a 'flash in the can'

12-16 — elektor december 1980 a flash in the cal E. Muller The only electronic components re- quired for the construction of the "rifle" are two nine volt batteries, an electrolytic capacitor, a low voltage light bulb and a lens with a focal length in the region of 30 ... 50 mm. The target consists of a simple optical schmitt trigger with an adjustable threshold so that it can be made to operate correctly despite variations in ambient lighting conditions. The circuit of the "light emitting pistol" is shown in figure 1. Two 9 V batteries connected in series charge a capacitor. When the microswitch (S) is closed the In addition, the light is concentratec into a beam by a small bi-convex lens. li is therefore important to mount the bulb at the focal point of the lens. An example of possible pistol construc- tion is shown in figure 2. The micro. switch is mounted so that it will be operated when the pistol trigger pressed. A closer approximation of the true rifle range may be obtain...