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matherp
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Posted: 26 March 2018 at 8:58pm | IP Logged Quote matherp

Prompted by redrok's thread I've designed a PCB for a MM2 based Nixie clock.

The requirements I designed to were as follows:

Low cost Nixie tubes
Easy to solder
12V supply
GPS or DS3231 as clock source
IR or push button control
Minimum off-PCB connections

The layout I've come up with is as follows:




All components are through hole except for the HV5530PJ-G which are 1.27mm pin pitch (easy to solder) and the DS3231 if fitted.

Power supply is 12V feeding a cheap high voltage converter like this.

The Nixie tube set is also cheap. This is the set I have ordered

These can be soldered direct to the PCB or connected using standoff sockets

The PCB is 167mm * 69mm cost USD55 for 10 including HK post shipping (PCBGogo)

The circuit is:

2018-03-26_202109_Nixie_-_Project.pdf

The key component is Microchip's high voltage 32-bit serial to parallel converter HV5530PJ-G This is an SMD part but is on a 1.27mm pin pitch (easy). This runs on 12V logic and coupled with the MOSFET level changers completely isolates the MM2 from the high voltage supplies to the Nixie tubes and allows three tubes to be driven by a single chip. The 4-dots comprising the "colons" can be individually driven allowing alarm setting and status to be indicated by your software.

I'm currently waiting on parts to prototype the key bits of the circuit. Assuming this is OK I'll get some PCBs made. If you are interested in a PCB, WW has agreed to stock them but please note:

WARNING HIGH VOLTAGES

This project uses high voltage (180VDC) to drive the Nixie tubes. If you want to build this or other high voltage projects you should ensure you are fully familiar with the safety requirements of working with high voltages. The 12V supply to this project must be fully isolated from the mains.

I believe the track to track clearances on the PCB are adequate for the 180V low current supply, certainly they are greater than the pin spacings on the driver chip but any builds based on this design are at your own risk





Edited by matherp on 26 March 2018 at 9:01pm



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redrok
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Posted: 26 March 2018 at 10:23pm | IP Logged Quote redrok

Hi Matherp;

Very Nice!!!!!

I see there are Console and ICSP connection, very handy.

I might suggest breaking out at least 1 of the unused pins for use with
a precision 1 pulse per second input. Although, I see, one could use the
ICSP connector for this.

I suggest this because I have been using a cheap U-BLOX GPS receiver
which supplies a 1PPS timing pulse. I have been using the internal uMITE RTC,
Real Time Clock, for time counting. Of course this is not very accurate.
By watching the 1PPS and switching between 2 "Option Clocktrim" values
the internal clock is disciplined to very high precision.

( Btw, I assume this is "Legal" as I've been doing this once per second
for about a week. Clearly this operation hasn't "Worn Out" anything yet.
Am I correct about Clocktrim not wearing out?)

A kind of "Poor Mans" phase locked loop synced to the GPS timing pulse.
Works very nicely. Technically there is up to +- 10mS timing jitter due
to my software but plenty good enough for a clock.

redrok
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matherp
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Posted: 26 March 2018 at 10:31pm | IP Logged Quote matherp

Quote:
I might suggest breaking out at least 1 of the unused pins for use with
a precision 1 pulse per second input. Although, I see, one could use the
ICSP connector for this.


There is one on the GPS connector which matches the pinout of the GPS module I'm using.

Quote:
Am I correct about Clocktrim not wearing out?

Yes, it just writes to a memory register so can be used as often as wanted with no impact
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redrok
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Posted: 26 March 2018 at 10:53pm | IP Logged Quote redrok

Hi Matherp;

I guess I hadn't seen the GPS connector.
I have that same GPS, works very reliably.
I have a little 555 timer "Missing Pulse Detector" watching
the 1PPS pulse from the GPS. Its been running for over a year
without missing a single pulse. (Except, of course, when I'm
messing about with it. :^) )

How do I get the PCBoard? Put me on the list for 2 please.

Thanks!!!
redrok
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bigfix
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Posted: 29 March 2018 at 5:41am | IP Logged Quote bigfix





For the hardcore "neon" technology fans - but not stable in the end...

All Nixie/Bulb Clock

cheers
Guenter
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matherp
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Posted: 13 April 2018 at 1:35am | IP Logged Quote matherp

The Nixie tubes arrived yesterday and......

The footprint was upside down on my layout and I want them at the top of the PCB so had to do some serious rework. However, other than that the circuit seems to work nicely when prototyped.
I've also put a footprint for a TEMT6000 light sensor on the front of the PCB so the clock can be auto-dimming.




2018-04-13_013313_Nixie_-_Project.pdf
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redrok
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Posted: 13 April 2018 at 5:14am | IP Logged Quote redrok

Hi Matherp;
I wish I had caught that as I did look over the layout when you first posted it.

I have a text file I have been using in my Nixie Clock design.
This has been very useful so I don't get things confused.
------------------------------------
IN-12B
IN-12B Number sequence Front to Back
3 8 9 4 0 5 7 2 6 1
 
()=Pin# Top View 
        Top Of Number
     6       (6)       6
     5   (7)  ^   (5)  7
     4 (8)   /|\   (4) 8
     3 (9)  IN-12B (3) 9
     2 (10)   |    (2) 0
     1  (11)  | ->(1)Anode
       d.p. (12)
 
()=Pin# Bottom View 
        Top Of Number
     6       (6)       6
     7   (5)  ^   (7)  5
     8 (4)   /|\   (8) 4
     9 (3)  IN-12B (9) 3
     0 (2)    |   (10) 2
   Anode(1)<- |  (11)  1
            (12)d.p.

()=Pin# Bottom View 
         d.p.(12)
     1  (11)  | ->(1)Anode
     2 (10)   |    (2) 0
     3 (9)  IN-12B (3) 9
     4 (8)   \|/   (4) 8
     5  (7)   v   (5)  7
     6       (6)       6
        Top Of Number
------------------------------------
IN-2
IN-2 Number sequence Front to Back
3 8 4 7 9 5 2 0 6 1

()=Pin# Top View 
        Top Of Number
    7        (7)        7
    8    (6)  ^   (6)   6 
    9  (5)   /|\   (5)  5
    0 (4)     |     (4) 4
Anode  (11) IN-2   (3)  3
       Bump   |  (2)    2
             (1)        1

()=Pin# Bottom View 
        Top Of Number
    7        (7)        7
    6    (6)  ^   (8)   8 
    5  (5)   /|\   (9)  9
    4 (4)     |    (10) 0
    3  (3)  IN-2  (11)  Anode
    2    (2)  |   Bump
    1        (1)

()=Pin# Bottom View 
             (1)        1
       Bump   |  (2)    2
  Anode(11) IN-2   (3)  3
    0 (10)    |     (4) 4
    9  (9)   \|/   (5)  5
    8    (8)  v  (6)    6
    7        (7)        7
        Top Of Number
------------------------------------
redrok
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RyanHammond
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Posted: 17 April 2018 at 11:42am | IP Logged Quote RyanHammond

Hello, this is a pretty cool project. I am hoping you are willing to share the time clock code. I am working on something similar, not using nixie tubes, but using shift registers to drive regular common anode 7 segment leds for a clock. Your ideas would be of great help. Learning lots on this forum and the micromite is a great tool. I am somewhat amazed that this isn't as widely known as it deserves to be. Thank you for your help.
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TassyJim
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Posted: 27 April 2018 at 3:53pm | IP Logged Quote TassyJim

Saw this in an "antique" shop today.



It's still on the shelf it you are interested. The price is over the top - $1750.00 Beside it is a fake (or butchered) radio with an old digital clock planted in the center.

Jim

Edited by TassyJim on 27 April 2018 at 3:54pm


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RyanHammond
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Posted: 28 April 2018 at 12:00pm | IP Logged Quote RyanHammond

Has there been any progress on your project matherp? Dying to see the end game here. This is beyond cool!!!
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CaptainBoing
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Posted: 06 May 2018 at 5:27pm | IP Logged Quote CaptainBoing

just seen this...

https://www.youtube.com/watch?v=ge_9CNiZZ_A

Edited by CaptainBoing on 06 May 2018 at 5:28pm
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