Large Club Control Panel

[JAL3]

I'm starting this thread trying to gather some information for the construction of a large club control panel.

I have lots of questions and I am still trying to piece some things together in my mind before I jump in with my questions but I was asked a question in another thread https://www.rocketryforum.com/showthread.php?t=7909&page=2

It seems to have wandered from the original post in that thread so I am starting a new one so people with no interest in this topic won't have to endure it.

 

[JAL3]

The question that prompted this thread is this:
Originally Posted by BobCox
What is the purpose of the 25-foot cable? Does it control a relay, or does it provide current directly to the igniter? When you start getting into longer leads, it is nice to have the battery and relay right next to the pad to minimize the resistive losses in the leads. The control lines can be arbitrarily long and fairly light weight since they only need to carry enough current to trigger the relay.

My club normally launches from a car battery. Right now we use heavy extension cords, some 12 AWG and some 14 AWG to run from the controller and battery to the pad. My expectation is that with the heavy cords, the loss is minimal.

This approach has some good points.

1. In an emergency, any extension cord will work. We can launch in the middle of nowhere and be fairly confident that if a replacement was needed, something that will work can be found.

2. It minimizes the wiring work. Nothing has to be done to the extensions and our current controller uses regular grounded 110 outlets.

3. Everyone from the new guys to the old hands understands it.

4. Its bought and paid for.

It also has some bad points.

1. The potential exists that our launch equipment could conceivably be plugged into AC power some day since those are the connections.

2. Each extension cord can handle 2 launching circuts. The ground prong is connected to the negative lead and each of the other blades goes to a single launch station. That means that lots of cords have to be run for bigger launches with multiple pads and requirements.

3. People sometimes "borrow" the launch cords to do things around the house.

What I wanted to do was to develop a standard cord that would handle all of our LPR and MPR needs. Each cord would control 8 possible firing circuits. They would have a common ground much like our present system.

That means that I need 9 conductors. Based on the limited searching I have done, 9 is an oddball number of conductors. I have found them but they tend to be very light wiring, 20AWG or worse.

There seems to be a little more available in 10 conductor but I stress the word "little". In theory I don't mind the extra conductor because I can think of possibilities for it later on.

I would like to find wire that is heavy, 14 or 16 AWG. Does anyone know a source?

That assumes, of course, that the wire would be heavy enough. I don't know that. I was thinking in terms of 50 foot cables so that minimum separation can be maintained for several racks from the spectator line. What would be the minimum gauge needed for that?

The cables would use molex type connectors at each end. One end plugs into the control system and the other to the rack itself.

Most of the racks would have 4 launch stations built in. Additionally, each rack would have a jacks to run 4 more extensions to power individual pads for special needs or if somebody wants to use his own pad. If somebody needed a tower setup, the LCO could tell him to set up as a sattelite of pad E and hook up to circuit 5. I was thinking in terms of 25 feet for these cable to give maximum flexibility. These would be simple 2 conductor cables and should be easier to find.

Assuming that the primary cable run is 50 ' and the satellite extension is 25' and allowing 6 feet for the runs within the racks and the actual clips gives me a max run of 81 feet. I know there will be some loss but being as electrically ignorant as I am, I don't know how much.

My working theory thus far has been that most problems can be solved with heavier wire assuming I can find the wire.

I have not considered relays for the LPR or MPR pads because of my previously mention electrical ignorance. I would feel much better if I could get pad clusters A-F working right before I try something completely new to me.

I do plan on relays for HPR clusters down the line.

 

[JAL3]

I should probably clarify something here.

At present, my club has no need for a controller like I describe or for the launch racks I want to build. I'm doing it because I want to do it not because we need it.

 

[BobCox]

John,

My expectation is that with the heavy cords, the loss is minimal.

That's a whole lot to digest in one bite, but let me start with the losses in the wire. The table below shows the resistance per foot for common wire gauges:

Wire Gauge Resistance per foot
10  .00118
12  .00187
14  .00297
16  .00473
18  .00751
20  .0119

AWG 14 has a resistance of 0.00297 ohms per foot. If you run that to a pad 81 feet away, it will have a resistance of 0.00297 * 81 * 2 (because it runs there and back), for a total of 0.48 ohms. A typical Estes igniter has about 1,0 ohms of resistance. That means that the igniter will only see 1.0 / (1.0+0.48) = 67.5% of the battery voltage. With a cluster of 2 igniters, their parellel resistance will be 0.5 ohms, and they will only see 0.5/ (0.5+.48) = 51% of the battery voltage. With a cluster of three, the igniters are down to 40%, and the trend gets worse as the cluster gets larger. That does not include the losses in the connectors and clips. Wire with higher AWG will be even worse.

 

[billspad]

That means that I need 9 conductors. Based on the limited searching I have done, 9 is an oddball number of conductors. I have found them but they tend to be very light wiring, 20AWG or worse.

There seems to be a little more available in 10 conductor but I stress the word "little". In theory I don't mind the extra conductor because I can think of possibilities for it later on.

I would like to find wire that is heavy, 14 or 16 AWG. Does anyone know a source?

Try an electrical wholesaler. CMASS has two 30' 12 conductor cords and that's where I got it. I can't remember if they're 14 or 16 gauge but I don't think they're any smaller. Those cords go from the controller to two splitter boxes where the cords to the pads connect. The low power pads are zip cord which is 16 or 18 gauge and connect with 1/4" phone plugs. The high power pads use regular extension cords using the ground and neutral conductors. The high power pads all have relays as do four of the low power pads.

 

[bobkrech]

Try an electrical wholesaler. CMASS has two 30' 12 conductor cords and that's where I got it. I can't remember if they're 14 or 16 gauge but I don't think they're any smaller. Those cords go from the controller to two splitter boxes where the cords to the pads connect. The low power pads are zip cord which is 16 or 18 gauge and connect with 1/4" phone plugs. The high power pads use regular extension cords using the ground and neutral conductors. The high power pads all have relays as do four of the low power pads.

It's at least 14 AGW. It was a pain to wire the connectors because the wires were so heavy.

Bob

 

[JAL3]

Thanks for the input.

It looks like I'm still in the conceptual phase as I digest this.

 

[darkhelmet]

I've used DB25 cables for launch control signals, such as:
https://www.opentip.com/product_info.php?ref=8974&products_id=1047198&affiliate_banner_id=4
50ft, 25 conductor. $14
https://www.opentip.com/Electronics-Computers/Cables-To-Go-Ft-Db-Cable-p-1047194.html
100ft, 25 conductor, $26.
Make sure they are the "printer" type of cable with all the conductors & pins connected (as the link above mentions).
Most likely these printer cables are 22 or 24 awg. You can double-up or triple-up conductors, also add the shield to the ground return. But, you would will probably need a relays at the other end.

 

[Handeman]

You really have three methods you can use on this.

1. Brute Force - Large gauge and expensive wires and switches and push multiple amps of current from the controller to the pad.
2. Remote Brute Force - Use a remote battery and only push lower control currents through wires to the control relays at the pads.
3. Remote Control - Use an "intelligent" controller with a communications protocol to talk to an "intelligent" pad unit that acts on the commands sent through a communications wire or by wireless.

The first is the easiest to build, is expensive, and looses effectiveness as the distances grow. 81 feet may be pushing the limits of good performance without the uses of the more expensive large gauge components.
The second uses more inexpensive components, but requires more parts. It is more complicated to build and maintain, but can easily handle distances to 500 ft or more.
The last is the most technologically challenging and requires some serious engineering to do it right. It is the easiest to use and has almost none of the drawbacks of the other systems.

Our club used that second method for a lot of years but the maintenance was getting to be a big hassle. One of the member built us a wireless control unit and two wireless pad units. These have had their issues during initial use but with experience and some modifications, have been working quite well lately.

Which ever way you go, it will take a balance of time, money, and experience to get to a dependable system that works for you. The more time and experience you have, the less money you need, and vise versa.

Good Luck

 

[JAL3]

You really have three methods you can use on this.

1. Brute Force - Large gauge and expensive wires and switches and push multiple amps of current from the controller to the pad.
2. Remote Brute Force - Use a remote battery and only push lower control currents through wires to the control relays at the pads.
3. Remote Control - Use an "intelligent" controller with a communications protocol to talk to an "intelligent" pad unit that acts on the commands sent through a communications wire or by wireless.

The first is the easiest to build, is expensive, and looses effectiveness as the distances grow. 81 feet may be pushing the limits of good performance without the uses of the more expensive large gauge components.
The second uses more inexpensive components, but requires more parts. It is more complicated to build and maintain, but can easily handle distances to 500 ft or more.
The last is the most technologically challenging and requires some serious engineering to do it right. It is the easiest to use and has almost none of the drawbacks of the other systems.

Our club used that second method for a lot of years but the maintenance was getting to be a big hassle. One of the member built us a wireless control unit and two wireless pad units. These have had their issues during initial use but with experience and some modifications, have been working quite well lately.

Which ever way you go, it will take a balance of time, money, and experience to get to a dependable system that works for you. The more time and experience you have, the less money you need, and vise versa.

Good Luck

For me, option 3 is completely out. I was going with option 1 because of my discomfort with flowing electrons in general. I can solve all the equations I learned in school but its still voodoo to me and I have no intuitive feel for it. I never have. I like the elegance of option 2 but a troubling factor is that each pad cluster would need its own battery and keeping everything topped off and working seemed more complicated than just buying some bigger wires.

 

[powderburner]

John,


That's a whole lot to digest in one bite, but let me start with the losses in the wire. The table below shows the resistance per foot for common wire gauges:

Wire Gauge Resistance per foot
10  .00118
12  .00187
14  .00297
16  .00473
18  .00751
20  .0119

AWG 14 has a resistance of 0.00297 ohms per foot. If you run that to a pad 81 feet away, it will have a resistance of 0.00297 * 81 * 2 (because it runs there and back), for a total of 0.48 ohms. A typical Estes igniter has about 1,0 ohms of resistance. That means that the igniter will only see 1.0 / (1.0+0.48) = 67.5% of the battery voltage. With a cluster of 2 igniters, their parellel resistance will be 0.5 ohms, and they will only see 0.5/ (0.5+.48) = 51% of the battery voltage. With a cluster of three, the igniters are down to 40%, and the trend gets worse as the cluster gets larger. That does not include the losses in the connectors and clips. Wire with higher AWG will be even worse.

I know I've slept since I took those EE courses in college, so my circuitry design is kinda rusty, but Bob's example posted here is why you get pushed quickly to the relay approach. Then you only have to run "signal" power levels through the long wires and the "power" remains at the pad. As Handeman points out, a relay system may take a bit more maintenance, but I think it is the way to go for 90% of club low-power (or mid-pwr) launch controller setups.

 

[klkiese]

It's at least 14 AGW. It was a pain to wire the connectors because the wires were so heavy.

Bob

You probably got socapex cable. It's used a lot in theatrical lighting. Lot's of ready made options out there or you can probably find bulk cable and build your own solution. The nice part is it should coil nicely (do a search on over under or figure 8 cable wraping.)

Here is one site:

https://www.stagelightingstore.com/s.nl/sc.25/category.94119/.f

 

[Micromeister]

John:
Back in the Stone age late 60's when Narhams first begin some of the NASA employees who were working with the club donated our first Launch system and built a 3-rack (6 pads each) system. To this day we are still using the racks although over the last 20+ years I've completely rewired and modified all 3 racks and built a semi-self-contained additioal rack, additional controllers, relays and cables. The origial 50foot 7 wire bundled control cables were 18ga. Stranded copper. this cable still does a lot of launching the New racks 50foot 7 wire cable is 14ga stranded copper appliance wire. and all extension leads out to our away pads are 16/2 white appliance wire. micro clip leads on the individual rack leads are 24" long 18/2 white appliance wire. With these cables and leads we have all the capability needed to do whatever power suppling needed and have had no problems with clusters.

I do agree and recommend for Cluster applications Relays are always the way to go. Far better to move or add a power source and relay control cirucit as close to the motor clusters location as possible then try to use wiring heavy enough to carry the extra of load. building a few "away pad relay add-ons is easier and generally will end up costing less and be less in the way of bulk storage of the heavier wire and mass of the system

Looking for sources of cable and wiring depends on your situation. Most electrical supply houses should be able to supply 14ga Stranded copper 1000v 90° fixture wire in 500' rolls or 14ga THHN Stranded copper Not quite as flexible but will do the job nicely. Trouble is you really don't need 3500feet of wire. One alternative would be to check with your local Electrical Sign manufacturers. We all use this wire in the construction process and should be in a position to sell "cut-to length" amounts of the wire in the colors you'd like. There are also on-line industrial supply houses (McMaster-Carr of one) that will sell wire and cable by the foot (cut to length). Allied electroics on-line can be a source for other products needed to complete your controller and away pad relay boxes and other components.

 

[JAL3]

OK

Let me back up a bit.

Supposing all pads were rigged for relays, can the batteries be charged in parallel? I am assuming right now 7 batteries for 7 pads, not including the away cells. I know that if somebody has to remember to change them out regularly, things will slip between the cracks. Somehow, just hooking a trickle charger to a lot of cells at once seems to be wrong, but I don' know enough to say.

 

[billspad]

OK

Let me back up a bit.

Supposing all pads were rigged for relays, can the batteries be charged in parallel? I am assuming right now 7 batteries for 7 pads, not including the away cells. I know that if somebody has to remember to change them out regularly, things will slip between the cracks. Somehow, just hooking a trickle charger to a lot of cells at once seems to be wrong, but I don' know enough to say.

I've done it and it's wrong. You can get away with it if the batteries are all at the same state of discharge but if there's a bad one it will screw everything up. I'll let someone else fill in the technical explanation.

I charge my clubs batteries between launches. The hardest part is lugging all the batteries in. I hook them up one at a time in my workshop and move the charger to the next when when I see one is done.

 

[darkhelmet]

OK

Let me back up a bit.

Supposing all pads were rigged for relays, can the batteries be charged in parallel? I am assuming right now 7 batteries for 7 pads, not including the away cells. I know that if somebody has to remember to change them out regularly, things will slip between the cracks. Somehow, just hooking a trickle charger to a lot of cells at once seems to be wrong, but I don' know enough to say.

You can have one battery per cluster of 7 (or 'x') pads. One relay per pad, all relays in one box powered from the same battery. Use 14 or 16 gauge extension cords from the cluster box to each pad box. For clusters, use the pad closest to the cluster box with a short 12-gauge extension cord.

So, just two batteries. One at the relay box and one at the control box at the range table. Add another group of pads, add one more battery.

 

[BobCox]

Our Tripoli club has 6 individual pads for high-power and one 6-rod rack for low power.

The low-power rack is about 30 feet from the launch table. All 6 rods on the rack share a single car battery.

Our high-power pads are spaced 50 feet apart in a straight line away from the launch table. The first pad is at 50', good for anything up to H motors. The pads at 100' and 150' handle J motors and below. The pads at 200' and 250' work for K and down, and the 300' pad does L.

Each high-power pad has a single rod or rail, a car battery, and a relay box. The leads from the relay box to the igniter are about 5 feet long and look like lamp cord or speaker wire. The relay box has a beeper and a momentary-contact switch with a current limiter to test continuity at the pad.

A single long multiconductor cable is used to connect all the pads together. The cable is about the diameter of an outdoor extension cord, but has many more conductors (18, I believe). Every 50 feet the outer insulation is slit open and three conductors are brought out to an
XLR3 connector. For each pad, one conductor is used to to trigger the relay, one to report continuity to the controller, and one is for ground.

So, just two batteries. One at the relay box and one at the control box at the range table. Add another group of pads, add one more battery.

You could get away with a single battery out near a rack or nearby group of pads and using it to power the control box. The only current draw in the controller is from the LED and beeper, so it can easily get the needed current from the big battery out by the pads.

 

[atticus]

I agree with Bob on this.
One battery for each rack or closely spaced group of pads is all you need.
A separate battery at the controller for the relay trip circuit isn't needed and can even limit your options.
Our club uses one relay box each for a ten pad LPR rack, a six pad group of MPR and a group of three HPR pads.
Three batteries in three separate circuits working out of one control panel.
Tim

 

[Micromeister]

OK

Let me back up a bit.

Supposing all pads were rigged for relays, can the batteries be charged in parallel? I am assuming right now 7 batteries for 7 pads, not including the away cells. I know that if somebody has to remember to change them out regularly, things will slip between the cracks. Somehow, just hooking a trickle charger to a lot of cells at once seems to be wrong, but I don' know enough to say.

We use up to 8 at pad relays and gelcell batteries along with the 2 Heavy wet cell batteries that carry the contol load, you can daisy chain two or three if they are identical but it's better to charge them individually or in pairs. Those little cheapy HF trickle chargers do two at once fine
while you may think it gets to be confusing, charging batteries become routine very shorty, even with youth groups.

 

[JAL3]

Once again, I would like to thank everyone for their input. It is giving me quite a bit to think about. It's also giving me a headache.

Steel, concrete and timber never treated me like this!

 

[JAL3]

We use up to 8 at pad relays and gelcell batteries along with the 2 Heavy wet cell batteries that carry the contol load, you can daisy chain two or three if they are identical but it's better to charge them individually or in pairs. Those little cheapy HF trickle chargers do two at once fine
while you may think it gets to be confusing, charging batteries become routine very shorty, even with youth groups.

One of my concerns is that place where the GSE is stored is not inhabited or even regularly visited. When it does happen, 99% of the time its yours truly who goes and gets the stuff. My worry is one of practicality. Would I really get around to getting that stuff switched out as needed.

I'd like to say yes but I know me too well to say that.:y:

 

[RimfireJim]

One thing you might want to think about, JAL3, is a list of "musts" versus "wants" for your system design. For example, you describe having multiple racks each with 4 built in stations, PLUS 4 extensions for each rack, creating your need for a 9-conductor cable. Realistically, would you really use that many stations? Would one extension per rack handle most needs? Could the extension take the place of one of the built-in positions (in terms of launch control)? Only you can answer these kind of questions, but taking a hard look at your "wish list" can help you make wise trade-offs when it comes to system cost or useability.

 

[JAL3]

One thing you might want to think about, JAL3, is a list of "musts" versus "wants" for your system design. For example, you describe having multiple racks each with 4 built in stations, PLUS 4 extensions for each rack, creating your need for a 9-conductor cable. Realistically, would you really use that many stations? Would one extension per rack handle most needs? Could the extension take the place of one of the built-in positions (in terms of launch control)? Only you can answer these kind of questions, but taking a hard look at your "wish list" can help you make wise trade-offs when it comes to system cost or useability.

You're absolutely right about this and in this respect I have already lost the battle. What my club NEEDS right now is really not much more than a circuit or 2 more than we already have and what we have will work OK but needs some minor overhauling.

What I was looking at building is a gold plated Pie in the Sky system that we don't need now and really don't need for the forseeable future. To me, it is an exercise to see if I can and will be a learining experience as I go along.

That said, I want it to be not only usable but beneficial. I want it to not only work but work well and be preferable to what we have now. That is a hard order to fill with my electrical expertise.

 

[darkhelmet]

You could get away with a single battery out near a rack or nearby group of pads and using it to power the control box. The only current draw in the controller is from the LED and beeper, so it can easily get the needed current from the big battery out by the pads.

Depending on the gauge & length of the control wire and the condition of the battery, using a single battery may cause "chatter" when the relay is actuated. The reduced voltage due to the igniter load on the battery and the drop in the control line could be below the threshold needed to hold the relay coil active. It cycles in/out as the load is removed and the voltage increases enough to engage the relay, then disengages again once the load draws down the battery. This is a very common problem. It's easily solved by having a cheap second battery at the main launch controller.

 

[Micromeister]

You're absolutely right about this and in this respect I have already lost the battle. What my club NEEDS right now is really not much more than a circuit or 2 more than we already have and what we have will work OK but needs some minor overhauling.

What I was looking at building is a gold plated Pie in the Sky system that we don't need now and really don't need for the forseeable future. To me, it is an exercise to see if I can and will be a learining experience as I go along.

That said, I want it to be not only usable but beneficial. I want it to not only work but work well and be preferable to what we have now. That is a hard order to fill with my electrical expertise.

Another thing you might want to consider is the number of color cables "commonly" available for a given wire guage or cable size. You'll find it's a lot easier wiring if you have all different jacket colors to work with. 7 wire cable is pretty common, over that the selection becomes much smaller and the wire gauge usually smaller as well. Over time 6 pad racks have showen to be most easily chosen for a couple reasons; Number of wires in the trunk cable (7 wire) is one, overall length of the rack is another usually between 72 and 84 inches. Smaller rack with 3-4 positions can make handling a bit easier but can create a bigger cable storage problem with more 5 wire cables. Heres a photo of one of our 82", 6 position racks and a photo of another sections 3 position system. Both work well it depends on your storage area.
OBTW Narhams stores our systems in a u-store it. our batteries are charged every other month by that months Launch Manager or club pres.
I as (ROMC) Range Operations & Maintenance Committee Chair usually keep the 6-8 relay batteries at my place since they are only used occasionally with the at pad relays.

 

[MarcFTL]

You may want to take a look at the Club Launcher from pratthobbies.com. Our Tripoli club uses several standalone ULS Launchers from Pratt and I know Doug also designs Launch Systems to Spec and his pricing is extremely reasonable. Sometimes less expensive than doing it yourself.

 

[JAL3]

You may want to take a look at the Club Launcher from pratthobbies.com. Our Tripoli club uses several standalone ULS Launchers from Pratt and I know Doug also designs Launch Systems to Spec and his pricing is extremely reasonable. Sometimes less expensive than doing it yourself.

I appreciate the input and believe me, it makes sense. Part of my rationale though is to learn through doing. Electricity has always been my personal demon and I want to beat it or at least come to a mutual accommodation.

 

[JAL3]

I'm going to try taking a different tack here for a while and build up from a very simple base. I'm starting with a simple circuit to get peer reviewed and make sure I understand things right. From there I will add to the complexity of the diagram piece by piece, not going to the next step until the present step is mastered.

For many of you out there, this may seem silly because of the basic level I am starting at. For me it is not. I am pretty confident of the first few revisions I am going to throw out but that does not preclude me from missing something very basic or being shown a better way.

This first diagram is the bare bones, NAR minimum for a launch circuit as I understand it. Its a battery, a key, a switch and a pair of clip leads. I'll add continuity, etc. later. Do I have the basic minimum down correctly?

N.B. No need to be merciful. I make no bones about having any knowledge or grasp of electrical parts at all. Whenever I think I understand something, that is a danger sign that I am really messing up bigtime. Its kind of like my understanding of women in that respect. (That is not a jab at women; it is a realization of my own ineptitude)

 

[BobCox]

This first diagram is the bare bones, NAR minimum for a launch circuit as I understand it. Its a battery, a key, a switch and a pair of clip leads. I'll add continuity, etc. later. Do I have the basic minimum down correctly?

Looks right so far.

 

[MartyAMC]

Here's a link to the one I built for an upcoming Boy Scout launch. Relatively simple and great learning project.

https://www.kevincook.net/Hobbies/Rocketry/LaunchController/index.html