ELECTRIC HEATER POWER CONTROL DEVICE Russian patent published in 1997 - IPC

FIELD: electrical engineering. SUBSTANCE: device has push-button power setting element and overpower switch. Pushing one button increases power of energized heating elements and pushing other button decreases this power. Push-buttons are connected through resistors to power supply and first button is connected through pulse shaper to input of first NOR gate, second one being connected through NOT gate to second input of OR gate. First input of OR gate is connected to output of NOR gate and its output, to complementing input of binary reversing counter whose reversing input is connected to output of first NOR gate, and initial state setting input is connected to output of initial setting unit. Counter outputs are connected to decoder and those of the latter, to display. In addition, decoder output "0" is connected to second contact of second button, output "5", to second contact of first button, and output "3", to second input of first NOR gate through overpower switch. Device also has heated entity and its temperature sensor, and zero supply voltage detector connected to inputs of second NOR gate, three AND gates whose first inputs are connected to output of second NOR gate and second ones, to counter outputs, first, second, and third heating elements connected to ac power buses through first, second, and third switches, respectively; control input of each switch is connected to respective AND gate output, safety thermal switch placed between ac supply mains and ac supply buses, as well as power supply connected to them. EFFECT: improved reliability of power control. 7 dwg