GB1297807A - - Google Patents

Abstract

1297807 Automatic speed control SIMCOM CORP 26 Nov 1969 [30 Dec 1968] 57957/69 Heading G3R [Also in Divisions G4 and H2] A film carrying digital data used to identify invalid credit cards (Division G4) carries speed control marks 104 along one edge, and is transported between two shaded pole motors 100, 102. Light passes through the marks to cause light sensor 212 to feed pulses to an amplifying transistor 240 which via capacitor 244 and resistor 246 produces an output signal proportional to the speed of the film. The signal is fed to a full wave rectifier formed by diodes 248, 250 which produce a negative output which operates to reduce the normal positive potential appearing across capacitor 252 when the film is not moving. The potential on the capacitor is adjusted by potentiometer 254 to forward bias transistor 257. When the film speed reaches its required value transistor 257 ceases conducting and transistor 260 conducts. Transistor 260 controls transistor 234 which controls the discharge of a capacitor 228 connected by relay contacts 226 to one of the motors 100, 102. The film is alternately driven from a reel coupled to one motor to a reel coupled to the other motor so that one motor always rotates in a clockwise (CW) direction the other in a counter-clockwise direction (CCW). Thus one motor is directly driven and the other is controlled by the above described circuit to provide a desired amount of tension. A simplified form of motor control is shown in Fig. 9 wherein motor 100 is controlled by triac 400 and motor 102 is controlled by triac 402. The triacs are under the control of respective reed switches 404, 406 which are operated by the motor associated with the other triac. The film strip 80a carries an opaque portion 408, along one edge which is detected by sensor 410 to forward bias transistor 412 to switch off transistor 413 and render transistor 414 conducting. Transistor 414 operates reed switch 404 and motor 100 is energized. Motor 100 intermittently operates switch 406 to operate triac 402 and intermittently energize motor 102 to produce controlled drag. At the other end of the film opaque portion 417 causes the motors to be stopped and the absence of an opaque portion at the other edge ensures that motor 102 is energized to return the film when operation is commenced.