Wireless Launch Control

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flight4

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This is my wireless launch controller. Low or high power, it doesn't care. A work in progress over the last few years. I'm calling this one the last prototype. The insides are still incomplete. I'll be capturing the build of this and the wireless field boxes over the next few weeks. Its slightly older brother is a 4 pad variation I built for SoAR for the GRITS regional launch held this month in GA. That 4 pad wireless launched all the M+ projects from the far-away pads at 500'+ with 100% success. The design range is 2000' LOS. Enjoy the build.

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Very Nice looking layout.

I've been intrested in wireless systems for a long time, but have been reluctant to presue building one as I've always run into the same problem area. Stray signal interference and/or unintended launch by stray signals.

How has your system compensated for these increasing use and channel crowding headaches?
My guess is these are not as many of these problems in less congested sparcer populated regions then here in the East and Northeast??
 
I've been designing a wireless controller off and on (mostly off) for a while. Mine uses a touch screen to reduce the number of mechanical switches. Truth be told, I really don't need one. It's just a side project.

It works just like the wireless service at a Starbucks. There may be 10 people on the network, but you only get the information you request. You are automatically assigned a unique ID number (address) that is sent with every request. The computer reads this number, processes you request and sends it back with the same address.

For a wireless launch controller, the trick is that you send a command string from the launch controller to a microcontroller at the pad. The microcontroller decodes the command string verifies it's talking to the right microcontroller and launches the indicated pad(s).

This eliminates the chance of an unintended launch.

The microcontroller at the pad also sends a command string back to the launch controller with a report of which pads have continuity.

I believe most wireless chips have a built in, unique address to prevent the chance of any crosstalk. But even still, without the proper command, nothing would happen.

This is only one approach. I'm interested to hear what Flight4 comes back with.

By the way, to market a wireless launch controller, you would have to have it approved by the FCC and that is a whole different ball of wax...........

Bones
 
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Thanks for the comments. At first I tried using some very small 433mhz ISM band [VIMEO][/VIMEO]transceiver modules. These worked well point to point. But developing a protocol for multipoint communications (think multiple wireless field boxes) became more trouble than it was worth. So I switched to 2.4ghz DSSS multipoint zigbee modems. They are awesome. And still only as big as a postage stamp. Better still, they are already FCC certified. I could use the 433mhz modules legally under my ham license if I wanted. But FCC certified is so much better, and the product could be sold if I wanted. The zigbee modems support AES encryption which is critical. With the UHF modules I had to implement my own encryption. On top of encryption I also implement a very strict safety protocol in software to ensure safe launch operations. There are physical safety controls also. This is all transparent to the LCO of course. He just sees a user interface typical of many relay systems. All by design. I'll comment on other features in other posts. Enough for now.
 
Here's the 4 pad wireless variation (the slightly older brother) that I built for SoAR - Greater Atlanta. The graphics are printed and laminated, vs engraved like the 8 pad version above. But is otherwise virtually identical.

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I posted this block diagram a good while back and it hasn't changed too much. It helps set the stage for the build. The system (wired or wireless) is built from modules. Pad modules, relay modules, etc. The same modules are used for wired or wireless, although I've been focused mainly on wireless. A wired system is cheaper to build, however, especially for low power where cable runs are short.

View attachment Controller Block Diagram v2.0 Rev 0.pdf
 
I call this first module the LCO Master Controller. It's only used with wireless since it is the interface between all the pad modules and the wireless network at the LCO end of the system. Despite its central role this module is by far the simplest. Basically a CPU and headers to connect to other things. There's a connector for DC voltage in, power LED, heartbeat LED, sonalert and launch button buss, and a connector for remote programming the CPU. The two header receptacles accept the wireless interface module which will sit over the CPU.

The first photo shows the module with just the SMT components installed. The second & third photos show the mostly complete board. The last photo is the module test fitted into the enclosure. Also shown are the rechargable batteries and voltage regulator. I chose to use two batteries so the system would run as long as possible, say for a three day launch. The 4 pad system just has one battery. The module can measure the input battery voltage so it can actually warn the LCO and eventually shut down if the voltage is getting too low (a safety feature). Of course the system will accept an external battery input also.

The heatsink for the regulator is just a piece of aluminium bar stock. The regulator actually belongs on the PCB, but with a clip on heatsink it actually stands up a little too tall in this enclosure, so it was easier to move it. The module can also accept a backup power supply in the form of two super capacitors. The regulator and the supercaps fill the space to the right of the black capacitor in the second photo. But backup power isn't really needed at the LCO end. So the supercaps aren't installed.

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Someone should develop an iPad app + adapter for launch control.

But this looks pretty amazing too. I'm always hesitant wrt wireless launch control for the reasons already given..

Would Bluetooth be an option? Or an ad-hoc WiFi network?
 
Someone should develop an iPad app + adapter for launch control.

But this looks pretty amazing too. I'm always hesitant wrt wireless launch control for the reasons already given..

Would Bluetooth be an option? Or an ad-hoc WiFi network?

Android maybe. I'll leave iPad stuff to others.

Bluetooth and WiFi certainly an option, but with tradeoffs. For example, consumer type BT and WiFi generally needs a computer to attach to. So you're talking laptop basically. Or something equivalent like a portable computer, tablet, WinCE type device, etc. At all ends like all clusters of pads.

Now there is some pretty cool industrial control gear out there that could be adapted for field use. Programmable computer units, I/O modules, network interfaces, BT, WiFi, etc. But all very expensive.

People also adapt garage door openers, which can make a pretty neat wireless launcher. Some will build only with found parts to keep costs low.

My goal was to produce something more purpose built to a specific set of physical requirements, yet very flexible in terms of operating software. And cheaper too, especially at scale. But everyone should buy or build and use what works best for them.
 
So what does the LCO Master Controller actually do?

If this were a wired system vs wireless, each Pad Control Module would connect to a Relay Module via a Cat5 cable. Basically point-to-point. Each Pad Control Module controls 4 pads. And obviously each Relay Module supports 4 pads out on the field. A large controller with 8 Pad Control Modules controls 32 pads. And there are 8 Cat5 cables running out to 8 clusters of 4 pads, for a total of 32 pads. That's basically the club system I built a few years back.

A goal of wireless, of course, is to eliminate wires. So no more Cat5 to the pads. The LCO Master Controller consolidates the functionality of one or more Pad Control Modules into a single wireless LCO node. This doesn't mean the Cat5 cables now plug into the LCO Master. That would be ugly. Rather, the LCO Master implements an inter-circuit communication buss that is also supported by the CPUs on the individual pad modules. That's basically a 2 wire buss from the LCO master and daisy-chained to each of the pad modules in turn. The LCO Master learns how many pad modules are on the buss, then polls those modules for inputs and status continuously at about 10 times per second. Any outputs such as continuity or pad select status are sent to the modules at the same rate.

So in short, the LCO Master Controller gathers inputs from the Pad Control Modules, and then delivers these wirelessly to the various wireless Relay Modules in the field. While at the same time enforcing safety protocol. The LCO Master Controller also gathers wireless input/status returned from the Relay Modules such as continuity, pad select and master arm status and such and either sends these to the pad modules to process/display, or processes them locally in order to enforce safety protocols.

On top of the LCO Master Controller goes a roughly 1.5" x 2" interface board which in turn holds the zigbee wireless multi-point modem. The interface board has the zigbee power supply, some filters, and status LEDs. The zigbee is a self-contained module that plugs into the interface board. I'll have pictures of those soon.
 
Time to get started on one of the Pad Control Modules which is probably the most complex of all the modules in the system.

It may be hard to visualize but this board actually sits under the top panel directly below the various LEDs and switches. The module controls 4 pads so the 8 pad wireless controller will have two of these under the top panel. It mounts upside down and the LEDs and switches for 4 pads all solder directly to the board.

On the large controller I built a few years ago all the LEDs and switches were wired individually. That was around 100 LEDs and a bunch of switches. Two wires per component. A whole lot of wires. These were all formed into harnesses and routed to controller PCBs. The controller PCBs were in turn wired to a backplane where Cat5 cables were connected to run to the pads. It all worked fine but it was a whole lot of work. Too much work, too much time. Wire is expensive too.

I decided if I was going to build more of these (I was considering the wireless design at the time) I would have to eliminate most if not all of those wires. There were a few design iterations but what I ended up doing was moving all the controller functions to this board now sitting under the panel. Lots and lots of wires eliminated. Even the Cat5 cable now connects direct to the board. The master arm switch, sonalert and launch button are still separate but that's about all.

The rectangle area at the top left of the board is for the RS232 interface and Cat5 connector. There are actually two versions of this board. On the other version that rectangle is a separate piece and connects as a daughterboard. Works the same. The version used depends on the application. The 8 pad controller uses an enclosure that is relatively shallow. So the daughterboard makes the assembly too tall. But in the configuration shown here it works fine. In a larger controller where the grouping of modules horizontally and vertically is more dense, and the enclosure is taller, the daughterboard version works best.

Another design choice was that this module uses two CPUs instead of one. Microcontrollers actually. One CPU would be more than enough but it would need to have enough I/O pins for all the LEDs and switches and other functions. A 28 pin CPU would work but there was no way I could fit that on the board. The locations of the LEDs and switches were fixed since they soldered directly to the board from the panel above. Everything else had to work around them. So I ended up using two smaller CPUs which fit ok. One to handle display, which is all the LEDs, and the other to do everything else. That worked out great and the two communicate via a single serial pin.

Of course I could have used SSOP or TSSOP CPU packages which are really small, vs the DIP packages. But at the time I had almost no experience with surface mount technology. And also as I would experiment with and test these boards, I would sometimes mess up and blow out the CPUs. Replacing a DIP in a socket is a whole lot easier than replacing a tiny soldered on SSOP or TSSOP. So it's DIPs for the IC and CPU chips now and forever. That said, there was still a lot of other stuff to put on this board. And it was a real challenge to design. But it works.

Enough background babble for now. Time to build.

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All the SMD components soldered onto the Pad Control Modules. They're not all easy to see or find but there's about 28 SMDs on each board, front and back. Mostly resistors, a few capacitors, and the big one is a voltage regulator.

Since this is an 8 pad wireless controller I am building two modules.

Next are all the thru-hole components.

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Of course the pad controller needs its brains. The microcontrollers can be programmed in or out of circuit. Out of circuit is easier when building initially. The middle picture is the programmer and a ZIF socket. Remember those?

Programming only takes about 10 seconds. These programs are not very big.

The last picture is the two 4 pad controllers all dressed up, programmed, and ready to play. Of course there are still a bunch of LEDs and switches missing. But we'll get to those.

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The main and wireless controllers at GRITS looked and performed great. Keep up the good work.
 
That is awesome. Grits is lucky to have you. Our main system is failing miserable. We spent about 1/4 of the time at our last launch fight with it.
 
That is a really nice looking design - very sophisticated. Looking forward to seeing your updates as things progress.

I’m sure most clubs could really benefit from such a system. Perhaps you are considering making some of the modules available to others in kit form. I believe this is how these types of devices are often sold - so that various approvals are not required.

Regards,
Dan
 
These are some photos of the relay module. This is the module that sits out at the pads. It's the largest of all the modules, and though all the large parts make it look complicated, it's really not. I use a 40 pin microcontroller on this one only because I have the space for it. Don't really need one that big.

Originally this was a fairly small board, then I added a second board for the relays. For wireless I had to add the two smaller relays, and at that point I decided to make it all one board. Cheaper than two separate boards and also eliminated a bunch more wiring.

As with all the modules the SMTs go on first. These pictures are from a few weeks ago and I think my soldering technique has improved since then.

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These are the various thru-hole components laid out (parts for 2 boards), and then installed. And finally the relays. I haven't put them on yet but the two super capacitors that make up the backup power supply go just below the voltage regulator. I'll put those on later.

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That is awesome. Grits is lucky to have you. Our main system is failing miserable. We spent about 1/4 of the time at our last launch fight with it.

I agree..We(ICBM/ROSCO) REALLY need a system such as this! Is a real bummer when the cord get fried on the away pad and your nest in line to launch a rocket..

Maybe if Ed or Wally saw this I think we could persuade David to make one for us?
 
I design them but I don't manufacture them. Express PCB. Quick turnaround. Reasonable price. Excellent quality.
 
Now it's time to build a few wireless interface modules. This is mainly an electrical interface. But I added some LEDs for status and such and for that I had to add transistors and other stuff to drive them. So although small, about 2" x 2", it's an annoying little board with too many parts.

The middle photos show the various SMDs. The last photo is the completed assembly. Except for a small pushbutton at bottom center which is missing. I seem to have suddenly run out of really small pushbuttons. So I will add those later.

For the 8 pad system I needed to build three of these modules. Took about 1.5 hours to build all three.

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Panther John, This is a different system than the one that Eric was looking at. The one he is looking at is from Quickburst. I think all would prefer this system.

Great system. I wish I had flight4's skills.

Chuck
 
Panther John, This is a different system than the one that Eric was looking at. The one he is looking at is from Quickburst. I think all would prefer this system.

Great system. I wish I had flight4's skills.

Chuck

I agree. This would be an awesome system for the club.
 
That is awesome. Grits is lucky to have you. Our main system is failing miserable. We spent about 1/4 of the time at our last launch fight with it.
I agree it's time to replace it. It was built for LDRS 1996.
 
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