# two batteries, two voltages, one ic?

OK so i am making a nixie tube clock. to power it im going to use two batteries, small 12v camera batteries (because of space constraints).

Im going to take one to a boost circuit to get the might 180v that go to the nixie tubes. With the other one i am going to put it through a 7805 to have 5v power for my atmega328 and all the other regular voltage stuff.

The way im going to work the nixie tubes is going to be through one si/po shift register and two 74141s, one for each tube i will use. now from the arduino im going to send the output to the shift register and from that im going to take it to the 74141s.

Here lies my problem. how do i get the output of the 74141's to be 180v? do i make the input of the 74141's 180v and the a,b,c,d inputs 5v from the arduino? but ehat do i ground it to? the arduino and then i ground the nixies to the other battery that i boosted to 180v? or how would i do this? and thank for the help in advanced.

I believe the 74141 should run off the same voltage as the atmega 328...5v. The 74141 don't apply 180v to the tube. They only ground the appropriate filaments of the tube. The high voltage is applied only to the tube's anode.

In this example he is using the microcontroller to drive an inductor (pulse width depends on the coil inductance) to create the 170v on C1. The lower right corner of the circuit is the high voltage generator. The microcontroller is used to regulate the high voltage by sensing the reference voltage at the R3-D2 connection. Note the output of the high-voltage generator/regulator only goes to the tube (through R4 for current limiting). This is a safe way to produce the high voltage rather than using a rectified mains source.

Why are you using batteries to power a nixie clock? They are very power hungry, and making a nixie watch practical on batteries takes some real design experience...

It sounds to me like you don't really get how the clocks work yet, try to study some more schematics before you jump in to this or you will just waste money. The SN74141 does not apply high voltage to anything, it only connects/disconnects the nixie's cathodes to/from ground.

yeah i think your right, i need to learn quite a bit more about nixie tubes before i start on the watch... what power source do you think i should use to power this watch once i think im ready to take it on?

So you are planning to make a wristwatch, and not a clock? Just letting you know, that will be a very difficult project and probably cost several thousand dollars to develop, and the power supply will be especially difficult. If you are building a full-sized clock, there are plenty of nixie power supplies available on ebay for very cheap, but if I remember you are in Eastern Europe and it is difficult to ship there. In that case, a simple boost converter will work. I think I posted a link on your other thread, but if not, check out http://sites.google.com/site/willyager/nixie-clock . Simply do some research on boost power supplies (I got started from ladyada's VFD "ice tube" clock power supply, she even has a great power supply calculator), and you should be able to replace the ATTiny45 in my schematic with an arduino. BTW, a great way to learn about this is to google for "nixie schematic", "nixie power supply", "nixie multiplexing" etc.

yeah well ive been researching for a while, i found a really nice boost converter with a 555 timer. i dont think itll work too good and any small disturbance would blow it. but im only looking to power two small in-17’s i know they still take alot of power but i hope i can put a couple of batteries in series, even though i know changing batteries every 2 weeks isnt too cheap lol. but yeah i have some ideas in mind… the actual componenets wont be too hard. its the boost converter that bothers me… it seems like itll take up too much space.

No good reason to use a 555 when you have a microcontroller. But it’s your watch, lol, so look around and see what you find.

ok thank for the schematic, ill look around =)