The schematic for the Amplifier Board, using the application Kicad, is now finished. It’s a complicated collection of applications, one to layout the circuit, another to layout the PCB, another to create the Gerber files – whatever they are, I’m just reading the button pop-ups. I am no Kicad expert. I balance those people up at the other end of the spectrum. The first time I created the schematic, most of the other associated apps refused to have anything to do with my .sch file. So I took someone else’s, who had created a similar file, and am now in the process of replacing all his work with my own. Hopefully when I get to the other apps, they are a little happier.
At the moment I am over-writing the second sheet which has the PSU on it. In laying out the charging circuit I have come to realise something rather important about the new design ethos. That ethos being partly that all the relays have been removed, the ones that switched the charging circuits in. The charging circuit is now completely in parallel with the batteries, only being switched on and off, not switched in and out (sorry, this point is rather complicated) thus reducing lots of cost (a PCB with loads of relays on it plus all the wiring) and also improve the signal quality as a relay contact is removed from the signal path.
The problem with all this is that the relays switching function allowed me to charge the batteries at the same time as the amplifier got powered. So the music could still play while the batteries are being charged. If I now provide a charging source that is powerful enough for music to play, it will charge the batteries too fast and damage them. The result is, there is either music playing and when the batteries run out of steam you have to switch to charge mode and wait for enough power to arrive. Probably overnight. One or the other. Hmmmm…
The start of the PSU schematic layout using Kicad.