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Typically in Arduinos, most of the 5 V outputs that have a limited amount of current (40 mA).

Are there any 3D printer boards, or is there even a more usual spot, where you can get a 5 V output that isn't capped by the microcontroller?

I know that USB 2.0 is (typically) limited to 500 mA especally when connected to a laptop. Just wondering if there was a way to for e.g. get a 200 mA output from one of the 5 V pins, or more if there is a stronger power supply connected to the USB port.

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    $\begingroup$ I believe the USB port is generally a “device” port, which will not supply power, as opposed to a “host” port, such as on a PC. $\endgroup$ – DoxyLover May 21 at 20:39
  • $\begingroup$ That's true and one interpretation of what I said, but i still meant if you had a 3D printer board powered only by USB and not 12V, is there a pin somewhere on the board to get more of the 5V power from the USB? $\endgroup$ – K Mmmm May 22 at 14:24
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Any pin that is labeled as "5 V" can supply the full amount of current. Looking at, for example, the Arduino MEGA pinout, we can see several pins labeled in red with "5 V". These are the pins you can use. Most 3D printer boards will expose the 5 V pins at several points. For example, the endstop connectors often have a 5 V pin that can be used.

The pins that are limited to 40 mA that you are thinking of are the digital pins, i.e. the pins that can be switched on/off by the microcontroller. These are actually more limited than this, and while in some cases drawing 40 mA from them may be possible, it is not a good idea.

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  • $\begingroup$ I have confirmed this. I was confused because I had a fairly common two pin solid state relay (SIGNAL, GND only). And it could work on the constant 5V pins, but not on the digitally controlled pins, probably because there is less current on the latter, even when the signal is set to high. It is annoying because it can't be digitally controlled unless i add another mechanical relay (defeats the purpose of using a solid state relay) or if I use it at a 12V extruder port (one less heater) $\endgroup$ – K Mmmm May 22 at 14:13
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Any 5 V "output" on those main boards would be used to power a USB host. This is because the electronics actually runs on 3.3 volts. It would be better to splice the input power (the 12 to 24 V) and use a buck converter to get down to your required 5 V. Select the right one, and you can have all the current you need.

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