How To Build A Wireless Launch Controller

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It is not a question of meeting my criteria but meeting the plain meaning of the NFPA requirements.

But that would work although the alarm output looks weird. As near as I can tell it has battery + connected to both sides. PAD+ and GND would do the job.

Or is this a side effect of trying to fit two schematics on a single page?

Yes, it is a compound schematic. For the controller, the Alarm connector is not used.
The alarm connector is meant for an audible buzzer that would sound, if when the Pad Disable Switch is open AND the leads are shorted AND the relay is closed, it will not provide enough current to start but will give a warning that there is a serious problem
The Pad does not use the key switch, it uses a high current switch in series between the battery supply and the REL+. When the switch is open there is no high current voltage source to the relay also no current supplied to the coil of the relay. So if the FET fails, processor fails, or relay fails, there is no battery current supplied to PAD+. The continuity circuit will supply a small sense current as well as the current supplied by the Alarm circuit if there is a fault in the hardware.
 
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Attached should be a .zip file that contains schematics, BOM and software for the single pad wireless project using an Arduino Uno.


View attachment DIY Shield.zip


I am adding an additional .zip file which contains a program to allow you to configure the XBee when it is attached to the shield.
Once attached and powered-up, you can upload this program and it will allow the Digi.com XCTU software to interface to the XBee.
I am also including a sample configuration file. Please, Please, Please, if you make your own, make your own private encryption key!

View attachment XBee for Shield.zip
 
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Does NAR/NFPA/etc. say *where* the safety interlock has to be? Put it at the pad, too. Only when everyone is heading away from the pad preceding the launch, does the last person at the pad (the launch DIRECTOR perhaps?) enable the interlock and allow the firing circuit to be energized. This simplifies the problem a lot.
Beat me to it. That's exactly what I was going to suggest. That would be a safety interlock in addition to the one at the launch controller. The RX box holding it would also have an LED and/or an audible alarm indicating that an errant fire command was being received to prevent the safety interlock from being enabled. Further, each pad RX would be at least 30 feet from the pad in the direction of the LCO table, enough to prevent injury if every safety mechanism failed and the rocket was launched the moment the safety interlock was enabled.
 
Beat me to it. That's exactly what I was going to suggest. That would be a safety interlock in addition to the one at the launch controller. The RX box holding it would also have an LED and/or an audible alarm indicating that an errant fire command was being received to prevent the safety interlock from being enabled. Further, each pad RX would be at least 30 feet from the pad in the direction of the LCO table, enough to prevent injury if every safety mechanism failed and the rocket was launched the moment the safety interlock was enabled.

This is the kind of thinking we need for safety. It includes the designed-in factors and the human factors for how the launch equipment is operated.

The best place to include the check for launch activation is at the relay itself and with the fewest number of components (and with no software required to detect it). That is why I recommend a second pole on the relay with a simple alarm buzzer closed through that path.
 
...

Here's my non-wireless simple launch circuit that incorporates much of the safety features David mentioned. I've shared this on the web many times. At least 10,000 launches have been done based on this design over the past 20+ years. Adding a simple/secure wireless link in between could be done without introducing too many additional failure modes. XBee + Arduinos + libraries + control software does not make a simple wireless link, but it's accessible to hobbyists without professional EE background.

Link: View attachment 324599

...).

I have returned to the hobby after about 40+ years of being on/off, and I've been searching for good launch controller plans and/or understandable to non-electricians schematics for a low/mid-power setup. I want to have a little distance between me and the pad, and a relay setup fits the bill. I just haven't been able to find any until now that are easy enough for someone without an electronics background to assemble without taking a community college Electronics 101 class. This looks like a great schematic and easy for me to understand and source the parts. I hope you don't mind if I build this for my own non-commercial use.
 
My schematic is free for anyone to build a controller from. You may have a hard time finding some of the old radio shack parts. But, take the general idea and make substitutions.
 
I've read through these old wireless launch controller threads and was determined to build something that would work. It's only for my own personal launch, not for a club, or kids. This actually turned out to be way easier than I imagined. I grabbed one of the dozens of 12 v latched relays you can find on Amazon. This one worked just fine - https://www.amazon.com/gp/product/B00W8V4KQ4/?tag=skimlinks_replacement-20

I paired it with a 12 V 7ah battery for under $20, https://www.amazon.com/gp/product/B00BSEJWCO/?tag=skimlinks_replacement-20

Typically these boards don't come with instructions but was able to correctly wire it up and get it working, from reading others comments on Amazon. The board comes with a pigtail antenna which is easy enough to wire up to a larger antenna. I have successfully lit up a 12V light bulb from over 400 feet away, on a single keypress of the transmitter. I have also lit up an Estes igniter on this same setup so I know positively it does work just fine. I took the relay board and hot-glued it into a larger enclosure, the load wires (ignition) will be wired to mini-clips on a 15' length. I installed a huge antenna on top of the enclosure box, wired directly to the board. Works wonderfully. Awesome range.

My total out-of-pocket on this was under $60
 
I just finished something similar. I used a Bluetooth LE module an arduino and wrote an iOS app to control everything. It gets at least 30m of range in the open. Hard safety/lockout at the pad combined with several lockouts and safeguards in the software. I added a remote continuity check and a remote voltage readout for both batteries as well.

The icing on the cake is that the app will optionally start recording a video automatically when you hit the arm button so you can film and launch at the same time...

The schematics and all the code is at https://github.com/barnstar/BTLauncher for anybody interested. iOS only. Android support is left as an exercise for the reader.

Well under $100 Canada-bux including the 3.7v and 12v batteries and case. $1200 if you include the iPhone though :)


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IMG_20190128_135018295.jpg This system works great and was simple to build. The control is using a Bilusocn fireworks controller. Mine is 12 channel, but they also make other units, 4 channel or 8 channel and others. Look on eBay you will find them in seconds. They are inexpensive and have a 400' range. I tested it to 250' The blue box is a surplus mil-spec box. Power switch is 400 amp contacts from a car starter box that failed. The Bilusocn outputs last about .75sec. and are 5v. Channel 1 is connected to fire a relay with the continuity peizo buzzer (From an AeroTech Launch controller) Channel 2 is for fire. There is a 2 contact connector to plug in a blinking strobe light to indicate armed status,this also is the charging port for the 2 7.5AH Brick Batteries in parallel. Digital display voltage meter less than $2 from China.

https://rover.ebay.com/rover/1/711-...0001&campid=5338413729&icep_item=352509426090

https://rover.ebay.com/rover/1/711-...0001&campid=5338413729&icep_item=142832718831
 
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