Control systems - initial musings

I always enjoy projects that involve a mix of hardware and software development and this project provides a nice opportunity to scratch that itch. 

At a basic level it is fairly trivial to control the amplifier. All that's really needed is a transistor or two to take the PTT input from the transceiver and drive the two coaxial relays (transceiver input and amplifier output). The transceiver can deal with delaying the onset of RF for the time taken for the relays to change state (around 20ms).

But that would be boring! There are sensors to monitor:

• Forward power
  
• Reverse power
• Heat sink temperature
• 50V supply voltage
• 50V supply current
• Fan actual RPM

...and things to exercise control over:

• Fan required RPM 
• Amplifier status: off/standby/Tx
• Amplifier bias
• Error conditions such as high VSWR, over voltage/current/temperature, etc.

All this points me in the direction of a microprocessor controller. Most likely this will be Arduino-based, probably using a Teensy 4.0 SBC because it is more than capable of handling all the I/O, is small and inexpensive. Eventually I will design a PCB to mount it and all the supporting electronics on to but initially breadboarding will suffice.

Once we have a microprocessor controller it becomes relatively easy to implement a separate control head and that is a good thing because the operating position chez 'WGV is cluttered enough already without adding a 19 inch rack's worth of additional hardware within arm's reach. I am envisaging a remote control head with a single TFT touchscreen display, powered directly from the amplifier. We can use RS232 for this, so only four control wires are needed: Ground, Tx, Rx and +5V. The touchscreen removes the need for any physical switches, so the control head will simply be a small 3.5" screen that can go anywhere in the shack.

I've used Nextion displays for this sort of thing in the past and with their built in processor and RS232 interface I think they will be perfect in this application as well. I am not yet ready to start coding but ideas are forming in my mind and I won't be able to resist making a start soon!