hexreader, thank you for replying.
Yes, sorry, I have been told, on this forum, many times not to forget the 0.1uF cap so what did I do? Forgot it! Cheers.
I was experimenting and when I put in the 20pF cap, the stability improved. Maybe I’ll not need this on the PCB version.
Switch is drawn very badly as I couldn’t find a real switch on LTSpice. It is shown wrongly because what it really does is to take pin RA5 either high or low in order to select the mode.
ebastler thank you too.
I should have said that the LM35 and pot take too much current when the unit is in logging mode during which the PIC sleeps and the display is off. This can be for up to an hour so it seemed like a good idea to reduce the current and preserve the battery. Before the MOSFET it was taking around 100uA to 200uA depending on the software.
Again, apologies for the diagram of the switch (see above) and the pot: there was no pot in LTSpice but, in reality, it is wired correctly on the board.
Indeed, I do wish to get a PCB properly made so that I can take a simple project “all the way”.
MarkF thank you for that, I’ll go and look. I was going to use EasyEDA to get it made.