NE555DR

The NE555DR from Texas Instruments is the industry-standard precision single timer in an SOIC-8 package. It can be configured for monostable (one-shot) or astable (free-running) operation, producing timing intervals from microseconds to hours. The output can sink or source up to 200mA and is TTL-compatible when operating from a 5V supply. The threshold and trigger levels are internally set at 2/3 and 1/3 of VCC respectively, but can be adjusted via the control voltage pin.

The NE555 contains two comparators, a set-reset flip-flop, a discharge transistor, and a resistive voltage divider network (three 5kΩ resistors creating 1/3 and 2/3 VCC references). In monostable mode, a falling edge on the TRIG pin (below 1/3 VCC) sets the flip-flop, driving the output high and turning off the discharge transistor, allowing the external timing capacitor to charge through the external resistor. When the capacitor voltage reaches 2/3 VCC (THRES pin), the flip-flop resets, the output goes low, and the discharge transistor turns on to rapidly discharge the capacitor. In astable mode, the capacitor charges and discharges between 1/3 and 2/3 VCC through two external resistors.

• Precision time-delay generation for industrial sequencing
• LED flasher and strobe light circuits
• PWM motor speed control with adjustable duty cycle
• Tone and frequency generation for alarms and sirens
• RFID and biometric system timing