I need to connect the vcc pin to a bluetooth module but then I need to sue it again for a relay module what do I do?
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\$\begingroup\$ Technically there is no reason why you can't just connect them in parallel... But I don't think the onboard regulator can handle the current draw from the relay. You can get a wallwart ran through your own regulator (with more current output) to get an external source of more current. \$\endgroup\$– Jarrod ChristmanCommented Oct 26, 2014 at 14:22
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1\$\begingroup\$ Dan, you should not use the VCC pin (the output of the onboard 5V regulator) for a relay power supply, you will blow things up if you draw too much current from it. Also, there is only one female pin socket for VCC available, you will need a breadboard or another PCB to make it easier to branch the VCC pin connection out to multiple devices \$\endgroup\$– KyranFCommented Oct 26, 2014 at 14:26
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\$\begingroup\$ Hmm will it handle 2 5v a outputs from vcc? @JarrodChristman \$\endgroup\$– dan14941Commented Oct 26, 2014 at 14:26
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\$\begingroup\$ @KyranF bluetooth modules uses at max 10mA and relay 20mA is that fine? \$\endgroup\$– dan14941Commented Oct 26, 2014 at 14:34
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\$\begingroup\$ What is the relay doing? 20mA is probably only the contact coil to hold it open/closed. 20mA is okay for the Arduino board but that of course depends what other crazy stuff you are running and not telling us about. I suggest you put some nice big capacitors close to the Bluetooth module (various capacity, 1uf, 10uf, 100uf for example) so that during pulsed currents (like during transmission) you will not have drops in the VCC rail and have strange resets/failed packets. \$\endgroup\$– KyranFCommented Oct 26, 2014 at 18:50
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You just use the same pin twice. You can connect as many items to the 5V pin as you like as long as you don't draw more than around 750mA absolute max (the regulator is rated at 800mA, and the Arduino itself takes about 50mA or so of that).
Note that as you increase the current draw the regulator will get hotter, so if you want to use higher currents it would be worth investigating using an external 5V power source.
