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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3answers
41 views

switching with transistor

I want to feed the load by 1.2V source. I want to control it by a voltage changes between 0 to 2 V. I want the switch be closed and feed the load if control voltage is lower than 0.2V and switch be ...
-2
votes
0answers
39 views

Powering circuit from PC's USB port

I am working on a circuit connected to computer with FTDI FT232RL. The circuit have got some op-amps and one MCU. Total power consumption (including FTDI chip) is near by 80 mA /h (at 5V). My ...
3
votes
1answer
73 views

should AC ground (earth) and DC ground be connected?

I have a power supply (AC --> DC) powering an microcontroller and DC electric motors. I also have the same AC powering a speed controller, which feeds to an AC motor. Should I be connecting the ...
0
votes
2answers
57 views

Splicing laptop power brick [on hold]

So today I picked up my laptop's power brick , and it slipped out of my grasp. By reflex I grabbed the power cable, and the already frayed cable gave way at the general area of the power brick. ...
0
votes
3answers
120 views

Generating electricity by moving door handle to produce 3 Watts?

I want to attach a generator to a door handle and have the output charge a battery. My system needs to provide about 3 Watts. A similar question was asked here and I referenced it to get an idea of ...
0
votes
2answers
46 views

FPGA power input isolation

I am working on a design that has at least a dozen FPGA's. In the past I have had an FPGA get damaged by a faulty voltage regulator and short out the supply input to ground.Chasing down which FPGA ...
1
vote
1answer
53 views

Are there any effective estimates for up-rating resistors power capability by adding airflow?

I'm considering using a bank of resistors similar to this: http://www.vishay.com/docs/31842/fve.pdf 300-400 watt "corncob" wirewound resistors. I understand that they can be run over their spec'd ...
0
votes
1answer
39 views

24v power supply to 24v and a Arduino

I have a Power Supply of 24 volts and 2.5A. I need something like that: http://i.imgur.com/z4oJukD.png I need a power supply of 24V and almost 1500mA and another of around 8 volts and 500mA (to ...
0
votes
0answers
28 views

How to calculate the rms value of phasor sinusoid voltage and current while they are represent in frequency domain

My question is just as the title. As rms value is the square root of the integral of the sinusoid function over a period factoring a period, it require time so time domain must be involved if I want ...
0
votes
1answer
52 views

How can the source impedance of an energy source be made zero?

With regards to the Maximum Power Theorem (Princeton.edu); The theorem was originally misunderstood (notably by Joule) to imply that a system consisting of an electric motor driven by a battery ...
0
votes
0answers
27 views

beaglebone black doesn't autoboot when powered over jack or vdd pins

I have a BBB and it works quite well however when I power it over the Barrel connector or over the vdd pins rather then use the usb connection it doesn't automatically boot. When I put the barrel ...
0
votes
1answer
26 views

Little doubt about amplifier current requirement and THD + N

So for this amplifier IC - PAM8403 - which is a 3W + 3W class d, what is the current requirement or in other terms, what will be the load current. I know since this is an audio amplifier, load current ...
2
votes
2answers
96 views

Lithium Battery Charger IC - Charging and Power

Basically, for the circuit I'm making, I need it to be powered by a Lithium battery. Also, this Lithium battery has to be able to be charged via USB. I have seen external chargers for doing so, ...
0
votes
2answers
73 views

How is the ability of a single charger to charge a range of types of mobile phones achieved?

Chargers that are supplied with eg an Android phone can be plugged into some other non-Android type phones and charge them successfully. How is this inter-brand and inter-system charging possible? ...
0
votes
2answers
78 views

How to compute CPU power consumption

I am working on a problem for which I need to know how much power will be consumed on a given CPU as the parameter sizes are increased. The following properties/attributes of the CPU are available: ...
4
votes
4answers
1k views

How to reduce 28 V to 24 V under load?

I need to PWM control six 24 V DC fans with a total load of 10.6 amperes. That's easy, right? Just PWM to a few MOSFETs. However, my system voltage is 28 V. At 28 V I'm out of ...
0
votes
0answers
51 views

Resettable fuses in parallel to limit output current

What are your experiences with this? it is reliable do use PTC smd to limit 15A? the datasheet has a hold value and a trip value. How I choose the values?
-1
votes
2answers
62 views

Motor required for lifting and lowering an awning bar

I believe Electrical Engineering is the best place to ask this question since it concerns engineering and electrical components. I am trying to design a simple system (like a mini garage) that ...
0
votes
1answer
59 views

Newbie Question for power supply [duplicate]

I am sorry if I am asking a basic question here but have no idea what I am talking about :). My question is this: I have a digital camera that requires DC supply. I have a couple of power supplies ...
0
votes
2answers
48 views

Does a Breadboard Compatible DC Barrel Jack Have to be Connected to Positive and Ground to Receive Power from an Outlet?

I am using an Arduino to control an electric lock strike but I don't know how to power the lock with sufficient power. To control the lock from the Arduino, I am using a TIP31 transistor (It is NPN). ...
0
votes
2answers
84 views

What is the name of a circuit that delays powering of another circuit?

I'm having trouble figuring out the name of this circuit. It needs to delay turning "on" a 12V circuit and a 120VAC circuit, after a 5V circuit has been turned on. Example: Turn on 1x power ...
3
votes
2answers
84 views

Why is power reflected when there is an impedance mismatch? [duplicate]

I understand that when there is an impedance mismatch between an output stage, for example from an amplifier, and an input stage, for example, a transducer; power is reflected. I would like to know ...
2
votes
1answer
62 views

Can a toroidal transformer be wired as a common mode choke?

I am looking to build an ac power line conditioner. It was suggested that I use a transformer with dual 6.3v secondaries wired in a common mode choke configuration. This is done by using the in-phase ...
0
votes
1answer
56 views

I have one central 300w power supply running at 5v. How can I split this into 3 equal “ports” that use 20amps each

I have one central 5v 300w power supply. I want to basically split the power among 3 different ports instead of blowing the whole 60 amp load. How can I share the power evenly. Thanks!
3
votes
3answers
288 views

Does it make sense to power multiple 12V devices from one single power source? [closed]

I have a number of devices (External hard disks, switches, router) on my desk. Each ones comes with a own power supply. This leads to a waste of space and a mess with all the cables. Does it make ...
-1
votes
0answers
39 views

What impact has a modulation type on the power at the output of modulator?

Assume that we have a modulator right after a laser diode which is emitting 10mW signal. The modulator has attenuation of 10db. We can easily calculate that at the output of the modulator we'll have ...
1
vote
1answer
69 views

Why does the volatge drop is huge once a load is connected to a generator?

At no load condition the generated voltage at transformer secondary output is 140 V ac. When a 60W resistive load is connected the voltage drops to 27 V ac. The pmg generator rating is 1 KW 415 V and ...
1
vote
2answers
144 views

What are the two gate leads on a thyristor?

I have a simple question: what is the second gate lead on a power thyristor (see the figure below) ? What is it physically attached to ? I understood that the thyristor turns on when you force a ...
0
votes
0answers
50 views

Programmable Power Strip [closed]

I am developing a system that requires I cycle on/off the power-state of each outlet in a power-strip. Does anyone know of a solution that uses either USB or a direct serial-interface to accomplish ...
1
vote
1answer
80 views

Watt/Amp Hour, Watt/Amp Minute Confusion

I am somehow very confused about amp/watt hour and minutes. I am trying to size a battery to see how much load I can get away with before it hits the 50% discharge zone. I plan on connecting a ...
1
vote
2answers
77 views

How much energy does cache memory consume in a modern processor? [closed]

What fraction (on average or range) of total processor energy consumption does the cache subsystem consume in modern processors (say post 2009)?
2
votes
0answers
56 views

LTSpice showing negative transistor power

I'm using LTSpice to model a LC oscillator, driven by a NPN transistor. When I used the power calculating function on the transistor, LTSpice indicated that during part of the cycle the power ...
-1
votes
1answer
65 views

DC-DC power supply module help needed [closed]

I have purchased this little brick (link below) that I though would allow me to input for example 12V DC and output a lower output voltage, for example 5V DC, but I'm now testing it and it seems to ...
1
vote
4answers
132 views

Is Power consumed by a motor under various load conditions constant?

Does a motor (dc /Induction/Synchronous ) consumes more power when operating at higher load than when operating at some lower load? Or power consumption remains constant/same in both cases? What I ...
2
votes
2answers
54 views

How important is td(on), (off) and tr rise/fall. How close do they need to be for a primary side mosfet

I have a power supply with a mosfet on the primary side that has failed. I am attempting to repair it, however, I am having difficulty finding a replacement. The part number svd4n65f and has a td(on) ...
0
votes
0answers
17 views

avgpower in spice for subthreshold leakage

Assume one NMOS transistor is defined in a spice code. There are two sources ...
2
votes
1answer
55 views

why ohmic losses increase with resistance?

Electrical newbie here. I'm trying to get understanding how is resistance involved with power dissipation (ohmic losses, eg. heating). Primarily I'm looking at Electromagnet coil, it says the losses ...
1
vote
1answer
80 views

Converting clock radio from 60 hz to 50 hz

I have an old clock radio that works fine, except for one detail. The clock is made for 60 hz mains but I would like to use it in a country where 50 hz is the standard. As the clock directly relies on ...
0
votes
1answer
52 views

Recirculating currents = Eddy currents?

When people say recirculating currents in the context of a power system, do they mean Eddy currents? I'm just confused about the terminology and I couldn't find anything online to clarify this.
0
votes
0answers
40 views

Can a CAN bus support power over ethernet?

I'd like to reduce my loom for a battery box. Every time I run a line i.e. CAN or low voltage power, it has to be isolated from the master controller which communicates with each slave. I'd like to ...
0
votes
0answers
47 views

USB powered device - best practices

I build a USB powered device prototype with usual protections including esd protection, ferrites, ovp, soft start (inrush limit). I didn't put any current limiting switch as my system doesn't consume ...
0
votes
1answer
61 views

Physically sharing 5v and ground between multiple sensors

I'm using the Adafruit Trinket with two sensors that both need to be connected to power/ground pins (Trinket has one 5v output power and one ground). The final size of a whole thing matters so I ...
1
vote
1answer
82 views

Calculating single phase load from 3 phase power measurements

I need to record kW & kWh for individual phases on a circuit that has a 3 phase power meter that outputs the following data: Total for all three phases: kW kWh kVA kVAr power factor ...
1
vote
2answers
88 views

Electrical Induction, what are the cable limits before it becomes a problem

I have a little hobby that has 3 power cables coming and going (each cable is 12V DC, 7.55 amp max). Now these cables are ridiculously long (approx 5m+) and the equipment having to be mobile is small ...
0
votes
2answers
161 views

Voltage regulator up to 100v? [closed]

I want to make a power supply that outputs 90v DC, and I was looking for a 0...100v voltage regulators, but I don't find any...? How can I achieve this if I can't find them? The input voltage of the ...
1
vote
1answer
54 views

Choosing Correct Switching Power IC for 5v 2A Output from 2S Battery

I am designing a Power Circuitry for a Application that needs to feed 1x Beaglebone Black (5v), 1x Device with 600mA (5v), and 2x XBeePro Modules (3.3v) via a 2S (7.4v 1Ah LiPo) Pack. The Plan ...
1
vote
1answer
54 views

How to detect the power source when multiple power sources are available?

I have very little background in electronics, I'm from software background. I'm interested to design a system in which there is an 8-bit micro-controller which should get powered from two different ...
0
votes
1answer
62 views

power consumption of a FPGA

How to get the dynamic power waves of a FPGA when a program is running in VERTEX-5. Where to connect the DSO to FPGA
0
votes
1answer
60 views

Using 60Hz clamp meter for measuring current that is not 60Hz

What should I expect when I use a clamp meter rated for 60Hz to measure current that is not 60Hz (Eg. 100Hz) ? Will the RMS current value be higher/lower accordingly?
0
votes
1answer
76 views

Circuitry filters and decoupling capacitors example

I have some question that i want to ask using an circuit example. What help provide an inductor in Vin and Vout, a short of noise filter? Can i change voltage regulator and maintain same inductors ...