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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489 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 ...
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DC Motor as DC Generator + Output Polarity Switcher

I am working on a hobby circuit. And got a quick question. I am using regular mini DC Motor as DC Generator. If the motor is rotated one side it generates few volts. If the motor is rotated in ...
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162 views

Reversed polarity of CR2025

My bike light uses two CR2032 batteries, which I replaced with CR2025 and some padding. It stopped giving light, so I removed the batteries and measured voltage. One battery gave 2.8 V, and another -1 ...
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Can I trust in visual inspection to identify LED terminals?

In the figure above, LED A is a regular 5mm LED and the visual identification of its terminals polarity is well known. As you can see, on LED B the anode is identified by the longer leg, but the ...
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392 views

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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1answer
8k 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?
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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
14k 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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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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748 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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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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1answer
248 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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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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Invert polarity with DPDT relay

I'm trying to wire a 12v DC motor to a DPDT switch so I can control the spin direction (by inverting the polarity) it uses two digital pins, one of them to set the direction of the motor and another ...
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1answer
2k views

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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944 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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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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737 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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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
333 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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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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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 ...
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Puzzle: diode polarity in a vintage tachometer circuit

Once again, I'm trying to reverse engineer an old tachometer circuit--1970s vintage this time. There are three diodes on the circuit board, and two have absolutely no markings whatsoever. Can anyone ...
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Don't reversible 2 prong plugs have to account for orientation?

I don't know much about electrical hardware, so forgive any naivety. Anyways, I've been wondering: since 2 prong plugs (the reversible ones whose prongs are the same size) can be plugged into a ...
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50k views

How to check DC polarity using a multimeter

How can we check DC polarity using multimeter? If the DC cable (the positive and negative end) is connected in the cable rack (terminal block) how can one identify which cable is positive and which ...
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1answer
224 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
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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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3answers
851 views

How to remove energy from inductor using semiconductors?

So I have this coil and I'm driving dc current through it. This coil has inductance and thus stores energy from the dc current. I have to remove this energy before I can change the polarity of my h-...
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1answer
7k views

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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1answer
106 views

How can a battery get reverse charged? (other than by being charged backwards)

I have an old lead-acid car battery that got taken out of my car by AAA 5-10 years ago when it died during a cold winter. I stashed the battery away and forgot about it. Recently I dusted it off and ...
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93 views

When is a non-polarized electrolytic capacitor inappropriate?

I am recapping a vintage power supply and I've done similar before but I'm a hobbyist non-expert. My understanding has always been that using a non-polarized cap is acceptable where an polarized ...
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2answers
347 views

Which one is the positive side?

I'm newbie, thus my simple question. In the schematic below, which side of the capacitors is the positive? Why? Or are they assuming that I have to use ceramic capacitors? Usually my schematics come ...
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1answer
447 views

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
871 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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550 views

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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173 views

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
1k 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
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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81 views

Replace ONE 25v 47uf capacitor with FIVE 60v 10uf capacitors parallel?

MY 1000 Watt True Sine Power Inverter blew a 25V 47uf capacitor. The shell was rattling around inside, and the ribbons were exposed. Yay, I found the problem! Sooooo, how can I tell the mounting ...
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1answer
65 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
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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
1k 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
174 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
748 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
755 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 ...