[sdiy] trouble driving cmos from modular signals

[Dan Snazelle]

Sent from my iPhone

On Sep 14, 2012, at 11:08 AM, Dan Snazelle <subjectivity at hotmail.com> wrote:

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> Sent from my iPhone
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> On Sep 14, 2012, at 7:26 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
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>> Peter could well be right about it being speed not levels that is causing the problem.
>> 
>> However, if it were levels, you might be able to make it work by putting a voltage divider between the rails on the input, and then feeding that with a diode - biasing the input to a midpoint value essentially. It's dirty but it can work, especially on 4000 series CMOS.
>> 
>> HTH,
>> Tom
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> 


Ill try both pieces of advice and report back. Its funny because a 4051 on the same board, seems to be able to take ANY signal as data!


Thanks


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> Tom,
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> I took a 10k to +v and a 10k to ground
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> 
> I tried connecting the signal into that divider with a diode (tried both directions) and i had no luck
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> 
> Did i maybe interpet your suggestion incorrectly?
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> 
> Thanks!
>> 
>> On 14 Sep 2012, at 07:24, Ullrich Peter wrote:
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>>> Hi!
>>> 
>>> The problem with the 4017 could be that not the levels are the problem but the signal edges.
>>> The 4017 needs fast edges to work properly. Slow rising signals will not work.
>>> 
>>> So a Schmitt trigger on the clock input could be necessary.
>>> Something like a 40106 (Schmitt trigger inverter) - use two if non inverting is needed.
>>> 
>>> Ciao
>>> Peter
>>> 
>>> http://www.ullrich.at.tt
>>> 
>>> 
>>> -----Ursprüngliche Nachricht-----
>>> Von: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] Im Auftrag von dan snazelle
>>> Gesendet: Freitag, 14. September 2012 06:48
>>> An: *SYNTH DIY
>>> Betreff: [sdiy] trouble driving cmos from modular signals
>>> 
>>> normally when I interface a modular signal into a counter, say a +/-5volt VCO signal into a 40xx,  (in this case a 4017)
>>> 
>>> 
>>> i put it through a resistor with a diode to ground, or a diode with a resistor to ground.
>>> but i am working right now with a 4017 which WILL NOT 
>>> 
>>> see the VCO output unless I put it through a level shifter module first and add a bunch of gain.
>>> 
>>> 
>>> i would LIKE to find a passive solution  to this predicament,  but I am not sure if that is possible.
>>> 
>>> (maybe 2 diodes and a resistor?)
>>> 
>>> 
>>> 
>>> THANKS FOR ANY HELP!!!
>>> 
>>> 
>>> 
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