# Tagged Questions

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.

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### Off-grid Solar with DC Backup

I would like advice on a potential new set up I am looking at installing in my home. I have a small water heating system that runs @ 150w 24v DC, I intend to use the solar to power the heating system ...
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I'm using the NTE0506MC DC/DC converter which boosts 5V to 6V. The output voltage I'm measuring with no load is 9V not 6V. In page 3 of the datasheet they mention that it needs a minimum load of 10% ...
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### What are the factors that significantly affect the life span of a DC motor?

I'm currently planning to run a DC motor continuously on solar power. So I would like to know which things I should be very careful about for optimum lifespan of the motor. I found the following two, ...
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### AC DC Analysis of diode

in the following circuit: Im looking to find what $v_D(t)$ is given $V_γ = 0.7 V$ and $r_f = 0$. Now when doing the DC analysis, find that $VDQ = 0.7 V.$ But im having trouble finding ...
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### Choosing the correct brake resistor for DC motor

I have a DC motor running on 24VDC rated 150W (~6,25A), how do I calculate the correct brake resistance?
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### SEM Permanent Magnet DC Motor DPM 30R4 1500RPM 24VDC Output: 0-25kW & Brake

I am in the plannning stages of a project to build a pig rotiessiere. I have the above mentioned motor, but I am unsure of what type of power source is needed to run the motor and what can I do to ...
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### Frequency of fluctuations in power in an input power design circuit

I am thinking about the following power design circuit in section 6.1 : http://www.arndaleboard.org/wiki/downloads/supports/BaseBoard_Specification_Arndale_Ver1_0.pdf Is it possible to calculate how ...
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### Providing DC power with failover DIY for IP camera

I'm building a simple battery backup box for a 5V IP camera. I've got a few options for battery, sealed lead battery or a mix of portable LIPO style "USB" power bricks. I've seen boards built for ...
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### Battery powering an unknown DC motor

I know nothing about motors. I have DC motor (sealed in a casing) that uses 6v/12v 1a (mains switching power supply) with 2.1x5.5mm DC connector. It has variable speed controller, reversible ...
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### How much current draw will a dc-dc converter have in this situation?

I am trying to make a mobile computer for my Raspberry Pi. The problem here, is powering the Pi, screen AND the USB hub from the same power source. I have bought this: ...
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### 1-pole and 2-pole DC circuit breaker

My question is rather simple, when and why do one use a 1-pole or 2-pole circuit breaker in DC (+24VDC and GND)?
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### Will a 40W incandescent AC bulb operate on a 330V DC voltage? [closed]

Will a 40W incandescent AC bulb operate on a 330V DC voltage or not?
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i m trying to connect a de sauty's bridge(AC bridge) output to a precision rectifier. The problem is the output of the bridge (AC bridge) changes drastically to 5volts as soon as the connection is ...
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### How to build “two power sources” in a microcontroller circuit?

My circuit has a microcontroller, it uses power from a DC transformer (120V to 12V DC). My circuit also control an pneumatic valve which also use 12V DC. Almost every time when the pneumatic valve ...
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### DC circuit breakers in automation plant

I am currently working on designing the power grid of a automation plant. Since i already have a background in automation, the rule of thumb i usually follow is to have circuit breakers in front of ...
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### Frequency and magnitude of power variations in a DC circuit.

I have a 5 V 5 A power source which is connected to a simple development board with a processor that draw current dependent on utilization. I use a multimeter that measure 1000 samples / s to measure ...
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### Electrical saftey of metal panel-mount DC jacks

Context: I have a robotic arm with a series of servo motors, that together draw up to 3A from my bench supply (depending on the load on the servos). To make it easier to transport the robot around, ...
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### Can supplying DC power into an AC device break the device?

I have an AC device that takes 12 volts 47-63Hz AC. It is a water softner that is essentially an electromagnet. I lost the original plug and supplied it with 11.2V DC, it came on for a few minutes and ...
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### I think I am looking for a specific DC relay switch

I am looking for a switch not sure what kind though. let me explain: I have two sources one creating DC 12v, second one creating around 6v DC. One source works for about 12 hours each day then ...
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### Why are the power transmission/distribution systems AC and not DC?

Is there a good reason why we are not in the process of completely converting our electrical transmission system to DC? The main reason for using AC on the grid (no offense Tesla, I love you man) was ...
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### 2 full bridge with 2 secondary winding in series… is it possible?

simulate this circuit – Schematic created using CircuitLab Is this possible? Think of the center tap transformer as a 2 winding connected in series
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### How is current lowered as Voltage is increased in AC power transmission

I was reading about power transmission on wikipedia and came across the explanation of the efficiency of AC power transmission that said power in the load = (I^2)* R while power transmitted= IV. The ...
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### Which electro motor to use for steering a kite? (guestimation marathon)

I'm doing a pet project in which I want to fly a kite from my computer. For this to happen my plan is to build a little box hanging under the kite which includes a raspberry pi (connected to my laptop ...
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### Mixing AC and DC power in a circuit

This is likely a noob question, apologies if the answer is obvious. I'm trying to control a furnace using a 3.3V microcontroller. The furnace operates by connecting a common 21V AC "hot" line to one ...
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### DC Voltage Grounded with AC Input

This is an image from a book showing us how to solve BJT circuits via AC analysis: So I understand that when doing AC analysis to ground all the DC voltage sources but I don't understand why. Can ...
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### Should I use multiple voltage regulators?

I have five devices that need to be powered. I would like to use one DC source to power the four devices. Should I use voltage dividers, voltage regulators or a mixture of both? Also, any ...
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### DC-DC isolation for my car stereo… Where do I start?

I recently noticed that my jeep's stereo whines with a frequency that seems proportional to the rpm of my engine (and alternator), and is louder when my headlights are on. If my stereo was powered ...
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### (How) can I run a microcontroller and DC motor from the same battery?

I have a microcontroller (a PIC10F200) that I'm using to control a DC motor. It's a very simple circuit. A button is pushed and the pic sends output for certain increments of time. The thought is to ...
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### Common DC ground with two bridge rectifiers

I have an old AC transformer with many taps off it at different voltages. Connecting a voltmeter to tap 2 and tap 3 gives 25V and connecting it to 3 and 4 gives 5V. I connected them to two bridge ...
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### How to wire a 12V DC fan to a Molex connection?

I have a 12V DC fan with two wires (black and red). I want to solder it to a Molex 8981 connection (powered by an ATX power supply). Here are the details for the connection: I'm guessing the fan's ...
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### advice on a transformer for power-supply

i know this type of question is common and yes i could just buy a known transformer for \$10 on ebay or something. either way :) i am interested in building my own power supply, something variable ...
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### Lower Voltage of 15 VDC Power Supply to 13 VDC for DC Blower

I have a centrifugal blower, model 007-A42-32D, that uses 12 VDC at 17.5 amps. The performance information provided by the manufacturer, SPAL Automotive, was acquired at 13 VDC. I have a power supply ...
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### Will a device capable of receiving a 200 Vrms input signal happily accept a 200 VDC signal?

To the best of my knowledge, Vrms is used to express an AC signal as the equivalent DC signal that would produce the same power dissipated in a resistor R; I believe this is best calculated using a ...
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### Can someone explain impedance in simplest way? [duplicate]

I know in DC it is Resistance of the load. In AC is it impedance of a line correct? can someone please help me understand impedance and types of impedance. Zero Sequence, Positive sequence and 2 ...
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### Why does this insulator separate two conductors with equal voltages?

Here goes a view-from-below picture of a 3 kilovolts DC railway catenary Here B is a suspension cable, C is a two-stranded contact wire - one which the train pantograph touches. Between B and C ...
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### Protect DC Circuit from too much voltage

How do I protect a 3v DC circuit from being damaged if someone accidentally plugs in a 12v power supply? The circuit will draw much less than 1 amp.
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### PIC pins change state when DC motor connected

I'm new to PIC programming, and having trouble getting getting it control a DC motor. It's a PIC18F25K22, and a TI L293D driver. Power is suppliued by a 5V linear regulator connected to a desktop ...
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### Does a resistor in an AC circuit produce the same heat as in a DC circuit?

Does a 1k ohm resistor produce the same heat in a AC circuit which has an rms voltage of 10 volts (60 hz.) as it would in a 10 volt DC circuit?
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### Different materials for cathode and annode in the same DC supply?

I have just seen a diagram of the 787 Dreamliner's battery system. In it, the negative terminal is copper and the positive is aluminium. In a DC system I understood that the current at the supply was ...
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### Easiest / cheapest way to build a dc power supply in the 150VDC range

I am looking to build a power supply to power a 150 V DC armature motor that will pull a maximum of 4 A. The cheapest I have seen so far is the following on ebay. I'm looking to build one myself but ...
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### When to use Nodal Anaylsis / Mesh / Superposition?

I'm studying these three methods and i'm confused on exactly which one is used when. This is a very broad question. Therefore, could some explain in general terms the difference of the three methods ...
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### Node Analysis - current calculation

I have a cicuit here that's giving me trouble when finding out what V1 and V2 equal.The book says that I1 is traveling through the 8 ohm resistor (R1) towards ground. But when I build the circuit on ...
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### Can this ultrasonic emitter be DC driven?

The datasheet of this ultrasonic specifies that the maximum driving voltage is 10 Vrms, which suggests that it should be driven by an AC. Is my assumption correct? ...
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### KCL Node Analysis

I can do mesh analysis with KVL no problem however trying to switch over and to KCL with Node analysis I cannot understand. How do you determine current coming in to the node? I don't understand how ...
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### Generate DC pulse after switch turned off?

I've got a power source (say 12V DC) that I'm monitoring with a relay. I want to send a pulse (over 5V DC) to another relay for 60 seconds after the first power source has been turned off. A ...
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### DMM and Power Supply

If I connect a digital multimeter directly to a DC power supply, the voltage shown on DMM is higher on the power supply. For example, if the source is 3.29 V then DMM shows 3.31 V. What is the reason ...
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### Quick release connectors - 2 poles, max 1.5kW 12V DC?

What quick release connectors are good for connecting 2 pairs of wires? 2 poles Max 1.5kW 12V DC? (optional) Splashproof
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### What do I do with the extra “ground chassis” tab on a DC power jack?

Product Link Datasheet I have about fifteen 9v wall warts within specs for the circuit; I'm going to use the one that fits the jack. There are three solder tabs on the jack. One for the positive ...