Key Switches

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PSLimo

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KO103D, KO103C.jpg
Hey Guys,

Years back I bought key switches from Aerocon where the key could only be removed in the on position.

A member gave me a link to a switch where the key could be removed in both positions which will work.

Does anyone know where to get key switches like the one posted that only removes in the on position?

Thanks in advance,

Phil
 

dmo

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Electronics distributors like DigiKey and Mouser carry a variety of similar switches.

This DigiKey search returns 59 in stock options. These are not technically "only removes in the on position" switches. They are SPDT and DPDT switches where the key can only be removed in 1 position. Both positions are ON or OFF depending on how you wire them.
It appears that the switch you have is the KO103C701. Both DigiKey and Mouser have it in stock. It is a few cents less expensive at Mouser. That switch is only rated at 1 Amp, so you might want to consider a different switch.

David
 

Voyager1

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If this switch is for a launch controller, then you want one that retains the key in the on position and removable in the off position. You don't want it removable when the system is on, as you might need to turn it off at short notice, or misplace it when the system is armed. If the switch is SPST, then the wiring is not relevant; if it's SPDT, then it is. If this switch passes the ignition current, then it will need a rating of 10A+, preferably. If it's for a low current part of your circuit, then a lower rating is fine. This is usually the case for a relay-based system.
 

Grog6

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I use odd keys from surplus sites;it lowers the odds of some jackass having one that will fit. :)
 

Grog6

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Something to keep in mind: there are current ratings for both ac and dc. dc eats contacts, at higher voltages.
But switches using only low voltages can switch the full rated current below about 28V.
 

Steve Shannon

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I’m not a fan of key switches (in rockets) and there are lots of threads on TFR about selecting appropriate altimeter switches, but, some things to keep in mind with key switches:
  1. Key switches are made to be secure, not necessarily reliable.
  2. A key switch is not less susceptible to vibration. In fact, I’ve never seen a keyswitch with shock or vibration ratings on the spec sheet.
  3. A key switch can only be disarmed with the key. If something happens, such as a key is lost, disarming the rocket becomes much harder.
  4. A lost rocket with a key switch cannot be disarmed if found by someone else.
  5. If you forget your key at home you might be disappointed because you cannot arm your rocket.
  6. The only two things key switches have going for them are that they look cool and they cannot be accidentally turned off.
 
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Grog6

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I'm putting two keyswitches; one will disable the pad, the other powers up the controller. Key fires relay for controller power, which enables the arm circuit and lights on the pad. I'm adding chasing leds into the groove of the rail; fits perfect.
All the relays for the controller are 24v, the pad is all 12v, except for the Fire and Arm contactor.
Pad has lights to show current mode, safe, and armed.
A person would be able to walk up to the pad, while it was armed, see it was armed, and disable it.
 

Steve Shannon

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View attachment 486872Hey Guys,

Years back I bought key switches from Aerocon where the key could only be removed in the on position.

A member gave me a link to a switch where the key could be removed in both positions which will work.

Does anyone know where to get key switches like the one posted that only removes in the on position?

Thanks in advance,

Phil
Amazon has key switches like you’re asking about.
 
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PSLimo

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Hey Guy's,

Thanks for the input, I should have been more specific in my question.

key.JPG


I use these for arming electronics not launch controls. Very visible with a "remove before flight" flag on them. If the key only removes in the on position, if the flags gone your electronics are armed. If the flags there you know the electronics are off when handling the rocket.

The ones I have were bought from Aerocon over 10 years ago I'm still using them today without failure.

I just can't find a 1/2" hole mount key switch that only removes in the on position like the ones in the pic above.

Phil
 

Grog6

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Here's one for $5
It's 3/4 tho.
 

Johnly

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Why a key switch would be my first question.
The second would be if they can handle repeated launch and landing stresses without undergoing some form of mechanical failure.
Personally, the best switch I've found for this application is the Fingertech 40A power switch that arms and disarms with a 3/32" allen wrench
 

Grog6

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I really like the allen key switch above; it's much lighter than the solution I'm using.
 

PSLimo

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Hey Tony,

"Here you go - looks like an exact match"

That is the switch I posted a picture of. Now that I looked closer at the picture it looks like it has 4 solder terminals so I should be able to wire it removable in on position only. I guess the 2 pole remove in on position only aren't around anymore.

"Why a key switch would be my first question."

I use the Allen and screw switches on my smaller, higher flying rockets but on larger rockets I like the visual of the "remove before flight" flags.

Here's a pic of the rest of the rocket in post #10.

Capture.JPG


Hope to see you guy's at a launch soon.
 

Steve Shannon

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Hey Tony,

"Here you go - looks like an exact match"

That is the switch I posted a picture of. Now that I looked closer at the picture it looks like it has 4 solder terminals so I should be able to wire it removable in on position only. I guess the 2 pole remove in on position only aren't around anymore.

"Why a key switch would be my first question."

I use the Allen and screw switches on my smaller, higher flying rockets but on larger rockets I like the visual of the "remove before flight" flags.

Here's a pic of the rest of the rocket in post #10.

View attachment 487017

Hope to see you guy's at a launch soon.
There’s a better way to do the remove before flight.
 

manixFan

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Hey Tony,

"Here you go - looks like an exact match"

That is the switch I posted a picture of. Now that I looked closer at the picture it looks like it has 4 solder terminals so I should be able to wire it removable in on position only. I guess the 2 pole remove in on position only aren't around anymore.

"Why a key switch would be my first question."

I use the Allen and screw switches on my smaller, higher flying rockets but on larger rockets I like the visual of the "remove before flight" flags.

Here's a pic of the rest of the rocket in post #10.

View attachment 487017

Hope to see you guy's at a launch soon.
The description says it’s single pole-single throw, on-off. Here’s the exact same switch but in SPDT so you can wire it either way:


If you go the switch route, you can’t go wrong with the one above. Being double throw you’ll be able to wire it so it’s only on when you can remove the key.
 

Grog6

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That pull-pin switch is what I use on the rocket.
I bought the pins from mcmaster, and some aluminum tubing at hobbylobby.

Choose-a-Color T-Handle Locking Quick-Release Pins
These are awesome!
 

PSLimo

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Thanks Tony,

I wouldn't have caught that but that's the perfect switch for what I want to use them for.
 

cwbullet

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Hey Tony,

"Here you go - looks like an exact match"

That is the switch I posted a picture of. Now that I looked closer at the picture it looks like it has 4 solder terminals so I should be able to wire it removable in on position only. I guess the 2 pole remove in on position only aren't around anymore.

"Why a key switch would be my first question."

I use the Allen and screw switches on my smaller, higher flying rockets but on larger rockets I like the visual of the "remove before flight" flags.

Here's a pic of the rest of the rocket in post #10.

View attachment 487017

Hope to see you guy's at a launch soon.
You can add a flag to an allen wrench, but I get the point.
 

manixFan

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Thanks Tony,

I wouldn't have caught that but that's the perfect switch for what I want to use them for.
You’re welcome. The difference is hard to catch since the photos are identical and technically a SPST switch should only have two contacts, not the four shown. Likewise a SPDT should only have three. But it’s likely just a generic image of the switch and what you get may look slightly different, or only some of the contacts are active.

While I understand the pros and cons of each type, to me it seems whatever works best for you, as long as it does not pose a safety hazard, is the right way to go. Once I use something and it works, I tend to be a creature of habit.


Tony
 

jbr

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there were key switches on a full scale amramm I bought, one fell apart in testing
I replaced both of them with screw switches

YMMV
 

Buckeye

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There’s a better way to do the remove before flight.
Why is this better? You must re-assemble the av-bay with the electronics armed, before you can insert the rod to disarm. That sounds like a potential safety problem.
 

Steve Shannon

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Why is this better? You must re-assemble the av-bay with the electronics armed, before you can insert the rod to disarm. That sounds like a potential safety problem.
I’m not sure why you think that. You assemble the av-bay without any energetics and insert the pull pin. Put a piece of tape over the end of the pull pin so it cannot be accidentally removed. Now your electronics are unpowered.
Once it’s unpowered connect your ematches to your terminal strips on the bulkplates. If you’re one that likes to test the continuity of your matches this is when you do it, away from others and definitely before you have any BP loaded.
Finally, load your BP, connect the bay into the body tubes, load your chutes, and shear pin the joints that separate.
Put the rocket on the rail, stand up the rail, insert the igniter but don’t connect it, remove the tape and pull the pin (now your electronics are armed), and then connect the igniter.
 

Buckeye

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I’m not sure why you think that. You assemble the av-bay without any energetics and insert the pull pin.
If you directly wire ematches to the altimeter (no terminal blocks), then the pull pin switch is probably not a good choice.
 

Steve Shannon

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If you directly wire ematches to the altimeter (no terminal blocks), then the pull pin switch is probably not a good choice.
I would agree. Safety must be considered at each level of design. I spent 23 years dealing with control systems. We had lots of terminal strips. They just make everything easier. I would alternately consider using a two conductor plug and socket instead so that I could plug in my charges after assembling my av-bay.
 
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Grog6

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Iagree on the two terminal plug, in fact, I'm in favor of plugs everywhere. I use Molex plugs everywhere, so im not trying to use a #1phillips in the field, or worse, a 1/8" flat screwdriver.

Much easier to hear the 'click as it locks in.
 

OverTheTop

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I use pull pins, but I have two pins; one for energetics safing, one for powering the altimeter. When working on the bench I use a wooden skewer in lieu of the real RBF pin and flag. These can be short enough that you can assemble and disassemble the rocket without withdrawing them. The RBF pins and flags get swapped in at the end of prep, and one at a time so the energetics can't get excited. A pair of needle-nosed pliers or a dental pick easily extracts the skewers.
 

Voyager1

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If you directly wire ematches to the altimeter (no terminal blocks), then the pull pin switch is probably not a good choice.
You don’t wire them directly. You would use terminals on the outside of the avbay bulk plates to connect to, or flying leads through the plates to twist and tape to ejection charges.
 
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