Launch Controller Build

Been meaning to do a write-up on this for a little while now, plus a few club members have been inquiring...

Background
One of my objectives for an "in-season project" this year was to build some better personal launch equipment. First up was the tower, which has since worked wonders. The other thing I wanted to build was a single-pad personal launch controller. I wanted something more robust than a glorifed-Estes Electron Beam controller, which I had built many years ago and is what I was using before. I also took a look at a wireless system, Wilson F/X, (no, not me, a different Wilson) but that would have cost upwards of $500. Way more than I wanted to spend, so I opted to build my own wired system.

I was very happy with the results! My system consists of a controller, wire reel, pad box, and battery.

Construction and Photos

Pad Box

Here we have the pad box, which goes out at the "rocket end" of the equation. Under the blue cover is an on/off toggle switch, as well as a power indicator LED. The wires on the left have red and black battery clips which connect to the pad battery. Said battery is a 12V lawnmower battery which I got from O'Reilly Auto Parts. The wires coming out the front go to the rocket (alligator clips), and the extension cord out the right side plugs into the wire reel.

Wire Reel

This was the easy part - a 500' reel of wire made up of 2 x 250' reels of lamp cord, spliced in the middle. (Solder/heat shrink tube.) On each end of the wire is an extension cord plug.

Controller

On the controller end we have not 1, but 2 momentary switches. (The push-button and the toggle switch.) To launch, plug the controller into the end of the wire, then push and hold BOTH buttons to fire.

How is everything wired? Well, take a look...

Since I'm certainly not an electrical engineer, I needed a little help from the folks at Surplus Gizmos in order to get the pad box to do what I wanted it to do. And here we have the result, nicely color-coded for your viewing pleasure. (Also so you can tell the wires apart...)


As you can see, I used 2 relays - one 6V and one 12V. Essentially the controller trips the small relay, which then trips the bigger relay. But the diagram can explain it better than I can - I hope...

The controller is much simpler. Yes, I did figure this one out on my own...


1 standard 9V battery to send current to the 5V relay at the pad box. Along that is where I installed the 2 "inline" momentary switches.

The system in action:


Here you can see the pad box, wire reel, battery, and clip leads all in place. I made the wires extra long so as to distance the components from the pad, and away from rocket exhaust/flying debris.

When launching a rocket, the steps are as follows:

1. Place rocket on pad/arm altimeters, etc.
2. Insert igniter.
3. Connect igniter to launch system.
4. Turn power switch at pad box ON.
5. Retreat.
6. When ready, and only when ready to launch, plug the controller into the end of the wire.
7. Hold BOTH switches to launch.
8. When launch is complete, unplug controller from wire.

Continuity
You asked...continuity. NO, my system does NOT check continuity. The red LED at the pad box simply indicates whether the system is armed or not. To be perfectly honest - I really don't care that much. I always use my own homemade igniters which I check with a multimeter before use so I know they'll work anyways. If I really wanted to, I could add a continuity check at a later date, separate from the firing circuit.

Safety Features
Of course, the system is designed with some safety features, as well.

• The power switch at the pad box must be powered ON in order to launch. The rocket will not launch if it is powered OFF.
• The controller is plugged in to the wire ONLY when ready to launch. It is impossible to accidentally send current to the relay when the controller is unplugged.
• BOTH momentary switches at the controller must be held in order to launch.

Parts
All the parts for this entire project I sourced from:

• Home Depot
• O'Reilly Auto Parts
• www.digikey.com
• Surplus Gizmos, a local electronics shop.

Conclusion
Overall, this was a really fun project - not too challenging and very affordable. I may build another one of these over the winter, just for giggles and so I can have 2 on hand. Heck, if there is interest, I may even start selling them...

Drawback - now that I have both my own pad AND controller, I never want to use club GSE again... :wink:

Enjoy!

Nice project.... Does the controller use a standard 9V battery? What voltage drop do you see over the 500' of cable??

Comment. Use inexpensive automotive relays and sockets to make your life easier.

Examples.

https://www.allelectronics.com/make-a-store/item/rly-351/12vdc-spdt-40a-automotive-relay/1.html good for over 100 amps in launcher applications.

https://www.allelectronics.com/make-a-store/item/srly-2/socket-for-automotive-relay/1.html

https://www.allelectronics.com/make-a-store/item/srly-4/dual-socket-for-auto-relay/1.html

Yes wirenuts for connections. No solder, easy reconfigurations.

Use switches with 0.25" push on connectors = no soldering.

Examples.

https://www.allelectronics.com/make-a-store/item/pb-226/spst-n.o.-momentary-pushbutton/1.html

https://www.allelectronics.com/make-a-store/item/lrs-30a/12v-rocker-switch-w/amber-led/1.html with built-in led.

Example 0.25" Push on connectors https://www.allelectronics.com/make...-terminals/quick-disconnect-female-1/4/1.html

These components make it easy to reconfigure if you make a mistake or want to change the circuit.

Bob

Lee697 said:

Nice project.... Does the controller use a standard 9V battery? What voltage drop do you see over the 500' of cable??

Click to expand...

Thanks! Yes, just a standard 9V battery in the controller. I need to double-check but I think the voltage drop is usually between .5 - 1 volt.

bobkrech said:

Comment. Use inexpensive automotive relays and sockets to make your life easier.

Examples.

https://www.allelectronics.com/make-a-store/item/rly-351/12vdc-spdt-40a-automotive-relay/1.html good for over 100 amps in launcher applications.

https://www.allelectronics.com/make-a-store/item/srly-2/socket-for-automotive-relay/1.html

https://www.allelectronics.com/make-a-store/item/srly-4/dual-socket-for-auto-relay/1.html

Yes wirenuts for connections. No solder, easy reconfigurations.

Use switches with 0.25" push on connectors = no soldering.

Examples.

https://www.allelectronics.com/make-a-store/item/pb-226/spst-n.o.-momentary-pushbutton/1.html

https://www.allelectronics.com/make-a-store/item/lrs-30a/12v-rocker-switch-w/amber-led/1.html with built-in led.

Example 0.25" Push on connectors https://www.allelectronics.com/make...-terminals/quick-disconnect-female-1/4/1.html

These components make it easy to reconfigure if you make a mistake or want to change the circuit.

Bob

Click to expand...

Cool stuff - thanks Bob! Actually the relays I used aren't automotive-grade, but work in the exact same fashion.

The reason I strongly recommend the automotive 1" cube relay is that in a pinch you can go to a local auto parts store and get one, and if you're really desperate, you can even take one out of your car!

Bob

bobkrech said:

The reason I strongly recommend the automotive 1" cube relay is that in a pinch you can go to a local auto parts store and get one, and if you're really desperate, you can even take one out of your car!

Bob

Click to expand...

Good point - I actually do keep a spare relay on hand for whatever reason every time I bring my controller to a launch.

I don't want to hijack the thread but I will make one comment. I built a wireless system that has two pad box's good to one box is good to 300ft and the other 1500ft. Total investment less than $200.

amarillo_rocket said:

I don't want to hijack the thread but I will make one comment. I built a wireless system that has two pad box's good to one box is good to 300ft and the other 1500ft. Total investment less than $200.

Click to expand...

Good to know however as far as I know wireless systems are way beyond my technical/programming abilities...

These past few weeks I built a duplicate of this system using mostly some spare parts I had lying around. It'll be good to have an extra system on hand for whatever reason, plus they're just fun to build! :wink:

I made a few modifications to Version 2 of which I'll outline below, but the rule this time was that I had to source everything locally. Thanks to Home Depot, Surplus Gizmos, plus stuff I had in my shop already, this was a piece of cake.

Pad Box

Externally this is exactly the same as the original version - on/off switch with power indicator LED, battery wires on the left, clip leads on the front, and launch controller wires on the right.

However, inside it's a little different. I only used a single 12V relay when, after doing some testing, I realized that the current from the controller end (9V) was enough to trip the relay by itself. This meant I opted to leave out the 5V relay for simplicity's sake and ease of wiring. (The inside of my other pad box is a tangle of wires; this one is much cleaner.) The controller wires are tied to the coil of the relay, the negative side of the pad battery is tied to one side of the clip leads, the positive side of the pad battery is tied to the normally-open contact of the relay, and the other side of the clip leads is tied to the relay output.


And here we have the entire pad assembly. In the words of Steve H, "All things begin with a trip to Home Depot in search of inspiration." In the electrical department I picked up a standard 15' extension cord (same as before) for connections, and 30' of lamp cord. One other change from last time was to use a heavier/more robust wire with bigger clips at the pad end, so here we are.

I also wanted to lengthen the clip leads so as to provide more distance from larger motors. The 7' of wire I gave myself between the pad battery and relay box also proved to be unnecessary, so conversely I shortened these. In Version 2, we have 27' (I think) for the clip leads, and 3' for the battery. (Changed from 23' and 7', respectively.)


More hefty battery clips this time.


Larger alligator clips at the igniter end.

Controller

And now for the controller itself, with some new whistles and bells. For starters, I saw that large green industrial control button at Surplus Gizmos, and just knew I HAD to turn it into a launch switch. The arming switch is an on/off (not momentary) toggle switch just like at the pad box. In addition to the LED, I also added a beeper. When you arm the system, the LED powers on, and the beeper sounds. Then as soon as you push the launch button, everything goes silent at the controller and the igniter fires. (9V battery inside the controller sends current to the relay, same as before.)

You'll notice all the extension cord plugs are the same on each respective system. So, while a few of the new components are wired slightly differently, functionally they are exactly the same and you can use everything interchangeably. This can be particularly helpful if, in the event a pad box goes out (blown/fused relay, water damage, bricks, etc.), you can just swap out for the other one.

Since the 500' wire reel is the most expensive part, I still only have 1 of those for the time being.

AlnessW said:

These past few weeks I built a duplicate of this system using mostly some spare parts I had lying around. It'll be good to have an extra system on hand for whatever reason, plus they're just fun to build! :wink:

I made a few modifications to Version 2 of which I'll outline below, but the rule this time was that I had to source everything locally. Thanks to Home Depot, Surplus Gizmos, plus stuff I had in my shop already, this was a piece of cake.

Pad Box
View attachment 256409
Externally this is exactly the same as the original version - on/off switch with power indicator LED, battery wires on the left, clip leads on the front, and launch controller wires on the right.

However, inside it's a little different. I only used a single 12V relay when, after doing some testing, I realized that the current from the controller end (9V) was enough to trip the relay by itself. This meant I opted to leave out the 5V relay for simplicity's sake and ease of wiring. (The inside of my other pad box is a tangle of wires; this one is much cleaner.) The controller wires are tied to the coil of the relay, the negative side of the pad battery is tied to one side of the clip leads, the positive side of the pad battery is tied to the normally-open contact of the relay, and the other side of the clip leads is tied to the relay output.

View attachment 256410
And here we have the entire pad assembly. In the words of Steve H, "All things begin with a trip to Home Depot in search of inspiration." In the electrical department I picked up a standard 15' extension cord (same as before) for connections, and 30' of lamp cord. One other change from last time was to use a heavier/more robust wire with bigger clips at the pad end, so here we are.

I also wanted to lengthen the clip leads so as to provide more distance from larger motors. The 7' of wire I gave myself between the pad battery and relay box also proved to be unnecessary, so conversely I shortened these. In Version 2, we have 27' (I think) for the clip leads, and 3' for the battery. (Changed from 23' and 7', respectively.)

View attachment 256411
More hefty battery clips this time.

View attachment 256412
Larger alligator clips at the igniter end.

Controller
View attachment 256413
And now for the controller itself, with some new whistles and bells. For starters, I saw that large green industrial control button at Surplus Gizmos, and just knew I HAD to turn it into a launch switch. The arming switch is an on/off (not momentary) toggle switch just like at the pad box. In addition to the LED, I also added a beeper. When you arm the system, the LED powers on, and the beeper sounds. Then as soon as you push the launch button, everything goes silent at the controller and the igniter fires. (9V battery inside the controller sends current to the relay, same as before.)

You'll notice all the extension cord plugs are the same on each respective system. So, while a few of the new components are wired slightly differently, functionally they are exactly the same and you can use everything interchangeably. This can be particularly helpful if, in the event a pad box goes out (blown/fused relay, water damage, bricks, etc.), you can just swap out for the other one.

Since the 500' wire reel is the most expensive part, I still only have 1 of those for the time being.

Click to expand...

Where is the safety disconnect? as shown in the photo this system is not NAR Legal. You Must install some sort of either Keyed lockout or phono plug safety "pull plug" to make the system safe while you are out at the pad Loading models. Its a safety Issue and not very hard to install.

Micromeister said:

Where is the safety disconnect? as shown in the photo this system is not NAR Legal. You Must install some sort of either Keyed lockout or phono plug safety "pull plug" to make the system safe while you are out at the pad Loading models. Its a safety Issue and not very hard to install.

Click to expand...

There are several "breaks" in the system as I outlined in an earlier post - what are you looking for, exactly? Unplugging to controller and bringing it with you to the pad solves the "make the system safe" issue you mention. Plus switches...

AlnessW said:

what are you looking for, exactly?

Click to expand...

NFPA 4.13.2-3 (and therefore NAR) require two safety features for ignition systems:

1) Return-to-off: basically a momentary launch switch, something so if you drop it, release it, etc, it (and the rocket) return to a "safe" condition.
2) Removable interlock: This is what Micromeister is talking about, something you can do to ensure the system is not launch-capable. This "something" should be able to be carried to the pad to ensure safety. On Estes controllers, this is the sardine can key.

I think your green button meets #1. If your remote unplugs from the far end of the cable as you stated, that should be sufficient for #2. Many people add a more portable phono plug that breaks the launch circuit.

Edit: I just realized that the above might sound patronizing if taken the wrong way. I'm not trying to lecture, simply trying to answer a question that will be useful to others who stumble upon this thread. In my opinion, your controller meets the NFPA criteria.

bobkrech said:

Comment. Use inexpensive automotive relays and sockets to make your life easier.

Examples.

https://www.allelectronics.com/make-a-store/item/rly-351/12vdc-spdt-40a-automotive-relay/1.html good for over 100 amps in launcher applications.

Click to expand...

Yep, those are exactly the type I bought from the same source, although mine have tan cases. They didn't have sockets available when I ordered mine, but proper sized spade lugs work. I have a cheap starter solenoid for "master arm" which makes contact (not coil) power available to all of the relays in parallel for mass launches. 12V power is from a Harbor Freight jump starter.

zanfar said:

NFPA 4.13.2-3 (and therefore NAR) require two safety features for ignition systems:

1) Return-to-off: basically a momentary launch switch, something so if you drop it, release it, etc, it (and the rocket) return to a "safe" condition.
2) Removable interlock: This is what Micromeister is talking about, something you can do to ensure the system is not launch-capable. This "something" should be able to be carried to the pad to ensure safety. On Estes controllers, this is the sardine can key.

I think your green button meets #1. If your remote unplugs from the far end of the cable as you stated, that should be sufficient for #2. Many people add a more portable phono plug that breaks the launch circuit.

Edit: I just realized that the above might sound patronizing if taken the wrong way. I'm not trying to lecture, simply trying to answer a question that will be useful to others who stumble upon this thread. In my opinion, your controller meets the NFPA criteria.

Click to expand...

Thanks for posting this - and yes, my understanding was that both my systems meet said criteria. The green button in indeed a momentary switch. And personally I just find it easier to cut up a cheap extension cord to be able to plug/unplug the controller, as opposed to messing with little removable key thingies...

No hard feelings!