Fadal VH65(DC) 4th axis with 7i77 - where to start?

Ok, AMC 25a20 will run that motor, but you will need a 90v dc supply, you could also use an AMC drive with a built in rectifier and you would just need a 60v transformer ( 60x1.414 is about 84 volts).

To use the resolver, you need a whole different set up, prob a 5i23 and a 7i49 , which is silly for one resolver. Put an encoder on it and be done..

Unless you got a screaming deal on the VH 65, I’d sell it for the 3k it’s worth and buy a used $500 rotab off eBay. The Fadal guys highly prize those things....

There are AMC drives that would take a resolver input, and would output an encoder signal for the control. Such as this one.
www.a-m-c.com/product/dpranir-015s400/

JR1050 wrote: Ok, AMC 25a20 will run that motor, but you will need a 90v dc supply, you could also use an AMC drive with a built in rectifier and you would just need a 60v transformer ( 60x1.414 is about 84 volts).

To use the resolver, you need a whole different set up, prob a 5i23 and a 7i49 , which is silly for one resolver. Put an encoder on it and be done..

Unless you got a screaming deal on the VH 65, I’d sell it for the 3k it’s worth and buy a used $500 rotab off eBay. The Fadal guys highly prize those things....

I've got about a grand in to this one, so not a smoking deal, but no doubt I can sell it for more than I paid for it.

From my understanding, the only way to install en encoder would be to replace the motor....which goes back to just ditching it and starting with something else.

Can you give me an example of one of these $500 units? I'm not overly familiar with the options that work best with the platform. Checking ebay for "rotab" only turns up some high dollar and massive manual or hydraulic tables.

Todd Zuercher wrote: There are AMC drives that would take a resolver input, and would output an encoder signal for the control. Such as this one.
www.a-m-c.com/product/dpranir-015s400/

Thanks. I requested a quote and sent the motor specs to see what they say about the application. Curious what the cost for the drive will be.

Would this be plug and play for the most part? As in, I'm assuming the wiring and setup would be similar to the other 3 axis?

Replacing the resolver with an encoder is as easy as removing the coupler and three screws and bolting an encoder in its place. Take the cover off the motor, you will see the resolver mounted on an aluminum housing , the tach is under the housing. Get your self a hollow shift encoder and make a small adapter to go from the 1/4” motor extension to the encoder. It is that easy.

Searching eBay I found several sub $750 units
rover.ebay.com/rover/0/0/0?mpre=https%3A...2Fitm%2F372847988739

JR1050 wrote: To use the resolver, you need a whole different set up, prob a 5i23 and a 7i49 , which is silly for one resolver. Put an encoder on it and be done..

There are resolver to quadrature converters. One of those would probably be a good fit here.

The 7i49 is useful where you need to keep the absolute angle information to use it for commutation. But if this is a DC motor there really is no need for that.

Here is one example of a converter: www.pico-systems.com/resolver.html

The low-voltage board of an STMBL drive would work too (there is a shortage of the HV power drivers, so it is actually possible that there might be spare LV boards out there). That would report angle digitally on smart-serial to the 7i77 expansion port.

andypugh wrote:

JR1050 wrote: To use the resolver, you need a whole different set up, prob a 5i23 and a 7i49 , which is silly for one resolver. Put an encoder on it and be done..

There are resolver to quadrature converters. One of those would probably be a good fit here.

The 7i49 is useful where you need to keep the absolute angle information to use it for commutation. But if this is a DC motor there really is no need for that.

Here is one example of a converter: www.pico-systems.com/resolver.html

The low-voltage board of an STMBL drive would work too (there is a shortage of the HV power drivers, so it is actually possible that there might be spare LV boards out there). That would report angle digitally on smart-serial to the 7i77 expansion port.

I like this option. I'm waiting for a quote for the AMC drive mentioned above. Depending where the pricing falls, seems like either would be a viable option.

Any recommendations for a cheap-ish drive that will work with this DC motor?



I'd much rather keep the resolver and use a converter vs. trying to swap it out with an encoder. That at least leaves me with the unmolested rotary that I can sell down the road if I ever need to scrap this whole setup.

The Pico servo drive might work: www.pico-systems.com/pwmservo.html
Mesa have one, too: store.mesanet.com/index.php?route=produc...83_90&product_id=141

However: Both of those need PWM rather than the +/-10V that the 7i77 has available.

I think I would be looking on eBay in your position, to see what is out there for cheap and used.

You could consider the Granite Devices Argon. There is a resolver adaptor for that (for only €10) store.granitedevices.com/argondrives/8-a...-drive-85371000.html

This is where I get lost - trying to decipher what on ebay will actually work for my application.

I like the look of that Granite setup. Looks like it's right at $500 shipped with the adapter. More than I'd like to spend, but for the easy of installation and setup, it may be worth it. Same with the AMC one. I suspect it'll be in a similar price range.


I think the ideal situation price wise would be if I can find a $100-150 drive on ebay and pair with the $150 pico board. Just need to narrow down what drives to look for.

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NCPatrol wrote: This is where I get lost - trying to decipher what on ebay will actually work for my application.

The search term "DC servo drive -brushless" is a good starting point. (-brushless to exclude those)

Then try to look at the specs to see what the voltage and current is. Then I am afraid you need to look at specs online.

For example:
I found a Parker E-DC, but looking at the online data sheet: www.parkermotion.com/manuals/E-Series/E-DC_Qwk_Ref_A.pdf it turns out to be 48V, 5A and to be for 2-phase (stepper?) motors. So that's no good.

Whereas (looking at the labels) is +/- 10V control. It's a bit low-voltage for your application, so will be slower than ideal. But torque should be about the same as spec.

And then, there is this one:
Google for "Copley 422"
www.motiontech.com.au/wp-content/uploads...tor-Drive-241115.pdf
And find that is a 180V / 20A one, and pretty much ideal. Not least because it should be possible to run it from straight rectified 110VAC mains.