Power requirements for controller

I don’t have my machine yet but I’m doing my best to get things ready. Forum members have been very helpful with my other questions, now I’ve got one more. What’s the power rating for the controller in either amps or watts? My router is 6.5 amps so that leaves me with 9.5 amps on a 20 amp circuit for the controller,display and laser module. I would think that would be enough with some amps to spare. Any information is appreciated.

I have my controller plugged in to a UPS and my router plugged into another outlet that is on another 20amp breaker in my garage. Using the UPS because I know the field behind my home does take lighting strikes and it has traveled in to my house before and I would rather replace the UPS than the controller.

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Thank you for your help. A ups might be better than just a surge protected power strip since I may be using my lap top near by.

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Frank - what does the UPS say in terms of power for the controller? The Pi should be around 10 watts, but I don’t know what the steppers pull while cutting.


After watching an install Youtube I went to the Buildbotics web site and it sure looks like onefinity’s come with their 350w power supply. So 3 amps plus 6.5 amps for the router is less that the 15 amp max that most power strips and UPS’s have. I hope someone will let me know if I have any of this wrong.

The UPS normally can power PCs and servers I have setup that have much more of a load.

CyberPower ST625U Standby UPS System, 625VA/360W, 8 Outlets, 2 USB Charging Ports

Maybe @OnefinityCNC can answer the power specification of the controller. I’m not sure about the power it does not look the same as Buildbotics has theirs externally not sure what is inside 1F controller.

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The DC output of the Meanwell power supply is 9.7A. This is not equivalent to the AC input current. To calculate the maximum AC input current you also have to take into account the efficiency of the power conversion. Long story short, the maximum AC input current is typically 3.44A at full load.


So 6.5 + 3.5 = 10A - well below 15 or 20. But my shop vac pulls 9 I think, so 19 is over the normal limit (though I do have a 20A circuit dedicated to the machine). Looks like two separate circuits for me.

You never want a vac the cnc on the same outlet. The electrical noise could case very bad things during a cut.


Thanks support leader for providing an accurate number people can use for planning. I still have a month to wait but I’ll be ready.

@OnefinityCNC - thanks for the info. Though I am curious how there could be cross talk between two devices on the same circuit given the power to the controller should be well conditioned through the switching power supply? My ShopVac is intentionally not near the machine. And I would think the router would generate as much, if not more, noise than the ShoVac. Especially because it’s near the steppers and controller and spinning much faster than the shop vac. Is this conventional wisdom or backed by some real data?


I’m not an expert however I believe that both shop vacs and routers use universal electric motors and therefore would generate similar electrical noise.

Hi Peter - they should, but shop vac is a large inductive load when it starts. The router is inductive too, but ~50% of the load, so the in rush current will be lower.


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Tom, any thoughts on using a UPS to electrically isolate the controller from the other components in an effort to reduce the noise the controller is exposed to? I see that some folks are experiencing controller related problems that may be caused by noise. I wonder if a APC Smart UPS like the one below will do the job?


Hi Peter - in short, not really. A UPS or any power conditioning device will isolate interference from the line to the machine, after the point the device is installed. However, it won’t stop interface between the devices or crosstalk on the leads after the device. So imagine two wires running beside each other, like in a drag chain. There will be inductive coupling between the wires that creates induced currents and result in noise on the signal line.

For something like a router, noise on the power line is relatively immaterial since it’s an analog device where the amplitude of the voltage is really all that matters. For the stepper motors, it’s a little different since they are driven by pulses. Stray pulses could cause random movements of the steppers. The good news is, most stepper drivers have noise reduction techniques baked in, so we generally don’t have too many problems. Though it has been a problem before, like in the early days of the SO, and I guess some are still having problems, which is unfortunate…

Having a clean line voltage is a good thing, but it doesn’t stop “inline” interference from crosstalk or EMI. In this case, the aluminum case for the RPI is a good thing as it acts like a Faraday cage and blocks a lot of the electrical noise. The down side, as some have experienced, is it also blocks signals resulting in poor WIFI performance.

If you do choose to use a UPS, which is a great idea to protect against momentary power issues (brown out, surge, etc), and you connect your router to it, ensure you get a unit that produces a true sine wave. Most UPSs produce a simulated sine wave that is a stepped sine wave, which is really bad for analog devices that rely on a clean sine wave; this includes just about all inductive motors (router, vac, pumps, etc.) and some AC control circuits.

I hope this helps.


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This is very helpful Tom and I appreciate your response.

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I plan to use a UPS but only for the Onefinity controller and a Wi-fi camera to keep an eye on things from in the house. The router I’m not worried about. My main reason for the UPS is to guard against a breaker trip and losing everything in the middle of a job. And if you pause a job then it’s a little safer with the UPS backing up the controller. If the router loses power no biggie, but the controller is another story.

And the UPS gives you power conditioning which is a big plus.

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I’m in the process of designing the setup for a 1F Woodworker that I’ll order shortly. Recently, I’ve been thinking about details of the electrical setup.
You say that you want to use a UPS “to guard against a breaker trip and losing everything in the middle of a job”. I plan to use a UPS for the controller too but I don’t understand what “losing everything” means if didn’t use a UPS.
Also, you say “if the router loses power, no biggie, but the controller is another story”. If a breaker trips, I presume the router will stop running but the controller will continue. Isn’t this a recipe at least for breaking the router bit? I guess I don’t understand all the consequences of the controller losing power.

Hey Bob @crz383, hey Bob @Bob_D,

in fact retaining the position where you were in the running g-code program and the positions of the axes after emergency stopping the program due to detected power loss does not work with the stock controller even if it is hooked to a UPS, at least not without using internal controller software functionality directly.

In general, you could wire a safety circuit which is able to tell the controller (assumed to be on a UPS) that something is wrong (e.g. the power to the milling motor is gone), and generally, UPSes have the ability to signal the power loss and to trigger actions then, but the Onefinity controller, which is derived from buildbotics.com controller, only has an input pin for “estop” (pin 23), which sets the controller in “estopped” mode, but this mode lets you loose the point where you were in your program and you also loose the positions of all axes. Unfortunately, a hardware input pin for “pause” is not present on Onefinity or Buildbotics controller, so in case you want to be able to pause the program and to resume and continue program execution later (e.g. when power outage is over), the only way would be to write a webpage-operating program that “presses” pause on the (webbrowser-based) controller interface software (instead of triggering “estop”). This is possible but I would say the effort could be bigger than implementing an additional hardware I/O pin for “pause” in the original controller software.

Also one should be aware that even if you were able to trigger “pause” by an external I/O pin, controller will terminate the gcode line before pausing, so if the milling motor ceased to run because of power outage, the bit will be broken anyway, and also even if paused and resumed, the controller is not able to re-run the last command.

Anyway, a “pause” input pin or hardware button is a yet unfulfilled feature request for Buildbotics Controller and for Onefinity Controller.

Thanks, Aiph5u. That’s more or less what I gathered from reading other posts. So, it seems the only (but not necessarily small) benefit of having the controller on a UPS is to provide power conditioning and isolation.
Has anyone used a UPS to provide backup power to the router and presumably the dust collector. If so, which UPS did they use. It seems it would have to be a fairly sizeable one.