cool down time the microprocessor controller 13 will have a default mode which will be activated if no information from the operator is forthcoming and the microprocessor controller 13 has been instructed to begin the drying process once the microprocessor controller 13 has been activated in block 101 it will energize the tumbler motor 25 in block 102 an enabling signal will also be applied to the burner control circuit 23 as depicted in block 103 initially the temperature will increase from ambient to the set point drying temperature preselected by the operator the microprocessor controller 13 monitors the temperature by measuring the exhaust air temperature with a temperature sensor 15 as is shown in decision block 104 once the temperature has stabilized at the set point temperature block 105 will disable the burner 7 the drying cycle proceeds in a loop until the drying time t 0 has expired and after 34 107 34 as determined by decision block 107 continuously checking set point temperature 108 the burner 7 is enabled or disabled by block 109 and block 110 depending on whether the temperature is above or below the desired temperature t 1 when the elapsed time equals the preprogrammed time set into the microprocessor controller 13 by the operator through keyboard 29 the microprocessor controller 13 disables the burner 7 at block 111 and enters decision block 112 block 112 is the decision block which insures that the temperature is.