Prototyping an Arduino Uno based sequencer

Background

The existing switching unit for my EME station is built around a sequencer designed by DL4KH that I bought at Ham Radio, Friedrichshafen back in 2005. This unit provides sequential control logic for the transverter, power amplifier and LNA and antenna changeover relays mounted at the masthead to prevent hot switching. The sequencer has five relay driven outputs with a 40ms delay between each stage. The delay can be changed by swapping out a resistor and jumpers can be used to set relay outputs to either the switching voltage or ground.

I’ve used this arrangement successfully with different configurations for many years and so far never lost a masthead preamp or rf relay.

Prototyping

I reviewed several Arduino based sequencer designs that I found on the internet and put together a simple sketch to replicate the logic of my existing unit. I then assembled an external circuit on breadboard to test the Arduino code.

During this process I came across Tinkercad, a free, online tool for design, electronics and coding. The tool allows you to build simple circuits including Arduino based designs, upload a sketch and run a simulation.