Hello,
When i connect my arduino by usb to my pc or to the iphone adapter (5v 1a) my arduino works as aspected. But when i use a adapter with 9v 1200ma i have some problems: a piezo buzzer sounds bad and when i put a pin high for opening a transistor the arduino resets.
With the 5v adapter i measured about 4v from the pin which is connected to the piezo buzzer, with the 9v adapter i measured about 3,5.
Does anybody what i'm doing wrong?
Regards,
Thomas
Which Arduino board are you using ?
It is probably a heat problem of the voltage regulator.
The voltage regulator on the Arduino board makes 5V. If the input is 9V, the 9-5 = 4V is turned into heat.
Solution:
(1) Don't use the voltage regulator of the Arduino to power a lot of things, only a few leds and sensors. Use a seperate power supply for the components.
(2) Lower the input voltage to 7V or 7.5V.
To me, it sounds like excessive ripple is getting through. Can you try a different adapter?