Improving the Accuracy of the Solder-Time Desk Clock

The "Solder:Time Desk Clock LTE" from SpikenzieLabs (www.spikenzielabs.com/Catalog/watches-clocks/solder-time-desk-clock-lte) is a fun kit to assemble and results in functional clock that doubles as a conversation piece.

The only down-side to the clock is that it is based on the DS1317 Real-Time Clock (RTC) IC which can drift by 50 parts per million (ppm). This can be up to 4 seconds per day. Since this can add up to a couple minutes per month, the time needs to be reset every month or two.

The DS3231 is a highly accurate version of the Real-Time Clock. It has a built-in, temperature compensated oscillator that is accurate to +/- 2 ppm. This keeps accurate time within 5 seconds per month.  The DS3231 is functionally compatible with the DS1317, but is only available in a larger 16-pin footprint. This project provides an adapter PCB that allows the DS3231 to plug in to the DS1317 socket.



As can be seen in the photo, this increases the height of the RTC. This is not a problem as the LTE version of the kit has no case. It should not be a problem in the standard (case) version either since the new height is still below the top of the TO-220 voltage regulator, but that has not be verified.

Parts List:

QTY
Description
MFG Part Number
Digikey Part Number
~ Price (U.S. $)
1
DS3231 RTC DS3231S# DS3231S#-ND   $13
1
SMD Header HDR100IMP40F-G-V-SM HDR100IMP40F-G-V-SM-ND    $1
1
Adapter PCB
 See below
N/A
 $1.35

Note that only 8 of the 40 SMD Header pins are used. Another way to get the needed header pins is to buy the following: PA0001-ND Chip Quik Inc. Proto-Advantage SOIC-8 TO DIP-8 SMT ADAPTER
This has the advantage that it comes with a small alignment PCB to make soldering the SMD Headers in place easier.

The adapter PCB is available from OSH Park:  https://oshpark.com/shared_projects
The project name is "ds3231_adapter_v2" and is available for $1.35

Assembly is straight-forward.  The DS3231 IC is mounted on the top side with orientation as shown on the PCB silk screen.  The SMD header is mounted on the bottom in two rows of four pins each.  Although not complicated, the surface mount soldering involved means this is not a beginner-level project.

I created this adapter in 2023 and is operating flawlessly.  Since that time, an 8-pin SOIC of the DS3231 is available, but it is NOT pin compabible with the DS1317.

If you have any comments or questions, I can be contacted at:
Kerry Imming – kcimming@pobox.com