pwm frequency (hz)

[soenlin]

so I can hit the test button on my laser psu and it fires the laser but the dsp does not want to fire it.

I am thinking the pwm frequency (hz) needs to be changed but not sure what number to use here.

It is set at 20000 by default but is there an easy way to tell what to set this at?

I am using.

Laser tube
http://www.lightobject.com/High-Quality ... P1028.aspx
Features
• Small beam spot (<=5mm)
• Low beam divergence.
• Low threshold current (4.5mA)
• Better laser head design
• Ceramic high voltage wire jacket
• Stable output

Specification
• Power: 80W (100W peak)
• Triggering Voltage: 28KV
• Operating Voltage: 22KV
• Current: 26~28mA (Recommned 26mA and under)
• Life Span: 2,500 hours at 26mA or below
• Overall length: 1350mm or 53inches
• Diameter: 80mm or 3.15inches
• Water Cooling
• Water Cooling: Water compressor chiller is required
• Water temperature: 20~25'C (68~77'F).
• Warranty: 6 months

Laser psu

80W 80Watt Tube Laser Power Supply PSU DIY CO2 laser engraving cutting machine
http://www.ebay.com/itm/80W-80Watt-Tube ... 058797978?
model hy-t80-110v
201603032058
● Specially designed for 80w laser tubes
● Easy Control: The start and stop of laser can be easily controlled by TTL level.
● TTL signal indication, water Through signal indication and laser output indication.
● Application: Sculpture and cut acrylic, fabric, double color sheet and rubber, etc
Type T80
Input Voltage AC220V or AC110V（to be specified when placing order）
AC frequency 47—440HZ
Max Input Power 550W
Max Input Current 3A
Max Output Voltage DC 40KV
Max Output Current DC 28MA
Efficiency ≥90﹪（full load）
Mean Time Between Failure (MTBF) ≥10000H
Response Speed ≤1ms（from the switch Signal is given to the output current up to 90% of the setting current）
Pressure-proof Input-Output, Input-Shell: AC1500V 10MA 60S; Output negative is connected with machine shell.
Environmental Operating Temperature：-10~40℃，Relative Humidity (RH)：≤90﹪
Cooling Way Force-Air Cooling (FAC)
Dimension L×W×H=280*173*97(mm)

[Techgraphix]

If you can't fire the laser from your DSP, either manual by pressing the Laser button on your display Or va the program loaded in the memory, there is something wrong with your wiring or settings
Do you get any message on the display, like "idle" or Water Protect etc?
Don't know what kind of controller you use, but mine (LO-X7) has two laseroutputs. Although i only have one laser attached i have to shortcircuit the WaterProtect wire to GND for both LaserOutputs.
If a doorswitch or emergencyswitch is set OR it is programmed wrong in the controller, the laser will not fire anyway..
I did some tests in the past with the frequency but i could not notice any difference from 10.000 to 50.000 so i set it back to 20.000

Kees

[soenlin]

using an x7 http://www.lightobject.com/X7-DSP-Contr ... -P940.aspx

I don’t see any messages of idle or water protection when I try to cut the duck or a 50 x 50 mm box. Machine moves around but laser does not fire.

I also only have 1 laser so I will go into laser 2 and make sure that the water pump / open connection / foot pedal are all closed.

Laser two has no wires in it at this time so I may have to look at that and see if there is anything wrong in settings. ( I have not yet called for tech support) just trying to get as much done as I can before I bother lightobject.

Thanks,
brad

[soenlin]

http://www.lightobject.com/Water-flow-p ... -P815.aspx

So I found that my water flow sensor is not triggering. if I hook the two wires together and bypass the sensor my laser fires with laser button on dsp or when program runs.

I need to try to tighten down the screw on the top and see if that lets the laser run.

[triumphstephen]

Hi Guys,
Jumping in here to see if you have any info on my problem which I am thinking may have to do with the pwm frequency setting.
Like yours, mine defaults at 20K. In the manual it says the range is between 20K and 80K (LO-X7 manual page 21). It also says that if the setting is too low it will lead to unbalanced power with "Heavy Point" appearing during processing.

I am trying to engrave a large piece of acrylic which is mostly solid fill with dots here and there. The power level is the same for the whole piece.

I am getting "stripes" so to speak

running left to right (X direction) that are maybe around 5-8mm wide in the Y direction. Every once in a while it will engrave a much deeper line for one and up to a few passes then settle down again (can't see in in this photo), but it still gives me the "change in power level" every few mm. Obviously it doesn't have to do with the closeness of the laser to the lens otherwise it would be changing in the other direction.

I'm thinking that my pwm frequency setting is too low. The question is; "what is the correct setting?" Does the power supply care or is there an optimum setting for each particular brand of power supply and if so where do you find the information?

Has anyone had this problem or know the answer?

-SF

[Techgraphix]

So I found that my water flow sensor is not triggering.

Did you hook up this flowswitch to the HSP-supply instead of the controller??
IMHO is connecting this switch to one of the LASER-connectors of the controller the best way ( i have written that quite a few times here): You will get the appropriate message on your display. At least, that should be..
On the HSP-supply, you should connect the WP to GND in that case..
Kees

[Techgraphix]

Jumping in here

Hi Stephen,
It's better to start your own topic as this problem is somewhat different from soenlin's.
but for this time:
I see some banding too (vertical stripes)..
The horizontal striping can be a instable tube.. I had that with an old dieing tube.. After i placed a new tube this problem was gone.
It can also be some interpolation effect when your scanlines are close to the step-resolution of your Y-stepper..
You might use the next trick to get a more equal surface:
Open your picture (with the dots) in Photoshop or a similar program. If you use a scangap of 0.08 (~316dpi) set the picture size to the right dimensions with a resolution of this 316 dpi. Adjust de levels from 0-255 to 64-255. convert to Black/white (1 bit) with a dithering you like (Floyd-steinberg for instance). Instead of an equal picture you will get a lot of dots.. The result, when lasered, will be a much more even surface.. Maybe even your horizontal stripes will be gone??

I tested about all PWM frequency's but i didn't experienced any difference at all.. All engraved parts where exactly the same crips and equal..

Kees

[triumphstephen]

Hi Kees,

Thanks for the information.

It is possible it is a tube on the way out. This one came as a spare when I bought the machine. It is a good quality tube but I don't know how old it is. I just changed it out a month or so ago when my first tube fried due to cooling failure so it doesn't have much time on it but the age may be the problem. Any insight on that is really appreciated.

I did as you suggested and it makes a big difference but still not perfect. I just am not sure what the de levels are you referred to. Where do I find those settings?

This came to me as a .ai file and I use Corel x7. I converted it to a bitmap then to black and white inside Photo-Paint at the resolution you suggested.
I am still playing with settings as it is a little too dense for the client's requirements.

I am assuming that if I change the dpi of the image, i have to change the scan gap to match as well as the dpi setting in Raycam?

I will remember to start a new topic next time.

Thanks,

-SF

[SWMS]

To wade in here with the PWM...

Roughly speaking without diagrams...

If you divide 1 by your PWM frequency that will tell you the time in seconds of one pulse of the laser (that's on)

If you set your laser power at 60% the laser fires for 60% of the pulse

So to take this to the extreme. If you had a PWM of 1, the laser would fire for one second. If you chose 60% power it would fire for 60% of 1 second. On a moving laser you'd end up with a dotted line and a burnt surface if the laser head was moving slow enough.

Take that to the extreme the other way and you get a nice smooth line but not so much power.

When The PWM is 20000 one pulse is 0.00005 seconds so the difference between 20000 and 30000 to the human eye will be negligible.

At least that's how I understand it.

Nice explanation here.

http://donsthings.blogspot.co.uk/2016/1 ... l.html?m=1

[Techgraphix]

I just am not sure what the de levels are you referred to. Where do I find those settings?

In Photoshop this is called "levels" and looks like this:

Clip0002.jpg (34.46 KiB) Viewed 3201 times

What do you see there? I filled a plane with a black to white gradiënt, selected the lower part and made 100% black a kid of gray (64/255)
As you can see the black isn't real black anymore..
When i convert this to gray-scale and to Bitmap with dithering you will see that the Black on the left side stays black but the adjusted level becomes a dotted pattern:

Clip0003.jpg (9.76 KiB) Viewed 3201 times

In that way the laser has to start and stop every time at a more-or-less randomly frequency.. This will reduce vertical banding significantly..

Kees