28 Sep 2016 · 2 min read
This week, I made a
FabISP,
an in-system programmer for AVR microcontrollers.
Milling the PCB
I milled a PCB (using these
traces
and
outline).
I used fab modules to calculate toolpaths for the
Roland SRM-20 milling machine, using all the default settings. I used a 1/64
end mill for cutting PCB traces and a 1/32 end mill for cutting the outline:
![](media/week3/mill.jpg)
After working through it carefully, everything worked on the first try, and I
ended up with a nice finished PCB with pretty clean traces:
![](media/week3/pcb.jpg)
Soldering Components
Next, I soldered the
components. Before starting, I picked out all the parts and made sure I knew what was going where:
![](media/week3/components.jpg)
As I soldered components, I tested for continuity to reduce the amount of time
I would have to spend debugging later. After about half an hour of soldering, I
had a board that was ready to be programmed:
![](media/week3/ready-to-program.jpg)
Programming
I used Debian 8 (Jessie) and followed the
instructions
for using Ubuntu (Ubuntu is based on Debian). I needed to use sudo
when
running some of the commands that talked to USB devices, but besides that, the
instructions worked perfectly.
After programming, I removed the zero-ohm resistor and solder joint to finish
my programmer:
![](media/week3/finished.jpg)
21 Sep 2016 · 3 min read
I used the laser cutter to build a press fit construction kit.
I’ve only used a laser cutter once before, and I didn’t really know what I was
doing back then, so in my design, I ended up with loose joints because I didn’t
understand what a laser kerf was. Back then, I compensated with epoxy glue, so
I didn’t end up with a nice friction fit design. This time, I wanted to make
sure I got it right, using a parametric modeling tool and making sure it was
really easy to tune the parameters until everything fit perfectly.
Design
I took the “press fit construction kit” part literally — I designed a part
that was designed to fit together with other copies of the same part, forming a
construction kit that could be used to make all sorts of (mostly very boxy)
shapes.
I used Fusion 360 to parametrically model a square shape with 3 cutouts on each
side for slotting into other copies of the same shape. Parameters included
things like piece size, slot spacing, and most importantly, material thickness
and laser kerf width.
![](media/week2/design.png)
Cutting
I was cutting this on a Universal PLS 6.75. When cutting, I had to experiment
with laser settings to get good results. Initially, I was using the materials
database, setting the material to balsa wood (it was actually cardboard),
0.160” thickness, with a +50% modifier for vector cutting.
![](media/week2/tuning.jpg)
That didn’t make clean cuts through the material, so I switched over to manual
control. I tried using 70% power, 8% speed, 300 ppi, and setting the thickness
to 0.160”. That worked a little bit better, but it wasn’t quite perfect — I
still didn’t get clean edges on some of the pieces I was printing. I tried
boosting the power to 75%, and I consistently started getting nice pieces.
Experimentation
After getting the laser cutter parameters tuned, I did my first real cut:
![](media/week2/first.jpg)
After playing around with the physical pieces, I felt that the notches were too
close together, so I tweaked the design and cut some new pieces. I was happy
with the new results, so I cut 60 copies:
![](media/week2/cut.jpg)
The pieces looked quite nice when neatly laid out on the laser cutter bed:
![](media/week2/copies.jpg)
Final Result
After printing, I ended up playing with the pieces for some time, and I ended
up with this art:
![](media/week2/result.jpg)
Bonus: Laser Cut Laptop Stand
After getting some experience with the laser cutter, I was interested in making
something useful for myself using the tool. I decided to make myself a laptop
stand, designed parametrically in Fusion 360:
![](media/week2/laptop-stand.jpg)
14 Sep 2016 · 1 min read
For my final project, I plan to make a large (~2 meter wingspan) RC glider
capable of serving as an FPV / aerial video platform.
I’ve made a quadcopter before, so I have some experience with building RC
vehicles:
![](media/week1/quadcopter.jpg)
Even though I built the quadcopter myself from parts, it wasn’t from scratch. I
used an off-the-shelf injection-molded frame, and I used an off-the-shelf
flight controller that runs open source software.
For the glider, I plan to do much more from scratch. I plan on buying a motor,
servos, a video camera, a radio receiver, and a radio transmitter. I want to
construct the airframe by hand, and I want to design and build my own flight
controller and program it myself. I’m also going to look into designing and
fabricating my own propeller, which I would like to do if possible.