Thunderstorms - Printable Version
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Thunderstorms - laulau - 14-05-2016
Hi,
This morning we had a thunderstorms and my raingauge became crazy!
We had ~13mm of rain in a half hour but WD registered ~563mm
The rain counter made leaps from 50 to 100mm sometimes.
The rain gauge is on a pole at 50cm above ground and the cable goes underground to the TX unit at about 6m.
There was electrical activity with strokes not very far. Can my problem come from that ?
What can i do in this case ?
Thanks
RE: Thunderstorms - werk_ag - 15-05-2016
(14-05-2016, 16:40)laulau Wrote: There was electrical activity with strokes not very far. Can my problem come from that ?
It's almost sure that it is. I never saw spikes in the rain gauge, but have already saw large spikes in the anemometer readings, when there are very close thunderstorms. No problem with that because the anti-spike routines take care of it, but unfortunately there isn't any anti-spike routines implemented for the rain gauge (this behaviour was never reported before).
One thing that can help is use a shielded cable, and connecting the shield to earth in just one end of the cable.
RE: Thunderstorms - laulau - 15-05-2016
May this help by changing the internal pull-up to an external one with a lower value?
Or maybe change the debouce value ?
RE: Thunderstorms - werk_ag - 16-05-2016
You can try just add an external pull-up, and keep the internal pull-up active, both will be in parallel. Keep in mind that a too low value raises the current through the reed switch, and can cause other problems. See the reed switch specs.
Playing with the debounce default value may help also, but what value to use? You can adjust it to allow one or two clicks per second, which maybe is more than we can expect even with a heavy rain, but I really don't know if it will be effective to prevent thunderstorm interferences on the cable.
RE: Thunderstorms - laulau - 16-05-2016
I didn't find the Davis reed switch specs but i assume that 1mA is not too much for it.
I have measured 132µA that is ~38kohm as internal pull-up (10 to 50 kohm in Nano datasheet)
If i add a 5.6k in parallel that gives ~4,9k equivalent and ~1mA if i'm right.
Debounce default value is 500µs, I'll go to 100ms that's 200 time higher and allows 10 clicks per second.
I have to wait the next thunderstorm to check the efficiency, but in the meantime i'll change the cable also and perhaps come back and try without software and hardware modifications.
RE: Thunderstorms - werk_ag - 17-05-2016
Please report back your investigations. Thank you.
RE: Thunderstorms - laulau - 18-05-2016
shielded cable installed and pull-up resistor also. No software modification for the moment.
I'm waiting for an other thunderstorm to see if hardware modifications helps !
RE: Thunderstorms - werk_ag - 18-05-2016
According to Blitzortung, there are some now, not very far from your location!
RE: Thunderstorms - laulau - 18-05-2016
We have some rain but thunderstorms were at about 40 Km near the Swiss border.
RE: Thunderstorms - laulau - 07-06-2016
Hardware modifications are not sufficient, I still had false rain readings. I since changed the debounce value to 200ms in the software but not had a thunderstorm with high electrical activity to see if it helps.
Perhaps this night or tomorrow according to forecast!