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Circuits designed by David Johnson, P.E.
Last Updated on:
Thursday, March 22, 2012 07:56 AM
Master Category List
- Dave's Circuits
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Copyright © David A. Johnson, PE - ALL Rights Reserved.
LINKING to Dave's circuits is permitted but DO NOT COPY to your WEB SITE server! |
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Pulse Width
Modulator (PWM) Circuits |
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Computer Controlled PWM Circuit
There are times when you wish to control a pulse width modulation (PWM) signal
with a DC voltage, ranging from 0v to 5v. This voltage is often created by a
computer interface. The circuit below performs this voltage to PWM
conversion. PWM signals are often used to control the speed of DC motors and
can also be used to control LED lamp light intensity....
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PWM Circuit for Motor
Speed Control
Sometimes you want to slow down a brush type DC motor. The most efficient way to do
this is with a pulse width modulation (PWM) technique. The hobby circuit below can
operate from about 3 volts to 15 volts. The frequency is fixed at about 2KHz but the
pulse width can be varied from nearly 100% to 0%. ...
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Reduced Power Relay Driver
Aug 3, 2008
Relays can handle a lot of power. However, for certain power sensitive designs
you would like to reduce the power needed to hold a relay closed. The circuit
below performs such a task. It uses a single CD4093 quad NAND gate. When
the “on” logic input signal is detected, the relay is first pulsed on for about
500ms. This is sufficient time to insure the relay is fully closed.
After that initial pulse the relay is then driven with a square wave signal, whose
duty cycle can be adjusted. The signal duty cycle can be adjusted from about
10% to 90%. In most cases a 50% duty cycle will hold the relay closed.
This reduces the average DC current required by the same factor, which means a 4:1
reduction in power. The circuit can operate over a wide 3v to 15v range.
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