In previous posts I’ve covered all hardware necessary for assembling the robotic vehicle. Whole robotic chassis is based on TANK-02 from Hobbyrobot. TANK-02 comes as a set, which consist of Tamiya gear box TM70168, Tamiya tracks TM70100 and foundation with wheel suspension. The gear box includes two 3V DC motors labeled FA130, which should be replaced with motors for higher voltage. The reason is, that four AA batteries used as a power supply will produce voltage form 5 to 6V, which might decrease the motor life-time. Motor I’ve choose as a replacement is SPEED 250 from Graupner. This motor has good rotation speed, voltage 7.2V and size is same as FA130 motor, so it’s perfect replacement. The gear box can be assembled in four variants with different ratio. I’ve test them all and I can recommend you to go with ratio 114.7:1.

While TANK-02 is only the “first floor” of the chassis, the second floor has to be made. Second floor shape should be the sameas the TANK-02 foundation with holes drilled in appropriate positions. The material can be plastic, acrylic sheet or balsa wood, whatever is best for you. I was lucky to get TANK-02 surplus foundation from Hobbyrobot, that’s why the color is same as well as the holes are pre-drilled. Eight plastic standoffs and 16 bolts (M3x10) are used for mounting the platforms together. Don’t forget to put two elastic bands on the second platform before completing.

Micro Framework Vehicle - right profile 640x480 Figure 1. Assembled robotic vehicle

Putting parts on the breadboard

As it’s visible from figures, putting parts into the breadboard is not complicated. Be precise and patient when wiring the parts together. There is a one integrated circuit that we didn’t talk about before. It is a 74HCT04 6xInvertor with 6 inputs and outputs. Function of this circuit is to receive signal on it’s input and send it’s inverse value to the appropriate output. It means logical 1 as input will be logical 0 on output (and vice versa). The reason why I’m using the inverter is level shifting and protection. As you already know the L293D has 5V logic, while Digi Connect ME has 3.3V logic. Normally it should be OK, especially when L293D is in input mode and Digi Connect ME is 5V tolerant. In this particular case when we dealing with DC motors, you can not be sure of what currents are flowing in the system. That’s why I’m using the inverter, it’s better to burn 74HCT04 for 20 cents than Digi Connect ME for 40 USD. I’m pretty sure that everything will work fine event without inverter but why to risk it. Remember, that with inverter in the system the control logic for L293D will be inverted :)

Parts list:

Wiring the breadboard step-by-step

One picture says more than ten paragraphs. Here are three photos, which illustrates wiring of the breadboard very clearly. I believe that it should be easy to build your own robotic vehicle by this pictures. Photos are 1600x1200 so all details are visible (click images to resize). Be patient and precise, cut the wires of necessary length and try to use some color codes.

Micro Framework Vehicle - Wiring the breadboard 640x480 Figure 2. Wiring the breadboard

Micro Framework Vehicle - Ghosts on the breadboard 640x480 Figure 3. Ghosts on the breadboard

Micro Framework Vehicle - Assembled breadboard 640x480 Figure 4. Assembled breadboard