When Bart and Bert entered Professor Ventura's lab, the reaction could not be another: two big smiles and a lot of exclamations and questions! In fact, there was a beautiful drone on the workbench, and the Professor was working in the open box of the remote control transmitter!
- Wow! A drone with a remote control! Bart exclaimed.
- When did you buy it? We didn’t see you traveling these days? - Bert asked.
- When are you going to try it? - Bart asked without letting the Professor answer the first question.
- Calm down! One question at a time! - The Professor stopped working on the transmitter and looked at the two of them, with the screwdriver in his hand, he continued - I’ve had the transmitter and the receiver for a long time, I’ve developed them with components purchased at Mouser Electronics, as I always do, and I have worked on them every night in my house. Yesterday it was ready.
- Wow! And you didn’t say anything to us! - Bart complained.
- I wanted to surprise you! In fact, I just wanted to show it after testing and making sure it works perfectly! - the Professor said this somewhat frustrated, for not having been able to hide the drone until the time of the test.
- Whatever Professor! - Bert complained.
Seeking to "repair" things, the Professor then had an idea:
- Why don’t you help me try it on?
- Of course! - replied the two of them.
Bart and Bert were already going to get the drone and the little transmitter box, which the Professor had just closed, to take it to an open place when they were interrupted:
- Wait a minute! Before we go I need to explain some technical details about this project, because it’s a control a little different from the conventional ones! Don’t you want to know how the "thing" works?
- Different? - Bart stuck the transmitter in his hand.
- Yes! I have added some "sophistications" to both the transmitter and the receiver, and it is good that you know them, in case I need your "technical" help!
- Let's go then! - Bert said as he settled into a chair, knowing that Professor Ventura's explanation would not be too short, and he would certainly use the whiteboard, as he always did.
Picking up the black pen, the Professor began by drawing a block diagram that corresponded to the transmitter. At the same time he went on explaining:
- In the transmitter, I increased the power well over the conventional types, to ensure that the drone does not leave the range of the device, getting lost. For this purpose, I used a Microchip’s Lora board (Long Range) purchased from Mouser, in order to ensure the widest possible range for the digital control system.
- What power did you get? - Bart asked curiously.
- In this type of communication, it is not the power that matters, unlike the old-fashioned remotes, with frequency modulation, PWM or amplitude. It is a digital system with spread spectrum technology and frequency hopping. The band is narrowed, with some loss in the data rate, and this increases the penetration of the signal. With a watt fraction it can go on for kilometers ... Nowadays there is a Lora system that, using a small battery of 2.7 V, can reach more than 5 km. They will be the future of the Internet of things.
- IoT. Wow! - Bart completed
- But regarding the coding system we have something more interesting. Long ago, I bought at the scrap metal some boards of industrial remote controls used in elevators, conveyors and cranes, as well as other machines that must be controlled by wireless operators.
- Like the conveyors carrying lemons at Lemonmill? - Bart was referring to the lemon-based beverage factory, which was the city's biggest industry.
The Professor confirmed:
- Yes, that's right! On the boards of these devices there were very interesting coding and decoding integrated circuits, because by operating with digital codes they contained everything for an efficient and safe multichannel remote control! They do not need coils that are hard to calculate and wind, or anything! Just connect them to the transmission and reception system!
- Wow! Lora board. This makes designing easier! - Bart commented.
- Especially the receiver’s design where we have weight and size limitations, like in the drone! - The Professor said.
Going to the drone, the Professor explained how the flight controls worked:
- We have several servos that are digitally triggered by the channels. We have one for each engine. I also left free channels for other functions we can add. The interesting thing is that the controls are proportional allowing very precise maneuvers!
Bert was not quite sure what a "proportional" remote control was. The Professor explained:
- In the proportional system you do not simply turn on or off anything at all, but move it linearly or continuously so that it is placed in any chosen position between two points. In a car without this feature, either it flips all the way to the right or all to the left and has no precise control of its movement. With this feature you can turn the direction a little or too much, making a more or less closed curve, and smoothly!
The Professor said this, drawing curves of various rays on the whiteboard.
- Can we go then? - Bert was impatient.
- Of course!
Equipped with a large arsenal of things which, in addition to the drone and the transmitter, included a tool case, in case the drone needed some maintenance, a great Zeiss 10 x 50 binoculars and even a bottle of water with a pack of cookies, there three of them were off to the chosen place.
Professor Ventura's car can only reach the cemetery on the top of the hill which links the city to Newville. From there they took a path along the wall of the cemetery and, passing through the woods, they arrived at a slope with low vegetation. This slope ended in a huge abandoned pasture, one of the few large areas of the city not taken by the lemon crops. In fact, Lemon city had its entire economy based on the lemon crops and the juice factory!
- Here is perfect! - The Professor came to a halt, placing the heavy load on the floor.
The three of them were on the slope, and from there it would be easy to control the drone, for the sight they had, and for the possibility of making emergency landings on soft, easily accessible land.
They triggered the control. The four electric motors went into operation and the drone rose smoothly.
- It works! Look how it answers to commands! - Professor Ventura, enthusiastic with the transmitter in his hand, was familiar with the controls, making several maneuvers.
The three of them were enjoying themselves very much with the little flying device, without worrying about other things that happened at that moment in the quiet Lemon city.
The harvest of that year surpassed expectations, and the lemon trucks came in and out of Lemon city, leaving their precious cargo in the storage silos. The huge special dump trucks carrying more than 20 tons of lemons came from everywhere to the factory. These trucks, however, had an interesting feature: the body movement of loading and unloading lemons was automated! Yes, that's right!
A wireless card placed in the operator's cabin of the silo powered the truck body when the truck was positioned, and that made it lift and drop all the lemons in an access opening. It was all automatic! At the end of the operation, the operator lowered the body and signaled to the driver to leave the place! The control was sophisticated because it was possible to trigger based on the number of the truck.
But there was one dark spot to consider: the systems used on Professor Ventura's remote control and on Lemonmill's trucks were the same and even the frequency range was the same! Worst of all, the teacher's board had a long distance reach! And it was because of this that things began to take an alarming course!
At that moment Professor Ventura, Bart and Bert excitedly tested the drone, less than a kilometer away, and therefore within the range of the transmitter, climbed heavily up the slope from Newville towards Lemon city, another truck loaded with lemons!
Just above the middle of the slope, the truck crosses with a character well-known in the city, and also to our readers: Tubald Wheathercock and his tuba! Cheerfully the band's musician had finished his afternoon performance in the bandstand, returning, as always, whistling a Sousa march.
Used to the comings and goings of the trucks, he only cared about them when the heavy vehicles passed through Newville, shaking things up a little at home. So he did not even look at the heavy vehicle. In fact, he did not like lemons!
- Lemons! Balls!
Tubald was less than 50 meters from the truck when Professor Ventura's remote control transmissions were picked up by the receiver of one heavy vehicle and the result was interesting: the coding that Professor had used to control one of the drone's functions was the same as the one which programmed to activate the truck body to unload it! And, that's exactly what happened in a few seconds!
The body creaked, and more than 20 tons of lemons were dumped on the street into a strange torrent, which began to gain speed downhill! The driver only realized this when the truck "got lighter", but it was too late to interfere with the manual control! Right in front of the avalanche, a first target moved carelessly: Tubald!
The little man, noticing the strange noise of the lemons, looked back and what he saw made him scream in terror:
- Wowwwwwwwww!
Jumping, and holding his tuba tight, he ran as fast as he ever did in his life! ... Behind, a live green wall of lemons threatened to overtake him! Tubald still thought of leaving the front of the torrent, letting it pass, but there was no possibility where he was: on one side there was a long wall and on the other a barbed wire fence!
The interesting thing about all this is that the topography of the place made the street run like a channel directing, very well, the lemons behind Tubald towards Newville.
Tubald, running from the "avalanche" of lemons, crossed the bridge over the creek and ran as fast as he could into Newville! Many lemons fell into the creek, but what was left was more than enough to scare anyone and wreak havoc!
- My house! Finally! - The musician exclaimed breathlessly, still chased by thousands of lemons which seemed to have a special interest in reaching him.
The musician practically broke through the front door, crossed the living room and entered his bedroom, as he always did when he was frightened, plunging, with the tuba and everything else he was carrying, under his bed! He only had time to shout at his wife:
- Ginevra! Help me!.
As always, when Tubald hurried into the house, Mrs Weathercock took her broom, expecting the worst, knowing she had "trouble" ahead of her. But this time the problem was not going to be solved with one or two brooms!
Hurrying to the front door, which was open, the woman did not even have time to scream! She was knocked down and dragged by the torrent of lemons, as she dropped the broom in astonishment! The lemons, as if controlled by an invisible hand, invaded the bedroom where Tubald was, forming a mass of at least two meters thick, covering everything, burying the poor musician with his tuba under the bed.
The driver of the truck, desperate, arrived shortly after, parked the heavy vehicle at the door of the house, which was "flooded" with lemons, and with him the residents of Newville, who, removing the lemons as they could, tried to rescue Mr and Mrs Weathercock.
Ginevra shouted at the “helpers”:
- Save my husband first! He is "buried" in the room! Poor Tubald! He will drown right in the lemons he hates so much!
At this point, Professor Ventura, Barto, and Bert collected the drone that had made a forced landing on the other side of the pasture!
- That’s it! The last battery is almost discharged! Let's go! Thanks for the test! - The Professor said.
- Let's get out though here! It’s easier. - Bart commented, pointing to the wire fence and a nearby trail in the woods.
- You’re right! We’ll end up in Newville and we can go up the slope!
That's what they did, except they did not expect to find a scene of such confusion at Newville’s entrance, a crowd in front of Tubald’s house, an empty Lemonmill’s truck, the street with lemons everywhere, and the house invaded almost "up to the ceiling" by the little fruits! The Professor stopped with Bart and Bert, just in time to see a groggy Tubald with his tuba being pulled out of that mess!
- What happened? - Asked the Professor astonished at the "demages."
- The load of the truck loosened, just up the hill, and the torrent of lemons invaded the house! Luckily no one was hurt! - Someone explained.
- Good! - Agreed the Professor.
A friend of the Professor, who knew that in 99.9% of the city's confusion, he was involved and that it was a coincidence he was next door, commented:
- Thank God you have nothing to do with it this time! Do you?
- That's right! And you see! - commented the Professor, looking seriously at the inopportune observer, but at the same time, relieved, with which Bart and Bert agreed nodding their heads and saying.
- Thank God!
The Musician, who had been removed "physically intact" with his instrument in hand, tried to blow it to see if there had been any damage:
- Pffffff! - No sound came out
- It's stuffy! - and turning the tuba at least a dozen lemons came out!
Then He exploded:
- Argh! I hate lemons! I hate lemonade! Now my house, my wife and my precious tuba will have the taste of this damn fruit for the rest of my life! There could be no greater misfortune!
Mrs Weathercock began crying and as some neighbors comforted her the driver of Lemonmill tried to make the damage seem fixable saying the company would pay all damages, including buying a new tuba ...
The Professor was already leaving the room, holding the transmitter, when, without by mistake he pressed a button on it. The rest of the battery charge was enough to feed the circuit once more. The parked truck was right beside the house and he noticed then a slight hum and the truck body moved! Stopping, for a moment, he pressed another button, but now with Bart and Bert watching! The body moved a little more!
The Professor swallowed hard knowing he was in the trouble maker.
Bart looked sideways, to see if anyone had noticed that, as he wispered to the Professor:
- Who said we have nothing to do with it? You better get out of here, and fast before someone finds out! - The three of them sneaked out of the crowd, trying to hide the transmitter, and very quietly so as not to raise suspicions.
Fortunately, the real cause of the "disaster" for our heroes' happiness wasn’t discovered. The dangerous drone and the remote control were "deactivated" and the three vowed not to speak for a long time about them.
