[Solved] RTC 1307 Problem

I havent put a decoupling capacitor... is it necessary??
and GND is not flaky because I have wired it in different breadboards using different wires..

I have just now tried putting the .1uF between Vcc and GND of the breadboard. but still nothing... It works only when I touch it :frowning: Should I specifically place the capacitor at some place? or put any capacitors for crystals??

Wow, everything is right and it still doesn't work..

This simply means there is something else we don't understand...

Ideas anyone??

Do you have pull-up resistors??

Have you tried another Arduino??

Hmmm....

yup. Pull up resistance used are 2.2k and connected as given in http://www.glacialwanderer.com/hobbyrobotics/?p=12
and yes I checked with another arduino still works only when I touch. :frowning:
Cant figure out why its working erratically and its driving me nuts... =(

Upload a picture of how you were touching the crystal on the cap or across the leads?

It has to be crystal I guess... but i changed like 7-8 crystals but still nothing...
IC is fine because I can set and read time from it. Problem is that it is not "running".
Is it some ground problem of the crystal (Because something like that is mentioned in the datasheet of 1307)?? I had shorted the arduino gnd and 3V battery gnds and I am not using any capacitors...
Can someone help me fix this?? because its driving me nuts and I am pretty sure its not a wiring problem...

The Maxim DS1307 data sheet shows a recommended layout for the crystal in Figure 2. This would imply that not only are the electrical characteristics of the crystal important but so is the physical layout. I have successfully used a pc board layout that did not include the recommended ground plane, but a solderless breadboard introduces a lot of extraneous capacitance which may be your problem.

Don

Upload a picture of how you were touching the crystal on the cap or across the leads?

I am touching the metal cap on top not the leads... and touching always doesnt make it run (Abt 80% of the time when I touch it runs) and that too not always at the correct speed..

I have successfully used a pc board layout that did not include the recommended ground plane, but a solderless breadboard introduces a lot of extraneous capacitance which may be your problem.

I too am guessing this to be the reason... any way to correct this??

000:

Upload a picture of how you were touching the crystal on the cap or across the leads?

I am touching the metal cap on top not the leads... and touching always doesnt make it run (Abt 80% of the time when I touch it runs) and that too not always at the correct speed..

I have successfully used a pc board layout that did not include the recommended ground plane, but a solderless breadboard introduces a lot of extraneous capacitance which may be your problem.

I too am guessing this to be the reason... any way to correct this??

  1. Ok, that is a bit strange.
  2. Use a perf board to build your circuit on or a PCB kit?

Like this:
http://www.inmojo.com/store/inmojo-market/item/rtc-module-ds1340z/

or this:

http://www.sparkfun.com/products/10160

This is my version :wink:

http://www.inmojo.com/store/liudr-arduino-and-physics-gadgets/item/rtc-real-time-clock-module-%2B-eeprom-slot/

My guess is that crystal capacitance does not match the DS1307 requirements.
What is the Cl of the crystal? Verify that this matches the DS1307 requirements.
Does the ESR specification of the crystal match the drive capabilities
of the DS1307? Both of these specifications are important for stable operation.

For low frequency crystals I use a guard ring around the crystal. These
devices are high-impedance and are susceptible to noise.
Pictures of my layouts are at Loading...

(* jcl *)

My guess is that crystal capacitance does not match the DS1307 requirements.
What is the Cl of the crystal? Verify that this matches the DS1307 requirements.
Does the ESR specification of the crystal match the drive capabilities
of the DS1307? Both of these specifications are important for stable operation.

How do I find this? because I I got the crystals from a local shop and no way to know the values... I still am thinking its the capacitance problem of the crystals..
By the way what is CI and ESR?

Use a perf board to build your circuit on or a PCB kit?

I tried building on General purpose line PCB board earlier but it didnt work same problem... but I will give it a try once more...
Cant use/order pref board its too expensive for the stuff I am building considering the shipping charges...

Cl is load capacitance. For the DS1307 the required load capacitance is 12.5pF.
This capacitance is internal to the DS1307.

ESR is Effective Series Resistance. For the DS1307 the maximum ESR is 45KOhms.

These values effect startup and stability of the clock. You need the datasheet
for the crystal to get these numbers. If your layout is correct (see the MAXIM
datasheet) the best thing to do is to order a couple of crystals from Mouser
or Digikey.

(* jcl *)

thanx... I guess i will try changig the crystals then... :expressionless:

I've used this from dipmicro.com without any problem:

http://dipmicro.com/store/XC4-32768

The load capacitance is 12.5pF. The effective serial resistance is not given though. And it's out of stock.

Thanx u guys :slight_smile: appreciate the help but ordering such a small thing online is very expensive :frowning: Lemme try a few other local shops here :slight_smile:

000:
Thanx u guys :slight_smile: appreciate the help but ordering such a small thing online is very expensive :frowning: Lemme try a few other local shops here :slight_smile:

You in USA by any chance?

nope. All the way in India. Here price of the crystal in the shop is half of what is given in the link u gave just now :wink:

000:
nope. All the way in India. Here price of the crystal in the shop is half of what is given in the link u gave just now :wink:

I was about to offer you one for free if you're within USA, in a tiny envelop. :wink:

I guess a local shop is better option for you.

I was about to offer you one for free if you're within USA, in a tiny envelop.

Wow thanx for the gesture :slight_smile:

I guess a local shop is better option for you.

Exactly.. Here each crystal cost around Rs. 4. That's like less than 0.1$ :slight_smile: If no crystal here works I guess i got to order from somewhere :frowning:

Just post here or on bars forum asking for good shops (online or local) in India. Lots of friends in India visit this forum and should be able to point you to places for parts.

Will keep u guys posted... Because this is 1 problem I cant get a fix on... Never had I had this kind of a problem... I have finished the entire project just need to get this part running...
So I will update if I get it working :smiley:
Once again Thank you all for your help.. :slight_smile: