--===============2133647100== Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by pch.mit.edu id m2PGYP9d006793 =20 Hi: =20 =20 This sounds interesting to me. Could please show a little drawing of h= ow the zener and diodes are put across the relay? Thank you very much. =20 This application is for DC motor,actually the problem never happened o= n a small motor, but the controller is just bad on a big one. > From: rgrazia1@rochester.rr.com> To: piclist@mit.edu> Subject: Re: [EE]= question on a motor noise problem 2: motor> Date: Tue, 25 Mar 2008 00:26= :30 -0400> > I'm sorry I have not followed this thread so I may be talkin= g out of turn > here. But what is the picking voltage of the relay? Can y= ou try tacking a > zener across the coil of the relay? Or a zener and a f= ast switching free > wheeling diode? If the transient is very fast, the z= ener will not work > but if it is slow enough it might work. The reversed= diodes with the zener > in parallel might work. Varistors can sometimes = shunt motor noise, but > they must be carefully selected. Is it a DC moto= r? Is it a servo or > stepper? If it is a DC motor I am not sure that a v= aristor is a good > choice. I have only used them on AC motors. But someo= ne else on the list > would know. I have had good success with diodes to = shunt transients and > back emf. I would be interested to know how you so= lve the problem.> > > ----- Original Mess age ----- > From: "Cedric Chang" > To: "Microcontroller di= scussion list - Public." > Sent: Monday, March 24, 2008 = 11:42 PM> Subject: Re: [EE] question on a motor noise problem 2: motor> >= > > >> >> On Mar 24, 2008, at 5:56 PM, gardenyu wrote:> >>> >> Thanks a = lot for your kind reply.> >>> >> I would look at D2 tomorrow, if this is = really an issue, do you> >> have any suggestion on cutting this surge off= ? RV2 is supposed to> >> be a surge protector, maybe it's not strong enou= gh.> >>> >> It's some new version that I have, for some reason the design= er> >> didn't like the snubber,> >>> >> the relay is certainly a problem,= I noticed before that when it's> >> turned off and not yet turned on, th= e voltage can rise quite high> >> that causes the relay to click back and= forth for times. Do you> >> have any suggestion on related problem? Than= k you so much.> >>> >>> >>> From: cc@nope9.com> Subject: Re: [EE] questio= n on a motor noise> >>> problem 2: motor> Date: Mon, 24 Mar 2008 15:49:53 -0600> To:> >>> piclist@mit.edu> > I wo= uld resume that circuitry not shown ( some> >>> form of logic ) gets > a = surge of voltage applied to it and that> >>> it enters some unexpected > = state. My recommendation is to measure> >>> the voltage at pin 2 of D2. >= If you are getting drive voltage at> >>> pin 2 after the "stop" is pushe= d, > then your logic is getting> >>> hammered by a voltage spike.> > Are = Q4 and Q? ( the Q below Q4 )> >>> acting as an active motor brake ? > The= circuitry shown does not> >>> seem to offer any snubbing of the > voltag= e spike you would get> >>> from the motor. The relay is going to > allow = the motor to be> >>> disconnected for several milliseconds, > certainly l= ong enough to> >>> allow voltage spiking to occur. I am > assuming the re= lay is a> >>> "break before make" variety, otherwise I > don't see how th= e relay> >>> contacts would survive.> > This design seems a bit strange t= o me.> >>> I await the commen> >> ts of o ther > PLs. The fact that R25 is missing renders C20 as> >> useless.> > = cc> -- > http://www.piclist.com PIC/SX FAQ & list> >> archive> View/chang= e your membership options at> http://> >> mailman.mit.edu/mailman/listinf= o/piclist> >>> >> > Without seeing the rest of your circuit, i cannot sug= gest a "best> > solution". I can suggest that you put a voltage snubber o= n the DRIVE> > + line. The maximum voltage you apply to the DRIVE+ line d= ictates> > the voltage rating of the parts you use for the voltage snubbe= r. Try> > first putting an MOV ( metal oxide varistor ) across DRIVE+ to>= > ground. Multiply the maximum voltage for DRIVE+ by 1.1 and select an> = > MOV that has that voltage rating. Without knowing how much current> > y= our motor draws and it's inductance, I would say start with an MOV> > tha= t absorbs about 5 Joules. I also don't know where you buy parts,> > so I = cannot suggest a source for the MOV.> >> > cc> > -- > > http://www.piclis= t.com PIC/SX FAQ & list archive> > View/c hange your membership options at> > http://mailman.mit.edu/mailman/listi= nfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive> Vi= ew/change your membership options at> http://mailman.mit.edu/mailman/list= info/piclist _________________________________________________________________ =D3=C3=CA=D6=BB=FAMSN=C1=C4=CC=EC=D0=B4=D3=CA=BC=FE=BF=B4=BF=D5=BC=E4=A3=AC= =CE=DE=CF=DE=B9=B5=CD=A8=A3=AC=B7=D6=CF=ED=BE=AB=B2=CA=A3=A1 http://mobile.msn.com.cn/ --===============2133647100== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: 7bit -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --===============2133647100==--