Build Your 1min-20hr Wide Range Timer Circuit

Description

A substantial assortment of auto-shutdown timers is available, spanning from one minute up to twenty hours across three distinct scales, utilizing S1. Immediately upon application of power to the circuit, the IC1 [555] commences its oscillation and delivers clock pulses to the IC2 [4017]. The IC2 [4017] and IC3 [4020] collectively generate a count rate of 81920 before the output signal from the IC3 [4020] transitions to a high state, activating Q1.

LM555 Timer

The LM555 is a versatile integrated circuit commonly used as a timer or oscillator. This particular implementation utilizes the 555 timer IC to generate the clock pulses for the timer circuit. Its operation is based on positive feedback, creating a self-sustaining oscillation. The 555 timer is known for its simplicity and reliability, making it a popular choice for a wide range of timing applications. Its core functionality lies in its ability to produce a continuous square wave signal with adjustable frequency and duty cycle, crucial for accurate timing in this circuit.

4017 Decade Counter

The 4017B is a decade counter integrated circuit, a type of digital delay timer. In this design, the 4017B is employed to count up to 8192 pulses. This counter IC converts a series of input pulses into a sequential output, representing the counted value. The 4017B operates based on a ripple clock system, where the clock signal is fed to each flip-flop stage, counting up sequentially. This IC provides a precise and predictable way to measure and control time intervals. Its utilization here facilitates the counting of pulses from the 555 timer, ultimately triggering the output signal.

4020 Decade Counter

The 4020B is another decade counter integrated circuit, similar to the 4017B, but typically offers slightly different timing characteristics. This component is utilized to provide the final count rate before activating the relay. The 4020B's core functionality rests in its ability to count up to 8192 pulses. It operates similarly to the 4017B, relying on a ripple clock system to ensure accurate count progression. The IC’s purpose is to accurately count pulses and trigger the final output, marking the completion of the timing interval. Its accurate count contributes to precise timing control within the circuit.

BC214 NPN Transistor

The BC214 is a general-purpose NPN bipolar junction transistor. In this circuit, the BC214 serves as a switching device. When the output signal from the 4020B goes high, the BC214 is activated, allowing current to flow through the relay coil, effectively turning it on. This transistor’s switching capability is vital for controlling the external load, in this case the relay. Its switching properties ensure that the relay is engaged only when the timing interval is complete, and it’s a common choice due to its adequate performance for a variety of applications. The BC214 efficiently controls the relay based on the output signal from the 4020B.

Circuit diagram

Part list