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Questions tagged [motor]

An electrical actuator that converts electrical energy into rotational motion or sustained linear motion (linear motor). There are many types of electric motors. If the specific type of motor is known, it is helpful to use or add a more specific tag, such as dc-motor, brushless-dc motor or induction-motor.

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Why does a Tesla car use an AC motor instead of a DC one?

I was just watching a mega factory video and wondered why they use an AC motor which requires a power inverter instead of DC which may be powered directly from their DC battery? Introducing an ...
55
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3answers
8k views

Fan speed switch: why OFF :: HIGH :: MED :: LOW?

Many AC fans, including inexpensive floor models, have a rotary speed control which rotates from OFF to HIGH to MED to LOW. Since the switch does not rotate 360°, you have to rotate it backwards to ...
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1answer
46k views

How can I implement regenerative braking of a DC motor?

I know that many electric cars are able to convert the momentum of the car into stored energy in batteries, rather than convert it to useless heat at the brake pads. How does this work? How can I ...
34
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2answers
7k views

How does a laser printer control the laser to produce such high resolutions?

I opened up a broken laser printer yesterday to find one of the important sections (this is an example photo from Google Images), trying to learn from the design of the laser+polygon mirror motor ...
33
votes
6answers
157k views

What is a “digital” motor?

Dyson keeps going on about their new "digital" motor. What is a digital motor? How can a motor be digital, if it is inherently analog? Is it just marketing doublespeak?
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2answers
64k views

Purpose of the diode and capacitor in this motor circuit

I'm hooking up a small DC motor to an arduino using an NPN transistor using the following diagrams I found online: The circuit works, and I'm successfully able to make the motor run. Now, I'm ...
30
votes
8answers
233k views

How are current and voltage related to torque and speed of a brushless motor?

I know that electric vehicles have different performances depending on battery and motor, but it's not clear how electrical and mechanical units are related. Can anybody please help? Will a 100V ...
29
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11answers
17k views

I'd like to learn how to make my own USB gadgets

I've been writing Linux character device drivers for other people's stuff for some time. I'd like to find a new hobby and the thought of making my own USB gizmos seems really neat. I would be ...
27
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6answers
63k views

How to drive brushless motor with Arduino?

Is it possible to drive a brushless motor directly with Arduino? Or should I revert on controlling a brushless motor ESC with PWM pulses?
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5answers
3k views

Does cassette tape change its velocity while playing?

Looking at the old cassette tape, From the POV of the head, let's say that it reads at speed \$v\$ (the magnetic medium scrolls at speed \$v\$). But looking at the right wheel, which is the one that'...
25
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6answers
17k views

How do I physically work with a hobby motor?

How do I incorporate a hobby-style motor into a project, physically. How do I mount it and connect a wheel to it? (Assume that I have a working H-bridge or even switches, and am not concerned about ...
24
votes
1answer
23k views

How can I measure back-EMF to infer the speed of a DC motor?

I'm interested in measuring the back-EMF of a motor to determine a motor's speed because it's cheap and requires no additional mechanical parts. How can I measure the back-EMF when I'm driving the ...
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votes
2answers
55k views

Difference between Brushless Motor and Stepper Motor

I think I understand the operating principles of a brushless motor and a stepper motor, but I'm a little confused about the difference. Is a brushless DC motor a very basic stepper motor? With ...
22
votes
3answers
68k views

How to drive a MOSFET with an optocoupler?

What's the proper schematic for driving this MOSFET from a microcontroller pin through this or this optocoupler? The MOSFET will drive a motor @ 24V, 6A.
21
votes
3answers
8k views

Why should I worry about a motor causing my supply voltage to shoot up when the back-EMF can't exceed the supply voltage?

I have heard people say that in motor control circuits, one must take precautions to keep the motor from feeding back into the power supply, causing the supply voltage to rise, consequently breaking ...
20
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4answers
5k views

Why do refrigeration compressors stall when switched off and on quickly; or, why do I need to wait three minutes before restarting my air conditioner?

All of the air conditioners I've worked with have the following words on them: Before restarting, wait three minutes. In the event the air conditioner's compressor is switched off and back on too ...
19
votes
3answers
30k views

Is it possible to drive a stepper motor greater than 1000 rpm?

How could I achieve this? What are the stepper motor facts and principless that I have to keep in mind to design a circuit to achive this goal? Are there any readymade/open source alternatives and ...
19
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4answers
26k views

How diodes protect H-bridge DC motor driver?

I don't really understand how these diodes in this circuit and similar circuits (like driving a relay circuit) protects the controller circuit from the energy stored by the inductance of the coil. I ...
18
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3answers
3k views

Why don't all motors burn up instantly?

A motor rated for 3S (11.1 V) has an internal resistance of 0.12 ohm. The maximum current is 22 A. 11.1 V / 0.12 ohm = 92.5 A Doesn't this mean ...
17
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3answers
46k views

Why is PWM used to control DC motor speed instead of using a variable resistance?

My question is at the end (to change the speed) we are controlling the input voltage of a DC motor in both PWM (pulse width modulation) and variable resistance cases. Is the only reason for choosing ...
16
votes
4answers
4k views

Why does magnet wire need to be insulated?

What is it about having multiple coils that enables the magnetic field? Why can't I just have one big wire or threaded wire on a motor? Sorry, it's kind of a baby question but I couldn't find the ...
16
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2answers
9k views

Why connect capacitors to motor body?

So I've found a motor circuit which looks like this: Since many users here believe that my hand-drawn circuit schematics are in fact pictures of flying spaghetti monster, I'll also provide a written ...
16
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3answers
3k views

In a DC motor, is there one commutation point that is optimal in all respects?

This recent question got me thinking about commutation timing, and why advancing it can be desirable. However, I wanted to consider more deeply the underlying phenomena, and I'm pretty sure my ...
15
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7answers
117k views

Torque kgcm (what is kgcm)?

I know what torque is but I find difficult to understand what Torque: 3kgcm means ? I am not sure, how much weight that motor can carry, and I want to know how I can calculate that. Please give me ...
15
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3answers
31k views

Control differences between ac induction motor and brushless dc motor?

I have a fairly solid background in industrial AC motor control (soft starters, VFDs, etc.) but something that I'm certainly NOT well versed in is brushless DC motors... the type found in every hard ...
14
votes
7answers
9k views

Why are rectifiers-inverters used to drive AC motors instead of using the rectified current to drive DC motors?

I understand the advantages of using a rectifier-inverter system to drive an AC motor instead of simply plugging it into mains power, as it allows much better control of its speed and performance; but ...
14
votes
3answers
3k views

Why is it harder to turn a motor/generator with shorted terminals?

The shaft of an unconnected motor is easy to rotate relative to a motor with shorted terminals. If a resistive load is connected to the terminals, the turning difficulty is somewhere in between. Why ...
14
votes
12answers
4k views

Tracking rotation with extremely high accuracy

I would like to track the angular position of a fairly slow motorized rotating arm (direct-drive; see illustration below) -- but require angular accuracy of under 0.05°, and similar resolution. As @...
14
votes
2answers
3k views

How is this design for a basic PCB pick and place?

I have zero experience with any serious mechanical design, but out of necessity and curiosity, I'm attempting to build a pick and place machine (for my hobby projects as well as low-volume PCB ...
14
votes
4answers
1k views

H-Bridge Fly-Back

Sorry if this question is a little long, but I though it prudent here to discuss the state-of-the art as I know it before asking the question. ISSUE When using an H-bridge to drive a bidirectional ...
13
votes
4answers
9k views

How can I sense the motor's current?

I need to drive a DC motor @ 24V, 6A with a MOSFET. How can I sense the current that the motor is drawing with a microcontroller? I have to know when the motor is stalled.
12
votes
2answers
13k views

Does a DC toy motor emit AC when you spin it?

I just watched a video on Facebook by somebody who built a project to run an LED using a 9 volt DC motor scrounged from a battery operated toy. They simply wired the LED to the motor and then used a ...
12
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6answers
28k views

Very Slow Electric Motor

A customer has asked: I want to slow down a small hobby sized DC motor to a user variable range that runs from slow to zero RPM. I would simply use a wall wart for a power supply and a ...
12
votes
4answers
3k views

Is it valid to consider back-EMF in a DC motor equivalent to increased inductance?

I know that back-EMF can be considered as a voltage source in series with the motor which is proportional to speed. This is the common understanding, and I totally get it. Before I understood this, I ...
12
votes
2answers
64k views

Why are the letters U, V and W used in AC motors to represent the windings?

I am connecting up an AC motor and was wondering if this labeling system was representative of something? Or just another set of letter like X,Y,Z? I could not find any information regarding this in ...
11
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3answers
2k views

Capacitors and motors

Every RC car I've cannibalized has had a small ceramic capacitor soldered on to the contacts of the motors. What is the purpose of having this? What happens to the performance of the motor with out ...
11
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3answers
5k views

Arduino Stepper Motor

How do use use an Arduino with a Stepper Motor?
11
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2answers
1k views

What role does this diode play?

I've just bought an Arduino Uno kit, and am going through all the projects in the booklet that comes with the kit. From even the simplest LED and resistor circuit, to get a feel for the Arduino board, ...
11
votes
4answers
3k views

Why don't brushless motors “short”?

You always learn in school that you should never short terminals of a battery because the wires overheat from the large current. If you look at a brushless motor, you'll see that its nothing but ...
11
votes
2answers
8k views

Continuous rotation 'servo' vs DC motor

Under what circumstances should I prefer a continuous rotation 'servo' to a DC motor, or vice versa? It seems to me that to use a DC motor, I'm going to need three pins from an MCU -- two for forward/...
11
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4answers
16k views

Explanation for Differing Stator Winding Orientations

As a layperson, I'm trying to understand the basic configuration for an induction motor or generator. I've looked at many diagrams and photos/cutaways of stator wiring and I've noticed two different ...
10
votes
3answers
3k views

In a brushed DC motor, why do the brushes have springs?

In trying to understand brushed DC motors, this post has been very helpful but I still have some fundamental questions about the brush mechanism. For instance, what is the purpose of the spring? (...
10
votes
2answers
3k views

How can a synchronous motor have RPM other than 3000/3600?

It is said, that synchronous motor is rotating at the same speed as magnetic field rotates. But three-phase made magnetic field rotates as the frequency of current, i.e. 50 or 60 times per second, ...
10
votes
5answers
33k views

Braking a DC brushed motor

What would happen if I short the terminals of a DC motor together while power is disconnected but it is still freewheeling? According to several sources, it would brake the motor. This makes sense. ...
10
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3answers
1k views

Reduce EMI generated by old AC motor from an electric knife

I have an old electric knife (220V 50Hz) which seems to produce a lot of EMI. Some clues on that were a "bzzzz" noise from PC speaker I noticed sometimes when someone use it. Recently I bought a ...
10
votes
3answers
8k views

Voltage spikes when driving DC motor with N-channel MOSFET

I'm trying to drive a DC motor (12V, 100W) with MOSFET IRFP054N. PWM frequency is 25 kHz. Here's the schematic: I know DSEI120-12A is not the best diode for this but I don't have any better right now....
10
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4answers
49k views

How do I find the voltage range for an unknown DC motor?

I have a small unmarked motor with a burned out speed controller board. I'm able to figure out that the motor is a DC motor because it has two wires coming out of it and there's a rectifier on the ...
10
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3answers
1k views

Locking up a DC motor with constant supply a bad thing?

I am working on a little pen plotter project and for one of my motors (which supports the pen) I have used a small DC motor obtained from an old DVD drive. I have noticed that if I supply a constant ...
9
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4answers
13k views

Why use DC motors for driving elevators?

This New York Times article says that on November 14, 2007 Consolidated Edison Company was going to end supplying direct current to the remaining several buildings that used those to run elevators. I ...
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3answers
2k views

shooting object by using a DC motor

This is not directly electrical, but I am working on making a real life version of a coin block from Mario. Basically I use an LDR and to detect if someone punches the block and then use a transistor ...