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GPS-Driven, FPGA-Decoded Nixie Tube Speedometer, Part 2

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Max The Magnificent
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Call me...
Max The Magnificent   12/3/2013 3:05:45 PM
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Call me "old fashioned" if you will, but I LOVE anything to do with Nixie Tubes...

Victor Lorenzo
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Re: Call me...
Victor Lorenzo   12/4/2013 6:29:06 AM
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@Max, "Call me "old fashioned" if you will, but I LOVE anything to do with Nixie Tubes...", Call me too.... I specially like those green nixies from the old cassio calculators, all contained in the same vacuum tube.

Max The Magnificent
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Re: Call me...
Max The Magnificent   12/4/2013 10:16:19 AM
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@Victor: I specially like those green nixies from the old cassio calculators, all contained in the same vacuum tube.

Tasty!!! One of my background hobby projects is to build a simply 4-bit processor out of a mix of tecxhnologies (relays, vacuum tubes, transistors, magnetic cores, etc.) and you can be Nixie Tubes will feature in there somewhere...

Victor Lorenzo
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Re: Call me...
Victor Lorenzo   12/5/2013 2:19:14 AM
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@Max, "One of my background hobby projects is to build a simply 4-bit processor out of a mix of tecxhnologies"

Something like this (http://www.youtube.com/watch?v=4IxWSvlcP3c/http://hackaday.com/2010/06/08/duo-128-elite-4-bit-cpu/)? We could say it's a "computer-in-a-box" ;)



I hope it will be more portable than this:



Perhaps you're interesting in taking a look at this too: http://www.northdownfarm.co.uk/rory/tim/tim-8.htm/http://www.youtube.com/user/rapidrory?feature=watch.

Max The Magnificent
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Re: Call me...
Max The Magnificent   12/5/2013 10:32:40 AM
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@Victor: Something like this...

Well, that is very tasty -- but I was thinking something more like this paper I wrote ages ago.

Victor Lorenzo
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Re: Call me...
Victor Lorenzo   12/5/2013 1:48:47 PM
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@Max, That's a RAM!!! "A ball bearing in its associated left-hand receptacle could represent a logic 0, while the right-hand receptacle could represent a logic 1 (or vice versa)"

At least for this RAM type the 'charge' and its 'stable states' will be more 'visually' representable. We will even be capable of seen the 'charges moving' from one stable state to the other! I'll like to see that!

David Ashton
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Re: Call me...
David Ashton   12/5/2013 6:48:00 PM
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@victor... "I specially like those green nixies from the old casio calculators"

They're actually vacuum fluorescent displays (VFDs), not Nixies as such, but I'm being a bit pedantic.  They are very nice.  I was lucky enogh to get a few huge (like 9 by 5 inch) 16 char x 4 line dot matrix VFDs not long ago and am working on driving one with a PICAXE soon.

I also have some Sperry 7-segment displays which work like Nixies (neon gas discharge) but with segments instead of the complete  numbers that Nixies have.

There are certainly some tasty displays out there.....

Victor Lorenzo
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Re: Call me...
Victor Lorenzo   12/6/2013 2:46:57 AM
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Hi @David, "but I'm being a bit pedantic"

In no way you're being pedantic. Thanks for making me note that.

David Ashton
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Re: Call me...
David Ashton   12/6/2013 4:19:20 AM
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Thanks Victor.  I used to have a bunch of those old green VFD displays - they had 10 segments and you could make most letters with them as well as numbers.  You find them a lot in old video recordersas well - as you say they are multi-digit in one glass envelope - but they are usually special purpose ones and difficult to use.

Like you I find the old displays very pleasing - much nicer than the angular 7-segment LEDs that are everywhere these days.

antedeluvian
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Re: Call me...
antedeluvian   12/6/2013 9:53:38 AM
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David

they had 10 segments and you could make most letters with them as well as numbers.  

I remember doing some work with those "star burst" VF displays. The ones I used had 18 segments including the decimal point and the second point to make up a colon. I was trying to make a cash register for the dry-cleaning industry. I think I still have a display sitting in a drawer. To drive it (at least to decode from binary the the display format) I used a brand new chip from TI- the AC5947N (I probably have a couple of those in my drawer as well) made in a brand new technology (I2L, that is I squared L for Integrated Injection Logic). Neither the chip nor the technology lasted in the market and I had to look for alternatives. But I'm not bitter.

David Ashton
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Re: Call me...
David Ashton   12/6/2013 6:21:33 PM
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@antedeluvian...They had some funny old displays in those days.  My dad used to work for Burroughs and I got some out of some defunct desk calculators.  They were made by Itron.  Alas, I foolishly got rid of them when I left Zimbabwe :-(

I remember reading about integrated injection logic a long time ago....like ECL it could not compete with the behemoth of TTL.   Another case of good technology getting sidelined by a more popular but inferior technology.

zewde yeraswork
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Re: Call me...
zewde yeraswork   12/12/2013 9:08:18 AM
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It's worth holding on to old defunct parts. You never know what you'll be able to go back and integrate with even, in this case, five decades later attaching a speedometer to an old vehicle.

Max The Magnificent
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Re: Call me...
Max The Magnificent   1/23/2014 2:16:06 PM
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@zewde: It's worth holding on to old defunct parts. You never know what you'll be able to go back and integrate with...

I could kick myself for all the stuff I've let slip through my fingers.

Max The Magnificent
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Re: Call me...
Max The Magnificent   1/23/2014 2:18:55 PM
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@David: Like you I find the old displays very pleasing - much nicer than the angular 7-segment LEDs that are everywhere these days.

I think everyone finds them pleasing -- if you have something like that Nixie-Tube clock we were talking about last year, for example, engineers just stand and drool stare :-)

betajet
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Old-fashioned Displays
betajet   1/23/2014 2:36:30 PM
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My favorite numeric display is the one on The Time Machine control panel in the 1960 movie.  The numbers are beautifully rendered in a 19th Century typeface.  The fact that I found this more interesting than Yvette Mimieux shows that (1) I was pretty young when I saw the movie, and (2) definitely a born engineer.

Max The Magnificent
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Re: Old-fashioned Displays
Max The Magnificent   1/23/2014 2:48:46 PM
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@betajet: The fact that I found this more interesting than Yvette Mimieux shows that...

You are a very strange person indeed LOL

David Ashton
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Re: Old-fashioned Displays
David Ashton   1/23/2014 5:04:41 PM
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I remember that movie!  It was really good as I remember, though it was about 45 years ago I saw it - during one of our movie nights at boarding school.  I didn't remember that the female star was Yvette Mimieux, but I seem to remember her character was called Weena?  I remember she was pretty cute (maybe I was older than you were when I saw it :-), so did someone else, as I saw the name carved into a schooldesk some weeks later.

I dimly also remember the typeface on the panel - it was rather ornate.  I must try and get the movie again.

Totally off-track, but another movie I saw at the same boarding school was "Operation Crossbow", about the V1 and V2 rockets in WW2.  Fascinating as I remember, but I have never seen it again either.  A visit to Ebay is indicated I think.

Stargzer
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Re: Operation Crossbow
Stargzer   1/23/2014 6:43:52 PM
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@David:  Operation Crossbow at Internet Movie Database, with Sophia Loren!

David Ashton
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Re: Operation Crossbow
David Ashton   1/23/2014 6:57:34 PM
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Thanks - the 1960 Time Machine is there too

http://www.imdb.com/title/tt0054387/?ref_=fn_al_tt_2

I should try and get these movies and see if I like them now as much as I did then.....

Caleb Kraft
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Re: Call me...
Caleb Kraft   12/5/2013 5:38:40 PM
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glass and glowing electrodes? I'd call you names if you DIDN'T like them!

Max The Magnificent
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Re: Call me...
Max The Magnificent   12/5/2013 5:45:04 PM
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@Caleb: glass and glowing electrodes?

Q: "Do you have the electrodes?"

A: "No, I always walk this way!" LOL

bobdvb
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VHDL
bobdvb   12/4/2013 5:51:34 AM
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Okay, I admit I don't know much about VHDL and FPGA programming, but a lookup table for the speed? Was that really the most efficient mechanism? At least I would have expected the leading 0's to have used something shorter.

Victor Lorenzo
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Re: VHDL
Victor Lorenzo   12/4/2013 6:36:54 AM
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@bobdvb: "Was that really the most efficient mechanism?" It depends on what your primary parameter "efficiency" referes to. Lookup tables are very efficient in execution time (clock cycles required for completing), but could eventually require much more LEs or cells in applications like this one.

Stargzer
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Re: VHDL and Lookup Table
Stargzer   1/23/2014 2:24:50 PM
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@bobdvb:  "...but a lookup table for the speed? Was that really the most efficient mechanism?"

"Somewhere in the basement" I have an old book on "Assembly Level Programming for Small Computers" (back when a "small" computer would have been a TTL mini with 4K or so of memory).  It has routines for using lookup tables to do multiplication or trig functions for systems that didn't have multiply or divide instructions or were just plain too slow.  Of course, the 50MHz clock on that FPGA should be fast enough for math, but sometimes a lookup takes a lot less cycles than carrying out the calculation.  The blinding speed and surfeit of memory available these days has for the most part done away with the need for really tight code, but if you're on a budget ... . 

vvc0
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Reducing Lag
vvc0   12/4/2013 2:45:11 PM
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It should be possible to reduce the speed update lag by employing an accelerometer to calculate the velocity during times of acceleration or deceleration. This might be slightly more compute intensive in an FPGA, but should be do-able in a microcontroller as well.

Stargzer
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Nixies
Stargzer   1/23/2014 1:48:08 PM
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Back in Ancient Times I remember a piece of telecomm troubleshooting gear that used Nixies instead of 7-segment displays.  They advertised that when there were quick changes in the low-order digit you could see the change on the Nixie as two or more digits were displayed in the same tube, but on a 7-segment you might only see an "8".  I think it was call the Range Rider, doing Bit Error Rate tests and so on.

Some surplus place used to sell a tube with multiple segments and they included a circuit to display segments at random to create random patterns, like a random blinking light circuit.

 

Max The Magnificent
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Re: Nixies
Max The Magnificent   1/23/2014 2:34:31 PM
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@Stargzer: Back in Ancient Times...

I remember them well :-)

Stargzer
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Retro-Futuristic
Stargzer   1/23/2014 2:31:22 PM
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@Luke Miller

That last photo is so cool!  It's definitely Retro-Futuristic, almost Steampunk (or are you planning to replace the engine, too?).

Max The Magnificent
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Re: Retro-Futuristic
Max The Magnificent   1/23/2014 2:38:15 PM
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@Stargzer: It's definitely Retro-Futuristic, almost Steampunk...

Have you been following my Prognostication Engine blogs? Like the recent one on lighting up vacuum tubes using tri-state LEDs (this links to the earlier ones)

zewde yeraswork
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holding on to defunct parts
zewde yeraswork   1/23/2014 2:47:13 PM
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Holding onto that which seems to no longer have any use is an important way to remain cutting edge without actuaollly remaining cutting edge...everyone understands the uefulness of use but no one understands the use of the useless.

Max The Magnificent
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Re: holding on to defunct parts
Max The Magnificent   1/23/2014 2:51:52 PM
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@zewde: ...everyone understands the uefulness of use but no one understands the use of the useless...

My head hurts :-)

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