Technical data
Enclosure design	Switch cabinet
Output contacts	1 C/O contact, 2 C/O contacts
Time function(s)	Cyclic timer, Fleeting on break, Fleeting on make, Impulsgeber, Off-delay, with control signal, On- and Off-delay, On-delay, Pulse extender
Width	22,5 mm
Type	BC 7935N
Variant
Contact equipping	1 changeover contact
Nominal voltage	AC/DC 24 - 240 V
Time range	0,05 s - 300 h
Approvals and Markings	UKCA

The Dold multifunction timer relay BC7935N.81 is an industrial-grade timing control device for regulating time-dependent processes in enclosures. It features an operating voltage of AC/DC 24 to 240 V and a continuously adjustable time range from 0.05 seconds to 300 hours. The device is designed for use in industrial environments in accordance with IEC/EN 61812-1 and offers flexible function selection via a rotary switch. The contact configuration includes a changeover contact rated for switching operations with a nominal operating voltage of AC 250 V. The width is 22.5 mm, enabling compact mounting in standard enclosure modules.

Applications
This timer relay is suitable for applications requiring time-controlled sequences, such as in automation technology, production control, or lighting regulation. The variety of functions allows adaptation to different control requirements, such as delays on switching on or off, pulse generation, or blinking functions. The functions are selectable via a rotary switch and include delay on pickup, delay on drop-out, make-before-break function, break-before-make function, pulse generator, pulse shaper, and a symmetrical blinking function. Time addition via control input B1 for certain functions enables flexible control, for example, during interruptions in the timing sequence.

Functions and Equipment in Detail
Eight different time functions can be selected via the rotary switch, including delay on pickup (AV), delay on drop-out (RV), make-before-break function (EW), and break-before-make function (AW). The AV/RV function allows for delay on pickup and drop-out. The pulse generator and pulse shaper functions are used to generate short switching pulses, with the pulse shaper function (IF) enabling continuous signal conversion. The blinking function (BI) operates symmetrically and starts with a pulse. The timing sequences are continuously adjustable and selectable across ten time ranges, with an adjustment accuracy of ±10 %. The repeatability is ≤2 %, and the re-arming time is ≤50 ms.

Technology Explained Simply
The device operates with an operating voltage of AC/DC 24 to 240 V, with DC 12 V also supported. The voltage influence values are ≤1 %, and the temperature influence is 0.05 % per Kelvin. The output contacts consist of a changeover contact with a contact material of AgNi, designed for high switching capacity. The thermal current rating is 4 A, and the electrical life is typically 150,000 switching operations at AC 15 (1 A, AC 230 V) and 100,000 switching operations at DC 13 (1 A, DC 24 V). The mechanical life is 10⁸ switching operations. The permissible switching frequency is specified as 36,000 switching operations per hour. The short-circuit resistance requires a maximum fuse rating of 4 A gG/gL.

Compatibility and Accessories
The timer relay is designed for use in enclosures and complies with standards IEC/EN 61812-1 as well as EN 61000-4-2 to -6 for electromagnetic compatibility. The enclosure protection rating is IP 40, and the terminals are rated IP 20. The operating temperature ranges from 0 °C to +60 °C, and the storage temperature ranges from -40 °C to +60 °C. The relative humidity is up to 93 % at 40 °C. The operating altitude is limited to ≤2000 m. The insulation test voltage is 2.5 kV for 1 minute (type test). The overvoltage category is III, and the rated impulse voltage is 4 kV at pollution degree 2. Radio interference suppression complies with Class B limits according to EN 55011.

Mounting and Installation
The device is mounted in enclosures and has a width of 22.5 mm, enabling installation on standard 35 mm DIN rails. The terminal connections are designed for connecting the operating voltage (A1/A2), the control input (B1(+)), and the output relay (15, 16, 18). The LED indicators signal power supply (green LED) and contact position (yellow LED), with the yellow LED blinking during the timing sequence and the pulse/pause ratio reflecting the state of the output contact. The functions RV, IF, AW, and AV/RV are activated via control input B1(+), while for functions AV, EW, IE, and BI, the timing sequence can be interrupted by closing B1(+) and resumed upon opening (time addition).

Advantages in Operation
The BC7935N.81 offers high flexibility with its eight selectable functions and a wide time range from 0.05 seconds to 300 hours. The continuous adjustment allows precise adaptation to specific requirements. The LED indicators facilitate diagnosis and monitoring of the operating status. The high mechanical and electrical life, along with robust construction for industrial environments, ensures reliable long-term use. Compatibility with various operating voltages and support for time addition extend the application possibilities in complex control systems.