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Slider Motor Controller (SMC)


Controls up to 16 slider motors. For use in tracker-action organs or electric-action organs with slider chests.



Pipe organ slider chests have slider motors which push or pull the chest sliders in or out. These motors have solenoids which require a lot of current for a short time to operate. The Slider Motor Controller (SMC) controls pairs of solenoids and in turn, the push and pull actions. The SMC is a standalone product that may use serial or parallel control (at the same time if necessary) and may be connected to other systems as well as the Classic Organ Works control system. 



  • Contains driver systems for up to sixteen slider motors (typically 2-6 Ohms) at a maximum of 10 Amps each, and can operate on supplies to 28V.
  • On and Off outputs are pulsed independently for adjustable periods (typically a quarter second) and the drivers are protected against overloads, short-circuits or both being on together. The supply voltage is nominally +12 Volts but may be from +10 Volts to +28V.
  • Outputs are pulsed initially at full power to overcome "stiction" on old slider motors and then provide steady reduced power (adjustable) for the rest of the pulse period.
  • All outputs are powered for the same period, typically longer than the motor needs to move, so that end-of-travel bounce is eliminated, resulting in quiet operation.
  • Typically, operating Sforzando and Cancel pistons can cause every slider motor to be operated, resulting in momentary currents as high as 150 Amps. The SMC unit is optically isolated from all inputs in order to prevent these high currents from upsetting other sensitive circuits via ground loops.
  • Internal circuitry ensures that at switch-on the motors are set to the Off state unless the console has stops selected, in which case the motors will move to their selected positions. Similarly, if the serial data stream is interrupted, the motors will not change state upon restoration of the data unless the data has changed, when they will move to their required positions.
  • The unit is split into two identical halves, of up to 8 stops each, which may be powered either by a single chamber supply or independently from two separate high-current power supplies. This is done principally to allow operation at full load from commonly-available power supplies (which are not paralleled). In most cases, a single 75A - 14V supply would be sufficient.
  • Normal inputs are from the Classic Console Control Computer (CCC) in serial form, but the unit allows for the sixteen parallel stop inputs to be wired directly if preferred. These parallel-wired input controls may be active-high (+5 Volts to +15 Volts = ON) or active-low (0 Volts = ON). Input-polarity selection is automatic. Typical input currents are 2 to 6 milli-Amps per stop from the switch contacts or input source.
  • A common supply return from an external source (of any DC voltage up to +28 Volts, but nominally +12 Volts) for the stop input switches may be included with the stop inputs. Alternatively, the common switch supply of +5 Volts or +12 Volts may be provided by the SMC unit by setting links. Either way, the SMC is isolated from the console system.
  • Output diagnostic LEDs indicate overloads or open-circuit connections.
  • Back-e.m.f. protection is incorporated into the drivers so that no extra diodes or resistors are necessary.
  • Protection is also included against reversed supply connections.
  • Each output is doubly-protected by internal current-limiting and by a self-resetting fuse.
  • The unit consists of a metal box, approximately 18" high (plus mounting flanges) x 9½" wide x 2½" deep. It is recommended that it be installed vertically.
  • No special ventilation is necessary.
  • Inputs are via circular connectors. Screw-terminal strips are used for output connections and each solenoid has its own terminal pair.


Product Documentation

SMC-2 datasheet: View Online | Download


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