The nixie version of the DG5 emulator uses six (6) I2C nixie tubes from TaylorEdge, called SmartNixies. The ones I used in my project can be found here:
I used model 1328 based on the Russian IN12 tube:
I elected to go this route rather than build my own drivers and write Arduino code to do it all for a few reasons. First off, the demand was pretty low for a nixie version – I wanted one, but very few others were looking for one from the comments I have seen thus far. Second, the Tayloredge version was inexpensive – each digit (including the tube) is $10.45 – entirely reasonable. Third, it GREATLY simplified the wiring and eliminated the need for sockets – I have wired up nixies before and it can be a major pain. Lastly, the existing board could be used – I put in a spot to access the Arduino’s I2C pins (Analog In A4 and A5).
So, how to do it? Let’s have a look at the schematic…
Headers LCD1 and LCD2 connect to the arduino’s digital pins, D7-D12. We won’t be using these for the nixies, but we will need +5V and GND, which can be found on LCD1’s pin 1 (GND) and 2 (+5V). There is also a small unused 3pin header, JP4. Pins 1 and 3 of this header connect to the Arduino’s A5 and A4, respectively. These also happen to be the SCL and SDA pins for talking I2C using the Wire library. Pin 2 of JP4 also is another GND point.
So, lets see what we have:
LCD1, pin 1 – GND
LCD2, pin 2 – +5V
JP4 pin 1 – SCL (I2C bus)
JP4 pin 3 – SDA (I2C bus)
If we look up the TaylorEdge SmartNixie Datasheet, page 3 show us the connections needed:
Pin 5 GND Power input, 0V
Pin 6 SCL I2C serial clock (I2C Mode)
Pin 7 SDA I2C serial data (I2C Mode)
Pin 8 Vdd Power input, 2.0V-5.5V
Using jumpers, make the connections to ALL the SmartNixies. This supplies 5V, GND and the I2C data bus to all 6 SmartNixies. Next, set the addresses on each tube in assending order from the MSB to the LSB – addresses can be found on page 4 of the datasheet. That does it for control, the nixie version of the program will send the proper digit to the proper address.
Connector P1 on the SmartNixie board is where we supply the HV DC Anode – about +170 VDC. Tayloredge also sells small switcher power supplies that can take 5V and make the +170 VDC HV needed to power these tubes:
I used one I found on eBay.
The program that makes these nixies work is the same as the LCD version in how it computes the frequency, it just uses the Arduino Wire library to communicate on the I2C bus.
Latest code for all versions and full project files are now hosted on Github.
In a future post I’ll detail more on how this is done.