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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
TTL Lunettas?
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Appliancide*



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PostPosted: Fri Mar 20, 2009 7:29 am    Post subject: TTL Lunettas?
Subject description: Any disadvantages vs. CMOS designs?
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Just wondering because I have access to more TTL than CMOS chips.
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Rykhaard



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PostPosted: Fri Mar 20, 2009 7:46 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't see why not - thinking ONLY, at the voltage level. (I don't know about TTL with interfacing outside of TTL, for sure.)

Just keep the voltage level across all of the TTL (74xx, 74LS, 74HC, 74HCT) at +5V / Ground and everything should be fine. (If I'm not mistaken, 74Cxx will operate at +15 / Ground. I'd have to check datasheets to be sure.)

I know there's a heck of a lot more stuff available from the TTL world than the CMOS world, but I've never personally worked WITH TTL for anything. CMOS and Linear only, since 1982.
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RF



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PostPosted: Fri Mar 20, 2009 10:04 am    Post subject: Reply with quote  Mark this post and the followings unread

I recall mosc saying in one of the early posts on this thread that they used TTL and then moved on into CMOS Lunetta's (I assume as it became available)

EDIT
here - http://www.electro-music.com/forum/topic-23215.html

SNIP
Stan taught us about the joy of the surplus electronics stores, and he was into building really simple digital circuits that clocked at audio rates. For example, you make simple oscillators using digital inverters with RC networks. If you uses NAND gates instead of inverters, you get some sort of neat modulation when you hook up another oscillator to one of the free gate inputs. Run the osc into a modulo-N converter and you can get different pitches based on the code you put on the four inputs.

All these simple circuits, usually just one "naked" IC, are hooked up to banna jacks so you can make patches.

Shift registers were used a lot as were up/down counters, filp flops, and whatever we could find in the surpluss stores. We started with RTL, moved to TTL and then CMOS. Experimentation was the only rule.
/SNIP


bruce

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richardc64



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PostPosted: Fri Mar 20, 2009 10:47 am    Post subject: Reply with quote  Mark this post and the followings unread

TTL logic levels aren't as consistent as CMOS and swing nowhere near rail-to-rail. There should be no problem interfacing with CMOS, though, as long there's pull-ups on inputs and outputs. Which brings up another potential problem: TTL inputs are very difficult to passively pull down, needing something like 470 ohms or less.

One other thing: although you can construct a schmitt-trigger oscillator with TTL, (74LS14 inverters or 74LS93 NANDs,) the feedback resistance cannot be as large as with CMOS, so you can't get as wide a frequency range.

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Appliancide*



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PostPosted: Sat Mar 21, 2009 9:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the responses guys. I have a few CMOS chips around , but we are studying TTL in school right now so I thought I'd see if they were useful in the Lunetta world.
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Adam-V



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PostPosted: Sat Mar 21, 2009 6:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

TTL uses more power than CMOS I believe so if you're looking to run your lunetta off batteries, TTL may not be the way to go otherwise I can't really see any reason not to use TTL (other than voltage compatability issues if you want to interface with a regular modular)

Cheers,
Adam-V

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