What is Dc: Definition and 1000 Discussions

Hi, I'm new here and had a question relating to my senior design project in mechanical engineering. My project ends up involving a small DC electric motor, which needs to be able to be reversed and it would be nice to be able to have some speed variability. I'm aware of speed controllers and I...

I was a little surprised to find out that the IEEE recommends using "ac" and "dc" for alternating/direct current rather than "AC" and "DC." (Google "Recommended Unit Symbols, SI Prefixes, and Abbreviations - IEEE") Apparently non-capitalized is the "correct" way but I've mostly seen them...

Hello guys, My teacher gave me a question regarding calculation of equivalent resistance, trying to solve which I'm losing my sanity. I feel a bit ashamed because this is my first post and I'm using it to ask a doubt, a little selfish of me. But it's kind of urgent so I don't really have a...

Homework Statement I just learned that in a DC motor you use a commutator to convert the AC current to DC. And in my other course I learned that you can convert AC current to DC using a rectifier circuit. If this is the case, why don't we use a rectifier circuit in a DC motor to convert the AC...

Hello, I am an Environmental Engineer with very little knowledge of electrical engineering, yet I am working on a project and need a little help. I need to pulse DC current. I have a power supply that will be putting out about 15 vDC and I need to pulse this current at this same voltage. At...

Hello I know what is AC signal and DC signals purpose.. but may I know how to convent AC signals to DC signals to feed into the PIC?? Help pls

I'm looking for a DC Motor to power a small 50lb robotic platform with maximum speed of 10mi/hr. What should I be looking for? I've made some basic assumptions of 8" or 12" diameter wheels and so the rpm rating should 420 rpm and 300rpm respectively to attain 10mph. I plan to use at least two...

Homework Statement The coil of a DC motor has a resistance of 2.0 ohms. The motor is runned by a battery of 12 V and an internal resistance of 0.5 ohms. a) Calculate the current at the moment the motor is started b) Calculate the current when the motor is running at 600 RPM , when there is...

The solution states that after the switch is opened the initial current through the inductor is 20 A (in the pink box). I don't understand why its 20A. Surely the current has split at circuit junctions meaning the current arriving at the inductor is less than 20A? Thanks

If you study a DC signal under an appropriate scope, you can see the switching transitions ; a pwm signal. But if you examine a battery, no matter how high temporal resolution you reach, you see a dc signal. What might be the explanation for this? electrons are being generated by a chemical...

Hi everyone i am Julius a 400L student, this is my first post as a new member of this great forum. Please,i want to know a step by step practical guide on how to convert AC to DC , i join this forum for me to properly learn (PRACTICAL) from the masters here and it will be my pleasure if i can...

If in the DC motor specs doc says that it can handle + - 16 Volts maximum and 3A of peak current but the nominal voltage is 6 V and the continuous current is 1A... it means that it is safe if you feed it with 3A during the time of start up? Supposedly it is only meant to be at the start...

I have a Geared DC Motor rated 12V, 0.6A, 180RPM, 3kg.cm, 66% Efficiency. I measured the impedance of the disconnected motor at 45 Ohm. I want to use it with a with a simple 12V 1A DC Power Supply in a Field Current Control Circuit to be able to dial in variable speeds. Will the circuit in...

People of physics forum i have come here to ask for help. i am trying to model a armature controlled dc motor with no load but and opposite force in the form of frictional damping the expression i have raised and am assuming it to be right is ωout/Vin = k/(L(s)+R)(I(s)+C)+ kt.k...

Homework Statement in a real time scenario, when we buy a dc geared motor.could we run it as generator ? how much current would a dc geared motor produce when run as generator? could anyone please provide me the equation to find the generated voltage in case the said motor is bought with the...

Hello, I have a little wireless camera that I want to power on a battery. The camera requires 12V ~1 amp DC to run. I am a DIY kind of person and have a few lead acid batteries from work, all of them are 12V DC, but they range from 4.5 amp to 12 amp. I've worked with AC power in the past...

I have a fisher price baby swing. It has 4 1.5v batteries of size D. I tried to convert it to a 6v DC charger but that didn't work. The charger specification is output=400mA 2.4VA. If someone can help me please to find a right charger as this doesn't work correctly and swing does not swing as...

What sort of company would I contact to have something like this made? I am looking to have made a Variable DC power supply capable of outputting up to 300-400 amps and up to 30v(and as little as well below 1 into the decimal region). Preferably as small as possible. My only requirements for...

I am trying to create a backup dc power supply that is charged by a battery which ranges between 10 and 21Vdc. The backup supply needs to output 20W (10V, 2A) of power for 5 seconds when the battery is disconnected. I have performed some research into how long the capacitor in the backup supply...

I wanted advice I saw that DC supply, function generators, and Digital Oscilloscopes were really expensive and I wanted to know is there some way you can use software to turn your PC into a variable DC supply and/or a Function Generator thanks

Hi, I had this power electronics lab experiment where we control the speed of a separately excited dc motor using thyristors. The dc motor is rated at 1500 RPM but we do get readings where the speed is above 2500 RPM. How is that possible? Thanks

Hello, I'm in the process of calibrating a thermometer/datalogger (Omega DP470) that uses a thermocouple type T (-200-350 deg. C range), and I need a DC voltage source that can feed a steady voltage of 39.000 mV. I believe at this point I can either purchase a precision voltage source that...

Please suggest what does N1 and N2 mean in the attached dc network.

A dc voltage supply that starts with a transformer, into a bridge rectifier, into a big capacitor, into some sort of chip, into a smaller capacitor. Since yall are smart I'm hoping you know what I'm talking about with this crappy description. I was wondering if running the signal through the...

I understand the basic gist of the whole DC brushless motor, but I don't understand why there needs to be a sensor. Why can't the controller just alternate between phases at a constant rate? What I mean is that if there are a fixed number of ways the coils can be charged, why not just alternate...

Hi, I'm attempting to make a model of a DC motor capable of calculating the efficiency of the motor for different values for torque. I have managed to make a code to generate the torque-speed-power plots for given inputs, however I have been unable to figure out how to calculate the...

Hello. Just started learning about how to model a DC motor. A simple model consists of the input Voltage in series with an inductor, a resistor and a back emf. I have two questions. Why have both the inductor and the back emf (voltage source)? If you know that at a voltage V and a load L1...

1. Find the number of poles for a 1200 kW separately excited generator, if the average voltage between commutator segments is 15 V and the armature ampere-turns per pole on full load is 10000. The generator has single turn coil and is lap connected. Ignore all losses. Homework Equations...

I have completed a DC generator chapter from my course book. Below mentioned questions have been asked in previous examinations, but my course book doesn't help in solving these. Please help me with the reference books which will be helpful in solving these type of questions. I am pursuing...

I've been looking around for formulas on how to calculate different aspects of DC motors and buck converters such as average current. The reason is that I'm about to pick switch frequency for a motor, and don't know what characterics I can expect if I alter the switch frequency. Papers and...

Ok I need help here... I am attempting to light LEDS off the phantom power of an amplifier/mixer. traditionally the average mixer/amp used for DJ shows has a "Phantom Power" option. When activated it sends about 48v to each microphone...some mics need it...some don't... I intend on using...

Hello again, I am having a bit of trouble understanding superimposed voltage. Here is the problem: A sinusoidal AC voltage source is in series with a DC source. Effectively, the two voltages are superimposed. Draw the total voltage across RL. Determine the maximum current through RL and the...

Currently using resources like: http://www.matterandinteractions.org/Content/Articles/circuit.pdf http://www.phy-astr.gsu.edu/cymbalyuk/Lecture16.pdf I don't seem to understand why the surface charge densities shown in the pictures are stable. I understand that the densities shown create...

If I have a circuit with R = 1Ω L = 300μH V = 20V i0 = 5A I know that I can use the equation at the bottom of page 13 to calculate the current rise given any starting current and input voltage: i(t) = (V/R)[1-e-t/τ] + i0e-t/τ This is fine, and stops increasing at 20A as expected...

Hello, I have a question, How can I calculate the working time for the following scenario: I have 12V 7.2AH LEAD ACID SLA DEEP CYCLE BATTERY Then I used DC 12V to AC 220V Power Inverter USB 1000W to give me AC I connected one 100w lamp .. For how long it will work ? how can I...

We know that Universal Motors have field winding always in series with the Armature.They do not have field in shunt because of shunt fields' inductive reactance & they will produce negligible torque on AC supply. Also because of different phase angles of currents in series & shunt path, the 'DC...

Hi, a newb on eleng here. Recently I've been working on my project. I need to get a high DC (1000V - 10000V ) output voltage, low current (10-30mA would be fine) from a DC input voltage (9-12V). I'm thinking to use a transformer but it only able to amplify an AC voltage right? Thanks!

Hello people! I've been absent from this forum for quite a while. But now I return with questions regarding a little project I have to do. So basically I have to make a AC and DC power supply. I need 24 V AC output and 0-30 V DC power supply. I have a transformer(I think its 220V/24V)...

1) My understanding is that the output of a DC generator has the form Vmax*|sin(2πft)| for 2 poles. Having more poles makes the output smoother but it would still have ripples. Is this correct? 2) In many places, I have seen the EMF of a DC generator written as: \phi * (NZ/60) * (P/A). What...

Homework Statement So today in lecture, my professor talked about VRMS. I understand VRMS and its relationship to DC power dissipation, however, in lab today I became very confused. In lecture, we were told to use the VRMS value when applying Ohms laws/power equations (P=VI). Then, later, in...

Hello, i am new here, and i hope there is someone here that could help me with this : Homework Statement I have a DC alternator and i want using inverter to make AC. Homework Equations Is there possible without using ACCU ? The Attempt at a Solution I tried directly without...

Hello everyone. I have just bought myself a multimeter just for fun. So I've been going around testing voltages and current of things... I have a few questions, and more to surely come later... 1st. When they say Direct Current flows "in one direction" and Alternating Current flows in "both...

I've been able to get all of the problems up to this point, but I have never seen a problem like this before, so here it goes: 9. Below is shown a simple resistive current source. The resistive load is represented by a 10 kΩ potentiometer. What is the current through the resistive load over...

http://www.cnn.com/2013/09/16/us/dc-navy-yard-gunshots/index.html?hpt=hp_t1

DC "transformer" I just had an idea not using induction as in regular AC transformers, but using the electric field in a capacitor using DC in order to transform DC voltage directly without advanced electronics. The idea is using a special capacitorl. The capacitor have a primary pair of foils...

hello, I need a dc generator which would generate 19v and 1.5A current(roughly i want it to generate 30watts of power) at 1000rpm. I require it for a college project. the size of the generator should be small so that i can handle it easily.

Is there a formula that shows the relationship between AC power and DC power? Something on the lines of, for example: Power of AC ... = Power of DC ... ? Thank you.

Hello guys I'm looking for a motor for my arrow saw project. I would like to use it to cut carbon arrows. Found one motor in the shop that is pretty small and will work perfectly with my jig. But it's rpm's are only 1650 and I need at least 8000 RPM. Is it possible to increase the motor RPM's...

Hi! Homework Statement Homework Equations V = IR Kirchhoff Current and Voltage Law. The Attempt at a Solution I am facing difficulty with this RC circuit. I tried looking up solutions but all I could find were either exclusively series or parallel. My first guess was to take Total Current...

Homework Statement I used a similar motor to this one in a prac, and then realized that the arms either side of the coils were not magnetised. I was wondering where the magnetic field comes from, and without any special equipment is it possible to calculate it? Homework Equations t=bain