Launch control system

[Reed Goodwin]

Well, I completed my launch control system this weekend. I still need to solder the alligator clips on, but other than that, it's done. The box that has the three sets of wires coming out is going to be near the pad. It has a relay in it so that I didn't have to run really heavy wire up to the controller. The box with the toggle switch, LED, and pushbotton is the controller. The two boxes are connected by 70 feet of three-conductor cable. On the controller, the toggle switch arms the mechanism and the pushbutton fires the ignitor. Then the system is armed, the LED lights up. The whole system is powered by a 12V lead rechargable battery from an electric-start lawn mower. I also built a launch pad. Pictures are soon to come.
Reed

 

[Reed Goodwin]

Alright, pictures.
https://community.webshots.com/photo/149374218/247572375XFppLE This is my launch controller.
https://community.webshots.com/photo/247576266/247576266jqUUVK This is the system. I have now added the alligator clips, but the picture was taken before that.
https://community.webshots.com/photo/247581260/247581260AZMTTU This is my pad. I have yet to add a blast deflector. Not visible in the photo is a screw that tightens onto the rod to keep it in the 4x4.
I am happy with this system.
Reed

 

[11bravo]

You wouldn't by any chance have any schematics or diagrams would you?
It is VERY close to what I would like to come up with.

Greg

 

[Derek]

The safety interlock is a device to prevent an unauthorized party from activating the launcher, particularly when someone is at the pad setting up a rocket. Thus, it should be removable so that when one approaches the pad, one can be SURE the launcher is disabled.

If the interlock is not removable, I wouldn't use the launcher (whether the safety code is explicit about this or not) - too much chance a kid (especially a spectator's kid) will do something undesirable.

 

[Dbarrm]

A lot of these small production launchers use a phono jack from the fireing box to the pad. You can pull the plug and take the box with you. That way you always have positive controll.

Dan

 

[Reed Goodwin]

Hmmm. That is interesting. I guess that the only was that I could do that now is to make the controller a plug-in device so that the cord coming from the controller has to plug into the cord going to the pad. That would definitely be removable
Reed


EDIT: Dan, you took the words right out of my mouth...

 

[Reed Goodwin]

Originally posted by 11Bravo
You wouldn't by any chance have any schematics or diagrams would you?
It is VERY close to what I would like to come up with.

Greg

I did this from memory, but I think it is right. If anyone sees any problems, please speak up. It was done on MS Paint with text added later. Just don't forget the safety plug by the controller.
Reed

 

[11bravo]

Would something like this work as the relay-
https://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7946886633&category=6763
This is the part (knowing what stuff is) that I don't do so well with.

Greg

 

[Reed Goodwin]

I am not really sure. I got mine from Radio Shack. The only problem was that it was a PC mount, but I fixed that by adding a PC board to it just big enough for the conections to be made and then soldering all the wires to the board. I will try to post a pic.
Reed

 

[OARJeepr]

Originally posted by 11Bravo
Would something like this work as the relay-
https://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7946886633&category=6763
This is the part (knowing what stuff is) that I don't do so well with.

Greg

Yeah that relay would work just fine. Its an automotive relay so its designed to work with 12 volt systems. The coils on them will usually work with as little as 6volts. And they handle more than enough current. The only thing is you can go to an auto parts store and buy one cheaper or at least at the same price than that seller has them when you include shipping.

 

[Dbarrm]

His cable going to the pad will be connected with a Phono jack so that he can pull out the cable and take the box with him to the pad. That is his interlock.

Dan

 

[Borderline Sci]

If you use a DPDT relay you can put an LED on the other side to tell if the contacts are open.
Here is how I do it.
In the lower left corner is a simple one relay system, the rest is a multiple relay system for NOS and GOX system.

 

[Reed Goodwin]

Well, I was hoping to trust the electronics of the launcher. Anyhow, once I get into HPR I will probably make adjustments to the system so it will be safer. Since I am not the electronics expert (that's my dad's job), I will wait until I can talk to him more about that little bit... Also, thanks for the correction.
Reed

 

[Reed Goodwin]

Here's the corrected schematic.
Reed

 

[OARJeepr]

It doesn't even have to be a dpdt relay. Just wire a led in parallel off the relay. The resistor required for a led in a 12v system should ensure that current flows through the ignitor and not the led when you are trying to launch a rocket. On the other hand, if there is no rocket hooked up and the relay is fused shut then the led will glow, and you will know not to hook up an igniter. You could even put a piezo in there if you wanted to.

 

[Reed Goodwin]

Seeing all these suggestions about putting some sort of indicator about the realy has convinced me, when I get the time, to add a LED after the relay.
Reed

 

[11bravo]

How about this?
I don't know exactly what a relay is or why they are used in rocket launchers.
Could someone give me the skinny?
There is a spot in the diagram that I have to add one if it would help with anything or be necessary for any reason.
Ideas?
Other suggestions?

Reed-
I see that you have some resistors in your controller.
What do they do for the set up?

Thanks,

Greg

Sorry, had to zip the file.

 

[Reed Goodwin]

The relay allows you to not have to run heavy wire up to the hand-held controller. You would add one at the box at the pad. On a relay you have a minimum of four pins: two that go into a coil, one that is the main power in and then one for the main power output. The realy can either be Normally Open or Normally closed, or both. For my system, I connected my main power out to the normally open pin. When you energize the coil, the switch inside the relay flips the circuit closed, providing power to the pad. I hope that helped. As for the resistors on my ontroller, they save my LED from being fried by the 12V system.
Reed

 

[OARJeepr]

Bravo,
Are you going to control just one launch pad with your setup? If its only one pad and you aren't looking to be 200ft from the pad then you really don't need a relay. Like Reed said, a relay is a remote switch and allows you to control high current circuits without having to run a bunch of heavy gauge wire.

Most LEDs are designed to operate somewhere around 2volts. A 12 volt system will usually do a good job of blowing one. Resistors are commonly used to bring down the voltage so the relay doesn't fry. A 1/4 watt resistor between 500 ohm and 1000 ohm should work for most LEDs on a 12 volt system. You'll need one for each led too.

 

[11bravo]

Or I could get leds made for automotive use.

I was planning on being at least (to start anyway) 100' away.
Since they are cheap, guess a relay wouldn't hurt a thing.
I'll piddle around with the diagram a bit as see if I understand how it would be added.
As for the horn, suppose a motorcycle horn would work?
Any reason it wouldn't?

Over all, you guys that know how electronics work, would my design work?
Would it meet safety requirements for the national organizations?
I'll post the updated diagram I come up with in a bit.

Thanks,

Greg

Forgot. It'll just be one pad. The three outs are for clusters if I want.

 

[11bravo]

OK, this is what I've come up with for a relay diagram.
Does it look correct?
I've also done a little research on relays and think I understand what it would do in this case; please let me know if I'm wrong.
In the case of the attached file, the current travels all the way out to the control box and back.
If there is a voltage loss (and there will be) due to resistance in the wire or other components, it is no big deal for the continuity circuit but may be for the firing circuit.
This way, the lower current from the firing circuit goes to the relay that closes a switch that basically creates a short from the battery to the launch circuit so it gets a full shot of power.

 

[OARJeepr]

That should work fine. I wouldn't worry about any voltage loss. Like I mentioned earlier automotive relays will usually close on as little as 6 volts. One more thing automotive LEDs are the same as any other LEDs they just have the correct resistor already installed.

 

[LtSharpe]

Remember the NAR code is just a guideline. You aren't breaking any law if you don't follow their 'rules'. Use cannon fuse if ya want Not my preference but whatever flips your weasel. I use a homebrew wireless rig myself built on a rc plane radio system.

Originally posted by Henry8minus1
It has always been my understanding that a launch controller needed a removable safety key/pin to be compliant with the NAR safety code. However when I looked at the Model Rocket Safety Code the third item states:

"Ignition System. I will launch my rockets with an electrical launch system and electrical motor igniters. My launch system will have a safety interlock in series with the launch switch, and will use a launch switch that returns to the "off" position when released."

What is the definition of a “safety interlock”? Does it have to be removable? Under the High Power Rocket Safety Code it states that the ignition system needs a removable safety interlock. So does this mean you don’t need a removable safety interlock to fly rockets up to G power?

The reason I ask is it was my understanding (which could be wrong) that a toggle switch was not compliant as an arm switch (safety interlock). I was going to point this out, but after looking at the safety code as listed on the NAR website I see that the toggle switch may be compliant to use with rockets up to G power. Could someone help clarify?

 

[shreadvector]

I'm looking at my copy of N.F.P.A. 1122 2002 edition and 4.13.3 clearly says: "The system shall be equipped with a removable safety interlock in series with the launch switch."

Any proposed changes to N.F.P.A. 1122 should be sent to someone like Trip Barber who is involved with the revision process and also making sure the simplified NAR MRSC agrees (and is easy to understand).

Originally posted by LtSharpe
Remember the NAR code is just a guideline. You aren't breaking any law if you don't follow their 'rules'. Use cannon fuse if ya want Not my preference but whatever flips your weasel. I use a homebrew wireless rig myself built on a rc plane radio system.

 

[LtSharpe]

Again, the NFPA and the NAR are NOT the law. The law is your state fire marshal who by the way can choose to adopt or not adopt whatever they want to in the NFPA docs, and many do pick and choose.

Originally posted by shreadvector
I'm looking at my copy of N.F.P.A. 1122 2002 edition and 4.13.3 clearly says: "The system shall be equipped with a removable safety interlock in series with the launch switch."

Any proposed changes to N.F.P.A. 1122 should be sent to someone like Trip Barber who is involved with the revision process and also making sure the simplified NAR MRSC agrees (and is easy to understand).

 

[LtSharpe]

And furthermore the safety interlock is right between your ears,, meaning it's common sense and personal responsibility. The cheap estes launch controller although perfectly nice for what it is is not something I would depend upon if it really mattered,, which again, IT doesn't because in the end no matter how you are firing the rockets they are STILL actually fired off at some point. The means by which you ignite them is completely unimportant. More important is the surroundings like dry brush, grass and shake roofs...

Hell by the reasoning in the NRA code a fuse makes more sense because you have to light it, it can't get accidentally picked up and a button pushed. Imagine if daddy gets the rocket all ready,, puts the key in and the clips fall off the ignitor, so he says hang on junior let me go fix that. Junior in the meantime goes and picks up the controller and pushes the button while daddy is fiddling with the igniter and end of the motor in his fingers....

It all boils down to personal responsibility and common sense.

Originally posted by LtSharpe
Again, the NFPA and the NAR are NOT the law. The law is your state fire marshal who by the way can choose to adopt or not adopt whatever they want to in the NFPA docs, and many do pick and choose.

 

[OARJeepr]

And at the same time cannon fuse does not fit NAR reasoning becuase once its lit you can't stop it from launching. If someone/something wanders too close then your in a little bit of trouble with fuse.

 

[LtSharpe]

Yup I would agree, once it's lit all bets are off but it's the same with once the rocket is fired with any system. Once the engine is lit it's out of your hands, at which point it could still cause damage to people or property either way. I would say the safety interlock is more designed to protect people since once the rocket does leave the pad anything can still happen.

Originally posted by OARJeepr
And at the same time cannon fuse does not fit NAR reasoning becuase once its lit you can't stop it from launching. If someone/something wanders too close then your in a little bit of trouble with fuse.

 

[11bravo]

***This is not meant to be condescending, although it will probably sound that way***
LtSharpe-
I don't know what your military history is, but I'm going to act like the "Lt" means lieutenant as in military.
I think the "safety interlock" is something like the M-fiftywhatever firing device on an M-18 Claymore. You take it with you when setting up specifically so some schmuck cannot come along and fire the thing when it would be a really BAD thing to have happen.

As for cannon fuse; I don’t know what you’re talking about, that sounds like something safety minded little ‘ol me would never do. No way. No how. Too dangerous. OK, so maybe I’ve done it ONCE. Just once. Twice. Only twice. Or maybe three... ALL RIGHT! What do you want? I’ve used it a lot and I liked it. There. Do you feel better? Making me break like that. Man, there goes the weekend.

Greg

 

[LtSharpe]

hehe I've never used fuse myself but I often thought of trying it. I'll see a pile of the stuff at the gunstore(I guess he sells it to small bore cannon guys or whatever) and I think I could use that on rockets but I always seem to have enough igniters lying around,, and there is a certain satisfaction involved in pushing a button and receiving instant gratification of seeing the launch.

No I am not a military person, the LTSharpe refers to a character in a british tv series called Sharpe's Rifles about the 95th Rifle Regiment in the napoleonic wars. Maybe I'll change my nick so people don't get mixed up. I understand the whole point of the interlock, my scenario about inexperienced daddy and 'junior' I think is still valid though.

Originally posted by 11Bravo
***This is not meant to be condescending, although it will probably sound that way***
LtSharpe-
I don't know what your military history is, but I'm going to act like the "Lt" means lieutenant as in military.
I think the "safety interlock" is something like the M-fiftywhatever firing device on an M-18 Claymore. You take it with you when setting up specifically so some schmuck cannot come along and fire the thing when it would be a really BAD thing to have happen.

As for cannon fuse; I don’t know what you’re talking about, that sounds like something safety minded little ‘ol me would never do. No way. No how. Too dangerous. OK, so maybe I’ve done it ONCE. Just once. Twice. Only twice. Or maybe three... ALL RIGHT! What do you want? I’ve used it a lot and I liked it. There. Do you feel better? Making me break like that. Man, there goes the weekend.

Greg