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Questions tagged [reverse-polarity]

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Reverse voltage protection for TBD62083

Good day everybody. This is my first question on this site so bare with me :) . I am working on general purpose driver using TBD62083 (replacement of darlington array ULN2803). As you can see the ...
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25 views

Looking for circuit, reversing polarity of DC motor

Consider I have 2 inputs, A and B. I need help with a circuit that does the following if only A is active (A,B : 1,0), then the motor should run clockwise if only B is active (A,B : 0,1), then the ...
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63 views

Can I put a low current relay between line (or neutral) and the ground wires to detect polarity?

Can I put a low current (<5 mA) 230V coil, NC (normal close contact) relay between one wire of mains and the ground (earth) wire in order to check mains polarity? In theory if the wire is line (...
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475 views

Voltage monitor circuit (reverse polarity protection with high voltage cut-off)

I want to make a circuit which performs these tasks: 1) Protect the load against reverse polarity. 2) Protect the load against over voltage. Load = Raspberry pi Reason for this circuit - Pi is not ...
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1answer
46 views

How to rapidly switch polarity of two plates?

If I have two metal plates, with P1 connected to V+, and P2 connected to GND, how can I alternate the polarity of these two plates? I wish to have P1 connected to GND, and P2 connected to V+. Then ...
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1answer
78 views

Can an electrolytic capacitor be charged reversed bias by a small voltage? [duplicate]

In this monostable circuit the C1 capacitor is reverse biased. When T1 is closed and C1 is discharged what will happen on the right side of C1? Will it charge up to 0.6 volts so that T2 can be ...
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1answer
50 views

Trying to come up with a overvoltage overcurrent reverse polarity protection circuit, is option 3 done right?

I´m reading for the past week about P-Channel mosfet reverse polarity protection circuits. Then I´ve found this post http://kaktuscircuits.blogspot.com/2014/07/reverse-polarity-and-overvoltage.html ...
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45 views

P-Channel MOSFET reverse polarity protection on NMOS array chip

I'm trying to achieve reverse polarity protection for the TPL7404LADR chip which is basically an updated version of the ULN2003 darling transistor array. To do this I want to use a P Channel MOSFET ...
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17 views

Mixing Reverse Polarity Protection PMOS with a Piezo Element

I have a circuit that powers some leds when vibrations are detected. I am trying to integrate a PMOS for reverse polarity battery protection. When the PMOS is present the circuit simulation fails as ...
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1answer
52 views

MOSFET selection for high current application

I am designing a reverse polarity protection using the LM74610 chip.Now, my circuit can take peaks of about 90Amps and constant of 50-52Amps. This is quite a load and I want to select the right MOSFET....
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42 views

Using P-MOSFET with Gate and Source have same voltage to protect reverse current

I have a question when I am working on MP2639A 2-cell LIPO charger (+8V4) from USB +5V. The recommend schematic uses P-MOSFET to protect reverse current from Load back to a USB plug. taken from ...
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76 views

Diode behavior when reverse biased with small voltage

I'm designing a simple circuit to use a lithium-metal coin battery as a backup power supply, and I'm considering something simple like this: simulate this circuit – Schematic created using ...
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31 views

Simple Animatronic - slow repeating/reciprocal motion for a window display

I am trying to rig a contraption to pull a model hot air balloon back and forth along a curved horizontal track. Its motion is both horizontal (6’) and vertical. I have built the track and rigged the ...
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1answer
51 views

Circuit protection component arrangement

I was reading this thread and decided that in general it's better to place the reverse polarity protection diode D2 after the TVS rather than before it, and to instead use a bidirectional TVS for D1 (...
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1answer
116 views

How does this BJT affect the circuit? If it does, how should I simulate on Circuitlab to see the effect?

I am trying to understand how NPN Q23 in the picture below affects the operation of the left circuit. If it doesn't then what we get is the circuit on the right with the only transistor now being Q30....
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2answers
127 views

How to tell if a capacitor is still good?

I was replacing a 400 V 120 µF capacitor in a power supply (AC 120 V - 19 V DC 4.62 A). I tested the dc out end while it was still plugged in and got 0.07 V. As far as I can tell although being ...
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53 views

Reverse voltage on MIC5225 in particular and other LDO in general

This question has been asked many times before, for example about LD1117, MCP1703, LM78M05CT, MIC2920A, ADP7142 etc. Why am I asking it again? a) From reading all those topics it seems that the ...
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1answer
57 views

Can a reverse battery be considered a resistance?

In a simple circuit with 2 batteries and a simple load, one of them supplies 10V and the other 3V. The 3V one is reverse, in a way that the total output of batteries is 7V. Can this 3V battery be ...
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1answer
252 views

Reverse voltage protection circuit explanation

Considering this circuit : (The complete schematic can be found following this link - page 23) It is connected on the return path of an IC to provide reverse-voltage protection. I understand that ...
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3answers
349 views

A question about reverse polarity protection diode

Is the function of 1N4001 before the 5V regulator reverse polarity protection? Is this a fine method? And I sometimes see 1N4148. Can any diode(besides zener) be used for such function?
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3answers
205 views

Reversing P-channel mosfet for polarity protection component selection

Situation: I'm trying to implement a reverse polarity circuit using a p-channel mosfet and a voltage divider using a resistor + schottsky diode. More information here if you need a refresher. The key ...
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64 views

What will happen if P-channel Enhancement type MOSFET gate kept open while connected as diode in real case

[ I am using MOSFET as diode for polarity protection of system. Vehicle supply of 12V is applied to drain & system is connected to source. Gate kept open purpose. I have simulated attached ...
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2answers
481 views

High-side vs low-side reverse polarity protection

I need to make a reverse polarity and over-voltage protection for a fairly powerful device (45W @ 12V input) and after some research I noticed a weird peculiarity. A typical reverse polarity ...
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1answer
53 views

Reverse polarity protection for symmetrical input

I have a symmetrical voltage input I need to protect agains reverse polarity, and over-voltage. Here is the reverse polarity protection I designed. Is it correct ? I can't find much information about ...
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1answer
66 views

LED behavior during 24 VAC negative half cycle

I don't understand why the green portion of LED3 is able to conduct. Since the path marked in green represents the negative half-cycle of the 24VAC isn't the green LED reverse biased therefore no ...
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1answer
115 views

Reverse Polarity and TVS Diodes Not Working?

This is a follow up to this issue: Damaged TPL7407LA Transistor Array (*Updated With Scope Testing Images*) We are experiencing both reverse polarity and transient voltage spikes in our automotive ...
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1answer
643 views

Replacing two LEDs with a 2-pin, bicolor LED, using a circuit that reverses polarity based on two inputs

I'm working with a commercially available circuit that can optionally be configured to disable its internal LEDs and use two external LEDs. This post discusses the use of external LEDs. One LED or the ...
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1answer
307 views

Have I fried the transistor in this circuit?

It was a germanium PNP transistor. I might've pressed the button too. I saw transistors used as capacitors that were connected like this, but they weren't germaniums. What current (if any) has flown ...
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2answers
276 views

Protecting a power supply from inductive load

I recently got a PeakTech 6225A power supply for my hobby of making/"tinkering"/messing around. I get many parts that I want power separately to diagnose them. I also get a lot of electromotors and ...
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38 views

Low Side Reverse Protection Diode + Wide Battery Input Range

Quick background: I'm working on a very wide input range for a battery powered application (capability for two different types of chemistries). In the original design, a low side NFET was used as ...
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1answer
104 views

Is it possible for a voltage multiplier to be used to provide both positive and negative voltage?

What I was wondering is it is possible to use a single voltage multiplier to provide a negative and positive voltage. Referring to this voltage doubler circuit, if you connect a capacitor to the top ...
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3answers
331 views

How to find Voltage based on reference nodes?

I came across this problem and I'm trying to really understand it. VB is the voltage drop across a particular element, it is the change in voltage from node a to node b. Find the value of VB in ...
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2answers
349 views

How do I calculate the diode parameters for reverse polarity protection?

I understand that a diode allows current to flow in one direction only, and that inserting a diode in series with a power source will protect the circuit from a reverse polarity battery. How do I ...
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1answer
62 views

High Side Driver IC - Application Information

I have a question regarding VN5025AJ-E: High side driver IC. Datasheet link - https://www.st.com/resource/en/datasheet/vn5025aj-e.pdf In the figure you can see the application schematic. In the ...
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3answers
621 views

Reversing USB power polarity, but no black wire

My goal is to create a USB-to-USB cable with reversed polarity in order to charge an old Gameboy Advanced SP. I could just go on Amazon and buy a charging cable, but I do enjoy a fun little project ...
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1answer
237 views

What part of a mobile phone charger makes it safe to be charged with opposites polarity? [closed]

A mobile phone charger works regardless of whether the charger is the right side up or upside down. As I know, batteries should not be charged with wrong polarity. How do those chargers accomplish ...
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1answer
56 views

How to deal with extra pins on reversible connectors?

I want a header on my board to be reversible. The header has 4 UARTs, 4 power pins (VA,VB,VC,VD), and power (3V3) and PWM for a servo. The functions of most of the signal pins of the header are ...
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161 views

NMOS Gate RC Filter Values

I am designing a Reverse Polarity Protection circuit for a project by using an n-channel MOSFET. A basic schematic is shown here. I've added an RC filter so that the voltage on the Gate pin changes ...
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1answer
150 views

Protecting against reverse polarity

I'm building a JTAG programmer for the old Motorola 56k devices and I want to add some circuit protection before having some boards built. I'm more of a firmware/digital guy, but here's what I came up ...
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2answers
267 views

Protecting microcontroller digital output pin from ESD, reverse connection, and other possible user error

I want to protect an output pin from ESD, reverse connection, and other possible user error that might cause damages to my circuit. This pin output pulses depend on the amount of water passing through ...
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1answer
359 views

P-MOSFET allowed some reverse current, L7805CV destroyed. Why?

I was experimenting with reverse voltage protection using a P-channel MOSFET. I hooked up an IRF9510PBF in the following configuration (diagram from Nick Gammon's site, will change if requested): ...
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1answer
187 views

Circuit Testing failed (Reverse polarity and Buck-Converter)

Hello guys, today I tested my circuit. Its a simple Reverse Polarity Protection Circuit with a Buck-Converter. As I supplied voltagae to my circuit, everything was well (3.5V output). Going higher ...
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70 views

How to connect a generator and LED device of different polarities?

I have a device that generates light impulses when connected to a LED device. The intensity of the light is regulated by a potentiometer, within the generator. There are 2 independent channels. The ...
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1answer
524 views

How should I go about protecting a supercapacitor from reverse polarity?

I have several supercapacitors in series, and they're quite old and probably drifted from their original spec by quite a bit. Completely draining them in series will draw at least one of them below 0v....
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265 views

Is it possible to connect/disconnect TP4056 using a combination of N and P channel Mosfet?

I'm trying to design a parallel charger for 4 18650 batteries using 4 TP4056. The main idea is to isolate each battery when the "External Power" is connected, so each charging circuit can charge its ...
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2answers
210 views

Can I buy an ideal diode? How do I OR two power supplies together

I'm trying to switch over from USB power to external power if it's present. (External power is 6V to 13V). The current is 2A. To do this I'm using diodes 1 and 3. See image below. ("OR" configuration....
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1answer
363 views

Polarised capacitor - negative voltage?

I designed a circuit that is similar to the circuit on the picture below. The main difference in my design is that I am using a 3V battery and more LEDs. I am using UNPOLARISED capacitors because I ...
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1answer
482 views

Power supply protection to charge a battery

I am using a power source to charge a battery. To protect the power supply from reverse polarity conection of battery I included a PMOSFET transistor like showed: simulate this circuit – ...
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3answers
1k views

Is placing a diode in conduction path to ground OK?

Are there any drawbacks to placing a diode in the conduction path to ground for reverse polarity protection? A major plus is cost, because you can use multiple low current diodes, instead of one ...
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1answer
141 views

How to protect my DIY bench power supply from reverse polarity?

I have been playing with arrays of 18650 batteries for the last 10 months, charging and discharging them all the time with my LM338K based power supply, that, until tonight, where I inadvertently ...