# Tagged Questions

65 views

### Measuring Voltage and Curent Simultaneously with Probe?

I have very little experience with electricity, but I am doing a project in which I need to measure power output of solar cells. I am currently using this: ...
296 views

### Can electric bulbs be powered by connecting the negative terminal to earth?

I have a very fundamental question, will an electric bulb glow with one point connected to the positive terminal of the electric line and the other point to earth? In my school some 10 years back I ...
110 views

### Paralleling of 2 power supplies with different voltages

I have 2 full bridge dc-dc converter from 12 to nearly 170 volts. each one are designed to 250 watts... I am designing the transformers and is very complicated to make exactly equals by homemade and ...
77 views

### Why does the current still increase in CC mode in a power supply?

I use a power supply where the specs shown here: http://electronics123.net/amazon/datasheet/ps613u.pdf I want to use it as a current source but the current is not stable in cc mode. Here what I ...
71 views

### Can I use the following power supply as a constant fixed current source?

Might sound silly for many of all but is this device's knob for the current for obtaining constant current or limiting the max current? Can I use this Dc power supply to obtain a constant current ...
80 views

### High Current Battery Power

I'm looking to power about 10m of RGB LED strips (60 LEDs / meter) from a battery of some sort. Max current draw for the 10m run is 36A @ 5V. My initial thought was to get a ~12V RC Car battery and ...
78 views

### Determining resistance per load with only power and volts

I have a extra credit problem in my class and I'm slightly stumped as to where to go next after I determine the It, Et and Rt. I am starting with a total power of 2 watts and 32 volts. I know to get ...
425 views

### Determine with Arduino if 220V AC power is on or off

What would be ways to determine with example with Arduino, is current 220V AC socket on or off state? Any other than using relay (noisy) or current sensing sensor (too big)?
204 views

### Why does the voltage changes in this simple circuit?

I'm beginning to learn electronics, and there's something I just can't grasp. I was told that a high resistance in a circuit would lead to a smaller current passing through it, but the voltage would ...
154 views

### about power, voltage and current

I started to learn some basic idea on circuit building last semester. I got some chance to build up some simple circuit to construct some cooling system (with fan and some other IC). I thought I ...
293 views

### Why is it bad to mix new and old batteries?

I've seen warnings that it's bad to mix new and old batteries -- why? Is it a matter of a battery's age or a battery's voltage/current (remaining)?
75 views

### Kilowatt hour from Complex power

How can I calculate Kilowatt Hours from: Complex Power = 1,5 kVA Electrical current consumption = 10 A It's three-phase electric power.
230 views

### Higher current LED driver for persistence of vision display

Project needs We need an inexpensive LED driver IC that: Can source or sink at least 15mA/LED Has an SPI-like interface (not I2C) Has a separate latch pin Has at least 256 grayscale intensities ...
196 views

### Vacuum cleaner power rating does not match line voltage and current rating

I have a vacuum cleaner on which is proudly written: 12.0 Amps 1300 W Assuming a 120 V (RMS) power supply, how would the power consumption of the vacuum cleaner be calculated given the 12.0 ...
70 views

### Frequency Scaling and current draw

I am trying to power a RPi of 4 AA's, and my mobile power device can only output limited current (500mA), but I can underpower my RPi by frequency scaling. Is frequency scaling and current draw a ...
52 views

### Values in a solar array

My dad had just bought a solar array of 4kW together with an inverter, a kaco powador 4400. The array is now running and generating electricity. I am trying to understand how it all works, but ...
123 views

### Why does my bluetooth dongle use more current when paired then when idle?

I have a bluetooth dongle which is connected through USB to my PC. I wanted to measure the current drawn and hence I connected an ammeter in series with the 5V line and am measuring the current. I ...
283 views

### Is there any way to boost DC current?

I'm designing a circuit to charge mobile battery. My source is giving a DC output of 15V, 100mA, whereas I need DC 6V, 450mA for charging. Is there any way to boost DC current?
90 views

### Can I power an interactive 'live' wall with copper tape and a 15v ac adapter?

I'm working on a class project to make a living wall with LEDs, paint, and copper tape spiral magnet speakers. I have a 15v ac adapter to power the wall and copper tape to connect the LEDs in parallel ...
249 views

### Power management for a 5V 12A load

I need to deal with a peak load at 5VDC and about 11.25A but I'm not sure how to manage this. I have 5 individual loads of 2.25A and small loads from an MCU and some LEDs all of which should fit into ...
116 views

### loudness of speaker [closed]

Given a speaker is 30 watts, which is louder, the one with higher current through it or the one with higher voltage across it. Lets say both speaker has variable impedance (so we can vary both current ...
111 views

### Power and energy measurment for embedded system -help needed

I am trying to measure the power consumption of a low power embedded system. As the embedded system consumes current in random pulses from the battery pack, I am using an oscilloscope to analyze the ...
2k views

### How to calculate Power Rating for Zero Ohm Resistors?

Base on my earlier question, since there supposed to be zero voltage (V=IR) drop across a 0Î© resistor, how do we select the power rating of such component? Example, let say I were to connect a zero ...
462 views

### Are capacitors and inductors capable of absorbing positive power?

A resistor is capable of absorbing positive power. Why wouldn't this be true for capacitors and inductors?
167 views

### Getting high current pulses from a low current source?

I need to switch on/off a coil draining a high current (close to 1A) during intermittent small intervals (500 ms). Unfortunately, my source is only capable of 100mA in small bursts (say 100 ms). So, ...
163 views

### Current/milliamp rating of adapter versus device requirement [duplicate]

Possible Duplicate: Choosing power supply, how to get the voltage and current ratings? My DC adapter for a cordless mike has broken It' ratings are: Input 230-240V ~ 50Hz 30mA Output 20V ...
208 views

### How to determine USB hub speed type?

I'm developing a driver for multiple USB speeds and according to the universal specification, I'm allowed to draw a greater amount of current from a USB 3.0 hub than the other versions. Is there a ...
407 views

### Blowing a Fuse to Permanently Disable Functionality

Certain electrical designs require permanently disabling hardware functionality on the fly. Sending an overcurrent to a weak fuse may be a method for accomplishing this, breaking the circuit in a ...
556 views

### Limiting the short circuit current of a power supply

I'm using a repurposed ATX power supply for my hobby projects since it's got 3.3/Â±5/Â±12 outputs, all of which are really convenient. But one thing I didn't really think about until I slipped my probes ...
241 views

### How to best estimate power consumption for a system?

I'm not an engineer, I'm a software guy getting into hardware - so bear with my ignorance! I'm in the process of building a system with many components (e.g. a computer, many sensors, a few motors, a ...
385 views

### about power supply on what length of copper wire we should use

Could you help me on the equivalent current of three phase alternating current having 400v( volt ), 530 kw power and the available cross-sectional area of a copper wire, its length 350 m for carring ...
1k views

### What happens if usage current exceeds DC adapter current rating?

I have a DC adapter 5 V, 350 mA. I'm using this adapter to be fed into a 3.3 V regulator which powers up my bluetooth device and a few LEDs. My question is: what happens if I source 300 mA from this ...
1k views

### How much current does a microSD card use?

I am building a uC board which uses an 3.3V microSD card as a storage medium. To design the switching power supply for the 3.3V, I have to know what my total current draw from the supply will be. I ...
261 views

### Understanding electric power

While in a mood to purchase a Peltier strip, I visited the amazon page which stated the specs of a Peltier thermoelectric cooler, one stated 12 V and 92 W and other one stated 12 V and some 77 W. As ...
359 views

### Measuring power/current

I was wondering if someone knew how to measure power/current and then interface it to a micro controller to store the data onto some external memory. I basically want to measure the power a device ...
366 views

### Is it possible to calculate effective value of a signal from its average value?

I have a signal which I want to calculate its effective value. The signal is a voltage value read on a 33.3m$\Omega$ resistor connected series to a 220V AC power line. My aim is to calculate the ...
379 views

### Help with current draw in a circuit [duplicate]

Possible Duplicate: Limiting current from a 5v power supply I'm trying to build a DIY Xbox Kinect adapter to be able to plug the Kinect into my computer, but I'm getting some shaky ...
1k views

### Why does electric arc in a switch prefer a curved path over a straight path?

Recently I found this video of a 500 kilovolts line being opened under load. When the switch contacts are pulled apart an electric arc predictably starts. While the contacts are close to each other ...
395 views

### Have I got these simple power calculations right? (for battery consumption)

Lets say an ideal AA battery I have provides 2.0 Watt hours. It could be different, just a quick search for this example. My very simple load is the battery connected to a 5mm LED. The LED has a ...
4k views

### How to carry high current on PCB

I need to pass high current on some part of my circuit. I used an online PCB track width calculator to see that required track width is about 5mm and minimum clearance is 1mm, which makes it about 7mm ...
285 views

### Shunt resistor specifications do not contain thermal resistance data. How come?

I'm looking at the specifications of an ohmite shunt resistor: http://www.ohmite.com/catalog/pdf/10_series.pdf It is a 0.005 ohm resistor, rated at 2,3,5 and 7 Watts (4 different parts in the same ...
226 views

### Current sharing controller

We want to implement current sharing from two supplies on our PCB. There are dedicated ICs to implement this functionality, but we could only find UCC39002 from TI. How come no other manufacturer ...
832 views

### Trying to understand the relationship between voltage, current, and power

Please forgive this ultra-noob question, but I'm a bit confused. I've been reading about how neither voltage nor current alone constitute power in a DC circuit. Instead, power is a combination of both ...
405 views

### How can I design my FPGA power supply if I don't know how it will be used exactly?

I'm designing a little dev board for FPGA experimentation using the Cyclone IV EP4CE10 but I am having a bit of trouble estimating the power requirements. I understand this depends almost completely ...