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Driver
Circuits, Page 7b
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Last Updated on:
Wednesday, November 29, 2017 05:38 AM |
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Circuits Designed by Dave Johnson, P.E. : |
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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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Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
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Red LEDs function as light sensors - 20-Mar-08 Issue of EDN
You can build simple LED illuminators using the red LED to sense
ambient-light level..... [Design Idea by Geoff Nicholls, Glinde, Germany] |
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Reduced Power Relay Driver - 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.
. [Designed by David A. Johnson] |
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Rolled-Off Noise Source - This is a circuit that generates white noise,
rolled-off to drive earphones or a small speaker. White noise creates is a "rushing"
sound, which sounds something like air rushing by your ear(s). White noise would be flat
with frequency,(circuit added 6/07) |
| RS232c Line Driver IC Drives Power MOSFETs -
10/24/96 EDN-Design Ideas.....Easy to effect an interface between power MOSFETs and TTL
circuits.
[Design Idea by Santosh Shetty, NCRA, Pune University, Pune, India] |
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RTTY Terminal unit - This circuit may be connected directly across your rig
speaker terminal and used to drive a teleprinter coil directly. A normal teleprinter coil
requires 80/80 volts to energise the coil, but this is connected in series with a 2.7K
resistor to give a sort of constant current. The teleprinter coil never has more than 20
volts accross it,..... [from Harry Lythall's website] |
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