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 Posted: Jun 21, 2007 - 05:21 AM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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i think such a big thing is a good way to gain attention on technical university 
i'm confused now... i wanted to use 1Hz to wake up micro every second and let it perform operations, it is upgrading its memory content about current time, sending proper data to lcd controller and putting itself back to sleep, but being runned by the internal clock all the time. that's how i understood Edward's idea, and anyone please correct me if i'm wrong.
as Kevin suggested before, i'd like to use DS1306 or such, like 1302 or 1305. friend of mine has already supplied me with some datasheets and i study them to find the best one.
uhhh, i get new ideas about the powering all the time, so maybe to make it straight to all of you, here is my current best option:
attiny and rtc are supplied by rechargable battery, and using DS1305 ability to recharge its power supply the battery will be charged partially by solar cell. another cell will exclusively supply the lcd. but if rct and attiny will use funny uAmps then instead of rechargable pack probably i'll use a cheap model of coin cell, use simplier DS1302, but the lcd will be still dependent from solar cells.
but if someone gives me a good point why not using solar cells, i'll do my best to find a good rechargable battery pack, and put a DC input onboard.
go on guys, you make really good job guiding me and making this project real  thank you all for your efforts. |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 21, 2007 - 10:48 AM |
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Joined: Jan 03, 2006
Posts: 4410
Location: Hemel Hemsptead, UK
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Posted: Jun 21, 2007 - 11:31 PM |
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Joined: Apr 20, 2007
Posts: 6061
Location: Long Island New York
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putting the tiny to bed and waking it up every second is not very efficient. A good idea is to use a coin cell RTC and wake the tiny up with a pushbutton when you want to see the time. The tiny can poll the RTC and then send the time to the led's. SOLAR!? cool.
Jim |
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Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first
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Posted: Jun 22, 2007 - 12:30 AM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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hm, sounds reasonably too. but what if i want to make it work without using such a button? i always get annoyed by simple things that need two hands to be operated. is keeping attiny up all the time the only way to achieve this effect?
perhaps that could be done too, the solar cells i checked out produce up to 70mA, so maybe it could serve as the battery charger. or maybe not..? |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 22, 2007 - 01:46 AM |
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Joined: Apr 20, 2007
Posts: 6061
Location: Long Island New York
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I guess this is no longer a wristwatch.
Here is an idea....make a list of everything you want this clock to do, and post it. Then a practical design can be created.
One good tip, look at the maxim/dallas website for the RTC chips. they will sample just about anything in 5pc quantities for free, and they pay the freight usually!! |
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Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first
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Posted: Jun 22, 2007 - 08:04 AM |
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Joined: May 26, 2004
Posts: 2538
Location: Las Vegas, Nevada
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Well to share some practical experience, using a Mega48V, if you run a 32kHz crystal on Timer 2 and wake up on the 1 second counter overflow to keep time, the average power consumption is in the 5 microamp range and it will keep time for a couple of days on the charge in a 0.33F supercap. A solar cell will put enough in the cap for another day if it gets light for half an hour. If the solar cell can deliver several mA you could use one supercap for the time and a second (or perhaps a rechargeable battery) for the display.
You could use a trembler (small weight on a spring contact) to turn on an LED display when you flick your wrist quickly.
A practical point about the Dallas chips (some - I haven't checked them all) is that you can't read them unless the Vcc (main supply pin) is at least a volt higher than the backup supply pin, because they think the Vcc is failing and go into a power-down mode. Unfortunately if you connect the battery to the main Vcc instead of the backup supply pin, the current consumption is quite high. |
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Posted: Jun 22, 2007 - 03:53 PM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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that's a great news, thanks for those. i've noticed very divided points of view about waking up atmel each second, so what i'm going to do is just check it out myself. if it won't work, i'll try to make it run all the time... somehow.
i've never thought of any capacitors before, i've been always thinking of rechargable batteries. but i guess caps are easier to charge with low current, such as the one produced by solar cells. still, i need to learn more about appropriate usage of such a cap without burning uC.
friend of mine is right now supplying me with philips PCF8583. this circuit quite fits to what you all said about RTC before, operates on dead low current, keeps time and date. Anyway, as Jim adviced, i'll take a look into the maxim/dallas website. even if i won't use them to this project, i know i might need them for other circuits anyway
so, here's the requested idea list:
*LCD graphic display:
1. two options:
-either the ordinary timestamp in text mode or fancy graphic mode (i know it's a lot of code work, but i'm experienced with some languages), or:
-hours, mins and secs presented in binary code, either as 0-1s in text mode or kind of dots or sth in graphic mode.
2. notepad view, triggered by a button shows a png image temporarily instead of an hour. previously the image was meant to be kept in external memory chip, but i thought its hell to hard for such a dumb newbie as me, so probably i'll invest more money in more complex tiny or mega and store the picture file in it, and put onboard kind of input to update those files.
*Other stuff:
1. Solar supply, making the 'clock' maintenance free, if only it's possible,
2.(future plan) add a buzzer onboard and make a metronome function (i'm a drummer), but i guess the previous ideas are complicated enough to give it up for a while. |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 22, 2007 - 08:30 PM |
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Joined: Apr 20, 2007
Posts: 6061
Location: Long Island New York
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What you are asking for is not that much, hardware wise, the firmware is gonna be a hump. The supercap is a good idea. I did not think of that and the solar cell/cap is a good combo. I am guessing that for the LCD you are going to create custom graphics for the digits.
Jim |
_________________
Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first
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Posted: Jun 22, 2007 - 11:30 PM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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yes, it isn't that much indeed, partly because i've been thinking of making it all in assembler, to have kind of constructive way to spend summer holidays. but uh... we'll see.
your guess was right, i'm going to customize the display format. it depends only on the progress with asm. I've skimmed through the avrfreaks article for newbies and i thought it shouldn't be THAT bad.
so the issue of powering AVR and RTC i guess is solved then, thank you guys!
but i still ned some instructions on how should i connect the supercap, a solar cell, avr and rtc (meaning powering only for now), because i don't think that's as simple as paralell connection of everything altogether.
but let's not forget about lcd. by the way i've found a fancy one:
http://www.sklep.avt.pl/photo/_pdf/LCDGRAF3.pdf
it'd be nice of anyone who could tell me if it's easy to connect to avr, and if it needs a driver or something...
so, about the lcd. my last plan was to power it from the seperate solar battery as well.
Theoretically, the power from the solar cells should be enough for both purposes, but those cells provide 0,5V and 70mA, which needs to be transformed into 5V and minimally 4mA (in case of the LCD). Does anyone have any idea how to do that?
thank you guys again. |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 23, 2007 - 12:07 AM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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| btw peret, are you sure that 0.3F is neccesary to make it work? i guess this is quite much. and expensive. and big. |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 23, 2007 - 12:29 AM |
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Joined: May 26, 2004
Posts: 2538
Location: Las Vegas, Nevada
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Quote:
i guess this is quite much. and expensive. and big.
Check the bottom right of this catalog page - at US $1.85 the 0.33F is actually the cheapest when you only buy one or two. As for size, it's 10mm diameter and 5mm thick. There are some 3.3V supercaps that are only 7mm diameter, but I haven't yet found a smaller 5V type. |
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Posted: Jun 23, 2007 - 03:07 AM |
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Joined: Apr 20, 2007
Posts: 6061
Location: Long Island New York
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You really do not need to run the LCD off of a separate power supply. The 4ma is when the led backlight is on, so if you make that switched, you will be ok. as far as the solar cell/cap thingie, that is a snap. It basically is a parallel connection. do you have the specs on the solar array?
The connection to the lcd from the AVR is easy. What AVR are you planning on using? I think the Tiny you originally were looking at may not be big enough, especially with the custom graphics, but those could be stored in external eeprom.
Jim |
_________________
Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first
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Posted: Jun 23, 2007 - 05:02 AM |
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Joined: Mar 28, 2001
Posts: 20311
Location: Sydney, Australia (Gum trees, Koalas and Kangaroos, No Edelweiss)
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Quote:
solar cell/cap thingie, that is a snap.
So this is a wristwatch...will the solar panel be worn on top of the head by the user? Perpas with one on those twilring thingys? Where is Gwen!! She could have come up with the appropriate graphics  |
_________________
John Samperi
Ampertronics Pty. Ltd.
www.ampertronics.com.au
* Electronic Design * Custom Products * Contract Assembly
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Posted: Jun 23, 2007 - 05:30 AM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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right, another big note for you folks
following peret's suggestion, i managed to find 5V 0.22F capacitors on internet auction, please take a look:
http://www.allegro.pl/item204767780_kondensator_podtrzymujacy_0_22f_5v_sred_28mmx12_5.html
for further purposes i bought 5 of them. (and paid $1.5 with shipping )
the specifications for the 1st candidate for my lcd is quite poor as i've chosen one of the cheapest, it contains only physical dimentions and pinout. so for powering research purposes i'm presenting you a datasheet for the closest model (maybe even the same) of the same manufacturer. here it is:
http://www.artronic.pl/o_produkcie.php?id=612
as far as i'm concerned, the current of 2mA is used for displaying only, and the backlight needs circa 150mA to operate.
here are the solar cell's parametres:
http://www.allegro.pl/item204954024_ogniwo_sloneczne_70ma_bateria_sloneczna_.html
(bottom of the page)
this thing is quite small, so it'd be a waste of chance to shrink the project physically if i won't transform it into 5V.
i think the atmega is becoming the more justified option every day, with such a speedy ideas development i think i'll need 8 output pins to get along with lcd.
here's my list of current questions:
*how can i transform 0,5V into 5V without bigger losses? will i get lineralily decreased current (10x smaller) or less?
*what are your concepts of using the capacitors and solar cells? how much capacitors and cells would you use, providing the backlight will be switched manually? would you divide the capacitors into uC and LCD suppliers or rather treat them as one? (if you suggest using more than 5 capacitors, please write as soon as possible, i'll try to order more of those to the same shipping)
*my dad keeps a lot of old computer stuff. i remember that being a kindergarden boy i played with multum of different chips, which were used as ram modules back in xt and at computers, 512B each, maybe 1kB, not sure. what is the chance that they are eeproms? btw if they're not, what are those anyway?
*lcd specs tells me to use 8-bit data bus, what is written as the specification of 8 pins. is that meaning that i'll need 8 output pins on my atmega to control lcd?
i can't remind any more questions right now, it's too late already. thanks. |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 23, 2007 - 05:38 AM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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js wrote:
will the solar panel be worn on top of the head by the user?
i'm surprised with your sense of sarcasm.
i guess that if i get myself tanned, despite spending all the time possible indoors and during the winter, i could use the unommitable light rays to produce voltage instead of skin diseases, right? |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 23, 2007 - 04:39 PM |
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Joined: Apr 20, 2007
Posts: 6061
Location: Long Island New York
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THe lcd can operate with either an 8bit bus or 4 bit. You just need to configure the lcd in your code and use the appropriate data lines. for 8bit use all 8, for the 4 bit use the upper 4 bits D4..D7. I can send you the two init files for the lcd, one for 8bit, and one for 4bit, but i only know assembler right now, so that is what you will get
Let me know
Jim
As far as the solar cells go, I suggest a baseball hat, and attach the cells to the brim!! If you are indoors, change all your light bulbs to sunlamps!! HAHA |
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Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first
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Posted: Jun 23, 2007 - 08:28 PM |
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Joined: Aug 20, 2005
Posts: 1109
Location: Pool of Goo
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light reading for those not old enough to remember the Pulsar Watch
or to have worn one.....
http://www.ieee-uffc.org/history/step.pdf
mactom...if you not married to the AVR try the TI MSP430 ...micro designed from the ground up for deep sleep apps...and even Softbaugh..they have a small module with lcd that will probably get the job done..TI even gave away at seminars in the past a module that does just this and more....recently went to a TI MSP430 seminar and still feeling the glow!....for the freaks doesn't the Butterfly fill the OP's need? ..never heard the term "faggy" display in my neek of the woods ....gotta love international forums |
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Posted: Jun 23, 2007 - 10:43 PM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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jim, i'd love to see your init files for lcd, put them here or use my e-mail address. thanks!
bluegoo - after all i've learned about atmel you could imagine my determination to use it. and, i used "faggy" to express how not cool are alphanumeric displays in my opinion btw i considered using nokia 3210/3310/etc display, but these are not cheap enough to compensate their small size. |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 24, 2007 - 02:33 AM |
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Joined: Jun 15, 2007
Posts: 110
Location: Gdańsk, Poland
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so, i'm kind of engaged with avr, and even if it won't work as well as i plan, i'll be satisfied with my attempt. i guess this topic is getting boring to all of you, so i'd like to re-ask the last question i really need answer for before abandoning it:
Quote:
*what are your concepts of using the capacitors and solar cells? how much capacitors and cells would you use, providing the backlight will be switched manually? would you divide the capacitors into uC and LCD suppliers or rather treat them as one?
please refer to datasheets from my previous post, basically solar cell is 0.5V 70mA, capacitor 0.22F and lcd is 5V 4mA. don't forget about avr and rct.
just to remind you all, thank you all for your efforts to help me do my best with that issue. if someone is interested on further development of this project and would like to help in the future, hit me on priv so i could add some of you to buddies. i promise i won't bug you too often, i've got univ pals to annoy too see ya |
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Not entirely familiar with AVR thingies... yet.
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Posted: Jun 24, 2007 - 04:38 AM |
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Joined: Apr 20, 2007
Posts: 6061
Location: Long Island New York
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Jeez, louise, we are doing the kid's homework!!!
I hope the teacher is hot!
I'll post the init files.
Do you want the posts on this forum or to your email? I will provide a very detailed explanation on what they do. |
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Jim
I have decided that I am no longer going to plan anything in advance. In a court of law this is called Pre-Meditated, and does not look good for the defense.....
Timer function not working properly? Check CLKDIV8 Fuse first
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