close-up of a hook
on negative lead of l.e.d.
10. 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.
11. 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 joints. Trim excess link wire using wire cutters.
12. 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. The picture below shows this stage in the construction of the triangular pattern:
9. 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 in the construction of the triangular pattern:
The l.e.d.s flash independently at slightly different rates to produce a sparkling display. 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”.
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.
To construct this project you will need to use the following tools (not supplied):
Assembly Instructions for Project 14: D.I.Y. L.E.D. Display
Please read through these instructions very carefully before starting assembly.
Think SAFETY. Act SAFELY.
You're important . . . so also read through the safety guidance sheet provided with the kit.
PROJECT 14: D.I.Y. L.E.D. DISPLAY
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. Once you are happy with your design on paper, place the paper design on the top side of the foam board so that the removable REVERSE label is underneath. Place the plastic l.e.d. template in the correct position for the first l.e.d. and carefully push a sewing needle through both holes on the template so that the foam board is pierced. Check that the leads of the l.e.d. just fit through the holes you have made and, if necessary, use a sewing needle with a larger diameter. Continue making pairs of holes for the rest of the l.e.d.s you intend to use.
2. Choose one of the l.e.d.s and gently push its leads through one of the pairs of holes on the top surface. Continue pushing until the base of the l.e.d. lies flat on the surface of the foam board.
3. 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 (see picture below).
13. Screw the foam board to the wooden base, if required, at a suitable position.
14. 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.
(negative part of circuit covered with yellow insulation tape)
negative lead next to flattened edge on l.e.d.
close-up of soldered connection
4. Bend the negative lead of the l.e.d. so that it lies flat on the surface of the foam board and points away from the positive lead.
5. Choose a second l.e.d. and push its leads through another pair of holes on the top surface. Bend the negative lead so that it lies flat on the surface and points away from the positive lead. Repeat this procedure with the remaining l.e.d.s. If the l.e.d.s are close together then care will be needed when bending leads away from other leads.
6. Using pliers, bend the end of each negative lead into a small hook as shown below:
Skill level: * BASIC
Project constructed on foam board.
Soldering recommended but project could be made by simply twisting wires together.
This kit was developed following enquiries from customers at craft markets and enables you to make your own arrangement of light-emitting diodes on foam board. As an example, the picture above shows a triangular design of l.e.d.s with the foam board in a landscape orientation. The kit contains ten l.e.d.s, solder, link wire, insulation tape, a piece of unpierced foam board measuring approximately 10 cm by 16 cm, a battery box and a wooden base.
You will need to spend some time designing your layout of the l.e.d.s on paper. It is much easier to alter the design on paper than it is to alter the foam board after it has been pierced with holes which might be in the wrong positions. Consider the spacing between the l.e.d.s - if they are too close together then the circuit will be difficult to make.
How many of the l.e.d.s do you want to use in your design? Should the l.e.d.s be arranged randomly or in a regular pattern? Do you want to use the foam board in a landscape or portrait orientation? Does the foam board need to be reduced in size or should it be cut to give a non-rectangular shape? (Foam board is easy to cut with a craft knife.) Where should the wooden base be positioned, assuming it is to be used?
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. If fewer than ten l.e.d.s are used then the lifetime of the batteries will be longer.
The circuit diagram for ten l.e.d.s is shown below.
7. Bend the positive leads of the l.e.d.s so that they lie flat on the foam board and in different 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!
8. 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. Make sure that none of the positive leads are in contact with this negative link wire. Solder the 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.
close-up of a link wire and hook connection before soldering
soldered link wire connecting the negative leads together
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