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MiniGerbil - Test Fire too Hot

I've installed a MiniGerbil (v1) on my K40 according to the wiring - it all works (thanks!) - but I'm worried about two things -

  1. As the analog control is now unconnected - Test fire now uses full power (30mA) when we all know anything above 15mA is bad. I know its very short - but the Amp needle hits max for the brief tests we need do for centering mirrors, targeting etc - are these very high pulses bad for the tube?
  2. The MiniGerbil seems to work by sending PWM at full 0 and 5V signals now - is that correct? so the tube will be working at 30mA - just  in very short bursts that average out to the 40% power level I have set in Lightburn. Are these multiple 30mA pulses bad for the tube?

The original setup with the Nano, the power supply box receives a variable voltage from 0..5v - so say 2.5V would mean the tube is given only half available psu power or 15mA - rather than the now I have Gerbil Installed, the full on, overpowered, 30mA for half the time(ie. 50% duty cycle)..

I dont want to burn out the tube! thanks.

Hi, the laser power is controlled via G code commands e.g. S100 will send 10% power, S500 will send 50% power based on the configured S parm (normally configured as 1000).

The laser application will have also a S parm configured which should match e.g. 1000. See https://awesome.tech/what-are-settings/

$30 defines the laser range is is usually set to 1000.

The thing we need to figure out is does the software application send the correct S commands or is the PWM wiring loose. A loose wire on the PWM input on the laser power supply will usually just float at 5V dc.

You can issue a G code command via the console to test the laser power firing via a few S commands to see if the PWM arrives or if the laser just get an on signal. e.g. S100 followed by S250 etc. Check if the laser power varies, if not then a loose PWM wire should be investigated. You need to put the controller in "CNC" mode because in "Laser" mode the laser does not fire when the gantry is not in motion (safety feature to prevent fire). Use the S32 command to set the CNC mode e.g. S32=0. Don't forget to revert when you're done with testing via S32=1. See our post to configure a test button in Lightburn  https://awesome.tech/test-fire-button-in-lightburn/

We have another section to debug the laser operation https://awesome.tech/mg3-mini-gerbil-debugging-laser-operation/

Let me know if that helped you further. Cheers Paul



Cheers, Paul awesome.tech

Thanks- but my issue is not that.wiring is sound as per instructions. Its was working fine, and in lightburn 40% shows 15mA on the meter… and I stick to that.

But my issue are..

1. the k40 panel red test fire button. Does actually fire - but Fires at 100%  -not 40% because installation instructions say to disconnect the analog laser power potentiometer. Thanks for the post to that macro- there is also a test fire feature hidden in lightburn(its an option in lightburn settings you need tick and agree to have it appear)

2. Before- the IN terminal on the K40 psu was an analog voltage. The voltage never went over 2.5v(as set by the analog k40 panel power level potentioneter).. so the mA was 15mA max. But now the IN is 5v..0v…5v…0v (the way pwm works).

I know this “averages” to half power 15mA - but its still spiking to max power, just in short bursts. I was concerned this might stress the tube.

And then two weeks after installing(shortly after posting above)- my k40 PSU has died. It seems to be the flyback that failed. I’ve replaced the whole psu but i dont want to blow another or worse, the tube.

Do you think its related to the gerbil being installed?

Has anyone considered reducing the pwm from the gerbil from 0..5v to say 0 to 2.5v max?

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