Generic(cheap) Encoder Source

[mikkojay]

Hello,
I have lurked here for a while, and have started assembling some parts to make a home-built milling machine. I bought a sherline z-axis with spindle on ebay about a week ago. I also bought a couple of linear stages that arrived in the mail today.
Here is my main question:
The linear stages I acquired came with what appear to be nice servos, but the encoders appear to have been removed. They are MCG servos that are rated at 9 amps. I called MCG and they actually emailed me the datasheet for it- I thought that was pretty cool of them. The datasheet shows that the motor originally had a 1000 line encoder. Under that, it says, "w/index & line drivers".
I would like to find some used/inexpensive encoders that will work with a Gecko drive. I have not ordered the drive yet, as I need to make sure all of my parts will be compatible before I start shelling out cash.
I poked around on ebay, and basically stopped because I was not altogether sure of what I was looking for.
Any suggestions would be greatly appreciated.
Hopefully the cost of an encoder by itself will not eclipse the cost of a typical ebay motor/encoder combination...
I like buying stuff on ebay, but man, can I get carried away sometimes!
Thanks, Mike

[Al_The_Man]

What is the shaft size for the encoder? Usually the cleanest way is through-shaft encoder like Renco, There is a Guy selling three on eBay right now, but they are 1/2" shaft diameter.
If you are buying encoders off of eBay, I recommend going with New or NOS as I have been burned a few times with used and it a hastle even if the seller refunds.
I am not sure what the resolution limit is with Gecko though.
Al.

[mikkojay]

Thanks for the reply-
The shaft diameter on the encoder end looks to be 1/4 while the drive end looks to be 3/8.
Here is the interesting twist to this one:
I called the surplus company that I got the stage from, and they told me that the stage has a built in linear encoder already. I looked on the cable coming out of the linear encoder, and it said "Heidenhain". I looked around the web, and it looks like they make some really high-dollar stuff.
That takes me to the next question-
Would it be possible to track down a pinout for the linear encoder, or should I just save myself the trouble and go with a rotary?
Also, is it even feasible that a Gecko could be used with such a linear encoder? Half of the fun in these types of puzzles is figuring it out, as long as it doesn't wind up costing too much-
Thanks, Mike

[Al_The_Man]

If the coupling is tight enough between the motor and linear scale you may be OK what is the part number for the Heidenhain? Also they are usually very high resolution and again it depends on wether Gecko support the hi res.
Al.

[mikkojay]

I had to take the table apart, but after doing so, the part info was right there-
I will try to upload a pic, this will be my first attempt (drumroll...)
The model is LS473. Taking the table apart also revealed that the ballscrew and slide rails / bearings were made by THK which I believe is a good thing.
The table only has 4" of travel, but I think that will suffice for my first experimental machine's Y axis.
Thanks Again, Mike

[unterhaus]

All the MCG motors I have came with Renco encoders on them. I see no reason why you couldn't get one of the U.S. Digital encoders to work on there. Alternatively, keep a watch on Ebay for encoders. Rencos have shown up pretty often in the past.

Are you sure it's not a brushless motor? Gecko doesn't offer any brushless drives. That's a very high end part you have, I find it hard to believe that they would have saddled it with brushed motors.

[Al_The_Man]

The challenge is to determine which pin out, I don't have it for the LS473 but if you email Heidenhain support they usually get back the same day with the info.
If it has the 12 pin connector on the end. This is usually the pin out.
1 Pink /B
3 Red I
4 Black /I
5 Brown A
6 Green /A
8 Gray B
9 Shield
10 0V
12 5+dc
It works the same as a standard rotary incremental encoder, the definition is in µm.
Al.

[unterhaus]

some of the LS series are analog out which means that you have to get the appropriate analog/quadrature converters. My eyes aren't good enough to read the label, if it has a little sine wave with 1uA or 11uV on there, you need the converter. If it has TTL, you are good to go.

Since I will never find such a good deal in my life, I'd say you should gloat a little more so we can be properly envious of you

[Al_The_Man]

Originally Posted by unterhaus some of the LS series are analog out which means that you have to get the appropriate analog/quadrature converters.

I have found the Sine wave out type has 9 pin connector and 12 pin for TTL.
Al.

[mikkojay]

Thanks for all of the info- this site kicks @$$!
I looked at the datasheet that I was emailed by MCG, and there is a note in the spec table that makes me guess this is a brushed motor:
*DC Resistance @25 deg. C .86 ohms

* DOES INCLUDE CONTACT DROP

Wouldn't the mention of contact drop only pertain to a brushed motor?

I took a picture of the motor along with the encoder connector.
I sent an email to tech support at Heidenhain, so we will see if they get back to me. The connector itself has 9 contacts, with 2 of the contacts receiving 2 wires (10 wires and a shield).
I can't wait to fire this baby up!

Thanks, Mike

[Al_The_Man]

Two wires, so it is most certainly DC servo, strange there does not appear to be external access to brushes though.
Al.

[mikkojay]

Hey Al,
That's a good point about the brush(?) access-
I couldn't help myself and spooled it up with my 12vdc bench power supply. It seemed perky and smooth, which makes me want to establish my driver/encoder plan all the more!
-Mike