Im going to have an Arduino Pro Mini 3.3v placed outside. Im considering using a solar cell to power it. Im not sure about whether this is a good idea though. I guess the setup is something with a solar panel which is charging a battery that is powering the Arduino?
What is your experience with solar powered Arduinos? How to do it? What parts is needed? How many watt for the panel? Which battery would you recommend?
Thanks a lot!
It is easy to power an Arduino with a solar cell, but not very interesting unless it does something. What ELSE would you do with a solar powered Arduino, and for how long?
jremington:
It is easy to power an Arduino with a solar cell, but not very interesting unless it does something. What ELSE would you do with a solar powered Arduino, and for how long?
Thanks for reply!
Im planning to add a bunch of sensors like temperature and then transmit the data to receiver. For how long? Hmm.. As long as possible I guess 
You will need to work up an "energy budget". Figure out the total power requirements of the Arduino, sensors and radio, and match those up with the expected total amount of solar energy (determined by weather patterns and expected hours of sunshine per operational day at your location) that you can collect and store, for a given solar panel and battery combination.
jremington:
You will need to work up an "energy budget". Figure out the total power requirements of the Arduino, sensors and radio
What do you mean? Let's say I'm using the LM35DT Temperature sensor. It operates between 4v-30v. Ill probably give it 5v though a boot converter. The transmitter needs 3v-12v. (More Volt = better signal). Lets say I give it 5v. Arduino Pro Mini 3.3v needs minimum 3.3v. My "energy budget" is then 5v+5v+3.3v = 13.3v?
jremington:
and match those up with the expected total amount of solar energy (determined by weather patterns and expected hours of sunshine per operational day at your location) that you can collect and store, for a given solar panel and battery combination.
According to this: "Average annual hours of bright sunshine is 1,495 for the entire country".
The important issues are not volts but total current requirements (amperes), total power requirements (watts = volts times amperes) and overall total energy consumption in Joules (watts times seconds of time that the equipment is to be in operation).
The solar panel must be able to supply more than enough Joules of energy to run the equipment for the amount of time you intend to run it, given the solar energy available at your location (Oregon is not the same as Arizona). If you intend to run the equipment at night, then you need a battery able to supply the needed total energy, and of course the solar panel needs to be able to run the equipment while the sun is shining, as well as recharge the battery.
You have a lot of reading to do, and since this has been done many times before, google is your friend.
Oh lordy, you have no idea what he's talking about.
Read up on volts, amps, watts, and watt-hours.
You should also carefully study the sleep mode on the different AVR chips available, and figure out how to put your different subsystems to sleep when they aren't being used. The lower you can make the duty cycle on your different subsystems, the lower your total power use.
For lowest power use you probably want to build a custom board rather than using an Arduino. That way you can optimize for low power.
I saw a post on a forum (EE Stack Exchange?) on getting the lowest possible power draw from an AVR chip. He got it down to less than 2 micro-amps.
You should look at using a buck/boost power supply with low quiescent power use instead of the linear power supply built into Arduinos. That will reduce your base power usage when everything is asleep.
Wasd9595:
jremington:
You will need to work up an "energy budget". Figure out the total power requirements of the Arduino, sensors and radioWhat do you mean? Let's say I'm using the LM35DT Temperature sensor. It operates between 4v-30v. Ill probably give it 5v though a boot converter. The transmitter needs 3v-12v. (More Volt = better signal). Lets say I give it 5v. Arduino Pro Mini 3.3v needs minimum 3.3v. My "energy budget" is then 5v+5v+3.3v = 13.3v?
jremington:
and match those up with the expected total amount of solar energy (determined by weather patterns and expected hours of sunshine per operational day at your location) that you can collect and store, for a given solar panel and battery combination.According to this: "Average annual hours of bright sunshine is 1,495 for the entire country".
Powering devices from Solar is quite an exercise, in so far as determining the power budget and the Solar Panel size and
battery capacity.
There are many factors to consider, but if you need the device to be reliable, ie not stop working then you need to look at the worst case scenerio for the Solar generation, which is usually maximum sun hours in the middle of winter, plus an allowance for
1 to 2 weeks of consistantly cloudy weather.
http://pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation
You then also need to accurately determine the devices power consumption,over at least a day, if its variable.
Its a fun thing to do though, especially when you eventually get it right.
Agreed, this is a technically challenging project, especially if you want the result to be reliable and functioning for long periods under all weather conditions.
Here is a fairly well documented and successful example of a solar powered, remote water tank sensor in the not-so-sunny climate of New Zealand: The finished Arduino wireless water sensor | Lifeboat Farm
I'm building a small unit using a 5 cell nimh pack (2000mAh) and one of these 9v panels..2w...plus a regulator to charge the cells.
Load for me is minimal so as they say you will have to work out the loading and the recharge ability.
Might be a start for you.
