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Bredhurst Receiving and Transmitting Society

ILC title

Part 2

Practical 3.

Construct a simple circuit containing a battery, resistor, LED, lamp and switch.

Your lead instructor will provide all the parts required for this little project and will ensure that the lamp is of the correct voltage for the applied battery.

This project will need you to achieve some more solder joints on relatively large pads using a battery, switch and lamp.

The alternative is to use a battery, switch and LED (light emitting diode) with a current limiting resistor. Note that if a current limiting resistor is not used with a standard LED so much current would flow around the circuit the LED would be destroyed. Maximum current through the LED should not exceed say 20mA.

As there is no such problem using a lamp this might be your preference, in that case if you are trying this away from the course ensure the lamp is rated at the voltage applied to the circuit else it will either light burn out if too low a voltage value, glow dimly if near to the right value or not glow at all if much too high a value.

simple battery lamp and switch circuit

To see an animation place cursor on diagram.

The battery should be supplied to you for the project in a suitable holder which will have a solder tag connection for the - end and the + end.

To link the battery terminal to the switch you will need to make a solder connection to the solder tag on the battery box to one "leg" of the switch. It does not matter which side to the switch is connected to the battery (or you might be supplied with a wire already connected to the battery box as it is all to easy to melt a plastic battery box even when you are experienced in soldering!!).

Also for this project is does not matter if you connect the + (positive) or the - (negative) to the switch but it is usual to "make or break" the circuit with a switch in the + POSITIVE lead from the battery. So it is suggested that you adopt this convention from the start and connect the + of the battery to the switch.

Then link the other side of the switch to one side of the lamp which should be supplied to you in a small holder which will also have solder tags.

The last connection is to make the link between the other side of the lamp and the remaining battery terminal.

Looking at the circuit diagram above you can trace round from the battery across the switch through the lamp and back to the battery so that when the switch is "made" or "closed" a complete circuit is made and the lamp will light.

It is likely that the lead instructor will have made up a board that can be re-used by other students for this project. The board will have been the stripped of the components and you will have to solder them in the correct location according to a simple diagram of "component" placing.
This is the actual board used by the BRATS Club in the ILC practicals. It was very simply made and at that at the start of the practical only the switch and the lamp holder are mounted on the board.

To make the switch operational the two side of the switch pads marked "SW" have to be linked appropriately.

Similarly with the lamp. The yellow marking are to show that there is a break in the board beneath the lamp holder which links to the crossing track.

The task is therefore to consider the circuit diagram and then consider from where to where to make the connections. If such a concept is new to you then the lead instruction will give you some more information about reading a circuit diagram and how to relate the pads on the PCB to the joints on the circuit.
Right click here to download a large B&W version of the board. Then print it out so that you can annotate you ideas before committing to soldering!!

This will therefore also test your ability to :-

  • read a simple circuit diagram and

  • correctly identify components and their values as appropriate

  • make the correct placement of parts and

  • complete the soldering of the joints.

This is all in preparation to to task which lies ahead namely making up a larger project than this simple exercise.

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