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Is this an acceptable way to drive a Laser Diode?
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Psi:

--- Quote from: StillTrying on June 03, 2019, 09:15:18 pm ---Could the PWM frequency be aliasing with the regs switching frequency.

--- End quote ---

yeah, that would definitely cause power fluctuations like he is seeing.
wholder:
That makes sense.  I hooked the module up to 12V DC using my bench power supply and the total draw is about 130-150 mA, which a about 2 Watts.  I'm guessing that a lot of the power is being consumed by the circuit and I have no idea what the typical conversion efficiency is for a blue laser diode.  It was sold as a 300 mW laser, but I think that's suspect, as I have another laser engraver with a 500 mW laser (at least that's what the label on the module says) that puts out significantly more power.

So, I'm thinking I should just replace the laser with something designed for TTL control and that can run at 12 volts.  Anyone have any suggestions for a good replacement module in a cylindrical case that will fit (diameter is 12 mm) in the existing holder?

Wayne
ptricks:
I used a 5 watt laser on an engraver and use an sxd driver.
You can put the driver in the case but I don't recommend it because the driver generates heat and the diode does as well so you would be using a heat sink for the driver that gets hot.
The go to for most people is the SXD drivers , search on ebay for  SXD Laser Driver
VE2UM:
...Also, have the switching transistor / MOSFET connected in PARALLEL with the Laser diode.

Energetically, this is less efficient, since current is always on, but, the MOSFET will short-out the Laser diode to 0v when switched on. and let the resistor reapply bias to the laser when turned-off, reducing Laser overvoltage to nearly zero.

This method also works for constant-current supplies. The only difference being that the MOSFET must be ON before turning-on the CC supply to protect the laser diode.
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