[sdiy] 555-based ADSR that refuses to work with 9v

[Pete Swarbrick]

Hi All
Well I happened to have one of these circuits on a bit of veroboard in my 
desk here at work  which is using  the ST NE555N and a TL081.
I can get it to work down to +/- 4V or so with no probs. Your problem does 
sound like a wiring thing to me too.
Just thought you'd like to know....
Best of luck
Pete
----- Original Message ----- 
From: "Scott Gravenhorst" <music.maker at gte.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Friday, January 27, 2006 2:44 PM
Subject: RE: RE: [sdiy] 555-based ADSR that refuses to work with 9v


> music.maker at gte.net wrote:
>>If the large resistors are a problem, the CMOS version (7555) might help.
>>The datasheet I have says "Extremely low input currents of 20pA".  It also
>>claims a PS voltage of 18V (abs. max.).  However, since these are series
>>pots, just reducing their value by turning them "down" should cause the
>>circuit to work at some point - if that's what the problem is.  I can't 
>>see
>>anything about the circuit that would prevent it from working at 9 volts 
>>and
>>I don't see a reason that you even need a negative supply at all (You 
>>mention
>>a +/- 9V supply, are you connecting the -9V as the circuit's ground?  That
>>could be a problem).  I'd bet the circuit should work from a single +5V 
>> >supply.
>
> Well, except for the opamp part, that needs a dual supply, but still, pin 
> 1 of
> the 555 should be connected to zero volts (ground) and not -V.  I don't 
> know
> that you're doing that, but just in case...  It really sounds like 
> something is
> miswired.  In this schematic, watch the crossovers versus dots where dots 
> mean
> to connect and no dot means jump over.
>
>>
>>
>>=?us-ascii?Q?Jaroslav_Lukes?= <lsh.synth at seznam.cz> wrote:
>>>> From: Karl Ekdahl [mailto:elektrodwarf at yahoo.se]
>>>> Hi Jaroslav, i've tried changing the 4.7k to Reset
>>>> since it seems the VCC feed was to low, but without
>>>
>>>Not that,I was think about resistors with Mohm values (A/D/S/R).
>>>
>>>> any luck. The 555's i tried are CA555CE from Harris
>>>> and RCA, and also a NE555N from ST. Earlier i also
>>>> tried NE556A from ST. I can't verify wheter this
>>>> circuit does actually run from a +-15 since i don't
>>>> have anything but a +-9V supply here (i've moved
>>>> recently).
>>>
>>>Hmmm. I think that you use all versions that are less or more different 
>>>from
>>>original. Use 555 from philips or TI. In my country before many years was
>>>published list of differences between mfgr's for 555, but I could not 
>>>find
>>>it now. I was remember Philips and TI only that are good.
>>>
>>>Regards, JL.
>>>
>>
>>---------------------------------------------------------
>>- Where merit is not rewarded, excellence fades.
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>>
>>-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
>>-- Linux Rex         | RedWebMail by RedStarWare
>>-- FatMan: home1.gte.net/res0658s/fatman/
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>>-- Autodidactic Master of Arcane and Hidden Knowledge.
>>
>
> ---------------------------------------------------------
> - Where merit is not rewarded, excellence fades.
> - Hydrogen is pointless without solar.
> - What good are laws that only lawyers understand?
> - The media's credibility should always be questioned.
> - The only good terrorist is a dead terrorist.
> - Governments do nothing well, save collect taxes.
>
> -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> -- Linux Rex         | RedWebMail by RedStarWare
> -- FatMan: home1.gte.net/res0658s/fatman/
> -- NonFatMan: home1.gte.net/res0658s/electronics/
> -- Autodidactic Master of Arcane and Hidden Knowledge.
>
> 


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