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3 Way switch to enable test fire

Just prior to receiving my Mini Gerbil I eliminated the K-40 Digital display for the pictured analog display. Does the bottom red circle show the proper placement of the 3 way switch you elude to in your install instructions?

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Yes that a great way to depict it. Well done!

Cheers, Paul awesome.tech

I've recently added a switch wired as thomasw3 depicted in his diagram since it's much more convenient for me to hit the test button while at the laser rather than walking back and forth between the computer using a macro.   It works fine but am having a problem with the Mini Gerbil at power up.

The problem I'm having is the Mini Gerbil PWM pin is at 5 volts when it's powered up,  If I hit the test fire button it will test fire at full power if the switch is live to the MG.  If I turn the switch to the pot it fires accordingly to the power set through the pot.

It's not until I initialize the MG with Lightburn that the PWM pin goes Low (150mV) so that if I accidentally hit the test fire it does nothing.

So what I think I need is to have the PWM pin default at Low state rather than at 5V when it's powered up regardless if I'm connected to a client application or not.  Is there a way to do this or do you have any other suggestion?


Yes we could change the firmware to have a low level instead of 5V DC at start up.

Other suggestion is to use a relay (for PWM and LO signals). The relay either switches the PWM and LO wires to the MG controller or to pot and LO to Gnd (relay coil via a PUSH button).

Cheers, Paul awesome.tech

Thanks Paul

Yes please create a firmware with PWM pin to startup Low.    I understand what your saying about adding relays but I'd rather the firmware start up Low for safety reasons, and throwing more switches / relays at it doesn't seem like an ideal solution.

You might also change the $10=31 to $10=1 in the new firmware.



Hey Paul,

Any idea on when you think you'll be able to create the modified firmware?  I've completed my replacement control panel and have ordered a ST-Link V2 that should be here by 1/16/20 so that will be the final piece to my conversion and I'm anxious to get it completed. 🙂

I replaced the digital panel that seemed to have switch bounce no matter which switch I pressed, adjusting 10's would sometimes adjust 1's or .1's etc.. both up and down.  I think the new panel works better and even like the way it looks better. 🙂


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