Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

How to get a good time accuracy in a clock with DS 1307?

Status
Not open for further replies.

sn_burki

Full Member level 5
Joined
Feb 18, 2003
Messages
260
Helped
16
Reputation
32
Reaction score
11
Trophy points
1,298
Location
Pakistan
Activity points
1,623
I have made a clock with DS1307 + atmel. The major problem is time accuracy, the time on display was very fast (20 second advance in a minute), I tried my best to solve the problem, then when I put 104 capacitor on the supply pin, it bacme controlled but still in one one hour it is 2 second advanced. I want it 99.99% accurate but dont know how to do it? I m using 32 kHz crystal. Please sugget me how to get my goal???? Plz give me some useful points, plz dont tell me to change the crystal as not availble in market.

also tell me how to calebrate the clock to get 100% result (accuracy).

regards.
 

problem in ds1307 clock get stop

you should get a temperature compensed cristal oscillator (tcxo) to achieve the best precision
the easyest is to get a maxim ds32khz chip, which is available as sample...
regards,
 

accuracy 32 khz watch crystal

Standard watch crystals have an accuray of 10 or 20 ppm, equivalent to about 1 or 2 seconds a day. It should be
achievable also with DS1307, if you follow the datasheet suggestions for suitable circuit layout.
 

ds1307 ds32khz

Ok suppose I go for DS 32khz, dont you think that this will increase the size and cost of the circuit, secondly I will have to use 3V extra battery with DS 32 khz too. I am already using a 3V battary with DS 1307.

Is it possible to use one battary with both DS 1307 and DS 32 khz?????? But then the life of the battary will come to bottom???? what would you say???
 

msp430f5438 crystal

Hello!

Just curious: I can understand that you can easily detect and approximately
measure a 20 second drift in a minute, but how do you measure the 2 second
drift for 1 hour? I mean, are you sure that the drift does not come from your
measurement reference?

Beside this, as said previously, if you use a regular crystal, you should get
a fair precision (you want 99.99% = 100ppm, less accurate than most crystals).

Have a look a **broken link removed** page 7 for the layout.

As for the DS32khz, it may be a good idea, but be aware that this chip is
awfully expensive (7.42 USD / 8.53 USD on digikey depending on the type).
The 1307 is about half this price. It depends whether it's for hobby or production.
If it's for production, then the precision you are asking for can be easily reached
by the 1307.

Dora.

sn_burki said:
I have made a clock with DS1307 + atmel. The major problem is time accuracy, the time on display was very fast (20 second advance in a minute), I tried my best to solve the problem, then when I put 104 capacitor on the supply pin, it bacme controlled but still in one one hour it is 2 second advanced. I want it 99.99% accurate but dont know how to do it? I m using 32 kHz crystal. Please sugget me how to get my goal???? Plz give me some useful points, plz dont tell me to change the crystal as not availble in market.

also tell me how to calebrate the clock to get 100% result (accuracy).

regards.
 

how accurate are the ds32khz samples

yes I checked it with my stop watch many times and I detected 2 second delay per hour, it means around one minute delay perday. So every 3rd day I will have to calebrate the time which is awful for me.
I am making this clock for my home and still I want it extremely accurate. I want to apply some techniques on regular crystal to get maximum accuracy, because I have seen many clock made on regular crystal but very accurate.
regards
 

ds32khz ds1307

Hello!

OK, so the price is not really a problem.
I have never used ATMEL processors, and I am guessing here, but you want to
build a simple clock, or your processor will have other tasks?
In any case, you can make a RTC / calender by software on the processor
itself. On some processor, you can just plug a 32 K crystal and use it as
a clock reference, and there is a way to finetune the clock. For example,
I am using a TI chip (MSP430F5438) which allows to calibrate the crystal by
software. The software calibration resolution is +/- 2ppm (if I remember
correctly), so you could have a clock 10 times more accurate than a
regular crystal which would therefore drift less than 1 minute per year.
Probably you have some ways to tune the clock on ATMEL processors too.
Check the docs.

Dora.

sn_burki said:
yes I checked it with my stop watch many times and I detected 2 second delay per hour, it means around one minute delay perday. So every 3rd day I will have to calebrate the time which is awful for me.
I am making this clock for my home and still I want it extremely accurate. I want to apply some techniques on regular crystal to get maximum accuracy, because I have seen many clock made on regular crystal but very accurate.
regards
 

accurate ds1307 crystal

why dont you try 32.768 KHz Crystal
i used it and got impressive results
 

rtc 1307 calibration

I have used 32.768kHz crystal with DS1307 and it was pretty accurate. There is probably something wrong with the crystal you are using.
 

32khz clock accuracy

It is an very old and common problem with Ds1307. It is supposed to use with 32.768 Khz crsytal and when you use that, the actual frequency will be some where else and thus you do not get stability. The only way getting out is to find a accurate crystal (Of course you cannot measure while buying). Or other solution is to get it from old computer mother boards or junk quartz wall clocks which will have pretty accurate crystals. Good luck
 

ds1307 capacitor

saeed_pk said:
why dont you try 32.768 KHz Crystal
i used it and got impressive results
What you mean by impressive result???? how much accuracy you got from it?
 

32.768khz crystal esr measurement

Hello,

Check the datasheet for the DS1307 looking for the capacitive load requirements of the crystal. I use the DS1337 and it calls for a 32.768khz crystal with a 6pf load. I didn't see this when I first started using the DS1337 and the clock was always off. The 6pf crystal made a huge difference.

HTH,

BobK
 

ds1307 time drift

sn_burki said:
I have made a clock with DS1307 + atmel. The major problem is time accuracy, the time on display was very fast (20 second advance in a minute), I tried my best to solve the problem, then when I put 104 capacitor on the supply pin, it bacme controlled but still in one one hour it is 2 second advanced. I want it 99.99% accurate but dont know how to do it? I m using 32 kHz crystal. Please sugget me how to get my goal???? Plz give me some useful points, plz dont tell me to change the crystal as not availble in market.

also tell me how to calebrate the clock to get 100% result (accuracy).

regards.

you get accuracy with standard 32.68Khz crystal but crystal must have these specifications i have built a clock 32.68Khz crystal error is 1min in six month check capcitance of crystal must be 12.5pF

Nominal Frequency fO 32.768 kHz
Series Resistance ESR 45 kΩ
Load Capacitance CL 12.5 pF

Regards
Fragrance
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top