I am trying to use 4 Ultrasonic Sensors HC-SR04, and 3-4 other sensors such as BNO055 to an Arduino UNO, can UNO drive them by its 5V or need an external 5V?
The question is more what current can your power supply offer to the Arduino (and the voltage you feed the arduino with)
You need 15mA per HC-SR04 if they all trigger at the same time (which comes with technical challenges, if they only shoot one at a time the quiescent current < 2mA)
a BNO055 would probably draw the same ~15mA
you'll have to look the current needed for the other sensors, if they are around 15mA too then you total current draw would be 8 x 15 = 120mA
So if you power through USB, you have ~400mA give or take to play with so with 120mA for your sensors - you should be fine.
If you will be using 5V thought your whole project then @J-M-L answer is correct with a decent 5Vdc power supply.
If you are going to supply your project through the DC socket on the UNO, then NO, the internal 5V regulator on the UNO cannot supply much more current than for the UNO board and one or two peripherals.
I'll use an external 5V.
Indeed the regulator can play tricks on you depending how you power
Something NOT to read (EDITED - it's a poor article)
Not a very good or helpful article at all.
to be honest I tried to help by sharing one of the first google hit.
what' wrong with that article?
Multiple blunders and mis-explanations such as "But on the Arduino Uno, we have a low drop-out voltage regulator. It dissipates less power in the form of heat". Now while the following sentences suggest that this allows the use of a lower input voltage, it is factually nonsense. And may not even be relevant to fake "UNO"s and clones - because people will often use these.
"The barrel connector needs a constant DC voltage supply in the range of 6-12V." Rather amusing, you may consider it acceptable but in fact, the whole purpose of the regulator is to permit a non-constant supply voltage!
"The Arduino Uno obviously cannot accept both inputs. Because without some management in place, that would lead to a surge in voltage." Called out in the comment section - this article appears to be quite recent - this is clearly foolish.
Worst of all, it completely misses what we have discussed here, the severe limitation of the on-board regulator which is really the most important point to understand. The article's focus on the cleverness of the supply switching mechanism - which really only exists to avoid the voltage drop of the diode used in the Nano - is basically irrelevant to deciding how to power the UNO so I feel the article really is not useful at all.
now I read it too, indeed was not a smart link...
Only if you use it as a low dropout, ie lower input voltage than that needed by a regular LM78XX or LM79XX regulator.
Ohms law still presides in ALL cases.
I looked at the link..... I didn't get past the corporate jargon of the first sentence
It is important to understand the power supply routes on the Arduino so that we can properly leverage the onboard facilities to optimize the overall power sourcing of our projects.
I was surprised it didn't include synergy.
LOL … time to play buzzwords bingo !
Did it really say that?
It does too!
I am afraid (well, not really) that I did not notice. I think my innate noise rejection filter was fully engaged and passing only potential technical/ engineering data.
Must be my synergy.