enc28j60 has problem when it reset a relay after while

[Sharagim]

Hi,
I have a problem with enc28j60 module and xmega64a3.
It is trying to reset a relay which wants to handle a 220V , but after a few reset enc28j60 module wont reply to requestes.
You can see the schematic on below.
Thanks it in advance.

 

[andre_luis]

Sharagim,



The main reason for occurrence of this reset, could be some spike generate by relay coil coming from +5V bus to +3,3V across regulator.
I could suggest investigate other power supplies topology in order to guarantee better isolation of both voltages ( signal and power ).

Other likely possibility is at layout scope.
Check if 3,3v and 5v nets are too much near, enough to couple induced spark current.


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[Sharagim]

Thanks for your reply.
In this project I am using a 220v to 5V switching supply, you mean change it ?
I have attached my PCB ,maybe you can spend a few seconds and take a look.

 

[andre_luis]

Sharagim,


I noticed you did´t drawn a GND copper plane, which could shield some induced spike current.
Other effective proceeding could be distribution of a greater amount of decoupling capacitors along Power supply and Signal supply bus.

In a safe layout design, you must place power components - such as Tyristors and Relays - at a separate region from others.


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[Sharagim]

for troubleshooting I changed opto output transistor and relay power supply with another 5V power supply. So that part is completely is on different from the micro and enc. I put opto,transistor and relay other board (vera board) and move it about 20cm apart. but yet I have that problem
Really I find it amazing. Maybe you have something else for me.
Thanks

 

[bigdogguru]

What type of loads are the relays switching?

You maybe experiencing the effects of Relay Transient or Contact Arc EMI, in which case you will need to implement appropriate snubber or EMI suppression circuits to reduce the generated EMI.

Relay Protection & EMI Suppression



R-C Snubber Noise and Arc Suppressor

BigDog

 

[andre_luis]

Just a test :



If is provided at your design greater voltages such as 12v, try use a Relay rated to that specification.
The reason is that required force to move contact is directly proportional to amount of coil winding turns :

It means that antenna coupling effect perhaps could be potentiated at smaller relays.

**broken link removed**




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[Sharagim]

Thanks for replies.
Load is 60W lamp, nothing special.
As I mention before I have this problem when there isn't load.
with load happening much faster.
I will change the relay tomorrow and will give feedback here.

 

[Sharagim]

Hi,
I found a a temporary solution which is 20ms sleep just after port toggle in this way I don't have such a problem with this device but when I try to run another device I have a problem again , when I toggle first device port I see enc problem again on second device ad vise versa !?
I put these two devices about 1 meter apart but not helped !? Even when I toggle a switch manually by hand I see this enc problem .
Is it possible which this noise coming from AC cables? ARC could be in 1 meter distance ? any idea to help me ?

 

[andre_luis]

This reset occurs when Ethernet port is connected to network cable ?
And are you using RJ-45 connector with built-in transformer ?


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[Sharagim]

thx for reply.
Yes , it is happening when the cable is connected !? and the module has build in transformer.
When I removed the cable I trying toggle sometimes and I didn't see any problem with enc

 

[andre_luis]

Sharagim,


Take a measure on cable to check if ground shield is properly connected to connector.

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[Sharagim]

I tried different cables and I problem exist on all of them.
The only way which I dont have such a problem is to move it about 10m-15m from first device .
My current load is a Contactor which is handling a lamp. maybe inductive load make this problem now?

 

[andre_luis]

Sharagim,


Contactor is a device which can produce and induce an expressive spike on relay bobin.
Take im mind you placed Ralay too much near to RJ-45 connector, at surelly this could be the mean reason for problem.


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[Sharagim]

My current sch is like this :
opto -> Transistor -> Relay -> Contactor
When I remove Contactor this is happening rarely but with Contactor it is happening very fast.
Is there any way to reduce Contactor spike (snub, diode , ...) ?

 

[andre_luis]

Sharagim,


You routed power tracks just bellow RJ-45 connector, which can easily induce some interference to enc28j60 during Contactor commutation. The recommended proceeding is to route a plane down, electrically connected to the body of connector.

Taking a more accurate overview at the PCB layout, I could not find chassis pins of RJ-45 connector, and I presume you didn´t used a shielded model. I wish not say this, but considering placement and routing issues, this layout design is very willing to suffer with this problem, and even risk to burn other devices connected to the same LAN.



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[Sharagim]

100% I am agree with you. this design has many problems now I am trying to make it better and I have a few questions:
1- Which is better for putting on relay coil ? RC snubber or Diode ?
2- What is your idea about varistor on ac input ? do you think if it helps ?
3- My enc28j60 is on a module , so I have socket (5x2) which is about 15mm , what should I do for them?
BR,

 

[andre_luis]

1- Which is better for putting on relay coil ? RC snubber or Diode ?
You can use both, although there are a peculiar kind of snubber topology, which contains R-C-D elements.
2- What is your idea about varistor on ac input ? do you think if it helps ?
I agree to apply varistor only to protective purpose, but due to foreseen surge current due to cutoff action, this could worsen
3- My enc28j60 is on a module , so I have socket (5x2) which is about 15mm , what should I do for them?
These arduino-like modules are not well suitable to aggressive actuators such as relay drive solenoids


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[Sharagim]

After collecting advises I changed :
1- SSR relay to help me toggle on zero cross.
2- Trying to keep away enc module from power lines.
3- Using ground plane.
I have attached the new PCB design below, I am appreciate your comments.

 

[andre_luis]

Sharagim,


I noticed that fixation holes on attached mainboard are not connected to GND plane, and it could improve reliability.
Check on ENC28J60 module if their holes are connected to its Ground, and once confirmed, you can use metalized screw to distribute equipotential GND.


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