Non-powered "spindles"

jhllt67
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Joined: Fri May 04, 2012 1:57 am

Re: Non-powered "spindles"

Post by jhllt67 » Sun May 06, 2012 6:56 pm

Ok, I got the machine back together enough to take some pics.
0506121431.jpg
Laser diode and driver mounted to the Z axis
0506121431.jpg (135.39 KiB) Viewed 2327 times
0506121431a.jpg
Closeup of the LM338 based driver board
0506121431a.jpg (155.24 KiB) Viewed 2327 times
0506121434.jpg
The laser assembly with heat sink and fan.
0506121434.jpg (158.49 KiB) Viewed 2327 times
Excuse the image quality, had to use my phone.

jhllt67
Posts: 47
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Re: Non-powered "spindles"

Post by jhllt67 » Sun May 06, 2012 6:58 pm

Also here are a couple of test cuts I made.
0506121436.jpg
1/16" basswood on the left, 1/8" plywood (cut with multiple passes) on the right.
0506121436.jpg (143.1 KiB) Viewed 2327 times

pourcirm
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Re: Non-powered "spindles"

Post by pourcirm » Sun May 06, 2012 7:22 pm

That looks great for a homemade laser solution.

Can you post more details about your setup? It'd be great to see a schematic of the driver and how you wired everything up. I know I linked to a few earlier, but seeing the results you got it'd be nice to reconstruct a proven system. Are you using the laser diode you linked to on eBay?

- Ryan

jhllt67
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Re: Non-powered "spindles"

Post by jhllt67 » Sun May 06, 2012 9:31 pm

Thanks.
I am using that diode I linked along with this
http://www.ebay.com/itm/360412944068?ss ... 1497.l2649
and a small heat sink and fan from Jameco.

I whipped up a quick schematic of the driver.
CCdriver.png
CCdriver.png (7.91 KiB) Viewed 2323 times
Its not pretty but it is functional and fairly rugged.

It has current adjustment from .5 to 1.8 amps but most of the range of the pot is wasted. A 5 ohm pot would be perfect but I wasn't able to find one of those.

You will need a heat sink for the LM338 because it will be dissipating a lot of power (over 10 watts if you are running 12V). The resistors also need to be beefy.

pourcirm
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Re: Non-powered "spindles"

Post by pourcirm » Sun May 06, 2012 11:52 pm

Thanks for the schematic. Out of curiosity how do you control the laser's state? Obviously you need to turn it on and off for cuts. I was thinking a relay from an arduino running Grbl should be able to handle the 12 volts the driver uses?

jhllt67
Posts: 47
Joined: Fri May 04, 2012 1:57 am

Re: Non-powered "spindles"

Post by jhllt67 » Mon May 07, 2012 12:10 am

So far I haven't been turning it off. I just set the G0 speed high enough that it doesn't have time to cut (still leaves a very fine line).

I have been working on adding software control but I haven't perfected it yet. I just started experimenting with a mosfet on the ground coming back from the diode. A relay would probably work as well but I've been trying to keep everything solid state. Plus there could be a very large number of on/off cycles when doing something like laser engraving that would really cut down on a relays life.

pourcirm
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Re: Non-powered "spindles"

Post by pourcirm » Mon May 07, 2012 6:26 am

The mosfet is probably a better idea now that you've brought it to my attention. Relays can get rather expensive and using it rapidly over long cutting times can't help the life expectancy.

I've been working on a CNC/3D printing capable driver based around an ATMEGA chip and I'm thinking the mosfet system I'm using there might work. It's based on a bunch of different 3D printing platforms and how they manage when the heaters, fans, etc are on. Basically your 12 volt supply comes in straight to the + pin of the "attachement" and then the ground is routed back through a mosfet and some resistors to both a ground point and a digital pin on the controller which can control when the system switches states. The attached picture probably shows what I'm talking about better. The resistor values may not be right for this application and the mosfet may need to be changed, but it should show the basic diagram at least.
lasercontrol.png
Laser Control
lasercontrol.png (10.02 KiB) Viewed 2301 times
Did you design this laser driver circuit or find it somewhere else? I ask because most of the ones I've found have quite a few less resistors and actually place the pot on the LM's adjust pin rather than the out pin. I'm just trying to find the best driver and I'm curious if there are benefits in wiring everything one way or the other.

- Ryan

JCPhlux
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Re: Non-powered "spindles"

Post by JCPhlux » Mon May 07, 2012 7:16 pm

What if you put a switch on the z axis like an end stop to turn the laser on and off. raise the laser and it is off lower it and it turns on.
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Enraged
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Re: Non-powered "spindles"

Post by Enraged » Mon May 07, 2012 8:28 pm

JCPhlux wrote:What if you put a switch on the z axis like an end stop to turn the laser on and off. raise the laser and it is off lower it and it turns on.
ha, that's so simple, yet brilliant. Good idea!

JCPhlux
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Re: Non-powered "spindles"

Post by JCPhlux » Tue May 08, 2012 1:05 am

Enraged wrote:ha, that's so simple, yet brilliant. Good idea!
Every now and then I have a good idea.
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John R Cutburth II
Twitter @JohnCutburth

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