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Learning soldering wires and connectors

Prerequisite: WsIaR? Cable!, LiPo Batteries

Standard Procedure

  1. Apply heat shrink tubing first if the other end is a dead end.
  2. Solder as the method mentioned below.
  3. Pull the solder joint to check its mechanical strength.
  4. Check the electrical connectivity of the solder joint.
  5. Check the polarity if you are soldering connectors. NEVER REVERSE THE POLARITY. Every year boards made by M2 and even computers are fried due to reversed polarity.
  6. Apply heat over heat shrink tubes.

Solder wires together

Solder wires together

  1. Cables should be spliced before soldering. There are 2 common splicing methods:
    • cross the 2 ends of the wires and twist them together (a.k.a. Western Union splice)
    • unravel the strands of the 2 ends, intermesh the 2 strands together and twist them together There are also other splice such as T-splice and Rat-tail splice, but they have weaker mechanical strength.
  2. Apply solder over the joint. For thicker wires (e.g. AWG 15), flux may be necessary as heat cannot be transferred readily across the wire.

Watch the following video to see how it's done:

Solder over a surface with a hole

Solder joint with rocker switch

When soldering wire to a surface with a hole (e.g. terminals of rocker switch), it is similar to what you've done in Learning basic soldering skills:

  1. Pass the raw wire through the hole. You may want to twist the raw wire so that it can be held in place.
  2. Solder the wires just like soldering through hole components, which you have learnt from the article Learning basic soldering skills.

Watch the following video to see how it's done:

Solder over a flat surface

Solder joint with a T plug

Solder wires over a flat surface (e.g. terminals of T plug) is a little bit tricker. It is difficult to hold the wire, the flat surface and apply solder at the same time.

  1. Tin the raw wire and the flat surface with solder seperately.
  2. Hold a soldering iron between the tinned raw wire and the tinned surface and solder them together. Make sure the solder on both side is molten, otherwise cold joint will be made.


When soldering a cheap T plug from Chinese manufacturers, the plastic melts easily and the contacts may be dislocated. You may plug another T plug on the other side to prevent dislocation.

Watch the following video to see how it's done:

Heat-shrink tubing

Animation of heat-shrink tubing, before and after shrinking

Heat-shrink tubing is suitable to insulate a solder joint. It is suggested to heat up the tubing with a heat gun or a lighter. (Please don't use a soldering iron)

heating up heat shrink tubing

Assignment 02

Power it Up

Requirement of assignment 02

Here you're gonna drive a motor with a AQMH2407ND DC motor driver. Connect a 2S LiPo, a Blue Pill, the motor driver and a motor like the photo above. You'll need:

  • A cable with T plugs in 2 ends and a rocker switch in the middle
  • A cable with a male T plug and a Euroblock
  • A motor connected to a Euroblock

The interface of AQMH2407ND is similar to the L298N module you have tried in Arduino Tutorials (Learning basic control). Here is the AQMH2407ND Manual. Be careful to the polarity of the power input.

See Also