[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]

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

[unterhaus]

what is that circuit board on the side of the motor? Did the Heidenhain connector go on there? That's a custom cable, but it seems fairly likely that the scale is TTL. I'm starting to think that they didn't use a rotary encoder even though the motor has a double shaft.

I looked at one of my Heidenhain scales, it didn't have the sinusoidal drawing like I remembered.

[mikkojay]

I went and snapped a couple closeups of the board for you.
The encoder plugs into it, as well as 3 "electric eye" type limit switches.
Then the motor, of course. It looks like there is a socket for a motor brake also.

[N4NV]

Made sure that what ever encoder you use takes less than 50mA. If you plan on using Gekco's, that's all they can supply. The Rencos I purchase off ebay take 125mA. The US Ditigal encoders are under 50mA.

Vince

[Al_The_Man]

It appears the encoders go 'straight through' to the board. I found the specs on LS 400 series and the closest I found was the LS476 which is TTL 4µm 140ma total.
Each individual output should be under 50ma, is it possible to use a separate 5v encoder supply when using Gecko's?
Al.

[mikkojay]

Hey Al,
I received a datasheet in pdf format from the folks at Heidenhain (impressive, < 24hr response). I wasn't sure if I could upload a pdf here, so I snipped a couple of pieces out and saved them as a jpg. If it is legible, could I get your opinion of what you see? I am pretty new to servo theory, so its still a little Greek to me.
Thanks again to everyone for all the great feedback on this subject!
Mike

[Al_The_Man]

The Ua1's are the A phase, the Ua2's are the B phase and the Ua0's are the Index or marker pulse. The Bar is the complement to the non-barred.
Al.

[mikkojay]

I just looked at the diagram for a Gecko 320.
It shows encoder inputs for +, -, A & B.
Does that mean that all of the "Not" encoder wires would remian disconnected, and the Ua0 is not used? I just want to be sure before I order something and fry it.
It also seems apparent that this encoder would use an external 5v source to satisfy the current requirements of the encoder. Does this sound feasible?
Thanks, Mike

[Al_The_Man]

If the Gecko's do not use the marker then leave them disconnected. Normally if an encoder uses an external source only the AB signals are connected as well as the 5v common is connected to the Drive common, this you should confirm with Gecko as I have never used them.
Al.