--0__=85256AA000702B388f9e8a93df938690918c85256AA000702B38 Content-type: text/plain; charset=us-ascii Feedback is what you need. Simply sense the RPM and control it with PWM. You will get close to the full torque at any RPM. At slow speeds however, you will not have the benefit of the armatures inertia. For momentarily applied loads this often get confused with torque. Scott adastra cc: Sent by: pic Subject: [EE}: DC-PM motor, speed vs torque? microcontrolle r discussion list 08/06/01 03:28 PM Please respond to pic microcontrolle r discussion list We are working on a (PIC driven) application which uses a 90 Volt DC-PM motor. In some circumstances we want to lower the speed to about half of its full-scale value, but we still need the torque we get out of the motor at its full speed. Of course we can lower the speed by lowering the DC drive voltage, but it seems that the torque also falls off proportionately to the lowered voltage. Does anyone know of a control technique (PWM maybe?) that allows lowering the speed while maintaining the torque? I am obviously not a motor expert. Am I trying to break the laws of physics here? Any suggestions welcome. Thanks very much, Foster -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics --0__=85256AA000702B388f9e8a93df938690918c85256AA000702B38 Content-type: application/octet-stream; name="$RFC822.eml" Content-Disposition: attachment; filename="$RFC822.eml" Content-transfer-encoding: base64 UmVjZWl2ZWQ6IGZyb20gc2pzbXRwMDEudW5pcGhhc2UuY29tIChbMTAuMTAuNDkuMjM5XSkNCiAg ICAgICAgICBieSBzanNtdHAwMS51bmlwaGFzZS5jb20gKExvdHVzIERvbWlubyBSZWxlYXNlIDUu MDdhKQ0KICAgICAgICAgIHdpdGggU01UUCBpZCAyMDAxMDgwNjEzMTU1NDY2OjM0MDY5OSA7DQog ICAgICAgICAgTW9uLCA2IEF1ZyAyMDAxIDEzOjE1OjU0IC0wNzAwIA0KUmVjZWl2ZWQ6IEZST00g Y2hlcnJ5LmVhc2UubHNvZnQuY29tIEJZIHNqc210cDAxLnVuaXBoYXNlLmNvbSA7IE1vbiBBdWcg MDYgMTM6MTU6NTMgMjAwMSAtMDcwMA0KUmVjZWl2ZWQ6IGZyb20gUEVBUi5FQVNFLkxTT0ZULkNP TSAoMjA5LjExOS4wLjE5KSBieSBjaGVycnkuZWFzZS5sc29mdC5jb20gKExTTVRQIGZvciBEaWdp dGFsIFVuaXggdjEuMWIpIHdpdGggU01UUCBpZCA8MjEuMDAzQzcxMDhAY2hlcnJ5LmVhc2UubHNv ZnQuY29tPjsgTW9uLCA2IEF1ZyAyMDAxIDE2OjIyOjMxIC0wNDAwDQpSZWNlaXZlZDogZnJvbSBN SVRWTUEuTUlULkVEVSBieSBNSVRWTUEuTUlULkVEVSAoTElTVFNFUlYtVENQL0lQIHJlbGVhc2Ug MS44ZCkNCiAgICAgICAgICB3aXRoIHNwb29sIGlkIDY2MDkgZm9yIFBJQ0xJU1RATUlUVk1BLk1J VC5FRFU7IE1vbiwgNiBBdWcgMjAwMQ0KICAgICAgICAgIDE1OjMwOjQ5IC0wNDAwDQpSZWNlaXZl ZDogZnJvbSBNSVRWTUEgKE5KRSBvcmlnaW4gU01UUEBNSVRWTUEpIGJ5IE1JVFZNQS5NSVQuRURV IChMTWFpbA0KICAgICAgICAgIFYxLjJjLzEuOGMpIHdpdGggQlNNVFAgaWQgMjQ2MDsgTW9uLCA2 IEF1ZyAyMDAxIDE1OjI4OjUwIC0wNDAwDQpSZWNlaXZlZDogZnJvbSBzZXJ2ZXIuaW5kcmEuY29t IFsyMDQuMTQ0LjE0Mi4yXSBieSBtaXR2bWEubWl0LmVkdSAoSUJNIFZNIFNNVFANCiAgICAgICAg ICBMZXZlbCAzMjApIHZpYSBUQ1Agd2l0aCBFU01UUCA7IE1vbiwgMDYgQXVnIDIwMDEgMTU6Mjg6 NDggRURUDQpYLUNvbW1lbnQ6IG1pdHZtYS5taXQuZWR1OiBNYWlsIHdhcyBzZW50IGJ5IHNlcnZl ci5pbmRyYS5jb20NClJlY2VpdmVkOiBmcm9tIG5ldC5pbmRyYS5jb20gKG5ldC5pbmRyYS5jb20g WzIwNC4xNDQuMTQyLjFdKSBieQ0KICAgICAgICAgIHNlcnZlci5pbmRyYS5jb20gKDguMTAuMS84 LjEwLjEpIHdpdGggRVNNVFAgaWQgZjc2SlNhTDA5MzEwIGZvcg0KICAgICAgICAgIDxwaWNsaXN0 QG1pdHZtYS5taXQuZWR1PjsgTW9uLCA2IEF1ZyAyMDAxIDEzOjI4OjQwIC0wNjAwIChNRFQpDQpS ZWNlaXZlZDogZnJvbSBmb3N0ZXIgKHZjMi0xMjctMS5hZHNsLmluZHJhLmNvbSBbMjA2LjE2OC4x OTUuMjExXSkgYnkNCiAgICAgICAgICBuZXQuaW5kcmEuY29tICg4LjEwLjEvOC4xMS4zKSB3aXRo IFNNVFAgaWQgZjc2SlNXWTAxMTk0IGZvcg0KICAgICAgICAgIDxwaWNsaXN0QG1pdHZtYS5taXQu ZWR1PjsgTW9uLCA2IEF1ZyAyMDAxIDEzOjI4OjM0IC0wNjAwIChNRFQpDQpNSU1FLVZlcnNpb246 IDEuMA0KWC1Qcmlvcml0eTogMyAoTm9ybWFsKQ0KWC1NU01haWwtUHJpb3JpdHk6IE5vcm1hbA0K WC1NYWlsZXI6IE1pY3Jvc29mdCBPdXRsb29rIDguNSwgQnVpbGQgNC43MS4yMTczLjANCkltcG9y dGFuY2U6IE5vcm1hbA0KWC1NaW1lT0xFOiBQcm9kdWNlZCBCeSBNaWNyb3NvZnQgTWltZU9MRSBW NC43Mi4zMTEwLjMNCk1lc3NhZ2UtSUQ6ICA8MDAwMDAxYzExZWFkJGVjNmIxMjIwJDAyMDAwMDBh QGZvc3Rlcj4NCkRhdGU6ICAgICAgICAgTW9uLCA2IEF1ZyAyMDAxIDEzOjI4OjA3IC0wNjAwDQpS ZXBseS1UbzogICAgIHBpYyBtaWNyb2NvbnRyb2xsZXIgZGlzY3Vzc2lvbiBsaXN0IDxQSUNMSVNU QE1JVFZNQS5NSVQuRURVPg0KU2VuZGVyOiAgICAgICBwaWMgbWljcm9jb250cm9sbGVyIGRpc2N1 c3Npb24gbGlzdCA8UElDTElTVEBNSVRWTUEuTUlULkVEVT4NCkZyb206ICAgICAgICAgYWRhc3Ry YSA8Zm9zdGVyQEFEQVNUUkFOLkNPTT4NClN1YmplY3Q6ICAgICAgW0VFfTogREMtUE0gbW90b3Is IHNwZWVkIHZzIHRvcnF1ZT8NClRvOiAgICAgICAgICAgUElDTElTVEBNSVRWTUEuTUlULkVEVQ0K WC1NSU1FVHJhY2s6IEl0ZW1pemUgYnkgU01UUCBTZXJ2ZXIgb24gU0pTTVRQMDEvU2VydmVyL0pE U1VuaXBoYXNlKFJlbGVhc2UgNS4wN2EgfE1heSAxNCwgMjAwMSkgYXQNCiAwOC8wNi8yMDAxIDAx OjE1OjU0IFBNLA0KCVNlcmlhbGl6ZSBieSBSb3V0ZXIgb24gU0pTTVRQMDEvU2VydmVyL0pEU1Vu aXBoYXNlKFJlbGVhc2UgNS4wN2EgfE1heSAxNCwgMjAwMSkgYXQNCiAwOC8wNi8yMDAxIDAxOjE1 OjU3IFBNLA0KCVNlcmlhbGl6ZSBjb21wbGV0ZSBhdCAwOC8wNi8yMDAxIDAxOjE1OjU3IFBNDQpY LU5vdGVzLUl0ZW06IDE3Ow0KIHR5cGU9MzAwOyBuYW1lPSRIb3BzDQpYLU5vdGVzLUl0ZW06IE1l bW87DQogbmFtZT1Gb3JtDQpYLU5vdGVzLUl0ZW06IENOPVNKU01UUDAxL09VPVNlcnZlci9PPUpE U1VuaXBoYXNlOw0KIHR5cGU9NTAxOyBmbGFncz00NDsgbmFtZT0kVXBkYXRlZEJ5DQpDb250ZW50 LVRyYW5zZmVyLUVuY29kaW5nOiA3Yml0DQpDb250ZW50LVR5cGU6IHRleHQvcGxhaW47IGNoYXJz ZXQ9Imlzby04ODU5LTEiDQoNCldlIGFyZSB3b3JraW5nIG9uIGEgKFBJQyBkcml2ZW4pIGFwcGxp Y2F0aW9uIHdoaWNoIHVzZXMgYSA5MCBWb2x0IERDLVBNDQptb3Rvci4gSW4gc29tZSBjaXJjdW1z dGFuY2VzIHdlIHdhbnQgdG8gbG93ZXIgdGhlIHNwZWVkIHRvIGFib3V0IGhhbGYgb2YgaXRzDQpm dWxsLXNjYWxlIHZhbHVlLCBidXQgd2Ugc3RpbGwgbmVlZCB0aGUgdG9ycXVlIHdlIGdldCBvdXQg b2YgdGhlIG1vdG9yIGF0DQppdHMgZnVsbCBzcGVlZC4gT2YgY291cnNlIHdlIGNhbiBsb3dlciB0 aGUgc3BlZWQgYnkgbG93ZXJpbmcgdGhlIERDIGRyaXZlDQp2b2x0YWdlLCBidXQgaXQgc2VlbXMg dGhhdCB0aGUgdG9ycXVlIGFsc28gZmFsbHMgb2ZmIHByb3BvcnRpb25hdGVseSB0byB0aGUNCmxv d2VyZWQgdm9sdGFnZS4gIERvZXMgYW55b25lIGtub3cgb2YgYSBjb250cm9sIHRlY2huaXF1ZSAo UFdNIG1heWJlPykgdGhhdA0KYWxsb3dzIGxvd2VyaW5nIHRoZSBzcGVlZCB3aGlsZSBtYWludGFp bmluZyB0aGUgdG9ycXVlPyAgSSBhbSBvYnZpb3VzbHkgbm90DQphIG1vdG9yIGV4cGVydC4gIEFt IEkgdHJ5aW5nIHRvIGJyZWFrIHRoZSBsYXdzIG9mIHBoeXNpY3MgaGVyZT8gIEFueQ0Kc3VnZ2Vz dGlvbnMgd2VsY29tZS4gVGhhbmtzIHZlcnkgbXVjaCwNCiAgICAgICAgRm9zdGVyDQoNCi0tDQpo dHRwOi8vd3d3LnBpY2xpc3QuY29tIGhpbnQ6IFRoZSBsaXN0IHNlcnZlciBjYW4gZmlsdGVyIG91 dCBzdWJ0b3BpY3MNCihsaWtlIGFkcyBvciBvZmYgdG9waWNzKSBmb3IgeW91LiBTZWUgaHR0cDov L3d3dy5waWNsaXN0LmNvbS8jdG9waWNzDQoNCg0K --0__=85256AA000702B388f9e8a93df938690918c85256AA000702B38-- -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics