Constant Current Load gremlins: 2

Me: 0

Leaving a project in the middle of getting your @$$ handed to you is no fun. I hope I’m not the only one who gets a little frazzled when I have to leave the work bench before I get to fix the “big hold up”.. or magic bug.. or whatever it is that’s keeping your blinking light from doing it’s thing.

Kerry Wong came up with a Constant Current Load that was tweeted the other day. I bought some parts from digikey and went to work this weekend. Friday evening I designed and etched a simple board for the IRFP150Ns and shunts… then Saturday I had a little time in the morning and strip boarded the op amp circuit with a potentiometer input. I have a PIC dev board I bought from ebay that I’ll use but I’ll go into that another day. Saturday we lost power in a storm and Sunday I was suckered into installing wall heaters for my sister.. so a very tired Monday and Tuesday evening I have been tinkering with this thing… it’s not entirely obvious what I did wrong… probably a little error I’ll catch after catch up a bit on sleep.

I’m planning on using this for a constant current power supply. I believe Dave (EEVBlog) or perhaps someone else came up with a similar idea but they were using it for a way of testing batteries. I recommend just buying a West Mountain Radio CBA (computerized battery analyzer) if that’s the route you are going. The software is  pretty decent. I have a CBA-III but it only works on Windows XP.. I was pretty annoyed when they didn’t come out with a user updatable firmware patch for Windows 7. It’s a solid tool if you work with SLAs  or lithium batteries regardless of my little rant a couple years back.

So my primary laptop is a 1 year old Vaio that took a nasty dive at a science fair I was demonstrating my Sumo RoombaBot for a high-cap school. The USB boards died because it sheered the driver off the PCB and blew out traces, etc… no fixing it anyways. I have an old XP laptop I program for now but I was considering one of these Windows Surface 2 tablet/laptops but they only have 1 USB port… that or perhaps I’ll just suck it and buy another Vaio!? Choice choices. Anyone reading used a Microsoft Surface for any development work at all? Spice?, MPLAB?, anything besides email and browsing? Shoot me a reply or e-mail. Thanks!

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