Irby Electronics

close-up of a hook on

negative lead  of l.e.d.

A resistor is usually connected to a light-emitting diode to reduce the current flowing through it in a circuit. Too much current can cause the l.e.d. to burn out. However, these are special l.e.d.s and they do not require resistors.

All of the positive leads of the l.e.d.s are connected to the positive side of the battery. All of the negative leads of the l.e.d.s are connected to the negative side of the battery. This is an example of a circuit in which the components are connected “in parallel”.

This project requires two 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 40 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 (only needed if soldering is to be attempted)
  • small pliers for bending component leads and link wire
  • small wire cutters for cutting link wire
  • slotted screwdriver for securing foam board to wooden base.


Assembly Instructions for Project 6: Circle of Light L.E.D. Display
Please read through these instructions very carefully before starting assembly.

8.      Twist the black lead from the battery box around the negative link wire at any convenient position and solder them together. The picture below shows this stage of construction:

PROJECT 6:   CIRCLE OF LIGHT L.E.D. DISPLAY

Skill level:      *            BASIC       
Project constructed on foam board.
Soldering recommended but project could be made by simply twisting wires together.

This circuit contains ten light-emitting diodes (l.e.d.s) arranged in the pattern of a circle. The l.e.d.s flash independently at slightly different rates to produce a sparkling display.

The circuit diagram is shown below.

negative lead next to

flattened edge on l.e.d.

9.      Cover the negative leads and negative link wire with pieces of insulation tape. This will prevent a hazardous short‑circuit occurring should a positive part of the circuit accidentally touch the negative link wire. To aid clarity in the picture below, yellow insulation tape was used to cover the negative link wire but black insulation tape is supplied in the kit.

10.     Make the end of each positive lead into a small hook. Connect all of the positive leads of the l.e.d.s together by passing the remaining piece of link wire through each of the hooks. Squeeze each hook and link wire connection together using pliers and solder the ten joints. Trim excess link wire using wire cutters.

11.     Twist the red lead from the battery box around the positive link wire at any convenient position and solder them together. It is not necessary to cover the positive link wire with insulation tape. Your circuit should look like that in the picture below:

close-up of

soldered connection

3.      Bend the negative lead of the l.e.d. so that it lies flat on the REVERSE side of the foam board and points towards the centre of the circle of pin holes.

4.      Choose a second l.e.d. and push its leads through another pair of pin holes on the top surface. Bend the negative lead so that it lies flat on the REVERSE side and points towards the centre of the circle. Repeat this procedure with the eight remaining l.e.d.s. It is recommended that the negative leads of the remaining l.e.d.s are all bent so that they point towards the centre of the circle of pin holes. This arrangement makes it much easier to connect up the link wire in stage 7.

5.      Using pliers, bend the end of each negative lead into a small hook as shown below:

Irby Electronics

black lead from battery box

Some marking of the surface of the foam board is unavoidable during construction but this can be minimised by careful handling. The connections between the components could be made by just twisting wires together but a soldered joint makes a better electrical connection.

1.      Position the foam board so that the removable REVERSE label is underneath. Choose one of the l.e.d.s and gently push its leads through one of the pairs of pin holes on the top surface. Continue pushing until the base of the l.e.d. lies flat on the surface of the foam board.

2.      Identify the positive and negative leads of the l.e.d. 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 is nearest to the flattened edge on the l.e.d. capsule:

6.      Bend the positive leads of the l.e.d.s so that they lie flat on the foam board and in the opposite directions to the negative leads. To avoid confusion with the negative leads, do NOT bend the ends of the positive leads into hooks at this stage of construction!

7.      Pass the length of link wire through each of the hooks on the negative leads and squeeze the hook and link wire connections together using pliers. Trim the excess link wire using wire cutters. Solder the ten joints, taking care to avoid touching the foam board with the soldering iron. All of the negative leads of the l.e.d.s are now connected together.

Think  SAFETY.   Act  SAFELY.

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

completed circuit


(negative part of circuit

covered with yellow insulation tape)

soldered link wire

connecting the negative

leads together

Colours

12.     Screw the foam board to the wooden base.

13.     Assembly is now complete. Check, again, that the bare positive link wire is not touching the negative link wire at any point. Place two new AA batteries into the battery box and switch on.

Enjoy!

  • 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 a link wire

and hook connection

before soldering