ripple current calculation? - 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 29th January 2007, 07:54 PM   #1
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Question ripple current calculation?

Hi,
I have assembled a timer with relay.

The supply is a nominal 9Vac bridge rectified and minimal smoothing.
The scope shows ripple on the DC feed of 12V to 14V (flat topped saw tooth) when driving the 555 timer and it's few components.
The supply drops to 3V to 13.5V (10.5V of ripple) when the relay pulls in.

The relay is 400r and the timer draws about 5mA.

How does one calculate the ripple current in the first and only smoothing capacitor? Iripple=Vpk/[relay resistance] + timer current?
__________________
regards Andrew T.
  Reply With Quote
Old 29th January 2007, 09:59 PM   #2
diyAudio Member
 
bays_9a5tt's Avatar
 
Join Date: Jan 2005
Location: Zagreb
hi Andrew, you might find Power Supply Designer good for your calculations.
www.duncanamps.com/psud2/index.html
  Reply With Quote
Old 29th January 2007, 10:41 PM   #3
AKN is offline AKN  Sweden
No snake oil
diyAudio Member
 
AKN's Avatar
 
Join Date: Aug 2005
Location: In the middle of Sweden
Send a message via MSN to AKN
Hi Andrew,

Wondered how to calculate ripple current myself, however found this:

http://www.powerdesigners.com/InfoWe...tics/Caps.shtm

Under calculation examples there is formulas that seems comprehensive.
__________________
/ Anders
  Reply With Quote
Old 30th January 2007, 09:39 AM   #4
diyAudio Member
 
ifrythings's Avatar
 
Join Date: Oct 2005
C=Iload / 8 x F x Vout

Iload is in Amps

F is in Hz

Vout is desired ripple in V

So, C= 1Amp / 8 x 60Hz x 1Vripple = 2 083uF
  Reply With Quote
Old 30th January 2007, 09:42 AM   #5
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Calculating ripple current is not easy. In the end we used a current clamp on the big power amps to measure it.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 30th January 2007, 04:24 PM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
the 22uF allows the circuit to work correctly and after running for an hour still felt cold.

10uF does not work, so I will adopt 33uF or 47uF (I have a few in stock).
BUT,
the ripple current for a range of 22uF varies between 37mA and 50mA and that seems very close to the running current that the circuit consumes.

4fun's link shows a calculation method, but, it is more complicated than I expected so I will try a few numbers and see what pops out.

Thanks for the replies.
__________________
regards Andrew T.
  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
Ripple current ? woody Solid State 2 12th January 2009 10:09 PM
Ripple current in capacitors. beppe61 Power Supplies 5 3rd September 2006 11:37 AM
whats ripple current of c johndiy Solid State 9 2nd September 2006 11:37 AM
ripple current calculation metebalci Parts 1 24th July 2004 09:10 PM
psu problem / ripple current / esr metebalci Solid State 3 30th April 2004 09:56 AM


New To Site? Need Help?

All times are GMT. The time now is 03:05 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