Simple Under-Voltage Cut-Out

Sensitive low-current
relay coils often operate at much lower voltages than their typical
ratings. This can be undesirable in some applications, where low supply
voltages can result in erratic system behaviour. In some instances, this
problem could be overcome simply by inserting an appropriate value
zener diode in series with the relay coil. This reduces the voltage seen
by the relay coil, so causing it to drop out earlier. If desired, a LED could be included when a spare set of “normally closed” contacts are available to indicate relay dropout.

Circuit diagram:

Simple Under Voltage Cut Out Circuit

Simple Under-Voltage Cut-Out Circuit Diagram

Author: Jay Williams
Copyright: Silicon Chip Electronics

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