Quartz Alarm

[Gaetan Boren]

Nosnooze button. Snoozing just prolongs the agony of getting up, and actually makes you feel less well rested than if you just got up the first time. A snooze button also ensures that you never get up on time.

It seems odd to talk about a system architecture for something as simple as an alarm clock, but it is a non-trivial system, and a fair bit of thought went into its design. This photo shows all the components, before installation in the enclosure:

The timekeeping part of the Wake-O-Matic is a smooth sweeping analog quartz alarm clock movement. I purchased a pair of these from eBay, complete with hands, for a ridiculously low price from a seller in China. I wanted a smooth sweeping movement to avoid the once-per-second tick normally associated with quartz movements.

The alarm output (yellow wire in the photo) turned out to be a simple open-collector to ground (black wire), pulsed at the frequency and repetition rate of the alarm sound made by the movement. I removed the built-in piezo speaker, as I did not want to hear that sound.

R1 and C1 form an integrator whose output (the junction of R1 and C1) goes low over the course of about two milliseconds after the pulses begin. R2 pulls it back high about two seconds after the pulses end. There is of course some ripple in the integrator output.

IC1A, half of an LM358 dual op-amp (a TL072 would work too) is configured as a voltage comparator with hysteresis. R4 and D1 form a 0.7V reference. When the integrator output drops low, the comparator output goes high. Feedback resistor R6 ensures that it remains that way despite the ripple in the integrator output.

Arming switch S1, when in the armed position as shown, allows current to flow through LED1, indicating that the alarm is armed. When the switch is moved to the other position, the positive input to IC1A is pulled to ground, causing the output to go low. Now, C2 discharges through R9 and D3 in a matter of seconds.

The control of the sound from the music board, and a separate white LED, is handled similarly, but with a few differences. Current cannot flow through Q2 until the output of IC1B reaches about 4.4V, which is the sum of the 0.7V base-emitter drop of Q2, and the 3.7V forward voltage of white LED4. Notice that this is about the same level at which LED2 reaches full brightness, so LED4 will slowly start to light after LED2 is fully on.

S2 and R19 are not shown on the board, as they were added after the rest of the project was completed, with R19 soldered directly to S2 on the back panel. Notice that there is also provision for a second timing capacitor, C2opt, which would double the time for each of the phases of the wake-up progression.

One of the requirements was that this clock be immune from both power failures and the need to regularly replace a battery. Therefore, it operates from a rechargeable battery consisting of ten low self-discharge AA nickel metal-hydride (NiMH) cells, delivering about 13V when freshly charged. A DC adapter provides current to keep the battery charged.

Note that unlike many bedside alarm clocks with a backup battery, the Wake-O-Matic is fully functional during a power outage. Not only is the timekeeping completely unaffected, but the alarm will work without external power too. Battery life in the absence of external power is about 20 hours.

In the event of a power failure, the battery voltage will drop over time. When almost depleted, the battery will be at about 11V. When the power returns, the adapter will provide enough current to fully recharge the battery in a few days, starting at about 200mA if the battery is empty.

This is a somewhat unorthodox way to treat a NiMH battery, which is typically charged (with the device turned off) using a peak detection technique, and then allowed to discharge in use to a certain level before recharging. The method used here is more like float charging of a lead-acid battery, but I can get away with it here due to the very low currents involved. The charging current rarely exceeds C/200 except after a long power failure, at which point charging commences at a C/10 overnight charging rate.

With the innards completed, it was time to turn my attention to the packaging and aesthetics. I had originally planned to build an enclosure and dial in the style of a vintage mantle clock, but the need to fit all that hardware inside it changed my mind. Instead, I decided on a simple box made from birch plywood, with rounded edges to show off the layers of wood. I also settled on a simple dial design that suited the hands that came with the movement.

I made the enclosure in two pieces, one consisting of the sides, top, and front, with the bottom and back making up the second piece. All the parts of the front are held together with glue. The bottom and back piece are screwed together, and this is then attached to the remainder of the enclosure with four screws: two on the bottom near the front and two on the back near the top.

Although I had an approximate plan for where to place all the components within the enclosure, and I was confident that everything would fit, much of the final arrangement and assembly was done by moving things around until they did fit.

The Chord EGG circuit board was screwed to the top of the enclosure on small wooden stand-offs that were previously glued in place. The control board, with the orange and white wake-up LEDs on it, was then mounted to a wooden bracket behind the Chord EGG, facing the rear panel.

With all the major components in place in the forward part of the enclosure, the rear part was drilled and cut out appropriately. I made a window for the two wake-up LEDs out of a scrap of plastic fluorescent light lens, and fit this into a rectangular opening cut into the case back.

I drilled holes for the arming switch, amplifier volume control, and the clock and alarm setting shafts. The latter were made by gluing extensions, each consisting of a brass tube and a wooden dowel, to the small knobs supplied with the movements. Black and red heatshrink tubing over the ends of the respective dowels make it easy to see which knob is which.

The two battery packs were mounted on the bottom panel as shown in the photos, initially using Velcro, but later with a fabric strap instead. The arming LED is also mounted on the bottom, where it can be seen only by its reflection off of the surface the clock is standing on. A set of four rubber feet complete the enclosure.

I had to make a few adjustments, such as narrowing the clock and alarm setting extension dowels to provide enough clearance where they pass the control board, but in the end, everything fit together nicely.

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There are enough blogs, sales ads, forum threads and YouTube videos that if interested one can piece together most of the history of the Alarm Quartz and then reasonably deduce the remainder. Now I was going to write out a bunch more but in writing this I found a VERY good descriptive breakdown of this model of Alarm Quartz and rather than re inventing this here it is and the link as well, thanks vintageseiko.nl!

This quartz however is refreshingly simple, it has a scale with center marker to set the alarm in increments of 5 minutes. That however makes the alarm inherently less accurate and thats why the scale is there. Within that zone the hour hand must be to trigger the alarm, also when the time is not set exactly by a five minute signal the alarm may ring sometime between 5 minutes to and from the designated alarm time.

There is a seperate winding mechanism for the alarm crown, even though this is a quartz. Freqent alarms therefore do not impact battery life, but you will be happy to see the battery hatch on the caseback to easily swap it yourself.

I am a newbie here, so I apologize for my newbie question.

I have a "vintage" Seiko dress design 7T32 quartz chrono alarm - watch has not run in 8 years, last used crown screw broke/fell off.

As it is "vintage" and my wedding gift, I have nosalgic reasons to return it somehow to working condition.

Question : Is there an alternate movement, either quartz or automatic, that would fit in the 7T32 case - 30mm ?

At the least, I am interested to know what available movement will work to replace the original 7T32-7C69 (blue on gold)

So how frakenwatch do you want to go? I think ANY 7Txx movement can fit in the case. The part that matters is getting a spacer ring that fits the movement to the case's diameter. But this is just a plastic ring and one you have could probably be easily modified to fit another 7Txx. The two crown and three pusher layout of the 7T32 is less common. If the donor movement has a different arraignment, it will be rather ugly to say the least. But at least the main crown will always be there at 3 o'clock so the time can be set!

The dial itself needs to fit the case and there is usually a bezel ring meant to fit the dial and case. Thickness is an issue too with the bezel ring fitting the case. However, these don't really come in that many different sizes.

But you might be able to repair your watch. If the circuit board has not been damaged then the remaining parts are attainable. The exact correct crown might not be available, but one that fits and looks close will be.

This is a Scratch and Dent Seiko. It had a button issue, has been fixed.

Put on your flight suit and get ready for take-off. This impressive looking new Seiko Flight Chronograph is equipped with an E6B navigational slide rule for pre-flight and in-flight calculations, such as measuring ground speed, distance, fuel burn, wind set, and many other useful computations and conversions. It has full chronograph functions with a 1/5 second resolution, 60 seconds, 60 minutes, repeats up to 12 hours, stopwatch, and a countdown timer. There is also an alarm function that can double as different time zone. The hands and hour markers are treated with Seiko's Lumibrite for telling time in the dark. Includes a tachymeter scale, date window, screw-down crown and chrono pushers, yellow sweep hand, and a stainless steel bracelet with a push-button release deployant clasp. The watch is powered by a battery operated Calibre 7T62 quartz movement.

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