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).

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Arduino Clamp ammeter

I am using an Arduino Uno as a watch dog for a project I a doing; its job is to monitor what is happening in the system and shut down the system if it is not operating within spec. One of the ...
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4answers
1k views

What are the highest DC and AC voltages or currents that can be considered as safe?

By safe I mean safe for us when we touch a wire that is not insulated. I have heard that human body resistance is normally 50k Ohm when dry and 20K Ohm when wet. Therefore, these voltages or currents ...
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0answers
36 views

Node voltage analysis of PMOS charge pump

Why is it that the voltages at nodes A and B are 3.7 V and 7.4 V respectively at a certain phase, i.e phase 1? And just the ...
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4answers
388 views

How many volts can a 1 Watt 8 ohm speaker take?

I am working on an Arduino project and the sound is too low because the output pins on my Arduino UNO is only 40 mA. I can hook up an NPN transistor to amplify the sound, but I don't want to blow the ...
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1answer
39 views

How to switch power supply between two sensors

I have two ultrasonic sensors, when one sensor acts as a transmitter other acts a receiver and vice-versa. How can I supply power for the 1st sensor for 20 microseconds and switch the power source ...
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2answers
85 views

voltage drop alternative to resistor [duplicate]

My application requires me to drop voltage from 12v to 6v or any other lower voltage. I have used resistors but they are not efficient for prolonged use as they tend to heat up and burn my fuse. I ...
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0answers
67 views

Potential difference in a capacitor

As I simulated the circuit below, it shows that the potential difference across Cx is the amount of potential being stored on C3 and C4 during charging phase. How do we get the potential difference of ...
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1answer
35 views

Finding Equivalent Thevenin Resistence

For the following circuit: I'm solving for the Rth at node 2. In the solution guide, it shows that the Rth = (10k || 10k). I don't understand how this is so, by following the resistence equivalent ...
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1answer
66 views

Unregulated AC-DC adaptor voltage response

This is my first post. I'm a long-time computer programmer but new to this field of hobby electronics. I bought a 12V 800mA AC/DC adapter to feed my circuits. Seems it's unregulated since the ...
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1answer
45 views

How can I measure the pressure from my strain gauge?

I bought a strain gauge from RS components, and I want to find out how can I get the pressure from the measured voltage on the strain gauge. I managed to the Wheatstone bridge and supply it with a ...
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1answer
54 views

Minimum AWG of a battery wire

I have a 3.7V one-cell polymer battery 350mAh 25C. It's linked to a board over a 50mm wire. What would be a good AWG diameter to ensure a maximum voltage drop inferior to 2%?
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1answer
60 views

Manuals vs certification plates

If a device manual with a stated model reads 220-240V 50/60 Hz must the certifcation tag match? Is this different on a per country basis? (In this case Germany) For example this manual excerpt: ...
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1answer
36 views

Cutoff and Conducting diodes

Why is D1 considered cutoff and D2 considered conducting ? Note : I am working with constant voltage model where the diode voltage is 0.7v and I need to figure out I and V. Please explain why D1 is ...
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1answer
134 views

Volts and frequency worldwide

If an electrical certification tag reads 220-240V 50/60 Hz can the device be used on both 220V 50 Hz and 240V 60 Hz?
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3answers
118 views

Why do most batteries or circuits use a 12V supply?

I have seen most of the circuit using 12V supply, is there any reason behind this? Is there any reason to choose 12V in all systems like battery-powered devices?
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2answers
85 views

Changing the voltage of a power supply

I have an old laptop power supply which provides 3.5A at 20V. I want to re-purpose this for another project for which I require 3A at 5V. If I cut the output cable I'm assuming I'll find a +20V wire ...
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0answers
30 views

12V/ 10A+ Arduino motor controller [closed]

I have two linear actuators rated at 12V and max 5A (per actuator). I am looking for a dual channel motor controller that can drive these two actuators with an Arduino. Any suggestion regarding a ...
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0answers
27 views

Parameters affecting the performance of a charge pump

A charge pump which can reduce the influence due to threshold voltages, keep low voltage difference between any two electrodes in a transistor, and can be implemented using a low-cost twin-well CMOS ...
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2answers
44 views

Interfacing battery to fpga

Is there any way to interface a battery with voltage range 0-5V to a fpga with ADC range at 3.3V while maintaining full input voltage range i.e 0-5V mapping on 0-3.3V. I have gone through the ...
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2answers
59 views

How to purchase the right transformer for an electronic device [closed]

I just purchased an IP telephone that comes with no power transformer. I think the manufacturer assumes that buyers will be using power over ethernet. On the back of the phone where the power jack ...
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1answer
64 views

Application of charge conservation

I don't know how to start formulating equations or finding equations for this circuit, I have to prove this by mathematical equation. My adviser told me by charge conservation but I don't know how to. ...
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2answers
57 views

Convert a ringing telephone voltage of 90V AC to 3.3V 1000mAh DC current so that it only triggers when the telephone is ringing?

How can I convert and step down a ringing telephone voltage of 90VAC current to 3.3V 1000mAh DC current so that it only triggers when the telephone is ringing? Bridge rectifier? Inductor? Step Down ...
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2answers
91 views

Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

I recently encountered a scenario where I attempted to use a Energizer EN500 modified sine wave inverter to provide power to a Dell 180 watt AC adapter. The circuit powering the inverter was 12 volt, ...
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2answers
68 views

Do batteries have a delay when adjusting to a new load?

So I am creating a battery voltage measure, and it takes a reading both when the battery is in open circuit, and when it is loaded with a 100mA constant current. I have set it up and the reading is ...
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0answers
45 views

Charge conservation

How can I apply the theory of charge conservation for this charge pump circuit. Specifically on the pump circuit. How do I get the charges on the capacitors?
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1answer
91 views

What do you use to connect simple battery holders?

I'm sorry for this very rudimentary question, I'm completely new to this hobby. I need to have a ~30V power source and I want to buy 22 AA batteries and connect them in a series. I intend to use ...
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2answers
66 views

Thermocouple Simulation Test Circuit and Voltage Comparator Circuit

I have a challenge that I would like to share with you. (at least a challenge for me) The resistor R8 (10 turn potentiometer) can be adjusted from ~0 to 1K Ohm to output voltages from 3mv to 30mv. ...
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2answers
94 views

What is the difference between the substitution principle and Thevenin theorem?

The substitution principle (as seen in this book; in italian, sorry) Let A and B be any two part of an electrical network with voltage and current sources and only resistances, connected by ...
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1answer
110 views

How to supply 2 different voltages to a circuit every 2 minutes

For executing a (stress) test scenario, I need to simulate the following behavior on my circuit: for 2 minutes, deliver 11V to the circuit for 2 minutes, deliver 14V to the circuit for 2 minutes, ...
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2answers
1k views

What is the best way to convert 1.8 V to 5 V?

I connected HC-SR04 ultrasonic sensor, to single-board computer BeagleBoard-xM. Trigger pin requires 5 V DC. However, control pins of BeagleBoard-xM can provide only 1.8 V DC. What is the best way to ...
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2answers
49 views

What is launchpad's I2C & SPI voltages?

Does anyone know what voltages TI Launchpad's I2C and SPI run at. I think it is 3v3 from a comment on a post, but can't be sure. Thanks
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0answers
21 views

Internal volts in arduino for percent battery [migrated]

I'm working on a small project that is creating me a headache. I know arduimo (ATmega 328P .... etc. ..) has an internal voltage source code millivolts, but I would like to know how the full source ...
2
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6answers
745 views

Reducing voltage with resistors

I have been looking around for an easy way to convert 12v to 5v. I have seen some people saying that a simple resistor is all that is needed. ...
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4answers
183 views

Can I run 12v car fan on 8v

I am planing to upgrade the radiator fans on my car and I would like to do some modifications to reduce the noise and have them run at lower speed when a curtain temperature is reached and run at full ...
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1answer
45 views

Known voltage/current source

I am working on an EVM for an electricity meter. Its manual says the EVM requires a known voltage and current source for the calibration. I bought a power supply and measure the output of the PSU by ...
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3answers
212 views

What prevents abrupt voltage change in a circuit with a capacitor?

Let's say we have a simple circuit consisting of a power supply and a resistor, and currently the input voltage is 0V. We now apply a voltage of 5V to the circuit (like a step increase - ...
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1answer
38 views

Different Vcc and input voltage into flip flop

I am building an LED matrix using flip-flops. I will have 128 rows in the matrix, so I am using 16 octal flip-flops, where all inputs to are shared and come from a microcontroller, which uses 5V ...
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2answers
72 views

How to customize the 'write' to instrument?

I'm communicating with Power Supply RIGOL DP832A via Ethernet. ...
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2answers
65 views

How to reduce voltage of a dynamo to 5 volts

A friend and I are going to make a bike-powered charger. There is a video of KipKay making one. But he uses a 12 volt 6 watt dynamo and there is a schematic that he follows to lower it to 5 volts. Can ...
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votes
1answer
62 views

Supply voltage drops AFTER connecting to device [closed]

I have a 19V 2.1 amp (power mentioned is 45 watt) laptop adapter connected to a 19V 2 amp laptop (in description power mentioned 10.2 watt). When I plug the adapter, the multimeter shows the rated ...
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0answers
33 views

Hot Tub Blown fuses [migrated]

I recently had a power outage that blew one of our air conditioning fuses (which we were able to fix) and one of the fuses (out of two) in our spa equipment service control board. Next to both fuse ...
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1answer
86 views

What kind of amplifier to use?

I'm driving an LED from the output of an optocoupler. Example, I'm trying to find surface errors on a sheet. When the sheet is flat the average output voltage is around 2.45V (based on the circuitry I ...
3
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4answers
143 views

Trying to understand negative voltages

If I were to have an IC (Just some standard 5v microcontroller), and for some reason I only had a -5v supply, could I technically connect -5v of the supply to the GND pin of the micro and the ground ...
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2answers
50 views

PMOS, NMOS length width concept for low power circuit

Why for low power consumption width of NMOS taken same as length of feature and Width of PMOS taken as 2.5 times width of NMOS ? e.g for feature size 180n width of NMOS 180n and width of PMOS 450n. Is ...
2
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8answers
588 views

How do households get their power?

I'm a little confused about the whole kilowatt hour thing. I get its 1000 watts in 1 hour but I don't get how you figure out how much voltage and current is running through the house. I did a little ...
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0answers
66 views

Why is there a voltage spike when Arduino resets?

An Arduino is powered by a AC/DC converter and reads voltage from a sensor. Why does the voltage reading spikes up really high whenever Arduino is reset? In this scenario, Arduino is used as a ...
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2answers
147 views

How can two steel balls with same amount of charge be at different voltages?

Maybe this is the most fundamental question, but still it eludes me. Is it possible for two balls each containing 1 Coulomb of charge be at different voltage levels, say 1V and 2V relative to a ...
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2answers
92 views

Why is a binary system used instead of decimal system when interpreting voltages? [duplicate]

In physical computing, binary is used to perform calculations. Typically, 1 corresponds to high voltage (3V-5V), and 0 corresponds to low voltage (0V-2V). Perhaps it is not feasible due to the ...
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1answer
86 views

Don't understand spec sheet

I'm planning to buy a photo-interrupter, and I had a look at the spec sheet, but I didn't see much on the current/voltage of the device. I was thinking that it could run on 20mA, but I am confused ...
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1answer
60 views

Measure 208v single phase with Current Transformer

I have a single phase 208v circuit that I want to measure the amps on. What is the proper way to measure the amps? This is for a connection with 2 hots and a ground wire, no neutral coming from a ...