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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75 views

What is the point / name of this circuit? Reverse voltage protection + current mirror?

I stumbled across this circuit on page 8 of the Nano Pi Duo 2. What purpose does it serve? I recognize the MOSFET arrangement to be a reverse voltage protection circuit and the PNP transistors form a ...
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1answer
58 views

Identifying a SOIC-8 IC with “302F” marking

I have a board with an unidentified SOIC-8 IC marked "302F". I am looking for the part number of this component that is mounted in a 2 cell battery pack PCB designed for AIBO robots by SONY ...
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1answer
56 views

How do I protect a unipolar ADC input against a bipolar signal?

I am designing a circuit that should convert a unipolar differential audio signal using an ADC. The signal varies between 200mV - 28V peak to peak and I'm planning to use the TI PMC6020 ADC that ...
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67 views

Why do op amps need input protection when the input impedance is very high?

From what I understand, the input impedance of an op amp is very high (ideally infinite) and almost no current flows into the op amp. If that is the case why do we put a resistor in series with the ...
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1answer
109 views

How does this dice rolling circuit work? [closed]

I'm having trouble understanding how this whole circuit works. I am just a beginner trying to challenge myself but I can't seem to be able to.
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1answer
64 views

Voltage surge suppression technique in high-speed switching based electronic circuit

I am working on a circuit that transmits ~1MHz sine wave(20V amplitude) in RLC based circuit scheme, also transmits high-frequency signals(pulses(non-periodic)) ~20MHz(10 %DS)(20V) in a CR-based ...
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1answer
26 views

Makeshift Passive USB Charger 5V OVP

I was looking to protect my 5V device from 20V, since the charging port is Type-C, but used for USB 2.0 communication without any power delivery or bc. Expected to be charged with 1A-1.5A from the ...
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1answer
38 views

Arduino Pro Mini (3.3V) ATMEGA328P: Measure 0-5V/0-10V and 0-20mA analog inputs

I'm looking on how to design circuitry in order to safely measure 0-5V and 0-10V analog inputs from my bare bones "pro mini alike arduino" (ATMEGA328P) powered from 3.3V external power ...
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1answer
41 views

Can I use USBLC6-2SC6 to protect 3.3V bus and lines?

In a small board where space is important I need to place ESD protections near some 3.3V bus with I/O lines (4 pin: 3.3V, GND, digital input, digital output). The most sensitive IC to protect is an ...
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2answers
61 views

What kind of MOSFET to use with this battery protection IC

I'm working on this hobby project and I am trying to create a PCB for it. I want to power the project with 2 18650 batteries. Because the product needs to be used by other people as well, I would like ...
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1answer
66 views

Add current limiters to data pins

I have a hobby project powered by a micro-controller (particle photon if you must know). One of the features is 3.3V, 100mA max output. Each digital data input is able to drain or source a max of 25 ...
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72 views

Review of PCB Design Requested: AC/DC Converter to ESP32 Module to Control a Relay

I am designing a circuit board that will sit in an enclosure that will eventually sit in a garage to control a dust collector via an external relay. I have designed the PCB and I just wanted to make ...
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1answer
62 views

Why do we generally add capacitors in series with AC sources when DC also exists in the circuit?

This is probably a noob question but, essentially, why do we often place capacitors in series with AC signal sources? I understand that we sometimes want to isolate the DC signal to "its own"...
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1answer
41 views

High side smart load switch input protection

I am in the process of designing an input protection circuit for my smart load switch (TPS27SA08) This circuit is intended to provide reverse polarity protection and overvoltage protection: The input ...
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2answers
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Help Needed to Identify/Source Varistor S14 K140 0023

Could someone please advise on how I interprate the codes on this Varistor below.. I'm almost there, I can find the S14 / K140 on RS Components, But im unsure about the last 4 digits. RS Website PN:...
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Why does a circuit breaker voltage rating differ between AC and DC?

I'm looking at circuit breakers from Allen Bradley's 1492 series: (https://configurator.rockwellautomation.com/api/Doc/1492-SPM%20Specifications.pdf) For each circuit breaker, it lists a AC and DC ...
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59 views

How to force the FS312F (DW01A-G) battery protection IC to automatically enable itself when reaching the overdischarge release voltage or above

The IC successfully cuts off the battery when the voltage goes below 2.9V (2.4V with DW01-G), but it doesn't reactivate itself when it is reaching its overdischarge release voltage. I would like to ...
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49 views

Active voltage limit circuit

In my application there is a signal from 0-10V. The signal gets into 4 different OPAMPs with different gains which are supplied from +- 5V. I would like to limit the input voltage to the OPAMP to 0-2....
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2answers
44 views

Grounding Ignition Coil Using IGBT ckt…Not Working + Can't Understand?

I am a hobbyst, and recently been working on a small project of my own, Creating a rev limiter of my own. Following is my circuit which will explain a lot about what I am trying to do. First of all ...
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1answer
33 views

“The following branches form a loop of rigid branches (shorts) when added to the circuit” error in Hspice

simulate this circuit – Schematic created using CircuitLab I am trying to do the transient analysis of this circuit. Given, Initial Conditions I(L0.1-)=10A, I(L0.4-)=20A ...
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1answer
48 views

Why is this Schotty diode breaking a PoE PD module board?

I've designed this simple circuit that uses a Silvertel AG9205 PoE PD module in order to extract 5.65V from the RPI PoE header pins. Here it's the schematic: In order to be careful, I've placed a ...
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61 views

Single breaker for 2 devices

I am working on a project and trying to figure out the appropriate circuit protection scheme. We have 2 AC/DC battery chargers that will be housed in a single enclosure, being powered off 220VAC. ...
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1answer
65 views

How to protect low-voltage hardwired device against 120 V AC miswiring ? (I need a resettable solution)

I need to protect a hardwired device, made for AC low-voltage transformers (e.g. doorbell), from miswiring to a 120 V AC power line. It actually occurs no matter how many warnings I put everywhere. ...
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1answer
43 views

Overvoltage protection develops heat, is ok?

considering my old question: Here, i've made the following circuit using equivalent components on SMD, here is the schematic: And these are the parts that i've picked from LCSC: Fuse: Link here ...
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14 views

Lolin32 using 6V power supply to power the board through the JST Ph-2 pin connector

I'm using the Lolin32 microcontroller board and noticed there is a JST Ph 2-pin connector which takes a lithium ion battery. I noticed a chip (MCP73831) used to automatically recharge the battery if ...
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1answer
36 views

What is the 0V reference for MOV's input protection on power supply?

In some application notes for MOVs I see example usage in power supply design where each input line (N, L) from the mains are protected with a MOV to a ground voltage reference (as well as a ...
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61 views

Protection circuit for fake-USB device

I'm developing a set of sensor modules that connect to a controller board, that's also developed by me. Though the communication between controller and slaves is RS-485, I'd like to use a USB-C ...
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682 views

How does this overvoltage protection work?

I was looking around for low cost and effective overvoltage protection, and I found this from this page: With this part list: RXE025 - 250 mA PTC resettable fuse Zener diode – 5V6, 1 watt Resistor – ...
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1answer
47 views

How do I design a circuit to allow for two power supplies of the same voltage?

I am currently designing a circuit which utilises a 18650 battery which passes through a TPS63000 buck-boost converter, converting the voltage to a steady 3.3V. I require the circuit to interface with ...
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1answer
64 views

Overcurrent protection, limit for nominal current or stall?

Background: I'm currently working on a robotics design that will drill through soil. I have selected a 48V motor who's nominal current is 3.17A and has a stall current of 42A. I will be driving the ...
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14 views

Moeller IZM air circuit breaker malfunction

I have the Moeller IZM circuit breaker charged, but it there is no action happening when pressing the ON or OFF buttons. what is the possible cause for that ?
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53 views

What are the determining factors for using a polyfuse in electronics circuit design?

When designing electronic circuits (PCBs) I often wonder if I should use a polyfuse (aka polyswitch, PPTC, PTC resettable fuse) at the power inputs and outputs or not. So basically what I am asking ...
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1answer
26 views

GPS Logger Trigger Circuit Integration

The Arduino UNO and GPS shield logs the coordinates by the use of the trigger inputs. The trigger takes +ve 5 to 15v on a pin. (See Image 1) It is designed to be used to log, each time a solenoid ...
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1answer
82 views

How could a dental lab micromotor start at high current and torque without damaging anything?

If you are familiar with dental micromotors, there are generally two kinds of them in foot pedals: simple switch or variable speed (like throttle.) The simple one acts like a push button to be ...
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1answer
66 views

DW01-AG circuit disabled

I wonder what's wrong with my circuit. Voltage between VIN and GND is 0.5V instead supposed 3.3V. Is there design issue? Assembly was maded by JLCPCB VIN voltage: stable 3.3V from PSU (VIN - B_GND) (...
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2answers
87 views

Digital input protection circuit [closed]

Can anyone explain to me how this circuit works? I am familiar with the traditional Zener diode as voltage regulator (with a resistor,) but I couldn't tell what the fuse does here and why the 10K ...
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3answers
57 views

protect op amp input from overvoltage from piezo sensor

I use a piezo to register the moment of a knock via a micro controller's analog in (1.8V Max) So far I used the scheme in the figure without any diodes. This works so far, but depending on the knocks ...
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21 views

Electrostatic discharge threats to microcontrollers on a PCB in a semi enclosed metal case?

Can the microcontrollers on a PCB inside a metal case (one side is open) get damaged by ESD when the case is touched? If so what can I do to protect the components inside the case from getting damaged?...
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1answer
58 views

Calculating the resistance for a high brightness led beads chip

If I'm playing with these little toys: A 10W, 9-12V High Brightness LED Beads Chip: (https://www.aliexpress.com/item/32901524656.html?spm=a2g0s.9042311.0.0.27424c4dfKjvBR) A fixed power supply that ...
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34 views

What PolyFuse should I have to protect 150 Ohms 0.5W resistor?

I need help selecting a polyfuse for protecting a 150 Ohms 0.5W resistor. My goals are: To make sure that the resistor won't take any damage when I apply voltage over 3V onto the 150 Ohm resistor I ...
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39 views

How to have a seperate power supply of same value to power microcontroller and motor? [duplicate]

I was creating a project which include the micro controller(ATmega328) and the 5VDC motor pump. so i made the circuit shown. motor is actuated by relay. the moment motor is 'ON' the micro controller ...
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25 views

I want to design a Protection circuitry for ICR18650 Lithium-Ion cells

I am trying to design a protection circuitry for ICR 18650 Lithium-Ion cell (3.7V,2200mAH). I made a battery-pack by connecting 3 cells in series to get output voltage of 11.1V. During charging/...
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1answer
47 views

Shortcircuit protection using transistors

I'm designing a short-circuit protection circuit for x2 AA battery (3V) and I'd like some tips from the community on how can I make it a low power mode circuit. When V_out is short cirtcuited, the ...
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40 views

Why is there a peak in drain current

I am simulating the double pulse test to test the working of the Overcurrent pin. Although I like that there is no phase lag between the sense voltage and the OC pin voltage, I am getting this peak in ...
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1answer
93 views

Do I need >5V power supply to adequately protect against overvoltage >5V? Seems contradictory

My circuit requires 5 volts and roughly 4 amps. I am using a 5V/10A power supply. I would like to protect against overcurrent and overvoltage (>5V). Protecting against overcurrent seems ...
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1answer
35 views

NTC Inrush current limiter datasheet

I have been looking at B57238S0100M0** NTC which is rated with R25 = 10R I_max = 5A R_min = 0.16R I already inspected the resistance vs temperature curve and it appears to be straight forward. ...
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1answer
59 views

Oscillating sense current in overcurrent protection

I'm stuck at overcurrent protection for SCT3160KL using UCC21732 (or UCC21750, trying to see differences in Desat and Overcurrent protection). This is my circuit Waveforms I see that there is a lot ...
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44 views

Cycle-by-cycle overcurrent protection

I'm designing a gate driver for my SiC MOSFET SCT3160KL using gate driver UCC21732-Q1 from TI. I am using overcurrent protection, active Miller clamping, UVLO and also overvoltage protection by using ...
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1answer
76 views

Overcurrent simulation for Mosfet

I am designing a gate driver for SCT3160KL using a UCC21732 gate driver ic from Texas Instruments. I have made roughly made the circuit using the ic, but I want to test its overcurrent protection ...
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24 views

Device circuit protection

when applying net voltage to my device and converting the AC to DC, what type of protection should my circuit have? I've already thought of overcurrent and reverse polarity, because I'm going to be ...

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