The timer circuit, utilizing 555 timers, operates without a transformer, drawing power directly from the mains voltage. However, it’s crucial to handle such connections with extreme caution due to the high risk involved. Components like R1, C1, C2, D1, D2, and D3 are fundamental to the power supply circuit. Capacitors C1 and C2 should have a working voltage of 25V, while D3, a zener diode with a voltage rating of 12V, and the power rating of resistor R1 should be 1W. The 1μF capacitor is designed to reduce the mains voltage from 220V.
The voltage output of the Beseleme circuit is determined by the D3 zener diode. U1, the 555 integrator, is the integrated timer available from various manufacturers such as NE555 and LM555, all functioning in the same way. The timer’s duration in the circuit can be adjusted by changing the resistance of R4 or, alternatively, using a trimpot in place of this resistance. It’s important to exercise caution and adhere to safety protocols when working with this circuit due to the inherent risks associated with mains voltage.
Here’s a breakdown of the components involved:
555 Timer IC (Integrator):
- The 555 timer IC is configured as an integrator, meaning it performs mathematical integration on the input voltage signal. It accumulates the input voltage over time, producing an output signal that represents the integral of the input voltage.
- The transformer is an electromagnetic device that can step up or step down voltages. In this circuit, it may be used to adjust the voltage level or provide isolation between different parts of the circuit.
- A relay is an electrically operated switch. It can be controlled by a small voltage and current, typically from the 555 timer IC. When the relay is energized, it can control higher-power devices or circuits.
OPERATION OF THE CIRCUIT;
Upon initial power-up, capacitor C4 begins charging through resistor R4. The charging duration of C4 is determined by the resistance of R4. During this period, the RL1 relay contact remains open as the output Q of the U1 connector is in position 1. Once capacitor C4 is fully charged and reaches 12V, the output Q of the U1 connector drops to 0V. Consequently, relay RL1 closes the contact, and LED D4 illuminates, indicating the ten position.
The LM555 is a highly stable device designed for precise time delay or oscillation generation. It offers additional terminals for triggering or resetting if needed. In time delay mode, the duration is accurately controlled by an external resistor and capacitor. For astable operation as an oscillator, the frequency and duty cycle are precisely regulated using two external resistors and one capacitor. The circuit can be triggered and reset by falling waveforms, and its output circuit can source or sink up to 200mA or drive TTL circuits.