old Lacrosse WS3600 Weather Station
My Old Weather Station Installation
The rain gauge cable was lengthened a few metres. The wind sensor cable was lengthened by perhaps around 10 metres.
This shouldn’t be on the roof (readings potentially affected by high winds) but I couldn’t find anywhere else that I could wire to that wasn’t either affected by a rain shadow (from building, fence or bush) or sprinklers.
The wind sensor should be much higher (theoretically 10m above ground) but I think this will suffice. There is nothing taller for 40 or 50m, and even then that is only a few thin trees.
Testing the rain gauge
Electrical
The reed switch is open circuit at each of the rest positions, and closes as the see-saw tips. This means you cannot use a multi-meter to test the wiring and switch with the rain gauge at rest (because the switch is open-circuit and looks the same as a broken wire).
If you have the cable unplugged and you connect your meter (on the Resistance or Ohms setting) across the outer cores of the plug (or across the reed switch) and dribble water into the gauge, the switch should close long enough to cause the meter to flicker or beep (it closes for between 110 and 150 milliseconds each tip). If it doesn’t, remove the cover and position the see-saw mid-way with your fingers and check again. In this position, you should see a few ohms or less. (If not, the reed switch is probably faulty.)
If you have the cable plugged in, you should measure about 3V across the ends of the reed switch with the see-saw at both rest positions. As the see-saw starts to tip, you should measure 0V until it reaches the other rest position. As mentioned above, when it tips normally with water, the switch only closes for a very short period of time. Most meters will not have to time show 0V, but will probably flicker as the see-saw tips.
Mechanical
3.5 cm3 (or 3.5 milli-litres) of water should cause the rain gauge to tip and register 0.51mm of rain.
Rain Gauge Repairs
The reed switch in the rain gauge failed. I replaced it with another switch the same length (14mm) purchased from a local electronics shop but it gave multiple registrations for a single “tip” of the buckets – particularly if water was dribbled into the gauge quite fast.
On investigating, I found that the “see-saw” had a small amount of movement along its axis (the hinge point). If it was slid close to the reed switch, the switch failed to open when the buckets were at rest in one of the 2 rest positions. If the see-saw was slid as far as it could go away from the reed switch, all was well.
I tried re-positioning the reed switch 5mm higher up the PCB. Although this solved the problem of the switch being closed at the rest position, it opened at the mid-point of the movement (which would have resulted in 2 registrations for each tip of the buckets).
I eventually installed a shorter (10mm) reed switch. I was able to install it such that it always opened at the rest position (although when the see-saw was close to the switch, it only just opened).
I recommend that if you replace the reed switch, you carefully check that:
- The switch opens in both rest positions with the see-saw positioned as close to the reed switch assembly as it will go, and
- The switch closes when the see-saw starts to tip with the see-saw positioned as far from the reed switch as it will go (and remains closed until nearly at the other rest position)
Note there is no need to apply any pressure when moving the see-saw sideways on its axis – just very gentle pressure.
Some Technical Details of the Rain Gauge
- The reed switch is connected across the outer 2 cores of the 4-core cable. (This means that if you extend the cable using one of the commercially available joiner sockets, you don’t have to worry that the cores are swapped.)
- The open-circuit voltage across the reed switch is about 2.8V
- The short-circuit current is about 30 micro-amps. This is VERY small and leaves the signal susceptible to electrical interference. However, on the flip-side, it means that cable length (and resistance) will not be a problem as long as you can avoid electrical noise from being induced into the cable. This can be done by simply running the cable away from other electrical appliances and wiring, using twisted pair cable (instead of flat phone-type cable) or shielded cable (but with the RJ11-type connectors on the ends, connecting the shield to a ground gets messy).
- The reed switch closes about 13mm from the magnet, and opens about 14mm from the magnet.
- There was some switch bounce on switch closing with my new 10mm reed switch, however, the bounce was all done in about 41 microseconds (very repeatable). There was no switch bounce on switch opening.
- The switch was closed for between 110 and 150 milliseconds with my new 10mm reed switch.
- Collection area is 125mm x 55mm
Cable Details
PC Data Cable
Note that although this does look peculiar (no connection to RD for example) – it is correct. The WS3600 does not use an asynchronous serial protocol (ie normal RS232 serial as used by PC serial ports). Instead it uses a synchronous protocol using the handshake lines.
| RS232 Function | DB 9 Female | RJ12 |
| CD | 1 | n/c |
| RD (to PC) | 2 | n/c |
| TD (from PC) | 3 | 2 |
| DTR (from PC) | 4 | 3 |
| 0 V | 5 | 1 |
| DSR (to PC) | 6 | 5 |
| RTS (from PC) | 7 | 4 |
| CTS (to PC) | 8 | 6 |
| RI (to PC) | 9 | n/c |
Thermo-Hygro-to-Display Wiring
This cable needs a “cross-over” (ie 1->4, 2<->3, 3->2, 4->1)
Wind and Rain Sensor Wiring
Thermo-Hygro Cabled vs Wireless Behaviour
When the Thermo-Hygro unit is communicating with the base station (display) via wireless, a little icon (perhaps looking like radio waves) appears to the right of the outdoor humidity display when the base station is interrogating the thermo-hygro unit. The icon stays displayed for 5-6 seconds each time it communicates, and display data updates at the end of this time. If the wind speed is below 10kph, the base station transmits every 128 seconds. If the wind speed is above 10kph, it transmits every 32 seconds.
When the thermo-hygro unit is cabled to the base station, the little icon is never displayed. The display updates at the same rate as described above (when communicating via wireless).