Electronic Circuits and Tutorials
Electronics Schematics - P

 Safety and Protection Circuits

Advanced Polarity Protection With MOSFETs: Advanced Power Switching and Polarity Protection for Effects

Amplifier Thermal Protection:

Audio Amp Output Power Limiter:

Audio Level Control Device: compressor circuit based on LED and photodiode

Battery Discharge Monitor:

Battery Protection Circuit Allows Surges: 06/05/97 EDN-Design Ideas / Circuit monitors two lithium-ion batteries and protects both of them against Overcharging, Overdischarging, and under voltage

Circuit Breaker has Programmable Delay: 01/16/97 EDN-Design Ideas / This circuit provides overload and short-circuit protection to a5V power-supply output

Circuit Detects & Disconnects Over voltages: 04/25/96 EDN-Design Ideas

Circuit Ensures Safety in Power on operation: 04/24/03 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit

Circuit folds back current during fault conditions: 11/28/2002  EDN - Design Ideas / You can use monolithic linear regulators at currents lower than 5A for most applications. Most manufacturers of these devices integrate current-limiting and thermal shutdown to prevent damage during fault conditions. For currents greater than 5A, most linear supplies use controllers that allow the user to select the pass element to handle different current requirements

Circuit guards Against Battery Reversal: 07/06/95 EDN-Design Ideas

Circuit Prevents Deep Discharge of Batteries: 09/26/96 EDN-Design Ideas / To avoid the deep discharge that can destroy or shorten the life of a rechargeable battery, you must disconnect its load before the discharge is complete

Circuit Protects Against AC Line Disturbances: 07/29/98 EDN-Design Ideas / operates by switching off the power supply upon detection of under voltage or over voltage conditions

Circuit Protects Battery From Over discharge: 04/12/01 EDN-Design Ideas / PDF contains multiple circuits - scroll to find the one of interest / In some applications, it is undesirable to Over discharge the battery, because it could irreversibly reduce the battery's capacity and the number of discharge/charge cycles. This circuit protects a single NiMH (nickel-metal-hydride) cell by disconnecting the load from the battery when it gets discharged enough.

Circuit protects bus from 5V swings: 11/14/2002  EDN - Design Ideas / 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 appropriate termination voltages of protection diodes or termination resistors.

Circuit Protects Computer's Input: 05/26/94 EDN-Design Ideas 

Circuit Protects FPGAs From killer Spikes : 04/23/98 EDN-Design Ideas

Circuit protects system from overheating: 11/08/2001 EDN - Design Ideas / The two-chip circuit in Figure 1 provides fan control and over temperature warning and shutdown signals to protect systems from excessive heat.

Circuit Provides Flexible gain Ranges: 06/21/01 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit.

Current Limiter Provides Latch up Signal: 01/01/98 EDN-Design Ideas / Current-limiting circuit both signals a latch-up condition and prevents latch-up-induced over current destruction of a CMOS IC or group of ICs

DC Fault Protection Circuit for Audio Amplifiers: Circuit ideas how to replace traditional CD protection relays with MOSFETs

Dual comparator thermally protects lithium ion battery : 09/18/03  EDN-Design Ideas / Most manufacturers recommend that you don't change lithium-ion batteries at temperatures lower than 0°C or higher than 50°C. You can monitor both thresholds by adding a thermistor and dual (window) comparator to a lithium-ion battery charger (Figure 1).

Electronic Fuse Emulates Fast or Slow Blow Fuses: 11/09/00 EDN-Design Ideas / PDF contains multiple circuits - scroll to find the one of interest / The electronic-fuse circuit in this article combines the properties of a current transducer and a solid-state relay to disconnect low power at preset levels. Using this circuit lets you avoid the bother of stocking and replacing fusible links.

Electronic Fuzing: National Semiconductor Application Notes,05-Aug-1995

High side driver has fault protection: 09/05/2002  EDN - Design Ideas / High-side drivers find common use in driving grounded solenoid coils and other loads. Short-circuit protection for such drivers is essential for avoiding damage from wiring faults and other causes. Polymer fuses are generally too slow, and discrete current-limiting circuits are large and cumbersome.

High Voltage Circuit Breaker Protects to 26V: 09/11/98 EDN-Design Ideas

Isolated Driver Forms Solid State Circuit Breaker: 03/03/98 EDN-Design Ideas

Logic PSU With Overvoltage Protection: 5 volt regulated power supply for TTL and 74LS series integrated circuits, includes output Over voltage fault protection

Loudspeaker Protection & Muting:

MOSFET Beats Murphy's Law: 12/22/94 EDN-Design Ideas

Open collector output provides fail safe operation : 09/04/03  EDN-Design Ideas / It is common practice to use digital open-collector outputs for control units in industrial applications. Using these outputs, you can switch loads, such as relays, lamps, solenoids, and heaters.

Overload & Reverse Current Circuitry Protects Battery & Load: 03/01/96 EDN-Design Ideas

Overvoltage Protection for LM317:

Overvoltage Protection: describes crowbar technique that provides a useful defense for fast Over voltage spikes and transients that could cause damage to more sensitive components

Polarity protector out performs Schottky diodes: 02/06/03  EDN-Design Ideas / The polarity-protection circuit in Figure 1 is a high-performance alternative to the usual series diode (often Schottky). The circuit incurs a much lower voltage drop than even the best Schottky diode.

Power line outage flashes red alert: 06/13/2002  EDN - Design Ideas / This Design Idea expands on a circuit in a previous one to configure a power-outage detector with a flashing alarm (Figure 1, Reference 1). The circuit plugs into a mains outlet and uses trickle-charged nickel-cadmium batteries. The green-LED monitors the presence of line voltage. The BZV55-C4V3 zener diode, D1 protects the batteries against over voltage.

POWER SUPPLY FAILURE ALARM: This circuit employs an electrolytic capacitor to store adequate charge, to feed power to the alarm circuit, which sounds an alarm for a reasonable duration when the supply fails.

Protection Circuit Covers a Wide Range: 07/17/97 EDN-Design Ideas /

Protection for your Electrical Appliances: The simple circuit given here switches off the mains supply to the load as soon as the power trips. The supply can be resumed only by manual intervention. Thus, the supply may be switched on only after it has stabilised.

RS232 Overvoltage Protection Circuits:

Safety device uses GMR sensor: 07/10/03  EDN-Design Ideas / This Design Idea presents a differential safety device to prevent risks arising from current leakages in household applications. The proposed circuit uses a new method for differential current sensing (Figure 1).

Spark gaps Provide ESD Protection: 09/01/97 EDN-Design Ideas

Speaker Protector:

Supervisory IC Protects System Against Overvoltage Conditions : 05/13/02 Electronic Design - Ideas for Design / Careful design limits overvoltage on the supply input of integrated circuits, and avoids compromising an IC's specifications. Overvoltage damage can cause an immediate failure, or accelerate an early-life reliability failure.

Thermal switches provide circuit disconnect : 09/04/03  EDN-Design Ideas / A single temperature sensor can provide an interrupt to a microcontroller when the measured temperature goes out of range. You need multiple temperature sensors when you have to monitor more than one hot spot.

Transistors offer thermal protection for controller: 07/19/2001 EDN - Design Ideas / When a switch-mode power-supply controller, such as On Semiconductor's NCP1200, operates at a high ambient temperature, you should protect the entire power supply against lethal thermal runaway.

Two buttons provide safe start: 07/06/00 EDN-Design Ideas / - This circuit provides a safety interlock that checks the actuation of two pushbuttons before enabling a relay. When you push both buttons, the circuit actuates the relay. At that point, you can release one of the switches without the relays switching off. The circuit was intended to lock out the engine of an underwater propulsion unit.

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