then not all of the pins in the bus are
C. 2 (I/O)
Commit (Input only)
Commit (Input only)
B. 2 (I/O)
B. 3 (I/O)
B. 5 (I/O)
B. 6 (I/O)
B. 7 (I/O)
+5V (Regulated five volts)
Vin (Input voltage)
C. 6 (I/O)
C. 7 (I/O)
Each plane was created on
FreePCB, and based on a generic
plane I initially created. Opening the
generic plane and then modifying it
for a new one ensures that the new
plane fits the other existing planes.
Each plane has the dimensions of
a PC104 card, and has a minimum of
the 2 x 18 pin SIP and four 1/4”
diameter holes in the corners. When
stacked together with the SIP and
spacers, each plane is 5/8” apart.
The Planes (So Far)
To date, I am happy with four
planes that I’ve created. There is
more work to do with regard to
tweaking older planes and building
new versions. For one, I found the
Model CubeSat could use all the I/O
on the bus, so I will need to focus
more attention on the PICAXE-18M2
version of the control plane.
Currently, I’m experimenting with
the following planes as I write this
article: power; microcontroller;
photometer; and radio.
The initial version of the power
plane uses four “AAA” cells, but will
eventually contain a rechargeable
lithium polymer battery. That’s
because I find it’s too much trouble
to destack the CubeSat when the
batteries are dead.
Real CubeSats use hot wire
cutters to release deployables like
antenna elements and solar panels.
That’s too hazardous for students, so
instead, the power plane (which is
always located at the bottom of the
stack) contains a micro-servo that lifts
a pin to release CubeSat deployables.
For now, I’ve bolted a length of
metal tape measure to the top of the
CubeSat’s airframe to act as its
deployable antenna. Attached to the
ends of the metal tape are loops of
Dacron string that reach the metal
pin attached to the micro-servo’s
horn. When the servo rotates up, it
lifts the pin and releases the antenna
elements. The antenna then snaps
out with a pop that will startle you if
you aren’t prepared.
Soldered to the underside of the
power plane is a momentary tactile
This replicates the switch
CubeSats use to detect that they’ve
72 August 2015
The Model CubeSat kit contains a
series of PCBs like this one.
Instructions included in the kit —
along with the top silk on each
PCB — will explain the proper
placement of the electronic
The current radio used in the Model CubeSat doesn't need an
antenna. So, the “antenna” is just bolted to the top of the CubeSat's
plastic frame. In the future, I plan to connect the antenna to the radio.
That way, an amateur rocket can launch the Model CubeSat several
thousand feet into the air where a ground station can communicate
with it during its descent.
The power plane with its
battery holders, switch, and