HW projects - Weather station

the weather station setup

This is my weather station project page. The weather instruments in the setup are based on 1-Wire bus and devices by Maxim (formerly Dallas Semiconductor).

About 1-Wire:

1-Wire bus and chips are designed so that only one wire is required for communications and to power up the connected devices. This is archieved by charging a small capacitor inside each device from the data line to supply it for the periods when the bus is in low state (while it is communicating with the devices). The signal / power wire also requires a return path so two wires are actually needed.

It is also possible to power up most of the 1-Wire devices externally which is useful in high load networks with lots of connected devices. Also, in some cases additional circuitry may require external current / voltage. The bus wiring can be quite long, possibly several hundreds of metres if good cabling and proper adapter (bus master) is used.

Current weather station setup:

Module:	Function:	Model:	Manufacturer:
Temperature sensors	Measuring temperature	DS18S20	Maxim (Dallas)
Wind instrument	Wind speed & direction (+temp)	TAI8515	AAG
Humidity sensor	Measures relative humidity	H3-R1-K	Hobby Boards
Rain gauge	Measures precipitation	Rainew 111/RG1-R1-A	RainWise/HB
Barometer	Measures atmospheric pressure	B1-R1-A	Hobby Boards
Solar sensor	Measures solar radiation	S3-R1-K	Hobby Boards
Lightning detector	Counts nearby lightnings	LD4-R1-A	Hobby Boards
1-wire RS232 adapter	1-wire to PC interface	DS9097U-009	Maxim (Dallas)
PSU / OVP module	Power supply & OV protection	-	DIY
6 Channel hub	Active switch needed for star topology	6CH1-R3-A	Hobby Boards
LCD modules	Two 20 x 4 LCD displays for viewing data	-	DIY / HB
Current software	Data capture and plotting	Oww 0.83.1 / RRDtool	Oww/RRDtool

Weather station news / updates:
30.5.2010 - 1-Wire adapter fixed. It had a shorted protection diode. Added one additional temperature sensor and restored connection to the wind instrument to get it running again.
23.5.2010 - The DS9097U 1-Wire adapter (bus master) died along with one hub segment during a thunderstorm. I moved the weather mast cable branch to undamaged hub part and fixed the 1-Wire adapter.
5.1.2010 - Added two new temperature sensors (wine cellar and compost bin). Modified the hub to to feed itself from pre-supplied external power from bus cable instead of using external AC-adapter.
3.12.2009 - Two 20 x 4 character backlit LCD modules added for viewing live sensor data. Wind vane seems to have a tendency to jam near sub-zero temperatures because of frost build up.
17.11.2009 - Hub added, barometer and two additional temperature sensors now connected.
16.10.2009 - Station permanently installed, data publicly available. Barometer, rain gauge and six temperature sensors still disconnected from the bus since the system seems to have issues related to cable impedances due to my mixed and sloppy daisy chain / star bus topology. I will get a 1-Wire hub to fix it.
5.9.2009 - ...or so I thought. There were some odd daily spikes from instruments using DS2423 counters (wind speed & lightning detector). It took some time to figure what was wrong and it turned out to be a timing issue related to periodic Linux chron NTP corrections. Switched to daemon (NTPD) to prevent any glitches from happening. More info about this from Karl Uppiano's website.
31.8.2009 - Everything OK, database and available sensors operational.
30.8.2009 - Added project info page and mounted the station outside for testing.

The station @ weather underground:

• main ws info page

• general info
• temperature
• wind
• humidity
• rain
• barometer
• solar
• lightning

• weather data page