10/2018 – 12/2018
Gecko Robotics develops and operates robots to perform infrastructure inspections. During my internship, I designed and assembled PCBs to aid in these assessments.
Camera switching PCB
To help the worker drive the 100ft tethered wall-climbing robot, a front and back-facing camera must be integrated into the robot. The cameras need to be able to switch between viewing the front vs. viewing the back. I created 2 different designs to enable 2:1 camera switching.
I designed and assembled a 4 layers PCB that handled different signal integrity issues. The creation of this board required: a digital switch that could handle the nominal data bit rate of 1.485Gbits/s, differential signals used to reduced common-mode noise by allowing for traces to be as close together for max noise rejection that connected to 50-ohm impedance cable equalizers (cable equalizers used to return attenuated high-frequency signals caused by skin effect and dielectric losses back to their normal signal), a cable driver used to switch the camera signals, and 75-ohm impedance single-ended traces treated as transmission lines and proper impedance matching of coax cable to prevent reflection of signals.
I created a 2:1 camera switch PCB schematic for an analog camera (TVI). This schematic was implemented into other engineer's peripherals boards for the robot. Due to the fact that TVI cameras are not thoroughly documented regarding signal speed, a TVI camera was hooked up to an oscilloscope to see how fast the switching speed needed to be, which was noted to be speeds less than 250MHz. To provide the voltages for switching speed for this analog camera a (-) and (+) voltage need to be used for the internal amplifier. A -5V was created through a voltage inverter that was then used for the highspeed multiplexer to switch the analog signal, Proper 75ohm impedance termination to prevent signal reflection is also used in this design.
During my internship I also created some different breakout boards to go inside the robot
High current tether breakout board
I worked with mechanical engineers to make a board that would fit inside the robot and breakout connections from a tether to other boards. Calculations were made to find how thick the copper layers needed to allow the board to handle 15A coming out of the VCC pin (distance between the yellow arrow on the backside of PCB).
High voltage Coax ethernet breakout board
Worked with mechanical engineers to make a board that would fit inside the robot and breakout connections to a coax connector, ethernet, and high voltage. Calculations were made to figure out how thick the high voltage traces needed to be to handle 365V.