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Gated comparator - strange movement

Gated comparator - strange movement

2015-06-18 by spunraddish

Hi again guys,


I just built up a gated comparator and it works - with some reservations. I find that certain pulses reallocate and disappear around step 5-6, sometimes removing pulses 5 through 8. There are only specific patterns that seem to hold (as movement) during loop enable, where I first observed this: 01110000, 01010000, and 10101111, though none of these are absolute, which is problematic - I was hoping to be able to catch specific beat patterns and shuffle them. Another thing that occurs is the reallocation into a more regular pairing from unpaired positions at steps 5-6. I switched out the 4015 for a new one, and there was no difference. I resoldered many of the pads, made no difference. I used a push-pull pot for the input attenuator as a loop enable/ input off configuration. One of the only things I can consider is that I perhaps destroyed one of the SMT caps (maybe I just need to get rid of one) OR that there are traces that are damaged, which on a look over didn't appear to be the case. I have 4 inch wires coming from the board to the panel, twist-pairing the LED anodes to the designated inputs.


Any ideas?


Thanks

Eric

Re: Gated comparator - strange movement

2015-06-18 by Ken Stone

There should be an RC lag built into the data line at the 4-5 junction to deal with this issue. Make sure the capacitor is installed and connected.
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On Thu, Jun 18, 2015 at 12:06 PM, spunraddish@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Hi again guys,


I just built up a gated comparator and it works - with some reservations. I find that certain pulses reallocate and disappear around step 5-6, sometimes removing pulses 5 through 8. There are only specific patterns that seem to hold (as movement) during loop enable, where I first observed this: 01110000, 01010000, and 10101111, though none of these are absolute, which is problematic - I was hoping to be able to catch specific beat patterns and shuffle them. Another thing that occurs is the reallocation into a more regular pairing from unpaired positions at steps 5-6. I switched out the 4015 for a new one, and there was no difference. I resoldered many of the pads, made no difference. I used a push-pull pot for the input attenuator as a loop enable/ input off configuration. One of the only things I can consider is that I perhaps destroyed one of the SMT caps (maybe I just need to get rid of one) OR that there are traces that are damaged, which on a look over didn't appear to be the case. I have 4 inch wires coming from the board to the panel, twist-pairing the LED anodes to the designated inputs.


Any ideas?


Thanks

Eric




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

Re: Gated comparator - strange movement

2015-06-18 by spunraddish

Thanks for the response, Ken. I replaced the capacitor to a film one, reheated a bunch of joints, and added a few jumpers just to be safe, and nothing in regards to the reorganization of the patterns- there are specific clock frequencies that seem to be more inclined to erasing all steps, and there are certain patterns that incline the steps to go 7 high, often when it's more than 4 steps - I'm going to try to jumper a few more spots, but perhaps this has to do with other capacitors?

Re: Gated comparator - strange movement

2015-06-18 by spunraddish

Nope, did that and did a few more mods, to no effect - in loop mode there are only 4 eventualities - no steps on, 3 steps on, two steps on with a space between them, and 7 steps on. When not in loop mode, it seems there may be a sort of logic to when step 6-8 stay on and off, as I've obtained mostly rhythmic patterns that repeat after 3-4 cycles, not without error though. Faster patterns have less errors outside of loop mode. In loop mode, when I lose all steps, it's a relatively slow clock and they disappear around step 4. When it organizes to the other two patterns, it is a quicker rate.

Perhaps it has something to do with the 1n cap value?

Re: Gated comparator - strange movement

2015-06-18 by Ken Stone

It may have more to do with the speed of the clock chip. Try adding a 1M between pins 7 and 5 of the TL072 that is used to process the clock signal.
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On Fri, Jun 19, 2015 at 4:37 AM, spunraddish@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Nope, did that and did a few more mods, to no effect - in loop mode there are only 4 eventualities - no steps on, 3 steps on, two steps on with a space between them, and 7 steps on. When not in loop mode, it seems there may be a sort of logic to when step 6-8 stay on and off, as I've obtained mostly rhythmic patterns that repeat after 3-4 cycles, not without error though. Faster patterns have less errors outside of loop mode. In loop mode, when I lose all steps, it's a relatively slow clock and they disappear around step 4. When it organizes to the other two patterns, it is a quicker rate.


Perhaps it has something to do with the 1n cap value?




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

Re: Gated comparator - strange movement

2015-06-19 by Richard Brewster

When the 4015 was swapped, did you try a different manufacturer? I discovered years ago when I built the Burst Generator that some CMOS chips can have spurious output glitches. Now I use only Texas Instruments CMOS chips.

Richard Brewster
http://pugix.com

On 6/18/15 6:40 PM, Ken Stone otherunicorn@... [cgs_synth] wrote:
Show quoted textHide quoted text
It may have more to do with the speed of the clock chip. Try adding a 1M between pins 7 and 5 of the TL072 that is used to process the clock signal.

On Fri, Jun 19, 2015 at 4:37 AM, spunraddish@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Nope, did that and did a few more mods, to no effect - in loop mode there are only 4 eventualities - no steps on, 3 steps on, two steps on with a space between them, and 7 steps on. When not in loop mode, it seems there may be a sort of logic to when step 6-8 stay on and off, as I've obtained mostly rhythmic patterns that repeat after 3-4 cycles, not without error though. Faster patterns have less errors outside of loop mode. In loop mode, when I lose all steps, it's a relatively slow clock and they disappear around step 4. When it organizes to the other two patterns, it is a quicker rate.


Perhaps it has something to do with the 1n cap value?




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

Re: Gated comparator - strange movement

2015-06-19 by spunraddish

Hi again Ken and Richard,

Thanks for your help.

I've tried placing a 2M trimmer between legs 5 and 7 of that particular 072, but without results until rsistance too low locked up the 072 - I may try one from a different manufacturer, since I'm getting a slightly different set of patterns that hold, I gained a 01101100 aside from the previous mentioned conditions. I notice that it is between steps 5 and 6 that when there is typically a space (101), it disappears (110) at that position.

The CD4015 I had is from texas instruments, though said to be at the end of it's life cycle, should I try one from a newer batch?

Re: Gated comparator - strange movement

2015-06-19 by neilbaldwin70

If you can I'd definitely try more 4015s. I had a terrible time with them recently when building a Rollz-5. The problem I had was one or more of the gates not closing down properly and allowing signal to bleed through. I tried 4 different ones before landing one that worked properly.

On 19 Jun 2015, at 16:30, spunraddish@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Hi again Ken and Richard,


Thanks for your help.

I've tried placing a 2M trimmer between legs 5 and 7 of that particular 072, but without results until rsistance too low locked up the 072 - I may try one from a different manufacturer, since I'm getting a slightly different set of patterns that hold, I gained a 01101100 aside from the previous mentioned conditions. I notice that it is between steps 5 and 6 that when there is typically a space (101), it disappears (110) at that position.

The CD4015 I had is from texas instruments, though said to be at the end of it's life cycle, should I try one from a newer batch?

Re: Gated comparator - strange movement

2015-06-19 by Ken Stone

Lower resistances between the op-amp pins would not help. It's a measure to speed up the transition time. Try a different TL072. "End of life" for chips means they aren't making them any more. The chip itself is still viable. Add another 100n directly across the 4015's power pins too. Maybe that will help.
Show quoted textHide quoted text
On Sat, Jun 20, 2015 at 3:29 AM, neil.a.Baldwin@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

If you can I'd definitely try more 4015s. I had a terrible time with them recently when building a Rollz-5. The problem I had was one or more of the gates not closing down properly and allowing signal to bleed through. I tried 4 different ones before landing one that worked properly.

On 19 Jun 2015, at 16:30, spunraddish@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Hi again Ken and Richard,


Thanks for your help.

I've tried placing a 2M trimmer between legs 5 and 7 of that particular 072, but without results until rsistance too low locked up the 072 - I may try one from a different manufacturer, since I'm getting a slightly different set of patterns that hold, I gained a 01101100 aside from the previous mentioned conditions. I notice that it is between steps 5 and 6 that when there is typically a space (101), it disappears (110) at that position.

The CD4015 I had is from texas instruments, though said to be at the end of it's life cycle, should I try one from a newer batch?




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

Re: Gated comparator - strange movement

2015-06-22 by spunraddish

Thanks everyone! I switched out the 072 and placed a cap across the power pins of the 4015 and it works just fine! I find that I get the previous issues only with a particular source of clock in my staple system as it pertains to the gated comparator, and I know it's not pulse width or clock rate; it may something to do with the output level, I'll investigate this on my own. Strange, since it works just fine with other clocks that are bipolar oscillators with entirely varied pulse-widths.

Again, thanks!

Eric

Re: Gated comparator - strange movement

2015-06-22 by Ken Stone

The output of that clock probably has sloped transitions.
Show quoted textHide quoted text
On Tue, Jun 23, 2015 at 4:26 AM, spunraddish@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Thanks everyone! I switched out the 072 and placed a cap across the power pins of the 4015 and it works just fine! I find that I get the previous issues only with a particular source of clock in my staple system as it pertains to the gated comparator, and I know it's not pulse width or clock rate; it may something to do with the output level, I'll investigate this on my own. Strange, since it works just fine with other clocks that are bipolar oscillators with entirely varied pulse-widths.


Again, thanks!

Eric




--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

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