Key Switch

[DAllen]

Just wondering...I am looking for a key switch for my L2 project. I don't *need* a switch because I could revert to the ever reliable twist and tuck method. Regardless, this is more about looks than anything. I love the idea of having a "REMOVE BEFORE FLIGHT" tag hanging off my rocket and twisting a key and removing it on the pad. That's just plain cool.

I've found some spots that sell key switches but I know nothing about the vendors. I was wondering if anyone could point me to a good web site to buy one.

1. It needs to be as light as possible. A 3 lb. ignition key switch is cool and all but is slightly overkill.

2. McMaster-Carr is an awesome site but there are no photos of the key switches that I could find. I like photos.

3. I would really rather not have the soldering pad thingy for the terminals. I would rather have the screw-type connections. If you are confused by what I am saying here, think "HORRIBLE SOLDERING SKILLS." lol


-DAllen

 

[FROB]

You can find those at a security system wholesaler, or electronics surplus stores, for example:
https://www.73.com/a/0611.shtml
https://www.surplussales.com/Switches/SWAssort-1.html

 

[REAPER]

DAllen

Howdy, I've had good luck with the switches from Aerocon https://www.aeroconsystems.com/info/contact. I've used both the screw switches and the ones with a key.The keyed ones do look cool with the "Remove Before Flight" flag. On my 5.5 Polecat Nike-Smoke,I'm using a NC phono plug from Radio Shack.just pull the plug and the electronics are armed.The keyed switches and the phono jack do require soldering though.Good Luck!! Correction: The screw switches I used were from Newton's 3rd Rocketry.they have wire leads already attached. You can wire them directly to your alt,pwr supply;etc,no soldering required.

 

[FROB]

Forgot to mention:
Some people discourage the use of key switches to arm on-board electronics, (and i kinda agree) because if the rocket is first found by anyone other than you after a launch, they wouldn't be able to disarm it, even if they knew how. if the rocket has any charges that didn't go off, it could be a safety hazard.

 

[DMcCauley]

Forgot to mention:
Some people discourage the use of key switches to arm on-board electronics, (and i kinda agree) because if the rocket is first found by anyone other than you after a launch, they wouldn't be able to disarm it, even if they knew how. if the rocket has any charges that didn't go off, it could be a safety hazard.

Nonsense.
Several flaws in this argument.

1. The odds of someone finding your rocket before you do are very remote.

2. Someone familar with rocketry, should know not to touch your rocket. You shouldn't have to protect AGAINST ignorance.

3. Someone not familiar with rocketry won't know what those "Switches" are anyway or how to use them, so no sense putting them in.

4. Someone familiar with rocketry shouldn't touch your rocket anyways. You shouldn't have to protect AGAINST STUPIDITY

So, go ahead and use your key switches. I use CKK key switches which can be ordered from digikey. I've used them from slow birds to mach flights using warp-9 motors and never had a problem. Very reliable!

 

[DAllen]

Forgot to mention:
Some people discourage the use of key switches to arm on-board electronics, (and i kinda agree) because if the rocket is first found by anyone other than you after a launch, they wouldn't be able to disarm it, even if they knew how. if the rocket has any charges that didn't go off, it could be a safety hazard.

Good point...but what about the twist n tuck method? If I do that and the wires are inside the ebay you just about have to take everything apart to get at the wires. It's sort of the same situation. This issue you mention lends itself to a whole different discussion. If you run across someone else's rocket it ought to be left alone if at all possible until the owner is contacted for this very reason. Even if I knew exactly how to disarm the thing I am not going to do so until the owner specifically requests I do so.

-DAllen

 

[jderimig]

Nonsense.
Several flaws in this argument.

1. The odds of someone finding your rocket before you do are very remote.

Happens to me all the time. Otherwise I'd might be out of rockets.

2. Someone familar with rocketry, should know not to touch your rocket. You shouldn't have to protect AGAINST ignorance.

Tell that to a court.

3. Someone not familiar with rocketry won't know what those "Switches" are anyway or how to use them, so no sense putting them in.

A little labeling goes along way.

4. Someone familiar with rocketry shouldn't touch your rocket anyways. You shouldn't have to protect AGAINST STUPIDITY

See #2

 

[FROB]

Good point...but what about the twist n tuck method? If I do that and the wires are inside the ebay you just about have to take everything apart to get at the wires. It's sort of the same situation. This issue you mention lends itself to a whole different discussion. If you run across someone else's rocket it ought to be left alone if at all possible until the owner is contacted for this very reason. Even if I knew exactly how to disarm the thing I am not going to do so until the owner specifically requests I do so.

-DAllen

After trying a few different approaches,
for mid power and the smaller high power rockets (up to J class, but mostly lower, depending on airframe size) i now use the twist & tape method with a small square of red electrical tape holding the bare copper twist down against the BT and covering the hole. its extremely simple, reliable, lightweight, and easy for anyone to disarm.

For Larger and more complex or bigger L2 (and potentially L3) i use toggle switches with short stubby levers that need a lot of force to toggle them, installed horizontally, 1 for each pyro battery, which short the ematch when off, and 1 to power each altimeter, also shorting its power input when off.

I haven't done any high altitude or L3 launches yet, but I have seen and had rockets get hung up in a tree out of reach only to fall out hours or days later and found by others. I have seen others loose rockets regularly and these are often found by people with no knowledge of rocketry such as farmers, hours to days later, and can get tossed in the back of a pickup and kept as a souvenir or handed to a kid as a toy if there aren't danger markings (and a label on them thats says "if found, please call... for a reward" is a good idea too).
I am planning to do some min-dia. high altitude, more L2, and potentially L3 rockets this season, and those will also have large warning labels next to the arming switches, saying not to move the rocket until it is disarmed, and indicating how to do that, in big bold letters.

I thinks it's important that we all remember that this is a hobby with a lot of potential dangers and risks, but we have an exemplary safety record in spite of that because we tend to take these seriously. By doing everything in our power to minimize the dangers, however remote they may be, we help to insure that safety record stays as good as it is, and in so doing help avoid further incursions on our individual or collective rights to pursue the hobby.

 

[DMcCauley]

Happens to me all the time. Otherwise I'd might be out of rockets.


Tell that to a court.


A little labeling goes along way.


See #2

Sorry. Your making some huge assumptions here.

1. You assume whoever finds the rocket knows exactly how the rocket works and what the switches do.

2. That someone will even assume what the labeling means and how to interpret the state the rocket is when they find it.

Again, its all rubbish.

In the end, the rocket is YOUR responsibility and you should be accountable for it at all times, even when lost.

If your rocket lands somewhere and is lost, then its YOUR fault for launching it in the first place. Your rocket should always be under your control and launched per the conditions and field size.

If you feel your rocket will land somewhere where someone will inadvertently find it before you or whatever, than you shouldn't launch to begin with.

 

[DMcCauley]

After trying a few different approaches,
for mid power and the smaller high power rockets (up to J class, but mostly lower, depending on airframe size) i now use the twist & tape method with a small square of red electrical tape holding the bare copper twist down against the BT and covering the hole. its extremely simple, reliable, lightweight, and easy for anyone to disarm.

No its not.
You think some Joe Smoe finding your rocket is going to know to disconnect the wires taped again the BT?

Do you think he'll do that BEFORE picking up the rocket? I don't think so.

Its only EASY to disarm if you BUILT the rocket and have a full working understanding of how it works.

It would be negligent for you to assume that anyone finding the rocket will understand the disarming procedure, even if it was written right on the rocket.

 

[pyrovette20]

DAllen

Howdy, I've had good luck with the switches from Aerocon https://www.aeroconsystems.com/info/contact. I've used both the screw switches and the ones with a key.The keyed ones do look cool with the "Remove Before Flight" flag. On my 5.5 Polecat Nike-Smoke,I'm using a NC phono plug from Radio Shack.just pull the plug and the electronics are armed.The keyed switches and the phono jack do require soldering though.Good Luck!! Correction: The screw switches I used were from Newton's 3rd Rocketry.they have wire leads already attached. You can wire them directly to your alt,pwr supply;etc,no soldering required.

Ive used Aerocon in the past with very good results with both key switches. Dont use the phono plug method. The high G-force could momontarilly open the switch and reset the electronics in flight (not good).

 

[DMcCauley]

Ive used Aerocon in the past with very good results with both key switches. Dont use the phono plug method. The high G-force could momontarilly open the switch and reset the electronics in flight (not good).

Actually, the phono plug is a great idea if you implement it properly.

There is a very simple circuit you can devise using a p-channel MOSFET and a phono plug. The beauty of this circuit is that the circuit is armed when the phono plug is removed, therefore no worries about momentary disconnects in the switch.

Of course, as usual there will be advantages / disadvantages of each.

Here is a schematic of the P-Channel phono plug implementation i used for a video payload and photo as well.

https://www.danielmccauley.com/sojars/projects/arcasvideoschematic.pdf

 

[REAPER]

Ive used Aerocon in the past with very good results with both key switches. Dont use the phono plug method. The high G-force could momontarilly open the switch and reset the electronics in flight (not good).

WOW,I read this and my heart dropped. Has anyone else had this problem. I had figured that because the rocket is overbuilt(my trademark,LOL)that G-forces wouldn't come into play. I had already installed the phono jack with the contacts on their side so if G-forces were high ,they would act on the edge of the contacts not their face. I'd really like to NOT have to enlarge the switch hole on an already finished av-bay. Any advice would REALLY be appreciated!!

 

[DAllen]

I donno if that is truly a problem for all altimeters. I know my HiAlt45k will operate for about 2 or 3 seconds (or more) after disconnecting the battery. Most motors I use with it only burn 1.5 to 2 seconds at the most. If you are really worried about it can you just remove the phono plug thingy and revert back to the tried and true twist and tuck in the existing hole? I know nothing about the phono plug method but if you orientate the contacts correctly couldn't you avoid the vertical gee's?

The phono plug method interests me, does anyone have a linky to a site explaining how it works?

-Dave

 

[REAPER]

I donno if that is truly a problem for all altimeters. I know my HiAlt45k will operate for about 2 or 3 seconds (or more) after disconnecting the battery. Most motors I use with it only burn 1.5 to 2 seconds at the most. If you are really worried about it can you just remove the phono plug thingy and revert back to the tried and true twist and tuck in the existing hole? I know nothing about the phono plug method but if you orientate the contacts correctly couldn't you avoid the vertical gee's?

The phono plug method interests me, does anyone have a linky to a site explaining how it works?

-Dave

I really can't remember where I got the idea,I think it was in the "old" TRF. I did orient the contacts,I really thought that was enough because the rocket is pretty heavy and I think the lift-off should be fairly slow. I'll know the weight for sure tonight, I was going to make any adjustments to the CG after I get home from work. I just realized our NAR #'s follow one another,LOL. Thanks for the response,I appreciate the input.

 

[DAllen]

I think I am going to use a phono switch. Simply because buying spare phono plugs is going to be a little cheaper and easier than having additional keys made in case I loose a key. Besides, I already have a few phono plugs laying around the house in some old instrument cables that no longer work well. Not only that but the phono jack *I think* is going to be lighter than a key switch anyways.

Attached is a photo I found and labeled the 2 primary contacts A and B. Once the plug is removed A is going to touch B. If I orientate the jack with A on top then the more G's the rocket goes through the harder A is going to press on B simply because it obviously has way more mass.

I think this discussion on whether or not high g loading using this method is a moot point. Even if you have a violent ejection that causes enough G's to separate A and B for a split second (which isn't very likely with proper ground testing) I know my HiAlt45k will be okay because it can operate without power for 2 or 3 seconds after the battery is disconnected. Unless you are going to go mach 3 or have a super critical launch I think this is the way to go on most DD applications provided there is enough room in the ebay.

-Dave

View attachment Phono Switch.pdf

 

[REAPER]

I think I am going to use a phono switch. Simply because buying spare phono plugs is going to be a little cheaper and easier than having additional keys made in case I loose a key. Besides, I already have a few phono plugs laying around the house in some old instrument cables that no longer work well. Not only that but the phono jack *I think* is going to be lighter than a key switch anyways.

Attached is a photo I found and labeled the 2 primary contacts A and B. Once the plug is removed A is going to touch B. If I orientate the jack with A on top then the more G's the rocket goes through the harder A is going to press on B simply because it obviously has way more mass.

I think this discussion on whether or not high g loading using this method is a moot point. Even if you have a violent ejection that causes enough G's to separate A and B for a split second (which isn't very likely with proper ground testing) I know my HiAlt45k will be okay because it can operate without power for 2 or 3 seconds after the battery is disconnected. Unless you are going to go mach 3 or have a super critical launch I think this is the way to go on most DD applications provided there is enough room in the ebay.

-Dave

Dave

Thanks for the picture,that is exactly the same phono plug I'm using. Upon looking at my av-bay last night,I have already re-oriented my plug just the way you mentioned.(great minds must think alike,ha-ha). Also a little side note.the phono plug is the same one I use in my Pratt Hobbies Universal Launch Controller. After I arm the electronics I can walk to my controller and use the same plug if I want to. Thanks for the update.

Lloyd

 

[RandyM]

3. I would really rather not have the soldering pad thingy for the terminals. I would rather have the screw-type connections. If you are confused by what I am saying here, think "HORRIBLE SOLDERING SKILLS." lol


-DAllen

One suggestion I will give you is to learn how to solder. It's really not that hard and a really good skill to have for rocketry. Here's a link to a really good tutorial:

https://www.youtube.com/watch?v=BLfXXRfRIzY

I really like the screw switches for newtons 3rd. you can find a "key" for them in any hardware store!

 

[ga1ba2]

How about this one from Harbor Freight

https://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92688

 

[Kaycee]

How about this one from Harbor Freight

This one is probably best left to drag racing--CARS, not rockets and such me thinks.

 

[Handeman]

I would agree, it's about 3" diameter and probably weighs a half pound. Of course, some of the projects might be able to use it.

 

[georgegassaway]

Dont use the phono plug method. The high G-force could momontarilly open the switch and reset the electronics in flight (not good).

There are other kinds of switches where that kind of thing might happen in theory. One way to resolve that would be to mount the switch "sideways" if at all possible, so that fore-aft G lads could not affect it.

But in any case, I too will caution against phono plugs. Because quite simply I have had some R/C Rocket Boosted gliders develop problems when I used them as switches. Eventually, the spring contact stopped pressing hard enough to reliably maintain electrical contact. Fortunately, IIRC, I did not lose any models to it, but I sure had some very inconvenient pre-flight dead models where the only way to fly them was to bypass the switch and directly plug in the battery to the receiver (Still a safe way to fly, but it meant the inconvenience of plugging it in shortly before light and unplugging right after landing. But at least those did not involve pyrotechnics, I would never want to have to plug in a battery to turn “on” a system that was going to fire an upper stage or ejection charge).

I no longer use phono plugs for switches on anything that a phono plug failure would cause a crash.

I will also mention that for some conventional switches, like slide switches, I mount those so that moving them "down" is "ON". Not so much for G-forces, as I do not fly stuff at overkill speeds, but simply if the model hit anything in flight, it would not slide the switch "off" (OK, not likely for a rocket to hit another rocket, or even a bird, but I have been doing this since I started flying R/C. And R/C RBG's could possibly hit something as they leave the launcher. Also, I once saw an R/C plane fly away when a guy was doing a touch-and-go landing, and the moment after he gunned the engine to take off again, a rock got kicked up into the switch and turned the R/C gear switch off. But the throttle was stuck open and the model trimmed out nicely so it climbed up and up and drifted farther and farther away, till it ran out of fuel. In any case, all other things being equal, if a person is using a switch where the choice is moving it up for on, or down for on, might as well arrange it for down to be on, up to be off.

- George Gassaway

 

[DRAGON64]

Kind of late in replying, but I have had great success with Electrical Switch Locks for many years. But, I have also had the advantage of rescuing many of these types of switches from old Gateway 2000 and other pre year 2000 computer housings. There is a sources for these similar switches at ebay:

item number: 260376634266

My Link: Electrical Switch Lock

Attached pic: 2-used in my Level III rocket; they fit very clean in the airframe...

 

[FredA]

If you just gotta have a "Remove before Flight" tag on your rocket, shove it in the nozzle.

Please don't use Keys or the dreaded Twist and Tuck.

People who find your rocket will not be able to disarm it.
You are possibly endangering anyone who comes upon your rocket before you.
You are nieve to think that they won't touch it.
You must hope they are smart enough to disarm it and must give them the opportunity to do so....

Don't think it won't happen to you....
Accidents do happen.

Leaving Balls last year, we were one of the last groups to leave the playa. On the drive out, we came across a booster section that was lying on the ground beeping.
No one was around but us.
Nobody really wanted to mess with it, but we had to -- otherwise it would probably still be on the playa -- remember, we were one of the last groups out.....

It was a freaking twist and tuck...beeping hard -- not properly deployed -- probably with hot charges -- YIKES!

We carefully rolled it over and then had to search to find something that could fish out the wires...

I felt like a bomb-squad guy....nobody should have to do this.

Sure, happy ending....
But what would you do?
Maybe we should have left it on the playa as a "lesson" that would never be taught to the owner.
Perhaps we should have buried it so no unsuspecting person would stumble upon it.

It, for sure, wasn't going in the van until we were certian it was safe.

I retuned the rocket to the owner, along with the stern message that nobody on the team liked having to disarm something that way.

Don't put anyone at risk.
Use an switch that can be actuated by anyone.
Better yet, label the swtich "ARM" and "SAFE".

Use best known practices -- not cool looking ones.....

You won't always be the first person to find your rocket.

FredA

 

[FredA]

TRF is slow as a dog -- the first post timed out and I hit post again....
What's this forum server from, an Intel Atom?

 

[Terry_TBR]

Here is an idea...

The payload bay needs one or two holes drilled in it so that the pressure sensor can operate correctly. Drill the holes opposite each other and use a "through hole" switch positioned between the two holes. When the pin is in, the switch is forced open. When you remove the pin, the switch closes. This would allow the pin to be placed through the rocket very similar to how bombs are armed on military aircraft.

Though switched like this do tend to be a little heavier than normal switches. Not sure how it would compare to key/lock mechanisms.

I thought this might look pretty cool especially for those that fly scaled models of military missiles.

 

[DAllen]

FredA...Rest assured if I go to Balls and fly some uber-complicated project really really high I will NOT use twist and tuck after spending all that money. I ended up using the phono plug method and honestly and I am not real crazy about it. I think Randy's method (Newton's 3rd switch) combined with labeling will be what I use from now on seeing how 100% of the launches I have been too most anyone has a screwdriver somewhere.

Also, when I twist and tuck, I leave about 1/2" of wire folded downward outside the rocket with a small piece of tape over the hole holding the wire in place. You'd be surprised how well blue painters tape can hold up in the airstream at 300+ mph. That's not how everyone else does it? That's nuts! Otherwise I'd have to take apart the stupid ebay to disarm it. I hate walking all the way back to the flight line listening to the dumb alt beep. Granted, if I had a mach project this just wouldn't be practical or sensible.

Another way to do the "dreaded" twist and tuck that I think would work for Fred is to drill 2 holes for the switch wire. Have the wire sticking out the one hole twist the wires together when ready to arm and carefully shove the wires into the other hole so you have a "hump" of wire that can be pulled on with a pair of fingernails. Pull till the loose end comes out and untwist to disarm. Carefully placed labels and anyone can do it. Anyone tried that?

-Dave

 

[FredA]

If you need to use a screw-switch.
At least go buy yourself a plastic screwdriver.
They are made to SAFELY tweak electronics.

Poking a metal screwdriver blindly into a EBAY hoping to hit the screw and only the screw is asking for trouble.
And, unfortunately, I find very few plastic screw drivers at launches......

Maybe if you glue in some sort of guide tube.

But blindly poking at a circuit attached to BP charges with a conductive tool is plain NUTS in my book.

Me -- I use common 4PDT slide switchs made by switchcraft. Never had one fail.

If you are really worried about the switch opening under vibration, put a capacitor behind it for power circuits....pyro's will NOT be effected as a ms wide interuption will not interfere with a 0.5->1 second pulse.

Use a switch...
Everybody knows how to use them.
They don't fail (really)
One 4PDT can do everything, including disconnecting and shunting your pyro's with your average 2 channel altimeter.

PS: Balls is not the only place where the owner is not the person who finds the rocket.... be safe.... YOU know how to disarm your rocket... Help the guy who finds it be safe too....to the BEST OF YOUR ABILITIES.

 

[Terry_TBR]

If you need to use a screw-switch.
If you are really worried about the switch opening under vibration, put a capacitor behind it for power circuits....pyro's will NOT be effected as a ms wide interuption will not interfere with a 0.5->1 second pulse.

If you went digital you could come up with a pretty simple solution to avoid interruptions using something like a one-shot trigger that would be connected to the gate of a mosfet. When the trigger went off it would put current through your pyro for however long the one-shot trigger remained set.

But it is doubtful that adding the digital logic chip to the board would be all that useful unless you are already using some form of a PLD. A capacitor would be the easier solution if not.

 

[RandyM]

The Newtons 3rd screw switches are designed to be on the outside eliminating all of your concerns about poking inside the rocket. They work great and are not very expensive.

https://www.newtons3rdrocketry.com/shop/popup_image.php?pID=42

https://www.newtons3rdrocketry.com/...id=42&osCsid=62211d24d53250fafded7544c6521ddf

If you need to use a screw-switch.
At least go buy yourself a plastic screwdriver.
They are made to SAFELY tweak electronics.

Poking a metal screwdriver blindly into a EBAY hoping to hit the screw and only the screw is asking for trouble.
And, unfortunately, I find very few plastic screw drivers at launches......

Maybe if you glue in some sort of guide tube.

But blindly poking at a circuit attached to BP charges with a conductive tool is plain NUTS in my book.

Me -- I use common 4PDT slide switchs made by switchcraft. Never had one fail.

If you are really worried about the switch opening under vibration, put a capacitor behind it for power circuits....pyro's will NOT be effected as a ms wide interuption will not interfere with a 0.5->1 second pulse.

Use a switch...
Everybody knows how to use them.
They don't fail (really)
One 4PDT can do everything, including disconnecting and shunting your pyro's with your average 2 channel altimeter.

PS: Balls is not the only place where the owner is not the person who finds the rocket.... be safe.... YOU know how to disarm your rocket... Help the guy who finds it be safe too....to the BEST OF YOUR ABILITIES.