Wavelength Technology

笢恅唳
Ronar-Smith® Laser Optics
Temperature controller--WTC3293-14000 Series
GENERAL DESCRIPTION:

Simply stable temperature control. Wire your thermoelectric cooler and thermistor to the board with the cable provided. Add the appropriate DC power supply and indicate the expected voltage on the jumper. With the output disabled, adjust the on-board 12-turn trimpot and watch the setpoint temperature change on the 4-digit display. Switch to Actual and display your thermistor temperature. Watch the LED tree to see ※over / under temperature§ or ※stable at setpoint§ status. Enable the output current and watch the temperature quickly lock in on the setpoint.

FEATURES:
• Low noise, maximum temperature stability commercially available
• Display thermistor temperature directly - no tables to convert resistance to temperature
• LED indicator shows over temperature, stable at setpoint, or under temperature status
• Adjust setpoint with a 12-turn potentiometer or an external voltage
• Control temperature using a 10k次 thermistor
• Fixed resistors set Proportional Gain, Integrator Time Constant, and thermoelectric current limits
• Enable/Disable Output Current Switch
• Includes Output Cable & DC Power Supply
• Works with a wide range of thermoelectrics



Quick Reference: CONFIGURATION

The display is calibrated for a specifi c 10 kohm thermistor, the TCS610:
where is in Kelvin; R is in ohms,
1/T = A + B(ln R) + C(ln R)3
A = 1.1279E-3; B=2.3429E-4; C=8.7298E-8
Bias Current is also chosen for this thermistor: 100米A
Fuse: For safety, a 3A fuse is included on the board. Replacement part number is Littelfuse 297 003
(ATO MINI 3A).
Power supply input jack accepts a 2.5mm diameter plug.

ORDERING INFORMATION:
 The boards are confi gured for the power supply you intend to use.
﹛
﹛ +7V or +9V +12V
Order WEI part number: [WTC3243 & thermal
solution kit included]		 WTC3293-14001 WTC3293-14002
Power Supply:               Order WEI part numbers: 7V DC supply: PWRPAK-7V  9V DC supply: PWRPAK-9V 12VDC supply: PWRPAK-12V

Note: Control temperature range for the 10k次 sensor is 10∼C to 50∼C

OPERATING THE WTC3293-14000.

STEP 1: SELECT POWER SUPPLY VOLTAGE and INSTALL JUMPER

This board has been designed to work with various thermoelectrics. The power supply voltage must
be tailored to the resistance of the thermoelectric to keep the WTC3243 intact. You need a power
supply voltage high enough to drive the thermoelectric, but not too high to overdrive the WTC3243.

1. Determine your maximum thermoelectric voltage and current: Vmax, Imax.
2. The WTC3243 drops about 1.7V, so the minimum power supply voltage is Vmax + 1.7V.
3. Choose from available power supplies. For example, if your thermoelectric will need 5V, the minimum supply voltage is 6.7V. WEI offers a 7V power supply.
4. Calculate the actual power dissipated in the WTC3243: Power = Imax x [Vsupply - Vmax]. For example, if you need 1.5Amps and plan to use a 7V supply, Power = 1.5 x [7-5] or 3 Watts. The maximum power dissipation of the WTC3243 is 9 Watts (with fan & heatsink).

Install a jumper indicating which power supply you have selected on the header near the DC input plug. 

NOTE: When you plug in the supply, make sure the Enable Switch is OFF. Do not operate with a voltage less than 7V.

WHY? The WTC3243 is designed to drive currents as high as 2.0 Amps. The resistance of the thermoelectric will create a voltage drop across the thermoelectric proportional to the current (Voltage = Current x Resistance). The voltage drop across the WTC3243 will equal the power supply voltage minus the thermoelectric voltage. If the power dissipated by the WTC3243 is too high (Power = Voltage x Current), the WTC3243 will overheat and be destroyed.

STEP 2: SELECT HEAT AND COOL CURRENT LIMITS

To protect the thermoelectric from over current damage, set the heat and cool current limits as follows.
The standard product is shipped with 2.00k次 resistors for 0.5A cooling and heating limits.
Resistors should be 5% metal fi lm. Carbon resistors will introduce noise and instabilities.

Table 1
Current Limit Set Resistor vs Maximum Output Current
﹛
Maximum Output Currents (Amps)

Current Limit Set Resistor,(k次) RA,RB

Maximum Output Current (Amps)

Current Limit Set Resistor, (k次) RA,RB
0.0  1.60  1.2  3.05
0.1 1.69  1.3  3.23
0.2 1.78 1.4 3.43
0.3 1.87 1.5 3.65
0.4 1.97 1.6 3.88
0.5 2.08 1.7 4.13
0.6 2.19 1.8 4.42
0.7 2.31  1.9  4.72
0.8 2.44 2.0  5.07
0.9 2.58 2.1 5.45
1.0  2.72 2.2 5.88
1.1 2.88 2.3 6.36

OPERATING THE WTC3293-14000

STEP 3: SELECT PROPORTIONAL GAIN AND INTEGRAL TIME CONSTANT

To optimize the control loop (minimize overshoot, settling time, avoid cycling, etc.) change the control parameters as shown below. If the load doesn＊t stabilize, contact the factory for troubleshooting advice. Resistors should be 5% metal fi lm. Carbon resistors will introduce noise and instabilities.


Table 3 Proportional Gain and Integral Time Constant settings

Load Size P value; Resistance I value; Resistance
Small (~0.25 oz)* P = 10 A / V
R = 10k次		 3 seconds
R = 31.6k次
Medium P = 10 A / V
R = 10k次		 3.75 seconds
R = 24.9k次
Large P = 20 A / V
R = 24.9k次		 4.5 seconds
R = 20k次

*Default

Note: If you want to use values not listed, use the web based WTC3243 design calculator to determine resistance values.
STEP 4: WIRE OUTPUT CONNECTOR

Connect the Thermoelectric wires to the Red and Black cable wires as shown. If the polarity is reversed, the system will only heat. Connect the thermistor wires to the Green and White cable wires (polarity is not important).

Table 4 - OUTPUT CABLE wiring for Thermoelectric
PIN # Wire Color Function
1 RED OUTPUT B - Positive TE wire
2 GREEN SENSOR +
3 WHITE SENSOR -
4 BLACK OUTPUT A - Negative TE wire

Table 5 - OUTPUT CABLE wiring for Resistive Heater
PIN # Wire Color Function
1 RED OUTPUT B - One side of RH
2 GREEN SENSOR +
3 WHITE SENSOR -
4 BLACK OUTPUT A - NO CONNECT
Connect other side of RH to V+ Change RLIM A to 1.5k次 to limit the cooling curent to ZERO.
Resistive Heater operation assumes NTC sensor.

Note: If you want a wiring diagram with values, use the online WTC3243 design calculator.

OPERATING THE WTC3293-14000
STEP 5: VIEW THE SETPOINT and ACTUAL TEMPERATURE


The switch next to the setpoint potentiometer determines whether Setpoint or Actual temperature is displayed. When the setpoint is displayed, the rightmost decimal point is lit. The resistance to temperature conversion software assumes the thermistor bias current is 100米A and the thermistor is characterized by the Steinhart-Hart relationship: 

 1/T = A + B(ln R) + C(ln R)3


where T is in Kelvin; R is in ohms, A = 1.1279E-3; B=2.3429E-4; C=8.7298E-8 (TCS-610) 


If another thermistor or bias current is used, the temperature display will not be properly calibrated. To use another sensor or change the calibration, contact the factory.



STEP 6: ADJUST THE SETPOINT TEMPERATURE


The setpoint temperature can be adjusted from 10 to 65∼C either by using the onboard 12-turn potentiometer.


The VSET wire pads can be used as test points to monitor the potentiometer setting or for
connecting an external voltage source (such as a function generator). If an external voltage source is used, set the setpoint potentiometer approximately mid-range (1 to 1.5V). The input voltage range is 0 to 2.5V which corresponds to 0 to 25k次 of thermistor resistance. [Transfer function is 10k次 / V.] 


STEP 7: ENABLE THE OUTPUT CURRENT & MONITOR IN-RANGE STATUS


The switch next to the In-Range indicator enables and disables current through the thermoelectric. The green LED on the In-Range indicator lights when the actual temperature is within 0.05∼C of the setpoint. If the actual temperature exceeds the setpoint, the upper LED will light. If it is below the setpoint temperature, the lower LED will light.
MECHANICAL SPECIFICATIONS



Max height from top side of PCB to fan is 1.5§
Standoffs are 0.625§ tall
Board thickness is 0.60§
Allow 0.375§ clearance from bottom side of PCB for airfl ow.

Wavelength Technology Singapore Pte. Ltd.
BLK 2, Bukit Batok St.24, #06-03/06-09, Skytech Building, Singapore 659480
Tel: 65-65649624 Fax: 65-65643862 Email: info@wavelength-tech.com Website: www.wavelength-tech.com