Review of Banggood digital clock kit #2

At Review of Banggood digital clock kit I wrote some comments on the Banggood large screen digital clock kit.

Clock01

As noted, the supplied instructions are in Chinese, but a bit of searching turns up Chenglish instructions on the net (https://www.dropbox.com/s/fb68yokgwvfx7ye/SKU142210%20instruction.pdf).

The reference to “whole point timekeeping” escaped me, but after more searching, it appears to be the result of conversion of Chinese to English… English speakers might know the facility as “hourly chime” where the clock chimes (emits a sound) at the start of each hour, in this case 3s of beeps.

I did see a writeup at LED Travel Clock in which the author discarded the MCU and its firmware, and made an auxiliary board and wrote his own firmware because of issues he had. My clock is probably of later manufacture did not suffer these problems.

One can look at a kit such as this and quickly think of a number of worthwhile extensions, but as it is, it is simple and inexpensive.

The greatest issue for hobbyists who might see it as a framework for some further development is the use of the Chinese STC15F204EA MCU as free MCS-51 development tools are no match for more modern platforms, platforms that are very popular with hobbyists.

If it were really aimed at hobbyists, it would have used a MCU with more appeal to hobbyists, and right now that probably means an AVR chip. If it were Arduino compatible architecture and the source code published under GPL, I am sure it would have much wider appeal (though Arduino doesn't yet have good support for EEPROM).

As mentioned in my original article, the DS3231 clock chip is more accurate but would require firmware changes as it uses a different protocol (i2c)… but again the standard Arduino DS3207 library provides support.

Reset procedure

On first powerup after construction, the clock should be reset as follows:

Method 1

  1. Press and hold the PLUS and FUNCTION buttons, then turn the power on, then release the function button (lower button).
  2. The clock should now display 7:59 which means reset was successful and five seconds later it should display 8:00.
  3. At the same time, the buzzer will sound loud for one minute, press PLUS button again to cancel the sound.

Method 2

  1. Apply power, then press and hold the PLUS button, and then press the FUNCTION button, and then release both.
  2. The clock should now display 7:59 which means reset was successful and five seconds later it should display 8:00.
  3. At the same time, the buzzer will sound loud for one minute, press PLUS button again to cancel the sound.

Time set procedure

  1. Press the FUNCTION button to set the time (hour digits and colon blink), press the PLUS button to increment the hours;
  2. Press the FUNCTION button again (colon and minute digits blink), press the PLUS button to increment the minutes.
  3. Press the function button again to set the alarm time (hour digits blink and colon is steady), press the PLUS button to increment the alarm hours.
  4. Press the FUNCTION button again (minute digits blink and colon is steady), press the PLUS button to increment the alarm minutes.
  5. Press the FUNCTION button again to display alarm time and allow setting the alarm ON/OFF (hour and minute digits steady and colon is steady), press the PLUS button to alternate alarm ON/OFF as indicated by the right hand point.
  6. Press the function button again to set the hour range for hourly chimes (hour digits blink and colon is steady), press the PLUS button to increment the chime start hour.
  7. Press the FUNCTION button again (minute digits blink and colon is steady), press the PLUS button to increment the chime stop hour.
  8. Press the FUNCTION button again to display chime start:end hours and allow setting the hourly chime ON/OFF (hour and minute digits steady and colon is steady), press the PLUS button to alternate hourly chime ON/OFF as indicated by the right hand point.
  9. Press the FUNCTION button again to complete the setting procedure, the time is displayed with flashing colon, and the right hand point is lit if the alarm has been set.

Alarm

Set the alarm time and ON/OFF as described above.

If the alarm is turned ON, the alarm will sound from the programmed alarm time for one minute and then automatically stop.

The sounding alarm can be silenced by pressing the PLUS button (not NOT press the FUNCTION button). There is no ‘SLEEP' facility.

Convenience

The clock suffers some problems:

  • The seconds in the underlying clock is not zeroed when a new minute is set, which means the next minute will tick over in 0-59s.
  • There is no auto repeat function on the PLUS button, so you have to press it 59 times to set the clock back 1 minute.