New Printed Circuit Board
After getting all the bugs worked out both in hardware
and software, a new compact PCB was designed for a four
inch box. This PCB (shown in Figure 1) contains all the
original features of the prototype design with some
additions mentioned in the Thoughts on Improvements
This 3. 8 inch square PCB can be installed in the 6 x 6 x
4 inch Cantex junction box as shown in Figure 2, but
should also just fit into a 4 x 4 x 4 inch Cantex box when its
corners are cut off.
Wire placement will be a challenge in a 4 x 4 x 4 inch
box. Be aware that there are other brands of these size
junction boxes that look similar to the Cantex boxes, but
their inside dimensions are smaller.
An ExpressPCB layout of this PCB is in the downloads
for this article. It includes the part positions on the board. If
you don’t already use ExpressPCB, it’s an easy matter to
download their free software so you can read the layout
and see the part positions.
Here are some important things to know about this
1. A header plug for an Arduino micro SD card
breakout board was included. This uses the SPI lines on the
Teensy 3.1/3.2. Jumper wires will be necessary for
connecting to the SPI pins 10, 11, 12, and 13 on the
Teensy 3.1/3.2, which are brought out to pads and then
connected to other pads just above the header plug for
the SD card. The SD card board is not necessary for
operation of the Quad_ROV, but was added for possible
troubleshooting. No code to write to the SD card appears
in the software.
2. The ESCs (electronic speed controllers) are
mounted vertically, with the power lines connected to the
PCB by 3. 5 mm bullet connectors. The positive
connections are at the edge of the board.
3. An LED with a limiting resistor is connected to pin
A2, and a second LED with a limiting resistor is
connected to pin 9. These can be used for any purpose.
An LED with a limiting resistor for a power indicator was
added to the 12 volt supply. The limiting resistor for the
power indicator may have to be installed on the bottom
of the PCB, depending on the size of the filter capacitors
used. If these LEDs remain inside the box, they may need
to be shielded from the video camera window as they
could cause reflections in the window and obscure the
video image. These LEDs can be installed in the box wall
to point outside by using marine epoxy in an
appropriately sized hole for the LED.
4. The four resistors installed under the Teensy
3.1/3.2 can also be installed on the bottom of the PCB.
A socket for the Teensy 3.1/3.2 is recommended, and may
necessitate installation on the bottom of the PCB.
5. The Adafruit 9-DOF board is installed upside down
and hung from four small rubber bands connecting the
holes on the board to size 4-40 stainless machine screws
installed in holes just outside the outline of the Adafruit 9-
SERVO 01.2018 35
Figure 1. The four inch PCB with all components soldered and partially
Figure 2. The four inch PCB mounted in the 6 x 6 x 4 inch Cantex box.