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celebutante
Joined: Jun 29, 2007 Posts: 37 Location: Los Angeles
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Posted: Fri Jan 11, 2008 12:52 pm Post subject:
another CMOS logic switcher question |
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Some of you may remember a post I put up re building a voltage patching device for my modular using CMOS logic. Got kinda of sidetracked, so I'm fooling with it again. The idea has evolved into something like the old Sequential model 700 programmer, minus the digital memory (instead having just four presets selected with a switch).
Mainly it will use 4052 chips to switch between CV's preset with trimmer pots. But I want to use it do some audio routing as well (so I can switch the saw and sqr osc waves on/off).
Since I managed to blow up a 4052 yesterday trying to run audio through it (I guess they're strictly intended for DC voltages... cue laugh track from those more experienced than I), I'm pretty sure the correct way is to use a transistor, right? Or should I be using an op-amp? How might I implement that?
thanks....
mitchell |
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celebutante
Joined: Jun 29, 2007 Posts: 37 Location: Los Angeles
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Posted: Fri Jan 11, 2008 4:43 pm Post subject:
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I just found this:
http://www.uni-bonn.de/~uzs159/
then go to "misc/signal switch"
But it's a bit confusing, because it appears that there's a a resistor/transistor combo hooked to the 4053's address lines; can't see why you'd do that. I guess the A, B, C of the 4053 isn't meant to represent the address lines, but instead the signal outputs from the the three lines above (and the switch shown in the three identical diagrams is just a manual two pos input selector switch?)... anyone?
mitchell |
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blue hell
Site Admin

Joined: Apr 03, 2004 Posts: 24420 Location: The Netherlands, Enschede
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Posted: Fri Jan 11, 2008 7:18 pm Post subject:
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The transistors are just inverters on the address lines, probably for matching it to an active low control circuit ... but the switches above just represent the the ones in the IC, not manual ones anyway. No need to get confused  _________________ Jan
also .. could someone please turn down the thermostat a bit.
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blue hell
Site Admin

Joined: Apr 03, 2004 Posts: 24420 Location: The Netherlands, Enschede
Audio files: 297
G2 patch files: 320
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Posted: Fri Jan 11, 2008 7:21 pm Post subject:
Re: another CMOS logic switcher question |
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celebutante wrote: |
Since I managed to blow up a 4052 yesterday trying to run audio through it (I guess they're strictly intended for DC voltages... cue laugh track from those more experienced than I), I'm pretty sure the correct way is to use a transistor, right? Or should I be using an op-amp? How might I implement that?
thanks.... |
Without a circuit it's a bit hard to answer ... the CMOS switches can handle AC alright, but but they can't handle signals below ground or above Vcc at all, and they might be killed if you try.
Do you have a circuit diagram somewhere? _________________ Jan
also .. could someone please turn down the thermostat a bit.
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celebutante
Joined: Jun 29, 2007 Posts: 37 Location: Los Angeles
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bugbrand

Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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fonik

Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Sun Jan 13, 2008 9:30 am Post subject:
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or even from +8V to -8V, that's what doepfer does on his switch.
according datasheet it is rated for operation from 0.5V-18V...
here is a link to my redrawn schematic:
http://modular.fonik.de/pdf/seq_switch.pdf _________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
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richardc64

Joined: Jun 01, 2006 Posts: 679 Location: NYC
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Posted: Sun Jan 13, 2008 10:11 am Post subject:
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celebutante wrote: | ...it appears that there's a a resistor/transistor combo hooked to the 4053's address lines; can't see why you'd do that. I guess the A, B, C of the 4053 isn't meant to represent the address lines, but instead the signal outputs from the the three lines above (and the switch shown in the three identical diagrams is just a manual two pos input selector switch?)... anyone?
mitchell |
No no no. The switches shown in the 3 identical diagrams represent the 3 analog spst switches within the 4053. They are controlled by the three transistors, which are there to protect 4053 control inputs from voltages greater than the 4053 positive supply. _________________ Revenge is a dish best served with a fork... to the eye |
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celebutante
Joined: Jun 29, 2007 Posts: 37 Location: Los Angeles
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Posted: Sun Jan 13, 2008 3:32 pm Post subject:
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thanks again all... I'm sure I can it going with all this info! I'll keep ya posted... right now I'm building A couple of Rene Schmitz 555-based envelopes which will be part of it (since I can't voltage control my .com envelopes, I realized I should just incorporate them, like the Sequential 700 programmer).
Mitchell |
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françois
Joined: Dec 23, 2006 Posts: 139 Location: Paris (France)
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Posted: Mon Jan 14, 2008 4:15 am Post subject:
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Hello,
Just a few remarks. If you read carefully the datasheet for the 4051/4052/4053 switches, you'll notice that they have three supply voltages : VDD, VSS and VEE.
VDD and VEE are the analog signal rails, and VDD-VEE can be as high as 20V (but 15V or maybe 18V is safer).
VDD and VSS are the logic control rails and can also be as high as VDD-VSS=20V. This allows switching analog signals such as ±5V pk-pk under control of 0/+5V logic. Or ±5V logic as I like it (using a LFO as a clock for example).
These switches will happily accept AC inputs, within a limited bandwidth of course (they are CMOS, not known for its very high speed). At audio rates this is not a problem. But never ever have the analog or logic signal exceed the rail supply voltages ! Unless you mean to build an electronic fireworks...
-- françois |
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richardc64

Joined: Jun 01, 2006 Posts: 679 Location: NYC
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Posted: Mon Jan 14, 2008 5:55 am Post subject:
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me wrote: | [The switches shown in the 3 identical diagrams represent the 3 analog spst switches within the 4053. |
Ooops. That should be "3 analog spDt switches..." _________________ Revenge is a dish best served with a fork... to the eye |
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