Paolo's Build Log

Hello CE members/users/readers,

I’m Paolo, I studied electronics a decade ago, but since strayed off into different fields. I rediscovered my interest in electronics a few years ago when I joined a local makers’ space. Now I work in the IoT field. I would like to develop my skill and understanding of all the basic principles in all areas of electronics, with the aim of becoming a true craftsman. I enjoy the learning process and hope to build up over time a portfolio of experience in a variety of digital, analog, electrical/electronic circuit development (theory/simulate/design/build/maintain). Aiming big but enjoying the process.

No current big projects in mind at the moment, rather first considering some basic principle circuits first to lay out the foundational building blocks to go on bigger.

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So for starters, I’m constructing an H-bridge from MOSFETs, which can operate with a higher supply voltage than 36 V which a L293D can provide.

The solenoid is designed to be powered at voltages up to 80 V, yet I’ll be triggering the H-bridge with a 3.3 V microcontroller (ie. an ESP32).


It’s actually a teleprinter solenoid, so it will be switched up to 50 times a second to send Baudot.

A simple H-bridge would be great that worked in the way illustrated in the block diagram but I’ll go on to challenge myself to extend it to add the following features:

  • Prevent accidental ‘forbidden’ logic states (to prevent shorting the MOSFETs)
  • Power disconnect mode
  • Primarily MOSFET-based, but after it’s all working, might then try to see how an equivalent BJT-based version would look like.

I found a nice in-depth article which looked good to help understand well enough to develop the idea further and add features without breaking it.

I’m building the physical circuit but as an aside, I might also try some simulations, as I haven’t used SPICE in years, so will be good just for fun to relearn it all. From that article, it seems a basic CMOS complementer circuit might be a good place to start simulations.

Circuit (when I have a working idea) and more developments to follow. Ideas/suggestions welcome.