Watch networks of the past
The old clock is now, though rarely, but you can still catch the train stations, bus stops and sometimes just on the streets of cities. Some of them are already more than half a century old, and they appeared at a time when most of the control circuits were created using a relay. But nevertheless, even in such old devices the possibility of remote configuration and synchronization was realized!
After reading the article, you will learn how the watch networks of the past were arranged and how you can revive the ancient technology with the help of Arduino.
Once I was approached with a very interesting request - to restore the working capacity of the vintage clock of the 1960s. They did not look very presentable and suspiciously resembled a door from the cabinet. At first glance it seemed that it was an artisanal craft. But in the lower right corner proudly flaunted the inscription "Arrow", from which it follows that the model is factory.
')
What immediately attracted attention was the mechanism, or rather its complete absence. On the reverse side of the clock is the drive arrows, which is a strange engine with a gearbox.
The engine, though similar to a stepper, has only two outputs from a single winding. The gearbox is made of brass and its gear ratio is 1:12, and thus it turns out that the engine rotates the minute hand, and the clock simply follows it.
Experimentally, it turned out that if you apply 24 volts DC to the motor winding, the minute hand takes one step. When changing the polarity of power, the arrow takes another step. Obviously, the control part of this entire electromechanical system is missing. A small glance at the story will help you understand where it went.
In the 60s, when electronics were just getting on their feet, various institutions, organizations and factories used a hybrid electromechanical clock to display the time. First of all, the need for them arose in the field of passenger transport - for more efficient dispatching of train, tram and bus routes.
A piece of photos S.I. Akhmerova from the photo album 1962, Novosibirsk. The clock hanging on the pole is part of the trolleybus communication system — drivers check their time against them.
It was required that several hours have the same readings, despite the fact that they could physically be located quite far from each other, for example, within the limits of a transport route or in a building. This task was solved as follows:
Illustration from the book by N.V. Sidorov, "Operation of electric hourly installations", 1962.
The picture shows almost the entire range of devices that could enter the watch network, and as it becomes clear, I got exactly the secondary clock. The network design is quite simple: the center is the so-called electro-primary clocks, which give alternating bipolar impulses once a minute. Group relays together with batteries serve as repeaters repeaters, allowing to carry devices over long distances. Since the current consumed by the winding of the relay is less than that of the clock mechanisms, the losses associated with the increase in resistance in long wires will be less. Batteries are also used as local power sources for secondary clocks.
It is clear that if there are secondary clocks, then you can try to find the primary ones. Unfortunately, the survey of the building where the alleged watch network was located did not give much results and the most tasty morsel of the system was not found. But in the literature of that time, the principle of their action is very well described:
This watch is a very interesting link in the evolution of technology. They still use well-developed methods of fairly accurate measurement of time intervals using oscillations of a pendulum, which is the heart of any mechanical watch. But here this heart drives electricity. The pendulum approximately once every few oscillations closes the power supply circuit of the electromagnet, which gives it a new impetus for the buildup. The yoke, with which the pendulum is connected, sways from side to side with the help of a small and large dog rotates the ratchet wheel. The meaning of this construction is that in whatever direction the pendulum would move, the wheel will rotate only in one direction. It has 80 teeth, and with a period of oscillation of the pendulum equal to 1.5 seconds, makes a half turn in one minute. Next comes the ebony lever mounted on the same wheel - it in turn closes the necessary contact groups:
A customized key allows you to manually apply pulses. Swinging his handle, you can change the time at once on all watches on the network!
Resistance in the circuit also plays an important role - the designers of the past did not spare the energy spent on heating the air, because thanks to the resistance sparking on contact groups decreases, which leads to an increase in reliability and durability of the device (at that time they paid more attention to these factors).
Now, having understood the principle of operation of the watch network, it was possible to safely make a simple device that emulates the primary clock, all the more so with the help of modern technologies it is easier than ever. But this story would be incomplete without one more thing, which, in my opinion, turned out to be even more interesting than electric primary hours:
This nondescript box turned out to be another secondary clock from the same clockwork network, but not as simple as the first. Inside is a very amusing mechanism:
On the door behind the dial there is an electromagnet that conducts the minute hand in motion. Hour, as in the past case, is connected with it by a gearbox. In addition to all this, there is a large gear, numbered from 1 to 24, and with a large number of holes for the pins (something like presser feet) that can be screwed in there. Inside the case there are fuses, resistors and an old relay. Together, this forms a very intricate pattern.
Appealing to the literature helped to understand that this is nothing more than a software clock. Using pins screwed into a large gear, you can set the on / off time of any electrical load at a certain time.
The mechanism has its own customized key, which allows you to adjust the clock manually and is connected to the anchor. Depending on the polarity of the voltage on the electromagnet, the anchor is attracted to one or the other side. The yoke converts translational motion into rotational. And the gears of the mechanism are designed so that the large program wheel makes one revolution per day, and the five-minute and weekly wheels - in accordance with their names. There are holes for the pins in the program and weekly wheels, which close the necessary contacts when turning the wheel. The accuracy of this "alarm clock" is five minutes. On the clock, I got the pins were set at the time: 8:00, 12:00, 13:00 and 17:00, and on all days except Sunday. So, once this watch informed the factory workers about the beginning of the shift, lunch and the end of the working day.
The operation of the mechanism involves the closure of contacts for a full minute. Of course, such a long signal would annoy everyone, because the components in the watch case provide a signal termination after a certain time. In accordance with the technologies of that time, a thermogroup is used for this case - two adjoining contacts, one of which is bimetallic (in the photo to the left of the relay). When current flows through the contact, it heats up and opens due to bending of the contact. This is another reason why accuracy is measured in minutes - the thermogroup must have time to cool down before the next operation. The opening time can be roughly adjusted by the adjustment screw.
So, the scheme emulating the primary clock will look like this:
It uses a 24V DC switching power supply, two relays and the Arduino controller itself. The 5V relay serves as a galvanic isolation, and closes the 24-volt relay, which in turn re-switches the power to the opposite polarity. This mode of operation is different from the usual, since the primary clock gave impulses, and here the voltage to the clock drive is constantly applied. This solution allows you to simplify the scheme at the expense of work.
Sketch for adruino is as simple as flashing LED:
However, there are some subtleties associated with the fact that the minute at the Arduino is not at all the real-time minute (this is due to the quartz resonator, the cycles, and the inertness of the relay, and this is another story altogether); : detecting the time interval and calculating the error. After that, to amend the value of the trimmer value. In this way I managed to adjust the clock with an accuracy of about a minute per day. Of course, you can do better, but this was not necessary.
Scheme assembly: a five-volt relay went through a lot in my life, so I had to fill it with silicone glue.
Good or bad, but now the watch network was not needed, therefore, the considered watches will continue their work in the form of ordinary self-sufficient devices that everyone is used to. They will, like half a century ago, count down labor moments and serve as a reminder of a bygone era, where many interesting things lurked in seemingly simple things.
After reading the article, you will learn how the watch networks of the past were arranged and how you can revive the ancient technology with the help of Arduino.
Once I was approached with a very interesting request - to restore the working capacity of the vintage clock of the 1960s. They did not look very presentable and suspiciously resembled a door from the cabinet. At first glance it seemed that it was an artisanal craft. But in the lower right corner proudly flaunted the inscription "Arrow", from which it follows that the model is factory.
')
What immediately attracted attention was the mechanism, or rather its complete absence. On the reverse side of the clock is the drive arrows, which is a strange engine with a gearbox.
The engine, though similar to a stepper, has only two outputs from a single winding. The gearbox is made of brass and its gear ratio is 1:12, and thus it turns out that the engine rotates the minute hand, and the clock simply follows it.
Experimentally, it turned out that if you apply 24 volts DC to the motor winding, the minute hand takes one step. When changing the polarity of power, the arrow takes another step. Obviously, the control part of this entire electromechanical system is missing. A small glance at the story will help you understand where it went.
In the 60s, when electronics were just getting on their feet, various institutions, organizations and factories used a hybrid electromechanical clock to display the time. First of all, the need for them arose in the field of passenger transport - for more efficient dispatching of train, tram and bus routes.
A piece of photos S.I. Akhmerova from the photo album 1962, Novosibirsk. The clock hanging on the pole is part of the trolleybus communication system — drivers check their time against them.
It was required that several hours have the same readings, despite the fact that they could physically be located quite far from each other, for example, within the limits of a transport route or in a building. This task was solved as follows:
Illustration from the book by N.V. Sidorov, "Operation of electric hourly installations", 1962.
The picture shows almost the entire range of devices that could enter the watch network, and as it becomes clear, I got exactly the secondary clock. The network design is quite simple: the center is the so-called electro-primary clocks, which give alternating bipolar impulses once a minute. Group relays together with batteries serve as repeaters repeaters, allowing to carry devices over long distances. Since the current consumed by the winding of the relay is less than that of the clock mechanisms, the losses associated with the increase in resistance in long wires will be less. Batteries are also used as local power sources for secondary clocks.
It is clear that if there are secondary clocks, then you can try to find the primary ones. Unfortunately, the survey of the building where the alleged watch network was located did not give much results and the most tasty morsel of the system was not found. But in the literature of that time, the principle of their action is very well described:
This watch is a very interesting link in the evolution of technology. They still use well-developed methods of fairly accurate measurement of time intervals using oscillations of a pendulum, which is the heart of any mechanical watch. But here this heart drives electricity. The pendulum approximately once every few oscillations closes the power supply circuit of the electromagnet, which gives it a new impetus for the buildup. The yoke, with which the pendulum is connected, sways from side to side with the help of a small and large dog rotates the ratchet wheel. The meaning of this construction is that in whatever direction the pendulum would move, the wheel will rotate only in one direction. It has 80 teeth, and with a period of oscillation of the pendulum equal to 1.5 seconds, makes a half turn in one minute. Next comes the ebony lever mounted on the same wheel - it in turn closes the necessary contact groups:
A customized key allows you to manually apply pulses. Swinging his handle, you can change the time at once on all watches on the network!
Resistance in the circuit also plays an important role - the designers of the past did not spare the energy spent on heating the air, because thanks to the resistance sparking on contact groups decreases, which leads to an increase in reliability and durability of the device (at that time they paid more attention to these factors).
Now, having understood the principle of operation of the watch network, it was possible to safely make a simple device that emulates the primary clock, all the more so with the help of modern technologies it is easier than ever. But this story would be incomplete without one more thing, which, in my opinion, turned out to be even more interesting than electric primary hours:
This nondescript box turned out to be another secondary clock from the same clockwork network, but not as simple as the first. Inside is a very amusing mechanism:
On the door behind the dial there is an electromagnet that conducts the minute hand in motion. Hour, as in the past case, is connected with it by a gearbox. In addition to all this, there is a large gear, numbered from 1 to 24, and with a large number of holes for the pins (something like presser feet) that can be screwed in there. Inside the case there are fuses, resistors and an old relay. Together, this forms a very intricate pattern.
Appealing to the literature helped to understand that this is nothing more than a software clock. Using pins screwed into a large gear, you can set the on / off time of any electrical load at a certain time.
The mechanism has its own customized key, which allows you to adjust the clock manually and is connected to the anchor. Depending on the polarity of the voltage on the electromagnet, the anchor is attracted to one or the other side. The yoke converts translational motion into rotational. And the gears of the mechanism are designed so that the large program wheel makes one revolution per day, and the five-minute and weekly wheels - in accordance with their names. There are holes for the pins in the program and weekly wheels, which close the necessary contacts when turning the wheel. The accuracy of this "alarm clock" is five minutes. On the clock, I got the pins were set at the time: 8:00, 12:00, 13:00 and 17:00, and on all days except Sunday. So, once this watch informed the factory workers about the beginning of the shift, lunch and the end of the working day.
The operation of the mechanism involves the closure of contacts for a full minute. Of course, such a long signal would annoy everyone, because the components in the watch case provide a signal termination after a certain time. In accordance with the technologies of that time, a thermogroup is used for this case - two adjoining contacts, one of which is bimetallic (in the photo to the left of the relay). When current flows through the contact, it heats up and opens due to bending of the contact. This is another reason why accuracy is measured in minutes - the thermogroup must have time to cool down before the next operation. The opening time can be roughly adjusted by the adjustment screw.
So, the scheme emulating the primary clock will look like this:
It uses a 24V DC switching power supply, two relays and the Arduino controller itself. The 5V relay serves as a galvanic isolation, and closes the 24-volt relay, which in turn re-switches the power to the opposite polarity. This mode of operation is different from the usual, since the primary clock gave impulses, and here the voltage to the clock drive is constantly applied. This solution allows you to simplify the scheme at the expense of work.
Sketch for adruino is as simple as flashing LED:
View code
void setup () {
pinMode (2, OUTPUT); // program pin two as output
}
void loop () {
digitalWrite (2, HIGH); // enable relay
minute (); // wait fifty seconds
delay (9535); // trimming value, about 9.5 seconds
digitalWrite (2, LOW); // turn off the relay
minute (); // wait fifty seconds
delay (9535); // trimming value, about 9.5 seconds
}
void minute () {
for (int i = 1; i <= 5; i ++) {
delay (10,000);
}
}
pinMode (2, OUTPUT); // program pin two as output
}
void loop () {
digitalWrite (2, HIGH); // enable relay
minute (); // wait fifty seconds
delay (9535); // trimming value, about 9.5 seconds
digitalWrite (2, LOW); // turn off the relay
minute (); // wait fifty seconds
delay (9535); // trimming value, about 9.5 seconds
}
void minute () {
for (int i = 1; i <= 5; i ++) {
delay (10,000);
}
}
However, there are some subtleties associated with the fact that the minute at the Arduino is not at all the real-time minute (this is due to the quartz resonator, the cycles, and the inertness of the relay, and this is another story altogether); : detecting the time interval and calculating the error. After that, to amend the value of the trimmer value. In this way I managed to adjust the clock with an accuracy of about a minute per day. Of course, you can do better, but this was not necessary.
Scheme assembly: a five-volt relay went through a lot in my life, so I had to fill it with silicone glue.
Good or bad, but now the watch network was not needed, therefore, the considered watches will continue their work in the form of ordinary self-sufficient devices that everyone is used to. They will, like half a century ago, count down labor moments and serve as a reminder of a bygone era, where many interesting things lurked in seemingly simple things.
Source: https://habr.com/ru/post/259575/
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