Not enough power for Arduino + Shields


For a test setup I use an Arduino Uno R3, a Bluetooth shield, and an Adafruit LCD shield. When I connect this setup to a standard USB port then the status LEDs are weak and nothing works. When using USB 3, which should have 1A current, everything works, but I can still see that some status LEDs are very weak. The LEDs are also weak when using a 9V standard battery pack.

Can it be that the two shields draw more current than the Arduino board can handle, or does it make sense to attach a power source to the Arduino which can supply more than 1A? Is it save to wire the 5V pins (of course GND as well) from the BT and LCD shield to an external 5V power source?


you need to figure out how much current everything uses. then you can pick a power source that can supply that

The most safest way of efficiency is to add separate power sources for shields, motors & other more power consuming peripherals with different power sources (even the arduino board, if possible. Mine has the facility to power up using external power adapter & USB for only Communication purpose) & connect all the GNDs together.

Yes, but can the Ardunino handle these power requirements, or is it common that you need an external source when running a BT and a LCD shield?

Let me explain in a simple way...
Just take the example of your LCD module. It may contain many small devices & we call the full assembled board as a SHIELD. all these components need power to run, just like in our case we eat food to get the energy out of it. you have to give power to the devices to get them work (to power up). The UART, SPI, etc. they are just protocols to communicate with each other & really dont draw too much current but If you use a shield that draws a huge current from the same source, it will definitely distribute deficient amount of current to all the other connected devices including the arduino. Go ahead with the I/O pins to add as much devices you can (for communication & logic) but it is always better to use separate power sources.
N.B: connect all the GND from different sources together.