Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th May 2011, 12:08 PM   #1
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Default reed relay question

i am working on a source selector and i would like if possible some info to choose parts especally between normal relays or reed relays ...

Since ampers per contact is not an issue for a source selector any of the above may be used

my approach is to either use one double relay per input but i could go as well for one relay /chanel for each input to minimize crosstalk figures ...

reed relay could be very much space saving since will only consume 14DIL like a small ic

concerns around choise can be
---crosstalk in case a LR relay is used
--- influense in the signal from the coil of the relay
a) in normal relay
b) in reed relay

kind regards sakis
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 19th May 2011, 12:13 PM   #2
effebi is offline effebi  Italy
diyAudio Member
 
effebi's Avatar
 
Join Date: Nov 2010
Location: Milan
Hi Sakis.
Reed relays are well suited for small signal since their contacts are absolutely sealed inside a glass bubble with vacuum or inerth gas inside.
They last years in very harsh (corrosive, etc) industrial environments.
Coil is very small , causes very small magnetic field and can be driven with small signal transistors (i.e. BC337) without any problem.

Last edited by effebi; 19th May 2011 at 12:16 PM.
  Reply With Quote
Old 19th May 2011, 12:19 PM   #3
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Quote:
Originally Posted by effebi View Post
Hi Sakis.
Reed relays are well suited for small signal since their contacts are absolutely sealed inside a glass bubble with vacuum or inerth gas inside.
They last years in very harsh (corrosive, etc) industrial environments.
Coil is very small , causes very small magnetic field and can be driven with small signal transistors (i.e. BC337) without any problem.
correct but in a reed relay the coil is just a few mm next to the contact

is there a chance that the power that flows through the coil will also have some effect on the signal ???
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 19th May 2011, 12:22 PM   #4
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Not in my experience.
They work very well with absolutely no noise issues.
I drive mine from a simple little LM1805 power supply, and I could have used the coils as a resistive load for source indicator LED's for a very elegant solution. As it was I never though about that and gave the LED's their own supply.

Shoog
  Reply With Quote
Old 19th May 2011, 12:29 PM   #5
effebi is offline effebi  Italy
diyAudio Member
 
effebi's Avatar
 
Join Date: Nov 2010
Location: Milan
Quote:
Originally Posted by sakis View Post
correct but in a reed relay the coil is just a few mm next to the contact

is there a chance that the power that flows through the coil will also have some effect on the signal ???
If you drive your coil with DC, regardless of the distance and the power of the coil, there will be no effect on the signal after the switching moment. The theory says that only a time-variabile magnetic vector (that is changing in module or direction) can induce a voltage on a conductor immersed in the field.
So , feel safe.
  Reply With Quote
Old 19th May 2011, 03:04 PM   #6
DRC is offline DRC  United Kingdom
diyAudio Member
 
DRC's Avatar
 
Join Date: Jan 2003
Location: UK (south west)
I have seen manufacture specifications where they advise against operating a (normal) relay in the energised state for long periods where there is little contact current flowing. Some outgassing due to heat may cause the contacts to eventually go open circuit. Better to go for a latching relay (or a reed switch).

dc
  Reply With Quote
Old 19th May 2011, 03:14 PM   #7
diyAudio Member
 
Join Date: Feb 2004
Location: england
Quote:
Originally Posted by DRC View Post
I have seen manufacture specifications where they advise against operating a (normal) relay in the energised state for long periods where there is little contact current flowing. Some outgassing due to heat may cause the contacts to eventually go open circuit. Better to go for a latching relay (or a reed switch).

dc
Or use a higher current to close the contact, then back it off somewhat to hold it there?
__________________
All this radio needs is a fuse
  Reply With Quote
Old 19th May 2011, 03:28 PM   #8
diyAudio Member
 
Join Date: Sep 2004
Location: UK
I would also endorse reed relays.

I have used hundreds/thousands of them for low level signal switching in automatic test equipment and their main benefits are:

Almost silent operation - just a very small ping!

Sealed contact envelope so no oxidation.

About 50mR contact resistance, stable over billions of operations

Although coil surrounds contact, only a few pF of capacitance, so negligible effect for audio frequencies and impedances.

Will last forever as long as high level switching of reactive loads is avoided (contact arcing). That will cause them to stick. No problem at signal levels.

I use a single reed form A relay with a 5v 10mA coil and a 0.2" x 1" footprint. This because I have a lifetime's supply in the workshop
  Reply With Quote
Old 19th May 2011, 04:33 PM   #9
diyAudio Member
 
Join Date: Sep 2010
Why not use these:

Digi-Key - Z117-ND (Manufacturer - G6K-2P DC12)

(Note the digikey picture is wrong - the 2P package is a standard 8-pin dip.)

They are designed for small signal use.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Relay Question SRMcGee Parts 2 31st January 2009 09:03 PM
YET another relay attenuator question robmil Solid State 0 14th April 2008 05:44 AM
Newbie Relay Question SRMcGee Parts 13 13th November 2006 02:54 AM
Mercury wetted or ruthenium for reed relay? mzzj Parts 14 17th August 2005 06:47 AM
Relay Contact Question lgreen Parts 1 2nd April 2005 10:09 PM


New To Site? Need Help?

All times are GMT. The time now is 05:46 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2