External power

[cliffw]

I have had a quick search of the forum, could not find any referance.
Has anyone used rechargeable batteries fed from a small solar panel like the garden lights with a led in them to run the remote sensors.
It would need something like an active zener regulator to ensure the voltage never got over 3 volts.
regards
Cliff

[hans]

see this:
http://www.reuk.co.uk/Solar-Battery-Cha ... LM317T.htm

haven't tested if the outside unit works on 2.4 volts(2x 1.2 volt rechargeables)
since it normally uses 3volts.
and if 3 nihm are used it would give 3.6volt,that could kill your unit.

maybe this:
http://thebackshed.com/Windmill/assemblyMini1.asp
with a 3 volt regulator is an option?

[bruce45]

very interesting

i have a few panels and bits so might give it a try and let you no how well it works in wet and windy Scotland

[GTB]

for the windmill - might i suggest a CD case for the tail to mount and protect the electronics

geoff

[cliffw]

Have a look at this site under the heading "Solar Power" at the bottom of the page.
http://dcurrey.actewagl.net.au/web/gauges.htm
Regards
Cliff

[hans]

great,so it works on 2.4 v

do you know if by that voltage the transmit signal range is a bit weaker?
my distance is just 6-7 meters,but some have it on their max range.

[beteljuice]

I don't know about the Watson (sic.), but certainly my LaCrosse 23xx which has 3v of battery in the sensor, when working cabled to the base is taking 4.5v.

I think perhaps people are being a little too cautious with MUST be <3v limit. I think especially in the cold rechargeable batteries are going to fade quite rapidily resulting in signal drop-out - by the same reasoning in the UK I suspect the solar 'garden light' panel won't produce enough charging power to keep the unit going in winter season - it would certainly assist the batteries and two of those small panels would probably work (although I would adjust the charge circuit to give say 3.5 > 4.0v).

My other meandering thought would be to remove tha batteries from the sensor altogether and have them 'remote' - after all energy (charging) = heat

[wswat]

http://dcurrey.actewagl.net.au/web/Solar%20Charger.htm

The solar cell panel is 60mm x 60mm in size and are common in solar garden lights in Oz. The maximum open circuit voltage I have seen from it is 4 vdc
I chose NiMh batteries (nominal voltage of 1.2 vdc) because NiMh batteries have almost no Memory Effect compared to NiCd batteries.
The weather station is only 25 mtrs from the console and the outside night temperature during winter often dips in to the minus C arena and as of yet there has been no indication of data loss with the 1000ma NiMh batteries. I have no idea what the drop out voltage is for the Watson/variant 1081 remote sensor controller circuitry and would like to know if any one has some information.
On very sunny days the solar cell will push up to 80 ma in to the 2 NiMh batteries and on overcast days the charge current falls to 8 ma so there is a huge variation in charge availability. But because the Watson/variant 1081 remote sensor controller appears to use low amounts of power based on the "published" alkaline battery life of approx 12 months then even overcast days should provide sufficient recharge for the previous nights weather data updates.
An adjustable zener circuit is used as 3 volt zener diodes are difficult to obtain and having an adjustable circuit allows for any voltage tweaks that may be required.
I had never intended to use a single solar cell for anything more than 2 battery cells but just out of curiosity I put together a quick test circuit still using a schottky diode to prevent reverse current drain, 1 solar cell, and 3 x 1000ma NiMh batteries without any voltage regulation circuit. The results are as per the attached pictures and only intended for informational purposes. I suspect that with a maximum of 4 vdc, when available, would be at the minimum charge voltage for 3 NiMh batteries and I have no idea if this would work long term.