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Potentiometer needed with mini gerbil?

Hello all,

 

Getting ready to update my panel...

Purchased 10 turn potentiometer and 6 digit display before purchasing gerbil and realizing that pwm is controlled via gerbil.

What are the main reasons for or against keeping a pot on the panel?

 

Thanks

Josh

Hi Josh,

A potmeter is not required unless you want to manually adjust the power by hand rather than using the buttons on the screen (PC or laptop).

One caveat: Lightburn does not turn off the laser in between moves but sets the power parm S to zero. That works fine when Mini Gerbil is controlling the laser beam but an issue when you manually set the power via a potmeter. However you can use the Inkscape application (our version of it on our awesome.tech github page) which does uses the M4 on and M5 off commands in between moves.

Hope this helps, cheers Paul

Cheers, Paul awesome.tech

I only ordered my board a few days ago and can report I'm very happy that it arrived today 🙂

 

Is it possible to connect the side of the pot that would usually be connected to the PSU to the PWM wire from the Mini Gerbil?

 

I still like the idea of a manual control on the laser so if I'm sending too much power to the laser at least I can read it from the ammeter and turn it down.

 

I have the 40w Co2 tube in my K40, and have read to keep the max power around 15mA, if I can set the PWM from the board to maximum, then turn the pot so that the maximum reading is 15mA, then I'm hoping this would give me a good set point for judging what power is actually going to the laser, and hopefully give me the maximum range for burning grey scale images as well as prolonging the life of my tube.

 

I would also like to try installing some DRV8825 drivers (I have on a GRBL board on a CNC) - these should be a direct drop in for the A4988's and will do 1/32 stepping as opposed to 1/16 (obviously I'l have to double the steps per mm setting) - will there be any issues if I want to use the 8825's oin the Mini Gerbil?

 

Thanks !!

Edited to add :-

Installed the board last night (pot not connected) and all is working well, I still like the idea of having the pot control, but happy running without it for now).

 

Reading up - it looks like the PWM 'pulls down' the signal to the PSU (rather than my initial thoughts on it being a pull up). I suppose connecting the pot between the PWM out from the board and the PWM 'in' on the PSU would work, but I will leave that for another day.

 

 

 

Installed the board last night (pot not connected) and all is working well, I still like the idea of having the pot control, but happy running without it for now).

You could do so and remove the PWM wire. M4 and M5 are commands that switches the laser on and off but lightburn just does not use these commands to speed up the comms. The just use a S=0 command to switch of the laser (strength=0).

Cheers

Cheers, Paul awesome.tech

Thanks for your reply Paul.

I wasn't wanting to remove the ability to set power from Lightburn.

From what I have been reading, most recommend the max current for the K40 laser to be set at 12-16mA.

 

I'm exploring the possibility of keeping the pot in circuit and when Lightburn is set to 100% power, I can use the pot adjust the current so when at 100% from Lightburn, my laser is getting somewhere between 12-16mA.

 

The logic behind this is no matter what output I select in Lightbnurn, it won't be going over the max recommended current for the tube, so I can extend the life of the tube, but also get better granularity for burning grey scale images.

I haven't had the chance to explore this further as I'm enjoying playing with the machine as it is for now, certainly a project I will look into as winter approaches.

 

Thanks again for your response.

 

Matty

 

 

 

 

 

 

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