Path: ...!weretis.net!feeder9.news.weretis.net!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!nnrp.usenet.blueworldhosting.com!.POSTED!not-for-mail
From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: An actual circuit
Date: Fri, 24 May 2024 19:06:50 -0400
Organization: BWH Usenet Archive (https://usenet.blueworldhosting.com)
Lines: 162
Message-ID: <v2r6ib$2ftd$1@nnrp.usenet.blueworldhosting.com>
References: <v2o5p4$3102$1@nnrp.usenet.blueworldhosting.com> <a38v4jpecnm460gf7ghqfgpmpespoie6f8@4ax.com> <bk815jh3skuecf1tap8o41rpgdh5kkq8o5@4ax.com> <v2qdh5$u4j$1@nnrp.usenet.blueworldhosting.com> <v2qmeq$2eknc$1@dont-email.me> <v2qnhm$2586$1@nnrp.usenet.blueworldhosting.com> <uts15jlh0oo1hin58uu4a574kg5q3j9q5b@4ax.com> <v2qsu1$nc0$1@nnrp.usenet.blueworldhosting.com> <1cv15jdls60tjfcndqe9qm7bgjdtchv9u9@4ax.com> <v2r325$2h00c$1@dont-email.me> <v2r3sb$15r9$1@nnrp.usenet.blueworldhosting.com> <v2r4od$2h9gp$1@dont-email.me>
Injection-Date: Fri, 24 May 2024 23:06:51 -0000 (UTC)
Injection-Info: nnrp.usenet.blueworldhosting.com;
	logging-data="81837"; mail-complaints-to="usenet@blueworldhosting.com"
Cancel-Lock: sha1:4mBi1o4IsLY0kNfZyKzXGGCytGc= sha256:YrYwl0NKCqRhxIr07uvd+UC/VcKXqg8YhT9f2I92uBo=
	sha1:3VXO7xGu1CKOYWjrVKRM3SUAy+g= sha256:g/91zUr5ew604wlzi+vYHp4gY7FPLNSAGMnahqJEgiA=
X-RFC2646: Format=Flowed; Original
X-MSMail-Priority: Normal
X-Priority: 3
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
Bytes: 7173

"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message 
news:v2r4od$2h9gp$1@dont-email.me...
> Edward Rawde <invalid@invalid.invalid> wrote:
>> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
>> news:v2r325$2h00c$1@dont-email.me...
>>> john larkin <jl@650pot.com> wrote:
>>>> On Fri, 24 May 2024 16:22:23 -0400, "Edward Rawde"
>>>> <invalid@invalid.invalid> wrote:
>>>>
>>>>> "john larkin" <jl@650pot.com> wrote in message
>>>>> news:uts15jlh0oo1hin58uu4a574kg5q3j9q5b@4ax.com...
>>>>>> On Fri, 24 May 2024 14:50:19 -0400, "Edward Rawde"
>>>>>> <invalid@invalid.invalid> wrote:
>>>>>>
>>>>>>> "Jeroen Belleman" <jeroen@nospam.please> wrote in message
>>>>>>> news:v2qmeq$2eknc$1@dont-email.me...
>>>>>>>> On 5/24/24 17:59, Edward Rawde wrote:
>>>>>>>>> "john larkin" <jl@650pot.com> wrote in message
>>>>>>>>> news:bk815jh3skuecf1tap8o41rpgdh5kkq8o5@4ax.com...
>>>>>>>>>> On Thu, 23 May 2024 13:06:46 -0700, john larkin <jl@650pot.com>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> On Thu, 23 May 2024 15:35:00 -0400, "Edward Rawde"
>>>>>>>>>>> <invalid@invalid.invalid> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> I was having a conversation with a younger person who seemed to
>>>>>>>>>>>> be
>>>>>>>>>>>> of
>>>>>>>>>>>> the
>>>>>>>>>>>> view that to make an LED flash you would need something to 
>>>>>>>>>>>> decide
>>>>>>>>>>>> when
>>>>>>>>>>>> it
>>>>>>>>>>>> should be on or off. So that would be some kind of software or
>>>>>>>>>>>> digital
>>>>>>>>>>>> system.
>>>>>>>>> ...
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> The classic NPN astable circuit can hang up, with both 
>>>>>>>>>> transistors
>>>>>>>>>> saturated. I wonder if he jfet circuit can hang too, with Idss
>>>>>>>>>> grounding both drains and not enough gain to oscillate out of 
>>>>>>>>>> that
>>>>>>>>>> state.
>>>>>>>>>>
>>>>>>>>>> Even when they have a hang state, luck usually kicks them off 
>>>>>>>>>> into
>>>>>>>>>> oscillation. Your source resistors and  asymmetric drain 
>>>>>>>>>> resistors
>>>>>>>>>> help it start up. Try making both drain resistors 3.3K.
>>>>>>>>>>
>>>>>>>>>> If you make the source resistors lower, it will hang up.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Yes I noticed both points when I was designing it.
>>>>>>>>> I wanted to have it start up by itself, preferably without a
>>>>>>>>> kickstart
>>>>>>>>> capacitor.
>>>>>>>>> So I had a complicated circuit with two more diodes and a 
>>>>>>>>> transistor
>>>>>>>>> in
>>>>>>>>> the
>>>>>>>>> hope that I could detect the hang state and force it off balance.
>>>>>>>>> I couldn't get that to work
>>>>>>>>> Then I accidentally made R2 3,3k and R6 3.3k and I didn't see how 
>>>>>>>>> it
>>>>>>>>> could
>>>>>>>>> start so quickly with no other help.
>>>>>>>>> Eventually I noticed 3,3k which maybe LTSpice takes as 3k.
>>>>>>>>>
>>>>>>>>> If R2 and R6 are both 3.3k then LTSpice says it slowly drifts into
>>>>>>>>> operation
>>>>>>>>> after 40 seconds.
>>>>>>>>> But why does it go one way and not the other?
>>>>>>>>> Is that an artefact of asymmetry in the simulation?
>>>>>>>>> Or is there some hidden asymmetry in the circuit I'm not seeing 
>>>>>>>>> when
>>>>>>>>> R2
>>>>>>>>> is
>>>>>>>>> 3.3k?
>>>>>>>>
>>>>>>>> Below are a pair of astable circuits. The left one is like yours,
>>>>>>>> with a hangup state. I start it by specifying an initial condition.
>>>>>>>> The right one will start all by itself.
>>>>>>>>
>>>>>>>
>>>>>>> Thanks for that. I guess I'm biased towards components I could 
>>>>>>> easily
>>>>>>> get
>>>>>>> in
>>>>>>> the 70s. And also through hole components I can easily build a real
>>>>>>> circuit
>>>>>>> with.
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> I like to use surface-mount parts on a Dremeled PCB.
>>>>>>
>>>>>> https://www.dropbox.com/s/7bihbjbaojvta0z/Z382_1.JPG?raw=1
>>>>>>
>>>>>> https://www.dropbox.com/s/zaftysxtgclxj82/Z412_Proto.JPG?raw=1
>>>>>>
>>>>>> You can do fast, 50-ohm picosecond stuff this way too.
>>>>>>
>>>>>
>>>>> Thanks I probably do have some copper clad board I could do that with.
>>>>>>
>>>>>
>>>>
>>>> Use a round-end carbide dental burr. They are cheap on ebay.
>>>>
>>>> It's cool, kind of an art form. Takes some practice.
>>>>
>>>> I have a few square feet of gold-plated copperclad FR4, which is even
>>>> nicer. Regular copperclad looks grungy after a few months.
>>>>
>>>>
>>>
>>> I'm not nearly as posh as you are
>>
>> Not sure why that made me laugh.
>>
>>> , so for my purposes a spritz of Krylon
>>> clear acrylic on a clean board is a ticket.
>>>
>>> You can solder right through it, and it keeps the copper looking nice 
>>> for
>>> a
>>> long time.
>>
>> I seem to remember, a long long time ago using copper clad board, some 
>> clear
>> sticky tape and a very sharp knife.
>> Followed by Ferric Chloride.
>> An etch resist pen could also be used if the tape removal didn't go 
>> exactly
>> as planned.
>>
>> But yes it's true that after removing the etch resist you might want
>> something to keep the copper looking nice and shiny.
>>
>
> Oh, I haven't etched a PCB in forty-odd years. This is strictly dead-bug
> stuff.

47 years ago in my case when I made an external keyboard because the one 
supplied by Sinclair was useless.
https://en.wikipedia.org/wiki/MK14

>
> Cheers
>
> Phil Hobbs
>
>
> -- 
> Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC 
> /
> Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics