Skip to content

12. Input Devices

For the group assignment, the task involves examining the analog levels and digital signals of an input device or devices. Participants are required to document their findings on the group work page and share personal reflections on their individual pages regarding the insights gained from the task. Meanwhile, for the individual assignment, each member will measure something by integrating a sensor into a microcontroller board they have designed and reading its data.

Assigmnent checklist

Item Activity Status
1 Linked to the group assignment page. Done
2 Documented what you learned from interfacing an input device(s) to your microcontroller and optionally, how the physical property relates to the measured results. Done
3 Documented your design and fabrication process or linked to the board you made in a previous assignment. Done
4 Explained the programming process(es) you used. Done
5 Explained any problems you encountered and how you fixed them. Done
6 Included original design files and source code. Done
7 Included a ‘hero shot’ of your board. Done

Group Assigmnents

In this assignment, we will address the following tasks:

  • Probe an input device(s)’s analog levels and digital signals.
  • Document your work on the group work page and reflect on your individual page what you learned.

Individual Assigmnents

In this assignment, we will address the following tasks:

  • Measure something: add a sensor to a microcontroller board that you have designed and read it.

Design - Autodesk Eagle 9.6.2 Education

  1. Schematic
  2. Board

Manufacturing: FlatCAM

  1. To configure the production, double click on the FlatCAM v8.991 beta application.
  2. Then we import the gerber file, being SMD we will use the “Top Layer” file.
  3. Then we align as much as possible with the first quadrant with the “Offset” tool we can zoom to verify the alignment and find the vector, however, in this case Vector: (-4.826, -0.254).

  4. We analyze the milling cutter to use Shank Diameter 3.175 mm Tip Diameter: 0.1 mm Angle: 30deg

  5. And the thickness of the copper of the fiberglass board, according to the conductivity tests carried out, the best value for the “Cut Z” was obtained.

  1. With this data we use the “Calculators” tool to find the tool diameter, which in this case gives us as a result 0.1965.
  2. We return to the gerber file and copy this value obtained to finally use the tool “Generate Isolate Geometry”.
  3. As a result we obtain the contour of the tracks and click on “Generate CNC Job” to create the .NC file that will be used in the Mini CNC. It is important to indicate “Cut Z” which in this case is - 0.035. We do not worry about the “Feed Rate” and “Spinde Speed” because we will control them manually with the DSP and the inverter respectively.
  4. This tab will appear and we click on “Save CNC Job”.
  5. In the “View CNC” section we can see the generated code and modify it if necessary, but in this case it will not be necessary.

  1. Click on “Save CNC Code” to select the location of the file and assign a name and click on “Save”.
  2. . Drills There are some components that are being used that need this type of files as is the case of the circuit power stage terminals that are the most suitable for these applications and commercially in Peru are not found in this type of SMD components. We analyze the drill to use and we see that it has a diameter of 1.4 millimeters.
  3. Then we click on the “Project” section and then we click on “File”, “Open”, “Open Excavation”, “Open Excavation” and “Open Excavation”. Open”, ‘Open’, ‘Open Excellon’ and select the file with the ‘Drills’.
  4. The “Excellon Object” tab will open, if it does not appear we can look for it in the “Project” section looking for the selected Excellon file and click on Drills.
  5. We do not worry about the “Feed Rate” and “Spinde Speed” because we will control them manually with the DSP and the drive respectively, but if we change the “Drill Tool diameter” by 1.4 and align the holes with the same parameter that we indicated with the tool “Offset” Vector: (-7.244,10.3) and click on “Create Drills Gcode”.

  1. Then this window will appear and we must click on “Save CNC Gcode”.
  2. Select the location of the file and assign a name and click on “Save”.
  3. Cutout We analyze the cutter to be used and we see that it has a diameter of 3 millimeters.
  4. We open a new gerber to cut the edges of the board which is usually found as “Cutout” or “BoardOutlineLayer”.
  5. As in previous operations we do not worry about the “Feed Rate” and “Spinde Speed” because we will control them manually with the DSP and the drive respectively, but we change the “Drill Tool diameter” to 3 and align the holes with the same parameter that we indicated with the tool “Offset” Vector: (-7.244,10.3) and click on “Cutout Tool”.

  1. Then we indicate the cutter diameter, the gap size, the margin and the number of gaps that prevent the part from moving during the machining process.
  2. Then we click on “Generate CNCJob Object”.
  3. Click on “Save CNC Code”.
  4. Select the location of the file to transfer it to the machine.
  5. Save this file in case it is necessary to make a correction later.
  6. Select the location where the file will be saved and click on “Save”.

The 3 Gcode files will be transferred to the machine for manufacturing on a USB memory stick.

How to straighten or flatten a buckled electronic board for machining?

Using a sacrificial plate, we will level the working surface of the machine by performing a pocketing or roughing on the plate.

  1. Place the bolts on the platform.
  2. Turn on the hot air gun.
  3. Set the temperature to 320 degrees.

  1. The bolt tightening pattern should be as follows.

  1. Apply the heat gun to the Bakelite surface in a circular motion at all times.
  2. Place the cover and the nuts without tightening them.
  3. Tighten the nuts with a wrench, avoiding overtightening the nut as this may cause damage to the MDF.

  1. Wait about 5 minutes until the bakelite plate cools down.
  2. Loosen the nuts and remove the cover.
  3. The final result is as follows.

Issues, musings, and learnings.

Last update: June 6, 2024