erbedo:
Sorry if my question is silly, but I'm not really good with electronics.I have to power a device with 3V and 200 mA. So the 3.3V output pin of the arduino seems great, and in fact I can power my external device which runs fine.
The arduino product page for Uno still only rates the 3.3v pin as having 50ma capacity. This probably a legacy spec when the FTDI was supplying the 3.3v pin on older arduino boards. The Uno uses a dedicated 3.3vdc voltage regulator to supply that pin, but I would think it's safe ratings is around 100ma or so, so you may be really stretching it drawing 200ma. But if it works it works I guess.
However, I have to switch the power to that device via software, so I thought a transistor would help me. I connected the 3.3V to the emitter, one of the arduino pins to the base, and the collector goes to my device.
NPN or PNP transistor? No resistor on the base is a good way to damage both the transistor and the output pin.
The fact is with this configuration I got too much voltage or current to my device, which doesn't work well. How can I switch the 3.3V from on to off? Do I have to use the transistor? If yes, how can I use it to make it pass only 3.3V and 200 mA?
Use a relay?
Thank you in advance