Electronic Switches for the inexperienced

[James Bond]

I am working on my electronics for my Loc 7.5 R2 Variant of the V2 in-between sandings. This is my first big rocket with electronics. I have an ARTS 2 and a Perfectflite HA45 that I will use. I am also planning on using 2 separate NoMatch systems for ejection. My plan is to push a drogue out at apogee and use a chute tamer to unfurl the main. I know, I know, where is my backup for the chute tamer but I am still working that part out.

My question is more about the ON/OFF switches. I guess I will need an on/off switch for each altimeter. Should I have an on/off switch for the NoMatches? If so, a separate switch for each for a total of 4 on/off switches. What kind of switches and where can I get them? I need to switch on and off at the launch pad so I must have outside access to them. I have no soldering skills what so ever so it has to be idiot proof. Please share your experiences and recommendations.

Thanks in advance,

Shaken, not stirred… sometimes with a lemon peel
007

 

[overby]

My question is more about the ON/OFF switches. I guess I will need an on/off switch for each altimeter. Should I have an on/off switch for the NoMatches?

I have separate switches for altimiter power and for ejection charges. I posted some pictures and schematics on the thread titled "Altimeter Switch Mount."

Glen Overby

 

[Dbarrm]

I used one of these for my L2 bird and all others after that. Soldering is not hard after a little practice. Spend 10 minutes practicing and you will be able to solder good enough to wire up this switch.

 

[James Bond]

Ok, I forgot to mention that I really do not understand too much of this electronic stuff, so please me gentle with me. Let me know if I got this right.

Are these the same switches? https://68.178.208.82/cgi/PF_Store/...page&thispage=SS5GL13.html&ORDER_ID=325826158

Would I use 2 of them? One to power up both Altimeters and then one to arm all charges?

If I were to go to the store and ask for wire, what would I ask for?

If I use simple ematches to fire the charges, how would I wire it?

Thanks, more questions to follow:

007

 

[James Bond]

"I used one of these for my L2 bird and all others after that. Soldering is not hard after a little practice. Spend 10 minutes practicing and you will be able to solder good enough to wire up this switch. "

Thanks, how does this switch work? I see the slot so I assume you simply use a screw driver to click it on and off. Is this correct. What exactally would I have to solder here?

 

[Dbarrm]

That type switch can be wired to turn on or off when the arm is pushed down. I would use two switches, in case one failed the other would still be active. You can make it where one screw or pin turned on both switches. As for the wiring, have the wire from the altimeter going to the match pass though he switch so when the switch is off no current gets to the match. As for wire size, that depends on the amount of current your match will draw at max current.

Dan

 

[Dbarrm]

Thanks, how does this switch work? I see the slot so I assume you simply use a screw driver to click it on and off. Is this correct. What exactally would I have to solder here?

This switch is used for dual voltage electronics. It will have 3 pins on the back of it. One is the output and the other two are inputs. you would pic one for your output. Lets say you connect your input to the 110V input pin. When you have the switch set to 220 (nothing connected to that input pin) the switch would keep your input and output wires disconnected. When you switch it to 110 they would be connected. Basically you are turning it into into a on off switch.

Dan

 

[als57]

Are these the same switches? https://68.178.208.82/cgi/PF_Store/...page&thispage=SS5GL13.html&ORDER_ID=325826158

007

Not the same switches.

Missleworks sells a switch simular to the one shown. Also they sell a 9V battery holder that works well.

Al

 

[James Bond]

I kind of like this one at:

https://www.missileworks.com/mm5/me...de=MWC&Product_Code=SW-2&Category_Code=cat060

However, I am still confused. Please bear with me. Out of the 3 prongs in the back, 2 will connect to the ARTS 2 power terminal and the other remain bare? A second switch will provide the same functionality for the HA45 altimeter and connect the same way. Is this correct?

Since the pyro charges are connected to leads that attach to the altimeters, do they need a separate on/off switch? This is where I am getting confused. If the alt is powered off, so would be the charges or am I missing something.

If a separate on/off switch is required for the charges, for extra safety, how would this connect up? Would the 4 charges wire into one switch or possibly be split into 2 switches for redundancy?

Thanks for everyone’s patience.

007

 

[Dbarrm]

Its like this. You go from the + side of the battery to the switch, out of the switch to the alt. Neg from battery goes to alt. Below is a bad pic.

Dan

View attachment switch.JPG

 

[als57]

I kind of like this one at:

https://www.missileworks.com/mm5/me...de=MWC&Product_Code=SW-2&Category_Code=cat060

However, I am still confused. Please bear with me. Out of the 3 prongs in the back, 2 will connect to the ARTS 2 power terminal and the other remain bare? A second switch will provide the same functionality for the HA45 altimeter and connect the same way. Is this correct?

007

That's the switch I had in mind.

Not familar with the ARTS2. Typically the switch is used to make or break the positive lead of the battery going to the altimiter. The negative (black) lead just connects to the altimeter.

If your using separate bateries and separate alts ; then 2 switches of the type you are looking at would be needed.

Hope that helps.

Al

 

[Larry_Pollack]

I kind of like this one at:

https://www.missileworks.com/mm5/me...de=MWC&Product_Code=SW-2&Category_Code=cat060

However, I am still confused. Please bear with me. Out of the 3 prongs in the back, 2 will connect to the ARTS 2 power terminal and the other remain bare? A second switch will provide the same functionality for the HA45 altimeter and connect the same way. Is this correct?

Since the pyro charges are connected to leads that attach to the altimeters, do they need a separate on/off switch? This is where I am getting confused. If the alt is powered off, so would be the charges or am I missing something.

If a separate on/off switch is required for the charges, for extra safety, how would this connect up? Would the 4 charges wire into one switch or possibly be split into 2 switches for redundancy?

Thanks for everyone’s patience.

007

These have 4 terminals at the base of the switch.

I swear by these, you cant go wrong with them. Just be sure to pack one or two flat blade screw drivers in your range kit.

 

[blackjack2564]

Or you can simply just..........twist and tuck.

Skip the switch, run your on ,off arming wire out the vent hole, twist wires together, tape, and tuck back in the hole. Just about everyone in our club uses this method. Successfully.

 

[James Bond]

Thanks to everyone that responded. You all are really helpful. I will go with this switch https://www.missileworks.com/mm5/me...de=MWC&Product_Code=SW-2&Category_Code=cat060 and move on with my next phase, ejection.

Bond

 

[jrcox]

Or you can simply just..........twist and tuck.

Skip the switch, run your on ,off arming wire out the vent hole, twist wires together, tape, and tuck back in the hole. Just about everyone in our club uses this method. Successfully.

I tried that techinique "Once", I was very fortunate and did not get hurt when I had to dis-arm the electronics and ejection charges on the pad. I would never recommend that type of a proceedure to anyone. If you have to remove the rocket from the launch pad, the only way that "I" could safe the charges was to remove the shear pins by pushing them into the rocket, slide the forward section off, cut the wire to the ematch, open the ebay, cut the power On/off wire and cut the other ematch wire. This was a 4"x9' hybrid rocket and all of the work was accomplished on a ladder. I was fortunate to not have an accident and will never again try that technique. The various safety codes have requirements for arming HPR, however they should include dis-arming methods also. If someone knows which document requires switches to dis-arm, please let me know.

MTC
John

 

[Crazyrocket]

I typically use MW switches on my bigger rockets. However, I do use the twisted wire technique that was mentioned above. The only difference is that I do not tuck it back into the rocket; I just tape the twisted wire to the side of the rocket with electrical tape. Works well and have not had problems with it...even going near mach. This slight variation allows you to easily disarm the electronics if needed without taking the rocket apart.

 

[uncle_vanya]

I tried that techinique "Once", I was very fortunate and did not get hurt when I had to dis-arm the electronics and ejection charges on the pad. I would never recommend that type of a proceedure to anyone. If you have to remove the rocket from the launch pad, the only way that "I" could safe the charges was to remove the shear pins by pushing them into the rocket, slide the forward section off, cut the wire to the ematch, open the ebay, cut the power On/off wire and cut the other ematch wire. This was a 4"x9' hybrid rocket and all of the work was accomplished on a ladder. I was fortunate to not have an accident and will never again try that technique. The various safety codes have requirements for arming HPR, however they should include dis-arming methods also. If someone knows which document requires switches to dis-arm, please let me know.

MTC
John

John I had a screw switch armed altimeter sled break during a hard landing. The screw switch was no longer lined up with the hole and I could no longer disarm the rocket. I had to dismantle the rocket and because I did not use any type of terminal blocks (it was my first electronics bay) I had to cut the live charges with an armed altimeter. I was careful and very nervous. After that I moved away from the design which had only used one threaded rod to hold the sled. I still have qualms about any design I do without an external switch - but they are sometimes needed.

I have a friend who files twisted wires a lot - but he does so with the electrical tape to the side of the rocket method.

 

[jrcox]

To Brad & Glen's response

At least you had a method to disarm. My point was that tucking the wires back in the airframe "may" lead to an unsafe condition.

John

 

[Larry_Pollack]

I tried that techinique "Once", I was very fortunate and did not get hurt when I had to dis-arm the electronics and ejection charges on the pad. I would never recommend that type of a proceedure to anyone. If you have to remove the rocket from the launch pad, the only way that "I" could safe the charges was to remove the shear pins by pushing them into the rocket, slide the forward section off, cut the wire to the ematch, open the ebay, cut the power On/off wire and cut the other ematch wire. This was a 4"x9' hybrid rocket and all of the work was accomplished on a ladder. I was fortunate to not have an accident and will never again try that technique. The various safety codes have requirements for arming HPR, however they should include dis-arming methods also. If someone knows which document requires switches to dis-arm, please let me know.

MTC
John

The only way I feel comfortable with this method is using an access panal (hatch). All you have to do is remove the panal and do some wire cutting.

section 2.4 of the NAR level 3 reqirements states that you have to "externally" disarm all pyrotechnics. It goes on to say that this means the pyro charge has to have the connection from the power source to the charge broken.

A switch isnt explicitly stated, but it seems strongly implied. With that said, I have been told by one L3CC, that if you say "I will disarm the charges by removing the access hatch and clip the lead wires", that is sufficient.

I suppose its up to the L3CC or TAP members to decide.

Is there anything besides level 3 requirements for the capability to disarm?

 

[uncle_vanya]

At least you had a method to disarm. My point was that tucking the wires back in the airframe "may" lead to an unsafe condition.

I think we are in "violent agreement". I was scared and worried about tripping the charge during the disconnection. The altimeter had been crashed and was in an unknown state. I was very very very nervous. Charges were in the 1.5-2g range and were in ejection canisters like N3 sells.

 

[jrcox]

The only way I feel comfortable with this method is using an access panal (hatch). All you have to do is remove the panal and do some wire cutting.

section 2.4 of the NAR level 3 reqirements states that you have to "externally" disarm all pyrotechnics.

Let's think about this, you have the resources, skills and time to build an access panel, but do not include a switch? Why would cutting wires be a prefered mechanism?

Anyone working on an L3 project is at a point in rocketry that they should be setting the standards, to include reliabilty and safety. If NAR requires an "External" Disarm for L3, why do they not have the same safety requirements for any flight involving electronic deployment and pyrotechnics?

One of my fears is that someone finds a rocket in the field and brings it back to the LCO desk with live charges on-board. And yes, I have been at a launch when this has happened. Having an external switch that anyone can dis-arm with standardized markings would help to improve safety.

IMO
John

 

[FredA]

"Having an external switch that anyone can dis-arm with standardized markings would help to improve safety."

Like this:

Twin 4PDT.
One for power - one to disconnect and shunt four pyro channels.

Easily actuated by anyone in the field.

 

[jrcox]

Yes, and where's the fancy schematic?

 

[FredA]

"where's the fancy schematic?"

Here

 

[Juerg]

How about that:

(Spacetec SafeSwitch 3, do do some advertisement ;-) )

3 independent screw-switches, can be cut appart if needed.

Juerg

 

[jcsalem]

I've used "push-on push-off" style switches for all of my altimeter bays. I build them onto the altimeter sled itself. This makes it easier to swap the sled between rockets. I arm it using a straightened paper clip through the vent hole to push the button. Be sure to get a pushbutton that stays pushed in when it's on -- that way you can tell whether it is on by feel.

My favorite switch was the old POPO switch that PerfectFlite sold (it's still listed on their web site). Unfortunately, they were discontinued by the manufacturer (E-Switch). Its replacement (model P227EE2B20A available from Digi-Key) is significantly larger but I still use it. They're basically on-off switches for PCs. I don't like any of the Radio Shack switches because they're either low current or stay in the same position whether they're on or off.

I use a switch to arm the altimeter but not one to shunt the charges. Once the charge dissipates from the capacitor (just a few seconds max), the only way I can think of that the charge will fire would be due to static electricity. Other than being hit by lightning I think this is unlikely. Of course, my ejection charges are always under 2g so the downside of an accidental firing is much less than on some of the larger rockets.

I agree that it's very important to have a way to disarm the altimeter if you need to pull it off the pad.

Jim

 

[Art Upton]

I've used "push-on push-off" style switches for all of my altimeter bays.

Hi Jim,

I used that style once in an Ebay sled where I would use a poker to arm it from the the hole.

I thought it was pretty kewl.

I had it fail however once on a high thurst flight and quit using it.
I do understand you have flown yours many times however.

I do forget the digikey number of the switch it was.

 

[jcsalem]

I used that style once in an Ebay sled where I would use a poker to arm it from the the hole.

I had it fail however once on a high thurst flight and quit using it.
I do understand you have flown yours many times however.

That's good to know about. What kind of failure was it? Was it a permanent failure (the switch came apart) or was is just a temporary failure while the rocket was accelerating?

BTW, the POPO switch is a double pole switch. I wired both poles in parallel thinking that if one pole temporarily failed due to thrust that the other might still be okay. No failures that I can pin on the switch yet...

It's a challenge trying to find a reliable switch that can withstand high current and high thrust.

Jim

 

[FredA]

"It's a challenge trying to find a reliable switch that can withstand high current and high thrust."

Don't sweat the current rating.
The rating applies to the ability of the contacts to open and close under load without arcing or welding.
You are not actuating the switches while there is any significant current draw.

Also - vibration is not a real concern unless you have a super-sensitive altimeter. If you are really worried, double up on contacts and/or put a cap behind the switch to provide some "ride through" should the contacts open briefly. Millisecond long opens in the pyro channel should be insignificant over a 0.5-> 1 second pyro latch time....the pyro will fire.

Considering the above, almost any switch that has a reasonable snap action will work for our applications.

 

[jcsalem]

Don't sweat the current rating.
The rating applies to the ability of the contacts to open and close under load without arcing or welding.
You are not actuating the switches while there is any significant current draw.

Interesting. I hadn't thought about that. That gives me a few more options.

Jim