WIZnet Developer Forum

W7500P Industrial Application Issues

I’m using a 5V Relay with WIZwiki-W7500P demo board. When the relay is active, the LEDs of the Ethernet socket go out and the ethernet connection is broken. We see this problem on a card we use with the W7500P. Can this processor not be used in industrial applications?


can you share your electronics schematics to evaluation? I’m afraid your relay does not have protection against voltage spikes, natural when you interrupt the circuit on an inductor. Maybe the “free-wheel diode” is what you need to garantee safety to your MCU.

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Sending the schematic.

  1. This product makes the customer hinge on the electrical panel and there are various relays and contactors in panel .Customers often do not set circuit protection components(as free-wheel diode).
  2. Other ethernet modules(Tibbo ethernet module, LPC17XX+DP83848 used module, ) we use have never experienced this problem.W7500P-Schematic.PDF (372.4 KB)


I can’t find where you connect the module on the W7500P in the schematics, is it there? I use the W7500 to switch a 12V solenoid, but i make use of a transistor to secure that there is no excessive current drawn from the pins. If you are using a relay module, it’s probably already there. One thing that might be occuring is that your relay is drawing more current that the 5v regulator can supply, that you could check monitoring the 5v voltage with an osciloscope or even a multimeter.

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Hi mutlu.

I think GND and AGND are separated, and it seems that EMI is showing such a symptom.

We recommend that you change the L3 of WIZwiki-W7500 to Oohm and test it.

In addition, connect the body of RJ45 to earth GND.

And I need to know how you connected the relay.

Thank you.


Hi Scott,

Sending the connection diagram.

I made them specified. Problem saw an improvement, but not enough.
Before the changes, 90% of the ethernet connections were disconnected
when the relays were active. Problem this situation fell to 30%.

I’m waiting for your help. Thank you.

2.02.2018 11:57 tarihinde Scott Jeong yazdı:


The answer I sent to the Wiznet about the problem;

Wiznet–> Please note that our previous comment was not taken into account in the schematic of customer.

Mutlu–> We implemented exactly what was recommended in the WIZNet Forum. Our current schematics are as attached.

Wiznet–> Do not separate GND and AGND.

Mutlu–> R44(0 ohm) instead of FR3 and GND plane expanded. We also use the instructions specified in the attached file(PHY IP101 LAYOUT GUIDELINES).

Wiznet–> Remove R30, R32, R34, R36(49.9 ohm resistors)

Mutlu–> There are places in the pcb, but not installed.

Wiznet–> Use of ESD protector IC

Mutlu–> We use TPD4E001(U9) for ESD protector. Look at the schematic.

Wiznet–> Shield GND of RJ45 should be isolated to system GND.

Mutlu–> We used a 2.2n 1kV cap between system GND and shield GND.

Wiznet–> Schematic of customer has much different from our W7500 Ref. schematic.

Mutlu–> There is no difference between schematics because we make the above items.

Emko_Schematic.pdf (59.9 KB)

Hi mutlu.

Is there GND on the top side?

When you look at the photo you uploaded, it looks like there is no GND side on the top side.

Did you set GND to trace?

The MDI signal must be protected by GND.

You should also have as much GND as possible.

Therefore, GND should be plane. But your board seems to lack it.

The MDI signal must be protected to GND as much as possible.

It is recommended to connect the shield of RJ45 to ground GND.

Please send us your Gerber file and it will help us.

Thank you.


Hi Scottt,

I’m sending the Gerber file. You can examine.

Thank you.

gbr.zip (37.2 KB)

Hi mutlu

I said,

There is no GND on your board TOP. Only in Bottom.

This seems to be the cause of the problem.

Please listen to my opinion.


Hi Scott,

We have observed this problem at WIZwiki-W7500P ,
your demo board.

  So could you send us a gerber or pcb file that could be a

reference to us?

  Does it solve the problem if the card is 4-sided? Is this

absolutely necessary?

Thank you.

Deat mutlu

We do not have Gerber or PCB data to refer.

You can refer to the URL below.


And what does this mean?


Hi Scott,

I meant to say 4 layer pcb drawing. For example, your WIZ750SR(https://github.com/Wiznet/W7500x-Serial-to-Ethernet-device/tree/master/Hardware_Materials/Reference_WIZ750SR) card has four layers.

In my first W5500 project i see same problem. I m using 5V relay and drive with transistor. If relay on W5500 lose connection. I add a diode to relay bobin (reverse polaritiy) then circuit work fine.

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