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Bourgie59
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Do I need an index on my encoder?

I have an Oriental Motor with an encoder, however the encoder does not have an index output, is the index output required by the nudrive?
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Kyle_V
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Re: Do I need an index on my encoder?

Hi Bourgie59. While an index pulse is often times nice to have in rotational systems, you certainly don't have to have one. I'm assuming that you have stepper motors, in which case, you don't even have to wire in the encoder (if you operate the motors in open loop.)

Oriental Motors are very common and most of us here in the Motion group at NI have experience hooking them up. If you need more information, please let us know.

Kyle V
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Buechsenschuetz
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Re: Do I need an index on my encoder?

Usually the index pulse is used to detect an absolute position of a drive (incremental encoders do not, as the name implies, indicate absolute position). If don't have this need or if you have other possibities to detect absolute position (a REF switch, for example) you won't need an index pulse. However, even when using a REF switch an index pulse is useful to detect absolute position more accurately than it would be possible with a switch (be it a mechanical one or an optical switch).

When using a REF switch to detect absolute position make sure that this switch is debounced (in case of a mechanical switch), and that the drive always approaches it from the same direction to avoid hysteresis effects.
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Doravari
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Re: Do I need an index on my encoder?



Kyle V wrote:
Hi Bourgie59. While an index pulse is often times nice to have in rotational systems, you certainly don't have to have one. I'm assuming that you have stepper motors, in which case, you don't even have to wire in the encoder (if you operate the motors in open loop.)

Oriental Motors are very common and most of us here in the Motion group at NI have experience hooking them up. If you need more information, please let us know.

Kyle V





We just got an oriental motor with encoder as well and are wondering whether it is okay to leave the index pin on our MID-7602 unwired. Our application is constant speed control. Can we do without the index signal?
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Lorne H.
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Re: Do I need an index on my encoder?

Suresh,
 
"We just got an oriental motor with encoder as well and are wondering whether it is okay to leave the index pin on our MID-7602 unwired. Our application is constant speed control. Can we do without the index signal?"
 
Yes, it is ok to leave the index line for the encoder disconnected.
 
Lorne Hengst
Application Engineer
National Instruments
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cforem5
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Re: Do I need an index on my encoder?

Hi,

 

I have an Oriental Motor stepper motor and quadrature encoder without an index. I was wondering how to wire the encoder to a NI9512 stepper drive. Currently I am powering the motor with the Danaher P70530 DC power drive so I have a P7000 to NI9512 connectivity kit and I have the encoder connected to the channel A, channel B, COM, and 5V out pins on the 37 pin connector but I am getting no response from the encoder. Any suggestions? 

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Buechsenschuetz
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Re: Do I need an index on my encoder?

I am not familiar with this particular unit but according to what I have seen on the NI9512 datasheet your connections seem to be OK. 

 

I think you should first check the hardware. Check with an oscilloscope whether you see pulse trains on the A and B input of the driver unit when you move the drive or turn the encoder shaft. When using a 2-channel scope hooked up to both A and B channels you should see approx. 90 deg phase shift between the two channels, i.e. the rising slope of a channel B pulse should occur right between the two slopes of a channel A pulse.  

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cforem5
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Re: Do I need an index on my encoder?

I'll find an oscilliscope and work on that. Are you familiar with the softmotion module at all? If so, in the software under axis properities >> encoder settings I have to set the state of ch A and ch B when an index pulse is received. I am wondering if this means I need to have an encoder with an index to use this software on that axis because there is no radio button or option for an encoder without an index? Is this correct or is there a way to get around this?

 

Please let me know, thanks

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Buechsenschuetz
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Re: Do I need an index on my encoder?

I think the settings for the phase of A and B channel when the index occurs have rather to do with the detection of the index pulse. We do not use Labview but we had some problems with the detection of the index pulse, and NI told us that there should be a certain phase relationship between A, B and Index channel. So my best guess is that the settings you asked about have little or nothing to do with the detection of the A and B channel pulse. The NI motion controlles use the index pulse for the FindIndex routine only.