REV1mini DCC Model Railway Autoreverser

About the Product

The BLOCKsignalling REV1mini is a compact DCC model railway autoreverser for reversing loops, wyes and turntables, providing fast automatic polarity switching without programming or adjustment.

When a locomotive crosses a track break and encounters a polarity mismatch, the REV1mini detects the resulting short circuit in less than five microseconds and automatically switches the polarity of the isolated track section. Polarity is corrected within approximately 10-20 milliseconds, preventing the DCC command station from shutting down and allowing the train to continue through the reversing section.

The REV1mini has a detection level of approximately 1.75A and is designed for use with DCC command stations capable of providing 2.5A output or greater. It is a solid-state design with no moving parts and requires no programming or adjustment during normal operation.

Key Features

• Automatic DCC track polarity switching.
• Ideal for reversing loops, wyes and turntables.
• Short-circuit detection in less than 5 microseconds.
• Polarity correction within approximately 10-20 milliseconds.
• Approximately 1.75A detection level.
• Designed for DCC command stations rated at 2.5A or greater.
• Compact solid-state design with no moving parts.
• No programming or adjustment required.
• LED indication of power and output polarity.
• Automatic protection against persistent short circuits.
• Automatically restores power after a persistent short is removed.
• Compatible with Hornby™ HM7000 when the track is DCC powered.
• Suitable for layouts up to OO/HO scale.
  

How the REV1mini Works

The REV1mini supplies power to an electrically isolated section of track where the rail polarity may need to be reversed to match the adjoining track.

When a locomotive enters the isolated section with matching polarity, it simply continues normally. If the polarity does not match, the locomotive's wheel pickups briefly bridge the two opposing track feeds.

The REV1mini detects this condition almost immediately and swaps the polarity of its output, removing the short circuit before the DCC command station has time to shut down.

This automatic operation allows trains to pass through reversing sections without the operator manually changing track polarity.

DCC & Hornby™ HM7000 Compatibility

The REV1mini is designed exclusively for DCC track power and must only be connected to the output of a DCC command station.

It is compatible with Hornby™ HM7000 when the track itself is supplied with DCC.

The REV1mini is not suitable for HM7000 layouts where the track is supplied directly with 15V DC and the locomotive is controlled by Bluetooth/App. Connecting 15V DC to the REV1mini may damage the module.

For other track-power systems:

• REV7K-4A 15V DC Model Railway Autoreverser - for Hornby™ HM7000 layouts using a constant 15V DC track supply
• REV2 Universal DC/DCC Model Railway Autoreverser - for layouts requiring compatibility with variable DC, DCC or 15V DC HM7000 track power

DCC Command Station Requirements

The REV1mini has a short-circuit detection level of approximately 1.75A. The DCC command station therefore needs to be capable of supplying sufficient current for the REV1mini to detect the polarity mismatch and operate before the command station itself shuts down.

For this reason, the REV1mini is specified for use with DCC command stations capable of providing 2.5A output or greater.

Good electrical connections are also important. Track and module connections should ideally be made close to the track breaks to minimise resistance and ensure sufficient current flows when a polarity mismatch occurs. 

Typical Layout Applications

The REV1mini can be used with several common DCC model railway track arrangements where automatic polarity reversal is required.

Reversing Loops

A reversing loop creates a polarity conflict where the loop reconnects to the main track. The REV1mini allows the loop to be electrically isolated and automatically changes its polarity when required.

The loop requires four track breaks. When a train reaches a boundary where the loop and adjoining track have opposing polarity, the REV1mini automatically switches the loop polarity so the train can continue through the points and return to the main layout.

For best performance, connections to the loop should be made close to the track breaks, while the REV1mini input should preferably be connected to the DCC bus or directly to the DCC booster output.

Turntables

The REV1mini can automatically control the polarity of an electrically isolated DCC turntable bridge.

The turntable track must be electrically isolated from the approach tracks using track gaps or insulated rail joiners. The REV1mini OUT1 and OUT2 terminals then supply the turntable bridge and automatically correct its polarity when required.

Where tracks run straight through the turntable, they should be wired with matching polarity to allow longer trains to pass across the bridge.

Wye Layouts

A wye creates a point where rails connected to opposite sides of the DCC bus would otherwise meet and cause a permanent short circuit.

By creating an isolated track section and powering it through the REV1mini, the module can automatically switch its polarity as a train enters or leaves the section.

The isolated section connected to OUT1 and OUT2 must be at least as long as the longest train that will use it.

Automatic Short-Circuit Protection

If the REV1mini detects a polarity mismatch, it normally corrects the problem simply by reversing its output.

However, if reversing the polarity does not remove the short circuit - for example, because a locomotive has derailed - the REV1mini automatically shuts down its output to protect the module.

After approximately 5 seconds, it restores power and checks again. If the short circuit is still present, the output is switched off again. This cycle continues until the fault has been removed.

LED Status Indication

On power-up, the red PWR LED indicates that the REV1mini is operating.

The yellow NORM and INV LEDs indicate the current output state:

• NORM - OUT1 and OUT2 correspond directly with IN1 and IN2
• INV - the output connections are reversed, with IN1 connected to OUT2 and IN2 connected to OUT1

The LEDs therefore provide a simple visual indication of the current polarity state of the REV1mini output.

Electrical Requirements

• Track Power: DCC only
• Detection Level: Approximately 1.75A
• Recommended DCC Command Station: 2.5A output or greater
• Polarity Detection: Less than 5 microseconds
• Polarity Correction: Approximately 10–20 milliseconds
• Maximum Recommended Scale: Up to OO/HO
• Input: DCC command station output, DCC track bus or DCC-powered track
• DC Compatibility: Not compatible
• AC Compatibility: Not compatible
• HM7000 Compatibility: DCC track power only

Do not connect the REV1mini directly to a DC or AC power supply.

Wiring

The IN1 and IN2 terminals connect to the DCC command station output, DCC track bus or DCC-powered track. These two input connections can be connected either way around.

The OUT1 and OUT2 terminals connect to the electrically isolated reversing section controlled by the REV1mini.

The isolated section should have no other electrical feed from elsewhere on the layout.

Track Occupancy Detection

The REV1mini draws a small operating current from its DCC input. On layouts using track occupancy or train detection systems, this may cause some detectors to indicate that the reversing section is occupied even when no train is present.

The instruction manual includes dedicated wiring arrangements for using the REV1mini alongside track occupancy detection systems. 

Documentation & Support

For complete installation instructions, additional wiring information, track occupancy detection, troubleshooting and testing procedures, please download the latest instruction manual:

User Instruction Manual