SunRover Solar Powered Robot Computers Installed
Recently, we pulled the equipment bay off of SunRover and replaced it with a bigger box and a better power and ground distribution system. We did this specifically because we were having problems with some of the electronics when the motors were stopped with the TRex “brake” command. This was injecting a large spike of noise into the SunRover system and causing a few boards to flake out, but interestingly, not the computers. See here for a more through discussion of grounding in robots.
Below is a picture of the current Equipment bay with some of the major components installed. There are two more layers of electronics to be added, through the use of our “circuit board condo”.
Below is an annotated picture of the new Equipment Bay. Note the liberal spacing of power and ground distribution screw terminals.
Power on is Tomorrow
Before we power on the equipment bay, we will do another complete check of the power and ground distribution system to make sure it is all connected and is not shorted together or mis-wired anywhere.
What is SunRover?
SunRover is a tracked solar powered robot designed to move around and explore the area while sending back reports, tracking weather, managing a power budget tightly and providing a platform for testing new sensors and equipment as they become available.
The Block Diagram
The major subsystems are shown to the right. It takes a lot of thought to put together a good block diagram. You make a lot of design decisions that might be difficult to change later in the design. Here is a list of the major system decisions:
- Use a prebuilt Track and Motor controller system
- Solar Powered system
- Solar Panels will be shifted from one subsystem to another according to demand and task set
- Two major computers: Raspberry Pi 2 for higher levels of control and an Arduino for power management and turning devices and sensors on and off
- Dual WiFi communication Paths
- SunRover control panels using RasPiConnect [ www.milocreek.com]
I realize I am looking at an unfinished assembly but it looks to me like you have doubled up on some of the power wires but not gone to the trouble of twisting power and ground other than one red/blk pair. If you still have some interference problems then such might help the situation. I also see loops of power going from one strip to the next, I would be for keeping these as short as possible.
David,
Excellent points. The main thing we wanted to accomplish with this redesign was reducing the noise coming from the motors into the electronics. So, the main thing to do, after a bunch of checking and testing, was to reduce the incidence of ground loops. Hence the focus on having a heavy copper connecter, looped around the box with “star” connections for grounds running off the main ground. Your point about wrapping the power wires with ground connections is a good one and we will do that. Plenty of room still in the box. Power and ground going into the motor compartment will have a ferrite bead on them and also will be wrapped together. The motor chassis ground is not going to be connected to the equipment bay ground.
While we liked the smaller box for robot, we now know just how bad of a power distribution design it was. Live and learn!
Thank you for your comments!
SDL