Hi, I'm working on a solar powering my Arduino for an outdoor application. The Arduino needs power 24/7 so I'm working on a rechargeable battery and solar panel to power it.
For example, I want the Arduino to run off of the battery when there is no sunlight and off of the solar panel when there is light. When there is light, the solar panel needs to supply power to the Arduino while recharging the battery. I have a couple ideas for the circuit but I'm a beginner and would like to ask if either would work as I don't want to damage my hardware.
I think the diode circuit will work. But, you might need a resistor in series with the charging-diode to keep the current down to a "trickle".
Check the specs on the battery to make sure it's OK to continuously trickle-charge it.
And, make sure you've got enough battery capacity. If that's a "regular" 9V transistor radio battery it may not last through the night or a cloudy day.
IMO, just run the board from the battery the whole time. The battery is a reliable source. Running it directly from a solar panel. Could be done yes, but i don't see the point frankly.
You might even ditch the comparator circuit, and use the arduino ADC. Once the voltage goes below a certain (safe) threshold, switch the power supply. But you'd still need a sizable capacitor to bridge the switching gap.
The solar panel obviously needs to accommodate the board plus the trickle charge.
Wawa:
It all depends on the type of Arduino.
How about starting with ZERO parts and an UNO.
There is already a diode between DC socket and Vin (pre-regulator), so you could...
Connect the battery to Vin and ground.
Connect the solar panel to the DC socket.
Yes, there is a 5volt regulator on the UNO.
Vin is the regulator input.
DC socket in goes through an extra reverse protection diode to Vin.
UNO and other Arduino schematics are all available online.
The way I have posted works.
But it's crude, not good for most battery chemistries, and waistes power.
If you search for "solar power" in the search box on top of this page, you will find a lot of info.
It might be wise if the OP starts with explaining what he wants to do with the Arduino.
And the hardware he already has.
Leo..
I make my own panels and voltage regulator/charge controller circuits. They're not hard to build. I agree with just running the battery constantly. Just let the daytime light-panel-charge controller top off the battery during the day.