The Design Process: From Schematic to Prototype

In this hands-on tutorial, you will learn a simple method of taking an idea and making it a reality.   At the end, we’ll go step-by-step through the design process of a simple noisemaker circuit.

Introduction

Fail to plan, plan to fail.

Brainstorm

“I want to build my very own ____.”  Fill in the blank.

Once that’s settled, congratulate yourself on the easiest part of your project.

Start with your idea: what are you trying to make?  What do you know about it?  Has it already been built?

 

What exactly are you trying to build?

Research

  • Do your homework!  At the very least, you will want to have a working knowledge of electronics if you want to tackle larger projects.  Too many half-done prototypes collect dust due to getting stuck.  Find someone who can help!
  • What do you need?  Do you have the tools to successfully build a working prototype?  At what level will you consider it done (nothing is ever really done)?
  • You are going to Google a lot.  It will save you time and energy, so search and read up on every detail of your project.  See what’s out there, get some ideas for approaches you will take, and get inspired by the cool stuff people are building.
  • REMEMBER – There are few ideas that have not been done, and most great audio circuits are merely improvements on an existing product.  See if your what you are building exists already; you might be able to skip this whole design process and get down to making some noise.  In that case, you’ll probably want to check out our Reverse Engineering Tutorial.
  • The best way to design a circuit is to find one that has already been built.   This will cut your development time in half and give you a solid foundation to build on.  Don’t steal, give credit where credit is due, and make something cooler out of what you find!

Design

  • I prefer the black box model when dealing with a new project.
  • There are many unforeseeable issues that may arise during your design.  Lay out the specs as best as you can.

Schematic

Prototype

 

 

 

Once you have a general idea of what you want to build,

 

 

There are basically two methods of design: bottom-up or top-down.  Both have their strengths and weaknesses, but the purpose of this tutorial will be to demonstrate the top-down design methodology.  You will see how this can make design into a series of achievable goals.  Bottom-up design is best suited for experimentation rather than design.

Once we have an idea of what we want, we just keep asking ourselves questions until a solution emerges.  Research is a fundamental necessity and can shave off hours of exploring pointless solutions.

Start with a box.  It will be a black box, as we can not see its internal workings.  We name this box whatever we are designing.  In this tutorial, we will be designing a simple fuzz pedal.

How is the circuit powered?

What is the input/output?

How is the signal processed?

What are the expected results?

What are the design parameters for the circuit we are designing (small enclosure, guitar pedal standards, digital control, LCD display)

Etc.

The first steps involve an idea.  Once the idea is written down, a black box diagram is made to show the flow of the circuit and to slowly take apart the circuit until it is capable of being rendered with electronics.

What are we making?  A fuzz pedal

What’s a fuzz pedal?  An electronic audio circuit that accepts a guitar signal as an input and outputs a distorted guitar signal.

What parameters of the guitar signal are important? Voltage, frequency, etc.

THere’s more to come…

 

Top-Down Design

Start with an idea, and expand it as much as possible.

ex. I want to design a new fuzz guitar pedal.  This pedal should be switched with a true bypass switch scheme utilizing a mechanical 3PDT switch and a Status LED.  The power is only engaged if there is an instrument plugged in.  It will use one 9V Battery or a AC-DC Adapter for power.  The input signal will be a guitar, and the output will be reminiscent of a “sweet spot” Fuzz Face with more tonal control.

What are the parameters for a guitar pedal such as the one described above?

Constrain yourself and then decide what features is important.  There will always be trade-offs.  Remember the Designer’s Tradeoff Triangle: Cheap, fast, and good.  Pick two.

The black box model method for design/engineering works wonders for the DIY community as well.  Basically, you peel layers off the design onion by describing as much as you know about the project, defining more elements of the product undergoing the design.  As you define more and more of the black box, your design actually starts to resemble a finished product.  The unknowns are further whittled down to smaller black boxes, where you either find areas where you need to learn more or gather facts about the project.

The opposite of the top-down design process is the bottom-up design process, an approach that I find works wonders for experimentation, but creates more work when used for projects with more constraints.

The Top Down Design process requires you to constantly ask questions.

Who will use this?

For example power supply options can range from a simple  battery powered option to integrating DC power or even AC power that will be regulated and filtered.

When you finally get down to the basic circuit you will need for your circuit, you will find the Internet to be a great resource.  Remember, whatever you are designing, 99% of the time someone else has done something similar.  Use your Google-foo to find resources that you will  need for your project.

Find variables with components such as resistors and capacitors.

Start compiling reliable, reusable circuit portions that you can draw on for your next project.