Need Hardware Choice Help

From the diagram you can see that the drives close the loop to the encoder and possibly only take step and direction like a Gecko 320 drive so as far as EMC is concerned they are just open loop step and direction drives like steppers.

If I was going to the expense of servos I'd get drives and motors that can be closed loop. RobH has been getting some from flea bay for his machines...

John

Maglin wrote:

I did just that. I purchased 6 BD30A8 Advanced Motion Technologies analog servo drives on flee bay. They are PWM/Dir open loop drives when driving brushed servo's.

Careful there, as far as I can make out, those are brushless servo drives. Are you absolutely sure that they can drive brush-type motors?
If they can drive both types, then they sound great, as you can use just about any motor you can find at the right price.
In the development branch of EMC2 there is a "glue" hal module called bldc. That will produce Hall-pattern signals for brushless drives even from motors with no Hall sensors, as long as they have an encoder. I have used it to drive some motors I found on eBay which have Resolvers as feedback.

My drives happen to have a current monitor output that is 0-10v proportional to the drives current output of 4 a/v. Would I be able to setup a page in EMC2 to graph and monitor the current output pin?

Yes, but not particularly easily. A common way to do this is with a voltage to frequency converter, connected to a counter-mode encoder module in EMC2 (or, in your case, in the 5i23 frimware). The encoder velocity can then be used in HAL as a voltage/current value.
Mesa do a compatible card (THCAD) but that is probably overkill for what you need. A cheap-as-chips 555 counter/timer chip can do the job
ecelab.com/circuit-vco-555.htm
Or, for a little more a dedicated chip such as the LM231N

Maglin wrote:

I got an email back from Mesa and it's either use TTL and the 7i42TA or use differential encoders and use the 7i47S which seems like the better way to go. I can get a differential converting cable for the CUI encoders.

Seems a bit of an odd thing to do, to me, spending money on converting TTL encoders to differential, then back to TTL at the interface. It ought to be more interference-resistant using differential signalling, but TTL (home-made encoders) is working fine for me, just wired directly to the Mesa cards.