Rotary Encoders

[MartB]

I have been asked to provide our mechanical department with a part number for a rotary encoder. They are specifically asking for an absolute rotary encoder with a hollow shaft (size to be discussed at a later date), and with an internal gearing so they can achieve an internal ratio of their choosing to avoid having any external mechanical sprocket arrangements (for example, one rotation can be 20 degrees etc).
I have little to no experience in this area and was hoping someone could point me in the right direction.
I have done a little research and found some offerings from Sick Stegmann and BEI but none of them mention any internal gearing (in fact I'm starting to wonder if this is even an option as I've never heard of it either, but I like to be proved wrong).

Any help anyone could give in this area would be appreciated.

As a side note we'll be using it in conjunction with a Compact Logix processor. At this point I'm thinking an SSI card would be the best way to go as I haven't seen any ethernet offerings (ethernet would be ideal by the way) but again I'm open to suggestion here.

Many thanks.

 

[Clay B.]

I have used encoders that you can select the number of pulses per revolution but have never heard of a gear ratio. Depending on how fast the encoder turns decides the frequency of the pulses. So the faster the RPM's the lower the pulse counts I used. I do not remeber the brand name but I do remeber I got mine from my local AB Rep. You should be able to do the same.

 

[MartB]

I've already got a call in to my local AB guy (to pick his brains as much as anything else) but I think he's on vacation this week, and I don't really have the luxury of waiting for him.

 

[OkiePC]

http://www.amci.com/index.asp


These guys make great stuff for PLC interfaces and resolvers with multiple gear ratios but I don't know about the hollow shaft part...

Paul

 

[Pego]

Take a look here:
http://www.heidenhain.com/index.php?WCMSGroup_785_177=487&WCMSGroup_479_177=785&WCMSGroup_2238_177=479&WCMSGroup_487_177=855&WCMSArticle_Template_45_11891=HeidenhainProduktDB&op=catview&search=category&CS_UID=18267

The links does not seem to take you directly to the right page.
Look for EQN425

Positions per rev8192 (13 bits)
Distinguishable revolutions4096

 

[monkeyhead]

http://www.photocraftencoders.com/Hollow Shaft Encoders.htm

Here's some programmable hollow shaft encoders. I don't know if they have any field bus options (didn't research too deeply), but it might fit the bill for you since the number of pulses per revolution can be changed.

I've never heard of the internal gearing thing before, but my exposure to encoders isn't that extensive.

 

[MartB]

Thanks for all the great links - still going through all the information I've gathered, but it seems like the internal gearing thing would be accomplished by getting a programmable encoder (at least that's the conclusion I'm drawing to at the moment).
Now all I have to do is decide on one and stick with it!

Once again thanks to everyone for their input.

 

[CBowman]

TR Electronic has a line of ETHERNET IP Rotary Encoders that may be of interest to you. Check out their site.

www.trelectronic.com

 

[Clay B.]

http://www.amci.com/index.asp


These guys make great stuff for PLC interfaces and resolvers with multiple gear ratios but I don't know about the hollow shaft part...

Paul

This is the brand I used. It basically had a set of dip switches that allowed you to change the pulse count.

I have never seen a hollow shaft encoder.
The hollow shaft criteria sounds like a bad idea anyway. Most encoders use coupling and belts to reduce the amount of vibration going into the encoder.

Now I have seen hollow shaft "resolvers" which is another aniumal all together. The web page Okie lists has resolvers on them. I have seen hollow shaft resolvers used on dancer arms.

 

[allscott]

Hollow shaft encoders are very common. Quite often used on non drive end of a motor.

Also the OP is looking for an absolute encoder.

 

[MartB]

I've spoken again to the guys in mechanical and they are insisting on hollow shaft absolute encoders (for various reasons). They also tell me that I should be able to find one with internal gearing that they can use so that - for example - 20 revolutions would only register as 1 revolution on the encoder.
I told them I had found programmable encoders and asked if that would achieve the same thing but they all looked at me as if I had two heads.
Also spookily enough, nobody can give me an example of the internally geared encoders or can even recall a manufacturers name (now I'm really starting to think they don't exist), even though they're sure they used one a 'few' years ago.

So here's my next question, with a programmable encoder, can I achieve what they are asking? i.e. count 20 turns of a shaft and register it as 1 revolution on the encoder? Or am I missing the point completely?
If I'm understanding the information on these encoders that I'm reading about, it is possible to define the number of counts in one revolution?

Hopefully someone has some experience in this, I'm trying to justify not wasting any more time looking for a mechanically geared device when I believe (rightly or wrongly) that a programmable encoder would do the same thing.

 

[Gil47]

Using multi range gear box's on encoders.????
With an internal gearing so they can achieve an internal ratio of their choosing

You have mechanical guys who are very religious,
I can see them now on there knees, hands clasped and praying,

Please god let it be Electrical.
???? Do they want that with a VFD

Me thinks the cure will be by scaling with a programable encoder, or scaling in a PLC

 

[Rich1955]

Me thinks the cure will be by scaling with a programable encoder, or scaling in a PLC

That would be my choice and why would you need anything else?

 

[MartB]

My choice too, I'm just trying to determine if the programmable part of the encoder is essential or not?
It seems like it would simlpy make life easier and I'm struggling to find anything like our mechanical guys have described (I'm starting to think they're blowing smoke up my butt about this internal gearing thing anyway).

Does anyone have any experience with programmable encoders that they are willing to share?

 

[CBowman]

Programmable encoders allow the end user to change the resolution, or pulses per revolution. Their non-programmable counterparts are usually programmed from the vendor to the specific needs of the end user. Programmable allow more flexibility in the field. The programming is usually VERY straight forward, either via a PC or a handheld unit.

As for the internal gearing comment. I believe they are talking about a multi-turn encoder. It uses internal gears to turn satilites.

http://www.trelectronic.com/index.php?fuseaction=customerFirst.login

If you login to this site there is more information. You can also pose your questions to their customer support.