GB1096797A - Lamp control circuit - Google Patents

Abstract

1,096,797. Transistor pulse circuits. R. L. SEIDLER. Sept. 20, 1965, No. 39933/65. Heading H3T. [Also in Division G4] A circuit, Fig. 3, for flashing a lamp 24 comprises a bi-stable circuit including transistors 17, 20, 23 the state of which is switched by a pair of relaxation oscillators employing unijunction transistors 11, 12 respectively. When the supply is first connected, the charge on capacitor 14 builds up until transistor 11 conducts producing an output pulse on line 18 which causes transistors 17, 20, 23 to switch to their conducting state and light the lamp 24. After a further time period capacitor 16 charges to switch on transistor 12 producing a pulse at the junction of resistor 30 and capacitor 22 which switches off transistors 17, 20, 23 and extinguishes the lamp 24 until the next pulse on line 18. In order to modify the pulse spacing and/or width a bi-stable circuit 32 is included which is switched by pulses from transistor 11. When this circuit is in one state, resistor 13 is shunted by resistor 33 to give a short time constant for relaxation circuit 11, in the other state, the resistor 33 is isolated by diode 34, and the relaxation circuit has a long time constant. The flashing lamp pulses are thus alternately separated by short and long gaps 41, Fig. 4 (not shown). If a similar connection is made to the time constant circuit of relaxation circuit 12, i.e. resistors 15, 43, alternate long and short pulses are also produced 45, Fig. 4 (not shown). In an alternative arrangement, Fig. 5, bistable circuit 32 is switched by a third relaxation circuit 46 operating at a lower frequency. When first switched on, this circuit produces a train of regularly spaced pulses until relaxation circuit 46 fixes changing the state of bi-stable circuit 32. Transistor 37 then conducts and its low collector potential inhibits operation of oscillator 11 until the next pulse from oscillator 46 switches circuit 32 back to its initial state.