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NE555 Duty Cycle Adjustable Pulse Frequency Square Wave Signal Generator Module

The NE555 Square Wave Pulse Generator Module is a compact, versatile signal generator based on the classic NE555 timer IC in astable (free-running) mode. It produces a continuous square wave output with adjustable frequency (~1 Hz to over 200 kHz) and duty cycle, making it ideal for driving stepper motors, generating clock signals, testing circuits, and prototyping. Two multi-turn potentiometers and a 4-position jumper block give you precise control across four selectable frequency ranges.

⚡ Key Features

Wide Frequency Range -- Adjustable from approximately 1 Hz to over 200 kHz
4 Selectable Frequency Ranges -- Jumper block selects the timing capacitor for coarse range selection
Adjustable Duty Cycle -- Two multi-turn potentiometers (RA and RB, 0–10 kΩ each) for fine control
Flexible Input Voltage -- Operates on 5V to 15V DC
Square Wave Output -- TTL-compatible at 5V VCC
LED Indicator -- Onboard LED flashes with the output signal for visual confirmation
Ultra-Compact -- Measures just Approx. 31 × 22 mm (1.22 x 0.87 inches) L × W
Simple 3-Pin Interface -- VCC, GND, and OUT with standard 2.54mm header spacing

📐 Specifications

Main IC	NE555 Timer
Operating Mode	Astable (free-running)
Input Voltage (VCC)	5V – 15V DC
Input Current	~15 mA at 5V; ~35 mA at 12V
Output Signal	Square wave (TTL-compatible at 5V VCC)
Output Amplitude	~4.2V peak-to-peak (at 5V VCC) to ~11.4V peak-to-peak (at 12V VCC)
Maximum Output Current	~15 mA (VCC = 5V); ~35 mA (VCC = 12V)
Frequency Range	~1 Hz to >200 kHz (jumper-selectable)
Potentiometers	2× multi-turn (RA and RB), 0–10 kΩ each
Frequency Selection	4-position jumper header (selects timing capacitor)
LED Indicator	Yes -- flashes with output frequency
Output Pins	VCC, GND, OUT (2.54mm header)
Board Dimensions	Approx. 31 × 22 mm (1.22 x 0.87 inches) L × W

🔧 Jumper Settings & Frequency Ranges

The 4-position jumper block selects different timing capacitors to set the approximate frequency range. Place the jumper on only one position at a time.

Jumper Position	Capacitor Value	Approx. Frequency Range
Position 1	100 µF	~1 Hz to ~50 Hz
Position 2	1 µF	~50 Hz to ~5 kHz
Position 3	0.1 µF (100 nF)	~500 Hz to ~50 kHz
Position 4	0.001 µF (1 nF)	~50 kHz to >200 kHz

🔌 Pinout

Pin	Function	Description
VCC	Power Input (+)	Connect to 5V–15V DC positive supply
GND	Ground (−)	Connect to DC supply ground / common
OUT	Signal Output	Square wave output signal

🎯 Typical Applications

Stepper Motor Driver Clock -- Generate step pulses for driver boards such as the A4988 or DRV8825
PWM Motor Speed Control -- Use the adjustable duty cycle for basic PWM control of DC motors through a MOSFET or motor driver
LED Dimming -- Adjust duty cycle to control perceived LED brightness
Microcontroller Clock / Test Signal -- External clock source for interrupt handlers, timing routines, or serial communication
Audio Tone Generator -- Produce square wave tones in the audible range (~20 Hz to ~20 kHz)
Circuit Testing & Prototyping -- Generate known-frequency signals for testing filters, amplifiers, and counters

🚀 Quick Setup

Connect power: Wire your 5V–15V DC supply to the VCC (+) and GND (−) pins.
Select frequency range: Place the jumper on the position that covers your target frequency (see jumper table above). Only one position at a time.
Fine-tune frequency: Adjust the multi-turn potentiometers to dial in your target frequency. Use an oscilloscope or frequency counter on the OUT pin to verify.
Adjust duty cycle: Turn potentiometer RA to change the HIGH time and RB to change the LOW time. Both affect frequency -- iterate between them to reach your desired combination.
Connect output: Wire the OUT pin to your target circuit. Connect the module's GND to your target circuit's ground (common ground is essential).

💡 Tip: The onboard LED flashes visibly at low frequencies (below ~30 Hz). Above ~30 Hz it appears continuously lit -- this is normal. Use a scope or frequency counter to verify output at higher frequencies.

⚠️ Important Notes

Do not exceed 15V input or reverse polarity -- either condition can permanently damage the NE555 IC.
Frequency and duty cycle are interdependent -- adjusting one will affect the other. This is inherent to the NE555 astable circuit design, not a defect.
Minimum duty cycle is approximately 50% -- in the standard NE555 astable configuration, the HIGH time is always at least as long as the LOW time. Duty cycles below 50% would require an external diode modification not present on this module.
Output is not buffered -- practical continuous output current is limited to ~15–35 mA depending on VCC. For higher-current loads, use the output to drive a transistor or MOSFET.
Not precision-grade -- intended for prototyping and applications where approximate frequency and duty cycle are acceptable. For precision timing, consider a microcontroller-based PWM generator.
Use a regulated power supply -- frequency stability depends on supply voltage stability and ambient temperature.

📦 What's in the Box

1x NE555 Duty Cycle Adjustable Pulse Frequency Square Wave Signal Generator Module

🏪 About Envistia Mall

Envistia Mall is a US-based electronics retailer specializing in development boards, sensors, modules, and components for makers, engineers, and educators. We ship from the United States with fast handling times. Product documentation and technical support are available at our dedicated support site.

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