Where power is a primary concern for the design under discussion. Use the "low-power" tag when that applies.

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0
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1answer
63 views

milliwatt-hour meter [on hold]

I am looking for a way to design something that can tell me the cumulative power draw of a circuit -- the same concept as a Kill-a-Watt, but measuring mWh rather than KWh. An added bonus would be the ...
5
votes
2answers
194 views

PCB's and designing power connections

I've designed a few PCB's now, but never put much thought into good practices. They were small boards and most of the emphasis was put into just making sure everything that needed to be connected was ...
3
votes
2answers
93 views

Switch on computer with microcontroller

I'm making a simple microcontroller based circuit to turn on a computer when certain events are triggered. I am interfacing it using the PCs soft power switch pins on the front panel header: There ...
0
votes
0answers
52 views

Low-pass filtering a 120 volt AC line to remove noise

I have active monitors (speakers) plugged into a 120 V line and they are picking up 120 Hz noise being generated by the TRIACs of the Lutron light dimmers in my house. The dimmers are on different ...
-4
votes
1answer
81 views

Expressing a circuit in the form of block diagram [on hold]

I am doing an electronics project for 12th grade in electronics.This project is about water level controller.I have component list along with the description and I have soldered the circuit as told.I ...
0
votes
2answers
53 views

Singnals, filters and power output

I have couple of questions: A square signal goes through a low pass filter and in the output of a circuit we get a sine. What happens there? Give a scheme? This is really weird, because, from what ...
-1
votes
0answers
14 views

What guage wire/cord do I need for these outdoor lamps? [migrated]

I have two 700 watt outdoor halogen lamps, each connected to a splitter, then back to a power source. Given the distances illustrated below, what gauge cord should I use?
1
vote
4answers
304 views

USB PC Current Limit

USB2.0 specification says a device can draw 500mA. In my new design, I like to build it such that with correct adapter the device can draw 1A. My concern is with equipment out there. I cannot build a ...
0
votes
0answers
48 views

Hotswap used as power prioritizer

I've been trying to use the LTC4228 as a power prioritizer with currents up to 70A. I've chosen NMOS transistors that could fit the application but I'm not able to go above 10A loads (it shuts down ...
1
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2answers
45 views

Calculate the average power dissipation in Joules

I'm self-studying this problem, and it seems that have a problem solving this. The only thing I didn't understand is this solution is how to calculate the average power dissipation. It's never ...
1
vote
2answers
82 views

When a voltage pulse is sent through an open transmission line, what happens to the voltage at the end of the line when the pulse is reflected?

From what I understand, the voltage doubles since the reflected and incident pulses add up. But then why don't all open terminations have double the source voltage since we can consider the voltage ...
0
votes
1answer
42 views

Transfer function for six-pulse controlled rectifier

I need to determine the transfer function for a six-pulse bridge rectifier, implemented with thyristors. More precisely, I need to determine the relationship between the output voltage (pulse) and ...
-2
votes
0answers
34 views

Why should power factor in an LCR circuit be unity, when we know that in that case the power loss in the LCR circuit is going to be maximum? [closed]

It is said that if power factor is unity there is gonna be a huge current in the circuit, which is gonna increase the power loss in the device which is using the LCR circuit. How is this power loss ...
0
votes
1answer
62 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: ...
0
votes
1answer
59 views

Power supply for usb devices

I had a question that I was hoping someone could help with. I am building a cluster of raspberry pis to do research on and I decided the best way to power all the nodes was through micro usbs. (I ...
0
votes
2answers
44 views

Help me about the complex power in circuit analysis?

In circuit analysis, the complex power is S = P + jQ. For the avarage power P, we can use wattmetter to measure P. But how we can measure the reactive power Q in the circuit ?
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votes
2answers
62 views

How to Mount Power Supply to PCB

How can this 5V 3W power supply board be mounted and electrically connected to a custom designed PCB? Or will it be better to get this power supply board instead due to the right angled pins ...
1
vote
1answer
86 views

Using attenuators to damp reflections on transmission line?

I have a 3m long transmission line that transmits a 100ns bipolar square pulse every 200us. At the beginning of the coax cable is a pulsing circuit board, that generates the waveform, then it sends ...
0
votes
0answers
28 views

Average signal power (signals and systems - discrete signal)

I am trying to find the average signal power of some discrete functions. For a finite interval, I can use the formula: ...
0
votes
1answer
22 views

Fixed thermal Trip vs fixed magnetic trip current ratings

I am looking into a series of 2 pole circuit breakers (Sprecher + schuh 's series KTU7 UL489 molded case circuit breakers) and they seems to have 2 ratings, a thermal trip rating and a magnetic trip ...
0
votes
0answers
39 views

2 Transistor 2:1 MUX with negative waveform

My PTL(Pass transistor logic) 2:1 mux show -ve waveform at at some inputs combination ckt and waveform show below: simulations perform at 180nm tech, 250mhz,1.8v power supply. How to cope this ...
1
vote
1answer
135 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?
0
votes
3answers
120 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?
1
vote
1answer
33 views

Checking my understanding of “branch in parallel current” warning

A datasheet for a power connector I was looking at tonight has this warning: Note: Do not branch in parallel current which exceeds the rated current. If branched in parallel, current ...
1
vote
2answers
86 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 ...
0
votes
1answer
25 views

XBee Power Consumption, RX Current and TX Peak Current

I'm trying to find out the max power consumption for an XBee Series 2 2mW module so as to pick out a suitable power supply for the system. The docs state that it has a TX Peak Current of 40 mA and RX ...
0
votes
0answers
53 views

Cranking, Load Dump and Reverse voltage Protection Automotive [closed]

How to protect a Circuit from Load dump, Cranking and reverse Voltage for an Automotive Application. It will be a great help if anyone can share their experiences with the schematic. Here is one ...
0
votes
1answer
32 views

Detecting battery module AVR removal

I am working on a module (based on ATTiny) that will be plugged and unplugged onto a MCU systems. This MCU system powers up the ATtiny module and when this module is removed, the MCU system has to ...
0
votes
2answers
88 views

Power supply for 144 LEDs in parallel?

I appreciate any help as I try to figure this lightbox project. I need to wire up to 144 3V (built-in resistor) LEDs from flickering tea lights (normally battery powered). Not sure how many to wire ...
1
vote
1answer
40 views

Do Cable Connectors/Terminal Blocks impact power requirements?

I am planning on using a bunch of spare ego-T parts to build some mods and was thinking of hooking some AA battery block via some Cable Connectors/Terminal Blocks to an LED, Button and 510 Threaded ...
0
votes
2answers
24 views

ABB S203-C25 25A per line or total

I am completely new to EE. I have ABB S203-C25 curcuit breaker installed. My question is 25A is per line (i.e. total 75, or 25A is total limit)?
2
votes
2answers
62 views

Input voltage for LM4862 audio amplifier

I just started working on an embedded side project that requires me to pump .wav files through headphones. My main microcontroller is a PIC32, and my audio amplifier is an LM4862. For the DAC ...
0
votes
1answer
84 views

Can I use 2uF or 10uF capacitor instead of a 1uF with the LP2951 voltage regulator?

I want to learn to program and use microcontrollers, and therefore I'm setting up a small power supply. The voltage regulator I've selected says I need a 1uF capacitor at the input pin. So my ...
2
votes
3answers
259 views

Why does this current source absorb but not deliver power?

Question (Extracted from a book): Determine the voltage across each current source, the current through each voltage source, and the power delivered or absorbed by each source. Official Answer: ...
0
votes
2answers
45 views

How did I calculate the power for this source?

Let the circuit be: Given that Ix = 5A and Vy = 10V, calculate the power absorbed or delivered by each source. My solution: 10A source delivers 100W (P=UI= (-10 + 20)x10 = 10 x 10 = 100W). ...
0
votes
0answers
34 views

Real world efficiency of a LM3150 Webench DC power supply design?

When designing a DC/DC step down converter with TI Webench with these parameters: Vin min: 11.4 V Vin max: 12.6 V Output : 5.0 V Iout : 8.0 A Ambient temp: 30 ºC Then turn the efficiency knob ...
1
vote
2answers
72 views

Can I use a double insulated power supply with a metal framed sculpture with LEDs

I have built a tree shaped wire framed sculpture with LED lighting. The LEDs each have a positive supply to the anode via an insulated wire and resistor, and the cathodes are connected directly to the ...
-2
votes
1answer
48 views

Electrical consumption by the cellular phone [closed]

After the invention of cellular phone technology, how much more electricity is being use by cellular phones in the United States?
2
votes
1answer
112 views

USB 5v power filtering

I am creating a pcb that splits a single USB input into 3 outputs (one with data/power carried, two with just power), and I was wondering what is the best way to reduce noise on the power line as this ...
0
votes
1answer
60 views

Can my dead Lead Acid batteries be reused?

I have two 12V 4.5Ah sealed Lead Acid batteries from an old electric scooter. The scooter is a decade old, and packed up a few months after purchase. The batteries were literally left as is for ...
0
votes
2answers
56 views

Powering SMD 5050 strip via LM2596 DC/DC converter

I decided not to order / use the power supply typically sold with SMD 5050 kits. I heard a lot of explosion stories regarding those dodgy stuff. I want to make my own (power supply to drive SMD 5050. ...
1
vote
2answers
77 views

Any good method for the power down sequence?

In my circuit, +12V would be supplied by an external power source. After two regulators, two more voltage source(+5V and +3.3V) would be produced and supply power to adc AD7682.Because of the maximum ...
0
votes
1answer
64 views

Safe line IR laser which will be seen from 15 meters by camera module

What characteristics (wavelength, mW) IR line laser should have to: be seen by camera module from 15 meters outdoor in day-light too safe for eyes line as big as possible thickness of line should ...
0
votes
2answers
119 views

How to select value of resistor to dicharge a capacitor? [duplicate]

How to set the value of bleeder resistor to dicharge 10kV capacitor, which has capacitance value of \$5\mu\$F?
0
votes
2answers
57 views

Best place for a switch when using an always connected power adapter

I recently bought this: http://smile.amazon.com/gp/product/B00II1MN5I and am planning on using it for under cabinet lighting in the kitchen. ...
-2
votes
0answers
42 views

Can I power my multi-effect processor with a nintendo adapter? [duplicate]

I've bought a multi-effect processor called "ZOOM PLAYER 3030". The vendor gave me the wrong AC adapter, so I can't use it. He told me that he will give me the wright adapter if I visit him next ...
1
vote
1answer
71 views

Single phase energy meter measurement

In a single phase meter measurement, the power is being measured by using the instantaneous power which is p(t) = v(t) * i(t). But as we need to sample the voltage and current to get the power, hence ...
0
votes
1answer
30 views

Is it advisable to try to discover a place to make a ground connection on a board with a separate AC power supply?

I am building a device consisting of a microcontroller (an Arduino mini) attached to various output devices, which will be triggered using a wireless doorbell receiver. The receiver is a single board ...
0
votes
2answers
53 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 ...
0
votes
2answers
66 views

Is it possible to power an Arduino Uno with a Raspberry Pi?

I have an Arduino Uno and a Raspberry Pi that I'm using to control some LEDs in a computer case. Power is coming from a Molex connector from the computer's PSU. I want to place the Arduino and the Pi ...