Buzz from DC-DC buck step down converter - how to isolate? - diyAudio
Go Back   Home > Forums > Design & Build > Construction Tips

Construction Tips Construction techniques and tips

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 3rd August 2013, 08:24 AM   #1
hoffsta is offline hoffsta  United States
diyAudio Member
 
Join Date: Dec 2011
Default Buzz from DC-DC buck step down converter - how to isolate?

I just installed a Raspberry Pi inside an old 80's boombox using a DC-DC buck step down converter power supply to deliver the needed 5v, like this one:
Amazon.com: 5 pcs LM2596 DC-DC Buck Converter Step Down Module Power Supply Output 1.23V-30V: Car Electronics

I wired the input of the buck converter from the 12v DC side of the boombox's AC-DC power supply, just straight positive to positive and negative to negative. As soon as I turn on the box, there is a great deal of noise and I can actually hear the Raspberry Pi doing its thing with the screeches from the wi-fi and sd card reader.

Obviously I needed to do something different with the ground on this but how? There is no third, ground lead on the AC unfortunately. Thanks!
  Reply With Quote
Old 3rd August 2013, 08:47 AM   #2
diyAudio Member
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Send a message via Skype™ to JonSnell Electronic
Why not use a simple LM7805 with the snubber caps on the input and output leads (pin 1 to 2 \and 3 to 2, 100nF to stop HF noise). Then if you connect to the power supply ground, not the input ground, (to avoid a loop), it should be quite.
__________________
www.flyingmole.co.uk For World Wide support for Flying Mole, Class D, Refurbishment and Repairs. www.jonsnell.co.uk
  Reply With Quote
Old 3rd August 2013, 08:52 AM   #3
hoffsta is offline hoffsta  United States
diyAudio Member
 
Join Date: Dec 2011
Hmmm. Well the truth is I don't know very much about electronics yet. I've just been winging it by reading online and soldering modules together. I went with the buck because I plan on running this box with batteries part of the time and I read that the switching PS is much more efficient than the linear.

Is there any way to solve this with the stuff I already have soldered in?
  Reply With Quote
Old 3rd August 2013, 09:16 AM   #4
diyAudio Member
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Send a message via Skype™ to JonSnell Electronic
Unfortunately the kit you chose may be upsetting the Rasberry due to inherent HF noise. Make sure you have chosen the correct ground point. Experiment with different points starting from the power supply smoothing common ground between the + & - smoothing caps if dual rail or the main ground point on the main smoothing if single rail supply. Also the positioning of the module may affect the noise.
__________________
www.flyingmole.co.uk For World Wide support for Flying Mole, Class D, Refurbishment and Repairs. www.jonsnell.co.uk
  Reply With Quote
Old 3rd August 2013, 03:53 PM   #5
hoffsta is offline hoffsta  United States
diyAudio Member
 
Join Date: Dec 2011
Thanks for the tips- Unfortunately, I don't have time to investigate this today. If moving the ground point doesn't fix this, would I be better off (efficiency-wise) to use a LM7805 as described above or just wire in a simple 5v AC-DC converter, like the guts of a cell-phone charger?
  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
DC-DC step down converter design elmurry Power Supplies 3 15th February 2012 06:55 PM
DC-DC step up converter? markusA Power Supplies 9 28th October 2010 04:32 PM
we can offer power module of DC/DC Converter & AC/DC Adapter auling Vendor's Bazaar 0 12th May 2009 03:48 AM
DC-DC buck regulator layout -> what's your opinion? Danko Power Supplies 14 31st December 2005 03:31 PM
DC-DC step-up converter sasha Everything Else 10 1st March 2004 08:12 AM


New To Site? Need Help?

All times are GMT. The time now is 09:57 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