How to Design a Square or Triangle Wave Oscillator from a 555-Timer Integrated Circuit

Target Audience
This is intended for anyone who wants to simply and cheaply make a generator for a square, triangle or blended waveform that can be frequency and amplitude adjustable. I expect that this audience is primarily constituted of audio enthusiast who want a base for a synth and beginner electronic hobbyist who want a clock pulse for a digital chip or clock.

Difficulty Level
If you have no experience with circuits, this will be challenging, and hopefully a learning experience. If the schematic below looks simple, this will be easy.

Things You Will Need
-One ‘555’ integrated circuit (I used a lm555, the ne555 is in the LTspice default library under misc and functions the exact same)
Datasheet
You can buy one from DigiKey for 45 cents

-One TLV272 or similar rail-to-rail
Datasheet
They cost 41 cents at DigiKey

-Either
1. Batteries with a combined voltage of 5-12 volts and a module to hold them.
OR 2. A DC voltage source between 5 and 12 volts, such as an old cell phone charger.

-Three potentiometers
(These are required if you want the frequency, amplitude, or triangle wave-shape to be adjustable. If you do not, they can be substituted by resistors).
The cheapest ones are 65 cents
These logarithmic versions are scaled better for audio applicationst

-Resistors (values to be decided below)
-Capacitors (values to be decided below)

-LTspice or similar spice program to simulate the circuit.
My schematic is in LTspice

-Either
1. A breadboard and wires to use it
OR 2. A perfboard, soldering iron, solder, 2 8-pin IC sockets, at least one foot of wire, and the basic tools to cut and strip it.
OR 3. A perfboard, a wire-wrapping tool, wire at the necessary gauge for the tool, and tools to cut and strip the wire.

Tips and Warnings
-Solder often contains lead. Wash your hands after handling it and try to not inhale the fumes while soldering.
-Soldering irons are very, very hot, some reach 900 degrees.
-Solder the sockets and then add the chips. The heat can damage the IC’s.
-Swapping the power and ground inputs can destroy the IC’s internal parts, so don’t do that.
-Start with the volume at a minimum and turn it up until it is at a good level. This oscillator uses voltages high enough to blow the drivers on any headphones.
-If you use this signal generator with a low-impedance load, make sure to run the outputs through a voltage follower that can handle the currents that your load will draw. The TLV272 has two OpAmps on the chip; the other one can be used as the voltage follower if one is needed. Meaning you just need to look up what a voltage follower is, and connect the other side of the chip accordingly.


Detailed explanation of the 555-timer integrated circuits used as an oscillator is here.

Step 1 Decide the range of frequencies and output voltages that you want from the signal generator.

This design supports a maximum output voltage of 12 Volts peak-to-peak.
Use a DC power supply with a voltage greater than or equal to the maximum peak to peak output voltage that you want.
The power supply must be between 5 and 12 Volts for the chips to work.

The TLV272 used in this design has a maximum frequency response around 3MHz, if you just want a higher frequency oscillator consider using a ceramic resonator or crystal oscillator instead of this design.