AT89c52 with RTS DS1307

[Rajagopalk]

My name is Rajagopal 70 years old, I knows basic electronics but no experience in current programming.

I have purchased a few 7 segment 4 digit pcbs with AT89C52, RTC DS1307, 74LS595 (4nos), and ULN 2003 (4nos) 12hrs format and program preloaded assembled clock PCBs.

I did 12” , and 15” height and 4’ long LED display with driver circuits, this clocks are working since 2- 3 years, with Accuracy and good condition.

I made a another display for another clock board, but my soldering mistake it was not work , found the fault and modified it and found working 3 digit only, the 4th digit of 10hrs digit not work, I mean, run from 0 : 0 0 to 9 : 5 9 after 9 : 5 9 it is not going to 1 0 : 0 0 instead 1 0 : 0 0 it is going again 0 : 0 0 (three digits zeros) and run up to 9 : 5 9 then again going 0 : 0 0 and run up to 3 : 5 9, after 3 : 5 9 it is going to 0 : 0 0 it mean, it is working as 10hrs + 10hrs + 4hrs for 24hrs, instead 12hrs format (12hrs + 12hrs = 24hrs).

Removed DS1307 ic and replaced a new DS1307, but working as above. Not only one, few new DS1307 ics replaced but same as above.

Now I doubt in AT89c52, what happened changed the program code in the AT89C52 it self, may it will possible?.

Circuit and program are designed with AT89C52 for 12 hrs format earlier it was worked I assembled two clocks still it is working, some unknown reason RTC DS1307 is changed to 10hrs + 10hrs + 4hrs for 24 hrs format why?, and how to get it back to 12hrs format, may any one help me, please.


Schemetic :

 

[embRTS]

Sir,
For changing back to the "12 hour" Format you have to access the "HOUR register" of DS1307
as the following things are mentioned in the Datasheet also

"Bit 6 of the hours register is defined as the 12-hour or
24-hour mode-select bit. ,
When high, the 12-hour mode is selected. ,
In the 12-hour mode, bit 5 is the AM/PM bit with logic high being PM."

So access the register's bit and try !!!

 

[andre_luis]

At first sight, I would say that such failure could not have relation with the hardware scope, once it makes no sense due to systematic behavior - almost predictable - as you described.

Are you sure this entire design ( hardware + firmware ) already worked before, or it is still under developing ?



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[Rajagopalk]

At first sight, I would say that such failure could not have relation with the hardware scope, once it makes no sense due to systematic behavior - almost predictable - as you described.

[Are you sure this entire design ( hardware + firmware ) already worked before, or it is still under developing ?]



+++

Thanks,
Yes, earlier it was worked correct 12hrs format that is after (0)9 : 5 9 it ran to 1 0 : 0 0 but some unknown reason now it is going after (0)9 : 5 9 to (0) 0 : 0 0, I mean the forth digit of 10hrs digit (showed inside the brackets) that is not light up, only three digits are working.

 

[Rajagopalk]

Dear all,

Now I found the problem, now it is working as usual, I did in reset pin number 9 of AT89C52 just touch a wire with 5 volt positive 3 - 4 times now it is work as 12hrs format, after (0) 9 : 5 9 it is going to 1 0 : 0 0 and as usual, I mean the 4th digit of 10hrs digit is working, I think this happen is reset problem (why, I don’t know), This circuit is already having reset circuit that is one 10mfd capacitor connected with 5 volt positive and one 10 k resistance is connected with ground.
And I am having another one problem in it, that, when touch with a metal piece (forceps or naked screwdriver) in any (positive or negative) pins of any ICs in this circuit, suddenly changes going in the display digits I mean, some segments are, on or / and off (Random) its self, after fraction of seconds it is back to normal, working OK, why this happen, this circuit have connected a 100 N disc capacitor in each 74LS595 ICs vcc to with ground.

Thanks.