[neonixie-l] Re: Boost converter inductor sizing question

[gregebert]

You may want to consider other topologies, such as flyback.

I spent a *LOT* of time debugging the DC-DC converter for my wristwatch 
project, with simulations and bench-testing. In the end, I got it working 
but my simulations were way-off because I did not have proper modeling of 
my transformer. 

The main problem I had was saturation, because I used such a small 
transformer due to space-constraints. Lesson-learned: Use an oversized 
inductor and stay well-away from Isat. You'll know it's saturating because 
it will get warm, and even warmer while under load. 

Another area you need to be careful about is the kick-back when the 
switching device shuts off. Depending upon the topology, your switch should 
be rated at the max output of your converter, NOT the DC input supply 
voltage. If you go with a flyback transformer (I used a 10:1 ratio), the 
kickback is *ideally* lowered by the turns ratio; in reality it's 
substantially higher due to leakage inductance and other factors.

Be mindful of the ESR of the capacitor you are using for output filtering. 
Simulators, such as LTspice, will display the RMS current of device (a very 
handy feature).

Expect to spend a lot of time on the bench with a scope. Monitoring the 
current thru the inductor/switch with a scope can be tricky, because noise 
will couple into the scope's ground lead and make you think you have 
horrible ringing/overshoot when you really dont. There are some good 
techniques online, such as removing your scope's ground lead and 
probe-shroud, and connecting the ground at the exposed metal ring near the 
probe tip.

Lastly, you will find that DC-DC converters work beautifully under almost 
no load. Once you start loading them down, they dont work *as* nicely, but 
they definitely *do* work. Welcome to the real world.

Most importantly, when you do get it working, congratulate yourself on your 
accomplishment.

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[neonixie-l] Boost converter inductor sizing question

[SWISSNIXIE - Jonathan F.]

Hi

Modern switchinh regulators don't 'just switch' they are more advanced, to 
determine a suitable inductor, you need to take a look at the datasheet of the 
IC.

The converter from the link you showed, works perfectly, i rebuild that one a 
few times. If you have stability problems, you can solder a cap, whats also 
described on the page.

For panaplex, a lot of panaplex display are specifically designed for multiplex 
operation, what results in a much higher current. Be sure to check if the 
current rating is for continous drive or multiplex drive.

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[neonixie-l] Boost converter inductor sizing question

[ZY]

Hello. I'm trying to build a boost converter for my project to boost 12V to 
150-220V. I'm looking at various converter circuits online, like this one: 
http://desmith.net/NMdS/Electronics/NixiePSU.html, and they use inductors 
on the order of 100uH to 150uH, and use drivers that switch at something 
like 300KHz. But when I look at the wikipedia equation for discontinuous 
mode output voltage, it's this: 

Vo = Vi * (1+Vi * D^2 * T)/(2*L*Io)

If I plug in Vi = 12V, D = 0.92, T = 1/30, L = 0.0001, and Io = 0.025, 
I get something like 93V, which is far from what I want to be at. So I'm 
curious about what I'm doing wrong here.

Also, from what I've read so far, it seems like it's bad to switch between 
continuous and discontinuous modes due to stability? Since my digits would 
turn on and off, my current draw can swing wildly, so I can't really 
guarantee that I would stay in one mode right? Do modern controller ICs 
just handle this without us having to worry about it?


Also just an extra tag along question. I see some nixies use anode 
resistors when they already have cathode resistors. What is the point of 
the anode resistor? Wouldn't the cathode resistor already limit the 
current? I'm looking at the SP-101 Panaplex datasheet and they have a 2.2k 
anode resistor. Wouldn't this affect the brightness depending on how many 
segments are turned on?

Thanks in advance.

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Re: [neonixie-l] Re: IN-13 currents

[Jon Jackson]

No embedded image...


On Tue, May 17, 2016 at 4:40 AM, Joe Croft  wrote:

> Hi Jon,
>
> I have embedded the picture below. It's a good guess if you post the
> circuit on a forum, you don't mind others re-posting it. I am definitely
> using in IN-13. 3 legs vs 2, it's hard to miss the 3rd leg ;).
>
> Gregebert,
>
> Sadly, for the 'art' of the clock, it has to be an IN-13 if for no other
> reason, to keep the size of the board in check, not to mention the drivers!
>
> -joe
>
> On Tue, May 17, 2016 at 1:52 AM, Jon  wrote:
>
>>
>> I don't see a circuit in the link - it links on to a dead site. Can you
>> post here? Some thoughts...
>>
>> Are you sure you are using IN-13 not IN-9 ? 13mA to fully light the tube
>> is around what might be expected for a slightly cathode poisoned IN-9. It's
>> easy to check even if the tube markings have worn off: IN-13 has three
>> terminals, IN-9 has two.
>>
>> I would expect both tube types to require about 150V to strike reliably,
>> and then the voltage across the tube will drop down to the maintenance or
>> running voltage in the 95V - 105V range. Were you anticipating something
>> different?
>>
>> Jon
>>
>>
>>
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[neonixie-l] DT-1704C sockets

[Dylan Distasio]

Hi all-

Does anyone know which socket to use with DT-1704C tubes?  It looks like a
9 pin mini but I was hoping to confirm.

Thanks!

-Dylan

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