Temp. regulator for fixing process in photocopier - has control stage galvanically separated from measuring stage and receiving optical signal from lamp acting as gradient amplifier

摘要

A temp. measuring stage used to maintain a constant temp. in the fixing process of a photo copier, includes opto-electrical coupling with the control stage. The measuring resistor (1) is located as near as possible to the heater (3). An adjustable resistor (4) is varied to control the output of a transistor (6) controlling a lamp (7). The control stage (II) receives the optical signal (8) and uses it to switch the main stage (11) controlling the heater. The measuring and control stages are galvanically separated by the lamp so that the former can be driven by a weak d.c., e.g. 24v. The latter, however, can be supplied by mains a.c.