Irby Electronics

Irby Electronics

1.      Identify the positive and negative leads of the light-emitting diode, D1. A light-emitting diode will not work if it is connected the wrong way around and so correct identification of the leads is important! For this type of l.e.d., the negative lead is shorter and it is next to the flattened edge on the l.e.d. capsule (see picture on wiring diagram above).

2.      Push the positive lead of D1, without bending it, through hole F10 and, using pliers, bend the negative lead so that it fits through hole
I10. Spread the ends of the leads slightly apart and carefully solder. Avoid solder splashing across the copper tracks where you have soldered the l.e.d. Trim excess wire from the leads of the l.e.d. using wire cutters.

3.      It does not matter which way around a resistor is connected in a circuit. Using pliers, bend the leads of the resistor, R1, so that they can be pushed through holes A20 and F20. Spread the ends of the leads of the resistor slightly apart and carefully solder. The pictures below show this stage of construction:

Think  SAFETY.   Act  SAFELY.

You're important . . . so also read through the safety guidance sheet provided with the kit.


close-up of

top surface showing

l.e.d. and resistor

4.      Push a terminal pin from the track surface through to the top surfacein position A25 and solder on the track surface. The terminal pin is a tight fit and pliers are usually needed to squeeze it through the hole. Push another terminal pin through position I25 and solder it. (Terminal pins have a habit of jumping off the table and are never found again – two spare terminal pins are provided in the kit.)

5.      Twist the red lead from the battery box around the terminal pin in position A25 and solder them together. Twist the black lead from the battery box around the terminal pin in position
I25 and solder them together.

6.      Assembly is now complete. Carefully compare your circuit with the wiring diagram and the pictures above. Correctly place three new AA batteries into the battery box and switch on.


  • If your circuit doesn’t work and the batteries become hot then you have made a short‑circuit. This is a potential fire hazard! Switch off immediately, remove the batteries and check your circuit to find the problem before continuing.
  •  If the problem isn’t a short‑circuit, please recheck your soldering and your batteries.

close-up of

track surface

showing soldered joints

A resistor is usually connected to a light-emitting diode (l.e.d.) to reduce the amount of current flowing in the circuit. Too much current can cause the l.e.d. to burn out. In this circuit, a 47 ohm resistor (R1) is connected to the l.e.d. (D1).

The “surprise” about this circuit is that such an ordinary-looking l.e.d. can produce such a colourful display. For a really spectacular display, place a cut-glass container such as a tumbler or a tea light holder over the l.e.d.

The l.e.d. changes colour over about 30 seconds and then the cycle repeats. Unfortunately, it is not possible to alter the rate at which the l.e.d. changes colour.

This project requires three AA batteries (not supplied in this kit). In a test of this circuit, a set of Duracell Plus Power batteries was still producing a good output of light after 140 hours of continuous use.

To construct this project you will need to use the following tools (not supplied):

  • small, low power soldering iron, e.g. 15 watt, 18 watt or 25 watt
  • small pliers for bending component leads
  • small wire cutters for cutting component leads.

Assembly Instructions for Project 7: L.E.D. Surprise 2
Please refer to the wiring diagram and read through these instructions very carefully before starting assembly.

Skill level:      * *            INTERMEDIATE
Project constructed on track board.
Soldering essential.

This is a very simple circuit containing a single light-emitting diode. The circuit diagram is shown below. The same circuit is used in Project 1 but Project 1 is constructed on a base of foam board.