Then and now – 37 years in electronics

In 1985 I completed the final year project for my electronic engineering degree. The project I chose was an ultrasonic level detector. Here is the introduction from my report which explains the use scenarios…

Without getting too technical, the solution involved using a special purpose ultrasonic transceiver integrated circuit (LM1812 by National Semiconductor) surrounded by some driving circuitry and feeding into a digital logic section which implemented the level detection and control output. Here’s the ultrasonic transceiver part of the circuit…

The ultrasonic transceiver circuit.

The interesting part of this which is pertinent to this story is that the LM1812 IC cost $10.50 at the time, and it was relatively fragile. By that I mean that during my testing of this circuit, until I figured out what I was doing wrong, I destroyed a number of them. Each time I rushed down the street to buy another so I could continue getting the circuit to work. I can’t remember exactly how many I ended up buying, but it was more than I would have liked! All up, the total cost of components for this project (not counting the busted ones!) was $46.38.

1985 cost of components

Fast forward to now, Jun 2020. I had recently bought a Raspberry Pi Pico, a small programmable micro-controller. While I was wondering what I could use it for I came across the above final year project report and the thought struck me I could redo that project using today’s technology. It’d be interesting to see how the field had changed. The other motivation for doing this was to become more proficient in the Rust programming language – one of the newer languages I’ve been tinkering with in my spare time.

I discovered the was at least one ultrasonic transducer module that was compatible with the Pico, so I bought one and set to work doing the programming. Interesting change #1 – instead of spending most of my time with components and soldering, I was coding. The hardware is about as simple as you can get…

Interesting change #2 is the cost. The Pico cost $5.75 and the ultrasonic transducer module $8.05 – total cost $13.80! Adjusting for inflation, the component cost of my final year project in today’s dollars would be $141.63!!

It is unfortunate that I don’t have any pictures of the original project. All I have is the final report which I have scanned into a PDF.

However, since technology is so advanced today, I can show you a video of the new version in operation!

And, if anyone is interested, the source code for it is available on GitHub.

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