Theory Of Operation; Schematic Diagram - Elenco Electronics SP-3B Assembly And Instruction Manual

THEORY OF OPERATION

The solder practice kit consists of a circuit oscillating
at one hertz (one cycle per second). The oscillator
consists of two transistors Q1 and Q2, and resistors,
R1 - R11 and capacitors C1 and C2.
configuration is known as a multivibrator circuit.
When voltage is first applied to this multivibrator
circuit, one transistor (possibly Q1) will conduct
faster, causing transistor Q2 to stay off. Q1 will
continue to conduct until it saturates. At this point,

SCHEMATIC DIAGRAM

Q2 will start to conduct, causing Q1 to rapidly cutoff.
This process continues alternately causing Q1 or Q2
to conduct. The output will be a square wave. The
This frequency is determined by the time constants of
resistor R6 and capacitor C1, also R12 and C2. Two
LED diodes are placed in the collectors of the
transistors and will light when current is passing
through them. Resistors R1 - R5, R7 -R11 determine
the current passing through the LEDs.
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