GB901462A - Electronic timing circuit - Google Patents

Abstract

901,462. Discharge-tube relay circuits; pulse circuits. LABORATORY FOR ELECTRONICS Inc. Aug. 13, 1958 [Aug. 13, 1957], No. 26072/58. Class 40 (6). Fig. 1 shows a timing circuit in which capacitor 16 is charged at a rate determined by the value of the variable resistor 14. When the voltage approaches the value at the top of potentiometer 24, a valve 28 conducts and causes a regenerative changeover of the cathodecoupled pair 23, 28, thus energizing relay 19. Contact 36 closes and energizes relay 38 which first moves a pawl 39 to the next step on the ratchet 48, then discharges capacitor 16 via contacts 18. This action releases relays 19, 38, so that the spring 49 moves the pawl-andratchet 48 to the next position. The ratchet 48 may be coupled to a stepping switch or a counter. Contacts 18 may alternatively be operated by relay 19 which in this case may be provided with a time delay. The voltage at the tap of potentiometer 24 is made 62% of the charging voltage at the tap of potentiometer 10 so that the time delay is equal to the product of capacitor 16 and resistor 14. Variable resistor 34 may be adjusted so that the circuit is freerunning in the absence or failure of contacts 18 or may be adjusted so that relay 19 is held energized at the end of the timed period until the circuit is reset by discharging capacitor 16 by means not shown. Switch 83 may be thrown to join contacts 84, 87 so that the capacitor 16 charges rapidly from the tap of the potentiometer 10 and discharges slowly via variable resistor 14. Pentodes may replace the triodes 23, 28. In Fig. 2, the re-setting is carried out by a monostable circuit such as that comprising valves 52, 56. When the capacitor 16a has discharged sufficiently to cause conduction of valve 28a, the cathode-coupled pair 23a, 28a change over, causing valve 52 to conduct and cutting off valve 56. The rise of the anode voltage of valve 56 drives valve 40 into conduction, discharging capacitor 16a and hence cutting off valve 28a. When capacitor 69 has discharged, valves 52, 56 change over, cutting off valve 40 and starting another timing period.