Wireless Launch Control

cwbullet said:

I just priced a fireworks system in a pelican box. $1300 to run 3 pad boxes that will control up to 18 pads per box.

Not cheap.

Click to expand...

you have to remember there needs to be ALOT mroe safety with a fireworks setup. Alot of them have feedback. They need to know if there is a short/cont. problems, etc. Since being near/over top of a mortar will KILL your if not carefull. Unlike standing next to most rockets they will scare the **** out of you and might burn you but thats it.

Ben

So much good stuff in this thread that it’s hard to keep track of it all. I really like the way this system is constructed. Amazingly clean and lots of nice features.

I think you have pretty much all of the key features that people need or can add them by changing the firmware. You could keep track of any “high current” events out at the pad. The system could tell you when a fault condition is detected. …. so many possibilities.

One really nice feature is support for bi-directional communication between the controller and the box out at the pad. This means you can remote arm/disarm the pads (which primitive one-way only wireless systems cannot really do).

If you end up doing a design with support for multiple banks I would suggest providing a strobe output that signals that the bank is selected. You probably thought of this already.

I have seen this in several wired systems. When the bank is selected by the LCO, the strobe is illuminated out at the pads. This prevents you from launching a rocket from the wrong bank. Sometimes the LCO forgets to switch to the proper bank so visual confirmation of bank selection is helpful – please don’t ask why I know this.

Dan

ben_ullman said:

you have to remember there needs to be ALOT mroe safety with a fireworks setup. Alot of them have feedback. They need to know if there is a short/cont. problems, etc. Since being near/over top of a mortar will KILL your if not carefull. Unlike standing next to most rockets they will scare the **** out of you and might burn you but thats it.

Ben

Click to expand...

Suprisingly, this actually isn't the case. All the safety is at the remote boxes. All the "cheaper" wireless systems I've seen for fireworks are trigger only from the remote handheld. Very few have bidirectional capability, so there's no feedback. The biggest reason I started on this path is because I want to be able to check continuity from the launch console as well as locally at the pad.

flight4 said:

That's great. I'm curious to know how many pads your design will support, and what you are using for wireless radios?

I can't wait to see your thread.

My parts cost appears somewhat higher than yours (but maybe not, if you were talking about $ for a personal system) but I am also at a point in the design where I know exactly what every cost is. And it does add up.

My system is obviously designed for club use. But there's no reason a 4 pad version couldn't be used as a personal system.

Click to expand...

For radios, I'll be using the XBee, as well. They really are so well supported in the hobby robot industry, and I just can't see reinventing the wheel.

My original design basically maxxed out at ~6 pads. I had 12 pins available on the pad control box, and I was direct driving each pad through a pair of pins. 1 pin for pad enable, 1 pin for continuity return. Launch command, module enable, and other misc items take the other pins.

I haven't decided on how to wire, and if I choose to get pcbs made, I know that will be a major cost item that's not yet in my numbers.

... you know what... I guess it's time to start a new thread. While I'm still a ways out from building, I'm happy to share the basic design and layout, but I don't want to take your thread too far off topic, which is a build thread for your system.

Cheers,
- Ken

Dan_G said:

If you end up doing a design with support for multiple banks I would suggest providing a strobe output that signals that the bank is selected. You probably thought of this already.

Click to expand...

Yes, you'll see that when the field box gets built. There's an RCA type jack that supplies fused 12v anytime the master arm is activated. Our club uses this output to connect to and flash a blue strobe. Very handy around the low and mid power pads.

ben_ullman said:

They need to know if there is a short/cont. problems, etc. Since being near/over top of a mortar will KILL your if not carefull.

Click to expand...

I expect an experienced pyro will get the being near/over top of a mortar stuff out of the way BEFORE connecting the firing circuits.

My kids don't load mortar tubes but they do load rockets on pads. My system will be A LOT safer than a typical fireworks panel.

flight4 said:

I expect an experienced pyro will get the being near/over top of a mortar stuff out of the way BEFORE connecting the firing circuits.

My kids don't load mortar tubes but they do load rockets on pads. My system will be A LOT safer than a typical fireworks panel.

Click to expand...

Correct but if you have a 1200 shell show loaded and a rack looses cont. You have to walk out there and check it.

Plus the fireworks industry is alot larger than the rocket one. So people have put more money and research into them. I have a buddy who does fireworks in DC. he let me play with this laptop simulator. The program is $2k alone plus his company has close to $20k in firing boxes on the ground at one time!!

This things looking great :clap:

Ben

The fireworks system I looked at have bidirectional communication and keys to turn off the system both at the away boxes and remote. It is very safe and very expensive. It will control up to 1800 pads with additional pad boxes. It is just more than most need.

I have a demo box coming and will post more after a trial.

Yep, those fireworks folks have killer systems. I know the high end systems can tightly synchronize the fireworks with music. I have no idea if these are developed in-house or what. Everything is obviously computer controlled with very accurate timing and they can simulate their entire show so they know exactly what it will look like. These systems must be mega expensive.

Dan

Dan_G said:

Yep, those fireworks folks have killer systems. I know the high end systems can tightly synchronize the fireworks with music. I have no idea if these are developed in-house or what. Everything is obviously computer controlled with very accurate timing and they can simulate their entire show so they know exactly what it will look like. These systems must be mega expensive.

Dan

Click to expand...

Fire One

I have worked shows using the old systems and Fire One and vastly prefer the later. With the first system the operator is going to fire all of the cues in order so all of the shells must be wired to the firing rails in order. A total PITA.


NFPA 1123 has a requirement that before you connect power to the firing system even to run continuity checks, everyone leaves the area. They are nearly as paranoid as I am.

Rule 1: Never put anything over a mortar tube that you aren't willing to lose.

Pretty amazing looking products. One thing I have noticed about a number of fireworks controllers is they are CD output. Obviously suitable for firing e-matches, even many e-matches. But I wonder how they would do on our mid and high power ranges.

Ok enough about fireworks.

I know Cobra Firing Systems has an optional battery addon that allows you to fire other types of ignites with a charge of 18v and 6-8 amps.

Just a few more comments on the field box options before I commit these boards.

Pictured is the high density configuration supporting 8 pads. These are still two 4 pad clusters so they can be managed independantly. So two master arm relays. Only one wireless module is needed here since the boards can communicate with each other via a two wire inter-circuit communication buss. Basically one board receives the message via wireless and forwards it to the other. That saves a little on complexity and cost.

I believe I mentioned in the vernk box sidebar earlier that I ordered a 100A industrial contactor to check out. It came in today and omg the thing is freaking huge. That's it in the second photo. 5/16" studs on top. My current PCB design won't work with the contactor since I don't have an output to drive it, but the changes would be fairly simple if I decided to incorporate it later.

Now with two of those in the box what I could do with the current PCB is make one the master arm relay (contactor), and the second a parallel pad relay (contactor) connecting to a separate 50 or 100 amp outlet. That plus a truck battery would launch anything! Serious over-engineering. Maybe later.

The last photo is the configuration I will go with for these two pad boxes. This is the most flexible arrangement, since it allows the boxes to be used next to each other or far apart on the field. I will also be using the dipole antenna and not the patch antenna. This way distance is not an issue and I can use the boxes for near pads or far away pads. That's a 16" RP-SMA pigtail that I fabricated to move the antenna up to the panel on top. You can see why the board has to be tilted for this configuration to make room for that cable. RP-SMA connectors are expensive. Ouch!

Trying not to lose momentum here. Spent some time today with Sketchup refining the cutout and drill patterns for the top panel But that's about all.

Ok, finally, I hope. I'm having some trouble with this version of Sketchup. Maybe they took some some features out of the free version.

If it works this pdf is a pattern for the top panel of the field box. The dimensions aren't very critical but you don't want to be too sloppy on the large rectangle.

The holes over by the sonalert are for the fuse and the beacon connector.

View attachment Relay Box Top Panel 4 Pad Rev 2.pdf

flight4 said:

Ok, finally, I hope. I'm having some trouble with this version of Sketchup. Maybe they took some some features out of the free version.

If it works this pdf is a pattern for the top panel of the field box. The dimensions aren't very critical but you don't want to be too sloppy on the large rectangle.

The holes over by the sonalert are for the fuse and the beacon connector.

Click to expand...

Let me know if you want this drawn in Inventor or AutoCad.

Ben

Time for some cutting. Nothing fancy. The layout is straightforward. Start with a pilot hole for the sabre saw. The cutout is for the 20A electrical outlets. The fit is pretty close. Then the rest of the various mounting holes. A few of them also need a relief cut on the back due to the thick panel.

One more to cut out (I'm making two field boxes).

This is the second panel cut out and some components test-fitted. I haven't drilled the hole for the antenna connection yet. I haven't decided where to put it. I'm leaning toward the location shown in the photo.

That's a 5.5 dbi antenna that I just got in the mail. That would be about a 100% increase in gain over the stock antenna.

The stock antennas worked fine in field tests up to 800 or so feet LOS. So I doubt I will have to deal much with these 'upgrades'. But it's nice to have options.

The components shown are power switch top left, heartbeat LED below it. And further down a Mini DIN-8 connector for the in-circuit programming interface. To the right is the antenna of course, the fuse for the electronics and beacon, RCA jack for the beacon, and big loud sonalert. In the middle are 20A duplex outlets for the pad ignitor cables.

Next I need to drill a few more little holes, then prime and paint. While the paint is drying for a week or so I can work on the lower panels.

The field boxes look great. Is there any continuity indication at the pad? This is not really essential. I know you have the capability to check at the launch controller.

Dan

There certainly is. It's built into the ignitor cables actually, so it's literally right there at the pad. You see continuity (or lack of) immediately as you are hooking up your ignitor. No need to walk over to the field box.

Another feature of the design is extremely low current for continuous continuity monitoring. This was a very important requirement due to the sensitivity of certain types of ignitors. The current through the ignitor will be about 470 microamps (less than half of 1 milliamp) plus or minus around 30 microamps.

flight4 said:

There certainly is. It's built into the ignitor cables actually, so it's literally right there at the pad. You see continuity (or lack of) immediately as you are hooking up your ignitor. No need to walk over to the field box.

Another feature of the design is extremely low current for continuous continuity monitoring. This was a very important requirement due to the sensitivity of certain types of ignitors. The current through the ignitor will be about 470 microamps (less than half of 1 milliamp) plus or minus around 30 microamps.

Click to expand...

Have you considered all of the failure modes of having an active circuit near the ends of the igniter leads? It's much safer to have a complete disconnect while connecting the clips, then moving a few feet away to check continuity.

jsdemar said:

Have you considered all of the failure modes of having an active circuit near the ends of the igniter leads? It's much safer to have a complete disconnect while connecting the clips, then moving a few feet away to check continuity.

Click to expand...

It's an independent circuit within the cable. The LED is about 24" back from the ignitor clips and is fully encased within clear shrink tubing.

If the voltage regulator on the relay module failed through such that full battery was applied to the electronics (highly unlikely), first it would blow out the CPU and nothing would work. But more importantly the current to the ignitor for continuity detection would either be zero, or would increase to only about 1.4 milliamps, which is still safe.

Other than that, failure modes that might increase current to the ignitor would all most likely involve physical damage. Like if the field box got run over by a truck. At that point, hopefully, the potentially unsafe situation would be obvious.

Would you mind sharing your continuity circuit. The circuit used in our system is primitive at best. It uses an old school PNP transistor as a switch. The test current is 500ua. If the transistor shorts, then you will see about 15-20ma through the igniter. This is not ideal, but this is below the no-fire rating for most common e-matches and igniters.

The extra resistor between the base and emitter just makes sure the transistor stays off when the switch is open.

Dan

(Now that I look at this circuit again I realize that regardless of the failure mode the current though the igniter will probably never exceed 500ua)

It's not that fancy. 5v is dropped across a 10k resistor and the ignitor, and that is buffered to a high impedance input on the MCU. Everything else is basically done in software. The launch relay configuration is similar to yours.

flight4 said:

It's an independent circuit within the cable. The LED is about 24" back from the ignitor clips and is fully encased within clear shrink tubing.

If the voltage regulator on the relay module failed through such that full battery was applied to the electronics (highly unlikely), first it would blow out the CPU and nothing would work. But more importantly the current to the ignitor for continuity detection would either be zero, or would increase to only about 1.4 milliamps, which is still safe.

Other than that, failure modes that might increase current to the ignitor would all most likely involve physical damage. Like if the field box got run over by a truck. At that point, hopefully, the potentially unsafe situation would be obvious.

Click to expand...

Where's the current-limiting resistor for the LED?

What type of connector are you using for the igniter? Can a short in the connector or in the cable put too much current to the igniter?

Is there a arming disconnect to allow someone to connect leads with the continuity circuit completely disconnected?

Does this really justify more than two wires in the igniter leads?

The limiting resistors are on the relay module. They are actually larger in value than other limiting resistors in the system. Given the output impedance of the MCU and the limiting resistor, LED current is limted to less than 9 milliamps. I also measured a dead short to the MCU output and it was 22 milliamps. Add the resistance of a 10 foot ignitor cable and ignitor and the values will be a bit less.

The ignitor [cable] connector is a UL approved 3 prong plug. Of course UL approved it for AC electrical applications and not rocketry. But the quality is sufficient. A short is a remote possibility, especially in the case of physical damage, as I mentioned before. It would take a lot. The cables are robust.

Yes, there absolutely is an ignitor disconnect that allows someone to connect leads with the continuity circuit completely disconnected. Just unplug the ignitor cable. Additionally, one could also power down the controller and disconnect the battery to be extra sure.

Sounds good. 22ma is highly unlikely to cause a problem. Even those touchy Quest Q2G2 igniters need more than 100ma. I'm sure you could detect the problem and fix it (or at least take that pad out of service) before it causes any issue.

Dan

flight4 said:

The limiting resistors are on the relay module. They are actually larger in value than other limiting resistors in the system. Given the output impedance of the MCU and the limiting resistor, LED current is limted to less than 9 milliamps. I also measured a dead short to the MCU output and it was 22 milliamps. Add the resistance of a 10 foot ignitor cable and ignitor and the values will be a bit less.

The ignitor [cable] connector is a UL approved 3 prong plug. Of course UL approved it for AC electrical applications and not rocketry. But the quality is sufficient. A short is a remote possibility, especially in the case of physical damage, as I mentioned before. It would take a lot. The cables are robust.

Yes, there absolutely is an ignitor disconnect that allows someone to connect leads with the continuity circuit completely disconnected. Just unplug the ignitor cable. Additionally, one could also power down the controller and disconnect the battery to be extra sure.

Click to expand...

Sounds like reasonable assumptions.

I don't think there's much of an advantage to complicated a simple 2-wire igniter lead. Everyone is familiar with going back to the pad box to check continuity. Even though you understand it is safe, the experienced user will feel uncomfortable with an active circuit when connecting leads.

A bigger benefit would be a resistor and LED between the leads that would indicate a powered set of igniter leads. Only the two wires are needed. It will show if the leads are hot (stuck relay, or failed ignition path). I usually touch the leads together to look for a spark.

Today's meager progress is akin to watching paint dry.

The panels have their final holes drilled and are lightly sanded. I finally drilled the antenna which I moved a little more to center.

Then a light coat of primer to get things ready for final color. I'll hit it with another light coat of primer in a bit and then it will dry for at least 24 hrs.

I'm off to Chattanooga with my boys tomorrow for a lacrosse tourney (long day) so it will have plenty of time to dry.

And with paint.