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"Pocket Watch"
1976 Designed
and built by Jerry This clock was built to utilize the battery in Polaroid SX70 camera film packs (3.5 inches by 4.2 inches by very thin). The clock components were spread out in a single layer and occupy about the same surface area as a battery. Two batteries were connecting in series to deliver 12 volts. The assembled clock easily fits in a shirt pocket. Because the 7 segment, 6 digit LED readout (HH MM SS) requires a lot of current, it illuminates only when asked. The NS MM5314 CMOS integrated circuit contains the circuits for dividing 60 Hz down to hours, minutes, and seconds, the time setting circuits, and the driver circuits for the 7 segments. Visible are the 6 driver transistors, one for each digit. Also visible is the quartz crystal (983040 Hz), variable capacitor, and resistor that form the local reference frequency. The RCA CD4060AE (divide by 2 to the 14th power) integrated circuit divides the reference frequency down to 60 Hz. However, the joke was on me. The SX70 batteries were designed for high current for a few seconds, not very low current for many hours. Even with the LED readout off, the clock ran for only 24 hours. And then the batteries were depleted! |
| "Pocket Watch" shown with two 6 volt Poloroid battery packs. |
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