Multi-unit lashup

Model Connectors

This 1.6 inch scale locomotive makes clever use of small spring loaded oil cups to model multi-unit connectors.

External Links

• "Multi-unit train control", Wikipedia
• "MU Lashup Wiring Standard", Chaski.org
• "Riding railkits mu cable", Chaski.org
• "US Loco MU Control"
• "How One Engineer Operates Several Diesels" (PDF)
• "Operation and Maintenance of Diesel-Electric Locomotives", US Army
• "Locomotive Command and Control Module (LCCM) - Functional Requirements", AAR

Proposed Standard

Aaron Gonthier wrote 22 August 2019:

I am working on a standard for locomotive control wiring for battery electric locomotives. It uses a premade Ethernet cable to go from the motor controller (or other control device) to the handheld throttle. The purpose of the standard is to make it easy to change out a broken cable or swap handheld throttles, cables and controllers from one locomotive to another with a minimum amount of rewiring. Ethernet cables are available most places in North America, from big box stores to convenience stores. They work with analog or digital control systems and allow for basic controls and a minimal amount of electronics in the handheld throttle.

Having only the essential controls simplifies wiring, with only throttle, forward/reverse, horn and optional brake controls. Lighting controls can be on the locomotive or integrated with the reverser controls using a relay on the locomotive.

My hope with this proposed standard is to make it a little easier for people building and maintaining battery electric locomotives. Your input is appreciated.

Aaron Gonthier

Mill Brook Railroad

Windsor, VT

Editor: Please note the pinout below is modified from Mr. Gonthier's initial description.

Description

• Two Multi-unit lashup cables are defined. Connector #1 is required, Connector #2 is optional.
• All signals range from 0 volts D.C. (ground) to 12 volts D.C., +/-10%
• The signals use "positive logic" (e.g. 12 volts D.C. indicates the signal is active)
• Units (locomotives) are to provide RJ-45 sockets on both ends for Connector #1, and an optional second RJ-45 connector on both ends for Connector #2
• Every signal is carried through the locomotive from front to back and, unless otherwise noted, are not modified by the locomotive
• Signal voltages may need to be converted to different logic levels on each locomotive
• Up to four units may be joined together without further signal amplification
• The source generating each signal must supply a minimum of 100 milliamps for 0 and 12 volts D.C.
• Each unit must consume no more than 20 milliamps from a given signal. This is sufficient for driving the coil of one automotive relay in each unit.

Connector #1

Pinout mapping for RJ-45 Socket and Plug

• Pin 1. 12 volts D.C. (Signal high) - white/orange
• Pin 2. Brake Release (optional) - orange/white
• Pin 3. Forward - white/green
• Pin 4. Ground (Signal Low) - blue/white
• Pin 5. Horn - white/blue
• Pin 6. Reverse - green/white
• Pin 7. Brake Apply (optional) - white/brown
• Pin 8. Speed - brown/white

Notes:

a. Each unit provides 12 volts D.C. to Pin 1 through a 5 amp fuse and an appropriate diode, such as a 1N5400, to prevent reverse current to the unit's battery. Each unit provides a minimum of 1 amp.

b. Logic Table for Forward/Reverse

Forward (Pin 3)	Reverse (Pin 6)	Action
Ground	Ground	Power to drive motor deactivated, headlights off
12 volts	Ground	Drive motor is set in forward direction, speed is indicated by Pin 8, forward headlight is on
Ground	12 volts	Drive motor is set in reverse direction, speed is indicated by Pin 8, reverse headlight is on
12 volts	12 volts	Apply dynamic brakes

c. Logic Table for Brake Apply/Release

Brake Release (Pin 2)	Brake Apply (Pin 7)	Action
Ground	Ground	No Action
12 volts	Ground	Brakes are released
Ground	12 volts	Brakes are applied
12 volts	12 volts	Emergency Stop, Power to motor is deactivated, brakes are applied (optional), forward and reverse headlights on

d. Pin 8 provides speed information to the drive motor of each unit. A signal of Ground results in no power to the drive motor. A signal of 12 volts D.C. results in maximum power to the drive motor. Some drive controllers, such as the Syren-50, require a 5 volt D.C. maximum input, so signal conditioning will be required. An eight notch throttle can be simulated by providing the following voltages to Pin 8:

• Ground - No power to drive motor (idle)
• 1.5 volts - Notch 1
• 3.0 volts - Notch 2
• 4.5 volts - Notch 3
• 6.0 volts - Notch 4
• 7.5 volts - Notch 5
• 9.0 volts - Notch 6
• 10.5 volts - Notch 7
• 12.0 volts - Notch 8

Connector #2 (Optional)

• Pin 1. 12V (Signal high) - white/orange
• Pin 2. Headlight High Beam - orange/white
• Pin 3. Headlight Low Beam - white/green
• Pin 4. Ground (Signal Low) - blue/white
• Pin 5. Bell - white/blue
• Pin 6. Air Compressor - green/white
• Pin 7. Number Board Lights - white/brown
• Pin 8. Step Lights - brown/white