Re: [neonixie-l] IV-11 VFD clock, some questions
Actually, brightness is a needed feature when this displays are used as intended. They were designed and are still used with heavy optical filters in front, to enhance contrast and visually eliminate the tube mechanical internal structure from the users view. We of course like to see the tube naked, but we have to live with the cost of the features :) Gastón On Tuesday, November 19, 2013 7:01:33 PM UTC-3, Adam Jacobs wrote: I think that one of the features of Vacuum Fluorescent Display is brightness. To paraphrase someone wiser than me: If you find yourself thinking up more and more convoluted mechanisms for making it work, then that's often an indicator that you're barking up the wrong tree. -Adam On 11/19/2013 12:48 PM, David Forbes wrote: Also, if your VFD is too bright, you can reduce the brightness by reducing the duty cycle, which is done by turning off the anodes on for some time in each cycle. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/27d28f9e-d3d9-40d8-841c-674f673e1bd9%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
I know the difference between a nixie and a VFD tube but I have to say that your explanation is very nice to summarize all the loose bits of information in my head. So If I have a 6 volt supply for my four filaments (in series) I would not need a resistor. I think the 7806 won't get that warm with roughly 400ma going through it but I can always take a simple switching psu for it or attach it to my (metal) enclosure. I will simply use a DC filament supply then to keep things simple (this project is going to be complicated enough). My only remaining concern is the driving method, I would like to order all my parts off ebay and/or tayda electronics. Places like mouser etc have (in my opinion) ridiculous shipping rates so I would like to avoid them. Another point is that the max6921 costs around 6-7 dollar a piece +1 euro for a plcc socket, I am trying to keep the costs down a bit. So a method to avoid using these drivers is preferred. HV5812: cheap but shipping costs are 40-50 dollar MAX6921 expensive and/or high shipping costs Op dinsdag 19 november 2013 20:06:50 UTC+1 schreef Adam Jacobs: Hi Gideon, I think that you have some confusion regarding how VFDs are driven. VFDs are not nixie tubes or anything even similar. Nixies are not vacuum tubes, they are cold-cathode (neon) tubes. With nixies, we place ~180vdc across the anode cathode via a current-limiting resistor. The reason for current-limiting in a nixie is because as current increases, nixie impedance decreases, causing the neon tube to rapidly begin dissipating a catastrophic amount of heat. Nixies, being neons, regulate voltage to their maintenance voltage. Any reasonable voltage above the striking voltage will work fine. VFDs are triodes: Hot-cathode vacuum tubes. Ideally, the filament is driven with an AC supply of the designed voltage (via the two filament pins, usually a couple of volts) and the anode segments are driven with a voltage regulated DC supply at the designed voltage (usually 20-30v for direct and ~60v for multiplex). The grid is driven exactly the same as an anode segment and is used to turn the display 'on'. There are no current-limiting resistors used for driving the anode segments or the grid! In my VFD clocks, I used the trick (which I learned from here) of driving the filaments with DC. This works fine if you are using individual numeral VFD tubes, I wouldn't try it if you are using the big multi-numeral VFD display tubes. The (known) current draw of the filament is used for calculating a resistor-divider. One leg of the filament is tied to ground, the other leg to +5vdc via the resistor. If you go with this approach be sure to do your math on the front end. These filaments draw a lot of current, which means a lot of heat dissipation in the voltage-divider resistor. Driving this setup via a linear regulator supply would need a very large heat-sink. I would recommend using a switching supply like the LM2575. Obviously, if you have an AC supply that is the correct voltage for the filament then no resistor is needed. For a schematic: http://elbastl.sweb.cz/6-digit-VFD.zip I liked Maxim IC's 6921 driver IC. I know you specifically called it out as not an option, but it worked well for me. Specifically, I used the PLCC package because I work exclusively in protoboard and there are easy DIP PLCC sockets. There are numerous advantages in my opinion to the dedicated VFD driver chip. Instead of 8 dedicated GPIO pins (7-segments + grid), the 6921 uses a standard SPI interface. This would be even more advantageous on 16-segment VFDs. One thing you mentioned: Yes, 60v applied to the anodes will be VERY bright, even if multiplexed. I had to move my VFD clocks to bright places like my desk at work. a LOT brighter than equivalent nixie designs. I spent some time dialing back the supply voltages before finally giving up and accepting that VFDs are just designed to be bright. -Adam On 11/19/2013 5:09 AM, Gideon Wackers wrote: I want to build a four digit VFD clock (three of them actually) without using drivers like the max6921. I have two possibilities at this moment, one is this http://i.imgur.com/D4FGaV1.jpg and the other being this one http://i.imgur.com/5fMc7ty.png . Which would be best? Another question is the resistor that I will need: 0.0035/25*3 = 0.00042 60/0.00042 = 140k = 130K or 150K ohm for R1 and 100k for R2 For the grids the same circuit applies but with a slightly different value for R1 due to the different current. But this implies that I use 60 volt. A few people said that the tubes are very bright at the recommended 50-70 volt for multiplexed tubes so if I lower the voltage to 40 volts I would suddenly need only 100K for R1. Will I bump into problems if I lower the voltage to lets say 40 volts but when my resistors are calculated for 60 volt? I want to make the filament
Re: [neonixie-l] IV-11 VFD clock, some questions
So now I only have to figure out wether my two transistor driver is a good way to drive my IV-11 tubes :) I was hoping someone more versed in the intricacies of transistors would address this, but they haven't, so I'll take a stab at it. I want to build a four digit VFD clock (three of them actually) without using drivers like the max6921. I have two possibilities at this moment, one is this http://i.imgur.com/D4FGaV1.jpg This one has Q1 in a common base configuration, which does not provide current gain. It seems to me like it would put Q1 into its linear region (due to the drop across R1), so you might have to fiddle with the R values to get Q2 to turn on and off reliably. Since you're dealing with low currents, it should work fine. and the other being this one http://i.imgur.com/5fMc7ty.png . This is a more traditional common emitter configuration, where both transistors can give current gain. Instead of the usual series base resistor to limit current, there's an emitter resistor which does double duty of limiting both the base and collector currents. Which would be best? I'd slightly prefer the second over the first (although there are reasons you might want to use the first one, involving current limiting and the like). They both work essentially the same way: the PNP transistor is kept turned off by its base bias resistor to V+, until the NPN transistor turns on, and pulls the base down toward ground, thereby turning on the PNP transistor, which then provides V+ out of its collector to drive the VFD anodes/grids. The NPN transistor's emitter resistor limits the current flowing through both transistors (it does not control the amount of current available to the VFD, except in a sort of indirect fashion - normally the transistors are fully off or fully on). Another question is the resistor that I will need: 0.0035/25*3 = 0.00042 60/0.00042 = 140k = 130K or 150K ohm for R1 and 100k for R2 For the grids the same circuit applies but with a slightly different value for R1 due to the different current. As I said, those resistors don't really control the current into the VFD. However, the VFD doesn't need to be current limited, so all the resistors do is protect the transistors and microcontroller. But this implies that I use 60 volt. A few people said that the tubes are very bright at the recommended 50-70 volt for multiplexed tubes so if I lower the voltage to 40 volts I would suddenly need only 100K for R1. Will I bump into problems if I lower the voltage to lets say 40 volts but when my resistors are calculated for 60 volt? Again, the resistors are only there for current limiting, and they're not terribly critical. If the transistors turn on and off reliably, and there isn't too much current through them, you're fine. - John -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/503D6874-D978-43FF-9203-45EBB30472AA%40mac.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
Thank you very much for this reply, I'll just order a few values and see what works. But I am missing one thing to complete the story; why are current values given in the datasheet if there is no need for current regulation? or should those be seen as normal values that you will see during operation just as with the filament current. Op dinsdag 19 november 2013 21:36:56 UTC+1 schreef jrehwin: So now I only have to figure out wether my two transistor driver is a good way to drive my IV-11 tubes :) I was hoping someone more versed in the intricacies of transistors would address this, but they haven't, so I'll take a stab at it. I want to build a four digit VFD clock (three of them actually) without using drivers like the max6921. I have two possibilities at this moment, one is this http://i.imgur.com/D4FGaV1.jpg This one has Q1 in a common base configuration, which does not provide current gain. It seems to me like it would put Q1 into its linear region (due to the drop across R1), so you might have to fiddle with the R values to get Q2 to turn on and off reliably. Since you're dealing with low currents, it should work fine. and the other being this one http://i.imgur.com/5fMc7ty.png . This is a more traditional common emitter configuration, where both transistors can give current gain. Instead of the usual series base resistor to limit current, there's an emitter resistor which does double duty of limiting both the base and collector currents. Which would be best? I'd slightly prefer the second over the first (although there are reasons you might want to use the first one, involving current limiting and the like). They both work essentially the same way: the PNP transistor is kept turned off by its base bias resistor to V+, until the NPN transistor turns on, and pulls the base down toward ground, thereby turning on the PNP transistor, which then provides V+ out of its collector to drive the VFD anodes/grids. The NPN transistor's emitter resistor limits the current flowing through both transistors (it does not control the amount of current available to the VFD, except in a sort of indirect fashion - normally the transistors are fully off or fully on). Another question is the resistor that I will need: 0.0035/25*3 = 0.00042 60/0.00042 = 140k = 130K or 150K ohm for R1 and 100k for R2 For the grids the same circuit applies but with a slightly different value for R1 due to the different current. As I said, those resistors don't really control the current into the VFD. However, the VFD doesn't need to be current limited, so all the resistors do is protect the transistors and microcontroller. But this implies that I use 60 volt. A few people said that the tubes are very bright at the recommended 50-70 volt for multiplexed tubes so if I lower the voltage to 40 volts I would suddenly need only 100K for R1. Will I bump into problems if I lower the voltage to lets say 40 volts but when my resistors are calculated for 60 volt? Again, the resistors are only there for current limiting, and they're not terribly critical. If the transistors turn on and off reliably, and there isn't too much current through them, you're fine. - John -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/0ba935a7-397b-4a2e-88e6-10f67704d633%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
On 11/19/2013 1:36 PM, John Rehwinkel wrote: I want to build a four digit VFD clock (three of them actually) without using drivers like the max6921. I have two possibilities at this moment, one is this http://i.imgur.com/D4FGaV1.jpg and the other being this one http://i.imgur.com/5fMc7ty.png . Which would be best? I'd use the more traditional design with a resistor in series with the base of the NPN transistor driven by the CPU, rather than the emitter resistor as you showed. More or less like this: http://www.dos4ever.com/nixie1/multiplexing.gif That resistor R5 from base to emitter of the PNP transistor can be a lot lower value, as low as R6/Vanode. It will make the anode turn off faster, the lower resistance it is. The transistors can be any type rated for more than the VFD anode supply. Also, if your VFD is too bright, you can reduce the brightness by reducing the duty cycle, which is done by turning off the anodes on for some time in each cycle. -- David Forbes, Tucson, AZ -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/528BCE92.509%40dakotacom.net. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
I'd use the more traditional design with a resistor in series with the base of the NPN transistor driven by the CPU, rather than the emitter resistor as you showed. David has a point - the disadvantage is it uses one more resistor, the (large) advantage is the functions are now separated - R7 limits the current out of the microcontroller pin into the base of T2, and R6 limits the current through T2 into the base of T1. Since they're separate, they can be different values (as, in fact, they are). You might have to tweak R6 a bit lower, since the supply voltage will be less for VFD use (R7 is fine). - John -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/71D973B2-2B82-4568-BC33-FE5331DAF359%40mac.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
http://i.imgur.com/CFTb8gI.png is this what you mean? Eagle was being weird today so I had to draw it in lochmaster Why is that better than the original two ideas? I would like to understand everything :) Op dinsdag 19 november 2013 21:48:18 UTC+1 schreef nixiebunny: On 11/19/2013 1:36 PM, John Rehwinkel wrote: I want to build a four digit VFD clock (three of them actually) without using drivers like the max6921. I have two possibilities at this moment, one is this http://i.imgur.com/D4FGaV1.jpg and the other being this one http://i.imgur.com/5fMc7ty.png . Which would be best? I'd use the more traditional design with a resistor in series with the base of the NPN transistor driven by the CPU, rather than the emitter resistor as you showed. More or less like this: http://www.dos4ever.com/nixie1/multiplexing.gif That resistor R5 from base to emitter of the PNP transistor can be a lot lower value, as low as R6/Vanode. It will make the anode turn off faster, the lower resistance it is. The transistors can be any type rated for more than the VFD anode supply. Also, if your VFD is too bright, you can reduce the brightness by reducing the duty cycle, which is done by turning off the anodes on for some time in each cycle. -- David Forbes, Tucson, AZ -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/605f3a58-2171-4e25-8437-89bde256c741%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
I was typing the previous reply while you posted it, that clears some things up. You mention tweaking the value, is there a way to actually calculate it? (I'm not that much into transistor calculations as you may have noticed) Op dinsdag 19 november 2013 22:06:16 UTC+1 schreef jrehwin: I'd use the more traditional design with a resistor in series with the base of the NPN transistor driven by the CPU, rather than the emitter resistor as you showed. David has a point - the disadvantage is it uses one more resistor, the (large) advantage is the functions are now separated - R7 limits the current out of the microcontroller pin into the base of T2, and R6 limits the current through T2 into the base of T1. Since they're separate, they can be different values (as, in fact, they are). You might have to tweak R6 a bit lower, since the supply voltage will be less for VFD use (R7 is fine). - John -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/22dc8faf-3472-4492-ab68-6fddc738a31d%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
FYI David: On the clock that I built with IV-11 tubes, I initially started with an anode voltage of 60v; which is the median multiplexed voltage as per this datasheet: http://www.tromop.eu/cms/media/IV-11%20datasheet.pdf and a 1/6 duty cycle (16.67%). That clock was bright. Couldn't sleep in the room with it running, way too bright. I tried lowering the anode voltage supply to 50v, which is the minimum voltage listed in the datasheet for multiplexed mode. This helped, but not enough; not by a long shot. So, then I started lowering duty cycle. I can't remember how low I eventually took it, but I soon realized that I wouldn't be able to get the brightness as low as I needed without introducing some very noticeable flicker. So, I moved the voltage back to 60v and the duty cycle back to 1/6 and moved the clock to a much brighter location. Works perfect. :) FYI, this was with the filament @ 1.5vdc. I don't know enough about VFDs to know if lowering the filament voltage might have helped. I think that one of the features of Vacuum Fluorescent Display is brightness. To paraphrase someone wiser than me: If you find yourself thinking up more and more convoluted mechanisms for making it work, then that's often an indicator that you're barking up the wrong tree. -Adam On 11/19/2013 12:48 PM, David Forbes wrote: Also, if your VFD is too bright, you can reduce the brightness by reducing the duty cycle, which is done by turning off the anodes on for some time in each cycle. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/528BDFBD.2080509%40gmail.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
Hi Gideon, How many of these clocks are you planning to build? If it is just a few, then I wouldn't sweat the costs too much. Both of those companies (used to be - I assume still) are very generous with samples. I agree that the Supertex and Maxim parts can be difficult to obtain for a low price in individual quantities from normal vendors. I've got a drawer full of Supertex and Maxim samples, I'd be happy to mail you the parts. FYI, requests for samples get a much more positive response if you use a company or university email and describe a plausible project in the request. Any time that I can't find some obscure part that is listed for a project, I move to the obscure part manufacturer's website and request a sample. No problem. Contact me off-list with your address parts request and I'll see what I can do. Of course, if you're designing a clock for mass production, then all bets are off. :) -Adam On 11/19/2013 11:39 AM, Gideon Wackers wrote: I know the difference between a nixie and a VFD tube but I have to say that your explanation is very nice to summarize all the loose bits of information in my head. So If I have a 6 volt supply for my four filaments (in series) I would not need a resistor. I think the 7806 won't get that warm with roughly 400ma going through it but I can always take a simple switching psu for it or attach it to my (metal) enclosure. I will simply use a DC filament supply then to keep things simple (this project is going to be complicated enough). My only remaining concern is the driving method, I would like to order all my parts off ebay and/or tayda electronics. Places like mouser etc have (in my opinion) ridiculous shipping rates so I would like to avoid them. Another point is that the max6921 costs around 6-7 dollar a piece +1 euro for a plcc socket, I am trying to keep the costs down a bit. So a method to avoid using these drivers is preferred. HV5812: cheap but shipping costs are 40-50 dollar MAX6921 expensive and/or high shipping costs Op dinsdag 19 november 2013 20:06:50 UTC+1 schreef Adam Jacobs: Hi Gideon, I think that you have some confusion regarding how VFDs are driven. VFDs are not nixie tubes or anything even similar. Nixies are not vacuum tubes, they are cold-cathode (neon) tubes. With nixies, we place ~180vdc across the anode cathode via a current-limiting resistor. The reason for current-limiting in a nixie is because as current increases, nixie impedance decreases, causing the neon tube to rapidly begin dissipating a catastrophic amount of heat. Nixies, being neons, regulate voltage to their maintenance voltage. Any reasonable voltage above the striking voltage will work fine. VFDs are triodes: Hot-cathode vacuum tubes. Ideally, the filament is driven with an AC supply of the designed voltage (via the two filament pins, usually a couple of volts) and the anode segments are driven with a voltage regulated DC supply at the designed voltage (usually 20-30v for direct and ~60v for multiplex). The grid is driven exactly the same as an anode segment and is used to turn the display 'on'. There are no current-limiting resistors used for driving the anode segments or the grid! In my VFD clocks, I used the trick (which I learned from here) of driving the filaments with DC. This works fine if you are using individual numeral VFD tubes, I wouldn't try it if you are using the big multi-numeral VFD display tubes. The (known) current draw of the filament is used for calculating a resistor-divider. One leg of the filament is tied to ground, the other leg to +5vdc via the resistor. If you go with this approach be sure to do your math on the front end. These filaments draw a lot of current, which means a lot of heat dissipation in the voltage-divider resistor. Driving this setup via a linear regulator supply would need a very large heat-sink. I would recommend using a switching supply like the LM2575. Obviously, if you have an AC supply that is the correct voltage for the filament then no resistor is needed. For a schematic: http://elbastl.sweb.cz/6-digit-VFD.zip http://elbastl.sweb.cz/6-digit-VFD.zip I liked Maxim IC's 6921 driver IC. I know you specifically called it out as not an option, but it worked well for me. Specifically, I used the PLCC package because I work exclusively in protoboard and there are easy DIP PLCC sockets. There are numerous advantages in my opinion to the dedicated VFD driver chip. Instead of 8 dedicated GPIO pins (7-segments + grid), the 6921 uses a standard SPI interface. This would be even more advantageous on 16-segment VFDs. One thing you mentioned: Yes, 60v applied to the anodes will be VERY bright, even if multiplexed. I had to move my VFD clocks to bright places like my desk at work. a LOT brighter than equivalent nixie
Re: [neonixie-l] IV-11 VFD clock, some questions
I'm going to make three clocks (Christmas presents for girlfriend, brother and sister), but I'll see if I can get samples approved with my university email. Thank you for your generous offer to send me some samples but I'll first try to get my own samples at a reasonable price. Op dinsdag 19 november 2013 23:09:11 UTC+1 schreef Adam Jacobs: Hi Gideon, How many of these clocks are you planning to build? If it is just a few, then I wouldn't sweat the costs too much. Both of those companies (used to be - I assume still) are very generous with samples. I agree that the Supertex and Maxim parts can be difficult to obtain for a low price in individual quantities from normal vendors. I've got a drawer full of Supertex and Maxim samples, I'd be happy to mail you the parts. FYI, requests for samples get a much more positive response if you use a company or university email and describe a plausible project in the request. Any time that I can't find some obscure part that is listed for a project, I move to the obscure part manufacturer's website and request a sample. No problem. Contact me off-list with your address parts request and I'll see what I can do. Of course, if you're designing a clock for mass production, then all bets are off. :) -Adam On 11/19/2013 11:39 AM, Gideon Wackers wrote: I know the difference between a nixie and a VFD tube but I have to say that your explanation is very nice to summarize all the loose bits of information in my head. So If I have a 6 volt supply for my four filaments (in series) I would not need a resistor. I think the 7806 won't get that warm with roughly 400ma going through it but I can always take a simple switching psu for it or attach it to my (metal) enclosure. I will simply use a DC filament supply then to keep things simple (this project is going to be complicated enough). My only remaining concern is the driving method, I would like to order all my parts off ebay and/or tayda electronics. Places like mouser etc have (in my opinion) ridiculous shipping rates so I would like to avoid them. Another point is that the max6921 costs around 6-7 dollar a piece +1 euro for a plcc socket, I am trying to keep the costs down a bit. So a method to avoid using these drivers is preferred. HV5812: cheap but shipping costs are 40-50 dollar MAX6921 expensive and/or high shipping costs Op dinsdag 19 november 2013 20:06:50 UTC+1 schreef Adam Jacobs: Hi Gideon, I think that you have some confusion regarding how VFDs are driven. VFDs are not nixie tubes or anything even similar. Nixies are not vacuum tubes, they are cold-cathode (neon) tubes. With nixies, we place ~180vdc across the anode cathode via a current-limiting resistor. The reason for current-limiting in a nixie is because as current increases, nixie impedance decreases, causing the neon tube to rapidly begin dissipating a catastrophic amount of heat. Nixies, being neons, regulate voltage to their maintenance voltage. Any reasonable voltage above the striking voltage will work fine. VFDs are triodes: Hot-cathode vacuum tubes. Ideally, the filament is driven with an AC supply of the designed voltage (via the two filament pins, usually a couple of volts) and the anode segments are driven with a voltage regulated DC supply at the designed voltage (usually 20-30v for direct and ~60v for multiplex). The grid is driven exactly the same as an anode segment and is used to turn the display 'on'. There are no current-limiting resistors used for driving the anode segments or the grid! In my VFD clocks, I used the trick (which I learned from here) of driving the filaments with DC. This works fine if you are using individual numeral VFD tubes, I wouldn't try it if you are using the big multi-numeral VFD display tubes. The (known) current draw of the filament is used for calculating a resistor-divider. One leg of the filament is tied to ground, the other leg to +5vdc via the resistor. If you go with this approach be sure to do your math on the front end. These filaments draw a lot of current, which means a lot of heat dissipation in the voltage-divider resistor. Driving this setup via a linear regulator supply would need a very large heat-sink. I would recommend using a switching supply like the LM2575. Obviously, if you have an AC supply that is the correct voltage for the filament then no resistor is needed. For a schematic: http://elbastl.sweb.cz/6-digit-VFD.zip I liked Maxim IC's 6921 driver IC. I know you specifically called it out as not an option, but it worked well for me. Specifically, I used the PLCC package because I work exclusively in protoboard and there are easy DIP PLCC sockets. There are numerous advantages in my opinion to the dedicated VFD driver chip. Instead of 8 dedicated GPIO pins (7-segments + grid), the 6921 uses a standard SPI interface. This would be even more
Re: [neonixie-l] IV-11 VFD clock, some questions
Does anyone know whether it is a bad idea to go below the recommended multiplexing voltage as mentioned in Adams comment?? Op dinsdag 19 november 2013 23:01:33 UTC+1 schreef Adam Jacobs: FYI David: On the clock that I built with IV-11 tubes, I initially started with an anode voltage of 60v; which is the median multiplexed voltage as per this datasheet: http://www.tromop.eu/cms/media/IV-11%20datasheet.pdf and a 1/6 duty cycle (16.67%). That clock was bright. Couldn't sleep in the room with it running, way too bright. I tried lowering the anode voltage supply to 50v, which is the minimum voltage listed in the datasheet for multiplexed mode. This helped, but not enough; not by a long shot. So, then I started lowering duty cycle. I can't remember how low I eventually took it, but I soon realized that I wouldn't be able to get the brightness as low as I needed without introducing some very noticeable flicker. So, I moved the voltage back to 60v and the duty cycle back to 1/6 and moved the clock to a much brighter location. Works perfect. :) FYI, this was with the filament @ 1.5vdc. I don't know enough about VFDs to know if lowering the filament voltage might have helped. I think that one of the features of Vacuum Fluorescent Display is brightness. To paraphrase someone wiser than me: If you find yourself thinking up more and more convoluted mechanisms for making it work, then that's often an indicator that you're barking up the wrong tree. -Adam On 11/19/2013 12:48 PM, David Forbes wrote: Also, if your VFD is too bright, you can reduce the brightness by reducing the duty cycle, which is done by turning off the anodes on for some time in each cycle. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/b8deb5d8-2cb6-47ad-87b2-999149b4b870%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
Mine run from 18v low brightness to 35v for full brightness for the last 3 years and have had no issues. Sent from my iPhone On Nov 19, 2013, at 4:16 PM, Gideon Wackers gideon.wack...@student.uhasselt.be wrote: Does anyone know whether it is a bad idea to go below the recommended multiplexing voltage as mentioned in Adams comment?? Op dinsdag 19 november 2013 23:01:33 UTC+1 schreef Adam Jacobs: FYI David: On the clock that I built with IV-11 tubes, I initially started with an anode voltage of 60v; which is the median multiplexed voltage as per this datasheet: http://www.tromop.eu/cms/media/IV-11%20datasheet.pdf and a 1/6 duty cycle (16.67%). That clock was bright. Couldn't sleep in the room with it running, way too bright. I tried lowering the anode voltage supply to 50v, which is the minimum voltage listed in the datasheet for multiplexed mode. This helped, but not enough; not by a long shot. So, then I started lowering duty cycle. I can't remember how low I eventually took it, but I soon realized that I wouldn't be able to get the brightness as low as I needed without introducing some very noticeable flicker. So, I moved the voltage back to 60v and the duty cycle back to 1/6 and moved the clock to a much brighter location. Works perfect. :) FYI, this was with the filament @ 1.5vdc. I don't know enough about VFDs to know if lowering the filament voltage might have helped. I think that one of the features of Vacuum Fluorescent Display is brightness. To paraphrase someone wiser than me: If you find yourself thinking up more and more convoluted mechanisms for making it work, then that's often an indicator that you're barking up the wrong tree. -Adam On 11/19/2013 12:48 PM, David Forbes wrote: Also, if your VFD is too bright, you can reduce the brightness by reducing the duty cycle, which is done by turning off the anodes on for some time in each cycle. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/b8deb5d8-2cb6-47ad-87b2-999149b4b870%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/9397A3A6-AB80-4B4E-A914-31B1D56975E7%40yahoo.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
Does anyone know whether it is a bad idea to go below the recommended multiplexing voltage as mentioned in Adams comment?? It won't damage the VFD or anything, but it slows down the electrons, so you could get ghosting while multiplexing. I'm guessing the numbers in the datasheet are to produce the rated brightness. Since you don't want the rated brightness, I'm guessing you're fine with multiplexing it with reduced voltage. Reducing the duty cycle should work too, naturally. - John -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/F3D78D67-10BC-496B-A44D-4C3E556A3BE7%40mac.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [neonixie-l] IV-11 VFD clock, some questions
If there is one thing I like it is an answer like that :) I tried to request three samples of the supertex drivers, we'll see if they grant me some. Thank you all for the comments, suggestions and solutions up to this point. I got more (practical) answers here in less than 24 hours than two weeks of forums got me. Op dinsdag 19 november 2013 23:38:09 UTC+1 schreef Spencer: Mine run from 18v low brightness to 35v for full brightness for the last 3 years and have had no issues. Sent from my iPhone On Nov 19, 2013, at 4:16 PM, Gideon Wackers gideon@student.uhasselt.be javascript: wrote: Does anyone know whether it is a bad idea to go below the recommended multiplexing voltage as mentioned in Adams comment?? Op dinsdag 19 november 2013 23:01:33 UTC+1 schreef Adam Jacobs: FYI David: On the clock that I built with IV-11 tubes, I initially started with an anode voltage of 60v; which is the median multiplexed voltage as per this datasheet: http://www.tromop.eu/cms/media/IV-11%20datasheet.pdf and a 1/6 duty cycle (16.67%). That clock was bright. Couldn't sleep in the room with it running, way too bright. I tried lowering the anode voltage supply to 50v, which is the minimum voltage listed in the datasheet for multiplexed mode. This helped, but not enough; not by a long shot. So, then I started lowering duty cycle. I can't remember how low I eventually took it, but I soon realized that I wouldn't be able to get the brightness as low as I needed without introducing some very noticeable flicker. So, I moved the voltage back to 60v and the duty cycle back to 1/6 and moved the clock to a much brighter location. Works perfect. :) FYI, this was with the filament @ 1.5vdc. I don't know enough about VFDs to know if lowering the filament voltage might have helped. I think that one of the features of Vacuum Fluorescent Display is brightness. To paraphrase someone wiser than me: If you find yourself thinking up more and more convoluted mechanisms for making it work, then that's often an indicator that you're barking up the wrong tree. -Adam On 11/19/2013 12:48 PM, David Forbes wrote: Also, if your VFD is too bright, you can reduce the brightness by reducing the duty cycle, which is done by turning off the anodes on for some time in each cycle. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+...@googlegroups.com javascript:. To post to this group, send an email to neoni...@googlegroups.comjavascript: . To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/b8deb5d8-2cb6-47ad-87b2-999149b4b870%40googlegroups.com . For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups neonixie-l group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/29f3b01e-31a7-4428-89ab-a7add002b654%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
