Hi everyone, this is my new nixie clock. It is my version 2.2 The first model isn't on instructables. you will see picture later. Almost the same. Difference is, no leds, some parts are in a dip package and as well board is more larger. So this is my new surface mount version. Trust me, this clock remains nobody indifferent.

A special Tank you to Jacques Laubscher, we work together on the Version 2.2 pcb.

We remove the 7404 to add a real gate driver: MCP1416.

We rearrange and enlarge the GND/VCC wire.

We rearrange the other wire to have more space in between.

We change the reset Button to INT1 (interrupt 1) to be able to add option. To be program later.

We change the Battery package for a regular one. This makes more room to pass larger wire.

We add 2 decoupling capacitors. One for the gate driver and one for the atmega328 on the other Vcc pin.

We enlarge the power jack hole and move it to the right to make more room to the pcb hole.

We enlarge some component pad. All is hand solder, it help.

We add a ds3231 soic8 footprint to be able to install 2 types of packages.

We connect the 5v to the ISP header. Now, we must program without 12v power supply.

Features:

-IN-14,IN-8 Nixie tubes. I prefer IN-8. Number 5 isn't a number 2 up side down.

-High voltage power supply is built-in.

-High voltage digital adjustment saved in eeprom.

-Low voltage power supply can be 9v to 12v

-6 leds, digitally adjusted (push button) can be turn off. brightness saved in eeprom

-Nixie saver animation but not too often

-Little in-3 can be on, off or flashing, saved in eeprom.

-No ghosting effect.

-No exotic parts.

-Almost all discrete components. Not very expensive to do.

-Time and date as well.

-DS3231 so time is accurate and keep by battery. (+- 2ppm)

-Supported AVR are atmega 48, 88, 168 and 328

Step 1: Schematic

Click on picture, at bottom left you will see an arrow (download original) click on to have full resolution. Or download the pdf below.

Nixie tube clock sm2_2.pdf
Download

Step 2: Parts List.

In the file part partlist_2..txt you will fine what you need to buy. All parts are listed. I included part number of all major components except resistor. All kind of 0805 sm resistor will do. But R32 and R33 are 1206 package 1/4w.

I bought in-8 and in-3 on ebay. My first one is working for 6 years now without any problem.

IRF644 can be replace by IPN60R3K4CE, or IPN50R2K0CEATMA1. Package is smaler but will fit

You can install those neon bulb instead between the nixies tubes: A1D-T Digikey part number: A1D-T-ND

Parts list here

Step 3: Gerber File

This is the file you need to send to a pcb manifacturer. You can also upload the file here to have a preview result: https://www.pcbway.com/project/OnlineGerberViewer.html

Normally you must order 5 or 10 minimum quantity. Just ask me if you whan to have only 1. I have some in my lab so maybe i could help you.

Gerber file available here in Nixie tube clock sm_2023-12-05_2.2_Instructable.zip

Step 4: Solder.... Before and After

You need a challenge try to solder surface mount! 0603 led are very fun :)

An advice, solder L1 only at the end. Do the programming section and if you see led7 turn on and off at the beginning you will know that all is perfect.

If all is good, install L1 and you can do the voltage adjustment.

Step 5: Atmega Programming

Plug in your USBasp or USBtiny device in your computer and let Windows detect the device (it will report driver not found). If a window pops up asking to search for driver, just close it or click on Cancel.

At this point, download and run Zadig, it should detect the USBasp or USBtiny, or any libusb device that you have. Then in the selection box (see picture), choose libusb-win32 (v1.2.6.0), click on Install Driver, and wait for the installation to complete. Check in device manager for atmel usb device = ok. No excalmation mark anymore Download code below on this page and unzip files in a folder. I create a batch file to program the chip with .hex and fuses bits at same time. Connect USBasp or USBtiny cable in your board and you need to connect the power connector of nixie clock too.

Attention here: If you program the uC for the first time. no need to do anything. But if you are doing an update, I suggest to enter in programming mode to disable hvps. To do so, unplug the clock, press and hold (H) and plug back in. All led will be on and led7 will be flashing. see video.

Double click on program usbxxx.bat At the end, code and fuse bit are programmed. You can use atmega 48,88,168 or 328. P or not.

NixieTubeClock 2.2

Step 6: Voltage Adjustment

To enter in voltage adjustment setup. Push and hold enter button and power on the clock.

Or if you are starting the clock for the first time, the eeprom is empty and clock will enter in voltage adjustment setup by itself.

A 72khz square waveform is feeding L1. So, the coil is collapsing 72,000 times by second. This create high voltage back emf. Those spike are passing by D4 and store by C7 as low pass filter. At this point (tp1) the tension can be up to 185v with a 12v psu and 184v with a 9v psu. You can go even a bit more with a irf644 but the goal here is to have 170v.

The duty cycle of the waveform change the output voltage. More the duty is high more the back emf is huge resulting in a higher tension.

At the beginning voltage is set to have an output of 37% duty cycle on. You should be already around 170V if you are using a 12V adaptor. But a double check is advice. By pressing on + or - button you will increase or decrease the output voltage.

You can monitor the output voltage with a volt meter between tp1 and gnd. I suggest to set the voltage around 170v.

I set the maximum duty cycle to stay above 58% to protect the coil. It can happen, depending of the mosfet and the coil, if you go too high the voltage will be decreasing. The coil is saturated and can't give more feedback.

Step 7: Make a Nice Finish

Is up to you to do any kind of finish for your clock. On my side, my first clock is on a rock. And my last one is on piece of wood.

Step 8: User Manual and Conclusion

Only 3 buttons to adjust the clock.

Enter, +H, and -M

Time:

Push and hold Hours (H) or Minutes (M) and push enter. Each push increase the the clock. If you hold it a while, it will change quickly

Date:

Remove power, push and Hold (M) et plug back in. Push Enter to change day, (H) for month, (M) for year. Power cycle the clock. Only press enter button to pass from time to date.

LEDS:

Press and hold + or -

Little in-3:

press and hold (M) and (L), press enter.

HVPS:

Power off, press and hold enter, power on. Click on + or - to adjust voltage. press enter when done to save it.

Programming mode:

Power off, press and hold (H), power on. 6 led will be on and led7 will be flashing. HVPS is off.

The engineering of this clock was very fun. And i'm very enjoying of the final product. It looking very well and it's always impressing for people who doesn't know nixie tube. I had so many good comments, if you build this clock you will have too. Now if you have any question, any bug, any suggestion. I'll be happy to ear you.