Economical battery tester - battery condition in a flash

Battery testers are used to give a decisive answer concerning the condition of a battery. The voltage level is normally used as an indication of the battery when it is in operation. Obviously the test circuit most not form a considerable additional load during the measurement procedure. This particular battery tester consumes a negligible amount of energy. A brief single flash of the LED indicates that the voltage level of the battery in the portable radio, cassette tape recorder and so on is still sufficient. This flash is produced as a result of capacitor C1 discharging across LED D1, which is only possible when the battery supplies enough voltage. Depressing switch S1 will cause transistor T1 to conduct, so that C1 can discharge across the LED via the current-limiting resistor R3. The minimum battery voltage required is determined by the voltage divider R1/R2. The value for R2 and R3 must be calculated as follows: UB economical battery tester R2 -, , R3 - 0 6 x R1 [2] - 0...