{"product_id":"cdu4c-fc","title":"CDU4C-FC High Capacity Fast Charging Model Railway Capacitor Discharge Unit","description":"\u003cp\u003eThe BLOCKsignalling CDU4C-FC is a \u003cstrong\u003ehigh-capacity fast-charging capacitor discharge unit (CDU) for model railway points motors\u003c\/strong\u003e, designed for \u003cstrong\u003elarge layouts, multiple points and demanding point-motor installations\u003c\/strong\u003e. It provides a powerful, short-duration current pulse for reliable operation of solenoid point motors while helping protect the motors, switches and layout power supply.\u003c\/p\u003e\n\u003cp\u003eThe CDU stores electrical energy in its capacitors and releases it as a \u003cstrong\u003ehigh-current pulse\u003c\/strong\u003e when a point switch is operated. This provides strong, positive movement of the point motor without requiring the layout power supply itself to deliver the full switching current. \u003cspan class=\"contents\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eBecause 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. \u003cspan class=\"contents\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eThe \u003cstrong\u003efast-charging design recharges in a fraction of a second\u003c\/strong\u003e, making the CDU4C-FC particularly suitable where several points need to be operated in quick succession. This rapid charging is achieved without requiring a larger power supply.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eHigh-capacity fast-charging capacitor discharge unit for model railway points motors.\u003c\/li\u003e\n\u003cli\u003eProvides a high-current pulse for strong and reliable point operation.\u003c\/li\u003e\n\u003cli\u003eDesigned for large layouts and multiple point operation.\u003c\/li\u003e\n\u003cli\u003eSuitable where point motors are located some distance from the controller.\u003c\/li\u003e\n\u003cli\u003eHelps protect point motors from overheating and burn-out.\u003c\/li\u003e\n\u003cli\u003eReduces electrical arcing and damage to switch contacts.\u003c\/li\u003e\n\u003cli\u003eHelps prevent voltage fluctuations elsewhere on the layout.\u003c\/li\u003e\n\u003cli\u003eRecharges in a fraction of a second for rapid successive point operation.\u003c\/li\u003e\n\u003cli\u003eSuitable for operating multiple points when the layout wiring and power supply are appropriate.\u003c\/li\u003e\n\u003cli\u003eBuilt-in Discharged and Ready LED indicators.\u003c\/li\u003e\n\u003cli\u003eConnection for an optional remote Ready LED on a control panel.\u003c\/li\u003e\n\u003cli\u003eCompatible with conventional twin-solenoid model railway point motors.\u003c\/li\u003e\n\u003cli\u003eAccepts either AC or DC power supplies.\u003cbr\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch3\u003eFast Charging\u003c\/h3\u003e\n\u003cp class=\"PDq2pG_selectionAnchorContainer\"\u003eConventional capacitor discharge units can take around a second to recharge after operating a point. The CDU4C-FC uses a \u003cstrong\u003efast-charging circuit\u003c\/strong\u003e that allows it to recharge in a fraction of a second, which is particularly useful when several points need to be switched rapidly or in succession.\u003cspan class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eThis makes the CDU4C-FC particularly suitable for \u003cstrong\u003elarge model railway layouts, complex pointwork and applications where several point motors may need to operate together\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cp\u003eThe fast-charging system achieves its rapid recovery without requiring a larger power supply.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003eLED Status Indicators\u003c\/h3\u003e\n\u003cp\u003eTwo built-in LEDs provide a clear indication of the CDU's operating state:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eYellow Discharged LED:\u003c\/strong\u003e Illuminates while the CDU is discharged and remains illuminated while the point switch is operated.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRed Ready LED:\u003c\/strong\u003e Illuminates when charging is complete and the capacitors have charged to over 15V.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThese indicators make it easy to confirm that the power supply is connected correctly and that sufficient charge is available for point operation. \u003cspan class=\"contents\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eThe CDU4C-FC also provides terminals for an \u003cstrong\u003eoptional remote Ready LED\u003c\/strong\u003e, allowing the charged status to be displayed on a model railway control panel. A suitable series resistor is already incorporated into the CDU for this connection.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003eWiring\u003c\/h3\u003e\n\u003cp class=\"PDq2pG_selectionAnchorContainer\"\u003e\u003cstrong\u003e\u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0994\/4009\/9673\/files\/Screenshot_2026-09-14_171318.jpg?v=1789402413\" alt=\"\"\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe CDU is connected between the layout power supply and the point operating switch. The negative CDU output is normally connected to the \u003cstrong\u003ecommon connection of the point motor\u003c\/strong\u003e, with the remaining point-motor connections operated through the point switch.\u003c\/p\u003e\n\u003cp\u003eThe optional remote Ready LED can also be connected to provide a convenient indication on the control panel when the CDU is fully charged.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003ePower Requirements\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eAC input:\u003c\/strong\u003e 12V to 24V AC.\u003cspan class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDC input:\u003c\/strong\u003e 15V to 35V DC.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRecommended power supply current:\u003c\/strong\u003e 1A.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDC input polarity:\u003c\/strong\u003e Not polarity sensitive.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTypical high-current wiring:\u003c\/strong\u003e Approximately 1.5mm² (16 AWG \/ 18 SWG) where appropriate.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe CDU can be powered from a suitable dedicated supply or a compatible auxiliary output on a model railway controller. A \u003cstrong\u003e16V AC auxiliary output\u003c\/strong\u003e is a common option. Suitable DC supplies can also be used and, when using DC, the input does not need to be connected with a particular polarity. \u003cspan class=\"contents\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eFor fast-charge operation, a \u003cstrong\u003e1A power supply\u003c\/strong\u003e is required. Adequately sized wiring is also important because point motors require high current during operation, particularly when several points are operated together or are located some distance from the CDU.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003ePoint Motor Compatibility\u003c\/h3\u003e\n\u003cp class=\"PDq2pG_selectionAnchorContainer\"\u003eThe CDU4C-FC is intended for conventional \u003cstrong\u003etwin-solenoid model railway point motors\u003c\/strong\u003e operated by short electrical pulses.\u003cspan class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eThe manual specifically covers \u003cstrong\u003eHornby and Peco point motors\u003c\/strong\u003e. For Hornby point motors the common wire is normally black, while for Peco point motors the common wire is normally green. \u003cspan class=\"contents\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003ePassing-contact switches can also be used. The manual discusses both \u003cstrong\u003eHornby R044 and Peco PL-26 passing-contact switches\u003c\/strong\u003e. When using a Hornby R044, it may be necessary to pause briefly around the centre position to allow the CDU to recharge as the lever is moved.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003eWhich CDU Do I Need?\u003c\/h3\u003e\n\u003cp class=\"PDq2pG_selectionAnchorContainer\"\u003eFor compact layouts where only one or two points need to operate at the same time, the \u003ca href=\"https:\/\/blocksignalling.co.uk\/products\/cdu1c-fc\" title=\"CDU1C-FC\" rel=\"noopener\" target=\"_blank\"\u003eCDU1C-FC Fast Charging Capacitor Discharge Unit\u003c\/a\u003e will normally be sufficient.\u003cspan class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003eFor larger layouts where several points may need to operate simultaneously or where point motors are further from the controller, the \u003ca href=\"https:\/\/blocksignalling.co.uk\/products\/cdu2c-fc\" title=\"CDU2CFC\" rel=\"noopener\" target=\"_blank\"\u003eCDU2C-FC Fast Charging Capacitor Discharge Unit\u003c\/a\u003e provides greater storage capacity.\u003c\/p\u003e\n\u003cp\u003eThe \u003cstrong\u003eCDU4C-FC Fast Charging Capacitor Discharge Unit\u003c\/strong\u003e provides the highest storage capacity in the range, making it the best choice for large layouts, demanding point-motor installations and maximum capacity for future expansion.\u003c\/p\u003e\n\u003cp\u003eThe \u003ca href=\"https:\/\/blocksignalling.co.uk\/products\/cdu4c-fc-led\" target=\"_blank\" title=\"CDU4CFCLED\" rel=\"noopener\"\u003eCDU4C-FC Fast Charging Capacitor Discharge Unit with Ready LED\u003c\/a\u003e is also available, supplied with a remote LED for mounting on your control panel to indicate when the CDU is fully charged.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003eDocumentation \u0026amp; Support\u003c\/h3\u003e\n\u003cp\u003eFor full installation instructions, wiring diagrams and troubleshooting guidance, please refer to the product instruction manual:\u003c\/p\u003e\n\u003cp\u003e\u003ca title=\"CDU4F\" href=\"https:\/\/drive.google.com\/file\/d\/1bngowK7JPPuBlO4N79ggLMHQhTSQOv0F\/view?usp=sharing\" target=\"_blank\"\u003eProduct Instruction Manual\u003c\/a\u003e\u003c\/p\u003e","brand":"BLOCKsignalling","offers":[{"title":"Default Title","offer_id":56860636283225,"sku":null,"price":16.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0994\/4009\/9673\/files\/cdu4f-fast-charging-capacitor-discharge-unit-1249063962.jpg?v=1784048654","url":"https:\/\/blocksignalling.co.uk\/products\/cdu4c-fc","provider":"BLOCKsignalling","version":"1.0","type":"link"}