Electromagnetic compatibility PSoC5- Cortex ARM-M3

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Anonymous
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Hello. 

   

I made a pcb with PSoC5 (CY8C5566AXI-061)and wrote a simple program that increments a variable every second, and displays it on LCD. 

   

I programmed the PSoC, the program works fine.

   

But when i place an old soldering gun (like this http://goo.gl/6ujlt) near the microcontroller, and i repeatedly press and release the soldering gun's button, the counter displayed on lcd resets (so, i guess the microcontroller resets) or sometimes increments with 10, or changes the text position.

   

The soldering gun was placed near the microcontroller at about 1-2cm. 

   

I wonder if there will be any problems with this mcu being used in a industrial environement.

   

Is there someone who used it in such environement?

   

I tried shielding the mcu with a thin metal foil soldered to ground but nothing changed.

   

What can be done to improve mcu's imunity to EMI?

   

P.S. I didn't knew where to post this question in the forum, sorry if this is not the right place. 

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13 Replies
Anonymous
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Hi adrian_,

   
   

 

   
   

Please refer to AN57821 for circuit board layout considerations.

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Anonymous
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 I'm afraid that this is not a design problem.  Is there someone who used PSoC5 in industrial environment? Do they work fine in such environment? I want answers from someone who used PSoC5 in this environment. Many thanks.   

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Bob_Marlowe
Level 10
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I'm afraid that EMC HAS to do with design. The electro-magnetic pulse of a transformer can intrude a circuit easily when there is not enough taken care for that.

   

Take your crt-scope and see, how it triggers when acting the solder-gun. The soldering side of the gun is a coil (with 2 or 3 winds) and can easily induce voltages into a pcb.

   

In an industrial environment there are sources for EMC: The power-supply / power line and electro-magnetic noise which must be shielded.

   

 

   

Bob

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Anonymous
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 I wrote the same program (that increments a variable every second and displays it on LCD) on PSoC5 CY8C5568AXI-060 module which came with CY8CKIT-001.I used the development kit for the same experiment as above, and same things happened. I still want to know if there is someone who used PSoC5 in industrial environment. Thanks in advance.  

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Anonymous
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The heating element of the soldering gun can be considered as an extension of the secondary coil of the transformer and conducts a large amount of current. Soldering guns are typically equipped with a mechanical switch which rather abruptly interrupts the current flow when released, causing large di/dt changes. The large magnetic flux changes caused by soldering gun will certainly induce voltage spikes in your circuit. You can improve your design by sandwiching the signal lines between planes.

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Anonymous
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 Here is the pcb (2 layers). I would apreciate if someone could spend some time and take a look and tell me what is wrong. Thanks in advance.

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Anonymous
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I've encountered similar behaviour when developing my home automation system,which involved AC relays switiching in close proximity of the controller.Adding a simple RC snubber fixed it.Maybe it could help you too..

   

Nice PCB design! just curious,did you design it for hobby purposes? or with some specific application in mind?

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Anonymous
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 Thanks, the pcb is the work of one of my colleagues 🙂 . This is not a hobby project. This board will be used in industrial environment and we don't know if this mcu can work in such environment. I don't know if the problem is the mcu or the pcb design. 

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Anonymous
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I guess a snubber,and a 4 layer board as well as using ferrite beads on all connections to and from the board,could help.

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Anonymous
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 We don't have quite a specific aplication for this board. It will be used in automation systems, that's for sure. Snubber circuits are used for inductive loads(like motors, coils ...) for preventing high voltage spikes, and reduce EMI . We only design the logic control of the automation system, and we have to make sure that our design can work in close proximity to the power electronics. The pcb from above, is for the main board to which we connect other modules (like LCD's, keypads, sensors).      

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Bob_Marlowe
Level 10
Level 10
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Will you please explain "snubber" to me? Even my favoritre translater comes up with something far away from electronics.

   

Here in Germany, where everything is ruled, controlled, checked and certified there are some DINs concerning EMV conformability. They principially state two different modes:

   

1st. The device may not GENERATE noise into its environment (power-lines, neighbours etc)

   

2nd. The device must not suffer from noise from the outside ie. must be shielded to prevent disturbance.

   

Shielding the traces of the pcb between two ground-planes is really recommended, shielding the whole device within a "can" could prevent from magnetical influence and is widely used for rf- or HFdevices.

   

 

   

Happy shielding (sorry, smileys don't work here)

   

Bob

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Anonymous
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 snubber is a device used to suppress ("snub") voltage transients in electrical systems, pressure transients in fluid systems, or excess force or rapid movement in mechanicalsystems. (http://en.wikipedia.org/wiki/Snubber)

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Anonymous
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 Hi,

   

Typically, the EMI performance is a system related and not only chip. The traces on the board picking up the electro-magnetic interference noise. Therefore it is good to relook at the PCB once, with several suggestions coming out here.

   

Also, testing the system with solder gun for EMI is not good method to rely upon. It is better to put the board under standard tests which create measured radiation levels and test the board. Depending on where you use your board in end application, proper test should be done. I once did EMI/EMC testing for CapSense applicatoin. The test standard was :

   

IEC 61000-4-3 for Electro Magnetic Susceptibility (which we are talking about here).

   

This standard applies radiation of intensity 10V/m to the DUT. The frequency range of the test is 80 MHz to 1 GHz. The radiated signal is amplitude modulated by 1kHz signal to the depth of modulation of 80 %.

   

IEC 61000-6-3 for Electro Magnetic Emission 

   

This standard measures radiation levels emitted by DUT at different antenna heights and orientaion. The raditaion emitted by DUT should be less than 30 dBuV/m to pass classB limit.

   

So, for your application, along with suggested board improvments, please go through standard tests to checkwhere the system (board and chip) performs. 

   

http://www.iec.ch/about/brochures/pdf/tools/emc2002.pdf

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