Dark-Room Timer

111 EE February 1989 INTERMEDIATE PROJECT A series of projects for the not-so-experienced constructor. Although each article will describe in detail the operation, use, construction and, where relevant, the underlying theory of the project, constructors will, none the less, require an elementary understanding and knowledge of electronic engineering. Each project in the series will be based on inexpensive and commonly available components. 2. Dark-room timer This month"s intermediate project is a low-cost timer that should appeal to the many photography enthusiasts convinced that the simple equipment in their dark-room can beat the print quality offered by high-street photo development centres. Providing an accuracy of one-third f-stop, the timer should be of particular interest for those who like to influence the contrast of the print by experimenting with different exposure times. Optimum print quality of a photograph can only be achieved when the photographic sensitive paper is ...