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 Forum index » DIY Hardware and Software » fonik's place
8-Step Sequencer with voltage controllable pattern (VCPS)
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fonik



Joined: Jun 07, 2006
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PostPosted: Sat Oct 22, 2011 4:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

do i understand you correctly: the sequencer doe not clock because the clock is to high, even after the schmitt trigger?
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diablojoy



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PostPosted: Sat Oct 22, 2011 5:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

hi matthias yes it seems that Q1/Q2 are adding some gain
taking the incoming 10 volt clock signal and spitting out a 12 volt clock signal after the diode drop from D21 the level is still just too high at around 11.1 volts
with around a 9 volt clock signal it must be just low enough to work
say 11 volts after D21
I cant see any differance with my scope but at that voltage level i really dont have enough resolution on the screen

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diablojoy



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PostPosted: Sat Oct 22, 2011 6:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

after a bit more thought on this i think i will try adding
another diode in series with D21 the extra diode voltage drop should get the pulse level down to below 11 volts and seems to be the easiest
solution to implement.
we shall see how that performs.
edit : well it does get the voltage down but it's not the solution Confused
something else is going on here and i just cant see it
checked R46 - 46.8K to grnd so that is OK
will try changing Q2 first and then Q1 if i have too
after that i am out of components and idea's

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diablojoy



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PostPosted: Sat Oct 22, 2011 7:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

changing Q1 still not working
changed Q2 also still not working
seems the highest clock pulse where it will
work is roughly 9 volts now, damn i think i may have gone backwards

need to think some more
and i should have put sockets in for Q1 and Q2

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fonik



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PostPosted: Sun Oct 23, 2011 7:45 am    Post subject: Reply with quote  Mark this post and the followings unread

IF the level would be the problem, then i could not see wy attenuating it should not work... so might it still be another issue? where is the lower level of both clocks? is there a difference in the "slope" of the clock (the should not actually be a slope in a clock signal)?
scratch

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diablojoy



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PostPosted: Sun Oct 23, 2011 1:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Where is the lower level of both clocks ?
both appear to be at 0 volts i think this is what you mean yes?
I can not see any slope on any of the clock signals
before or after Q1/Q2
just nice square waves displayed on my scope
I think i would need a far better scope to see anything
master clock is at 7 volts which will step the seq
M2C clock is at 10 volts which wont step the seq
I have to attenuate the M2C clock down to 9 volts
at that point the seq will then start stepping
i have tried this at the full range of BPM
20 BPM all the way up to 400 BPM and even at that rate the seq
will step if the M2C clock is attenuated down to 9 volts or less
my thought was that the output of Q2 should not rise above 10 volts in theory but i see at just over 11 volts there
the max input voltage on the 4017 clock input pin is 11 volts
going by the data sheet
tring an extra diode to drop the level did acheive that but still did not step the 4017 and the square wave still looked perfectly square on the scope
I don't know Confused still thinking about that
the only thing that has changed the result is a voltage divider to ground
to lower the pulse level before the sequencer input
so I do have a way to work around this issue
but i would rather understand why it occurs

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Dave Kendall



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PostPosted: Mon Oct 24, 2011 6:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi.

I might be way off here, but if R46 was decreased, wouldn't that lower the voltage at the CLK input pin (14)?

Just a thought......

cheers,
Dave

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diablojoy



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PostPosted: Mon Oct 24, 2011 1:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
if R46 was decreased, wouldn't that lower the voltage at the CLK input pin (14)?


yes i think so too
I will try lowering R46 value next, however i am confused as to why
the extra diode did not work, it did indeed drop the level
to the clock pin but made no difference to the stepping or non stepping of the 4017 and yet the wave form still looked ok on the scope i would have thought that the wave shape would have to have been a fair way from square to be a problem with this type of circuit
last night i did try a diode on the sequencer's clock input jack this also did not work
so i am now thinking any extra diode must have a bad enough effect on the wave shape so as to prevent stepping even though it is not obvious
on the scope.

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diablojoy



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PostPosted: Tue Oct 25, 2011 2:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

ok so lowering R46's value did not solve the problem
R46 at 30K = 10.5 volt square pulse well under the max
input to the 4017 still stepped when clocked from master clock but still did not step from M2C so i think it is reasonable to rule out the clock level
at this point in the cct as being the problem
this only leaves Q1/Q2 which i have already changed out before
so I am at a bit of a loss at this point.
perhaps i could test the HFE of the transistors used and select some from the opposite end of the scale ? not sure about that the validity of that though, as Q1 and Q2 are just being turned on surely.
maybe my next step should be to panel up a sequential switch as Matthias suggested as it has the same front end circuit and see how that performs then if still no result after that maybe panel up a second VCPS so i can do a more direct comparison though that will obviously take far more time.

cheers
denis

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diablojoy



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PostPosted: Wed Oct 26, 2011 2:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Ah small breakthrough perhaps Smile
was doing some more testing tonight after work and
still getting nowhere fast when out of frustration more than anything else
i tried manually stepping the sequencer, it was stepping through fine but
fortunately or i probably would never have seen it i still had the clock incoming from the M2C running very slowly and the damn thing kept resetting itself to the first step on every clock pulse Shocked
So i tried a another clock signal into the reset jack [an even slower clock]
with the M2C clock still running into the clock input
and eureka it worked. Smile
a bit of quick thinking and i next tried tying the reset input to ground
and again the sequencer is stepping fine. Smile
so that makes my next suspect actually part of the reset cct
specifically R52 - 100k which ties the reset to ground to stop the input floating when not in use though how this affects the clocking only when it is above a certain level is Confused I will run over it in my head to see if i can figure out a proveable theory
Out of time tonight will check have to check it out tomorrow night so i will sleep on it [ I do my best work asleep apparently ]

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fonik



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PostPosted: Wed Oct 26, 2011 3:49 am    Post subject: Reply with quote  Mark this post and the followings unread

it actually is R43 that ties the counter ICs reset input to ground. the parts R52, C27, D16, R53, R39 form a simple clock to pulse converter.
so this behaviour is intended: the reset is just a reset and not an inhibit. it resets the sequencer to step 1. from the rising edge of any incoming reset signal (squared) a short pulse is created, so that the sequencer keeps running (now starting from step 1), no matter how long your reset signal is.
hope that helps.

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diablojoy



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PostPosted: Wed Oct 26, 2011 5:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Matthias your cct description does indeed help a great deal
I had only had a quick glance over that part of the cct previously
I suspect this input must be floating and getting an induced voltage
from the clock input which is only high enough to affect the reset
when the clock pulse exceeds 9 volts [the two inputs wiring runs next to each other and are loomed together] thus R52 is still the most likely candidate.
This problem never arose before simply because previously the sequencer was never clocked with an high enough signal to produce this affect
so a mix of two problems most likely
it would explain very nicely why the sequencer sits on step one and refuses to move if it is being clocked and reset at the same time.
wish i had been smart enough to have thought of that scenario before but in the end I got lucky Embarassed .

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diablojoy



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PostPosted: Thu Oct 27, 2011 12:09 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Matthias and Dave for your support
fault is now fixed
ground side of R52 proved to be open or at least greater than 20 meg to ground
reflowed solder on both sides of the board
sequencer now stepping happily away
there was indeed a very noticeable short spike [above 1 volt certainly]being induced from the clock input to the reset input before i fixed R52 there is nothing above 50 mVolts now but i also ended up moving the reset and clock wiring away from each other afterward just to be on the safe side.

cheers
denis

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Dave Kendall



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PostPosted: Thu Oct 27, 2011 1:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice one - glad you got it fixed Cool
It was a weird one for sure......

cheers,
Dave

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fonik



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PostPosted: Thu Oct 27, 2011 8:12 am    Post subject: Reply with quote  Mark this post and the followings unread

happy ending! Very Happy

actually i wanted to emphasize how helpful it could be to do the "greenlining" of a circuit as part of troubleshooting, however, in this case you naturally focused on the clock circuitry, whereas the error hid itself in the reset circuitry - really nasty.

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emdot_ambient



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PostPosted: Thu Oct 27, 2011 9:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow, tough little bugger to figure out, but I'm glad to see you made it through!

All this bug stuff makes me shudder for what's in store for me...me with over 90 PCBs in various states of completion and 2 19" wide panels still in the wiring process. Shocked

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diablojoy



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PostPosted: Thu Oct 27, 2011 1:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks again guys
in the end it came down to a lucky break of actually noticing
the small clue with the reset behaviour, i really should have picked
earlier that the sequencer was always at step one when plugged in to
the M2C no matter what step it was sitting on when stopped prior
first bad soldering joint i have had in a long long time
ah well seems i may have to look at my soldering procedure.

emdot you are not alone Laughing I am in the same boat maybe even a little worse though i havent done an exact count of how many boards
i still have to panel or even start it would be at least that amount
it will just take time.
the one i am dreading most to start is the six appendage boards
[the hexappendage instrument ?] i have planned to build
but before that is my next one the 8 SympleSeq boards in one panel
with lots of mods to do including my first 4 layer board. now i am really sweating over that one as well Rolling Eyes

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emdot_ambient



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PostPosted: Thu Oct 27, 2011 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've got 2 VCPS boards...and I think they're pretty much completed. But no sense working on them when my first two big dual synth voice (2 VCO, 2 VCF, 2 VCA, 2 EG, 2 Mixers) and expander (4 LFO, Noise, Sample/Hold, Fonik VCRM and Quantizer) panels aren't done yet.

Just designed a 2U MOTM panel (not using MOTM grid) dual 292c LPG with 2 Fonik VC Mode expansion boards that I'm really keen to build, too...those LPG boards were the first boards I bought from the forums...like in 2009!

Kind of depressing really.

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tommi



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PostPosted: Mon Nov 07, 2011 2:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Fonik, I 've tried the little circuit you 've shown on page 10 of this thread, the ADC chip is now awake! Thanks for sharing!
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fonik



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PostPosted: Mon Nov 07, 2011 3:03 am    Post subject: Reply with quote  Mark this post and the followings unread

tommi wrote:
Fonik, I 've tried the little circuit you 've shown on page 10 of this thread, the ADC chip is now awake! Thanks for sharing!

you are welcome!

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billy pilgrim



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PostPosted: Thu May 17, 2012 8:38 pm    Post subject: VCPS sequencer boards ? Reply with quote  Mark this post and the followings unread

Matthias,

Do you have any boards left ?
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SydHeresy



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PostPosted: Mon Jun 11, 2012 7:42 pm    Post subject: Re: VCPS sequencer boards ? Reply with quote  Mark this post and the followings unread

billy pilgrim wrote:
Matthias,

Do you have any boards left ?


I too would be interested if there is going to be another run, or if there's any leftover.

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fonik



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PostPosted: Mon Jun 11, 2012 10:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

no boards left. and currently i don't have any plans to do another DIY PCB run, i am working on the fonitronik eurorack module prototype II instead Very Happy
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billy pilgrim



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PostPosted: Wed Jul 04, 2012 7:06 pm    Post subject: erroneous trigger ? Reply with quote  Mark this post and the followings unread

As there were no boards left I made one based on Matthias' board and comprehensive schematics. It works perfectly with the one exception that an extra trigger is generated at "end of gate". If anyone has a clue why that might be I'm keen to know, I've tried everything I can think of without success.........billy
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billy pilgrim



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PostPosted: Sun Jul 22, 2012 8:46 am    Post subject: Re: erroneous trigger ? Reply with quote  Mark this post and the followings unread

In case it makes the situation more apparent I've included a screenshot,
only stage 1 on. top trace, trig; bottom trace, gate.
It's easy to see the extra trigger pulse.
Could anyone confirm that it's the expected behaviour ?
That would help, thanks, Billy

billy pilgrim wrote:
As there were no boards left I made one based on Matthias' board and comprehensive schematics. It works perfectly with the one exception that an extra trigger is generated at "end of gate". If anyone has a clue why that might be I'm keen to know, I've tried everything I can think of without success.........billy



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