GB1491314A - Control of electrical apparatus utilising power during preferred periods - Google Patents

Abstract

1491314 Control circuits for storage heaters LONDON ELECTRICITY BOARD L SHEPHERD and W G PEGRAM 23 April 1976 [29 April 1975] 17859/75 Heading H2H A circuit for controlling the supply of power during 'off-peak' periods to a load such as thermal storage apparatus comprises a counter operative at the start of the period to count signals at a frequency determined by a first adjustable analogue timing circuit until a predetermined count is reached whereupon the counter causes closure of a switch S1 to supply power to the load and simultaneously commences to count signals at a frequency determined by a second adjustable analogue timing circuit until a further predetermined count is reached whereupon the switch is opened to interrupt the supply of power to the load. At the start of the "off-peak" period, the counter in an integrated circuit 20 starts to count signals at a frequency determined by the first timing circuit including an adjustable resistor 23 and a capacitor 21. When the predetermined count is reached, an output at pin 9 of the circuit 20 switches off a transistor Tr3 which in turn switches on transistors Tr1 Tr2. A relay 10 closes the switch S1 to energize the load and simultaneously changes over a switch S2 so that the counter continues counting signals at a rate determined by a resistor 24. When the further predetermined count is reached, the output voltage at pin 4 of the circuit 20 deenergizes the relay to disconnect the load from the power supply. The resistors 23, 24 may be thermistors. In a modification, Fig. 3 (not shown), a diode senses the external temperature and controls the duration for which power is supplied to the load in dependence on the external temperature.