Simple Pulse Generator

Simple Pulse Generator

This circuit is used to provide positive going pulses. The pulse width varies from 10µs to 100 ms at the rate of 20 pulses per second to 1 pulse per second and adjusted by a 1 MΩ potentiometer. Transistor T1 and T2 form a relaxation oscillatory circuitry. The frequency of oscillation depends on C1 and VR1. The pulse width is varied by a 47KΩ (VR2) potentiometer. Any required pulse width range is selected by the switch SW1 below

Position of switch SW1 Pulse width
1 10 µs to 100 µs
2 100 µs to 1 ms
3 1 ms to 10 ms
4 10ms to 100 ms
PARTS LIST
Resistors (all ¼-watt, ± 5% Carbon unless stated otherwise)
R1 = 33 Ω
R2 = 47 K Ω
R3 = 47 Ω
R4 = 33 Ω
R5 = 2.7 KΩ
VR1 = 1 MΩ LOG
VR2 = 47 KΩ LIN POT.
Capacitors
C1 = 1 µF/16V
C2 = 0.0022 µF
C3 = 0.022 µF
C4 = 0.22 µF
C5 = 2.2 µF/16v
Semiconductors
T1 = SL100
T2 = SK100
IC1 = 74121
Miscellaneous
SW1 = 1 pole 4 way switch