We made a simple board with exposed components, wires and open push to make momentary circuit through various components and a light bulb.  This is used in the Electronic Parts and Symbols mini class to demonstrate show actually parts and their function.  We also use a box of old parts and a couple of old boards with parts on them to show further parts.


A DC wall wart and an AC wall wart were mounted on the board to provide the power and connected to the circuit with a DPDT knife switch.  The board can be used to demonstrate:


·        An open circuit

·        A closed circuit

·        A short circuit (blows a fuse when current does not go through bulb, yet the same size fuse is not blown in the circuit which has the bulb)

·        A resistor restricts the flow of electricity (bulb is dimmer)

·        A rheostat is a variable resister.

·        A capacitor will not pass DC (unfortunately, it won’t pass AC either)

·        A diode will pass DC in one direction

·        A diode only passes part of the AC (bulb is dimmer)

·        The difference between AC and DC (little graphs on the board help with this)


Also on the board is a TNC connection so an HT can be connected.  This circuit contains a 50 ohm resistor as a dummy load and a wire running from the center connector to a capacitor then to a mini light bulb and then a foot or so of wire of wire.  When the transmitter is turned on, the bulb lights:  This indicates:


·        There is current flowing in the antenna wire, i.e., RF have energy.

·        RF waves pass through capacitors.

·        You should stay away from antennas.

·        The bulb lights even through the antenna is an open circuit.  How come?

·        The intensity of the light varies as the wire is moved about.  Why?


While a much more sophisticated demo board could have been developed. We wanted it simple so the scouts could easily see what components were in the circuit.