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Reviews (8)
Aug 26, 2016
Fun kit. Instructions in Chinese. 24 Hour Display only.
1 of 1 found this helpful This goes together quickly. The PCB labels things well enough that written instructions are not needed. I works IF YOU INSTALL ALL THREE JUMPERS. One is under the center two digit display. The backup battery does save the time for future restarts OK. There are no instructions (at least not in English) on how to set the clock time. Only one push button to program it with. You can program the minutes and hours time but not the seconds. The only way to get the seconds right is to remove the battery and apply power exactly at zero seconds on the hour. Minutes are programmed by holding the button down for two seconds until the minutes are flashing. Repeatedly press the button until the correct minutes are shown. Then hold the push button down for another two seconds until the hours digits flash. Repeatedly press the push button until the correct hour shows. Then hold down the button for more than two seconds, the digits will stop flashing and you're done. Don't count on this clock to keep good time. As received it would loose 64 seconds per day. Putting a 22 pf capacitor across the crystal reduced that to 17 seconds/day. Beyond 22 pf the oscillator's frequency didn't increase anymore and in fact decreased. It appears that one would need to get a bunch of 12 MHz crystals and select the one that will reduce this error further. Some kind of quick change socket would be needed. Repeated soldering/desoldering would likely lift the PCB pads.. I'm at a loss what to use thist for. Not accurate enough. Grandson didn't want it because of 24 hour format. Some trimmer for the crystal would be highly desirable. Experimenting, it was determined that the clock frequency needs to be 12.003 MHz due to some latency somewhere in the programming. My clock was running slow. It was necessary to change the two 30 pf caps near the crystal to 10 pf. This brought the error down to 3 seconds/day. If your clock is running fast a 10 - 20 pf cap across the crystal will slow it down. P.S. You can't measure the frequency with a frequency counter. The input capacitance pulls the clock frequency. Even using a 10x scope probe to the counter pulls it significantly. To get near 1 second/month the clock error must be no more than 5 Hz.
Aug 01, 2018
works but high price
Price way to high for a product which used to be in the $20 range.
Apr 21, 2016
oldie but goodie
Bought to replace old one with failing display. It is a used unit but 100% operational and clean.
Can't beat the $20 price. Of course the screen display technology is old but useable.