The arduino mega with a motor shield. Pin 9 has been removed from the motor shield.
Locomotive Model Plans
Carton Built Models
Laser Cut Models
An external 12 v power supply is used on the motor shield.
A jumper wire is soldered in place between pins 4 and 13 on the motor shield.
Both the mega and motor shield are clones.
A video of an attempt to read the decoder on an ho scale engine is sent separately. A third party read that decoder and operated the engine on his system.