Monday, February 15, 2016

Saturday meeting

We got together on the 13th for a bit of chat and fiddling with our projects.

The yet-unnamed Water Tank Bot  (WTB?) took a big step forward with test mounting the body.   It has 3D printed custom brackets mounting the tank bottom to the supporting seat frame atop the wheelchair chassis.

The tank doors came out really nice using a very simple but smart build sequence.  First, the hinge line was cut in the tank.   Next, the piano hinges were mounted via pop rivets, and then the final cuts in the tank were made on the top, bottom and split center of the doors.   The doors swing easily and have perfect alignment.

Behind WTB? is the CopperBot, which recently had some detail work for better antenna mounts, less camera vibration, and securely mounting the RCA 833A tube.

The First Person View base station was rigged up on the bench for a demo and to measure power requirements.   With the receiver and 7" display, it's pulling 0.416 amps off a 12v SLA.   It will need a bit more power with a small audio amp and speaker.

Tuesday, February 2, 2016

Copperbot Moving Test

Here is a short video of the CopperBot driving around:

The speaker and FPV video camera servos are being exercised by the Raspberry Pi through their range of movement while it's driving under remote control.    While this may not appear exciting, two problems had to be solved to get here:

First, the Raspberry Pi would reset whenever the R/C started driving the bot around.   This was solved by adding some electrolytic capacitors on the power supply at the Arduino and servo boards.

Next, driving the bot was difficult to control, which turned out to be bad configuration of the Sabretooth controller.   Switching the mode to "independent" matched the R/C transmitter programming, and now it's much intuitive to control.

The Raspberry Pi also recorded compass, accelerator and gyro data while moving.   Later processing it in a spreadsheet, I was able to derive code that will give it good compass heading data.   The sensor suffered from a lot of vibration, however, so the frame needs reinforcing and the data will need smoothing to hopefully mitigate the shaky information.

Saturday, January 23, 2016

Introducing CopperBot

Here are a few pictures of something that's been in the works for a while: a Remote Operated Vehicle called CopperBot.

The CopperBot ROV is built on an electric wheelchair base, giving it an excellent weight load and outdoor mobility.    The hardware has evolved from simple R/C control with the addition of a live audio and camera feed, a Raspberry Pi, and a stereo audio amplifier with articulated speakers.   It is a work in progress with lots of future modifications imagined.

As you can see, the structure is constructed mostly from copper PC board and wire.   The boards are from a surplus collection and are easy to work with wire to create structures, shapes and hardware mounts.

The Raspberry Pi camera and FPV (First Person View) video camera are mounted on a homebrew pan/tilt servo assembly, with a 5 ghz transmitter sending live audio and video to the base station.   This lets the pilot look around without the bot moving.

The radio link works great, but I need to package the base station hardware.   Currently it's a pile of components strewn across a table, wired together and working, but not portable.

The CopperBot design isn't pure utilitarian, nor was there a lot of formal engineering design.   It was built and grew organically as hardware expanded and new modules were added, but each part needs some thought about strength, weight, power and wiring, position for access and possible replacement or repair.

The RCA 833A above is along for the ride purely for the reason it looks awesome.   The mounting still needs work to allow easier removal.   The Raspberry Pi is behind it to the right, and the stereo amp is the smaller blue board to the left.

Looking to the back, the venerable 827-R transmitter tube visually powers the rig with a copper heat sink, partially hiding the actual motor controller below.

CopperBot is now mobile, can play music and make noises, look about with the camera live feed.   The Pi can move the camera and speakers, and soon will be switchable for motor control.   It can connect to a network, and the Pi provides a simple web API for data and commands.

CopperBot is intended to be interactive.   It supports text to speech over wifi and thus the pilot can talk dynamically with people while also controlling sound effects, lights and music.

A gyro / accelerometer / compass will soon go behind the transmitter above the wheel axis.  It will send position and motion data to the Pi.  In the future, it will be interesting to see if the data might be used for inertial navigation.

A second Raspberry Pi might be added to split up the load of sensor reading, hardware control, network wifi access and routing, base station web services, a web site, camera operations, text-to-speech synthesis, sound effects and whatever else gets added.

There are a lot of ideas to keep busy in the coming months:  adding a programmable LED lighting system, building a nicely packaged base station, the software interface, perhaps a second Raspberry Pi.   It really needs a cup holder, could carry a cooler.   Some more practical additions might include a protective shell body and an electric string trimmer.  

There is plenty of room to evolve ... and add more copper.