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
Two 7809 ground loop
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [6 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
kaputtpanzer



Joined: Nov 02, 2009
Posts: 100
Location: Cologne
Audio files: 5

PostPosted: Sat Jun 01, 2019 2:55 am    Post subject: Two 7809 ground loop Reply with quote  Mark this post and the followings unread

Hello,

while designing a power supply pcb for manufacturing, a question popped up. The systematic of the circuit looks about the same as this one here: https://cdn.instructables.com/ORIG/FZG/YM90/G5703OX4/FZGYM90G5703OX4.jpg
I am using two 7809 and now I wonder what happens if I connect both pin 2 to common ground and also using the same, big heat sink for both regulators (so both to220 heatsink junctions are connected to ground). Isn't this closing a form of ground loop? Somehow I can not really think straight, right now.

Thank you! Laughing
Back to top
View user's profile Send private message
kaputtpanzer



Joined: Nov 02, 2009
Posts: 100
Location: Cologne
Audio files: 5

PostPosted: Sat Jun 01, 2019 3:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Posted Image, might have been reduced in size. Click Image to view fullscreen.

I know it is a pretty common thing to do, but my brain is telling me something is wrong.
Back to top
View user's profile Send private message
PHOBoS



Joined: Jan 14, 2010
Posts: 4391
Location: Moon Base
Audio files: 624

PostPosted: Sat Jun 01, 2019 12:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

I am pretty sure pin 2 is physically connected to the backside of the regulator, so by mounting them both on the same heatsink
you're basically just creating a lower resistance between pins 2 of both regulators, which is a good thing. At least that's what I think.

I might have some old broken TO220 component I can crack open to check.

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
kaputtpanzer



Joined: Nov 02, 2009
Posts: 100
Location: Cologne
Audio files: 5

PostPosted: Sun Jun 02, 2019 4:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey Phobos,

thank you very much for your answer. Today my brain is not that foggy anymore and I think what you said is completely right Cool

Actually I could use a multimeter to check if those things are physically connected haha. I'll do it later.

EDIT: So i did test it, they are connected! .00 ohm between them hehe
Back to top
View user's profile Send private message
PHOBoS



Joined: Jan 14, 2010
Posts: 4391
Location: Moon Base
Audio files: 624

PostPosted: Sun Jun 02, 2019 7:11 am    Post subject: Reply with quote  Mark this post and the followings unread

I also cracked one open to see if it is indeed not connected in some other way.

I think the only way you could get problematic groundloops is if you use long wires to connect them and have them also connected
to different circuits which share another ground connection between them. Actually with modular synths you are creating groundloops
all the time (at least with shielded wires) but usually that isn't a problem.


TO220_s.jpg
 Description:
 Filesize:  230.21 KB
 Viewed:  18 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

TO220_s.jpg



_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
kaputtpanzer



Joined: Nov 02, 2009
Posts: 100
Location: Cologne
Audio files: 5

PostPosted: Sun Jun 02, 2019 3:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh wow thanks for the good picture! Very interesting indeed!
Well, the plan is to power some guitar pedals with the two regulators, that share the same heatsink. I think, what you said about the cable is right. I have built a few circuits where I accidentally made some ground loops. It was never a problem, when it was inside one circuit. Probably the cables play a big part. I almost never have this common ground hum in my circuits and signal paths.
But when I power a few pedals with my psu, my circuit should provide the best possible current and stable voltage. But I guess I will just, have to make some measurements when it is finished. Actually if pin 2 and the heating tab is connected inside the regulator, there is not a real ground loop. In the worst case, the regulators need some of these heatsink isolator things.
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 [6 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
e-m mkii

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