ENG - Scylla HPA – a new control unit for HPA systems
Scylla HPA from Czech manufacturer JeffTron is a new generation of programmable control unit with wireless configuration through a mobile app, designed for most HPA systems currently available on the market.
The unit supports both single-solenoid and dual-solenoid systems, including PolarStar F2, PolarStar F1, PolarStar JACK, Wolverine Inferno Gen 2 and other systems controlled by 5V electropneumatic solenoids.
Unlike conventional FCU solutions, all electronics are located directly inside the gearbox on a single PCB. There is no need for an external FCU in the stock and no additional multi-wire FCU harness running through the gun. This makes the installation cleaner, leaves more space for the battery and reduces the number of cables that can potentially be damaged.
All settings are configured wirelessly through the mobile app. The app allows complete configuration of the unit, saving custom profiles with different settings and easy firmware updates.
Profiles make it possible to instantly change the gun's configuration according to current requirements – for example for different play styles, power limits or BB weights.
Scylla HPA also allows independent configuration of individual firing modes. Different parameters can therefore be set for semi-auto and full-auto modes, such as power, rate of fire or other values affecting the operation of the HPA system.
The unit does not use mechanical switches for trigger or fire selector detection. The trigger position is detected by a Hall effect sensor and a magnet mounted on the trigger. The fire selector position is detected by an optical sensor using a sticker placed on the selector plate. Both sensors can then be precisely calibrated in the app.
Another advantage is the very low power consumption and the ability to check the current battery status directly in the app.
The unit features increased EMC immunity to electromagnetic interference, ensuring reliable operation even when radios are used during gameplay.
The Scylla HPA unit is supplied in a small compact box containing:
Scylla HPA control unit with wiring and JST connector
Set of stickers for the fire selector plate
Trigger magnet adapter compatible with standard trigger designs
M2 screw for mounting the unit inside the gearbox
Scylla Dogtag and stickers
Installation of the unit itself is very simple. The unit only needs to be secured inside the gearbox using the supplied M2 screw, or the original gearbox screw can be used instead.
The mounting hole is marked directly on the unit as “screw”.
When installing the unit into non-standard gearboxes, such as Krytac or G&G, the marked section of the PCB can be removed to ensure compatibility. Instructions for this modification can be found in the unit's manual.
The wiring is long enough to be routed into the stock and is fitted with a JST connector for standard small HPA batteries.
If the battery is placed inside the pistol grip, the excess wiring can simply be coiled and secured with a cable tie.
The unit can be powered by both 7.4V and 11.1V batteries. Thanks to the JST connector, it is compatible with standard small HPA batteries commonly used with conventional FCU units.
The magnet adapter is identical to the one used with the AEG version of the Scylla V2. The magnet is inserted into the main part of the adapter, after which both parts of the adapter are fitted onto the trigger and secured using two screws. A third screw can then be used to precisely adjust the fit of the adapter on the trigger.
A detection sticker is applied to the selector plate for fire mode detection. Two versions are included in the package – a short version designed to be applied to one side of the selector plate and a long version that wraps around the entire selector plate.
Personally, I prefer the short version of the sticker. However, I recommend thoroughly degreasing the surface of the selector plate and, if necessary, lightly sanding it to improve adhesion.
The fire selector position can then be precisely calibrated in the app.
The solenoid connections are marked directly on the unit. Each connector is labelled with the corresponding output:
N – Nozzle solenoid
P – Poppet solenoid
On dual-solenoid systems, the individual solenoids are connected according to these markings.
When using a single-solenoid system, such as the Wolverine Inferno or PolarStar JACK, the solenoid is connected to the connector marked P.
The unit includes an external output for connecting additional accessories, such as a hop-up chamber tracer unit or an electric magazine.
The output operates directly at the voltage of the connected battery and its switching behaviour can be configured in the app.
To connect external accessories, simply solder the wires to the prepared solder pads marked OUT+ and OUT-.
App
The Scylla HPA is configured using the JeffTron mobile app, which is also used with the Leviathan and Scylla control units for AEG guns.
The app allows complete configuration of the unit, saving profiles, calibration of individual sensors, firmware updates and monitoring of operating information.
Parameters
The Parameters tab allows complete configuration of the HPA system, including firing modes, rate of fire, trigger response, solenoid settings and external output functions.
Each parameter includes an “i” information icon which, when opened, displays a detailed description of the function of that particular setting.
One of the main advantages of Scylla HPA is the ability to configure parameters independently for individual firing modes.
After disabling shared settings, semi-auto and full-auto modes can be configured independently. This makes it possible to set different power levels, rates of fire or other parameters depending on the specific application.
The behaviour of the external output can be configured in the app according to the connected accessory.
The output can be activated only during a shot, remain permanently active or stay active for a defined period after each shot. This makes it possible to adapt its function, for example, for a hop-up chamber tracer unit or for controlling an electric magazine.
Profiles
The app allows users to create and save custom profiles containing the complete configuration of the unit.
Profiles are stored directly on the mobile phone, and once activated, all saved parameters are immediately written to the unit.
This makes it easy to switch between different gun configurations without having to manually readjust individual parameters. Separate profiles can therefore be created for different power levels, BB weights or play styles – for example a DMR setup, a 1.7 J / 0.32 g setup or any other configuration according to current requirements.
Calibration
The Calibration tab allows the individual sensors of the unit to be configured. The app provides precise calibration of the trigger and fire selector, as well as the option to enter the original shot count when upgrading from an older FCU unit.
Thanks to the Hall effect sensor and the magnet mounted on the trigger, trigger sensitivity and the activation point can be precisely adjusted directly in the app.
During calibration, the unit displays the current trigger position and allows the activation point and reset point for the next shot to be adjusted independently.
This makes it easy to adjust the trigger travel according to the user's preferences.
The fire selector position is detected using an optical sensor and a sticker placed on the selector plate.
The app guides the user step by step through calibration of the SAFE, SEMI and AUTO selector positions. After calibration is complete, the boundaries of each position can be fine-tuned for precise fire selector detection.
Thanks to software-based adjustment, correct selector operation can be fine-tuned even when individual gearboxes have different manufacturing tolerances.
When upgrading from the original FCU unit, the existing shot count of the HPA system can be entered manually.
This feature makes it possible to preserve the gun's usage history even after installing the new Scylla HPA unit.
The entered value is stored separately as the original shot count, while the unit also maintains its own shot counter from the moment of installation.
Statistics
The Statistics tab displays basic operating information for the Scylla HPA unit.
Available information includes the original shot count entered when upgrading from the previous FCU unit, a separate shot counter for the new unit, shot time, cycle time, rate of fire and current battery status.
Battery status is displayed as both the current voltage and an estimated charge percentage.
Settings
The Settings tab allows the basic configuration of both the app and the Scylla HPA unit to be adjusted.
The app allows the device name to be changed, a connection password to be set, firmware to be checked and updated, and basic app settings such as language, appearance and temperature units to be adjusted.
The settings also include Technical Lock, which allows selected unit parameters to be protected against unwanted changes.
Technical Lock
Technical Lock allows selected unit parameters to be locked against unwanted changes by the user.
This function is particularly useful for fully tuned custom builds, where important values affecting correct operation can be locked after the gun has been configured.
The technician can select the specific parameters to be locked – for example the HPA system type, solenoid timing, rate of fire, sensor calibration or other unit settings.
When the lock is activated, the current date and shot count are also saved, making it easy to determine the status of the unit at the time it was locked.
This concludes our overview of the Scylla HPA unit, its installation, main features and configuration options available through the mobile app.