It took me a while to design and print a button for the new tape counter. Whilst the first approach was working it was not so stable and too thin. From four prints I was able to use two. Need to figure out the best way to add supports for a better outcome. However, I had to redesign it. I was also using a resin which is black but kind of transparent – that was not mentioned when I ordered it. Means I need to get another – this time really black – resin and print the overworked button again. For the moment I use the first design since the button is working fine.
There are several OLEDs available. Unfortunately only cheap, rubbish Chinese displays which do not fit perfectly but I was not able to find another one. The space is limited and we need to find some compomises. So I had to remove 2mm of the PCB ending up removing the connector and tighten the displays flex cable. With some points from the hot glue the display got fixed to the front panel. To remove the connector I had to re-solder the cables on the PCB and connect them via a cable on the PCB of the counter. Not a good solution and for the next one I should directly connect it to the PCB – which also needs a redesign since I forgot to cut an edge and therefore I was not able to use the pin connector.
For the counter I need to store the last position when the Sound Machine is powered off so that the last position on the tape is available when switching back on. I ended up using a RAM instead of EPROM. The latter one has limited write cycles and it is more complicated to store the position when someone is using the power switch. That would ne a huge capacitor to keep the CPU alive until the position gets stored. The RAM chip is a DS1307N, basically a clock IC with some RAM powered by a CR2032 battery. That would also give the opportunity to display the current date and time.
Anyway, there is still a lot to go and I have another idea to measure the position of the tape when it gets entered. I am doing some research on my idea – to measure the current used by the capstan – let’s see if it is working or not…
