Questions tagged [polarity]

Polarity is a conceptual entity. Pole means a direction. However, an object is called as "having polarity" or "having specific polarity" means a preference to a differential-behavior of something in forward and backward direction.

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Fundamental questions about BJT transistors

Take a standard NPN transistor. The doping of each element of the transistor is in the name. This is what is inside the transistor... Source of image: Bipolarer - Transistor, gif The left "slice" of ...
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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?
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Inverting (Buck-boost) converter polarity problem

I have trouble understanding something in the circuit below. It is inverting converter, seems quite easy, but the part I don't get is when the switch is OFF we have forward-biased diode, i.e. plus on ...
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1answer
12k views

Determine polarity of crystal oscillator [closed]

A two-pinned 13.824 MHz crystal oscillator broke away from the pads on a PCB board. One pad is labeled + and the other is GND. Do two-pin crystal oscillators have specific polarity?
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3answers
353 views

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 ...
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1answer
557 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 ...
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1answer
237 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 ...
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2answers
14k views

How to find polarity of terminals of a circuit using meter?

Title may not me appropriate but i have a basic question that may be a beginners question so forgive me in advance. If we have a PCB and two wires are coming out for the battery connection. One will ...
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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 ...
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1answer
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Does the polarity of my AC adapter match that of the device? [closed]

Looking at the symbols, I think the polarity matches the adapter and device (tip positive), however the design of the symbol is different which is is confusing me, so I want to be 100% certain that ...
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1answer
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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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Does reversing polarity in AC damage the equipment? (Sonoff Wifi Switch) [closed]

Firstly, I am a beginner. Excuse me if this is a dumb question. I have ordered a Wi-Fi switch named Sonoff. I have a doubt whether the device will work if the polarity is reversed or will it get ...
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760 views

Trying to understand flyback diodes and general diode orientation

Let's start with this: I know the top image is of a flyback diode. I also get that its purpose is to protect the power supply from a voltage spike when the electromagnet releases. So I've gotten that ...
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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 ...
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1answer
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Reverse polarity protection with MOSFET: low voltage drop, 1-50V supply

I have a circuit that tests DC PSUs. They are typically unregulated and unsmoothed, up to 50V. It performs tests to establish I/V curves, down to about 1V, and up to about 3A. I want a sub-circuit ...
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1answer
308 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 ...
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1answer
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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 ...
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1answer
631 views

What's the polarity of this capacitor?

Please, help me to determine the polarity of a RWA1C101MEG capacitor. I see a fat stripe on one side of the capacitor: Is this a positive or negative terminal?
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1answer
179 views

Why is the electrolytic capacitor not polarity sensitive?

The issue I was making a project in which I had to use a 2.2uF electrolytic capacitor in series with a microphone and weirdly, the circuit works even if I toggle the polarity of the capacitor, that ...
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How can I use relays and deal with reverse polarity with the Arduino?

I have a toy car that I wanted to make autonomous. It has a motor for rear drive (seen in the bottom of the photo hidden in the gear-box) and a motor for rack and pinion steering (located just above ...
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4answers
997 views

Can you damage logic gates by connecting two outputs together and powering one?

As the title says, would this cause problems in a circuit, and if so, how do you get around it (other than connecting them both through an OR gate)? Furthermore, could you stop this with a buffer? ...
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1answer
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Can I damage a device using opposite polarity? [closed]

I have a device that requires input of 12V DC with positive polarity and a power supply that outputs 12V DC negative polarity (see figures below). Can I plug it in to try to see if it's working or ...
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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,...
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Polarized Electrolytic Capacitor - Reverse Polarization

There is one small problem in my understanding of polarized capacitors. The thing is that when using polarized capacitor, you should apply positive voltage terminal to anode and negative voltage ...
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2answers
807 views

On using an electromagnet in a magnetic stirrer

What's the simplest and cheapest way to use one or more electromagnet to to stir a stir bar ? That is, how to control the speed at which the polarities are reversed. I don't want any mechanical part (...
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Identifying polarity of capacitor from PCB printing

I took out the old capacitor and didn't remember to check the polarity because I assumed the board would have more standard markings. Is there any way to figure it out with a meter or by the printing?
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Transistor switch without polarity

I've successfully used an Arduino Uno to trigger Halloween props by closing the normally open circuit on an SRD-05VDC-SL-C relay. I am basically replacing a contact switch and tapping into each prop's ...
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3answers
885 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
980 views

74HC595 Shift register - output pin polarity

Most shift register tutorials I've seen have the output pins connected to ground (for instance: http://www.arduino.cc/en/Tutorial/ShiftOut), however I've seen at least one circuit that connects them ...
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1answer
2k views

How to build an H-bridge using MOSFETs? [duplicate]

I want to reverse the polarity of my current source, which is a capacitor in this case, in the middle of discharging phase. Also the capacitor bank is being discharged through a coil to make a short ...
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3answers
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 ...
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1answer
64 views

Why I don't get horizontally-polarized TVs in the satellite from time to time? [closed]

Something like once every 2 days I cannot watch horizontal SAT channels for about a half day. It says "no signal". During this "no signal" time I get very rarely watchable time. Like 1 minute in an ...
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3answers
737 views

Reversing USB power polarity, but no black wire

My goal is to create a USB-to-USB cable with reversed polarity in order to charge an old Gameboy Advanced SP. I could just go on Amazon and buy a charging cable, but I do enjoy a fun little project ...
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2answers
875 views

Polarity of capacitor on PCB

I've removed a capacitor, but like the n00b I am, have forgotten which way round it went. From this picture can you deduce the polarity? It was removed from the board in the circle with the two ...
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2answers
131 views

How can I find removable plugs for standard pin headers? [closed]

I'm making a right angle adapter for a module with a 2x10 pin layout that has one blocked. How can I find the little plastic pins to block a hole, ideally ones that are removable? I realize I could ...
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3answers
603 views

What do you call a device that reverses polarity?

I am replacing a DC power supply used in a lab experiment. We need to be able to choose a positive or negative current. Bipolar power supplies in our power range (around 1 kW) are expensive, so I am ...
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2answers
1k views

On/Off DC power indicator [duplicate]

I am pretty sure that this should be simple but the answer is eluding me. Basically I would like a simple 12V DC circuit that lights one LED (red) when a power switch to a pump is off and would ...
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1answer
688 views

DMM Auto-Polarity / Polarity detection

I have understood how auto-ranging is typically achieved on a digital multimeter, but I'm having trouble finding an example of how (DC) polarity is handled. How does the meter know if a voltage is ...
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2answers
2k views

simple h-bridge polarity reversal

I am trying to reverse the polarity on a rather beefy motor (5 amp, 60v) in the most simple way possible. I need to build an h-bridge just to reverse the current, I am controlling speed elsewhere. ...
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1answer
159 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
461 views

Slot assignment in JST SM connectors

I am using JST SM connectors for connecting two sets of wire. There are two slots in 2-pin connector. I wish to know, what is general convention for assigning the polarity to these slots? Is it slot 1-...
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1answer
190 views

ESD and Electrolytics

Consider the simple circuit schematic below: 1) Would a high voltage (say 1kV-25kV) human body ESD discharge event (1ns rise time, 100ns total) at OUT have a negative effect (damage or destroy) the ...
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1answer
572 views

Monopolar DC transmission line: why is the preferred polarity negative and water used return path?

How and why energized conductor is of negative polarity for Monopolar link in DC transmission. And how can water be used as return path? And why negative polarity cause lesser radio interference? ...
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2answers
313 views

Solid state relay (SSR) - alternating polarity

I'd like to control a slave clock, via a relay(s), which needs an alternating polarity pulse once a second. The attached circuit incorporates two SPDT relays which do this (one relay activated one ...
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1answer
82 views

Circuit for controlling AC signal polarity in real-time

I'm going to start a project on a controlling speaker array and I need to control the signal's polarity fed into each speaker. I want to make a 'router' or 'controller' to make it easy, so I don't ...
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1answer
56 views

EM wave polarization check

I am trying to recall the quick way to check the EM polarization theoretically, I mean if I have a wave described as (ssume capital letters are vectorial fields) \begin{equation} \ E = E_o *exp(j* \...
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1answer
6k views

Coil Winding Sense of Inductor/Transformers and Output Polarity

Given a solenoidal coil, if it is wound in one sense (say clockwise), would the output from it, in terms of polarity, be equivalent to another coil, wound in the opposite sense (counter-clockwise), ...
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2answers
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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 ...
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1answer
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 ...
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1answer
2k views

How do the hybrid-pi models between N-channel and P-channel JFETs differ?

This is the hybrid-pi model of an n-channel JFET. An answer on here claimed that the only difference between p-channel and n-channel JFETs is that voltages are reversed. How would this apply to the ...