Solar Radiation
I know that in the cloudy UK this question doesn't seem very important but in the southern countries it does. I wonder if Clive and others could suggest 1-2 sensors for solar radiation (W/m^2) and UV Index to be attached to the station in order to have some useful solar data. Thanks.
Re: Solar Radiation
I've not had any direct experience but hopefully someone else here has. Radiation/UV sensors were something we wanted to put on but had to drop due to cost. We'd be interested to hear how you get on.
thanks
thanks
Re: Solar Radiation
well, for UV index you can look at a SI1145 sensor. I'd say something around 10$EECmakrin wrote:I know that in the cloudy UK this question doesn't seem very important but in the southern countries it does. I wonder if Clive and others could suggest 1-2 sensors for solar radiation (W/m^2) and UV Index to be attached to the station in order to have some useful solar data. Thanks.
This also outputs light level (visible and ir), but a TSL2561 would be better for this (+5$)
then you need a place where to put these. I used a light bulb (lol)
solar radiation seems to be something harder to achieve..
Edit to add: for UV consider also a VEML6070 sensor, that does not return a proper UV index, but is cheaper (5$)
Re: Solar Radiation
sorry for necroing this, but i've just received my VEML6070 sensor and.. i discovered that a brand new VEML6075 is outMassi wrote:Edit to add: for UV consider also a VEML6070 sensor, that does not return a proper UV index, but is cheaper (5$)

6075 will do UVA and UVB (while 6070 only senses UVA)
i do not know any pre built breakout board with veml6075, however
Re: Solar Radiation
I'm abusing of the RPF Weather Station section (please clive let me know if this is only for "official" weather station, or for "raspberry weather station" in general
)
If anyone is going to add a VEML6070 uv sensor to the station, here is a working python code for it. This obviously uses pigpio
I think the calculation of index and power is "a little" (lol) approssimated.
I based my assumptions on datasheet ( http://www.vishay.com/docs/84310/designingveml6070.pdf page 4) and on definition of UV Index (1 index: 2.5 mW/m2), but i think that in UV Index also UVB enters, information i do not have with this sensor.
First sensor i see with TWO used i2c addresses.. one of them conflicts with the default address of the TSL2561 sensor, that has to be set to another address.

If anyone is going to add a VEML6070 uv sensor to the station, here is a working python code for it. This obviously uses pigpio

Code: Select all
#!/usr/bin/env python3
#coding=utf-8
'''
A python class to manage VEML6070 UV A sensor
'''
import time
import pigpio
import bisect
class VEML6070:
#i2c addresses
addrLow = 0x38 # first i2c address of VEML6070 (write -> config, read -> LSB of UV)
addrHigh = 0x39 # second i2c address of VEML6070 (read -> MSB of UV)
#constants for the SD part of config register
sensorEnabled = 0x00
sensorDisabled = 0x01
#constants for the IT part of config register
intTime_1_2T = 0x00
intTime_1T = 0x01
intTime_2T = 0x02
intTime_4T = 0x03
scaleFactor = {
intTime_1_2T: 0.5,
intTime_1T: 1,
intTime_2T: 2,
intTime_4T: 4
}
refreshTime = { #in ms
intTime_1_2T: 62.5,
intTime_1T: 125,
intTime_2T: 250,
intTime_4T: 500
}
def __init__(self, bus=1):
self.pi = pigpio.pi()
self.i2cLow = self.pi.i2c_open(bus, self.addrLow, 0)
self.i2cHigh = self.pi.i2c_open(bus, self.addrHigh, 0)
#initializing sensor as disabled and with standard integration time
self.sdnMode = self.sensorDisabled # before set_integration_time()
self.setIntTime(self.intTime_1_2T)
def setIntTime(self, intTime):
self.intTime = intTime
self.pi.i2c_write_byte(self.i2cLow, self.prepareCmdValue())
def sensorEnable(self):
self.sdnMode = self.sensorEnabled
self.pi.i2c_write_byte(self.i2cLow, self.prepareCmdValue())
def sensorDisable(self):
self.sdnMode = self.sensorDisabled
self.pi.i2c_write_byte(self.i2cLow, self.prepareCmdValue())
def getUvaRaw(self, integrationTime=intTime_4T):
self.sensorEnable()
# wait two times the refresh time to allow completion of a previous cycle with old settings (worst case)
time.sleep(self.refreshTime[self.intTime]/1000.)
msb = self.pi.i2c_read_byte(self.i2cHigh)
lsb = self.pi.i2c_read_byte(self.i2cLow)
self.sensorDisable()
return (msb << 8) | lsb
def getUvaIndex(self, uvRaw):
#scaling value by integration times
uvRaw = uvRaw / self.scaleFactor[self.intTime]
uvIndex = bisect.bisect_left([187,374,560,747,934,1120,1307,1494,1681,1868,2054], uvRaw)
return uvIndex
def getUvaPower(self, uvRaw):
#since it's all linear and every UV index equals a radiation power of 2.5 mW/m2, and every UV index equals to 187 (rounded..) "raw" UV reading, i can calculate the radiation power as uvRaw * 2.5/187 mW/m2
uvRaw = uvRaw / self.scaleFactor[self.intTime]
uvPower = uvRaw * 2.5 / 187
return uvPower
def prepareCmdValue(self):
cmd = (self.sdnMode) << 0 # Shutdown mode setting (bit 0)
cmd = cmd | 0x02 # reserved (bit 1)
cmd = cmd | (self.intTime << 2) # Integration time setting (bits 2 and 3)
#ack and reserved bits to 0 (bits 4-7)
return cmd
def close(self):
self.pi.i2c_close(self.i2cLow)
self.pi.i2c_close(self.i2cHigh)
self.pi.stop()
if __name__ == "__main__":
sensor = VEML6070()
uvaRaw = sensor.getUvaRaw()
print("UVa Raw: {:5}".format(uvaRaw))
print("UVa Index: {:5}".format(sensor.getUvaIndex(uvaRaw)))
print("UVa Power: {:5.3f} mW/m2".format(sensor.getUvaPower(uvaRaw)))
sensor.close()
I based my assumptions on datasheet ( http://www.vishay.com/docs/84310/designingveml6070.pdf page 4) and on definition of UV Index (1 index: 2.5 mW/m2), but i think that in UV Index also UVB enters, information i do not have with this sensor.
First sensor i see with TWO used i2c addresses.. one of them conflicts with the default address of the TSL2561 sensor, that has to be set to another address.
- morphy_richards
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Re: Solar Radiation
Did you solder directly onto the SMD pads? IS there any chance you can post a picture of how you connected it? Connecting SMD components might put some people off unless they can see how it was done 

Re: Solar Radiation
no way! lol
i bought a breakout board from china of a VEML6070 with a 270k rset resistor
then googling for the datasheet i found the veml6075 sensor, but couldn't find any board with it..
i bought a breakout board from china of a VEML6070 with a 270k rset resistor
then googling for the datasheet i found the veml6075 sensor, but couldn't find any board with it..
Re: Solar Radiation
Although my experience is in commercial meteorology, cheap and reliable pyranometers aren't really available. The SP Lite2 is over £300, and it's a budget unit. The Davis 6450 is roughly half that price. They also tend to have fearsome power requirements to keep the glass window heated and free of mist.clive wrote:I've not had any direct experience but hopefully someone else here has. Radiation/UV sensors were something we wanted to put on but had to drop due to cost.
(Edit) … although a bit more reading dug out some potentially promising results using a phototransistor attenuated behind layers of PTFE tape. Like all weather sensors, making the enclosure would be the tough part.
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Re: Solar Radiation
Well, i installed my veml6070 outdoor.
As you can see..

i used a old light bulb to install veml6070+tsl2561 to get visible, infrared and UVa
Now, the problem: the VML is giving me something like 40% less UV index than what i was expecting. I intended the light bulb to be more or less completely transparent to UV, am i wrong? what am i missing?
As you can see..

i used a old light bulb to install veml6070+tsl2561 to get visible, infrared and UVa
Now, the problem: the VML is giving me something like 40% less UV index than what i was expecting. I intended the light bulb to be more or less completely transparent to UV, am i wrong? what am i missing?
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Re: Solar Radiation
I believe pond UV filters use transparent quartz because normal glass blocks too much UV, my guess is that a normal light bulb will do the same. Using a light bulb is a nice idea though.Massi wrote:Now, the problem: the VML is giving me something like 40% less UV index than what i was expecting. I intended the light bulb to be more or less completely transparent to UV, am i wrong? what am i missing?
Re: Solar Radiation
i was so proud of my light bulb (i did miracles to set up both sensors LOL)sparkyhall wrote:I believe pond UV filters use transparent quartz because normal glass blocks too much UV, my guess is that a normal light bulb will do the same. Using a light bulb is a nice idea though.Massi wrote:Now, the problem: the VML is giving me something like 40% less UV index than what i was expecting. I intended the light bulb to be more or less completely transparent to UV, am i wrong? what am i missing?
i couldn't find any "official" data about glass filtering, i'll make a deeper search tomorrow.. i expect something aroud 40%, as said, in case i'll offset my code..
Re: Solar Radiation
Standard glass does block some uv radiation. In working with screen printing I found out there is a sheet plastic that is used in tanning equipment that allows most uv and ir to pass. Ask at a sheet goods supplier for some thing that passes uv. Bonus is that it is resistant to breaking.
Re: Solar Radiation
I have a number (over 30) of used Kipp & Zonen pyranometers similar to the SP Lite2. These are an older model (2004 or so), without the bubble level and leveling screws but are weather sealed. They were removed from stations that were used to monitor the solar radiation on PV panels and have been exposed to a few years of radiation. As is typical for this type of units, they can be expected to have lower sensitivity than when new ( ~ 2%/year). While there are services that will re-calibrate them, one can come up with a fairly good calibration by using the Apogee clear sky calculator (http://www.apogeeinstruments.com/when-t ... alculator/ ). These are analog out, approx 90 micro-volts/Watt/m^2.
I would be happy to spread them out to the community for packing and shipping costs, I have no use for them. I am in Massachusetts, USA.
Ned
P.S. I also have a similar number of NRG #40 anemometers, removed from the same systems.
I would be happy to spread them out to the community for packing and shipping costs, I have no use for them. I am in Massachusetts, USA.
Ned
P.S. I also have a similar number of NRG #40 anemometers, removed from the same systems.
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Re: Solar Radiation
I can't help with the circuit, but there are a few pre-wired uv sensor modules available. These contain a gallium nitride photo diode to measure uv in the approx range 200-300nm, plus opamp and a few other components. The circuit outputs a linear regulated voltage 0-1V, corresponding to a uv range of 0-10.
The 3 pinouts are for voltage in, ground, voltage out.
Adafruit (UK) list the ML8511 @ £10.40 incl VAT
Adafruit (USA) list the GUVA-S12SD, no price shown
These could be the basis for a uv sensor for the weather station.
Hope this helps.
The 3 pinouts are for voltage in, ground, voltage out.
Adafruit (UK) list the ML8511 @ £10.40 incl VAT
Adafruit (USA) list the GUVA-S12SD, no price shown
These could be the basis for a uv sensor for the weather station.
Hope this helps.
Re: Solar Radiation
Acrylic plastic is mostly transparent at UV range, just get as thin as possible, 3mm is too thick, I tried.
I just got some microscope cover slips, very thin glass, still to try.
But I am only using an i2c Lux sensor not a UV one.
I just got some microscope cover slips, very thin glass, still to try.
But I am only using an i2c Lux sensor not a UV one.
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- yv1hx
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Re: Solar Radiation
Although an UVI range from 0-10 can be useful for most high latitude regions, in most cases the UVI ranges can exceed the 12+ figure.julespiman wrote:I can't help with the circuit, but there are a few pre-wired uv sensor modules available. These contain a gallium nitride photo diode to measure uv in the approx range 200-300nm, plus opamp and a few other components. The circuit outputs a linear regulated voltage 0-1V, corresponding to a uv range of 0-10.
[...snip...]
Other possible(?) disadvantage is the need of implementing an ADC for converting the analog magnitude to digital values that can understand the RasPi.
I live in a coastal region, near 10°25" degrees North, and our UVI proms are usually 13~14 most day a year.
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- yv1hx
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Re: Solar Radiation
BTW, Good Idea the use of microscope glasses, I will give a try.Gavinmc42 wrote:Acrylic plastic is mostly transparent at UV range, just get as thin as possible, 3mm is too thick, I tried.
I just got some microscope cover slips, very thin glass, still to try.
But I am only using an i2c Lux sensor not a UV one.
The glass (or plastic) window is a very critical component of the device, so the designer must choose the window material wisely.
As far as I know, most plastics and glasses are opaques to the UV light, the App note "Designing the VEML6075 into an Application" from Vishay, recommends the following:
http://www.berghof.com/en/products/ptfe ... ical-ptfe/
http://www.aetnaplastics.com/site_media ... _Sheet.pdf
Quote from the same App note:
MECHANICAL CONSIDERATIONS AND WINDOW CALCULATIONS FOR THE VEML6075
As already mentioned, this UVA / UVB sensor will need a well-selected cover that is not only completely transmissive to visible
light (400 nm to 700 nm), but also to UVA and UVB wavelengths (280 nm to 400 nm).
Teflon or polytetrafluoroethylene (PTFE) is a known optical material that allows transmission of UV up to near infrared signals.
A teflon diffusor (PTFE sheet) radiates like Lambert’s cosine law. Thus PTFE enables a cosine angular response for a detector
measuring the optical radiation power at a surface.
Using a 0.4 mm teflon diffusor placed on top of the VEML6075 sensor generates a very close to cosine view angle response.
Compared with the ideal cosine response, the measured view angle response error of a 0.4 mm teflon diffusor is less than 10 %. [...snip...]
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Re: Solar Radiation
Hi Ned,nrich wrote:I have a number (over 30) of used Kipp & Zonen pyranometers similar to the SP Lite2. These are an older model (2004 or so), without the bubble level and leveling screws but are weather sealed. They were removed from stations that were used to monitor the solar radiation on PV panels and have been exposed to a few years of radiation. As is typical for this type of units, they can be expected to have lower sensitivity than when new ( ~ 2%/year). While there are services that will re-calibrate them, one can come up with a fairly good calibration by using the Apogee clear sky calculator (http://www.apogeeinstruments.com/when-t ... alculator/ ). These are analog out, approx 90 micro-volts/Watt/m^2.
I would be happy to spread them out to the community for packing and shipping costs, I have no use for them. I am in Massachusetts, USA.
Ned
P.S. I also have a similar number of NRG #40 anemometers, removed from the same systems.
I am currently building my own weather station with a Raspberry Pi 3, which I am planning to take on fieldwork with me to Greenland next summer. Do you still have your old Kipp&Zonen pyranometers? It would be easy for me to recalibrate them, as I have a lot of weather station data, from Europe and Greenland. I would love to see how close I can get to a 10000 $+ weather station with my 400£ budget set for this project. I would also be interested in some of the anemometers if you still have them?
Cheers,
Stefan.
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Re: Solar Radiation
Ned, I just drop you a PM a few days ago..nrich wrote:I have a number (over 30) of used Kipp & Zonen pyranometers similar to ...snip....
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Re: Solar Radiation
Ned,nrich wrote:I have a number (over 30) of used Kipp & Zonen pyranometers similar to the SP Lite2. These are an older model (2004 or so), without the bubble level and leveling screws but are weather sealed. They were removed from stations that were used to monitor the solar radiation on PV panels and have been exposed to a few years of radiation. As is typical for this type of units, they can be expected to have lower sensitivity than when new ( ~ 2%/year). While there are services that will re-calibrate them, one can come up with a fairly good calibration by using the Apogee clear sky calculator (http://www.apogeeinstruments.com/when-t ... alculator/ ). These are analog out, approx 90 micro-volts/Watt/m^2.
I would be happy to spread them out to the community for packing and shipping costs, I have no use for them. I am in Massachusetts, USA.
P.S. I also have a similar number of NRG #40 anemometers, removed from the same systems.
Do you still have any more of the pyranometers? I am working on a project for school and need to measure solar radiation.
Sam
Re: Solar Radiation
clive wrote:I've not had any direct Solar Panel Cleaning services but hopefully someone else here has. Radiation/UV sensors were something we wanted to put on but had to drop due to cost. We'd be interested to hear how you get on.
thanks
Hello clive.
About half of the radiation is in the visible short-wave part of the electromagnetic spectrum.
The other half is mostly in the near-infrared part, with some in the ultraviolet part of the spectrum.
The portion of this ultraviolet radiation that is not absorbed by the atmosphere produces a suntan or a sunburn on people who have been in sunlight for extended periods of time.
Re: Solar Radiation
Nrich,
I may be much too late but if you have a pyranometer / anemometer, let me know. I'm in Quebec, not too far ... I found you post as I'm looking for measuring UV and transfering my WS from arduino to Pi3.
J Guy
I may be much too late but if you have a pyranometer / anemometer, let me know. I'm in Quebec, not too far ... I found you post as I'm looking for measuring UV and transfering my WS from arduino to Pi3.
J Guy
Re: Solar Radiation
Hi, do you happen to still have them, and wish to send?nrich wrote: ↑Fri Jul 29, 2016 12:07 pmI have a number (over 30) of used Kipp & Zonen pyranometers similar to the SP Lite2.
I would be happy to spread them out to the community for packing and shipping costs, I have no use for them. I am in Massachusetts, USA.
P.S. I also have a similar number of NRG #40 anemometers, removed from the same systems.