Break Make Plug - i.e. the Remove before flight

[spence]

Guys- I'm sure this is somewhere in the forum but did not find it. The simple "Remove before flight" pin makes the circuit when pulled. Where can I get that with the proper spring loaded socket? I have not used that in my Electronics Bays yet , but.... I have an idea for a cool night flight light show and want to turn on a bunch of LED lights at apogee, and the pull pin seems like the easiest way to make the circuit live. Thanks in advance and Happy New Year!

 

[MikeyDSlagle]

I'm not sure what your looking for.
If your looking for a pin, I may can help ya there. I forget the size but I found a piece of copper tubing that it fits nicely.

 

[PBic]

Guys- I'm sure this is somewhere in the forum but did not find it. The simple "Remove before flight" pin makes the circuit when pulled. Where can I get that with the proper spring loaded socket? I have not used that in my Electronics Bays yet , but.... I have an idea for a cool night flight light show and want to turn on a bunch of LED lights at apogee, and the pull pin seems like the easiest way to make the circuit live. Thanks in advance and Happy New Year!

Check pages 12 & 13 here - https://www.perfectflite.com/Downloads/StratoLogger manual.pdf

 

[FMarvinS]

As suggested above, in the perfect flight stratologger instructions a rod in a pull-pin switch (aka snap switch) is easy to use. The ones I use are the SS-5G-13 switches (Digi Key) with a 3/32 inch diameter rod (in place-switch open; rod removed-switch closed) as shown in the attached photos. The switches are placed in a 3D printed enclosure that I printed that enables turning on or off both switches with only one pull-pin. Tonimus ( in his L2 cert thread of the Wildman AAD 98) has a novel approach and uses a cotter pin as the pull-pin switch. The 3/32 inch diameter cotter pin that is one & a half inches long works well and is easy to attach the flag to it. Handeman, in his L3 build has very well displayed similar switches on his AV-sled and he used finishing nails as pull-pins. OverTheTop-had a thread in which he turned on 4 switches with one pull-pin. He uses a small Allen screw driver as the pull-pin with the flag attached to the handle. In terms of the removal flag, Aerocon Rocketry sells them; however, I had several printed at my local UPS store on vinyl which is cheap (~$2.50 each) and they work well.



Fred, L2
KG4YGP
member of ICBM, S.C.

 

[JohnCoker]

In the olden days, we used 1/8" phono jacks. They have three connectors, making both a normally-closed and a normally-open connection. I stopped using them because people said they were unreliable, even though I had no problems with them.

 

[qquake2k]

Here is how I did it:

https://www.rocketryforum.com/showthread.php?44764-Mile-High-build-thread&p=440867#post440867

 

[FMarvinS]

Hi John,

I also initially used 1/8th inch female phono jacks and 3/32 cotter pins; however, even when I switched to the American made (better quality) ones, they functioned intermittently. On 2 occasions just before placing the rockets on the launch rail, I cancelled launches due to faulty switch functioning. My remedy was to switch to snap-switches as posted above.

Fred

 

[OverTheTop]

I vote for the snap-acting ("microswitch") switches too. Phono sockets as an NC switch are unreliable, particularly when they are used in vibration environments for connection (the sideforce from the contacts provide contact force for the outer ground).

 

[spence]

Guys- I'm sure this is somewhere in the forum but did not find it. The simple "Remove before flight" pin makes the circuit when pulled. Where can I get that with the proper spring loaded socket? I have not used that in my Electronics Bays yet , but.... I have an idea for a cool night flight light show and want to turn on a bunch of LED lights at apogee, and the pull pin seems like the easiest way to make the circuit live. Thanks in advance and Happy New Year!

Thanks All ! Got the info I was looking for!

 

[Reinhard]

For our current club projects we're using Omron D2F-A and D2F-A1 switches on a simple custom PCB. When the Pin is pulled out a bit, the electronics power up, when it is pulled out completely, it gets armed. On multistage rockets, the latter is done with a long string tied to the pin, to make sure nobody is standing right next to the rocket when the upper stage motor gets armed. The string method is admittedly kind of a kludge. For example, I almost accidentally pulled the pin prematurely when the sting got caught on the walkie talkie clipped to my belt.
We are using switches without levers, to reduce susceptibility to vibration. In a future design iteration, I'd like to try out ball lock pins (aka quick release pins) that latch into some kind of 3D printed socket when fully inserted, to make it less sensitive to handling mishaps (taping the pin to the rocket works too, in the mean time).
A minor drawback of our pull-pin approach is that the avionics will be powered and armed while the ebay gets assembled or disassembled, which limits the time frame when igniters can be connected.

Reinhard

 

[Handeman]

A minor drawback of our pull-pin approach is that the avionics will be powered and armed while the ebay gets assembled or disassembled, which limits the time frame when igniters can be connected.

Reinhard

I avoided the powered electronics by adding screw switches in series with the pull pins that are covered by the fin can BT. You can shut power off when the rocket is apart, before you remove the bay from the payload tube or open it up. Just don't forget to turn on the power switches before assembling the rocket or nothing happens at the pad when you pull the pins.

 

[Cl(VII)]

This post got me to tinkering, and here is what I came up with. The switches have the lever removed, so only the weight of the button itself when worrying about an accidental off from G-loading. Took a lot of tinkering to get the rod to consistently depress the button(s), not be too snug, not be too loose, and not hit the flat edge of the button and jam. I got weird looks from my wife when I said things like "0.05 mm too much that time", but it ended up working pretty well.

 

[cerving]

Chris, that looks like another Very Useful 3D printed product...

 

[Cl(VII)]

Chris, that looks like another Very Useful 3D printed product...

Thanks, I hope they prove to be.

 

[soopirV]

Users of microswitches- are they oriented as shown in the photos, or do you mount them horizontally? Seems like a high G event could cause the switch to bounce? I built a timer using a levered microswitch as a G-switch to detect launch, but did have to add mass to the lever, so maybe the internal spring tension is high enough to stay closed?

 

[Cl(VII)]

Users of microswitches- are they oriented as shown in the photos, or do you mount them horizontally? Seems like a high G event could cause the switch to bounce? I built a timer using a levered microswitch as a G-switch to detect launch, but did have to add mass to the lever, so maybe the internal spring tension is high enough to stay closed?

I believe the operating force on the button for the one I show is 0.5 N. It doesn't have a lever, and the button itself weighs approximately nothing, so I'm guessing only a destructive event would make that trip. In the case of a lever I don't have a balance handy that can measure the lever weight, but it is really small too.

 

[mpitfield]

This post got me to tinkering, and here is what I came up with. The switches have the lever removed, so only the weight of the button itself when worrying about an accidental off from G-loading. Took a lot of tinkering to get the rod to consistently depress the button(s), not be too snug, not be too loose, and not hit the flat edge of the button and jam. I got weird looks from my wife when I said things like "0.05 mm too much that time", but it ended up working pretty well.

I have several snap action switches but I haven't used them for two reasons. 1) soon after purchasing them I came to the conclusion that it is generally believed to be subject to failure due to vibrations and G loads. 2) I have yet to have a compelling reason to use it and I believe that there are better choices.

My original reasons for considering using them was because it intuitively seemed like a great visual reminder, it is pretty convenient to just pull something to arm and last but not least the cool factor of pulling the remove before flight pin. However the above reasons steered me away.

Having said that, removing the lever (or using ones that do not have a lever) and mounting the switch on this 3D printed Pull-Pin Switch Block (PPSB) is well thought out and arguably makes them that much more reliable. If you can print the PPSB with enough resolution to get the tolerances that are required for securely mounting the switch reliability, as well as a means to securely mount the PPB on it's side in the AV bay, then this may get more traction.

I am looking forward to following your progress and hearing about successful flights and discovering the failure limits and modes.

Nice one Chris

 

[Cl(VII)]

I have several snap action switches but I haven't used them for two reasons. 1) soon after purchasing them I came to the conclusion that it is generally believed to be subject to failure due to vibrations and G loads. 2) I have yet to have a compelling reason to use it and I believe that there are better choices.

My original reasons for considering using them was because it intuitively seemed like a great visual reminder, it is pretty convenient to just pull something to arm and last but not least the cool factor of pulling the remove before flight pin. However the above reasons steered me away.

Having said that, removing the lever (or using ones that do not have a lever) and mounting the switch on this 3D printed Pull-Pin Switch Block (PPSB) is well thought out and arguably makes them that much more reliable. If you can print the PPSB with enough resolution to get the tolerances that are required for securely mounting the switch reliability, as well as a means to securely mount the PPB on it's side in the AV bay, then this may get more traction.

I am looking forward to following your progress and hearing about successful flights and discovering the failure limits and modes.

Nice one Chris

It is hard to see from the pics, but the holes in the switches go through the holder as well. Also, the switches click into the holders quite securely even without the screws. In this configuration they would be mounted flush with the sled, but a 90 degree mount would be possible.

 

[OverTheTop]

I usually mount them horizontally, but occasionally vertical.

 

[Cl(VII)]

I usually mount them horizontally, but occasionally vertical.

How do you pull the pin when it is mounted vertically? Or worse yet, replace it in a stand down situation?

 

[Handeman]

I've been using those types of switches for years, but always mount them with the button down/aft. That way the motor thrust is forcing the button to it's open position which is the "in flight/ON" position. I've never had a problem with that positioning, even on +80G flights. A caveat to that, I use the Perfectflite altimeters which have capacitors on the power side so momentary breaks in power will not affect them. YMMV with other altimeters.

 

[OverTheTop]

How do you pull the pin when it is mounted vertically? Or worse yet, replace it in a stand down situation?

Switch is mounted vertically (instead of laying down), but pin still pokes through the airframe. Operation as per normal.

 

[Cl(VII)]

Switch is mounted vertically (instead of laying down), but pin still pokes through the airframe. Operation as per normal.

Gotcha. I had a different definition of vertical in mind. I was thinking pin in the z-axis, which led to.my confusion.

 

[FMarvinS]

I have several snap action switches but I haven't used them for two reasons. 1) soon after purchasing them I came to the conclusion that it is generally believed to be subject to failure due to vibrations and G loads. 2) I have yet to have a compelling reason to use it and I believe that there are better choices.

My original reasons for considering using them was because it intuitively seemed like a great visual reminder, it is pretty convenient to just pull something to arm and last but not least the cool factor of pulling the remove before flight pin. However the above reasons steered me away.

Having said that, removing the lever (or using ones that do not have a lever) and mounting the switch on this 3D printed Pull-Pin Switch Block (PPSB) is well thought out and arguably makes them that much more reliable. If you can print the PPSB with enough resolution to get the tolerances that are required for securely mounting the switch reliability, as well as a means to securely mount the PPB on it's side in the AV bay, then this may get more traction.

I am looking forward to following your progress and hearing about successful flights and discovering the failure limits and modes.

Nice one Chris

Hi mpitfield,

These microswitches function well either in a 3D printed enclosure (see post #4, enclosures that I printed and use) or without the enclosure. As a matter of fact, Handeman used these switches successfully on his level 3 flight and as far as I understand, our Australian colleague has used them on 2 stage launches successfully. In order to minimize concerns about vibratory or high G effects, mounting the switches so that the lever faces aft would have the effect that during upward flight acceleration, the switches would be in an electronically closed position. Furthermore, compression of the lever is dependent upon the amount of force applied and several available switches have higher force requirements for lever movement (see digi key catalog where these values are enumerated) which could further minimize the hypothetical effects of vibration during flight. Another benefit of these switches is the relatively low cost-usually between $1.75 and $2.50 each.

Fred, L2
member of ICBM,
Camden, S.C.
KG4YGP

 

[OverTheTop]

For my comments on switch bounce, have a look at this post:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019&start=21

Whatever orientation you end up using, treat it like it is going to bounce. Ejection charges and other off-nominal forces can bounce the airframe.

 

[Handeman]

For my comments on switch bounce, have a look at this post:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019&start=21

Whatever orientation you end up using, treat it like it is going to bounce. Ejection charges and other off-nominal forces can bounce the airframe.

Fortunately our rockets are not dependant on switch bounce for life support. What does work is if you use those switches for power for your altimeters and you use altimeters that have capacitors on the power legs like the Perfectflite I use. Even if you have switch bounce, it won't affect the operation of the altimeters because the capacitors will provide power during the switch bounce and prevent power issues with the altimeter electronics. If you have a switch failure, which is a whole different animal, all bets are off.

 

[OverTheTop]

Yep. Supercaps are wonderful things.