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 Safety / Protection Circuits, Page 3
Safety / Protection:  #-B     C-D     E-K    L-N     O-R      S      T-V

Last Updated on: Thursday, April 07, 2016 12:59 PM

Circuits Designed by Dave Johnson, P.E. :
    This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was designed for a device powered from a single 1.5 volts button cell battery.  However, the circuit will operate with higher voltages as well.

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Battery (12v) Load Cutout Circuit -  Lead-acid batteries should not be discharged below a certain point if they are to last.  Also, you don’t want certain 12v powered devices, which might be plugged into a car’s cigarette lighter outlet, to drain the car battery down to a point where the car… [Hobby Circuit designed by David A. Johnson P.E., 8/22/09]

Battery automatic power-off has simpler design -  03/31/05  EDN Design Idea    implified circuit provides timed battery cut-off to save power… [by Yongping Xia, Navcom Technology, Torrance, CA]

Battery Discharge Monitor -  Here is a battery monitor circuit which disconnects the load when the battery is discharged, preventing a a deep discharge which could cause permanent battery damage. The battery is automatically reconnected when a battery charger or other DC source… [Copyright © 1998 Wenzel Associates, Inc.]


Battery Protection Circuit Allows Surges -  06/05/97 EDN Design Idea   Circuit monitors two lithium-ion batteries and protects both of m against Overcharging, Overdischarging, and undervoltage… [by Ron Lenk, Temic/Siliconix, Santa Clara, CA]

Beeper indicats Check Engine -  When driving down a busy road, you may not notice a “check engine” indicator light that suddenly turns on within the car’s instrument panel.  You could drive for many miles before noticing the light.  To provide an audible indication of trouble, the hobby… [Hobby Circuit designed by David Johnson P.E., 7/09/06]


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Bias supply provides short-circuit protection -  09/16/99 EDN Design Idea    Most power-supply designs require protection from a short-circuit fault condition. One of the methods of short-circuit protection is cycling, or the "hiccup-mode" method. This method is an effective way of controlling a short-ci… [by Dave Kim, Linear Technology Corp, Milpitas, CA]

Blown Fuse Indicator -  It is a circuit that can check the status of a fuse. It has got a bi-coloured LED which turns to green if the fuse is fine and turns to red if the fuse is blown up. Modifications can be made for a buzzer to sound in case of fuse gets blown.… [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Blown Fuse Indicator -  a simple way to see if a fuse has blown without removing it from its holder… [Andy Collison's website]

Blown-Fuse Indicator for AC load -  This simple circuit to monitor the state of fuse and mains power supply is highly useful for AC-powered appliances. Sometimes these appliances suddenly stop working and we don’t have any clue what has gone wrong. The problem can be so simple that it can be rectifiedjust by replacing the fuse. This circuit helps to identify such problems. … [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Blown-Fuse Indicator Sounds An Alarm -  07/10/08  EDN Design Idea   A simple blown-fuse-indicator circuit sounds a buzzer and flashes an LED when a fuse blows.  Safety fuses or fusible links see wide use in modern electronic equipment to protect the load and the power supply—especially batteries—against short circuits and excessive load current. Fuses are inexpensive and simple, and a wide range of parts is available. However, you must replace them when they blow, and, when they do, you need an indicating circuit that warns you about its failure, especially when the fuse body is ceramic or sand-filled for improved protection against arcing.… [by Vladimir Oleynik]

Broken Charger-connection Alert -  Detects if a device is not properly connected to its supply.Suitable for battery chargers, portable appliance supplies etc.… [Flavio Dellepiane's web site]

Bus from 5v Swings -  11/14/02  EDN Design Idea   The circuit in Figure 1 automatically detects voltage and protects a bus, such as a 3.3V-limited PCI bus, from 5V signal-level swings. You can also use the circuit to determine bus-voltage swings within one bus-cycle for setting ap… [by Said Jackson, Equator Technologies Inc, Campbell, CA]

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