I have my hardware happily working and started to play with the Controller.app (and I have do admit I do not understand it yet).

At the beginning the gondola was moving at a reasonable speed, but suddenly, while setting the parameters for the machine, the movement got infinite slow and it does not matter what I try (reset EEPROM, upload the machine specs), I don't get the normal speed back. Here are my settings so far:
http://gontarczyk.org/gs/polargraph/polargraph-controller/

For example if I make a MOVE DIRECT, I see the command BUSY: C17,2028,2066,20,END.

C26 command gives:

0. 132
1. 3
2. 112
3. 3
4. 80
5. 71
6. 88
7. 88
8. 65
9. 66
10. 67
11. 68
12. 0
13. 0
14. 95
15. 0
16. 144
17. 1
18. 8
19. 0
PGNAME,PGXXABCD,END
PGSIZE,900,880,END
PGMMPERREV,95.00,END
PGSTEPSPERREV,400,END
PGSTEPMULTIPLIER,8,END
Executed basic.
READY_200

Any idea what I am doing wrong? Even after hours of trying I can't solve it.
g.

I suppose you've tried changing the maxspeed and the acceleration speed? Either by re-sending the values from the controller or by tweaking them through the touchscreen interface. Vector drawing ("draw direct") will always be slower than regular moves, but I've had at least one occasion when vector drawing suddenly turned slow. It moved, but almost imperceptibly, only a couple of motor steps a second.

I never got to the bottom of it, and I was busy trying to fix other things so I was never sure if it was a real problem or just a symptom of messing around. It went away after the next reload of the firmware - but the changes in the firmware did not contain any intentional changes to do with that side of things.

sn

I'm curious - could you try bumping the acceleration up high, 1500 or so? There is a link between the regular acceleration speed and the speed used for vector drawing, but it's always been a bit weird.

sn

Well that is kind of good news because it makes it clear that it's something to do with state rather than something broken.

Investigating sleep mode is a start though - I wonder if there's something being unset when it goes to sleep that doesn't get reset when it starts up again. I will start a proper bug hunt now I know it's not a one-off. Yes, there is a sleep mode 🙂 It cuts power to the motors after something like 10 minutes of inactivity - it raises the pen, then just lets go. It's because holding the pen in one place can lead to the motors heating up. They aren't going to catch fire or anything, but they could soften the plastic of the sprockets. Personally I like to raise the pen and then draw it into the centre at the end of a drawing, so that when the motor cuts out it doesn't whizz back uncontrolled.

In my experience, the oscillations that lead to hot motors have been to do with trying to hold the motors in a position in between steps while microstepping. When I first started using the microstepping drivers I had this, but it should never happen now - it should always finish and start on a full step. That's what the step multiplier is for - the controller supplies the position in full steps, but internally that value is multiplied by 8 (step multiplier) to make the movement smooth.

The other thing that leads to bad motor behaviour is having the current turned up too high on them. The little adjustment screw on the motor drivers themselves controls this, and putting it up too high (clockwise) makes the motors hot, noisy and angry - over-driven. They really snap from step to step rather than microstepping, but I can't imagine that that is your issue either.

I'm keen to sort this out, so if you manage to replicate the behaviour, please let me know what the trick is. I will do the same.

OK, roving: A verb, to rove, that is, to move around an area, somewhat autonomously. It probably isn't the best word to use, but in this case, it is used to describe a couple of features that involve configuring a particular area as "live" and telling the machine to restrict it's drawing to that area. There's couple of entries about it here on the site:
http://www.polargraph.co.uk/2012/08/polargraph-v1-2-vector-sprites-guide/
and
http://www.polargraph.co.uk/2012/08/norwegian-pixel/

If you can think of a better name, I'm open to suggestions 🙂

cheers!
sn

Hi Sandy,

After a busy week I am back in the game.

Finally my Polargraph is up and running, and beside this initial speed problem (which never happened again), the whole building of the machine was straight forward and hassle-free - even for a newbie. Again, thanks a lot for making public this project.

Two tiny questions remain:

a) At the moment I run my stepper with 8 Volts to avoid those oscillations, but after about an hour of drawing I measure up to 50 °C temperature for the stepper. For me this is a little bit high?

b) If I want to run the machine only with the polarshield, how do I set the home point?

So, I am not completely off. Maybe I put that thing on the balcony, we should have the coldest night of this winter. 😉

Okay, that home command will do, but I wonder if there is a particular reason why there is no home button on the Polarshield (except your time) or why it is not coupled with the "motors on" button?

I think I see your argument and maybe I just use the wrong name for what I want to do:

Without any connection to a PC I want to switch on the server (or I have to reset it when I put in a SD card), hold the gondola at the home position, press MOTOR ON which keeps the gondola in place and then I would press the HOME button to tell the server that the gondola is at the home position (like having the command in the file). Then I would choose a command file to draw.

The server anyway knows about the machine size or pen size or other parameters, why it can not know which are my home coordinates? So I would add them to the UPLOAD MACHINE SPECS command.

There are other discussions in the forum about using end switches to get some zero or home position, and this one would be just an easy manual approach.

Sure, your solution works as well, just this would add some extra comfort. 😉

g.