Summary
An analog, potentiometer-based tweaking device that outputs a pulse train; two knobs allow adjustment of frequency and duty cycle.
Reasoning
- It would be (mostly) a testing tool.
- It would have applications both as a test platform for inductors, for example, to experimentally determine the proper frequency of a buck/boost converter.
- Tuned appropriately, it or a similar circuit could serve as a simple toy synth.
Specification
- Capable of/adjustable to frequencies within human hearing range
- Capable of/adjustable to frequencies useful for driving an inductor-based DC-DC converter.
Progress
- Intelligence
- Design detail: An analog PWM with adjustable frequency can be made using as little as a single quad op amp IC. Two amps are used to make a triangle/square VCO[1] using output from one potentiometer to control the frequency. The third amp is configured as a buffer for the voltage from the second potentiometer; the output controls the duty cycle. The fourth amp is used as a comparator, comparing the VCO’s triangle output to the duty cycle control. This comparison operation of a control voltage with a triangle or sawtooth wave yields a pulse train corresponding to the duty cycle input.
Requisites
- Tasks
- Develop concrete schematic
- Then fabricate/plan PCB; circuit may be simple enough to assemble on perfboard
- Then assemble circuit on PCB.
- Then test circuit for an audible application.
- Then install product in project box.
- Materials
- Pending concrete schematic
- Project case
- [1] An animated example ↩