Problem getting a laser to work

resam

@appjaws which laser and laser control board did you buy?
Most of them use a "simple" PWM signal between 0-5V to control the laser intensity.

I doubt that your laser really has a 50%-ish PWM signal as "full power" signal...

appjaws

I've just measured the voltage on the Fan0 pin and it is fluctuating between 5.5V - 10.7V.
Do you think I am over driving the PWM input?
The problem I had no information supplied with the 2000mw laser and control board that I bought.
I have tried to find out the correct voltage but was unsuccessful.

This is a picture of the laser I bought

keyz182

@appjaws said in Problem getting a laser to work:

I've just measured the voltage on the Fan0 pin and it is fluctuating between 5.5V - 10.7V.
Do you think I am over driving the PWM input?
The problem I had no information supplied with the 2000mw laser and control board that I bought.
I have tried to find out the correct voltage but was unsuccessful.

The ones I've seen have all been 5v PWM controlled, so maybe you're over-driving? Do you have a link to where you bought it? And/Or some high res images of the top+bottom of the PCB?

appjaws

I bought it on ebay and the supplier has no information.
I could take some photos of the board but I will need to dismantle my setup first.
I wonder what size of resistor I could connect in series to reduce the actual voltage reaching the control board

resam

Me, and others here on the forum use the HEATER_3 pin with a few extra components, instead of the fan output. Somebody even made a custom PCB for it.

https://duet3d.dozuki.com/Wiki/Laser_PWM_control

appjaws

I did start with that plan but could not get my lashup to work. I now have a better understanding so perhaps I'll try heater 3 again.
Thanks for your help.

appjaws

I still haven't got the heater 3 solution as explained in the article "Controlling a PWM Laser with the Duet Board" The diagram indicates that the expansion header pin 8 is heater 3 but I have a constant 3.29 volts between that and pin 2 which is grd.
So I am wondering if the old version 6 boards, which I am using, have the same pin assignments as the version 2 boards.

So I have reverted to using the fan connector with the output reversed and a pull-up 1K resistor connected to +5V.
This is the results of checking the voltage at different S values.
Svalue Voltage Laser
0 4.4
10 2.58
11 2.47
13 2.33 ON
15 2.27
20 2.19
40 2.05
60 1.97
80 1.88
100 1.77
120 1.64
140 1.51
160 1.39
180 1.27
200 1.14
220 1.08
240 0.87
250 0.78
252 0.77
254 0.75
255 0.74 OFF

The increasing S values at the top end result in the power of the laser reducing.
Clearly I have something wrong but I am at a loss as to what to do next.