Model TC-24-25 Temperature Controller

APPLICATION
The TC-24-25 is a bi-directional controller for thermoelectric assemblies. The "H" bridge configuration of the solid state MOSFET output devices allows the bi-directional flow of current through the thermoelectric modules. This allows the thermoelectric assembly to both heat and cool. Highly efficient N-channel output devices are used for this control mode.

This controller is PC programmable via an RS485 communication port for direct interface with a compatible PC or via an RS485 to RS232 converter (included). The RS485 communications interface has 1500 VAC isolation from all other electronic circuitry minimizing interference from noise or errant signals caused by common ground loops. The easily accessible communications link permits a variety of operational mode configurations. Field selectable parameters or data acquisition in a half-duplex mode can be performed. This controller will accept up to 32 addressable interfaces, over a maximum of 4,000 feet of communications cable.

This controller can be ordered without the RS485 to RS232 converter and cables in OEM quantities to reduce cost.

Once the desired set parameters are established, the PC may be disconnected and theTC-24-25 becomes a unique, stand-alone controller. All parameter settings are retained in non-volatile memory.

The user friendly communications software requires no prior programming experience to establish operation. A command set can be provided for qualified personnel to program a software interface or use as an embedded control. The software is designed to run on Windows 95 and higher PC's.

Mechanically, the control printed circuit board is mounted to a metal bracket that is suitable for either horizontal or vertical orientation. Input and output connections are accessible via screw type terminal strips, fast-on terminals and 0.100 center connector.

TECHNICAL DESCRIPTION
The TC-24-25 is capable of operating from an input supply voltage of 12 through 24 VDC, common to many available thermoelectric modules. The self-contained MOSFET output devices deliver load currents from 0.1 to 25 Amperes (NOTE: Consult appropriate installation instructions for power supply and heat sinking requirements for high current operation). This unit will control total load power up to 680 W with a finite temperature resolution of 0.05°C.The output signal to the thermoelectric module is Pulse Width Modulated and is PC selectable for either 675 Hz or 2700 Hz operation. Pulse Width Modulation averages the amount of energy provided to the module and reduces the extreme temperature excursions that are experienced with an "on / off" system. This tends to extend the life and reliability of the thermoelectric devices. The PWM control scheme affords control stability of up to ±0.05°C at the control sensor for certain applications. The controller tuning structure allows designation of a variety of control features. The computer set value provides for manual control of the output and polarity, from 0% to 100% of load power. Proportional bandwidth (P) in degrees, integral reset (I) in repeats per minute, and the derivation rate (D) in minutes may be configured for P, PI, PD, or PID control. In addition, a deadband control (on/off) with an adjustable hysteresis may be selected. Differential temperature control is offered when two input sensing thermistors are chosen. A control temperature range of -20°C to 100°C is standard when using the thermistor sensor probe for the PC's primary set temperature. Additional external set temperature input types may be selected, including a remote set temperature potentiometer, a 0 to 5 VDC signal, and a 0 to 20 MA current loop. These secondary inputs are used to define and "map" the secondary input to an adjustable temperature range. Differential set temperature control may also be selected from this configuration menu. All temperatures may be consistently displayed in °C or °F via the PC. Differential control is accomplished by selecting the primary set temperature with the second thermistor input and establishing the offset with the computer set temperature. The unit will control the differential between Input 2 (reference temperature) and Input 1 (actual system temperature).Two types of control output modes may be selected. This determines the direction of the current flow through the thermoelectric module during the heat cycle. This current flow may be from Wire Point WP1 ( ) to Wire Point WP2 (-). Alternatively, this current flow may be reversed from WP2 ( ) to WP1 (-) as selected in the configuration menu. Several alarm types may be selected which provide a 5 VDC output, rated for 25 MA of current. They consist of no alarm function, tracking alarm, and fixed value alarm. Alarm set temperature values are entered in the setup menu. The computer-controlled selection is available for additional embedded controller input/output options. The alarm setup menu also provides for selection of an alarm latching condition. The alarm sensor may be either the control temperature sensor or a secondary thermistor sensor. Using a secondary thermistor embedded in the thermoelectric assembly's heat sink and controlling the setpoint via computer, the alarm can be configured as an overtemp thermostat for the heat sink. This option is available when the temperature setpoint is programmed via an external computer. The various alarms have the ability to determine the status of the output power to the thermoelectric assembly. Power may be maintained during an alarm condition or the main power may be shut down.

The TC-24-25 comes with one MP-2379 thermistor. If you would like to purchase additional thermistors, please indicate when ordering.

SPECIFICATIONS

• Self-contained, 0.1 to 25 Ampere load rating
• Bi-directional control for heating and cooling applications (H-Bridge operation)
• Input voltage from 12 to 24 VDC
• PC programmable via RS232 or RS485 communications port
• Control temperature of -20°C to 100°C with standard series sensor
• Proportional (P), Integral (I) and Derivative (D) control that can be selected as P, PI, PD or PID; or on/off with an adjustable hysteresis
• Pulse Width Modulation of output
• Selectable modulation frequency of 675 Hz or 2700 Hz
• Control stability of ±0.05°C
• Temperature resolution of 0.05°C
• No computer programming experience is required to use the communications software program
• Non-volatile memory retention of parameters
• PC configurable alarms for 5 VDC at 25 MA
• 1500 VAC isolated RS485 communications interface
• Set temperature selectable
• PC set with controller stand alone operation
• Remote user set temperature potentiometer
• 4 to 20 MA current loop
• 1V to 5V adjustable range
• Differential temperature control
• Physical dimensions: 15.2 x 9.2 x 7.0 cm
• External power supply required