Wireless Launch Control

We normally set up 10-15, but we have set up as many as 30. It depends on the launch, be we need more of a system for the high and away cells. Your system would be perfect for that sort of set up.

flight4 said:

Just curious. How many pads do you guys normally set up?

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Normal monthly launch, 5 at model rocket distance, 5 at J distance, 5 at L distance, and an away cell if there are going to be any M flights. Larger launches it"s 10, 10, 5, and 5 at the away cell.

The happy family. The big ones are the relay modules. I finally committed the 30A relays and Super Capacitors. They are $$ so I leave them to the end. In the middle is the LCO Master Controller, and below are the Pad Control modules and three wireless interface modules.

I am proficent at electronics but its not worth my time to reinvent the wheel. Would you consider doing a 'group buy' on just the boards and publishing a parts list? That way I could place a Mouser order and have a nice launcher.

Ben

A group of one?

I haven't decided if I would try and sell these. But even so I doubt I would offer kits or bare boards. That would require a ton of additional documentation. A well written assembly guide takes a lot of time. I could never recover my costs. I don't even have an operating manual yet.

Electronics and computers have been my hobby a lot longer than rocketry. This is all supposed to be for learning and fun.

But hey you never know.

David,

I can respect desire to keep it fun. I have throughly enjoyed following you build.

Chuck

flight4 said:

A group of one?

I haven't decided if I would try and sell these. But even so I doubt I would offer kits or bare boards. That would require a ton of additional documentation. A well written assembly guide takes a lot of time. I could never recover my costs. I don't even have an operating manual yet.

Electronics and computers have been my hobby a lot longer than rocketry. This is all supposed to be for learning and fun.

But hey you never know.

Click to expand...

Maybe you misunderstood, I dont want you to to anything for me but get the boards. I can handle putting them together and such. Unless you want to release the board files, then thats a different story

Ben

Oh I understand just fine. But I wonder how you're going to program the 7 CPUs, and the wireless radios. Maybe that's the 'and such' part :wink:

Now back to the build.

I think we are finally past the tedium of building circuit boards and into the fun stuff.

The first photo is the naked top panel. This is for an 8 pad system of course. Same panel as the first photo in the thread but without the parts installed. The panel is 4mm clear anodized aluminum.

Second photo shows all the LED lenses pressed in. The fit on this panel is extremely good and most parts fit snug. But I still like to tack the lenses in place with a few dabs of epoxy to make sure they don't move.

Same panel with the pad select switches installed. I 'level' these so that just .1 inch of ferrule is above the panel on the other side. This way they appear consistent.

The second photo shows one of the Pad Select modules in place for a test fit. So finally we can see where this board fits behind the panel. If you look close you can see how the switch solder lugs fit through the pads on the board. You might also see where the LED leads will come up through the board.

Originally I planned to use mini switches with solder tails vs lugs, which seemed to make sense. But those switches cost twice as much as these for some reason. So I just made the holes bigger for the lugs and it works out great.

Everytime I build a prototype I find a few new things to tweak. With this 8 pad version the master arm led is relocated to just above the D-hole for the master arm switch. And it's a bit close to the edge of the board.

It will be fine and I had already planned to move that LED and switch down about .1" to improve spacing on top of the panel. But I might add a cool little notch for the LED on future boards for no good reason.

Here it gets a little tricky. The select and continuity LEDs are all in place. Short lead, flat side toward the switches (very important). All LEDs tested in-place with a button cell. These are all 8000 MCD super bright red and green LEDs. These have proven to work better than great even in full sunlight.

The tricky part is the circuit board, that previously fit so nicely over just the switch lugs, now also has to fit over all these 16 or so LED wires. It's a bit of a dance to get all the leads to all go all in their right holes. Seems impossible at first, but like anything once you get the hang of it, not too bad.

Next is to try and repeat this feat of dexterity on the other side. Then some more soldering.

Ha Ha. Did it!

Not saying this build is perfect. But it gets easier each time.

I’m really enjoying this thread. I’m guessing that there is no wireless launch controller currently available that has this feature set. I have seen a wired controller design that has some pretty advanced features (https://www.vernk.com/LaunchController.htm) but not wireless.

I certainly understand your comments. Documenting the design to where someone else could build one would indeed be a big task. I think you can tell there is some demand for such a system. I’m not sure of what it would take to make these things available in some form – a lot of work no doubt. My current clubs have good launch controllers, but it would be great if something like this was available.

To the extent you wanted some assistance in documenting the design or anything else, I’m sure you could find some volunteers to help (myself included).

Dan

Yes, Vern's controller is very impressive. I would love to get a peek inside. I'll bet all those circuits are hand wired. Yikes!

Glad you're enjoying the thread.

Yep, I'll bet it is all hand wired. The Italian version shows how they wired one of the boxes.

https://www.acmeitalia.org/tecnica/sistemi_lancio/img_centralina/800bank_open.JPG

Our club's launch system is done the same way (by hand) - just not as elaborate as Vern's design.

A PCB implementation should really help with reliability.

Dan

That's amazing. Actually there is a circuit board in there for the electronics. Single sided by the look of it so maybe hand-etched.

I love Verns controller also. It is very professional looking on the outside. I have looked at the designs many times and contimplated building it myself, but I do nto have that skill set. My solder skills are not up to an electronics board.

I am sure their is a market for a controlled. It may nto be large, but clubs would be will to pay for a well made system that is more reliable. Ours is just too long in the tooth and fails every launch. We had 2 boxes fail to work and only 3/5 bads work on the 3rd. I know the officers are working the issue, but it is obvious we need a better system, expecially since we have 2 larger rgional type launches this year.

It does 30 pads an is wired with phone or cat5 cable to pad boxes that contain relays.

David,

if you ever consider selling one, let me know, I'm interested!

Yep, it looks like some sort of a proto board. I did the same thing for my club for the continuity circuitry ... crude but effective.

I’m not sure if you noticed, but Vern has a nice approach for solving the “relay problem.” Would you mind sharing how you address the following:

Most home brew launch systems use Bosch style automotive relays. The problem is, those relays are only rated for 30-40 amps. But they are cheap and generally work great. Absent some form of current limiter circuitry, a typical HPR igniter will pull more than 30-40 amps. I suppose there could be some debate on just how much current. Of course the peak current depends on lots of factors such as the type of battery used, the wire gauges used … Those Bosch relays seem to tolerate this current spike pretty well. But this is not an ideal situation since your are exceeding the capacity for the part - albeit for a short time period.

So Vern uses automotive relays as a pad select only …. “ power is actually switched on and off with a high capacity 100A industrial grade contractor switch. (U9 in the drawing. Part number 576-3007.” Vern also has an alarm that will sound if the relay contacts get welded - very clever.

I can tell you that our club’s launch controller uses Bosch style relays and we do not have a current limiter. We just replace the relays on a regular basis.

Dan

That's an intresting issue. Though in practice we have never had a relay problem. My design is very typical. There is a 50A automotive type master arm relay, and for the pads I have 40A power relays. Of course these relays are always conservatively rated. I actually looked at some higher current relays for the system I built a few years ago. Main issues were cost and size. Industrial contactors run $20-$40 and up, where my power relay was $3.50. I had never thought of Vern's method with the contactor though. Interesting.

The relay module does have the ability to measure and monitor current flow. The thought was that excessive current or excessive duration could indicate a problem, and the pad could be automatically shut down. But I haven't experimented with that yet. The pad and relay modules also monitor the master arm relay status. If the relay gets welded it will be detected when the master arm is switched off, and the entire node will be disabled.

I think having an accessory box for high power clusters and such would be a great option. Plugs into the regular pad box, has a dedicated battery--maybe a truck battery. 100A or 200A contactor (again cost), up to 8 parallel outputs. It's not a new idea.

That sounds good to me. This is the advantage of a system that includes a microcontroller. You can detect faults like a welded relay contact. I’m not sure how Vern hooked up his alarm for this condition.

I would love to have a simple analog current limiter circuit – perhaps like 30 amps. I just cannot figure out how to implement. This would be a great safety feature for simple systems using Bosch relays. There is no need to deliver 30 amps to an igniter, this is just what happens since the igniter is effectively a direct short while it is burning. So while the igniter is burning, and folks are holding the button, the current is only limited by the smallest wire gauge.

If course if the igniter leads are shorted (e.g., the clips are shorted), the current is totally maxed out. It’s got to be in the 100-200 amp range if you use car batteries as the power source. Under these circumstances you know the standard procedure … if the igniter does not light, try again … perhaps two or three times. You have continuity, so you just keep pushing the button. The launch box effectively becomes an arc welder. I have no solution for this other than to change the relays on a regular basis.

Dan

Based on the schematic Vern's alarm is pretty simple. The sonalert is connected to the contactor output and sounds whever it is closed. If it welds then the sonalert keeps going and will alert anyone approaching the pads.

The short circuit w/ button mashing LCO scenario is exactly what I was thinking of with the current detection at the relay module. I still need to figure out the parameters, but regardless of how often the LCO hits the button or how long he holds it, the module detects the probable short and disconnects the current. I will also probably have the pad module beep a few times and flash the continuity LED as a short circuit indicator. All easy to do in software.

I would have to agree it is very unique. I have also seen them with a flashing sign instead of a sound. I like the sound more because you do not need to look at it to know the circuit is live.

Do you think the average person can wire Vern's set up? What are the boxes made of?

Sorry, I hijaxed the topic a little.

I'm sure Vern could answer your questions about the boxes. Not sure what type of box he uses for the remote bank control units. The launch controller is housed in a Pelican Case (very high quality). As for the wiring, it could be done by someone with some electronics experience. You just have to be careful and check all your connections before powering up. Most home brew units look kinda like this ... but Vern's boxes have a lot of features which translates into lots of wires.

Dan

And now back to our regularly scheduled thread.

The first photo isn't much different than before. Except that everything is soldered now and the leads clipped off. These modules are now married to the panel. The other photos are just different perspectives on the pad control module.

I've had some thoughts on using sockets for the LEDs. There's not enough clearance but if I cut off part of the lens clip it will work. Why? Some day this module might have to be serviced. Being able to easily remove it from the panel will be a plus.

Each prototype is another opportunity to refine.

Dan_G said:

If course if the igniter leads are shorted (e.g., the clips are shorted), the current is totally maxed out. It’s got to be in the 100-200 amp range if you use car batteries as the power source. Under these circumstances you know the standard procedure … if the igniter does not light, try again … perhaps two or three times. You have continuity, so you just keep pushing the button. The launch box effectively becomes an arc welder. I have no solution for this other than to change the relays on a regular basis.

Click to expand...

An autoreset thermal breaker will protect the circuit and wiring from a dead short. I've been using them in launch controllers for 15 years without a problem. Choose the amp rating such that a few seconds of normal igniter current doesn't trip the breaker but >20A for 10 seconds will. They'll reset automatically in a few seconds, depending on ambient temperature. They're available in automotive-style fuse packages and in circuit board thru-hold and surface mount packages.

Yep, I thought about using a resettable fuse type device – like a polyswitch. The specs on these devices are confusing at best. In a nut shell, it was the response time is that bothered me. 10+ seconds is a heck of a long time to have a direct short running through your relays. I was not sure that the device would trigger quick enough to protect the relays. I’m glad you were able to get them to work, but I was not sure I could get one of these to function as intended.

In an ideal world, I would love to use something like an industrial strength LM317 (three terminal adjustable regulator) to limit the current. Current limiting circuits based on these devices are nice and simple. I never did locate a device with a suitable current rating. I have an EE degree but I quickly realized that making a current limiter circuit for 20-30 amps in the analog domain was beyond my skill set. It also appeared that the circuit components would be expensive to say the least.

It seemed to me that a microprocessor controlled device with a current sense resistor and some form of switch was a better way to go (i.e., software controlled switch as a current limiter). However, this is also a huge project – as we can all see in this thread.

Dan

Ah yes, back to this thread :wink:

Minimal progress, but I got the master arm switches permanently installed. A little bit of epoxy ensures they won't get loose in their D-holes.

Seriously, thanks for all the comments. I learn things too and get ideas. I ordered a 100A industrial contactor today. Basically a honkin fat relay. I'm going to figure out some way to build it into the field box.

Looks great. Is this unit set up for selecting 3 separate 8-pad field boxes? Does this correlate to heartbeat A, B and C? If so, how does one select between each bank of pads?

Dan

Did you order the face plate? Is it laser engraved?