electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » DIY Hardware and Software
tempco power rating
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [4 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
wicked1



Joined: Apr 24, 2009
Posts: 14
Location: stl

PostPosted: Mon May 07, 2012 9:35 am    Post subject: tempco power rating Reply with quote  Mark this post and the followings unread

How big do tempco's need to be? I've got several and just noticed they are 1/16 watt!
I ordered them years ago, as people on the SDIY mailing list suggested them. The person who made the post said to order some part number, 1/6 watt.
So, I ordered that. It looks like 1/6 is not a common size and the bag says "1/16 watt". (Im thinking the 1/6 the guy on the mailing list specified could have been a typo, and 1/16 is exactly what I want)

Will those work? I found some other posts where people were talking about using 1/10 watt SMD tempco's, so maybe 1/16 isn't too far off.
I'd obviously epoxy them to the chip they're adjusting.. I'd imagine being so small it wouldn't take much to fluctuate.

My concern w/ them being so small is self heating, or something.
Thanks for any advice.
Back to top
View user's profile Send private message
andrewF



Joined: Dec 29, 2006
Posts: 1165
Location: australia
Audio files: 4

PostPosted: Mon May 07, 2012 3:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

i think in a typical VCO, where approx 18mV/oct is expected at the base of the transistor pair (so say it sees a max of 180mV), a 1k tempco won't have to deal with more than 0.05mW (a lot less).
1/16W rating should be fine.
Back to top
View user's profile Send private message Visit poster's website
frijitz



Joined: May 04, 2007
Posts: 1682
Location: NM USA
Audio files: 54

PostPosted: Mon May 07, 2012 4:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

andrewF wrote:
i think in a typical VCO, where approx 18mV/oct is expected at the base of the transistor pair (so say it sees a max of 180mV), a 1k tempco won't have to deal with more than 0.05mW (a lot less).
1/16W rating should be fine.

Andrew --

I believe the question is whether self-heating affects the resistance enough to give an incorrect reading, not whether it's going to burn out.

Way back when, Bernie went through the thermal analysis, but I don't remember the details.

When I was characterizing the Panasonic SMT tempcos I saw clear evidence of self-heating. But others have told me they don't see any problem. For me, this is unresolved.

Ian
Back to top
View user's profile Send private message
wicked1



Joined: Apr 24, 2009
Posts: 14
Location: stl

PostPosted: Wed May 09, 2012 7:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok, thanks.. Like Ian said, i'm sure they won't overheat in the sense of a standard resistor failing, but even a little warming would cause the compensation to drift...
Maybe I'll buy a few larger from one of the usual synth vendors, and save these tiny ones for a less critical project. (Im building 3 new vco's and I want them all to be stable and work well together)
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [4 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
Niio2

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use