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Dave's Circuits
Circuits designed by David Johnson, P.E.

Master Category List - Dave's Circuits
 Last Updated on: Sunday, July 27, 2008 07:41 PM


Alarm Circuits
UNPLUGGED POWER CORD ALARM 
Many medical devices, such a portable X-ray and ultrasound equipment, carry their own batteries. However, the frantic pace of some hospital emergency rooms might cause the device to be shoved off into a corner without being plugged back into an AC power source to recharge their batteries. So, I designed this circuit to emit an audible alarm whenever the device’s power cord was unplugged from the wall for a period of time. The device was designed to snap onto the outside of a power cord, where it senses the AC electric field emitted. No direct connection to the internal wires of the power cord is needed. I also included a low battery voltage monitor.

Click on Drawing Below to view PDF version of Schematic

Circuit Unplugged Power Cord Alarm designed by David A. Johnson, P.E.

Alarm Circuits
Master Schematic Category List - David A. Johnson, P.E.

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