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Author Topic: Pendant  (Read 4003 times)

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Pendant
« on: January 21, 2011, 11:53:20 PM »
Ok, the obvious cheap easy pendant is a USB numeric keypad. 

HOWEVER... it might be nice to have something like the MPG pendants with a dial handle, but I think they do it backwards.  Why not something like that, but generating keyboard scan codes via USB rather than taking up an LPT port on the machine.  Seems like a more elegant solution. 

Re: Pendant
« Reply #1 on: January 22, 2011, 04:32:55 AM »
Keyboard response is pretty sluggish compared to a parallel port. You are going through all sorts of layers of code before it gets to where you want. Thats one of the reasons cheap USB IO devices are not used for things like limits and home switches. Latency sucks.

Offline Greolt

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Re: Pendant
« Reply #2 on: January 22, 2011, 03:42:08 PM »
Have you tried an MPG via Pokeys USB?

You might be a bit surprised how well it responds.

Greg

Offline Hood

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Re: Pendant
« Reply #3 on: January 22, 2011, 03:52:56 PM »
Greg, does it now work in Velocity mode? I dont have the PoKeys set up now but I could never get the MPG to act like it should when in Velocity mode, it was fine in Step mode and I know Scott tried hard to get Velocity working and maybe he eventually managed.
Hood
Re: Pendant
« Reply #4 on: January 22, 2011, 04:37:38 PM »
I was thinking a simple device capable of generating programmable keyboard scan codes could do the trick and I don't think response of a mnaul device is all that critical if using it for manul moves for positioning.  Now it you are a virtuoso doing freehand carving via pendant it could be a whole-nuther story.  LOL. 

Just program it to match the same keys you use for manual control at the keyboard. 

Offline Hood

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Re: Pendant
« Reply #5 on: January 22, 2011, 04:44:14 PM »
The response is critical if using the MPG for jogging, you need the axis to stop the instant you stop winding. Nothing more scary than coming up fast on a part, stop winding and the axis continues for a short time  ;)

Hood
Re: Pendant
« Reply #6 on: January 22, 2011, 04:51:09 PM »
Hmmm..... i was thinking a little differently.  If you are in step mode, why hot have rotating the jog wheel generate the same keyboard scan code as you are using to step.  Or are you saying even if you do it this way Mach can't keep up with the keyboard buffer? 

Offline Hood

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Re: Pendant
« Reply #7 on: January 22, 2011, 05:09:55 PM »
Step mode is different, I use the MPG in two modes, first I use it in Velocity mode for general jogging of an axis and when I get close to the place I want I switch to multi step mode (rotary switch on console) and sneak up on the part. It works well via the PP and the SS but only the step mode worked well with the PoKeys, I have not tried any other method of connecting a MPG to Mach.

Having said that multistep mode can still catch you unawares, for example if you have a large step value set and wind fast then the axis will continue long after you stop as physically the axis cant keep up with the speed you wind. I only ever use 0.01mm steps when in multi step mode. My switch has positions for Velocity,  0.01, 0.1 and 1mm but have found I only ever use Velocity and 0.01 multistep.

Suppose all this doesnt really relate to what you are wanting but its worth keeping it in the back of your mind if you do build something.
Hood
Re: Pendant
« Reply #8 on: January 22, 2011, 06:48:11 PM »
Well.... actually....  There are some really neat programmable game pads out there that you can program macros into and all kinds of stuff.  Some of the more serious RPG players use them.