Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [fail-safe]

17 questions
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How is a mains-connected medical device made safe against electrocuting me?

I am in physical therapy now. Some of the devices are connected to wall power, and used for muscle electrostimulation. The patient information states that no single malfunction can connect me to 230V, and any malfunction that would allow a second…
Mołot
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Fail-safe half-bridge

I've been thinking about this for a while now, to use in the powered jaw of some publicly accessible, human-sized animatronics. I want a lot of force to be available to move quickly, and to demonstrate some decent bite strength, all with feedback…
AaronD
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Determining values when designing with thermal fuses; calculating influence of location/proximity to heat source & properties of protective coverings

The root question: Are there any best practice rules or guidelines for spec'ing out a system with a non-resettable thermal fuse? What criteria is used to determine what rating fuse is needed? I'm primarily talking about the fuses you find in most…
JCReardon
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How can I detect a power failure on a 120V circuit and activate a battery-powered indicator light?

I recently got a new septic system installed. It's a Presby/mound system whereas our old system was gravity fed to a single tank with fingers. The mound system has a pump tank and the tank is wired on a 120V 20A circuit from the main…
AimFireReady
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Dual NMOS as AC switch

I would like to preface this by saying that my project here is an educational exercise, and I hope that by sharing it and requesting feedback, some other fine folks will learn from it too. I know that the correct solution here is "use a gate driver…
PyroAVR
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Intentionally tripping a fuse to disable a circuit in an unrecoverable fault condition?

I'm building a device that regulates the atmospheric composition of a space using a gas sensor and a control loop to actuate a solenoid valve to release compressed gas into the space. Due to the nature of this task, it should be clear that such a…
AJMansfield
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Manual overriding a DC-motor with H-bridge

I have created the following circuit where I use a VNH7070BASTR full bridge motor driver to control a DC-motor. The goal is to open and close a drawer using a rack and pinion system. A new requirement that I have is that the drawer can ALWAYS be…
wardn
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Opening fail-safe electrical strike door with a spring

I have a 12V fail-safe electrical strike currently installed and working on a door, but I want it to open slightly when it is powered down, but a spring apparently won't do as my strikes keep themself locked if they have a constant force acting on…
Neil
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Disconnect main power if sub-module failed

I am working on a power supply for a stepper motor driver which requires 48 V and 12 V to operate. The 12 V rail must present all the time if it was cut off for any reason then the 48V should also be disconnected! I am feeding the 48 V to a DC-DC…
Muhammad Nour
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How to design/build a relay-triggered "crowbar" circuit?

(This is a continuation of Failsafe for relay contact welding.) I'm trying to wrap my head around something like a "crowbar" circuit, only, instead of tripping on over-voltage, it should trip when a signal is sent (i.e. when a certain wire goes from…
Matthew
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Failsafe for relay contact welding

So, I'm fiddling with a design for a widget, and one of the "fun" parts is to ensure that power is reliably cut without human intervention. Power is normally controlled by relays, which have at least a theoretical potential to experience contact…
Matthew
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Failsafe circuit for a bistable latching solenoid

I am new to embedded circuits and working on a problem with which I need help. I am using ESP32 soc for controlling a bistable valve using DRV8833 driver module. Please refer to this link for valve specifications or a quick reference is available…
Vyshakh P
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Is there such a thing as a fail-safe, low-power relay?

Background Let's say I have a device. I can't give details, but, like many heat-producing devices, it's intended to be used for a limited period of time, but if left on indefinitely can be very dangerous. Let's also assume that: The device needs…
Matthew
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Turning a circuit off using a 240v signal

I have a home-built controller for a HERMS brewing system (Heat Exchanging Recirculating Mash System). The purpose of this controller is to drive liquid (wort) from a large mashing vessel (a cooler box), through a heat-exchanging coil that is…
Matt
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Use attiny as an external watchout timer

I like to failsafe an Atmega8 mcu despite having its own WDT. does it make sense that if I add an attiny to the circuit to check if each loop is taking a specific time, if not reset the Atmega chip?
sina rahbari
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