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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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 ...
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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 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 ...
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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 ...
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Flip polarity on Darlington Tip120

I have an RC Car that I tore apart and I am attempting to rig it to an arduino. The front wheels can turn left and right based on which way the current is flowing and the rear wheels will go either ...
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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). ...
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How to fix servo motor broken by wrong polarity [closed]

I accidentally plugged in my servo with the wrong polarity (with the order of wires being signal, ground and power). It immediately started releasing the 'magic smoke', but I managed to unplug it ...
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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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How do I figure out the correct polarity of a DC barrel connector

I'm in the U.S. and I bought a digital wall clock from the U.K. which came with an AC adapter with input 230V/50Hz/90mA and output 9V/800mA. Now I could get a transformer to convert 120V to 230V but ...
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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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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 ...
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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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Why are leads from the negative terminal considered grounds?

I'm using a 9V battery with a 5v regulator as a power supply. What I can't grasp is why I place the regulator in the (+) lead of the battery. If electricity is electrons flowing, and the excess ...
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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 ...
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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 ...
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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 – ...
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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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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 ...
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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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Making dc barrel usb cable and can't find the positive polarity

I have found out that my dc barrel is tip positive. after cutting the the barrel I realized that there is on insulation inside the black insulation itself to identify which one is positive and which ...
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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 ...
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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?
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Help 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 ...
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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 ...
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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?
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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 ...
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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/...
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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?