Solar story

[claude]

Hello everybody,

This is the tale of a man that lived too far to have access to the toys you're all playing with. As a result, this man being so passionate about RE energy started to make his own toys. And here's one of his favourites - his tiny solar system.

The PANEL

The saga started in one day when a supermarket around here had solar lamps at discount price. So I headed there and buyed 9 of them. There were very nice solar lamps, stainless steel body, a 600mA NiCad inside along with one LED and a booster/charging circuit. I gently took apart all the solar cells on top. This was easy. Too easy, I'd say. The individual output was dissapointing, 2V at 50mA max. But I went on with the plan.

I connected all the cells in series and got 18.9V at 50mA. That's 0.9W of power. Talk about dissapointment... But hey, it's supposed to be fun so let's carry on.

Took some plywood and drilled 9 big holes equally spaced. Put one 0.3mm aluminium sheet over that and glued the cells over the holes so that I can have acces to the poles on the back. These cells were already waterproofed so the only exposed area were the contacts on the back. The plywood received one aluminium frame (I like aluminium) made from a single profiled bar used for stairs I guess...

I connected the cells in series and covered the connecting wires with a sheet of plastic. The whole thing was waterproofed using silicon caulk all over the sides.

The result started to look like a solar panel!

I then made a panel support and put it outside my window. It looks like this:

Pretty neat. My father-in-law suggested me to use gas pipes. And they were already threaded so I could turn the panel on E-V axis.

I also kept all the 9 ex solar lamps in original shape so they could be used again someday. The leds were nice, the batteries were cheap but useful and the booster circuit also usable.

As I was looking at my first solar panel I realized it's just a toy. No real power can be obtained this way except by using hundreds of these tiny cells. The volts were OK but the mA's were way low. So I started to think small. It's not like I had a choice. I'll be using one of my 12V ledbulbs I made a while ago (more about this at http://www.fieldlines.com/story/2007/1/28/215243/977 ) as a load and a 1.3 Amps litle SLA battery I found around here for daylight charging.

The LIGHT

I started working at the ledbulb circuit since I needed it to turn itself off in daytime and on at night. The solar lamps were great for this but the circuit was not usable as it was designed fot 1.2V. So I made a light sensing circuit along with one ledbulb placed inside a solar lamp.

This is the photodiode on top of the lamp.

This is the ledbulb inside. The wires comes trough the lamp's foot and the circuit is inside the lamp's top side. It was nice to use this lamp as I was starting to feel sorry for dismantling them.

This particular bulb takes around 30 mAmps and uses 7 white LEDs. The day/night cycle worked great. No power consumption while turned off. That's was good.

The BATTERY.

The original lamps came with 600mA NiCads. I decided that my panel could charge a 1.3Amps small SLA, given enought time and sun. I was not thinking about the time it would take at first. To test my rig I connected the battery to the panel and the lamp to the battery. It worked like a charm, and my wife was happy that her flowers could now enjoy permanent light. The voltage was more than the battery wanted but the low 50mA current made overcharging a very low risk. As days passed by I noticed the battery going down to 11.8 Volts in the morning and I started to think maybe the load is too much. Or the panel is too little. It was sunny so what could be wrong? I then realized that the panel was only surface-charging the battery. It was charging but tha balance was negative, meaning It charged a little less than it discharged. This was discouraging again. I could make another led bulb with less leds ... hmm... I put aside the project for a while. And got interested in all sorts of electronic circuits.

I found a low voltage alarm circuit for 12V SLA's and a LED voltmeter circuit. Gradually, my mine started to put all this together. A solar controller, with low voltage alarm, LED voltmeter, some voltage regulation, a low voltage disconnect feature, all this would be helpful to make the most of my tiny solar stuff. I've had help, I must admit. Credits can be found at the end of this diary entry. Without help, what follows would have not been possible.

The CONTROLER

I started making a circuit that featured LOW Voltage Alarm & Disconnect, LED Voltmeter and 13.7V Regulator in one piece. It was pretty hard for a beginner in electronics like me but I made it. This was the PCB. Toner transfer method using regular paper and nail polish cleaner.





The 13.7V Regulator is is in fact a PB137ACV regulator. Thanks Glen for suggesting it to me! It takes up to 800mA (with cooling) and it's so very simple to use. For my need it was perfect. It's a great asset for lower than 1A systems.

As the ordered components started to arrive, the controller was taking shape.





Then, I looked for a fusebox that would hold my circuit along with the battery. I found this one and it looked OK to me.





And I started to make the front panel. This was first printed on a laser printer and then all the holes were drilled after the self-adhesive label was laid upon a white plastic piece.





I mounted the switches (Alarm buzzer off, Load on/off disregarding the LVA, Circuit OFF, and some I will explain later.) This was the end result. Pretty good.





The wiring got messy because of the so many options I wanted to have. I drilled holes for the external power connectors. Those are Panel IN, Load OUT (with LVD protection) and Aux IN for a future bigger SLA if I'll have a future bigger panel.





The whole circuit was now complete. Time to test it. Actually, I tested every circuit on this board as I finished it so I expected no surprizes.





I was lucky with this box. A little big and bulky but the plastic was soft and never cracked no matter how many holes I drilled into it.





The whole circuit was now complete. Time to test it. Actually, I tested every circuit on this board as I finished it so I expected no surprizes.





It was time to put it in its final place. Guarding my wife's flowers and taking care of their light without me constantly checking the battery.

This is the final setup. You can see the panel rim outside the window and the lamp in the flower pot. The controller box will be mounted on the green wall behind.

CONCLUSION

Man, this was fun! It took a month and a half to get to this point but mostly because my spare time is limited.

All in all I ended up with a solar toy. There are benefits, of course. Using this panel I can leave the light on all night but I have to wait two days to get the voltage back in.

PROs

• My wife is happy :-) This surely beats everything else.
  
• It was my first solar energy approach. The benefits are small but the amounts of fun I had and the educational value is huge.
  
• Great for flowers. (Don't laugh but the flowers were smaller at first, without this light. It looks like the added light really helped)
  
• Upgradeable. The circuit is connected so that one external battery can be used instead of the internal one. With a bigger solar panel this would really make a usable system.
  
  

CONs

• There are a lot of con's. I won't count them all here, there aren't that important. The main problem is that the coltroller is a load all by itself, taking 15mA just to show the voltage. My limited input current made me add a switch that bypasses the whole circuit and feeds the battery directly from the panel, via the PB137ACV. In this mode, the load is off so no other factor can lower the voltage. This made the charging process so much faster. With the circuit on, the charging current was around 30 mA and without it up to 50mA's - the whole panel output. I tried to lower the circuit consumption by using blinking led's but nothing changed. One future solution would be to use a 555 timer-based flashing circuit set to a low frequency to feed the LED voltmeter. The LV Alarm must be fed continuously but it takes VERY little power.
  
• The price. This was one expensive toy in the end. But overall cheaper than its commercial counterpart. The solar lamps were cheap. But cheap multiplied by 9 gets expensive. And the power output is very low. The rest is not so expensive.
  
• The dissapointment I get when people outside ask me how many TV channels do I get by using that weird panel-like antenna...
  
  

CREDITS

There are a few persons I'd like to say thanks. To my wife for her never-ending understanding. To Glen, a great guy and a real friend. Without his help this would not have been possible. To my father-in-law that helped me make the panel mount without asking too many questions. :-)

The RE energy here in Romania is regarded as rich-people's way to escape everyday's living costs. No real government support is provided so far and the PV panels available here have VERY expensive prices. Windmills and such are nowhere to be seen. Water generators are only used when isolated touristic locations are too far up in the mountains to be connected to the grid. The environment policy embraced by our country after joining the European Union states that a minimum of 6% of the country's energy must come from renewable energy sources. So I guess things will have to change around here someday. Hopefully, soon enough.

Cheers,

Claude

[ghurd]

So, how many channels does it get?

G-

[fungus]

Wow!

Very neat and professional looking. Great job, even if its tiny output :-)

If only my projects looked as good as that

What IC's are used in the circuit to sense the voltage? I'm guessing some sort of op-amp?

What was the total cost of the system?

[claude]

Everyone, please notice that G. is still not getting it :-)))

[claude]

Yes, Op-amps. IC's used are LM3914 Dot/Bar display driver and LM339 for the low-voltage alarm. As for the total cost, the parts involved were purchased from various sources and prices while some were recovered from electronic junk.

I couldn't say how much was this all. I'm not even sure I want to know that. I don't need another dissapointment. All I can say is that you must be really passionate to carry on with so little benefits and so many expenses. The next time I'll surely look more careful at price vs. gain balance.

So Angus, this is not something I reccomend to others. This is just me learning on my own expense. And on this great board we all come back to.

Claude

[AbyssUnderground]

All I can say is that you must be really passionate to carry on with so little benefits and so many expenses.

I guess this can be said for all small solar systems, just like my own. It costs a lot and gives little benefit. Its the fun that counts though :-)

[tecker]

Next step 50 watt  window shades and 102 Chanels .

[americanreman]

Some of the best work and workmanship I've seen on this board.

Credit where credit is due..

[Norm]

Yeah he is on the slow side LOL !

My system took a little longer to make I had to

hot glue the plastic caps with the solar cells

onto a hunk of cardboard.

(6 of them that originally charged 2AA rechargable NiCDs each) they now charge 5 NiCD

C sized sticks in a couple of hours....put the

whole thing in the seat of a folding lawn chair

and reposition it every couple of hours.

You did a real nice job....It would have taken

me a year to do what you did.

              ( :>) Norm.

[tecker]

Yes Don't stop there improve on your lot .

[wooferhound]

When I built my solar system

http://www.fieldlines.com/story/2004/6/10/20567/9536

I used a momentary pushbutton switch to check the voltage.

This prevented Battery discharge by Not displaying the voltage all the time.

[claude]

Hy Norm,

There are several types of solar garden lights. I've seen 0.5W, 1.0 W and even 3W ones. But there were too expensive. I think I bought the weakest cells ever made. I'll rectify that, I KNOW I bought the weakest cells ever made.

Some beter cells would improve things dramatically. But given the cost of solar panels around here, I'll have to wait for better times.

Thank you for your nice words.  

Claude

[boB]

Well Done !  Very nice job !   Looks like you've done some electronics

packaging before ??  What is your day job ?

No wonder it's such low power though...

You just need to make it MPPT !! {:-)  (not really)

I bought some on sale solar yard lamps but they're

plastic.  Not nearly as nice as the ones you found.

boB

[claude]

I thought about that. Yet, it's one good option. But one 555 timer could be set to feed the circuit for two seconds every minute for instance. This would certainly improve things.

Someone on this forum doesn't understand why people waste so much power just to see how dead the battery gets. He's so right. But knowledge is power. Not electric in nature, obviously... :-))

I recently found one super-cheap chinese analog voltmeter. It works without the internal battery too but the scale need to be replaced. The best thing is that it uses less than one miliamp to show the voltage. This will be one of my next projects. Will keep you posted.

Claude

[claude]

To be honest, i've never made any electronic circuits before. This hidden hobby of mine emerged some 4-5 months ago. As a kid I always liked electronics but never put anything in practice. The Internet served me well in teaching me all the stuff I needed to know lately. I'd give Google a Nobel prize if I could. For expanding people's horizont. Electronic packaging? No, nothing like that either.

My day job is graphic designer. I have a degree in Visual Arts. Go figure. I like to make things look nice, and I guess it's obvious.

As for MPPT idea, it did crossed my mind. But you can't get more from less. Cheap cells will behave like cheap cells no matter what you do.

Claude

[Bruce S]

Claude;

   The workman's ship is off the scale!!!

This looks are better than some commercial quality I've seen popping up.

The idea of pay back versus costs involved : I wouldn't worry too much, just think how long this will be working, or even better.... when for some unknown reason the mains goes out and that light comes on and you're the one with a little light.

Plus look long term, no bulbs the burn out, no extra mains power to use (extra saving already) coolness factor for your wife to show off her very healty plants.

Question? since you've put this together, have you had any extra power to have a dump load circuit? just thing that with those cheap AA-NiCds you have left over, you could arrange them for +11Vdc and let them act like an set of backup batteries.

In as far as taking care of the flowers.=> When you have time, and have the junk stuff around , keep an eye out for the Red LEDs and Blue ones. for younger plants the Red shift light will have them growing with stronger thinker stalks. If you're up to growing vegetables then use the Reds for getting them to stay strong and once on thier 3rd set of leaves switch to Blue.

The Blue shift will help the Veggies and flowering plants to flower and produce fruit 2x faster than normal which includes CFLs plus almost no heat.

The current testing going on in the labs here is 5 Reds to 1 Blue.

That diffenbacca plant you have there will need for you to begin adding extra legs to the light pole:--)

[claude]

Thanks Bruce!

I made my peace with this project. It's ready for future bigger panels and external batteries. It's a matter of time until my hobby budget gets a raise :-) It depends on the plants good condition :-)))

Reply: No, I had no extra power. I don't have enough, actually. I anticipated the situation. Therefore no dump circuit is involved. I wish I had extra power to actually aford one dump load. It would made me feel... well.. spoiled I guess.

Those cheap Nicads are too cheap. I have enough 1200mA that were cheap so I got around 20 pcs. I use them around the house. But your idea is a good one. Provided I have that extra power.

About flowers. Well, You got my wife's attention, that's for sure. Now I'm assigned to make a red&blue light thank you very much :-).

The pole is temporary. I will ad soon a higher wall-mounted spot light and solve the problem. Also this will allow a more evenly spread light since the present lamp has too many reflections, as you can see in the night photo.

Thanks again for reminding me about the half-full part of the glass. I needed that.

Claude

[Bruce S]

claude;

  No problem,Always willing to share.:-)

I too, look forward to your next light.

Don't throw those NiCds just yet:--)

Cheers

Bruce S

 

[Spdlmt150]

Beautiful work. Seeing what you have done for a small system as this, I can only imagine the postings we'll see later on when you start pushing some amperage! And trying to figure the dollar value on learning is hard - My first solar system was a handfull of calculators butchered for the cells to trickle charge a AA battery. I don't want to think about what it cost, but it led to 16A of solar running lights through my whole house, as well as running the computer that is posting this comment. Keep up the good work.