TDA7293 datasheet - Page 6 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 27th January 2013, 04:43 PM   #51
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
An LED uses so little current you should run it from just one rail. That cuts the dissipation down in the resistor. Value of the resistor depends on how bright you want it but I would think 10K to 33K would be nearer the mark (and thats on one 36v rail). Modern LED's are really efficient and bright at 1 milliamp.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 27th January 2013, 05:26 PM   #52
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
oh... well i was calculating for 20mA... i think ill go with 22k

one more question... are you doing calculations, or have you done this before? (just wondering)

also i want to make a power switch, and i am making a small controll, on wich will be just the mute volume and on/off swich. i know i cant run the 220 ac to the controll, so i was wondering, whats happening when i cut the power right after the reservoir caps? or should i do it at the 220ac with relay?
  Reply With Quote
Old 27th January 2013, 05:31 PM   #53
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
if i am right, then i can just turn it off after the reservoir caps, am i right?
  Reply With Quote
Old 27th January 2013, 06:17 PM   #54
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
You are best switching the AC mains really. One reason is that this ensures both rails appear and collapse together. The last thing you want is the circuit latching and putting DC across the speakers. A relay to switch the mains is fine.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 28th January 2013, 09:24 AM   #55
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I prefer to know if the supply rails have drooped badly.
To know if this is happening, I use a series combination of limiting resistor, LED and Zener.
The Zener voltage could be anywhere from 10% of rail voltage up to 90% of rail voltage.
At the 90% end the LED will go dim when the rail droops just slightly. OK for a regulated supply.

For a 40Vac winding generating 58Vdc I would use green LED + 39V Zener + 8k2 for about 2mA @ full voltage and drops to 0.5mA @ 45Vdc and by 40Vdc the LED will be OFF.
__________________
regards Andrew T.
  Reply With Quote
Old 28th January 2013, 05:23 PM   #56
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
i cant do it with a relay... i would turn off its own power source... i would be left with a relay doing a "trrrrrrrr" sound... if could use a double swich, and turn it right after reservoir caps. i would put another swich on the power supply just for safety, but i think the relay and the reservoir caps shouldent drain enough voltage, for me to notice on my electricity bill...
  Reply With Quote
Old 28th January 2013, 05:52 PM   #57
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Mere technicalities

You need a tiny auxilliary supply using a small tranny to power the relay. The electricity consumption is negligable. Or... you use a small Nicad/NiMh battery to power the relay and as soon as the amp power appears the main circuit starts charging the battery.

You don't want to be switching the DC rails with switches for reasons already mentioned.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 28th January 2013, 06:30 PM   #58
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
well i actually like the battery idear, i had a simmilar thought, with a capacitor...

something like this
Click the image to open in full size.
  Reply With Quote
Old 28th January 2013, 06:39 PM   #59
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Hmmm.... can't quite follow your idea there.

There are many ways you can do this. Start with the relay contacts in series with the mains. That's the switch part taken care of. The relay coil is connected via a battery and low voltage switch. That allows the relay to operate. Problem... the battery goes flat quickly. Solution... the battery is charged by the working amplifier PSU via a diode and resistor.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 28th January 2013, 06:59 PM   #60
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
Click the image to open in full size.
  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
need help with TDA7293 weatherlight Chip Amps 21 23rd November 2013 09:49 AM
Tda7293 lasstss Chip Amps 2 14th December 2004 04:36 AM
Where can I get a TDA7293??? mfish0305 Solid State 2 18th January 2004 03:19 AM
Tda7293 chengtaw Solid State 0 18th April 2002 01:19 PM


New To Site? Need Help?

All times are GMT. The time now is 08:43 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