by Jeffrey Putney | Mar 30, 2015 | Fab Academy
Table Design I started by creating flower table design in tinkercad. I then used 123D Make to turn the 3D model into a 2D cut plan for the CNC Machine. I was then able to import the cut file into Rhino where I had to edit the file and add drill points at every inner corner so that the pieces would easily slide all the way together. This isn’t a perfect solution but it does take care of the fact that our cutting bit has a certain radius and can’t cut all the way into corners. At this point the file was ready for the CNC Machine. CNC Time So it was off to the hardware store for some 3/4 inch MDF board. Because our Fab Lab doesn’t have large CNC Machine we had make friends with the architecture students who have a facility next door to us. They were nice enough to let use their machine for a weekend to get our projects done. We used there C.R. Onsrud 98C machine for our projects. The work flow was straight forward as they usually use Rhino for their projects and had a presets ready to go for generating files that cut MDF on the machine. I used a 1/2 inch cutting bit for the project. All I had to do was load up the file and hit run and I had a new flower shaped table. The hardest part was probably sanding all the edges. MDF cutts pretty rough and makes a mess when you sand it. But after it’s sanded it actually looks quite good. After sanding I just...
by Jeffrey Putney | Mar 16, 2015 | Fab Academy
Datasheets and Software Serial This week I read through the ATtiny summary datasheet. The main thing I learned is why the standard serial communication library can’t be used with the ATtiny44. Looking at the Arduino Serial library I saw that it mentions it uses a chip’s UART for communication. But our ATtiny’s apparently don’t have UARTs. As you can see if you search the ATtiny summary datasheet you won’t find a UART. Luckily the SoftwareSerial library has been written which implements the UART functionality in software and that library has been bundled into the Arduino environment. The Datasheet also mentioned the QTouch library which I would like to learn more about in the future. This weeks project This week the plan is to create a microcontroller board that provides 2 way communication with the serial port on the computer. I started testing by opening the Examples->SoftwareSerial->SoftwareSerialExample in the Arduino software. At first this refused to compile for the ATtiny44. I realized from the code comments that this example file was attempting to also use the hardware serial port: //Receives from the hardware serial, sends to software serial. //Receives from software serial, sends to hardware serial. So I went through and removed all the references to the Hardware Serial connection, which look like this: Serial.begin(4800); //Start Hardware Serial Connection Instead of this: mySerial.begin(4800); //Start Software Serial Copnnection In other words we only want to work with the `mySerial` object, and not the `Serial` class. 2-way Serial Communication Code #include <SoftwareSerial.h> SoftwareSerial mySerial(0, 1); // RX, TX const int buttonPin = 2; int led = 7; int incomingByte = 0; // for...
by Jeffrey Putney | Mar 10, 2015 | Fab Academy
Motivation For my final project I need a solar collection system that can charge a battery in bright indoor condition. So for this weeks assignment I chose to design a circuit and subsequent board based on the TI BQ2505 Ultra Low Power Energy Harvester Chip and a 5V boost converter chip to so that this version can at least charge a cell phone. Circuit Design The first step was following the reference designs from the data sheets and creating a schematic in eagle. The trickiest part here was choosing all the resistor values to set the battery charge values and hysteresis points. Board Layout This took some time and iterations with trying to mill the boards. The only packages available for the two chips where no lead packages that required traces that only the .010 inch mill bit could mill out. To increase the chance that traces would survive milling I had to create copper pour sections that widened as soon as they left the chips pad areas. Milling I lost a few .010 bits before I realized the set screw was too striped and no longer tightning far enough Reflow Soldering This actually went pretty smooth. surface tention managed to seperate the almost all the solder between the smallent surace mount pins though a few had the be reflowed after with a fine tip soldering iron in order to get them to seperate. It worked!!!! Even under desk lamp lighting the circuit was able to power up and provide a charge current for the Li-po battery. The boost converter was also able to start up and provide a...
by Jeffrey Putney | Mar 7, 2015 | Fab Academy
Scanning For scanning this week I used an XBox Kinect and the ReconstructMe software package. The scan process was as simple as starting the script and rotating slowly while I stood in front of the Kinect. I then fixed a few holes and cleaned up the bottom edges with netfab Basic. To make sure eveything the final model was in good shape I opened it in Tinkercad and checked that I had some humanoidish object like looked a little like me. STL file of the scan can be downloaded here. 3D Printing The goal for 3D printing this week was to create something that couldn’t easily be made by a subtractive fabrication technique. So I chose to remix this Math Gyro Maker part that provided a good template for interlocking rotational joints. I modified the outer and inner ring to recreate the logo from the Heartland Maker Fest event I help organize. Here’s the first print from our Up Mini 3D Printer printing with ABS plastic: The rotational joints were a bit loose and could have been made with tighter tolerances, but they worked perfectly. And it’s a necklace! The final STL file can be downloaded...
