Questions tagged [fail-safe]

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1 answer
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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 ...
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0 votes
5 answers
117 views

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 ...
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1 vote
1 answer
53 views

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 ...
0 votes
1 answer
51 views

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 ...
1 vote
1 answer
92 views

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 ...
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3 votes
2 answers
167 views

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 ...
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-2 votes
2 answers
178 views

When the power goes off, a line must be grounded - how?

I need a line to be grounded as power to a board is failing. Complicating the issue is the fact that this line is critical to circuit operation and cannot tolerate even nanoVolts of additional noise ...
  • 13.2k
1 vote
3 answers
198 views

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 ...
0 votes
2 answers
421 views

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 ...
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0 votes
1 answer
80 views

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 ...
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0 votes
1 answer
69 views

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?
1 vote
0 answers
97 views

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 ...
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1 vote
2 answers
68 views

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 ...
  • 135
0 votes
1 answer
77 views

Fail-safe joystick connection

I am looking for ideas to implement fail-safe function in joystick control box. At present, the 5V joystick HF11S10 is connected to STM32 ADC inputs via simple 5.1k:9.1k divider. We are revising the ...
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