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Questions tagged [fail-safe]

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Relay with bypass switches haywire

The lamps are normally operated by relays. When the relay or relay driving circuit fails totally, the bypass switches are to be used as fail-safe to operate the lamps. The key operated switch which is ...
Kumaran's user avatar
  • 33
0 votes
0 answers
41 views

Can SP2T RF switches be considered failsafe?

I am looking for a RF switch that is failsafe. For failsafe I mean: a device that defaults to a useful state during total power loss (no supply voltage, no control voltage) for a RF switch, a device ...
Alessandro Cuttin's user avatar
4 votes
2 answers
146 views

Safety of dual male / single female Y cords

On Amazon there are Y cords with two male plugs and a single, higher current female socket. These are advertised as providing a way to power equipment with higher current demands than a single outlet ...
711's user avatar
  • 41
2 votes
1 answer
117 views

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 ...
JCReardon's user avatar
0 votes
0 answers
82 views

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 ...
Muhammad Nour's user avatar
16 votes
3 answers
3k views

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, ...
Mołot's user avatar
  • 689
0 votes
1 answer
209 views

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 ...
Matthew's user avatar
  • 572
0 votes
5 answers
437 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 ...
Matthew's user avatar
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1 vote
1 answer
326 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 ...
AimFireReady's user avatar
0 votes
1 answer
268 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 ...
Vyshakh P's user avatar
1 vote
1 answer
169 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 ...
PyroAVR's user avatar
  • 133
3 votes
2 answers
260 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 ...
AaronD's user avatar
  • 5,676
-2 votes
2 answers
183 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 ...
Dirk Bruere's user avatar
  • 13.8k
1 vote
3 answers
278 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 ...
AJMansfield's user avatar
0 votes
2 answers
753 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 ...
Matthew's user avatar
  • 572
0 votes
1 answer
110 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 ...
Matt's user avatar
  • 101
0 votes
1 answer
102 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?
sina rahbari's user avatar
1 vote
0 answers
161 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 ...
wardn's user avatar
  • 11
1 vote
2 answers
111 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 ...
Neil's user avatar
  • 135
0 votes
1 answer
92 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 ...
Maple's user avatar
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