Electronic – How to i drive this 5v Relay board with RPi

gpioraspberry pirelay

Beginner here, so this problem came up:

I got a 250vac 30A relay board which seems to require 5v to be driven.
It has 4 input pins: GND, IN-, IN+, VCC
What are the IN- and IN +?

My rpi output pin does not seem to be able to triger the relay when connected in the IN+ (although the board's led does turn on and off)
Here is a pic of the 4 pins:
enter image description here
Here is the ebay link: Ebay Item Link
The manufacturer page: chinalctech Link

Please note that my relay (pic #1) has 4 connection pins while the other two (pic #2 and #3) have 3 pins.

update:
Thanks for the plenty of answers, I went through all of them, then went back and tested the things you guys suggested.
The GND and IN- pins are indeed connected through the jumper present in just behind them. I think it's in place in case you want to power the 5v input from another source on VCC and GND, then fire the relay with the IN+ and IN- connected to the GPIO and GND respectively.

That said, it seems like although i am powering the board with 5v on its VCC and GND, the switch wont fire unless it has 5v on IN+. I tried connecting the board to a usb 5v source like this (jumper shorting GND:IN-): 

5v+ : VCC  
GND : GND

Then got a wire of the same 5v+ and touched the IN+ pin. The switch fired whenever the pin touched 5v.

Update 2:
I tried to replicate the same connection on the RPi 5v rail, (5v:VCC, GND:GND, test 5v: IN+) the relay does not fire. (jumper shorting GND:IN-)

I guess i reached the bounds of my E.E. knowledge, please advise, what am I missing?
Is it an Amperage issue?

Best Answer

Here is a likely schematics of your relay module:

optical isolation relay

Relay to Raspberry connection:

VCC to +5V
IN+ to GPIO
IN- to GND
GND to GND

GPIO is configured as push/pull output, no pull-up, no pull-down. Relay is turned on by writing 1 to the port.

Alternate connection if the first one can't activate relay:

VCC to +5V
IN+ to +5V
IN- to GPIO
GND to GND

GPIO is configured as open-drain output, no pull-up, no pull-down. Relay is turned on by writing 0 to the port.

As voltage between IN+ and IN- is more then 2V, GPIO is never forced above 3.3V, so it should be pretty safe.

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