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rimpul
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Regarding Suppression of Back EMF

09/21/2011 3:19 AM

Hello,

I am using microcontroller atmega64 to drive the induction motor. But due to back EMF my code in the controller gets rebooted that is, code will get initialize again and again due to back emf.... .so is their any method to solve this problem??

Regards

Rimpul
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PWSlack
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#1

Re: regarding suppression of back emf.

09/21/2011 4:01 AM

How about wiring a silicon rectifier in series with the motor?

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PWSlack
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#6
In reply to #1

Re: regarding suppression of back emf.

09/21/2011 6:27 AM

And another reverse-biased in parallel across the motor terminals?

It is assumed that everything is DC here.

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#7
In reply to #6

Re: regarding suppression of back emf.

09/21/2011 6:37 AM

Induction motors are AC n'est ce pas?
Del

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PWSlack
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#9
In reply to #7

Re: regarding suppression of back emf.

09/21/2011 7:47 AM

Ah!

Then disregard the above. It is something other than the motor back-EMF that is causing the problem.

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#2

Re: regarding suppression of back emf.

09/21/2011 4:22 AM

Microcontrollers are sensitive to spikes on the voltage rails, specifically negative going spikes can often cause the micro' to reset.

You need good isolation between the power rails and the microcontroller supply. It is best to isolate any feedback signals with opto isolators.
Look for any path for negative spikes coming down the power rails. Radiated noise can also be a problem Is this on a circuit board you have laid out yourself?
I've had boards where a few links of copper wire between differnt points on the ground plane have solved the problem.
For a more considered comment we need to see a circuit diagram and a circuit board layout.
First port of call is to get a 'scope of the power supply to the micro'.

Suppression round the motor and a big ferrite torroid on the leads may help too.
Del

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rimpul
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#3
In reply to #2

Re: regarding suppression of back emf.

09/21/2011 5:16 AM

thank you for your reply..

but sir i am using relay to trigger the start and stop of the motor..so it is possible to suppress across the relay rather than the motor??

regards

rimpul
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#4
In reply to #3

Re: regarding suppression of back emf.

09/21/2011 6:02 AM

supress across everything!
Relay contacts will certainly arc and cause interferrence, so yes they need supressing.
Del

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rimpul
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#8
In reply to #4

Re: regarding suppression of back emf.

09/21/2011 7:27 AM

thank you for your suggestion sir..

sir can you please tel me which diode should i use to suppress the back emf because in IN4007 i am not able to suppress it? or should i use any other protection circuit across the relay?

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rimpul.
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PWSlack
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#5
In reply to #3

Re: regarding suppression of back emf.

09/21/2011 6:26 AM

The relay should have a rectifier wired across it reverse-biased, so as to stop the back-EMF from the coil when the magnetic field collapses at switch off. It might not be the motor at all!

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Andy Germany
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#13
In reply to #2

Re: regarding suppression of back emf.

09/22/2011 7:21 AM

Liked your Post, that's the way to go...opto isolators.

GA.

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regsoft
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#10

Re: Regarding Suppression of Back EMF

09/21/2011 11:06 PM

How big is the motor you are driving? You could probably drive it with a triac directly or an opto-triac for the same or less cost by the time you tame the relay.

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UsernameJUDGE
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#11

Re: Regarding Suppression of Back EMF

09/21/2011 11:18 PM

Use lots of ferrite beads on data cable

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Tonymech
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#12

Re: Regarding Suppression of Back EMF

09/22/2011 1:05 AM

Hi Rimpul

Would a thin steel plate to ground around the noisy bit reduce the radiation reaching the micro. We install radio remote control units for screens and occasionally the receiver gets put in a shed or steel cabinet and the remote control doesn't work. I've had similar problems with micros motors and solenoids. Maybe post a photo of the setup.

Tony

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Rockyscience
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#14

Re: Regarding Suppression of Back EMF

09/22/2011 8:22 AM

You might look in to placing an external brake module and resistor on the drive.

It must be sized correctly for the motor.

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FLIPFLOP
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#15

Re: Regarding Suppression of Back EMF

09/22/2011 5:35 PM

add a reverse biased diode between the motor and microcontroller. make sure you select one with the correct characteristics for you application.

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Sasnak
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#16

Re: Regarding Suppression of Back EMF

09/23/2011 9:51 AM

I hate to be the simpleton here but, the last time i continuosly recieved a code like that on a drive, it was a very minor short to ground. Dosen't make sense I know. The rubber tape wrapping the kearney connector had rubbed off just enough to leak to the case on the motor. Even thought it may seem redundant, you might check all connections. Make sure of proper grounding per manufacture specs, and, use a megger to check insulation on the motor. Good Luck!
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Users who posted comments:

Andy Germany (1); FLIPFLOP (1); PWSlack (4); regsoft (1); rimpul (2); Rockyscience (1); Sasnak (1); Tonymech (1); user-deleted-1105 (3); UsernameJUDGE (1)

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