# 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).

4,590 questions
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### Low voltage form a NAND logic gate then the state is high

I've been trying to learn how to use logic gates. I wanted to use logic gate to bump digital signal from 3.3V MCU to a 5V. I took a T74LS38D1 and mocked the solution using two switches connected to 3....
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### Is the voltage supplied by an LCD backlight inverter in a laptop dangerous in any way?

It is my understanding that in a laptop, voltage from a low voltage (say 10V) battery can be converted into higher much higher voltages by way of inverter for an LCD display module. Is this voltage ...
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### How to reduce transformer secondary voltage?

Trying to make a bench power supply. What would be a cheap easy way to reduce voltage (to protect the series pass transistor)? 3 Amp transformer has these terminals 12-6-0-6-12. No load voltage is 33 ...
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### Finding the supply voltage, knowing the resistance and current

I am learning the basics of electrotechnics. I had this task for my university that I failed doing and I want to learn how to solve it anyway. Thanks for assistance! :) Here is the exercise task: I ...
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### Basic Ideal Op Amp Circuit Analysis

I am trying to familiarize myself with operational amplifiers by going through this book by Sergio Franco. This is a basic question regarding the example given on page 16, which I am struggling to ...
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### Summing up batteries

I am a little confused, shouldn't I take into account the maximum battery voltage when trying to add-up batteries in order to achieve certain voltage? For instance if I want to drive a 48V 1000W DC ...
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### Connecting a Solar Panel and Power Supply in parallel, in order to power up a load

I am using a Solar Module to charge a LiPo battery. The current supplied by the solar module goes into a battery charger IC and from there to the battery. This works fine. Now I want to add an ...
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### Voltage translation for vehicle throttle sensors

I am working on a EV car conversion and I'm replacing the original throttle pedal. The two throttle sensors of the new throttle pedal are different. That means the output voltages have a different ...
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### Arduino: read different voltage values in a range from -12 to +12V

I would like to trigger different functions in Arduino related to the following voltage values: -12V, 0V, 6V, 9V, 12V (the range is from -12V to +12V). According to the value of the voltage read (-...
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### Why do our electrical utilities use transformers way over their rated KVA?

My parents' house and my house have different electric utilities, but both are rural electric cooperatives. We both have 120/240V (60 Hz) split-single phase service (this is in the United States state ...
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### How do I connect an oscilloscope to a power supply or function gen.?

I'm supposed to sketch a circuit for my class but the one thing that has me completely confused is the ground connection. For example: I have a breadboard with a 10V dc power supply and two ...
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### Vpp of oscillation of LCR circuit

Edited: I'm having a trouble to estimate Vpp of a RCL oscillation circuit. I found a peak to peak inductor voltage (Vpp_L) varies with the different combination of LC, which makes sense because the ...
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### Is rated current supposed to vary based on voltage?

Recently I have been reading a lot of datasheets and noticed that many manufacturers specify a current rating for their products (especially connectors) without specifying at what voltage the current ...
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### What should be the voltage rating of bootstrap capacitor?

BST_1P is the bootstrap capacitor connection pin for high-side gate driver of TAS6422. In the datasheet it is suggested that, this capacitor should have minimum rated voltage of 16 V. What is the ...
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### Decrease voltage in circuit

If I have 90 VDC 3.5 A, and I want to reduce to 12 volt, in excellent efficient the amps will be around 25 A. Can I use a 12 V L7812 regulator?
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### How can I change the circuit or the current to effectively heat up the diodes based on their current rating?

I'm extremely new to electrical engineering, and I was experimenting with diodes in series. I soldered six 1N4007 diodes together, and I connected them to a DC power supply (RSR ET122) with a constant ...
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### Necessary voltage to charge NiMH using Solar Panel

I'm trying to understand which voltage I need to charge my NiMH batteries so I can purchase the components to do this. Actually I have 2x AA Ni-MH 1.2 V 1900 mAh and 4x Solar Panel 2 V ...
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### Can I test if a battery is connected to a circuit?

I have a 12 V rechargeable lead acid backup battery that is connected to a circuit. When the battery is not in use there is a constant 12 V applied for charging, and when the battery is in use there ...
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### What is the maximum amount of ripple input voltage a linear regulator can handle?

Greetings fellow EE's: Referring to the classic LM78xx series, I notice there is no specification on the maximum amount of ripple voltage these devices can handle at their input terminal. So for ...
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### Have i understood voltage correctly?

I am not from an engineering background, so this may be very simple and stupid but: Voltage is the difference in electric potential between 2 points Voltage drop describes the reduction in energy of ...
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### Calculate battery state of charge percentage

What is the correct formula to calculate battery state of charge percentage based on the battery type (12v, 24v, 48v and so on) and the current battery voltage. For example if I have a 12v battery ...
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### Is there any difference between voltage drop and voltage across a component?

Voltage drop across a component describes the reduction of energy when current moves through passive elements, is this the same as voltage across? What about for capacitors, technically current does ...
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### How to wire together 3 power supplies for 3 different pd rails with the same reference 0v

How would I wire together 3 bench power supplies to get potential differences of +12, +24 and -6V, all with respect to the same 0V? All 3 of the bench power supplies have positive, negative and ground ...
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### Current in a single terminal voltage source?

I know there can't be voltage without current, but how can I calculate the current in a wire if I only have the voltage and there is supposed to be no resistance?
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### Is my solution to prevent leakage between power rails correct?

I have two boards with identical comparator circuitry (shown below). I want to detect in each board when the other is plugged in. My concern (in the picture) is that when I connect the two boards if ...
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### KCL / KVL Circuit Analysis

I have a question regarding using KCL / KVL to analyse the circuit below to find all currents and voltages. My question is : When performing KCL at the top centered node, what way should I assume ...
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### Relay if powered with ac supply then turns adjacent circuit on automatically

I took the idea from the below link to build my own relay board. http://www.electronics-lab.com/project/toggle-on-off-switch/ I connected 3 of this in parallel with voltage. All seems well until I ...
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### Modify a 1629 magic eye tube circuit to a 6E5S tube?

I've an EICO 950B capacitance tester with me. It has an aging 1629 magic eye tube. I have a bunch of 6E5S tube with me. Can you guys guide me with the modification? I know the first step to this is ...
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### Can I use a power supply with the same voltage but a different amperage? [duplicate]

I have an old router with a 12v 1.5a rating, and its power supply died so I'm using a 12v 1.2a power supply. I have a MIDI keyboard with a 9V 500mA rating and I have a 9V 200mA power supply and one ...
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### High resistance op amp

I'm making a simple op amp circuit to use it as a compactor. I connect the non-inverting point to a simple circuit and the inverting to a 3 volt dc supply. the circuit should compare the voltage at ...
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### NPN transistor as switch (actual voltage readings)

I started learning Transistors with this tutorial from the Sparkfun website. The tutorial is good and pretty easy to understand. So I decided to put my learning to the test and assembled a simple NPN ...
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### Writing the Nodal and Mesh equations for large circuit and large supermesh

Here's my circuit: simulate this circuit – Schematic created using CircuitLab I have defined the node 'voltages' and the mesh current directions and the currents themselves. What I want to do ...
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### Why do I measure 5V in this circuit when I should measure 3.3V?

I have an audio processor board that has a 5V -> 3.3V LDO. For some very strange reason, when I measure the voltage of the output of the LDO, I read 5 instead of 3.3V -- which by the way is a lethal ...
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### Confused about KVL / KCL / ohm's law

I am confused about when to use KVL/KCL or ohm's law to solve the circuit question? I need to compute voltage in point B and point C, every current pass through R1 R2 R3 R4 R1= 100 ohm, R2=300 ...
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### Current feedback amplifier input structure

This is an input stage of some obsolete CFA (current feedback amplifier): Current feedback amplifier is a transimpedance amplifier, which converts current signal at its input into voltage signal at ...
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### Advice for low voltage electrolysis system please

I want to setup a simple electrolysis system with an energy source, two cables, a graphite anode and a steel cathode submerged in sea water. A low voltage of exactly 1.23 V needs to be applied over a ...
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### ATtiny20 ISP, low voltage on MISO

I have been trying for quite some time to program a factory-new ATtiny20. After unsuccesfully trying with a USBASP and with ArduinoISP, I decided to take a look with my scope. Turns out the device is ...
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### Powering 3 identical laptops using a solar panel

I have 3 identical laptops rated at 45W and 20V. The combined wattage of all 3 is 135W. I want to charge these laptops via a solar cell. Do I go for a solar cell rated 135W 20V or one rated 45W 20V?
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### Can identical DC power supplies with common ground produce varying voltage on same circuit?

For large installations of 5V LEDs, this PixLite page suggests using "power injection" from supplemental power supplies. Their wiring sample says: Note that the DC ground of all power supplies ...
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### Do electronic devices require more current when alkaline batteries goes low?

I know that alkaline batteries' voltages go down when they're at low charge (from 1.5V~1.7V to 1.0V). For typical electronic devices like remote controls or bluetooth mouses/keyboards (that uses two ...
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### Where does the indicated negative voltage terminal lie on this circuit?

Does the negative voltage terminal lie after the 150v source ?
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### How to connect a LED G13 Tube directly to a power socket?

I am trying to build my own cheap lighting for my greenhouse. I have found a couple LED tubes that would be perfect for the task, only they are supposed to be mounted on a lamp of some sort. They have ...
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### Exercise about voltage thresholds of logical port

I don't understand how professor resolves this exercise! I have two connected logical port and I want to calculate the time of transition from low to high for example. In the solution, the minimum ...
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### Understanding constant current/constant voltage charging of LiIon battery

I'm trying to understand exactly how CC/CV charging of a LiIon battery works and I tried to replicate it with a cheap bench power supply (RD Tech DPS3003) and a Samsung INR 18650-25R. The bench power ...
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### 100V “rated” wire on 220V supply [closed]

I am genuinely sorry for posting such a basic, basic, basic question. Moving to Thailand (220V) from Japan (100V). You cannot buy an extension cord in Thailand that is flush to the wall. Here in ...
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### Difference between more batteries and boosting voltage

For example if i need 18V for a project, what is the difference if i use 2 9V batteries and 1 9V battery boosting it to 18V? Thanks in advance.
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### Basic Voltage divison question - is this correct

Just having some doubts. For the following circuit No current to Vg
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### What will be the behavior of this circuit?

i have a circuit for which i have simulated its output. But i can't seem to understand how it works. Here is the circuit.. simulate this circuit – Schematic created using CircuitLab For ...