by Petre Petrov:
This simple, robust, and low-cost signal generator, based on the LM386 power amplifier IC, provides a trio of audio-band signals with three different simultaneous outputs at the same frequency: square/rectangle (SQW), triangle (TRG), and sine (SS).
Audio Function Generator Provides Three Simultaneous Square, Triangle, Sine Waveforms - [Link]
ajoyraman @ instructables.com writes:
PC sound cards form a readily available Signal Generator for testing electronic circuits. The utility of these signal generators is limited because the outputs are AC coupled and limited to ±2V.
Taking advantage of the two channels provided by the sound card this Instructable shows a scheme which uses one channel to output the Sin/Square/Triangle waveform with a fixed gain, while setting up a 441 Hz PWM square wave on the second channel. This PWM waveform is converted to ±8V averaged and summed with the first channel to provide a DC offset controllable by the duty-cycle setting.
PC Sound Card Signal Generator Interface - [Link]
This project uses the Simple LED Animation Kit (SLAK post) with red/green LEDs arranged in a triangle.
The three sides of the triangle are connected in parallel. Even though there are 18 bicolor LEDs (36 individual LED elements), the PIC16f628A is controlling only 6 bicolor LEDs (12 individual elements) and these are duplicated around the triangle.
NewDimension: Triangle LED Animation - [Link]
This is simple MAX038 generator. It produces sine, triangle and square waves from 1Hz up to 22MHz. The Amplitude, offset and duty cycle are adjustable to offer wide range of generated signals.
Frequency adjustment is made as a rotary switch S8 with a capacitor bank and variable resistor P7. Amplitude, offset and duty-cycle are performed via variable resistors. Switch S5 selects generated waveform.
MAX038 generator- [Link]