Hi: My first post.

I have acquired a solar panel that produces 160mA at 10.5v in full sunlight and I want to build it into a circuit that charges a battery to power a light that comes on after dark. Outdoor security light concpet.

I need the light to shut off automatically after the battery gets below the required voltage after the light has burned for 2-4 hours. I know I will need a photo-detector, relay and maybe some kind of comparator for shut off.

So here's my question, what components do I need and how to configure them around my solar panel? What kind of battery would the panel be best suited to charge? What is the brightest light I could operate for a few hours (2-4 max) each night and how to make the light switch off automatically once the batt. gets drawn down too much. I have no components at this time except the solar (10.5v, 160mA) panel and no idea how or what to wire up to make this work.


Thanks in advance for any and all input. Please be "overly descriptive" if possible since I'm still in the "electronics for dummies" phase.

(schematic copied from post by "Audioguru" from another thread)


I want to build this essentially, but modify the light to something more powerful (more LEDs?) and rig the circuit so it will switch off automatically if the batts. voltage drops to low during the night - don't want continuous batt drain if it gets too weak to power the light. Also, given the specs of my panel, what battery and how many should I choose to charge?


Greatfully yours,

Solar1

 

Why biuld when you can buy.Buy lamps for $5.00 each you get everything battery, leds, and a nice lamp. for you to make such a thing out of parts will cost a lot more. You will see. Besides why solar I wired mine in the ground using 5 LEDS each from a phone charger unit and disconnected the solar panels. And guess what I never shut them off 15 lamps only 3 watts. That is cost effective since rechargeable battery costs $3-4 bucks each. DO THE MATH.

 

Winter, summer and the time of the day makes a huge difference in the amount of current from a solar panel.
Your panel produces 160mA only at noon in summer if you are located fairly far south.

Measure the very small output from your solar panel at 10:00AM and at 3:00PM in winter to see how low is the power. Only 20mA? At noon in the middle of winter the "160mA" solar panel might produce only 80mA.

 

Hey solar1,
Try 3 LED's. @ 10.5 max V, 3 AA batteries should be your range. Might seem strange to only have 3.6V charged from 10.5V, but that probably be the most efficient use of your solar panel. Lotsa luck!
Dan

 

At noon in the middle of winter the "160mA" solar panel might produce only 80mA.

Once again, you've got your facts wrong, old man. COLDER IS BETTER for solar panels. Measure them yourself and see!

 

Hey solar1,
Try 3 LED's. @ 10.5 max V, 3 AA batteries should be your range. Might seem strange to only have 3.6V charged from 10.5V, but that probably be the most efficient use of your solar panel. Lotsa luck!
Dan

Dan:

Now we're talking - that's exactly the kind of thing I need to know.

The only thing that worries me is once turned on at night, how will the lights turn off if the batts get too low? Or, is that even a problem for rechargeables? Should I even be concerned about that?
Thanks Dan, anything else you suggest?


Italo:

As for the economics concerns, I want to build this to learn, and also to find a use for my solar panel - it is not all about the "cheapest" way to have a light. I want to learn to build circuits by doing - not buying a pre-fab unit.

 

Winter, summer and the time of the day makes a huge difference in the amount of current from a solar panel.
Your panel produces 160mA only at noon in summer if you are located fairly far south.

Measure the very small output from your solar panel at 10:00AM and at 3:00PM in winter to see how low is the power. Only 20mA? At noon in the middle of winter the "160mA" solar panel might produce only 80mA.

Audioguru:

Thanks, now that's the kind of stuff I need to know. The 10.5v, 160mA was measured at 12:00 noon Jan 5th on a clear winter day at the optimum angle to the sun.

I will take your suggestion and make the other measurements (10AM, 3PM) and post them here.

Thanks,

Solar1

 

LED's can be expensive, but they are efficient. How about a simple 3 hour timer after it is triggered? They also have some much brighter LEDs for more $. By much brighter I mean incandescent bright.

Check this company out...

http://www.philipslumileds.com/products/line.cfm?lineId=19

 

LED's can be expensive, but they are efficient. How about a simple 3 hour timer after it is triggered?

Bill:

How should I build the 3 hours timer? Is the timer a pre-fab component that I build into the circuit somewhere?

Thanks for the LED link.

Solar1

 

Once again, you've got your facts wrong, old man. COLDER IS BETTER for solar panels. Measure them yourself and see!

I was not talking about the temperature, I was talking about the low intensity of the sun in winter.
In winter away from the tropics the sun is low in the sky and shines for only 6 hours per day. The intensity is low so the output current from a solar panel is also low.

This site has a map and a chart of Europe with a solar panel perfectly facing the sun. The numbers represent the number of hours of daylight, cloud cover and sun's angle. http://lightbucket.wordpress.com/2008/02/24/insolation-and-a-solar-panels-true-power-output/

Paris has 7.4 times as much sun intensity in July than in December.
Oslo, Norway has 25 times as much sun intensity in June as in December.
I don't know how far north you must be for continuous night-time in winter.

 

I'll have to get back with you on the timer, a 555 could almost do it, but not very reliably, especially with the temperature variation. Something like a CD4060 CMOS IC could, but some designing would be needed.

It would be a single chip part, with a transistor to drive the rest.

 

I was not talking about the temperature, I was talking about the low intensity of the sun in winter.
In winter away from the tropics the sun is low in the sky and shines for only 6 hours per day. The intensity is low so the output current from a solar panel is also low.

Point taken. But Solar panels tested in Eastern Oregon in January produced more power than identical panels in Arizona in August. Both temperature and light intensity must be factored in.

I hope to have more detailed info by March, and will post it when I get it.

 

I think my project almost same as solar1 project. I need to know how to make the light brightness vary with surrounding brightness. my project is Solar Street Light. What the suitable software to simulate the circuit in order to know the efficiency and to make sure the circuit is working.

 

I think my project almost same as solar1 project. I need to know how to make the light brightness vary with surrounding brightness. my project is Solar Street Light. What the suitable software to simulate the circuit in order to know the efficiency and to make sure the circuit is working.

You need to start your own thread, or if you already have a thread, ask this there. Trying to steer a project from someone else to yours is call Hijacking a Thread, and is strongly discouraged.

 

thanks for your advice... and sorry if i hijack this thread...

 

The solar power output is less in winter. Resons being is the same as moving this solar panel to the tropics in the same hour. No body discussed the efficiency of solar yet. Learning on a project is not to expand the design but ruther to use minimumn components with maximumn efficiency. Any body that design will agree to that. WHATare you going to learn copy a circuit that uses 3 transistors while only a diode and a resistor can do the job.

 

Thanks for the tips and input one and all.

I'll update my "progress" as it occurs - or not - as the case may be.

 

Finally got the thing to work on my breadboard. However, I discovered there was an error in the original diagram. There was an extra wire connecting the inductor and the LED that shouldn't have been there. Once removed, the circuit functions perfectly. I have highlighted in red the segment that was taken out.

I also changed the source to 3, AAA batts. and used a white LED.