# Opt laser not responding to % power changes
**URL:** https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375
**Category:** 🔥 Laser
**Created:** [May 9, 2026, 8:15pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375 "2026-05-09T20:15:20Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@batr54](https://forum.sienci.com/u/batr54)
#### Post date: [May 9, 2026, 8:15pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/1 "2026-05-09T20:15:20Z")
checked d/c voltage out of pwm and only reads 0 . I have 1.61 gsender version and most updated firmware.
When move power slider nothing happens. If I place opt laser in test mode and run off opt controller interface I get correct % changes. Any hints? I have tried every configuration with spindle and laser and nothing seems to work. I have altmill 4x4 with spindle setup.
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### Author:  [@paullarson](https://forum.sienci.com/u/paullarson)
#### Post date: [May 9, 2026, 8:37pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/2 "2026-05-09T20:37:22Z")
you can check the output by measuring its voltage with a multimeter. You will get different results if you measure DC vs AC, but you can still tell.
The output is a PWM signal (Pulse Width Modulation). The signal ranges from about 0V to 5V. Off would be 0V and full on would be a steady voltage close to 5V. For intensities in between the signal will be a series of pulses. At low intensities the pulses will be more off than on (lower duty cycle) and at higher intensities the pulses will be more on than off (higher duty cycles). Off = 0V and on = ~5V.
Here’s an example of PWM.
[](https://forum.sienci.com/uploads/default/original/1X/e41853f08a3f900d13ec2a64695a348256ea462a.png "image")
[image1251×541 10.8 KB](https://forum.sienci.com/uploads/default/original/1X/e41853f08a3f900d13ec2a64695a348256ea462a.png "image")
I made the following measurements (note $31 in the table should be $30):
[](https://forum.sienci.com/uploads/default/original/1X/0223b916c97be2d4f740649574c8cb01d973586c.png "image")
[image1143×227 8.69 KB](https://forum.sienci.com/uploads/default/original/1X/0223b916c97be2d4f740649574c8cb01d973586c.png "image")
Essentially you are just looking for change on the outputs with a a change in power %. The GRBL “s” commands control the intensity as shown in the chart. In my case I have max spindle speed set to 1000 ($30=1000).
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### Author:  [@batr54](https://forum.sienci.com/u/batr54)
#### Post date: [May 9, 2026, 10:49pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/3 "2026-05-09T22:49:20Z")
Thankyou for info. I did place a d/c volt meter across pwn/gnd leads. Using pwm2 I get 0 at 0% and as soon as i move slider to 10 % etc or greater the meter goes and stays at 4.95 volts. I do not think i am getting any duty cycle changes as expected. Any thoughts Bart54
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### Author:  [@paullarson](https://forum.sienci.com/u/paullarson)
#### Post date: [May 10, 2026, 2:29am UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/4 "2026-05-10T02:29:59Z")
Are you using a Longboard or a Super Longboard or ??? There are also some extra control in Gsender to set laser mode or spindle mode, etc. It’s a bit confusing at first. I see the Opt controller/adapter/driver has a display. Does it display the PWM/laser power percentage? If so, what does it say as you adjust power?
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### Author:  [@batr54](https://forum.sienci.com/u/batr54)
#### Post date: [May 10, 2026, 9:49pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/5 "2026-05-10T21:49:09Z")
I am using SLB-Ext. When i use opt controller and have unhooked SLB, the laser gives correct % of increasing or decreasing power. (shows increasing % of PWM) So I have eliminated opt controller as a problem. . The controller for opt in test mode source. When attach to SLB and change power on Laser, the opt controller jumps straight to 100%. If i unhook and use mutimeter it goes from zero to 4.95 volts No in-between.
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### Author:  [@paullarson](https://forum.sienci.com/u/paullarson)
#### Post date: [May 11, 2026, 1:38am UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/6 "2026-05-11T01:38:11Z")
What have you set $730 to? I think this is the right location for the SLB. It was $30 on the LB.
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### Author:  [@batr54](https://forum.sienci.com/u/batr54)
#### Post date: [May 11, 2026, 7:46pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/7 "2026-05-11T19:46:34Z")
Hi Paul. Thanks for your input. I finally solved my problem. I was setting up everything correctly. I decide either my 1.61 download was corrupt or my firmware. After exporting all data, I erased all copies of gsender and old firmware. Reinstalled and after placing all eeprom settings I wanted, did a hard reset and also turned on and off my g\_computer. Solved the issue. Once again thanks for hanging in there with my problem.
Bart
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### Author:  [@paullarson](https://forum.sienci.com/u/paullarson)
#### Post date: [May 11, 2026, 8:05pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/8 "2026-05-11T20:05:35Z")
I’m glad you figure it out, Bart. Happy burning!
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### Author:  [@gwilki](https://forum.sienci.com/u/gwilki)
#### Post date: [May 11, 2026, 8:17pm UTC](https://forum.sienci.com/t/opt-laser-not-responding-to-power-changes/26375/9 "2026-05-11T20:17:42Z")