| ??? 12/13/05 05:10 Modified: 12/13/05 05:12 Read: times |
#105112 - Re: Why Encoder. Responding to: ???'s previous message |
Dear Sarang,
Thanks for your reply, why are you using the stepper motor with encoder? I mean steppers can be precisely controlled by the processor. I use encoder since i need precise positioning which is not really possible with an open loop stepper. Stepper do miss steps even with nominal loading. If you are saying that your shaft vibrates then its because you are not getting perfect holding. How many phase stepper are you using? If it is 6 leads then for 50kg cm motor the current required will be more than 2A/phase in bipolar connections. And then your L297 and L298 combination will not work effectively. You need to cascade multiple L298s or use seperate 2 MOSFET bridges. The motors are Sanyo Denki type 103H-8222-5041 biphase bipolar with 4 leads. The stepper drives are not home made but Orion make 3.3Ampere drives BPD-3A3 and according to manufacturer of drive they can be used with upto 80Kg-Cm sanyo denki bipolar motors. The drive has 2 paralleled L298's as I said earlier. Also if you are using the current control of L297 inbuilt chopper then use it on inhibit lines instead of A, B, C, D lines. This is one of the common problem while designing the L297 + L298 drive As I said drives are proven ones from a reliable manufacturer. These drive handles all the chopping logic and current sense stuff on their own the drives too have micro inside. These drive cant have any common problems. The most important thing is the basic phenomena of stepper is to exhibit hystresis (As Steave said, stepper moves in discrete step angles and so he suggested to put rubber type disk to your motors shaft) What I mean is it gives resonance around the step angle and then settle to the final position, which hampers the accuracy of stepper and this may be resulting in your encoders output error. Yes, I will surely use some damper. Thanks & Regards, Prahlad Purohit |
