TE Technology TC-24-25 - Manual (Page 4)

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General Description
The TC-24-25 is a bi-directional control for independent thermoelectric modules or in conjunction with
auxiliary or supplemental resistive heaters for both cooling and heating applications. The "H" bridge
configuration of the solid state MOSFET output devices allows for the bi-directional flow of current
through the thermoelectric modules. Highly efficient N-channel output devices are used for this control
mode.
This controller is programmable via an RS485 communication port for direct interface or via an RS485
to RS232 converter which can then be connected to the serial communications port of a computer. 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.
Once the desired set parameters are established, the TC-24-25 can be disconnected from the computer,
and it 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 is provided for qualified personnel to program a software interface or use as
an embedded control.
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 and fast-on terminals.
Technical Description
The TC-24-25 is capable of operating from an input supply voltage of (12 to 28) VDC, common to many
available thermoelectric coolers. The self-contained MOSFET output devices deliver load currents from
(0.1 to 25) A. (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 0.1 °C or 0.1 °F.
The output signal to the thermoelectric module is pulse-width modulated and can be set for either 675 Hz
or 2700 Hz operation. Pulse-width modulation (PWM) averages the amount of energy provided to the
module and reduces the extreme temperature excursions that are experienced with a thermostatic control
system. This tends to extend the life and reliability of the thermoelectric devices. The PWM control
scheme affords control accuracy to within ±0.1 °C or ±0.1 °F at the control sensor.
The controller tuning structure allows designation of a variety of control features:
1) The Computer Set Value provides for manual control of the output, from 0% to ±100% of load power.
2) Proportional bandwidth (P) in degrees, Integral reset (1) in repeats per minute, and the Derivative rate
(D) in minutes may be configured for P, PI, PD, or PID control.