16 Step Sequencer - External Clock Problem

JCM · Joined: Jul 21, 2008 Posts: 15 Location: MPLS

So I have my MFOS 16 Step Sequencer up and running and everything seems to work as expected. Unfortunately I can't seem to get the External Clock Input to work. I try sending it a Square Wave from my MFOS VCO's and it just freezes the clock. The Square works for the External Start and I'd expect it to work for the Clock, but is this just not a good clock source? If so then what?

adhmzaiusz · Joined: Jan 17, 2008 Posts: 59 Location: toronto

Freezes the clock? that sucks! I hope I dont have this same problem when I finish mine because I really want to sync the sequencer to my computer

You checked all the values of resistors etc?

Which parts list did you go by? I dont know if you noticed but there are 2 sequencer pages on the mfos page for the same sequencer, and I noticed that the parts list is different between them...maybe you are going by the old site?

Good luck!

Adam-V · Posted: Mon Jun 22, 2009 5:00 pm Post subject:

Starting with the obvious.
Have you double checked your wiring?
Did you make the necessary changes to R23 and R18?
Did you add the diode to block the negative part of the VCO waveform? If so, check that it is the right way around.

If all of the above checks out, then it is possible that you are trying to clock it faster than it can handle. You probably need to clock it with something in the LFO range rather than the audio range.

It is also possible that, since the VCO will output a 10Vp-p signal centred around 0V that the peak of the positive part of the signal (being only 5V) is not quite big enough to trip the schmitt trigger which, for a 12V supply could require at least 6V. If this is the case, adding transistor or comparator input stage would solve it.

Cheers,
Adam-V

JCM · Joined: Jul 21, 2008 Posts: 15 Location: MPLS

Thanks for your reply Adam-V, it was helpful.

Adam-V · Posted: Tue Jun 30, 2009 4:38 pm Post subject:

To test it, grab yourself a 9V battery and a battery snap, connect the negative wire to ground (0V) on your sequencer and briefly touch the positive wire to the clock input. That should clock it at least 1 step. It will probably step a few stages due to contact bounce as the wire makes intermittant connection with the input but it will give you an indication that your external input is functioning.

Cheers,
Adam-V

Budgrubber · Joined: Dec 27, 2006 Posts: 72 Location: USA