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Making a basic solar powered string of led lights isn't too difficult. This instructable will require no electronics knowledge and no programing.
What were will be doing is upgrading some old battery powered mini lights to LEDs and then using some basic components, charging the batteries with a small solar panel. With the aid on 1 IC and 1 inductor, we can automate the string so it turns off and charges during the day and turns on at night.
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Solar panel - $1.5 off ebay.
QX5251F (IC) - $0.20
Inductor 220uF- $0.02
Battery(ies) - $0.50 x 2 = $1
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> $5
Got these ...
http://www.diodes.com/datasheets/ZXLD383.pdf
instead. Because of this and your diagram here I think I got an idea of how to wire it right but not 100%. With this chip instead of the one you have here, a) my wiring below should work right? (on my chip) (see pic).
Will this charge bat? and keep the solar cell from draining power?
Mine don't blow up if you mess the wires, so hopefully yours don't either.
From draining, I'm not sure. The IC I used says it has an internal blocking diode. This one says DIODE array, which seems to be where you would put the inductor, but you might need a blocking diode. You can get them anywhere for 1 cent or so.
BTW nice job on finding a substituion.
The QX IC is prop, but there are alternatives. You can rip one out of a cheap made in china solar led lamp. You just can't be sure of the quality of the IC, but that may not be a big deal for you.
If you really want and the QX, send me a pm and we can work something out.
Basic goal:
Build an efficient circuit that can run a large LED array at 3.4 volts 20 ma per LED (full brightness). I would love to be able to do between 10 and 30 on a single circuit, but I can always do 2 circuits if it is more efficient that a single circuit. Obviously I know the more leds I use the big the solar panel I will need and larger battery capacity.
Set up:
When I take apart my basic cheap solar light I can only run 1 or 2 color changing led well off the current circuit, if I add a third LED they start to flicker. I currently have modified a few to run 2 LEDs or 3 with some flickering and they will run all night on a full charge with a cheap 600 mah recharable battery.
This circuit runs at about (it varies up and down) 13 ma and with 1 led the volts across it measure about 2.3, with 2 leds about 2.1 each.
This is way to dim, based on an instrucitble or a comment on one, someone tried adding a second battery in series to boost the voltage. I tried this and it worked great I found the best results before the leds get dimmer then I want is 6. I can add more and the circuit only draws slightly more power, but the leds get dimmer then I want, I have tried up to 17, but really 6-8 is best. Below is a chart of the approximate ma and volts (measured across each led) that is draw for different number of LEDs (all color changing or white rate 3.4-3.6 volts and 20 ma).
1 LED = 60 ma / 3.6-5 volts (varies up and down)
2 LED = 98 / 3.3 - 4.4
3 LED = 103 / 3.1 - 3.6
4 LED = 106/ 3 -3.3
5 LED = 108 / 2.9 - 3.2
6 LED = 112 / 2.7 -3.1
10 LED = 120 / 2.7 - 2.9
17 LED = 122 / 2.4 - 2.6
This was all tested on fully charged batteries and the batteries dies the voltage drops.
Problem:
This seems to drain my batteries MUCH faster than it should. With a 6 LED array it should consume about 340 ma per hour, so if I wanted it to last 10 hours that would be 3400 ma. (I have other solar panels that I plan to swap out to provide enough power). I thought that two 3000 ma batteries would last at least 7 hours even taking into account i can only use the first 80% before the voltage drops too low. However my lights dies after only a few hours!
I read your comment on one of BrownDog's instrutables about no name rechargeable batteries and figured that that may be the problem. So I added two more 3000 ma batteries in parallel, for a total of 2.4 volt 6,000 ma battery pack. This lasts on full for brightness for 5 hours and then gets dimmer over the next 3 hours until it dies. I really want my lights to last at least 10 hours, this is 3400 ma. If only 50% of my battery is good and I can only really use 80% of that, does it mean I REALLY only have 2400? How do you test the batteries to see how much they really hold? I have tested with my millimeter after I have charged them and I get about 1.4 unloaded so I assumed they were fully charged to 3000 ma.
What I would love to know is how you are able to light 10 led off two1.2 volt batteries in series with 2000 ma all night?
By doubling the input voltage am I reducing the efficiency of the circuit?
I have attached pictures of my set up, circuit and a close up of the IC. Would you recommend changing the inductor to up the current, as add my batteries only in series to give longer life and not extra voltage (also more solar panels)? What do you think would be more efficient?
As for your batteries. There is no such thing as a 3000mAh battery so I'm guessing if you test them you'd find something like 1000mAh, if you're lucky. Also, you can't use all the power in a battery. That is to say it's not going to go zero. When it's 'drained' it will probably have a charge of .8v or .9v. That's like 50%. So your math of 6000 is really more like 1000mAh. SUCKS huh? Stick to name brands. They are actually cheaper in the long run.
BTW, 1000mAh is huge for solar lights and should last you days.
That IC might have a limit V. The QX claims a limit of 1.9v, but I've tested it as high as 3.4. That doesn't mean it won't burn out in a day or so.
I sugguest your really remove the diode and cap from your circuit and then try like 3 leds. Then double it. Then test and then double it. The inductor I used limited me to 10 leds. Not the brightest. If you want more you'll need a different inductor, but you'll have to experiment with your IC. Good luck.
Based on what you said I need to leave the circuit as is. If I don't remove my capaciotr and diode, but change my inductor to 33uh or 20uh instead or the 47uh that is currently in there will I still be able to up the current? If so and my IC can handle it that would be a great way to get a few more LEDs at full brightness.
**Small note on my battery use, I am trying to power between 10-20 LEDs in a single array at full brightness to light up some fiber optics. This would last for days for a normal light, but these are huge sculptures several feet across. i am stressing the filaments and I need very bright light for it to leaks from all the stress points the way I want. I have tested this with a single high brightness 3.4 volt 20 LED that is powered by a 4.5v battery pack and it looks amazing. I want to get my solar powered lights up to that level and have them last all night. :)
Good Luck and post a pic when you get it fired up.
*****Have you tried your circuit with 2 batteries? *****
I have tried changing my inductor on my circuit but I assume it barely makes a difference since the capacitor(which I need for my color changing LEDs) is limiting the final output voltage. Right now there is a ceramic disc capacitor with 104 on it, based on similar images I have found on the web I assume this is .1uF 50VDC cap.
Currently my unmodified circuit uses a 47 uf inductor, a mystery IC circuit, a IN5819 Diode and a .1 uF capacitor. With that 1 battery and 1 color changing LED the circuit draws about 13 ma from the battery and about 3.5 ma and 2.8 to 5 volts to the LED.
*****Where did you get your induction to amps chart? Is this from your own tests? *****
My amp output based on induction input is very different from yours. What is the best way to test? Trial or is there a formula I can use? Based on your info I think a 22 uF inductor could double my amps. Then should I double my capacitor size to .2uF. If I get a much bigger capacitor like .5 uF would this still work and just give me more headroom to go a 10 uF inductor? Would this decrease the circuit effiency?
Thanks in advance for all your help! I am really new electronics and circuits, I have 10 + awesome sculptures I am trying to get lit right and every time I think I finally got things working I hit one more road block. :(
I don't believe changing the capacitor will make a difference in the efficiency, but it might change the behavior of your circuit, but I don't think so for you. If you needed a bigger capacitor, my guess is that your leds would always be red. The capacitor is only there to keep a charge on the led so it cycles through the colors.
Assuming your IC works the same as mine, it doesn't work like you think. The IC has a built in light switch. Very simply, when the solar cell puts out any juice the switch trips. Whether there is enough charge from the solar doesn't matter to the switch.
Are you sure it's not burnt out?
You might have to start from square one. Get one to work with way it was supposed to work, then add another and adjust your inductors as you go. If you go to the end product and it doesn't work you have several parts to troubleshoot versus just the one thing you changed from the last step.
Skipping all these there are inexpensive LED controllers. I have NOT used them, but they are designed to do all kinds of things. Some just light 10 leds some make 30 leds chase or blink. If you are interested in some the bigger ones I can send you some links. The ICs can run from $2-$10 bucks if memory serves.
Part of my problem with my IC is it only turns off once the I get at least .45 volts from my solar panel. This works fine with the solar panel that is included with the garden light. As soon as even a tiny amount of light hits it it produces at least this. I want to replace it with CIS solar panels rated at 5 volts open circuit and 100 ma short circuit. These are great in full sun, but inside with a light on they only produce about .1 ma in the circuit, not enough to turn off the light.
Do you know how many volts your circuit needs to shut off? I have contacted the supplier and I think I will order those, it seems the simplest way. Then I can change the inductor to my ma requirements, and add a diode and capacitor to the end for my color changing LEDs.
I would also love the link for some of the LED controllers you mentioned, more options are always better :)
Also if I use a 100 uf inductor will that make my lights about twice as bright but use my batteries about twice as fast?
Sorry for the basic questions I am really new to this. Thanks in advance :)
As for the second question, yes. The lower UH inductor you use, the brighter it will be, but it will burn through the batteries faster.
If you find super cheap solar lights, WITHOUT a photoresistor, the odds are they are using a similar IC. You could use that to mod if you wanted something different.
The QX5251F though, takes a lot of punishment. I've tested with a lithium battery and it didn't blow up. I'm going to test it with a 5v Solar panel and see if it works and for how long.