Hey guys. I’m working on a box to house all of the power and controls for my MPCNC.
I’m curious if anyone knows (or can measure) the rough current draw (amps) of an MPCNC running a Dewalt 660? (or 611?)
I bought one of these switched IEC 320 plugs (https://smile.amazon.com/gp/product/B00YU0GPGO/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1) to put in the back of the box, and it’s got a 10 amp fuse. The Dewalt says 5 Amps on the box, which is presumably it’s upper limit, not it’s default running draw, but I want to make sure a 10 Amp fuse is appropriate, or if I should drop it down to something smaller (5 or 7 amp?)
I don’t expect that the arduino/lcd/steppers draw all that much, so I figure it’ll be fine, but thought I should see if someone knows better?
Disclaimer: I know next to nothing about electronics, but I haven’t fried anything yet.
The power brick for my RAMBo says 6A, and with the RAMBo, a 5V regulator, Raspberry Pi and webcam pulling on it, the RPi power LED doesn’t light up consistently, so I’d guess it’s pulling all it can get of that 6A.
Since 6A + 5A = 11A, I think your 10A fuse may be a hair under, actually.
Jason you are close except the 6A is at 12V, Amp ratings should either come stated as watts or 6A@12V, but usually do not. It is kinda funky but because of this machine I have learned way more about this than in college about this stuff. So Watts is what is actually being used (in a way) 12v*6A=72W (72W max… we actually use far less, under 3A, even when heating up a nozzle and running the drivers). So then the conversion is 72W/120V=0.6A. Hence Otto’s picture.
Hope this doesn’t come off wrong, I am just really starting to dig into electronics and I am starting to really like it. This Watts things is what kicked it off for me and “unlocked” electronics. It all makes so much more sense now.
Nick 10A definitely enough. There is a start up surge but I think most house circuits are 10-15A anyway (mine are 15A).
The fuse should be protecting primarily the downstream the wiring - the equipment should be protecting itself. The mini-Rambo and RAMBO all have fuses to protect their circuits and downstream loads. The RAMPS also has fuses for downstream loads, but this does not protect the underlying arduino mega providing 5V to the RAMPS so in some cases folks have blown the 5V regulator - since the max current the regulator can regulate is highly dependent on the regulator chosen by the board maker, you really can’t protect this one very easily. Which leaves the router and the wiring to the electronics as the only things needing (extra?) protection. As long as you are using at least 18 gauge wiring (smaller numbers equals bigger wire, so 16 gauge can carry more current than 18 gauge - here’s a simplified reference table), the 10 Amp fuse will work fine and you shouldn’t need to use a lower rated fuse.
The fuse should be protecting primarily the downstream the wiring – the equipment should be protecting itself
This this this. Most modern electronics are pretty good at not being greedy. Unfortunately there are manufacturers that will just slap a UL listed sticker on thrir stuff. A fuse “in theory” should work, but like stated above, they are usually downstream. If you’re really concerned you should be looking into mosfets.
I’m going to butcher my explanation here, but a mosfet will deal with the heat generated when your device asks for too much energy.
The fuses that you are thinking of will only protect the power supply itself.
Disclaimer: my explanation is extremely over simplified and fundamentally wrong, but it’s the best that I can put it into words.
At the end of the day, you need to be more worried about your power supply burning down your house more than your machine
Cheap, unlisted electronics will ask for too much power, and the psu will give them what they ask for. I’m really not doing my own explanation any justice(I understand the stuff but I can’t explain it)
