3 led indoor solar panel circuit?

[PlanR]

Greetings everyone,
Completely new to the world of electronics but I've read up as much as I can. I'm trying to design a circuit that would power three 20ma led bulbs for several hours a night(preferably all night). A requirement is that it be solar powered using only indoor ambient light only, is this even possible? My plan is to use a 6 volt solar panel charging with some AA batteries. My understanding is that solar panels aren't yet efficient enough for this too work. Any insights would be greatly appreciated.

 

[BradtheRad]

One bright white led can be an adequate nightlight for a hallway or stairs.

At 20mA, 3.6V, for 10 hours, it will use 720 mW-hrs of juice.

You can charge 3 AA in series directly from a 6V solar panel. If it is in direct sun for a few hours, you might get by with a panel rated for a few watts. This is similar to how the solar-powered pathway lights work. When charge current drops near zero, a device disconnects the PV panel from the batteries, and connects the LED's.

However room lights will provide only a fraction of sunlight. You'll need a panel rated for several watts, and place it close to a lamp. But not so close as to heat it up.

To use 3 led's will require even more watts.

Somewhere you might find a formula telling what luminosity you'll get from room lighting, compared to sunlight.

 

[PlanR]

thanks for your input, putting this near a lamp won't be an option, so it looks like i may have to go with a rechargable batteries, reduce the number of LEDs to two and putting some sort of timer on it or a remote on off switch as the lights will be hard to access. I just need the LEDs to light up each evening for about 5 hours. any ideas here?

 

[tpetar]

What light source for indoor ambient light you have (metal-halide lamp, halogen, sodium bulb, neon, mercury bulb,...), and on what distance ?

For solar cells, from personal expirience sun light is more effiecient then any other light source. You need to put solar cell closer to bulb light source to have some results.

In other hand lots depends from what solar cells you have, quality, efficiency, light spectar ?

Solar cells from small solar garden lamps, best works on sun as light source, with artificial light give poor results.

Maybe better consider some other power source.

 

[PlanR]

There is no real light source other than the ambient light that filters through the windows each day, hence the decision to abandon the solar panel altogether. I only would want them on for about 5 hours each evening. a simple switch would work, but the LEDs will be high up on the wall , so thats a no-go and has me researching some sort of remote I could use to the circuit off and on.

 

[tpetar]

There is no real light source other than the ambient light that filters through the windows each day, hence the decision to abandon the solar panel altogether. I only would want them on for about 5 hours each evening. a simple switch would work, but the LEDs will be high up on the wall , so thats a no-go and has me researching some sort of remote I could use to the circuit off and on.

What LED diode you have in mind 5mm high bright 35mA, 1W,....
What battery you have in mind Li-Ion, lead acid,... ?

For sure we should see 3 LED will go in serie or in parallel connection, and do you need voltage StepUp.

 

[PlanR]

pair of 3mm super flux LED
**broken link removed**

power would come from a pair of rechargable NiMH D cell batteries (10,000 mah) run in series.

by my calculations I could get about 3 months usage running 24/7, if I could some way to only have them on for 5 hours a days I would be able to go over a year without a recharge. but my math is probably off so i'm not sure how to account for forward current or if if thats even necessary.

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By the way, I just started reading up on electronics yesterday and have you to buy anything, breadboard has been ordered. I think I may have found my new hobby, this stuff is fascinating :smile:

 

[tpetar]

Try to get solar panel 10W or 20W its not expensive todays.

 

[PlanR]

Try to get solar panel 10W or 20W its not expensive todays.

unfortunately for my application, the size of them makes them unfeasible. Out of curiosity though, do you think it would work with ambient light only?

 

[tpetar]

unfortunately for my application, the size of them makes them unfeasible. Out of curiosity though, do you think it would work with ambient light only?

From post #5 You say :

"There is no real light source other than the ambient light that filters through the windows each day, hence the decision to abandon the solar panel altogether."

If windows are in clean shape and you have appropriate period of time when direct sun light falls on solar cells, you will get charging. You can make experiment. Solar cells should not be in shade.

 

[PlanR]

i may have mispoke, there will not be enough sunlight to power this thing. I'm looking into a remote on off switch, but i'm afraid this device does not exist. in my mind it would be a simple on off switch, with either very low power consumption or with its own lithium ion battery giving it juice, its only job would be to recieve an ifrared sigal from a handheld fob that would in turn power off and on the circuit.