Input for absolute beginner launch controller

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Unprofessional Rocketeer
Looking for thoughts on my 12v launch controller? I have never worked with electronics before, I think that's evident. Its my first try at this. I was trying to make a series of switches in order. I don't understand building in continuity lights and buzzers I wasn't trying to do that. Not opposed to it but I couldn't get resisters. I wanted a series of failsafe's. Kinda if/then switches. This will all be cleaned up with butt end fittings before I install it in a pretty box. Sorry for the web of wires. It was worse and this is the best I could do for the video. I drew it out a couple times but looked even worse.

If my low expectations work, great. If something is amiss, I am open to changing it. It was a lot of trial and error to get this far. I see a blip on the multimeter when I flip switches. I hope that isn't enough to start an igniter. Again thanks for any input. I love this community.

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Sandy H.

Just some initial comments, but I hope they start a good conversation to get you exactly where you want to be.

Looks like you've got the key switch safing the whole unit. Check.
Once you turn the key, you get an indicator saying the unit is 'live'. Check.
You have a flip up cover to prevent accidental switching of the arm switch. Check (not sure if required, but nice to have).
You have an industrial quality lighted pushbutton that indicates 'armed'. You push the button and get voltage at the outputs. Check-ish.

It would be ideal to see your schematic, even if it isn't picture perfect. That would make it easier for those smarter than me to see any possible faults.

At this stage, I'm not clear what happens if you actually burn the igniter. Specifically, do any of the lights change state or if you have an open circuit (i.e. bad igniter, already burnt igniter, clip fell off etc.) do you have any indication? I'm not sure its required, but it is a nice feature.

My biggest concern would mostly be 'what do you plan to launch?' If you're going to be flying in your own back yard on single Estes ABCDE engines, I think you've covered all the basic safety requirements that Estes controllers have. If you are going to be flying in a public park, I think the key is the key (see what I did there. . . ) to being good as well. If the controller isn't in your hands, the key better be.

If you are planning on launching clusters with this controller, it might not be ideal. A relay based launcher keeps the path to the igniters short, but the trigger far away. While the pushbutton you have might be good for 20 amps, if you run 50 feet of 18 gauge wire to the rocket, it has to pass the current 100 feet (there and back) to get voltage to the igniter. You get voltage drops along that path and things get less reliable. Bigger wire helps, but the long travel path is not ideal in general.

Personally, I built a relay launcher years ago and that's what I use when/if I fly solo. I do like clusters, so it made sense at the time.

If you want the buzzer to work, definitely post the schematic and someone can help with that.

Last comment is just personal preference, but I hate wire nuts. I am ok with crimping (with proper tools, not the $5 kit from the auto parts store) using the proper crimp sizes and wire loading. I'm ok with soldering if wire sizes and prep are logical (i.e. 2watt iron and 3/0 wire, not good). I'm ok with terminal blocks if they are properly made. The only time I use wire nuts are in home wiring projects to keep the inspectors from asking questions. Others may disagree, but that is my feeling. If you get more comments about wire connections than your project, I apologize. I might have just started the electrical version of a glue thread. . . not my intent. Obviously, burn a few igniters in controlled settings before using it, but I imagine you already planned to do that. Sandy. AcadiaRockets Unprofessional Rocketeer Just some initial comments, but I hope they start a good conversation to get you exactly where you want to be. Looks like you've got the key switch safing the whole unit. Check. Once you turn the key, you get an indicator saying the unit is 'live'. Check. You have a flip up cover to prevent accidental switching of the arm switch. Check (not sure if required, but nice to have). You have an industrial quality lighted pushbutton that indicates 'armed'. You push the button and get voltage at the outputs. Check-ish. It would be ideal to see your schematic, even if it isn't picture perfect. That would make it easier for those smarter than me to see any possible faults. At this stage, I'm not clear what happens if you actually burn the igniter. Specifically, do any of the lights change state or if you have an open circuit (i.e. bad igniter, already burnt igniter, clip fell off etc.) do you have any indication? I'm not sure its required, but it is a nice feature. My biggest concern would mostly be 'what do you plan to launch?' If you're going to be flying in your own back yard on single Estes ABCDE engines, I think you've covered all the basic safety requirements that Estes controllers have. If you are going to be flying in a public park, I think the key is the key (see what I did there. . . ) to being good as well. If the controller isn't in your hands, the key better be. If you are planning on launching clusters with this controller, it might not be ideal. A relay based launcher keeps the path to the igniters short, but the trigger far away. While the pushbutton you have might be good for 20 amps, if you run 50 feet of 18 gauge wire to the rocket, it has to pass the current 100 feet (there and back) to get voltage to the igniter. You get voltage drops along that path and things get less reliable. Bigger wire helps, but the long travel path is not ideal in general. Personally, I built a relay launcher years ago and that's what I use when/if I fly solo. I do like clusters, so it made sense at the time. If you want the buzzer to work, definitely post the schematic and someone can help with that. Last comment is just personal preference, but I hate wire nuts. I am ok with crimping (with proper tools, not the$5 kit from the auto parts store) using the proper crimp sizes and wire loading. I'm ok with soldering if wire sizes and prep are logical (i.e. 2watt iron and 3/0 wire, not good). I'm ok with terminal blocks if they are properly made. The only time I use wire nuts are in home wiring projects to keep the inspectors from asking questions. Others may disagree, but that is my feeling. If you get more comments about wire connections than your project, I apologize. I might have just started the electrical version of a glue thread. . . not my intent.

Obviously, burn a few igniters in controlled settings before using it, but I imagine you already planned to do that.

Sandy.
Awesome thanks. I have a lanyard for around my neck that the key stays on. I do have 50 feet of 14guage, but realizing that maybe too heavy? What would be a good balance gauge and length for composite engine igniters? This controller is for launches smaller than my Tripoli clubs trailer but bigger than my 3/8 rod 6vt kit. The buzzer works like in the video to give a warning that the controller is armed, but does not indicate continuity. The wire nuts are just for getting it setup. I have wire crimp connectors when I think its ready. I plan to use the 12vt car battery starter in the pictures as power. Thanks for the help. Keep it coming. Thanks.

Voyager1

Well-Known Member
I would stick with the 14 AWG wire (or lower). That’s about 0.25 Ohms over 2 x 50’ lengths. The igniters are typically 1-2 Ohms, depending on brand. You want to drop most of your 12V over the igniter, not the cable.

Sandy H.

If you're only lighting one igniter, even a composite motor, 'big' wire without relays will work fine for medium distances like 25ft. I like larger wire, as Voyager1 indicated, you need to drop the voltage at the igniter, not on the wire going to/from the igniter.

I wouldn't recommend buying a 50ft spool of 14ga wire, cutting it in half and running it out to the pad, though. That will be a rats-nest for sure, as the two wires will by default try to go exactly where you don't want them to go and their buddy will go the opposite of that as well! Consider grabbing an extension cord from the local big box store. They are orange, so easier to see and not trip over, they are encased in a single cord so they can't get twisted and they are generally cheap.

I would choose to put a plug arrangement on the controller and make a 6ft-ish plug to igniter link and just use a regular unmodified extension cord. Make the short/igniter length with the female connection so somebody couldn't plug it in a wall and get live leads. Make your controller plug the male source so even if someone plugged that into a toaster and used your controller, they couldn't make toast. That's probably not the most perfectly safe thing to do, since whenever someone sees a plug and a socket, they plug it in, but at least think about what will be live and what won't. Or you could strip the ends of the extension cord and wire an uncommon plug/receptacle on it to eliminate the concern.

One regret with my relay launcher is that I made my control leads permanent at the launch box and relay box. . .much more of a pain to wind and store than plugs and wires.

Sandy.

StreuB1

Well-Known Member
I always used a 9v battery, lamp cord, and alligator clips.

Sandy H.

I always used a 9v battery, lamp cord, and alligator clips.
Heh-heh. Me too, when I was younger. I bet we were at shorter distances than per current recommendations too. Still here, with 10 fingers and toes, but I thought the OP put some good effort in to building a nice controller and commented as such.

At the end of the day, if I had to launch a model rocket to save humanity, I'm pretty sure a car battery, alligator clips and possibly some duct tape would be involved, safety code be dang'd.

Sandy.

ep29030

Mark N.
Here is a simple schematic for a single pad launch box. This one has a green LED power indicator and a continuity test switch. I used this schematic to make 4-pad launchers for county 4-H Aerospace groups. Uses 12V power (battery). If you want the continuity light to stay lit all the time once igniter is connected, then omit the Momentary (Continuity) Pushbutton in the schematic.

OverTheTop

Well-Known Member
Here's one I prepared earlier. Still quite simple but with a few extra features. Share and Enjoy.

Unprofessional Rocketeer
I would stick with the 14 AWG wire (or lower). That’s about 0.25 Ohms over 2 x 50’ lengths. The igniters are typically 1-2 Ohms, depending on brand. You want to drop most of your 12V over the igniter, not the cable.
14 or lower? so an even heavier weight wire like 12 gauge? That seems to be a little unwieldy? I want to do at least 50 feet to stay Tripoli legal but could go out as far as 100 foot,? would the voltage drop be too much? I want to to fit the reel in a reasonable sized box. I am using guitar plugs in the side of the case to keep 110v looking plugs out of the equation. Thanks for all the great ideas!

neil_w

Slowly reviving

Remember that current will be flowing in both directions so you'll need to double the length of your wire (e.g., a 25 foot wire would add 50 feet of resistance).

Unprofessional Rocketeer
Improvement. Cleaned up connections and made continuity light work. Also poorly drawn schematic

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Voyager1

Well-Known Member
14 or lower? so an even heavier weight wire like 12 gauge? That seems to be a little unwieldy? I want to do at least 50 feet to stay Tripoli legal but could go out as far as 100 foot,? would the voltage drop be too much? I want to to fit the reel in a reasonable sized box. I am using guitar plugs in the side of the case to keep 110v looking plugs out of the equation. Thanks for all the great ideas!
If you’re planning on going further than 50’ then I’d seriously consider a relay-based system. Also, there is no real reason for dismissing 110V connectors completely. I understand your concern here, but if you choose your connector gender correctly and clearly label them, then there is little chance of plugging mains power into your launch system. They are very robust and you could also use standard extension cables as your field cable(s). Another advantage of using a standard 3-conductor extension cable is that you can parallel 2 of the conductors to further reduce the cable resistance.

A very popular and reliable launch control system manufacturer and vendor in the USA employs 110V power connectors in their systems.

prfesser

If you’re planning on going further than 50’ then I’d seriously consider a relay-based system. Also, there is no real reason for dismissing 110V connectors completely. I understand your concern here, but if you choose your connector gender correctly and clearly label them, then there is little chance of plugging mains power into your launch system. They are very robust and you could also use standard extension cables as your field cable(s). Another advantage of using a standard 3-conductor extension cable is that you can parallel 2 of the conductors to further reduce the cable resistance.

A very popular and reliable launch control system manufacturer and vendor in the USA employs 110V power connectors in their systems.
Strongly agree, a $5 relay makes the length of the cable pretty much irrelevant. (FWIW a friend tried making a controller with 50 feet of speaker cable. Didn't work even on 12V, not enough juice reached the starter.) Re: extension cords, if one is really worried about accidentally plugging into the mains...cut off the plug end of the cord and wire in a socket instead. This way the controller and pad have to have plug ends, there's not much opportunity to accidentally plug something into a live socket. The Darwin-award-candidate would have to carry/drag the controller or the pad to a suitable socket. Sandy H. Lifetime Supporter As a note for the OP, your controller can still be used to trigger the relay, so if you do decide you want to tweak the plan and move to a relay system, you don't have to start from scratch. The most simple change would be to just use smaller wires (cheap/easy) to trigger the relay and add a battery/relay near the pad. You would lose continuity indication, but all other safety features (except for 'welded relay') would be in place. If you want to test for continuity, it would be easier to do it at the relay box vs back at the controller. If you're only launching D or smaller engines, however, you only need to be 15 feet away, so a direct launch arrangement is fine/common. Sandy. Voyager1 Well-Known Member As a note for the OP, your controller can still be used to trigger the relay, so if you do decide you want to tweak the plan and move to a relay system, you don't have to start from scratch. The most simple change would be to just use smaller wires (cheap/easy) to trigger the relay and add a battery/relay near the pad. You would lose continuity indication, but all other safety features (except for 'welded relay') would be in place. If you want to test for continuity, it would be easier to do it at the relay box vs back at the controller. If you're only launching D or smaller engines, however, you only need to be 15 feet away, so a direct launch arrangement is fine/common. Sandy. Yes! However, if you do use 3-core extension cable, or any suitable 3-core cable, for the pad relay triggering, you can use the 3rd conductor for continuity at the LC end as well. Sandy H. Lifetime Supporter Yes! However, if you do use 3-core extension cable, or any suitable 3-core cable, for the pad relay triggering, you can use the 3rd conductor for continuity at the LC end as well. Nice. I didn't think about that option. Its almost like if you have a group of like minded people working together, you can solve problems. Sandy. AcadiaRockets Unprofessional Rocketeer Nice. I didn't think about that option. Its almost like if you have a group of like minded people working together, you can solve problems. Sandy. could someone draw that out? a three wire extension with a battery in the middle? Five Well-Known Member Looking for thoughts on my 12v launch controller? I have never worked with electronics before, I think that's evident. Its my first try at this. I was trying to make a series of switches in order. I don't understand building in continuity lights and buzzers I wasn't trying to do that. Not opposed to it but I couldn't get resisters. I wanted a series of failsafe's. Kinda if/then switches. This will all be cleaned up with butt end fittings before I install it in a pretty box. Sorry for the web of wires. It was worse and this is the best I could do for the video. I drew it out a couple times but looked even worse. If my low expectations work, great. If something is amiss, I am open to changing it. It was a lot of trial and error to get this far. I see a blip on the multimeter when I flip switches. I hope that isn't enough to start an igniter. Again thanks for any input. I love this community. Looks like you know a little something about electronics. Sandy H. Lifetime Supporter could someone draw that out? a three wire extension with a battery in the middle? Based on post #8 schematic, I made the following sketch. Kind of gross looking, but I hope it gets the point across. If I made a mistake, hopefully someone corrects me. Sandy. Attachments • 197.3 KB Views: 34 teepot Well-Known Member I used as much as 200' of lamp cord and a 12 volt car battery. Now it's a wireless relay. Voyager1 Well-Known Member could someone draw that out? a three wire extension with a battery in the middle? Here's a quick and dirty relay-based launch controller with a 3-core field cable. The system is powered from the 12V battery at the pad. Could also add a battery switch at the pad end and a 10A circuit breaker. It provides for continuity check at pad and LC. Attachments • 1.8 MB Views: 40 Last edited: RocketRev Lifetime Supporter Last comment is just personal preference, but I hate wire nuts. I am ok with crimping (with proper tools, not the$5 kit from the auto parts store) using the proper crimp sizes and wire loading. I'm ok with soldering if wire sizes and prep are logical (i.e. 2watt iron and 3/0 wire, not good). I'm ok with terminal blocks if they are properly made. The only time I use wire nuts are in home wiring projects to keep the inspectors from asking questions. Others may disagree, but that is my feeling. If you get more comments about wire connections than your project, I apologize. I might have just started the electrical version of a glue thread. . . not my intent.

Obviously, burn a few igniters in controlled settings before using it, but I imagine you already planned to do that.

Sandy.

For finished products I absolutely agree with Sandy, that using wire nuts is not a good idea in a portable end product like a launch controller, but for building and testing, wirenuts make it easy to readjust things while one is learning what one is doing and adding new features into a prototype which is in essence what Acadia is doing.

I also suggest using old fashioned incandescent light bulbs in place of the igniters for testing. I use running lights for trailers. They ae already designed for lighting up at 12volts. What is a light bulb if not a thin nichrome wire designed to heat up when you send voltage thru it. The advantage is that it does not burn thru every time you use it. I test every Wilson F/X launch system with them before I ship them just to make sure they work. For the most part, its harder to light them than it is an igniter and the real problem with testing with actual igniters is that you only get one test per igniter unless something didn't work of course.

And if you're planning to fly just low power and single motors, then I suggest using AWG #18 wire between the battery and the ignite clips is fine and dandy. But if you're thinking about doing clusters, go with #16 AWG wire between your 12v battery and your igniter leads. I've gotten 9 igniters to lght off of one #16 awg igniter lead.

Good luck with the conntroller build.

neil_w

Slowly reviving
Maybe dumb question: why a momentary single-pole switch for continuity? That just means you have to remember to check it, and there's nothing to force you to. Obviously it's not a disaster if you don't check continuity beforehand, but it is certainly preferable to.

An alternative would be a double-pole switch (either momentary or not, discussed shortly) with the second pole in series with the launch button. This means that you must activate the continuity check in order to launch.

If you use a momentary switch for the continuity check, then it becomes a two-handed launch process, much like the Estes PSII controller, where you must hold down both at once to launch. With a latching switch, you just need to make sure it's turned on beforehand. Possibly, you wouldn't want a latching switch because you don't want continuity current flowing while people are at the pad, so maybe momentary is the only safe way to go.

Just pondering.

Grant_Edwards

Well-Known Member
What is a light bulb if not a thin nichrome wire designed to heat up when you send voltage thru it.
Well, it's actually a thin tungsten wire designed to heat up when you send current through it.

I agree that incandescent bulbs make good test loads. I used 12V 10W incandescent motorcycle turn signal bulbs to test my launch controller because that's what I happened to have laying around. It's powered from a 3S LiPo battery (11-12V), so a 10W bulb draws a little under 1A.

RocketRev

Well, it's actually a thin tungsten wire designed to heat up when you send current through it.

I agree that incandescent bulbs make good test loads. I used 12V 10W incandescent motorcycle turn signal bulbs to test my launch controller because that's what I happened to have laying around. It's powered from a 3S LiPo battery (11-12V), so a 10W bulb draws a little under 1A.
You're probably right on the tungsten. I use "ear mount" clearance market lights from trailers on my pad-boxes. they work great and last a long time. Though I will admit that I have no idea how many watts they are.