Screw Switches

Seen something that has been extremely useful in the rocketry world? Post it here and share your sources.

Moderator: Moderators

drew
Southern fried goodness
Southern fried goodness
Posts: 869
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Screw Switches

Postby drew » Fri May 19, 2017 12:34 pm

So I've been looking into screw switches recently. Basically I'd like to stop using the cheap push button switches I normally buy from Jaycar. Whilst they have worked flawlessly for me in the past (all the way up to Mach 2.2 in fact) I'd like something that's in a smaller form factor and a bit more "robust" if you will. For a few years now I've been wanting some of the MissileWorks screw switches, specifically ever since I saw Al Bychek use them at THUNDA 2015 on his MD flight. So I've ordered a handful of them and should have them in a couple weeks. Specifically this switch.

http://www.missileworks.com/store/#!/6-32-PCB-Screw-Switch/p/38076724/category=5760490

That said recently I've come across the much smaller screw switches that Crazy Jim is now using. Sure they're more than twice the price of the MissileWorks model but they appear smaller. Yesterday I noticed that the AeroPac 100k team has switched (pardon the pun) over to them for their two stage stack AV bay switching needs. That sealed it for me. I'm going to get some of these as well.

http://www.fingertechrobotics.com/proddetail.php?prod=ft-mini-switch
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

martymonsta
Engineer
Engineer
Posts: 709
Joined: Mon Oct 13, 2014 11:57 am
Location: Drouin Vic.

Re: Screw Switches

Postby martymonsta » Fri May 19, 2017 8:40 pm

Hey Drew. I've used the missile works one in the past, however, my current av-bay designs have moved away from them. A few things to be aware of, they have a habit of screwing themselves in or out with slight vibrations. So as you walk out to the pad they can screw themselves in and arm your electronics prematurely or wind themselves out and fall somewhere in your rocket and leave you with a trip back to the flight line to pull the rocket apart and find the wayward screw. I tried a design that included a hatch so that I could see exactly what was going on but it was mega fiddly. I've gone to a pull pin setup now with micro switches, really minimizes the complexity and stress at the pad.
Many years ago the great British explorer George Mallory, who was to die on Mount Everest, was asked why did he want to climb it. He said, "Because it is there."
Well, space is there, and we're going to climb it

MARS #21
AMRS #41 L2/LCO/RSO/CO

User avatar
OverTheTop
It's only money...
It's only money...
Posts: 2590
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Screw Switches

Postby OverTheTop » Fri May 19, 2017 8:55 pm

I've gone to a pull pin setup now with micro switches, really minimizes the complexity and stress at the pad.


Tried a few things, and the pull-pins are my preferred method. Just so simple and easy to not forget.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

User avatar
CATO
Mr Smiley
Mr Smiley
Posts: 1939
Joined: Thu Dec 24, 2009 6:20 pm
Location: Sydney, NSW
Contact:

Re: Screw Switches

Postby CATO » Sat May 20, 2017 7:36 am

OverTheTop wrote:
I've gone to a pull pin setup now with micro switches, really minimizes the complexity and stress at the pad.


Tried a few things, and the pull-pins are my preferred method. Just so simple and easy to not forget.

Agreed.
"In thrust we trust"

AMRS 21 L3

Impulse:
2018: 7,455 Ns (46% M)
Ns 17: 5,973; 16: 34,558; 15: 35,955; 14: 6,016; 13: 10,208
PB - Gorilla N2717WC, H: 10,260', S: 1.14M

drew
Southern fried goodness
Southern fried goodness
Posts: 869
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: Screw Switches

Postby drew » Sat May 20, 2017 11:26 am

So do y'all design your pull pin switches yourselves or are they COTS hardware?
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

User avatar
OverTheTop
It's only money...
It's only money...
Posts: 2590
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Screw Switches

Postby OverTheTop » Sat May 20, 2017 12:05 pm

I buy Omron micro-miniature microswitches with arms (and wire pigtails) from Digikey, then build some structure around them. I get the sealed ones for improved reliability.

Something like this:
AltsCompleted.JPG
AltsCompleted.JPG (102.71 KiB) Viewed 786 times


sledtop.JPG
sledtop.JPG (36.96 KiB) Viewed 786 times


Details on the entire build here if you are interested:
viewtopic.php?f=6&t=5019
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

User avatar
SpaceManMat
Astronaut
Astronaut
Posts: 2036
Joined: Mon Dec 15, 2008 9:56 pm
Location: Brisbane

Re: Screw Switches

Postby SpaceManMat » Sat May 20, 2017 1:29 pm

drew wrote:So do y'all design your pull pin switches yourselves or are they COTS hardware?


I've looked for COTS ones they are usually far too big and heavy. Would be nice if one could be sourced, especially after one that PBC mounted.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

drew
Southern fried goodness
Southern fried goodness
Posts: 869
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: Screw Switches

Postby drew » Wed May 24, 2017 10:07 am

OverTheTop wrote:I buy Omron micro-miniature microswitches with arms (and wire pigtails) from Digikey, then build some structure around them. I get the sealed ones for improved reliability.


Cheers OTT. Do you mind sharing which model you use. I did a search on Digi-Key's web site and they have 109 different Omron sealed switches!?!?
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

User avatar
OverTheTop
It's only money...
It's only money...
Posts: 2590
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Screw Switches

Postby OverTheTop » Wed May 24, 2017 11:22 am

D2HW-C212MR.jpg
D2HW-C212MR.jpg (26.06 KiB) Viewed 749 times


https://www.digikey.com/products/en?keywords=SW727-ND

There are a couple of different variants, depending on whether you want the wires out the side or the bottom. Make sure you get one that has access to NC (normally closed) contacts for the pull-pin use. Some of the two-wire variants only have NO (normally open) contacts accessible. It is all in the part number. The data sheet on the attached link will let you look at what variant(s) you want.

Sealed, and with a lever. I prefer pigtails rather than QC connectors. Better sealing too I think.

You might just need to put a tiny bend in the end of the lever to stop it catching on the pin. That's what I do.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

drew
Southern fried goodness
Southern fried goodness
Posts: 869
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: Screw Switches

Postby drew » Wed May 24, 2017 11:49 am

Thanks mate, much appreciated. I'll have a look at the data sheet and order a handful for testing!
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

User avatar
Viking
Rocket Crew
Rocket Crew
Posts: 462
Joined: Sat May 16, 2015 2:54 pm
Location: Perth WA

Re: Screw Switches

Postby Viking » Wed May 24, 2017 1:03 pm

~30 cents each cheaper and free delivery(for 5 or more), 6-7 days lead time though. E14 might have similar available next-day.
http://au.element14.com/omron-electroni ... dp/2069755
Simon
WARS #24 / AMRS #54 L2

User avatar
OverTheTop
It's only money...
It's only money...
Posts: 2590
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Screw Switches

Postby OverTheTop » Wed May 24, 2017 3:11 pm

Postage is free for E14 if you spend over about $50 IIRC.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)


Return to “I could use that”

Who is online

Users browsing this forum: No registered users and 2 guests