Need Hardware list and tipps for 5-Dot-Matrix printing with Wifi-Modules

Hello guys I just received a project from my local Soccer-Club to be able to print letters on the play field (grass-surface). Mainly for cheering purposes, maybe also for advertisement later on. The idea is pretty straight forward: There are 5 RC-Cars with down facing spray cans, used as printers [-P-] as shown below. Those 5 RC-Cars have all the same specs, this means you can expect one defined speed V.

O O O O O O O O O O -P-|RC-Car-1 O O O O O O -P-|RC-Car-2 O O O O O O -P-|RC-Car-3 O O O O O O -P-|RC-Car-4 O O O O O O O O O O O -P-|RC-Car-5 ----->V (I hope it is obvious that this is going to write "COOL" ^^)

All those "O" 's represent a spray-puff and thus generating letters with this so called 5-Dot-Matrix method. The challenge is to make it wireless (WiFi). I was thinking of getting: 5* ESP8266 v-07 ( I choose v-07 to be able to add an antenna if increased range is needed in the future) 1* Arduino Uno, this one will be carry the code for the pre-selected words. (This can also be carried by RC-Car-3 as so called Leader/Commander) 5* Servos to interact with the spray cans to create those puffs 5* 3.3V Power supplies (Maybe Coin-Cell battery) for the ESP8266's 1* Battery for the Arduino Uno But I am not sure if i can even work with this setup.

I mean I need to be able to connect everything like this (unless someone tells me otherwise):

Spray-can - Servo - ESP8266 = RC-Car-1 Spray-can - Servo - ESP8266 = RC-Car-2 Spray-can - Servo - ESP8266 - Arduino Uno = RC-Car-3 Spray-can - Servo - ESP8266 = RC-Car-4 Spray-can - Servo - ESP8266 = RC-Car-5

As mentioned the Arduino Uno contains the commands for all the other RC-Cars. This means that ESP8266 connected to that Arduino needs to be able to independently control (over WiFi) 5 Servos. Servo from RC-Car-1 & RC-Car-2 & RC-Car-4 & RC-Car-5 & its own servo. Is it even possible to connect one ESP8266 with 4 other ESP8266 over WiFi at the same time? Does it even have to be at the same time? I could perhaps add delays (sleep-times) with experimenting... Is there already a code for 5 Dot-Matix Printing?

Thank you very much for your attention

Best regards.

Capt_Kaplan

P.S. : It has to be over WiFi with 5 independent RC-Cars. I know it could make my project way easier if i just added a long stick of PVC-Pipe and made wired connections to each Servo and mount that on rails or something, but this needs to be versatile. :D

Before proceeding with your project, please verify that an autonomous RC car can find its straight way, starting dot position and dot distance in grass land. It may be possible to remote control the track of one such car manually, but 5 of them at the same time???

Eventually tanks with crawler tracks, instead of wheels, may keep their track and distance better.

Compass modules may allow to align the cars into the same initial direction.

Once you solved all these problems, the remaining code is not really complicated. Most RF modules have network capabilities, so that you can control any number of client stations from a single master controller. In the simplest case you transmit the dot pattern to each car, then let the cars do their job autonomously. Then the code for each car is exactly the same, except for its unique network address.

What makes you think that five cars running in grass at the same speed will cover the same distance for each car.

While this project sounds interesting it is going to be one hell of a lot more complex to actually make it work.

Grumpy_Mike: What makes you think that five cars running in grass at the same speed will cover the same distance for each car.

I agree, perhaps the OP is under the impression that the 'speed controller' in the cars are just that.

They are not of course, just a form of un-calibrated power controller. The actual ground speed could vary greatly because of;

Differences in the surface hieght of grass or bumps etc.

Varying voltage levels from the batteries.

Variaitions in the motors, power controllers, RC system etc.

Rather than plan the end game, the first step would be some practical experiments to see how you are going to sync up 5 seperate RC cars so they are running at the same ground speed and direction.

I am totally aware of the struggle of getting the same distance after a certain time with 5 cars. The cars itself will be big and heavy, the gras is more or less even (It is in a superb condition when it comes being flat). The wheels are big enough to compensate the mini-hicks. I actually tried it with 4 Cars last weekend for trial and error purposes and was pretty satisfied with the result. The grass surface itself is not the drawback in this project. I am really grateful for your replies!

DrDiettrich: Before proceeding with your project, please verify that an autonomous RC car can find its straight way, starting dot position and dot distance in grass land. It may be possible to remote control the track of one such car manually, but 5 of them at the same time???

Eventually tanks with crawler tracks, instead of wheels, may keep their track and distance better.

Compass modules may allow to align the cars into the same initial direction.

Once you solved all these problems, the remaining code is not really complicated. Most RF modules have network capabilities, so that you can control any number of client stations from a single master controller. In the simplest case you transmit the dot pattern to each car, then let the cars do their job autonomously. Then the code for each car is exactly the same, except for its unique network address.

Rather than plan the end game, the first step would be some practical experiments to see how you are going to sync up 5 seperate RC cars so they are running at the same ground speed and direction.

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As mentioned I did experiments and it works like a charm. But you've got some fair points on that varying voltage levels... I might take a look to that if the cars aren't aligned enough. I wish i could get some answers regarding to the shopping list for the hardware.

Best Regards!

I wish i could get some answers regarding to the shopping list for the hardware.

You can't get any sensible answers for things until you know exactly what you are going to do. Projects as complex as this don't work like that. Unless you are copying something someone else has done, then you never know what snags and difficulties you will find.

If you try and buy all the stuff now, you will end up buying stuff you don't need and have to buy stuff later.

You need rotary encoders, telling how far a car has moved. These encoders also can be used to control the motor speed, if required.