Sounds great, Enrique! How about a digital picture? I'd love to see what you are doing. --Bob Enrique Avalle wrote: > Dear Bob, et all: > > Finally yesterday I had a full sunny day down here. I noticed that one of > the solar panels was a bit weird: there are two conductive lines, > plated-like that go thru the panel, and below of it there is a black "pap= er" > that has very small lines of also plated-like lines. In this particular > panel the paper was badly placed, and for most of the smal lines, > misaligned. I did my best to realign them and ensure better contact. > > I also made the A/D converter work only once per second, turned on browno= ut > flag (it was off), and switched to internal clock (4mhz internal) pulling > out my crystal oscillator (this paragraph intent was to lower energy usag= e). > > > It finally worked ! The 16f690 works like a charm and tells me the time > since it has been powered up, the realtime oven temp, the mean temp during > the time it has been exposed to sun, and the volts that the solar panels > give to the circuit. It works ! Anyway if I place my arm over the solar > panels, voltage goes down into less than 4 volts and so the LCD just can= =B4t > be seen. It still draws power, I asume, so I will power it up by using one > of my PIC's Free pin used as an output, turning the LCD ON only if I have > more than, say 4,3 volts from my solar panels, just to maximize power to = the > processor (Nobody wants the PIC resetting and thus loosing the temps and > time, because of a large cloud !!!) ... > > Now I am working in optimizing my code (I am using picbasic pro). (yes I > know, most of you are assembler purists ... But hey ! I managed to do this > code from scratch in less than 10 hours !!) > > :) > > I will post the project's URL when I finish documenting it in html. If > anyone is interested in details, just ask !! > > Regards, > > Enrique. > > = >> -----Original Message----- >> From: piclist-bounces@mit.edu = >> [mailto:piclist-bounces@mit.edu] On Behalf Of Bob Axtell >> Sent: Viernes, 30 de Marzo de 2007 02:09 p.m. >> To: Microcontroller discussion list - Public. >> Subject: Re: Solar powered 16f690 & lcd >> >> Enrique Avalle wrote: >> = >>> Dear Friends, >>> >>> I am NOT proficient in electronic matters, and so I am = >>> = >> taking it slow = >> = >>> and easy, hobby like. Anyway, As I usually give my free = >>> = >> time to a non = >> = >>> profit organization down over here (I am in Uruguay, South America) = >>> named PROFAUNA, I proposed the addition of electronics / = >>> = >> Pics to some = >> = >>> of current Profauna's projects. >>> = >>> = >> I would be interested in assisting you to help in solar power = >> applications. >> = >>> One very interesting project involves distribution of solar cooking = >>> ovens among our country people. I designed a PIC 16f690 = >>> = >> based system = >> = >>> which displays in a 2x16 LCD such information as cooking time, real = >>> time temperature and also the mean temperature received among the = >>> whole cooking lapse, a truly needed aid among solar cooking = >>> = >> oven users. >> = >>> It works fine, being powered by 4 AA batteries. Problem is: = >>> = >> I wanted a = >> = >>> 100% ecological / very non serviceable / autonomous = >>> = >> solution (at least = >> = >>> to show off as an interesting achievement) so I bought 5 = >>> = >> SOLAR PANELS = >> = >>> (each one said to give 1 volt / 400 mah). Previously, I measured my = >>> circuit, and it used 5volts & less than 10mah. >>> = >>> = >> The problem is that solar cells are rated in strange ways. In = >> 99% of all cases, solar cells are used to charge batteries. = >> The reason is that clouds sometimes cover the sun and at that = >> moment cannot deliver enough voltage to drive an application = >> directly, so the application doesn't run correctly. >> >> Actually, you might think about reducing the needed current = >> for your PIC16F690 project; 10 mA seems like a LOT of current = >> for what you are doing; for example, you might want to turn = >> your temperature measuring devices on only occassionally; = >> that should drop your drain to 100uA or less on the AVERAGE. >> The super cap can deliver the instantaneous 10mA needed when = >> you need to measure. Surely you need to measure no often than = >> once per second or every 15 seconds? Have the PIC16F690 = >> provide the actual voltage to the temp devices, by connecting = >> the temp devices to a free PIC pin. The LCD display uses = >> current only when it is written to; without a backlight, = >> LCD's draw almost no current at all. >> >> What you should do is to charge a SUPER CAP, which will keep = >> enough energy available for a peak load. These devices are = >> more expensive than normal electrolytics but less than = >> batteries, and will provide the energy for most low power = >> applications. You will need to install a 5.1V zener across it = >> to keep it from being damaged by a very intense sun. Use a = >> precise 100mw zener, not a leaky 1watt zener. A better way to = >> do this is to use a diode (anode end) on the + lead of the = >> super cap to the zener attached to the diode's cathode end; = >> this will ensure that the zener diode will not drain the = >> super cap at all. I would experiment with 0.47F @ 5.5V Super = >> Cap as a start; you can probably get by with 0.22F @ 5.5V. = >> ALL ELECTRONICS sells very inexpensive Super Caps. >> >> >> >> = >>> Problem is: I measure the solar panels (connected in = >>> = >> series) and they = >> = >>> give me in eccess of 5volts under direct hard sun. I plug = >>> = >> the panels = >> = >>> to my system and NOTHING HAPPENS. >>> = >> Not surprised at all. I am very familiar with solar panel = >> applications. >> >> >> = >>> I plug the batteries and it works fine. >>> >>> I think it might be the necessary startup power (is there a = >>> = >> PEAK ?) ... >> = >>> = >>> = >> almost always. >> = >>> Any measurement / corrections / indications / advise and or = >>> = >> ideas is = >> = >>> welcome. I am planning to buy a >>> >>> Artesyn Technologies DC/DC Converters Non-Isolated Point of = >>> = >> Load 15W = >> = >>> 0.59-5.1V 3A Vertical Mount = >>> http://www.artesyn.com/media/pdfs/ldo03c.pdf >>> = >>> = >> why? >> >> = >>> In order to place between the solar panels and my system. Is this a = >>> good idea ? >>> >>> = >>> = >> waste of money, I think... >> >> = >>> Regards, >>> >>> Enrique. >>> >>> P.d. I am placing my whole system (circuit design, software) in the = >>> public domain, as I think it will be good for other people to work = >>> with and improve upon. >>> >>> = >>> = >> --Bob >> -- >> http://www.piclist.com PIC/SX FAQ & list archive View/change = >> your membership options at = >> http://mailman.mit.edu/mailman/listinfo/piclist >> = > > > > = -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist