DS1307 Breakout Board

Adafruit’s got a handy breakout board for the DS1307 RTC available. This chip isn’t nearly as accurate as the DS3231 used in the Chronodot but it’s quite a bit cheaper. The breakout makes this easy to breadboard or plug into an Arduino and has everything you need; clock crystal, a backup battery, filtering capacitor, and pull-up resistors. Our favorite part is that Adafruit designs are open source so you can etch the board yourself if you checkout the files from their git repository. This will make a great addition to our prototyping hardware collection.

Incidentally, we were surprised to see the choice of 2.2k resistors for the I2C bus pull-ups. We were under the impression that 4.7k was a standard value here. We’d love to hear your thoughts on this in the comments.

[via Dangerous Prototypes]

28 thoughts on “DS1307 Breakout Board

  1. must be over engineered, they didn’t even bother soldering all the components in, and some of the ones they did solder in are cold

    wonder how much one could save if they offered a “I know how to solder” version

  2. The norm allow between 1k and 4.7k

    Using lower value resistors allow faster speed on the bus (particularly when it has a strong capacitance)
    However using 1k resistors makes problem when you mess and put 2 series in parallel
    I personally always put 2.2k resistors…

  3. Ground pin left unsoldered on that IC?

    -and this is the NICE one they wanted to take pictures of? hmmm…

    “I know how to solder version.” FOR THE WIN!

    Well observed.

  4. You are looking at the solder leakage through to the top surface. The pins will, I’m sure, be soldered just fine on the underside. Surely you guys have seen double sided PCB before!

    There is no standard for the I2C pull-up value. 2k2 will provide a quicker rise-time – this may be important if you are planning on running the bus at 400kHz.

  5. You guys are idiots. There are so many things wrong with your comments I don’t know where to start.

    The “ground wire” (I assume you mean the ground connection of the clock chip) is soldered just fine in that picture, they just used a bit too much solder on the other pins so you can see it from the top side of the board on those pins. You don’t solder an IC from the top of the board! And Osgeld, where are these mystery components that they didn’t solder in? Nope, they’re all there. It doesn’t matter if the battery connections on the side are soldered in anyway, that is just for stability.

    And, if you actually clicked the link you would know the pictures they used in their tutorial are different and don’t even have these non-issues you are referring to.

    AND, you can’t say that this was “over-engineered.” It is what it is, a simple breakout board with the necessary components needed to run the RTC chip. If you want anything less than that it won’t work correctly, and if you want anything more you might as well build it yourself.

    4.7k is a standard value for I2C. Lower values will raise the current consumption of the module by a little bit, but the trade off is higher I2C speeds or better stability at the same speed.

  6. look at the underside of the board, I can count 3 cold solder joints and 2 pins not soldered at all

    so since these parts dont need to be connected as demonstrated then why have them, they must be redundant RIGHT?

  7. This looks like a cool little product. Regarding the solder quality, this board looks fine. I have bought several products from Adafruit in the past and have never received anything but high quality products. I’m sure this board will be the same.

  8. What pictures are you even looking at? The only pictures I can find of the bottom of the board are on the soldering instructions page. There is only one picture (from the top) on the adafruit store page unless I am missing something here. Get off your high horses, the soldering is fine. The soldering job isn’t professional, sure, but the circuit would work fine as-is. There are no cold solder joints in the pictures I have seen.

  9. on the linked page, and yea zoom into them, you can see friggin gap tween the pin and the solder blob on one of the battery connections, and the IC, one pin of the IC isnt even soldered, another pin is barley soldered to the pad, and looks cold at the base, and one pin of the crystal is questionable, it almost looks soldered but you can see the pad under it screaming cold joint

    it may be fine if its going to never experiance shock, but I would take the extra second (especially if I was using it for promotional matertials) to make sure my board doesnt fall apart if I dropped it

  10. What impresses me most about Adafruit projects is the clarity and follow-up information during the step-by-step construction instructions. Very precise photos of the construction in progress, plus explicit details of WHY they’re putting that component in there.

    Buy a kit from Cheney, Rainbow, Velkman, or any of the others, and show me where they tell you that cap Cx is inserted here to filter the voltage blah blah blah. Or that resistors Rx and Ry form a voltage divider for blah blah blah. They have nothing more than a basic insert-this-here and solder it, then insert-that-there and solder it assembly instructions. Sometimes not even that much. No learning, just assembly. Adafruit’s instructions involve actual learning of how the circuit works while you’re actually building it. You can actually learn about electronics while building an Adafruit project.

    I wish these were around when I was first learning electronics.. would have saved me from a lot of misinformation and aggravation.


  11. Osgeld, have you ever soldered before, or have you just read about it? Sparkfun has some decent tutorials for beginning soldering.

    “you can see friggin gap tween the pin and the solder blob on one of the battery connections”
    If you have ever soldered a large hole like a battery connector or a barrel jack you would know the hole doesn’t have to be completely plugged with solder in order for there to be a good connection. It doesn’t matter if you can see a gap, it is still soldered.

    “one pin of the IC isnt even soldered”
    Wrong, all of the IC pins are soldered. You are just looking at a shot from the top of the board where the angle is misleading. You can’t tell if a pin has been soldered unless you see it from the top and bottom at multiple angles.

    “another pin is barley soldered to the pad, and looks cold at the base”
    How do you barley solder? Infuse wheat grain with the rosin or what? Anyway, you don’t need the entire pad covered in solder, but I agree they could have used a little more here.

    “and one pin of the crystal is questionable”
    Not at all, you are again looking at the solder that was pulled through the hole, not at the pad where the connection is made.

    “but you can see the pad under it screaming cold joint”
    You can’t say if something is a cold joint or not without testing the pin/pad/wire for continuity. To say that something is a cold joint just because it doesn’t look quite right is inacurate.

    it may be fine if its going to never experiance shock, but I would take the extra second (especially if I was using it for promotional matertials) to make sure my board doesnt fall apart if I dropped it

  12. Who cares? I mean REALLY, what does it matter what the pictures of the solder job THEY did look like? It comes as a kit, so you can do as good or as bad a job of soldering as you feel like doing. I personally take the extra time to make sure all my connections are pretty damn good, and clean my boards afterwards, but I’m also a little OCD about my projects. I bet the one in the assembly instruction would work JUST as good as one that someone took a lot more time and patience with. As far as assembly instructions go, they’re pretty good. Like people have said, a lot of other kits you wouldn’t get this kind of detail out of. I bought the USBTinyISP from Adafruit before (as a kit), and 3 years later it’s still going strong quite happily. I found the DIRECTIONS to be quite awesome, so quit ‘yer bitchin’ (on both sides of the coin). Just my two cents worth.

  13. Most I2C devices have a current sinking capability of 3mA, some 6mA. This limits your pull-up resistors on the lower end. On the higher end the time constant of your circuit (mainly pull up and bus capacitance) limits pu resistance. The exact value depends on the speed class you are using. You could take series resistance, wire resistance and driver resistance into account, but those are usually not relevant.
    Anyhow, are there none on the Arduino board? This way every device adds it’s own pull ups.
    Do the math, some circuits with short path and only few devices still do with 10k at 3.3V

  14. How odd! I’m using that same chip on a project I’m working on right now! I suppose its a pretty common hobbyist chip.
    I’ve become quite familiar with wiring this chip up over the last few weeks, I’m just wondering what that sole capacitor is there for? I’m presuming its a +5v bypass capacitor, but I never bothered with one on my schematics – works just fine.
    I couldn’t find an eagle part anywhere until I passed by AdaFruits Eagle library, which has it, thanks AdaFruit!
    I wonder why this board doesn’t just have the SMD version of the chip (which IS in the default Eagle libraries).
    I love Maxim ICs, I once bought a philips RTC chip, and that involved finding the right capacitors to improve the timing! I ended up having to put variable capacitors in place for fine control. Furthermore Maxim include a cool backup battery feature, along with spare RAM in the chip and a far more condensed and easy to work with BCD time registers.

  15. …btw thanks to those for the tips above when choosing the right I2C resistors, I thought 4.7k was the norm, and didn’t realise you can reduce it to improve high speed 400khz I2C mode.

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