Dual TT Motor Test Bed

When designing a robot or other devices that uses TT Geared motors, it is nice to have a way to test circuit designs and software before designing the chassis that will hold all the parts.  The Dual TT Motor Test Bed provides a way to mount the motors and test out your motor controller circuits and the software that you develop or adapt to run them. 

Circuit

The breadboard in the photos is my test setup.  It includes a Pico, a Dual H-Bridge Model, a Power Supply for the motors.   There are buttons and trim pots used to control the direction and the speed of each motor and an optional third button to ground the Run pin on the Pico; this has the same effect as removing and reinserting the USB cable (not shown).

Neither a Pico nor a Raspberry Pi 4 outputs enough power to run the DC Motors.  I use a dual 18650 battery pack for powering the motors while my laptop powers the Pico through an USB cable.

The circuit schematics for my setup can be found on GitHub at:

• https://github.com/sflebrun/Pico-TTMotorTestBed/blob/main/doc/CircuitSchematics.pdf

Software

My code for running my setup can be found on GitHub at:

• https://github.com/sflebrun/Pico-TTMotorTestBed

Hardware

Dual TT Motor Test Mount:

• TT Gear [Yellow] Motors and Wheels Kit
• 4 - M3x30 screws
• 4 - M3 nuts

Electronics: (Optional)

Please not that these are the parts that I used, unless noted.  Feel free to any equivalent parts.  Using a different H-Bridge module will probably require circuit and software changes.

• Breadboard
  • For assembling circuit.
• Raspberry Pi Pico
  • Microcontroller.  An Arduino can be used instead or a SBC such as the Raspberry Pi.
• TB6612FNG Dual DC Stepping Motor Driver Module
  • This is an H-Bridge controller board.  It uses MOSFETS.  An L298 module can also be used.
• 3 Push Buttons for Breadboards
  • 2 buttons are to control the directions of the two motors.
  • 1 button is connect to the RUN GPIO pin and is optional.  This button allows new code to be downloaded into the Pico without having to remove and re-insert the USB cable.
• 2 - 10k Ohm Trim Breadboard Potentiometers
  • Used to control each of the motor speeds.
• Breadboard Jumper Wires - male to male
  • I used both wires and preformed breadboard jumpers in this circuit.
• Motor Power Supply
  • Any DC power supply should work so long as it provides 5 to 8 volts DC at 3A (1.5A per motor).  I prefer rechargeable batteries though AA battery packs can also be used.
  • 18650 Battery Case with on/off switch for two batteries
    • Note, I added breadboard male pins to the lead wires so that the battery pack could be easily attached to the breadboard.
    • WARNING: Do not connect this power supply into the rails that are connected to the Pico 3.3V Vcc.  This will burn out the Pico.  
      • Pico gets its power from the USB cable.
  • 2 - 18650 rechargeable Lithium Ion Batteries
    • NOTE:  These are not the batteries that I bought a couple of years ago.  That company no long is selling them on Amazon.
    • You might consider getting a package that also includes a charger for these batteries if you do not already own one.
    • The last time I bought 18650 batteries I bought them as part of a package that also included a headlamp and a recharger.  It was cheaper than buying the batteries separately.
• USB Cable [Not Shown]
  • Micro-USB connector for the Raspberry Pi Pico
• Laptop or other Computer
  • Used to power the Pico and to download software to the Pico
  • The software writes to the USB cable allowing debugging information to be displayed on the laptop.

Print Settings

Printer:

Creality Ender 3 Pro

Supports:

No

Resolution:

0.2 mm

Infill:

20%

Filament:

PLA or PLA+