Do you need a resistor on a relay module?

Other Hardware General Electronics
1

Hi guys. Newbie question. I have one of those arduino relay modules that came in my kit. The ones that have the 3 pins ( VCC, GND and IN). Now obviously VCC is connected to my arduino 5v,the GND to ground, and the IN pin connected to an arduino output pin to control it. My question is do you need to put a resistor to connect the arduino output pin to the relay module IN pin? I know that arduino pins should only be used for a max of 40ma and you can potentially burn out a pin if you suck too much current from it. but I dont know if the module itself already has a resistor in it. ( it looks like it does, but I'm not sure.
Heres a pic of what I have:

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Thanks for your help

2

Show us a schematic of the board.

Nothing is obvious, that relay has a 12 volt coil.

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3

Schematic is not that easy for a relay module... But it's general enough, if it's a relay module (like the tons that are made for the Arduino) then no, straight connection is fine.

4

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"Schematic is not that easy for a relay module"

Shouldn't take more than a few minutes to trace the cct. and draw a schematic. :wink:

Looks like 3 resistors, one diode, two LEDs a relay and a transistor.

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5

True, but it shouldn't take more then a second to realize a relay module is designed for a uC :slight_smile: