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Sixth Sense Design Challenge

21 Posts authored by: dougw Top Member
The Sixth Sense Design Challenge had a mystery finisher prize which just arrived. It turned out to actually be 3 prizes, all very cool. There was an arduino MKR Zero which is a small but powerful MKR arduino with an ARM Cortex M0 and an SD card slot. This is a very useful form factor and will be the basis for a great project, as yet undecided. There was an arduino MKR 1000 which also has an ARM Cortex M0 but it also includes Wi-Fi. Another great project waiting to be launched. The third priz ...
  GraffitiBot is a fully autonomous ground vehicle capable of printing graphics on the surface it is traversing. This crude attempt artistic rendering at writing "E14" demonstrates what the GraffitiBot accomplished on the last day. Update The challenge has ended, but I did not stop experimenting with the GraffitiBot. As shown above, the bot spays too much fluid and drips where it shouldn't. I had ordered some syringe dispenser needles to achieve more precise nozzle flow, but they did no ...
Well - it is the last day of this marathon design challenge and everything pretty much needs to go flawlessly to produce actual graffiti. But of course a lot of things are not going right. All the subsystems have been tested and are working well, but the bot is just making puddles. I thought the nozzles would be problematic, but the main drive is not running properly, so put on the troubleshooting hat and dive in. It looked like the batteries were dying, so take some time and charge them up. Sti ...
The GraffitiBot is now fully functional for printing graffiti although there is still a lot of room for improvement of the print head nozzles.  It took quite a bit of work to get the hoses to curl properly without kinking. The kinks were making it difficult to purge air bubbles from the hoses. It was also very difficult to get each individual nozzle to be clear and smooth. The pores are so small, any tiny whisker of plastic completely messes up the output. I have some tiny drills, but they ...
This is a big day - the GraffitiBot made its maiden voyage! This was just the first attempt at programming an autonomous route that would test the steering and the main drive. It is literally a dry run, there are no pumps or even reservoir on board. I could spend some time to make it look more impressive and get some better camera angles, but I need to start working on the hydraulics - the nozzles need a lot of work, not to mention the software. Getting this far has taken a lot of work, bu ...
I have finally managed to wire up the motor controllers to the MCU. Here is a video showing what it looks like: Next I will try to program the MCU to run the steering and drive motors in a simple autonomous route. There is nothing like trying to make a full system run properly in one day while avoiding catastrophic errors, but what is life without a little drama....   Relevant Links Sixth Sense Design Challenge: About This Challenge Sixth Sense Design Challenge: Technical Documents Sixth ...
Another eventful week - most of it spent in Washington, has made the rest of the week ultra busy. The challenge deadline is looming and the mechanical design really needs to get done so I can start wiring everything up. The design of the front end and the chassis turned out to be quite complex, partly because there are limits to what a 3D printer can do and I always try to print without any support structure. Here is a video of the CAD models: Unfortunately my CAD software cannot animate the ...
The PTF Series PTFM101C1G0 RTD from TE Connectivity is a platinum RTD making it very stable and accurate and it is tiny as shown in a previous blog, allowing it to respond quickly to temperature changes. Although the Nucleo MCU has a 12 bit A/D converter, I wanted to implement an RTD interface with even higher accuracy. I chose a Maxim MAX31865 chip which is specially designed to handle RTDs with its internal 15 bit A/D converter. This chip has an SPI interface and is mounted on a small circuit ...
This update explains how my pump controller circuit card was modified to allow it to control the steering motor and the main drive motor. The steering motor needs to be able to reverse, so the unipolar outputs needed to be altered to work as an H-bridge. This required replacing 2 N-channel FETs with P-channel FETs and tying some drains together. The FETs are individually controllable via software, so high current shoot-through can be avoided by turning off one direction before turning on the ot ...
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, ...
Thankfully the final PCB has arrived back from the printers. Today I assembled the fourth and last custom PCB for the GraffitiBot project and fortunately it went together without any problems. The schematic and board layout were published in blog 4. This card uses an MCP23008 I/O expander with I2C interface to drive 8 FETs that control the pumps. I had to use this chip because I ran out of microcontroller pins to control all the pumps. The field effect transistors have a very low gate thres ...
This is the big milestone tenth blog in this design challenge, but there is still a lot of work to do with only 4 weeks left. My LCD PCB finally came back from the being printed, so I can connect up the liquid crystal displays and start programming. The schematic design and PCB layout were covered in blog 5. Here is what the bare card looks like: It is red because that was the lowest cost color at the time of ordering. Here is what it looks like assembled with connectors for 2 LCDs, 3 sens ...
This blog describes assembly and testing of the TE Connectivity magnetic angle sensor. The circuit design was described in a previous blog. The PCB arrived a couple of weeks ago, but I had to wait for parts to build it. I had ordered parts from Newark using a shopping cart I won in a Project14 contest. They came in this week accompanied by an $18 shipping charge but I am now able to assemble these cards. Here is what it looks like. Note the sensor chip is on the underside of the card to allo ...
I finally received enough parts to assemble the load cell signal conditioning circuit board. The circuit schematic and PCB layout for load cell signal conditioning were covered in a previous blog. The TE Connectivity FX1901 load cell will be used to measure the amount of fluid in the Graffitibot reservoir by weighing it. It isn't clear which variant of load cell (in terms of full scale output) I have, so I will have to hook it up and see what the output looks like. Also I am not quite sure h ...
Two of the PCBs I designed for the GraffitiBot came in but I won't have enough components to assemble them until at least next week. Here is what they look like: One interfaces to the load cell and one interfaces to the magnetic angle sensor.   While waiting for parts I have started looking at the software. ST Microelectronics has written a lot of software for this sensor tile and I am including some of the links in this blog. There are multiple links on each of the pages I have linked. ...