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