Monthly Archives: April 2016

Hardware

A makeblock 3d printer chassis

My Mendelmax 3d printer has come to age and I’m not anymore satisfied with the format and design, so when I found some 50% discount on makeblock parts at my favourite tech store EXP Tech, I decided to start a new 3d printer design from ground up using makeblock components.

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I’m not yet sure which basic hardware principle the 3d printer will finally have (CoreXY vs traditional 3 axes, but definitely not a delta system), using v rail sliders vs linear motion guides or traditional round motion shafts.

I bought so many makeblock parts that I might be able to test out any of these concepts.

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Further I was able to get a milling spindle and a capacitive distance sensor, and maybe I’ll add a laser engraving option later on.

Also replacing the electronics RAMPS and arduino with more capable stepper drivers and 32bit microcontroller with floating point support might change the way my old Mendelmax used to print things, allowing bigger speeds and more smooth and exact positioning than before.

We will see, lots of stuff to try out in my holiday.

Makeblock

Makeblock Lab Kit

Ordered a whole bunch of additional Makeblock components with a 50% discount at EXP Tech.

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Now I have enough components to re-create my 3d printer in Makeblock parts. There should also be enough parts left to build a few more wheeled robots for my son, or even a plotter.

 

 

Microcontroller

Connecting the Pixycam via NodeMCU WiFi

Finally, whenever I tried to connect my 4 Pixycam for realtime coloured object tracking for the Teddy Robot, I experienced trouble wheter connecting them via USB (saturating the USB Host adapter bandwidth, or colliding due to a previously non-existing Pixycam Device enumeration), connecting them via serial or I2C to my micropython boards (bandwidth problem, not enough serial lines for 4 cameras), connecting them via SPI (previously no slave selection support on pixies).

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Now with the NodeMCU board and SPI SS support in the latest Pixycam firmware, I managed to run the color object tracking code on only one microcontroller querying 4 cameras via SPI on one bus in full speed and even transmitting all the block data via Wifi to a websocket server.

With slower arduino or even maple or micropython STM32 boards this would have never been possible.

The websocket server has a low enough latency of 2ms, which is great via WiFi. When trying to relay the same data via MQTT I got a lot of stack traces again. One day I need to directly embed ROSserial via WiFi to see if the websocket translation into ROS can be omitted.

Microcontroller

Experimenting with the ESP8266 NodeMCU

Another microcontroller finally found its way into my hands.

The ESP8266 based NodeMCU is running at 80Mhz (or even 160MHz) and has WiFi built in for a ridiculous pricetag of only 10 Euro.

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Initially they come with an embedded LUA interpreter preinstalled, to allow some easy scripting of event based code rather than writing and compiling C code. As LUA is not completly reentrant after Wifi events and also consumes a lot of processing power, my projects will be further written in C, so I evacuated the LUA bootloader.

Compared to Spark Cores and their always connected to the cloud behaviour, they can be configured within the standard Arduini IDE (using the ESP8266 plugin). Code can even be flashed over the air and/or served from a webserver. And if neccessary they can provide an Accesspoint of their own.

Some drawbacks that I’ve already found is that Wifi disconnects when using the only analog pin on the board, and I’ve seen lots of stack traces and crashs whenever the Wifi background timing gets disturbed to much by local code. Otherwise for short codepaths the NodeMCU can instantaneously turn every small arduino project into a more capable Internet of Things project, without much effort and/or changing of lots of code.

I’m even thinking about replacing my 5 Spark Cores which are monitoring temperature, humidity, windows, doors, light and motion at my home. Only the analog thing loosing Wifi connectivity is a showstopper for me.

For more digital projects and lots of serial communication, this is the way for me to go, so I am ordering another 2 NodeMCUs.