Basler Electric MOC21XX through MOC24XX and MOC29XX Motor Operated Potentiometer

INTRODUCTION

The MOC2XXX series of motor operated controls consists of a motor-driven, variable potentiometer and the limit

switches required to provide remote adjustment of resistance or voltage. MOC2XXX controls can be specified for

ac or dc operation with 24-, 32-, 48-, or 120-volt control power.

MODEL NUMBER DEFINITION

The model number for this series of MOCs consists of the prefix MOC2 followed by three digits. The first digit

establishes the input control voltage. The second and third digits establish the output control element

characteristics. Table 1 lists the available model numbers and the corresponding operating characteristics. For

example, MOC2305 has a 32 Vdc control input and a 500 ohm, 2 watt potentiometer.

FUNCTIONAL DESCRIPTION

Control Power

Control power of 24 Vdc/Vac, 32 Vdc/Vac, 48 Vdc/Vac, or 120 Vdc/Vac is applied at terminals 1 and 2. (The MOC

model number determines the nominal input voltage level.) As necessary, it is rectified and decreased to 24 Vdc

at terminals 3 (negative) and 4 (positive). This 24 Vdc is applied to the motor through a network of external

switches which allow application of the 24 Vdc in either polarity. The polarity is determined by the need to raise or

lower the system parameter controlled by the MOC.

Potentiometer Output

The potentiometer serves as the adjusting element of the MOC and is connected to terminals 14. 15. and 16. The

potentiometer wiper arm, connected to terminal 15. moves toward terminal 14 when a raise command is received.

A lower command moves the wiper arm to move toward terminal 16.

Terminals 8 and 13 are connected internally to switches that provide the centering feature for the potentiometer

wiper arm.

Raise and Lower Inputs

When a raise or lower input is received, voltage is applied to the motor, causing it to rotate and move the slider of

the potentiometer.

If a raise input is received, the polarity of the applied motor voltage causes the motor and potentiometer to rotate

in the clockwise direction. This clockwise rotation continues until 24 Vdc is removed from the motor due to

removal of the raise input or activation of the clockwise limit switch.

If a lower input is received, the polarity of the applied motor voltage causes the motor and potentiometer to rotate

in the counterclockwise direction. This counterclockwise rotation continues until 24 Vdc is removed from the motor

due to removal of the lower input or activation of the counterclockwise limit switch.

Rotational Limit Output Contacts

Two sets of SPDT output contacts indicate the rotational limits of the MOC control potentiometer.

The clockwise limit is indicated by contacts at terminals 8. 9. and 10. At the clockwise limit, the contacts at

terminals 8 and 9 open and the contacts at terminals 9 and 10 close.

The counterclockwise limit is indicated by contacts at terminals 11. 12. and 13. At the counterclockwise limit, the

contacts at terminals 11 and 12 open and the contacts at terminals 12 and 13 close.

Dynamic Braking

Dynamic braking is obtained by placing a short-circuit across terminals 5 and 7. An available accessory switch

provides the necessary contact arrangement for the raise/lower function and dynamic braking.

ACCESSORIES

MOC2XXX accessories consist of switch and dial plate sets. Each set is supplied with a rotary, three-position,

momentary-action switch with a pistol-grip handle.

For a switch with a blank dial plate, order Basler part number 9174805106.

For a switch with a dial plate labeled LOWER/OFF/RAISE and FREQUENCY CONTROL, order Basler part

number 9174805107.

For a switch with a dial plate labeled LOWER/OFF/RAISE and VOLTAGE CONTROL, order Basler part number

9174805108.