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 Forum index » DIY Hardware and Software » YuSynth
Clock Divider
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Blue Hell
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Joined: Apr 03, 2004
Posts: 22319
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PostPosted: Thu Dec 07, 2017 4:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

chatted a bit with wmonk about this puzzle ... maybe it gives some ideas?

Code:
[22:49:40]   Jan   for .. whenyou like a puzzle ... :: http://electro-music.com/forum/post-431923.html#431923
[22:52:37]   wmonk   oh, he is confusing pin numbers with output numbers, it seems
[22:52:39]   wmonk   
[22:52:51]   wmonk   probably a short somewhere too
[22:52:56]   Jan   heh .. dont think so
[22:53:23]   wmonk   and rotary switches, they work in mirror, or something like that
[22:53:28]   Jan   he mentions bothdivision rate and pin number in some posts - correctly
[22:54:00]   Jan   actually one of the few people posting accurately about experiments
[22:54:11]   Jan   or - seemingly so
[22:54:40]   wmonk   hmm
[22:54:47]   wmonk   oh, he used +/- 6V signals
[22:54:56]   wmonk   on a chip thats powered from 0 - 15V
[22:55:03]   wmonk   most chips dont like that
[22:55:23]   Jan   clipped in the input circuits
[22:55:32]   wmonk   oh yeah
[22:56:23]   [INFO]   Font size is 7pt
[22:56:31]   [INFO]   Font size is 9pt
[22:56:50]   wmonk   the +/-3V square wave... hmm, that might be a gain of the schmitt trigger problem
[22:57:07]   Jan   yeah that may be a tad low
[22:57:40]   wmonk   I have that thing in my modular
[22:57:45]   wmonk   the yusynth clock dividers
[22:57:50]   wmonk   no problems whatsoever
[22:57:51]   Jan   ah
[22:58:00]   Jan   designseems solid tome
[22:58:21]   wmonk   I used the PCB layout of his website though
[22:58:35]   Jan   he is breading it
[22:59:36]   Jan   now in most cases .. when it dont work .. the circuit is not what you thinkit to be ... but cant come up with a model
[22:59:45]   wmonk   aha
[23:01:18]   wmonk   looking at datasheet and schematic
[23:01:45]   Jan   Ihave the COS/MOS book on the tab;e too
[23:01:48]   wmonk   pinout in schematic is correct according to datasheet
[23:02:02]   Jan   andhad checked that as well
[23:02:06]   wmonk   so either there is some floating CMOS input pin
[23:02:14]   wmonk   not that hard on a breadboard
[23:02:28]   Jan   yeahcould be .. but allthree behave the same he sez
[23:02:52]   wmonk   in that case its three times the same error
[23:03:06]   wmonk   not that hard on breadboard either
[23:03:09]   Jan   een ezel in het algemeen
[23:03:30]   wmonk   if you are convinced something is good, it usually isnt
[23:03:40]   Jan   yeah - could be
[23:04:00]   Jan   whenit was copied over section by section
[23:04:17]   wmonk   diodes reversed would fuck it up too
[23:04:26]   Jan   he checked those
[23:04:47]   wmonk   and rotarty switches are evil, how you need to wire those
[23:04:59]   Jan   sometimes yes
[23:05:09]   Jan   but he works with wires
[23:05:32]   Jan   bypassingthe switches .. or .. replacing .. I hope
[23:05:49]   Jan   and assume
[23:06:31]   wmonk   100nFs in place as close as possible to the chip?
[23:06:41]   Jan   I think you are right about some fuckup in the breading
[23:06:42]   wmonk   especially with breadboards
[23:07:06]   Jan   yeah could be .. or grounding was my latest - and last prolly - idea
[23:07:44]   Jan   oh damn .. some breads dont have continues power rails
[23:07:54]   Jan   you needto patch those
[23:08:02]   wmonk   yup
[23:08:21]   Jan   going topaste this discussion intothat thread, ok?
[23:08:40]   wmonk   sure
[23:08:44]   Jan   k

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PostPosted: Fri Dec 08, 2017 12:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Jan, thanks for thinking along and trying to find help! But I think I have found the reason for the strange behaviour. Btw: I built it on stripboard (veroboard), not on a breadboard.

I recently built the MFOS 32 step sequencer, and Ray was talking about a strange reset at some pin that he could remove by adding a 1nF cap to ground (he called it a glitch removal cap). So I took out a 1nF cap and... Bingo!

When I add a 1nF cap between pin 7 and ground, the strange behaviour is gone! (pin 7 is were the 3rd division is, just before the 4th were things go wrong).

Then I noticed that 1 of the dividers was still acting strange, even with the cap. The only difference was that it's tracks were longer than those of the other two.

I has to do with stripboard, and the fact that adjacent strips/tracks can influence each other, especially when those tracks are long. For instance by forming a capacitor, resulting in stray capacitance. But I guess that there are more effects that can occur like sensitive parts picking up electric fields. I have built many circuits on stripboard and two times before I have had issues that could be solved by minimizing the length of the tracks.

So now I have shortened the track were pin 7 is soldered as much as possible. I only could shorten it by 0,75 cm, but the total length was only 1,5 cm so I effectively cut it in two. And now, all three dividers work normal, even without the 1nF cap! That is, with the +6 Volt gates. Fingers crossed: I still have to put the switches and the wires back in place.
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Blue Hell
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PostPosted: Fri Dec 08, 2017 5:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Great :-)

And re. the strip board turning into a bread board .. that's what happens with chinese whispering!

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