FROGmini DCC Model Railway Automatic Frog Juicer

About the Product

The BLOCKsignalling FROGmini is a DCC model railway automatic frog juicer, designed to automatically switch the polarity of live frogs on points and turnouts for smooth, reliable running.

It eliminates the need to use microswitches, point-motor contacts or other mechanical methods of changing frog polarity. The FROGmini monitors the current flowing to the frog and automatically selects the correct polarity as a locomotive passes through the points.

If a locomotive encounters the frog with the incorrect polarity, the FROGmini detects the resulting short circuit and rapidly switches the frog to the opposite polarity. The correction takes place quickly enough that the rest of the DCC system is unaffected.

Key Features

• Automatically switches live frog polarity.
• Designed specifically for DCC model railway layouts.
• Solid-state design for extremely fast switching.
• Detects a short circuit within approximately 5 microseconds.
• Removes the short circuit within approximately 1–2 milliseconds.
• Helps provide smooth running through live-frog points and turnouts.
• No mechanical moving parts or switch contacts to wear.
• Eliminates the need for microswitches or auxiliary point-motor contacts.
• Detects double-short conditions that could otherwise shut down the DCC booster.
• Automatically retries after a persistent short circuit.
• LED indications show module operation.
• Simple three-terminal connection.

Automatic Frog Polarity Switching

The frog can be at either polarity as a locomotive approaches the points.

If the polarity is already correct, the locomotive simply passes through normally. If the polarity is incorrect, the locomotive's wheel pickups create a brief short circuit as they contact the frog.

The FROGmini detects this short circuit within approximately 5 microseconds, removes it within approximately 1–2 milliseconds, reverses the frog polarity and restores power.

This all happens automatically without the operator needing to manually select or control the frog polarity.

Simple DCC Connection

The FROGmini has just three connections: T1, F and T2.

T1 and T2 connect to the DCC track or power bus, while the centre F terminal connects to the frog. It does not matter which DCC rail or bus wire is connected to T1 or T2, as the module automatically selects the appropriate feed for the frog.

The diagram above also shows the typical modifications required when using an electrofrog point, including insulated rail joiners, removal of the appropriate wire bonds and installation of new links.

Short-Circuit Protection

If a short circuit occurs between both rails and the frog, the FROGmini cuts power to the frog for approximately 5 seconds before automatically attempting to restore it.

If the short remains, the module continues attempting to reapply power at 5-second intervals until the short circuit has been cleared. This prevents the fault at the frog from continuously short-circuiting the DCC feed.

Compatibility

The FROGmini is designed exclusively for DCC layouts and requires sufficient current from the DCC system to detect the brief short circuit used to determine when the frog polarity needs changing.

• Control System: DCC only.
• Minimum Current Required: 1.7A.
• Recommended Scale: OO/HO and smaller.
• DC Layouts: Not compatible.
• Hornby HM7000 Bluetooth: Not compatible when operating as a Bluetooth/DC system.

The manual specifies that a minimum of 1.7A is necessary for short-circuit detection and that the module is suitable for OO/HO scale and below.

Important Point Requirements

When using electrofrog points, modifications to the point may be necessary to correctly isolate and power the frog.

The manual specifies the typical arrangement using insulated rail joiners beyond the frog, isolating the frog from the appropriate rails and adding new electrical links to maintain power to the remaining rails. The frog feed is then connected directly to the FROGmini.

Always check the requirements of your particular point or turnout before modifying it.

Documentation & Support

For detailed information on point modifications, installation, wiring and operation, please download the latest instruction manual:

Product Instruction Manual