ethernet W5100 problems - stops working

i've bought some Arduino Nano, maybe clones

with Relay card

and Ethernet Module

I am using this hardware in 2 configurations:
one is a OneWire-Shield, connecting all available pins to DS18B20-Sensors and sending to my Automation software. This one works fine, without any problems.

The other one is including a Relais and operates a temperature control valve (open and close).
the nearly same sketch is running on a arduino uno ( i think its original)

with this ethernet shield

on the nano i have the problem, that the ethernet shield stops receiving and sending, the arduino is running great (visible about the serial console). When i used tcpdump, it seems as the shield is not answering to arp-requests, and in consequence its no more reachable via ethernet.

Resetting the Ethernet shield has no effect, powering off the complete circuit, including relais, arduino and shield makes it working again. I cant figure out the problem, as the other arduino is working fine over and over.

Thanks for your thoughts...


Please post your code in the forum and don't provide links to the online editor as you seem to be the only that is able to see the content there. Use code tags!

I don't understand if the setup with the UNO and the Ethernet shield is working because you don't say anything about that but start to write about a Nano board not working although just before you told us that the Nano board is working.

Please provide wiring diagrams of all the setups you have (may be hand drawn).

Hi pylon,

i have three boards (code follows)
Board a) is an Arduino Uno with ethernet shield and Relais. It is almost always working (no more failures with last code version)
Board b) is an Arduino Nano with ethernet shield, but without Relais. It is always working from the beginning until now. I never had any Problems caused by the Arduino with that.
Board c) is an Arduino Nano with the same EthernetShield as Board b) and the same Relaisshield as Board a). It is not working at all, as the Ethernet shield stops communitating while the arduino itself works as designed.