12v relay

sorry for my bad english and if i put in a wrong section,

i buy this relay months ago,
after asking in this forum turn out this relay is 12v,

i don't know why maybe because it 12v, it has a jumper,
what jumper do?
and what COM pin do?
i have 12v adaptor, how to use it to this relay?

sorry i ask this because it doesn't come with the manual

note : images at attachment

thanks for reading

(deleted)

spycatcher2k:
NOT an Arduino question. Support comes from your supplier for stuff you buy!
Or use google - 12V relay module Arduino

i buy this relay months ago,
even the note purchase has gone,
i have using google to search com pin, but always come out is com port from connecting from pc to arduino,
i desperate enough to ask in here because i can't find it in google


picture

dave-in-nj:


picture

yes?, will you explain me what com pin does? and how to use it?

There isn't a lot of detailed information on that board, but the few sites that mention the COM pin indicate it is the common ground point for the inputs to the optocouplers.

With the jumper installed, the arduino and the power supply for the relay board share a common ground.

Removing the jumper and connecting COM to ground on the arduino will completely isolate the arduino from the relay driving circuitry.

Should be easy enough to verify by looking at the board, and checking with an ohmmeter.

You also need to verify that there is a current limiting resistor between the IN pin and the optocoupler, from pictures of the board it appears to already have the resistor, but some websites indicate it does not.

Always hard to find good information on the cheap generic boards.

david_nc:
There isn't a lot of detailed information on that board, but the few sites that mention the COM pin indicate it is the common ground point for the inputs to the optocouplers.

With the jumper installed, the arduino and the power supply for the relay board share a common ground.

Removing the jumper and connecting COM to ground on the arduino will completely isolate the arduino from the relay driving circuitry.

Should be easy enough to verify by looking at the board, and checking with an ohmmeter.

You also need to verify that there is a current limiting resistor between the IN pin and the optocoupler, from pictures of the board it appears to already have the resistor, but some websites indicate it does not.

Always hard to find good information on the cheap generic boards.

thanks for the reply,
correct me if i wrong, vcc is 5v right?,
where i must put the 12v power input, i afraid the 12 volt will damage the arduino

That looks to be the same board.

The 12V supply goes to VCC and GND on the relay board.

If you leave the jumper in place, GND on the relay board goes to GND on the arduino.
If you remove the jumper, the COM pin goes to GND on the arduino, and the arduino had no connection to GND on the relay board.

1 Like

david_nc:
Raspberry Pi Store | The Pi Hut

That looks to be the same board.

The 12V supply goes to VCC and GND on the relay board.

If you leave the jumper in place, GND on the relay board goes to GND on the arduino.
If you remove the jumper, the COM pin goes to GND on the arduino, and the arduino had no connection to GND on the relay board.

thanks for reply,
so put 12v adapter + to VCC, - to GND beside VCC, arduino (numbered)pin to relay(numbered) pin,
then, where i must put GND from arduino,
sorry if ask to many, i read if you put wrong voltage, it will fry the arduino

Safest way would be to remove the jumper, and connect GND from arduino to COM on relay board.

david_nc:
Safest way would be to remove the jumper, and connect GND from arduino to COM on relay board.

that is answer that i need to know,
thanks a lot, i give you karma point

the relay board, like all relay boards has 3 separate voltages.

the output of the relays can be anything. they are completely isolated from the input, so no need to discuss them.

the relay has a label, in this case it is SRD-12VDC
this means that the coil inside of the relay is 12 volts DC.

that is the second voltage you need to be concerened aobut.
and this one is REQUIRED to be on a separate power supply. this 12VDC does not come from the Arduino.
the power supply has to be sized to be able to deliver enough power for all the relays to be on at one time.

now, the 3rd voltage.
the tiny squares near each relay that have 3 legs, are the transistors that send power to the coil
the larger squares are the opto isolators that signal the transistors. these opto isolators are what the Arduino drives.

an opto isolator can be thought of as an LED, if you can drive an LED, you can drive the opto.
the opto isolator should get power exactly like an LED, use a resistor to current limit the power.

I cannot read the label on the opto, it might be an AC/DC opto which means that there is no + or - that needs particular attention. so, if you connect your common to the ground for the opto's, then you feed each one with a 5v output from your pin, with the resistor to limit current.

that means. Arduino ground to the common pin
a wire from your output pin, to a resistor (330 ohm to 1k ohm) and the other side of that resistor the relay pin.

use the BLINK sketch and select your Arduino pin in that to the relay high, then low.
you should hear it click each time.

if you connect the common to the Arduino 5V, then you bring any one pin to ground (with a resistor in-line) and that will turn the opto to the ON state and the relay will click.

for the large relay boards it is prefered that you feed the common with 5 volts, then use the pins to bring to ground.
the 8 channels,

If you use a resistor selected for 20mA, and used arduino ground to the common.
your Arduino board would have to output 160mA if they were all high. this is called SOURCE
The Arduino PIN is the source of the current.

if you connect the Arudino 5v to the common and use a resisistor for 20mA for each signal line, then the Arduino would SINK the 160mA. the pins would bring that to ground.

the Arduino UNO is listed as being able to SOURCE up to 200mA from the all the output pins combined.
the UNO is listed as being able to SINK up to 400mA from all the output pins combined.

That is why it is preferred to put the 5V to common and use a resistor between each pin on the relay board and your pins on the Arduino.

This webpage has some of the best pictures I've found for that board (appears to have the same silkscreened numbers as the OP's), unfortunately its not in English, but google translate does a fairly good job on it:

Hi,
This is strange. I do business with Keyes and have access to their English and Chinese Taobao sites. That relay board is nowhere to be found!

Search on their Chinese site of "12V继电" (12 V relay) finds only a 16-channel board.

Maybe it was a special for a customer and then some were sold into the market??

All the pics i found were years old

Maybe discontinued ?

Maybe good reason!

dave-in-nj:
the relay board, like all relay boards has 3 separate voltages.

the output of the relays can be anything. they are completely isolated from the input, so no need to discuss them.

the relay has a label, in this case it is SRD-12VDC
this means that the coil inside of the relay is 12 volts DC.

that is the second voltage you need to be concerened aobut.
and this one is REQUIRED to be on a separate power supply. this 12VDC does not come from the Arduino.
the power supply has to be sized to be able to deliver enough power for all the relays to be on at one time.

now, the 3rd voltage.
the tiny squares near each relay that have 3 legs, are the transistors that send power to the coil
the larger squares are the opto isolators that signal the transistors. these opto isolators are what the Arduino drives.

an opto isolator can be thought of as an LED, if you can drive an LED, you can drive the opto.
the opto isolator should get power exactly like an LED, use a resistor to current limit the power.

I cannot read the label on the opto, it might be an AC/DC opto which means that there is no + or - that needs particular attention. so, if you connect your common to the ground for the opto's, then you feed each one with a 5v output from your pin, with the resistor to limit current.

that means. Arduino ground to the common pin
a wire from your output pin, to a resistor (330 ohm to 1k ohm) and the other side of that resistor the relay pin.

use the BLINK sketch and select your Arduino pin in that to the relay high, then low.
you should hear it click each time.

if you connect the common to the Arduino 5V, then you bring any one pin to ground (with a resistor in-line) and that will turn the opto to the ON state and the relay will click.

for the large relay boards it is prefered that you feed the common with 5 volts, then use the pins to bring to ground.
the 8 channels,

If you use a resistor selected for 20mA, and used arduino ground to the common.
your Arduino board would have to output 160mA if they were all high. this is called SOURCE
The Arduino PIN is the source of the current.

if you connect the Arudino 5v to the common and use a resisistor for 20mA for each signal line, then the Arduino would SINK the 160mA. the pins would bring that to ground.

the Arduino UNO is listed as being able to SOURCE up to 200mA from the all the output pins combined.
the UNO is listed as being able to SINK up to 400mA from all the output pins combined.

That is why it is preferred to put the 5V to common and use a resistor between each pin on the relay board and your pins on the Arduino.

sorry for late reply, i thought this thread is done,
anyway, thanks for the reply,

to be honest, i dont understand about ohm or mA,
i google and youtube this device for hours yesterday,
every other 12v relay have separate power 12v input using bolt,
the one i have is only "pins",

anyway after i google today , i found this :

and the manual :
https://www.jaycar.com.au/medias/sys_master/images/9183398527006/XC4418-dataSheetMain.pdf

after i read it i know you must put the 12v power input + to VCC, - to GND next to VCC,
now the things that i do not understand is, what COM and GND next to COM do?, and what that "jumper" do?

correct me if i wrong,
but is COM is connected to 5v from arduino,
and GND next to COM connected to GND from arduino?,
is that right?

sorry if i ask very newbie question, i just dont want to fry up my device

Remove the jumper.
test the 12V gnd to the ground pin where the jumper was. these should be connected.

Test the 12V gnd to the com pin where the jumper was.

if you show that the 12v ground and the jumper ground to be the same circuit, remove the jumper and do not use

If the com is not connected from this test, then that is good.

connect the 5v from your Arduino to the com pin.

get a resistor, a 330 ohm, a 1,000 ohm (same as a 1k ohm)
or anything in-between.

connect one side of the resistor to an output pin on your Arduino board
connect the other side to any of the relay pins

open you IDE and open the example blink
add the output pin from above to the example so that it will blink that pin at the same time it blinks the LED

you should hear the relay click on and off.

sorry, I am using Ubuntu and there is no easy to use PAINT program that I can add notes on the photo.

dave-in-nj:
Remove the jumper.
test the 12V gnd to the ground pin where the jumper was. these should be connected.

Test the 12V gnd to the com pin where the jumper was.

if you show that the 12v ground and the jumper ground to be the same circuit, remove the jumper and do not use

If the com is not connected from this test, then that is good.

connect the 5v from your Arduino to the com pin.

get a resistor, a 330 ohm, a 1,000 ohm (same as a 1k ohm)
or anything in-between.

connect one side of the resistor to an output pin on your Arduino board
connect the other side to any of the relay pins

open you IDE and open the example blink
add the output pin from above to the example so that it will blink that pin at the same time it blinks the LED

you should hear the relay click on and off.

sorry, I am using Ubuntu and there is no easy to use PAINT program that I can add notes on the photo.

sorry i quite late right now, i will ask to my relative in the morning, i dont get what ohm do, i will give you the report tomorrow

resistor is measured by ohms.

you select a resistor using the color bars. the color bars tells you what the ohms are