Product Overview
The NE555 Delay Monostable Switch Module is a compact, precision timing control board designed to provide accurate and adjustable time delays for 5V systems, including automotive electronics, microcontroller projects, and industrial automation. Based on the legendary NE555 timer IC from Texas Instruments – one of the most popular and reliable integrated circuits in history – this module generates precise timing pulses for equipment that requires a delayed startup or shutdown sequence .
The module operates in monostable mode, meaning it produces a single, stable output pulse each time it receives a trigger signal. When a low-level trigger signal is applied (such as pressing a button or receiving a signal from a sensor), the output relay instantly activates and remains active for a preset duration before automatically deactivating . This makes it ideal for applications like protecting vehicle electronics during ignition, preventing current surge damage, and controlling lights, fans, pumps, or other electrical loads.
The onboard potentiometer allows stepless adjustment of the delay time, typically ranging from 0 to 10 seconds, with the ability to extend the delay range by replacing the timing capacitor . An ultra-bright LED provides visual confirmation of the relay’s active state, and the built-in relay supports loads up to 250V AC at 10A or 30V DC at 10A, making it suitable for controlling both high-voltage household appliances and low-voltage DC equipment.
The 5V version is specifically designed for low-power applications and systems powered by 5V logic, such as Arduino, ESP32, Raspberry Pi, and other microcontroller projects .
Key Features
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Monostable Timing Mode: The module triggers a single timing pulse when a low-level signal is received – perfect for equipment requiring a delayed start after ignition or button press .
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Adjustable Delay Time: Onboard potentiometer allows stepless adjustment from 0 to 10 seconds; the range can be extended by replacing the timing capacitor. Delay formula: T = 1.1 × R × C .
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5V DC Operation: Designed specifically for 5V systems, including Arduino, ESP32, Raspberry Pi Pico, and other 5V microcontroller projects.
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High-Power Relay Output: Built-in relay rated at 250V AC / 10A and 30V DC / 10A, capable of controlling lights, fans, pumps, motors, and other electrical loads up to 2200W .
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Easy Triggering: The module activates with a low-level signal (0V), making it simple to interface with switches, sensors, or microcontroller outputs .
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Visual Status Indicators: Power indicator LED confirms module is powered, while a separate timer LED indicates when the relay is active and the timing cycle is running.
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Excellent Temperature Stability: The NE555 chip offers 0.005%/°C temperature stability, ensuring reliable operation across varying environmental conditions .
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Standby No Power Consumption: The module draws minimal current when idle, preserving battery life .
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Relay Flyback Protection: Built-in protection diode suppresses voltage spikes from inductive loads.
Technical Specifications
Pinout & Connection Guide
The module features clearly labeled screw terminals for simple wiring .
Input Terminals (Power & Trigger)
Output Terminals (Relay Load)
Typical Wiring for Microcontroller Projects:
Usage Guide
Monostable Operation (One-Shot Mode)
In monostable mode, the module behaves as follows :
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Idle State (Steady State): The relay is OFF (NO open, NC closed). The timer LED is OFF. The module waits for a trigger signal.
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Trigger Event: When the TRIG terminal receives a low-level signal (0V), the timing cycle begins immediately. The relay activates (NO closes, NC opens), and the timer LED illuminates.
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Timing Period: The output remains active for the preset duration (0–10 seconds). The timing interval is determined by the potentiometer and timing capacitor: T = 1.1 × R × C .
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Cycle Completion: Once the preset time elapses, the relay automatically deactivates, the timer LED turns off, and the module returns to its idle state, ready for the next trigger signal.
Important: During the timing cycle, additional trigger pulses are generally ignored (non-retriggerable), ensuring the timing period completes without interruption .
Power-On Behavior
This module has a specific power-on behavior: When power is applied, the relay does NOT activate immediately. Instead, it waits for the preset delay time, then activates and remains active as long as power is applied . This is a delay-on-make or delay-on-operate function – ideal for protecting devices from inrush current during power-up.
Adjusting the Delay Time
The onboard potentiometer allows stepless adjustment of the delay time:
Extending the Delay Range: The delay formula is T = 1.1 × R × C . To achieve longer delays:
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Replace the 100µF timing capacitor with a larger value (e.g., 220µF, 470µF)
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Or replace the potentiometer with a larger fixed resistor
Example: With a 100kΩ resistor and 100µF capacitor: T = 1.1 × 100,000 × 0.0001 = 11 seconds .
Wiring Example for Arduino
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Power: Connect DC+ to Arduino 5V pin
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Ground: Connect DC- to Arduino GND
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Trigger: Connect TRIG to Arduino digital pin (e.g., D2)
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Load: Connect your protected equipment to COM and NO terminals
Arduino Code Example:
const int triggerPin = 2;
void setup() {
pinMode(triggerPin, OUTPUT);
digitalWrite(triggerPin, HIGH);
}
void loop() {
digitalWrite(triggerPin, LOW);
delay(100);
digitalWrite(triggerPin, HIGH);
delay(5000);
}
Protection for Vehicle Installations
When installing in 5V vehicle systems (some modern vehicles have 5V logic), this module provides protection:
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Connect the module’s power to a switched 5V source
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The trigger input (TRIG) can be connected to a momentary push-button
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Prevents sudden high current from burning components during power-on
Q: What is the difference between monostable and astable mode on the NE555?
In monostable mode (this module), the NE555 produces a single output pulse of a fixed duration each time it is triggered. In astable mode, it continuously oscillates, producing a square wave . This module is configured for monostable operation only.
Q: What types of loads can I control with this module?
The built-in relay supports both AC and DC loads up to 10 Amps :
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AC loads: Lamps, fans, small pumps, heaters (up to 250V/10A, maximum 2200W)
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DC loads: 5V/12V/24V LED lights, DC motors, solenoids, water pumps (up to 30V/10A)
Q: Can I use this module with an Arduino or ESP32?
Yes. The module operates on 5V DC and accepts standard TTL low-level trigger signals (0V). Connect the module’s TRIG terminal directly to a digital output pin on your Arduino or ESP32.
Q: Can the module be triggered multiple times while it is already running?
Generally, the NE555 in monostable mode is non-retriggerable. During the timing cycle, additional trigger pulses are ignored, ensuring the timing period completes without interruption . Some configurations can be modified for retriggerable operation.
Q: How can I make the delay time longer than 10 seconds?
Use the formula T = 1.1 × R × C . To increase the delay:
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Replace the timing capacitor (C) with a larger value (e.g., 220µF, 470µF)
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Increase the resistance (R) by turning the potentiometer clockwise or replacing it with a larger fixed resistor
Q: What is the power-on behavior of this module?
When power is applied, the relay does NOT activate immediately. It waits for the preset delay time, then activates and remains active as long as power is applied. This is a delay-on-make function – perfect for protecting devices from inrush current during startup.
Q: Can I use this module with 3.3V microcontrollers like ESP8266 or Raspberry Pi Pico?
The module is designed for 5V operation. For 3.3V systems:
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Some modules may work with 3.3V supply, but timing accuracy may be affected
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The NE555 is specified for operation down to 4.5V
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Use a logic level converter for the trigger signal, or power the module from a separate 5V supply
Q: Does this module have reverse polarity protection?
Most NE555 modules do NOT include reverse polarity protection. Always double-check your connections before applying power to prevent damage.
Q: What is the standby current consumption when idle?
The module draws minimal current when idle (relay OFF). The NE555 chip itself draws approximately 2-3mA , and the rest of the circuit draws negligible power .
Q: What happens if I press the trigger button continuously?
In standard monostable configuration, pressing the trigger continuously during the timing cycle will not restart the timer. The timing period will complete as set, and additional triggers will be ignored until the cycle ends .
Q: Is the relay protected against inductive loads?
Yes. The module includes a flyback protection diode across the relay coil to suppress voltage spikes when the relay de-energizes . However, for highly inductive loads (motors, solenoids), additional external protection is recommended.
Q: What is the minimum trigger pulse width required?
The NE555 trigger input responds to low-level signals lasting longer than the propagation delay. For reliable triggering, ensure your trigger pulse is at least 10-20ms (microcontroller pulses of 100ms are more than sufficient) .
