I'm a begginner electronics fan. I purchased a OSEPP SC10050 Monocrystalline Solar Cell (100mA, 5.0V) and connected it to my Arduino, but even at strong light it doesn't seem to power it at all. What am I doing wrong?
What am I doing wrong?
You're not showing us how you wired it?
Well, there is no wiring. I just connected it to the power. There are no other connectors on it. See the attached image please. Thank you!
So, your cell outputs 5volts, and you've connected it to a jack that requires a minimum of 7volts?
Gotcha. 
What's the most power it can take? Can I connect two parallely to generate 10V? Thanks a lot.
10V works, 100ma may not be enough. (recommented 7-12V input on jack)
You can't connect anything in parallel to get a higher voltage - you'd need to connect in series.
If the cell never puts out more than 5.5volts, you could bypass the onboard regulator completely, and connect to Vin.
Thanks a lot. Got it now.
If I understand your photo correctly, there's no way that the solar cell is going to be able to power the UNO and five LEDs. It will have enough trouble powering only the UNO unless it is in bright sunlight.
Pete
If its not in direct full sunlight you won't get 100mA or anything like that (10mA if overcast would be about right, less than
1mA with artificial lighting).
Take it out in direct full sunlight and measure the open-circuit voltage, then measure the short-circuit current. If its
adequate to power an Arduino via the barrel jack I'd expect about 9 to 11V open circuit, and if its good for 100mA at
max power point it will probably manage 120mA or so at short-circuit.
Silicon PV panels give maximum power at roughly 70--80% of open-circuit voltage.
Alternatively count the individual cells it is made from, they are connected in series and will produce about 0.45 to 0.5V
each at max power point. Thus to provide enough voltage for 7V barrel jack I'd expect around 15--18 individual cells.
For reference the standard panel configuration used to charge 12V lead acid batteries is 36 cells, giving about 16 to 17V
which allows for better charging performance in overcast conditions, though 32 cells would be OK in full sun.
Thanks a lot!