insert the electronics. In the past, I have tried using a six
inch coupling with one end threaded and then using a six
inch threaded plug. Even with the use of Teflon tape
around the threads, there was still some leakage. These
large threads were made to have pipe-joint compound for a
tight seal, which does not work well for ease of removal.
Instead, I used a six inch black rubber cap sealed with a
metal hose clamp; this has worked very well. The entire six
inch tube is held in place underneath two 1/2 inch PVC
cross pieces at the top by two eight inch band clamps.
The top of the main tube has a 1/2 piece of Plexiglas
vertically glued with marine epoxy for attachment of the
up/down motor, and two 1/2 inch PVC threaded couplings
also glued in with marine epoxy to receive the PVC plugs
containing the wires feeding into the tube.
A Hall-effect switch was added with a third 1/2 inch
PVC threaded coupling glued into the main tube. A Hall-effect switch and LED are potted into the coupling with
marine epoxy. A 1/2 inch PVC plug with a Neodymium disk
magnet cemented into it acts as the switch. When the plug
is screwed into the coupling, it triggers a 12 volt 20 amp
relay inside the main tube, activating the 12 volt circuitry.
The relay contacts are wired in parallel with the main power
switch. This allows power to be turned on and off without
having to open the main tube. This circuit continuously
draws about eight milliamps of current from the battery,
which is not a problem for a 15 amp-hour battery.
That’s all for this installment. In the next issue, we will
cover the electronics package that reads the joystick and
linear potentiometer, and then controls our motors. SV
SERVO 03.2016 41
Item Description
A1 Adafruit 9-DOF (Optional)
B1 12V 15AH
B2 9V Battery
BTS7960B Motor Driver ( 3)
C1 1,000 µF, 16V
C2 2,700 µF, 6.3V
D1 Blue LED
F1 18A Mini Circuit Breaker or Fuse
FL Flood Lamp (Optional)
H1 Hall-effect Switch 3144
J1 Three-pin Header
J2 Three-pin Header
J3 Three-pin Header
J4 Four-pin Header
M1 Left Motor, Johnson Pump 500
GPH
M2 Right Motor, Johnson Pump 500
GPH
M3 Up/Down Motor, Johnson Pump
500 GPH
P1 Header Socket
P2 Header Socket
Q1 TIP127 PNP Darlington Transistor
R1 8.2K 1/4W Resistor
R2 4.7K 1/4W Resistor
R3 1K 1/4W Resistor
R4 1K 1/4W Resistor
R5 5K 1/4W Resistor
R6 5K 1/4W Resistor
R7 20K 1/4W Linear Potentiometer
R8 4.7K 1/4W Resistor
R9 8.2K 1/4W Resistor
R10 4.7K 1/4W Resistor
Relay 12V 20A Contacts
Switch 20A Contacts
Switch Mini Toggle
U1 Arduino Nano
U2 Arduino Nano
U3 LM7805 5V Regulator
Video Camera, NTSC
Miscellaneous
1/2 inch PVC Pipe
1/2 inch PVC Elbows
1/2 inch PVC Tees
1/2 inch PVC Threaded Couplings
1/2 inch PVC Threaded Plugs
Six inch PVC Pipe
Six inch PVC Pipe Cap
Six inch Rubber End Cap, with Band Clamp
1/4 and 1/2 inch Plexiglas
PVC Cement
Marine Epoxy
Silicon Cement
Eight inch Band Clamps
Nylon Cable Ties
Various Screws, Nuts
Hookup Wire
Cat5 Cable, 50 feet
Petcock Valves ( 2)
Ceramic Tile