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Author Topic: Has anyone got practical experience of Solar  (Read 463 times)
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I'm designing a project that will be deployed remotely and run from batteries. I was wondering if anyone had practical experience of powering an Arduino for months from batteries/solar, particularly in the UK or at around 53-54 degrees north latitude.

If so it would be great if you could let me know what was the arrangement of solar panel and batteries, which model of Arduino, did you put teh Arduino to sleep, did you use GPRS, etc, etc.
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I spent almost 3 months at London a while back, only two things I was missing are food and solar. Lately I went back London after Olympic, the food is no longer is problem ( beat most cities at north American if not all). Is solar no longer is problem after Olympic?  smiley-razz

Here are procedures to select batteries and solar panel;

1.Solar Radiation (Watts/m2)
Solar Radiation, noaa.gov
go though history daily report, found out Solar Radiation data. use system total Watts with Solar Radiation data to define solar panel size and batteries.

2.Use low power RF-link instead of GPRS.

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 smiley-grin

Nope, still no sunshine!

Can't use low power RF because of the range.
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Arduino board itself is not ideal for low-power designs. There are several topics dealing with low power here.

The atmega328p can draw ~uAmps when sleeping and waiting on watchdog or timer interrupt. Even much less when waiting on external waking up.

You have to describe in detail what you actually want to do. Maybe you do not need solar when running "something" for months. It depends on the scenario..
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Ok, I'm thinking about a remote rain gauge, say to be deployed 30 minutes walk from the nearest road. Ideally it needs to run for a month or two between visits and would have a GSM modem for sending back data, say once per day. Potentially the rain gauge could wake up the Arduino when a rainfall event occurs, or it could use an external counter which gets read by the Arduino.
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Great - so tell us how much time takes the actual GSM communication on per day basis and how much current the GSM module takes during that communication (worst case). That would be the largest power draw. Based on that you can create a power budget and decide what kind of battery you need..
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The GSM part sounds as if it'll soak up a lot of power and I see that being your main problem.

If you 'only' need it to run for a couple of months, would you consider just using a big battery? It'd be more reliable than a big solar panel, also a lot more robust, less vulnerable to being nicked, less vulnerable to dirt, snow, frost damage ...

I don't know whether any of these factors are important to you, but solar power doesn't strike me as a very convenient source of year-round power somewhere as far north as the UK.
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Ive made a number of remote operated devices which run off Micros In my case using PICS not Arduinos , but the principle is the same.
You need to know the daily power draw of the device to be powered.
You then need to know the worst case sun hour value for the middle of winter, usually around 2 - 3.
You then have to allow for multiple days of cloudy weather , usually 5 days is a good compromise , but varies somewhat depending on your latitude.
You can then size the battery and the solar panel to suit.
Try and reduce the power draw of the device to an absolute minimum when its not doing anything useful.

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Can't use low power RF because of the range.

The range?
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Thanks for the replies.

Power draw for the GSM? Don't know yet because I am at the early stages of the design. The time for which the GSM is active is presumably affected by signal strength and quality whilst transferring data so could be very site specific.

Range? 15 - 20 miles, possibly with a mountain in between.

Using a big battery is an option. It all feels a bit "chicken and egg" it seems that the only way will I really know the power draw is to build one, but then having built one, if I can't power it, it is a bit of a waste of time building it.
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