inside. I tried a 4 x 4 x 4 inch box, and while I could
squeeze everything inside, working with it was just too
difficult. With a custom designed PCB, a 4 x 4 x 4 inch box
could probably be used.
When I designed the PCB, many additional general-purpose pads were added to accommodate additional
circuitry. This worked very well when changes were
necessary as the design progressed.
The pin-compatible Teensy 3. 2 has replaced the Teensy
3.1, but since I had a Teensy 3.1 on hand, I used it. The
additional program space and clock speed (compared to
some of the Arduino models) were helpful with this
The Quad_ROV includes an onboard video camera
with a standard NTSC video signal sent back up the tether
on a twisted pair. This NTSC signal then connects to an
RCA style jack mounted on the joystick controller box.
This is a very simple and inexpensive 12 volt camera,
available in many styles on eBay or Amazon as well as other
The style I chose has a small sensor and lens mounted
on a 1-1/2 inch square PCB that makes mounting it easy.
This camera was selected because there’s not a steel case
to magnetically interfere with the Adafruit 9-DOF. This
camera is simply an aid when moving the Quad_ROV
underwater since the image is not high quality.
If higher quality video is desired, something like a
watertight GoPro camera can be easily attached to the top
platform of the Quad_ROV.
The 450 mm quadcopter frame kit was assembled
according to the supplied instructions. I used stainless steel
screws in place of the ones supplied, and used Loctite Blue
Threadlocker on all the screws when assembling the frame.
As mentioned previously, the circular motor mounting
plates weren’t used and 1/4 inch thick Neoprene rubber
was substituted. Vibration can be a real problem for the
sensors, and this greatly reduces vibration from the motors.
The motors are mounted upside down from a normal
quadcopter (since the boat propellers push instead of pull
as previously mentioned).
A 1/4 inch thick piece of expanded PVC measuring 6 x
2-3/8 inches was screwed to the bottom piece of the
quadcopter frame. This piece then has two holes that allow
1/4 - 20 bolts to attach the plastic junction box. Stainless
steel screws were used throughout (see Figures 2 and 3).
To reduce vibration between the arms and the junction
box, three layers of 1/4 inch Neoprene rubber were used;
one between the bolt head and washer and expanded
PVC; one between the expanded PVC and junction box (as
wide as the expanded PVC and the full length between the
bolts); and one between the junction box and nut with
Added to the top of the arms at the ends is a set of
four 1/8 inch expanded PVC pieces attached above the
motors. The ends were rounded, so these serve as
propeller blade guards to prevent the propellers from
28 SERVO 12.2017
Figure 2. Top of the 450 mm quadcopter frame, before motor mount
disks were replaced with Neoprene rubber.
Figure 3. Bottom of the 450 mm quadcopter frame, showing 1/4 inch
expanded PVC measuring 6 x 2-3/8 inches.