trouble arduino to control 4 servos.

[Carellano]

good day .

I'm new and I'm trouble arduino to control 4 servos.

       it happens that when handling them by bluetooth or serial monitor, the servos start to shiver - vibrate and / or make involuntary movements. If I send a command to a servo move , another makes any uncontrolled movement. It's crazy.

      The servo are connected to an external source of 5V and 650 mA .

      Programming is correct.

Please help


P.D.  excuse my English is not very good.

[PaulS]

The servo are connected to an external source of 5V and 650 mA .

Each servo probably wants 6V and about 1 amp. Your power supply is likely undersized.

Programming is correct.

One of us agrees with that statement. The rest of us need a lot more proof.