Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

ripple current calculation?
ripple current calculation?
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
Thread Tools Search this Thread
Old 29th January 2007, 07:54 PM   #1
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
Question ripple current calculation?

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
bays_9a5tt is offline bays_9a5tt  Croatia
diyAudio Member
bays_9a5tt's Avatar
Join Date: Jan 2005
Location: Zagreb
hi Andrew, you might find Power Supply Designer good for your calculations.
  Reply With Quote
Old 29th January 2007, 10:41 PM   #3
AKN is online now AKN  Sweden
No snake oil
diyAudio Member
AKN's Avatar
Join Date: Aug 2005
Location: In the middle of Sweden
ripple current calculation? Send a message via MSN to AKN
Hi Andrew,

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


Under calculation examples there is formulas that seems comprehensive.
/ Anders
  Reply With Quote
Old 30th January 2007, 09:39 AM   #4
ifrythings is offline ifrythings  Canada
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
richie00boy is offline richie00boy  United Kingdom
Did it Himself
diyAudio Member
richie00boy's Avatar
Join Date: Nov 2003
Location: Gloucestershire, England, UK
ripple current calculation?
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, modules and more.
  Reply With Quote
Old 30th January 2007, 04:24 PM   #6
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
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).
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


ripple current calculation?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

Forum Jump

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 04:21 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio