Re: Homebrew Davis Solar sensor
Posted: Fri 29 Nov 2013 12:00 pm
Sorry if it´s offtopic but y have a question that can be very interesting for homebuilt (any) sensor for Davis Vantage Pro2 system.
I study in deepth different theories for implement third party sensors on Davis Vantage Pro stations because the only official option isn´t cheap (the Envoy8x + datalogger + PC + wireless kit for third party sensors).
I thing that SOLAR RADIATION IMPUT OF ISS davis Vantage Pro Pro2 are the best for this pourpose because it has the best precission with theorical 1077 steps ( 1800wm2 / 1,67uV steps) very close to therorical 10 bit signal 0-1024 steps. This 10 bit precission can alow precission for many type of sensor signals cheating the console,
The idea is Cheat the console with a "electrically compatible" third party sensor connected to Solar sensor ISS imput, the Davis vantage Pro system will processed this signal as Solar Radiation but isn´t true, i will get the processed signal in remote server and recalculate to the true signal unit to obtain real gauge. I thing that temperature compensation are internal in sensor and does no affect to third party sensors could connect here. The processed and filtered signal in console to 10 minutes media in console are so good for this pourpose, and no problem timming 50s-1minute or 5 minutes for low signals.
My sensor I thing is "electrically compatible":
IMPUT
Operating voltage from 2.7V to 5.5V ( 2.3mA-3.3V 3.1mA-5V) (original sensor 1mA typical)
~50mS power up initialization (
OUTPUT
Analogic Voltage 10bit 0-1024 (imput voltage scaled, if 3v imput 0-3v ouput 10bit signal)
TEST the THEORY: (fail)
I fail to test this teory with a simpliest test: in ISS Solar radiation IMPUT RJ-11 I bridge the imput YELLOW wire supply signal 3VDC to analogic 0-3VDC GEEN wire output signal, and bridge the Red and Black Ground wires.
And activate sensor in weatherlink ( in console didn´t configure anything), no reads in console and no reads in wheaterlink
Would read equivalent 3VDC imput maximun scale 1800w/m2 but none read seems.
any idea that are wrong? in nest weeks I try whit the distance sensor but i thing anything are bad in my theory.
sorry bad Inglish, thanks for attention.
edit. a will try the bridge voltage sensor with a resistor for lower than 3v voltage signal because newe info about maximun mA current in ISS sensors supply are:
The input IS linear...
The minimum display value for UV index is 0.5 at 0.070 volts.
The step voltage (from say 1.0 to 1.1 UV index) is 0.0143 volts per step.
The MAX input for 16.0 UV index is 2.395 volts.
The short circuit current from the ISS is 28 mA.
With a 2.67 mA load, the ISS voltage is 2.723 volts
With a 1.383 mA load, the ISS voltage is 2.858 volts
Open ckt. ISS voltage is 3.003 volts.
The ISS samples the UV sensor every 50 seconds for 2 seconds (the 3 volts IS switched NOT constant).
PM me if you would like a copy of the spreadsheet.
Bill
I study in deepth different theories for implement third party sensors on Davis Vantage Pro stations because the only official option isn´t cheap (the Envoy8x + datalogger + PC + wireless kit for third party sensors).
I thing that SOLAR RADIATION IMPUT OF ISS davis Vantage Pro Pro2 are the best for this pourpose because it has the best precission with theorical 1077 steps ( 1800wm2 / 1,67uV steps) very close to therorical 10 bit signal 0-1024 steps. This 10 bit precission can alow precission for many type of sensor signals cheating the console,
The idea is Cheat the console with a "electrically compatible" third party sensor connected to Solar sensor ISS imput, the Davis vantage Pro system will processed this signal as Solar Radiation but isn´t true, i will get the processed signal in remote server and recalculate to the true signal unit to obtain real gauge. I thing that temperature compensation are internal in sensor and does no affect to third party sensors could connect here. The processed and filtered signal in console to 10 minutes media in console are so good for this pourpose, and no problem timming 50s-1minute or 5 minutes for low signals.
My sensor I thing is "electrically compatible":
IMPUT
Operating voltage from 2.7V to 5.5V ( 2.3mA-3.3V 3.1mA-5V) (original sensor 1mA typical)
~50mS power up initialization (
OUTPUT
Analogic Voltage 10bit 0-1024 (imput voltage scaled, if 3v imput 0-3v ouput 10bit signal)
TEST the THEORY: (fail)
I fail to test this teory with a simpliest test: in ISS Solar radiation IMPUT RJ-11 I bridge the imput YELLOW wire supply signal 3VDC to analogic 0-3VDC GEEN wire output signal, and bridge the Red and Black Ground wires.
And activate sensor in weatherlink ( in console didn´t configure anything), no reads in console and no reads in wheaterlink
Would read equivalent 3VDC imput maximun scale 1800w/m2 but none read seems.
any idea that are wrong? in nest weeks I try whit the distance sensor but i thing anything are bad in my theory.
sorry bad Inglish, thanks for attention.
edit. a will try the bridge voltage sensor with a resistor for lower than 3v voltage signal because newe info about maximun mA current in ISS sensors supply are:
The input IS linear...
The minimum display value for UV index is 0.5 at 0.070 volts.
The step voltage (from say 1.0 to 1.1 UV index) is 0.0143 volts per step.
The MAX input for 16.0 UV index is 2.395 volts.
The short circuit current from the ISS is 28 mA.
With a 2.67 mA load, the ISS voltage is 2.723 volts
With a 1.383 mA load, the ISS voltage is 2.858 volts
Open ckt. ISS voltage is 3.003 volts.
The ISS samples the UV sensor every 50 seconds for 2 seconds (the 3 volts IS switched NOT constant).
PM me if you would like a copy of the spreadsheet.
Bill