Hello from O'fallon Missouri

[Pyropawpaw]

Hello, I'm new to the forum. I built rockets as a child, and now I'm enjoying building and flying rockets again with my grandkids. All my rockets up until recently have been cardboard. I completed and flew my first fiberglass DD (Wildman 2" Punisher SS), what a game changer. This past summer I joined NAR and successfully completed my L1 on a modified LOC Ultimate, and flew some interesting cluster flights on it after my L1 flight. I've also joined Tripoli. I have built (actually overbuilt) a 7.5" LOC Doorknob for my L2, and plan to fly it on a J800. I've also designed and built a launch controller for low power with safety features that I haven't seen anywhere else. I'm currently have my eyes on a MAC performance 4" Black Fly. I'm looking forward to being able to interact with others who share my enthusiasm for this sport.

 

[Hobie1dog]

to the forum

 

[smstachwick]

Welcome!

I’d love to see that controller.

 

[Pyropawpaw]

Welcome!

I’d love to see that controller.

 

[teepot]

Welcome to the Forum. Greetings from Southern Nevada. Near Lost Wages. {Las Vegas}.

Dave

 

[DRAGON64]

Hello from ALabama, welcome to the Rocketry Forum!

 

[mjennings]

Welcome be sure to check out Saint Louis Rocketry Association! Nice flying field at Buder Park at 44 and 141. Mostly lpr and nor at that field. I haven't been around much lately but a good group of people.

 

[Pyropawpaw]

Welcome be sure to check out Saint Louis Rocketry Association! Nice flying field at Buder Park at 44 and 141. Mostly lpr and nor at that field. I haven't been around much lately but a good group of people.

Thanks! I’ve looked at the website, but haven’t attended any of their events besides NARAM. With the exception of NARAM, I don’t think they had any HPR events this year. I’ve been going to Elizabethtown KY and Springfield MO to fly. It looks like Launchcrew in Holland IN is closer to me but I haven’t been there yet.

 

[mjennings]

I know they've done HRP at a farm in North St Charles county in the winter but I've never made it to a hpr launch. I don't see any on the calendar at the moment either.

 

[Stewman]

Thanks! I’ve looked at the website, but haven’t attended any of their events besides NARAM. With the exception of NARAM, I don’t think they had any HPR events this year. I’ve been going to Elizabethtown KY and Springfield MO to fly. It looks like Launchcrew in Holland IN is closer to me but I haven’t been there yet.

Welcome to the forum - Tripoli MO-KAN flies at Miller MO, next launch is 3rd Saturday in March. Maybe see you there.

 

[RocketRev]

How about sharing the details for your controller?
What are the safety features you are not seeing elsewhere?
24v or 12v?
Just wondering.

Brad

 

[jqavins]

How about sharing the details for your controller?
What are the safety features you are not seeing elsewhere?
24v or 12v?
Just wondering.

Brad

What he said. Are those two different controller builds, or does the one controller need two boxes?

 

[Pyropawpaw]

How about sharing the details for your controller?
What are the safety features you are not seeing elsewhere?
24v or 12v?
Just wondering.

Brad

I used a 24VAC/DC PLC that I happened to have for the logic. It has two batteries - 24v for the control system, and 12v for the ignitor. The blue box stays at the pad and contains the batteries and the PLC. The grey box stays at the flight line. The two are connected using cat5 cable with standard connectors. Both boxes have a safety key-switch, continuity test buttons, LEDs, and audible continuity alerts. The key-switches are removeable in the unarmed position only. All the switch inputs from the operator have small on delays. The firing circuit has an off delay of 1 second. The ignitor outputs are good to over 40 amps. Some of the safety features - Both sides of the 12V line (+ and -) are controlled and switched separately. After the system boots, it checks to make sure each switch is working as intended. It's not allowed to come into an armed state until all conditions are met. Once the system is armed, an alarm and flashing light are activated at the pad. It cannot fire the ignitor until it's been armed for 5 seconds. The plug on the ignitor cable is a non-standard type - using a standard 120VAC three pole wall plug with alligator clips on the other end has always bothered me. A child finding one of these and plugging it into a wall receptacle could end in disaster. Anyway, it was fun to build and has been 100% reliable.

 

[jqavins]

Impressive. Overkill, but very impressive.

 

[Pyropawpaw]

Impressive. Overkill, but very impressive.

Not really if you want to fly clusters using ignitors in parallel.

 

[jqavins]

The power supply isn't overkill. The number of interlocks, while admirable, seems over the top. And I don't mean to insult the work, by any means. Also, on one point I couldn't agree more; I hate the use of standard wall plugs for igniter leads.

 

[Pyropawpaw]

The power supply isn't overkill. The number of interlocks, while admirable, seems over the top. And I don't mean to insult the work, by any means. Also, on one point I couldn't agree more; I hate the use of standard wall plugs for igniter leads.

I understand, and appreciate your honesty. I probably see these things from a different perspective than the majority. I'm in a business where any unintended operation will very likely result in injury or even death to the user. We follow a prescriptive code that states the failure of any single component in the system cannot cause unintended operation. Components can fail in several ways. If everyone does what they're supposed to do, the risk is greatly reduced. Unfortunately, that doesn't always happen, we get distracted or complacent. A good example of this comes from an article in the latest edition of High Power Rocketry (Tripoli) about two senior rocketeers who were updating their altimeter software in a hotel room with the motor and ignitor installed. The motor was ignited in the hotel room. Thank goodness no one was permanently injured, but the hotel room was badly damaged. It also resulted in an article in NFPA magazine, which brings unwanted negative attention to our sport. This is why I believe engineering controls should be the first method to make things as safe as possible, but it's true that most probably see this as over the top.

 

[jqavins]

I certainly understand all that. I work in the rail industry as a systems engineer for rolling stock. My current specialty is brake control systems, and I'm nearing the end of an internal academy program to become a RAMS engineer. So yes, I get it. Perhaps I'm overestimating what you've done; at first look it seems like no double failure could cause unwanted actuation, which would be above and beyond. And I'm missing something to understand how the delayed responses help.

Maybe I'll take on an analysis of your system as an extra exercise for class.

 

[Pyropawpaw]

I certainly understand all that. I work in the rail industry as a systems engineer for rolling stock. My current specialty is brake control systems, and I'm nearing the end of an internal academy program to become a RAMS engineer. So yes, I get it. Perhaps I'm overestimating what you've done; at first look it seems like no double failure could cause unwanted actuation, which would be above and beyond. And I'm missing something to understand how the delayed responses help.

Maybe I'll take on an analysis of your system as an extra exercise for class.

I'm enjoying this discussion. It's designed that no single failure can cause unintended ignition. The on delays are essentially de-bouncers - less than .5 seconds duration. When two devices are operating together at a distance, transients can and do occur, and the on delays, along with some other measures, help to mitigate that. If one pecks at the launch button nothing happens. This is true for all buttons and switches. There are other safety measures built in as well. The ignitor output has an off delay. I designed it that way because I believe it makes for a more positive ignition. The ignitor output is shorted until it fires (the short is also removed during the time we're performing a continuity check). After the ignitor fires, the controller cannot come back into a ready or armed state until it's reset by pushing a button. I used the continuity test button for this. It then goes through all the checks again (this takes about 1.5 seconds), and the process starts over. So the point is, before each launch, it self tests to make sure we have control of everything, and if we do not, it cannot fire the ignitor. To the operator, it doesn't appear different than any other system, with the exception of having to press the ignitor continuity test button to reset the system after launch, but we do that anyway.

 

[jqavins]

I totally get switch debouncing, and I don't even think of a "legitimate" button push until after the debounce period. Then I took statement to be additional delay, after the fully debounced button push is detected. But I get it now.

Independently switching both the + and - from the 12 V battery? OK, if you only switch the + then a single failure can power the system up. But it still needs to be first armed and then receive a fire command, so that's a triple failure. Switching the - as well means firing prematurely would require four failures. Am I missing something?

 

[Pyropawpaw]

We can independently switch both sides of the line or use two device in series to switch only one side of the line and accomplish the same thing. The point is that we're using two devices instead of one to energize the ignitor.

In the situation you're describing above, lets say we're only using one FET to turn on the ignitor. If that FET was shorted, merely arming the system causes the ignitor to fire. That is a single component causing unexpected or unintended operation - in this case firing the ignitor before a command was given.

Now if we take the same situation, but use a FET and a relay to fire the ignitor, and again the FET is shorted, arming the system would not cause unintended operation because we still have control over the relay. In order for the failure to occur as described in the first paragraph, both the relay and the FET would have to fail simultaneously in the closed state.

I hope I'm explaining this in a way that make sense. It might easier to describe with a schematic.

 

[jqavins]

You're explaining very well the part I already know. I'm focusing specifically on using two switches to switch both the positive and negative battery terminals.

 

[Pyropawpaw]

Using the circuit you've drawn as the example, if the two switches coming from the battery are closed and the arming switch is closed, you only need the firing switch to close and the ignitor fires. The launch button among other things, actuates the firing switch. If the firing switch has failed in the closed state, that one failure will cause the ignitor to be unintentionally fired before you press the launch button. You would need the redundancy of two firing switches to remove this possibility, and as I've already stated, it doesn't matter if you put the two switches in series on one side of the line or switch each side of the line with the two devices as I've done.

Maybe this is what you've been missing: The flight line unit and the pad unit are 100' or more away from one another, the power feeding the ignitor at the pad doesn't actually go through the key-switch, the arm switch, or the launch button at the flight line. The reason for this is it would require heavy gauge wire running between the pad and the flight line to carry the ignitor current. I use standard cat5 cable - it couldn't carry that kind of current. A wireless commercial controller is similar, the buttons/switches actuated at the flight line wirelessly pilot relays that energize the ignitor leads. On the controller I've built, all switches feed inputs on the computer in the pad unit, and the batteries reside in the pad unit only. Does this help?

 

[mrwalsh85]

Hey there - Mike Walsh here, Tripoli Prefect. If you would like to send me a PM for more details, please do.. We hope to fly Oct 21 and Dec 16 - those are our scheduled HPR launch dates for the remainder of the year.

Do you still need to obtain L2? If so, have you taken your L2 exam?

Please send me that info in your PM.

Thanks,
Mike Walsh