Pico systems closed loop servo boards.....

[pete from TN]

Just got done reading an article in the Digital machinist magazine I have been getting and noticed a small ad at the bottom of the page touting a true closed loop board that uses Gecko drives somehow. Checked their website and it has a gecko board that uses some other board and allows closed loop. IS this true and is anyone here using this system on their machine?

It says in the ad that the system will maintain dro control even when the geckos are powered down. Sounds real cool and the board is only about $100.00 . Do you need to use the other board or can you just use this with an existing breakout board like my C11g? Any and all information on this would be most appreciated...peace

[Bubba]

Pete,
John makes interfaces for EMC!

From his page listing the board your referring to:
"Pico Systems has developed several products to interface the EMC motion-control program to motor drivers"

Sorry bout that!

[pete from TN]

Did not see that it was only for emc.... Sounds like Jon has to get his act together and work on a system that will run with MAch3.... Would not know the first thing about Linux or emc.... '


HEY BUBBA!!! hows it going man..... I have been out in the shop working on the enclosure and beleive it or not it is starting to look like a control unit. I got the Vector drive mounted, the fan mounted and ported and I am now working on all the little fuse mounts and switch mounts.

I ordered a female 110vac socket for the control unit and a fuse holder and bought a power switch at the shack yesterday. I also ordered a bunch of shrink wrap, some buss blocks, a cool new wire stripper that I used at Bills that I just had to have and a few other odds and ends. Should be here mid week I suppose. I am cutting all the holes for everything I have here and what I can from the specs on the net for each particular connection point and I am hoping to get this bad boy painted tonight. Then I maybe can insert the control board inside and start to permanently wire everything tomorrow and over the next week. I still gotta debug my darn computer and I am thinking I will wipe out all the harddrives and reload windoze and start with a fresh load without all the crap from the internet and my kids programs and all... I was also thinking about your saying that you mounted the control unit on the back of the machine and I had an idea that I might mount it to the wall behind the machine since my mill is on a large welded rolling stand I made when I bought the machine. That way I do not have to make such a large enclosure which will maybe save me a few pennies... What say ye? peace

[Bubba]

Pete,
Been hanging in there trying to stay cool. Darn HI is above 100 so am staying in the AC!!!

As far as: "Sounds like Jon has to get his act together and work on a system that will run with MAch3.... Would not know the first thing about Linux or emc.... '", He MIGHT say you should get your act together and jump on the EMC bandwagon

There is a lot to be said about both systems and I am NOT trying to start a flame war here. To each his own.

[pete from TN]

figured you would say that....haha...


I would think that if it can be done in one program it could be done in another.... no idea about how tho.... is Jon a member here? peace

[Bubba]

Yeh, I have seen several posts from Jon, but looks like he is busy on the EMC list this afternoon.

By the way, there is a board that I think Rogers Machine makes to do what you want.

[acondit]

Originally Posted by pete from TN I would think that if it can be done in one program it could be done in another.... no idea about how tho.... is Jon a member here? peace

Well, that would be a definite maybe. Mach was not designed as a real time controller. It is designed to work around some of the deficiencies of Windows (I am only talking about deficiencies related to real time control). So, if someone had access to the source code of both Mach and Windows, it might be possible to solve the real-time access problems.

EMC2 was designed from the ground up to be real time control software. It runs on version of Linux that has had the kernel modified to provide real-time access. Even so, some hardware grabs the processor and doesn't play nice, so that EMC2 won't run well on that hardware.

Alan

[skullworks]

A very popular card with the EMC2 crowd is the Mesa systems 7i43 Anything I/O card.

Well it appears it has caught the attention of the Mach developers... This $99 card can do stepgen as fast as the smoothstepper AND take back encoder position.

You are still at the mercy of the G320/340 internal fixed +/- 128 count following error - but they might be able to trip an E-Stop before it gets that far.

Eventually I figure they will write code to use this card for rigid tapping to.

A from the EMC2 camp.

[jmelson]

Originally Posted by skullworks A very popular card with the EMC2 crowd is the Mesa systems 7i43 Anything I/O card. Well it appears it has caught the attention of the Mach developers... This $99 card can do stepgen as fast as the smoothstepper AND take back encoder position. You are still at the mercy of the G320/340 internal fixed +/- 128 count following error - but they might be able to trip an E-Stop before it gets that far. Eventually I figure they will write code to use this card for rigid tapping to.

Of course, EMC2 has had rigid tapping for over 2 years, now. I also have a board that interfaces through the parallel port and support up to 4 axes, and also has digital I/O for limit and home switches, home to index pulse, and can do either step/direction or PWM for a digital servo amp.
It is not as cheap as the Mesa, but you don't need a bunch of breakout boards, adaptors and connector panels with it.

Jon

[jmelson]

Originally Posted by pete from TN Just got done reading an article in the Digital machinist magazine I have been getting and noticed a small ad at the bottom of the page touting a true closed loop board that uses Gecko drives somehow. Checked their website and it has a gecko board that uses some other board and allows closed loop. IS this true and is anyone here using this system on their machine? It says in the ad that the system will maintain dro control even when the geckos are powered down. Sounds real cool and the board is only about $100.00 . Do you need to use the other board or can you just use this with an existing breakout board like my C11g? Any and all information on this would be most appreciated...peace

No, you need BOTH the Universal Stepper Controller (USC) and the Gecko interface. If you already have the Gecko servo drives, it is a good solution to a number of problems. If you don't already have the Gecko drives, then it is cheaper to use my own servo drives.

The Gecko interface is designed to copy the encoder signals, via opto-isolators, to both the Gecko 320 and the USC. if you want to use this with steppers, there is no reason to use the Gecko interface. You put encoders on your motors and connect directly to the USC. You can flip a switch (on a per-axis basis) to convert each axis from open-loop (board counts step pulses) to closed-loop, using the encoder.

For the most part, none of this is designed to work with Mach or other breakout boards. In theory, if you had Mach set up to read encoders, the Gecko interface could be used to copy the encoder signals to the computer and Gecko 320 drives. I don't know if anyone has done this, but it should work.

Just to be complete, here's what the Gecko interface does :

1) provide power to the encoders all the time.

2) encoder signals come directly out to be sent to USC or computer.

3) copy encoder signals with opto-isolation for the Gecko 320 servo drive

4) power up and then reset geckos for one second when enable command is given

5) If any Gecko faults, power all Geckos off, connect to braking resistor to safely decelerate motors and light an LED to indicate which drive caused the fault. Signal the computer a fault has occurred.

6) When powering the Geckos on, the voltage is ramped up gradually to avoid current surges.

Jon

[HimyKabibble]

Originally Posted by pete from TN Just got done reading an article in the Digital machinist magazine I have been getting and noticed a small ad at the bottom of the page touting a true closed loop board that uses Gecko drives somehow. Checked their website and it has a gecko board that uses some other board and allows closed loop. IS this true and is anyone here using this system on their machine? It says in the ad that the system will maintain dro control even when the geckos are powered down. Sounds real cool and the board is only about $100.00 . Do you need to use the other board or can you just use this with an existing breakout board like my C11g? Any and all information on this would be most appreciated...peace

Pete,

That board, by itself, does nothing like what you describe. It does little more than buffer the encoder signals, keep the encoders powered even when the Geckos are turned off, and causes a fault on any one Gecko to shut them all down and E-Stop the controller software.

I truly do not understand the fascination people have with the whole concept of "closed loop" on a stepper controller. If you design a stepper based system correctly, and operate it within it's capabilities, closed loop is totally unnecessary. Lost steps are a result of poor design and/or improper operation. Period. No controller is going to be able correct a badly designed or badly operated stepper system on-the-fly without resorting to servo-like control algorithms. And if you're going to do that, simply use servos in the first place!

Regards,
Ray L.

[pete from TN]

I am using servos.... I have read a few things from mariss on the net concerning the gecko drives and in a nutshell you are right about the idea that if you run a system the way it was designed you should not need a closed loop and the G320's have a counter that internally monitors position and faults if there is a problem. There is a certain amount of allowance for that and for most things that would be just fine. However if you are really trying to get every ounce accuracy out of your machine would it not make sense to try to close the loop and get positional information fed back to the thing that is running the whole show in the first place? I have had a few conversations with a fellow that uses one of these closed loop setups that was custom made for a small high precision cnc router and he said he is very happy with it. He also said that he nearly never has to reset his position since the machine even remembers it's position when not in use. The idea that the encoders track things even when the geckos are off is pretty cool I think and should make for a more accurate machine I would guess...

Rigid tapping is also a very cool feature and I would love to see a homebuilt machine do it. I intended to buy a tapping head or possibly the tormach compression system. I know that Hoss was able to do it with his freak somehow, I want to be able to do that at some point as well.. What say ye? peace