[sdiy] Re: reset circuit for LFO

[Scott Nordlund]

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CMOS logic levels depend on power supply voltage=2C so you will need
to boost a 5V logic signal.=A0 Usually a pull-up resistor will do=20
the trick.

Alternatively=2C you can use a similar DGxxx part that uses TTL logic=20
levels regardless of power supply voltage.

> Date: Mon=2C 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
>=20
> 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.
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> However=2C 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.
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> This goes back to my question on if I am powering the cd4053 at 12V
> does it matter that the gates/clk are 5V?
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> cheers=2C
> Danjel
>=20
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> On Mon=2C Oct 19=2C 2009 at 10:06 AM=2C Danjel van Tijn <danjel at gmail.com=
> wrote:
>> oops not a diode to ground=2C 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=2C
>>> =A0 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_comparator=
.html
>>>>>
>>>>> A comparator with a diode like this might help me out.
>>>>>
>>>>>
>>>>>
>>>>> On Mon=2C Oct 19=2C 2009 at 8:16 AM=2C Danjel van Tijn <danjel at gmail.=
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 being
>>>>>> shorted to ground temporarily to cause a reset.
>>>>>>
>>>>>> As first experiment I had two wires: one to the timing cap and one t=
o
>>>>>> ground. Whenever I connected these together temporarily it
>>>>>> successfully reset the LFO.
>>>>>>
>>>>>> Next step was =A0wiring up a little board with the switch circuit. T=
he
>>>>>> reset jack was connected to one of the control inputs of the cd4053 =
so
>>>>>> that a short pulse would temporarily connect the LFO timing cap to
>>>>>> ground.
>>>>>>
>>>>>> So far it kind of works but not well: =A0If I feed at an LFO squarew=
ave
>>>>>> from a Plan B ELF LFO =A0it holds the Vulcan in reset while it is hi=
gh
>>>>>> and then allows it to cycle when it is low. However when I switch to
>>>>>> the alternative narrow pulse square waveform the pulses seem to be t=
oo
>>>>>> short to cause a reset.
>>>>>> Also when I connect a midi2cv converter and generate clock pulses or
>>>>>> 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=2C
>>>>>> Danjel
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Synth-diy mailing list
>>>>> Synth-diy at dropmix.xs4all.nl
>>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>>>
>>>>>
>>>>
>>>>
>>>
>>
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