AUTOMATIC CONTROL DEVICE FOR EXPOSING FOR COPYING MACHINE

摘要

PURPOSE:To make a copying machine easier to operate by constituting a titled device in such a way that optimum copying is automatically accomplished against fluctuation in source voltage or with various originals. CONSTITUTION:An AC power source 14 and a bidirectional thyristor 15 are connected in series to an exposing lamp 3. A voltage forming circuit 16 is connected to the power source 14 and outputs the voltage corresponding to the voltage at both terminals of the lamp 3 when the thyristor 15 is turned on. The output voltage thereof and a reference voltage 17 are compared by a comparator 18 and the signal corresponding to the magnitude of the difference is outputted if there is a voltage difference. The output signal of the comparator 18 is supplied via a trigger pulse generating circuit 19 to the gate of the thyristor 15. The quantity of the light corresponding to the original is therefore selected by varying the variable resistance which sets the reference voltage. The copying machine is thus made easier to operate.