MTH AIU:  Control Powered Switch Machines with AIU

(Aristocraft, LGB, USA Trains etc)



To control a 2 wire G scale switch machine (like Aristocraft or LGB) with the MTH AIU requires a couple of extra components to get working.  The AIU is designed to control 3 wire switch machines as is used in O and HO gauge. 






Control 2 wire powered switch machine with AC power and diodes: (Aristocraft, LGB)


To control a switch with AC power you will need two rectifier diodes and an AC power supply. (AC power supply can be from 12-18v)


The photos below will help explain how it should be wired up:



The two white wires are from the AC power supply.  One wire goes to one side of the Aristocraft switch motor and the other goes to "IN" slot(s) on the AIU port.  It does not matter which of the two wires is connected to the AIU and switch motor.


Next you will need to solder one end of two rectifier diodes together with the other ends facing the same direction for insertion into the AIU.  (Solder the diodes in opposite directions, one with the white line on the diode closest to you and the other being furthest away.  Then solder the now common soldered end of the diodes to a single wire and run that to the other side of the switch motor as shown. 


Ensure the power supply is plugged in and you now have the switch machine ready to go. 


Lastly, you will then need to use your DCS remote to add that switch port as a selectable switch.   Once added you can then use the straight and switched buttons to control the switch.




To simplify the install of several switch machines, this is how I chose to wire it up.


- I chose to run one wire from the AC power supply to the first AIU "IN" port and then run jumper wires from the first "IN" port to the second "IN".  I then repeated this for the number of switch machines I planned to add. 

- Next I ran the other wire from the AC power supply directly outside and then split it out from there to run to one side of each of the switch machines that I planned to power.  This saved me from having to run a dedicated power wire from inside the house to each switch machine.  This way I only had one.

- Next I then ran a wire from each pair of diodes outside to the designated switch machines.

- To simply swapping out AIUs or moving the AIU, I added the pictured multi pin connector inline in all the wires run to the AIU.  This way I can simply unplug the connector and remove the AIU.




NOTE: If the power supply you're using to power the switch machine is greater than 1 amp, you may want to add a 1 amp fuse or use a polyfuse between the power supply and the switches.  (I would add a polyfuse inline in each wire from the power supply for good measure.)   Polyfuses can be purchased here:






Parts list:

Here is a list of parts you can use to accomplish this:

        Diode will look like this: 





Control USA Trains Powered Switch machine with AC power and diodes:





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