can I use these encoders

[cncpete]

Hey all,

New to the board... really, really glad I found it. You all seem very helpful, which is really good because I am sure I will have tons of questions as my project starts to take shape. I recently aquired a bpt series 2 mill from my job, it took a little ass kissing to the right people but I ended up "aquiring" that and a sheldon lathe for free.... (way better than christmas) . So being that I was lucky enough to get these machines for free, I figured I would sink some money into the mill and make it cnc. So now I am in the process of aquiring parts (on a very tight budget, surplus this... ebay that). I found a great deal on some DC brush motors to run the axis' that have provisions for encoders on the back. The shaft is .187 dia. and they have 2 holes on 1.812 dia. (pretty std from what I can tell). I have a lead on some renco encoders with a .25 bore which I think I can make work with a bushing, but I don't know if they will work with the Gecko drives I plan to use. Here is the description:

1000 count A and B channel only, no reference mark, 1/4" hub size, Line driver output. have a special short cable with pins for a connector body, looks like AMP. Closed cover, glass disk 0.060" thick

Part number is: RM21B3-1000-1/4-5-CS-LD-C-G6-S

These are up on ebay, the guy seems to have a ton of them.

My concern is the "line driver output" what does this mean? are they TTL compatible like the Gecko instructions ask for? A guy at work mentioned using a step up resistor, what exactly does this do and why would you need it?

Renco's site shows this option or VC or VO. Can somebody please explain the difference to me?

Thanks a lot in advance for any help. Take care, Pete

[Al_The_Man]

They use a LM2901 comparator for output and the VC & VO the VO type is open collector and either have to work into a load or a provide a 10k pull-up resistor from the output to 5v (if that is what your supply is). One disadvantage with single output (non-differential) is that they are limited to the length you can run the cable as they are more prone to noise pick-up. Or if you have need a long encoder cable make sure the wiring has an overall shield which is grounded at one end and kept seperated from motor supply cables.
Al

[Al_The_Man]

Originally Posted by cncpete . I have a lead on some renco encoders with a .25 bore which I think I can make work with a bushing, but I don't know if they will work with the Gecko drives I plan to use. These are up on ebay, the guy seems to have a ton of them.

BTW that is Renco themselves selling end of run stock etc.
Al

[cncpete]

when you said "they", you mean the ones on ebay. I am sorry, but I think I am a little more confused now than before. The ones on ebay are single output (non-differential)??? or they are not? If I wanted to use these I would have to worry about noise and use shielded cable like you said, or are you talking about the VO only?

Basically, should I use these?? Are these not the ones where I have to worry about noise and use shielded cables?

Thanks a lot for your help

[Al_The_Man]

Originally Posted by cncpete Basically, should I use these?? Are these not the ones where I have to worry about noise and use shielded cables? Thanks a lot for your help

Basically both types VC & VO have the limitation of shorter distance capability, over differential type, especially if operated as low as 5v, a VO with the pull-up resistor is effectivly the same as the VC. If you have short distances, e.g. 4'x4' table then you should be ok with them. You may want to check with the system hardware you are using to see if they are compatible with 1000 line encoders.
Single ended are often used with higher voltage 12v to 24v in order to offset the noise problem. If your system allows it, the differential kind is usually preferable.
Al

[Bloy2004]

you can use them on the 320 geckos if you get the multiplier add-on. it isn't listed at the sight but can be gotten by calling Gecko. Basically it makes the 320 the same as the 340 servo drive. Your motors will run slower if i'm understanding this right, so I hope the motors you have are generous on the rpm's