A Quartz Watch That Uses Your Daily Activities as a Source of Energy: Trum "L Collection -Break Line-" / Casual Impressions

The model we reviewed this time was the swing generator-equipped model from Troom's new 2020 "L collection -Break Line-." Troom is a watch brand launched by Seiko Epson (hereafter Epson) in 2017 with the concept of "mastering analog watches with cutting-edge technology." This model uses a "swing generator," a quartz movement that generates electricity through the movement of the arm, making it possible to generate electricity even in places where light is difficult to reach.

Trum "L collection -Break Line-" swing generator model

　In addition to Troom, Epson currently produces Orient Star, Orient, and Smart Canvas watches. Troom's brand concept is to "master analog watches with cutting-edge technology." One answer to this is the inclusion of a quartz movement that generates electricity through the rotation of the rotor, making this watch a notable mechanical feature.

　After wearing it for about a week, I grew fond of the fact that the energy source that powers the watch is my own daily activities, and the more I considered how it works, the more I felt that Epson's deep and wide-ranging technology was packed into it. In addition to the appearance and feel, Epson provided me with detailed information about its operating principles, so I'd like to share those details with you.

Epson's answer to the challenge of perfecting analog watches

　Epson has been developing and manufacturing watches since its founding in 1942. Using the knowledge gained from this, the company has expanded into a wide range of fields, including printers, projectors, industrial robots, semiconductors, and sensing systems, and has become a company with advanced technological capabilities in each of these areas.

　Trum is a company that aims to perfect analog watches by combining Epson's various processing technologies, including miniaturization of sensors and devices and wearable technology. So, what are the essential elements in perfecting an analog watch?

　Of the various watches available, if I were to choose one to wear for a long time, I would choose one with an analog display and automatic winding. The advantage of an analog display is that the time is visible as a diagram, making it intuitively easy to understand. I choose an automatic winding watch because I feel that one of the joys of wearing a watch for long periods of time is the fact that the mainspring winds up through the wearer's daily activities. On the other hand, quartz watches are not affected by changes in accuracy due to differences in position or the amount of winding of the mainspring, making them particularly advantageous in situations where strict timekeeping is required.

　So what about this watch? The caliber ME25 it is equipped with generates electricity using a rotor that rotates according to the wearer's movements, and it is an analog quartz movement that keeps accurate time using the energy obtained. It makes sense that Epson came up with this mechanism, which they call a swing generator, as a way to perfect the analog watch that Trum aims to achieve.

　The principle of generating electricity through rotational motion is simple, similar to that used in bicycle dynamo lights, but Epson's advanced technical capabilities were essential to turn it into a practical wristwatch.

A movement that utilizes Epson's unique technology

　This swing generator reduces energy loss by connecting the rotor and generator without a switching mechanism, increasing the efficiency of converting kinetic energy into electrical energy. It also generates electricity through the bidirectional movement of the rotor, which is then stored in a secondary battery. While power generation and storage are often treated as a set in writing, while power generation is unavoidably caused by induced electromotive force, storage requires adjusting the direction of the current and preventing overcharging. Control is required here, and Epson's technological expertise is essential.

　If the bidirectional movement of the rotor is used to store electricity, the voltage generated by the clockwise and counterclockwise movement of the rotor will be reversed if power is generated as is, and so applying voltage to a secondary battery will not charge it. From a mechanical watch approach, it would be natural to install a switching mechanism like Seiko's Magic Lever to unidirectionally adjust the movement of the generator. On the other hand, from an electronic circuit approach, a simple solution would be to rectify the positive and negative voltages with a diode bridge before applying them to the secondary battery. However, this means that the forward voltage drop of the diode cannot be utilized, significantly reducing charging efficiency. Because the energy obtained from the rotor movement is not large, this results in a significant loss.

　Epson, on the other hand, did not adopt either of these approaches with the Caliber ME25. Instead, they used a charging IC that arranged a diode and a transistor in parallel to form a bridge and packaged it all together. And it was manufactured by Epson. When this IC detects that a voltage exceeding the forward voltage of the built-in diode has been generated, a transistor that bypasses both ends of the diode turns on, allowing current to flow for charging. Because the voltage drop across a transistor is orders of magnitude smaller than that of a diode, it is possible to utilize the generated voltage without waste. What's more, this IC even has an overcharge prevention function.

　The accumulation of these technologies has made it possible to achieve highly efficient, stable operation safely, and a power reserve of approximately 180 days, which is difficult to achieve with a mechanical watch.Because it is a quartz movement, as long as the charge level is sufficient for stable operation, there is no change in operating accuracy, and there is no curse of positional differences.

An exterior that takes into consideration both texture and usability

　By utilizing kinetic energy, sufficient energy can be stored even when the watch is often used in dark places, making it less susceptible to external environmental influences and offering advantages over photovoltaic power generation. Furthermore, since there is no need for light to pass through the dial, there is greater freedom in the selection and expression of dial materials. Taking advantage of this advantage, this watch features an elaborately finished metal dial.

　The white and red dials both have vibrant colors, which contribute to enhancing the contrast with the hands. The two-tiered dial has a smooth inner surface, while the red model's inner surface reflects light, creating a contrast with the matte outer surface. The borders between the tiers are finely polished, bringing out the sheen of the metal. I felt that the way the dials are varied without interfering with legibility was well-executed.

　The case is made of titanium and is coated with a protective coating. The edges are clear and the matte coating is uniform, creating a beautiful appearance. Titanium has low thermal conductivity, so it doesn't feel cold to the skin, which is great for cold weather. The case is fitted with a ceramic bezel, which has a lustrous finish and vibrant color, making it a beautiful watch. The 24, 6, 12, and 18 o'clock markers are also illuminated with luminous light.

　The white dial "TR-ME2010" comes with a green GAIFU® nylon strap made with high-tensile nylon thread, the same as aircraft tire cord, while the red dial "TR-ME2006," a retailer-exclusive model, comes with a red Chromexcel leather strap. Both models feature piping on the sides and a flat interior that makes them supple and comfortable against the skin. They also have an excellent texture.

　The display features a 24-hour hand, hour, minute, and second hands, and a date display at the 3 o'clock position. If the 24-hour hand is set to a second time zone, such as the time of an overseas base where frequent remote meetings are held, you can check the time at the other party at a glance.

　The crown is screw-in type. Pull it out one notch to adjust the hour hand in one-hour increments. Pull it out two notches to adjust the hour, minute, and 24-hour hands. It's impressive that the hour hand can be adjusted independently at this price. However, there is no quick date change; you have to move the hour hand forward or backward 24 hours to change the date. In actual use, the power reserve is very long at approximately 180 days, and if you keep it fully charged, it's unlikely to stop working. Changing the date should only need to be done once every few months, so it shouldn't be a problem.

Consideration of charge amount when worn for one day

　While automatic mechanical watches and the caliber ME25 share the same energy source, the movement of the rotor, there is a major difference in the way the energy is converted. In an automatic watch, the mainspring is wound simply by rotating the rotor (the amount of winding of the mainspring is determined by the cumulative rotation angle). On the other hand, the caliber ME25 will not charge unless the rotor's rotation speed exceeds a certain level (the generated voltage is proportional to the angular velocity of the generator rotor).

　This means that it would be difficult to charge the watch if you mainly work at a desk, where the rotor moves slowly. Perhaps to address this issue, a gear train is provided to increase the speed so that the generator can rotate at a sufficient rotation speed even with a slow rotor movement. Let's check the published guidelines for obtaining a charge sufficient for 24 hours of operation.

・3 minutes of running
・Walk 5000 steps (approximately 40 minutes)
・8 hours of desk work

　While running takes only about three minutes, walking takes 40 minutes, and desk work takes eight hours. This is where I feel like the characteristics of charging become apparent. However, mathematically, a total of 2500 steps (about 20 minutes) of walking and four hours of desk work will complete a 24-hour charge, so it is likely that most people will get a sufficient charge. The charging efficiency can be evaluated as very high. Originally, I would have liked to start using it from a stopped state and investigate the balance of charge and discharge, but this was not possible as the test unit was fully charged when I received it.

　Even if you're worried about the daily charge, you can check the power reserve by pressing the switch at 2 o'clock, which is reassuring. I personally found it fun to check the charge level after walking for a while, as it gave me a real sense that my activities were accumulating as energy. These points lead to an attachment to the watch.

　For those who mainly do desk work, the best way to use this watch stably is to fully charge it once and then walk around when you go out occasionally, so that you can make a profit over a long period of time. If you use it this way, the long power reserve will act as a big buffer, making it unlikely that the charge will run out.

There are some things I would like to request regarding the fit.

　So far we've focused on the technical aspects of what makes up a watch, but what about the packaging?

　Even setting aside my preference for compact watches, the case is quite large. Its diameter is 45.4mm, measuring 52.9mm from lug tip to lug tip. My wrist is a little large for a Japanese person, measuring 17.5cm in circumference, and the size of this watch just barely fits on my wrist. When worn, the supple strap, which conforms to the wrist, and the lightweight titanium case give the impression of balance. When my friend with smaller wrists wore it, the watch felt more like it was pinching his arm between the head and buckle than wrapping around his wrist.

　Visibility in bright places is good, with a high contrast between the hands and the dial. The hands generally seem thin compared to the size of the dial, so I would prefer them to be a little thicker. Also, in dark places, the luminous tip is small and easily blends in with the luminous part of the index, so visibility is not good.

　I understand that the size of a watch that feels right to you is largely influenced by personal preference, but given that Trum was designed to take advantage of Epson's strength in miniaturizing various devices, and that this watch runs on energy generated by the user and is intended to be worn for a long time, I felt that a more compact design would be more in line with the concept.

　Furthermore, since the device has a mechanism that allows stable operation even in low-light environments, the benefits would be more pronounced if it could be made more visible in dark places.

Amazingly high level of perfection in each component

　The "L collection -Break Line-" swing generator model featured in this article shows that Trum values ​​the advantages of quartz, such as high precision, and the fact that it is not affected by environmental factors by utilizing kinetic energy. Furthermore, the power generation that occurs with the movement of the arm also contributes to deepening the connection with the wearer. Furthermore, as the ingenious dial expression is one of the joys of analog watches, we felt that this was a compelling direction for perfecting analog watches.

　Epson's advanced technological capabilities shine through in each component of the watch that realizes this direction. The movement in particular is well thought out and utilizes Epson's unique technology.

　If you're interested in the concept, mechanism, and looks of this watch, we encourage you to pick one up and check it out for yourself. A closer look will surely convey its appeal. And don't forget to check how it fits. If the size suits your taste, this watch will be a great companion, keeping time and powering your daily activities.