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Project Notes

#370 DigitaSwitch/TS3A5018

Testing the TS3A5018 Quad SPDT Analog Switch with a simple 555 timer and Arduino demo.


Here’s a quick demo..



Digital switches seem to be well suited for switching applications that are more complex than can be achieved with a simple FET or BJT, but lower power than might be more suited to a relay. Particular applications I have in mind are switching amplifier gain stages, filter gangs, and circuit subsystems.

They are available in a range of pole/throw configuration, and importantly with defined make-before-break or break-before-make behaviour.

I’m testing a TS3A5018 here, which I obtained already populated on a convenient breakout module.

The TS3A5018 is a 1.8 to 3.6V device with four SPDT switches controlled from a single input, and a master active-low enable pin. It is guaranteed break-before-make (max 58ns).


Code Example

The TS3A5018.ino sketch uses two of the switches in a simple demonstration with an Arduino Uno and 555 timer:

  • one switch alters the timing capacitor in a 555 astable oscillator, switching the frequency from 1 Hz to 2.4 Hz
  • another switch changes the LED (color) running on the oscillator output

The TS3A5018 is only rated for 1.8 to 3.6V, so a 3.3V rail is used for the offboard circuit, and simple voltage divider level-shifts the Arduino output pin.





Credits and References

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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.