In 1990 a letter was published in the Model Railway Journal asking if there was a standard for connecting Hand Held Controllers to baseboards/control panels. Several clubs and manufacturers replied. Although there appears to be no standard, the majority use the same 5 pin 1800 type ‘A’ DIN plugs and sockets as described below
DIN (the German equivalent of the British Standards Institute) has standardised plugs and sockets for audio applications. Good quality ones are rated 2 Amps. at 100 V AC/150 V DC and so are very suitable for the 16 V AC input and 0-12 V controlled DC output of model railway controllers.
There are three types of 5 pin DIN plugs (not to be confused with the miniature DIN range), the ones considered here have the pins at 450 included angle (1800 total) and are known as 1800 or type ‘A’. They have become the MIDI standard for connecting computers and musical instruments, and so are likely to remain cheap and readily available for some time.
Latching connectors are available - the latching ones only latch with their counterparts, but will nevertheless mate (without latching) to other connectors of the same pin configuration. They are particularly useful with curly cables, allowing the cables to stretch rather than becoming unplugged.
Sockets are available with hexagonal nut fixing - suitable for sheet metal - and also with screw holes for either chassis mounting or fixing to wooden baseboards.
The cables are not attached to either the controllers, or to the baseboard. The advantage of completely separate cables is twofold. Firstly it makes for easier storage, and secondly it allows cables to be quickly swapped if a fault develops during an exhibition.
Ready-made leads are available with plugs at both ends, but care must be taken to ensure they are not reversing types (i.e. pin 1 should go to pin 1 etc.). Ready-made MIDI leads are suitable; some Audio leads do not connect pin 2 - this may not be important. The type of lead where two screened wires are used is not suitable, and for model railway use a low resistance is very important.
A quantity of curly computer keyboard cables was purchased some time ago (sadly these are no longer available). These conveniently had 15 wires, and by soldering 3 to each pin it was possible to get a reasonable current rating. They have been fitted with latching plugs and have proven very successful with several exhibition layouts.
With the exception of 3mm scale, when looking forward from the driving cab of a locomotive it will move forward if the right hand rail is positive with respect to the left hand rail. The baseboard above illustrates how this relates to pins 3 and 5.
If the hand held controller has a slide or toggle switch for direction, the locomotive will move in the direction of the switch when operated from the “operator” side. If the same visual feedback is required when on the “audience” side, a DPDT switch can be incorporated in the baseboard to swap the track connections from pins 3 and 5.
A common practice for track wiring is to use “common return” whereby rails from several tracks are electrically bonded together. This has no effect on the wiring of the DIN plugs, but it is worth mentioning that controllers requiring external mains transformers must be fed from separate transformer windings.