Driver for IV-4 / IV-17 - 18 segment VFD tube - Page 1
Forum section: electronics / projects

author: MikeJazz
author_rank: Newbie
timestamp: February 20, 2017, 10:20:32 pm
content: Hello everone,As with my first post I'm looking for some help finding the right driver for a VFD. My first post being this ->https://www.eevblog.com/forum/projects/driver-for-ilc1-18l-8-segment-display/msg1128677/#msg1128677Ian.M kindly suggested using a MIC2981 to handle the high current of those large VFD's. And i plan on using a PCF8574 I2C I/O expander to drive the MIC2981.And I'm looking to do the same with with the IV-4's, but i'm looking for a driver that will handle the 18 segments and keep up with the current requirement and do all 18 segments. I have been looking at 20 bit shift registers but i'm not sure if thats the way to go. I'd really prefer to use I2C.these are the specs i have for the IV-4- Mike

author: Ian.M
author_rank: Super Contributor
timestamp: February 20, 2017, 11:02:35 pm
content: You wont find much if anything with an I2C interface. Microchip have a one-chip SPI solution - theHV5812which gives you 20 HV outputs with adequate drive capability for an IV-4. If you are stuck for I/O pins for the SPI interface to drive it, consider an I2C to SPI bridge - you'd only need one for all the tubes.

author: MikeJazz
author_rank: Newbie
timestamp: February 21, 2017, 03:35:18 pm
content: Thanks again Ian.I was recommended the I2C route by a friend because each tube would be individually addressable.And oh, i should probably mention that i'm trying to drive 16 of the IV-4's for a 16 character display. I guess a general description of my project might have been in order to begin with. The project is making a clock using the large ILC1-1/8L tubes. But it's not just going to be a clock, also a weather station and a music player. I'm thinking of using a Raspberry Pi 3 that i already have as the heart of it all, having it control the clock, the 16 character and adding a DAC to it for the audio.So, I have the idea to do all those things, but being a newbie here, I just don't quite know how.

author: SvanGool
author_rank: Regular Contributor
timestamp: February 21, 2017, 03:47:20 pm
content: There was an initiative a while ago in:https://groups.yahoo.com/neo/groups/smartsockets/info(you may need to subscribe)Chris Barron published a project for PCBs with 4x IV-17 on it using HV5812,and 4-line serial communication. I built an 8-character version and it worked perfectly together with a Raspberyy Pi.An OSHPark project related to this(for B-5971, using same principle):https://oshpark.com/shared_projects/J8ZsPa0shttps://oshpark.com/shared_projects/JCYNnnlRhttps://oshpark.com/shared_projects/mRt6r0tj

author: Ian.M
author_rank: Super Contributor
timestamp: February 21, 2017, 04:18:58 pm
content: I think that would benefit from a MCU as a display controller to offload the 16 character alphanumeric displays from the Pi. If you group the tubes in four groups of four, you could do 1/4 multiplexing with only four HV5812 chips, which would give very good brightness while keeping the component count reasonable. The MCU could handle the ASCII to segment mapping, and addressable access, presenting the Pi with a asynch serial or I2C interface, possibly emulating something more common.The alternative of simply throwing HV5812 chips at it for a static display is also possible - daisychain them all and use consecutive outputs or all the main segments of each character with the dot/comma segments all grouped together at the end of the chain. That way you send sixteen characters worth of two byte segment pattern + 32 bits of dots and commas, which with a 3.9Mhz SPI clock would only be about 9% slower to update the whole display than updating a single character by I2C, assuming one address byte and two data bytes at 400KHz.

author: SvanGool
author_rank: Regular Contributor
timestamp: February 21, 2017, 04:24:21 pm
content: @Ian.M : If you open the links and read the post twice, you will see it has an MCU (PIC). As I said already, it uses a bi-directional serial TTL-RS232 bus that can directly be coupled to TX/RX of a Pi. Which is all it needs from the Pi. You are re-inventing the wheel.

author: Ian.M
author_rank: Super Contributor
timestamp: February 21, 2017, 04:50:57 pm
content: I cant (easily) find a summary of the concept on the Yahoo group, but it looks like its a highly modular solution with many PIC MCUs, one per character or small group of characters. I'm sure its very versatile but its overkill when all you want is 16 ASCII starburst characters without a high parts count or excessive CPU load to update or maintain them. If no-one ever reinvented the wheel, the Tour de France would be lumbering along in ox carts with solid wheels shaped from a slice of a treetrunk.

author: SvanGool
author_rank: Regular Contributor
timestamp: February 21, 2017, 07:55:29 pm
content: There is one MCU per 4 VFDs. The OP may leverage what already has been done, Chris Barron spent months on defining characters, scrolling, fading and all kind of effects you can steer with a few simple serial commands. I hope you help the OP with your solution to finish the project before the VFDs are out-gassed.An example:Edit: remembered that IV-17 are VFDs, not nixies.

author: Ian.M
author_rank: Super Contributor
timestamp: February 21, 2017, 08:32:04 pm
content: That's reasonably tolerable for overhead for a one-off. For 16 characters, it only wastes 3 MCUs and probably 9 lines of HV driver, but gives you a turn-key solution.Its now up to the O.P to decide whether he wants quick results or whether the pleasure is in the challenge of the design, construction and programming.

author: MikeJazz
author_rank: Newbie
timestamp: February 21, 2017, 10:06:21 pm
content: Hi guys,First of, thank you for your interest and replies. It's really nice to get the input. I've been talking with my buddy who knows quite a bit more about this stuff then i do, showed him your suggestions and I think I'm going to try with an Arduino Mega2560. This is because i already have the Mega2560, and it will be easy to do some testing and breadboarding.And I like the idea of multiplexing 4 tubes and keeping the component count down.I do like the Chris Barron project though, and i'll take it as a source of inspiration.And just to reiterate a little on my own project here. I'm doing it as a learning project, both for the electronics and the programming part of it. So to that end I'm going to try and get my hands dirty in all the aspects of the project. Making the PCB, getting components, CAD drawings, the lot.Quote from: Ian.M on February 21, 2017, 08:32:04 pmI'll take the 2nd part please hehe. The end product isn't the whole point of this exercise, though I'll thoroughly enjoy that too. It's a "It's not the destination, it's the journey" kind of thing.Luckily my buddy has a CNC mill, so when it comes to making the case for the whole thing I'm sorted, thank you BrianI'll make a concept flowchart kind of thing in the next few days and post it here on the forum. I'd love to hear your thoughts on it.Come to think of it, I should just start a build log and keep everything in one place.In summery, using a micro controller makes a lot of sense to me, and I already have one. Multiplexing quad tubes also makes a lot of sense.Next up - Googling multiplexing of VFD's- Mike

author: tonyp7
author_rank: Newbie
timestamp: June 23, 2017, 07:24:16 am
content: Hey Mike,I know I am a bit late to the party, but I found your post on Google while doing some research.Have a look at SN75518N; it's all in one shift register + driver for VFDs. They are hard to find (no longer produced...), but a reseller on Aliexpress has some of them.EDIT:with datasheet

author: MikeJazz
author_rank: Newbie
timestamp: June 25, 2017, 07:28:11 pm
content: Hi Tony,Not late at all. I've had the project on hold for a bit due to lack of time, but moving into the summer holidays I think I going to start a bit of testing.So thanks for the input, i think i'll get a few if the price is reasonable.- Mike