A measure of the overall effectiveness of a system. For example, in power conversion, it would be the ratio of output power to input power.

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36 views

How to classify devices into photodiodes, photodetectors and photocells?

Is there a clear differentiation between the three? For example in terms of efficiency (induced current/incident power)?
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125 views

Practical Approach for getting maximum Power from a DC motor

Theoretically, a DC Machine achieves its maximum Power when back emf is equal to half the applied voltage. Why this condition is not realized in practice ? What is the Practical Approach for getting ...
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4answers
115 views

Why more, smaller transistors increase power efficiency?

Transistors, bjt, MOSFETs OK got it. More transistors = better computing got it. But compressing the transistors closer to each in my mind only helps reduce the physical dimensions. So does a CPU or ...
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2answers
65 views

Switching regulator efficiency TI LM2678 - measured vs. datasheet

I'm working with a TI LM2678-ADJ regulator (granted, on a breadboard) to power a 40" led strip. Trying to figure out why the measured efficiency is about ~15% lower than what the charts in the ...
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3answers
91 views

Light dimming regulator circuit

Here in this circuit, We have the load connected to a diac and triac circuit along with a variable resistance and a capacitor. When the circuit operation begins initially, the energy is stored in ...
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1answer
50 views

acknowledgment size for STOP-AND-WAIT protocol

I looked frame size range calculation for stop-and-wait protocol post but I have a similar (?) question. The question states. A channel has a transmission speed of 10 kbps. The transmitted frames are ...
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2answers
136 views

Most efficient way to generate 3-4 volts from less than 0.5 to 1.5 volts

I am looking for a way to convert power from a 1 farad supercapacitor charged by a solar cell into enough voltage to power an LED. The supercapacitor will contain up to 2 volts from the solar cell. I ...
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1answer
65 views

Measuring Li-Ion Battery voltage during charging/discharging

I am supposed to measure a Li-Ion Battery cell's energy efficiency. For this purpose i have built up the apparatus setup which charges and discharges the battery cell to calculate its energy. One ...
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1answer
39 views

Energy efficiency of Li-Ion Battery

My question is that does the energy efficiency for Li-Ion battery varies for different C rates ? For e.g if a battery is charged and discharged at a lower C rate, would it's energy efficiency would be ...
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1answer
160 views

PWM motor heating

Every man and his dog are controlling DC motors with PWM. Nowadays microprocessors are popular and offer more flexibility than 555 timers and general mixed signal analog electronic. The song remains ...
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2answers
59 views

Transformers and Electric power Ltspice

i was looking for the Energy conversion efficiency of my circuit in Ltspice, but i find out that my Transformers is giving me strange power values i mean with K = 1 the P1 should be equel to P2 but in ...
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1answer
68 views

Why so different lumen efficiencies between mains and 22V halogen?

I was looking for data about halogen reflectors I just bought. They are 50W, 230V. On the package I read 320 lumen and that looked ridiculous to me, then I found this document by GE: Halogen Lamps ...
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39 views

RC car circuit power optimisation

So... a bit of a long question I'm afraid. For a project, I have to design and build a 4x4 RC car with a few electronic functions. At the minute everything works but the battery (9v) seems to deplete ...
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3answers
117 views

(Ultra)capacitor Series vs. Parallel with (Buck-)boost converter

I've seen that many online schematics for using ultracapacitors as power sources place the ultracaps in series in order to increase the voltage that they can be charged to, lowering the capacitance of ...
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2answers
116 views

What does it says the transconductance efficiency (gm/Id) in an amplifier?

I understand the concept of the transconductance but it's not clear what does the transconductance efficiency (gm/Id) mean. Since gm is the variation of Id to the Vgs or vin voltage... What is the ...
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4answers
92 views

Light effiency or efficacy and watt to heat output

I am on a light forum and there are debates about watt heat output of lights. I'm using my common sense for the debate but can't find the data online to support my ideas. People are thinking that ...
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1answer
85 views

Power effeciency of Zener diode regulator

How to calculate the power efficiency of zener diode regulator? Is it correct to calculate it as the ratio of power delivered to load to the total power drawn from input source? If I am correct, ...
3
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1answer
86 views

Maximum output and efficiency for a simple transistor based amplifier circuit

1. Question What is the maximum output over \$R_L\$ and the maximum efficiency \$\eta\$ for the amplifier circuit shown below: Below you will find my solution. Is this done correctly? What would ...
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4answers
269 views

Switch Mode Alternative to LM7805/LM7905

I am attempting to design a dual rail power supply PCB for a university project. There are a number of restrictions - namely that it maintains > 80% efficiency regardless of the current draw. I was ...
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1answer
50 views

How to interpret step-up output current with respect to input/output voltage

I have a Pololu 12V step-up converter (U3V12F12) that I'm powering with a 3.7V 6600mAh lipo battery. The idea was to use it to power a dev board that requires a 12V input. The dev board draws about ...
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1answer
81 views

LED array at high current or high voltage?

Is it more efficient to drive LEDs at a high current and low voltage, than a lower current and high voltage? I'm in a situation where I have to design an LED driver for a custom CoB emitter, so can ...
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2answers
93 views

Definition of antenna efficiency

I have two definitions for antenna efficiency: \$ \varepsilon = \dfrac{P_{rad}}{P_{in}}\$ and \$ \varepsilon = \dfrac{R_{rad}}{R_{rad} + R_{ohm}}\$ Coming from physics, I was wondering if there is ...
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1answer
63 views

2x50w stereo vs 100w mono amplifier efficiency

Which is better for efficiency. mono 100w amplifier or stereo 2x50w It is important because I'am building a portable speaker and it is really important for me to use little power. Also which ...
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2answers
114 views

Powering nichrome, possible to do it with AC?

I am working on making a little nichrome-tipped pen for wax welding and planning to use a benchtop supply to provide the small amounts of DC needed to heat up the wire. Figuring out the right power ...
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2answers
377 views

LEDs and External Quantum Efficiency (EQE), how to find Light Output Power with test results? How to find power?

I'll try explain everything as clearly as I can as it's slightly complicated. I really need help as I'm quite new to this kind of experiment and work so any help would be extremely appreciated. I did ...
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1answer
176 views

Class J RF Power Amplifier

What is a Class-J Amplifier configuration? Does it work in a push-pull configuration similar to an A/B? How is it physically different to an A/B? Where can I see a basic schematic? I have read ...
3
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2answers
166 views

Does transformer humming cause notable waste of energy?

AFAIK transformers hum because alternating magnetic field causes pieces of laminated core to slightly deform and vibrate and that is simply a byprocess of how transformers work. However for the same ...
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1answer
93 views

What is the effect of pulsed discharge on watt hour (Wh) efficiency of lead-acid batteries?

When discharging a (lead-acid) battery you see a voltage increase (volts rise) as soon as the discharge is paused. source: http://uu.diva-portal.org/smash/get/diva2:461718/FULLTEXT01 In the quest ...
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2answers
639 views

Is there a voltage buck converter which also boosts output current?

Application: solar USB charger. I have a 9V solar panel. I use a buck converter circuit to bring it down to 5V before going into the USB battery charging circuit. Exact components: ...
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2answers
270 views

High-efficiency blinking LED circuit

I'm an artist currently working on an installation piece that requires a little more engineering knowledge than I possess. In short, what I'd like to achieve is a 2 LED blinking circuit with battery ...
3
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1answer
191 views

3-phase Brushless Motor - Are Volts and Amps at (X)RPM equal/similar when used as Generator?

If I have a Brushless 3-phase motor that spins at 3000rpm when given 6.0A @ 20v (no load) will it produce 6.0A and 20v (or anywhere close) when used as a generator and spun at 3000rpm?? And i suppose ...
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3answers
222 views

Which low pass frequency filter to configure to measure/calculate DC-DC converter efficiency?

I am measuring the DC-DC converter active power (P in watts) efficiency of a TI (Webench) LM3150 PCB that converts 12 to 5VDC. In the answer of question Measuring precisely the efficiency of a power ...
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3answers
376 views

“Efficiency” of Switching Power Supplies and Theoretical Energy Loss

I have heard that switching power supplies that convert, say, 110 VAC to 12 VDC, are very efficient. I understand that the power transistor that is regulating voltage is either on or off and spends ...
0
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1answer
68 views

Rechargeable battery configuration for 5V

I have 6x 18650 (3.7v) cells. I'm trying to build basic power-bank and wondering what battery configuration would be better for minimizing power loss in voltage regulation/conversion process? Edit: ...
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2answers
70 views

Stepping-down DC voltage (at low current) in the presence of an audio circuit

I'm trying to add a bluetooth audio receiver to an old 12V battery-powered boombox. The receiver board takes 5V and shouldn't draw much current, but I'm trying to understand which type of DC-DC ...
2
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1answer
2k views

What is the charge-discharge (Wh) efficiency for lead acid batteries at different SoC and charge current 10-35A/100Ah C10?

There is a 1996 Sandia study with the title "A study of lead-acid battery efficiency near top-of-charge and the impact on PV system design" for charge and discharge lead-acid battery amp hour [Ah] ...
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1answer
245 views

Wide input voltage range buck converter/circuit to 3.3V 150mA

I am building an appliance that should work in very wide range input voltage: In some scenarios input is 5VAC, in other scenarios it can be 250VAC. It's not a problem to convert AC to DC, then ...
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1answer
187 views

Using diodes to increase efficiency

So I have the schematic below and I am to insert diodes into the circuit to increase the efficiency of the circuit (can only insert diodes, not change the wiring). 'Target' is where I want the power ...
2
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1answer
1k views

DC 5V USB to replace AAA-battery source: down converter

I have a portable lithium battery-powered speaker which takes auxiliary sound input from a single AAA-battery powered pocket radio. The speaker includes a USB port for charging source devices: I ...
2
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1answer
114 views

Inherent exploitability and power state machines

I'm working on understanding power state machines in regard to mobile computing devices. Most of the information on this subject seems to stem from this article. It's not particularly important to the ...
0
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1answer
79 views

Using distribution transformers vs direct connection to primary switch gear

I am trying to learn more about transformers and low voltage electrical distribution. Say you have a medium sized industrial building with a primary switchboard feeding several load centers ...
2
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2answers
1k views

How to calculate a circuits efficiency with the help of LTspice

Note that this is not a question for circuit critique (and lots of things could be said about this circuit) but this circuit is only the base for the discussion of further points. Here it is (an ...
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4answers
785 views

Does a 1 watt 660nm LED put out more radiant flux than a 1 watt 630nm LED?

Given two LED chips consuming same or very similar amounts of DC power, One emitting light peaking at 630nm, The other at 660nm, In terms of output of (but light irrelevant to the sensitivity of ...
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2answers
147 views

Looking for an efficient audio amp circuit

It seems like all the circuits that I find are using outdated and inefficient technology that requires massive heat-sinks at anything beyond headphone levels. Is there any particular reason that there ...
0
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1answer
203 views

Comparison of the efficiency of DC motor current limiting / control methods?

I'm using the wheels and motors of an RC toy car as a simple robotics platform. The car has 2 motors, one drives the back wheels, the other steers the front wheels. The steering motor is stalled by ...
1
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1answer
411 views

Difference between spectral efficiency and bit rate

I am reading articles about error correcting codes, facing to a term "spectral efficiency". Due to the context, I guessed that it means "bit rate", but I wonder are these two terms equivalent or not? ...
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2answers
438 views

Low voltage cut out switching for a 6v input SLA to 5v output circuitry - or alternative ideas

I am currently modifying a wireless video door phone system with remote door release system, for use with a walking frame, for my elderly mother in-law, who lives alone. The 7"monitor runs a 5v 1a DC ...
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1answer
305 views

Internal impedance of Class AB amplifier?

This was a challenge problem that my instructor gave. Here is what a class AB amplifier looks like: I've looked everywhere to find out about internal impedance but I got nothing. This is the ...
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2answers
95 views

If the efficiency of a power supply is 60% when the input power is 25W, what power is delivered to the load

If the efficiency of a power supply is 60% when the input power is 25W, what power is delivered to the load? The formula for this problem is: $$ Efficiency = \frac {Pout}{Pin} \times 100% $$ Where ...
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3answers
3k views

What causes old power supplies to start humming?

I have a number of mains-powered devices that have begun humming (I assume at 50Hz, though I haven't measured it). These include clock radios, a speaker system, a lamp (20W halogen with a transformer ...