On Sat, 26 Feb 2011 01:52:43 -0800, DK Duncan <dun...@quantumlogic.net> wrote: > On Sat, 26 Feb 2011 01:57:57 -0700
> I had considered both actually. When issuing i DoIt drouge, the prompt > returns in about 2 seconds as expected. A subsequent t shows that the > ematch still has continutity so it's drawing current throughout the 2 > seconds and it doesn't open up. Right, most e-matches don't reliably open after they've burned. I've heard that they're actually designed to remain closed so that they can be connected in serial to ignite many charges with one switch. As Bdale says, we've got a 100µF cap on the 3.3V rail, which should be able to hold the 3.3V rail above the brown-out voltage for 50ms if the battery voltage drops to 0. What we've found is that the LiPo batteries appear able to source enough current that a typical e-match with at least 1.5Ω resistance won't ever cause the voltage to droop far enough to cause a problem. However, if you've got a dead short across your igniter terminals, I suspect you'd end up doing 'bad things' if you held that on for a long period of time. That's what we're trying to prevent here. > The processor didn't reset but I really don't want to risk it in > flight. I'll try backing off on the value to see where the ignition > point is at and then add a safety margin of 50% or so. Further ground > testing might show that the deployment charge opens the ematch but for > now I'm going to assume it remains conductive. I'd love to see this tested with a short circuit as well as one of your e-matches. What I don't know is whether this might burn out the FET or melt the PCB traces. I wrote the code to make this configurable, but it doesn't fit in the available program memory. So, as is often the case, the hard part will be to refactor some other code to make it small enough that the new bits can be included. -- keith.pack...@intel.com
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