custom made launch trigger, need help (pic)

[KINGZ]

I'm upgrading my younger brother’s rocket kit that I got him last year for Xmas, and advancing him to do more custom rockets. He want to follow me a mechanical designer so I'm trying to improve his mechanical abillity, but I only visit once a year, so I try to get him things he can do him self or do with me wile Im there.

Any way, he does not have the ability to launch cluster rockets, and I could buy a launch controller for that for about $45, but then they usually connect to a 12v car battery, which makes it hard for a 12 year old to carry around. So I want to build one with him when I go visit for xmas. Here is my idea, and I might need and electrical designer or engineer to make sure I got the wiring up to par.

The top and Bottom box is made out of .062 alum, the corner tabs are made out of .036 alum. The corner seams will be welded, and the corner tabs will be spot welded in place. Finish Powdercoat. I have not Design in the hardware, plan on flush mount press hardware on the top BSOS-032-14 with 10-32 FHSHCS on the botton.

The current controller to launch one electrical Match, uses a removable safety key to arm the system, Momentary Push button to ignite the electrical Match at the rocket base, the Elec. Match takes about 2-3 sec over a 20foot wire to ignite once the Momentary Button is held down, the controller uses Four standards AA batteries.

Here is some Electrical Specs on Estes Igniter Match, Link to PDF Sheet I hoping that if 4X AA batteries can launch one igniter in 2-3 sec over a 20ft 20ga wires that 2X 9V 400mAH batteries over a 30ft - 35ft 20ga wires can ignite 3 matches at the same time over .5 to 1 sec. I thinking that I need to ignite the matches faster to make sure they all ignite before launch.

Have not finish the base design on the box, but I plan on using a standard toggle switch, same 12v one used on cars as safety key, which when activated will light LED one, then when holding Momentary switch will light LED 2, and ignite the Electrical Matches. I found some nice bright LED, Link to LED Spec Sheet. I have also found a dual case 9V battery holder. and dual banna plug, male and Female. I did find a flush mount momentary push button normally open which I think means not connected, .75dia, by 1" tall. trying to find spec sheet.

I try to put together a basic wire schematic, since I do not have the software at home, I just wrote down each component. I have two ideas here they are. First one follows KISS, Keep it simple stupid. And the other one lol

The next one is more of a back up safety system, since the key is not removable on my design, it contains a second Momentary Push button so it takes two hands to fire. The second Switch would be mounted on the side like a CB hand held, this would keep a disaster from happening when he leaves the toggle switch on and puts the controller upside down on the ground pushing the button wile he tries to hook up the next rocket and firing in his face.

I was also wondering if adding a capacitor would help with the launch, i.e., if the capacitor charges, it could provide a better power flow to ignite all matches quickly. It would also be nice for an LED to light when the capacitor is charged. This may be asking too much. lol

When it comes to electrical design, I don’t know anything, so don’t bash please. Also if you know of any good place to buy any of this that would help. I know how to solder to make connections but everything else I need help with. I want to try to keep it under $50 for everything but the box and the toggle switch.

Note: I have not built a rocket in about 11 years or launch one, other then last year when I got my little brother started. so every bit of information is helpfull.

Thanks for the HELP.

 

[ghost]

Awesome CAD files!!! What program did you use?

For launching clusters, I highly advise against 4x AA batteries. Especially if it takes 2-3 sec to light one low current ematch. It should be instantaneous. Use 24 gauge wire everywhere and use a standard RC rechargeable 9.6V battery (https://www.radioshack.com/product/...&cp=&sr=1&origkw=9.6&kw=9.6&parentPage=search).
Also, for the electronics, do you want a continuity tester (it checks if the igniters are working). You don't really need one, but it's a fun add-on. Also, where is the removable key in your CAD drawings? Maybe I missed it...

Good luck!

 

[SCE to AUX]

First of all, nice looking drawings!

Your first schematic looks like it should work, but there is no means provided for checking igniter continuity before launch. The typical setup puts an LED or incandescent bulb in series with the igniter and the power supply, to provide an indication that the igniter is properly connected. The series lamp limits the current through the igniter to below the "no fire" rating. The launch button shorts out the series lamp, providing full current to the igniter and firing it.

Your second schematic will not work as drawn. You would want to put the capacitor across the battery in order to charge it, and have the launch switch place the capacitor (and battery) across the igniter to fire it. Your schematic has the capacitor in series with 2 LEDs and the igniter, so the LEDs will limit the discharge current to well below the amount needed to fire the igniter. Also, a capacitor large enough (10,000+ uF @ 12+volts) to be useful for this type of application is going to be a very tight fit inside your small handheld enclosure.

Typical safety practice (and the NAR model rocket safety code) requires the use of a safety interlock with a removable key of some sort. The guarded toggle is a nice touch, but technically not compliant.

 

[fastfreddie]

Continuity check isn't always a good thing. *If* the system will ONLY be used for Estes type igniters, then it's fine. But if there's ever a chance that an e-match would be used (i.e. Cesaroni pro 38) then a continuity check could fire the igniter. Because we fly HPR in our club, we've completely eliminated continuity checks on our systems. Just food for thought.....

 

[KINGZ]

Ghost,
I did it on Solidworks, its also owned by DS which makes Catia classified as the most advance CAD system there is. They made the software to compete againts Pro-E, Inventor, Unigraph, Solid Edge and a few others. sory for the history.

As for the removable key.......I.....I forgot about that, its been long time since Iv was involved with the hobby. The nock down safety toggle switch is safe, but If he ever wants to join a club or go to a shoot he will have to have it. I know the perfect key for this.... Something I was working with a medical safety device,

Just put in and turn 90deg to make contact and its free.


SCE to AUK
As for a continuity checker, thats not require but it would make for a better build, is there a wiring schematic for that laying around. Also any suggest LED that would work with it.

after doing some more research it seems that estes Matches does require more current then voltage, but testing from the link I provided above shows that a 20 amp inrush serge is require, so I would think a 1amp led would work I think, that also means I need to find a battery back that serges up to 30amps.

not sure on this lol,

 

[SCE to AUX]

The best source on the design of launch controllers that I know of is an Estes publication available on their Estes Educator website:

https://www.esteseducator.com/Pdf_files/1924_launch.pdf

Covers all the electrical theory you will need to design your own system, which isn't really much beyond the basics of Ohm's law. Schematics for several controllers are given.

The operating current for an LED is generally WAY below one ampere, typically in the 5-10 milliamp (.005-.010 ampere) range. An LED requires a series resistor to limit the current through it. The value of this resistor is determined by the maximum current and forward voltage ratings of the LED, the available supply voltage, and how bright you want the LED to be.

If you use an LED or a Sonalert (electronic beeper) for a continuity indicator, the test current will be low enough to be safe for use with E-matches or flashbulb igniters. This wasn't always the case with incandescent bulbs, such as the circuit used in the stock Estes "electron beam" controller.

 

[falingtrea]

Ghost,
after doing some more research it seems that estes Matches does require more current then voltage, but testing from the link I provided above shows that a 20 amp inrush serge is require, so I would think a 1amp led would work I think, that also means I need to find a battery back that serges up to 30amps.

not sure on this lol,

The model plane hobby has LiPoly packs that do 10C-20C surge, and they range from 500mA to 1500mA continuous packs, which would be 5 to 30 amp surge:surprised: But what is most important is wattage. That is why most high power systems are 12VDC or better. BTW, who was it that made a launch controller that let you plug a standard 7.2V 6 cell RC pack into it?

As for the LED, you want it to draw as little current as possible. The trick is to add a series resistor with the LED in order to limit the current. A high efficiency LED will work with only 5 mA of current.

To find the LED and resistor to use you can use the following formula:

(Vlu - Vledf) / Aled = series resistor where:

Vlu = Max Operating voltage of the launch unit
Vledf = the forward voltage of the LED (the voltage the LED works at)
Aled = the current you want through the LED (should be less than 0.020A for a continuity LED)

I would also suggest trying to use at least 18 gauge wire wherever possible. Electrical zipcord is pretty cheap.You could even buy a 15' 2 wire extension cord and cut the plugs off.

 

[Rick Lindsey]

If you're wanting to launch clusters, I highly recommend a "relay" style launcher, which puts a battery out next to the pad.

-Rick

 

[Art Upton]

Just an FYI,

the safety code requires a "Safety Interlock" device. It does not have to be a "Key".

https://www.nar.org/NARmrsc.html

Your cord connector since it could be removed qualifies, a few commercial launch controlers used this method. You unplug the controller from the cord and take the whole pocket controler with you to the pad instead of just a Key.

---------------------------------------------------------
3) 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.

 

[KINGZ]

Just an FYI,

the safety code requires a "Safety Interlock" device. It does not have to be a "Key".

https://www.nar.org/NARmrsc.html

Your cord connector since it could be removed qualifies, a few commercial launch controlers used this method. You unplug the controller from the cord and take the whole pocket controler with you to the pad instead of just a Key.

---------------------------------------------------------
3) 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.

Thanks for the info on the key system, I would rather leave the key out and use the wire as a disconnect. This will help alot.

 

[shreadvector]

Thanks for the info on the key system, I would rather leave the key out and use the wire as a disconnect. This will help alot.

As has been stated MANY times before, the NAR Safety Codes (Model And High Power) are abridged/abbreviated versions of the rules in the applicable N.F.P.A. codes.

The full text of the N.F.P.A. text for Model Rocket launch controllers is:

4.13 Model Rocket Ignition System.
4.13.1 The system used to launch a model rocket shall be
remotely controlled and electrically operated.
4.13.2 The system shall have a launching switch that returns
to the “off” position when released.
4.13.3 The system shall be equipped with a removable safety
interlock in series with the launch switch.

That has not changed from the 2002 version to the new 2008 version.

1125 is up to 2007 edition.
1122 and 1127 are up to the 2008 edition.

 

[Art Upton]

As has been stated MANY times before, the NAR Safety Codes (Model And High Power) are abridged/abbreviated versions of the rules in the applicable N.F.P.A. codes.

The full text of the N.F.P.A. text for Model Rocket launch controllers is:

4.13 Model Rocket Ignition System.
4.13.1 The system used to launch a model rocket shall be
remotely controlled and electrically operated.
4.13.2 The system shall have a launching switch that returns
to the “off” position when released.
4.13.3 The system shall be equipped with a removable safety
interlock in series with the launch switch.

That has not changed from the 2002 version to the new 2008 version.

1125 is up to 2007 edition.
1122 and 1127 are up to the 2008 edition.

Yes Fred, a removable cord is an removable interlock.

BTW, I need a link to your Model vs High Power graphic for the Genie thread.

 

[jadebox]

As has been stated MANY times before, the NAR Safety Codes (Model And High Power) are abridged/abbreviated versions of the rules in the applicable N.F.P.A. codes.

The full text of the N.F.P.A. text for Model Rocket launch controllers is:

4.13 Model Rocket Ignition System.
4.13.1 The system used to launch a model rocket shall be
remotely controlled and electrically operated.
4.13.2 The system shall have a launching switch that returns
to the “off” position when released.
4.13.3 The system shall be equipped with a removable safety
interlock in series with the launch switch.

That has not changed from the 2002 version to the new 2008 version.

1125 is up to 2007 edition.
1122 and 1127 are up to the 2008 edition.

A removable key would be better, but the battery clip is the "safety interlock" in Kingz proposed design.

And, fortunately, it's not "removable." I understand what they mean, but the wording is wrong in the NFPA. A safety interlock isn't very useful if it can be removed.

-- Roger

 

[Art Upton]

A removable key would be better, but the battery clip is the "safety interlock" in Kingz proposed design.

And, fortunately, it's not "removable." I understand what they mean, but the wording is wrong in the NFPA. A safety interlock isn't very useful if it can be removed.

-- Roger

Roger, the removable cord to the clips on the pad is the removable safety interlock. Same as it was on the DMB launch controller and others.

 

[jadebox]

Roger, the removable cord to the clips on the pad is the removable safety interlock. Same as it was on the DMB launch controller and others.

I said that the removable cord is the "safety interlock." But while the cord is "removable," the "safety interlock" is not. And rightfully so.

Interlock: A mechanical device that prevents a component from functioning when another component is functioning or situated in a particular way.

-- Roger

 

[Art Upton]

I said that the removable cord is the "safety interlock." But while the cord is "removable," the "safety interlock" is not. And rightfully so.

Interlock: A mechanical device that prevents a component from functioning when another component is functioning or situated in a particular way.

-- Roger

Sorry Roger, I'm confused?
Not hard at my age

I have a cord strung between the pads and the back of my pickup truck.

I have a misfire. I pull the cord out of the controler and put the controller in my pocket while I meander up the rocket and fuss with the clips and put in a new ignitor.

So the cord stays put, the controller gets removed?

If we really need to split straws on mechanical interlock, the dual trailer plug could get replaced with a phone jack and phone plug and you could use a shunt. But that would only add extra complexity and another failure poinit.

Reason I say this is this is how my current park flier controller works, except I have yet even another wire connector in the back that goes to a yellow jump start pack for power.

 

[shreadvector]

Yes Fred, a removable cord is an removable interlock.

BTW, I need a link to your Model vs High Power graphic for the Genie thread.

I understood, I was just making it clear for others.

The graphic is not mine (If I had mde it, it would not have looked as nice), but I keep posting the link. It is now located in the sticky thread at the top of the top forum.

The folks who are on the committee have commented on this in the past. Yes, a controller where you can unplug the control unit (like this one) to render it dead is good. Unhooking one battery clip is not in the intent of the code. A segment of the circuit must be removed rendering the system dead.

A safety key such as an Estes or Quest key removes a physical part of the circuit. A turn key that can only be removed when OFF also satisfies this intent since with the key removed, the circuit is broken and cannot accidentally be completed.

Disconnecting a battery clip is not safe, since it can be bumped and make contact and complete the circuit. Again, this has been explained by people who wrote the code.

It is not worth arguing about, it is simple safety and they have explained it.

 

[KINGZ]

So from what Im reading Disconnecting the main lead wires to the ignitor is allowed??

this would mean I have two safety devices and one Momentary lunch button: for the controller to function it would need the wires connected, the emergency spring loaded toggle switch to be held on, then a push button to lunch the rocket.

Also If I re-wire and remove LED 1, the system is compleatly shut off, unless the wires are connected, I would also need to put in a restor.

 

[jadebox]

Sorry Roger, I'm confused?
Not hard at my age

Don't fret. I'm just being pedantic. The NFPA text should read "safety interlock with a removable something or other." The "safety interlock" itself is a part of the design of the launch control system. It can't be removed.

-- Roger

 

[jadebox]

Ohh ... the reason that a removable key is better than the ability to unplug the controller is that the key becomes a "token" that you carry with you to the launch pads. That way, someone else can't re-activate the launch controller when you're setting up your rocket.

-- Roger

 

[Art Upton]

s and one Momentary lunch button: ....

Humm, I should look at putting a Lunch Button on my controler as well, Me want FOOOOOD

 

[KINGZ]

not a bad idea, LOL :surprised: Dinner for two please....


I should have a new working schematic tonight, after taking some notes from here and a few other places, I might have a set up that will launch up to a cluster 5, at once and could do a total of 9-11 launches between charge, And since I provide the motors, he will not be launching that manny at a time $$$$$$$$$$$........

 

[Rick Lindsey]

Ohh ... the reason that a removable key is better than the ability to unplug the controller is that the key becomes a "token" that you carry with you to the launch pads. That way, someone else can't re-activate the launch controller when you're setting up your rocket.

-- Roger

Of course, at our club launches the key is never removed *ponder*

-Rick

 

[Saks_Russel]

Nice layout.

The box can be purchased from Digi-Key or Mouser (online electronic parts sellers). Vendors off the top of my head are Hammond Mfg, LMB and Pac-tec. Somebody will have something pretty darn close to what you have drawn.

Fireworks launch systems use a momentary toggle switch that returns to open if you let go (also called a "dead man switch) and a wired "pen" with a board of recessed contacts for the individual cues. The dead man switch also has the common red flip cover you have drawn. The battery leads are disconnected when the system is not to be used. That is for class B explosives. The idea of disconnecting the little hand controller as the safety satisfies the spirit of the passage that Fred quoted at us since all it leaves is a pair of wires running along the ground without any power. Put a belt clip on the back side for easy transport.

Your little brother will be in good shape for a basic lauch controller with what you have designed and the addition of resistors for the LED's. You can omit the LED's and make it even simpler. A single launch controller doesn't really "need" to have a continuity circuit. Leave a more advanced design for later.

I have toyed with making a controller, but since I launch with a couple of well equipped clubs, I haven't had any need. Maybe some day.... after I get my pad built.

K

 

[Saks_Russel]

After a second to think.

If you want to make a simple "key". Use a headphone (big or small) jack and plug. Wire the jack in the box so the plug with shorted leads will complete the circuit. Just like a switch breaks a circuit. Add a spiral bracelet or fob to it so it can be worn on the wrist or stuck in a pocket.

You can get the parts at Radio Shack and if your brother ever loses the key, it 's cheap and easy to make another one.