Step 2: How it works: Transmitter

 The transmitter Arduino reads voltage levels from the three potentiometers on the controller levels, divides them by the reference voltage (5V), and comes out with an 8-bit value (for example, if the potentiometer is turned exactly halfway, it will return 128, because 128/256 = 1/2). A one - byte value is 8 bits, or 8 places in base two. The transmitter takes the potentiometer value and sends it the radio module, one byte every 0.5 ms ( the radio's max transmission rate is 2000 bps). For example, if the value is 200, the Arduino would pulse:

1 1 0 0     1 0 0 0

Where a 1 is "high" on the TX data line for 0.5ms, and 0 is "low" on the line for 0.5ms. Before it sends this, though, the radio transmits a 'start code':

1 0 1 0     0 1 0 1

This is what the Arduino on the other side is "looking for" -- it needs to see this value before it starts recording data packets, or else it might start recording in the middle of a packet and then everything would get thrown off. So, this is one complete data packet that the ground Arduino transmits ( it sends them out once every 10ms) :

[ start code ] [ motor #1 byte ]  *   [ motor #2 byte ]  *  [ servo byte]  *

The * indicates a HIGH pulse for 0.5 ms -- these are needed because the radio gets a lot of interference if you leave it sitting LOW to long.

You can see the levers and connectors leading to the Arduino and radio in the picture.
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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