TEACHER GOAL

This unit is the first of two integrating Lessons, the other being Lesson 18. After completing this lesson students will:

  1. Know how to solder, including detecting and repairing poor solder joints and solder bridges.
  2. Know how to configure the Motor Controller Shield and the smaller H-bridge breakout board to control two DC motors of the type explored in Lesson 14, and an additional three standard servos as described in Lesson 11.
  3. Know how to use a diital multimeter to test and debug their soldering and wiring work.
  4. Know how to upload and use testing programs for the infrared detection of obstacles, and for testing the proper functioning of the DC motors.

The lesson content is complemented with the following HowTo instructions:

  1. How To Assemble Rolling Robot Chassis (How To #1)
  2. How to Assemble Motor Controller Shield (How To #3)
  3. How to Configure and Use the Motor Controller Shield (How To #10 (under development)

COMMON STUDENT MISTAKES

  • Not cleaning the soldering iron tip. The tip of the soldering iron should be clean and shiney. If it is black it will not transfer heat well enough to ensure good solder connections. Twisting a hot soldering iron in a brass sponge will keep the tip shiny and silver-colored.

    Brass Sponge

 

 

  • Poor solder connections that do not electrically connect the pin and the solder pad. Notice on this example the solder does not bond with the solder pad. A similar connection is sometimes made where solder appears on the pad but not the pin. Neither will conduct electricity reliably.

  • Soldering two pins together with a solder "bridge", thus creating a short circuit.

To remove a bridge heat the solder until it turns liquid then invert the board. Holding tight, thump the hand with the board on the table. The excess solder will fall off.

 

 

 

 

ABOUT SOLDERING PINS ON CIRCUIT BOARDS

Three-step process:

  1. Apply soldering iron firmly to the solder pad and the pin. Allow enough time for both to heat enough to melt the solder.
  2. Apply solder, letting it melt and spread.
  3. Allow enough time to let the solder bond to both the pin and the solder pad before removing the soldering iron. Solder should appear to flow up the pin.