Display information vehicle systems  – direction indicators

The following types of inner and outer information display components – direction indicators – are produced with either LED or LCD panels (tableaus) for public transportation vehicles. Our company produces the following types :

• Outer direction indicators – outer LED panels (front, side and rear)
• Inner LED panes (single- or double-line)
• inner LCD panels for passengers (single- or double-faced)
• combined side LED/LCD panels (LED-outer/LCD-inner)
• Course number indicators

A basic description of the features of  vehicle direction indicators (LED or LCD panels) can be found below.

Displaying  Czech characters on LED and LCD panels

If we want the information LED or LCD panels to display Czech diacritics for both upper case letters and lower case letters without deforming the letters, the panels must be  capable of displaying the so called “descenders” (characters such as j, p, y, etc.) and accented ascenders (characters such as Š, Ř, etc.). The description of the way the characters are displayed  comes from Vít Hněvkovský.

To achieve a quality multiple line text display, the letters on individual lines must not touch and the lines should be separated by at least one line of display points (at least one line of diodes on LED panels and 1/10 of letter height on LCD displays).

Outer information LED panels (tableaus)

The outer information LED panels – vehicle direction indicators  are produced in three versions – front, side, rear -  in various sizes and with outstanding side readability made possible by using flat LED diodes. They are based on high-illumination LED diodes  (max. is up to 3 000 mCd/point with flat diodes or up to 10 000 mCd/point with lens diodes) and on a low-input power technology with extended lifespan with pre-convertors which manage the voltage of the LED diodes – for example the consumption of a side tableau can be mere 20 W! The panels naturally contain precise illumination regulation according to the surrounding light, as well as rotating and sliding texts. The long lifespan is made possible by the work regime of the diodes which is deep below the maximum voltage. A more detailed description of this technical solution can be found in the article: Low-input power LED panels with extended lifespan.

Outer vehicle  LED panels are produced in three basic series:

• VLP 19 with LED diode distance of 10 mm - low-cost solution
• VLP 24 with LED diode distance of 8 mm - full Czech text solution
• VLP 30 with LED diode distance of 6,2 mm - quality display of text and symbols

We were the first in the Czech Republic to integrate the technology of displaying texts with the help of dynamic fonts in our outer vehicle LED panels. The LED panel itself chooses the biggest possible font to ensure readability of the text from the longest possible distance. It is possible to send texts – stop names according to the definition from the CIS (Central information system) – directly into the panel and the panel itself  adjusts the text and optimizes the size of the text as well as the number of lines (see the attached demonstration video of slowed-down calculations – in reality this happens in a few microseconds). Thus it is not necessary to prepare special databases and to maintain these databases. Defining the ways they are displayed is enough!

This is made possible by an efficient control unit in the outer LED panel. The control unit can perform up to 1 billion operations in a second and it has 8 MBytes Flash and 2 MBytes RAM and all this for competitive prices. The changing  frequency of the display of the LED panel is about 300 Hz.

The following video shows an example of practical functioning of this technology when used in front VLP 24 vehicle LED panels including dynamic changing of the size of the font according to the length of the displayed text. The panel itself calculates and optimizes what is displayed on the graphic area of the panel i.e. determines the robustness of the font as well as its type and size. We are still optimizing the shape of the fonts and it can be prepared in accordance with the wishes of the customer.

Inner LED panels (displays)

Inner LED panels (single-line or double-line) supply the passengers with topical information regarding the number of the line (3 characters), the present and the next stop, the terminus (a minimum of 20 character in a distinctive font), the names of important stops on the route and transfer connections, the time and the tariff zone and others (for example a planned ¨lockout). Their general features are the same as those of the above mentioned LED panels

New display possibilities are brought mainly by double-line panels, they include for example information regarding the state of the follow-up lines and their delays, present happenings on the stop, etc..

Inner LCD panels for passengers

Inner LCD panels for passengers (single- or double-faced) usually use  wide-angle low-input power LCD displays with an integrated PC module including accelerated video (for example VCS 185E – 24V/0,9A, i.e. 24W in narrow profile). The panels can be controlled via all types of bus – Ethernet, RS 485 or IBIS (we prefer Ethernet). Data updates can be performed locally using a USB FLASH or remotely using WiFi transfers or our dispatching SW SPRINTER.

Combined side LED/LCD panels (LED-outer/LCD-inner)

Combined side LED/LCD panels (LED-outer/LCD-inner) are used as outer side tableaus on vehicles with a control unit similar to the control unit of the side tableau of the chosen series VLP – 19, 24, 30 lines of LED diodes and the  VCS 379A side inner LED panel is used for the inner display.

Course number indicators

To ensure easy displaying of the course number, we are preparing a new series of simple LED indicators which will display the course number. A detailed description of technical features will be provided shortly.

Basic features of direction indicators (LED/LCD panels) in public transportation vehicles

The basic features of direction indicators (mainly outer LED panels) in public transportation vehicles are:

• The color of the text on vehicle direction indicators – yellow, green, orange (the human eye is very sensitive to all these colors). Blue is usually not recommended because of its low visibility at night. On the other hand, red can be confusing for other drivers, therefore it should not be used for outer direction indicators (the terminus). 520 – 600 nm (i.e. green and yellow) or the range of 560 – 580 nm (yellowish green) are most often used as appropriate colors for outer direction indicators.
• Realization of individual light points can be performed with the help of :
  • flat LED diodes with the radiation angle of 120°  provided that the minimal luminosity of  one LED diode of the outer direction indicator is 50 lm/W and the voltage of one LED diode is 20 mA (minimizes electrical energy consumption). Flat LED diodes ensure good readability from all angles which is the reason why these diodes are suitable for side indicators (tableaus) or inner indicators.
  • lens diodes -  A lens always restricts the viewing angle and puts the ray in the direction defined by the lens. That is why they are primarily suitable for front and rear direction indicators (unsuitable for side panels). By directing the ray they allow for lower power consumption with preserved luminosity.
  •  DOT-LED or just DOT realization, i.e. revolving targets with a LED diode (we do not produce these). Their advantage is saving of energy in full sunlight, however, they are slow in reacting to revolving texts or other moving graphic patterns.
• The panels must allow fluent movement of revolving texts or graphic patterns which is the reason why we do not recommend using DOT-LED direction panels (useful mainly for displaying moving text on stops – dispatching messages, news regarding lockouts, etc.).
• Direction indicators must be equipped with  automatic luminosity regulation according to the surrounding light, or their luminosity can be controlled by commands from the on-board computer or the control display panel. Regulation of luminosity can be used between stops when it is possible to decrease the luminosity.
• Control interface – the RS 485 bus or Ethernet. We do not recommend using the IBIS bus because of its slowness which decreases the ability to display various patterns. Systems based on the IBIS bus thus use coded control to get rid of these negative features.
• Ways of controlling direction indicators:
  • coded - the code of the target is sent under which a text or a displayed character (symbol) is saved in the memory. In this case, it is necessary to update the list of codes and the corresponding texts and symbols in the indicator (panel). Appropriate only for the IBIS bus.
  • character (text) - the characters and if needed the types of fonts to be displayed are sent directly. Updating the panel is necessary only if the fonts are adjusted. We recommend using the Windows CP-1250  Czech coded character set for LED panels controlled via the Ethernet bus.
  • graphic, when a bit information regarding a graphic pattern or a text is sent directly into the panel. The panel “does not understand” the text and only displays this bitmap. The advantage of this is that it is not necessary to update the data but only in the case of an authorized FW control unit. It is not possible to use this way of controlling direction indicators with the IBIS bus. In this case, a special tableau control protocol is usually used.
• The lifespan of the LED panels produced by our company is at least 10 years. This is made possible mainly by the low-input power solution when the LED diodes as well as the surrounding components do not overheat. This can be attributed to the fact that our LED panels use LED diode voltage regulation.
• The minimum of four fonts on the direction indicator – the size encompassing the whole tableau – 100% of the height (appropriate for the number of the line), a font size encompassing 66% of the height of the indicator (appropriate for the terminus), a font size encompassing 50% of the height of the indicator (displaying texts with the same information importance), 33% of the height of the indicator (appropriate for stops on the route of the vehicle). We newly use the technology of “dynamic fonts” - the size of the window is defined and the panel adjusts the size of the text.
• Stops on the route of the vehicle are displayed dynamically – each stop is removed when the vehicle arrives at this stop. If the text does not fit on the line the names of individual stops rotate cyclically.
• The ability not to deform Czech diacritics (VLP 24 a VLP 30) – the minimum of light points for one  line of text is 10. ‘In this case it is possible to use ascenders/descenders – see the above text.