re: The joys of micro-electronics...

Well we lost a payload out of one of our rockets today. Nose cone came off the payload section. We found the nose cone, but not the altimeter. Went back after dark to see if the leds were still lit, but i guess the 40 mah died long before we got back. Or it landed in one of the yards to the south of where we launch.

Well, i got the GPS figured out, but can't get the two devices to\ talk to each other.

I'm using the HC12 433MHz Serial Port Communication Module. I'm sure the issue is in the code (most likely the pinouts) as I had the HC12's working earlier this week.

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Quick googling looks like the HC-12 boards are using the AT command sets, which kind of sucks. So not a really like a virtual com port.

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Yeah, they are serial communication only. I found this out the hard way today after tinkering with it most of the afternoon. I was finally successful in making it work on the prototype bread board(s).

The problem was both the GPS module and the HC12 use the same software serial protocol. Even though I had software serial assigned to different digital pins, they still interfered with each other. Basically you could only use 1 at a time. So after much pondering on how to rectify the situation, I was able to force the HC12 to use the Arduino's hardware serial port. After I was able to figure that out, my biggest challenge was able to format the LCD display. I was able to cobble together a less than optimum, but workable solution.

The next task will be able to shrink things down to a "flyable" package and to test it in the field. Stay tuned...

The boards came in last week. Got a couple of them soldered up over the weekend. Took them for a test flight yesterday and they worked perfectly.



Edited to add a pic of the base station:

You can get a 433Mhz wireless remote switch and module board for under $10.

I've used them to turn my old Mojo's into wireless.

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Probably reversed 2 if the terminals.

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That's what he did. At the time we were just plugging the battery into the programming pins of the Arduino. He reversed the polarity. Good news is, everything is pretty cheap to replace.

I came here to give an update on the wireless launch controller We're building. First off, turns out I picked the absolute WORST time to order parts from Aliexpress. They were stuck in customs for almost 2.5 weeks! ?? But they finally got here this week. My original vision was to build something similar to the IMPLS Fiver, but on a more budget friendly scale (that's beyond our budget at this point).






While kicking around home depot, we found a Husky brand metal saw horse. A couple of 2x3's later and we have a functional launch pad that pretty much looks like the above. (pics to come on another day). Ours is 4 stations instead of 5. We've used it a couple of times with his wired controllers and it sets up for 4 rockets in under 2 mins.

I ended up using a NodeMCU for the Button module and a D1 mini for the relay module. Mostly because the relays I ordered were 5v and the nodeMCU only works in 3.3v :facepalm: Anyway, that would end up working to my favor in the long run. I chugged thru the code and finally got a couple of working sketches. My original code a few pages back kept the relays open for 3 seconds. I've updated that to continuous on/off depending on the button push state. We've got 4 individual launch buttons. We also have individual arming switches. They have illuminated LED's in them.



So on the input side, they get 3.3v from the node MCU and the negative terminal of the switch is connected to ground. The other leg of the switch, it's connected to the launch button. The other leg of the button is connected to D1, D2, D5 and D6 respectively. When pressed the nodemcu sends a request to the relay module via wifi signifying which button was pressed...

The relay module sets up a wifi network called "rocket network" and looks for a the button push request. A couple of days ago I got that working flawlessly. Then I got to thinking. Since everything is going to be enclosed in a project box, I really need to be able to know if the two modules are connected to each other wirelessly. While trying to think of a solution to that problem, I came up with an idea. I have several hundred individually addressable WS2811 that I use in our Christmas decorations. My original plan was when wifi was connected, to have it burn steady green, and when disconnected flash red. I was able to make that work.

Then I got to thinking further. Why couldn't I read the state of the toggle switches and have the button push module send an "Armed" and "Safe" request to the relay module when one of the toggle switches is thrown? I had hoped simply have each of the individual switches send signals out to 4 unused GPIO pins, but given the start up nature of the pins I had remaining, that wasn't really possible. That lead me to another issue. If I simply connected all of the switches to 1 GPIO pin, the would back feed the individual buttons. So I'm reworking my circuit board to have the 4 inputs run thru some Schottky Diodes to isolate each individual 3.3v circuit. Those are on order from amazon (where I spent way to much for them...) I was able to hook up 1 switch to the correct GPIO pin on the D1. Running two WS2811's in series, I have the first one Burn Steady purple when connected to wifi and blink purple when not connected. When the Button push module detects 3.3v on the back side of the switch, it sends a signal "armed" to the D1 and it illuminates the second WS2811 fast blinks red. When "Safe", it slow blinks green. (I had to think about my red/green colorblind friends... :) )

So we have the following safety checks in place. 1). Both Modules have a removeable key lock. Both keys have to be inserted and turned on to power the units. 2). In addition, the Relay module box will have a toggle switch like above that powers the relay module itself. You could have the key on the relay module, but unless the toggle switch is flipped, you cannot complete the circuit. 3) As stated above, each button has it's own armed/safe switch. Finally we have the "Armed/Safe" lights on the relay box. With two keys, two switches, illuminated LED's and a button push, that should me more than enough fail safe's in place to prevent an accidental launch.

One of the original design parameters I wanted to include was having the D1 read continuity state of the individual leads/ignitors and display that on the launch button module, but ultimately I ran out of GPIO pins. The good news on that is, since we're using a metal saw horse as a pad, I'm going to be able to attach magnets to the back of the relay unit and mount it directly to the launch pad. I do have individual continuity leds on the relay module. We tested them in the bright sun, and you can seen them from a long way away. So so long as you have eyes on the launch pad, you should be able to see the continuity leds (even I could see them with my eyes getting worse with age.) It's not the solution I originally wanted, but I will take the tradeoff of the armed/safe led. That's more useful information than continuity going back to the button push module.

That's it for now. When everything is finally assembled, I'll post pics.

Budget update: Even with having to order twice from Aliexpress due to the customs snafu, I'm around $150 into this project, including the launch pad. The system I posted above runs north of $900.

Here are the things I can remember off the top of my head.

Saw horse $50
Aliexpress parts: $50 (I ordered more than I needed for this project)
Too many to fully itemize but here's a general list
1 node MCU
1 D1 mini
6 toggle switches
1 4 relay module
2 1 high current relay module (to switch from internal to external power)
2 key switches.
4 12mm push buttons (should have gotten 19mm).

2 Project boxes (7.87 x 4.72 x 2.95 inch ) $16
2 12v to micro usb power modules $9

Photos of the proto types up to this point. Still waiting on a few items to finish them off. Photo 1 is "Safe Mode". Photo 2 is "Armed". All done wirelessly.

We had as a project in middle school shop class to launch and recover a model rocket. I practiced at home and couldn't get the damn thing to launch . Took it inside and messed with it on the living room floor for a while. Got it to launch in there.I'm no Elon.

Minus not having all of the vinyl I needed for labeling them, they're "done".

Turns out my 12v - 5v converters are battery hogs so They're getting replaced. There is also a fair amount of rf interference in the cases. They struggle with wifi connection distances over about 30-40' (We got close to 300-400' feet with the prototypes.) Part of that is they broadcast on 2.4 ghz Channel 1, and that channel is really crowded. But I ordered a D1 mini with external an antenna to hopefully solve the problem. The d1 mini is currently on header pins, so that should be a "hot swap" when they get here.


These are awesome, but I struggled with the physical build. I grew up in the south and we had a saying down there, "10 lbs of taters in a 5 lb sack." That's kinda what getting everything in the boxes felt like. Took me WAY more time than it should have to get it right.






(These are older 12.5mm (1/2") buttons. I've since upgraded them to 19mm (3/4"))