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Modifying a Davis Anemometer with an Hall Effect sensor
#1
This message was originally posted by laulau, accidentally it was deleted, so I'm recovering it on a new thread.

laulau Wrote:Hi,
I gave it a try today withe a hall effect sensor.
it seems to work with the TX unit after bringing the magnet closer but didn' with the VP2 !

   

   

   

Any suggestion ?
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#2
laulau Wrote:Hi,
I gave it a try today withe a hall effect sensor.
it seems to work with the TX unit after bringing the magnet closer but didn' with the VP2 !




Any suggestion ?

Do you mean it works with WeatherDuino but it doesn't work with the original Davis VP2?
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#3
Hi,
The magnet position was deeper inside the wincup originally, i pull it out like this :
   
Yes it works with WeatherDuino, i use a spare TX board with wind debug.
With the original VP2 it don't, i suspect a impedance problem.
I have a 10K pullup with a 120 ohm serial resistor; the signal is low (0.15V) when connected to the VP2 transmitter even without the magnet in front of the sensor.
Laurent

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#4
According to the measurements I was able to make (with a voltmeter) the supply voltage supplied by the VP2 on the steering potentiometer is not constant: it is only present every 3s approximately. It cannot therefore be used to power the hall effect sensor.
This modification works in any case with a WearderDuino TX card which supplies 5V. Cool
I wonder how they do at Davis with their new anemometers with hall effect sensor which seem to be compatible with the older.
So unfortunately I have to replace a reed switch Angry because the anemometer that I am repairing is that of my Davis VP2.
Laurent

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#5
(29-01-2020, 10:14)laulau Wrote: According to the measurements I was able to make (with a voltmeter) the supply voltage supplied by the VP2 on the steering potentiometer is not constant: it is only present every 3s approximately. It cannot therefore be used to power the hall effect sensor.
This modification works in any case with a WearderDuino TX card which supplies 5V. Cool
I wonder how they do at Davis with their new anemometers with hall effect sensor which seem to be compatible with the older.
So unfortunately I have to replace a reed switch Angry because the anemometer that I am repairing is that of my Davis VP2.


Sometimes the KISS* concept of WeatherDuino reveal its advantages. Smile
Not having been projected to be operated by small batteries, give us some facilities.
Indeed, the Davis ISS gives power to the sensors just for a very small period of time. Perhaps the hall effect sensor used doesn't work with the low voltage provided by Davis (not sure, but I think it is around 2.5 to 3V), other option may be trying to use a small supercap to keep the sensor always powered.


*KISS, an acronym for "keep it simple, stupid" or "keep it stupid simple", is a design principle noted by the U.S. Navy in 1960.[1][2] The KISS principle states that most systems work best if they are kept simple rather than made complicated; therefore, simplicity should be a key goal in design, and unnecessary complexity should be avoided.
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#6
Stupid question from my side - which advantages has the hall effect sensor besides it does not use mechanic parts.
So it may last longer than the reed contacts.

Regards, engolling
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#7
(29-01-2020, 21:47)engolling Wrote: Stupid question from my side - which advantages has the hall effect sensor besides it does not use mechanic parts.
So it may last longer than the reed contacts.

Regards, engolling

It lasts longer, but I think the more important is that the pulse signal is more defined, less possibility of spikes at high wind speeds.
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#8
Hi,

Normally a Hall sensor will be sensitive to the polarity (N-S) of the magnetic field, but Reed Switches are not. [OT:] This may affect the operation of some anemometers such as the Fine Offset, which is intended to generate two pulses per revolution (but I don't recall exactly how the reed is positioned relative to the magnet).

Cheers,  Alan.
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#9
Hello Alan,

Is good to hear from you again, hope you are going well.
Indeed the Fine Offset anemometer modified with an hall effect sensor provides one pulse per revolution, instead of two when equipped with the read switch. That's the reason why on the WeatherDuino software there are two different settings: one for the "normal" Fine Offset anemometer the other for the modified version.

Rgs.
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