This week turned out to be a stubborn, frustrating struggle to get the drive motors under computer control. The libraries for the MiniMoto controllers I had purchased didn't work - the example wouldn't even compile. It was developed on an older version of the arduino IDE, so maybe that explains it, but I spent a lot of hours trying to get it working. Eventually, I decided to use my own motor controller card (that I had designed to control pump motors). All I had to do was assemble a second card, add some diodes to allow different drive voltages to be selected and change the I2C address so it didn't conflict with the pump card. I could get up to 16 speeds per motor, but after experimenting with loading the motors, I think I will limit it to just 3 speeds. Fortunately I had enough parts to get it all working. Also it is good that I had not designed the chassis yet as this card is a different size from the original modules I bought.
This week was a lot of work for just a little progress, but the build is coming along - all 10 motors are now under computer control (steering, locomotion and 8 pumps). I still need to reconfigure the steering driver FETs to operate in an H-Bridge so I can reverse the motor, which means I have to find some P channel FETs to replace a couple of the N channel FETs.
The main drive motor is definitely a little weak for this application as I discovered during my loading tests - hopefully it will be strong enough.
There is already enough electrical functionality working to be able to print graffiti - I just need to get the chassis designed and of course to design the software.
I might try to get the RTD working (to finish off the electrical subsystems) before diving into the mechanics and hydraulics.
Also I'm still waiting for the steering bearing, if it doesn't arrive soon, I may need to design a 3D printed plastic bushing.
Relevant Links
Sixth Sense Design Challenge: About This Challenge
Sixth Sense Design Challenge: Technical Documents
GraffitiBot Project Blogs
Sixth Sense GraffitiBot - blog 1
Sixth Sense - Kit Unboxing and Other Parts - GraffitiBot blog 2
Sixth Sense - Sensor Circuits - GraffitiBot blog 3
Sixth Sense - Interfaces - GraffitiBot blog 4
Sixth Sense GraffitiBot - System Interconnect - blog 5
Sixth Sense GraffitiBot - Wheels & Motors - blog 6
Sixth Sense GraffitiBot - ST Sensor Tile App - blog 7
Sixth Sense - Load Cell PCB - GraffitiBot blog 8
Sixth Sense - Magnetic Angle Sensor - GraffitiBot - Blog 9
Sixth Sense - LCD Interface - GraffitiBot - blog 10
Sixth Sense - Pump Controller - GraffitiBot Blog 11
Sixth Sense Main Drive Motor - GraffitiBot - blog 12
Sixth Sense Motor Controller Mods - GraffitiBot blog 13
Sixth Sense - RTD - GraffitiBot Blog 14
Sixth Sense Mechanical Design - GraffitiBot Blog 15
Sixth Sense GraffitiBot Motor Wiring - Blog 16
Sixthe Sense GarffitiBot - First Dry Run - Blog17
Sixth Sense GraffitiBot Hydraulics - Blog 18
Sixth Sense GraffitiBot Printing Graffiti - Blog 19
Sixth Sense GraffitiBot - Summary - Blog 20
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