[acondit]

I picked up some used Advanced Motion Control 30A8T Controllers (Brush Type PWM Servo Amplifier). They require a +-10v analog signal.

Has anyone used these?

Is there a simple circuit to convert PWM/Dir to +-10v output?

Or am I better off just biting the bullet for a Mesa 7i33TA Quad analog servo amp interface?

Thanks,
Alan

[Al_The_Man]

I have used A-M-C extensively but only with ±10vdc.
There was someone here some time ago offering a PWM to analogue convertor, not sure if they are still around.
But these amps are not very useful for Mach as the drive needs to close the loop, which the A-M-C. do not, they are for controller closed loop systems.
Al.

[acondit]

I use EMC2 which closes the loop so that is not a problem.

[Al_The_Man]

So you should be able to use ±10vdc, no?
Al.

[acondit]

Yes, but I don't currently have anything to generate +-10v, while I do have something to generate PWM/Dir. Hence the questions:
Is there a simple circuit to convert PWM/Dir to +-10v output?

Or am I better off just biting the bullet for a Mesa 7i33TA Quad analog servo amp interface?

[Iron-Man]

Yes, but I don't currently have anything to generate +-10v, while I do have something to generate PWM/Dir. Hence the questions:
Is there a simple circuit to convert PWM/Dir to +-10v output?

Or am I better off just biting the bullet for a Mesa 7i33TA Quad analog servo amp interface?

acondit

I will also be using MESA cards. Currently working on several projects. Here is a link to Elmo motion control for a proven circuit to convert PWM-DIR to +- 10V analog. Here is the direct link:
http://www.elmomc.com/applications/a...with-a-PWM.pdf

You will still need to close the loop with encoders in EMC.

Hope this helps,

Iron-Man

[acondit]

Thanks for the link. That is what I have been looking for.

I have a 7i43 and two 7i42TA daughter cards to which I can wire the encoders. I may go ahead and build one of these to try it out. I suspect given the parts count that buying the 7i33TA may be cheaper in the long run, since it will do the DA conversion for 4 servos. Then I could save one of the 7i42TAs for my next machine controller.

Alan

[samco]

there is also the 7i48 that does 6 axis analog. (I am using both the 7i33 and the 7i48 in my machine) (2 5i20 fpga cards)

sam

[Iron-Man]

Has anyone used this ( 5i25) card? I am still undecided on the 5i20 or wait for the 5i25.

Iron-Man

[acondit]

OK, I have another question. It appears from the manual for the 30A8T that it expects 0 to +10v on one pin and -10v to 0 on another pin. The 7i33 and 7i48 have a single output pin for each amp that swings from -10v to +10v.

How do you connect the 30A8T to the 7i33 or 7i48???

Alan

[Al_The_Man]

The 30A8 only requires two connections which strictly speaking are differential +- but if you have two conductor single ended the common goes to -ref pin and the + to the +ref pin.
Your controller card should alternate polarity to alternate motor direction.
Your 7i card should have a common to the ±10vdc signal.
Al.

[acondit]

Thanks Al,

OK, on the 30A8T
Pin 1 is +10v/3mA output
Pin 2 is signal gnd
Pin 3 is -10v/3mA output
Pin 4 is +15v(max) +Ref Input
Pin 5 is -15v(max) -Ref Input

Lets just take the connections for one servo and see if I have it correct:
The first three pins from the 30A8T are an anemic power supply.
You are saying that I connect the +/-10v signal from the 7i48 pin10 AOUT0 to 30A8T pin4 +RefIn.
Then connect the 7i48 pin11 gnd to 30A8T pin5 -RefIn.

Is that correct?

I edited this to attach the schematic for the 30A8T to show the input connections for it.

Alan

[Al_The_Man]

You are probabally not going to use 1 or 3 or even 2.
It looks like you have it right for 4 & 5.
That is the way I use them on Galil cards.
DigiKey are a source of the edge connectors if you need them.
Al.

[acondit]

Thanks, Al.

Yeah, that's why I made the comment (anemic) power supply.

I found the connectors at Mouser also. The housings (plastic) are slightly more expensive at Mouser than Digikey (3 for $4.17 vs 3 for 3.24) but the connectors (metal) are (48 for $4.80 vs 48 for $9.12). However, since I am already working on an order from mouser the real difference is shipping.

Alan

[Al_The_Man]

You also may want to look at using the inhibit in some way, I am not sure what the 7i cards have for an output?
The Galil have a MO command that turns an output off for each axis, I use this to feed the drive Enable's, one nice feature is that when the motors are off this way, the card keeps track of the encoder so that when you enable them the new position is recorded even though you may have physically turned the axis when they are off, this prevents error or a jump when re-enabled.
Failing anything of this sort , you could use relay contacts off an E-Stop relay.
Al.

[acondit]

Right, the 7i33 has an EnableOut and a corresponding /EnableIn for each drive. I was not trying to document all of the connections that need to be made. I was just trying to figure out how I was going to connect the analog command signals. I was afraid that having the +RefIn driven negative was going to be a problem.

Alan

[Al_The_Man]

I was afraid that having the +RefIn driven negative was going to be a problem.

Alan

No, that is just the drive notation, with a "±15vdc max differential analog input" it implies a ±dc polarity change of the signal in.
Al.