Here is an electronic code lock, which can be used as a door latch or key for ignition, etc. Operation is fairly tricky and there lies the beauty of the circuit. There are a number of switches, actually nine, which should be operated in a particular and owner – configured -sequence, or else the circuit [...]
This circuit was specifically designed to recharge alkaline cells. The unusual connection of the transistor in each charging unit will cause it to oscillate, on and off, thus transferring the charge accumulated in the capacitor to the cell. The orange LED will blink for around 5 times a second for a 1.37V cell. For a [...]
Resistors are measured in ohms, and have a wattage rating. Resistance value is marked on the resistor in an internationally accepted color code. Normally quarter-watt resistors are used in the following circuits unless otherwise specified. Carbon film and metal film resistors are generally used. Wire wound resistors are used for higher wattage resistors.