Handy Dandy Little Circuits #29

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The Inventors of
The First Transistor

Transistor story

Many old shapes and more to come

All about transistors

One transistor circuits

On the next two pages I show a few of the many circuits that uses only one transistor . The circuits shown can be modified and experimented with . One must remember always to use transistors that are rated for the current intended . Most transistor equivalents can be used with very small difference , if any .

This simple adjustable unregulated
power supply can be used for most
application by selecting a transistor
rated for the voltage and current
as required .

A timer to replaced the
old style piano timer .
Adjust RV1 for rate .

This is a fixed voltage output
regulated by a zener diode
See page 30 for zener resistance
(Rs)calculation.Select Q1and
zener for current required .

This little circuit should be
used with low voltage only .
It can have many applications
Fun to experiment with diodes
lamps , transistors , etc..

Check the desired moisture
level of your plants with this
meter . Use a small 1mA meter
A small case and two stiff metal
wires for probes will do .

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