Edit: this project has now been updated by an even Poorer man's Nixie Tube clock ...

https://github.com/roblatour/NixieTubeClock

Below however it the original project:

The project combines the following components to make a Poor Man's Nixie Tube clock

  - esp32 dev kit 1

  - nextion 3.5 inch display ( enhanced NX4832K035 )

  - wemos 18650 battery shield v3

  - 18650 battery

  - 3d printed enclosure

  - #4 1/2 inch screws x 8 

  - m3 8mm bolts and nuts x 4 

  - micro usb power cord + power block

  - this open source software

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Notes:

1. I'm not going to go thru all the instructions on how to program an esp32 or Nextion display, I'll let you figure them out as needed; however, in short at the open source link above your will find the software needed to load onto your esp32 board and to the Nextion display; the .stl files to print the encloser are also linked to above

2.  the printed encloser provides mounts for the wemos 18650 shield and the esp32 board 

3. the esp32 board I first used for this project was shorter than a second set of esp32 boards that I later bought.  Accordingly, I've included two printable .stl files for the enclosure - they are the same other than one enclosure has posts for mounting the esp32 which are further apart than the other - please make sure your check your esp32 board to ensure if you print an enclosure you print the right one

4. please read all the instructions below, before beginning

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You will need to tweak the esp32 software to add into it your network's user id and password before loading it

You should fully charge the 18650 battery before connecting the wiring

(to ensure I got the wiring right I had the power on as I connected everything - don't know if this is a great idea or not - but it worked for me)

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The needed wiring is as follows:

    - nextion RX pin to esp32 TX2 pin

    - nextion TX pin to esp32 RX2 pin

    - nextion + wire to wemos 5v + connection

    - nextion - wire to the matching wemos 5v ground connection

    - esp32 3.3v pin to wemos 3.3v + connection

    - esp32 grn pin to the matching wemos ground connection

    - micro usb cable plugs into micro power port on wemos 18650 battery shield (please see notes below about feeding the cable thru the enclosure and back lock piece)

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- Print the appropriate enclosure 

 - Add the components into the enclosure, securing them with the screws / bolts

   -- the screws are used to secure the esp32 board and the wemos 18650 battery shield within the enclosure

   -- the bolts and nuts are used to secure the Nextion display to the faceplate 

   -- for the bolts first screw a nut close to the top of the head before bolting the Nextion display to the faceplate, once the bolt is secured in the faceplate you can spin the nuts down from near the top of the head towards the faceplate to more tightly secure the board to the faceplate

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Note: the power cord needs to be fed thru the slot in the back of the enclosure, and once done the back lock piece should be threaded thru the portion of the power cord inside the enclosure before the power cord is connected to the wemos 18650 battery shield. 

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- secure the cable using the the printed components designed for that purpose

- make sure the clock is operating ok before you put the faceplate on the enclosure, I found the Nextion display a little finiky, you may have to try pressing on the menu options a few times before the behave as they should.

- make sure when you place the faceplate on the enclosure (next step) the slot at the back is closer to the bottom of the enclosure

- lie the faceplate on a table, and place the enclosure onto it and then apply pressure to snap the two together

- enjoy your Poor man's Nixie clock