 38.2:1, 114.7:1 and 344.2:1.  I went for the 114.7:1 ratio since speed is not a necessity.

The tank kit is not build to fit with this particular gearbox so I had to modify the base plate to accommodate the support bar that came with the gearbox but that was meant for another kit.

I want to have an standard Arduino board running as the brain for this project.  Since there will probably be a lot components to control, I needed to drive the motors using only 2 pins from the Arduino board.  So, the next step was to build a motor driver PCB that would accept the inputs from the Arduino and take care of the rest.  This was a perfect excuse to make my first homemade PCB.  I'll get to that in the next post.

LEGOtiny

After my last Mini RC Car project I knew I wanted to make a smaller better one.  Some months later and this is the result:

The reason why this one is in a LEGO body is because of this question on LEGO Stack Exchange where it was asked if it was possible to power the small LEGO City wheels.  At that point I had already started playing with micro DC motors and I also started using the ATtiny chip.  This was a perfect storm.  I had to build a super small LEGO vehicle.

Here are all the parts needed to make this build:

• Set of gears from a race track car
• LEGO wheels set
• LEGO brick 2x2
• Micro motor
• 0.1uf capacitor
• Transistor
• Diode
• ATtiny
• Socket
• Power adaptor

I'll go over the small details in an Instructables ASAP.  For now here's shot from the inside:

Here's a video where I show the final result:

Jumping on board

Here his a 'how-to' for running two low voltage (3.3V) micro controllers on a breadboard.

The first one is the chip(s) used with the TI LaunchPad. I've tested this setup with the MSP430G2211 and the MSP430G2231. The chip will run at 3.3V and is rated up to 3.6V.

This setup needs a 100nf capacitor between pins 1 and 14, then pin 10 needs to be connected to positive using a 47k resistor.  I use the LaunchPad board to program the chip before transferring it to the breadboard and this is pure laziness since there must be a way to program it in place.

The second one is the ATtiny (in this case the Attiny13) which can run the same code as the Arduino (ATmega328) and can be programmed using the Arduino IDE and uploaded using the Arduino board as an ISP for ATtiny.  You will find all kind  of help online for using the ATtiny13, ATtiny45, ATtiny85, ATtiny44 or ATtiny84.

The chip will run at 3.3V or 5V.  As you can see by this diagram, this is the most simple one to use.  No crystal and no resistor are necessary for running it.

His First Robot

We just finished this project so a created a page just for it.

This is a 5 hours project with my son Gérémy (7 years old at the time) who showed interest in doing some robotic using our old LEGO Mindstorm by building an RC car and wanted to build the RCX line following robot described in the Mindstorm books[...]

... read about the whole project

Control LEDs with Raspberry Pi

Using an old hard drive cable, I built a GPIO breakout cable then proceed to make an LED blink... a classic 'Hello World' of electronics.  I followed this diagram for the connections.

image from Embedded Linux Wiki

Plug the wires and follow these steps:

1. Boot the Raspberry Pi
2. Login as root (embrace your dark side)
3. Getting ready to output in GPIO4:
4. $ echo "4" > /sys/class/gpio/export
   $ echo "out" > /sys/class/gpio/gpio4/direction
5. Turn GPIO4 on:
   $ echo "1" > /sys/class/gpio/gpio4/value
6. Turn GPIO4 off:
   $ echo "0" > /sys/class/gpio/gpio4/value

Tada!

I'm now using WiringPI c++ library.  Here's a good reference to get started at Limina.Log. And a good pins reference table.