GD Servo Drive user experiences

[Xerxes]

Greetings!

This is a thread for user experiences about Granite Devices servo drives. All kinds of positive and negative feedback is welcome here as well as questions and suggestions.

Nearly half of the drives (from the first 100 units) are now sold, so I would expect that someone has them in real use by now. However, also stories about bench testings are welcome.

[daedalus]

Hi Xerxes,

My drives just arrived this morning, so i still have work to do before im doing my bench tests. That said i do have a couple of queries.

The pcb silkscreen identifies logic as +24v,gnd, and your spec sheet rates the logic supply as 22v max. Could you clarify which is the actual upper limit for the logic supply, as obviously 24v supplies are far more commonplace then 22v, so if 24v is ok it would make things easier.

Also with regard to cooling, am i right in thinking that with 300w motors i can get away with a ventilated enclosure, without adding external heatsinks to the back of the drives?

[Xerxes]

Hi,

Yes, silkscreen has printing of 24V but in one drive the input capacitor died at that voltage (that particular drive works still fine) so I specified the recommended voltage as 20V later. Most 24V power supplies have a trimmer potentiometer that adjusts voltage by few volts. Lower voltage is also better because it produces less heating.

Since the load is extremely varying different servo systems, there unfortunately are no definitive answers to heatsinking or power supply needs. The best way to determine the need of heatsink is to run drives hard for some time while keeping eye on temperatures. A thermometer sensor attached with thermal grease on drive's back plate is a good way to begin (you probably can't use your finger as sensor when enclosure is in place).

[daedalus]

thanks, will have to add some temp probes and try to leave some space for a heatsink in the chassis layout.

on further inspection my 24v supply has a pot on it, so i should be able to dial back a few volts.

I have braked motors so have the brakes and drives on this 24v supply. Both this supply and the dc bus supply are on an ssr which is computer controlled. I have done this because i need to be able to ensure the disabled pins are logic high before turning everything on. Does this seem like a logical way of doing things? (brakes are not stopping anything moving, so startup safety shouldnt be an issue).

after i have provided dc bus and logic supplies, but have disable held high does the encoder power get supplied?

when i set disable to low, how long a delay do i need to leave for startup before my pc starts sending commands?

on logic current requirements, am i right in thinking that you draw 200ma plus the encoder load?

if any of this isnt easy to answer dont worry, i can always do a bit of experimentation.

[Xerxes]

I have braked motors so have the brakes and drives on this 24v supply. Both this supply and the dc bus supply are on an ssr which is computer controlled. I have done this because i need to be able to ensure the disabled pins are logic high before turning everything on. Does this seem like a logical way of doing things? (brakes are not stopping anything moving, so startup safety shouldnt be an issue).

Sounds ok, but why you need disable at startup? One thing you might need to watch is nasty voltage spikes from brake coils. See how relays are driven safely and do something similar for brake control.

after i have provided dc bus and logic supplies, but have disable held high does the encoder power get supplied?

Yes. Logic supply is enough.

when i set disable to low, how long a delay do i need to leave for startup before my pc starts sending commands?

This depends on various parameters like phasing current and motor resistance. Typically it takes few seconds (the time before green led goes solid on).

on logic current requirements, am i right in thinking that you draw 200ma plus the encoder load?

Correct.

[dschbr]

I tested this first drive from Granite Devices with some unbranded 600 Watts Chinese brushless servo. After some little troubles with encoder wiring our motor can work very well.
The Pros:
Good torque and very responsive to step and dir commands from a EMC2 box. The software for PID adjust is very easy to install and use, and the Tero support is great and fast, also by MSN.
The Cons:
I think a better package(closed box) with DB9 Connectors and a better heat sink will be good complements for this hardware and software.
And 300VDC input will be good, or better: 115-230 VAC input from the wall.

Daniel

[Xerxes]

Thanks for the feedback!

I agree about your opinion. Pin headers will be probably replaced by Sub-D connectors some day. Pin headers were chosen because they save some PCB area and therefore reduce costs.

For easy interfacing I recommend using ribbon cable Sub-D connectors (see picture). Just put normal ribbon cable connector in the other end and you can easily get D-connector to outer wall of your enclosure without soldering a single joint.

We may start offering compatible heat sinks with drives when we find some with reasonable cost . Putting heat sink to every drive would be waste of money because smaller motors don't need it.

[walter]

But I like my heatsinks..

I also agree about the support- Five Stars across the board. Fast communication and very helpful. Great job guys!
_

[daedalus]

Truly A* on the support front. Personally i like the drives as they are, as we are all enclosing our electronics anyway boxing the drives individually would just rack up the cost for little benefit.

PS: I like your heatsinks too Walter, where did you get them? They look like cpu heatsinks.

[walter]

The heatsinks are 115mm x 76mm x 24mm, 600g all copper (Dynatron A5AG).

And how do you like my Fan Array?

( I think I went a little overboard this time..)
_

[Xerxes]

Looks more than overkill cooling
Lower air flow may be actually better because of reduced dust collection.

[dansutula]

Well, after years of lurking and learning, I finally decided, ordered, and received what I hope are the highest performance / best value servos I could find (for my 120VDC servo motors). Four VSD-1's from Granite Devices! I wired the money to Tero and about a week later, they arrived. Although it will be another month or more before I'm ready to test/use them, they sure look nice! I'll attempt to keep you all posted as I build a large DIY CNC router. I will be using a C11 Breakout Board from CNC4PC, Reliance brushed DC servos, Renco encoders, and Mach3.
Regards,
Dan