SunRover part 1: Track motor controller/power system

System Tests

In any system that connects batteries together, you have the possibility of shorting batteries or using too much current. It is always a good idea to add a fuse to limit current in battery systems. There is a fuse on the T'REX controller that I am using to limit the system current. I will probably add resettable fuses for each of the solid-state switches on the next version of the QPM board. For this setup, my system tests involved:

  1. carefully checking and rechecking the wiring before applying power
  2. (without batteries connected) checking the software carefully by running the software and checking the LEDs on each switch, which is a great feature on the QPM board
  3. hooking up the batteries and checking the voltage for each to ground on both stacking and unstacking modes

The wired boards passed all tests! When I hooked up the T'REX controller board, it worked perfectly (took about 15 seconds to completely turn on), and I could see the controller on the I2C mux channel 2, address 0x07.

Now I am ready to start connecting the solar panels to the Solar Panel Mux, which you can see in Figure 11 – the three QPM boards on the bottom. Once this is done, the hardware will be complete for the power management system for SunRover. Then, I will start working on the sensors and the motor control software.

Figure 12 shows the initial set of system tests. Note the 10.55V reading on the multimeter; this means the batteries are successfully stacked. The voltage is less than 12V because the batteries are partially discharged and I have loaded the batteries with a 10-ohm resistor (that means the batteries are supplying about 1A).

Figure 12: Successful QPM battery stacking test.


SunRover is a big, complex robot project, but it's filled with cool things to design and build. I will be adding a pan/tilt Pi Camera, LIDAR (to map surroundings), and other sensors. In my next article, I will finish up the Solar Power Multiplexer, mount the solar panels, and put the weather sensors on the robot. I will also be mating the electronics bay to the T'REX chassis, as I am almost finished with the Battery Bay and the motor controls.

Move over, HERO I. Granted, it won't be the Mars Rover, but it will be able to chase the cat. Maybe I should mount a MouseAir on the top [17], so SunRover can fire toy mice at the cat, too!


  1. HERO 1:
  2. TI Speak & Spell:
  3. Project Curacao:
  4. RasPiConnect:
  5. Dagu T'REX Tracked Robot Chassis:
  6. Dagu T'REX Motor Controller:
  7. LiPo 6600mAh batteries:
  8. SwitchDoc Labs Quad Power Management Boards:
  9. "Designing and Building your own Board" by John Shovic. Raspberry Pi Geek, Issue 11:
  10. WeatherPiArduino/WeatherRack sensors:
  11. Embedded Adventures AS3935 lighting detector I2C sensor:
  12. "Protect your Electronics from Lightning Strikes" by John Shovic. Raspberry Pi Geek, Issue 12:
  13. "Managing Solar Power Systems with SunAir boards" by John Shovic. Raspberry Pi Geek Magazine, Issue 10:
  14. Advanced Python Scheduler:
  15. "Oscilloscopes and Mixed-Mode Logic Analyzers" by John Shovic. Raspberry Pi Geek, Issue 12:
  16. Grove connectors:
  17. "MouseAir Launches Toy Mice for the Amusement of Cats" by John Shovic. Raspberry Pi Geek, Issue 05:
  18. SunRover code:

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