Testing the board
Nothing much has been happening over the last few days; other projects have been taking priority. Which isn't to say that no progress is being made on the business as a whole, but certainly nothing on the product development side. Right now, a lot of it is just waiting for phone calls and doing work that pays the bills but doesn't otherwise get me anywhere.
I've had a little bit of time to test the board. My usual trepidation applied. The board acted a little funny and got quite warm with the current limit set low - but that's not entirely surprisingly, because the input voltage was being dragged down to roughly the IC's minimum input voltage. With the current limit set to something sensible, it was definitely giving some output, but not the output that I was hoping for. My prototype board has a 1A current limit. With an 8V input, the output current was 1.4A, 5V in, 1A out. 12V in, 0.4A out. It's obviously doing something useful - if it wasn't operating, there'd be no output at all, given it's a buck-boost converter. I thought that my load (a 0.47R or 2R2 resistor) might be screwing things up, but the simulation doesn't confirm my results anyway.
I spotted a problem at home; the 'adjust' pin on the current limiter wasn't connected. I must have cut it when tidying up the IC pads by hand. Hooray for the blog - if I hadn't taken photos of the board before soldering, I never would have known! The track is under the IC. I rejoined it, but saw no difference. The simulation says that it'll work perfectly with that pin disconnected, which seems odd to me. It looks connected to me, but I'll have to get it under a microscope to confirm.
It's also possible that I've damaged the IC with my over-zealous soldering in the frypan, but I can't think of what would cause these symptoms A disconnected current adjust still seems like the most likely cause to me.
Other than that, I had yet another post written up about accounting software, but I can't find it. Oh well. I'm probably going to write my own system. One of my accounting friends says that I'll do it all wrong because I don't know anything about bookkeeping, but I figure that if I can find an easier way to get the right results, even if it's not the 'correct' way, that's better anyway. I get the impression that the accounting profession really hasn't kept up with technology too well. It's also quite likely that I don't know the area well enough.