Fab Academy 2015
How to make almost anything

Luis Peña Mendoza

    Assignment 6 - week 6 - Mar 04

    Redraw the echo hello world board, add (at least) a button and LED (with current-limiting resistor) check the design rules, and make it extra credit: simulate its operation

    Electronics Design

    The assignment for this week is to redraw the the echo hello world board, adding at least a button and a LED to the original design, using some of the proposed software. then make it with the Modela MDX20 and soldering the components.

    A. Download Eagle 7.2.0

    So for the first part of the assignent we have to download Eagle (Easily Applicable Graphical Layout Editor - Eagle is a software that allows us to develop PCB's, autorutear, generate schematics, develop libraries of components or electronic devices, etc.) and install it. Below I´ll describe the steps to follow:

    Step 1. Download and install the software Eagle 7.2.0

    Step 2. Download the board of the example the echo hello board.
    The echo hello board

    Step 3. I downloaded the libraries of the following link:
    Libraries

    Step 4. I installed the libraries, decompressing the file : The first thing we need for our assignment are the libraries with the componentes we are using in the Fab Academy, so go ahead and download it from here. Unzip it and place it in any directory you want.

    Open eagle, choose Options - Directories. Back in Eagle control panel search within libraries the folder "eagle libraries" right click and "Use all".



    Step 5. I opened Eagle: Basically Eagle allows us to work with two files simultaneously, the schematic and board - Schematic (.sch) : It is the representation of the circuit. Here we'll find the logical components.- Board (.brd) : Here we'll find electronic components and their connecting routes, distributed for obtain the file that will be used to mill the copper board. Now we're ready to start drawing our board. Eagle has two main views, the first step is to make the schematic file, so create a new project and a new schematic file.

    B. Redraw the the echo hello world board, adding at least a button and a LED to the original design

    We made the board design based on a schematic design that the instructor offered us, where we use the same controller board, and only change the sensors and actuators. In this way it was possible to optimize the use of the components. We ensure that the board is slightly reduced. The ATTiny44 was located near the center of the board, and we place the connector pin, on the outside, or more to the edge of the board, just as we did with the jack power which feeds the circuit, and after passing through voltage regulator feeds the other components. We try to locate the components well so that there were no crosses on the copper tracks, but we could not do as we would like, and we had to use a few small bridges. These bridges were 0 ohm resistors and used in all 3 bridges. Our final schematic should look like this:


    In the design of this second board, we present two LEDs and two switch with their respective resistors for proper operation. We resistances of 499 ohms Fab_Hello library, and encapsulation type 1206 to use them with the LED diodes having the same package 1206. In the case of the switch encapsulation was 6mm and manufacturer OMRON, with their 10k ohm resistors with the encapsulation type 1206. The switch needed input voltage VCC , so is that we implement one of the pinhead 1x6 . For LEDs and switches , connect the same GND. The 6 pinhead were distributed as follows: 1 VCC , 2 Switch1 ,3 Switch2, 4 Led1, 5 Led2 , 6 GND.The distribution on the plate was simpler than the Hello controller board .


    C. Milling, cutting, drilling and soldering

    The process for fabricating the pcb was the same from fab isp in electronics production assignment.

    Preparations to use the Models MDX-20 are: First, we must export the images of layers, layout, we want. 1. We select TOP, apply, and only the copper tracks are shown in png format export to a new folder, with a resolution of 900DPI, and give check to be monochrome. 2. Now select the PADS and VIAS, apply, and export in png format with 900DPI, and monochrome. These two images be joined in GIMP software Ubuntu. Second, once we have the image attached to TOP PADS, keep the image in a new location, and again using GIMP, select IMAGE, CANVAS, and add +20 to the value of the measure (X) of our plate , and similarly for (Y), we check in center, and accept the changes. These steps serve to create the DIMENSION, or square around our plate. Then select Image, Flatten Image, then creates a white border to central black color, and save this image to cutting board.

    We must be clear what are the names and where the images in png for milling and for cutting.
    To continue the Models must have the 2 images in PNG, the image of milling, cutting and image.

    Downloading link for my archives:
    Archives

    First, we entered the FabModules, and select make_png_rml and follow the steps.

    Step 1. We select the top MILL TRACES (1/64) This first step is important because otherwise we can not cut anything, or we err by making the stroke of the tracks.

    Step 2. Load the image with the Load.png button and verify the size or our board dx and dy in millimeters. We verified that the image which is going to make tracks.

    Step 3. We MAKE.PATH click, and select segments, so we'll see traces of milling. We enter the parameters of diameter (0.4) mm, overlap (0.5), intensity (0.5), offsets (1), error (0.9), z (-0.1) mm. And select Make.Path to update the changes. We must verify that no crosses on the slopes, otherwise we have to modify the design.

    Step 4. We place 1/64 milling tool and move to the point of origin (xmin, ymin) where engraving will.

    Step 5. seteamos the z until this next to the board.

    Step 6. Make.rml and Send.it

    We must remember the values ​​of xmin and ymin because they are the same for image cutting.

    Drilling: Before using any machine or tool must check the voltage with that work. In this case the drill works with 120V and has a transformer for this. Then in a test board drilled with a next to the size or pads milling tool, once we confirm the size or milling tool, adjust the hole and proceed to drill a pad at a time, and after performing cleaning each hole .

    Once finished, clean the work area and proceed to weld. Once we have the board ready , go to the schematic of the circuit and type RUN BOM to display the list of materials, and to apply. Since the components proceed to weld.

    Sodering: We must consider the polarity in the case of leds, and try not to confuse the capacitors. The technique we use for welding is to put some tin board on one pin component so sure, then solder the other pins, and ultimately reinforce the first pin. Communication solder pins ISP to last for comfort. We verify the continuity constantly using the multimeter.

    D. Testing

    To ensure that our work this well done, we tested the continuity of the copper tracks. Using the Multimeter AMPROBE 37XR -A, select the option of continuity, which resembles a wave. Then with tips positioned correctly test, proceed verification.

    By joining the points on the screen should show a resistance value, and additionally must make a sound. If the tips are joined not worth OL shown. We perform continuity test on both boards. For the controller board with the help of FABISP, we charge a test program from TERMINAL in Ubuntu, which turned us successful, and as proof, the red LED is lit on the board. Therefore the controller board ATTiny44 is ready to be programmed.

    E. Conclusions

    I feel that in this week I just scratched the surface of the wealth of skills, techniques and tools needed for producing good electronic designs. The PCB layout alone looks really like an art that will take lots of practice to be mastered. For which the many options available really require more dedicated time to be full understood.