Robot using already existing servo amplifiers

andypugh
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12 Jul 2014 03:14 #48665 by andypugh

Replied by andypugh on topic Robot using already existing servo amplifiers

I just realised that you only have 3 stepgens. The principle I showed above will work, but it can be rather shorter :-)

You would only actually use entries 0 1 and 4 of the output muxes (shrink them to 4 entries) then sel0, sel1, sel2 can also drive shoulder/l-wrist/r-wrist select pins.

If you can't figure out the changes then feel free to ask me to re-hash it.

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dimech
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12 Jul 2014 03:47 - 12 Jul 2014 03:55 #48667 by dimech

Replied by dimech on topic Robot using already existing servo amplifiers

andypugh wrote:
I just realised that you only have 3 stepgens.

Actually I need 6 stepgens. I didn’t show you the other board because is identical with the first one. But as you said the principles are the same.

Thank you I’ll keep you informed about the progress

Last edit: 12 Jul 2014 03:55 by dimech.

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andypugh
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12 Jul 2014 05:21 #48668 by andypugh

Replied by andypugh on topic Robot using already existing servo amplifiers

dimech wrote:

andypugh wrote:
Actually I need 6 stepgens. I didn’t show you the other board because is identical with the first one. But as you said the principles are the same.

Do it as 2 sets of 3, not 1 of 6.

The reason is that this approach divides your maximum step-rate. Only one channel can step at a time.

There is another important thing I failed to mention as a consequence of this, you need to set the step length and step space to (fractionally less than) 3 x base threads for each stepgen to make sure that the drive "sees" the step when it is that stepgen's turn.

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dimech
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12 Jul 2014 05:43 #48669 by dimech

Replied by dimech on topic Robot using already existing servo amplifiers

andypugh wrote:
Do it as 2 sets of 3, not 1 of 6.

These tow boards are parallel connected, so step, dir, strobe, are the same pins only the select pins change. Can I still do it 2 sets of 3?

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andypugh
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12 Jul 2014 06:04 #48672 by andypugh

Replied by andypugh on topic Robot using already existing servo amplifiers

dimech wrote:

andypugh wrote:
Do it as 2 sets of 3, not 1 of 6.

These tow boards are parallel connected, so step, dir, strobe, are the same pins only the select pins change. Can I still do it 2 sets of 3?

I am not sure what you mean by parallel.

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dimech
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12 Jul 2014 06:16 #48673 by dimech

Replied by dimech on topic Robot using already existing servo amplifiers

they take the same data from the parport

parport.0.pin-BB-out goes board1 pin1 and board2 pin1

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andypugh
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12 Jul 2014 06:34 #48675 by andypugh

Replied by andypugh on topic Robot using already existing servo amplifiers

dimech wrote:
they take the same data from the parport

parport.0.pin-BB-out goes board1 pin1 and board2 pin1

I would suggest that you should choose not to do that if it is possible to wire the other way.

You can have 2 sets of outputs, one for each board.

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dimech
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22 Jul 2014 19:03 - 22 Jul 2014 19:30 #49009 by dimech

Replied by dimech on topic Robot using already existing servo amplifiers

andypugh wrote:
I would suggest that you should choose not to do that if it is possible to wire the other way.

Unfortunately it is not possible I don't have enough parport pins for 2 set of 3.

I am confused with the self-driving mux. How the select pins participate on that?
(To avoid the confusion lets say select pin are the pins which select joint and address pins are the pins for muxes)
How am I going to open the select pin strategically?

Also strobe works at the rising edge. It cannot write the data with srobe 1 becomes 0.

I did some test with charge pump and worked not properly but motors moved. When I tried with the muxes nothing happens

Thank you!

Last edit: 22 Jul 2014 19:30 by dimech.

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andypugh
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22 Jul 2014 20:02 #49012 by andypugh

Replied by andypugh on topic Robot using already existing servo amplifiers

dimech wrote:

andypugh wrote:
I would suggest that you should choose not to do that if it is possible to wire the other way.

Unfortunately it is not possible I don't have enough parport pins for 2 set of 3.

A second parport is about $20, if you have a slot for one.

I am confused with the self-driving mux. How the select pins participate on that?

The mux outputs a 32 bit number. Some of those bits are separated out to drive the mux select pins. The values are chosen such that each output value sets the select pins to the address of the next value.
Because the inputs are read, then the output is written, and then the mux exits until the next thread invocation, this all works as a sequencer.

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dimech
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22 Jul 2014 20:12 - 22 Jul 2014 20:44 #49013 by dimech

Replied by dimech on topic Robot using already existing servo amplifiers

Ok now I see (or I think

) but do I have to make select channel pins following the pattern?

If you remember I also need a bit to open each channel. a multisw is enough?

I am sorry if my questions are stupid but I am new in this field and almost nothing is clear to me.

Last edit: 22 Jul 2014 20:44 by dimech.

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