Nixie-I2C is a collection of PCB designs and accompanying library designed to simplify using Nixie tubes with Arduino and ESP8266 based boards (and perhaps others in future).

Driving nixie tubes from microcontrollers can present several issues:

• Can rely on expensive/obsolute/irreplacable Soviet-era driver ICs (eg K155ID1)
• Or, if you drive the cathodes directly, requires a large number of pins from the microcontroller (e.g a numeric IN-14 nixie tube has 12 cathodes - 0-9 and left/right decimal places), so it becomes difficult to direct-drive multiple tubes without running out of IO pins
• If using the 'direct drive' solution above, you need a high-voltage capable transistor per cathode.

The main idea of this project is to provide a convenient driver board for a nixie tube, allowing it to be controlled from the microcontroller via I2C.

The PCB design here (which is tested and works) offers the following features:

• Bus based (I2C) - put all your tubes in a row on stripboard or similar!
• Designed for IN-14 nixie tube
• I2C address (3-bit) settable (solder-pads on underside of board), allowing 9 nixie tubes per I2C bus.
• Handles all HV switching, allowing a simple library interface to select the digit to be displayed. Uses cheap SMD NPN transistors (MMBTA42s)
• Has option for installing a programmable RGB (WS2812B) LED under the base of each tube, allowing bottom-lighting of any colour/brightness, without requiring ongoing control from the microcontroller (eg no PWM timing loops etc)
• Eagle brd/sch files provided
• Licenced under the OSHW framework

There is an accompanying library, which supports:

• Arduino or ESP8266
• Simple interface to setting a tube's display digit / decimal point status
• Slot-machine display for cathode protection
• Direct drive for up to 9 tubes (per I2C bus), no multiplexing/timer loops from the microntroller required

##Example

The library is designed to be simple and easy to use:

Nixie_i2c nix0(0x00);
nix0.slotMachineDisplayNumber(1);  //Tube now displays 1
delay(1000);
nix0.slotMachineDisplayNumber(9);  //Tube now displays 9