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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Simple Output Interface
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bugbrand



Joined: Nov 27, 2005
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PostPosted: Fri Mar 21, 2008 1:25 am    Post subject: Simple Output Interface Reply with quote  Mark this post and the followings unread

I've been thinking about how to standardize the output signals from the CMOS circuits. I'm running all the circuits at 12v and this means the outputs are a little 'hot'. I'm sure it'll be good to have the outputs buffered too. So, here's an initial simple idea on a module to go at the end of the chain...

I'm aiming for two things:
1) Gate mode - 0 - 5v signals (with 1k output impedence)
2) Audio mode - -5v - +5v signals (bipolar with 1k output impedence)

All we need to do (I think!) is make some simple comparators and then reduce the output swing in simple ways. LM358 / LM324 are ideal for our purposes. A ref voltage is made (R1 and R2) and feeds all -ve opamp inputs - I've just used rough values, but these should be fine 'cos we're just dealing with squares. The Opamp (powered with bipolar supply) then swings between V- and V+. This can easily be reduced to a (roughly) a -/+5v swing using a 2k / 2k voltage divider and if you add a diode into the path then that turns it to 0v to +5v. The output voltage levels are slightly 'rough' - I'm basing it on a 12v supply and these values will only give an approximation of 5v (you can do the maths if you want) - if you're worried about exact levels, then the values of R4 and R5 can be adjusted (also if you're running on 15v supply). I've drawn a switch over the diode so you can select Gate or Audio mode.

Does this seem like the right sort of approach?


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Quick output idea..
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OutputIdea.jpg



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Uncle Krunkus
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PostPosted: Fri Mar 21, 2008 2:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Looks good to me. Very Happy
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scriptstyle



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PostPosted: Wed May 21, 2008 10:30 am    Post subject: Reply with quote  Mark this post and the followings unread

i am going to need a output interface/mixer for my modules, so far i have bananna outs and 1/4 outs(audio). what im looking to have is something like 6 bananna ins 3 1/4" ins and 1 or 2 1/4 outs, and possibly a way to mix them. im running mine strictly on 0 — +5v, so i am not running a bipolar supply. i know i have made amps out of the lm386 before that run on 9v. im almost possitive i have some lm324's laying around.
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PostPosted: Sun May 25, 2008 10:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Looks OK if you're comfortable using an opamp as a comparator. More DIY circuit abuse, I love it! You might consider adding some hysteresis. The diode is OK, but then you're not utilizing the sink capabilities of the opamp, but that's OK, you have a pull-down resistor there. As long as you're not driving a capacitive load you won't get RC rounding of your edges. I dunno, it looks awfully unconventional, but there's nothing wrong with that! There's probably a hundred good ways to do this. Hmmm. I just realized that your source impedance is 1 kOhm, but your sink impedance is 2 kOhms. If that's not a problem you're good to go. Cheers!
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scriptstyle



Joined: Jan 22, 2008
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Location: nj

PostPosted: Tue May 27, 2008 7:50 am    Post subject: Reply with quote  Mark this post and the followings unread

im thinking about maybe using the lm324, i have not looked at the data sheet yet but im assuming that it only has 2 inputs so i would need 3 ic's to have 6 in's. im also looking into some of the resistor based mixers that nicholas colins has in his book "hand made electronic music" they might be more promising. im not 100% surte what yo mean by rounding? i am looking to keep the clipping down, it seems the the digital outputs clip during most settings.

can i run the above schematic on a 0 to +5v supply?
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