# Time Delay With One 555 Schematic Circuit Diagram

#### On-Delay Timers and Their Operation

Time delay with one 555: In this setup, the timer operates as an on-delay timer, implying that the contact switch doesn’t transition until the predetermined time is reached. The provided image illustrates that the input power is supplied to the timer coil, yet no output is generated until the preset time duration elapses. Only after reaching the specified time does the timer trigger the contact changeover. Such timers are specifically referred to as on-delay timers. To establish a time delay within a circuit, a monostable 555 timer becomes essential. To determine the resistor value necessary for a minimum output time delay of 500 ms. Given the utilization of a 10 uF timing capacitor, specific calculations are required.

#### 555 Timer Circuit for Pulse Delay

Many electronic circuits necessitate a brief delay for a pulse, typically ranging between 100 ps and 100 s. This delay requirement can be easily met using a straightforward circuit based on the popular 555 timer. This range is generally sufficient for a broad spectrum of applications. The 555 timer’s output transitions to a high state only when the potential at pin 2 drops below one-third of the supply voltage level, provided the level at pin 4 is high.

During quiescent operation, the level at pin 4 is low, leading to the charging of capacitors C1 through T1 and keeping the output in a low state. As the input goes high, T1 is deactivated, initiating the discharge of C1 through R1. In this configuration, the reset state is nullified, and the time delay is adjusted based on the discharge state of C1. Consequently, the output of the 555 timer transitions to a high state. The time delay in seconds can be calculated using the formula t = 0.69R14C1, where R1 needs to be equal to or greater than 10 kΩ.

#### 555 Timer Output

A collection of 555 circuits using the 555 Timer as an astable oscillator with different duty cycles. The standard TTL 555 can operate from a supply voltage between 4.5 volts and 18 volts. With its output voltage approximately 2 volts lower than its supply voltage VCC. The 555 can source or sink a maximum output current of 200 mA (but it may get hot at this level). So the circuit variations are unlimited. Note that the CMOS versions of the 555, the 7555, and the 7556 may have different voltage and current ratings.

The 555 Timer IC got its name from the three 5KΩ resistors that are used in its voltage divider network. This IC is useful for generating accurate time delays and oscillations.
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