I am trying to DIY my own UV sensor to use with a Davis Weather station.
Davis wants an outrageous price of over $300 for theirs which probably only has $20 worth of parts in it.
The specs I need are:
Detectable wave length 280 - 360 nm (UVA & UVB)
Analog output close to 150mv per uv index 1-15

The weather station has a 3.0 volt supply and turns on the sensor about every minute.
I know in the actual Davis sensor the is a photo diode and an amplifier, possibly a trimmer or multi turn pot to calibrate it with.
MY Questions:
1) Can someone recommend a ready made board that would come close to these specs?
2) Can someone recommend a photo diode that would have the required UV specs?
3) If I have to use a photo diode, what is a good amplifier chip to use?

I can handle the circuit building and such, just suck at component selection.

Thanks
Bob

 

How are you going to select that band to detect? Most common filters cut-off at short wavelengths (e.g., 280 nm), but transmit throughout the visible. A monochrometer will work, but short of that, you may find some specialized filters that will work, such as: http://www.asahi-spectra.com/opticalfilters/uv_broad_bandpass_filter.html

I suspect you will need either two detectors or a chopped optical system so you can compare total or visible to UV only.

As for the photodiode, have you even searched? Even DigiKey lists several options.

BTW, a 10:1 or 15:1 ratio of parts cost to price is probably not tha unusual. Have you considered the cost of your time plus shipping (for parts, not your time) for a DIY project?

John

 

Actually there are several manufactures of photo diodes specifically made to detect only the UV wave lengths I am interested in. There are also several diode/amplifier boards ready to be had that also detect the desired UV. Some use an analog output while others use a 12c output.
Since I can not control how the Davis station computes the UV index, I can only try to match the input voltages required.
I was hoping that maybe someone else has already gone down this path and could better direct my search. Even when I have found the desired electronics, I still have to build a housing and mount.
As for my time, that is why many call electronics a hobby. I have already built several projects to control my humidifier based on outdoor temperature and inside humidity. (PIC/LCD Based) and antenna rotor controller, several power supplies, numerous LED projects.
I like to tinker what can I say.

 

Sorry, I miss your point. Buy it or make it. $300 sounds like a bargain.

John

 

Have a sensor board working, But trying to get the proper gain out of the amp is a real bugger.
I either have too much, (can not get it to zero in total darkness) or have it so low that I loose response.
But hey, only $20 into it and some of my time.

 

Go ahead and post your schematic. Someone can likely help you smooth things out. Look into "instrumentation amplifier" circuits using op-amps. They are designed to give control of zero and span.

 

wayneh,
Thanks for the reply.
I do not have a schematic to post, would love a schematic to this thing.
I am using this sensor: http://www.thanksbuyer.com/a24b-uvm...ut-w-signal-amplification-linear-output-29218
I have googled myself to death looking for even a spec sheet. I did finally translate the Chinese to find out that the bottom trim pot (as shown in the photo) adjust the zero. and the other adjust the output or gain. I have the gain adjusted about where it should be but still cannot get it to zero out in the dark.
The zero adjust trimmer pot is 1K, I was going to try a 10K and if not a 100K and see if I can get it to zero out then.
It has the correct frequency response to UV light that I need.
Since this hooks up to a Davis weather station, I have no way to adjust the programming of the ADC inside the console.
Still is way cheaper than the $300 Davis wants for their UV sensor.

Bob

 

After reading up some more on OPAMPs that have a zero offset, I think I am facing the problem of too low voltage.
I can not read the markings on the opamp to see what kind it is, but I know it is rated (According to the web site) for Min 5 volts, I am only using 3 volts.
Hoping that it has a pin out similar to others I was thinking of replacing it with a 1-2 volt minimum variety.
Checking on Mouser now.