[tccrockets] Re: Anyone using magnetic switches for arming altimeters?
- From: William Ferry <woferry@xxxxxxx>
- To: tccrockets@xxxxxxxxxxxxx
- Date: Sat, 28 Feb 2015 17:17:16 -0800
Hi Richard,
I've used Featherweight Magnetic Switches on almost every flight I've
flown with an altimeter so far, I'm happy with it. Mike @ BAR sells them, as
do others online. Obviously you have to design your sled so that they're
reasonably close to the airframe, and they can be a bit touchy. Sometimes I
find when sweeping the magnet past that they toggle twice, so the end state is
the same as you started. There's a bright blue LED that lights on the board
when it's on, so I positioned the vent holes on my latest rocket's avionics bay
such that I can see the LED and get the visual confirmation that it's on or off
(of course the beeping of the altimeter can help also).
The board is smaller than a postage stamp, single-sided with
surface-mount components. It doesn't have any connectors on it, instead it has
3 mounting holes which double as the electrical connections (GND, IN and OUT,
labeled on the back-side). I've heard that there are different versions that
are different sizes, so there isn't a single hole pattern that works for every
one, but the 4 I have (1 from BAR purchased in 2014, and 3 from Performance
Hobbies last month) all happen to be the same. Mine are 3/4" by a bit over
1/2". They go for around $25, and each one has come with the magnet as well.
The boards do use a hall-effect sensor to detect the magnet, so even when
they're "off" they do still consume a bit of power for the sensor, I never
bothered to measure how much as I don't use these switches for long-term
powering-down of my altimeters, just to keep them off between when I prep the
rocket and when it's upright at the pad, and to turn things off post-recovery
to make the beeping stop. =)
I hope that helps. - Will
> On Feb 28, 2015, at 9:20 AM, Richard King <drrbk@xxxxxxxxxxx> wrote:
>
> Ideally, I would like to arm and disarm using an external magnet. Using
> simple burglar alarm type switches seems dicey. Does anyone use a switch
> that is “click-on, click-off” and is small enough for smaller sized AV bays?
> Thanks!
>
> Richard King
>
>
>
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