24 Hour Nixie tube clock w/o microcontroller

[Saimaster13]

I am going to be working on a 24 hr Nixie tube clock. It will be using a 32.768KHz crystal for the time base and digital ICs for the dividers and counters. Currently I have not started working on this, but I have made a 1Hz time base and a 0-59 counter (both components that will need to be used to make it.) I will post the progress as I go.

Also, everything will be made from scratch, except for the Nixie power supply which will be from a disposable camera.

[W4GNS]

I look forward to following this thread!!

[brad]

Excellent!

Love the old school technology mixing it up with new circuitry.

Be sure to post pics and details as you progress

[bitfogav]

You might want to check these out then?

http://www.seeedstudio.com/blog/2012/09 ... r-arduino/

nexieclocktube21.jpg (82.56 KiB) Viewed 22382 times

[Saimaster13]

Wow, that is pretty cool! Seems very artistic, something that isn't my specialty. Not very practical though if you want to make something else out of it, and my project will be from scratch. I might add some RGB LEDs to it now though.... they do look pretty cool with it, I was going to go with a single color LED before.

Thanks for the ideas!

[brad]

They are very cool! although I could just imagine the cost of 10 of them though!

[Saimaster13]

Ran into a problem.

I took apart a disposable camera and used it as a power supply, and it lit up the nixie tube nicely with a current limiting resistor. Problem is, when I got a mpSA42 transistor, hooked the emitter up to camera negative, the collector to the nixie, and the base to a 555 timer (I tested using 9V, 12V, and regulated +5V [lm7805] on the 555) the transistor only outputs around 30V when it should output close to 300. As the clock cycles, there also seems to be little to no change in the nixie tube brightness or the output voltage.

I connected the +300V to the base and the nixie lit up, but that is not very helpful when I want to use 4017 decade counters to run many mpSA42 transistors.

Can anyone think of a solution or offer any help?

Transistor datasheet if needed

[brad]

I would highly recommend using a darlington pair rather than one resistor to try and do it. Maybe some ULN2803 chips is what you want because there are eight of them in one chip and you don't need any interface resistors when using them with TTL circuits (it's all built in to the chip)

http://www.onsemi.com/pub_link/Collateral/ULN2803-D.PDF

[Saimaster13]

Are you talking about using that instead of the MPSA42 Transistors? Sadly, the nixie tubes need around at least 180V, and sadly, those seem to only go up to 50V.

[brad]

Oops, my mistake!

I didn't take into account the high voltage required by the tubes.

Have a read through this:
http://www.glowbug.nl/neon/HowToDriveNixies.html

He is describing how we interfaces digital circuits with nixie tubes. Infact, he uses the same high voltage transistors as you MPSA42. Maybe there could be some extra useful info there.

However, I would try and put in an extra transistor to drive the MPSA42. I.E the output of your 4017 goes to the base of a 2n2222a or similar, the emitter of the 2n2222a goes to the base of the MPSA42 and the collector of the 2n2222a goes to VCC. Then continue on as normal with your MPSA42.

[Saimaster13]

I have yet to try anything yet (haven't had the time) but I hear you are supposed to connect the 5V negative supply to the 300V negative supply. I also heard that that is obvious that that is supposed to be done. Is that supposed to happen? Have you guys ever heard of doing that? And why does that need to happen?

[brad]

I'm not sure I follow - why do you need negative power supplies?

[Saimaster13]

Well, its 0V, not negative (I guess, I'm not familiar with 0V.)

[brad]

Oh I get you now! you just mean the ground connection of the 5v supply to the ground connection of the 300v supply. Then yes, that is something that you want to do. You need a common ground in your circuit because all those electrons need to start somewhere

[Saimaster13]

They can't start from two places though? I mean, it is kind of like 2 circuits almost independent of each other... except for the fact that the timer output does not go through the transistor.

That is why, isn't it? The 555 timer outputs to the transistor, but the electrons do not move through that wire, so it does not activate the transistor.

Whereas if you connected the grounds, holes would be going from the positive output of the 555 through to the negative emmiter of the transistor, turning it on.