Questions tagged [circuit-protection]

A device, components, or safety measure designed to protect circuits from overvoltage, overcurrent, a combination of these; or the theory of same.

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49 views

Why is the maximum voltage of a surge, 6kV inside home wiring?

I was reading about the benefits and cons of series mode surge protectors vs MOV-based surge protectors for home use. First, why is the probability that a surge will exceed 6kV extremely low due to a ...
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3answers
73 views

Overcurrent protection in lab bench power supplies

In my school we used lab bench power supplies all the time as it is an electrical engineering school. Can someone point me in the direction of an implementation of an overcurrent protection found in ...
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Varistor - Place before or after the fuse? [duplicate]

What is safer? Before or after the fuse? In my case the varistor is 10mm, 275Vrms, and it is currently placed after a 250Vac, 7A, 20mm glass fuse. Would the varistor blow the fuse easily if placed ...
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28 views

Bidirectional protection or isolation for generic digital communications

I am redesigning a company product, it is a product for automotive maintenance and diagnostics. Currently in the product there is a FET BUS switch to perform the interface between the microcontroller ...
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4answers
62 views

What is wrong with the MOSFET IRF540N ? Even with the zero gate voltage, why current is still flowing through drain to source?

Actually I was developing the overcurrent protection using op amp LM-358 as described in the second picture . I made the circuit as described on this link https://circuitdigest.com/electronic-circuits/...
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What is a better way to prevent over-discharge in this low current circuit?

I made a nightlight and was very happy with the dim yet usable output and runtime (months), but my assumptions about battery safety were wrong. I expected the LDO 3.3 V regulator to stop output when ...
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1answer
72 views

400W inverter not charging power tool battery charger [closed]

I have a 2018 Ford SuperDuty with a factory 400 Watt AC inverter. When I plug in a Milwaukee charger, the circuit protection light starts flashing and the battery will not charge. The charger does not ...
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1answer
55 views

Where to fuse high voltage batteries connected in series?

I have modules of cells in series each with 48V. I wonder where is the right place to fuse the modules in series. (The current to trip the fuse is the same on every point). Version 1: simulate ...
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1answer
33 views

Fuse design for taking in account real-world very small transients

A bit of context I came up with this question after someone suggested that two fuses are better than a main one in the below configuration. The converters are SMPSs which regulate output voltage. ...
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0answers
38 views

IC Protector in AV Receiver (ICP-N15)

I'm fixing a Denon AVR-788 AV receiver that won't boot but would turn on with the light in front blinking red. Naturally, I looked to the Service Manual (link goes to schematic) and started following ...
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12answers
3k views

Is it worth it or safe to design your own power supply? [closed]

I am currently building some kind of game console based on a Raspberry Pi, with some features (one discussed here), right now I am using for this project a Meanwell power supply. However, I was ...
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2answers
125 views

Why would doing the “outlet challenge” cause notable damage to outlet and wiring?

WARNING!!! WHAT "PRANKERS" IN THE VIDEO DO IS MOST LIKELY VERY DANGEROUS AND MAY CAUSE DEATH, INJURY, FIRE OR OTHER DAMAGES AND IT SHOULD NOT BE TRIED IN ANY ELECTRICAL SETUPS WHICH ARE NOT DESIGNED ...
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1answer
105 views

Electronic Circuit Breaker

I want to protect from short circuit by using a miniature circuit breaker. But this has to be manually turn ON, when ever it is turned OFF. So I was thinking to make a electronic circuit breaker which ...
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1answer
63 views

Transformer switch off spike

From Wikipedia: When a transformer, electromagnet, or other inductive load is switched off, the inductor increases the voltage across the switch or breaker and cause extended arcing. When a ...
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3answers
47 views

BAT60A diode allows reverse voltage

I have designed a board and it can be supplied by USB and/or D-Sub connector. The board gets the 5V from USB or another board via D-Sub connector. I have placed 2 schottky diodes to prevent reverse ...
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1answer
71 views

How to add safety to line voltage connected to D-SUB?

Pins 13, 14, and 15 on the D-SUB connecter will be connected to 120AC line voltage when their respective relays are on. I can imagine a situation where line is shorted to neutral (dirty connector, ...
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1answer
33 views

Double DC Motor Compressor Circuit Protection

I'm a mechanic! So, please do not blame me for stupid questions. I did a lot of research using relays for switching DC motors. The following circuit is showing the current version I want to realize ...
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6answers
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Due to overcurrent, shouldn't I be extremely cautious when setting an I/O pin as Output?

The question can be applied to any microcontroller with I/O capabilities, but I’m currently working with the popular ATmega328p. Consider the following circuit: A simple SPST Normally Open switch with ...
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1answer
38 views

ATEX: PCB design for intrinsically safe, output capacitor

We're looking into restricted breathing or encapsulation concept because PCB has a complex circuit that makes it impossible to achieve SMD clearance under 'ic' or increased safety concept. I have a ...
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2answers
72 views

Vintage VCR PSU: finding circuit breaker [closed]

After a grueling 8-hour overhaul of a high end VCR, which included recapping the entire PSU, disassembly to fit the new capstan motor, and cleaning/oiling of the mechanism, got all working fine and ...
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0answers
76 views

Issue with TP4054/How not to damage li-po charger ICs

My issue is: The TP4054 I am using started drawing 150 mA after something I did. I know that I have probably fried it and the obvious answer is I should ditch it and take a new one. However I am not ...
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0answers
218 views

Will this reversible USB-A circuit work safely?

I'm working on a PCB USB stick with a reversible USB-A connector. This device should work reversibly with any normal USB host. I know that it works fine with just the topside, but I realized it ...
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3answers
111 views

How to suppress a short circuit to prevent fuses from blowing [duplicate]

I have a circuit that is modular and one of the modules involves interfacing from an external relay. Now this sub-module has a fuse set to blow a bit below what the main module's max current. (why ...
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2answers
46 views

Limit the amount of current passing through a circuit to a set threshold?

Here's the situation: I've added an aux input to an old hifi system by tapping into the circuit previously used by the magnetic read head of the hifi's built-in 8-track player. That part works pretty ...
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1answer
42 views

Li-Ion Protection IC Always in Overcurrent Detect Mode

I am seeing an issue with AP9211SA-AF-HAC7 Battery management system. The battery protection circuit, designed as per the schematic attached (the same as the reference design in the data sheet(https:/...
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40 views

How to prevent reverse current/voltage on a sense line?

I'm designing a rocket launch controller, that incorporates an Arduino to provide a safer and more controlled launch. Original rocket launch controllers used to use an incandescent light bulb and a ...
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1answer
70 views

Need Help identify ICs in battery protector PCB

Does anyone recognize these ICs? Manufacturer, model # etc. They are part of a lithium-ion battery protector. Many thanks for your help (I added the silkscreen, traces, and edited the pictures so it ...
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18 views

EV charger testing BS7671 CPC-earth test

As part of the standards for BS 7671 it states: A device which disconnects the charging point from the live conductors of the supply and from protective earth in accordance with Regulation 543.3.3....
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1answer
40 views

What method can be used for outdoors circuit protection when transmitting DC or analog signals?

For long time I have been looking for a source for this but I dont know how to articulate it. Sometimes I need to send analog signal or DC voltage for hundreds of meters by using STP cables. But the ...
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0answers
26 views

How to check broken Surge Protection Device

I have this type of SPD, how can i test if this device still in good condition?
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1answer
37 views

Connecting multiple LED strips in parallel to a 220v/5A power line (via 12V driver)

I would like to power 5 LED strips via a 220v/5A wall outlet (each strip is 5m in length). I will be consulting and employing the electrician for the best way to run the wiring but from the initial ...
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0answers
23 views

Interrupt circuit by voltage - Low Voltage DC

Non EE here, looking for some advice. I have a solar power and battery system in my RV. I am using UpCycled Tesla battery modules for my energy storage. I want to better protect the batteries and ...
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60 views

Back EMF protection

I made an ignition coil driver circuit which is nothing special - they are everywhere on the internet. What's really bothering me is the back EMF that would fry the 555IC. If I put a rectifying ...
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93 views

Over current Protection for Ne555 circuit?

I made simple frequency generator circuit with Ne555 but almost in every circuit Ne555 IC burns after few use. Ne555 starting to heat up then outputs weird signals , if I don't stop the supply Ne555 ...
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2answers
226 views

Reverse-polarity protection P-channel MOSFET

There are many ways one can build a reverse-polarity protection circuit. Using diodes, Shottky diodes, n-MOS in the return path and using a P-channel MOSFET on the positive side of the circuit. My ...
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1answer
48 views

USB-Battery load sharing circuit comparison

I have found two different load-sharing circuits on Adafruit modules: The 32u4 (left) only employs a schottky diode, while the nRF52 (right) uses an additional pull-down resistor as well as a ...
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0answers
66 views

How to protect a CONSTANT current DC motor from stalling?

What would be an efficient way to protect a DC motor that draws CONSTANT CURRENT (always 300mA) from self destroying when stalled for too long? Or is this even necessary on brushed DC motors? On other ...
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2answers
125 views

Can I use a 3.3v tolerant microcontroller to drive IR leds that require 5v with a darlington array?

I have a microcontroller that is not 5v tolerant and I need to drive IR leds just like in the attached circuit. What I thought of doing is using the 5v line from my raspberry pi as the load voltage ...
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2answers
67 views

Can i use 1 fuse for all the outputs to protect my power source from overcurrent?

Can i use 1 fuse for all the outputs to protect my power source from overcurrent by connecting the fuse to the ground wire? I have 3 outputs: 3.3V, 5V, 12V and i want to protect my power source when ...
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1answer
74 views

resistor placement for zener diode for over voltage protection

i have searched in over voltage protection (like mosfet ) , i wanted to use zener diode parallel so it wont dissipate power unless in over voltage protection , but its power is low so i read that i ...
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1answer
41 views

How do surge protectors interact with existing circuit protection?

I recently bought a power strip with a surge protector and it came with this warning. Do not install this product if there is not at least 10 meters (30 feet) or more of wire between the ...
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30 views

What's the proper way of mounting surge arresters on TN-S system?

I'm attaching a diagram with surge arresters put on each line. Most of the experts in the field say a proper defense against lightnings and switching events has three surge arresters - one between ...
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30 views

Switch gear & protection - Problem

I'm a B.tech student currently in my 4th year. I was learning Switch gear and protection and suddenly I came across a numerical problem while trying to solve it, I'm having a small doubt as: Is ...
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1answer
161 views

How to design over voltage protection Crowbar Circuit?

I'm designing a Crowbar over voltage protection circuit with following specifications, Maximum input voltage - 30V Maximum input current - 5A Output voltage - 5V Output current - 5A So I have ...
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1answer
59 views

Charging and discharging 18650 batteries with TP4056 modules via their power output terminals

I'm having those fancy ESP boards that come with a battery input pins/holders that can be connected to a battery to make them portable. They also have a dedicated USB port for charging/sketch uploads. ...
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1answer
67 views

Why doesn't the voltage source ever supply current in my circuit?

I'm trying to make a protection circuit for a battery. The PMOS is intended to prevent reverse current. The diode is intended to prevent the output voltage from exceeding 10V. When I simulate the ...
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2answers
87 views

Do I need a full BMS or just protection circuit?

I'm planning on building a custom battery powered speaker, and am quite new to rechargeable batteries. My amplifier needs 5V, so I thought I would put 2 18650 batteries in series, and use a step down ...
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1answer
179 views

500V generation, MOSFET Heating Problem

Referring to my previous post. I have successfully generated 500V. The problem I am facing an issue. MOSFET I am using for switching is FQB34N20LTM. The MOSFET is burning badly. The snap of drain ...
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0answers
63 views

Reverse voltage protect circuit

I am trying to add a reverse voltage protection circuit to my circuit. I searched for some circuits and simulated them with an online simulator (Circuit Simulator Applet). It might work as I need it, ...
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0answers
47 views

Dual supply source, how to do the switching?

I'm designing a circuit that I'd like to normally power from a 12-36VDC source, but want to have the option of also powering it via the USB connection during configuration. I've chosen the LMR16030 ...

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