I now have a working 1-wire circuit for my new wind sensors. It uses the usual reed switch and magnet for the anemometer but optical encoding for the wind vane (I was unable to produce an effective read switch version). I have overcome the need for more current than available parasitically from the 1-wire network by switching the LEDs on only during the reading process. A fairly large electrolytic capacitor supplies the LED current for the short period they are on, being recharged in the off period.
Attachment:
1-wire_vane_optical_gray-11-02-21.png
The anemometer reed switch is connected to a DS2423 counter chip which accumulates counts - 2 per revolution of the anemometer rotor. The count is then read periodically to determine the wind speed (and wind run). Circuitry to remove switch contact bounce is provided within the DS2423 counter chip.
For the wind direction :- A DS2413 dual PIO chip is used to switch the LEDs and the current in the photo-transistors produces a voltage across individual resistors and the 4 voltages are fed into a DS2450 4 channel analogue to digital converter chip. Using analogue sensing allows variation in light levels, sensitivity and opacity of the encoding disc to be allowed for in the software.
Power to the ancillary components, DS2423 counter and DS2450 A/D is provided parasitically from the 1-wire network by a Schottky diode and reservoir capacitor. The latter is made big enough so that the voltage only drops by a couple of tenths of a volt when the LEDs are on. Another Schottky diode is connected across the 1-wire network to trap possible negative going spikes on the line. This is standard procedure to protect the chips.
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