Can I use a Giga R1 Wifi GPIO pin as an output to turn on a 3.3v relay like this one...
Or do I need a buffer... or maybe an opto-isolator and a buffer?
Thanks for any help.
Or do I need a buffer... or maybe an opto-isolator and a buffer?
Thanks for any help.
There is no useful information about the input characteristics on the product page, except that the "trigger" is a low level. To avoid possibly destroying the MCU, use a transistor driver like this. Set output pin pin HIGH to turn on the relay.
Apparently that model (HL-54) does not have optoisolators.
Optoisolators are recommended, and, depending on your application, a must.
I would go for a module that includes optoisolators and also provides for separate power to the optoisolators and the relays.
The relays are labelled as "3V".
There's a transistor for each on-board.
"Isolation" is kind of bug-a-boo.
Have you tried this or are you being coy, asking in anticipation of buying?
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Those relays typically have a coil wattage around 360mW, a 3V one will draw about 360mw / 3V = 120 mA, your GPIO pins probably only source less than 15mA, enough to trigger a transistor and activate the relay on a separate 3V power supply.
Thanks for the feedback everyone.
What about this one?
It has "photoelectric isolation protection"...
And it looks like if you leave the jumper off...
The relay will operate from an external 3.3v power supply...
And not load down the processors output pin.
Currently I will need three of these in my system and I have room for them...
And I already have an onboard 3.3v and 5v power supplies... so no problem there.
Thanks for all the help.
That one can work.
Caution, the module pictured seems to have a 100Ω current limit resistor for the opto's LED. IR leds only drop about 1.2V from the 3.3V input, leaving 2.1V across the resistor, 2.1V / 100Ω = 21mA current into the GPIO pin. Can the Giga handle that without damage?
NvrMnd, maybe the 100Ω is for the transistor base and the 1000Ω is for the opto led, only about 2.1mA. Still think I would measure though instead of ass-ooming. 
What current can the 3.3Volt Arduino GIGA R1 pin can give?
The data sheet mentions 8 mA.
https://docs.arduino.cc/resources/datasheets/ABX00063-datasheet.pdf