long time timing circuit

(1) Circuit Principle: Figure 3-21 shows a long-term timing circuit . in the circuit. Al adopts FET input type transportation and storage TL082. The voltage
at the non-inverting input terminal is half of the saturation voltage (about 12V), while the voltage at the inverting input terminal is fixed at about +o due to the conduction of VD1. 6V. If the trigger terminal inputs a negative pulse above 6V, the Al output will show negative saturation, and the voltage at the non-inverting input terminal will be approximately -6V. The capacitor Ci is reversely charged through the resistor Ri. If the charging voltage exceeds -6V. Al J out reaches positive saturation, and the 10-timing period ends. Charging time T=R,Gln (Rz+R3) /R3, when Rz= Ra. TO. 7R1G.     (2) Component parameter selection The selection of components is shown in Figure 3-21, and there are no special requirements.