IV-11 VFD

[Spencer]

Hello All!

I have a question on this as it has stumped me or I am just slow. ;)  I have been using the IV-11 VFD tubes with a HV5812 shift register with the MCU multiplexing the display. 

I have discovered the PT6311 which will handle all of my multiplexing and was in heaven. After reading the datasheet, I discovered that it uses a negative supply for the VFD. I made a voltage inverter and tried testing it out on a tube to see what the connections are. This is where I do not understand it. I had been giving the tube about +25V to the grid and Anodes with the HV5812 but I am not sure what the connection is with the PT6311, if it even works with a VFD tube for a -25 power supply. 

The heater has +5V supply with an appropriate resistor in both circumstances.

I put -25V on the grid and Anodes, then tried just -25V to the Anodes and the grid to ground and it doesn't light up.

Does anyone have any suggestions?

Thanks,

Spencer

[John Rehwinkel]

> I have discovered the PT6311 which will handle all of my multiplexing and was in heaven. After reading the datasheet, I discovered that it uses a negative supply for the VFD. I made a voltage inverter and tried testing it out on a tube to see what the connections are. This is where I do not understand it. I had been giving the tube about +25V to the grid and Anodes with the HV5812 but I am not sure what the connection is with the PT6311, if it even works with a VFD tube for a -25 power supply.
>
> The heater has +5V supply with an appropriate resistor in both circumstances.
>
> I put -25V on the grid and Anodes, then tried just -25V to the Anodes and the grid to ground and it doesn't light up.
>
> Does anyone have any suggestions?

The VFD only cares about the difference of voltage between its elements. So the grid and anode have to be more positive than the cathode to light it. The PT6311 is arranged so that the cathode is run at -25V, and to turn segments on, the grids and anodes are pulled "up" to ground, making them more positive than the cathode. To turn them off, it pulls then down to -25V.

I have some commercial VFD inverters from surplus companies that produce -30V, along with a floating center-tapped 6VAC output to power the filament. I connect the -30V to the filament center tap.

The tricky part is interfacing logic to the PT6311 - sometimes it's easiest to float the logic supply.

- John

[Spencer W]

Thanks for the reply. I put the -25v on pins 1 and 11 (cathodes) and GND on pin 2(grid) and GND on a random anode to see if it would light up and nothing illuminated.

Sent from my iPhone

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[John Rehwinkel]

> Thanks for the reply. I put the -25v on pins 1 and 11 (cathodes) and GND on pin 2(grid) and GND on a random anode to see if it would light up and nothing illuminated.

The filament needs to be hot to emit electrons for the VFD to operate - this is normally accomplished by heating it electrically. I did kind of gloss over this -- you have to have voltage across the filament as well - this is true no matter how the other voltages are supplied. The "ideal" method is to have a small center-tapped transformer providing the AC filament voltage (generally something between half a volt to a few volts), and hook the -25V to the center tap. I often use a generic 6.3V filament transformer, with series resistors to drop the voltage to whatever the VFD filament needs. Some people don't want to bother with an AC filament voltage, and just run it with DC - this will work, but can lead to brightness gradients in some tubes.

So, just to light something, at a minimum, you'll need -25 volts at one end of the filament, -(25 + filament voltage) at the other end of the filament, and 0V at the grid(s) and anode(s) you want to light.

- John

[Spencer]

Got it working! It lights up now and it looks like I will have to change the filament resistor. I was using a 30 ohm with +5V but ooo boy does it get bright with that. I'll drop it down to around +1.5V and can take it from here.

Thanks again.

---

From: John Rehwinkel <jre...@mac.com>
To: neoni...@googlegroups.com
Sent: Saturday, July 20, 2013 12:54 PM
Subject: Re: [neonixie-l] IV-11 VFD

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[Bill van Dijk]

Spencer,

 

Attached is the schematic for my IV17 clock with a PT6311. It is a chip that takes a bit of figuring out, also on the software side. My clock displays time (why not eh?) and the full date in a marquee format as well as ambient temperature. I would suggest the PT6311 is possibly a bit of overkill for a 7 segment based clock design.

 

Bill v. Dijk

 

From: neoni...@googlegroups.com [mailto:neoni...@googlegroups.com] On Behalf Of Spencer
Sent: Saturday, July 20, 2013 2:29 PM
To: neoni...@googlegroups.com
Subject: Re: [neonixie-l] IV-11 VFD

 

Got it working! It lights up now and it looks like I will have to change the filament resistor. I was using a 30 ohm with +5V but ooo boy does it get bright with that. I'll drop it down to around +1.5V and can take it from here.

 

Thanks again.

 

---

From: John Rehwinkel <jre...@mac.com>
To: neoni...@googlegroups.com
Sent: Saturday, July 20, 2013 12:54 PM
Subject: Re: [neonixie-l] IV-11 VFD

> Thanks for the reply. I put the -25v on pins 1 and 11 (cathodes) and GND on pin 2(grid) and GND on a random anode to see if it would light up and nothing illuminated.

The filament needs to be hot to emit electrons for the VFD to operate - this is normally accomplished by heating it electrically.  I did kind of gloss over this -- you have to have voltage across the filament as well - this is true no matter how the other voltages are supplied.  The "ideal" method is to have a small center-tapped transformer providing the AC filament voltage (generally something between half a volt to a few volts), and hook the -25V to the center tap.  I often use a generic 6.3V filament transformer, with series resistors to drop the voltage to whatever the VFD filament needs.  Some people don't want to bother with an AC filament voltage, and just run it with DC - this will work, but can lead to brightness gradients in some tubes.

So, just to light something, at a minimum, you'll need -25 volts at one end of the filament, -(25 + filament voltage) at the other end of the filament, and 0V at the grid(s) and anode(s) you want to light.

- John

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[Spencer]

Thanks for the schematic. It would be overkill if it was just for a clock but I want to save cycles on the MCU since it was multiplexing the tubes and boosting the voltage. I was taking cycles away from the MCU and it was causing flickering. I looked at either a PT6311 or having a dedicated attiny to run the multiplex/booting and feeding via serial the tube display.

So it just looks like the filament voltage is biased (is that the current term?) to the grid voltage. So -18v filament one end and -20 the other end and grid/anode is -20v. I am using MC34063 inverted to generate the voltage. I'll give it a shot it and see what happens!

---

From: Bill van Dijk <bvd...@xplornet.com>
To: neoni...@googlegroups.com
Sent: Sunday, July 21, 2013 7:07 AM
Subject: RE: [neonixie-l] IV-11 VFD

To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/003001ce860a%24f3b03750%24db10a5f0%24%40com.

[Bill van Dijk]

Spencer,

 

there are a couple of (actually many) options. I have another clock that also multiplexes 60 LEDS as well as 6 7-segment displays in a 1-6 MUX. I control the multiplexing of the tubes by interrupts at about 300Hz, which ensures better timing. The power supply is probably more tolerant to a couple of missed or late cycles without any visual effects. Shift registers are also great tools for multiplexing, especially when used in conjunction with a BCD to 7 segment decoder. That way you can completely control 6 tubes with only one 8-bit port. I would suggest if you do feel inclined to add a small MCU to help out, dedicated it to the power supply, and keep all the clock functions as well as the multiplexing in the main MCU.

 

So many options..... :-)

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[Spencer W]

So many ways to tackle one problem. I get stubborn when one way doesn't work right the first time and will spend days getting it to work.

I'm trying to keep the interrupts free for some rotary encoders so either the pt6311 or the secondary MCU will be he way to go. Plus if I get the pt6311 working for this, I have a bunch of different tubes that I can use this one.

I have been eyeing the IV-17 for some projects and would love to see it work with this.

Either way, once I get everything figured out, I'll share with the group so someone else doesn't need to do the leg work.

-spencer

Sent from my iPhone

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[Spencer]

After spending several days playing with the negative voltages and testing it, it doesn't work as I was hoping. It seems that a lot of people use AC instead of DC and I can't find an example that uses DC for negative voltages. This was the closest I could find, http://threeneurons.wordpress.com/vfd-stuff/ , but it looks like its AC.

I was working with 2 tubes in series with a 30 ohm 2W resistor that has +5V applied to the first filament and then the other end is grounded, and the grid/anode was fed +30V with a HV5812 shift register. 

I put the -27V on the first end and GND on the other end of the filament, it lit up pretty bright on the filament and I tried with different resistor values but even the 2W resistors were heating up and the brightness of the segments wasn't there.

I then tried -27V on the first filament and different combinations of -27V and the +5V with resistors on the other end of the filament and the anodes were grounded, but nothing was working or it was very dim segments. 

While I would love to get this working, It looks like I should use a second MCU to handle the display/boost and another to handle all the other operations.

Thank you everyone,

Spencer

---

From: Spencer W <upnxw...@yahoo.com>
To: "neoni...@googlegroups.com" <neoni...@googlegroups.com>
Sent: Monday, July 22, 2013 7:33 PM

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[John Rehwinkel]

> After spending several days playing with the negative voltages and testing it, it doesn't work as I was hoping. It seems that a lot of people use AC instead of DC and I can't find an example that uses DC for negative voltages. This was the closest I could find, http://threeneurons.wordpress.com/vfd-stuff/ , but it looks like its AC.

Yeah, that's AC.

> I was working with 2 tubes in series with a 30 ohm 2W resistor that has +5V applied to the first filament and then the other end is grounded, and the grid/anode was fed +30V with a HV5812 shift register.

I'm not quite sure what that lashup is, my best guess is one end of one filament is connected to +5V, the other end to a resistor, the other end of the resistor to the other filament, and the other end of the other filament to ground. That's a kind of silly lashup. I'd connect +5V - filament - filament - resistor - ground. This would put the filaments at a slight positive bias, so grounding other elements would give solid cutoff.

You don't really need a resistor when running two IV-17 filaments in series, as they're rated for 2.4 volts, so two of them in series would need 4.8 volts - close enough to 5 volts. If you wanted to use a series resistor to give them more precisely the right voltage, you'd only need 4 ohms.

> I put the -27V on the first end and GND on the other end of the filament, it lit up pretty bright on the filament and I tried with different resistor values but even the 2W resistors were heating up and the brightness of the segments wasn't there.

You're dropping a lot of voltage there:

[Spencer]

Thanks John, I really do appreciate the response.

It looks like I will try to go with AC voltage on the filament as it seems to be the standard and easiest. ;) Found the information for the 555 and will play with that.

---

From: John Rehwinkel <jre...@mac.com>
To: neoni...@googlegroups.com

Sent: Monday, July 29, 2013 10:27 PM

Subject: Re: [neonixie-l] IV-11 VFD

Note that you want the resistor connected to ground, and the filament connected to -27V, not the other way around.  The IV-17 wants 47mA of current*, which is the same as 0.047 amps.  You want to drop the difference between your negative supply (-27 volts) and the filament voltage (2.4 volts), so you'll want the resistor to drop 24.6 volts.  Dividing 24.6 volts by 0.047 amps yields 523 ohms.  510 ohms is a common value, and would be close enough.  That resistor would be dissipating 0.046 amps times 24.6 volts, or nearly 1.2 watts - enough to make a 2 watt resistor fairly warm!  Since your resistor is dissipating more than ten times the power of the filament, and you need to make the filament hot, you're going to burn a lot of power this way (this is one of the reasons some of us like to use AC filament drive - then you can use capacitors to limit the filament power instead of resistors, and capacitors don't just waste power as heat).

Ideally, you'd have a supply that's 2.4 volts different from your -27V supply.  So if you had a -27V supply and a -24.6V supply, that would work with no resistor.  Similarly, a -27V supply and a 29.4V supply.  Normally, you'd split the difference and have a -25.8V supply and a -28.2V supply, so the average filament voltage would be -27V, but it's not critical.

> I then tried -27V on the first filament and different combinations of -27V and the +5V with resistors on the other end of the filament and the anodes were grounded, but nothing was working or it was very dim segments.

Going from -27V to +5V only makes the problem worse - now you're trying to get 2.4 volts out of a 32 volt difference.  -27V to ground is better.  You want to use the voltage that's closest to -27V available (as long as it's >= 2.4 volts different).  Since you only have the single negative supply, you're pretty much stuck with either the big watt-burning resistor or going to an AC filament drive.

> While I would love to get this working, It looks like I should use a second MCU to handle the display/boost and another to handle all the other operations.

I don't think another MCU is going to help with this problem.  You could use the MCU clock output to derive your AC filament drive, or some I/O pin that you have generating a pulsing signal.

* the current is key, that's what creates the heat that makes the filament thermionically emit electrons.

- John

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[vfdclock]

try to visit my website: http://vfdclock.jimdo.com.you can find answers on the web site.

在 2013年7月30日星期二UTC+8上午10时25分58秒，Spencer写道：

[vfdclock]

And I suggest you to read my article_"Creating INRC09SS49 VFD Module",the org was written in chinese,so try to trans it by using google tans.
http://vfdclock.jimdo.com/2013/04/26/inrc09ss49t%E5%9E%8Bvfd%E6%98%BE%E7%A4%BA%E6%A8%A1%E5%9D%97%E7%9A%84%E5%88%B6%E4%BD%9C/
http://u.jimdo.com/www36/o/sb03fefd490221d21/img/i159f994fa2a943fb/1367333708/orig/%E6%A8%A1%E5%9D%97%E7%94%B5%E8%B7%AF%E5%9B%BE.jpg



在 2013年7月20日星期六UTC+8下午9时10分53秒，Spencer写道：

[Spencer]

Thanks for the link. I went through it and saw how yours is set up. I actually found the post in the group about a year ago about the MAX628 and I went ahead and ordered some samples of that to see how it works out but I will keep this in mind also as it is always nice to see how others have come to the same solution!

---

From: vfdclock <zjjsz...@gmail.com>
To: neoni...@googlegroups.com
Sent: Thursday, August 1, 2013 9:43 PM
Subject: [neonixie-l] Re: IV-11 VFD

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[Spencer]

Just thought I would give an update on my adventures with the VFD tube. I actually found this schematic online, http://www.mikrocontroller.net/attachment/41640/VFD_Schaltung_Auszug.pdf , and saw it used a LM9022. 

Too bad it was discontinued from production a few years back but figured I would hit up the Chinese IC markets to see what is available, as you never know! I found a person that was selling these for not too expensive and decided to buy a bunch. The LM9022 arrived about a week ago now and I have been testing them out and it works perfectly.

 I do not know if these are knock offs/rebranded or just sitting in a warehouse but I used that schematic and I am getting the VFD to light up with the PT6311.

[John Rehwinkel]

> Just thought I would give an update on my adventures with the VFD tube. I actually found this schematic online, http://www.mikrocontroller.net/attachment/41640/VFD_Schaltung_Auszug.pdf , and saw it used a LM9022.
>
> Too bad it was discontinued from production a few years back but figured I would hit up the Chinese IC markets to see what is available, as you never know! I found a person that was selling these for not too expensive and decided to buy a bunch.

What package? About eight months ago, Grahame Marsh mentioned that he'd been able to find them at RS Components, I think the SOIC version. He obtained a few and sent them to me, but I haven't gotten around to playing with VFDs again yet, alas. Here's what he had to say originally in this group:

> Having said the LM9022 VFD filament/HV driver chip had gone unobtainium, I've found it back in stock with RS Components in the UK at about the same price that it was when I last bought them from Farnell. Anyone experimenting with VFDs might find this an interesting chip. I use it in my Approx Clock: 5V goes in and an AC for the filament and drive to a Dickson voltage multipler comes out.

- John

[Spencer]

The package is SO8N. Yah, I saw that post and actually tried that website first, then I went through different vendors to see if anything was in stock.

---

From: John Rehwinkel <jre...@mac.com>
To: neoni...@googlegroups.com

Sent: Monday, August 19, 2013 6:39 PM
Subject: Re: [neonixie-l] Re: IV-11 VFD

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[Nick]

RS are no longer stocking it - http://uk.rs-online.com/web/p/vacuum-fluorescent-display-filament-drivers/6512515 - marked as discontinued, and TI (the manufacturer) have also stopped selling & sampling them - they also don;t have a recommended alternative... http://www.ti.com/product/lm9022

Nick

[Nick]

On Tuesday, 20 August 2013 09:48:47 UTC+1, Nick wrote:

RS are no longer stocking it - http://uk.rs-online.com/web/p/vacuum-fluorescent-display-filament-drivers/6512515 - marked as discontinued, and TI (the manufacturer) have also stopped selling & sampling them - they also don;t have a recommended alternative... http://www.ti.com/product/lm9022

You could always look at Mike's pages - http://threeneurons.wordpress.com/vfd-stuff/ - he has alternatives

Nick 

[Grahame Marsh]

It was odd the way RS brought them back on sale but the discontinued manufacturing is a killer of course.  Pity as I found it a neat and easy chip to use (even if it was SMD).

Grahame

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[Nick]

On Tuesday, 20 August 2013 11:01:52 UTC+1, Grahame Marsh wrote:

It was odd the way RS brought them back on sale but the discontinued manufacturing is a killer of course.  Pity as I found it a neat and easy chip to use (even if it was SMD).

Grahame

The Fairchild FAN7387 looks like a good candidate - FET bridge driver with built-in oscillator  - http://www.fairchildsemi.com/pf/FA/FAN7387.html - very cheap, available in SO-8 or DIL8, drives 650mA directly, but requires 11V Vdd 

Nick

[John Rehwinkel]

> The Fairchild FAN7387 looks like a good candidate - FET bridge driver with built-in oscillator - http://www.fairchildsemi.com/pf/FA/FAN7387.html - very cheap, available in SO-8 or DIL8, drives 650mA directly, but requires 11V Vdd

Oh, hadn't seen that one, I like it. I had been looking at the TSC428/MAX628 that Konstantin uses, but it doesn't have the built-in oscillator (I'd just drive it with a microcontroller pin). They're both available in DIP packages for breadboarding, but you're right, the FAN7387 is about half the price of the MAX628.

- John