Who are we and what have we done?

We are the final year students at FIIT STU, Samuel Vanek and Dominik Puk.

As part of the Systems Thinking course, we have designed and created a "Messenger" project which is used to display a desired text between two people via a web application and a display in the form of a matrix LED display.

The solution consists of 3 parts:

• Fabricated box
• Web application
• IOT hardware

  Design of the solution

In the following chapter, we will present the design of our solution for the individual parts.

Component diagram

Our proposed solution consists of two main component parts:

• Local part - fabricated part + IoT hardware
• Web part

The Local part of our solution consists of the heart of our system, the ESP12. This ESP uses a matrix display to display information and also has a reset button. The devices will be stored in a fabricated box, which we will introduce later. It consists of three parts.

The Web part of the solution consists of a REST web service used for storing messages from the user part and sending them to the ESP12 for display if requested.

Web application

Design of the basic screen for sending messages to the local device.

The screen will have one text field where we can type in the text that is to be displayed on the device. The second will be a button that we can use to send the text itself.

Design of the box

Our box will consist of three parts:

• Box - LED matrix and ESP module components placed inside
• Front cover
• Rear cover

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Design of the box in which the LED matrix and ESP module components will be placed, along with dimensions, can be found in the image below.

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The top part of the image shows the box from the front. The LED matrix will be placed in the cutout. The pins of the LED matrix will be located in the cutout on the left, from where the wiring will lead to the back part to the ESP module. There will be circular cutouts with a depth of 1.1 cm in the corners of the box. The cutouts will be used to attach and easily remove the front cover.

The lower left part shows the box from the back. The ESP module will be attached to two columns on the left with screws. The pins and wiring from the ESP module will lead into the box, which is why there is a cutout in the right column on the bottom. The wiring from the column cutout leads to the cutout on the right, where it powers the LED matrix in the front. There are cutouts in the corners for attaching the rear cover.

The following image shows the designs for the rear and front covers, which attach to the box and create a whole for placing and protecting the components.

​On the left is the design for the rear cover. The cover is filled throughout. There will be holes in the corners for attaching the cover to the back of the box.

On the right is the design for the front cover. In the middle part of the image, the cover is shown from the front and its dimensions correspond to the front of the box so that the entire LED matrix is visible. In the top part of the image, the cover is shown from the back. The cutout in the middle is extended to fit a piece of plexiglass which will protect the LED matrix. In the bottom part of the image, the cover is shown from the top. There are cylindrical protuberances in the corners that will be inserted into the front of the box and secure the cover to the box.

Solution

In this chapter, we will describe the individual parts of the solution based on our design.

Fabrication

In this part of the solution, we will describe the process of fabricating the box model along with the iterations that arose from the deficiencies of the previous prototype. We created the box and cover model using the Blender3D modeling tool.

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First iteration

Model of boxView case_model_1.stl @ Wikifactory

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Front cover modelView predny_kryt_model_1.stl @ Wikifactory

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Back cover modelView zadny_kryt_model_1.stl @ Wikifactory

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The image below shows the first printed prototype.

Errors occurred during printing, resulting in the creation of the second iteration model. The design also had to be changed because it proved to be non-functional after implementation.

List of errors in the first prototype:

• Cylindrical protuberances on the front cover fell off during printing and also broke when inserted into the box

• Incorrect dimension of the thickness of the columns of the box. The columns are too thick, it is not possible to attach the ESP module to them because the pins of the module are obstructed by the columns.
• Printing error. The model separated during printing, resulting in the height of one corner of the box being smaller.

• Dimension of the height of the cutout for the LED matrix. The LED matrix is not securely placed in the box and has a large vertical clearance.​

  Second iteration of model

In the second iteration, we redesigned the front cover. Instead of protuberances, the cover will contain holes and will be attached to the box with screws. This solution does not provide easy manipulation and removable, but it is necessary in terms of strength and quality. The dimensions of the cover are retained from the first design.

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We also reduced the height of the cutout for the LED matrix to 3.5, narrowed the columns in the back of the box, and corrected the error in the model that caused the corner to curve.

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Final box modelView case_final.stl @ Wikifactory

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Final front cover modelView predny_kryt_final.stl @ Wikifactory

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3D printing of the individual parts took approximately:

• Box 8.5 hours
• Front cover 1 hour
• Rear cover 1.5 hours

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Web application

As stated in the design, the web application provides input for the text to be displayed and a button to send the text itself. This text is then saved on the backend of our web application and is made available upon request from the local part.

Hardware

Node MCU ESP12 - node_techFun

Matrix 32x8 - matrix\_techFunConnection

Final product

Description of final product

The local device operates in two modes:

1. AP - access point
2. Non-AP - display

The device is always in AP mode at startup or reset. In this mode, we can connect to the device via WIFI. After connecting, a web page is offered to us, through which we can change the WIFI network to which the device should log in. After saving to this WIFI, the device will automatically log in and switch to the second mode. If the device is within range of the last WIFI network when turned on, the device will immediately switch to Non-AP mode.

In Non-AP mode, the device periodically queries a web service to retrieve the text to be displayed. This text is displayed cyclically on the matrix display. If no text is received from the web service, a default message is displayed.

Ideas for improvement

1. Adding plexiglass in front of the matrix display
2. Improved web application
3. Creating different modes that the user can switch between (displaying account status, displaying messages, displaying...)
4. Expanding for multiple devices