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Custom Nixie Tube Clock Review

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Evangelopoulos Panagiotis:
Greetings,

I've always wanted to make a nixie tube clock and recently I decided to take on the challenge and build my own. I've made countless prototypes before but this is the first time I'm gonna
send the PCB to a professional manufacturer and not make it my own. So I'd like it to be as perfect as possible so I can be sure that it will work first time since I don't have the money to re-print the PCB.

I'll be driving each nixie tube separately since I don't want to fondle around with multiplexing. I'm using some K155ID1 nixie drivers and I'm driving those with a few daisy-chained 74HC595s to get the 36bit shift register that I need.

Please review the schematic below and let me know if I have any major flaws that will mess my circuit up.
Thank you in advance,
E.P.

NivagSwerdna:
Looking good

I would be tempted to
Add a couple of LEDs to the D's
Put the switches on the A0...A3
Bring out SQW from the DS3231 to a interrupt on change pin
Add either a ESP-01 socket for NTP sync or at least bring out RX to allow an external GPS module via a phono type socket.

Finally when laying out the PCB make sure you size the current limiting resistors as you need prob 0805.
Add a reverse protection diode
Add a PTC fuse

Looks fun

PS
It's hard to get it right first time, so use a cheap PCB place... I use elecrow because they have a cheap shipping option but use PCBShopper to find what is in your budget. (I was going to try JLPCB but their shipping options were too rich for me)

Evangelopoulos Panagiotis:

--- Quote from: NivagSwerdna on May 30, 2019, 08:31:04 am ---Looking good

I would be tempted to
Add a couple of LEDs to the D's
Put the switches on the A0...A3
Bring out SQW from the DS3231 to a interrupt on change pin
Add either a ESP-01 socket for NTP sync or at least bring out RX to allow an external GPS module via a phono type socket.

Finally when laying out the PCB make sure you size the current limiting resistors as you need prob 0805.
Add a reverse protection diode
Add a PTC fuse

Looks fun

PS
It's hard to get it right first time, so use a cheap PCB place... I use elecrow because they have a cheap shipping option but use PCBShopper to find what is in your budget. (I was going to try JLPCB but their shipping options were too rich for me)

--- End quote ---

Thank you for your help!

A few LEDs won't hurt indeed. Just for power indication or any other trouble-shooting stuff.
I thought that only the digital pins of the Arduino had a built-in pull-up resistor but it seems that the analog pins do that as well. So I'll
bring the switches over to A0-A3 so I can free up a few digital pins.
I'm using a RTC module that does not have a SQW output but I'll put a one pin connector at D2 in case i want to use the interrupt pin in the future.
Also thank you for the ESP-01 socket idea! It doesn't seem impossible that I'd want to make it wifi enabled at some point in the future!

I'll add protection as well.

I'll check those other two manufacturers as well since I was first thinking of JLCPCB.

Thank you again for your help.

NivagSwerdna:
To be honest there isn't much to choose between A's and D's...

Also some optional extras...

Piezo for alarm
Ambient light sensor
DS18B20 temp sensor

Some people also like neon colons between digits (Yuk!)
RGB Backlighting LEDs (Hm)...


If you do want NTP sync then an easy way to do this is to get a ESP module to fake a GPS message.  So on the board you just need to provide switched 3V3 and level shifted RX.  That way you also use an external GPS receiver too. 


NivagSwerdna:

--- Quote from: EvangelopoulosPanagiotis on May 30, 2019, 09:21:45 am ---Bring out SQW from the DS3231 to a interrupt on change pin
--- End quote ---
The DS3231 can generate 1Hz on SQW which is useful since you then can be accurate to <1s with a simple interrupt. Use a pin that can do proper interrupts... D2? D3?

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