SNAP CIRCUITSTM - Carl's Electronic Kits
SNAP CIRCUITSTM - Carl's Electronic Kits
SNAP CIRCUITSTM - Carl's Electronic Kits
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Project #246<br />
Two-Finger Touch Lamp<br />
OBJECTIVE: To show that your body can be used as<br />
Build the circuit on the left. You’re probably wondering how it can work,<br />
since one of the points on the NPN transistor (Q2) is unconnected. It<br />
can’t, but there is another component that isn’t shown. That<br />
component is you.<br />
Touch points X and Y with your fingers. The LED may be dimly lit. The<br />
problem is your fingers aren’t making good enough electrical contact<br />
with the metal. Wet your fingers with water or saliva and touch the<br />
points again. The LED should be very bright now. Think of this circuit<br />
as a touch lamp since when you touch it the light emitting diode lights.<br />
You may have seen such a lamp in the store or already have one in<br />
your home.<br />
Project #247<br />
One-Finger Touch Lamp<br />
The touch lamps you see in stores only need to be touched by one<br />
finger to light, not two. So let’s see if we can improve the last circuit to<br />
only need one finger. Build the new circuit, note that near point X there<br />
is a 2-snap wire that is only mounted on one side, swing it so the<br />
plastic touches point X. Wet a large area of one of your fingers and<br />
touch it to both metal contacts at point X at the same time; the LED<br />
lights. To make it easier for one finger to touch the two contacts, touch<br />
lamps or other touch devices will have the metal contacts interweaved<br />
as shown below and will also be more sensitive so that you don’t have<br />
to wet your finger to make good contact.<br />
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