Programmable Switching Sequence

PROGRAMMABLE SWITCHING SEQUENCE The proposed control circuit is shown in the diagram as containing two relays, but this number may be increased if necessary. The switching sequence is determined by the time delay of an RC network at the input of a gate that is used to energize a relay via a darlington transistor. When Si is connected to the supply voltage (as shown in the diagram), the input capacitor, CI, Cz, , begins to charge via a resistor, Rii, Riz, , and di- ode Di. After a given time, depending on the time constant of the relevant RC combination, the voltage across the ca- pacitor has reached a value sufficient to toggle the gate. The relevant transistor is then switched on, and the relay is ener- gized. By giving the input of each gate a differ- ent time constant, the sequence of switching is determined. When Si is switched to ground, the op- posite happens. Diode Di is reverse- biased and the capacitors, CI, Cz, , N1 N2 = 4584 32 SUPPLEMENT discharge via resistors Rol, ...