DC stands for Direct Current, which means the flow of electric charge in a single direction. Examples of a DC source are batteries, solar panels, dynamos.
4
votes
1answer
165 views
Implications of using 145 ohm cable for RS-485
My current workplace has made up some custom cables that have conductors for DC power and conductors for for RS-485 communications in the same bundle. My predecessor apparently had the cables ...
9
votes
2answers
2k views
How do the tiny AC->USB power supplies work?
The iPhone and Kindle both come with tiny power supplies that take in 120v AC and output around 5V at 0.85 to 1 amp. They seem to be too small and light to have a transformer, and generate very little ...
5
votes
3answers
850 views
How does DC transmission require several times less wire than AC?
In this YouTube video (scrolled to 5:55) there's a claim that replacing an AC high voltage transmission line with a high voltage DC transmission line allows for having seven times fewer powerlines ...
4
votes
1answer
351 views
How do I tell sleeve from sleeve shunt on this connector?
I need to change a DC jack to a different one (with long bushing).
I'm not to sure which terminal connector is what from the manufacturer's diagram.
The DC jack is a L712A from Switchcraft ...
0
votes
2answers
262 views
Problems solving strategies of experts in simple DC-circuit problems
There are many papers which study how students in high school and college think, when solving elementary DC-circuit problems. However I don't know any resources where the reasoning of experts is ...
1
vote
3answers
407 views
Questions about capacitors in DC
1.Does the current flow through the capacitor when (a) it's not charged, (b) it's partially charged, (c) it's fully charged ? How does the flow changes in time (ex.: exponentially, logarithmically, ...
0
votes
1answer
246 views
Building a simple switching regulator for DC12V -> DC5V
I want to build a circuit that provides USB power from a 12V battery (lipo or car battery).
I have an iPad that draws 2A from its charger: So I'd like to get up to 10W output.
What's a good choice ...
1
vote
1answer
623 views
What electric motor spec clues indicate easy speed control options?
I'm investigating HVAC fans etc to design my own system and controls, and having fully variable speed control is an important consideration to me.
I'm pretty sure there are types of AC motors that ...
4
votes
1answer
584 views
AC->DC supply, how to deal with chassis ground being connected to digital ground?
I have an external triple-output AC-DC supply with the following output pinout:
On the power supply, "ground" (pin 2) is internally connected to the ground wire of the mains plug. I'll refer to it ...
1
vote
2answers
319 views
Can AC and DC be converted and compared?
This is coming from an IT scenario;
An example server may have a power draw rating of 1.5A at 230V. When connected to a UPS and the mains power supply goes out, the UPS batteries are now providing DC ...
3
votes
2answers
2k views
What is the formal definition of Quiescent Point?
What is Quiescent Point? Is it necessary for it to be related with any V vs I , I vs I, or any such characteristic curves intersection point?
0
votes
1answer
216 views
Circuit and components for DC Fan
How to make a basic DC fan circuit with an on/off switch (source from batteries). I will be more than happy if I have the schematic and the component needed.
3
votes
3answers
486 views
Data over power line in a car
I am trying to build a communications system for a car, for turning gadgets on or off. One idea was to parasite on power lines, but what kind of components and signaling could be used for this? I am ...
0
votes
2answers
656 views
Connecting AC wires to a PCB
I am working on a project where I am using a microcontroller to control a 5V DC relay to control a mains device (an airconditioner).
In this circuit, I would need to connect the AC wires to my PCB ...
1
vote
1answer
483 views
Regulated DC supply - need help with calculations
I am in the process of making a regulated power supply to convert AC(220V, 60Hz) to DC(9V, 500ma). I have worked out all the calculations and would appreciate if someone could double check just to ...
0
votes
1answer
356 views
AC-DC converter (120-230VAC)
We are designing a circuit which should be powered directly from mains (230VAC), and have in the previous design used a normal transformer.
But in the next design we would like to use an AC-DC ...
1
vote
1answer
528 views
How to tell if brushless DC motor is wired delta or Y?
I have a brushless DC motor I'm working with, do not have any spec. sheets for it. How can I determine if it's wired in delta or Y formation? There is nothing on the label that indicates this. ...
2
votes
2answers
327 views
Shorting a DC power supply
I have this cheap DC power supply.
Tekpower DC Variable Power Supply, 1.5-15 V @ 2A, HY152A
It says it is limited by 15 V or 2 A. My question is, if I short it out, can it damage the unit? Is ...
4
votes
1answer
671 views
DC power supply simulation trouble
I'm trying to simulate a relatively simple AC->DC power supply in LTSpice, but it's not quite cooperating with me. I've followed this schematic:
only replacing potentiometers with resistors due to ...
1
vote
2answers
238 views
Automotive Clockspring Alternative
Theoretical question: I was told by an auto mechanic friend that replacing a clockspring in the steering wheel of a car with concentric conductive rings (separate ring for each component powered such ...
4
votes
1answer
528 views
Grounded AC-DC power supply, what connects to earth ground?
In an AC-DC power supply, how is earth ground typically used?
Take a common PC power supply as an example, does the earth ground connect to the metal chassis? Does it connect to the DC ground on the ...
2
votes
1answer
248 views
Will two 14Ga. wires handle the same load as one 10Ga. wire in a 12V DC application?
I'm wiring up a trailer brake controller unit on my 79 Jeep Wagoneer and I want to run 10Ga. supply wire to the unit. I bought 20 feet of 10Ga. wire while in town today and ran said 10Ga. wire to the ...
2
votes
1answer
233 views
DC-DC Regulator/Converter to Power Robot and Laptop
I have a small form factor Lenovo IdeaCentre PC that I would like to use as the primary controller for a large scale tanked robot. I've ironed out the accessory connections using usb->server ...
5
votes
3answers
1k views
Combining multiple AC/DC adapters
Many of us have lots of devices that uses AC mains (110V/220V) to DC (typically 12VDC) adapters. There's my LED table lamp, my Wi-Fi router, my Gigabit switch, my powered USB hub,.....
Such AC/DC ...
2
votes
1answer
138 views
Alternation of Magnet Poles in DC and AC Generators
I want to create a generator. The current design I am looking at has several magnets along a wheel, with coils around the outside of the wheel. The wheel then spins generating current.
I know that if ...
1
vote
2answers
399 views
Counting DC power pulses per minute
I need to implement a frequency counter (pulses per minute) of a DC circuit that goes up to 20 volts. A little background, I am building a linear power supply 0-20 volts, 0-3 amps for my relative who ...
-2
votes
1answer
420 views
Getting 5Volt DC from 12 Volt DC using LM7805 IC [duplicate]
Possible Duplicate:
My linear voltage regulator is overheating very fast
I have a task to develop a mobile charger from 12 Volt DC power,
now i have decided to use LM7805 for that....
but ...
14
votes
3answers
12k views
Switching DC with MOSFET: p-Channel or n-Channel; Low Side Load or High Side Load?
I think, it is time I understand working principle of MOSFET transistors...
Suppose that;
I want to switch voltage on a resistive load by a MOSFET transistor.
Any control signal between -500V ...
5
votes
1answer
366 views
Get multiple individual DC voltage sources from a single line
If I connect 2 6V batteries or two individual sources serially the combined voltage should be the sum of the voltage of each battery (i.e. 12V). Is it possible to get 12 volts from a single source or ...
0
votes
2answers
765 views
How to design DC Motor speed control, using PID
I am looking to control the speed of a DC Motor using PID, it is speed control. I understand how the PID works, but i have a few questions. Like,how would I find my gains for each of the PID, what ...
-2
votes
2answers
380 views
9V, 2A DC power supply [closed]
Please i Need a circuit diagram for a DC power supply that can give an output 9V, 2A. I designed one but it could not power the device for which i designed it because the current output is less than ...
4
votes
2answers
551 views
Why is there a capacitor in parallel with this fan? What is the benefit?
I understand that capacitors store charge, however this circuit is supposed to be a proportional controller. I just dont see why the capacitor is needed. Perhaps to reduce oscillation?
1
vote
2answers
1k views
When measuring AC via an ADC, is it bad to have common ground?
I've got a circuit that looks like this:
My input is low voltage AC at low current and I want to measure this with an ADC at 3.3V (eventually, haven't got there yet).
Is this safe/correct? It ...
0
votes
4answers
570 views
Creating Li-Ion charger with step up to 700mA from 500mA?
Canon apparently hasn't ever herd of something called USB-charging. The factory AC adapter for this battery(NB-5L) output's 4.2V's at 700mA. Most standard USB chargers output 5V at only 500mA. Would ...
1
vote
4answers
185 views
Circuit for determining the dc mean of a wave-form
I need to find the DC mean of a waveform whose maximum and minimum values will vary. The input signal has a frequency range of 0 - 3Hz, and will have a voltage range of 0 - 5V. I would like to find ...
4
votes
1answer
364 views
Purchasing a Switch - AC vs DC Current Specifications?
I'm trying to purchase several switches for a DC system with moderately low current (a few amps at 12V). When browsing for switches in parts catalogs (e.g. Mouser and Digikey) there are always ...
1
vote
2answers
526 views
Boost Converter for TTL circuits to drive large loads
I've got a small PIC-based TTL circuit device, powered by a 4.5V coin cell, that needs to drive a solenoid which requires 12V. Obviously my logic level device can't directly power that so I could ...
1
vote
1answer
323 views
How does an audio transformer work with DC in this circuit?
From my knowledge, there needs to be an alternating current for the transformer to be able to create magnetomotive force throughout the core.
Various nerve testers (say for standard school projects) ...
1
vote
1answer
185 views
When charging mobile decices using an external battery is DC > USB more efficient than AC > USB?
I bought a "jumpstart" battery that has a built in power inverter to support both AC and DC ports. I have it for a project but also want to use it for charging my mobile devices occasionally.
I do ...
3
votes
2answers
480 views
Very small AC to DC convertor
I'm building a simple temp PID controller for turning an SSR on and off (yes, I know I can buy them fairly cheap, but its a learning project) and I need DC to power my RBBB arduino and mains AC for ...
4
votes
5answers
268 views
Is direct current really better for pumped-storage hydroelectricity facilities?
Currently the article equivalent to War of the Currents in Russian Wikipedia section says that direct current is beneficial to pumped-storage hydroelectricity plants and provides no reference to that ...
1
vote
2answers
195 views
Powering a DC to DC power supply that came without an adaptor
I bought a mini ATX DC to DC power supply on eBay to use with a motherboard. Unfortunately I did not notice it came without any kind of adaptor. So what I have is basically two wires, red and black, ...
2
votes
1answer
288 views
How to conduct mesh analysis on a current source in series with a resistance?
How can I do a mesh analysis of the following kind of circuit? I'd normally put up Kirchoff's voltage laws for each of the two loops. If the current source wasn't in series with a resistance, I'd ...
1
vote
5answers
275 views
Crude/inexpensive AC to DC transformer
I am working on a circuit that is completly powered by 5VDC from a USB port. The circuit uses SSR's to turn on and off 120VAC from a standard wall plug; the 120VAC powers a high-power heater of sorts. ...
5
votes
4answers
442 views
I want to build a DC powered computer, what are the gotchas, where are the parts?
Google builds its servers with a Battery in the box so that they don't need a UPS. I'm wanting to do the same, but I'm wondering what all the gotchas might be for doing this, and where I'll find the ...
1
vote
1answer
194 views
At DC frequency, how long can wire be until signal attenuates almost completely?
Just got curious about this last night when I was wiring a couple of LEDs on my brother's long board.
For a simple DC circuit (Battery, resistor, LED), how long can I stretch the wire until the power ...
3
votes
5answers
2k views
how to build a high-power (4kW) switched-mode DC-DC converter?
I would like to build a switched-mode DC-to-DC converter which should support up to 4000 W of power. It should be able to act as a CCCV power-supply, so supply a constant current Imax up to the point ...
1
vote
4answers
717 views
dc motor and hung (not stable) pic
I'm running a dc motor using PIC16 family microprocessor.
I connect it to my pc, I can send a command to run the motor in certain speed or stop.
It works for small motor (3V, 100 mA). But the moment ...
11
votes
4answers
2k views
What is the role of capacitors in DC circuits like motherboard, graphic card etc?
I was just reading in Capacitors in DC Circuits that "Capacitors do not play an important role in DC circuits because it is impossible for a steady current to flow across a capacitor". I think it ...
4
votes
2answers
349 views
Actuator can use either 24V DC or 24V AC. What should I chose?
I will be using a damper actuator which can have either a AC or DC power supply. I do not have any strong preference for either, so what would you recommend? I assume that transforming 230V AC to 24V ...
