Arduino 4 Tube Multiplexed Nixie Clock

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Introduction: Arduino 4 Tube Multiplexed Nixie Clock

About: Ham Radio operator and electronics hobbyist.

There are lots of Nixie clocks out there, but I my goal was to build one from scratch. Here is my Nixie project.

I decided to build a 4 digit nixie clock. I wanted to save parts so I decided to make it multiplexed. This allowed me to use only a single 74141 chip for all 4 tubes.

This clock is currently set up for 12 hour operation.

I know the code is not pretty or optimized, but it works for me :)

Step 1: Schematic

I designed the schematic and board using EASYEDA https://easyeda.com

Step 2: Component List

ARDUINO NANO 1
K155ID1/SN74141 1
10k resistor 13
MPSA42 transistor 4
1Meg resistor 4
Neon lamp 1
LM7805 voltage regulator 1
10uf 50v capacitor 2
43k resistor 1
Nixie tube 4
DS3231 breakout board 1
PWR Supply - HV nixie power supply 1
330ohm resistor 1
12V PS - 12v power supply 1
MPSA92 transistor 5

Step 3: Circuit Board Design

Step 4: Populating the Board

Populate the board with the components. Start with the small stuff first, like resistors and transistors, and work your way up to the more complex items.

Step 5: HV Power Supply

I bought the power supply off eBay. NK01B. This little supply can power several nixies, I believe 6 or 8 at once.

Very easy to assemble and attach to your board. I used a 330 ohm resistor to set the voltage.

https://threeneurons.wordpress.com/nixie-power-supply/hv-supply-kit/

Step 6: RTC - Real Time Clock

I used a DS3231 Real Time clock Chip. I bought several off of eBay. They were cheap, and they keep excellent time.

https://www.ebay.com/itm/1pc-DS3231-Precision-RTC-Module-Memory-Module-for-Arduino-Raspberry-Pi

Step 7: Testing the Nixie Tubes

Step 8: The Code

Step 9: The Final Product

I put this into a cool project box with a clear lid, so you can see what it looks like inside.

Step 10: Modifications

I added a momentary contact switch between arduino digital pin 2 (D2) and ground, and digital pin 3 (D3) and ground. This allows me to add 2 buttons to adjust the time. The code has been updated to reflect this. I am using polling, with a delay to debounce the switches.

Initially the MPSA92 transistors were backwards, so I had to flip them around. I will update the silkscreen on the next run of boards.

I will need to update the cathodeAntiPoising code to cycle through all nixies, instead of just the first 2.

Initially 15K resistors were selected for the Anode resistors, but with multiplexing, you need a higher average current, so I swapped those out to 10K.

Arduino Contest 2017

Participated in the
Arduino Contest 2017

4 People Made This Project!

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20 Comments

0
RNTQNAMC6QZUZEYYDGY62V

Nice: It looks like the middle dot (Colon) doesn't do anything. It just stays on and doesn't flash for seconds. Is this correct?
Also is this a 12 hour clock or 24 hour clock?
If not how to make it 24 hours?
Thanks.

0
ferri_h
ferri_h

Question 7 months ago

Hi!
I would like to know which is the criteria in order to choose the transitors. I have been studying electronics for a couple of years now, but I have never worked whit PNP transistors. I would lije to know why do you use these kind o transistors to connect the anode to Vcc and I would also appreciate if you could tell me why is the second transistor used. I guess that is because the PNP is a power transistor and cannot be directly controlled by an arduino output, but I am not sure. Any kind of information related with that will be perfect for me.
Thank you veery much.

0
thewarden105
thewarden105

Answer 7 months ago

The MPSA42 and MPSA92 transistors were selected because of their high voltage capability.
See this site for more information. https://web.jfet.org/nixie-1/NixieTransistors.pdf
Also look up Nixie High-Side drivers.
I chose this circuit to reduce the number of Nixie Driver ICs that were needed. (because they are fairly expensive)

0
mr_sneezy
mr_sneezy

Question 1 year ago on Step 3

Is the PCB artwork downloadable here someplace so I can get one made, or can bare boards be purchased ?
Thanks.

0
thewarden105
thewarden105

Answer 1 year ago

Sorry, this was a one-off project and I only made 2 boards. You could recreate it in EasyEDA and then have a board made. But you would have to customize it for the parts and tubes that you have available.

0
olsaolsa
olsaolsa

2 years ago

Hi, great project! I’m just finishing it, and I can’t understand one thing ... What is the output voltage which goes from the HV Power supply(NK01B) to the board ?? The description says that NK01B supports a voltage range from 45V to 190V.
I use a different power supply, which allows me to achieve the same values, but I'm not sure what voltage to set ... I don't want to damage the circuit when connected to the board ...

0
thewarden105
thewarden105

Reply 2 years ago

On the HV power supply that I used, it uses a resistor to set the desired output voltage. I chose a 330 ohm resistor which sets the output voltage to 180V. You can also double check the specs of the Nixie tube that you are using to verify 180V is within its specification.

0
RoyZ11
RoyZ11

Question 3 years ago on Step 1

The original ardunix used a different set of resistors for the transistors driving the anodes- 33K, 470K and 100k vs your 10k, 1M, and 10K. Could you comment on the rational for your selection. I understand there is a formula for this type of setup, but could not find it being a noob! Thanks.

0
thewarden105
thewarden105

Answer 3 years ago

The reason that I used those values is that I found 2 or 3 other schematics on the internet that all used the 10K, 1M, 10K values. So I just went with those.

0
leomiranda
leomiranda

3 years ago

Adding switches as you described, will be possible to adjust the time (the actual code is able to d it)?

0
thewarden105
thewarden105

Reply 3 years ago

Yes the code provided allows time adjustment using the two switches.

0
leomiranda
leomiranda

Reply 3 years ago

Is D2 Hour and D3 Minute?

0
leomiranda
leomiranda

Reply 3 years ago

You say: "I added a momentary contact switch between arduino pin 2 and ground, and pin 3 and ground."

Is pin 2 "DO/RX" and pin 3 "Reset"?

0
thewarden105
thewarden105

Reply 3 years ago

Sorry, D2 and D3

0
hongkunk
hongkunk

3 years ago

It's so cool!
It is necessary for me.
I want to make it.
Can I get a schematic?

0
leomiranda
leomiranda

Reply 3 years ago

The schematic is on Step 1.

0
hongkunk
hongkunk

Reply 3 years ago

Thank you.
I found a big picture.

0
Swansong
Swansong

3 years ago

That's a nice clock, it turned out great!