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32 Hz Clock Source From A Cheap Watch
Obtaining a 32 Hz clock source for Huff & Puff Stabilizers by using the LCD Refresh on a cheap watch.
This page is only indirectly about Huff and Puff Stabilizers. Its real intent is showing how to obtain a crystal stabilized 32 Hz clock source from a cheap watch, without destroying the timekeeping action of that watch. This lets you install that watch in the rig front panel where it serves as a station clock and still use it for the H&P stabilizer as well.
The first watch unit shown here is a simple one which does not contain alarm capability or the ability to operate in military or 24-hour mode.
Radio power will be used to trickle charge a NiCad battery which powers the watch inside a radio. Diode isolation will be used to keep the NiCad from discharging backwards through radio circuitry when the radio power is off.
[ insert picture or original clock/watch device ]
This is the watch-fob type watch that was purchased for $1.00 USD at a local 'Dollar Store'. It has been pulled out of the case and the front bezel spray-painted with gray paint to match the transceiver front panel. When opening your watch case, be careful to catch and save the two very tiny plastic plungers that are used to set time and date.
Here is a close-up picture of the watch movement from the front. You can see the 32768 Hz tuning-fork type crystal located horizontally above the LCD display. Also visible is the positive potential battery contact plate (that thin metal part with wings on it) and the two small metal contact studs that make up the Set Switches for adjusting time and date. The small hole centered directly under the LCD seems to have no purpose unless it is to help position the LCD for initial PCB installation during manufacture.
This is the back side of the watch unit. That large metal plate contacts the positive battery terminal and holds the battery in place. It folds around the case and becomes the common contact for Set Switches mentioned relative to an earlier picture. Next, we will remove the two screws holding this plate in position, and remove the battery.
In this picture the back plate and battery have been removed. Battery polarity was marked on the PCB and on the plastic case to make it easier to connect an external power source to the watch unit.
This is a little closer picture of the watch with it's battery removed. The two soldered contacts at the top are connections to the 32768 Hz tuning fork crystal. The dark component bridging a pair of PCB contacts on the right side is the fixed value tuning capacitor.
Very fine insulated wires will be soldered to the two battery contacts on this PCB. These will be used to provide external power from both a NiCad battery and a resistive voltage divider from the radio power supply. This way the radio will re-charge the NiCad cells when the radio is being operated.
Across the upper 1/3rd of the PCB you can see the elastomer connections (conductive rubber strips) that connect LCD segments to the watch circuit on the PCB. A very small insulated wire will be soldered to one of these PCB-to-LCD copper strips for the purpose of tapping off a 32 Hz signal for our Huff & Puff Stabilizer.
Basic circuit of the Watch Clocked H&P Stabilizer.
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