HB-25 making high pitch sound

Ryan D

Hello,

I have an HB-25 hooked up to a 6V (24AH) battery and to a motor that normally pulls about 3A and about 15A when stalled. I'm using an OOPic (yes, I'm a heretic) to generate control pulses within the required range (1.0 - 2.0 milisecond) with a refresh rate of 35 pulses per second. Since the grounds for my micro-controller and motor power source are already connected I didn't use the ground header pin on the HB-25 (didn't want any ground loops). The motor moves just fine, so, if I was deaf, I wouldn't know there was a problem. Basically, when the motor is being driven between stand still and about half speed, I hear a high pitch tone coming from the HB-25.

Should I be worried about this?

Ryan

D Faust

You don't have to refresh the HB-25, but I don't think that is your problem.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

LOOKDOWN ThisThread, [noparse][[/noparse]Your_?, My_?, Cool_Thing], looknum
LOOKUP looknum, [noparse][[/noparse]1, 2, 3], subnum
ON subnum GOTO Hope_this_helps, Thanks!, WOW!!
END 

Phil Pilgrim (PhiPi)

Ryan,

It's not unusual for motor controllers that use PWM for current control to emit high-pitched sounds. I have a computer-driven vinyl cutter that "sings" merrily as it does its work. My CNC mill also emits its own brand of "vocalization". I assume you're still young and thus sensitive to the higher pitches that escape the attention of older folks. Unless the HB-25 is overheating or malfunctioning, I wouldn't worry about it.

-Phil

Ryan D

I tried it with a different motor and the same thing happened. But now I think the noise is only generated when the HB-25 is outputting a duty-cycle that isn't great enough to cause the motor to start moving. I suppose I could avoid the noise by only having the HB-25 output the minimum duty-cycle to cause movement. Though I'd still like to know what causes the noise.

Ryan

Ryan D

Oh, Sorry. I posted that last reply before I noticed your response. Thanks for the info Phil. Ya, I've never used an H-Bridge before. It's not overheating or anything so I think this issue is officially resolved.

Thanks again,

Ryan

Duffer

Phil,

I·thought you (and others)·might find this amusing and interesting given your comment about youth and aural acuity.

http://en.wikipedia.org/wiki/The_Mosquito

The following is a quote from a New York Times article:

The device, called the Mosquito ("It's small and annoying," Mr. Stapleton, the inventor·said), emits a high-frequency pulsing sound that, he says, can be heard by most people younger than 20 and almost no one older than 30. The sound is designed to so irritate young people that after several minutes, they cannot stand it and go away. Designed to stop the practice of young people loitering in front of shops.

What a world we live in!

Steve

PJAllen

I read that wiki-entry on The Mosquito.· Classical music and opera·work well, probably better, and·they're just as effective on·loiterers over 30.

I can't hear the TV·horizontal flyback (15kHz) as well as I used to, I have to be close by nowadays;·of course they're not used in LCD TVs and so on.

Post Edited (PJ Allen) : 8/18/2007 12:48:21 PM GMT

LoopyByteloose

If you really want to know what exactly is making the noise, try putting one end of a wooden chopstick on the suspected component and the other end to your upper front teeth.

The sound transmission should be quite obvious. Personally, I would suspect the bigger capacitors are hitting a harmonic. But that is just a guess.

You may notice that touching something will quiet the noise. In that case, a bit of epoxy might eliminate the noise completely by securing the component to the board.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"Everything in the world is purchased by labour; and our passions are the only causes of labor." -- David·Hume (1711-76)········

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan