[sdiy] MFOS Seq ext clk in

[David G. Dixon]

Tom,

First of all, "I'm no synth diy guru; I only play one on the web."  Now,
with that disclaimer out of the way, here's what I think:

The clock circuit is based on schmitt trigger inverters.  If you are
powering the unit with +12V on the upper rail, then the typical positive and
negative trigger thresholds for CD40106 are approximately 7 and 4.5V,
respectively.  To be safe, one must have a voltage greater than 9V or less
than 2.5V reliably trigger the device.  Hence, if your incoming signal is 0
to 10V, then Bob's your uncle.  If it is the more typical -5 to +5V, then
the trigger will forever be in the high state unless you shift this input up
by 5V with a DC level shifter.

Hope this helps...
 
David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C. V6T 1Z4
Canada
 
Tel 1-604-822-3679
Fax 1-604-822-3619
 
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> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of Tom Adam
> Sent: Friday, June 05, 2009 3:04 AM
> To: 'sdiy DIY'
> Subject: [sdiy] MFOS Seq ext clk in
> 
> Guys,
> 
> I've got some issues with the external clock in of my MFOS 16 step
> sequencer.
> When I was building it, I checked this input with my function generator
> and
> it was working perfectly. But when I connect an LFO (CGS/MOTM) or similar,
> it's not working. Also when I use an arduino midi to analog clock thing,
> it's not working.
> Is this normal behavior? All other features of this seq are working OK.
> 
> I was checking some signals and I found that I need a rather large 10Vpp
> signal to get the external clk in to work. I don't remember if it was a
> 0-10V or -5 to 5V signal, but I can check that again.
> So now I'm looking for a solution for this. I would like to use my LFO's
> and
> arduino to drive this sequencer. Should I just use an amp with some level
> shifting? What if I drive it with a sine wave instead of a square wave?
> 
> BTW On the schematic it says "CMOS levels source and sink expected".
> http://www.musicfromouterspace.com/analogsynth/SEQ16_2006/SEQ16_2006.php
> 
> Any help appreciated!
> 
> Cheers,
> ToAd
> www.thebigear.be
> 
> 
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