LO DSP with 4 Axis Controller

Discussions and help on this commercial controller.

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LO DSP with 4 Axis Controller

Postby bdring » Sat Nov 26, 2011 2:11 am

I had to do a little work on my laser so I decided to install my new LightObject 2012 DSP controller. I wanted to get it to work with my 4 axis controller too.

The 2012 controller has a much simpler stepper driver interface. It has just three pins per axis. These are ....

DIR (Direction)
PUL (Pulse or Step)
DC5V

Just by looking at the pin names, I assumed it was designed to go into a transistor or optical isolater. These devices invert the signal. The pulse would go from +5V to ground and back.

The stepper drivers trigger on an edge so they would work either way, but timing issues on the DSP cause engravings to slowly walk off to one side if this is not right. The DSP has some options regarding rising/falling edge pulses, but these were not fixing the walking problem.

Fortunately I use a Schmitt trigger on my 4 axis, so that gave me some flexibility. The normal Schmitt trigger I use is a non inverting type. I selected this type for best compatibility with parallel ports, Arduinos, etc. The normal Schmitt trigger is inverting, so I bought I bought a few of those to test. It worked perfectly.

74HC14N Inverting
74HC7014 Non-Inverting

I can supply it either way now. Anyone with a 4 axis who needs to change it can get the 74HC14 from me for the cost of postage. It is a $0.40 part.
Bart
"If you didn't build it, you will never own it."
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Re: LO DSP with 4 Axis Controller

Postby dwessels » Sun Nov 27, 2011 6:37 am

Hey Bart,

Good to head that you are using the two together. That is what I have been using. I am using the 4 axis board without changing the trigger.

I think I would like to change it to match what you have. What did you connect the DC5V pins to on the controller?

Thanks
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Re: LO DSP with 4 Axis Controller

Postby dwessels » Sun Nov 27, 2011 6:42 am

bdring wrote:I can supply it either way now. Anyone with a 4 axis who needs to change it can get the 74HC14 from me for the cost of postage. It is a $0.40 part.


Bart,

I had ordered these and already have them:
http://search.digikey.com/scripts/DkSea ... 02-5-ND%09

Would these work as the replacement to work with the 2012 DSP?

Thanks
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Re: LO DSP with 4 Axis Controller

Postby bdring » Sun Nov 27, 2011 2:05 pm

@dwessels

I did not hook hook DC5V to anything. The only ground they share right now is at the 24V power supply.

I started with the non inverting trigger and things appeared to work fine, but I was having the classic walking problem.

angle.JPG
angle.JPG (23.83 KiB) Viewed 10795 times


I tried modifying the pulse edge setting under Manufacturers Parameters, but it did not go away. It might only affect the step signal. It looks like the problem is due to the timing of the direction change. The direction might change before the last step because I was triggering on the wrong side of the pulse.

mfg_params.jpg


The 74HC14 did the trick.
Bart
"If you didn't build it, you will never own it."
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Re: LO DSP with 4 Axis Controller

Postby bdring » Sun Nov 27, 2011 3:52 pm

Here is a schematic of they way I have it. I have the water switch and E stop in the loop to stop the laser power supply. I think there is a way for the LO DSP to know about that, so if the laser is not firing, the display would tell you if it is due to the water switch. I do not have that setup yet.

http://www.buildlog.net/cnc_laser/erp/g ... ber=D32018
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Re: LO DSP with 4 Axis Controller

Postby Engineerable » Mon Dec 05, 2011 5:01 am

Thanks! I was having the same problem using the 2012 DSP and the Laser Interface/Driver PCB. I didn't have a 74HC14, but I was able to find a 74HC04, which has the same functionality, without the Schmitt trigger. Appears to work fine.

Now, just need to resolve other issues with the DSP. The pause button stopped working. Now if I press pause during a run, most of the time nothing happens. Sometimes the laser will stop, jump to a new position, and start going again (having lost it's absolute position), and needs to be reset.

Then there's the laser firing on shut down problem of course.
http://TakeAparts.com - Post and view tear downs of stuff.
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Re: LO DSP with 4 Axis Controller

Postby SScnc » Tue Dec 06, 2011 12:52 am

I was happy to find the schematic Bart posted as I expect to order the interface/driver very soon, thanks for posting it. When you guys refer to the "flow switch", what exactly are you talking about ? Is it the switch (relay) that the microcontroller monitoring the flow sensor activates, or is it one of the simple sensors with a reed switch ? Or both ?
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