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Analog Potentiometer WITH pwm from MG2

Hi All,

Looking to get a definitive answer on this (Tried to search, found a similar post here: https://awesome.tech/k40-forum/topic/potentiometer-needed-with-mini-gerbil/#postid-2309 but no conclusion).

I have successfully connected MG2 to the K40 Power supply (type 1), disconnected the existing Potentiometer wire from IN port and connected the pwm from MG2. However, I'd like to keep the potentiometer active as well.

Someone on facebook has suggested to connect potentiometer to the IN port (as it was) and connect MG2 pwm wire to the L port. Would this work?

Can I connect both Potentiometer and the PWM to the same IN port?

Help would be appreciated. Thanks.


Hi Waqas Q,

we discourage connecting a potentiometer in any way, for several reasons:

  • the controller circuit isn't designed for it (for the reason mentioned in the next point). So we can't think of an easy way to hook it up that doesn't risk damaging the controller. Actually, probably the best way to do it would be to use a toggle switch, such that the K40's IN port is the centre pin of the toggle switch, the MG controller PWM signal is one side of the toggle switch, and the potentiometer output is the other side of the toggle switch. That way at least you keep the potentiometer disconnected from the PWM output and don't risk damaging it. You can manually switch between 100% digital and 100% analogue control.
  • Adding a potentiometer to a digital circuit is the 'worst of both worlds'. You have the software interface to contend with, and the inexactness of the analogue potentiometer. If they're both operational at the same time, you have a bizarre situation where the laser burns differently on the same potentiometer position, for different software settings. I'm keen to hear a reason why anyone would want this, it seems like a step backward to me.

If the underlying reason for this is that you want fine control over the laser output, I really encourage you to study up on the great control that is already available in graphics software such as Lightburn. The Gamma control is a game changer, once you understand how to use it.

If you can explain why you want analogue and digital control at the same time, we can design future controllers to feature it.

Best regards,



Waqas Q has reacted to this post.
Waqas Q

Thats a great response Dan. Thank you very much. The toggle switch way is genius (if I end up using it anyway).

So the first reason is, after connecting the MG2, the test fire button on the panel now fires at 100%, I have to align the mirrors etc, was looking for a way to test fire at lower power. I am very new to all this, just installed light burn and a very quick initial search told me that lightburn does not have test fire button. Thats why I immediately thought about having control over power using analog controls.


Second reason (and not too important) is to have a base max power restricted using analog control then use 0-100% of that max using lightburn. Lile you said, it might entirely be possible using just the lightburn so I will look into this.

But for my first scenario, do you have any advice or suggestions that I can use? I pretty much don't want to use 100% power on test firs button (because I have read everywhere 100% power damages the tube, not sure if it applies to quick test fires too but just wanted to be safe).

You're welcome.

Agree it's not ideal to use 100% power unless there's a good reason.

Here's our page that describes how to easily create a special test fire macro (great for mirror alignment) with your own choice of laser strength: https://awesome.tech/test-fire-button-in-lightburn/



Waqas Q has reacted to this post.
Waqas Q

Amazing, greatly appreciate your help. Thanks.

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