More controller musings

While I wait for components and metalwork to arrive I have been turning some of my earlier ideas for the controller into practical ideas for implementation. I've also written some basic code to test out a few ideas. This has led me to an initial proposal for the controller circuit and PCB layout for same. 

I've settled on an Arduino Teensy 4.0 as the processor. The power supply arrived and I've been experimenting with controlling that. The 240V AC inrush current at switch on is awesome. Fortunately there is a control feature that permits the PSU to be put into standby mode, with the fan stopped and negligible power consumption. I therefore see three distinct power modes:

1. Off - no power to the 50V PSU, only a small 5V PSU powered up to keep the controller alive, albeit sleeping
2. Standby - Power applied to 50V PSU but PSU in standby mode
3. Operate - PSU on, producing 50V

And then, of course, two operating modes:

1. Receive - amplifier biassed off, amplifier in bypass mode
2. Transmit - RF to amplifier, lots more RF to antenna!

The 240VAC power switching will, most likely, be via a suitably chunky relay. I might investigate solid state relays for this task. Similarly, using a small, low cost reed relay for the PSU control switching makes isolation of the PSU from the control logic very straightforward.

I've decided to have large, relatively low speed fans front and rear of the amplifier module. The logic in this is noise reduction although unfortunately the PSU fan is far from quiet and is not temperature controlled, so my quiet shack plans might be in vain! I've included circuitry to monitor amplifier heatsink temperature and vary the fan speeds as needed.

Other circuitry includes forward/reflected VSWR acquisition and 50V voltage/current monitoring. There are further processor inputs for PTT and outputs for the change over relays, amplifier bias and, of course, the remote control head. 

Using KiCad I've produced a PCB layout that will easily fit in the available space. The board is 65mm wide and 160mm long and it will sit horizontally to the right of the PSU. It's so cheap and easy to get PCBs made these days that it will probably not be too long before I get the first prototype into production.

Meanwhile, I have written some initial code for the Teensy 4.0 SBC. My plan is to get enough if it working to be able to try out the amplifier, lash-up style in the 2m UKAC on 7th December.