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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40 views

Node voltage calculation

I'm designing a protection circuit and I'm assuming the following hypothetical situation represented in the figure below, where I need to determine the value of Vx. Does anyone have any suggestions on ...
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2answers
68 views

High voltage power thermal fuse for DC

I am looking for ways to break a high voltage DC power line when an overheating scenario occurs. Preferably I would like to do so using a thermal fuse but can’t find any thermal fuses rated for high ...
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1answer
71 views

Can placing MOVs on an 240v input be ever a bad thing?

The power supply of my home lighting keeps failing. So far i have 10 of the same power supply failed. Upon inspection the thing that is always get damaged is the Electrolytic Capacitor after the ...
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2answers
48 views

Low noise voltage clamp for ADC

I have a sensor that can output 0 to 12 VDC. However, the ADC I am using can only convert 0..3.3 V. I am trying to limit the sensor output to 3.3 V to protect the ADC from damage. The sensor output ...
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1answer
31 views

Spark initiator combined with low-voltage, high-current follow on

I am aiming to add a spark initiator to my electric discharge machining (EDM) circuit, but I am unsure of how combine the high voltage (>1-10 kV) initiator and the existing lower-voltage, higher-...
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1answer
112 views

How does my crowbar circuit look?

Theory of operation: op amp detects higher-than-reference voltage and triggers SCR, which remains in low-impedance state until current drops close to zero (hopefully by blowing the fuse). Main ...
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1answer
45 views

How should fuse selection be made in discrete-time alternating current?

In my circuit,I have a resistive load(Lamp).(Rlamp=1 ohm).At the ends of the lamp is voltage V(t) in the picture.In the picture, there is the first 12 seconds of the signal.But you may think that ...
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2answers
120 views

Powering Multiple Raspberry Pi circuits via GPIO header power pins

Goal: I wish to power 3 Raspi. I am currently running 3 USB C wires powering the device, but I wish to build or find ways to power them all using GPIO header power pins. Background: Mechanical ...
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0answers
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Clamping for external reed/contact sensor

i'm trying to realize a low power input interface for reed/contact sensors for my MCU (ATMEGA328P), i've seen the Trevor_G answer to this question and i think that this will be the way to go, using ...
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5answers
284 views

Current limit to 500mA (maximum) at 12V

I have a 12V DC output which can output 1A (maximum.) I want a circuit that limits the current to maximum 500mA, so I don't accidentally draw more than 500mA as that would probably mean I have shorted ...
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1answer
38 views

Amplifier input protection

I'm working on building a voltmeter/ammeter as a hobby project. I'm pretty comfortable with power, and digital design, but I'd appreciate some input on the nuances of the analog side, specifically ...
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2answers
66 views

What kind of protection does a circuit need to have for reading the output of a CT?

A CT (current transformer) is installed to measure the line current for digital measurement and protection devices. In many cases, the CT is installed in open weather or on poles, making it vulnerable ...
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1answer
96 views

Does USB have some kind of current cutter that cuts the current for safety? [closed]

I accidentally got 24V into the GND on my Arduino and then the USB shut off - but not all of them. When I restarted my computer, then all USB shut off and they are not giving out any current. Notice ...
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1answer
66 views

Beginner seeking feedback on circuit design: SEPIC with adjustable voltage

I recently got very interested in electrical engineering. After watching a bunch of YouTube videos on circuit and PCB design, I figured it's finally the time to get a bit hands on. I decided to start ...
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2answers
74 views

Three-phase circuit breaker trip current

If a three-phase circuit breaker is specified as, for example, a 32 A breaker, does this mean the breaker will trip when the current in a single phase exceeds 32 A, or when the total current of all ...
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1answer
61 views

What will happen if I use RCBO where there is no neutral in the system?

I need some help. Could you please go through the scenario and try to answer my query below? This system is installed in a ship where there is no neutral connection available. A 440V/220V step-down ...
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2answers
92 views

Make a circuit to make sure a device only gets a maximum of 1A

I'm making my own smart home device with a Raspberry Pi. I will power the Pi on the same circuit as our bell. Now the bell transformer is 8V, 1A and the bell itself uses 0.5A. I'm thinking to replace ...
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1answer
52 views

How to know which opto-coupler is suitable for high current application?

I would like a suitable opto-coupler to use as isolation from a 12V and around 30A current and another for 5V and around 30A. Are there any good opto-couplers for those ratings?
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2answers
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Voltage divider plus Zener protection on op-amp input

I am designing a circuit to scale an input voltage to the range of an analog to digital converter pin on a microcontroller, and also provide electrical protection for the pin. I put together the ...
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2answers
702 views

FPGA over-voltage protection for input trigger signal

I don't have much experience with PCB design, but I am currently designing one to connect together several components for a work project. One of these components is connecting an external trigger ...
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1answer
68 views

ESD and overvoltage protection with varying clamping voltage

I am designing a PCB for analog multiplexing. I want to protect the signal lines against ESD and overvoltage. The voltage in the signal lines shouldn't exceed the limits of the two supply voltage ...
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4answers
74 views

Voltage protection with relay and Zener

I'm having a hard time finding a good way to protect a radio module if the voltage regulator fails and injects the battery's input voltage. The module is expensive, so I would like to protect it from ...
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2answers
74 views

How to connect a TVS diode

I want to use a 824021 TVS diode in my circuit. The input is 5V and the clamping for tehe TVS diode is at 7V. Which of the following two connection diagrams is correct A or B? Or a better way to put ...
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1answer
47 views

What are default rules to connect cold part to protective ground?

I have a device, what have hot and cold part. I want to protect cold circuit what contains user interface from HV leaks or breakouts. In professional PCB im frequently seen cold-common connected to ...
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1answer
26 views

Power a circuit with with 12V barrel jack and USB 5V

What if I use a Schottky diode at both the power rails in forward voltage mode and connect both the supplies? Will it damage my circuitry? Reverse current will not damage my device because of the ...
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2answers
1k views

Reverse Polarity Voltage Protection Using P-MOSFET

Could you please help me understand why in a reverse polarity circuit with P channel MOSFET Source of the MOSFET is connected to the LOAD and DRAIN to the power supply? I understand the concept of a ...
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2answers
72 views

How can I provide time-controlled current protection?

I need a component name or solution. I have a fan motor that I run with AC. I am controlling with MCU and driver. Operation logic: 0.75 s on, 9.25 s off. My circuit works flawlessly with this logic. ...
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0answers
65 views

How to best protect 12V from voltage transient spikes?

I am building an AC power supply and I decided to put digital current and voltage panel meters into it. I have an issue where whenever my main contactor engages and disengages, there is a transient ...
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3answers
245 views

Polarity of TVS diode is unclear

I have a question regarding the DESD1LIN2WSQ TVS diode by Diodes Inc. which I want to use to protect some 24V IOs of a microcontroller board. Until now, the TVS diodes I worked with always had the ...
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2answers
57 views

Using intelligent power switches (IPS) for fast short-circuit protection

I would like to ask for some help in implementing short-circuit protection on outputs of a PCB. I have a PCB, which is powered with 12 V DC from an external PSU. This power line gets routed to PCB’s ...
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1answer
67 views

Can a single 15 ampere power socket be converted into two 15 ampere sockets?

I have an existing 15 ampere socket, but want to install one more 15 ampere socket near it. The electrician suggested to install it from the existing socket. I have a doubt that since the socket was ...
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1answer
191 views

Purpose of a capacitor placed between the ethernet signal?

I came across attached Ethernet design for one my application. Since connector used here is with internal MagJack support external transformer is not used, The PHY used here is AR8031 part. In the ...
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2answers
99 views

Role of CAN bus protection circuitry

Here is CAN protection circuitry as suggested by MORNSUN in their datasheet of CAN transceiver with integrated power. I have few questions regarding few components used there: What is the purpose of ...
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3answers
499 views

Relay protection circuit

I came across a relay circuit that uses two diodes and a capacitor. I know the diode across the coil (D1) is a flyback diode and that capacitor (C1) is a filter capacitor. What is diode D2 for?
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2answers
517 views

IC protection diodes confusion

This question is (loosely) related to my previous question here. I wanted to check the ESD protection diodes of the LPC1114 MCU from NXP. So I measured all pins on a brand new LPC1114 MCU with a ...
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0answers
32 views

I wnat to design a circuit with a DC load but need help calculating the required circuit breaker, cable etc on the AC side of the power supply

I need to design a circuit with a knowing DC load of 24Vdc 20 watts. Now I have a Puls PIC 120.241D power supply that I can use. My question is I need to spec the protective device on the incoming ac ...
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0answers
38 views

input power sharing and with power limiting

According to this document which talks about how to do the power-sharing and power limits, these three figures are the power limit circuit, and I have three questions I am not sure how to solve. I ...
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1answer
82 views

How to protect reverse polarized when there are two different power sources

The meaning of the title is, when connecting a DC buck converter and a lithium-ion battery, to ask how to protect the converter from the reverse polarity of the battery first i will use ideal diode ...
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1answer
3k views

What is ORing and why is it named ORing?

I read some documents like the PoE application, it used ORing to protect the reverse input current. I would like to know what ORing is. I googled it, but I cannot find the answer. It seems like a ...
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1answer
49 views

Communication Line Protection

I intend to protect a BUS switches ICs, whose voltage on its pins cannot exceed 5.5V and 3.3V. The current cannot exceed 16mA. The circuits needs to opperate from 3.3V to 5V. But automotive ...
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32 views

Legacy battery system - series connection or boost circuit

Background. I have a legacy battery system that is comprised of twenty-four 12V Li-ion battery modules (self-protected), enclosed in a shell with the charging connection provided as a common ground ...
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2answers
324 views

Do AC input optocouplers require an ESD protection?

I intend on using a circuit I designed for detecting an AC input line for control purposes. One of the inputs will be accessed by third party users and a cable might be connected with a decent length(&...
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1answer
58 views

Would this SOT-23 P-FET be appropriate for reverse current protection with current up to 1A?

I've designed in reverse current protection on a board that I'm designing. The input voltage is 24V with a potential max current draw of 1A (depends on what is plugged in, parts of the PCB are modular)...
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3answers
54 views

Applying voltage to the output of turned-off voltage regulator LDFM33PUR

I have LDFM33PUR device in a circuit and it is responsible for generating stable 3.3V (for Micro-controller) from 5V input. I want not to use LDFM33PUR and rest of the circuit and just externally ...
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1answer
63 views

How to design a discrete flat-clamp TVS circuit

I need something similar to the Texas Instruments TVS3300 but for a higher voltage. The TVS3300 is basically a drop-in replacement for a TVS diode that clamps the voltage using an internal mosfet and ...
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1answer
60 views

Do I need a current protection?

I have a variable gain amplifier that can output a current of 90 mA. The output is directly connected to a µController I/O pin. My question is: do I need something like over-current protection, since ...
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54 views

Protection against constant overvoltage from power supply

I have a project using USB VBUS as power source. Fault to protect from: a bad AC-DC 5V adapter goes haywire, or a USB form factor device with non-5V output (some laptop AC-DC with USB type C?), or ...
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1answer
264 views

DW01A not allowing power in TP4056 circuit

Edit: Used wrong resistor at R_BAT1. The schematic was correct, the part I used was wrong. I am using the following charging circuit. It is the standard circuit taken from the datasheets. But it is ...
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1answer
33 views

battery protection circuit - identify discharge current rate that will trigger protection

We are considering to add a battery protection circuit to our system in addition to the protection circuit that already exists on the 4.2V Li battery pack itself. I know that the batteries have ...
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2answers
94 views

Current limiter using 2 bipolar junction transistors (BJTs)

I want to know where are the input and the output of this circuit in LTspice. I also need the values I should use for the resistors and the transistors in order to see clear results for current ...

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