Questions tagged [protection]

Ancillary circuitry added to a design that provides protection of the main circuitry to enable the main circuits continuing functioning. In some cases the protection circuitry is sacrificial, being destroyed or degraded in the act of protecting. But not all protection circuits may do this. Examples of faults protected against are: Overvoltage, ESD, overheating, Overloading (too high of a current draw) amongst others.

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69 views

Reverse polarity protection using back to back NMOS

Designing a circuit to measure short circuit current of a power supply every second. Measurement will be on for about 50ms every second. Heat design has been made for this about of time not constant ...
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How does this surge protection work?

This circuit signals an MCU via OU lead. I am not interested in the MCU side. I just show the concept. My question is very simple: How does the surge protection(actually ı meant detection) part work? ...
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Why location of CT is different for the two Circuit breakers in same substation layout?

This is a schematic diagram of a traction substation. In this traction substation protection system schematic diagram, at point marked 'A', CT is located after the 25kV CB. However, at point marked 'B'...
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Protecting RPi against lightning and high voltage

I'm making a remote weather station with a Raspberry Pi 4 and a few sensors. Problem 1: the anemometer is held on a iron rod (was already there, can't change), dangerously exposed to lightnings. ...
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how does it improve EFT immunity

how does this design really improve EFT immunity. where does EFT come from i guess (VDD) as spike ? in my estimation i would say (10k+100nF) is more robust from changes on VDD? in fact the 100pF is ...
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What polyfuses protect USB ports in a typical modern PC?

I would like to know what is the typical rating of a polyfuse used on modern PCs (desktop or laptop) with USB 2.0 and 3.0. TE Connectivity apparently recommended in 2011 that a single USB 2.0 port (...
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38 views

Zero Sequence current Understanding

In literature zero sequence current is called DC component. If it was DC component then how a zero sequence current in neutral grounded secondary of a transformer cause current in neutral grounded ...
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1answer
191 views

How to protect GPIO from back current? Diode? [closed]

After frying a Rpi with this montage 6 months ago: I followed advice from kind users here and modified the wiring to this back in February: It has been working fine for 6 months and suddenly ...
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18 views

Resetting Li-Ion battery protection PCB without disconnecting the load

Given is an 18650 Li-ion battery with built-in protection PCB. It is used to power an electrical load and can be charged by a dedicated Li-ion battery charger. In the schematics below, the battery is ...
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28 views

Programmable sensor signal reference voltage

I'm designing the front-end circuitry for an ADC. The ADC is to be used to read from sensors under two use conditions: An externally referenced sensor, whose signal line will either be 0-5V or ...
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Connectting intercom audio into sound card

I want to connect the intercom in my apartment to a sound card, both input and output. The voltage of the intercom mic and speaker signals (2 different cables) is 12V while not load is applied. When ...
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How dangerous is to have the USB (2.0) D+/D- lines are exposed in the open (ESD et al)?

Sometime ago I designed an bespoke enclosure for an el' cheapo action camera (GoPro clone), which pinned out the USB's power lines outside the waterproof enclosure - something like this, with the ...
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Fuses & current ratings - are there fuses that blow “fast” close to their nominal rating?

The context or reason for this question is the following: Reminder: the question is about the fuse, not about the TRIAC. The context may help to understand the question. A 230V output is controlled ...
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1answer
43 views

Help Identify Potential BLDC Protection Circuit

I am trying to determine the function of a small circuit on a separate PCB that feeds a more complex Brushless DC Motor PCB. As far as I can tell (from physically measuring between 9V-24V) the output ...
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18 views

TVS diodes configuration for AC differential signal

I would like to protect an adc from ESD and Overvoltage by placing tvs diodes. After a bit of reading configuration B seem to be the way to go for a Differential AC signal. But im not competent enough ...
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32 views

ESD Protection on serial relay switches

I'm trying to switch high-quality audio signals using 2 serial relays like the picture below. I'm not sure if this is the best solution to switch between 2 inputs and 2 outputs, but here it is. In ...
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1answer
30 views

Do PMOS Reverse Input protect on ORed power rail

As the title says, I have a power mux IC and two power inputs. I need them to be protected from reverse voltage input. The power mux i have already comes with a reverse voltage input protection but i ...
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Protect voltage level translator from reverse voltage input

I have a circuit that can interface with an external signal or power. And Those signal lines must be translated to a 3.3v level (and vice versa) because that what the circuit uses. And I would like to ...
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32 views

Series resistor or flat clamping for Analog input protection

I have an ADC whose analog input i would like to protect. I have found two papers from Texas Instruments which details on how to do so. Series Resistor Protection This is basically adding a series ...
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108 views

Choosing the diode for protecting an ADCs inputs

I am designing a a board based on a microcontroller that have differential analog pins. The data sheet says that although the MCU's ADCs are internally protected against ESD strikes I must still take ...
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70 views

Choose right transistor for Battery protection IC

I would like to use the BQ2970 as a protection cuircuit for my litium battery (Varta CP1254 A3). It has a max. continuous discharge current of 120mA and also max. charge current of 120mA. How do I ...
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38 views

Microcontroller output override another signal, protect uC when powered off

I have a digital signal from somewhere else and a microcontroller. The microctontroller can set it's output pins to be high, low, or high-Z. If the uC pin is high or low, I'd like the output to match ...
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30 views

Thermal protection effectiveness against short circuit

I'm using the L6201PS H-bridge to drive a 48V DC motor and I broke one of the H-bdridges (when I drive it in the forward direction now, both OUT1 and OUT2 are 48V instead of OUT1 at 48V and OUT2 at ...
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51 views

Providing high voltage tolerance and ESD protection to MCU

I am working on a design for an automotive application. Because its for testing and prototyping I expect the inputs to accidentally, or perhaps intentionally, be attached directly to the battery/...
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45 views

Is it safe to connect lithium protection circuit to positive terminal of the battery?

I'm designing a lithium battery powered circuit, and want to include a battery protection circuit (e.g. DW01, but the question is applicable to other chips as well). All example circuits I can find on ...
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52 views

Snubber circuit to protect SCR/Diode

In my circuit I need to discharge a capacitor into an inductive load using SCR. In order to make the circuit oscillate there'll be a diode antiparallel with the SCR, as you can see in the picture. My ...
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80 views

diodes selection for MOSFET protection against inductive load

Hello I would like to design protection for my N and P channel MOSFETS against inductive load. According to this article, Their IC is best but it cannot hanndle my application so i have to use the ...
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1answer
63 views

What should I look out for when driving high power relays with MOSFETs?

Initially I was designing a relay controller for lower powered relay, but since I could not find the optocoupler that is rated for my application, I turned to MOSFETs. and it so happens that the logic ...
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1answer
64 views

Difference between single circuit and double circuit transmission line protection systems

I'm doing a research on long three phase transmission line protection systems and I found many schemes such as distance protection, merz-price voltage balance system, split-conductor, "translay" ...
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85 views

Series diode in power supplies

If the power source is connected to another power source and input voltage is higher than output voltage a bypass diode usually used to protect the regulator: simulate this circuit – Schematic ...
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3answers
49 views

Using a DB3 diode as a flyback for a 24vdc relay

Can I use the DB3 diode as a flyback for a relay that works on 24v dc? [![enter image description here][3]][3] This is a new photo : [3]: https://i.stack.imgur.com/Snv9f.jpg
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1answer
44 views

Protect Jack plug circuit against transients and constant voltage

I have a question regarding input protection of a circuit. I have been looking all over the internet for awnsers, but can't seem to synthesize the right solution for my problem. To make my question ...
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1answer
56 views

Choosing the right PTC Resettable Fuse for a protection circuit

Power shield protection circuit specs Hello! Iv'e been creating an ESP32 power shield and started designing the protection circuit for the power supply with the following features: Reverse polarity ...
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7answers
8k views

Microcontroller - potential damage to IO pin

I'm revisiting a design I made. The circuit is powered by 24V with polarity protection. I placed a power loss detection before the polarity protection: In case the power pins were replaced, the 3v3 ...
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1answer
70 views

MOSFET full H bridge, voltage spike protection

Preface, I'm a hobbyist not a electrical engineer, so please be gentle. I was looking for a better than l298N motor control solution for higher currents and one that is similar price and size, but ...
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2answers
36 views

How to choose the right clamp diodes for CT overvoltage protection

I have seen back to back diodes and TVS diode (no both at the same time) used for protection in current transformers. In my case, I have a CT signal with a DC offset of 2.5V. The max voltage I will ...
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6answers
767 views

Short Circuit Protection of High speed Data lines

I need to protection data lines of a PIC32 micro-controller (SPI and parallel) running at ~10 MHz, from shorting to ground/Vcc or mis-wiring. I usually (in low speeds) use series resistors to limit ...
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0answers
105 views

How can I use 2 Tp4056 as protection circuit for diy 2s li ion battery?

Hi I want to use 2 Tp4056 modules as over-discharge protection circuit for my DIY 2s li ion battery pack. Those will not be used for charging! hence will not share input! The load is an arduino nano ...
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1answer
72 views

How to design a circuit that the input signal type(positive or negative) can be selected via software configuration

Firstly, Hello to all, I am trying to design a circuit for automotive application that circuit will read positive and negative input signals in the same pin via selecting the type of input in the ...
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33 views

Long bus powered device protection

I'm looking to have several devices attached to a long (total ~10 m) powered i2c bus. The bus would be regulated to 5V at one end and the whole system will operate in exposed outdoor conditions on a ...
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50 views

Are usb ESD protection like the PRTR5V must have?

I am making a custom pcb basing on Arduino's open source schematics and i noticed that their newer products always have a PRTR5V0U2X USB ESD protection wired like this: Are they a must have if you ...
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0answers
51 views

Overvoltage and reverse polarity diode protection - capacitor across “reverse” diode?

I've stumbled across a schematic as shown in the picture. It is an over-voltage and reverse polarity protection before LDO. V1 is input voltage of 12V, but it doesn't matter for my question. What ...
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1answer
28 views

Inverse time lag relays in protection

I'm dealing now with the different types of time responses of electromechanical relays: instantaneous, definite time lag, inverse time lag, and inverse definite minimum time lag. My question is: What'...
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63 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
87 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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1answer
68 views

How to calculate the power rating of zener diode for flyback protection?

I'm trying to calculate the power rating for the zener diode I'm using on my circuit for flyback protection. For example, if a flyback event occurs, the cathode of the zener diode is having a 30V ...
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1answer
37 views

SIPMOS as current source

I read this question and I have the same issue: acquire and protect an input with 5-24V range. I wonder if nowadays I can use a BSS126 as current source transistor. It's a depletion mode N-channel, I ...
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113 views

What is this Diode for?

This part of a schematic from the I/O board in the link below shows a 1N4148 diode in parallel with an optocoupler's input circuitry. What is this diode for? https://startingelectronics.org/projects/...
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139 views

What *fuses* an electric fuse?

I build a quite lot of projects to learn electrical engineering, and since I was first introduced to what's called a fuse around 2 years ago and I always put one in my high voltage 220V mains for ...
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39 views

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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