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Electronics Projects: Four Frequencies Generator

This DIY circuit generates fixed frequencies of 4MHz, 6MHz, and 10MHz using crystal oscillators along with an adjustable square-wave output ranging from 10Hz to over 100kHz.

Originally published on ElectronicsForU

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
2-Slot 18650 Holder with Protective Cover and On/Off Switch – Case Rs. 109.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

We don't carry yet: Supercap / UPS / Power Bank Module
Crystal / Oscillator
Capacitors
Potentiometer / Trimpot
Voltage Regulator IC (7805 / LM317 / 1117)
Header Pins / Terminals / Connectors
Custom PCB / PCB Fab
trimmers

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How It Works

The Four Frequencies Generator circuit is designed around a combination of crystal oscillator stages and an adjustable square-wave generator built on a single-side PCB. The fixed frequency generation relies on three discrete crystal frequencies: a 10MHz crystal (XTAL1), a 6MHz crystal (XTAL2), and a 4MHz crystal (XTAL3). These crystals interface with three 74C04 hex inverter ICs (IC1, IC2, and IC3) along with supporting capacitors (C1, C2, C3) and a resistor (R2) to form stable, high-precision clock oscillator circuits that output dedicated fixed-frequency square waves. Additionally, the circuit incorporates a 74C14 hex inverter Schmitt trigger IC (IC4) working alongside potentiometers and trimmers (VR1, VR2, VR3) and switches (S1, S2, S3, S4) to construct a variable-frequency relaxation oscillator. This adjustable section produces a continuous square-wave output spanning from 10Hz to over 100kHz. Power regulation for the entire system is handled cleanly by an LM317 adjustable regulator, which steps down and stabilizes input voltages supplied through the on-board connectors (CON1, CON2, CON3, CON4), ensuring steady performance across all active oscillator stages.

Why Build This

Provide a reliable, multi-frequency clock source for testing and debugging digital microcontrollers and embedded logic systems.

Serve as an in-house signal generator and calibration reference for verification equipment such as oscilloscopes and frequency meters.

Explore practical discrete analog-digital hybrid design by building crystal oscillators and variable Schmitt-trigger square-wave generators from scratch.

Real-World Application

Development, testing, and maintenance of digital and analogue electronic circuits, embedded systems, and test equipment like oscilloscopes, probes, multimeters, and frequency meters.

Skills You'll Learn

crystal oscillator design

Schmitt trigger clock generation

analog voltage regulation with LM317

discrete logic IC application

frequency tuning using trimmers and potentiometers

Safety Precautions

Flagged during content review — not in the original source

This circuit utilizes an LM317 adjustable voltage regulator and multiple active IC components powered via external connectors; ensure correct input voltage polarity and proper board handling to prevent component overheating or short circuits during bench testing.

Technology Tags

TTL

CMOS

FREQUENCY GENERATOR

CRYSTAL OSCILLATOR

PCB DESIGN

INVERTERS

SCHMITT TRIGGER

LM317 REGULATOR

Frequently Asked Questions

What determines the fixed frequencies of 4MHz, 6MHz, and 10MHz?

The fixed frequencies are governed by the specific quartz crystals utilized in the circuit: XTAL3 (4MHz), XTAL2 (6MHz), and XTAL1 (10MHz), working alongside the 74C04 hex inverter ICs.

How is the variable frequency output adjusted from 10Hz to over 100kHz?

The adjustable output is generated by the 74C14 Schmitt trigger IC (IC4) configured alongside the potentiometers and trimmers (VR1, VR2, VR3), which allow you to manually tune the RC time constant of the oscillator.

What is the function of the LM317 component in this project?

The LM317 acts as an adjustable linear voltage regulator, providing a stable and controlled supply voltage from the input connectors to power the logic and oscillator circuits safely.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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