Tamura Lumitime Clock Turns 1970s Mains Power Into Glowing Seven Segment Numbers With Gears and Contacts Alone

Japanese company Tamura Electric sold the Lumitime as a stylish desk or wall clock throughout the mid to late 1970s, giving buyers the futuristic look of digital numerals when affordable LED and LCD panels were still dim, tiny, or simply not ready for living rooms. Mark Furneaux opened one of these machines and found no counters, no decoder chips, and no real-time clock module. A synchronous motor tied directly to the 60 hertz household line supplies both power and timing, spinning at a fixed rate so the clock stays accurate as long as the grid stays stable.

Gears reduce the motor speed dramatically, gradually reducing it with a long chain of gears until you reach the three main shafts, which happen to be turning over at the correct pace for displaying minutes and hours. These shafts include patterned metal plates around which springy contacts move back and forth. Each plate has been carved out such that the contacts close and then open in the precise proper order to illuminate the appropriate neon lighting for each digit from 0 to 9. What you end up with is the classic look of a 7-segment display, all connected with good old mechanical switches. Behind the segments, the neon bulbs glow a nice warm orange, and out on the side, there’s a spinning star shape with a simple but effective moiré pattern that shows you how many seconds have passed.

The physical contacts function as a mechanical decoder drum, moving up and down past a set of plates, with one set handling the minute unit, another the tens minute, and a third the hours, with each one cut off so that only the correct bits receive power at the correct moment. To keep things from getting too exciting, resistors are placed between the power source and the lamps to keep the current under control. When a digit changes, and this is all part of the design, the contacts will temporarily make and then lose contact, flashing on and off intermittently. A handful of the versions even went so far as to include additional plates and levers for an alarm function that operated in the same manner.

Time and wear eventually take their toll on vintage clocks, and the most typical issue is dried out grease inside the motor, which, when seized, brings the entire thing to a halt. Then you’ll need to clean the bearings, add some new oil, and, if you’re lucky, reset the little ratchet that ensures the motor always begins in the correct direction. If you don’t get it properly, the motor will just spin backward and the display will begin counting down rather than up. After around forty years, the plastic gears in the reduction train begin to wear out.

The concept is still valid, and it’s beautiful. Here, a little bit of regular household electricity serves as both clockwork and logic. Tamura was even bold enough to name some of them “NO ICS,” emphasizing that there were no integrated circuits to be found, only a neatly designed series of spinning metal plates. So the Lumitime lies there, frozen in a delightful moment in time when people desperately wanted digital readouts but the cheapest method to get them was still this quite charming device.
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