[sdiy] trouble driving cmos from modular signals

[Dan Snazelle]

Sent from my iPhone

On Sep 14, 2012, at 7:26 AM, Tom Wiltshire <tom at electricdruid.net> wrote:

> 
> 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






Tom,


I took a 10k to +v and a 10k to ground


I tried connecting the signal into that divider with a diode (tried both directions) and i had no luck


Did i maybe interpet your suggestion incorrectly?


Thanks!
> 
> On 14 Sep 2012, at 07:24, Ullrich Peter wrote:
> 







>> 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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> 
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