Breadboard Prototyping

Inventor

I've always been a fan of breadboarding circuit designs. From college days through a brief engineering career and now my "middle ages" it has worked out well. Along the way I developed a few tricks to be shared with you in this thread.

To get things started, have a quick view of me teaching the first (and so far only) video of The Neat Freak Technique at double speed - funny.

https://youtu.be/KHQTkaCoQYs

More to follow.
Les

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Inventor · Posted: Thu Oct 03, 2019 6:00 am Post subject:

In the photo from the previous post we saw tools and breadboards gathered up and placed on a work surface. That's our starting point; now let's begin with the physical breadboards.

In the image below we see the breadboards that I have selected for this project. These are from Adafruit and cost about $6 each. The one on the right holds a minimal LM386 speaker driver and speaker plus a quad opamp test circuit for checking that the LM386 works properly. The test circuit consists of an artificial ground with active buffer plus a relaxation oscillator.

Those circuits are implemented with the jumper wire technique in which you buy or make overly long wires for quickly and easily connecting parts together in the desired way. That's a good first step, however in the long term it's a disaster waiting to happen because it is so easy to remove connections by accident.

What is needed is a plan of action that somehow combines the ease of jumpers with the benefits of my "Neat Freak Technique" that we saw in the video linked in the previous post. Fortunately I've got it figured out. I'll take the tangled mess of the above mentioned circuit and rewire it in the Neat Freak Technique.

To do this requires a god place for the new circuit to go, so I've joined together three breadboards including one dual battery supply. The supply has battery holders for dual 6V supplies (4x1.5V AA batteries). This means the artificial ground is no longer required, freeing up some complexity.

And finally, the batteries are already adhered to the bottom of one breadboard and the other two arrange well below it. This, however, is not flat - it curves and will easily separate. So what is needed is a wood or plastic object to attach them together. More on that in the future.

Yours peacefully,
Les

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Starting circuits from previous work.

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Inventor · Posted: Fri Oct 04, 2019 10:17 am Post subject:

Addendum: please be aware that I've gotten into some quandries running amok regarding making time to take the next step, so it will be a short while before I can post a progress update.

Yours truly,
Les

Inventor · Posted: Thu Oct 10, 2019 3:14 pm Post subject:

Success! Why such excitement? Read on... The short story is that the circuit has the behavior of a self-limited feedback squeal with more than a few applications.

Running on USB instead of other power sources makes this design easy to operate by computer, powered hub, or wall socket power source. This +5V connection is routed from the M0 Trinket PCB to all the other sub circuits. The feedback loop consists of a microphone, the microcontroller,and an LM386 speaker driver.

Around and around goes the signal; mic to Trinket to speaker and back to the mic, etc. Lather, rinse, repeat as they say. In the feedback path we have delay in the Trinket that sets the electronic frequency and another source of frequency regulaton. These work together to cause some fun interactions like speaking into the mic and having the voice all morphed and mixed with the feedback; holding hands in proximity to the mic and speaker for a Thevenin-like behavior, and other fun tricks.

Have a look at the two photos below showing the final circuit. Note that some of the parts near the center are unused as they are spares or planned for future involvement. The connected photo shows how the circuit was originally created, and the separated photo shows a fortunate happenstance in which the speaker and mic can be placed apart for different (and measurably consistent) behavior.

On the upper left we have our LM386 speaker driver with gain pot for trimming behavior of the loop. Well, there are lots of other details to discuss, too many for one post so I'll be back soon with more observations and descriptions. Until then, farewell and happy breadboarding!

Yours truly,
Les

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Breadboards fully separated

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Breadboards connected together

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