Author Topic: Solar light circuits  (Read 1623 times)

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Offline imidis

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Solar light circuits
« on: August 29, 2016, 10:47:22 am »
So playing around making some custom LED lighting and exploring circuits and necessities. I know the cap and diode are needed for a circuit that uses a micro controller for a color change led, or blink effects etc.

But I'm curious what advantages running with a cap/diode version may be. Bit of a noob to solar lights, but really enjoy seeing what I can do with em. Hard to find really in depth on the use of diode/ cap setup. More or less efficient, benefits?

First pic is a custom one (up on the trellis) , 7 cool white LED's, 1 - 1.2v 600 mah and is charged via a 60 x 60mm solar panel. IIRC the draw is around 10 or 11 mA when the LEDs are on.

Thank you kindly, just trying to get my head around it a bit more.   :)
« Last Edit: August 29, 2016, 12:18:04 pm by imidis »
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Offline Chalcogenide

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Re: Solar light circuits
« Reply #1 on: August 29, 2016, 03:59:09 pm »
The capacitor smooths out the output voltage; as a result, the current peak reaching the LED is reduced, and LEDs are marginally more efficient at lower current - however, you add the power consumption of the rectifier diode, so in reality you could even worsen the efficiency - that really depends on how hard you are driving the LEDs. If you are driving a really long LED strip, feeding it with DC instead of high frequency pulses also reduces the EM interference that the circuit emits.


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Re: Solar light circuits
« Reply #2 on: August 29, 2016, 06:37:16 pm »
The diode, inductor and capacitor in this arrangement is a typical boost converter topology.

White leds need at least 3 volts to work and the battery outputs only 1.3 or thereabouts. So this circuit boosts the battery voltage to 3 volts.

There's also a switching mosfet needed for a boost converter, this is integrated in the controller IC.   

Offline kmossman

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Re: Solar light circuits
« Reply #3 on: August 30, 2016, 06:08:52 pm »
As  stated.

Use the recommended values/type/part number.

Offline Audioguru

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Re: Solar light circuits
« Reply #4 on: August 31, 2016, 02:41:06 am »
I have many colors-changing solar garden lights. Many came with a white LED but no diode or capacitor so I added them when I changed the LED. The colors changing LEDs do not work with the quickly flashing output of the IC so the diode and capacitor smooths it into DC for the colors-changing processor.

The flashing is at such a high frequency that you cannot see the white LED flashing on and off.

I ran out of 1N5817 Schottky diodes so I tried an ordinary silicon 1N4148 diode that worked fine.

I replace the cheap Chinese Ni-Cad battery cell because it rusts away in a couple of months outdoors and I put lithium grease on the battery contacts. The cheap plastic-lens solar panels get sunburned so I coat them in water-based clear poly-urethane paint.

Modern cheap solar garden lights use an AAA 300mAh Ni-MH battery cell that does not rust and solar panels with a glass lens that does not become sunburned. I bought most of them for $1.00 each at Wal-Mart.   

Offline imidis

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Re: Solar light circuits
« Reply #5 on: September 01, 2016, 08:17:15 pm »
Yeah, the power consumption of the diode I was kind of curious about, the diode I had grabbed is not a schottky, I have ordered some. One of my solar light sets has a micro (chase, blink etc) and uses the traditional inductor, cap, diode set up to run a 40 LED string red, yellow, purple and green. It uses around 27mA, powered by a single 1.2v aa nicd. Thing lasts all night.

Seems most here have nicd, how are you finding the nimh, well besides no rust? Quite a few of the lights we've had for years and nicds still working, the solar panels tend to be the biggest issue with em.

Hmm, might have to test that clear poly, they definitely get baked here.
« Last Edit: September 01, 2016, 08:22:09 pm by imidis »
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