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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Is reverse polarity protection this simple?

I am working on a PCB design and need help understanding reverse polarity protection. The board will be powered with a 12V 5.4A power supply via barrel jack. I am planning on using this chip because ...
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-1 votes
0 answers
17 views

Distributed generation (DG) source model

Can we model a distributed generation (DG) source like wind or PV system as a current source in order to show the bidirectional current contributions in a meshed network?
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0 votes
1 answer
48 views

Battery high voltage protection

I'm making a coilgun with four 11.1V 1300mah 95C lipo batteries in series, providing 44.4V for the coils. Current will peak at 200A for short durations of time. Is there some common way to protect the ...
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-1 votes
2 answers
55 views

5V protection circuits

For my project, I'm using this solar shield in order to use some solar panels and a battery to power my Arduino. In order to protect the solar shield (where the maximum solar input is 6V) I would ...
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3 votes
2 answers
157 views

What is the purpose of this dual-facing diode?

I'm trimming off some parts from an eval board schematic, and I'm not sure what the purpose of this dual-facing diode / rectifier is. The voltage divider from R33 and R48 is scales by a factor of 10 ...
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1 vote
1 answer
44 views

Over Current/Short Circuit Protection Using op-amp and MOSFET

I wanted a circuit to limit the current to say 4A, and found this but it doesn't work in the Proteus simulator. What's wrong with this circuit? anyways to improve it? here is my expectation of the ...
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0 votes
1 answer
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mosfet to protect reverse plarity from a power suply range 10v-18v DC [duplicate]

hello I have designed a board that operates on 10v to 18v DC (2A) I need somehow to protect it from reverse polarity, am thinking to use MOSFET but how I can drive the gate in 10v-18v range
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1 vote
1 answer
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Linear Power Supply - Overload Protection Circuit

Summary and Context: Several years ago I bought a linear power supply from Pyramid, model PS-3KX. I would like to understand in detail how the "OVER-LOAD PROTECTION" really works, as said ...
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2 votes
1 answer
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Actual Line-to-Line voltage from per unit value

In this question, I am able to find the per unit phase voltages using the symmetrical components. Taking the base MVA and base voltage to be the same as that of the alternator, \$ (I_a)_1 = \frac{E_a}{...
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0 votes
1 answer
78 views

What is the purpose of the resistors in this circuit?

They are labeled as Rfbt and Rfbb; I understand the rest of the circuit, but I can't say what exact job those two resistors do.
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2 votes
2 answers
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Is swapping lion batteries (of same voltage, different capacity) on wireless headset going to affect anything? (charging, etc)

My wireless headset had a 400mAh 3.7V battery in it which was very low quality and ended up lasting very little. So, I replaced it with a 1200mAh 3.7V battery. The 400mAh battery had a protection ...
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0 votes
2 answers
55 views

Can a lower gauge jumper be connected to a high amperage circuit as long as it is going to an appropriate sized breaker?

The 14 AWG wire is connected to an appropriate sized circuit breaker to prevent that run of wire from drawing too many amps; however, my concerns would be that the 2/0 cable being in such close ...
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0 votes
3 answers
77 views

How to make sensor input look like high impedance on loss of 5V power?

I have a strain gauge sensor with a full-scale output of about 8mV and an output impedance of 5K ohms. We will be measuring its value with a max sample rate of 500Hz, and 10 bits of resolution. It ...
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0 votes
0 answers
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Arcing during dynamic braking in AC single phase series wound motor

My 240 V 800 W hedge trimmer starts and runs with minimal commutator sparking but arcs violently at the brushes on switch-off. When 'on', the DPDT switch routes power through field coils and ...
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1 vote
1 answer
72 views

Input over voltage protection circuitry around RBO40 for automotive use

I have been digesting input power protection circuits for automotive use for several days now. There are a lot of snippets here and there with either complete info (no parts) or incomplete circuits (...
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5 votes
6 answers
966 views

I²C overvoltage protection fail

I have a pogo connector with +8.4 V/GND/SDA/SCL. I would like to protect my microcontroller from overvoltage (+8.4 V could potentially touch SDA/SCL). I tried this circuit: But the thing is: There is ...
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0 votes
2 answers
114 views

Design of power input protection on NVIDIA Jetson Xavier NX (dev kit)

When looking at the schematics of NVIDIA Jetson Xavier NX developer kit, they use a P-channel MOSFET (AONR21357) before bringing power to a buck converter (TPS53015, not represented below). What is ...
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1 answer
81 views

Component selection for IGBT desaturation detection

I am designing a circuit for driving a DC motor, and want to include overload protection, for that I found that detecting desaturation is a good option to detect high current flow. I sketched the ...
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3 votes
4 answers
354 views

RS-232 Crossover, and Protection against shorting two TXD lines

I'm in the process of designing a USB to RS-232 converter for communication with some existing boards, and I ran into two problems. First Question I need a way to programmatically reverse the TXD and ...
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2 votes
3 answers
715 views

What causes the 7 volt peak in this 5 volt RC circuit, and why does a diode alleviate it?

I was reviewing this question on an RC circuit design from a Ben Eater video, and came across hacktastical's answer on how it was a bad design because it outputs 7 volts on release of the push button (...
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0 votes
0 answers
52 views

Reverse Voltage Protection using PMOS: Bias Resistor selection

1.How to calculate the bias resistor value (100R in snip attached) ?. 2.Is the resistor value depend on Zener clamping value?
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0 votes
1 answer
50 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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2 votes
2 answers
129 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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1 vote
1 answer
93 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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  • 557
0 votes
2 answers
82 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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1 vote
1 answer
35 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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2 votes
1 answer
144 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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1 vote
1 answer
50 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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5 votes
2 answers
240 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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0 votes
5 answers
450 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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-1 votes
1 answer
42 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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2 votes
2 answers
73 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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1 vote
1 answer
100 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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1 vote
1 answer
91 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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1 vote
2 answers
330 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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-1 votes
1 answer
162 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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  • 1
0 votes
2 answers
98 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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-1 votes
1 answer
58 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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  • 1
0 votes
2 answers
200 views

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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7 votes
2 answers
795 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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1 vote
1 answer
96 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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0 votes
4 answers
100 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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  • 1
0 votes
2 answers
116 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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  • 1,285
0 votes
1 answer
48 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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  • 33
0 votes
1 answer
41 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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4 votes
2 answers
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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  • 87
0 votes
2 answers
75 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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0 votes
0 answers
80 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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4 votes
3 answers
291 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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  • 2,394
2 votes
2 answers
70 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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