ELECTRONIC PHOTO ELECTRIC SWITCH DEVICES

The requirements of an ideal street lighting control device are summarized as one which will:- (a) switch the lamp on and off when required, (b) be unaffected by changes in voltage supply, (C) have a wide operating temperature range, (D) be maintenance free, (e) be easy to install, (F) be drift free, (g) have a long service life, and (h) be economically priced. Cheap thermal photo-electric controls fail to meet all these specifications, and with concern over their poor performance and quality, a study was conducted by the A.P.L.E. The three main recommendations from this study were:- (a) manufacturers should aim for an inverse switching of 1/2:1, (b) quality of manufacture, calibration and operation should be improved, and (C) an electric photo-control should be developed at an economic price. One type of electronic photo-control - the Horstmann EL10 model is described in detail. Thermal photo-electric and timeswitch controls are briefly compared with electronic photo-electric controls, and economic savings resulting from use of the latter are discussed. With their longer service life and greater reliability, electronic-controls are particularly suited to motorway use. It is concluded that future street lighting controls must be flexible, and that this is best met by electronic means. /TRRL/