GB867112A - Electronic timing device - Google Patents

Abstract

867,112. Valve relay circuits. PYE Ltd. April 8, 1959 [April 8, 1958], No. 11054/58. Class 40(6) An electronic timing device comprising a bridge circuit one arm of which comprises a gas discharge tube, and a relay connected across the bridge between the junction of two resistors and the junction of a third resistor and the tube, the arrangement being such that the bridge is unbalanced until the tube strikes, and energizes the relay to operate a contact which causes the tube to strike after a time delay, the bridge then becoming balanced to de-energize the relay and extinguish the tube. As shown, when button B is pressed, relay RL/N is energized, holding in over contact RL1, and opens contact RL2 to allow capacitor Cl to charge from the stabilized potential at the junction of R6 and tube T2 via resistor R4 until the triggering voltage of the tube Tl is reached. The tube will then fire and the voltage at the junction of R3 and Tl will become equal to the burning voltage of the tube. R1 and R2 are so arranged that the voltage appearing at their junction is also equal to the burning voltage of the tube, and the bridge is then balanced and relay RL/N releases. Contacts RL1 open, switching off the supply and contacts RL2 close discharging the capacitor. Further contacts on RL/N may be used to obtain an output from the timer. The reliability of the timer may be improved by connecting a germanium diode D in series with the relay coil. The time constant may be varied by making R4 a variable resistor, or providing several different values of resistor which may be switched into circuit. Alternatively, or additionally several values of switched capacitor may be provided for Cl.