How do I protect external roller shutters from crushing when they stop?

Question 1

When the bottom bar strikes an obstacle, the motor keeps running. Rigid hangers hold the curtain, so slats bunch in the cassette or tear at joints, creating up to 6 A stall current and 40 N·m torque that fractures aluminium profiles [Elektroda, Ryszard49, post #18246967]

Answer

When the bottom bar strikes an obstacle, the motor keeps running. Rigid hangers hold the curtain, so slats bunch in the cassette or tear at joints, creating up to 6 A stall current and 40 N·m torque that fractures aluminium profiles [Elektroda, Ryszard49, post #18246967]

Question 2

A microcontroller samples motor current every 10 ms. If current rises 40–60 % above the calibrated run value for >200 ms, it cuts power and reverses 3 cm [Mobilus Manual, 2023]. The method requires no external sensors—just the motor’s own supply wires, as CYRUS2 observed [Elektroda, CYRUS2, post #18243730]

Answer

A microcontroller samples motor current every 10 ms. If current rises 40–60 % above the calibrated run value for >200 ms, it cuts power and reverses 3 cm [Mobilus Manual, 2023]. The method requires no external sensors—just the motor’s own supply wires, as CYRUS2 observed [Elektroda, CYRUS2, post #18243730]

Question 3

Yes. An AC current transformer, a comparator and a relay can open the up/down line when current exceeds a set threshold, typically 3 A. Calibration must distinguish normal start-up inrush from a stall. Expect ±15 % tolerance; false trips may occur with frozen seals [Elektroda, miroslaw wielki, #18243840].

Answer

Yes. An AC current transformer, a comparator and a relay can open the up/down line when current exceeds a set threshold, typically 3 A. Calibration must distinguish normal start-up inrush from a stall. Expect ±15 % tolerance; false trips may occur with frozen seals [Elektroda, miroslaw wielki, #18243840].

Question 4

Running current averages 1 A for a 120 W motor. A stall pushes it to 4–5 A—roughly 4× increase [Somfy Datasheet, 2022]. Downward jams show only a 1.2× rise because gravity helps; rely on time-over-current rather than peak alone [Elektroda, miroslaw wielki, #18243840].

Answer

Running current averages 1 A for a 120 W motor. A stall pushes it to 4–5 A—roughly 4× increase [Somfy Datasheet, 2022]. Downward jams show only a 1.2× rise because gravity helps; rely on time-over-current rather than peak alone [Elektroda, miroslaw wielki, #18243840].

Question 5

Not directly. CT-01 outputs pulses while the curtain moves, but if a jam occurs near the end position the string stops moving although the motor still turns; pulses vanish too late. Designers intended it for burglary detection, not motor cut-off [Elektroda, Ryszard49, post #18244911]

Answer

Not directly. CT-01 outputs pulses while the curtain moves, but if a jam occurs near the end position the string stops moving although the motor still turns; pulses vanish too late. Designers intended it for burglary detection, not motor cut-off [Elektroda, Ryszard49, post #18244911]

Question 6

Answer

Attach a low-mass encoder wheel to the tube or use a string pulser (CT-01 style).
Feed pulses to a monostable set at 150 ms.
If no pulse arrives during commanded motion, the monostable drops, a relay opens the motor circuit. This three-part circuit costs ≈€15 and reacts within 0.2 s [Elektroda, Rysiek2, post #18244951]

Question 7

Possible but space is tight. The curtain can fill 80–90 % of cassette depth when over-wound, leaving <8 mm gap for optics. Detection may occur only after 4–5 extra slats have folded, already damaging paint [Elektroda, Rysiek2, post #18245196]

Answer

Possible but space is tight. The curtain can fill 80–90 % of cassette depth when over-wound, leaving <8 mm gap for optics. Detection may occur only after 4–5 extra slats have folded, already damaging paint [Elektroda, Rysiek2, post #18245196]

Question 8

They stop reverse rolling but transfer stall torque to the slats. In tests, rigid hangers sheared four profiles during a garage-door collision at 0.8 m/s [Elektroda, Ryszard49, post #18245360] Flexible ‘play’ hangers reduce breakage by 22 % yet allow limited rewinding [Somfy Tech Note, 2021].

Answer

They stop reverse rolling but transfer stall torque to the slats. In tests, rigid hangers sheared four profiles during a garage-door collision at 0.8 m/s [Elektroda, Ryszard49, post #18245360] Flexible ‘play’ hangers reduce breakage by 22 % yet allow limited rewinding [Somfy Tech Note, 2021].

Question 9

Mount a 5 A Burgess V-3 microswitch at the cassette top. When jammed downward, the coil of slats presses the lever, opening power. Wire it in series with the down line through a miniature relay. Cost ≈€5 and fits into the spare 12 mm next to the factory limit switch [Elektroda, miroslaw wielki, #18246950].

Answer

Mount a 5 A Burgess V-3 microswitch at the cassette top. When jammed downward, the coil of slats presses the lever, opening power. Wire it in series with the down line through a miniature relay. Cost ≈€5 and fits into the spare 12 mm next to the factory limit switch [Elektroda, miroslaw wielki, #18246950].

Question 10

Conceptually yes: magnets on every second slat create pulses; loss of pulses means stoppage. Real guides leave no 3 mm clearance for magnets, and adhesive can fail at –10 °C. Edge-case: ice can hold the shutter while magnets still pass the reed, giving a false safe signal [Elektroda, miroslaw wielki, #18245616].

Answer

Conceptually yes: magnets on every second slat create pulses; loss of pulses means stoppage. Real guides leave no 3 mm clearance for magnets, and adhesive can fail at –10 °C. Edge-case: ice can hold the shutter while magnets still pass the reed, giving a false safe signal [Elektroda, miroslaw wielki, #18245616].

Question 11

When jammed from below, vented slats keep moving until the vent holes close, delaying stall detection by up to 1 s and adding 30 % extra torque—enough to warp the bottom bar [Elektroda, Ryszard49, post #18246998]

Answer

When jammed from below, vented slats keep moving until the vent holes close, delaying stall detection by up to 1 s and adding 30 % extra torque—enough to warp the bottom bar [Elektroda, Ryszard49, post #18246998]

Question 12

Order 9 mm stainless retaining pins sold as “zakładki lameli” from shutter suppliers; packs of 100 cost about €6 [Aluprof Catalogue, 2023].

Answer

Order 9 mm stainless retaining pins sold as “zakładki lameli” from shutter suppliers; packs of 100 cost about €6 [Aluprof Catalogue, 2023].

Question 13

Mobilus M35DB costs €140–€170 for 20 Nm. Factories claim a 96 % jam-stop success rate and 30,000-cycle life [Mobilus PriceList, 2023]. Replacing two damaged curtains can exceed €300, so payback often occurs after one avoided incident.

Answer

Mobilus M35DB costs €140–€170 for 20 Nm. Factories claim a 96 % jam-stop success rate and 30,000-cycle life [Mobilus PriceList, 2023]. Replacing two damaged curtains can exceed €300, so payback often occurs after one avoided incident.

How do I protect external roller shutters from crushing when they stop?

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