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Model Railway Double Reverse Loop Wiring

How to wire two reverse loops on your two-rail layout for automatic operation

Here we show you how to wire the reverse loops and track switches on a double-loop layout with a single connecting main line. Wiring a reversing loop (or turn-around track) may seem complicated, but if you take one step at a time and check your work, you will have a fully automated reverse loop and worry-free train operation.
 
[Click here to review reverse loop fundamentals]
 
This plan is for a 'dog bone' type layout with a single track main line: It is completely automated, with automatic control of the track polarity and the track switches (or 'turnouts').
 
This system is an economical choice for:
  • DCC layouts
  • DC or AC layouts with single cab control (one train power pack or transformer)

Double reverse loop control for DC, DCC or AC layouts.


twin loop wiring with relay
This system, shown above, uses a DPDT relay to control polarity of the main line. The switch machines operate simultaneously, controlled by the D2T-2W or D2T-3W dual IR train detector.
 
When the track switches are aligned for the 'straight' track the relay is 'off.' The main line polarity will match the loop polarity at points marked 'M', allowing trains to cross at those locations.
 
• Click here to learn how a relay works. [pdf]
 
When the track switches are aligned for the 'curve' track the relay is 'on.' The main line polarity will match the loop polarity at points 'X', allowing trains to cross there.
 
Wire the switch machines so the switch points are aligned for the 'M' junctions when sensor 1 is triggered. If the points align the wrong way, swap the connections to the switch machine.
 
How it works: Assume a train is moving left-to-right on the main track, approaching the east loop, and the turnout is aligned with 'M'.
 
The train enters the loop and travels counter-clockwise. When it triggers sensor 2, the D2T-2W (or -3W) will throw both switches to align with 'X' and will turn on the relay. The main line and loop track polarities will now match at the two 'X' locations. The train returns to the main line.
 
Now the train approaches the west loop, moving right-to-left. The switch points are still aligned to the 'X' junctions and the track polarities still match there.
 
The train travels counter-clockwise around the west loop and triggers sensor 1. The D2T-2W (or -3W) throws both switches to align with the 'M' junctions and turns off the relay. Mainline and loop track polarities now match at points 'M' and the train returns to the main line.
 
Manual control of the turnout is possible, as shown in the D2T-2W installation guide and the D2T-3W installation guide.
 
For AC single cab and DCC powered layouts, this is all you need.
 
On DC layouts, manually changing the turnout positions will cause a train on the main track to change direction. If you choose to manually control the turnouts, first stop the train if it is on the main track!
D2T-2W Dual train detector for 2-wire switch machines
  such as Kato, Aristocraft or LGB.
• Also for slow motion Tortoise, Cobalt or SwitchMaster.
• Includes two infrared sensor pairs (IR LEDs & receivers)

$39.00

Include infrared sensors?
D2T-3W Dual train detector for 3-wire twin-coil switch machines
  such as Atlas, Bachmann, Peco, Kemtron, etc.
• Includes two infrared sensor pairs (IR LEDs & receivers)

$39.00

Include infrared sensors?
MRAPR-5 Relay, DPDT, 5 amp contacts
• For 9 to 14 volt accessory power supplies, AC or DC
• Easy installation, screw terminals and mounting holes
• On-board LED indicator and kickback protection

$9.15

MRAPR-8 Relay, DPDT, 8 amp contacts
• For 12 to 17 volt accessory power supplies, AC or DC
• Easy installation, screw terminals and mounting holes
• On-board LED indicator and kickback protection

$9.85

Tortoise™ slow motion switch machine
• Circuitron part no. 800-6000
• Includes DPDT contacts for frog power or signal routing

$17.50

Accessory power supply, PS1206
• Regulated 12vdc, 600mA, slim plug-in
• Can power up to 8 D2T-2W circuits with slow motion switch machines

$9.50


[ Choose a different type of reversing track ]


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