© 2023
22
WHY5640 TEMPERATURE CONTROLLER
TROUBLESHOOTING
PROBLEM
POTENTIAL CAUSES
SOLUTIONS
Temperature is decreasing
when it should be
increasing
-OR-
Temperature is increasing
when it should be
decreasing
The TEC may be connected
backwards to the WHY5640
The convention is that the red wire on the TEC module connects to TEC+
(OUTB) and the black wire to TEC- (OUTA). If your TEC is connected in
this manner and the problem persists, the TEC module itself may be wired
in reverse. Switch off power to the system, reverse the connections to the
WHY5640, and then try again to operate the system.
TEC wiring polarity is dependent on the temperature sensor type (NTC vs.
PTC). Verify that the polarity is correct for the sensor type you are using (see
Temperature increases
beyond setpoint and will not
come down
The heatsink may be
inadequately sized to dissipate
the heat from the load and
the TEC module, and now the
system is in
thermal runaway
Increase the size of the heatsink, add a fan to blow air over the heatsink,
and/or reduce the ambient air temperature around the heatsink.
The TEC and heatsink are
not adequately sized for the
thermal load
The heat being generated by the load may be too great for the TEC to
pump to the heatsink; a larger TEC may be needed. Consult our Technical
Note
TN-TC01: Optimizing Thermoelectric Temperature Control Systems
and Application Note
AN-TC09: Specifying Thermoelectric Coolers
.
Temperature does not
stabilize very well at the
setpoint
There may be poor thermal
contact between components
of the thermal load
Use thermal paste or washers between the load / TEC and the
TEC / heatsink interfaces. Ensure the temperature sensor is in good thermal
contact with the load. Contact the TEC manufacturer for recommended
mounting methods.
Unit may be operating
outside the ideal region of the
temperature sensor
The sensor type and bias current should be selected to maximize sensitivity
at the target temperature. Thermistors provide the best performance,
particularly for applications where a single setpoint temperature must
be accurately maintained. For example, at 25ºC a 10 kΩ thermistor has
a sensitivity of 43 mV / ºC, whereas an RTD sensor has a sensitivity of
4 mV / ºC.
Proportional control term may
be set too high
Reduce the value of the proportional term. For more information, reference
our Technical Note
TN-TC01: Optimizing Thermoelectric Temperature
Heatsink may not be sized
correctly or may not have
adequate airflow
Ambient temperature disturbances can pass through the heatsink and
thermoelectric and affect the device temperature stability. Choosing a
heatsink with a larger mass and lower thermal resistance will improve
temperature stability. Adding a fan across the thermoelectric’s heatsink may
be required.
Temperature does not
reach the setpoint
Current driven to the TEC or
heater may be insufficient
Increase the current limit – but DO NOT exceed the specifications of the
TEC or heater.
The controller may not have
sufficient compliance voltage
to drive the TEC or heater
Increase the power supply voltage; be certain to verify that the controller is
within the Safe Operating Area with Wavelength’s Temperature Controller
SOA calculator:
www.teamwavelength.com/support/design-tools/soa-tc-calculator/
The sensor may not have
good contact with the heatsink
and load
Use thermal paste or washers between the load / TEC and the
TEC / heatsink interfaces. Contact the thermoelectric manufacturer for their
recommended mounting methods.
The WHY5690 is not
producing current
Improperly configured Enable
ON / OFF Switch
Make sure that the Enable ON / OFF switch is set to the ON position.
The High Limit may be turned
all the way counter clockwise
(CCW)
Turn the Limit trimpot (LIMA or LIMB) clockwise to adjust the current limit.
Temperature is slow to
stabilize and is not within
the specifications with
Resistive Heaters
Setpoint temperature is
set close to the ambient
temperature
Set the temperature at least 10ºC above ambient when using a resistive
heater. A resistive heater is unable to precisely maintain temperatures near
ambient. Once the temperature overshoots the setpoint, the controller
turns off and relies on ambient temperature to cool the load. If setting the
temperature 10ºC or more above ambient is not possible, then choose a
thermoelectric controller, which can alternately heat and cool the load to
maintain a more precise setpoint temperature.
