Solar and UV sensors going off line - fix?

[Cookie]

There doesn't seem to be any further posts on the problems about the light sensor issue. Is this because everyone has swapped their equipment for a new one? Anyway I wish to post an update for anyone who may be interested. I've had problems, been getting the dreaded "--".
I tried the following:
- cover the sensors (not the photovoltaic cell however)
- added a capacitor
No success, the sensor micro controller seems to lock up. LED stopped flashing. On reading all the discuss posted on this threat I have come to the conclusion that many of the problems seem to be related to controller lock ups which is caused by a varying supply voltage (Over or under voltage).
So, some points to consider:
- alkaline batteries are the best re-chargeables for this job (best in frequent and shallow cycle situations, the equipment needs a nominal voltage of 3 volts not 2.4 volts)
- covering the photovoltaic cells to reduce over charging is unreliable and drastically impacts on charging efficiency
- the max charge for alkaline batteries should not exceed 1.65 volts
A suggestion to fix the problem which seems to be working for me.
- Place a capacitor across the supply (as described earlier in this threat), this will reduce voltage variations cause by sudden and short high current demands on the batteries
- Place 5 diodes (use any common low spec diodes e.g. IN4001's) in series, bands facing the "-" end across the power supply to stop the supply exceeding 3 volts (0.6x5=3.0v). The diodes can be added at the battery terminals that are unused on the light sensor pcb.
I did this modification some weeks back and my station has had no hiccups since. It used to lockup within hours of a reset in the morning.
I hope this might be helpful.

[kryder]

There doesn't seem to be any further posts on the problems about the light sensor issue. Is this because everyone has swapped their equipment for a new one? Anyway I wish to post an update for anyone who may be interested. I've had problems, been getting the dreaded "--".
I tried the following:
- cover the sensors (not the photovoltaic cell however)
- added a capacitor
No success, the sensor micro controller seems to lock up. LED stopped flashing. On reading all the discuss posted on this threat I have come to the conclusion that many of the problems seem to be related to controller lock ups which is caused by a varying supply voltage (Over or under voltage).
So, some points to consider:
- alkaline batteries are the best re-chargeables for this job (best in frequent and shallow cycle situations, the equipment needs a nominal voltage of 3 volts not 2.4 volts)
- covering the photovoltaic cells to reduce over charging is unreliable and drastically impacts on charging efficiency
- the max charge for alkaline batteries should not exceed 1.65 volts
A suggestion to fix the problem which seems to be working for me.
- Place a capacitor across the supply (as described earlier in this threat), this will reduce voltage variations cause by sudden and short high current demands on the batteries
- Place 5 diodes (use any common low spec diodes e.g. IN4001's) in series, bands facing the "-" end across the power supply to stop the supply exceeding 3 volts (0.6x5=3.0v). The diodes can be added at the battery terminals that are unused on the light sensor pcb.
I did this modification some weeks back and my station has had no hiccups since. It used to lockup within hours of a reset in the morning.
I hope this might be helpful.

Hi, "Cookie"

Can you take some pictures of your setup ?

Does it work yet, for you?

- Kryder

[Cookie]

Unfortunately I did not take any photos of the modification. The unit is back on the pole. As my post stated, the fix I suggest works for me and it still working. The weather continues to be hot and sunny here.

[aurion45]

Can you please post photo again? as I'm having the same problem on less sunny days.

Finally had time to take apart one of my 2 replacement sensor units from FO. There are changes/upgrade etc.
First up there has been some re-work (or bad work) on the back of the UV (?) sensor - and the xtal is not soldered


Next is what appears to be a new PCB layout with an extra hole. Also a wire leading off down to the solar sensor



And this is the other end of the new wire - it shorts over a set of blank smd pads



I haven't had a chance to look at what these changes mean at a technical level, but assuming the one currently on my roof has the same mods it certainly fixes the problem. There are no markings on the pcb that I can see that provide any clue to a revision a,b,c etc but there is certainly a difference between the layout on my original one versus this one.

Cheers
Colin.

[basetman]

An update to my setup... I have applied the capacitor and the diode "fix" and I have covered the UV sensor. During the winter (low solar radiation), everything was working fine. When spring arrived I started to have the UV/solar sensor lockup issue again... I have also tried changing batteries, but nothing changed. It usually stops transmitting at 697 W/m2. Has anyone come across any solution?
My next attempt to fix the issue is to cover the lux sensor and the solar panel and see what happens...

[basetman]

First day with the lux sensor covered was a success! No lockup in a sunny day! Although I needed to adjust the lux to W/m2 conversion factor to match the expected values for solar radiation in my area.
Someone had found a way to alter the sensor readings with a hardware mod (adding a resistor). Could you please be more specific? Where do I add the resistor and what resistance should it have?

[Werk_AG]

It seems that this type of weather stations have some kind of overflow problem with sunny days.
If cover the lux sensor solves the problem, I can make a suggestion that is not expensive to do ... try covering the sensor with a neutral density filter gel (ND 0.3). These filters are very resistant to heat and can take several years if applied inside the transparent cover.
Since the transmittance factor of the filter is known, simply apply the appropriate correction factor. In the case of the filter I suggested, readings are half the actual value, because this filter has a transmission factor of approximately 50%
These filters can be purchased in small sheets, at stores of lighting equipment for video and photography.

This link is just for reference for the filter:
http://www.leefilters.com/lighting/colo ... &filter=tf

[AllyCat]

Since the transmittance factor of the filter is known, simply apply the appropriate correction factor.

Hi,

Yes, I agree that adding an optical filter is probably much easier than trying to modify the (unknown) electronics circuitry. However, it might be necessary to optically calibrate the sensor rather than rely on a quoted ND value:

The reason is that most silicon sensors are also sensitive to Infra Red light (there is a current thread discussing the Foscam webcam), but it appears from the data for the quoted filter that it could be almost "transparent" to Infra Red light. Certainly FO claim a "Lux" measurement (which is, or should be, the same response as the human eye), but generally the meteorological requirement is for a watts/square meter value that includes the Near Infra Red part of the spectrum. So I would be surprised if FO have increased their costs by adding an unnecessary IR blocking filter.

@baseman: Do you have any idea at what Lux value (or converted w/m2 value in Cumulus) that the solar pod software appeared to crash? My (one) crash appeared to happen when the UV was hovering around the (ridiculous) value of 14, which I believe is the largest value that the FO interface/ protocol can report.

Cheers, Alan.

[basetman]

@Werk_AG: Thanks for your suggestion! I was wondering what material to use as a filter. I will probably try that!

@Alan: Well, my crash kept happening at around 697 W/m2 or 88.227 lux almost every time. I had already applied a filter (semi-transparent tape) on the UV sensor, which also gave ridiculous values, about twice the normal ones. Now, the UV sensor is reporting close to normal values. So, the crash appears to be caused by the lux sensor. As far as calibration is concerned, I don't need great accuracy since the lux sensor itself is not very accurate. I just want to be able to count sunshine hours or get a hint when heavy clouds are forming...
I would still prefer a hardware mod than adding a filter though...

[mcrossley]

Does anyone know if the FO uses the Reyax UV diode? I built my UV sensor for my Davis around this diode and found the output to be twice or more than the spec sheet says it will be.

[Werk_AG]

@Werk_AG: Thanks for your suggestion! I was wondering what material to use as a filter. I will probably try that!

As I said try to search at stores of lighting equipment for video and photography.

Yes, I agree that adding an optical filter is probably much easier than trying to modify the (unknown) electronics circuitry. However, it might be necessary to optically calibrate the sensor rather than rely on a quoted ND value:

The reason is that most silicon sensors are also sensitive to Infra Red light (there is a current thread discussing the Foscam webcam), but it appears from the data for the quoted filter that it could be almost "transparent" to Infra Red light. Certainly FO claim a "Lux" measurement (which is, or should be, the same response as the human eye), but generally the meteorological requirement is for a watts/square meter value that includes the Near Infra Red part of the spectrum. So I would be surprised if FO have increased their costs by adding an unnecessary IR blocking filter.

As you said Lux meters don't care about IR component, is must respond only to visible light. My suggestion was based on the assumption that the filter would be applied in the Lux meter of the FO.

The quoted ND value for gel filters from Lee or Rosco are quite reliable.

[Werk_AG]

Does anyone know if the FO uses the Reyax UV diode? I built my UV sensor for my Davis around this diode and found the output to be twice or more than the spec sheet says it will be.

Based in what I have been able to see in some photos, the sensor used is very similar ... if the sensor is the same, and if the FO followed the manufacturer's specifications, the fact that the sensor output, is much higher than that shown in the specifications, may possibly be the reason why the FO UV sensor behaves so strange when UV readings are above a certain value (can cause some type of overflow, resulting in U shape graphics ).

I also have noted that the output of the Reyax UV diode is higher than specified.

[ArjanH]

Hi guys

I have a WH3081. I also have the dreaded lock up problem. Well, really it has only locked up once but I have noticed a trend that makes me wonder if you all are looking in the wrong direction. If you look at the data on my wunderground logs it doesn't lock up but start going very erratic at almost exactly the same time every day. For 3 days in a row now it has gone gaga between 13:12 and 13:15. Given the 5 minute windows of the logs it in my view could have something to do with a time thing. Possibly 13:13:13 or something like that. In any case it really appears to be something to do with the time as for me in any case it is happening after the brightest point of the day.

I am wondering if a simple fix like going to an am/pm clock would fix the issue and have now reprogrammed the unit to work in AM/PM.

Whats the worst that can happen?

[ArjanH]

Cancel that ... the transmitter side of things doesn't keep time I don't think. Hmmm so why the similar times then?

[ArjanH]

I am such an idiot ....

I found the answer to my erratic Light and UV readings. At around 1 ish every day at the moment the suns moved in behind a tree.

I'm Stupid!