Downdraft design questions

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09 Nov 2020 23:17 #188824 by txtrone
Replied by txtrone on topic Downdraft design questions

Next step is to connect each trigger pin to a real output pin. (Remember what I said about diodes). I generally would do it like this:
net zone0 <= ddraft4x2.0.trigger-0
net zone0 =>  hm2_7i76e.0.7i76.0.0.output-00


I got it loaded and when I jog around the 'table' (simulated only since I have nothing connected to my Mesa card yet) the pins change as I moved from section to section. That's good stuff!

Refresh my memory, should I use some LEDs on the Mesa card to prove that the outputs are firing the same as the pins in the HAL confifuration?

Also, where does the is 'net zone' code belong? Is that the example code for zone 0 only? Should it look like this when I am finished?
net zone0 <= ddraft4x2.0.trigger-0
net zone0 =>  hm2_7i76e.0.7i76.0.0.output-00
net zone1 <= ddraft4x2.0.trigger-1
net zone1 =>  hm2_7i76e.0.7i76.0.0.output-01
net zone2 <= ddraft4x2.0.trigger-2
net zone2 =>  hm2_7i76e.0.7i76.0.0.output-02
net zone3 <= ddraft4x2.0.trigger-3
net zone3 =>  hm2_7i76e.0.7i76.0.0.output-03
net zone4 <= ddraft4x2.0.trigger-4
net zone4 =>  hm2_7i76e.0.7i76.0.0.output-04
net zone5 <= ddraft4x2.0.trigger-5
net zone5 =>  hm2_7i76e.0.7i76.0.0.output-05
net zone6 <= ddraft4x2.0.trigger-6
net zone6 =>  hm2_7i76e.0.7i76.0.0.output-06
net zone7 <= ddraft4x2.0.trigger-7
net zone7 =>  hm2_7i76e.0.7i76.0.0.output-07

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10 Nov 2020 01:25 #188832 by rodw
Replied by rodw on topic Downdraft design questions
That was painless!

That looks right. Yes, I only did one example! The outputs may need to be different as you might already be using a pin for torch on or something.

If you upgrade linuxcnc, you may need to redo the halcompile step as the component is not native to linuxcnc.

There is also a separate zone pin that publishes a numeric number for the current zone. If you were ambitious you could modify your GUI to display the number from that pin. Or add a row of GUI LED's for each zone.

Very cool. Can't wait to see how it works for you!

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10 Nov 2020 02:28 #188833 by rodw
Replied by rodw on topic Downdraft design questions

Refresh my memory, should I use some LEDs on the Mesa card to prove that the outputs are firing the same as the pins in the HAL confifuration?

Also, where does the is 'net zone' code belong? Is that the example code for zone 0 only? Should it look like this when I am finished?


I would keep all the connections in the ddraft4x2.hal file
I have used a 22mmm mount 24V LED light to confirm working but to use a LED you would need a 2.2k 1/2 W current limiting resistor

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10 Nov 2020 02:30 #188835 by rodw
Replied by rodw on topic Downdraft design questions
You could also confirm output operation just by jogging in to each zone and use a multimeter on the output

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10 Nov 2020 13:14 #188869 by txtrone
Replied by txtrone on topic Downdraft design questions

That was painless!


The pain is still coming, I have not yet connected anything to my Mesa card yet, just the card to the PC and a 5V power supply.

I got a small desktop 8U rack (last night) so I can start putting everything together for testing. Maybe this won't be as complex as I am imagining, no... I bet it will be.

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11 Nov 2020 21:55 #189049 by txtrone
Replied by txtrone on topic Downdraft design questions

This article suggests 3200-3600 CFM for a 4' x 4' table
www.hypertherm.com/learn/spark-the-blog/fume-control/
So for a table that size you would need a LOT of air. 16000 cfm.
Most commercial tables are zoned

Assuming you are going to use Linuxcnc's Plasmac, I would suggest you add an air activated shutter on each of the 8 outlets that is triggered based on the position of the x & y axis. You don't need seperate compartments to contain the air. Better that you don't
so by using 8 zones, you would reduce the air flow requirement to a much more reasonable 2000 CFM


Do you think either of these two fans would be up to the job?

www.grainger.com/product/DAYTON-7-1-2-HP...ressure-Blower-7D752

www.grainger.com/product/DAYTON-High-Pressure-Blower-7AV38

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11 Nov 2020 22:20 #189052 by txtrone
Replied by txtrone on topic Downdraft design questions
Working properly with the correct 5/2 valve. Thanks Rodw!

Added a speed controller (after this video was taken) and it was much smoother.

The following user(s) said Thank You: rodw, thefabricator03

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11 Nov 2020 23:04 #189061 by rodw
Replied by rodw on topic Downdraft design questions
This is gunna be an awesome experiment! I can't really advise on the fan size but I suspect either will do. You have a fairly small duct so perhaps the pressures will be higher...
The following user(s) said Thank You: txtrone

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11 Nov 2020 23:07 #189062 by rodw
Replied by rodw on topic Downdraft design questions
Also, you when you get it going, you could look at using an or2 component on zones 0 & 1, 2 & 3, 4 &5, 6 & 7 so both zones open together full width of your Z. but will need more fan output... BUt we can leave that for another day...

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11 Nov 2020 23:15 #189065 by txtrone
Replied by txtrone on topic Downdraft design questions

This is gunna be an awesome experiment! I can't really advise on the fan size but I suspect either will do. You have a fairly small duct so perhaps the pressures will be higher...


What would you go with? Direct drive 7.5HP open drip proof motor, or 5HP belt drive totally enclosed fan cooled? Performance wise they both have pros and cons, the belt drive does seem to have more 'torque' for lack of a better word, the CFM output falls more slowly that the direct drive. Somewhere between 5 and 6 in/SP the 5HP belt driven model passes the 7.5HP direct drive in CFM. I don't know if that makes a difference or not in my situation.

I am leaning toward the 5HP for some reason, normally I would be all about direct drive.

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