Re: [neonixie-l] VFD filament drive

> I wonder why there should be no air gap? Air gaps lower the inductance, but stabilize it and store energy in the gap. Working forward from this, you generally find flyback type circuits use gapped cores, and others generally instead opt for best coupling and highest inductance. - John --

Re: [neonixie-l] VFD filament drive

For mine I used one of those cheap eBay buck converters. 5v in, 1.x v out (adjustable). 8 iv11 tubes, running for a few years without a blip. If you needed AC, you could always just use an H bridge and a microcontroller pin to flip it at a suitable frequency with a smoothing cap. I found I

Re: [neonixie-l] VFD filament drive

You can use airgaps in transformers in some cases but this design should be without one according to Ed. I am using ferrite pot cores in some other designs where they are wound as a transformer but where the Q-value is of importance and there I use an airgap and also a trimmer through the

Re: [neonixie-l] VFD filament drive

Martin, I wonder why there should be no air gap? - Paul On Wednesday, September 1, 2021 at 1:55:30 AM UTC-4 Dekatron42 wrote: > Paul, > > I'll ask him, but a quick search at Digikey showed both some RM10 and > ETD29 cores, but only a few. Finding Ferrite cores today is not easy, I > have

Re: [neonixie-l] VFD filament drive

Paul, I'll ask him, but a quick search at Digikey showed both some RM10 and ETD29 cores, but only a few. Finding Ferrite cores today is not easy, I have searched some for other projects and they aren't usually stocked in the ranges that the manufacturers make them, and if you want something

Re: [neonixie-l] VFD filament drive

Hi Martin I tried to find a suitable core at digikey, but their parameters don’t map very well to the equation that Ed gives. Could he take a look at what they have and perhaps recommend something. For simplicity’s sake I just looked at toroids

Re: [neonixie-l] VFD filament drive

The amount of ringing is usually load-dependent, and is primarily caused by the transformer being non-ideal. Changing the coupling factor from 0.99 to 0.95 should make quite a difference in the ringing. That wont necessarily reflect reality, but it does show you the effect it has. Also, it

Re: [neonixie-l] VFD filament drive

I created the circuit in LTSpice so I could mess with various components and see how it affects things like frequency and wave form. Rings like crazy, so I added an RC snubber, which seemed to also necessitate tying the primary center tap to ground through a capictor/diode (I don't know if that

Re: [neonixie-l] VFD filament drive

Since transformers isn't my best area, I only have basic understanding of the intricacies but I have experimented some with different transformers in different cases like when driving Trochotrons and Dekatrons I decided to ask an acquaintance who has worked with transformers. His name is Ed

Re: [neonixie-l] VFD filament drive

Some of the vfd driver chips are what I was looking at initially. Bill On Wednesday, August 25, 2021 at 2:02:48 PM UTC-7 Paul Andrews wrote: > When I have time, I will try the driver at the link Martin gave ( > http://www.nutsvolts.com/media-files/Forum-Articles/QA_201110.pdf), but > without

Re: [neonixie-l] VFD filament drive

When I have time, I will try the driver at the link Martin gave ( http://www.nutsvolts.com/media-files/Forum-Articles/QA_201110.pdf), but without the transformer initially. As far as I can tell, the transformer is just to make the VFD drive isolated so you can pull it up above ground. On

Re: [neonixie-l] VFD filament drive

I also have some DT-1704 so this is great! I have two clocks that use them as well. Bill On Wednesday, August 25, 2021 at 1:37:56 PM UTC-7 Bill Notfaded wrote: > I'm kinda in the same boat Paul... VFD's hasn't really been my thing but > figuring out how to drive some weird ones is a new

Re: [neonixie-l] VFD filament drive

I'm kinda in the same boat Paul... VFD's hasn't really been my thing but figuring out how to drive some weird ones is a new hobby. I love your questions because it helps me figure out what I'm doing as well! Bill On Tuesday, August 24, 2021 at 12:57:53 AM UTC-7 Tomasz Kowalczyk wrote: > Did

Re: [neonixie-l] VFD filament drive

Did you try simple PWM? I once tried it, but didn't leave it on for long time, so I can't tell if it shortens the tube life or not, but by simple logic it shouldn't. For most of the time the cathode will be at the same potential. Also it's a nice method of elevating the cathode potential above

Re: [neonixie-l] VFD filament drive

Transformers are not ideal, so even with zero load, they consume inductive current. Most of the energy gets returned to the AC line, but some of it gets dissipated as heat (winding resistance, and hysteresis). This is why unloaded wall transformers still get slightly warm. You can measure the

Re: [neonixie-l] VFD filament drive

Thanks Martin, I'm OK with using a transformer. I would prefer something off the shelf, but perhaps I should just wind my own anyway. Seems like a useful skill to have. As with a lot of these things, I find that I have a lot of questions. For example, this statement: "The transformer is 1:1,

Re: [neonixie-l] VFD filament drive

> > I'm designing a clock for DT-1704 tubes and am stumbling at the filament > drive stage. They want 1.6V. I want to power it from 5VDC. I've tried wiring > them in series, but there is a noticeable brightness gradient if I do. I'm a big fan of series resistors (one per tube). It's

Re: [neonixie-l] VFD filament drive

I mean to try this on a device I'm building, but won't an H-bridge driver do ? It will provide an average potential of half the drive voltage giving the ability to place a grid or anode at a small negative potential, and if the filament requirement is less than the easy 5V it can be reduced using

Re: [neonixie-l] VFD filament drive

There is a nice article in NutsVolts magazine: http://www.nutsvolts.com/media-files/Forum-Articles/QA_201110.pdf where a powerful driver is shown, needs a small transformer but seems to be well designed with equations for calculations of the transformer. /Martin On Friday, 20 August 2021 at

Re: [neonixie-l] VFD filament drive

Theres a section on filament driving in my blog here: https://hannahmishin.com/blog/2017/4/30/russian-tri-color-vfd-indicator-clock *Hannah Mishin* * She/her/hers* *hannahmishin.com* On Fri, Aug 20, 2021 at 1:48 PM Toby Thain wrote: >

Re: [neonixie-l] VFD filament drive

On 2021-08-20 12:58 p.m., Paul Andrews wrote: > I'm designing a clock for DT-1704 tubes and am stumbling at the filament > drive stage. They want 1.6V. I want to power it from 5VDC. ... > FWIW I've used LM2575 1A adjustable step down for DC filament voltages in that range. --Toby > ... > >

Re: [neonixie-l] VFD filament drive

I used a 2.5VAC transformer for my NIMO clock, and use series dropping resistors to get the correct current. Those filaments run at 1.1 VAC and 200mA. Using AC cancels-out the brightness quirks when using DC. The series resistor will reduce the power-on current surge and therefore extend the

Re: [neonixie-l] VFD filament drive

Sorry for not being helpful, but I'd love to see your digivac clock when you're done! On Fri, Aug 20, 2021, 12:58 PM Paul Andrews wrote: > I'm designing a clock for DT-1704 tubes and am stumbling at the filament > drive stage. They want 1.6V. I want to power it from 5VDC. I've tried > wiring

[neonixie-l] VFD filament drive

I'm designing a clock for DT-1704 tubes and am stumbling at the filament drive stage. They want 1.6V. I want to power it from 5VDC. I've tried wiring them in series, but there is a noticeable brightness gradient if I do. I've tried powering them using a LM4871 to generate a square wave with