Cardboard switch and application

In the early years, simple switches with pretty obvious mechanism are the thing. For a cardboard switch you need to cut two pieces of card each about 10 mm by 50 mm. Score one through the middle, then wrap both in kitchen foil. Use two drawing pins as shown to complete the switch. Add two wires and a bulb holder and you have a simple circuit. An extension which we have used with some success is to make a clown’s face with a card switch built in as the nose. Press the nose and the eyes light up. The Clown has two eyes and we need two bulbs. How can we wire up the circuit so that both bulbs will be equally brightly lit?

A further extension could be to construct a model car dashboard to provide a similar opportunity (this might be more appropriate at later stages).

Suppose we made a model cardboard dashboard to include a horn (buzzer), side lights and headlamps (lamps)? We might wire the horn in series but how would we have to wire the lights? We could also use a different but no less overt switching mechanism such as a paper-clip switch.

Later we might return to similar problems but seek to improve both depth and breadth of understanding.

Paper-clip switch

Paper-clip switch and its use in series with a single lamp


Microswitch - wiring positionsAt P5 -7 or S1/S2 we might use less obvious switching mechanisms such as toggle switches or even microswitches.

As their name suggests these are miniature switches. They are used in such domestic applications as door operated fridge lights and to check for door closure on washing machines and dishwashers. Microswitches are more versatile than simple open or closed contact types such as card or paper-clip switches. They have two possible contact positions and thus the cloice of wiring them in either Normally Open (NO) or Normally Closed (NC) modes.

At Level E the design task might be to make a more sophisticated clown’s face as a toy for younger children.

How could we make it wink? This might need some simple electronics.

Microswitch in operation - wired as Normally Open
Normally Closed (NC) Normally Open (NO)
Microswitch wiring - Normally Open (NO) Microswitch wiring - Normally Closed (NC)
Circuit diagram for NC wiring of microswitch Circuit diagram for NO wiring of microswitch