Breadboard Mystery

Breadboards are a wonderful aid to electronic prototyping. They are small plastic blocks with lots of electrical sockets that will accommodate components or wires. Typically you have 2 horizontal rows of sockets in the middle which are lined up to take standard chips with 0.1″ leg spacing and vertical rows at either side, typically used for power rails.

The name arrived because in the early days of electronics, a way of prototyping circuits was to bang nails into a flat piece of wood and solder your valves (tubes) etc. to those. Obviously the most convenient piece of wood was the one in the kitchen. Quite literally, a breadboard.

So tonight I encountered a circuit online that intrigued me (a variation of the Joule Thief). Fancied a play. But couldn’t see a spare breadboard. They’re cheap, so I have several. I tend to use standard components of which I have a small stock, so there’s normally no need to dismantle a given circuit once I’ve done playing, just dump it on the shelf, grab another board.

On my desk I have this:

Ok, that’s an in-progress project, just trying to make a reasonable current limiter for a bench power supply.

On the shelf, firstly, this:

Also work-in-progress, I’m playing around with ultrasonics. But that’s momentarily on pause while I await a little signal generator module (I’ll use with an Arduino, is AD9833-based). I can do signal generation from my Bitscope, a PC-based oscilloscope or a homemade analog one, but neither can sweep around 40kHz – a little inexpensive hackery should sort that.

Next along:

This is a actually for future projects. A testbed for digital signal processing stuff, especially my ELFQuake thing but also music synth play. A variety of microcontrollers, ADC & DAC, plus, not shown, some rotary encoders as knobs to twiddle.

But it’s on the shelf for now while I get Chatterbox (which is in the same ballpark) nominally finished.

Next along the shelf:

Here the mysteries begin. I think this may have been audio amp experimentation. Based on the fact there’s my hacky signal generator on the stripboard on the right and a speaker on the left. I did need an amplifier for Chatterbox, but ended up forking out for a bag of $1-a-piece amp modules from China.

Now comes the real mystery:

I have absolutely no idea what I was doing here. On the left is a little audio amplifier module. Those are TL072 dual op amps, pretty good for audio circuits. But, they all seem to be configured as DC amplifiers/buffers, except for one that appears to be a precision rectifier. In the middle is an LM317 voltage regulator in what looks like a standard configuration. Absolutely no idea.

I mentioned this to my (Italian) girlfriend. She said “it’s all Arabic to me“. Fair enough, she doesn’t do electronics. But well put, this is like finding a notebook containing notes in your own handwriting, in Arabic, when you don’t know Arabic.

Hey ho. Steampunk archaeology, record the artifact, file away – that’s a free breadboard.

If you wish to learn more about breadboards, whether a newcomer or a stalwart fan, I strongly recommend Ben Eater‘s videos. This guy built an 8-bit computer from scratch, using logic chips on breadboards. Is a wonder to behold:

Last night I watched his tips. As someone commented, “When you realise you just watched Ben strip wires for 20 mins and you enjoyed it!“. Yup.


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