The GHowSA network initially started as a simple home weather station. This network was then extended to include other features such as electrical energy
monitoring and environmental monitoring and control of a vegetable garden. The initial experience and learning with the weather station led to the development of
several codes of practice for wiring one-wire networks that I use for the overall network
Network Wiring Practice
From experience I have found that adoption of the following points has resuted in a network that is stable with minimal data errors and generally
resistant to the vagaries of the South African weather including violent hail and rain storms. However lightning is still a problem and even with
optical isolation and good earthing a ground strike within a hundred metres will take the system down. The most susceptable component in my network
seems to be the USB to 1-wire adaptor (DS9490R). If there is a nearby ground strike the first sign of any damage is an increase in the data read error
rate which is rectified by replacing the USB to 1-wire adaptor (DS9490R). I always keep a spare of this adapter!
The following guidelines for one-wire network wiring have provided good results for me:-
- Refer to the detail information on one-wire networks in the
One-Wire-Design Guide v1.0
from Springbok Digitronics
- Use CAT5 cable with RJ45 connectors for all internal links and especially long runs (more than 10 metres)
- Choose a RJ45 wiring convention and stick to it!I use the
HobbyBoards wiring convention throughout the network.
- Provide a connection interface between internal RJ45 wiring and outdoor wiring and place the interface indoors. The
RJ45 connections of CAT5 cables are susceptable to condensation and moisture.
- Use good quality two (one-wire only) and three (one-wire plus power) core cables for all outdoor wiring.
- There must be no joints in the outdoor wiring.
- Keep the lengths of outdoor wiring as short as possible and preferably less than 10 metres.
- All outdoor slaves/sensors must be properly encased and wired using a waterproof gland.
- Use a hub to isolate major network branches. I use a 6 port hub to isolate the GHowSA weather network, the GHowSAG garden network
and the GHowSAE energy monitoring network.
GHowSA Network Configuration
The current configuration of the GHowSA network is shown in the figure below. Note that the atmospheric pressure sensor in the
office also serves as the interface to the external wiring for the GHowSAW weather system.