Elenco Upgrade Kit SC300 to SC750 - Manual (Page 21)

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Project #343
OBJECTIVE: To build a half wave rectifier circuit.
A rectifier changes an AC voltage into a DC voltage. A diode (D1) is
used because it allows current to flow in only one direction, for one
polarity of applied voltage. As the contacts open and close, it
generates an AC voltage across the transformer (T1). We can
measure the DC current from the transformer’s output using a resistor
(R2), a diode (D1), and a meter (M2). Set the meter to the LOW (or
10mA) scale. Turn on the slide switch (S1), the LED lights as the meter
points past the 5 scale.
Half Wave
Rectifier Circuit
OBJECTIVE: Measure the voltage using the
center-tap.
Use the circuit in project #343. Now see what
happens if you connect to the center-tap on
the side with more windings. Place the meter
(M2) across points A & B, then turn on the
switch (S1). The needle should deflect less,
about half as much as project #343. As you
use less windings, the output decreases.
Half Wave
Rectifier
Circuit (II)
Project #344
OBJECTIVE: To see the voltage difference
between an LED and diode.
Use the circuit in project #343. Replace the
LED (D1) with the diode (D3) and turn on the
switch (S1). The needle deflects higher,
because the voltage drop across the diode is
less than the voltage drop across the LED.
LED vs. Diode
Project #345
OBJECTIVE: See how resistance affects
current.
Change the 1k Ω (R2) resistor to a 5.1k Ω (R3)
and turn on the switch (S1). You will see that
increasing the resistance decreases the
current through the meter (M2).
Current &
Resistance
Project #346