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Which Circuit Is Best To Use? Answered

I am trying to configure a LED circuit that allows me to charge 1.2v batteries using a solar panel. But i also want the solar panel to be used as a light sensor(detector) so during the day it charges..then at night the battery kicks in and lights up my LED strips. This is my first upgraded version using a schematic software.. Please help.

Should i add 2 indicator LED's to let me know when the battery is being charged and when the battery is in use?

I attached two images..one containing a LM317T and the other without. Just need some advice! Thanks



Discussions

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iceng

Best Answer 4 years ago

First one assuming the red led fwd voltage even lets current flow. You may have to reduce the led count.

SOLsw.bmp
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islandboii242

4 years ago

Ok what if im using a LED Strip of lights...the strip contains about 60-80 LEDS?

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icengislandboii242

Answer 4 years ago

The strip uses much more current so you need a higher current transistor as the N channel MOSFET.

BUT there is no way you can expect a small solar array to charge an 80 AH battery needed to run the LED strip :-(

LED-strip.bmp
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islandboii242iceng

Answer 4 years ago

My battery will be 1800 mAh 10 1.2v AA batteries. Sorry i didn't Mention this, and the solar array will be 1.25 - 1.5 watts

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icengislandboii242

Answer 4 years ago

78 led / 3 => 26 groups x 19ma => 500ma @ 12V => 6 watts

1800 mah/ 500ma => 3.6 hours

Your solar cell needs to be bigger and stronger.

Your battery will run out in 3 hours.

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islandboii242iceng

Answer 4 years ago

I sent you a message in your inbox. What i wanted to know was your schematic does this have the two most important features i need which is:

1. Using Solar Cell AS Light Detector (Photo Resistor)

2. Battery charge protection (so battery doesn't over charge or drains?)

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icengislandboii242

Answer 4 years ago

As it gets dark base current begins to flow through the solar cell turned into a resistor turning on Q1 which raise the gate voltage about 10 volts which turns Q2 on to deliver heavy current to the LED strip...

LED-stripDark.bmp
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islandboii242iceng

Answer 4 years ago

Designed it in my software and here is your design on left...question about the battery being over drained.

Screen Shot 2015-03-21 at 5.57.32 PM.png
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icengislandboii242

Answer 4 years ago

Your circuit does not have a resistor to guarantee the mosfet gate is truly at zero and non-conducting discharged when going from dark to sunlight.

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islandboii242iceng

Answer 4 years ago

ok understood ...if i wanted to add a feature of red and green led to indicate when battery is being charged (red & green) via solar cell and the other led (green) when the battery is now being used after the sun goes down?

Also for the mosfet should i add a heat sink also because this circuit will be running 24/7.

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islandboii242iceng

Answer 4 years ago

ok awesome thanks...this is the final design with pcb..top and bottom layer. Let me know what you think.

Screen Shot 2015-03-22 at 1.36.15 AM.png
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icengislandboii242

Answer 4 years ago

Could you mean over charged ??

over drained means over dis-charged..

For over charging add resistance in series with charge path.

I worry more about not turning the mosfet fully on.

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steveastroukislandboii242

Answer 4 years ago

Your LEDS are probably ~12W. you need more than 12 hours of light for each hour of operation.

Steve

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islandboii242steveastrouk

Answer 4 years ago

:-( Looks like i need to redesign...What i am trying to create is a back light sign that uses solar/battery which gets charge during the day and after dark the led strips turn on. But i have a small space to work with for the solar array.

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steveastroukislandboii242

Answer 4 years ago

There are some changes you could make, by not using off the shelf LED strip, you can eliminate the dropper resistors and make a bunch of LEDs more efficient.

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islandboii242iceng

Answer 4 years ago

Ok i will use my original solar panel instead...its a 5 Watts Solar Panel

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Downunder35m

4 years ago

For less than 5 bucks you can get a solar garden light that has everything you need inside.

Your images show 12V batteries but your text says 1.2V - which one is it??

For 12V you want to use a proper solar charger with automatic shut off and overcharging protection.

Only a few bucks on Fleabuy.