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 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 ...
Marco Castro's user avatar
3 votes
1 answer
12k views

Troubleshooting why Powerbank Doesn't Charge Cell Phone [closed]

I have powerbank that provides 5v (presumably regulated) power, as typical of most usb interface powerbanks. I have been trying out my powerbank with different phones. It works on all except one. I ...
Arash Howaida'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
  • 1,885
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
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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
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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
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
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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
3 votes
1 answer
3k views

Designing an inverse polarity and overload (crowbar) protection circuit

There are some great resources on the internet and on this site about designing various protection (crowbar) circuits. For example, Leon's answer to a general circuit protection question. I'm looking ...
JYelton's user avatar
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0 votes
1 answer
3k views

Mesh Current Polarity, Equation Setup

Practicing Mesh Analysis I came across this problem and te answer is really alluding me and I believe is just one polarity that I'm not understanding, the problem is the following... Vs​=10V, R1=...
Marco Castro's user avatar
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
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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
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
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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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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
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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
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
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
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
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
4 answers
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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
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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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
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
3 votes
1 answer
12k views

Do electret microphones have polarity?

So do electret mics have polarity? The following circuits seem to contradict each other... 1) 2) Now the problem is one image shows polarity while the other one does not!! What's the holdup here?
Parth Sane's user avatar
3 votes
1 answer
422 views

Is there a convention for the polarity of voltage specified as \$V_{XY}\$? [duplicate]

Inspired by this answer, which includes the image: Which solicited the comment: No, you have the polarity of Vce shown backwards in the diagram [...] The diagram seems consistent to me: the ...
Phil Frost's user avatar
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3 votes
3 answers
75k 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 ...
ANKIT JAIN's user avatar
2 votes
3 answers
12k views

Does the input polarity matter for a 12V DC adapter?

I bought a car cigarette DC adapter yesterday with the following specs: Input: DC 12V Output: DC 17V I'm planning to connect it to a 12V battery I have at home,...
Bassel Alkhateeb's user avatar
2 votes
1 answer
384 views

Will an electrolytic capacitor work reliably with 0 VDC and 100 mVAC?

I ran across an instrumentation amplifier datasheet from "THAT Corporation", and noticed the polarized capacitor in series with the gain resistor: It is a typical 3 op-amp in-amp, so the differential ...
apalopohapa's user avatar
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2 votes
1 answer
1k views

rx_polarity inversion in USB3.x

As per USB3.x specification there is provision of rx_polarity_inversion can any one exactly says, what is the reason behind it? Edit: Normally connection of ...
Prakash Darji's user avatar
1 vote
2 answers
2k views

Peltier damage and efficiency when continuously reversing polarity

I am thinking about using peltier for both heating and cooling to maintain desired temperature profile in small area (2ft square at max) Can continuously changing polarity damage peltier module and ...
asim's user avatar
  • 590
1 vote
3 answers
3k views

Determine Polaritry of Aluminum Electrolytic Capacitor

I have an NIC aluminum electrylytic capacitor and am trying to figure out which wire is positive and which is negative. Forgive me if this is a stupid question since I'm a total noob at this. This is ...
user avatar
1 vote
3 answers
11k views

Motor polarity reversing circuit using just SPDT switches

I have a 6v DC motor that controls a physical system similar to a window blind, using one SPDT toggle switch and two SPDT microswitches for control. I have seen similar setups with hoists, however I ...
Jodes's user avatar
  • 5,084
1 vote
1 answer
2k views

Changing the polarity of electromagnet using H-Bridge

I have made an electromagnet using copper coil of 1.0 mm diameter, iron core of 2 cm dia & 8 cm length for my project. Supplied voltage is 12 VDC and current it consumes is 9.0 Amp. It has 1.5 Ohm ...
enterprize's user avatar
0 votes
4 answers
4k views

Using limit switches to reverse circuit polarity

I am designing a linear translation stage that will be driven with a DC motor. When the circuit is powered the DC motor will start turning in either direction, which will move the linear stage towards ...
AJAC1507's user avatar
0 votes
1 answer
443 views

How does the lead polarity work on a D'Arsonval galvanometer?

Following an illustration of D'Arsonval movement such as the following... I notice that the N polarized part of the coil is connected to the positive lead and the S polarized part of the coil is ...
Snoop's user avatar
  • 601
-1 votes
3 answers
1k views

Confused about polarity of Transformer

I am confused about the Transformer dot polarity. I got design from ST's edesign Suite. Here is schematic for that :- Now I need to order the design for transformer and the transformer design centre ...
MICRO's user avatar
  • 520