Author Topic: Micro-Solar LED Desk Lamp (Read 579 times)

ghurd · « **on:** February 07, 2008, 05:19:27 PM »

I am thinking about a small, stand alone, system for only my desk lamp.

The lamp will be LED and draw about 110ma at 12V, about 4 hours per day.

That means it needs a 5W panel. This is not the best, or even a decent place, for solar.

Ball park costs.

A good quality 5W PV, $80 to $100 (w/ S&H), I'll use $80.

SLA battery, $35.

LED Lamp, $40.

Brackets, $25.

Wire, $20 (very long run).

Hardware and controller, $20.

Total, $220.

That is to replace a grid fed 5W 120V CFL.

Pay back is 201 years!

BUT,

The battery will need replaced, say every 5 years. That's $7 per year for the battery.

The grid fed 5W CFL uses only $1.08 worth of grid power per year.

So if everything but the battery was FREE, I would be Losing about 50 cents a month with 'free power'.

Bigger is always better and more cost effective, but this mini-system took me by complete surprise.

I knew it would not be cost effective.

I did not know it would be THAT bad!

Time to dig out the old stepper motor windmills...

G-

DamonHD · « **Reply #1 on:** February 07, 2008, 10:31:09 AM »

This is pretty much what I have done since July last year, but with 80W of solar:

http://www.earth.org.uk/solar-PV-pilot-summer-2007.html

I do make use of the 'extra' energy to take my serevr off-grid a little each day...

Rgds

Damon

geoffd · « **Reply #2 on:** February 07, 2008, 10:32:46 AM »

Interesting costings, but if like me the Electricity company wanted 120,000 Euro to run a power cable to your house then your costings start to look gooood!.

Cheers

Geoff

zap · « **Reply #3 on:** February 07, 2008, 10:39:16 AM »

That's amazing... and sad.

I had the electric blanket on the Kill-O-Watt meter for a month. Blanket on high for about a half hour to an hour to kill the chill then turned off when I got in bed, just about every night... all of $.70 for a month. Grid power is still hard to beat here.

Maybe now that nanosolar has started shipping product we won't have long to wait? My lungs aren't good enough to hold my breath that long.

gotwind2 · « **Reply #4 on:** February 07, 2008, 11:49:07 AM »

Hey Ghurd.

I made one very similar 12 months ago.

5w panel, 7 ah battery and a 12v 11w cfl - still works today.

cost approx 100 u.k pounds ($200).

The only problem is that the anglepoise lamp is sprung for the lighter incandescent bulbs, the heavier cfl's make the lamp head drop down - I'm not sure what will happen when incandescants are phased out - a lot of drooping anglepoise lamps I suppose...

Ben.

http://www.gotwind.org/solar_anglepoise_lamp.htm

Norm · « **Reply #5 on:** February 07, 2008, 12:16:57 PM »

Time to dig out the old stepper motor windmills...

Indeed it is ....indeed it is Ghurd

....like in my diary....good ol' bike wheels!

good ol' vinyl blinds...good ol' RT steppers.

Another neat thing I figure you can get most of

the stuff at Goodwill, Salvation Army or such.

Thanks for the renewed inspiration.

Spdlmt150 · « **Reply #6 on:** February 07, 2008, 01:23:19 PM »

Small solar (or small re projects in general) tend to be far from cost-effective. Solar in general is too expensive to compete with utility power costs in most cases. If I had invested the money spent on solar panels several years ago into building windmills, I would need a substation by now.

It has been my experience that the larger the project the better the cost/return ratio seems to work out.

claude · « **Reply #7 on:** February 07, 2008, 01:33:51 PM »

Hi Glen,

You should design the whole thing using scrap items.

Here is my idea:

Solar panel - One VW panel should do. Use the embedded controller too. Heck, use your own controller! Connect that stepper motor windmill in parallel as well.

Lamp - salvaged, repaired & painted.

SLA Battery. Old UPS 7AH one.

LED bulb - handmade, using my recipe. By using one PWM circuit (I build one using a 555 timer) you could dim the light when you don't need it so bright.

Wires - new. Telephone wires? UTP cable?

LED controller - LM 117 adjustable voltage regulator set to output 9V for strings of three LEDs. This way you will have power even when the battery goes down to 11.8V.

220 USD is WAY too much in my opinion.

DIY skills can lower that cost.

To me time is the most expensive asset.

Claude

DamonHD · « **Reply #8 on:** February 07, 2008, 01:34:37 PM »

But remember that not everywhere has decent wind power, and the zero-maint aspect of PV has a distinct value all of its own...

Rgds

Damon

veewee77 · « **Reply #9 on:** February 07, 2008, 01:58:12 PM »

Claude,

Care to share your 555 PWM circuit?

Wunner'n

Doug

Bruce S · « **Reply #10 on:** February 07, 2008, 03:59:37 PM »

G-

Wow man you made a bummer of a day for me:-(.

I'm thinking these numbers were for brand new stuff?

Bruce S

Bruce S · « **Reply #11 on:** February 07, 2008, 04:06:11 PM »

Claude;

I too would like to have a look at that 555 PWM circuit. I've been working with linear pots to adjust LEDs. I'm starting to work with some of the newer K2 LEDs that are rated up to 3.72Vdc and 1Amp.

With respect to G-s post. I'm with you, but I would scrap the SLA and go with a NiCd set. I have been testing these and can run a 12Vdc LED set on 10.80Vdc and they light up with almost as much brightness.

Plus they can be run down to near empty >20% charge left and come right back up.

Cheers

Bruce S

americanreman · « **Reply #12 on:** February 07, 2008, 06:55:19 PM »

Got that right, small means small...you don't need 12v to run leds, it's a waste.

Go for 3 volts instead and use small encapsulated panels in series and parallel for your requirements. Nicads are the way to go, charge them and let them run completely down, recharge them again. If you match your solar output to your daily usage you can just let them run down (like outdoor solar garden lights). Nicads can cycle everyday for 3 or 4 years or more without replacement.

You could get the system down to little money out of pocket, especially if you score cheap garden lights and use the batteries and leds out of them.

richhagen · « **Reply #13 on:** February 08, 2008, 01:22:40 AM »

Ghurd, if you just took the $220 and put it in, or added it to, a CD at about 5% you would get about $11 per year in interest as well. So actually you would be losing about a buck forty per month everything else being equal, assuming you already have the 120V desk lamp set up. Small solar, heck, most solar if you have to store it is not cost effective yet. That is why there are not yet fields of silicon stretching across our deserts. I have done the same calculations for my rooftop array here, and it does not perform any better :-( actually I lose much more because of its size. Still it is nice to know that you can power your house for a bit if you have to. Perhaps that is why I have another batch of used panels sitting in my living room, waiting for good enough weather to go up there. For the moment, it is only cost effective if there is significant cost involved in getting grid power to the point of use, or if there are significant incentives on offer and the power generated does not have to be stored on site. If you have to add depreciation for a battery bank in addition to the panels and inverter, then there is no way to achieve grid parity at present in my opinion. Rich

claude · « **Reply #14 on:** February 08, 2008, 06:09:12 AM »

see this one: http://www.dprg.org/tutorials/2005-11a/

or, http://www.uoguelph.ca/~antoon/circ/pwm555.html

It's simple to make. One thing is that it won't go down to 0% or up to 100%. You could adjust (by using germanium type diodes) the output in between 2% -- 99 %. It's good enough for me.

I made it and used it along with a LM117 voltage regulator and a MOSFET-based current limiter and so I got a regulated voltage&current driver + PWM adjustment. Sweet.

It all looks like this (to the right, the 555-based PWM):

claude · « **Reply #15 on:** February 08, 2008, 06:11:47 AM »

Oh, I forgot, the three pins on the far side are for connecting the 50K Pot.

Claude

Bruce S · « **Reply #16 on:** February 08, 2008, 07:04:50 AM »

Claude;

Thanks for the circuits. Will be another one to try out. I like nice/simple and easy :-)

Will bread board it up for a good test.

Thanks Again

Bruce S

ghurd · « **Reply #17 on:** February 08, 2008, 07:56:32 AM »

Guys,

Everything needed is already here in more quantity than I care to admit. Except for one of Claude's fancy circuits.

A better plan for the use of power would make the numbers look better.

About 5X the money would get 15X the power.

Catch 22. There would be a LOT more power available in the summer, when the lamp isn't needed as much.

Anglepoise and CFL. I put rubber bands with the lamp springs.

LEDs on less than a 12V system is a complete waste of solar cells and power.

I need this lamp to be working when I need it. Draining a couple AAs and trying to see with 80% dead cells isn't going to do me any good.

Besides, there are more than enough nicds here to build a 12V 50AH pack.

The lamp will be a story by itself. If the lamp is on, and the battery is below 12.22V, then a tiny 12V transformer gets grid power to help supply some of the lamp power. It won't charge the battery because it doesn't quite make enough ma to power the bulb, but it will keep the battery from getting too low or me from being in the dark.

It will be able to use every drop of available RE.

Geoff must live on the moon!

G-

claude · « **Reply #18 on:** February 08, 2008, 11:10:05 AM »

G, you really got me thinking about THE LAMP.

Truth is I still have none to light up my desk. I rely for now on my good old 22" CRT monitor to make my keyboard visible. But The Idea of having my own LED lamp!

You are right, a 9V driver is a waste of power. But 12V out from a 11.8V battery isn't easy. One would need a Buck-boost converter to overcome this. And here's how a simple lamp becomes rocket science.

Claude

ghurd · « **Reply #19 on:** February 08, 2008, 11:23:43 AM »

The 9V driver is fine. I was talking about solar charging 3 AAs for an LED.

I only need about 9.1V for "full brightness".

That's 96 chips at about 4.5ma each. Pretty efficient. :-)

I don't want to run the battery lower than about 12.2V anyway, hence the grid-assist.

Maybe someday you will have Enough LEDs to build that lamp without so much worry?

Build the lamp already!

Me + Buck + Boost = Smoke

G-

Bruce S · « **Reply #20 on:** February 08, 2008, 11:42:10 AM »

Now I'm getting real curious about how much area you are looking to light up.

Work area ? desk top ? or whole room?

The newer Lexon II , III and K2 have some impressive lumens now. They're still within the 3.3Vdc range and even the newest one will hold a steady 3.6V 350ma with bliding light output. With I'd say, a 20 degree beam, that green one I took a picture of will put a light on my ceiling 12 feet up and when using a defusser will cast a nice glow on my office.

Digital camera seems to have problems with some of the different light colors but I can certainly try taking more if you wish.

50Ah of NiCd? that's it, do I need to ship more;_)?

I agree with the fact that the bigger, or more intergrated, you put on the RE the better the numbers look, but what fun is that?

Are you looking to use a dump controller in reverse to keep the LEDs lit?

Cheers

Bruce S

hydrosun · « **Reply #21 on:** February 08, 2008, 02:20:39 PM »

I know this isn't exactly what you proposed but why not a solar powered led flashlight. I bought one for my grandson for Christmas from bogo.com for $25. Bogo stands for buy one, give one. I bought one and they donated one to a third world charity. They've designed a rugged led flashlight with a built in solar panel that can light up a room or used closer for reading. It has a spring loaded clip to hang it up. It has 6 leds that were brighter than my brightest homemade 12 led light. So they must be using the latest efficient 5mm leds.

So this is a lot less than the small system you proposed and 1/2 the price is used to get the technology to places where it isn't just a toy to play with solar.

Personally I use my 12 volt led headlamps all the time. I have one battery pack from a video recorder that I've been using for led lights for the last 15 years. I have an old cell phone recharger that I recharge it off of the house 12 volt battery bank. One battery pack is two 6 volt nicad cell phone batteries that I tested and pulled out of the recycling bin 6 years ago. These battery packs seem to last forever at the low milliamps useage of leds.

Chris

zeusmorg · « **Reply #22 on:** February 09, 2008, 08:53:13 AM »

Why not buy one of those outdoor solar lighting kits?

Like : http://www.walmart.com/catalog/product.do?product_id=3331121#Features+%26+Specifications

Not saying that one is perfect, but you're talking all the components are already built, you could mount the panel to a gutter, run the wiring in through a window, and I imagine the batteries are just cheap nimh rechargeables, Also you're only talking 30 bucks, I'm sure there's cheaper ones out there too. I've seen them at dollar stores.

Considering the things are designed to run all night, I would imagine they would light up your desk sufficiently for a few hours.

americanreman · « **Reply #23 on:** February 09, 2008, 01:52:44 PM »

If you look around you can buy lights for around 3.00 a piece, make sure they have 2 batteries and not just 1 then you are getting higher output solar cells, it's a great deal, you can't buy the solar cell, batteries and led separately for 3.00.

I've been here and done this on my boat, even though I have a 12 volt bank, I chose to use 3 volts for the led lighting using nicads. You can beat the hell out of the batteries and they last for 4 or five years cycling them everyday.

full nicads will power a bright led for 10 hours and requires 1 small solar cell to recharge.
volt source for running leds is a waste, the panels cost more, bigger wire is needed, etc. You never have to worry about smoking your leds either because you are running them on 3 volts and of course no regulator is needed.

ghurd · « **Reply #24 on:** February 09, 2008, 02:53:30 PM »

You calculator needs new batteries.

With 2 full charged nicds, which in a simple charging circuit should be limited to about 1.35V, would be 2.7V.

Most white LEDs need about 3.15V for about 18ma.

Most need about 2.9V to glow much at all.

It won't need a resistor. It will need one of Claude's boost circuits.

Say with 24 LEDs at 18ma...

In a simple circuit (3.6V), 24 x 18 = 432ma. 4H run time is 1728ma. 1.5H insolation means 1152ma of panel. 3.6V + 0.7V + .3 for losses = 4.6V, meaning 10 cells though 8 may be OK.

With 10 cells thats 6.7W.

In a 12V system it needs 144ma, x4 = 576mah, 1.5H insolation is 384ma of PV, 36 cells, 6.5W.

Notice the wire can be a LOT smaller. And the system can have a diode loss, and still have 3V of additional losses.

The 12V system can use 2 VW PVs and have power to spare. ($30~50?)

The yard light toys make about 15ma Isc on the ones I played with. IF they made enough to charge 3 cells, it would take 116, but they don't, so it would take 232.

At $3 each, it's either $348 or $696.

My wife isn't keen on "A" PV, I won't ask about 232 mini PVs.

AAs won't cut it here either. We can go 3 days and not get up to charging voltage.

This is an example of costs for an average person to have a fully functional system.

I have well into double digits of 5W class PVs, 5 figures of white LEDs, a dozen new SLAs, and "a lot" of AA and bigger nicds here. My cost would be a fraction to put up a real system.

G-

Volvo farmer · « **Reply #25 on:** February 09, 2008, 03:28:34 PM »

Here's how I'd do it.

Lamp $15

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94818

Charger $2.50

http://tinyurl.com/2u9ntn

Batteries $7.50

http://tinyurl.com/323bvp

zeusmorg · « **Reply #26 on:** February 09, 2008, 06:08:09 PM »

Nice setup there volvofarmer.

There's only one problem i see with that setup, the charger gives you 2.6 V whereas the lamp uses 3 batteries and with the nimh's that would be 3.6 V. I suppose you could rotate the aaa's.....

americanreman · « **Reply #27 on:** February 09, 2008, 06:59:25 PM »

He's talking about a desk lamp, repeat 1 desk lamp...or am I missing something?

Leds work quite well with 2 nicad batteries, tell the makers of yard lights that their calculators all need new batteries and their leds need 2.9 volts instead of 2.7, see what they say.

About a square foot or less of pv and a few batteries should do the trick for a desk lamp, wholey moley.

ghurd · « **Reply #28 on:** February 09, 2008, 11:01:59 PM »

You are missing MORE than a few things. Some you may not know.

Mostly "he" is "me".

I (and he, and me) am talking about a real life replacement of a grid fed 5W rated CFL. It needs to come on when the switch is clicked.

Good marketing and crappy products is why solar has a bad rep.

Some barely glowing yellow novelty ain't gonna cut it. I watch every night as the neighbors yellow LED yard lights click off with the sun setting (not a typo. They come on a little before sunset. Then go off around sunset), and I know white LEDs will not be as good.

Show me a white LED that works quite well on 2 nicds.

Show me a white LED data sheet that shows a white LED with rated MCDs at 2.7V.

Show me a boost regulator that is more reliable than a 1/4W resistor.

Headhunters call me about LED design jobs, but I will not relocate. Or work 9-5, if I don't want to on that day.

But I decline. I have serious obligations here. And I almost like sorting resistors/TO-92s/TO-220s into tiny bags for someone excited about a new windmill in who-knows-what-corner-of-the-world.

Major brand names offer to put my name on their package.

I get the stuff you talk about in skid quantities. The boxes have my name printed on every one.

I have stuff made to MY specs in China, Taiwan, Hong Kong, Korea, etc. I don't have them put a different sticker on some Wally-World crap.

Do you remember, long ago, when you were selling those re-stickered Chinese inverters just like the inverters at Wally-World, but probably seconds (without your knowledge)?

Do you remember when someone asked about large quantities of 12V 175W and 400W inverters, but you said there wasn't a market or profit or something like that?

Yup.

That was me.

Anyway.

If you have the data sheets for those $3 yard lights with 2 nicds, a PV, and some kind of white LED that runs directly from 2.7V, 10 hours full brightness with yard light quality AAs, and no regulator, please post a link.

G-

(sorry TomW, Kurt, Woof, but you must have seen it comming)

DamonHD · « **Reply #29 on:** February 10, 2008, 03:01:17 AM »

You're being very restrained, sir: something leaps to mind about teaching grandmothers to suck eggs...

Anyhoo...

Taking this from another angle: when efforts are being made to put together solar lighting solutions for 3rd-world off-grid villages where the extra expense is far more than just an annoyance, how do/can they keep prices for the completed unit a little lower?

For example, how much of this could be integrated? Could the solar controller and CFL ballast be put on one board and share any parts?

Rgds

Damon

americanreman · « **Reply #30 on:** February 10, 2008, 06:34:22 AM »

Sorry sir, I just got caught up in the fact that people are talking about paying out 300.00 to run a desk lamp, I offered my 2 cents which in fact will work for quite a few people who are willing to try it out and save alot of money in the process.

With your knowledge why are you asking for help here again?

As far as the inverters are concerned, there is no market for a person like me to buy 175 watt inverters, pay the sea freight and try to sell them when you can buy them at walmart for next to nothing...I can't compete with that, nor would it make good business sense to try.

The inverters I was selling were top notch, brand new and unstickered in plain white boxes, I was trying to help this community and pass on the savings...with my knowledge of inverters and connections in China which are both very good.

Tell me where you can buy a 5000 watt inverter, with volt and amp meters and wireless remote for under 300.00? Don't get me started on dirt cheap magnets either.

Many people bought those inverters and magnets, do you see any posts about me selling junk or offering bad service? Attitudes like yours is what killed the project, I can get anything at any quantity out of China, I was just trying to help people on this board, there was no grand scheme in place to make large profits.

fungus · « **Reply #31 on:** February 10, 2008, 06:37:16 AM »

"With your knowledge why are you asking for help here again?"

As far as I can see he wasnt ..

americanreman · « **Reply #32 on:** February 10, 2008, 07:00:39 AM »

Then I guess my suggestion of buying solar lights and using the parts was a stupid idea, I mean after all for around 3.00 all you are getting is a 150 ma encapsulated panel, 2 800 ma nicads and super a bright led ;0)

You can surely buy all that separately for 25 dollars or more, sorry just my limited experience again...maybe its better to build a mill and put up a bank of 12 volt batts to run a led desk lamp...sorry I got involved and I apologize for any animals that have been harmed as a result of my stupidity.

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Author Topic: Micro-Solar LED Desk Lamp (Read 579 times)