Digital instrument for walk-in and display coolers with natural defrost function by compressor shutdown and permanent ventilation. It features a 16Amp powerful relay that commands up to 1HP compressors without the need of a magnetic contactor, associated a timer with a programmable cooling and defrosting times. It also has a programmable Digital Filter which prevents the compressor from constant switches while the door is temporarily open. This filter aims to simulate an increase in the environmental mass through sensor 1 (S1) thus increasing the thermal reaction time (thermal inertia). Besides, an internal datalloger to storage data, which enables to record the average temperature and the controller output status at user-defined time intervals. Therefore it allows to collect the data continuously without the need of a computer permanently connected, once all the data can be later sent via RS-485 serial communication.