nylon cord to the U-bolt. If the propulsion system fails,
this cord will be used to pull Pool Bot to the surface.
Test the completed Pool Bot on dry land before you
attempt your first “sea trial.” There are four main tests that
you should perform: propulsion system (e.g., press an SPDT
button and the correct motor should turn in the proper
direction); lighting system (e.g., turn on each LED switch
and seal the LED inside its respective jar); camera system
(e.g., turn on the closed-circuit monitor and ensure that you
are receiving a good video signal); and analog recovery
system (e.g., lift Pool Bot up off the workbench by pulling
on the nylon cord). If all tests are completed successfully,
then move onto your first sea worthiness test. If, on the
other hand, any of the tests were not successful, make
corrections to your construction and try the tests again.
Never attempt a sea worthiness test without a
100% successfully tested Pool Bot!
Before throwing Pool Bot into the swimming pool, a
sea worthiness test must be successfully performed. The
main objective with this test is to establish the buoyancy of
the ROV. Ancillary ballast and trimming will also be
necessary during testing.
First of all, disconnect the power supply from Pool Bot.
Likewise, switch OFF both LED lighting systems. Use a two
to three foot deep container filled with water (e.g., laundry
room sink, bathtub, barrel, etc.) and set the ROV into the
water. Ideally, Pool Bot should float perfectly level just
below the surface of the water. Flat washers are used as
ballast for obtaining the proper buoyancy, as well as for
trimming and/or balancing the vessel.
Carefully slip flat washers over the center keel pipe
piece. Depending on the air volume and glass thickness of
your jars, this step could take quite a few washers. Once
the proper buoyancy has been determined, slide the
washers forward and backward until the ROV rests perfectly
level just below the surface of the water. Secure the
washers in this position with two cable ties (one tie added
ahead of the washers and the other cable tie fixed behind
the washer line-up). If Pool Bot appears to be listing to
either port or starboard (i.e., tilting to the left or right), the
vessel will need to be trimmed. In order to trim your ROV,
slip a washer over the two inch support standards inside
each of the four elbows. Use as many washers on any/all of
the four elbows as needed to trim your ROV.
When all of the trim washers have been added, secure
each stack with a cable tie. Pool Bot should now be ready
for its maiden voyage.
Take your entire underwater ROV setup outside and
connect the power supply to Pool Bot. Test each propulsion
control switch to ensure that you have adequate power for
this voyage. If power looks good, flick each LED switch ON
and seal each jar, lower Pool Bot into the water, and press
the descent (Y axis; down) motor button. Away she goes!
Slowly pay out both the power supply umbilical tether
cable and the nylon recovery cord. Don’t be tempted to
braid the cable and cord together. One accidental tug on
the nylon cord could sink Pool Bot in a power loss short-circuit crash. Watch the video signal on the closed-circuit
monitor and methodically apply short downward thrust
bursts coupled with short bursts of forward (Z axis) thrust.
If properly balanced and trimmed, short motor runs are
ideal for navigating Pool Bot.
Once you’re comfortable “driving” your ROV around
the swimming pool, try to make your way over to the big
dark mass that you initially found lurking around the pool’s
drain. A skillful skipper should be able to glide up to that
mass and retrieve it with the aquarium net. Don’t be too
surprised, however, if that stagnant dark mass turns out to
be a slumbering snapping turtle that doesn’t like ROVs
disturbing its sleep. SURFACE! SURFACE! You’re probably
going to need a bigger boat! SV
Ballast. Flat washers are added to the center keel pipe piece
for establishing the ROV's buoyancy.
SERVO 05.2014 51
Pool Bot Parts List*
Two empty olive jars w/lids
Six Schedule 40 1/2 inch tees
Four Schedule 40 1/2 inch elbows
1/2 inch x four feet Schedule 40
7/8 inch flat washers (as many as
needed for ballast and trim)
14 inch cable ties
Waterproof automotive backup
camera (e.g., Etekcity 12V
Two bright white LEDs
Two 3. 7 volt LiPo batteries
Three Tamiya submarine motor
kits (e.g., Tower Hobbies,
Six SPDT switches (e.g., C&K
Components EP12, $4.83 each)
Three 9V battery connectors and
7812 voltage regulator
Tube waterproof silicone sealant
20 feet nylon rope
1/2 inch U-bolt with hardware
22-gauge stranded wire
Black construction paper
* This list also includes the
components for all of the optional