Download Support material

Touch Sensitivity
If electronics kits are not available a possible modelling activity board can be made as shown. This could be used to
show how the device functions.
If students wish to use a switching arrangement see the Resources for details on the construction of membrane
switches.
Some possibilities for solutions using probes are shown
Method of crossing foil tracks
Another solution, which allows the
connection pattern to be changed is
shown:
Alternative outputs
Any of the following can be substituted for the LED:
Buzzer: A low power device. Remove the protection resistor
Motor: use a low power motor eg Dick Smith P9000. Again remove the resistor.
Flashing LED: straight swap
Able or adventurous students might like to try building an astable circuit using two transistors which will flash two
LEDs alternately as the indicator. See the Electroflash web site
Touch Sensitivity
This can be achieved in two ways. Either use membrane switches or use the probe circuit with the addition of two
transistors (eg BC547) set up as a Darlington pair.
The two hands can be a student's or one of the teacher's and one of the student's. If the latter, the circuit is
completed by teacher and student touching finger to finger on their other hands.
Several possibilities arise with this circuit.