Questions tagged [polarity]

For questions about polarity considerations in electronics due to circuit components with polarity (e.g., diodes, transistors, polarized capacitors, batteries, etc.), polarity of quantities directional quantities (such as currents, voltages, electromagnetic fields, etc.), polarity symbols, etc.

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How does USB Type C handle reverse polarity / signal duplication

The new USB Type C connector doesn't have a physical reverse polarity protection any more. You can plug it in any way you want on both ends, there is also no A and B end any more, it's all the same. ...
timonsku's user avatar
  • 1,378
34 votes
6 answers
143k views

In an NMOS, does current flow from source to drain or vice-versa?

In an NMOS, does current flow from source to drain or vice-versa? This Wikipedia page is confusing me: http://en.wikipedia.org/wiki/MOSFET The above image confuses me. For the N-channel, it shows ...
PitaJ's user avatar
  • 495
31 votes
2 answers
43k views

Does MOSFET let current flow through source to drain as it allows it from drain to source?

Does a MOSFET allow current flow in reverse direction (i.e.; from source to drain)? I made a Google search, but couldn't find a clear statement about this matter. I have found this similar question, ...
hkBattousai's user avatar
26 votes
3 answers
11k views

Why do we use polarized capacitors?

I want to know if the polarized capacitor has some advantage that they are used in some circuits? For example, in a schematic of the BISS001 PIR controller IC, in some places, a polarized capacitor ...
Hamid Mousavi's user avatar
25 votes
1 answer
10k views

Reverse polarity protection

I read somewhere that this can be used for the reverse polarity protection in the circuit. But I am quite confused with its operation. Can somebody help me with this. simulate this circuit – ...
IamDp's user avatar
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23 votes
2 answers
40k views

How do I decide what capacitor to use in a circuit?

I am using a voltage regulator, and to get cleaner power, the datasheet recommends using a 0.33uF capacitor. However, it doesn't say what type it wants. Stupidly, I ...
Anonymous Penguin's user avatar
17 votes
4 answers
10k views

Does an over voltage, over current and reverse polarity protection IC exist?

I'm designing a circuit that has the following protection requirements: Reverse polarity Over voltage (60v max) Over current (approx 1A) There's quite a large input voltage range, 10v to 60v. 48v ...
raaymaan's user avatar
  • 1,324
16 votes
3 answers
4k views

What does the radiation from an antenna look like?

Just out of curiosity, I searched for antenna on Google Images, and what usually shows is something like this. So I really thought that an antenna radiates in a circular and equal pattern. But as I ...
Black's user avatar
  • 515
15 votes
5 answers
3k views

Why don't more devices incorporate full-wave rectifiers as reverse polarity protection?

Recently, I was introduced to the idea of using a full-wave rectifier, in order to protect against reverse polarity damage in DC devices. I hadn't even considered using a rectifier in an already DC ...
Jay Greco's user avatar
  • 1,847
15 votes
1 answer
9k views

What are the disadvantages of using a diode bridge for DC polarity?

As far as I understand, diode bridges are mainly used to convert AC into DC, but one can also use them just to ensure an expected DC output polarity for arbitrary DC input polarity. I have some small ...
Jakob's user avatar
  • 333
14 votes
9 answers
6k views

Is this an AC or DC signal?

My teacher says that this signal is DC, but if the polarity varies from 0V to -8V , shouldn't it be AC? He says that DC + AC = DC
JEAN LEONARDO 's user avatar
13 votes
4 answers
19k views

Are Peltier elements polarized?

I'm looking to add a Peltier element to one of my projects. However, I want to sometimes heat and sometimes cool, depending on the ambient temperatures on both sides of the element. Image from ...
Anonymous Penguin's user avatar
13 votes
3 answers
30k views

SMD LED polarity marking: is the cathode marking standardized?

SMD LEDs normally have some kind of marking like the following image from here indicates: The site states The CATHODE lead is always the lead to be identified with ALL LEDs, including surface-...
Rev's user avatar
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13 votes
2 answers
13k views

Why does this two terminal inductor have a polarity?

The Murata LQP03TN2N0C02D 2nH 0201 size inductor apparently has a polarity marking on the package: I don't see anything on the data sheet that suggests there's a difference installing it in a circuit ...
Adam Davis's user avatar
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10 votes
5 answers
6k views

Why is this 3-way speaker wired this way?

I found a service manual of a pair of 3-way speakers that were part of a mini integrated stereo system. These are Sony SS-H77 speakers, which have served me very well back in the day. Looking at the ...
ysap's user avatar
  • 345
9 votes
5 answers
102k views

What to do when a device doesn't specify it's DC polarity?

This is probably a very simple question but.. I've been trying to find replacement AC->DC adapters for various electronics around the house, but I ran into one which doesn't list its polarity. It ...
MrKatSwordfish's user avatar
9 votes
2 answers
96k views

Why is the negative contact in a battery bay always the side with some sort of spring?

Is this just purely convention, or is there some kind of technical reason behind it?
wwaawaw's user avatar
  • 193
8 votes
9 answers
15k views

AC polarity detection

How can I detect AC 'reverse polarity' (single phase) (without the use of ground/earth) and drive a led when the polarity is reversed? It should at least detect 230 VAC but it would be cool/...
zduk's user avatar
  • 203
8 votes
3 answers
31k views

Is a Schottky diode appropriate for reverse polarity protection?

To narrow the focus a bit from an earlier question: Is a Schottky diode appropriate for reverse polarity protection? I'd like to prevent mishaps from a user connecting DC power in reverse, but I'd ...
JYelton's user avatar
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8 votes
1 answer
9k views

Packaging polarity indication of a supercapacitor (polarity indicated by arrows)

I obtained some supercaps from an auction site. As is often the case for low cost components from such sources, these do not have supplied data and such branding as there is does not appear traceable. ...
IceCold's user avatar
  • 824
8 votes
5 answers
22k views

Confusion about dot convention in an ideal transformer

I am confused about voltage polarity and current direction in transformers , for example the equivalent circuit of the ideal transformer in figure(a) the instantaneous voltage polarity of the ...
iMohaned's user avatar
  • 1,491
8 votes
3 answers
15k views

How can the capacitor be connected in reverse polarity?

If the polarity changes every time the AC switches, then why doesn't the capacitor explode?
user8210's user avatar
  • 567
7 votes
6 answers
1k views

Inductor polarity

Let's say an inductor has DC current going through long enough for it to completely build it's electro magnetic field. If the source voltage then goes lower, the inductor will 'use' the energy stored ...
Charles-Ugo Brouillard's user avatar
7 votes
2 answers
7k views

Reverse polarity protection - PMOS vs Schottkey diode

I have a circuit running from 2 AA cells in series, meaning I get 3.0V when fresh (or 2.4V if NIMH cells) and it goes down to 2.0V, that's when my circuit cannot function anymore (no DC/DC onboard). ...
mindbomb's user avatar
  • 297
7 votes
5 answers
16k views

Aren't non-polarized plugs a little dangerous? Why still use them?

Sorry if there is an answer for this kind of question somewhere. I can't find it anywhere. Take a look at obvious toaster example: If you live in Europe and have non-polarized plug and a toaster (a ...
user avatar
7 votes
3 answers
3k views

Electrically switching between horizontal and vertical light polarization

I would like to be able to electrically switch between horizontal and vertical light polarization. This polarization filter is supposed to be portable attachment running on a battery in front of a ...
JarkkoL's user avatar
  • 171
6 votes
2 answers
12k views

Can current flow both ways through a transistor?

Last night I was experimenting with and motors and transistors. I was testing out NPN and PNP transistors to learn more about how they work and how I can use microcontrollers to control the speed with ...
Listen's user avatar
  • 69
5 votes
7 answers
21k views

How to memorize a diode's polarity in symbol? (self-answered)

How to memorize a diode's polarity, such as anode and cathode in symbol?
Always Confused's user avatar
5 votes
3 answers
9k views

Reverse polarity protection idea

I'm thinking about making a reverse polarity protection for a project. This is for a small line follower robot and I'm still deciding if I need a reverse polarity protection at all. It will be powered ...
cube's user avatar
  • 221
5 votes
6 answers
3k views

Determining the correct polarity of a supposedly wrong polarized capacitor

I'm fixing an audio interface (Scarlett) that was behaving poorly and found a likely culprit - a bulging capacitor. However, it appears to be soldered on the board backwards (based on the `screen on ...
court3nay's user avatar
  • 161
5 votes
2 answers
5k views

What direction to place electrolytic caps for AC coupling?

If using polarised electrolytic caps in an amplifier circuit as shown below, Does it matter which way round I place the caps? If so, why?
learnvst's user avatar
  • 1,281
5 votes
3 answers
2k views

LED anvil and post are reversed!

Typically, through-hole LEDs seem to have the cathode (-) side connected to the "anvil" and the annode (+) connected to the "post" (see diagram below). ...But I now have in front of me an LED that ...
Bort's user avatar
  • 5,132
5 votes
2 answers
4k views

Which symbol to use for polarized capacitor?

Ok guys, this has been driving me crazy and I would love an absolute universal answer (even though I know there are disputes)... Which symbol should I use for a polarized capacitor? At school they ...
Hreggviður Emil Eðvarðsson's user avatar
5 votes
1 answer
25k views

How to determine the electrolytic capacitor polarity from PCB printings?

I have this PCB board that I need to solder a capacitor to it. This is the board: And I'm not sure where should I solder the negative and where the positive. Can someone please explain what this ...
NoamC's user avatar
  • 117
5 votes
1 answer
1k views

Power line protection: overvoltage, ESD, voltage polarity

We are designing an industrial control board. The input voltage of the board is +12V, ground and -12V. Our previous design does not include any power protection and now I want to add over voltage and ...
richieqianle's user avatar
  • 1,612
4 votes
6 answers
8k views

Why plug is polarized in the US? What are the benefits?

I could not get a good hold of it, I searched online quite a bit. This must have to do with safety but then non-polarized switches are used through out the world with no issues are risks, so my ...
TheTechGuy's user avatar
4 votes
2 answers
1k views

Footprint for Electrolytic Capacitor

I plan on using this capacitor on my project: https://datasheet.lcsc.com/lcsc/2209011730_KNSCHA-RVT330UF50V167RV085_C5155333.pdf This is an electrolytic capacitor (this means it has polarity.). The ...
user1584421's user avatar
  • 1,349
4 votes
3 answers
458 views

Polarity of TVS diode is unclear

I have a question regarding the DESD1LIN2WSQ TVS diode by Diodes Inc. which I want to use to protect some 24V IOs of a microcontroller board. Until now, the TVS diodes I worked with always had the ...
Sim Son's user avatar
  • 2,753
4 votes
2 answers
2k 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 ...
Felix Lamouroux's user avatar
4 votes
1 answer
2k views

astable multivibrator: capacitor polarization

Looking at this circuit, I'm wondering if the capacitor polarization "+" is correctly draw. Assuming T2 is in cut, T1 is on, left capacitor will have a 0.7v in its right side (connected to T1 emitter) ...
pasaba por aqui's user avatar
4 votes
3 answers
458 views

Flyback Transformer Winding Direction

Looking at the basic Flyback Converter Topology, the coupled inductor polarity should be opposite in order for the circuit to operate properly. However, I am confused on how to implement the correct ...
Gman's user avatar
  • 101
4 votes
2 answers
18k views

Why is this power cable sometimes polarized and sometimes not?

I have a handful of power cables like this: Some have polarized male plugs, while others are not polarized. Given that the female end appears to be reversible, why are some of them polarized? I ...
End Anti-Semitic Hate's user avatar
4 votes
2 answers
20k views

Circuit to reverse polarity

I am doing a project on a door shutter opener where there are two states or signal I pass into the circuit: 0V: Door shutter closed 5V: Door shutter opens. I plan to accomplish this via motor ...
Prabhpreet's user avatar
4 votes
2 answers
1k views

Does my device need reverse polarity protection?

I'm developing a device with changeable AAA batteries running at 3V. Since the end user can change the batteries there is a chance they may be put in the wrong way around. The circuit basically ...
David Högberg's user avatar
4 votes
1 answer
4k 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)?
TRISAbits's user avatar
  • 1,368
4 votes
1 answer
539 views

help understanding this reverse polarity protection circuit

Going through LT4363 evaluation kit DC2062A-B (schematic here), I came across a reverse protection circuitry that protects downstream components from reverse transients and reverse DC voltage: In ...
fhlb's user avatar
  • 1,470
4 votes
1 answer
12k views

Polarity symbols on universal AC-DC adaptor

I have a universal AC-DC adaptor that has the following symbol by the polarity switch: Is it safe to assume that the top part of the diagram indicates the polarity of the inner surface of the ...
j_h's user avatar
  • 41
4 votes
2 answers
381 views

Can the electron source be known as the anode in one place and the cathode in another?

It is my understanding that in a Galvanic or electrolytic cell the electrode from which the electrons flow is known as the anode. Yet it is also my understanding that in a vacuum tube the electron ...
Mr.Wizard's user avatar
  • 185
4 votes
0 answers
128 views

High voltage power supply polarity for X-ray tube application

High voltage power supplies (HVPS) in the range 100 to 200 kV are used for working with X-ray tube. Some HVPS produce negative output voltage or even bipolar output including negative and positive ...
Sam's user avatar
  • 53
3 votes
2 answers
1k views

What is the polarity of this barrel plug with a double circle?

Related but doesn't answer my specific icon: How to tell polarity expected of a DC barrel jack? I have a dell laptop barral plug adapter, and I can't tell from the graphic whether the tip is positive ...
Stephen S's user avatar
  • 185

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