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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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Easy Overvoltage and Reverse polarity protection circuit

I'm looking for the simplest and most effective way to add an overvoltage and reverse polarity protection network to a signal line connected to an MCU, the maximum allowable voltage at the MCU pin is ...
404's user avatar
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1 answer
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Finding Is, Id of a Diode in reverse-bias mode

Excuse me, sir, I'm currently finishing my lab experiment report but I got stuck finding Id and Is of a Diode in reverse-biased mode. Here is the question: Vin is in the range of 0V to 18V with the ...
CÔNG NGUYỄN DUY's user avatar
1 vote
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53 views

Reverse current blocking FET circuit for batteries, does it work?

Based off of a previous post found here, I've created this circuit below to simulate the reverse current coming back from an FET. I've replaced the switch with a NMOS that's controlled by the presence ...
makotoyuki's user avatar
0 votes
1 answer
55 views

Clarification on the Application of a p-Channel MOSFET in a Circuit Diagram

I am seeking clarification on the application of a p-channel MOSFET as illustrated in the diagram below. Could someone please provide an explanation? In the diagram, legs 1, 2, 6, and 5 serve as ...
user23910965's user avatar
1 vote
4 answers
103 views

Polarity change circuit - reverse polarity with only one relay

I was looking for a polarity change circuit - (reverse polarity) with a single relay but I didn't find it or maybe I don't identify it, the only thing I've found are with two relays, do you have any ...
Lopez Jonathan Daniel's user avatar
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2 answers
72 views

Auto sun tracking relay wiring?

Ok here's a bullet list of what I'm working with • 1 5v DC 2 wire reversible electric motor • External 5v DC power source (battery pack) • 2 12v small solar panels ( for signaling left or right ...
WizardDave's user avatar
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2 answers
61 views

Does a negative base current in BJT npn mean that the operation mode is Reverse Active?

Given Vce = 2V, Ic = 1.7mA, and Ie = 1.6 mA, I used KCL to determine that Ib = -0.1 mA. Does this mean that the BJT npn is in reverse active mode?
user364328's user avatar
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1 answer
41 views

Appropriate Overcurrent, Overvoltage, and Reverse Polarity Protection Circuit for Raspberry Pi 4?

I'm new to electronics but I'm trying to power a Raspberry Pi 4 (model b) using an external power supply for testing purposes[5V @ 3A]. This is possible via the GPIO, using pin 2 and pin 6 as ground ...
MG404's user avatar
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1 vote
2 answers
79 views

How to protect a device from reverse polarity and over-voltage?

I am designing a device that will include a DC power jack. There is an external wall adapter that converts the 110-230 VAC from the mains to 20 VDC. Here is the schematic: I intend to use a standard ...
uz3il's user avatar
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3 votes
4 answers
1k views

How to choose reverse polarity protection - diode vs MOSFET

I am reviewing the power stage of a board which is to be connected to a wide range of cars and motorbikes, with internal combustion engines, old, new, 2 stroke, 4 stroke, etc. Current schematic looks ...
Jack's user avatar
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Reverse polarity, over-voltage and over-current protection for a "breadboard add-on board"

I am designing a small utility board that should attach to a breadboard and take power from it. It can be described as the opposite of this SparkFun Breadboard Power Supply: instead of powering the ...
tpimh's user avatar
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6 votes
2 answers
628 views

BJT B-E Zenering: whither the collector?

So, I'm trying to analyze how the circuit in this question behaves when subject to reverse battery (vs. being driven from OUT to IN), and I'm running into a severe snag in the process, though. It ...
ThreePhaseEel's user avatar
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1 answer
70 views

Reverse polarity protection for parallel connection of 18650 batteries

I want to use two Li-Ion 18650 batteries in the device. The batteries need to be connected in parallel and they can be removed from the device (holder). The device itself is protected from incorrect ...
Erni's user avatar
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3 votes
1 answer
232 views

Same MOSFET component but reversed arrow

I'm trying to implement a USB PD controller, STUSB4500, but the typical application example shows 2x P-Channel MOSFETs STL6P3LLH6 with different arrow indications. I'm now confused about the pins, T4 ...
Emerson's user avatar
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0 answers
53 views

High negative voltage cut-off for op-amp from dual-rail power supply

In the picture I have a circuit that prevents reverse polarity and cuts the voltage with respect to the Zener diode (15 V) as a voltage reference for positive voltage output. How do I apply the same ...
HuracanWind's user avatar
1 vote
1 answer
79 views

How to design short circuit and reverse polarity protection for PCB?

I have read many posts and articles about short circuit and reverse polarity protection design for a PCB, but still I am quite confused about the industry standard/common principles here. The ...
eidetech's user avatar
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87 views

Reverse polarity with feedback

The below is a reverse polarity circuit with additional components around it. I would like to understand the exact functionality of the additional circuitry in dotted lines.
Ravi Prasad's user avatar
3 votes
2 answers
249 views

TVS2201 clamping diode failed at 27 V

In the development of ESD protection and reverse polarity, I encountered a problem. The circuit is supposed to prevent reverse polarity (it does, we tested it). During testing, I applied a voltage of ...
douce's user avatar
  • 71
1 vote
1 answer
127 views

Trying to reverse a Crompton Parkinson motor

Completely out of my depth here ~ trying to repurpose an old sewing machine motor to turn a flour mill. Prezzie for the wife who is baking sourdough. But I need to reverse the direction. Tried ...
SimonM's user avatar
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4 votes
2 answers
186 views

How do the protection diodes actually protect the supplies in this case?

Regarding making a dual supply from two single supplies, I see two Schottky diodes are placed between the supply terminals in reverse biased way as in the following example I drew. The diodes are ...
user1245's user avatar
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Polarity Detection on Array Charging System for Autonomous Robot

Array Charging Concept I recently became interested in designing a charging system for an autonomous robot. The key requirement is that precise orientation of the robot is not necessary during ...
RemiFM's user avatar
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0 answers
65 views

Reverse polarity protection + inrush current limiting with mosfets schematic

What do you think about this schematic? I want to put this before a DCDC 24 to 5V with maximum 1A. Any comments or suggestions? The aim of this circuit is to have a soft start with the resistor R2 in ...
Gigapel's user avatar
  • 61
0 votes
3 answers
148 views

Connect a single LED to a reversable circuit?

I have a need to install a single small LED that will illuminate whenever a circuit is active. The circuit controls a small motor, and reverses polarity depending on which way the motor is operating. ...
Ryan Miller's user avatar
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0 answers
78 views

Reverse polarity protection with bidirectional current flow

I'm working on a reverse polarity protection circuit in order to avoid possible damage if the source (a 18650 3.7V battery) is mounted in the opposite direction. The circuit is straightforward; my ...
Filo_Gold's user avatar
2 votes
1 answer
230 views

Reverse polarity protection and inrush current limiting - back to back mosfets

I was testing this circuit in LTspice, it would protect my boards from reverse polarity and limit the inrush current to the input capacitor of a DC-DC (buck or LDO), but the simulation gave me this ...
Gigapel's user avatar
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0 votes
1 answer
214 views

Polarity on Current Transformer

In this part, What is the correct way of orientation? In which pin should I give the input signal? Should the current flow from P1 to P2? Please let me know the correct orientation and how to find it....
Freshman's user avatar
1 vote
1 answer
85 views

How to choose a MOSFET based on maximum forward voltage

I have a 5V DC input to a fixed 5V to 3.3V LDO (LM3940) that I want to add reverse polarity protection in front of via a P-channel MOSFET. What I am struggling to determine is how to analyze/choose a ...
Connor Spangler's user avatar
2 votes
2 answers
157 views

Which specific type of P-MOSFET is suitable for Reverse Polarity protection for 18650 li-ion battery circuit?

I'd like to make a reverse polarity protection circuit for 18650 3,7V Li-ion battery (like here: Can I use a p channel mosfet as reverse polarity protection but still charge a Li-Ion battery?) I only ...
iotdeveloper's user avatar
0 votes
1 answer
88 views

Alternatives to reversing polarity on a DC to DC step up converter?

I am looking to drive a 12V DC motor with an encoder attached (Motor Link). The battery I am using is 6V (Battery Link) which requires me to use a DC-to-DC step-up converter (Converter Link). To ...
Johnathan Maxwell's user avatar
0 votes
1 answer
222 views

Trying to make a 12V Timer Relay With Reversing Voltage, Problems when voltage reversed

So my idea seemed simple, try to hodgepodge together with parts on hand, a device that when one trigger is pressed, timer relay turns on for 5 seconds, it applies 12v to a set of leads, opening a ...
Traptmark's user avatar
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1 answer
71 views

Reverse voltage protection for four 18650 cells

I would like to protect my robot from reverse voltage which is powered by four 18650 cells. Is option 1 sufficient or do I need at least three diodes? I know that using diodes comes with a voltage ...
Michael Brown's user avatar
0 votes
0 answers
71 views

Will my circuit get damaged fom a reverse polarity event?

I have a FE1.1S USB Hub IC, the fe1.1S IC typically has its own 3v3 regulator but in this case an AP2213 LDO is powering the USB HUB. I would like to know if the USB hub is safe during a reverse input ...
DrakeJest's user avatar
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0 answers
48 views

Need help in understanding circuit of PMOS reverse

Given 2 PMOS enhancement: Vdd = 5 V, k1/k2 = 9, Vt = -1. I'm trying to find Voh, Vol, Vil, Vih. I would appreciate help and explanation.
roi sh's user avatar
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0 votes
1 answer
255 views

How to calculate the gate voltage and Vgs in this N-channel MOSFET reverse-polarity protection circuit?

The schematic below uses an N-channel instead of a P-channel to block reverse-polarity voltage from occurring. This means the gate voltage (and Vgs) must be positive. But there are two options I've ...
Mito's user avatar
  • 411
2 votes
2 answers
374 views

Will this NMOS MOSFET reverse-polarity protection circuit work?

Based on the helpful advice from the community, I realised the first schematic I made would not work as a protection for reverse polarity well due to a couple of flaws including the diode having to be ...
Mito's user avatar
  • 411
2 votes
2 answers
370 views

N Channel MOSFET reverse voltage protection proposal

While learning how to make a buck converter, I realised that using P channel mosfets for reverse voltage protection is one of the best ways, but I think it could be better using an N channel using the ...
Mito's user avatar
  • 411
2 votes
2 answers
780 views

How to limit P-channel MOSFET gate voltage?

While working on my first buck converter I thought it would be a good idea to add reverse-polarity protection. So I went and searched for what would be the best (and easiest) way to do it and found P-...
Mito's user avatar
  • 411
0 votes
2 answers
215 views

Reverse voltage protection of boost converter with Schottky diode shows small voltage output

I am testing reverse voltage protection using Schottky diode and found small but not trivial level of voltage leakage when combined with boost module in open circuit. Here, as you can see, the 12 V is ...
slyx's user avatar
  • 221
1 vote
3 answers
344 views

Is it an issue that type F outlets are not polarized?

A lot of European countries use type F outlets that are not polarized, i.e. you can plug in both orientations. This means that there is a big risk (50%) to invert live and neutral. Is that not a major ...
Cl00e9ment's user avatar
0 votes
3 answers
231 views

Where is my mistake with this reverse-polarity protection circuit?

I am trying to do reverse-polarity protection on a 24V PCB. I read up on the PMOSFET method and I thought I had understood it, implemented it as follows: If I connect the power supply correctly, the ...
K4KFH's user avatar
  • 199
0 votes
3 answers
223 views

How to reverse the polarity of a DC brushless hobby motor?

How can I reverse a motor safely that draws about 70 A on 4 s (14.8 V), and additionally how do ESCs (Electronic Speed Controller) that have this capability built into them do it?
wandy rge's user avatar
2 votes
3 answers
432 views

LED reverse voltage rating

I am looking at an LED and trying to understand the Reverse Voltage parameter because it doesn't make sense to anything I test on the bench. Pretty much every LED you find will specify a Reverse ...
Punchki's user avatar
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0 votes
2 answers
174 views

Struggling with a 12 V reversing motor

I’m struggling with wiring a reversing DC tailgate window motor in my jeep. It’s a circuit with two relays and two switches. I was able to wire the first switch without issues but wiring a second ...
tylerkdurdan's user avatar
12 votes
4 answers
3k views

Why is there a polarized capacitor symbol in an AC circuit?

I am confused. My question is very basic, someone please enlighten me. If polarized capacitors should not be used in reverse polarity then why does every textbook (like the one I am using, Grob's ...
Asim's user avatar
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0 answers
75 views

Is this a functional and reliable Reverse polarity protection?

Guys, I am trying here to design a UPS controlling board, I designed this circuit and it was to some extent functional and it draws approximately 16mA - 20mA (I don't want to use the traditional one ...
Hazardous Voltage's user avatar
10 votes
4 answers
2k views

Please suggest any improvements for this reverse polarity protection circuit

I'm using this circuit for reverse polarity protection. The load draws 20A (11 DC motors) continuously for 2 hours after which the battery gets replaced. Even with a heat sink, the MOSFET gets ...
WhiteShark's user avatar
1 vote
1 answer
139 views

High voltage polarity inverter circuit

I'm building a cloud chamber which needs to use an high voltage source. I'm using an electric fly swatter circuit which can generate about 4kV. The fact is that I want to use a button to switch the ...
Luke__'s user avatar
  • 309
9 votes
3 answers
2k views

Which reverse polarity protection is better and why?

You can find two such circuits using a diode that protects against reverse polarity, i.e. against wrong power connection. I wonder what is the point of using the D2 diode, since the current flowing ...
Jerzy Przezdziecki's user avatar
1 vote
2 answers
57 views

Selection of MOSFET

The datasheet for the LM74700-Q1 states that "The maximum V(gs) that the IC can supply is 13V, so a MOSFET with 15V minimum V(gs) should be selected." I don't understand for the MOSFET to be ...
Harkirat's user avatar
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0 votes
1 answer
102 views

Having trouble understanding sink current values for an LM74700-Q1 ideal diode controller

This is my first time referring/understanding a datasheet. As I understand it from a quick search, a sink current is the current (negative) which flows into a port, while source current is the ...
Harkirat's user avatar
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