Questions tagged [reverse-polarity]

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178 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
306 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
405 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
229 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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0answers
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
611 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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2answers
242 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
408 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
561 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
2k 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
158 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 ...
0
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3answers
68 views

Using two switches to each send current in opposite directions

I have two momentary switches, one to activate a solenoid and one to reset it. It is only possible to press zero or one of the two switches at the same time. Using a single battery, how can I wire the ...
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1answer
1k views

A question about preventing reverse polarity for supply rails of an opamp

Below is an example circuit: I have some circuits based on opamps similar to the ones above. I want to prevent a situation if one powers supply rails Vcc and Vee reverse way. Normally this would ...
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2answers
579 views

Switching power supply reverse driving protection circuit

I have already "designed" (more like followed the reference design from TI) a buck regulator based on the LM3671 (https://github.com/volium/PowerSupply_lm3671) and I've been very happy with the ...
0
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1answer
393 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
540 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
92 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
233 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
857 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
424 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 ...
1
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3answers
119 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 ...
2
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2answers
1k 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
94 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 ...
1
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1answer
537 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
332 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-...
0
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1answer
115 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
579 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
718 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 ...
0
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1answer
485 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
550 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 ...
1
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2answers
882 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 (...
2
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1answer
2k 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 ...
0
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1answer
93 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 ...
1
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2answers
797 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 ...
0
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1answer
203 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 ...
0
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1answer
210 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 ...
1
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1answer
629 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 ...
3
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3answers
5k 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
541 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
3k 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 ...
1
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1answer
266 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
567 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'...
0
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1answer
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 ...
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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
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 ...
1
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3answers
933 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
288 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 ...
4
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3answers
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 ...
2
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1answer
338 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 ...