The BLOCKsignalling CDU1C-FC is a fast-charging capacitor discharge unit (CDU) for model railway points motors, designed for smaller layouts and straightforward point-motor installations. It provides a powerful, short-duration current pulse for reliable operation of conventional twin-solenoid point motors while helping protect the motors, switches and layout power supply.
The CDU stores electrical energy in its capacitor and releases it as a high-current pulse when a point switch is operated. This provides strong, positive movement of the point motor without requiring the layout power supply itself to provide the full switching current.
Because the high-current pulse has finished before the switch contacts open, electrical arcing across the contacts is greatly reduced. If a switch is accidentally held in the operated position, the CDU limits the subsequent current through the point motor, helping protect its coils from overheating and damage.
Key Features
- Fast-charging CDU for model railway points motors.
- Single-capacitor design ideal for smaller layouts.
- Provides a high-current pulse for strong and reliable point operation.
- Helps protect solenoid point motors from overheating and burn-out.
- Reduces electrical arcing and damage to switch contacts.
- Helps prevent voltage fluctuations elsewhere on the layout.
- Recharges in a fraction of a second for rapid point operation.
- Built-in yellow Charging and red Ready LED indicators.
- Compatible with conventional twin-solenoid model railway point motors.
- Accepts either AC or DC power supplies.
Fast Charging
The CDU1C-FC uses a fast-charging circuit that allows the capacitor to recharge in a fraction of a second. This provides quicker recovery between point operations and can also be beneficial when using passing-contact point switches.
LED Status Indicators
Two built-in LEDs provide a clear indication of the CDU's operating state:
- Yellow Charging LED: Illuminates briefly while the capacitor is charging.
- Red Ready LED: Illuminates when charging is complete and the capacitor has charged to over 15V.
These indicators make it easy to confirm that the power supply is connected correctly and that the CDU has sufficient charge available for point operation.
Wiring
The CDU is connected between the layout power supply and the point operating switch. The negative CDU output is generally connected to the common connection of the point motor, with the remaining point-motor connections operated through the route switch.
Wiring Multiple Points
A single CDU1C-FC can be connected to multiple sets of points. The common wiring is simply paralleled between the switches and point motors as shown in the instructions.
The CDU1C-FC is the smallest-capacity model in the range, so if you need to operate several point motors simultaneously, one of the larger CDU models may be more appropriate.
Power Requirements
- AC input: 12V to 24V AC.
- DC input: 15V to 35V DC.
- Recommended power supply current: 1A.
- DC input polarity: Not polarity sensitive.
- Typical high-current wiring: Approximately 1.5mm² (16 AWG / 18 SWG) where appropriate.
A 16V AC auxiliary output from a suitable model railway controller is a common power source. Suitable DC supplies can also be used, and the DC input does not need to be connected with a particular polarity.
For fast-charge operation, the instructions specify a 1A power supply. Adequately sized wiring is also important because point motors require substantial current during operation.
Point Motor Compatibility
The CDU1C-FC is designed for conventional twin-solenoid model railway point motors operated using short electrical pulses.
The instructions specifically cover Hornby and Peco point motors. Hornby point motors normally use the black wire as the common connection, while Peco point motors normally use green.
Which CDU Do I Need?
For compact layouts where only one or two points need to operate at the same time, the CDU1C-FC Fast Charging Capacitor Discharge Unit is the most suitable choice.
For larger layouts where several points may need to operate simultaneously or where point motors are further from the controller, the CDU2C-FC Fast Charging Capacitor Discharge Unit provides greater storage capacity.
For large layouts, demanding point-motor installations or maximum capacity for future expansion, choose the CDU4C-FC Fast Charging Capacitor Discharge Unit.
Documentation & Support
For full installation instructions, wiring diagrams, LED indications and troubleshooting information, please refer to the Product documents section below.