The method I’ve chosen to find out where body heat is can’t be done at the price I want it. I’ve got the wrong phototransistors, or at least I’ve been told I have. I should put the two transistor test version together, and see if I can get any sensible reading, but it’s been hot and I’ve been busy and I’m a bad robot parent. I also need to tidy my room enough that I can solder in it. Even by my standards it’s been bad lately, as I’ve been working elsewhere. I’ve got borrowed kit here and there as well, which I need to move to my Place For Borrowed Kit. Maybe I’ll just fake a house fire and start again.