European railway clock
What is involved in getting an (old) station clock working again?
The familiar blue NS station clocks also work by means of pulse control. Some have the brand name “Bosch” on the dial. However, the movements in the older clocks are almost always made by TN, recognizable by the logo with the diamond shape:
SOURCE: Wikipedia.de
This page describes what is needed to get such a (double-sided) clock working again.
Connections
NS station clocks are typically connected to the 230V mains voltage. This powers the lighting and the seconds mechanism. A double-sided clock has two movements, one for each side. Each movement, in turn, has two connections:
- 230V (AC) for the second hand and
- a 24V (DC) pulse control for the minutes.
The lighting is often a single ring fluorescent tube that illuminates both dials. E.g. Philips TL-E 40W/830 1CT/12 or TL-E 40W/840 1CT/12. For sale here, among other places..
In addition to the 230V, the movement needs pulse control to make the hands step at the right moment, every minute. These pulses are usually 24 volts (12 and 48 volts are less common). Without a connection to a central master clock, as at a station, a pulse generator can generate these signals and keep the clock running on time.
A double-sided clock has its pulse inputs wired in parallel.
The image shows the TN movement with the two different connections. The minute hand can be adjusted manually using the small wheel (the left eye).
On the left side of the movement, a coil is also clearly visible: the hallmark of an electric slave clock.
12 or 24 volt pulses
On some versions of this movement, the pulse voltage can be adjusted. This is done using the black block at the pulse connection. Loosen the screw and slide the block to the left or right for the desired setting.
At the ends of the black block there are small triangles above the voltages (12 and 24 in the photo). The movement is set to the value that the triangle on the transparent plastic points to. In the photo this is 24 volts.
Sweeping second hand
The minute pulse is literally a synchronization moment; if it fails to occur, the second hand will remain stopped at 12:00.
Unfortunately, it is well known that the seconds mechanism in particular is subject to wear . We always advise checking that it works properly beforehand!
Wear on second hand
Wear of the second hand control is recognizable in two stages:
- A sound can be heard that can be described as rattling or grinding. It starts quietly but gets louder over time (sometimes over years). At some point it becomes so loud that we call it a racket. Especially indoors, that is unpleasant.
- The second hand no longer always goes all the way round, or even comes to a complete standstill.
This is caused by the synchronous motor (230V AC) that drives the second hand. The motor shaft rotates inside the plastic. Due to a lack of proper bearings, the plastic wears away slightly, thereby creating play on the shaft. As the play becomes excessive, the gears subsequently no longer mesh properly, resulting in the rattling sound.
Testing the operation
It is quite easy to test whether the seconds mechanism of a clock is still working properly.
To do this, connect the 230V to the clock or the separate movements. (Please be careful, as 230V can be painful!).
As long as the second hand is not at 12:00, it will complete its full rotation with the 230V connected. This will give a good indication of how quiet the movement still is. Give the hand a nudge by hand when it is waiting at 12:00 again.
By the way, a clock will also work perfectly well without the 230V connected for the seconds mechanism. With only the pulse control, the clock simply shows the time with the minute and hour hands.
Built-in
A pulse generator can be used in two ways:
- Internal; built into the clock, where the pulse generator is connected to the available 230V.
- External; the pulse generator remains outside the clock and the pulse control is fed into the clock via wiring.
Internal mounting is often a nice solution because the clock can then be connected with just a single cable (230V). However, this raises the question: how do we set the clock to the correct time?
The correct time display
- It is set to time ‘by hand’. For this, it has a button that generates a minute pulse each time you press it.
- Daylight saving time changes are not made automatically.
The 12/24V pulse driver can be used for these movements
Tips and tricks
Indoors or outdoors?
Will the clock be used indoors or will it be hung outside?
This is important because an outdoor clock is subjected to much more stress (including moisture and temperature), and this must be taken into account in advance regarding the materials used.
Our pulse generators are only suitable for indoor use. Anyone wishing to use it outdoors should place it in a waterproof housing.
For the DIYer: use a plastic food container with holes for the cables. Or use, for example, an IP65 junction box, available at any DIY store.
External pulse button
Optionally, a button/switch can be installed on the outside of the clock for a built-in (internal) pulse generator. The advantage of this is that the clock does not need to be opened to set it to the correct time.
This option is currently only available on request. We then supply the pulse driver with a button and a cable of the desired length. Ask for the price!
On the next generation of pulse generators, this will be a feature that is easier to connect and can be ordered directly as an option!
External light switch
In addition to the external pulse button, you can also add an extra switch on the outside of the clock to turn the lighting on and off.
Wireless
If you are a bit handy, the lighting can also be connected via KlikAanKlikUit, Philips Hue or another smart home solution.