Questions tagged [reverse-polarity]

For questions about the operation and/or protection of polarized electronic components when biased in reverse. Consider also using the "protection" tag and/or tag(s) for the polarized components in question (e.g. "diodes").

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Safety of a polarized DC breaker between the battery and the inverter

DC breakers use a magnet to blow the arc into the quenching channel. If the current is flowing in the wrong directly, the arc is pulled into the guts of the breaker and can cause the arc to be ...
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High side reverse voltage and overvoltage protection circuit

Can someone provide an explanation why I still have a 50Vp negative waveform after the rectifier (waveform on Vch2) and after the overvoltage (output voltage) we have the same positive cycle. It's ...
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Charging supercapacitors with reversed polarity

I bought six supercapacitors and connected them in series to get a total voltage of 16.2 VDC. The product's Mouser No is: 723-BCAP0450P270S18, Mfr. No is: BCAP0450 P270 S18, the datasheet can be found ...
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Selecting series resistor for a Zener diode

I am currently designing a device that will be powered by eight AA disposable batteries. For reverse polarity protection I am looking to use a P-channel MOSFET in the following configuration: ...
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Problem design a reverse polarity protection circuit

I´m trying to develop a circuit that is able to control a starter motor with mosfets and also send a signal to control an external relay. I was able to control the starter motor through the help of a ...
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3 answers
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Reverse polarity protection without Zener diode

I find the following reverse polarity protection circuit everywhere online. Reverse polarity protection using PMOS and Zener diode: Can you replace the Zener and resistor with a voltage divider as in ...
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2 answers
130 views

Capacitor with reverse polarity

In a "Snap Circuits" project ("Leaky Capacitor"), the instructions have me put a 470 uF polarized capacitor in backwards with the negative side towards the batteries. This is to ...
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3 answers
107 views

Adding nFET-driven reverse polarity protection to a switching regulator input

I'd like to protect my board mounted switching regulator's input from reverse polarity events without having to modify the existing run of boards we had created and populated. The primary regulator ...
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2 answers
121 views

Does this diode make any sense in this circuit?

Here is the entry stage of power circuit for an Arduino clone. Input voltage 7-12V DC, MP2307 regulates it down to 5V. Diode D1 is presumably there to protect against reversed polarity, but it will ...
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How to protect this circuit from shorting out / reverse polarity?

I'm building a device that uses multiple TRS jacks for power and communication. (I know that audio jack is not the best choice for power but it's important for overall design and I really want to make ...
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Breakdown voltage in diode and Zener diode, what are the practical differences?

Until now, I've only studied with diodes asuming they are ideal and I could tell the difference between normal diodes and Zener diodes. Now, I started to study non-ideal diodes and I see that this non-...
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PMOS reverse supply

I'm a little confused, can someone explain to me why this circuit conducts? I thought that the body diode of the PMOS was in reverse polarity and the source node of PMOS should be at 0V, but ...
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Power consumption for reverse polarity protection using p-channel MOSFET

I'm looking for a way to implement reverse polarity protection for a circuit that runs from a CR2032 battery (The operating voltage of the circuit is from 1.8 V to 3.2 V). I'm considering using the ...
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Polarity reversing by using laser sensor for signal

To edit this question I should add that I won't be using a switch I'm using a laser sensor so when a object passes in front of it the laser sensor will send the signal voltage. I'll be using a laser ...
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4 votes
2 answers
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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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Power MUX Circuit with 5V & 3.3V Regulation + Reverse Polarity Using LM358 - Questions & Concerns

I'm working on a circuit that can be powered via USB or via header pins. The goals are: The MUX will determine, and prioritize, the higher voltage supply. The MUX will provide reverse polarity and ...
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MOSFET as reverse polarity protection and power switch too

We have a system where there is main power supply as well as a single cell Li-Ion battery (4.1 V to 3.3 V range we'll use) as a backup battery. Its a low cost and PCB area constrained product. The ...
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MOSFET voltage drop seems way too high

As discussed here, I'm trying to use a MOSFET for reverse polarity protection. I got an IRFB7440PbF, which has a low Rds(On) (2mOhm,) suitable Vgs (I'm using a 5V power supply,) and what I thought ...
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P-MOSFET reverse polarity protection, resistor and diode or not?

I have a PCB with a DC barrel jack, for which I would like to have a reverse polarity protection. The circuit exists in 2 variants, one with 5V input, the other one with 12V input, at 6A. Note I also ...
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Polarity protection for mppt solar battery controller

I have a cheap MPPT solar battery charge controller I use as a lab for high school students. It has no reverse battery polarity protection and wanted to add some protection because we've lost some ...
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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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Reverse Battery Protection using P-Channel MOSFET

I read the TI document on page 5, according to this figure, when the GS of MOSFET from negative to positive the P MOSFET turned off, but why the Vout voltage will drop to minus.
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9 votes
3 answers
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Why is this 3-way speaker wired this way?

I found a service manual of a pair of 3-way speakers that were part of a mini integrated stereo system. These are Sony SS-H77 speakers, which have served me very well back in the day. Looking at the ...
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12 V, 7 Ah SLA battery reads 0 (zero) volts

I have a new 12 V, 7 Ah battery which reads 0 (zero) vokts. Let me explain the situation. I have a 800W UPS (for pc) whose battery wasn't giving enough backup. So I decided to replace the battery. I ...
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1 answer
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Are PMOS still ideal for Reverse voltage protection of 75 A

I am creating a power management circuit for a 20m RGBW led strip, these leds operate on 5v and would require a current consumption of about 60A. I will actually split it into 8 channels of 2or3 ...
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Custom VNH5019 carrierboard without reverse battery protection

I'm designing a custom carrierboard/PCB on which I want to mount a VNH5019A-E. My question is if I can leave out the reverse battery protection, including the external N-channel Power MOSFET, without ...
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Transient protection (TVS), for back to back N-channel MOSFET switch with user-accessible connections?

I am designing an electronic power switch device which can be placed inline between a power source and a load (e.g. a charger and a battery, or a battery and a load). It needs to be biderectional (i.e....
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Is using a TVS diode better than using a parallel reverse-polarity protection silicon diode?

I want to add a reverse-polarity diode to my design. It has an input of 24 V (230 Vac to 24 V power supply) which is fed to a 24 to 12 V converter. I plan to draw up to 4 A from the 24 V power supply. ...
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3 answers
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Physical power connector that does not allow reversed polarity power connection [closed]

I have used those XT60 power connectors to connect from my load to the battery. The battery is a forklift battery with a voltage of 48V. I have attached the male XT60 connector to the battery pack and ...
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DPDT Polarity Switch

I am trying to connect a USB relay to actuator, so when I press button 1 , motor goes up, when i press button 2, polarity is switched and motor goes down. I am trying to achieve this with a DPDT relay....
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Mosfet Protection Diode Part Number 3S4L VH10

Mosfet Protection Diode Part Number 3S4L VH10 I can not find it or anything like it. It has 2 leads like a diode, but uses a Mosfet. Very low voltage drop. I am using it for reverse voltage ...
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5 votes
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Why have both a Schottky Diode and a MOSFET for reverse voltage protection?

I was looking at this open-source power supply circuit for an automotive CANBus device. I am wondering it would include both a Schottky Diode (D1) and a MOSFET (Q1) on the power supply line. My ...
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Reverse polarity of 90 VDC motor with 2 foot switches

I am building a tool where I need to change the direction of the 90 VDC gear reduction motor with two foot switches. Power is coming from a motor controller with variable speed. Terminal 4 and 5 have ...
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1 vote
4 answers
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Need help in understanding the mosfet reverse polarity protection circuit

I am working on reverse polarity protection circuit. I found out that most of the people are using the circuit as is mentioned below. I have few concerns regarding the direction of MOSFET Why is it ...
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An impossible task? Reverse current/short circuit protection not only for load but also for power supply

This is a magnetic phone charger. It's a USB cable that plugs into a standard 5V phone-type charger. The magnetic "plug" has a (+) center-pin and a (-) round metal as the ground with a ...
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How to interpret different socket tester results with and without power strip?

I bought a socket tester (this one) in order to check the power sockets in the house I rent. Half of them seem to be correct and the other half is marked as "LIVE/NEU REVERSE" which is not ...
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1 answer
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USB reverse polarity protection - MOSFET

I am thinking about a relatively cheap and simple protection against USB reverse connection/reverse polarity. At the moment I am thinking about P-channel MOSFET, with the drain directed towards the ...
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3 answers
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Switching between inverting and not inverting a small signal

I want to be able to choose whether an audio signal being fed into an amplifier is inverted or not via a TTL signal. What's the simplest, cheapest, best way to achieve this? My goal is to replace the ...
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3 answers
340 views

BJT transistor, collector base junction

In many documents and books, the collector base junction of a BJT transistor is usually represented as an inversely polarized diode, however there is no collector base voltage that we must overcome ...
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2 answers
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Over voltage and reverse polarity protection

I was trying to make an over voltage and reverse polarity protection circuit and create a PCB that I can easily use in some of my projects. My level of electronics it's not so good, and that's why I'm ...
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1 answer
203 views

Reversed universal universal motor sparks and shows arcing even though brushes are completely perpendicular to the commutator

I need to reverse the rotation of the universal motor in question so I swapped the wires leading to the brushes and that successfully reversed the rotation, but now the commutator is arcing and is ...
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249 views

Oscillating DC polarity reversal for LED lights

I have a cheap battery powered LED light strand that had a corroded and non-functional control board. The LEDs looks like they are rated for about 3.3V with up to 20mA per bulb, and the original ...
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1 vote
1 answer
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Track loader actuators: Provide reverse capability for two DC motors, on board snow blower attachment

I bought a 7 ft wide John Deere snowblower and want to use it on an ASV track loader. The two companies use different strategies for running electrical units on attachments. This requires wiring up ...
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1 vote
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Protecting battery and USB inputs from each other

I have this circuit, which I expect will protect my primary cell from USB voltage and my USB port from being powered by the battery. My logic is; D2 will stop anything flowing out of the USB port ...
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1 vote
1 answer
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Using h-bridge with LED fairy lights

I have a string of LED fairy lights (5v) that when I connect to power, only half of them light up. If I reverse the polarity, the other half light up. It’s my understanding that I need a h-bridge to ...
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The Best Place for the Reverse Polarity Protection Diode

I have several RS485 devices. All of them are connected together and power by a 12V power supply. Each device has its own 5V voltage regulator. I want to use diodes for each of them to protect aginst ...
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Is this reversed P-MOS next to the battery for some other purpose?

I was handed a schematic with this P-FET next to the battery. My experience tells me that this would not provide any reverse polarity protection (which at a glance it what I thought it was for), but I ...
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Reverse current protection

I design a wearable, battery-powered device with a watertight enclosure. It will have a waterproof USB connector for battery charging. Here is a schematic. J2 is the USB connector, MCP73831 is the ...
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1 vote
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Reverse Polarity Protection p-channel mosfet

I am trying to design a basic reverse-polarity protection circuit using LTspice but I am not sure what values to use. The input voltage is 12 V, 100 ohms resistor and a 10 V Zener diode. What is the ...
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2 votes
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Reverse polarity protection with a MOSFET, am I doing it right?

I'm creating a simple LiPo charger and I would like to add a reverse polarity function to the module. The source voltage is 4.2V, the maximum current draw is 2A. Is this schematic correct? The MOSFET ...
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