off the wall

Subjects that don't have their own home
Post Reply
User avatar
ed
retired
Posts: 5384
Joined: Thu Jun 21, 2007 4:01 pm
Location: yorkshire
Contact:

#1 off the wall

Post by ed »

here's one...
does anybody know if there is any effect in potting a crystal oscillator in epoxy?
There's nowhere you can be that isn't where you're meant to be
User avatar
Mike H
Amstrad Tower of Power
Posts: 20157
Joined: Sat Oct 04, 2008 5:38 pm
Location: The Fens
Contact:

#2 Re: off the wall

Post by Mike H »

Can't think of any, except can't access any components if it goes wrong. (But applies equally to any potted)

:D
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
User avatar
jack
Thermionic Monk Status
Posts: 5493
Joined: Wed Dec 29, 2010 8:58 pm
Location: ɐılɐɹʇsnɐ oʇ ƃuıʌoɯ ƃuıɹǝpısuoɔ
Contact:

#3 Re: off the wall

Post by jack »

Potting the oscillator should have no effect, assuming the epoxy is non-conductive.
Vivitur ingenio, caetera mortis erunt
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#4 Re: off the wall

Post by IslandPink »

Make sure you can get the wires out !
"Once you find out ... the Circumstances ; then you can go out"
User avatar
jack
Thermionic Monk Status
Posts: 5493
Joined: Wed Dec 29, 2010 8:58 pm
Location: ɐılɐɹʇsnɐ oʇ ƃuıʌoɯ ƃuıɹǝpısuoɔ
Contact:

#5 Re: off the wall

Post by jack »

Just for completeness, why?
Vivitur ingenio, caetera mortis erunt
User avatar
ed
retired
Posts: 5384
Joined: Thu Jun 21, 2007 4:01 pm
Location: yorkshire
Contact:

#6 Re: off the wall

Post by ed »

jack wrote: Tue Mar 05, 2019 3:30 pm Just for completeness, why?
if you're asking me why I asked then..

It's something I have no experience of/with and I wanted to know if there were any issues associated.

but if you're asking about Mark's question then it looks like he's assumed I would be potting it before it was connected in circuit...and yes that would be a serious no no.
There's nowhere you can be that isn't where you're meant to be
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#7 Re: off the wall

Post by IslandPink »

a. I'm assuming it has wires
b. It was a joke
"Once you find out ... the Circumstances ; then you can go out"
User avatar
jack
Thermionic Monk Status
Posts: 5493
Joined: Wed Dec 29, 2010 8:58 pm
Location: ɐılɐɹʇsnɐ oʇ ƃuıʌoɯ ƃuıɹǝpısuoɔ
Contact:

#8 Re: off the wall

Post by jack »

It was more "what is your rationale for doing this"?

If the oscillator is running at RF frequencies then the change in dialectic constant surrounding it could well have an effect (depending on type of oscillator).
Vivitur ingenio, caetera mortis erunt
User avatar
ed
retired
Posts: 5384
Joined: Thu Jun 21, 2007 4:01 pm
Location: yorkshire
Contact:

#9 Re: off the wall

Post by ed »

I'll take that as a yes then...

most confusing though. In post 3 you said no effect and in the last post you said yes, some effect.

I think I'll just pot it and be damned.
There's nowhere you can be that isn't where you're meant to be
User avatar
Nick
Site Admin
Posts: 15706
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#10 Re: off the wall

Post by Nick »

jack wrote: Tue Mar 05, 2019 8:30 pm It was more "what is your rationale for doing this"?

If the oscillator is running at RF frequencies then the change in dialectic constant surrounding it could well have an effect (depending on type of oscillator).
I would doubt it, most quartz crystals I have seen are in a tin can anyway. Plus I don't think their resonant frequency involves capacitive effects so not sure how the dielectric constant around them would alter anything.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
jack
Thermionic Monk Status
Posts: 5493
Joined: Wed Dec 29, 2010 8:58 pm
Location: ɐılɐɹʇsnɐ oʇ ƃuıʌoɯ ƃuıɹǝpısuoɔ
Contact:

#11 Re: off the wall

Post by jack »

I was very careful to state "depending on type of oscillator"... There are several types of possible design here...

Obviously most quartz crystal based oscillators should be ok, but if this is an RF design using air-cored inductors potting it could be problematic...
Vivitur ingenio, caetera mortis erunt
User avatar
Nick
Site Admin
Posts: 15706
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#12 Re: off the wall

Post by Nick »

Look at the first post.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
jack
Thermionic Monk Status
Posts: 5493
Joined: Wed Dec 29, 2010 8:58 pm
Location: ɐılɐɹʇsnɐ oʇ ƃuıʌoɯ ƃuıɹǝpısuoɔ
Contact:

#13 Re: off the wall

Post by jack »

Yep. "Crystal oscillator" - no specifics as to the DESIGN of said oscillator, other than it had a crystal somewhere.

i.e. more information is needed for a definitive answer.
Vivitur ingenio, caetera mortis erunt
User avatar
Mike H
Amstrad Tower of Power
Posts: 20157
Joined: Sat Oct 04, 2008 5:38 pm
Location: The Fens
Contact:

#14 Re: off the wall

Post by Mike H »

Yes there are radio oscillators that use crystals for tight channel stability. :D
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
Post Reply