thinking about making my own launching switch.

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Nov 9, 2009
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im thinkin about making my own launching mechanism. Currently I have been using a simple 9V battery to launch rockets. A buddy of mine and I are really getting into this hobby. We were thinking of making our own launching mechanism using this:
and something similar to this:
you would have to flip up the red safety cover before flipping the switch beneath it. and in order to press the big red button (used to actually launch the rocket) you would need to have the switch activated. The only thing keeping us from doing this really is that we have no idea of how to go about wiring the thing up to work how we want it to. If anyone on this site knows how we could do this and is willing to share the knowledge we would be very grateful! thanks!
Welcome to this nutty hobby! While I've never built a controller myself this looks like a very nice guide:

Controller by James Bell

These guys know a thing or two about rockets:

Team Vastaas Controller

2 thing I think you are going to want:

1. A removable device such as a key switch so controller can be completely disarmed by the removal of the key. This is not only a typical requirement of controllers at NAR of TRA launches but is also a good idea.

2. Use a 12v compatible system. This isn't needed for little Estes motors but should you decide to start flying composite motors the ability to hook the system up to a car battery type power is what you are going to want. Next time you switch out your car battery keep the old one for this.

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just a FYI about those red safety switch covers - they should work the way you want but not sure a push button will fit in them - they are really designed to be used with a toggle style switch so that you have to flip up the red cover then flip the toggle up and then if you need to turn it off in a hurry you can just push down on the red part and it will turn off the toggle and then cover it up - what you may want to consider doing is having an arm switch using a toggle and that cover and a large red or orange light up launch button as they show in the link dallen posted - and a safety key should also be there

Not trying to tell you how to do it, just how those safety covers are designed
Here is a link to what you are looking for. I have a built a version of this controller. Mine can support 3 pads and I used speaker wire to go out to the pad(s). You may want to add up the cost of materials before you start this project because the cost of parts add up quickly. You may want to look at the Pratt hobbies website for ready made controllers.

Here is the link:
SteveF is correct, you need a toggle switch under the switch guard. A button will not work unless it is very small. As a matter of fact, most switches will not work well either as their base is too large.

I used two switch guards in a game controller I made a few years ago. Both of the switches I used were momentary switches, which I highly recommend if you do this project. Momentary switches are spring loaded and you must force them into the "on" position (or the "off" position depending on how you wire it). For a launch controller you want to wire it so that you must lift the guard and then push the switch into the momentary "on" position. When you close the switch guard it pushes the switch into the "off" position and keeps it there.

Here's some basic wiring diagrams of how the Estes controllers are wired, and how I modified mine to use LED indicators for continuity and battery connections indications. Using LED's or piezo buzzers instead of light bulbs greatly reduces the current passed through your ignitor during continuity checks, which is necessary for low-current type ignitors like the terrific Quest Q2G2 ignitors. DO remember though, if you use LED's, that they DO require the correct polarity to work-- if you hook them up 'backwards' they WILL NOT LIGHT UP even if they have power!

Wiring a basic controller of the type you're contemplating would be quite similar to these wiring diagrams below, just substituting your components in place of the Estes components in the wiring diagrams, and using heavier wire. I would also recommend a 'removable key' type of safety interlock since it's required in the model rocket safety code. If you get a key-type switch, make sure the key can ONLY be removed in the "OFF" position, as some can be removed on either the OFF or ON position. It's not necessary to use a true 'key' switch at all, as anything which physically completes the circuit is suitable-- IE the Estes "launch key" is just a piece of metal that bridges the contacts inside the controller to allow power to flow; if that piece of metal isn't there, the circuit is broken and no power can flow even if the launch button is pushed. Such commonly used 'circuit completion' type switches are the use of phono-jacks in which the lead wires have been soldered together to form a removable 'bridge' in the circuit, and I used a 110V plug with a short jumper wire inside it connecting through a 110V outlet installed in the control box with the leads going in one side of the outlet, through the plug, and out the other side of the outlet. When the plug is removed the circuit is dead.

You'll also need a 'momentary on' type switch for a launch button-- but these are readily available at auto supplies as 'horn buttons' or at Radio Shack.

Also, a TERRIFIC 12V power supply is a car jumper battery pack-- they are HIGHLY portable, use a great capacity gel-cell battery that won't spill or leak, and can take considerable deep discharge and won't sulfate up like a regular lead-acid car battery will, and they're easily chargeable in either the car or the house, and they serve double-duty when not needed on the launch field by riding in your car trunk in case your car battery goes down, or if you leave the lights on, or cold weather weakens your car battery and you need a boost to get started. They are fairly inexpensive (usually $40 and up) but HIGHLY useful and you just can't get a more portable, self-contained, and handy rocket launching power supply IMHO.

Good luck! OL JR :)


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