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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Fri Jun 01, 2012 2:16 am Post subject:
How should I start down this path? Subject description: Any stuff I should think about. |
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I've just done a big cleanup of "The Lab" and have realised that I have about 54 different kinds of 74LSXX chips.
I would have been the first person to say stick with CMOS on a Lunetta, but I'm thinking the 5V monster of 74XXXX technology could be a viable beast. I've looked at all the descriptions, and they seem to cover all the same functions as CMOS stuff.
Any considerations from those who have done Lunettas would be greatly appreciated in this planning stage.
"This is another fine mess you've gotten us into Ollie!" _________________ What makes a space ours, is what we put there, and what we do there. |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Fri Jun 01, 2012 3:04 am Post subject:
Re: How should I start down this path? Subject description: Any stuff I should think about. |
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Uncle Krunkus wrote: | I'm thinking the 5V monster of 74XXXX technology could be a viable beast. |
GO FOR IT! It can be done and there's no sense is letting good chips go to waste
The main consideration is that the input impedance is considerably lower in TTL, thus standard oscillators made with a 7414 require much lower resistance in the feedback path and much higher capacitance than CMOS equivalents. The maximum resistance which I found to work in 7414 oscillators was 2.2k. The output waveform have uneven duty cycle.
There are also minimum resistances that should be observed in making such an oscillator, check the datasheets to see how much current they can output without damage and add a limiting resistor of suitable value in the feedback path (in series with the pot, if a pot is used that is). I would say, probably about 330ohms is a good estimate.
Some TTL chips have open collectors or emitters on the outputs and so require a pull up or pull down resistor in all situations (again, another datasheet hunting trip is in order).
On the positive side they are significantly less susceptible to static discharge _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Fri Jun 01, 2012 4:04 am Post subject:
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Well,
to be honest, I think modern CMOS are virtually immune to all but the most buffoon like of buffoonicans. I haven't zapped a CMOS chip in 30 years of DIY electronics. Although some very learned people believe that you can reduce their lifespan with static, quite apart from the potential for complete cactusness.
I'm yet to see it.
But my main concern is interfacing problems.
Thanks for the tips Jingle.
What module does everybody covet?
Where am I going with this project?
What can I expect when I unleash the hords of demondem upon the earth and all it purveys,....hmm,.....hmmmm.
Anyway,......
Tell me things people!?! _________________ What makes a space ours, is what we put there, and what we do there. |
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Draal
Joined: May 18, 2010 Posts: 308 Location: Oak Park, IL
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Posted: Fri Jun 01, 2012 4:42 am Post subject:
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I dig multiplexors aka channel selectors with ABC controllers. Feed the inputs with a divider for your "octaves", and use anything from shift registers to more oscillators for the ABC controllers and you are makin' tunes.
I am building another lunetta (4000 series): a mini compared to my big one. It uses 4 oscillators each with a switch to change cap values, a 4052 multiplexor (I have a crap load to get rid of), a 4094 shift register, a simple passive mixer ala slacker, and my not so secret weapon, a PPL chip (cd4046) set up as pitch tracker. Turns even the most boring blips into something rockin'.
I don't need an R2R ladder or vco because the pitch tracker is quite audible and when I use the multiplexor and divider method, I run my divider at audio levels obviously so the divisions are actually heard. ABC select what order to play the divisions. Of course, there's absolutely nothing wrong using r2r ladders and vco's but I like to keep things as simple as possible. Keeps it fun . _________________ Zontar Prevails! |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Fri Jun 01, 2012 2:36 pm Post subject:
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Draal wrote: | Of course, there's absolutely nothing wrong using r2r ladders and vco's but I like to keep things as simple as possible. Keeps it fun . |
Also the digital control over frequency division is often better than R2R ladder control for un-exponentiated VCOs. I often find that one end of the R2R ladder has hardly any variation in pitch while the other has too much.
I've zapped a few chips in the past with static, I presume static anyway; because I have long hair and it was winter at the time.
What do you mean by interfacing problems anyways? Human interfacing or interfacing between devices? For the organics just add some switches, some dials and a patch bay and Bobs your uncle
As far as connecting in other signals, just make sure they are square waves and within the voltage limits of your ICs then you should be fine _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
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richardc64
Joined: Jun 01, 2006 Posts: 679 Location: NYC
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Posted: Fri Jun 01, 2012 9:12 pm Post subject:
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Yes, go for it, but keep a couple of things in mind.
TTL inputs are difficult to pull down with any resistance greater than 470 ohms or so. 1k would be unreliable. Unterminated inputs will "float" high, but that shouldn't be relied upon, either. I wouldn't use a pull up greater than 22k. the upshot of this is ENables/DISables will need to be active-low. And although diode Mickey Mouse logic can be added to inputs, it would have to be the AND configuration, diodes "pointing" away from the inputs.
LS TTL output voltages aren't as consistent as CMOS: typically 3.4V but can be as low as 2.7V. This will make building R/2R ladders -- or even binary weighted summing -- with any precision difficult. But Lunettas aren't about precision, right?
JingleJoe wrote: | The maximum resistance which I found to work in 7414 oscillators was 2.2k. The output waveform have uneven duty cycle.
| Although duty cycle asymmetry is not as severe with CMOS schmitt oscillators, it does exist. Compare what you get with a 10k feedback resistor vs 100k or 1M.
Overall, I think a mix of CMOS inputs and outputs with a TTL "core" would be a viable architecture. _________________ Revenge is a dish best served with a fork... to the eye |
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droffset
Joined: Feb 02, 2009 Posts: 515 Location: London area
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Posted: Mon Jun 04, 2012 1:03 pm Post subject:
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Very interested in what you come up with Unkle K!
There are lots of fun paths to explore:
--Interesting CV generation with r2r ladders, etc.
--Frequency divisions driven by interesting data generation with the shift registers, mux,etc.
--Awesome step sequencers
--Other, etc. _________________ ==================
Check out the FREE Intro to Lunettas Document
https://docs.google.com/document/d/1V9qerry_PsXTZqt_UDx7C-wcuMe_6_gyy6M_MyAgQoA/edit?usp=sharing
Edit: Spelling mistakes. |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Fri Jun 08, 2012 7:14 am Post subject:
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As a slightly relevant tangent: where do you chaps find those nice chests of tiny drawers?
What I really need is one them with drawers that are the length of the width of a tape of resistors and only about an inch wide. Then I'd be able to fit a good bundle of components in each one and a few ICs. _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Fri Jun 08, 2012 12:30 pm Post subject:
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Uncle Krunkus wrote: | I actually like these better.
They're all metal, with plastic drawers. |
Cor blimey they are nicer
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Got em for nothin. Un-Believable.
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Where!? I've scavenged from a closing down electronics shop or two but never found any chests of drawers _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
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mosc
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Joined: Jan 31, 2003 Posts: 18197 Location: Durham, NC
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Posted: Fri Jun 08, 2012 12:51 pm Post subject:
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Most of my "original" Lunetta stuff from the 70s is RTL, so I'd say going to TTL is a big step forward.
You will find things work a little differently from CMOS, but that gives it a special character. The main difference is power consumption and the threshold voltage of TTL is not symmetrical like in CMOS. In CMOS you can almost always drop an LED and a resistor on an output without too much trouble, but in TTL, it may have a more serious effect on the circuit. You may need to add buffers to drive the lights. Experimentation is, as always, the way to make progress. _________________ --Howard
my music and other stuff |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Fri Jun 08, 2012 5:03 pm Post subject:
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JingleJoe wrote: | Where!? I've scavenged from a closing down electronics shop or two but never found any chests of drawers |
Got it in one.
Dick Smith electronics, Kempsey. Just happened to be walking past as they were clearing out the shop. I got all the components they had for $200 and then they through in the cabinets they were all sitting in! Heaps easier to just let me "get rid of them". _________________ What makes a space ours, is what we put there, and what we do there. |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
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Posted: Sat Jun 09, 2012 5:33 am Post subject:
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I'll keep an eye out, but there's only about two electronic component shops in Liverpool now _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
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Psyingo
Joined: Jun 11, 2009 Posts: 248 Location: Canada
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Posted: Sat Jun 09, 2012 12:58 pm Post subject:
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JingleJoe wrote: | As a slightly relevant tangent: where do you chaps find those nice chests of tiny drawers?
What I really need is one them with drawers that are the length of the width of a tape of resistors and only about an inch wide. Then I'd be able to fit a good bundle of components in each one and a few ICs. |
I've found mine at hardware stores, places that sell power tools and stuff for workshops usually have them. Machinists and the like may have them for assorted hardware components. I've also found them with components like various screws and fasteners as a pack at places like harbor freight (USA). |
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