DC/DC converter giving acoustical noise
DC/DC converter giving acoustical noise
(OP)
Hello All,
I am using a DC/DC converter from 24V to 5V for my Arduino project. The converter is producing a high pitch sound that I would like to silence. I am using a TI MC34063AD in the Step-Down configuration on page 8 but coil 330mH instead of 220mH.
Any Suggestions?
Thanks
Markus
I am using a DC/DC converter from 24V to 5V for my Arduino project. The converter is producing a high pitch sound that I would like to silence. I am using a TI MC34063AD in the Step-Down configuration on page 8 but coil 330mH instead of 220mH.
Any Suggestions?
Thanks
Markus





RE: DC/DC converter giving acoustical noise
TTFN

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RE: DC/DC converter giving acoustical noise
Is this an FRP board?
Are the components exactly what's on page 8?
Is everything surface mount?
Keith Cress
kcress - http://www.flaminsystems.com
RE: DC/DC converter giving acoustical noise
I am not exactly sure what the material of the PCB is. The components are as on page 8 but I can also supply the circuit drawings if that helps.
RE: DC/DC converter giving acoustical noise
Next is the coil. If the windings are vibrating, then maybe a bit of glue would hold them fast, and thus stop the noise.
RE: DC/DC converter giving acoustical noise
Cheers
Greg Locock
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RE: DC/DC converter giving acoustical noise
That is an FRP board. Fiber Reinforced Plastic The standard green PCB
There are three possibilities for the noise.
1) The inductor coils as VE1BLL suggests. It would likely be the wires moving and glue would help.
2) Capacitors with high freq currents can also produce noise. However it's more usually ceramic caps that are surface mounted to the board and not aluminum caps like what I'm seeing.
3) Your piezo noise maker is REALLY close to the high current high frequency traces. You could have some of that current exciting it or its drive circuit.
In all cases you should be able to hunt down your culprit using simple mechanical means. Use a pencil eraser to apply some pressure to all the various suspects. Listen for any obvious audio responses to your probings.
If it is the inductor there are a lot of different style inductors that will be similar in size but radically different in construction. I'd consider trying a few to find a quieter one. Look to Coilcraft.
Keith Cress
kcress - http://www.flaminsystems.com
RE: DC/DC converter giving acoustical noise
Benta.
RE: DC/DC converter giving acoustical noise
Any suggestions how to fix that - except putting the entire PCB into a sealed box?
RE: DC/DC converter giving acoustical noise
Maybe.
RE: DC/DC converter giving acoustical noise
I'm not sure how you're driving the piezo.. Hard to offer suggestions. Can you put up at least that part of your schematic?
VE1BLL; Not sure what you're describing. I'm lousy at brief text schematics.
Keith Cress
kcress - http://www.flaminsystems.com
RE: DC/DC converter giving acoustical noise
RE: DC/DC converter giving acoustical noise
RE: DC/DC converter giving acoustical noise
Once peeled, if the beeping is revealed as being full volume, then perhaps it's trying to tell you something.
It'd be surprising if induced EMI would achieve full volume. EMI would normally be a relatively small signal, of course YMMV.
You could measure the voltage / waveform on the piezo to make sure.
RE: DC/DC converter giving acoustical noise
RE: DC/DC converter giving acoustical noise
Try a 10k or a 47k ohm resistor there.
Keith Cress
kcress - http://www.flaminsystems.com
RE: DC/DC converter giving acoustical noise
RE: DC/DC converter giving acoustical noise
RE: DC/DC converter giving acoustical noise
Keith Cress
kcress - http://www.flaminsystems.com
RE: DC/DC converter giving acoustical noise
- various resistors across the G-S pins of the mosfet: no effect. I even shorted the connection.
Then I took a metal plate and inserted it between the buzzer and the cap next too it (the cap between the coil and the buzzer) and that lowered the noise. It seems to me that the noise is introduced only by the EM field of the coil -> buzzer is too close and I have to re-design the board for the next revision.
RE: DC/DC converter giving acoustical noise
I can't tell what processor you have in there, but if it's a GPIO that FET is connected to, it's likely the GPIO line has an internal pull-up/-down that you can enable by flipping a register bit.
Dan - Owner
http://www.Hi-TecDesigns.com
RE: DC/DC converter giving acoustical noise
BTW: I have just another problem with my PCB and I started another thread: http://www.eng-tips.com/viewthread.cfm?qid=368902
Thanks for all your help so far!
RE: DC/DC converter giving acoustical noise
Dan - Owner
http://www.Hi-TecDesigns.com
RE: DC/DC converter giving acoustical noise
Dan - Owner
http://www.Hi-TecDesigns.com
RE: DC/DC converter giving acoustical noise
Have you tried a 200 ohm resistor across the piezo to swamp the magnetic leakage?
Keith Cress
kcress - http://www.flaminsystems.com
RE: DC/DC converter giving acoustical noise
Keith Cress
kcress - http://www.flaminsystems.com
RE: DC/DC converter giving acoustical noise
In the next rev I will have to pick a different coil and a new location for the buzzer.
Thanks to everyone looking into this!
RE: DC/DC converter giving acoustical noise
Try before you buy...
Dan - Owner
http://www.Hi-TecDesigns.com
RE: DC/DC converter giving acoustical noise
RE: DC/DC converter giving acoustical noise
Buzzer is too close to switching converter.
Maybe more easy, as sugested, is to move buzzer away by twisted wires of minim 10cm.
RE: DC/DC converter giving acoustical noise
RE: DC/DC converter giving acoustical noise
Perhaps use a less-amazingly-sensitive beeper.
RE: DC/DC converter giving acoustical noise
Dan - Owner
http://www.Hi-TecDesigns.com