[sdiy] Re: reset circuit for LFO

[Danjel van Tijn]

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.

However, 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.

This goes back to my question on if I am powering the cd4053 at 12V
does it matter that the gates/clk are 5V?



cheers,
Danjel






On Mon, Oct 19, 2009 at 10:06 AM, Danjel van Tijn <danjel at gmail.com> wrote:
> 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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>>>
>>>
>>
>