This open board electronic temperature controller is specifically designed with a proportional integral control algorithm to provide the most precise control to thermoelectric (Peltier effect) modules at the most economical price. The H bridge control provides a seamless transition between heating and cooling eliminating dead spots. Green LED for heat and blue LED for cooling indicate mode and simultaneous illumination indicates the load circuit is off due to an open sensor. Pulse Width Modulation controls the power level in the thermoelectric module at a base frequency of 1Khz. Power resolution is one of ±250 steps in the load circuit control.