Simple Launch Controller That Seems Complex?

[Kruegon]

I want to build a simple launch controller with a few features that make it seem and operate like a complex controller.

Anything electrical is new ground to me. It's not something I grew up doing, nor have I studied anything on it. You should imagine that I am "special" when discussing this. Use small words. Drawings need to be simple. But I need to build a launch controller and the plans u found online look like electrical engineers wrote them lol.

I'd like to build something that works like the one I saw on DogHouse rocketry. And I'd like to use this type of battery or its smaller counterpart:


I'd like a continuity test at the pad and at the controller. A strobe for when the pad box is active and the ability to plug in, or even build into the box a siren/wailer/alarm for when the pad is active. It's be awesome if the siren sounded like the NASA launch alarm at Cape Canaveral. Oh, and I definitely want to avoid any kind of programming. I learned a long time ago that it's not for me.

There's a second launch controller I want to build, but it's a different monster completely. With individual, external arming boxes. This one would be a simple 4 channel box with arming keys and switches so that the kids can switch on and arm their individual rockets from a small controller and the LCO could flip the master switch to launch it. Try to get the kids involved but still leave the actual fire control in the hands of the LCO. Good for school and scout launches.

Maybe I'll learn something unique and eye opening in this process. I'd be nice to be able to create our own launch systems from the pads to the controllers and everything in between.

 

[Buckeye]

https://www.rocketryforum.com/showt...ontroller-Schematic-for-Dummies-with-Pictures!

 

[Handeman]

Since you say you are new to electricity and electronics. You might want to visit a few sites to learn the basics. https://www.learnelectronicsonline.com/ Here's one you could try. I would suggest doing at least the DC Electronics courses including Ohm's Law. It will give you a basis to understand some of those "look like electrical engineers wrote them" posts and drawings.

As I'm sure you've seen, there are lots of different controllers out there, from simple to complex. I would say what you want with continuity check at both the controller and the pad, strobe lights, etc. you are getting into the complex. Have you decided if you want the battery at the controller or the pad? If you are going to put the battery at the pad, you might as well make it a multi-pad controller. If you do it right, you might be able to plug in the kids controllers into the same system.

 

[penquissciguy]

At the risk of posting an engineer's drawing, here's the schematic for the single pad launcher I've used for many years. Hopefully an explanation will help you understand what's going on.

S1 is the safety switch, which in my case is a keyswitch. You need a switch in series with the launch button to prevent an unintended launch. With S1 open, the launcher can't fire with a press of the launch button.

In order to have a continuity test, you need to have a current limited path through the ignitor and some sort of indicator. BAT1 is a 12 volt battery, very much like the one in your picture. My launcher uses a 12 volt, 50 mA LED indicator light. That's D1 in the schematic. It lights up when S1 is closed, S2 is not pressed, and there's a connection across the output (where the ignitor goes). S2 is a button from an arcade control panel. It is spring loaded and has two sets of contacts. One is "normally closed" - closed when the button is NOT pressed. This is the one that's used for the continuity test.

To launch the rocket, you need a low resistance path from your battery through the ignitor. When S1 is closed and S2 is pressed, the other set of contacts in S2 close - the "normally open" set. This activates relay RLY1. This is an automotive headlight relay. It connects the battery directly across the output, where the ignitor is connected. The battery dumps as much current as it can through the ignitor until the ignitor burns through or S2 is released.

This circuit is the simplest one I could come up with that satisfies the model rocket safety code and didn't dump high current through small switches. The automotive relay is rated for 40 amps, which is more than a small 12 volt battery can deliver under most circumstances.

Other indicators could be used in the continuity test, but the current must be kept low during the continuity test to prevent the ignitor from firing. In reality, the continuity test and the pad active indication are effectively the same thing in a launcher like the one I described above.

 

[sghioto]

Here's a modified version of "penquissciguy's" schematic which gives dual continuity and provision for strobe and siren. Two piece unit with simple four wire interconnect. Uses standard LEDs with a current limit of around 20ma for continuity check. Continuity is active but no power to pad relay or strobe until safety switch is activated.

Steve G

 

[sghioto]

Here's my version of your second request with 4 pads. This is very similar to what our club uses and can accommodate 5 pads with a 4 pair cable. All relays are the same 12 volt 40 amp auto type.

Steve G

 

[Kruegon]

Ok. I can understand about 1/3 of those lol. I really need to study some electrical diagrams. Learn what the different symbols mean at least. I'll see what I can make of these. The last one posted, is it an "all-in-one" or is it a relay where you have a master controller on the LCO table and thus at the pad?

I'm just now starting to build any launch controllers. I'm sure once I have the first one figured out, I'll be able to expand my ability quickly. Thanks for your patience with me and my questions.

 

[Kruegon]

S1 is the safety switch, which in my case is a keyswitch. You need a switch in series with the launch button to prevent an unintended launch. With S1 open, the launcher can't fire with a press of the launch button.

In order to have a continuity test, you need to have a current limited path through the ignitor and some sort of indicator. BAT1 is a 12 volt battery, very much like the one in your picture. My launcher uses a 12 volt, 50 mA LED indicator light. That's D1 in the schematic. It lights up when S1 is closed, S2 is not pressed, and there's a connection across the output (where the ignitor goes). S2 is a button from an arcade control panel. It is spring loaded and has two sets of contacts. One is "normally closed" - closed when the button is NOT pressed. This is the one that's used for the continuity test.

To launch the rocket, you need a low resistance path from your battery through the ignitor. When S1 is closed and S2 is pressed, the other set of contacts in S2 close - the "normally open" set. This activates relay RLY1. This is an automotive headlight relay. It connects the battery directly across the output, where the ignitor is connected. The battery dumps as much current as it can through the ignitor until the ignitor burns through or S2 is released.

Ok. That was explained extremely well. I think I even understand it! What is the purpose of the relay? I see a lot of relays. I must admit my ignorance. I have no clue what they actually do.

My launcher uses a 12 volt, 50 mA LED indicator light. That's D1 in the schematic.

The LED is 50mA. Does the LED act in place of a resistor to lower the current for continuity test without firing the igniter?

I'd like to get really good at this. And I've got a lot to learn. Guess I'll start with a single pad single controller. A hyped up Electron Beam controller. Expand out to a multi selectable equivalent. Then a single pad relay system like this one. Then a multi selectable version. Ultimately I want to be able to build a system capable of running 4 rods/rails per channel with up to 5 channels.

With my understanding of electrical systems, I figure I'll get the final versions done about 2 days before my death lol.

 

[penquissciguy]

Ok. That was explained extremely well. I think I even understand it! What is the purpose of the relay? I see a lot of relays. I must admit my ignorance. I have no clue what they actually do.



The LED is 50mA. Does the LED act in place of a resistor to lower the current for continuity test without firing the igniter?

I'd like to get really good at this. And I've got a lot to learn. Guess I'll start with a single pad single controller. A hyped up Electron Beam controller. Expand out to a multi selectable equivalent. Then a single pad relay system like this one. Then a multi selectable version. Ultimately I want to be able to build a system capable of running 4 rods/rails per channel with up to 5 channels.

With my understanding of electrical systems, I figure I'll get the final versions done about 2 days before my death lol.

Relays are a form of switch. They are made up of a coil (electromagnet) and at least one set of switch contacts. The way they work is that the electromagnet pulls the switch contacts closed when a voltage is applied to it. It's a way to use a little current to control a higher current load. Relays are used in places where a light duty switch is used to control a heavy load, like a little dash mounted switch turning on your car headlights. They are simple, rugged, reliable, and cheap, which is why you often see them in launch controllers.

LEDs have no current limiting ability on their own. They need to be paired with a resistor that limits the current. If you don't they'll happily pass as much current as the battery can handle until they cook themselves to death. In my case, I bought a 12 indicator light that was an LED and resistor in one package. They can be found on eBay or at electronics suppliers like Digikey or Jameco.

In your Electron Beam controller, the light bulb is both the continuity indicator and the resistor. Incandescent bulbs are just resistors that give off light as a byproduct.

 

[sghioto]

The last one posted, is it an "all-in-one" or is it a relay where you have a master controller on the LCO table and thus at the pad?

Correct I think. Two separate boxes connected by a 8 wire cable as long as you need. Controller at the LCO table and the "pad" box at the pads. Same for the first one I posted but that one only needs a 4 wire cable.

Steve G

 

[Kruegon]

Ok. I'll start working on figuring this out this weekend. Think I'll lay it out on a board and at with it. Then I can look at building a box. Still gotta order the parts for my rails and more buttons. Eventually, I want to have enough equipment built to supply a small launch if necessary.