The Frog Juicer is an electronic autoreversing device sold by Tam Valley Depot.
Live frog turnouts require power ("juice") to be supplied independently to the frog with the correct phase to match the route selected. The Frog Juicer supplies the power and switches the phase by electronic means rather than a mechanical switch. The device detects the short circuit caused when a locomotive passes over when the phase is incorrect and instantly switches to the correct phase.
The main purpose of live frogs is to eliminate stalling on switches with short wheelbase locomotives, such as a switcher. Locomotives with all-wheel pickup are not affected, but those without may be suddenly disconnected from their power source should both wheels of one truck be on a dead frog.
- Virtually idiot proof. If you use a manual switch for the frog power that isn't mechanically linked to the turnout then you will definitely get a short circuit when you forget to set it correctly. Even if you do use a mechanically-linked switch you will still get a short circuit if you run into a trailing turnout set against you. The frog juicer eliminates these problems.
- Electronic frog juicers have no moving parts and no contacts to get dirty and so they might be more reliable in harsh environments. For example, in outdoor applications they can be entirely sealed inside a waterproof enclosure.
- Not compatible with all DCC systems. Some entry-level DCC systems do not supply enough current during a short circuit to trigger the device to switch phase. So you will still get a short-circuit, the train will stop and lots of current will flow!
- Not compatible if you also want to run your layout in analog mode. For the same reason as above, the analog controller will not supply enough current to trigger it.
- Expense. More expensive than mechanical switches, especially if you're already using turnout motors (like the Tortoise Switch Machine) which have a mechanical switch built-in.
In addition to switching the phase of a frog, it can also be used as an autoreverser for crossings or turntables.
Frogs can also be paired, so both switch at the same time. Jumpers on the PCB allow these behaviours to be enabled.
The Frog Juicer works by monitoring the current flowing into the frog. When a locomotive shorts the frog to the adjoining rail, the Frog Juicer senses that and cuts power to the frog. After a short interval, the phase is reversed and power reconnected to the frog.
- There should be a section of normally powered DCC track between frogs, especially if they are close together. Otherwise the locomotive will stall.
- There should be no resistors or lamps between the Frog Juicer and the booster, otherwise, the device will not function correctly.
- The Hex Frog Juicer draws about 80mA, mainly to power the LEDs.
- Power Management Devices: If these devices are upstream of the Frog Juicer, adjustments to their reaction time may be necessary to allow the Frog Juicer to act before they react to the short circuit. This is also true of an Auto Reversing device