From regular use of the Monoprice Select Mini 3D printer, the heat bed temperature sensor began to fail. The problem was identified as an issue with the wiring attachment to the heat bed thermistor.
During the repair, the heat bed was removed, and unfortunately, in the process, a short across the heating element and the temperature sensor destroyed the electronics on the mainboard. The printer still works, but the heat bed temperature always reads 99 degrees Celsius. The printer starts, tries to print, but heat bead does not heat up.
Possible fixes include:
- New printer (https://www.amazon.ca/Monoprice-Select-Printer-Heated-Filament/dp/B01FL49VZE/),
- Warranty replacement,
- Mainboard replacement (https://www.mpselectmini.com/parts/mainboard),
- External heat bed temperature controller.
Option 1 is the most expensive, of course, but would guarantee a fix. Option 2 likely would not work as the issue was caused by actions which voided warranty. Option 3 is a half-way solution, but the mainboard costs about 1/3 the price of the printer, and ships from China which could take months, and includes risk of rejection at import customs.
Option 4 is quite likely the most interesting solution. To make it more interesting, why not build a custom controller? This is what we’ll do.
- Arduino mini (https://www.arduino.cc/en/Guide/ArduinoMini) which uses the ATmega328 architecture and runs at 3.3V
- Solu 1.3″ I2c IIC Serial 128×64 White Oled LCD Display Module
- KY-040 Rotary Encoder Module
- RFP30N06LE TO-220 Mosfet
- 10k resistor for power circuit
- 100K resistor for thermistor circuit
- 100pF capacitor for thermistor circuit
- Heat sink (for MOSFET)
- L78M5 to L78M10 positive voltage regulator. I used the L78M10 to supply 10V to the Arduino mini voltage regulator, which accepts up to 12V, and regulates to 3.3V.
- 0.33uF and 0.1uF capacitors for regulator circuit
- Prototype board and wires for connecting the circuits
- 100W + power supply. Need the power to provide enough current for the heating element.
Below is a picture of the prototype of the controller user interface running. The firmware is quite simple, and uses a PID circuit to regulate the heating output.
The circuit was placed in a more compact form on a soldered board which includes the power regulator, no USB circuit (firmware loaded using a programmer), and the heat-sink.
Print a nice case for the controller and print a nice knob for the rotary encoder.
Prototyping of components is now underway with the recent purchase of a very inexpensive 3D printer. The Monoprice Select Mini 3D printer is likely one of the most value for cost printers currently available. With this new printer, expect to see some rapid progress on developing the first user-ready prototypes of “Things!”
A platform for managing and integrating general IoT systems is being developed. The http://CleverMajig.com website provides a way for users to register and describe their IoT devices. Using a REST API, data sent to the CleverMajig.com is logged and managed for users.
Using channels and “Thinkers” a user can trigger various actions and do some basic processing based on the data being sent from the IoT devices. These can include simple tasks such as sending email alerts, or actually sending messages to other IoT devices to take an action. A simple example is a thermostat application which turns heating and cooling on and off based on numerous temperature sensors providing input.
Data sent to CleverMajig.com can also be analyzed using machine learning algorithms in batch mode to develop insights over longer time scales. One possibility is to use distributed temperature sensors around a house to determine which locations have poorer thermal insulation, or even to measure the thermal insulation value of a home.
The key is that having a general and easy to use platform with a simple user interface allows users to be creative in their use of IoT devices.
The first working test version of the real-time connection for a sensor with in situ application is in progress. This sensor runs sanitized wiring through the air lock which then goes through a waterproof housing into the liquid.
The sensor is connected over wifi which then transmits updates over an IoT backbone. Currently, it is logging temperature changes into a Google Spreadsheet.
The graph shows an example log from 26 hours. Not that the temperature fluctuated within a 2 degree Celsius range over this period.
Next steps include adding additional ambient temperature sensors and also to develop the in situ hydrometer sensor.
The central gateway for the network is the base station. Now working is a color LCD touch display for the base station, with a WiFi module, and a local radio communications module which connects to the sensor and control networks on the ultra low power wireless network.
In the above figure, at the bottom is the microcontroller (MCU) based on the ESP 8266 system on a chip, which includes 802.11 b/g/n WiFi standards. The display will show the user interface which is under development and is a touch screen, which enables the user to configure and set options. To the top right the low power wireless radio is shown, which is used to interface to the local sensor network, and control network.
At this point, the hardware for the base station is basically complete, and the primary work at this point is in further developing the software both on the embedded MCU, for the web-based service, and for the mobile applications.
The new temperature and humidity modules have arrived!
These modules have an on-board 8-bit processor to ensure the readings are calibrated. They have low power consumption making them ideal for the sensor node application. They consume 0.3 mA when taking a measurement, but only 60 pico Amps in standby!
Another step closer to putting the sensor node together. All of the basic parts are now ready, except for the power supply. Progress is being made on that as well.
Production of wine and beer has numerous factors influencing the quality of the product. Best practices are often determined by rule of thumb, or trial and error. Using modern inexpensive networked sensor systems, a much better method is possible.
some key factors:
- type of yeast
- type and amount of sugars
- rate of fermentation
- exposure to light
- sanitation and sterilization
Real-time monitoring of the liquid density and temperature, in combination with temperature control would enable the consistent and repeatable production of high-quality products. This can now be possible using an immersed sensing system.
The initial prototyping will involve a two-pronged probe to be inserted into the ground.
This probe works by measuring the resistance of a small current through the soil. The greater the moisture content, the more conductive the soil will become. This probe will be placed at the bottom of the solar powered sensor node, which will look like a garden solar light.
Of course, this sensor does not have to be always on, and so it will be important for the wireless node to be able to turn off the sensor between readings in order to conserve power. The total current draw of this sensor will have to be verified to manage the duty cycle.
Monitor temperature and humidity in various places within your greenhouse.
Options to include ability to connect to automation for air-circulation, heaters, ventilators.
For heated greenhouses, a single source of heat may not be dispersing throughout the interior, especially when the out-door temperature is low, the heating may not be applied ideally for plants near the edge of the greenhouse. By installing an automated monitoring system, the entire greenhouse can be configured to optimally distribute heat to all plants by turning heaters and fans on and off as required.
Is your lawn or garden on a timer? Do you manually water? Do you research the weather to see how much it is going to rain before watering? Finally, do you know the right amount of water to give each plant in your garden to make it thrive?
All of these questions can be easily resolved by the technology being developed to integrate and automate gardening. How it works:
- Base Station: A networked base station in the house connects to your home WiFi network and also the low power garden network.
- Distributed Sensors: Sensor modules which run on batteries and are charged by solar power are placed throughout the garden in strategic locations to collect information on ground moisture, temperature, humidity, and other information in real-time.
- Watering: You install a watering system to disperse water appropriately. There are many options for how to do this, with varying expense.
- Valves: Install wireless controlled water gates which can controlled manually from any internet enabled device, or, can be connected to a base station for automatic (smart) operation.
- Learning: By monitoring the level of moisture achieved by various amounts of water, the system learns your drainage and soil type to optimize when to water, and how much.
- Tuning/Zones: Not every plant requires the same amount of water. Configure your base station with information on what plants are near each sensor, and the base station will use this information to control the amount of water delivered.
The prototype of a sensor node is shown below. The screen is only to show the status of the system. Visible directly above the screen is the ultra low-power wireless module. The zig-zag wire is the antenna. To the left of the antenna, you can see the CPU.