Temperature Controller Technology and Applications

System Temperature Control Technology

Whenever you run a laser device, only a portion of the supplied power is converted to a light signal. The remainder is released in a form of heat, which, if left uncontrolled, can damage parts of your system, effectively reducing its longevity. This is particularly relevant for laser diodes as well as many other optical electric devices. For instance, a GaAs laser diode that operates in the near-infrared typically has a 10 000 hours working lifetime if the temperature is kept at 25 degrees C with temperature control. However, if no temperature controller is used, this amount can reduce by a factor of 2 for every 10 degrees above the ideal temperature. Consequently, it is smart to adopt some form of a cooling module operated by a temperature controller that could prevent potential damage and save your money. It also assures the quality of your laser beam, as redundant heat could impair the light emitting facets of your laser. This would lead to a loss of both the quantity and quality of the light produced. In order to avoid that, it is recommended to utilize an appropriate temperature controller coupled with a passive and/or an active cooling system.
 

 
Passive cooling system simply acts as a heat drain to which excess heat is transferred. A water tank with a fan is a common solution. While this may be enough for some low- and medium-power systems, a TEC controller with a Peltier module would provide a much safer approach.

TEC Controller Modules

TEC, which stands for thermoelectric cooler (also called a Peltier device), is a small-scale powered conductive ceramic. It is operated by a temperature controller, which cools one of its sides while transferring the heat to the opposite surface. The laser mount then acts as a heat sink for the hot side of a Peltier device. The cold side, on the other hand, is separated from a laser module with a copper or aluminium cold plate. Using a copper plate is preferred due to its superior thermal properties and a uniform temperature distribution. The control loop is completed by connecting a temperature sensor from the TEC controller to the cold plate. At Opt Lasers, we can offer you a pre-set system with a dedicated slot in the cold plate in which the thermistor from the TEC controller is already embedded. Such a solution offers the best response times since it negates the effects of thermal inertia. For high power applications, it is advised to add a water cooler by mounting it by the hot side of the TEC module. For optimal cooling, Opt Lasers offers a variety of professional cooling modules, Peltier modules and the corresponding TEC controllers. 

Currently, there are two major types of a TEC controller that are widely used. These are an on/off temperature controller and a PID temperature controller.

On/Off Temperature Controller Systems

The most basic form of heat damage prevention is utilizing an on/off type of temperature controller. Such temperature control switches on only if the sensed temperature is above (for cooling applications) or below (for heating applications) a certain setpoint. There is no intermediate state involved and the controller applies 100% of the power until the setpoint is reached. This type of a temperature control system is typically utilized in systems which do not require precise temperature control.

PID Controller Modules

Nevertheless, the most effective way to protect your device is to employ a PID TEC controller. PID controllers are being widely used for industrial process control due to being standard, time-tested and well-understood devices. In fact, approximately 95% of automated industrial processes utilize PID temperature controllers. Furthermore, as a result of process uncertainties, an elaborate temperature control system doesn’t necessarily provide better efficiency for a given set-up than a well-tuned PID temperature controller.

The PID acronym stands for Proportional, Integral and Derivative, and it refers to the three control processes that occur in this TEC controller: 

• The Proportional part in the temperature controller calculates a temperature adjustment that is directly proportional to the difference from the setpoint. The higher the proportion coefficient, the lower the power output for the same temperature difference;
  
• The Integral part looks for a systematic error between the setpoint and the temperature read by the TEC controller’s thermistor. The higher the integration coefficient, the slower the accrued integration term;
  
• Finally, the Derivative part in the PID TEC controller predicts future temperature variance and adjusts temperature accordingly. The higher the derivative coefficient, the stronger the system response to disturbances.

All in all, a PID temperature controller provides a control scheme that is rapid, pro-active, accurate and capable of swift response to sudden unknown changes. Temperature controllers and cooling modules from Opt Lasers offer professional heat management as well as additional functionalities. The Opt Lasers’ TEC-8A-24V-PID-HC-RS232 Programmable Temperature Controller boasts professional design, 0.1°C temperature accuracy and high maximum current at a competitive price. It also utilizes UART communication that allows you to properly tune PID coefficients that will let you reach unparalleled process efficiency and stable temperature, ensuring a long lifetime of your laser diode. Furthermore, Optlasers is happy to offer customized TEC controllers even for the most demanding of customers and can go from just an idea to a ready product in as little as 5 weeks. Customization of your TEC controller can be cost-effective in both small and large quantities and can consist corresponding adjustments:

• Addition of a touchscreen interface;
• Higher maximum current and/or voltage;
• User-adjustable or pre-set PID settings;
• Acceptance of diversified sensor types (e.g. thermistors, RTDs etc.);
• Automatic shut-off above a certain temperature;
• Multiple channels controlled independently by a TTL or an analog input;
• Communication with a computer via UART, RS-232, RS-485 or USB; 
• Bipolar output for cooling and heating.

Feel free to reach out to us if you have any questions or would like to present your requirements for a customized temperature controller.