Web access lab board (internet of things)

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Description

Lab board to connect almost anything to the web. This low cost solution uses a 3$ PIC16F628 microprocessor and a 15$ OpenWRT router.

15$ TP-Link WR703N router

Features

  • 6 wire terminals for I/O and power/ gnd
  • IR receiver
  • 2 user defined switches
  • Up to 6 status/debug led’s
  • Mini USB connector for power
  • Single sided PCB
  • SMD microprocessor (PIC 16F628) with ICSP connector
  • Measure wires for VCC, GND, SDA & SCL

Development

I have developed a lab board that connects to the serial port of a router running OpenWRT. This means that I can have a tiny stand alone device that controls various devices thru a web interface over Ethernet or WLAN. The PCB is using the same form factor as the low cost and tiny TP-Link WR703N router. I have modified the router so that the serial communication is available thru the micro USB port (see this post for details). The PCB can be made either using toner transfer, UV mask or milled with a CNC mill. I used the last option, giving me a PCB with drilled holes in less than 10 minutes. It took less than an hour to solder the components. Please note that a lot of components are 0603 size, so I recommend a good solder station with microscope. I used 1k resistors for the LEDs and as current protection for some I/O. This is a little bit too big for high speed serial communication, but it works for 9600 baud. I was thinking about making a voltage level conversion for the serial interface, since the data to and from the router is 3.3V and the PIC is running 5V. But for me it works great with just the resistors and internal protection diodes.

The single sided web access lab board

My first application for this board is a web controlled home automation system using 433MHz RF. But I think it can be used to a lot more…

Bill of Materials (BOM)

1x single sided breakout board (etch, mill or order)
1x PIC 16F62X
1x 5×1 0.1” pin header (preferably angled)
2x 0805 0.1uF decoupling cap
1x mini USB SMD connector
1x USB SMD connector
3x screw terminal (5mm pitch)
1x 0805 green power led (optional)
1x 0805 1k resistor (if power led is used)
6x 0805 red debug led’s (optional)
6x 0805 1k resistors (if debug led’s are used)
4x 0805 1k current limitng resistors
2x SMD switch (5.1×5.1mm) (optional)
1x miniature 4/8 MHz crystal (4.86mm pitch) (optional)
2x 0805 1-68pF decoupling caps (if crystal is used)
1x IR reciever module

Specification

Dimensions [mm]: 48 x 48

Version tracker

0.1                     First version of PCB
Future               No updates planned…

Documents

Rhino project file (2D lines)
2D export (.svg)

See also

Licensing
Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

8 Replies to “Web access lab board (internet of things)”

  1. Hi, thanks for the post, I wanted to ask you where can I find a list of components for this board, thanks.

    1. Hi
      I have added a list of components, didn’t have time to make an image where they shall be placed, let me know if you are uncertain of the placement.

      /johan

  2. Hello Johan, I am interesting in building your home automation system. I have little experience in pcb building and may have over reached. I have the tp-link router and flashed with the firmware. I have also connected and tested the serial link and all is working.

    I am having problems understanding where the lab access board is connected to the TP-Link Serial, and which RF switches do i need so the web access board can turn on/off a lamp.

    Please can you help, i think its a great project and haven’t seen anything like this on the web.

    Thank you

    Bashir

    1. Hi Bashir
      The lab access board connects to the router thru the USB cable. I altered the router to provide rx/tx signals thru the micro USB connector marker “power” on the router (described in a separate post). The mini USB connector on the access board works as power in for both devices. The rx/tx signals goes thru two current limiting resistors to the serial in and out of the pic.

      Several switches can be used, as long as you match the radio frequency of the switch with the radio transmitter connected to the PIC. I have used several different brands using 433MHz, the attached code is using the protocol for the self learning NEXA switches.
      /johan

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