Week 6: Mechatronics


We will go over our pull string prototypes.  Touch on some of the basics of mechatronics.  And then get our hands dirty with some in-class building.


Pull Toy Prototypes

Where is everybody on the assignment?  What’s do we think about the work so far?  What is holding us up?



Mechatronics is a multidisciplinary field of engineering that includes a combination of systems engineering, mechanical engineering, electrical engineering, telecommunications engineering, control engineering and computer engineering. via


For all intents and purposes, we’ve been doing mechatronics ever since we’ve controlled servos and motors in PComp.


Gear Ratio is defined as the input speed relative to the output speed.  It is typically written as: Gear Ratio = win : wout – more info

Torque is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. via

Pulse-width modulation (PWM) is a modulation technique used to encode a message into a pulsing signal. Its main use is to allow the control of the power supplied to electrical devices, especially to inertial loads such as motors. via


In Class

We will be working with off-the-shelf mechanical gear boxes and analog circuits to control two axels.

We will be putting together Tamiya 70168 Double Gearbox L/R Independ 4-Speed kits in class.  The gearbox can be assembled into four different gear ratios:

Type A, Gear ratio 12.7 : 1, 1039 rpm, Torque 94 gf·cm
Type B, Gear ratio 38.2 : 1, 345 rpm, Torque 278 gf·cm
Type C, Gear ratio 114.7 : 1, 115 rpm, Torque 809 gf·cm
Type D, Gear ratio 344.2 : 1, 38 rpm, Torque 2276 gf·cm


Steps to Assembly

  • Lay down paper
  • Open Parts (carefully)
  • Knoll all Parts
  • Pick Gear Ratio
  • Solder wires to DC motors
  • Put set screws in shaft collars
  • Assemble
  • Label Gear Ratio on housing


The two independent axels will work with 3mm hubs and shaft collars.


PWM to Control Speed

Using a circuit from Making Things Move (pages 158-162), we will be able to control the speed of a DC motor with an analog circuit.

We will be breadboarding and then soldering a permanent circuit.

We will need the following components:

Breadboard PCB
555 Timer IC
Capacitor, 0.1uF (2)
Tip 120 Transistor
Voltage Regulator
9V Battery Connector
9V Battery
Male Headers



Pull Toy Projects are due.  Have a robust finished toy.  Have it painted and ready to play with.


Related Reading/Viewing

PComp Lab: DC Motor Control Using an H-Bridge

DC Motor Clockwise Anticlockwise Control H-bridge Circuit

Intro to Fab: Mounting Motors