Circaflex™ is designed to interact with a number of devices and sensors without the need for electrical engineering or programming. However the power requirements of a TEC have three special requirements. First TEC's often require high current, such as 1-10 Amps. Secondly, the polarity must be reversed to change from heating to cooling. And finally, in order to drive a variable cooling or heating, a Pulse-Width-Modulated signal is commonly required.

In addition to those requirements, Circaflex™ also applies two other unique features. First is a dedicated fuse in case of a short circuit or other condition which draws more current than expected. 

The base version of Circaflex™ addresses two of those requirements. A number of PWM signals are pre-programmed and wired on the standard breakout board, and are configured with a duty cycle and a pulse period. With a TEC a pulse rate of 100-10000 Hz is appropriate. Also included on that standard board is a set of physical connections with a trace width and fuses rated at 2Amps. More current simply requires some further accommodations.

For the ability to change polarity, Circaflex™ but has undergone custom modifications in a few applications to achieve the requirements. Using a series of Solid-State Relays or MOSFET's, the most common configuration to drive a TEC is an H-Bridge, which changes the polarity of signals according to a control signal. Technically, four SSR's or MOSFET's must be switched, and some controllers will use a single control line, invert it, and use those two signals to control the switching.  Using the TTL digital control lines on Circaflex™ and the internal logic on the FPGA, we can control an H-Bridge using two digital lines. 

In order to prevent damage, it's very important that the switching of the H-Bridge be managed properly. The circuit which controls the H-Bridge switching must NOT be independent digital lines controlled by software, otherwise an incorrect condition could be propagated which would cause all four switches to be on (or off) resulting in a short to ground. Circaflex™ does this correctly by inverting the line in hardware, but without the need for circuitry to invert the control line. It is accomplished by the programmable logic gates in the FPGA, so that doing one or more can be managed by simply copying and pasting code in Circaflex™. 

The use of a TEC is very common in Medical Devices and BioTech Devices, along with numerous other actuators and sensors which make up the unique capability of a product or device. Circaflex™ was designed with these kinds of needs in mind and has managed TEC's in several customer applications.

Consider the use of Circaflex™ for your product, and the standard connector board can be used to control TEC's with a few components added. Yet it might be a wise starting point to speak to Cyth's Applications Engineers to help you decide the best way to proceed on your project.