Questions tagged [reverse-polarity]

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1answer
467 views

How to reverse polarity on only one device?

I have a temperature controller with two SPST relay contacts, one each for heating and cooling, and I want to use them to control a Peltier thermoelectric cooler (TEC), plus a fan and pump and ...
2
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1answer
823 views

LM741 op-amp, converting positive output to negative

I've got a few LM741 op-amps that I purchased by accident months ago, but now I'm in a situation where I believe they may be useful. What I want to do is convert a positive voltage to the exact equal ...
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2answers
104 views

A DC source and only a Reverse Diode

What will happen having only a DC source and a diode connected in reverse? Will the diode or the source overheat over time or something bad might happen if you let it operate like that?
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3answers
380 views

What role does this diode play in this reverse voltage protector circuit?

I have been trying to understand this schematic, which is I believe intended to be provide reverse voltage protection. I understand most of the aspects of this. The basic idea is that D3 allows ...
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2answers
1k views

How does electrolytic capacitors work?

Basically I am interested about the polarity of an electrolytic capacitor.How is the polarity of an electrolytic capacitor is defined and what if I reverse the polarity in a simple circuit containing ...
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4answers
477 views

Feasibility of reverse polarity feature

If I were to design a circuit for a small appliance that works in DC and I would want to allow it to work with the batteries in reverse polarity could I feasibly use a diode bridge? Would it make ...
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3answers
131 views

night day circuit voltage drop

I found this circuit on internet looking for a "ON when dark/OFF when light" circuit: When I mounted it, it worked as expected, the only problem is that voltage between A and B is 8.71v instead of ...
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1answer
66 views

Help me correct this circuit with N mosfet

I am trying to build a protection for my circuit in case someone attached batteries or any power supply in reverse even if the other supply is normally attached. As you can see I have 2 power ...
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2answers
2k views

What will reverse polarity in an Energizer AAA, unpowered, dead battery, circuit?

Circuit is a three-LED reading lamp. Batteries were left in for "a long time, but it worked last time I used it" according to Mom. Unknown if switch was 0 or 1. All three batteries were inserted ...
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0answers
98 views

Reverse polarity protection non-isolated power supply

I'm trying to design a circuit with reverse polarity protection. I have found numerous of examples but I can't get it to work for me with a non-isolated power supply. I'm open for suggestions. I ...
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1answer
731 views

MOSFET selection for reverse polarity detection

I'm building a reverse polarity protection circuit using an N-channel MOSFET (see figure below) For the battery I'll be using an 18650 cell which will range from 4.2 - 3.3V. The max discharge of my ...
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0answers
363 views

AC L+ and N- difference

Hey guys i'm on a project in which I have to use Safety Modules. I'm confused with the pin-out diagram of the safety modules. They reference L and N lines of an AC source. I'm leaving you the data-...
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1answer
129 views

Capacitor polarity in lamp flasher

simulate this circuit – Schematic created using CircuitLab I found the above circuit at: http://www.eleccircuit.com/a-lamp-flasher-circuit-using-transistors/ with a slight variant at: https:/...
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2answers
675 views

Short circuit problem (batteries getting HOT) within circuit

So I am making a circuit with a simple 12v dc motor in series with an NO microswitch and on off switch conntected to a dpdt switch to reverse the polarity of the motor. The first issue I had was to ...
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1answer
905 views

Micro switch off in forward and on in backward

I request some knowledge regarding a circuit I am building. Basic I have a circuit connected to a dc 12v motor and a dpdt switch to reverse the polarity of the motor and a variable potentiometer , I ...
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1answer
616 views

P channel FET reverse polarity protection - toggle switch on base

I am trying to add a reverse polarity protection in my circuit using a P channel FET, but I also want to have a SPST toggle switch in series with the gate for the user to turn the circuit on or off. ...
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1answer
572 views

protection circuits [closed]

I was wondering if anyone could help explain how these work? I know they are missing information, but I wanted a general idea on how they are meant to function. Why place two diodes facing each ...
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2answers
996 views

Sizing protection diodes

In designing basic upfront protection in a circuit, I've encountered a strange conundrum. I find it's very difficult to size both a reverse voltage protection diode, and a transient voltage diode (...
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1answer
3k views

Voltage Divider to protect P-FET gate on a Polarity Inversion Circuit

I'm trying to implement a polarity protection using the P-MOSFET technique on a 30v DC circuit How can I protect the gate of a IRF9540N (Vgs 20v)? I saw that I can use a voltage divider using 2 ...
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1answer
104 views

Circuit with reverse polarity data lines

let`s say I have 2 Microcontrollers and I want to connect them to send data between them. I have one dataline and GND (datarate or how to sync is not part of this question). Is there a possibility ...
2
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2answers
1k views

Reverse characteristics of power MOSFET

So, I'm designing a reverse battery protection circuit using a MOSFET, following this TI application note. I tested it, it works great, Rds(on) is low as expected. However, I'm not really comfortable ...
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1answer
259 views

Reverse polarity protecion on an electronic load

I want to add reverse polarity protection on my electronic load which will be capable of sinking 20A and with a max. voltage of 50V (max. power is limited to 250W). Because I want to go with low input ...
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1answer
284 views

Wiring Motor to DPDT Polarity Switch

I am trying to wire my motor (US Motors, Model: C55JXKNL-5041) to a polarity reverse switch. The diagram printed on the motor is as follows: BLU ____L1 BRN ____INS BLK ____INS ORG _^ WHT _^ YEL ____L2 ...
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1answer
755 views

Can a DMM continuity probe fry an IC?

I just finished soldering a QFN package to a breakout board, and was about to go at it with my multimeter in continuity testing mode to check for bridges, when it occurred to me that some ...
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5answers
6k views

maximum reverse voltage applied to a resistor-LED configuration

Consider the simple circuit below: simulate this circuit – Schematic created using CircuitLab LED datasheet: link Does the applying of a reversed 36 volts to this circuit damage the LED? ...
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2answers
648 views

Charlieplexing 7-segment display segments vs segment

I understand the principle of charlieplex and the use of tri-state. What I don't understand is, can I light all segments on a display at once or do I have to light one segment at a time? Say I have 8 ...
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4answers
4k views

Put 1 of 3 batteries the “wrong way” to prevent accidental turning on? [closed]

My headlamp accidentally turns on inside my backpack. If it used two batteries, I would put one the "wrong way" to prevent it from coming on. However, my lamp uses THREE AAA-type batteries. Can I ...
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1answer
315 views

Output of 4.8V due to reverse polarity series schottky diode?

I was reading through the Data Sheet for the Photon, an IoT dev board: https://docs.particle.io/datasheets/photon-datasheet/ and under the Power section it says: When the Photon is powered via the ...
3
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2answers
667 views

Dual rail reverse voltage protection

After watching Afrotechmod's tutorial about reverse voltage protection, I wondered if I could incorporate it in a circuit I'm working on. Unlike the circuit in the video, mine's dual supply, and there'...
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1answer
94 views

LDO outputting low voltage. LDO or auxiliary components fault?

I burned a circuit by applying reversed polarity voltage. I measured the LDO that is supplied with 5 V and should output 3.3 V, however it only outputs ~2 V. Now what can I deduce from ...
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3answers
1k views

Reverse polarity protection for a very low voltage devce

I want to add reverse polarity protection to a device which is powered by a single AA battery, so its voltage might go down to 0.8 V. Forward diode is too huge of a drop. I've already thought about ...
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1answer
2k views

Reverse Polarity & Load Dump Protection (TVS)

Based on this and other material I’ve read, I should have a diode for reverse polarity protection and a TVS for load-dump protection in an automotive circuit. I have prototyped the circuit and its ...
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3answers
1k views

What circuit will allow reverse polarity and continue to work?

I am looking for a circuit that will power my device with 12-24v no matter the polarity, the device will use around 1a maximum. I know a bridge rectifier should work but I cannot deal with the ...
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1answer
345 views

Reverse Current in N Channel Power Mosfet

I am designing a bidirectional current source to drive a large (~60A) current through a large inductive load (100's mH) and facilitate very fast switching times (as close to an 1A/us as possible). My ...
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3answers
10k views

Why reverse polarity causes damage

Is it because it can exceed the reverse breakdown voltage of semiconductors? For instance in low voltage devices say 1-5v is the reverse voltage rated a lot lower than that for damage to occur? Also ...
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1answer
390 views

Optocoupler in reverse-active mode

I was recently reminded that BJTs can be used in reverse active mode. Can somebody enlighten me whether and to what extent the same is true for optocouplers? Do the same limitations apply to reverse ...
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1answer
1k views

About 18650 batteries possible accidents with reversed polarity

We all know that lithium batteries are dangerous and can blow up if we use them the wrong way. My doubt is, if I accidentally place them in the following sequence in series (Pay attention to the ...
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1answer
240 views

Reverse Polarity Protection: Is this method safe!

Consider the above circuit. The N-channel MOSFET has been used as a low side switch to provide reverse polarity protection. A capacitor charges to the 12V supply(battery) voltage and subsequently the ...
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1answer
75 views

Reversing Polarity on Switch Mode PSU to use on Audio Equipment

I have a normal 12v 1amp switch mode psu. with positive pin, negative sleeve. I want to use it on a Roland ex3 s keyboard, which I got as a gift, but no power supply. The PSU specs match those of the ...
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1answer
357 views

Reverse voltage protection diode - necessary?

I'm designing a system to drive 5 strips of RGB LEDs, it will draw around 25 amps, at 12 volts. This system is only going to be used by me, and I have the suitable power supply coming in the mail. ...
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3answers
4k views

Is it possible to use a MOSFET for Li-ion reverse polarity protection when protecting a charger?

I've made a simple charger out of 4 TP4056 modules and 4 18650 sockets. These modules have overcharge, undercharge and overcurrent protection included, but I also want to know how simple it would be ...
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2answers
2k views

Reverse voltage protection and high-side current switch

Initially I chose a Infinion PROFET smart high side switch (ITS428L2). In the datasheet it is stated that this device can provide reverse battery protection with external resistor. Frankly, I am not ...
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1answer
503 views

Reverse voltage protection using a Power MOSFET at low voltages

I don't know as much about MOSFETs as I'd like to. However, I'm planning on using a Power MOSFET to limit reverse polarity issues on a 3V coin cell, i.e. just above 2.7V. How do I pick a power MOSFET ...
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4answers
408 views

Is this protection circuit designed properly?

I designed this protection circuit to avoid reverse polarity and over-voltage. Here is the circuit: simulate this circuit – Schematic created using CircuitLab Is the circuit designed ...
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2answers
1k views

Why is there a resistor in this reverse-polarity-protection circuit?

I was looking at the recommended reference implementation for a particular integrated circuit (the TI SN65HVS880, data sheet here). It runs off of a 24 volt power supply. The circuit diagram looks ...
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2answers
941 views

Do DC/DC converters provide reverse polarity protection?

I plan on using a TPS63061 as DC/DC to get a steady 5V from 4xAA batteries. The data sheet says: 8.3.4 Undervoltage Lockout An undervoltage lockout function prevents device start-up if the ...
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2answers
2k views

Motor Speed Controller Causing Relay to Lose Voltage and Stop Working

I'm having some trouble wiring up a camera slider where a motor moves the camera to one end of a slider and hits an NC/NO/C 3-pin switch which triggers a 12V 8-Pin DPDT relay to reverse the motor ...
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2answers
312 views

How can the reverse voltage of an LED decrease?

I recently build an LED matrix (for LED cube) and when testing I discovered that multiple other LEDs turned on when I triggered a specific one. Upon measuring I found out that several LEDs were "...
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2answers
69 views

Reverse of referencing everything from ground

Say we live in a world where p-type carriers just have more mobility and therefore switches faster than n-types, so we'll favour PNP's and PMOS's. So in such circuits, we reference everything from the ...
3
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1answer
428 views

Minimal reverse voltage protection

I'm designing a battery-powered circuit in which a power MOSFET, controlled by an ATtiny85 MCU, switches a resistive load (very, very low frequency). The battery is Li-Ion, fully charged at 4.2V. ...