Lock code unit with auto reset

The code unit, which operates with was designed to control an electromagnetic door lock with a four-digit code. It resets automatically after a short period. The keys that set code are designated S1-84 in the diagram. Each of them is linked to a bistable (flip-flop) in IC1. The connections are arranged so that when key[…]

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PCB drill control

The design presented PCB enables the PCB drill to be controlled with only one preset. as an aside. the rotary direction of the drill may be reversed. When the preset is at the center of its travel, the drill stops. The power supply delivers (immediately after the bridge rectifier) a voltage of about V for[…]

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4-bit random generator

The generator is based on a Type 4006 quadruple shift register, IC1. Two of the shift registers are four bits long, the other two, five bits: a total of 18 bits. Only the clock is common to the registers: all inputs and outputs are separate. Of the four-bit registers, only the fourth bit is available[…]

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Small power converter

The converter enables an existing positive supply voltage to be raised, to be lowered, or to be changed into negative potential. The new voltage is electrically isolated from source by a DIY transformer wound on a G2-3FT12 toroid. The primary winding consists of 30 turns. The number of secondary turns, n, is calculated from n= […]

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