Question: 15W Blue Laser Module PWM settings

[rjsavell]

I just bought a 15W LED 445-450nm LED laser module from eBay:

“High Power 15W 15000mw Blue Laser Head Diode Engraving Module For Engraver”

There are no instruction at all included but I have it setup and working. I am just not sure how high the PWM can be set. The only information from the seller is:

Output Power: pulse 15W average 8W
Modulation frequency: ttl can be modulated

Does anyone have one of these and know if you must keep the PWM duty cycle < 53% (8 watts out of the maximum of 15 watts) or if the laser module manages the power level to keep it at or below 8 watts and you need to run it at a 100% duty cycle for full power?

So far running it at 50% seems only slightly more powerful than my 2.5W LED laser :-(

Thanks so much!

Randy

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[kentavv]

I don't have this exact module, but a similar (no documentation) module that I received was not well suited for controlling power by PWM. It's been a while and I don't remember the explanation, but I decide that for true power control I would need to get one of the analog input modules. I think the problem was that the module took a while (relative to the PWM signal) to stabilize. Regarding the power level at different PWM settings, have you measured the current draw while running at 50 and 100%? Mine is not linear. As I'm sure you are aware, many of the higher output modules are over driven and may not last a long time. Hope this was at least of a small amount of value, as it was only my experience with a different module. Best wishes

[dharmic]

Ditto. Does that PCB say "PWM" anywhere? If not, I'm guessing that third line on the lead is an enable, not a modulation input. Fine for switching laser on and off as a mirror scans during a lightshow, no good for controlling output power.

Other clues: goes great at 100% ie DC high input signal.

Here's a guess...
- Higher power laser modules usually have a main lasing junction and some kind of on-die thermal measurement. There's usually three legs on the back of them.
- A decent driver will have three or four leads to the diode: power for the laser, and temperature feedback. It will self regulate, throttling back the diode current if it gets too hot.
- This driver looks like a cheap, nasty constant current unit. They will have set it at the factory to put out 8W worth of current into the diode and it will keep doing that whenever its on.

Your "full power" input on that unit is likely to be 8W output, your half power will be half the current of that 8W which is probably getting so close to your 2.5W that you won't notice a difference.

Run it at full power, see how she chooches.

[rjsavell]

Wildcat and Dharmic, thanks for the great input. I'll check the current (wattage) and run some tests and see what she does.

Just for the record I have asked the seller about this multiple times over the past 2 weeks and have still not received any useful info. I guess you get what you pay for...

Thanks Again!

[rjsavell]

To follow up, I setup a volt meter and an amp meter on the laser and it reaches 8W, 4.0 volts @ 2.0 amps with the PWM set to 65%, where 50% was around 4.0 watts. I could probably run it higher but at that level it will engrave in tool steel and cut stained glass. Well I am not sure the cut is the most accurate term, perhaps causes the glass to fracture along the laser line states it better.

Thanks again for the help!

Randy

[brian257]

I ordered a smaller blue laser module, or perhaps the same, but rated smaller, from Banggood and should have it in about a week or so. Can you give some data as the the speeds you get engraving in steel or aluminum and what you can cut some various materials at?