changing components in a second revision for my nixie tube project - Page 1
Forum section: electronics / projects

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 06, 2013, 06:21:35 pm
content: hello everyone.i have recently finished my revision 1 nixie tube clock and i would like to start work on a revision 2 to fix some of the errors that i had made (putting the CR1220 battery holder the wrong way round ect) and one of my main things that i would like to change is the driver chips for the nixie tubes themselves for two reasons.1, i used the wrong footprint on the board so the wholes are slightly to far apart from each other and the actual IC's them self as they re expensive and killed by static very easily and i am worried about when i move the clock off of the anti-static mat for actual use.current it uses some K155ID1 drivers and a BCD signal sent from some PCF8574 IC's to operate the tubes and i would like to replace them with something a little bit more modern and more reliableapart from the occasional glitch the whole project works fineany sugestions?also if you see anything on my schematic that looks like it needs modifying please let me know

author: kizzap
author_rank: Unknown
timestamp: May 07, 2013, 12:37:16 am
content: I like it, if you want to reduce the component count you could always replace the crystal with an resonator? accuracy is not all that important as you are getting your clock signal from the DS1307, and the MCU looks like it is just controlling the tube drivers for now. (this is assuming that this is a stand alone project, and that the rest of the atmega pins aren't being used to control something else. point of inquiry, why are they all connected to a header?)I wouldn't have the power coming in on the same header as the header all the IO signals are connected to either, I'd have it as a separate connector, like a plug pack, input 12v, and then have a LM7805 regulator on the board.8 digits? displaying the day or milliseconds?-kizzapQuick edit: I notice the "NIXIEPOWERMODULE" has a 5v out. Screw the regulator, power your MCU and logic off that.Also, you should consider some filter caps on all the ICs.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 07, 2013, 06:10:03 am
content: It displays dots between the digits, i had a couple spare so why notIve attached a pictue of it currently its all been designed ro fit in a nice compact space but thats another problem due to it being small i can fit a heatsink in there so hence for a need for version 2Alot of the arduino pins are connected to a header strip so that i can connect extra items at a later date for instance an alart to be triggered by an io pin at a specifc time.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 07, 2013, 06:13:20 am
content: I placed a 5v regulator at the edge of the board to make contact with the frame its going into to act as a heatsink as the one on the power module is tu ked away in the depths of the two boardsWhat are filter caps and where should they go?And what do you mean by not having the 12v on the same board as signal?

author: kizzap
author_rank: Unknown
timestamp: May 07, 2013, 09:06:53 am
content: QuoteYou won't NEED another regulator if you use the 5v output on the power module. Im not familiar with the chips you are using, or what Nixie Power module you are using, but I would believe that you should be able to power the circuit off it.QuoteHave a read of this:http://e2e.ti.com/blogs_/b/thesignal/archive/2013/04/23/bypass-capacitors-yes-but-why.aspx?social=social7390694when I said filter caps, I should have said bypass caps.QuoteSame HEADER. where the cable comes onto the board. I would have it as a separate connector.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 07, 2013, 12:31:53 pm
content: Quote

author: c4757p
author_rank: Super Contributor
timestamp: May 07, 2013, 12:40:11 pm
content: One suggestion, though it depends on your design goals. If you want to be able to make more of these, it would probably be a good idea to avoid obsolete parts (with the obvious exception of the Nixies) like the K155ID1. If you use a standard decoder like 74HC42 or CD4028 (or just output the bits directly with a serial-to-parallel like 74HC595), you can use little SMD transistors like MMBTA42 to do the high voltage switching. They're SOT-23, so usually small enough to fit directly under and around the Nixie sockets and not use any additional space.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 07, 2013, 12:40:46 pm
content: I do have some bypass caps, i belive there called decoupling caps aswell right?Eitherway my schematic is not the clearest in the top left are the decoupling caps i had trouble getting the vcc and gnd pins to show on the ic's so i manualy moved those caps next to the IC's when i designed the actual board, the next version if the schematic will have them next to the IC's.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 07, 2013, 03:59:40 pm
content: Could i replace the nixie drivers with discrete transistors? Perhaps some surface mount ones like so? :http://uk.rs-online.com/mobile/p/bipolar-transistors/7390473/[\url]

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 07, 2013, 07:46:00 pm
content: ok i have redesigned two of the tubes to use the transistors and some 74hc42 chips to operatethese are all in the surface mount packagesis there anything wrong within this schematic?