Bulb dial jerking transition / running backwards
  • Just finished building a second bulb dial kit - after a long period having built the first a year or two back with zero problems.

    The blue and green sections seem to go fine.  Having finished the red and connected all up I get the following...

    It runs backwards when first powered up
    The 'transition' between the seconds is slow and jerky - like instead of the nice smooth transition it should be the two LEDs alternate say 10 times visibly before the next one stays lit
    I've checked the joints on the chip and the crystal plus those between the boards and they seem ok.  I've also checked the polarity of all the red LEDs and they're fine too

    I'm a bit stumped about what to check next.  I can make it run ok if I change the direction the clock runs in the settings plus turn off the (supposedly) smooth transition but I'd rather it ran properly!  Incidentally it does this both with and without the Chronodot.

    Any help much appreciated.  Thanks, Dan

  • You are describing a number of different issues, so there may be more than one thing wrong here. 

    Your crystal and caps are likely just fine; it shouldn't be running at all otherwise. 

    I've never heard of a problem with the direction being initially set wrong. However, yes, there is an option to switch.  I'm not sure what is causing the bad fade issue-- that is one that I haven't seen before either. One thing to check: if you leave the chronodot off and let it run for an hour, does it seem to be keeping time reasonably well?

    A second question: Was the clock more-or-less behaving correctly after assembling just the blue and green boards?

  • Thanks for the reply Windell.  I think actually the green ring working was my imagination as I put it straight in to alignment mode and didn't pay that much attention.

    I've desoldered/removed the red ring and it still shows the same problem:

    It starts in reverse and the transition isn't smooth - the two LEDs flicking between them at full brightness during this and I've noticed the green (and red when it was still attached) have whatever LED is lit flicker at the same rate likewise.

    What has changed is though by virtue of how I was holding the base PCB my thumb brushed across the external/USB-TT connector.  The clock reset back to 12 and whilst still running backwards, the transition was now smooth.  I can recreate this over and over - it starts/boots backwards with the problem, touch the connector so it resets and it then works fine (but backwards).  Once it's running correctly I can then alter it to run the right way.  It seems to keep the time well in all conditions too.

    I'm stumped.  Maybe the ATmega didn't take the code properly - just one character stored incorrectly causing the random problems?!  I might have to give up on this one I think.
  • The fact that you have intermittent issues suggests that it's not an issue with the code. This sounds like a hardware problem. It could be an issue with a bad switch, a bad power supply, a cracked capacitor, or with a partial/intermittent short or open circuit in a few different places. 

    When you bump the USB-TTL connector, you are touching the reset pin (through a capacitor). This can potentially reboot the clock, and that's not necessarily a problem. The fact that it tends to run backwards-- at all --does suggest that the settings aren't being saved or read correctly, but that could again be due to one of the factors that I mentioned above.  

    The two things that I would check first would be to see if there is a possible soldering issue, and then to see (as I asked about earlier) whether it is keeping time correctly. You might try those.  Alternately, you might consider sending it back to us to take a look-- I'd be curious because of the strange effects that you are seeing. If you would like to do that, please contact us through our contact form to get an RMA.