Questions tagged [back-emf]
The back-emf tag has no summary.
189 questions
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Can I use simple resistor dividers and ADC inputs for back-EMF sensing in a drone ESC?
I'm designing my own ESC for a simple quadcopter drone. The ESC is powered directly from a 4S LiPo battery, and I'm now working on the back-EMF voltage sensing needed for sensorless commutation. The ...
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Using a transformer gate driver for MOSFET. Can back EMF breakthrough the gate and how the back emf is looks like in this case?
To reduce time of MOSFET switch , we need as much current as possible and recommendations says it can be like 5A.
So, if i make a transformer with proper driver to provide a 5A - 15V on secondary, it ...
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Back EMF regulator for brushed DC motor
I have a simple brushed DC motor controlled and expecting some sort of Back EMF when the motor switches its directions.. Motor will be running at 50V and 5A. I have no design experiences in Back EMF ...
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Short terminals of back driven BLDC motor?
I have a Maxon BLDC motor with a 250 times gearbox in front. When powered off the user can back drive the system. This motor is connected to a Maxon EPOS4. When the user spins the output shaft fast ...
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Designing a Braking Circuit for a BLDC Motor
I have a project that requires controlling a BLDC motor with quick stops. The problem is that when the motor makes a hard stop from a high RPM, the power supply shuts off. It seems the back-EMF ...
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Design of current boost converter part 2
This is a follow up of my previous question Current boost converter and as stated in the answers the issue with the current boost converter technology is the inductor who is in series with the ...
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How to suppress the back EMF in DDSM115?
I am working on a project which uses DDSM115 BLDC motor. When I rotate the motor (its a wheel, hence when I manually push the device) it injects a power back to my ...
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How can I prevent relay arcing when reversing a DC brush motor?
I'm fairly new to electronics and working on a project that uses a 25A 30VDC DPDT relay to reverse the polarity of a brushed DC motor (powered by a 24V battery). The relay has been failing by arcing ...
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Meaning of the Net Voltage on an inductor
I saw an old post "Inductor Back EMF Direction Relative to Changing Current" here on the "electronics.stackexchange" and I have the below queries.
The "net voltage" (we ...
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Path of back emf current in H bridge motor driver
When Q1 and Q4 are turned ON, the motor starts running. However, when Q1 and Q4 are turned OFF, does the back EMF current of the motor flow through D3 to the positive terminal of the battery, then ...
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Motor RPM control by continuous calculating back-EMF from total voltage drop and motor current
As I understand it, normally back-EMF is measured on PWM-driven motors by measuring the voltage during the off-phase of the wave. But this requires a microcontroller for timing.
The equivalent circuit ...
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Bidirectional Power Switch protection
I need to create a bidirectional power switch (replacing contactors) with power mosfets in parallel. Battery pack voltage goes from 12V to 48V and the load (generic, inductive, capacitive and ...
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Weird Hall signals on a BLDC motor
I am developing a BLDC motor controller. I have several BLDC motors and they all have similar Hall signals, but two of them have a difference in the Hall signals. They have a small pulse at the start ...
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What Causes Hand- Wound and Machine-Wound Motors to Have Different kV? Expected Efficiency and Power Differences?
I am trying to understand the motor power and efficiency of two identical motors with the only difference being the winding technique (hand-wound and machine-wound).
Both are essentially the same hub ...
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Why inductor don't discharge completely even when the duty cycle is 50%?
1] My simple buck convertor circuit description
I made this buck convertor on my breadboard- Falstad simulation
The battery voltage is 12 V
And the MOSFET is a N-channel enhancement mode MOSFET
The ...
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Supply voltage of BLDC motor increases during operation
I need some clarity on an issue I have been encountering with my BLDC motors.I am using 2 integrated driver BLDC motors to drive an RC truck sort of device, they run on 24v.
For the most part it ...
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Back EMF & Efficiency of a BLDC Motor
So I've recently designed and built a 3 phase, coreless, brushless DC synchronous motor. I'm trying to estimate its efficiency but struggling to figure out the equations. Specifically, how back EMF is ...
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How to protect N-type mosfets in parallel againt back EMF of a transformer
I saw this schematic on a blog and I tried building it but always burns some of my mosfets. I am using the oscillating and driving part of this schematic with the exception of the battery charger part....
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555 Timer for Motor Direction Control
I am building a circuit to control the direction of a DC motor using two 555 timers. The circuit diagram is given below.
There will be a potentiometer and when it is turned to the rightmost position, ...
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Debugging BLDC gate driver, unexpected back EMF waveform
I'm debugging an electronic speed controller I designed that uses a 3-phase gate driver, DRV8300DRGER, to control BLDC motors. The circuit is shown here (the 2 other phase aren't shown) with the ...
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What are the potentials at front and back of inductor when primary DC supply is disconnected in LR circuit?
I have been learning the basics of inductors in simple LR circuits with DC currents. I think I get most of it but I am a bit unclear about the secondary EMF produced by the inductor after the primary ...
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561
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Relation between back emf and flux linkage
I've encountered a problem when trying to figure out my Electric Machine homework. In the homework's answer, it said that the back emf of a DC motor is equal to the speed of the motor times the flux ...
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How to dissipate regenerative energy from a 400w brushless spindle motor connected to a 10-pound flywheel
I have a project where I have a 10-pound flywheel being spun up by a 48v 400w cnc spindle brushless motor at 5000 rpm, using a WS55-220S motor controller.
As such, when the power to the motor stops ...
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How to find the back-EMF constant of BLDC motor from a motor technical data?
I have a BLDC motor with these info (please don't pay attention to the striped column):
How from these info, how can I get the Back-emf constant ? Is it just 36V/4krpm = 9 V/krpm ?
Thank you a lot.
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Sizing MOSFET VDS to account for Stepper Back EMF
I'm having difficulty conceptualizing how the Back EMF of a motor, stepper in this case, can damage an H-Bridge MOSFET if the Vds aren't sized correctly. My main issue is my understanding of how the ...
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Electric Shock off spinning motor
This large blower powering an inflatable structure has no on/off switch, requiring the actual power plug to be disconnected to power down the item. I frequently get a painful shock off the plug, and ...
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Circuit to measure back EMF around an H bridge
I want to design a circuit with an H-bridge to control a brushed DC motor. In order to control its speed, I want to measure the back-EMF of the motor and make a PID control loop in software. I do not ...
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How can I clamp the voltage precisely from the back EMF of a brushed DC motor?
I am using DRV8412DDWR in a medical product, where we are driving two DC motors (graphite brushed) bidirectional using PWM.
In our application, we have to suddenly stop the motor. When we do that, we ...
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Bulk capacitor sizing to protect H bridge during motional EMF
I'd like to drive a 30 V motor with this H bridge driver and an Arduino.
The problem is that on top of working in forward motoring and reverse motoring conditions, it will also work in forward braking ...
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Voltage behaviour in battery-powered vehicle when motors regenerate
I am wondering how the voltage in a battery powered vehicle will behave in case its BLDC motors are acting as generators (i.e. while decelerating). In a system powered with a DC/DC converter for ...
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If you put a polarized capacitor parallel with a coil, can you leave the flyback diode out
I want to set a relay when an object passes an IR sensor.
The IR sensor controls the NPN transistor which powers the relay coil.
It may be that the passing object has some holes which allow the IR ...
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Troubleshooting a force feedback wheel with a DC motor that resets when blocked from rotating in a specific direction
I am troubleshooting a electronic force feedback steering wheel (Fanatec Porsche 911 Turbo S Wheel) that uses a DC motor for force feedback. The wheel restarts every time force feedback is activated, ...
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About the I1N1 = I2N2 equation
I have a silly question about this equation which is very frequently used in ideal transformer relations. If I draw the electrical equivalent circuit of the core, then the MMFs of 2 coils N1I1 would ...
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Is back-EMF an issue in a push-pull converter when both driving transistors are off?
For reference, I am talking about a conventional push-pull converter topology as discussed e.g. in this question.
Wikipedia has the following to say about transistor timing in the push-pull converter (...
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BLDC back-EMF zero-crossing detection using comparators: resistor confusion
I am building a sensorless BLDC driver development board using an RP2040 chip and I plan on detecting the back-EMF using comparators. After reading quite a bit about the BLDC phases and methods to ...
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Does Back EMF change according to stator current in SM?
The concept of Back EMF always confuses me in Synchronous Machines. If I have a synchronous machine and I manually rotate at "x" rpm, do I get the same back EMF as when I excite the stator ...
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Free wheeling (back EMF) diode for latching relay
I'm designing a circuit to drive a single coil latching relay. This uses two MOSFETs, arranged so current flows one way through the relay coil to switch it on, and then the other MOSFET activates to ...
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Understanding back EMF current in DC
I am trying to make a kicker solenoid. My circuit is:
12 V battery connected to DC step-up booster 300 V
diode A10A. The diode is rated for 10 A and 1000 V.
thyristor BTW69-1200 with external ...
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Switching inductive loads without flyback diodes
I came across a commercial design which switches coils using N-channel MOSFETs (two in one MOSFET in a SOIC package). It surprised me a bit that there were no flyback diodes in parallel to the coils. ...
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H-bridge back EMF
I've built a H-bridge circuit to control a brushed DC motor. A schematic of the H-bridge is shown below:
When designing the H-bridge I didn't add any diodes in parallel to the MOSFETs as I had ...
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Coil abrupt discharge BEMF amplitude
My goal it to understand and attain the highest voltage possible for an amateur experiment.
Can't find specs on BEMF properties, only that it's a "dangerous spike" on the instant a switch ...
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Circuit protection from voltage spike
In order to suppress the voltage spike getting from an AC single phase motor (it is an exhaust type fan connected to 10 A relay) can somebody please guide me to select a proper protection device.
To ...
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How to get the back EMF graph of my BLDC motor in an oscilloscope?
I have a BLDC motor and its controller. How can I see its back EMF graph using an oscilloscope provided I can see the phase-to-phase voltage graph?
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How pick/calculate flyback diode current value?
Say I have a design that switches a 5A coil using a MOSFET.
In order to protect the MOSFET, I place a flyback diode parallel over the coil.
If the coil is switched off, a back EMF current will flow ...
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Why use only one comparator for back-EMF (ESC build)
I’m working on an esc project. I’ve got the motor spinning by just using a timer to switch the phases on and off. Now I’m trying to include circuitry for BEMF reading. I was watching a video from ...
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4-20mA ADC, HV DC measurement & DC/DC PSUs schematic validation [closed]
Hello i am designing a small Li-ion battery charger based on an custom generator which produces 36v DC output and i have designed a PCB that controls the whole procedure and logs the measured data to ...
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Will a flyback diode damage my battery due to back EMF?
I am following this example of a sensored BLDC motor.
This post assumes conventional current flow.
I am trying to understand how the diodes in this circuit protects the rest of my circuit from back ...
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Will primary flux & secondary flux (back MMF) in a transformer attract or repel each other?
I couldn't find it on google or may be I am not using the right keywords, if my terminologies are not sounding accurate, please bear with me, I am beginner in electrical engineering.
When the primary ...
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Why does the signal and power supply in my custom ESC breadboard become so noisy when the motor is rotating?
I am building a custom ESC to drive my BLDC motor. The motor spins in open loop and I want to debug the back-EMF detection circuit, but as soon as the motor spins, the signal line of the MCU (MCU uses ...
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