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junaid_766
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« on: December 08, 2008, 08:23:56 08:23 »

i want to make a digital clock with 8051.
 i searched on internet and found two type of clocks, one which only use 8051 and other  which use RTC(e.g.DS1307) with 8051
i want to ask that which one is more accurate 
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pjve64
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« Reply #1 on: December 08, 2008, 08:43:09 08:43 »

RTC's are always more accurate. The DS1307 you mentioned is an i2c device which is more difficult to program.
The DS12885 for example connects directly to the AD0..7 bus of the 8051, and programming is much easier.
Have a look at the MAXIM website, there are lots of RTC's you can choose from.
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ficho
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« Reply #2 on: December 08, 2008, 10:08:32 10:08 »

http://www.kmitl.ac.th/~kswichit%20/Ajay2/clock.html
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brijbhoomi
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« Reply #3 on: December 08, 2008, 06:47:06 18:47 »


i have tested the mentioned schematic in protues but it is not working in isis
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FriskyFerret
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Put it in, take it out.


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« Reply #4 on: December 08, 2008, 08:42:16 20:42 »

Quote
RTC's are always more accurate.

It all depends on the crystal or clock source used. If you drive the clock input of an 8051 with a surplus +/- 5 ppb ovenized oscillator it will be a lot more accurate than a RTC using a +/- 50 ppm 32,768 Hz watch crystal. Of course, no one drives an 8051 with a $30 high precision oscillator.

In general, 32,768 Hz watch crystals have a much better accuracy and precision than the crystals usually used to form the oscillator circuit of a microcontroller.


Posted on: December 08, 2008, 08:38:54 20:38 - Automerged

brijbhoomi, I took a brief look at the circuit. The crystal oscillator in the RTC may not be completely modeled. Consult the data sheet and try driving one of the inputs with a logic-level square wave input. Did you look at the online help for the model to determine the limitations?
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brijbhoomi
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« Reply #5 on: December 16, 2008, 03:27:41 15:27 »

Actually nothing displayed on LCD screen may be something wrong with 4 bit initialization of LCD routine
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sohel
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« Reply #6 on: December 16, 2008, 05:43:26 17:43 »

i want to make a digital clock with 8051.
 i searched on internet and found two type of clocks, one which only use 8051 and other  which use RTC(e.g.DS1307) with 8051
i want to ask that which one is more accurate 

can u give me some time i will build one for u with 7 segment  calender. i am busy with "c" now. by the way which topology u want, multiplex or shift register and also cpu.
« Last Edit: December 16, 2008, 05:53:50 17:53 by sohel » Logged

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junaid_766
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« Reply #7 on: January 20, 2009, 08:47:49 20:47 »

can u give me some time i will build one for u with 7 segment  calender. i am busy with "c" now. by the way which topology u want, multiplex or shift register and also cpu.

i will b very thankful to u if u made i for me
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sohel
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« Reply #8 on: January 21, 2009, 10:07:32 10:07 »

please answer my request. Huh
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ali_asadzadeh
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« Reply #9 on: January 23, 2009, 08:49:33 20:49 »

you can build an accurate and easy rtc with the help of MT48t86 external ram and rct along internal cap and battery. just hock the rtc chip to the extranal ram bus and read and write time like general external ram.
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junaid_766
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« Reply #10 on: January 24, 2009, 12:51:46 12:51 »

can u give me some time i will build one for u with 7 segment  calender. i am busy with "c" now. by the way which topology u want, multiplex or shift register and also cpu.

 multiplex
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Mega32
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« Reply #11 on: February 14, 2009, 09:33:55 21:33 »

If you use mains power (trafo) for the power to the clock/project , then derive the "RTC clock tick" from the 50/60 Hz line frequency on mains.
That is extremely accurate over a 24/hr period.

Connect a MCU interrupt to : an opto w. a resistor to the low voltage AC , and remember to protect the opto led from the negative period of the AC with a diode.


Mega32
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