Hi, I'm using a digital output to controll a transistor like a switch. With the transistor I power the coil of a 5V relay, but the 5V comes from the arduino 5v pin because I don't have any other source of 5v in my project. Unfornately sometimes when the relay triggers the arduino resets (I imagine that because of the noise in the power produced by the relay coil). I find a solution adding a cap of 4700uF directly in the 5V and GND of my arduino. This seems to work (the leds in the other outputs dim a little bit) but now the arduino don't restart.
The other alternatve I have is to connect the transistor to another line that I have of 6~6.4 volts that I have to power a servo.
Which solution do you think is better? I think the 6.4 might burn the relay coil, but I don't feel confortable having a 4700 uF directly to the Arduino board, there is a problem or risk with that? If there is ok, probably the cap is the better solution.
I know that there are 6v relays but my local electronic store isn't open this weekend and I need to fix this for monday =(