Questions tagged [power]

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

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40 views

Push on long push off button circuit

I want to design something like this: There is a button, an input pin, an output pin, a voltage input, and a voltage output. If the button is pressed once while the device is off, it won't do anything....
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1answer
36 views

Practical High Current Transistor Connections

I'm designing a power supply with n+1 redundancy implemented with MOSFETs and an OR-ing FET controller. The power supplies are each rated for 35.7A output at 28V (TDK-Lambda CPFE1000FI28) and ...
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Distributed Computing not working in PowerWorld Simulator21

Not sure whether to post this here or in another part of Stack Exchange, PowerWorld itself is used widely in analyzing large scale power grids. I am trying to run a contingency analysis in PowerWorld ...
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28 views

Power supply circuit for two devices

I need to split the power from an AC/DC converter to two devices. The converter I have takes an AC input of 100 to 240V and outputs 48VDC and 30W power. I have one device that needs 48V and 30W and ...
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38 views

ATX Power Supply Pin Material? (gold or tin)

I'm planning to use an ATX power supply to power a small set of 12v devices. I've read plenty of guides about adapting ATX -> bench supply, but I can't seem to find any mention of the connector ...
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1answer
69 views

How to drop the voltage of a power supply?

I have a DC power supply which outputs 21V 2.2A. I want to use it to charge a car battery so I need to get the voltage down to 14V. I have a 3.9Ohm 100W resistor but am am I correct that that would ...
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1answer
36 views

Running AT90USB646/Atmega32u4 between 3.3V and 5V

I'm working on a battery powered project that will need the AT90USB646 µC. From the data sheet, I know it can take from 2.7V to 5.5V at 8MHz. However, apparently, lower voltages reduce power ...
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1answer
35 views

Preventing Raspberry Pi Zero from rebooting due to inrush when device plugged in

I have a Raspberry Pi Zero 1.3 and a standard USB OTG unpowered hub. When I plug in certain USB devices, the RPi reboots instantly. I believe this is due to "inrush": https://www.raspberrypi....
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2answers
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Building a power strip from scratch

I'm considering building my own power strip for multiple different reasons. I've been trying to research these, but haven't found much information. I obviously know what makes up a power strip, but I'...
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3answers
58 views

Which cable connection will result in a greater loss of power?

I know that running a power cable (the cable is carrying 5V DC, I plug in an AC to DC converter to the mains) that is, for example, 50m will cause losses in the power output. So if you measure at the ...
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1-2 second home power loss: some circuits stay powered - computer doesn't turn off. How is this possible?

We've been having some local power outages which last for about 1-2 seconds and maybe at times are only 500ms. I've noticed that we have two computers which stay powered and I'm trying to figure out ...
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1answer
122 views

Powering opamp from unregulated DC-DC Converter?

When using one of those unregulated, isolated DC-DC bricks (its output voltage can be as much as a few volts higher than its rating and varies with load) to power an opamp is a voltage regulator a ...
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51 views

Safety when creating electronics enclosure

I'm designing an electronics enclosure to be placed in series with the power cord for a device for control purposes and would like to know safest methods to do power breakouts within the plastic box. ...
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1answer
102 views

Power supply problem, what is the correct solution?

My result is "No" because the DC voltage is around 14.86 v and the ripple voltage is around 9.9 volts but I'm not convinced about the result especially for the ripple voltage. Does anybody ...
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1answer
29 views

Power loss while AC motor is regenerating? [closed]

You have an elevator raised and lowered by an asynchronous AC motor controlled by a VFD, which is powered by a central AC power supply. When the elevator is lowering, the motor regenerates the power ...
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1answer
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Programmable routing of VCC and GND (up to 500mA)

So... I'm designing a kind of retro CPU testbed (Z80, 6502...), akin to a generic programmer such as the xgecu. I have an Atmega2560 as my microcontroller, and a 40 pin ZIF socket. All ZIF pins are ...
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41 views

How do VA and W ratings of UPS supplies compare with mAh ratings for power banks?

I'm trying to figure out how to power a few devices during power outages. I've looked into UPS devices and also portable phone power banks. My biggest problem is how to compare the devices, apples-...
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3answers
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Need assistance to understand Power and Ohm's Law

Hello I'm looking at a light bar on a vehicle and the specifications say it draws 7.5A at 9-32V and the light bar says it has 36 x 5 Watt LED lights which would make a total of 180 Watts that this ...
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1answer
40 views

Op inverting amplefier circuit

i am using the LM741 amplefier i want to invert a negative voltage (-10V) to positive voltage (1V), my problem is : i dont get the 1v DC at the output. i get an ac signal at my oscilliscope. and i ...
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1answer
68 views

How do I wire this switching power supply

https://www.ebay.co.uk/itm/124258506002 How do I wire this power supply? It doesn't seem to have any connections and in my mind, it needs two for mains voltage, 2 for 12v out.
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Why is this 240V / 20A motor labelled 3HP?

Here's the motor badge: As far as I know, 115 V x 40 A = 230 V x 20 A = 4600 watts which is equivalent to ~6.2 HP, all presumably @ full load. So what does the "3 HP" mean? I know that in ...
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1answer
72 views

Power monitoring dificulties using ACS71020 30A SPI and PSoC 5lp

I'm currently developing a board for my dissertation that should monitor voltage, current and power consumption of a given load. For that purpose i chose to use the Alegro chip ACS71020, the one i ...
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31 views

Robotics Dual Battery System

Background: I'm designing a general purpose robotics controller. The controller is split into two boards, a power board, and a computation / data handling board. The controller is intended to be ...
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Buck converter synchronous

I am building a buck converter synchronous, input 24 V output 1,5 -10 V 20 Amp; with an IR2184 driver that has become a drivers destroyer, this one gets very hot and breaks down. The PWM signal comes ...
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2answers
56 views

Mechanical to electrical power conversion calculations [closed]

I'm working on an electrical power generation project , where the prime mover's shaft rotation speed is variable (for example a wind turbine). We have an initial guess at the optimal speed and torque ...
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5answers
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How to safely power a large LED strip project

I'm making an LED matrix with a board and 4X WS2811 strips (5 m length, 150 LEDs). Each strip is 45 W, takes 12 V and is 3.75 A. I have connected them in series and injected a 12 V, 60 W/5 A adapter ...
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60 views

Divide by 2 for “wasted spark” motorcycle rev counter input [migrated]

My motorcycle just got an upgraded ignition timing method. This new method fires the spark plugs twice each cycle which in turn increases the RPM * 2 according to the tachometer. Is there a way to ...
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Unreadable flashdisk / ERROR and RAW format on Windows 10 [migrated]

I'm a newbie and I want to ask.. When I insert FD into my PC, it is illegible and always format. and FD in RAW format, when I format from CMD a notification like this occurs : when chkdsk / R F: ...
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3answers
108 views

Using a 9V battery instead of a DC power supply

I have a DC power adapter that has the following specs: Input Voltage: 100-240V AC, 50-60Hz, 0.5A Output Voltage: 9V DC, 1.5A I am interested in taking a 9V ...
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1answer
41 views

Need Help on DC Jack and MOSFET Functionality Circuit

I'm trying to build a specific DC Jack that is supplying 24V power. The main feature of it is there is no voltage in the VCC pin in the jack until a barrel is connected to it. So the VCC pin only gets ...
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35 views

Switching battery and main power supply

I have Li-ion Battery (12.6V) and 15V power supply, also DC-DC buck converter set to 12.6V as charger for Li-ion Battery. My load can take both 12.6V and 15V. I want to use Li-ion battery as power ...
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Multipole Network Power Calculation

How do we calculate the DC power consumption of a multipole resistive network, if we know the currents of all the poles (pins) and all the voltages between the poles? Let's say for example, that we ...
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1answer
34 views

how to put Atmega328 to sleep mode and wake it up without button,without WDT

iam building a IR based faucet i need to include battery backup here iam using only ATmega328 with crystal and capacitor, iam not using regulator or LED ...i need to increase the battey life iam using ...
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1answer
67 views

Need help identifying components! Hardware

So recently I have come across a schematic diagram with pictures, but some of the parts in the build (A quadruped robot, more information in the hackaday link below) are not in the schematic, and I ...
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1answer
52 views

Derivation of energy in capacitor

While searching for something totally unrelated to this, I came a cross a website that derived it in this fashion: the instanteous power in a capacitor is given by $$p_c= v_c(t)\cdot i_c$$ since $$i_c(...
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1answer
31 views

can I hard wire the output power of a eu solar inverter to a us breaker panel/

I have a hybrid solar Easun inverter/charger rated power 3000va/2400w 230vac 50/60hz self sensing. The unit is set up with single EU 230v self sensing 50/60hz input to charge battery and the output is ...
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48 views

Need help wiring a power supply to UK rocker switch

I'm looking to wire up the UK rocker switch/plug to a power supply. There's a black cable coming from the live & a red one coming from Neutral. I don't want to blow anything up so I'm looking for ...
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1answer
52 views

How do I connect this crane machine motherboard to my power supply? What connectors do I need for the power supply header pins?

I bought a DIY crane machine online and I'm trying to work out how to set up the power supply. The power supply they provided in the photos looks setup like this, where elements are screwed into the ...
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2answers
39 views

ESD Protection Diode: I/O Protection on VBUS Line instead?

I'm looking at a few 4 channel ESD diodes for my USB circuit, specifically the ESD0524P and the PESD2ETH-X. For my circuit, I only need 2 channels, D+, D-, and a channel for VBUS. Looking at these two ...
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2answers
84 views

Does an AC lightswitch dimmer/light combination consume the same power no matter its setting?

I'm hoping to resolve an argument here. Someone else said that lightswitch dimmers don't actually cut back on power used, since they're just resistors and just divert the power to additional heat. I ...
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27 views

Will this power selection, soft power latching, buck cicuit work?

I designed power part of my circuit, but don't know will it work as I expected. This circuit should auto switch power between VBUS and VBAT (VBUS preferred), after power selection it should step-down ...
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1answer
76 views

Use capacitor to turn on led when power is off

I have two LEDs in the circuit green LED turn on when the switch is on also capacitor is charged, Now I want to turn on the red LED by using capacitor when the switch goes off. Please help me, how I ...
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1answer
73 views

High Voltage Safety Questions

I'm working on a project that uses 1700VDC provided from a 220V:1200V isolated toroidal transformer, bridge rectifier and filter cap. I have no experience with high voltages, so I'd like to ask you ...
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65 views

How does a Philips Hue Tap transmit a radio signal without a battery?

The Philips Hue Tap is a remote control for a Philips Hue lighting system. The buttons can be configured to trigger some action on the Hue bridge, such as turning lights on in a particular room. The ...
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41 views

Derivation of this mho circle equation?

I'm picking through Protective Relaying Principles and Applications by Blackburn and Domin (4th ed), and am currently figuring out distance relaying. Intuitively, I understand their operation. However,...
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2k views

Why would a “power switch” be designed this way?

This unit is an ARINC 429 bus analyzer, manufacturer "AIT" (Aircraft Interface Technologies), model "429A". Yes, it's confusing. Rated 115VAC/3A/60-440Hz. It has a 250W SMPS inside ...
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32 views

Type 1 surge protection: parallel or series?

Type 1 surge protection devices (SPDs) are installed at the outside edge of electric service, usually between the power meter and the meter base/socket, and protect the entire house. But how do they ...
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1answer
60 views

How to specify UV high brightness LEDs?

I'm trying to find high brightness UV LEDs appropriate for this project: https://www.instructables.com/id/UV-LED-Exposure-Box/ which includes: "The most critical parts of this project are the UV ...
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2answers
45 views

Li-Ion Battery Protection Circuit: Do I tie BAT— to Ground?

I'm designing a circuit that integrates both USB Power and a Li-Ion battery when USB is unplugged. For the battery charging/protection/boost part, I'm following the schematic given in this ...
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38 views

Power supply sensing circuit/Mosfet

I am with EE background and recently I had question in interview regarding “How to sense/know when device needs power?”. So, basically I had a good interview on different topics and one of them was ...

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