Status Boards

Status Boards
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Primary Contact	Michael Erskine
Created	11/03/2016
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QR code

Simple means of showing status of Hackspace stuff on web and physical boards.

• NodeMCU (ESP8226) with Arduino core for WiFi-enabled status board
• NodeJS server for HTTP access
• a good starter project for the NodeMCU_v2
• open source software on GitHub https://github.com/msemtd/nodemcu-statusboard

• Physical Prototype
• 
  First A4 lasercut prototype with 8 bits of data
• 
  prototype back showing ProMicro and wiring
• 
  functional prototype running with sample data

The driving of the 16 LEDs poses an interesting problem due to the limited number of digital outputs on the NodeMCU: we are looking for a simple low-cost solution so after looking at various ICs to perform the task I decided to throw in another inexpensive micro with plenty of I/O and control it with I2C, serial or similar.

Using a cheap ProMicro for I/O

The NodeMCU can tell the ProMicro what outputs to drive with a simple serial protocol: -

• ASCII for human convenience and same parsing code on both micros
• same interface on both UARTS - USB and HW for simplicity and testing
• The ESP8266-E is not 5v tolerant on the UART so I shall use a voltage divider
  • https://cdn-shop.adafruit.com/product-files/2471/0A-ESP8266__Datasheet__EN_v4.3.pdf

Power Profile

For my first tests I used a cheap 18650 power bank that one would normally use for recharging a mobile phone when off grid. It ran for less than 24hrs but I was not sure of the initial charge. Anyhow, there's no overarching need for this device to be battery powered so I will probably just run it from a spare mains phone charger but it has got me thinking about the power usage so I'm going to learn a little about that:-

• I'd like a generic current logger that I can attach to various devices - e.g. the SparkFun Low Current Sensor Breakout - ACS712 https://www.sparkfun.com/products/8883
• there may be ways of reducing the current draw for the LEDs
• The NodeMCU - is it a power hog?
• how efficient is our 5v ProMicro and can we save power by making simple mods and running it at 3.3v