Question 1

I'm still not clear with the jumpers are for.  What does optoisolation do here?

Accepted Answer

There are a few reasons why you would use isolation here. By the way, jumpers are for isolation - although the top jumper is futile. To use the optoisolator, disconnect the bottom jumper and connect the left pin to ground for the signal coming in to the board and connect the right pin to the ground of the voltage that activates the relay. The VCC should be connected to the voltage source that operates the relay (or if you want to remove the top jumper, vcc goes to the right pin, however it is the same as leaving the jumper on and just wiring it to the vcc input on the board. - I have used this setup to run a bank of relays off of an esp32. This allows you to run many relays without any significant voltage drop on the esp32. You will need to provide an alternate vcc for the relays. Imagine running 15 relays off of the ESP32. That would possibly cause a voltage issue on the board. If all you need to do is run 15 tiny leds (I guess 30 if you include the indicator on the board) your voltage drop would be much much lower. Because this uses optoisolation, the circuit that sends the signal (usually a microcontroller) and the voltage that powers the relay, can be totally isolated. You could use a battery for one and a computer usb for the other - no common ground between the two.  -- Not pointless by any means, but the circuit setup for this is goofy and causes you to scratch your head for a minute.

Question 2

Will 3v power the relay?

Accepted Answer

3V ok

Question 3

I want to run this realy on a 2 AA battery box (3v total) do i need to do anything with jumpers?

Accepted Answer

No need to change, 3V ok

Question 4

I put 3.3v on vcc and grounded gnd. when i put 3.3v on in, the red led lights, but the relay doesn't close. is there something i'm missing here?

Accepted Answer

It should work.  You are controlling a Transistor that is operating the relay.    Make sure there is enough current in VCC to activate the relay.  LED will light with only 1.3v and very little current.  The relay must have 3.3V VCC.  Also make sure your Arduino output line has the same ground as board.  Using separate power supplies can cause the problem.  Otherwise, I need more details about your connection.

ASIN	B07XGZSYJV
Best Sellers Rank	#29,937 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #3 in Optocouplers
Brand	Teyleten Robot
Brand Name	Teyleten Robot
Coil Voltage	3.3 volts
Connector Type	Crimp
Contact Current Rating	10 A
Contact Material	Silver
Contact Type	Normally Open
Current Rating	10 A
Customer Reviews	4.6 out of 5 stars 221 Reviews
Item Weight	0.27 g
Manufacturer	Teyleten Robot
Maximum Switching Current	10 A
Maximum Switching Voltage	250 volts
Minimum Switching Voltage	3.3 volts
Model	RK-S1B4-G97L
Mounting Type	Panel Mount
Number of Items	5
Number of Terminals	2
Operation Mode	Automatic
Part Number	RK-S1B4-G97L
Specification Met	cULus
UPC	724545020568
Unit Count	5 Count
Warranty Description	no

Teyleten Robot DC 1 Channel Optocoupler 3V/3.3V Relay High Level Driver Module Isolated Drive Control Board 3V/3.3V Relay Module for Arduino (Pack of 5)

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