Cetus3D MkII on 24V?

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clcorbin
Posts: 2
Joined: Wed Jan 30, 2019 7:23 pm

Cetus3D MkII on 24V?

Post by clcorbin » Wed Jan 30, 2019 7:27 pm

Question: Can the Cetus3D MkII be powered by 24V? It looks like the stepper drivers can handle it with problems (DRV8824). I guess the question is can the other "high" voltage caps handle 24V as well as the voltage regulators for the 5V and (I think) 3.3V supplies?

The reason I ask is I have a pair of isolated 12V supplies mounted on the workbench not 6 inches from the printer that I would prefer to use over the laptop supply that comes with it. Plus, the stepper motors will run better on higher voltage.

Thanks!

clcorbin
Posts: 2
Joined: Wed Jan 30, 2019 7:23 pm

Re: Cetus3D MkII on 24V?

Post by clcorbin » Mon Feb 11, 2019 6:00 am

So, I might as well answer the question. After reviewing every IC on the main board, I found nothing on there that couldn't handle a bit higher voltage. All the 5V and 3.3V stuff was fed from a DC-DC 5V converter that could handle way more than 24V.

So, I hooked it up to my 30V bench supply and dialed it up to 24V. It works just fine. You have a bit more voltage to the stepper drivers (we used to hit "4.5V" steppers with 90V supplies on the semiconductor manufacturing equipment I was responsible for) which is generally good. The heater has a bit more voltage and current, so it can heat up faster as well.

While I was messing with the board (getting ready for my TinyFab and Titan Aero to come in), I also replaced the DRV8824s with DRV8825s. They are pin compatible, but the DRV8825 DOES have a bigger ground pad on the bottom. I wanted them because they are rated to higher current AND they have about 1/3 the Rdson values which should make them a bit cooler running.

I also yanked the two resistors for each drive that sets the drive current and soldered down some TINY pots to make the current limits adjustable (again, more for the upcoming CPU board). That was a bit interesting and wouldn't suggest it unless you are very comfortable with your soldering skills.

Right now, it is mostly happy as a clam with the Titan Aero extruder mounted (the mount I made leaves the tip of the nozzle at the exact same place as the stock print head does) and the TinyFab driving it. I still need to get the heated bed installed as well as the autolevel "stuff" installed and configured. The only kink yet to worked out (one day of work, so...) is the TinyFab is NOT happy with the thermister that comes with the Titan Aero. It works perfectly with the stock Cetus3D one, but no settings in the config file have got that thing reading correctly on the Titan Aero stock one.

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