One such power supply that accepts an analog input is the Cotek AE series programmable switching power supplies
(http://www.cotek.com.tw/). These power supplies accept a 0 to 5 volt input signal which causes the output voltage of the
power supply to vary from 0 V to its full-scale voltage. The controller’s analog output signal can also be modified to limit its
output signal which, in turn, will limit the output voltage from the power supply.
RAMP / SOAK PROGRAMMING
The controller has a built in ramp and soak capability that provides eight different steps programmable as ramp or hold
(soak) functions. Each step can be repeated or groups of steps can be repeated multiple times. This is useful in creating a
multi-step procedure with various temperatures and times for complicated processes or tests.
PROGRAMMABLE, ENERGY SAVING, CONTROL MODE FOR COOLING AND HEATING ENCLOSURES
This control mode provides an energy efficient method for controlling the temperature in an enclosure only when truly
needed yet provides greater capability and thermoelectric cooler life than what an ON/OFF or dead band control mode
could provide. This mode allows the user to select a three different temperature ranges: (1) a temperature range where
no cooling or heating is needed and no output power is sent to the TE Device, (2) a temperature range whereby the
controller will proportionally increase cooling power as the temperature increases, and (3) a temperature range whereby
the controller will proportionally increase heating power as the temperature decreases.
TWO ALARM OUTPUTS
Two individual alarm outputs, each capable of sinking up to 2 A of current, are provided. These alarms can be triggered
based on sensor temperatures.
MULTI-SPEED FAN CONTROL OR OTHER LOAD CONTROL
The Alarm 1 output can be configured to provide PWM speed control of a fan (fan must be specifically designed for speed
control) with several customizable settings. Speed control is programmable as a function of the main controller’s output
power, and the control points are programmable via software. For example, the fan can be run at high speed only when
increased cooling capacity is needed, and at a low speed or off when the cooler is operating at a low capacity. The polarity
of the output signal can be reversed, so both two wire and three wire PWM controllable fans can be used. The PWM
output frequency can be adjusted to make it adaptable to a wide range of fans.
The fan speed control includes a setting to give the fan 100% power for a user-programmable number of seconds when the
output is first turned on. This operates the fan at full power to make sure the fan is spinning before reducing power. This is
most useful when low output levels are chosen.
USER PROGRAMMABLE SENSORS
In addition to the pre-programmed thermistor curves, a user programmable sensor is available. Through the computer
program a custom sensor curve (look-up table) can be created, saved in a separate file on the computer, and uploaded to
the controller. An infinite number of sensors can be created for use in the controller as sensor 1 or sensor 2.
CONTROL RANGE
The TC-720 is supplied with one MP-3193 thermistor which provides a control range from -20 °C to +100 °C. For controllers
with firmware revision K or later, the control range can be extended to -60 °C to +110 °C using the MP-3176 thermistor.
(Controllers with firmware revision J or earlier provide a control range from -40 °C to +70 °C using the MP-3176.) Several
other thermistor types are preprogrammed into controller to provide different control ranges such as 0 °C to +150 °C, for
example (when using optional thermistors). In addition, a User Programmable Sensor table can also be programmed into
the controller allowing it to read temperatures as low as -327.67 °C and/or up to +327.68 °C, subject to sensor type.
OVER CURRENT ALARM
The controller can be set to turn off the output if it exceeds a set current level. The controller will attempt restarting a
user-defined finite or an infinite number of times. This is useful for conditions that cause a temporarily high current level,
and instead of remaining off when the condition clears the unit will resume normal operation. (NOTE: This is not an analog
current limit, the circuit simply senses current levels and turns the output off if an over current condition is detected).
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