[sdiy] Re: reset circuit for LFO

[Scott Nordlund]

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God=2C is that obnoxious formatting my fault?=A0=20

Sorry.

----------------------------------------
> From: gsn10 at hotmail.com
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] Re: reset circuit for LFO
> Date: Mon=2C 19 Oct 2009 14:15:38 -0400
>
>
> <4ADC9B6F.7050704 at gte.net>
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> <439ccfd90910191005g3e119ad6q9e15659d3df05827 at mail.gmail.com>
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> CMOS logic levels depend on power supply voltage=3D2C so you will need
> to boost a 5V logic signal.=3DA0 Usually a pull-up resistor will do=3D20
> the trick.
>
> Alternatively=3D2C you can use a similar DGxxx part that uses TTL logic=
=3D20
> levels regardless of power supply voltage.
>
>> Date: Mon=3D2C 19 Oct 2009 10:25:50 -0700
>> Subject: Re: [sdiy] Re: reset circuit for LFO
>> From: danjel at gmail.com
>> To: synth-diy at dropmix.xs4all.nl
>>=3D20
>> ok I put a 22pF cap to stretch out the pulse and this is working great
>> when feeding a pulse signal from the Elf LFO. I also put a diode in
>> series for protecting against negative voltage.
>>=3D20
>> However=3D2C my midi2cv converter clock and gate (which have no problem
>> triggering things like the doepfer A160/161 or doepfer envelopes) are
>> not triggering it at all.
>>=3D20
>> This goes back to my question on if I am powering the cd4053 at 12V
>> does it matter that the gates/clk are 5V?
>>=3D20
>>=3D20
>>=3D20
>> cheers=3D2C
>> Danjel
>>=3D20
>>=3D20
>>=3D20
>>=3D20
>>=3D20
>>=3D20
>> On Mon=3D2C Oct 19=3D2C 2009 at 10:06 AM=3D2C Danjel van Tijn=20
>> wrote:
>>> oops not a diode to ground=3D2C a diode inline!
>>>
>>>> Is it as simple as putting a small cap between signal and ground of my
>>>> reset jack?
>>>>
>>>> Should I also be putting a diode to ground to protect the CMOS chip
>>>> from any negative voltage?
>>>>
>>>> cheers=3D2C
>>>> =3DA0 Danjel
>>>>
>>>>>
>>>>> You might try a "pulse stretcher" circuit essentially adding a small
>>>>> something picofarad cap
>>>>> to lag the incoming clock a bit... (would be simpler than adding a
>>>>> comparator and pulse
>>>>> conditioning circuit with debouncing etc?
>>>>>
>>>>> Best Wishes!
>>>>>
>>>>>
>>>>> Cynthia
>>>>>
>>>>>
>>>>>
>>>>> Danjel van Tijn wrote:
>>>>>>
>>>>>> Someone suggested using the circuit that Ken Stone used on the clock
>>>>>> input here: http://www.cgs.synth.net/modules/cgs13v2_gated_comparato=
r=3D
> .html
>>>>>>
>>>>>> A comparator with a diode like this might help me out.
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon=3D2C Oct 19=3D2C 2009 at 8:16 AM=3D2C Danjel van Tijn=20
> com> wrote:
>>>>>>
>>>>>>>
>>>>>>> A while ago I posted asking for advice on modding a Livewire Vulcan
>>>>>>> lfo so that it could be reset.
>>>>>>> Amos suggested using a CD4053 switch to control the timing cap bein=
g
>>>>>>> shorted to ground temporarily to cause a reset.
>>>>>>>
>>>>>>> As first experiment I had two wires: one to the timing cap and one =
t=3D
> o
>>>>>>> ground. Whenever I connected these together temporarily it
>>>>>>> successfully reset the LFO.
>>>>>>>
>>>>>>> Next step was =3DA0wiring up a little board with the switch circuit=
. T=3D
> he
>>>>>>> reset jack was connected to one of the control inputs of the cd4053=
 =3D
> so
>>>>>>> that a short pulse would temporarily connect the LFO timing cap to
>>>>>>> ground.
>>>>>>>
>>>>>>> So far it kind of works but not well: =3DA0If I feed at an LFO squa=
rew=3D
> ave
>>>>>>> from a Plan B ELF LFO =3DA0it holds the Vulcan in reset while it is=
 hi=3D
> gh
>>>>>>> and then allows it to cycle when it is low. However when I switch t=
o
>>>>>>> the alternative narrow pulse square waveform the pulses seem to be =
t=3D
> oo
>>>>>>> short to cause a reset.
>>>>>>> Also when I connect a midi2cv converter and generate clock pulses o=
r
>>>>>>> gate signals they are unable to cause a trigger.
>>>>>>>
>>>>>>> Right now the 4053 is being powered by the 12V rail... should I be
>>>>>>> using a lower voltage so that the logic signals from other devices
>>>>>>> like my midi2cv can actually drive the 40530 controls? i.e. Should =
I
>>>>>>> run it at 5V instead?
>>>>>>>
>>>>>>> Do I need any kind of trigger conditioning off of the reset jack?
>>>>>>> e.g. filter? schmitt trigger?
>>>>>>>
>>>>>>> cheers=3D2C
>>>>>>> Danjel
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Synth-diy mailing list
>>>>>> Synth-diy at dropmix.xs4all.nl
>>>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>=3D20
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>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
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> =3D20
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