Hi,
I made a small circuit with Arduino micro, connecting an LCD display (2x16) to it, a relay, an RFID reader and finally 3 LEDs and 2 active buzzers.
My doubt and problem is that everything is powered through the 5V and GND pins of the Arduino board, and that the USB port does not supply enough current to power the whole system. I conclude by adding that I should connect everything to the PC via a USB cable of about 5 / 6Mt. Result that more current is dispersed in the cable.
Is it possible to power the devices from an optional external current from the Arduino? because testing the devices no longer communicated correctly with the software.
With your system, it is almost REQUIRED! Power for the USB is usually limited to 1/2 amp and is monitored by the PC electronics so as to not damage the PC.
If you still need to communicate using the USB, get a powered USB bridge that will supply enough power for your project. You will still have communication, but will not be using the PC for power.
Not sure what that means.
Yes and often desirable. Connect the positive terminal of the external power supply to the positive terminal of the device, connect the negative terminal of the external power supply to the negative (ground) terminal of the device and to the Arduino board ground. Connect whatever IO between the device and the Arduino.
Yes that is a bit much for an Arduino's on board voltage regulator or even USB. The realy coil certainly should have external power. As much for the current that it needs as for isolating inductive loads from the logic power.
thanks, i solved it like this, but i didn't want to use this system, otherwise would you advise me to switch to arduino uno?
in direct current (DC), if the cable is very long, there is a current leakage. If the pc sends 1A, arduino receives 0.5A
Why? I understood you had power problems. Get proper power supplies for your projects.
yes, there is little power from the usb of the pc (USB 2.0)
In doing so, the arduino receives current from the usb and from the outside at the same time? Don't I risk burning everything?
There is no "current leakage". If the cable is long it has more resistance. That resistance causes a voltage drop in the cable. Ohm's law. If you have to have a long cable, increase the conductor size and therefor reduce the resistance.
None of the Arduino boards are power supplies. A large proportion of Arduino projects require external power because the boards are not power supplies. It is not at all unusual to need to supply more current for relays, motors, radio modules, etc. or multiple voltage supplies. I have projects that have 12V, 5V and 3.3V power supplies to handle the different components.
That is a tricky question. Some Arduino boards can handle being connected to USB and an external source at the same time and some cannot. I can't keep track of which can and which can't so I avoid powering the Arduino board by more than one thing. But that is for the Arduino board power.
The peripherals all can have their own supplies and the grounds all connect together (unless purposely isolated by a relay or optocoupler, for instance).