[Solved] RTC 1307 Problem

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:

PLEASE mark this Subject [SOLVED] when you figure this one out!

I keep thinking about it, even riding the bike tonight.

I'm about 4:1 it's the crystal characteristics.

You have the primary Engineering requirement: persistence.

Will surely do.. I gotta figure this one out anyway.. its an important component of my project.. This forum has helped me so many ways. I will post the answer once I get it figured out :slight_smile:

You have the primary Engineering requirement: persistence.

Hehe Thanx... :slight_smile:

Have you tried salvaging a crystal from an old watch - don't know what their frequency is but they are free

Yippee! got it working... I bought a new crystal from another local shop, its working nicely... Tried around 12 crystals for the entire project though and the 12th one worked :smiley: I think the stuff I bought from the earlier shop was from a bad stock or something ... Phew! What a relief...
Thanx again for everyone's support... :smiley:

Glad you finally got it working. Maybe you can start a list of good shops and bad shops and share with local electronics fans :wink: I don't have any shops near me except the RadioShack. I go there for replacement soldering iron tips. Man, they got me hooked when I bought their cheap iron. The tip is too fragile. Maybe not thick enough tin/chromium + too much power.

That shop is usually good.. :slight_smile: This might have been a really rotten stock :smiley: