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 "paper" 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 brownout flag (it was off), and switched to internal clock (4mhz internal) pulling out my crystal oscillator (this paragraph intent was to lower energy usage). 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