Control circuit

摘要

1,028,877. Transistor switching circuits. SQUARE D CO. May 1, 1964 [May 1, 1963], No. 18293/64. Heading H3T. [Also in Division H2] A circuit T for timing the various operations of a welding process comprises a capacitor 44 which during its charging periods can be sequentially associated with any one of resistors R2-R5 in an OR module and which is provided with a circuit including a NOR unit N14, a diode D1 and a resistor R1, whereby the capacitor can be rapidly discharged. When a terminal IT2 receives a " 0 " signal the NOR unit N14 is non-conductive and the capacitor 44 charges from a common positive supply COM over a circuit including terminal IT1, terminal OOR1 in the OR module, one of the diodes D2- D5 and one of the resistors R2-R5. When the voltage across the capacitor 44 reaches a given value Zener diode ZD breaks down and a signal is applied to NOR unit N15 to change the signal appearing at the output terminal OT1 of the NOR memory N15, N16. This change of signal is transmitted to the input terminal IT2 thus rendering the NOR N14 conductive to establish the discharge path for the capacitor 44. The particular one of the resistors R2-R5 associated with the charging of the capacitor 44 at any given operation in the welding process is selected by the appearance of a " 1 " signal at each of the diodes D6-D14 associated with a junction 48 or 50 or 52 or 54.