Author Topic: Solar Panel, Voltage Regulation  (Read 1553 times)

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Offline novice88Topic starter

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Solar Panel, Voltage Regulation
« on: February 19, 2010, 11:36:38 PM »
I want to charge my Mp3 player with solar panels, i'm thinking of getting a 2w panel, and connecting it thro a diode and then to USB. How do i control the voltage? will a simple voltage regulator like 7805 do? Or are there panels with specific voltage ratings? I want a 5v output. Please help.  :(

Offline Pratheek

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Re: Solar Panel, Voltage Regulation
« Reply #1 on: February 20, 2010, 01:38:47 AM »
A 7805 will work as long as the solar panels can provide anything above 6V. But the charger with a 7805 will be highly inefficient at higher input voltages because of the way the 7895 works - it converts electrical energy to heat energy to regulate the voltage. So if efficiency is not a concern for you, then go for the 7805.

Offline nottoooily

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Re: Solar Panel, Voltage Regulation
« Reply #2 on: February 20, 2010, 02:01:34 AM »
How about just bang a zener diode across it? Could be more efficient than a 7805/etc because there's no drop-out(?) voltage. I think this kind of cheap-ass regulator would be OK for solar because there's no worry about overloading the panel it like there is with a battery or mains transformer.

Offline Admin

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Re: Solar Panel, Voltage Regulation
« Reply #3 on: February 20, 2010, 04:37:30 AM »
You need to use a LDO regulator (low drop out voltage). A 7805 will waste ~30% of your energy.

Offline Soeren

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Re: Solar Panel, Voltage Regulation
« Reply #4 on: February 20, 2010, 08:01:45 AM »
Hi,

For greatest efficiency, you could use a MOSFET as the diode. It will have a lower voltage drop than even the best Schottky and with a little extra circuit, it can be the active part of the regulator => max efficiency possible.
Regards,
Søren

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Offline novice88Topic starter

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Re: Solar Panel, Voltage Regulation
« Reply #5 on: February 20, 2010, 10:00:42 AM »
I think i will try the zener and the mosfet and see which one works best, i like the zener idea coz i want the cut-off and it can also prevent the panel from leaking back... will post the results.

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Re: Solar Panel, Voltage Regulation
« Reply #6 on: February 20, 2010, 10:21:02 AM »
Hi,

For greatest efficiency, you could use a MOSFET as the diode. It will have a lower voltage drop than even the best Schottky and with a little extra circuit, it can be the active part of the regulator => max efficiency possible.

good point, I wasn't thinking . . .

Look into switching regulators.

Offline nottoooily

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Re: Solar Panel, Voltage Regulation
« Reply #7 on: February 20, 2010, 05:34:56 PM »

Look into switching regulators.

Yea those mosfets are great for reverse polarity protection. With a switching regulator you get to choose what voltage and current to operate the panel at, so if you're really clever you can design it to always draw the maximum power possible by staying in the peak efficiency region.

Having said that, the concept of efficiency isn't entirely relevent here. If the battery is already receiving the most power it needs, it's no more wasteful to dump the rest into a heater than it is to never use it at all.


Offline novice88Topic starter

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Re: Solar Panel, Voltage Regulation
« Reply #8 on: February 22, 2010, 06:27:07 AM »
Thank you guys, I used LM2575, but am getting a very low output current, am i using the wrong regulator here or are my inductor values wrong, i'm using it coupled with a L-150 inductor, can anyone suggest me any other regulators or atleast what i'm doing wrong here... :(

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Re: Solar Panel, Voltage Regulation
« Reply #9 on: February 22, 2010, 11:03:07 PM »
What is the rated output of the solar panel that you are using, and what are you actually getting?

Offline novice88Topic starter

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Re: Solar Panel, Voltage Regulation
« Reply #10 on: February 25, 2010, 03:12:25 AM »
Works perfectly once i had a panel suiting my rating. Used a zener coupled with a normal diode. Just that the panel is taking the longest time to reach its peak voltage everytime... :( Otherwise it works fine. Thanks!


Offline Soeren

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Re: Solar Panel, Voltage Regulation
« Reply #12 on: February 25, 2010, 07:28:53 AM »
Hi,

Works perfectly once i had a panel suiting my rating. Used a zener coupled with a normal diode.
What are the specs of the panel you're using now and how did you couple it?


Just that the panel is taking the longest time to reach its peak voltage everytime... :(
When put directly into bright sunlight or with slowly increasing light?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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