Flip-disc display

A bi-stable display element, also known as flip- dot, is an electromagnetically - mechanical device, which shows one of a toggle or rotary device, depending on the control of two different colored sides of the small plate. Bistable display elements are usually assembled into matrix displays and come in display panels, inter alia, in vehicles, such as buses, rail vehicles and metro or trams and at train stations and airports.

Design and operation

Usually located at the visible end of a bi-stable display element is a square plate ( display plate ) which is mounted diagonally rotatable. The two sides of this plate are colored differently, with one side mostly black, the other side usually in a strong contrasting color like white, yellow, orange or light green. At the core of the display plate is a permanent magnet. Behind the display plates is an electromagnet which exerts a force on the plastic sheet depending on the polarity and it turns so.

To prevent the pivoting back of the display plate in accordance with the deenergization of the solenoid, there is a latch, which consists of a non-round the axis of rotation in the simplest case. Partly also the remanence of the iron core of the coil the magnetic field is used to maintain the long term. The display platelets thus has two stable states, hence the term bistable.

The advantage of this type of display is that energy is only needed to turn around the platelets. At constant display no energy must be expended. So are bistable displays in such application areas of advantage in which the display changes only rarely.

Newer bistable display elements have additionally a built-in LED that illuminates the display plate, so that this type of display is easy to read even at night. Earlier, however, sometimes have light elements on the sides of flipdot matrix (example image local train ).

Other types

Instead of square indicator plates arrived earlier also predominantly cylinder front which are mounted for rotation about its own axis.

In control room alarm relays are used which indicate their switching state or save a state change; see relay.

Another design, but the same principle, have indicators that are used in seven- segment displays, such as those found in gas stations.

Bistable LCD

Bistable LCDs are LCD displays that retain their display without additional batteries or backup capacitors. Energy is required in this type of display for changing the orientation of the liquid crystals. Once in position, they retain their orientation until they are re-oriented in the next adaptation.

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