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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Fri Jan 03, 2014 7:01 pm Post subject:
mfos sequencer ext.clock dont work correct |
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My mfos 16step sequencer works with internal clock fine.
The external clock input works inly on a lfo.
A motm300 or oakley pulse/square dont run the sequencer.
The sequencer is connected with 15v psu.
Any idea ? |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Sat Jan 04, 2014 7:56 am Post subject:
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Hi LED-man.
I suspect that the problem might be that your modules are putting out a +/-5V square wave (after looking at the MOTM/Oakley manuals). The 40106 datasheet shows that at 15V (and 25°C) the typical threshold voltages are 8.8V to switch on and 3.9V to switch off. With a +/-5V input, the 40106 is never going to switch on, so you will need some kind of voltage shifter. If you confirm that your outputs are +/-5V, I've got a very simple circuit that should make it work (hopefully).
Gary |
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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Sat Jan 04, 2014 12:32 pm Post subject:
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Thanks, any schematic for this ? |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Sat Jan 04, 2014 3:41 pm Post subject:
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Hi again.
I thought about using a proper op-amp voltage shifter, but I don't think that it's necessary. You should be able to do it with a diode and a couple of transistors as in the attached schematic.
The diode just lets through the positive parts of the square wave. The transistors are switches i.e. fully on or fully off. You need 2, as they are also inverters, so the square wave produced by the first one will be 180° with the original square wave. The second transistor re-inverts the signal. I actually breadboarded it to sanity check the circuit and it works - I've also attached the oscilloscope traces. This was at 5Hz, but it works over a wide range of frequencies.
Let me know if you have any luck with this.
Gary
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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Sat Jan 04, 2014 4:28 pm Post subject:
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Thank you very much.
I'll try it next week. |
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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Mon Jan 13, 2014 3:11 am Post subject:
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works fine, have build this on a pcb.
have tried a motm300 pulse, oakley vco pulse and external clock from midi-cv interface.
HF coupling /DC coupler is optional (cap 2u2, 100n mlcc between +15V and 0V) |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Mon Jan 13, 2014 12:40 pm Post subject:
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Really glad to hear that it worked. I was thinking about an op-amp alternative if there was a problem, but I was fairly certain that it would be OK.
Gary |
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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Thu Jan 16, 2014 2:23 pm Post subject:
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work fine as a external module, nut not internal by breaking the signal from clock input jack.
by using as a internal modul behind the front panel, i have break the cable from ext input jack and connected this to the helper input, and connected the output to the cable that goes to the analog/digiboard input.
if i connect a clock to ext. input - sequencer works, if unplug the jack from mfos ext. in - the internal voltage is to high, with result that the internal clock don't work.
any idea ? |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Thu Jan 16, 2014 5:01 pm Post subject:
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Hi (again),
I've only just seen your post (it's 23:50) and I can see that it might cause problems as an internal (permanently connected) circuit. The easy answer would be to have it as a switchable input, which could disconnect the circuit when it's not needed. Unfortunately, this might mess up your front panel (if that's already been built).
I'll have another look at the circuit tomorrow and see if I can think of a more elegant solution. I have a couple of ideas, but I need to try them out first.
I'll get back to you when I've had an experiment...
Gary |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Sat Jan 18, 2014 5:02 am Post subject:
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analog_backlash wrote: | ..,but I hadn't realised quite the way that circuit works, with the external clock going through the inverter that is also the internal oscillator. |
Neither did I, I hadn't looked at the schematic , but just did and now I see what you mean. So basically the problem is that without an external
CLK connected that input needs to be left open/floating. Maybe some logic gate with a tri-state output can be used, or how about replacing the bypass
switch* in the circuit Gary drew with a digital switch (4066) that's closed when a jack is inserted. Allthough that only works with phono jacks (either
with a switch contact or using a stereo socket) not with banana's. I don't know what you are using. If you use banana's then you'll probably have to
install a switch.
*I think a single switch on the output of the level shifter should be sufficient but maybe I'm missing something. _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Sat Jan 18, 2014 5:48 am Post subject:
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Hi PHOBoS.
Your ideas of using a Tri-State buffer or a 4066 seem good, but as you say, that requires a switched jack input. I don't know what LED-man is using either.
I did think about just using a SPDT * switch, but I think I had guitar FX in mind, where they suggest that a true bypass is a better option. Probably here, it's not necessary.
Thanks for the input
Gary
* Actually, make that SPST! |
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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Sun Jan 19, 2014 4:02 pm Post subject:
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Thx, yes i have switched jacks.
I'll try tomorrow |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Sun Jan 19, 2014 4:41 pm Post subject:
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Hi LED-man.
For your information, I have tried a 4066 switch as PHOBoS suggested and it works perfectly. I haven't posted anything yet as I haven't drawn a diagram, but if you need any information, I can post that tomorrow.
Gary |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Mon Jan 20, 2014 2:54 pm Post subject:
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Thank you for the schematic.
Little failure, big pcb.
I can't etch pcbs, so i have to check to get this on a dot hole pcb or stripe pcb.
If not i have to use a dpdt switch. |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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Posted: Mon Jan 20, 2014 4:22 pm Post subject:
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Nice to know that works. I think you could do it without the extra transistor, just add a pullup resistor to the CTRL pin of the 4066 (13) and use a switch
contact to GND. It also depends on the connectors you use. The ones I have don't have isolated switch contacts, so it would have to be a (NC) switch to
GND. And if you leave out R5/R6 (not bad but no need for them I think) the circuit allready get's a bit smaller _________________ "My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube |
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LED-man
Joined: Feb 22, 2013 Posts: 40 Location: Germany
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Posted: Mon Jan 20, 2014 4:39 pm Post subject:
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Here my solution:
I have replaced the ext.start jack with a switch to break the output from the voltage shifter.
I cant invest to much time yet in this device, because i have to solder a yocto 808 clone until next week.
In 2-3weeks starts the TTSH, i have organized a german groupbuy for parts, so i must sort "few" parts.
Thanks for your support good guys.
I'm on muffs with same nick every day. |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Tue Jan 21, 2014 3:25 pm Post subject:
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PHOBoS wrote: | Nice to know that works. I think you could do it without the extra transistor, just add a pullup resistor to the CTRL pin of the 4066 (13) and use a switch contact to GND. It also depends on the connectors you use. The ones I have don't have isolated switch contacts, so it would have to be a (NC) switch to GND. And if you leave out R5/R6 (not bad but no need for them I think) the circuit allready get's a bit smaller |
Yes, that sounds like it would also work (but I haven't tried it yet). I was did wonder if a simpler circuit could be used. Thanks again PHOBoS.
Gary |
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