[NRVR-Members] Rocket PSA: Problems with 110/220 Rotary Switches & LiPo Probs with "Protection PCBs"

Thomas Tweeks Weeks tom at theweeks.org
Mon Mar 13 18:43:13 CDT 2017

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 speaker/LED 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 warning about using 110/220 AC style switches of this type:
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 check 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 Chinese supply of rotary switches), or an old time gremlin that is just now being 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 my 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 them, 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.

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