Setting the GRBL PWM to 5 kHz for a Synrad Series 48 laser Why

gplus
(Blue Transistor) #1

Setting the GRBL PWM to 5 kHz for a Synrad Series 48 laser

Why does it matter? Two excerpts from the Synrad manual:

Tickle frequencies [a ‘keep-awake’ signal at zero power] lower than 4.5 kHz may compromise laser performance, …, and stress the RF [radio frequency] electronics thereby reducing long term reliability while tickle frequencies greater than 5 kHz may cause unintended lasing.

Because laser output follows PWM input with a rise and fall time constant of ~100 µs, the laser cannot precisely follow Command signal frequencies over t kHz with duty cycles greater than 50%.

It seems that my options in cpu_map.h are 62.5 kHz, 7.8 kHz, 1.96 kHz or 0.98 kHz.

Can anyone see a workaround for this within the constraints of the GRBL configuration?

Failing this I may have to build and external PWM to analog low-pass filter and feed this into a 5 kHz PWM generator.

I’ve also asked on https://arduino.stackexchange.com/questions/55322/how-close-to-5-khz-can-i-set-the-pwm-frequency-on-an-uno-pin-11 where more details are supplied.

Many thanks.

(Claudio Prezzi) #2

I can’t see any solution for grbl on a Arduino Uno (ATmega328p). You could use a 32bit board like Smoothieboard, Cohesion3d or MKS SBase with Grbl-LPC or Smoothieware, where you can exactly define the PWM frequency.