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 Forum index » DIY Hardware and Software » fonik's place
PCBs for a Sequential Analogue Switch
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LektroiD



Joined: Aug 23, 2008
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PostPosted: Fri Oct 29, 2010 3:32 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
LektroiD wrote:
Having never owned or used a sequential switch before, I am not entirely sure how these work. My understanding is that they switch sequentially 1,2,3,4,1,2,3,4,1 etc etc.. However, mine is making completely random patterns (using manual trigger - I haven't yet triggered externally). Eg; 1,4,1,2,1,3,1,2,1,4,1,4,1,2 etc etc.. Is this how they should work?

i would think the debouncing of the switch is not working. check your ground wiring, and/or try another switch. BTW i tried three different types of momentaries and the debouncing circuit worked for all three types.
anyways, to narrow it down, try clocking it with an external trigger to test it. and yes, it should switch sequential: 123412341234...


Must be what you describe, since the switches I bought were cheap, and all works when clocked externally

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fonik



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PostPosted: Fri Oct 29, 2010 4:58 am    Post subject: Reply with quote  Mark this post and the followings unread

what's the type of switches? i tried
- momentary toggles (as seen on i.e. teknik's waesome builds
- digi-switches (as seen on the divider as part of the breakdown filter)
- schurter push button momentaries (as seen on my euro VCPS-Cool
... all working with the same debounce circuit.

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LektroiD



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PostPosted: Fri Oct 29, 2010 11:27 am    Post subject: Reply with quote  Mark this post and the followings unread

The switches used were the following:

http://www.rapidonline.com/Electronic-Components/Switches/Push-Button-Switches/Miniature-push-switches/64324/kw/push+switch

However, this is not a problem since I will never use manual control for this device anyway. I was just concerned at the test stage where the manual switch was the only test means I had available at my bench.

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LektroiD



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PostPosted: Sun Sep 25, 2011 10:19 am    Post subject: Reply with quote  Mark this post and the followings unread

I just replaced the switches in these modules (I built 2) for much better quality ones, yet I still have the same problem.. Any ideas?
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fonik



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PostPosted: Sun Sep 25, 2011 1:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

try different values for C8.
i know this is not an easy fix. i would do it this way: desolder C8, or if the legs still long enough just cut the cap off. if you desoldered it, solder pieces of i.e. resistor leg to the holes. now you can use alligator clips to try different values (i would try smaller values from 1n to 100n). if you finally found one that is working just solder it to the legs that are soldered already. this way you don't do too much harm to the board itself.

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camelneck



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PostPosted: Tue Sep 27, 2011 6:45 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
try different values for C8.
i know this is not an easy fix. i would do it this way: desolder C8, or if the legs still long enough just cut the cap off. if you desoldered it, solder pieces of i.e. resistor leg to the holes. now you can use alligator clips to try different values (i would try smaller values from 1n to 100n). if you finally found one that is working just solder it to the legs that are soldered already. this way you don't do too much harm to the board itself.


When I built my Sequential Switch, I had a problem with the manual step switch because I was using some fairly good quality switches that didn't have to be debounced much. Each push of the button was causing the CD4017 to advance by 2 steps instead of 1 step. Since I had 2 brands of CD4017 in my spare parts stock (I tried both Texas Instruments then Fairchild), I first tried changing the IC, hoping that the Fairchild chip wouldn't be as sensitive. However, this didn't help.

The next thing I did was remove C8 in order to see how this affected the behavior of the switch. I could now get the counter to advance 1 step at a time, but about every 3rd try it might skip 2 or 3 steps instead of a single step. Thus, I knew I had to lower the capacitance value of C8, but I wasn't sure how much.

Using alligator clips (so I wouldn't damage the PCB with repeated soldering) I gradually kept decreasing the value of C8 from 100nF to 47nF to 10nF, but I was still having the same problem I had when C8 = 100nF. Finally, I tried C8 = 4.7nF and the push button switch started working perfectly. The counter was advancing by 1 step every time I pushed the switch.

Just for the record, I decided to try values of 5.6nF and 3.3 nF for C8. However, the switch only operated perfectly when C8 = 4.7nF. So hopefully, you have a good assortment of spare capacitors that you can try because you may need them. (I used polyester box caps for C8, but other types of caps, including ceramic, should work.).
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emdot_ambient



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

Interesting. I haven't built any of mine yet, but it's good to know 'bout that C8 thing...probably will build mine anticipating trying different values. thumb up
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fonik



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PostPosted: Wed Sep 28, 2011 12:06 am    Post subject: Reply with quote  Mark this post and the followings unread

yes, interesting. for the VCPS-8 i used a different scheme which seems to work much better: the manual step uses the same debouncing circuit, however, it is applied to the discrete schmitt trigger of the clock input, not to the counter IC - seems to work much better?

anyways, i tried it with several switches, even with 4.-USD/ea momentaries from shurter, and all worked quite fine.

BTW i still have 10 spare PCBs left for sale.

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citric acid



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PostPosted: Wed Oct 05, 2011 5:29 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
yes, interesting. for the VCPS-8 i used a different scheme which seems to work much better: the manual step uses the same debouncing circuit, however, it is applied to the discrete schmitt trigger of the clock input, not to the counter IC - seems to work much better?

anyways, i tried it with several switches, even with 4.-USD/ea momentaries from shurter, and all worked quite fine.

BTW i still have 10 spare PCBs left for sale.

hi matthes,

i need a second do you have one left ?

BR,
Thorsten

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LektroiD



Joined: Aug 23, 2008
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PostPosted: Wed Oct 12, 2011 9:31 am    Post subject: Reply with quote  Mark this post and the followings unread

camelneck wrote:
fonik wrote:
try different values for C8.
i know this is not an easy fix. i would do it this way: desolder C8, or if the legs still long enough just cut the cap off. if you desoldered it, solder pieces of i.e. resistor leg to the holes. now you can use alligator clips to try different values (i would try smaller values from 1n to 100n). if you finally found one that is working just solder it to the legs that are soldered already. this way you don't do too much harm to the board itself.


When I built my Sequential Switch, I had a problem with the manual step switch because I was using some fairly good quality switches that didn't have to be debounced much. Each push of the button was causing the CD4017 to advance by 2 steps instead of 1 step. Since I had 2 brands of CD4017 in my spare parts stock (I tried both Texas Instruments then Fairchild), I first tried changing the IC, hoping that the Fairchild chip wouldn't be as sensitive. However, this didn't help.

The next thing I did was remove C8 in order to see how this affected the behavior of the switch. I could now get the counter to advance 1 step at a time, but about every 3rd try it might skip 2 or 3 steps instead of a single step. Thus, I knew I had to lower the capacitance value of C8, but I wasn't sure how much.

Using alligator clips (so I wouldn't damage the PCB with repeated soldering) I gradually kept decreasing the value of C8 from 100nF to 47nF to 10nF, but I was still having the same problem I had when C8 = 100nF. Finally, I tried C8 = 4.7nF and the push button switch started working perfectly. The counter was advancing by 1 step every time I pushed the switch.

Just for the record, I decided to try values of 5.6nF and 3.3 nF for C8. However, the switch only operated perfectly when C8 = 4.7nF. So hopefully, you have a good assortment of spare capacitors that you can try because you may need them. (I used polyester box caps for C8, but other types of caps, including ceramic, should work.).


I got one of my builds working perfectly with a 4n7, but the other is a little intermittent.. seems to skip occasionally. Maybe 4n7 is the perfect value, but due to only having that value in ceramics (20% tolerance), I guess it was a little out.. Maybe it would work better with a 5% of the same value... I'll try a few others, but I'd say 4n7 is pretty much bang on.
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LektroiD



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PostPosted: Sun Oct 16, 2011 5:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm wondering how hard it would be to add a switch to reverse the order of the sequence, so it counts backwards from 4 through to 1. Just thought of this as some of my patches would benefit from such a function.
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wmonk



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PostPosted: Sun Oct 16, 2011 5:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

LektroiD wrote:
I'm wondering how hard it would be to add a switch to reverse the order of the sequence, so it counts backwards from 4 through to 1. Just thought of this as some of my patches would benefit from such a function.

The circuit uses a 4017 decade counter for sequencing, and that can only count up. But with a clever switch you might be able to route those signals the other way around to the inputs of the analog switch. The LEDs would still count up, but it would switch the other way around. Rolling Eyes

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fonik



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PostPosted: Mon Oct 17, 2011 9:39 am    Post subject: Reply with quote  Mark this post and the followings unread

what about a 8-step up-down switch? could be used as sequencer with external voltage inputs as well?
i have thought of this before and it would be fun designing it. there is only one thin: as soon as i wanted to normalize the external voltage inputs to i.e. 5V i cannot use it as 1-to-8 switch, only as 8-to-1...
what do you think?

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citric acid



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PostPosted: Mon Nov 21, 2011 11:59 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
what about a 8-step up-down switch? could be used as sequencer with external voltage inputs as well?
i have thought of this before and it would be fun designing it. there is only one thin: as soon as i wanted to normalize the external voltage inputs to i.e. 5V i cannot use it as 1-to-8 switch, only as 8-to-1...
what do you think?


that sounds interesting....

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umschmitt



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PostPosted: Sat Dec 24, 2011 7:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey fonik. Great circuit here ! I had a idea while staring at the schemo : why not try a series of four 4-way rotary switches (diode protected at the output) between the 4017 and the analog switch to allow you to choose which in/out is on at every step, in a sequencerish fashion ? With the remaining connections on the switches, you could even have a cute little LED matrix to visualize things…
[Of course, starting from here, you may want to have an 8 step sequencer, then 8 ins/outs etc… Oh wait ! Now imagine a 8×8 matrix with LED things being the actual pins !]
Well… This what my mind went into when considering your design. Of course there might be issues preventing one to actually bring this to work, tech stuff isn't my strong side. I might simply need some sleep, too.

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keithwin



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PostPosted: Wed Jan 04, 2012 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Have you still got a couple of these left? I have been looking for a seq switch
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fonik



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PostPosted: Thu Jan 05, 2012 4:35 am    Post subject: Reply with quote  Mark this post and the followings unread

i will ask for interest in another PCB t=run pretty soon. the simplseq is beeing shipped, and maybe some might find the seqswitch usefull in combination with this sequencer project...
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emdot_ambient



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PostPosted: Thu Jan 05, 2012 8:02 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
...the simplseq is beeing shipped, and maybe some might find the seqswitch usefull in combination with this sequencer project...

Indeed. Right now it looks like I'm going to be using 3 of the sequential swithces with my quad sympleSEQ: one for CV outputs, one for Gate outputs, and one tied to the 4 sequencers' reset outputs, driving the clock inputs of the other sequential swithces. This set up turns 4 independent sequencers into a single sequencer with the number of steps variable between 1 and 64....IF it works

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citric acid



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PostPosted: Thu Jan 05, 2012 8:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Matthes,

frohes neues .

Yes i need 1 minimum. or 2 ?

Thanks,
Thorsten

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diablojoy



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PostPosted: Thu Jan 05, 2012 4:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Indeed. Right now it looks like I'm going to be using 3 of the sequential swithces with my quad sympleSEQ: one for CV outputs, one for Gate outputs,



regarding the gate outputs I would have thought you would not need one for there
just 4 diodes to OR the gates together and 2 sections of a 40106
to condition the resulting gates and a buffer for the output
or perhaps you have another cunning plan ? Confused

Quote:
and one tied to the 4 sequencers' reset outputs, driving the clock inputs of the other sequential swithces.

hmm thats interesting
the way i went about this was different as i am using a seq switch and a VC divider to send a clock pulse to each sequencer in turn but that brought about a possible issue regarding propagation delays which needed addressing as there is approx 160 -200 nanoseconds of delay
involved with the 4017 and DG412 chips of the switches
this may be enough to cause a double clocking of the sequencers
as the min clock pulse width required by the 4017 in the sequencers
is well under the off to on time of the switching .
I added 4 sections of a 40106 in the switched clock path
[240 nano seconds delay] to address this in my build .maybe your way gets around that , not sure though have to think about it .

edit :
matthias sorry for the slightly off topic reply here

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