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3
votes
2answers
200 views

How to calculate the Back-EMF energy on an Inductor?

The Back-EMF generated by an inductor in Volts is: \$V = -L\dfrac{di}{dt}\$ Where \$L\$ is the self-inductance and \$\dfrac{di}{dt}\$ the rate of current change. Now, let's say I want to store those ...
7
votes
2answers
125 views

Electrical behavior of holding magnets when you pull them apart

I'm going to buy a holding electromagnet and a strike plate to hold some things, and I want to design my circuit (arduino-controlled) not to fry like bacon. I'm aware that since a holding magnet is ...
0
votes
2answers
109 views

Why do AC motors have various back EMF shapes?

I just saw in one of the threads that apparently, a permanent magnet synchronous motor and a brushless DC motor have different back EMF shapes. But why? I thought those two were exactly the same in ...
0
votes
1answer
84 views

What is the path taken by the back emf current?

! Where will the current flow through? If ON current(back emf "current") will loop through A B and C If OFF current will(back emf "current") loop through x y and z
-1
votes
1answer
78 views

Calculating DC Brushless Motor Position

I am using a brush-less motor in one of my projects and I need a decent method of sensing the motor position so I know what coils to turn on and off. I looked a bit into sensing Back-EMF, but I did ...
1
vote
2answers
99 views

AVR main loop interference with relay

I'm working on a test program on an ATmega164A that toggles a 12V relay on and off (with no load) through a ULN2003A. For my test program, I'm toggling the relay at 100ms. I've got an IN4001 diode ...
2
votes
1answer
147 views

Harvesting Back EMF Possible?

Let me start by saying that I am not talking about the free energy or "overunity" idea of back EMF. When searching around for information I can only seem to find information from free energy sites, ...
0
votes
2answers
57 views

EMF due to inductance?

In a DC circuit, current starts to flow, and some time is needed for current to stabilize based on the time constant, there is EMF induced due to current changing over time. As soon as the current ...
1
vote
1answer
87 views

motor Back EMF phase differences

I am reading though a product manual for an amplifier that I am working with. It says that if you view the motor Back-EMF while it is disconnected from the controller and spun in a clockwise direction ...
6
votes
2answers
3k views

How to choose a flyback diode for a relay?

A diode is put in parallel with a relay coil (with opposite polarity) to prevent damage to other components when the relay is turned off. Here's an example schematic I found online: I'm planning ...
0
votes
5answers
7k views

Torque relationship to speed in a DC motor

I have a conceptual doubt about torque-speed relation in a DC motors. It's probably a gap in my thinking but I'm posting this question anyway. Torque and speed in a DC motor are said to be inversely ...
-1
votes
1answer
355 views

How to protect the switching device from back EMF when we connect the inductive load

Why the snubber circuit is necessary for inductive load and not for resistive load. What is the back EMF?. When we connect the inductive load how the back emf affect the switching device. how to ...
2
votes
1answer
373 views

BLDC speed and position from back-emf

I'm trying to make my own sensorless speed controller and I need to know the speed and the position. What are the basic techniques used to determine the speed and position of a BLDC motor from the ...
2
votes
2answers
444 views

Filtering Reverse voltage from a coil

I am working on a interface between an Arduino microprocessor and a old electromechanical pinball machine to track the scoring and light up some LED's based upon that. I made a circuit diagram... or ...
3
votes
3answers
266 views

Back EMF with Octal Driver / inverter

I have a project which I am using an octal driver/inverter (DARLINGTON ARRAYS) to allow a micro controller to control 4 electromechanical relays. I have been experiencing relay failure and ...
12
votes
3answers
2k 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 ...
16
votes
1answer
7k 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 ...
3
votes
1answer
371 views

Why do some transformers hum less or not at all when lightly loaded?

It can be observed that large power transformers hum more under load. For example, when some devices are powered up, there is brief "twang" sound: a loud hum that quickly decays as the filter ...
0
votes
0answers
282 views

higher back-EMF voltage like input voltage in Brushless DC Motor?

Currently I am working on simulation model for the non-control Brushless DC motor in MATLAB/Simulink environment. BLDC parameters are from the paper via IEEE online library. For now, I am not able to ...
2
votes
1answer
255 views

Inductance of a HDD BLDC Motor Phase

So I have set up a little experiment which involves a HDD BLDC Motor, a scope and a multimeter. Pretty simple, I know. Is it possible to determine the inductance of a phase by the voltage the phase ...
2
votes
1answer
4k views

What are the advantages and disadvantages of using signal diodes instead of resistors?

In the past to create voltage dividers or protect against back emf I have used resistors, but reading about signal diodes those situations are given as examples. I can't really comment on the inductor ...
6
votes
2answers
2k views

Do solenoids exhibit back EMF like motors?

I just purchased some pinball machine solenoids and was experimenting with them; DC resistance is about 30 ohm, they actuate at about 30 volts, and they hold at about 6. I tried controlling them with ...