Step 13: Liftoff!

Enjoy your command of the skies! Here's another video:

And another one, where it's slightly less than neutrally buoyant:


My motors and servo twitch and move erratically.
You have timing issues between the transmitter and receiver -- one of them takes slightly longer than the other to pulse / measure pulses. Try adjusting the initial delay -- the first thing that happens within the interrupt. You can also try adjusting the time (500 us) that the receiver waits between checking the data line, but I've had little success with that. If you're more competent at writing code than I am -- and you are -- try eliminating overhead from all the clumsy functions I use.

One of the motors won't move.
Check to find a wire loose. Also make sure your H-Bridges are solid. Fair warning -- the motors are great, but the wires they come with are really flimsy. The wire on one of mine snapped off, and I had to pop off the plastic cap and put in my own brushes.

My Arduino isn't blinking -- I don't think it's picking up radio signals.
Find an oscilloscope and make sure your transmitter is pulsing correctly. Jiggle your antenna. Check for bad solder joints on the receiver. Make sure you didn't add a function in the interrupt that clogs it up -- functions don't do well in interrupts. Pray to Philip The God Of Radios Working Properly. Sacrifice your firstborn son.

I sacrificed my firstborn son and now he's dead and my radio still doesn't work. Help?
I had the same problem-- your receiver probably isn't getting power. Check the wiring.

I'm having trouble keeping the reaction cool.
Try a couple rags soaked in ice water -- wrap them around the top half of the the vessel, where it gets the hottest. Make sure you've got in a basin of ice water.

How should I shed weight?
Avoid thick wires at all costs, make them as short as possible. Don't worry too much about the balsa.

My hands feel like they're burning.
You got lye on them, wear gloves.

How should I store my envelope when it's not in use?
If it's just for a day or two, I just leave it attached to the frame and some extra weights so it doesn't go anywhere. For long term storage, I separate the envelope from the frame and just leave it lying up against my ceiling.

What should I do with my salty aluminium oxide water?
I pour it on weeds. It's not hazardous.

I left my reaction unattended because I'm an idiot and now there's explosive steam billowing everywhere and I can't breathe and my envelope exploded and my table is melting and my house is burning down because I'm an idiot.
You're an idiot.
You blimp looks awesome, only the code is without any doubt the most incomprehensible code I have ever seen! I can't make heads or tails from it. Could you explain the how te code works? I really like the 433 MHz set I got, but I haven't found a clear code that I can adapt to my homemade rover. <br> <br>Thom
Darn, I have been trying to figure out your code for quite some time, IT-IS-SO-SIMPLE, I have tried to use virtualwire but then I can't use the servo library (they hate each other). Thanks for sharing it!
when I first read the title I accidently read &quot;Hydrogen bomb.&quot;
Nice work on this project! I had the same 433 Rx Tx units and could never get them to communicate properly! Definitely one of the best troubleshooting sections I've read!
this soo reminds me of the hindenburg. tho to be fair, hydrogen had nothing to do with the explosion. zinc paint(?!) was the problem. <br>very cool project. <br>tho 433mhz might not be legal in USA, but even a toy car with arduino could work
You are my hero. I have tried filling a smaller blimp with hydrogen in the same way, but using only very small amounts of lye (five attempts with no success). I would love to build a setup like this some day, especially one using a hydrogen fuel cell for power. One question: does the water buffer remove any steam or water vapor from the hydrogen entering the envelope? I always worried about getting water in it. Thanks for a very informative 'ible.
You're right to be worried about water vapor. It will only be a problem if you let the reaction get too hot, which will make it start steaming or even boil if it gets out of hand. If you make sure it doesn't get more than a little warm ( I dunno, 75 deg F), the water vapor will be negligible. If you're really worried about it, you could try running the gas through a percolator to cool it down before it enters the envelope (meaning some of the vapor would condense out). The buffer I have is mainly to prevent any water in liquid form that bubbles up from getting close to the envelope. Don't give up on lye!
Awesome. Love the chemistry lab details and the troubleshooting section.

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