Leaving X-former powered up - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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 15th May 2006, 11:49 AM   #1
Wynand is offline Wynand  South Africa
diyAudio Member
 
Wynand's Avatar
 
Join Date: Mar 2005
Location: Cape Town
Default Leaving X-former powered up

Does anyone see a problem leaving a transformer permanently on and using a "soft-on" feature to disconnect the psu after (or before) the supply caps?
  Reply With Quote
Old 15th May 2006, 11:58 AM   #2
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
The problem with that is you're switching high current DC, and that's a killer for relays. I'd just use a cheapo traffo to control your soft start, you only need a 100mA or so, so and old wallwart or similar will do.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 15th May 2006, 12:06 PM   #3
Wynand is offline Wynand  South Africa
diyAudio Member
 
Wynand's Avatar
 
Join Date: Mar 2005
Location: Cape Town
The reason for leaving it on and using relays is actually to switch the amp on with a microprosessor.

Would 10A relays not be sufficient?
  Reply With Quote
Old 16th May 2006, 01:02 AM   #4
CBS240 is offline CBS240  United States
diyAudio Member
 
CBS240's Avatar
 
Join Date: Aug 2005
Location: K-town
find an old, cheap, crapy clock radio and use the transfo out of it to drive the processor. They are usually quite small. Use a relay to switch on the primary of the big transfo. There is much less current on that side.
__________________
All the trouble I've ever been in started out as fun......
  Reply With Quote
Old 16th May 2006, 01:07 AM   #5
PM650 is offline PM650  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Tennessee
Practically all comercial amplifiers use what pinkmouse suggests, a small transformer to run a soft-start or even a simple relay switch for the main amp transformer(s) and other standby curcuits. Unless you're using a complex smps supply to get the voltages you need for the microprocessor and the amp supplies, it would be best to run only what is needed to switch the amp on and off from another smaller transformer, as pinkmouse said.

The relay contact rating may become irrelevant should you connect the relays between the caps and supply. Larger power supply capacitors effectively represent a short circuit to the power supply before they begin to charge; connecting a discharged capacitor to a supply could instantly destroy relay contacts, but (I would guess) this all depends on how much peak current the supply could source and the value (size) of the capacitors (and of course the relay contacts).

Someone else will probably be able to give you a definitive answer with more details on your project, though.
  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
Leaving D.I.Y everything must go sale...... exurbia Swap Meet 36 15th October 2008 03:42 AM
bg and suggestions of leaving the amp on jarthel Parts 3 29th June 2007 01:16 AM
Leaving tube preamp always powered on. stoolpigeon Tubes / Valves 31 20th April 2007 07:59 PM
Leaving a gainclone powered on? ahanlon Chip Amps 8 10th April 2006 02:19 PM
Leaving. fdegrove Everything Else 23 2nd December 2002 08:36 PM


New To Site? Need Help?

All times are GMT. The time now is 07:17 AM.


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