[sdiy] Re: reset circuit for LFO

[Danjel van Tijn]

oops not a diode to ground, 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,
>   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, Oct 19, 2009 at 8:16 AM, 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 to
>>>> ground. Whenever I connected these together temporarily it
>>>> successfully reset the LFO.
>>>>
>>>> Next step was  wiring up a little board with the switch circuit. The
>>>> 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:  If I feed at an LFO squarewave
>>>> from a Plan B ELF LFO  it holds the Vulcan in reset while it is high
>>>> 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 too
>>>> 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,
>>>> Danjel
>>>>
>>>>
>>>
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>>>
>>
>>
>