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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Interfacing lunetta with other modular
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colorbars



Joined: Oct 29, 2015
Posts: 8
Location: Canada

PostPosted: Tue Jul 31, 2018 5:44 am    Post subject: Interfacing lunetta with other modular Reply with quote  Mark this post and the followings unread

Recently shared with me from a long time lunetta mad scientist and forum member for protecting lunetta from eurorack etc and also protecting eurorack etc from lunetta! I’ve attached their diagrams for input and output protection, please comment if you have any recommendations or Improvements!


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PHOBoS



Joined: Jan 14, 2010
Posts: 3975
Location: Moon Base
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PostPosted: Tue Jul 31, 2018 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

ok, my thoughts on it, let's see

For the first circuit there shoud be a resistor in series with the input. Without this the diode will just short negative voltages to ground
which can be bad for modules (depending on the kind of protection they have) and it will also affect the signal if you would use it with
a passive multiple.

For connecting to digital inputs I'd use a comparator instead of a voltage follower. I actually did make a circuit for that recently:
Posted Image, might have been reduced in size. Click Image to view fullscreen.
(note: the AND gate is made by just having a switch in series).


For the second circuit the output should be taken from the connection between the zenerdiode and the 2K2 resistor, otherwise the zener
doesn't have much effect besides wasting current.

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Last edited by PHOBoS on Tue Jul 31, 2018 1:06 pm; edited 1 time in total
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colorbars



Joined: Oct 29, 2015
Posts: 8
Location: Canada

PostPosted: Tue Jul 31, 2018 12:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Like so, Phobos?


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Richarius



Joined: Feb 22, 2014
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PostPosted: Tue Jul 31, 2018 12:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS! Omg, omg. I thought I knew the littlest bits of theory over the years of DIY electronics but ... Surprised Smile

The above error corrections of yours, were as to my schematics that Colorbars had shared.

I remembered that the 2k2-2k7 as per the zener, is for current limiting as to the load that it drops. I had forgotten though, having to take the output from between the resistor and the zener. Thank you for THAT reminder! Surprised

The other one ... with the diode to Ground to protect from -V "coming in" I hadn't even considered the amount of current that COULD be transferred that way.
I believe now, that I had mistakenly assumed, the 100k to Ground impedence for the chip, from the LOGIC world, had applied equally, to the opamp world! Hence ... my often putting them to Ground, instead of in Serial.

I know that with Logic, with have to tie them either HIGH or to Ground and using the 100k gives that impedance. (All together, rather than floating the input.)

I'd posted that pair at my private Lunetta forum, for reference as ... that is exactly what I'll be doing within days - the 'interfacing' between my Euro rack and my Lunetta rack. Having had interfacing problems in the past ...

Here now - the comparator schfematic that you had posted earlier, works perfectly to take care of the +5V points from Euro, that wont do anything in a +12V Lunetta machine. Surprised

And the "AND" portion, you'd partially clarified but ... I still can't 'see' the AND function possibility, in the circuit? Sorry ... is it ... my age? Surprised Hahahaha.

Thank you for possibly correcting my errors! I never mind being shown, when I'm wrong with something! Surprised
Still learning and always will be. Smile

Off to prototype yet more new ideas, from earlier today. Very Happy

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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Tue Jul 31, 2018 1:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

colorbars wrote:
Like so, Phobos?

almost, but place the resistor on the input between the 100K resistor to GND and the diode, otherwise it will
form a voltage divider. Oh and I'd use 1K, although 100K will probably work fine too.

Richarius wrote:
And the "AND" portion, you'd partially clarified but ... I still can't 'see' the AND function possibility, in the circuit? Sorry ... is it ... my age? Surprised Hahahaha.

It's an AND function in the sense that it 'AND's the input signal with the state of the switch. Originally the switch was connected to V+ and I
created a more proper AND function using the comparators in a different configuration. But I realized I could get the same result with placing
the switches in series with the input signals. Embarassed

you can still see it in the way I designed the panel art:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

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http://phobos.000space.com/
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PHOBoS



Joined: Jan 14, 2010
Posts: 3975
Location: Moon Base
Audio files: 584

PostPosted: Tue Jul 31, 2018 1:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

oh and another thing. You could place the zenerdiode on the input of the opamp instead of the output. (So the circuit would
be exactly the same as the other one but with a zenerdiode instead) This way you don't get any extra current limiting from
the 2K2 resistor so you can drive a bit more with it. Downside is that it will 'pull more current' from what you connect to the input.

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http://phobos.000space.com/
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