SHS 2-8-0 TMCC Conversion
An improved plug in conversion that makes no changes in the Loco
 Only the tender has slight modifications

She is building up a head of steam.

(Click on images for larger picture)

The only modifications are to the tender's  board mounting posts.

The rear ones are removed and the front two are shortened by 1/8" and re-drilled for the board mounting screws 

There are three main components, The Electric RailRoad's Mini Commander and Sound Commander and the 2-8-0 Interface board.

This conversion was designed to keep the Loco completely stock and be a plug in unit in the tender using the original SHS connectors.
The mating header connector is a Mouser part number 575-641001.

The Interface board also is screwed into the front two mounting posts.

The only modification to the Mini Commander is a simple small heatsink added to the Mini Commander Triacs to ensure a long cool life. It made from .032 Sheet aluminum and held in place with a  #2 machine screw tapped through the heatsink and Triac's mounting holes. Be sure the heatsink does not touch any other components as it is not electrically isolated  from the Triacs.
A 6 pin socket was used on the Interface board. It holds the Mini Commander in place as well as connecting the serial signals to the Sound Commander board.

The socket also has the pin 4-5 jumper wired to program the Mini Commander for the Motor control feature.

The +5 volt switching regulator is used to supply the smoke element current.  It is very efficient and generates very little heat. A conventional regulator will not work in this confined space.

The SHS 2-8-0 Loco electronics uses +5 volts DC and the TMCC circuits use AC track voltage so care must be used to keep them isolated from each other. This was done by using opto-isolaters and the separate +5 volt supply.

The Smoke control is provided with a MOSFET switching transistor and has a very small voltage drop providing 4.5 volts and also runs cool. The stock 4.4 ohm smoke element can draw an amp or more.

LC-2 controls the smoke feature (Aux1, 8 smoke off and Aux1, 9 smoke on)

The Mini Commander must be programmed to be a "type 6" for the features to work properly.
The loco's chuff switch controls the chuff trigger to the sound board and also provides a smoke motor boost to modulate the smoke velocity

The Pins on the sound commander's programming connector are bent 90 degrees for clearance. The Sound Commander is fastened with a couple of pieces of foam strips to the chassis.

Also: See Improving the SHS Smoke Unit.

The Interface  Board Parts layout of the vector board prototype.


Schematic of "L interface board" and wiring.

PC board layout parts layout slightly different form vector board prototype to help trace paths. 

The bottom layer traces of the PC board

The top layer traces of the PC board

(Click on images for larger picture)
       This is the Wiring interconnections to the Mini Commander and Sound Commander board.
Here are the board dimensions. 

The 16 pin header part number is:
 Mouser  575-641001.

The 6 pin header part number is:
Moser 649-68685-306LF


This is the component layout view

Using a Program Run Switch (P/R SW) is optional as the Mini uses "Soft Set Technology" (TM) for programming board. If you feel you needed a switch it could be mounted under the tender water hatch. 


In back is the prototype. In front it the Printed circuit board version. 

     New Printed Circuit board version installed 
     and tested