One Arduino UNO, 2 separate power supplies ? ?

Hi all.

I have finally built my Arduino Weather station. I thought it might be good to power it by battery, and recharge the battery by Solar Panel. My main problem is i live in the centre of England, and the average sun shine hours are very poor especially in Winter.

My question is this, Can i power the Arduino during daytime hours from a 9 volt dc transformer, fed from my houses 240 vac mains supply, while the Solar Charger re charges the battery, then when the light levels drop, some kind of automatic switching devise will switch off the transformer supply onto the battery supply, then visa versa when the light levels rise again. I also intend to build a solar tracker to obtain maximum sunlight collection.

I have had an idea to use the 9 volt transformer connected to the Arduino external power supply, and the battery connected to the USB port, if this is possible, any advise would be appreciated, as i do not want to fry my equipment.

Can anyone advise on this

Yes, it is possible. The UNO can be powered from, or better to say connected to, barrel jack and USB at the same time. There is on-board electronic switch which prefers barrel jack. See the schematics. Same have Mega and other types.

Many Thanks for the info.

Ray

If you have a constant power connection to your mains why fiddling around with solar charger and batteries? Why don't you always power your weather station by the transformer from the mains?

Hi Pylon.

My initial thought was to go Fully Solar Power.That in it self will not work as i live in the centre of the UK, average sunshine hours per day is around 4.5 and the UNO would have now power in the night times.
Then there’s Battery Powered with re chargeable batteries, problem with this is i would need a least a 100 a/hr battery with a 100 watt PV panel, huge expense.

Electricity power on it’s own has 2 problems for me, it’s not Green, and the Weather station is at the bottom of a very long garden, which would give me a voltage drop problem, being connected to the house, therefore a combination fills my needs to be a bit Green, and thus keep the running costs down, and cheaper installation costs because with my current set up, i would need only a 20 watt PV panel + a 12 a/Hr Battery.

Any other ideas welcomed.

Regards

Ray

100 ah and 100w panel? Just how much does your weather station draw? That seems a lot when you see the commercial ones running on a couple of AA's and a solar panel measuring 100mm square.

Post some more and let others have a go at reduceing the load.

I had a car fridge that drew 25 amps a day and with an 80ah battery and 60 watt solar panel it was able to run for about a week.

Really curious to know more.

Daz

Electricity power on it's own has 2 problems for me, it's not Green, and the Weather station is at the bottom of a very long garden, which would give me a voltage drop problem, being connected to the house, therefore a combination fills my needs to be a bit Green, and thus keep the running costs down, and cheaper installation costs because with my current set up, i would need only a 20 watt PV panel + a 12 a/Hr Battery.

If you take the grey power of the PV panel and the battery into your calculation you can run the weather station for years on your mains without getting a bad conscience. The voltage drop is not as bad if you take wires built for the mains power instead of just signal wire. I run my external radiation monitor (5V) with a 25m cable with a voltage drop below 50mV.

House wiring from the hardware store gives you pretty big conductors pretty cheaply. Much better for long runs than skinny wires from the electronic store. Speaker wire is also a good source for fat wires.

If voltage drop is still a problem, use a 24V outdoor lighting transformer and an efficient power conveter at the bottom of the garden.

Solar power is always possible with a big enough panel and battery. By taking a little care with the power consumption you should be able to do it within a reasonable size and price.

The Arduino is very low current draw.

If you actually care about being green, you'll stick to just using mains power. And you'll get a 5V power supply instead of using a 9V. Get a 5V USB and be done with it.

The energy and resources used to make whatever components you plan on using to make this solar/battery contraption dwarf what power you might spare by not using mains at night. Your idea is simply false economy.

Hi all.

My weather Station Solar Panel and Battery are based on calculations off the Internet, as previously stated, i live in the Midlands area of the UK, Average sunshine hours for my area is approximately 4.5 hours per day, this is an average, in winter, we probably get, if we are lucky about 2 hours of sunshine per day,in the height of summer the average is around 6.2 hours per day. This equates to 16 hours of daylight in the Summer and only 8 hours in the winter, so my calculations are based on this figures. The battery will be working more in summer, as there are more daylight hours to re charge it, the transformer will be used therefore in winter to give the Solar panel more time to recharge.

Ray

The economics of running a mains supply as well as a solar panel and battery is not worth it unless you are doing this for the sake of doing it.

You have not mentioned the power it takes to run the station so a lot of guessing must be done.

The options you can look at are.

Run a mains power supply (9v) with heavy cable to the station.

Run a mains supply (12v) with lighter cable and place a buck converter (very cheap on ebay) at the station set to 5v.

Run a battery charger through light cable to trickle charge a battery at the station allowing the station to draw more power when needed and then sit idle allowing the battery to charge again.

Run a solar panel and battery monitored by the arduino with a connection to the mains that the arduino can turn on to boost the battery when sun fails to charge the battery adequately.

Run full solar and battery.

Most of the above would benifit from a boost/buck converter to stabilize the voltage (i would make it 9v and run it through the onboard regulator on adduino for a stable 5v) and putting the Arduino to sleep would save current usage making it more efficient, hence Greener.

Just my thoughts!

Daz