Filament Health Monitor (Part 3 – Electronics)

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The electronics seem overwhelming at first, but just take it one part at a time and you’ll get through it. Back in the BOM of Part 1, we ordered the following items:

  • D1 Mini Micro Controller
  • OLED Display Module, 0.91in
  • TCS-34725 RGB Color Sensor
  • HX711 5KG Digital Load Cell
  • DHT11 Humidity and Temperature Sensor

In addition to those items, you will need:

  • A small amount of double sided foam tape to mount the DHT11
  • 30AWG solid Wire Wrapping Wire
  • Wire Wrapping Tool
  • Several Headers (Most of the items come with headers, so you should have plenty from that)

The build we are going to conduct follows the following schematic:

Everything will be wired at 3.3V and we will use the D1’s 3.3V regulator to power it. The total current draw of all components is approximately 34mA. 30 AWG wire can handle roughly 150ma and the onboard regulator can provide up to 500mA. During boot it appears the D1 will consume up to 250mA, which leaves another 250mA to work with. Based on these numbers, we should have no problem powering all peripherals via the D1 3.3V regulator. For details on current draws, see the table below:

ItemCurrent Draw (Max)
D1 MiniUp to 250mA at Boot

If you followed the build in Part 2, the connections from the strain gauge to the HX711 have already been made. If you haven’t, these connections need to be soldered as the wire is not the right kind for wire wrapping. You will also have the 5 wires from the color sensor and 4 wires from the front LCD display free floating out the back. If you haven’t routed the LCD wires through the channel on the bottom of the base, do that now.

I would recommend you take care of the currently loose wires first and get them out of the way. Just follow the Schematic above and the Wire Wrapping Instructions provided in the link section. I took the DHT11 and straightened its pins with pliers before making its connections. Once the connections were made, I used double sided tape to mount it to the side wall.

If I were to build this again, I would have probably preferred to this D1 Shield which would have made things neater:

After wiring the DHT-11, just step through the remaining connections. NOTE: You should never exceed 3 connections per terminal (Given their size) and I would recommend no more than two. Daisy chain the power connections from board to board to maintain only two connections per pin. When everything is done we will move on to the software side: Part 4 – Softwaree–>

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