Generate Tickle Pulse for CO2 laser using duet3 board.

[Saurabh]

Hi @dc42 ,
I'm trying to interface my CO2 laser with duet 3. It has +5V TTL laser power control pin which is used to control the power for which I'm going to use LASER/VFD (v1.0 boards only) which is available on the board. But this CO2 laser need input of 5VDC PWM pulse of 1khz on Laser enable pin, I'm trying to produce on FAN pin out5. I used

M106 P2 S0.5 F1000   ; Turn On FAN 2 S0.5 for 50% duty cycle with frequency of 1Khz 

for 1khz of frequency on fan 2 but getting some random frequency value from 100Hz to 50000Hz on pin out5 with respect to ground. Looking for suggestion is it good idea to to use FAN pin for PWM tickle pulse and how can I measure it using DMM ?

[T3P3Tony]

Hi @Saurabh

have a look at this:

https://duet3d.dozuki.com/Wiki/Gcode?#Section_M106_Fan_On

specifically:

RepRapFirmware 3 Notes

The A, F and I parameters are no longer supported. Instead, specify the corresponding parameters in the M950 command when you create the fan.

So set he frequency in M905 when you setup out5 as a fan pin. with that setup the PWM frequency should work.

[Saurabh]

Yes I got that. Checked and corrected it. But still getting the random frequency. May be It's DMM issue. I'll check the signal on CRO. Thanks for the help.

[dc42]

If using a fan output to generate that pulse, you will probably need to add a pullup resistor to +5V. Try something between 1K and 10K.

[Saurabh]

@dc42 @T3P3Tony Sorry For the late reply. So, the connection I'm planning to use is given below.

;Gcode using to set output on pin
M950 F2 C"out5" Q1000							  ; create fan 2 on pin out8 for tickle pulse of frequency 1khz		|out8
M106 P2 S1 H-1

I'm don't have much knowledge of hardware. Can you help me with it? And what more connection can I do.