After the first conversation about the underwater radio, 3 months passed by. The guys still considered my idea to be unrealizable, but, as they say, the owner is the boss, so work went forward in full swing.
Our team grew — we were joined by two more talented electronics engineers, and more often we began to release new and improved versions.
Prototype #1 — “Box”
The “box” consisted of a large board on which engineers assembled the receiving part, and a bunch of removable parts for components, such as audio amplifier, radio and audio filters. At this stage, the size of the device is not important, but rather, the choice of components and their functionality is crucial.
All this was placed in a plastic case, which was printed on a 3D printer. The frame for the speaker had to be moved into a separate round case, and with wires connected to the receiver.
Yes, it’s certainly not what you’d want to see on a swimmer’s head, but the first step was done! Now, we need to make sure that it works as intended. It might be clumsy, but it’s functional. Let’s go to the pool!
Tests with my son Mishka showed that the device, which we called sonar (because of the ability to transmit sound underwater), penetrates 1 meter of water in the pool and about 150 meters in the air. That’s more than enough for swimmers.
There was nothing to be happy about, the result was predictable. This was textbook physics: the size of the antennae — one-fourth the length of the wave, 12.5 centimeters. There was no miracle.
But a miracle had to happen — we had to completely get rid of this long black thing. Everything, however, needs to be done gradually, and so, in the next step we will try to fit everything into one case and do it without wires.
Prototype №2 — “Tank”
After successfully testing the first prototype with an external speaker, we decided to hide the entire device in one case. But how are we going to fit a huge board, a battery and a bone speaker in a small round case no one had the slightest idea.
Then we printed out all the components on a 3D printer and tried to fit everything in a circle and try to understand what is the right form for their placement. Fortunately, the antenna does not need to be inserted inside yet — it will be external in this prototype.
When it became clear that this is possible, the electronics engineers sat down to develop a round printed circuit board with a hole in the center for the bone conduction speaker. The antenna of course is not going to fit yet, so it will stick out for now.
Right after we designed the second prototype we knew what it should be called. It’s a typical tank!
At the same time our guys began to test the heart of our device — the bone conduction speaker. We ordered a dozen different sizes and capacities and began to check which one gives the maximum power at small sizes.
Having made a choice on a large and quite loud speaker, the engineers inserted it into the case.
We did not know then that such a powerful speaker would eat up our entire small battery in 15 minutes. But at that moment it didn’t matter, because our task was to fit the prototype into a small case. And super autonomy is the second thing.
We made a two-layer board for components and ordered it in China. And a month later, we finally assembled the first “tank” that worked!
We ran to test it aaaand…the tank did not fire. Range of action — 50 meters. The speaker wheezed like Darth Vader having a cold, and the battery generally refused to support the life of our receiver.
Hmm, it turned out that just assembling a device is not enough to make it work. Debugging has begun. Here go versions — 2.1, 2.3, 2.43. So we got a small army of tanks with different weapons — from a huge black muzzle to a small rectangular gun on the tower. So we got a small army of tanks with different weapons — from a huge black muzzle to a small rectangular gun on the tower.
Finally, our tank troops won — the enemy was defeated, and the tankers celebrate the victory!
The antenna is tuned — it picks up 200 meters in the air, the speaker works reasonably well (but we will change it anyway) and the battery holds for half an hour.
Yes, we may have won this battle, but not the war — we realized that it was just beginning. Let’s move on — the protruding antenna from under the cap still does not inspire anyone, so we say goodbye to the tanks and say hello to …
To be continued.
