Asked February 9 2015

Community Question

Hey guys.

I have a couple of general questions regards running LED's off a digital port.

1. I hooked up a 3V LED to the signal and ground pins on D6 on my v4 earlier today, made a little digital on, sleep 5 seconds, digital off script to test it but all it would do is very quickly flash once. I changed it over to port D12 and it worked fine. Any reason why D6 didn't work? The port is fine as I tested it with a servo. I was just wondering if it's because D6 is also a UART port as well and this may have caused the issue.

2. Any ideas if I could power a set of 20, 3v fairy lights off the V4 signal and ground pins? I lent my multi meter out so I can't test the amp output of the LED's. They normally run off two 1.5v AA batteries. Could 20 bulbs be too much?

Thanks. :)
March 11 2015
Thanks Jeremie. I'll take a look.
March 11 2015
@jeremie I agree however I have learned the hard way with these cheap Chinese relays.
March 11 2015
@Steve...As mentioned before... I have and use these and they are guaranteed plug and play with the ezb4... They can switch up to 2 amps and are pretty cheap.... 5V relay
March 11 2015
@Steve Good find! The Songle pictured in reply #24 will definitely not work with 5v.
Edit: I meant 3.5 volts.
March 11 2015


5V 1-Channel Relay interface board, and each one needs 15-20mA Driver Current
Equipped with high-current relay, AC250V 10A; DC30V 10A
Standard interface that can be controlled directly by microcontroller, such as Arduino , 8051, AVR, PIC, DSP, ARM and so on
Contact independent wiring, safe and reliable
With screw holes for easy installation
Size: 42 x 24 x 20mm
Package Include:
1* 5V 1 Channel Relay Module Board

According to the write up, it should work at 5v.

EDIT: I've just seen your edit. No worries. ;)