[NRVR-Members] Rocket PSA: Problems with 110/220 Rotary Switches & LiPo Probs with "Protection PCBs"
jordan at truesdell.org
Tue Mar 14 04:58:48 CDT 2017
Scroll down to screw switches. I've got one if you want to see one in
On Mar 13, 2017 9:58 PM, "Thomas Tweeks Weeks" <tweeks-junk2 at theweeks.org>
> On Monday, March 13, 2017 8:45pm, "Bob Schoner" <bob.schoner at gmail.com>
> > Wow hadn't heard either of
> > those before. Thanks for passing that on. I know
> > it isn't elegant but I still am a fan of the simple "twist and tuck"
> > method. I prefer to leave the wires sticking out and tape them to the
> > outside of the body tube.
> Twist and tuck altimeter arming sounds about is simple as it gets Bob (and
> sounding more and more appealing ;). I'll have to keep that in mind as I
> finalize my avionics bay. :) Although for this L3, I would have three
> things to twist and tuck (two altimeters and one dedicated pyro supply)..
> it would be a shame if it turned in to twist, tuck and touch. <zzzzzap!> ;)
> > I guess unless you buy some military or aerospace grade of switches there
> > is probably a chance of failure.
> Might be able to ping Dr. Shinpaugh (or other friends I have in the
> cubesat industry) on sourcing some high-G switches.
> > I have several rockets with those
> > switches. I would suspect they are more like Kelly to fail after a hard
> > landing or some other traumatic event. Not really sure if I will replace
> > them or take my chances
> Well.. the root cause of those switch failures hasn't been stated AFAIK.
> It could be user error (inexperienced folks not rotating them far enough),
> or some cheap Chinese source that's recently released inferior switches
> that fail in high G scenarios. Who knows. Like the 9V battery failure
> experiment I've told you I want to try, this could represent another cool
> arduino data gathering experiment for capturing switch contact data
> watching for high-G contact bounces or faults. Now that I have a bay that's
> big enough to carry such payloads.. I can finally start getting some useful
> data out of some of my flights. :)
> (which is part of why I got into arduinos in the first place)
> > Thanks
> > Bob
> > On Mon, Mar 13, 2017 at 7:43 PM Thomas Tweeks Weeks <tom at theweeks.org>
> > wrote:
> >> Hey all.. esp you L3 guys.
> >> So I'm designing my ebay for my L3, and I just got the brand new
> >> PerfectFlight StrataLoggerCF in the mail (the new one with the
> >> connector).. and there's a little warning handout about common critical
> >> failure modes they're seeing back from their customers.
> >> Failing 110/220 Power Switches:
> >> There is new StrataLoggerCF power check feature & very surprising
> >> about using 110/220 AC style switches of this type:
> >> https://www.apogeerockets.com/Electronics-Payloads/
> >> I know these are very popular arming switch styles and have been for at
> >> least a 15-20 years or so (I have a couple in my own parts bin), but
> >> out what this leaflet from Perfect Flight is saying about them now:
> >> "We have had numerous reports of failures of the 110/220 rotary switch
> >> that is sometimes used [...] in rocketry applications. The failures
> >> typically in one of two ways, either as:
> >> * a switch that turns off when tapped or wiggled, or
> >> * a switch that exhibits a high resistance (several hundred ohms) when
> >> turned on
> >> [Our new WiringCheck] feature [... which performs a pre-flight
> >> load/no-load comparative battery test] is intended to reveal the latter
> >> type of problem, but we still do not recommend the use of this type of
> >> switch in rocketry applications. [...]"
> >> So in short.. I don't know if this is a NEW issue (e.g. from cheap
> >> supply of rotary switches), or an old time gremlin that is just now
> >> revealed. Either way, since this info was nowhere on the PerfectFlight
> >> website or on line documentation (it was thrown in as a warning card in
> >> latest purchase), I hope after this is archived in our mail list that it
> >> will serve as a warning to others. (someone might want to re-post it to
> >> RocketryForum.com, et al).
> >> Warning About Some LiPos:
> >> This little info card is useful, and also contains a warning about using
> >> LiPo cells with over-current protection circuitry shink-wrapped into
> >> as the short condition of some ematches will shut down such batteries..
> >> causing another type of critical power failure to a critical recovery
> >> component of your rockets.
> >> Just wanted to share.
> >> Tweeks
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