The bell determines the dynamic characteristicsThe days when sextons manually rang church bells with ropes are history. Today, all that is needed is the press of a button – the swing motion is now completely motorized and automated. But what seems like a simple procedure is in fact much more complex.
There are strict rules to protect bells, outlined in DIN standards for example, stipulating the maximum swing angle of a ringing bell relative to its perpendicular rest position. “The initial motion should be very smooth, so as to avoid rebound impacts, for example,” explains Markus Willburger, a designer with Philipp Hörz GmbH. Founded in 1862, this company with a staff of 50 based in Biberach, in southern Germany, manufactures almost everything for the belfry from tower clocks to bell cages – everything, that is, apart from the bells themselves. “A bell can weigh several metric tons, and every one of them has its own dynamic characteristics,” Willburger continues. “The maximum swing angle for each must be specified along with the corresponding number of stop limits, and finally the bell has to be smoothly slowed down to a stop. In between those points, it has to be kept precisely positioned so as to produce optimum sound.”
So-called bell-ringing machines drive bells automatically. Philipp Hörz GmbH installs such systems in churches throughout Germany, from the deep south to the far north, as well as in neighboring countries. In the past, the company used specially developed control boards. “But at some point their components became outdated, and their reliability declined,” Willburger explains. “Another factor is that replacement parts either no longer fit, or can’t be sourced at all.” Therefore the company decided not to continue investing in the development of new hardware, and it began looking for alternatives. What ended up being chosen was SIMATIC S7-1200.
“We are not programmers, but at Siemens we found expert partners to handle our software development,” Willburger says. He and his colleague Erich Müller defined the requirements and Siemens engineers implemented them. “It all worked excellently,” the designer enthuses.
Siemens sales executive Thomas Dehm explains: “To precisely recreate and calibrate the initial ring, we fixed an additional encoder on the motor shaft of a circuit board-controlled church bell. We could then use the S7-1200 controller to trace the sequences in TIA Portal.”
Once this know-how protected standard software module controlling the bells has been programmed in the controller and the control cabinet has been installed in the church, the bells have to be ‘tuned’ – that is, their parameters need to be set. With SIMATIC HMI KTP700 Basic Panel, the technician is able to easily set parameters for the initial ring, maximum swing angle and slowdown rate of each individual bell based on its weight, size and sound using simple plug-and-play control.
“Most churches have four bells, for which one S7-1214C controller is sufficient,” Dehm explains. “If there are more, a signal module is installed for additional inputs and outputs. Key factors in this are the fast counters of the CPU, with one rotary pulse encoder for each bell, as well as Sirius reversing contactors to operate the motors.” The encoders transmit the bell oscillation amplitudes to the controller, enabling it to measure the momentary angle. The controller switches the contactors depending on the angle, rotating the relevant motor to the left or right in a matter of milliseconds until the ever-wider-swinging bell reaches its maximum swing angle. As Willburger stresses: “The pulses must be precisely timed; that’s the major challenge.”
SIMATIC S7-1200 also sends a signal to the tower clock as a striking mechanism blocking function, preventing a hammer from striking the bell while it is ringing, as would otherwise happen every hour. Conversely, when thus programmed the clock can also send a digital signal to automatically make the bells ring.
A successful model of cooperationThe flexibility of SIMATIC S7-1200 enables custom solutions to be implemented, or special customer requirements to be met. For example, noise-insulating shutters in the church towers can be automatically opened or closed; or moving figures can be controlled; and more powerful motors for large bells can be connected. The controller can also be integrated into existing systems.
The SIMATIC S7-1200 Steuerungen are all running outstandingly well. Now we are really getting started with the marketing push.Markus Willburger, Designer Philipp Hörz GmbH
“As opposed to the previous control board, the S7-1200 controller detects the direction in which the bell is currently swinging,” says Willburger. “This means the motor will never swing the bell in the wrong direction.” Additional parameters make bell control much more variable and finer than before. The maximum swing angle can be more precisely maintained as a result.
A further plus-point of Simatic S7-1200 is the facility for remote control and maintenance of bell-ringing systems via the Sinema Remote Connect VPN platform. “If a Scalance router is installed in the church, the sexton does not have to be present; the bells can be rung by way of a smartphone or tablet,” Willburger explains. “And multiple churches can be controlled from a central point.”
Throughout the region Philipp Hörz GmbH has already supplied and installed a number of bell-ringing machines featuring the new controller. “They are all running outstandingly well,” Willburger reports with satisfaction. Looking to the future, and with new plans for further cooperation with Siemens, he says: “Now we are really getting started with the marketing push.”
Note on industrial security:
Appropriate security measures (e.g., network segmentation) must be taken to ensure secure operation of the system. Find out more about industrial security.