# Questions tagged [voltage]

Voltage, otherwise known as electrical potential difference (denoted ∆V and measured in volts) is the difference in electric potential between two points (adapted from Wikipedia). Voltage can be constant (DC) or varying (AC).

4,676 questions
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### Node analysis with voltage source in matrix form

simulate this circuit – Schematic created using CircuitLab Can you please check if my reasoning is correct? The sum of currents leaving node k is:  I_k = \sum_{i = 0}^{n} I_{ki} = \sum_{i = ...
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### Understanding 5V to 1.8V UART level-shifting circuit

Hopefully it's OK to ask very basic electronics questions here. I had a TTL 5V UART cable, however the board I had only accepts 1.8V max. So I found some online schematics that uses resistors and a ...
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### Multiple Voltages Needed - Can I Simply Cascade Power Supplies?

Electronics novice here... I hope this is a reasonable thing to ask here. I haven't "tried" anything because I'm not really having a problem. I'm just looking for guidance before I start. I am ...
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### Will a diode change how my IC works?

If I have an IC, any IC, with a V+ and a V- that has a minimum voltage requirement of 3V to operate. Say I supply that exact 3V, but I want to add a silicon diode to the V- to prevent a reverse ...
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### Artec QDD2 reverse voltage problem

Good day everyone, I have an Artec QDD2 overdrive circuit and I recently powered it up with reverse voltage by accident and it doesn't give any sound on the stages of distortion, however it is ...
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### Are my op amp nodal voltages correct?

I am wondering if my assumptions are correct. For the circuit attached I assumed that Va is equal to Vb and which will be equal to Vc since the difference input voltage must be equal to zero.
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### On a 3-terminal bench power supply (+, -, GND), are there positive and negative drivers behind each of the terminals?

In a 3-terminal power supply like this, are there individual regulators behind the positive and negative terminals? For example a LM317 on the positive and a LM337 on the negative? If not, what kind ...
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### transformer has continuity but no voltage output?

I have two old transformers that appear to be fine, however no DC voltage was measured on the secondary coil. I have measured: The input voltage: 229 AC the input coil ohms: 0.015 kOhms the two ...
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### Earth Fault in a TT Network: Current loop, or charges flowing from one grounding to the other?

There are serveral things I (yet) don't understand about the T-T-earthing system. The most important one is that I don't understand which way the the current takes in case one of the conductors (for ...
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### Whats the difference between a battery charger & Transformer to power a 12 V 3 A bilge pump?

I made a common mistake, identical to an earlier post "Using a 12 V 3 A bilge pump on a 12 V 8.5 A LED power supply". The pump was 3.8 amp so I purchased a 5amp led transformer, which just worked, ...
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### Find Voltage of inductor in LC series circuit with resistor in parallel

I have a LC resonance circuit with a resistor between the capacitor and inductor: simulate this circuit – Schematic created using CircuitLab I want to find the Voltage at L1, more specifically ...
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### Charging 4 protected li-ion batteries in series

I have bougth 4 protectected li-ion batteries from e-bay (these). And I would like to know if I could charge them in series with 24V 0.5A charger (this one). Since they are protected I conclude ...
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### Alternating Voltage

Is AC the same as an alternating voltage ?
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### Can you convert a small gas engine 220 volt starter to work with 120V?

My snowblower has a broken connecting rod so time for an engine replacement. Good price on a new replacement 11HP gas engine on Ebay but it's set up with a European 220 volt starter. The 120 volt ...
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### Where do I place the on/off switch in a multi voltage circuit?

I've got a simple Arduino setup where I need to supply a 3.3V Arduino with adequate power - and at the same time provide higher voltage to a sensor which needs 5V. The Arduino is powered by bypassing ...
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### Protective-Earthing the chassis with the earthing point being the star-point - How does it keep the Chassis at Earth potential?

I always understood that one of the two purposes of protective earthing is keeping the electric potential difference between the chassis of a devide and the ground (the ground I am standing uppon ...
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### Circuit that averages voltage

Suppose we have an oscillating signal V(t) with V(t) >= 0. I'm looking for a circuit that averages this signal over a given time so that I can read out the average value directly using a simple ...
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### Can open-circuit voltage be treated as voltage to find power dissipated? [duplicate]

Can open-circuit voltage be treated as voltage to find power dissipated? I combined all the resistors (including Vlamp) to get one resistor of 40/6 Ohms (Correct me ...
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### Can a Current Limiter Power Thermistor be used in line to reduce the brightness of a 120v incandescent bulb?

I have an application were I do not have the room for a dimmer switch but need to reduce the lumens of a 120v 25w incandescent bulb just a bit. There used to be a product called the Bulb Saver Button ...
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### What is the best way to get 7V from a benchtop 10V supply?

I have a 50 ohm load I am trying to drive at 7V. I currently have a 10V supply with a 10kohm potentiometer but I am expecting to run into trouble when I connect it as a voltage divider. I looked ...
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### Why the opposite of the passive sign convention is not the active sign convention?

Studying the fundamentals of circuit theory, I was reading the Wikipedia article on the Passive Sign Convention and found out about the Active Sign Convention (ASC). After searching many introductory ...
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### Megohmmeter, Insulation tester, megger

Can anyone please explain how does megohmmeter (insulation tester) work. Here is what I don't I don't understand: These little tester can produce e.g. 1000V, how is that done? What are the internals ...
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### Elimination of interfering voltage

I have a problem deriving a formula I will be using in my bachelor thesis. It's about eliminating interfering voltages during measurement. To understand how the interfering voltage is going to be ...
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### Voltage drop across buck converter

In my robot, I plan to have a GPIO pin on my Raspberry Pi connected to the insertion detection pin (pin 3) of a barrel jack (schematic here) so that my code can tell when the robot is externally ...
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### Voltage law not correct [on hold]

Is the voltage wrong? Across the resistor there cant be any voltage drop because the electric field of a battery that forces the electrons to move is constant for all points inside the conductor.Just ...
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### How can I check the voltage of a fan?

Is there a way I can connect 1 or 2 batteries to a CPU Fan that I dissasembled to check what voltage it is so I can use it at the highest speed?
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### Voltage divider resistance/wattage sizing

I am working on a small project currently -- I recondition hybrid car battery packs with a grid charging system, and I am working on a voltage sensing circuit that's monitored and available via a ...
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### 6 volt drop to 1.2 volts

I am working on a circuit for my deer feeder. I now have a 6 volt power source running the spinner on the feeder and it has a 6 volts solar panel recharging the battery. I made a new circuit control ...
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### Why does current not increase when the voltage increases in this case?

When talking about BJT transistors, a very common graph is the one shown below, that plots (VCE,IC) as an ascending function. As far as I know, the BJT manages VCE so that IC is beta times IB, being ...
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### Sensing high differential voltages using operational amplifiers

Is there any solution to sense high differential voltages using operational amplifiers (without using resistive voltage divider) ? The input voltage range is [-30, 80] Volts. I've searched on all ...
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### Voltage Drop and Safe Current Load on CAT5 Cable

I am going to use this passive PoE injector cable set to power a Raspberry Pi model B. The Raspberry Pi model B consumes between 700mA-1000mA (mine will also be powering the RPi Camera Module). Using ...
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### Push-Button Voltage Spike (not debouncing)

I have a circuit which reads push-button presses. If it is pressed, it turns on the door by rotating motor. In this system, safety and stability are keys. I added r/c filter to debounce button and ...
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### Dramatically increasing voltage in a circuit

Suppose I have a small AC generator, which produces an unstable current at 1 volt. How can I transform this into 10000 volts, decreasing the amperage accordingly? It does not matter if the output is ...
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### voltage transient protection for MV Motors

What types of transient voltage protection is applied on medium voltage motors and are these types of protection that are applied depended on the type of motor it is e.g Synchronous vs Induction motor?...
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### Can I use this relay?

I got this relay. In the product description they say: "belastet bis zu 10 Amp/250 VAC, 5 Amp 30 VDC." which means: "charged up to 10 amp / 250 VAC, 30 VDC 5 Amp". On the relay it is printed: 10A/...
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### Switch module test circuit design

I am doing a project to make a test box that would to test the switch module in the photo below. Please see circuit diagram below for inside of the switch. Please note this switch is not an ordinary ...
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### Measure voltage of the panel light bulb inside a vintage radio

I'm new to Electronics. I have recently received a vintage radio Pioneer TR-305. I am trying to replace the panel light bulb inside this radio. I opened the radio panel and found the bulb soldered ...
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### How can I calculate V1 and V2 in this circuit?

How can I calculate V1 and V2 in this circuit? This is what I tried so far: Calculate the voltage of R5 through voltage divider but I didn't find the way, I was looking about second OA circuit but ...
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### How does one determine the type (AC v. DC) and operating voltage of small motors?

I've become fascinated by Rolling Ball Sculpture (RBS) and plan to start building my first one soon. Typically a RBS uses a low-voltage, low-RPM motor to carry the marbles to the top of the structure ...
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### How can I sacrifice a bit of DC Voltage to transform it to DC current?

I made a project with using voltage doubler(which has input of 12V) which output is 43V(I expected 24V) but current is low when connecting the 150 ohm resistor,its about 150mA,but I dont need so much ...
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### How to connect one pin to ground when an another analog pin is triggered

I'm trying to combine two working electronics projects into one. I have a standalone piezo sensor that I can read values from when it vibrates via an arduino, and I have a standalone audio board (no ...
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### HV Capacitor power [closed]

Hi does anyone know what kind of high voltage power DC supply do I need using UK 50Hz to charge a high voltage capacitor 50/25kV.
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### Excessively high temperature reading with LM35

I am really new to electronics and I am just experimenting at the moment with a breadboard. My question here is related to the LM35 temperature sensor and Arduino micro controller. I am getting a ...
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### Why does a capacitor not discharge in the same cycle it is charging in a clamper circuit?

As far as I understand, in an AC circuit, a capacitor is supposed to charge as the voltage is increasing, and as soon as the voltage starts decreasing, the capacitor starts to discharge (Since it will ...
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### How can I change step-down my variable input voltage?

Ok so here's the deal: I have a variable DC Voltage source from 0-10V. I need to step that down to a variable source of 0-3V. This 0-3V DC will be fed to an Analog to Digital converter in a ...
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### How to use the electricity from a generator in an efficient way

I'm looking to buy a generator for producing electricity to power different things (e.g. a fridge), in a place where there's no electricity. For now, I do not have a fridge but I may have one in the ...
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### Is there any 433mhz rf transmiter/module/transceiver can work at 1v voltage or lower? [closed]

I am finding this kind of transmitter but it seems there is no such kind of components. Does anybody know? Thanks Because I want to use a msp430l092 which work can at 0.9v at least. Combining it ...
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### Trouble with optocoupler 4n35

I'm trying to ride a full bridge inverter using SPWM to control the MOSFETs, the signal SPWM that I use to control the MOSFETs comes from an NI elvis, but it only provides 5V and I know the fact that ...