The 'Leistungsstufe' released by fischertechnik in 1981 inspired me to develop a universal circuit board with short-circuit proof power outputs. That design adds current limiting with external cooling on the back of the module. The 3D printed housing is compatible with the classic electronics modules (the 'Silberlingen') from fischertechnik. The driver board (with two or four BD132 transistors) offers the possibility of connecting an external power supply at the back and basically only requires a control board with buses for the inputs and outputs. Completely assembled, one such “driver-Silberling” forms a functional “solid-state” alternative to two classic fischertechnik “Leistungsstufen” or four relay modules.
The (digital) outputs of the 'Silberlingen' built with discrete electronics are not intended to directly control lamps, motors, etc. For this reason, in most building examples with these electronics modules, as in the fischertechnik Hobby4 books, among others, the well-known RB I Relaybaustein (36392) is used to switch the final consumer. This article, which basically consists of two parts, examines which so-called 'solid-state' alternatives are available for the fischertechnik relay modules. A prerequisite in the development of both 'new' Silberlingen was that they should be both mechanically and electronically compatible with the traditional modules so that they could easily be used in existing building designs.
In cases where the contacts of a relay are used only as single make or break contacts, switching can usually also be taken over with a semiconductor, such as a current-limited transistor. In the continuation of this article, a home-built module with a double so-called “H-Bridge” will be discussed. With this it is also possible to replace a relay whose contacts are used to switch the direction of rotation of a motor.
I now use the previously discussed universal driver circuit board at the bottom of the enclosure of various, so far undiscussed here, homebrew modules. For example, the board makes it possible, if desired, to extend CMOS technology-imitated logic AND/NAND and OR/NOR module variants with “proprietary” driver outputs so that an entire relay module is not immediately required for each actuator (such as a simple control lamp, for example).
In the case of the homebrew module discussed here, the circuit board is used to build a universally usable module that can replace the relay module required in many classic building designs. Only one copy of the module discussed here replaces up to four fischertechnik Relay Bausteinen (or two LST Leistungsstufe Bausteinen).
The design of the circuit board at the top of the Silberling enclosure is very simple and is mainly used to accommodate the sockets for the 2.5mm fischertechnik connectors. Although for many homebrew electronics modules in the 'Silberlingen' enclosures I now use the Dupont experiment wire connectors on the lid, for this module I decided to use the PTN2-10 sockets discussed earlier. Once this top circuit board of the 'sandwich' is pressed into place, two connector rails on the board connect the buses to the respective input and output buses of the driver board located at the bottom of the module enclosure. On the output side, another four LEDs are provided to indicate the output status of the individual outputs.
The image to the right shows the new circuit board with the plug sockets and the cover that has yet to be mounted. Also visible is the back of the module with the four transistors of the previously discussed driver board. Also on this PCB are the two JST connectors for optionally connecting and looping an external power source. This optional 12-volt voltage input is electronically merged (over a Schottky diode) with the module's operating voltage provided via the metal strips on the side of the housing. The module thus “chooses” which supply voltage to use to power the connected consumers. Thus, connecting an additional external power source is not necessary. The connected consumers can also be powered by the voltage offered via the regular red connection clips. I also printed some insulating gray clips. I use these to neatly finish off superfluous (or unwanted) connections between modules. Of course, these are also useful if different rows of modules with separate power supplies need to be isolated.
I was able to immediately apply my “Quadruple Driver” module in some traffic light controllers. Each of these controllers shown could also be built fully functional with the original fischertechnik electronics modules. So in that respect, the module discussed here does not add any new functionality. But by using such driver outputs, up to five relay modules per control can be saved. In practice, it is very nice to have the same “solid-state” switching capabilities that we are now accustomed to from the TXT controller or other modern microcontrollers with driver outputs even when experimenting with the classic electronics modules.
