Saturday, August 30, 2014

ProMini clock shield with 7-segment bubble display

This clock was designed as a ProMini shield. It comes as a mostly-SMD kit, based on DS1307 with battery backup and the QDSP-6064 7-segment LED "bubble" display.


   US$18, free shipping to North America

The kit includes the following:
  • PCB
  • QDSP-6064
  • DS1307 SMD
  • 32kHz crystal
  • CR1220 coin battery
  • battery holder
  • 330 ohm resistor 0805 (8x)
  • tactile switch SMD (2x)
  • machined female pins



The assembled clock can be fitted with a LiPo battery shield for ProMini, as shown in this post (source code also provided there).
The current draw (measured at 20mA with an unmodified ProMini) can be minimized by removing the 2 LEDs on the ProMini board, as well as dimming the 7-segment bubble display through software (SevSeg library). One other way of maximizing the LiPo battery life cycle is by waking the clock from sleep mode at the press of the "minutes" button (on D2).

Schematic and board layout are shown below.




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