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# Questions tagged [reverse-polarity]

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### 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'...
84 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 ...
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 ...
1k 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 ...
957 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 ...
297 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 ...
9k 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 ...
344 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 ...
901 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 ...
199 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 ...
70 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 ...
327 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. ...
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 ...
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 ...
473 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 ...
385 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 ...
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 ...
883 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 ...
1k 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 ...
277 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 "...
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 ...
396 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. ...
652 views

### Multiple power input + Reverse polarity protection

I have the following power sources: AC/DC adapter (5V-36V) 5V USB I connected the two power inputs properly (diode) but I am not sure about the reverse polarity protection. I haven't found any ...
2k views

### I am building a simple reverse-polarity circuit using two relays. Will it create an endless loop?

I am planning on using the following circuit for my motorized value. But I'm bit skeptical about how this might continue to work. Although I'll be using two identical relays, my fear is that at one ...
429 views

### Adding reverse polarity protection to battery discharge circuit

I'll open with a caveat - I have zero training in the field but I do like tinkering. I'll try to make my question as specific as possible but do forgive if info is missing at this stage! First of all,...
798 views

My circuit's voltage input can range from 6V to 12.6V. I want to use a p-ch mosfet for reverse bias protection. However, the FET I want to use has a maximum VGS of +/- 8V, so I have to protect it in ...
790 views

### How can I prevent reverse voltage in my stop/tail light design?

I'm looking to modify the rear lights on my 72 VW beetle to enhance ascetics and improve safety. I intend to use LEDs to achieve this and feel that both the indicators and reverse lights should be ...
2k views

### How to detect reverse-polarity post-mortem?

Original - Apr. 13, 2015 There are many questions here about preventing reverse-polarity, most of them ending up with a series FET that is driven by the opposite supply rail: (shamelessly stolen ...
2k views

### Reverse polarity protection using MOSFET - what is the voltage drop after it?

I am using this schematic for reverse polarity protection of an IC (bq78412). However the same IC has an ADC that senses the source voltage and appears not to be tolerant to reverse voltage either. ...
7k views

### Does an electrolytic capacitor degrade each time it receives reverse voltage?

I know that I mustn't connect an electrolytic capacitor reversely. It will explode if I apply the reverse voltage long enough. But, what happens if the reverse voltage is apply for a short time? For ...
2k views

### Why do the 2N2222 and PN2222 avalanche differently?

I've been experimenting with a 2N2222 transistor (in the TO-18 metal case) and using it as an avalanche transistor -- by not connecting the base and having the emitter and collector connected in ...
263 views

### H-Bridge Power Supply Erratic Behavior

Description: I have built a copper plating tank to plate circuit boards and am using a technique called Reverse Pulse Current plating to help aide in the copper plating process. What that involves is ...
6k views

### Reversing polarity of motor with timer

I have a timer that allows me to preset times and run a motor for a predetermined amount of seconds. I need this to reverse polarity as soon as this predetermined time has expired. The timer is a ...
954 views

### Circuit with reversing polarity and two microswitches

I am building a time-lapse camera slider with the following components 2rpm DC gearbox motor PWM with reversible DPDT switch to reverse motor 2 SPST Microswitches I am trying to wire the ...
4k views

### Reverse current protection for a battery-operated circuit

I'm planning a hobby project with the following characteristics 3.3 V circuit, battery operated (by regulating standard AAA batteries) Most of the time in "sleep" mode, so I need a very small ...
64k views

### Change Direction of 12v DC Motor Rotation using Relay

I want to make a circuit to change 12 Volt DC Motor direction and move some thing between two points. Using Relay or some basic limit switches.Like this Image. I got a Circuit As i want... AUTOMATIC ...
268 views

### Controlling direction of current flow through pin depending on the type of device connected

I have a small portable device - lets call it MASTER - which can be inserted into two different accessories - CHARGER and SLAVE. You can check very rough block diagrams in the attached picture. ...
3k views

### Do serially connected diodes share equal reverse voltage?

If I place three cheap 200 V rated diodes across a 500 V supply instead of one expensive diode, is the system guarantied to work correctly? My worry is the situation at which two of the diodes share ...
2k views

### Input protection circuit with P MOSFETs and SPDT for ON-OFF switch

I am making a circuit which may draw up to 3-4 Amps, so I am avoiding using a Schottky diode as fool-proofing it from incorrect polarity on the battery (12V, automotive style) input. I have used P ...
20k views

### limit switches to control motor direction

I am trying to use two limit switches and two DPDT relays to control the direction of the motor. When the power is applied the motor should rotate one direction (direction for this question isn't ...
17k views

### How does USB Type C handle reverse polarity

The new USB Type C connector doesn't have a physical reverse polarity protection anymore. You can plug it in any way you want on both ends, there is also no A and B end anymore, it's all the same. So ...
564 views

### Battery Polarity

I was bored at work, and remember when i was little, putting batteries in the wrong way would stop the object from functioning, then decided to try reversing the polarity of the batteries in my torch, ...
370 views

### How to measure the negative voltage on the ADC with only positive voltage reference available?

I have a Phocos CA-08 controller where I wanted to measure a solar cell and a battery voltage with the MCU. The first thing I made was to connect grounds of CA-08 (solar and batt sockets) to MCU ...
1k views

### Why don't solar cells produce visible light when supplied with electricity?

... A cursory Google search didn't reveal an answer... Is the energy conversion a one-way process?
2k views

### Are Supercapacitors Polarized

There seems to be conflicting information on the internet. Are super capacitors polarized? For instance, could you charge them and then suddenly invert their polarity (à la charge pump)?