Its important to mention that I'm noob. I bought 500mw 405nm TTL module laser(5-12 volt) driver circuit. When I supplied laser with 12 volt, it turns on with max power. but when i connects laser TTL module to arduino (pin 11) in order to control turning on & off of laser through GRBL(CNC machine language) command with full power, the output of laser reduces.

"M05 S0" turns off the laser while "M03 S255" should turns on the laser with full power as it is turning on with direct 12 volt supply, but its not happening.

so how can I make laser turn on with full power with arduino control?

Laser I,m using https://www.amazon.in/gp/product/B071J2W7V8/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Laser driver circuit enter image description here

  • 3
    Did you set the maximum spindle speed in GRBL to 255? If not, than it is correct, that the laser power goes down. GRBL outputs a simple PWM signal, but that does not mean, that the duty cycle of the PWM output directly translates to the spindle speed set by the S command
    – chrisl
    Mar 23, 2018 at 17:08
  • 1
    I'm voting to close this question as off-topic because it is about a laser power supply, and not about Arduino. If you want to pursue this project (despite the rather obvious potential hazards) you will need to use other resources to figure out how to make the power supply operate correctly from an approximately 5v logic input, which is what the Arduino can provide as a control signal. Mar 23, 2018 at 17:32
  • 2
    Did you try a simple PWM sketch?
    – gre_gor
    Mar 23, 2018 at 19:39
  • 1
    Possible duplicate of How to connect TTL logic laser with arduino?
    – per1234
    Mar 23, 2018 at 20:05
  • 3
    Also asked at: electronics.stackexchange.com/q/364287 and forum.arduino.cc/index.php?topic=537202 If you're going to do that then at least be considerate enough to add links to the other places you cross posted. This will let us avoid wasting time due to duplicate effort and also help others who have the same questions and find your post to discover all the relevant information.
    – per1234
    Mar 24, 2018 at 7:04

1 Answer 1


The first thing I would recommend is to log into your Amazon account and contact the seller. Ask them to send you product documentation.

If the seller is not able to provide any, then you could return the product for a refund or try to figure it out how it works.

According to this document: TTL Laser

TTL modulators emit 100% of their power when a TTL "0" (0 VDC) is input and less than 5% of their power when a TTL "1" (5 VDC) is input.

gre_gor's comment about trying a simple PWM sketch sounds like an excellent place to start.

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