5V 4 Channel Relay Module 10A (CE05279)

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A versatile relay board with opto-isolated inputs. Each channel can drive up to 10A @28VDC

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Hi. Can you please explain what the opto-couplers are for?

Hey Mike,

The opto-couplers provide a full “air gap” between the sensitive digital control logic and the the relays (which can be very noisy electrical devices). This will prevent things like an Arduino being reset or damaged by coils that are de-energizing.

This got me thinking a bit more, so I did some research. I stumbled onto this read which makes a pot more sense. If you find other advantages then please do share!

5V 4 Channel Relay Module 10A

SKU: CE05279

Hi, can I clarify if these can be driven directly from a Pi3’s GPIO without extra circuitry? I think the opto isolation says this, but I’m not sure, thanks.

If you remove the jumper VCC / JD-VCC you can connect the Pi 3.3V to VCC and Pi 5v to JD-VCC
The Pi. 3.V then only supplies the input (diode) of the opto-coupler and will not damage the GPIO at all.
That is ther whole purpose of opto-isolators or opto-couplers.

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Do you have a case which would accommodate a

5V 4 Channel Relay Module 10A


Hi Robert,

Welcome to the forum! Sorry for the delay getting back to you.
If you are still searching this enclosure should comfortably fit the relay module.


Will these work with arduino?

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The product description includes a * Customer recommended resource #1 which links to a detailed description of the item. This includes the comment “…which is compatible with Arduino control board.” so you can assume it works just fine with Arduino.



Yes it does, and even if your board uses 3.3V logic rather than 5V I’ve tested this particular module myself and it still triggers fairly consistently all the way down to about 2.8-2.9V


I’m having an issue with switching mains live wire.
I’ve got 2 Pis 1st pi controlling first 2 relays 2nd pi controlling last 2.
Now relay 2 and 4 controlling 12v dc and its working fine but when trigging relay 1 and 3 (mains live wire) it turns on but doesn’t turn off.
Vcc is connected to power supply
Ground is common across both Pis running on same 5v 14amp power supply and the jumper is in. Not sure what’s going on pls help

hello. My system is utilizing the JST connectors. Why did you opt for screw terminal blocks and not JST connectors? Can this be changed to match my system requirement?

Hi Shane
What sort of a mains load are you switching? The contacts could be welded but this is pretty unlikely as the relays are rated for 15A @ 250VAC. Or if there is a snubber circuit across the NO contacts and the load is very light there could be enough leakage to keep the switched device “ON”.
A bit of a circuit diagram would be handy.
Cheers Bob

Hi Simon
Using screw terminals makes this device completely universal. The manufacturer cannot accommodate everyone’s connector type.
Another reason, the relays are rated for 250VAC and the output connectors have to be rated in a similar fashion. I don’t know what the JST connectors are rated at but I doubt it is 250VAC. If you are not switching this voltage that is your business but the manufacturer has to allow for it…
Converting to your use would not be easy as the pin pitch on those screw terminals would probably be 5.08mm and your JST 2mm or 2,54mm. You will have to make up some sort of adaptor or cut the JST connectors off and just use the wires.
Cheers Bob

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Its just to turn on a 3d printer so not a big load.
I had previously had the same circut on a dual relay and it worked so i have no idea whats diffrent. Oblusly appart from having the 4 relay board and signal wire from 2 pis but surely thsy cant have anything to do with it.

Earth and netrul go to the printer then
Live wire just goes into the in and then from NO strait to the printer

Hi Shane
Is the dual relay board the same circuitry as the 4 relay model ?? It would be nice to have a circuit of this board to see exactly what the inputs and outputs are. A bit hard to find as the manufacturer or supplier is not even quoted. CORE PLEASE TAKE NOTE. Without this information one could only guess and one gets a bit fed up with guessing.

One question, does removing power to the board release the relay ??

Can’t get much more basic than that.
Some possibilities
There is a snubber circuit across the NO contacts that is not on the dual board, or different component values on the 2 boards
If the relay contacts remain closed with no power the relay contacts somehow have become welded.
The relay driver transistor is latching on and not releasing the relay
The opto coupler is somehow remaining on.

One thing you can do is remove the mains voltage connections and using a multimeter or some other indication make sure the relay is activating and releasing when it is supposed to.
You could also swap the DC and AC switching between relays and see if the problem transfers with the swap.

There are other swaps and things to do but without the device on a bench in front of you and a circuit of that board it is going to be difficult to isolate the problem. But the first thing to do is make sure the relays are operating correctly without any load connections.

Contact Core and ask for a circuit for that board.

Just found a circuit for that board, a screen shot of one channel follows

This is a straightforward opto coupled relay driver. There is no snubber circuit across the NO contacts so disregard that problem.
To activate the relay you must switch the inputs to ground.

There is one other possibility. You say you have the jumper fitted and I am assuming “JD-VCC” is 5V to operate the relay. Now if your input from the RPi is 3.3V you could have your problem.
Scenario: You switch input to ground, thus switching the opto and activating the relay. You now switch the input OFF which will return the input to 3.3V. This will leave 5V - 3.3V = 1.8V across the opto LED. This could be enough to keep the opto on enough to keep the transistor partially on and prevent the relay releasingThis is a bit of an iffy situation and I think would be unreliable anyway.

A possible solution as I see it would be to:

  1. Remove the link.
  2. Connect JD-VCC to 5V to operate the relay. I would not try to drive the relay with 3.3V. This has come up before and although some may say it is OK the reduced voltage and the voltage drop across the transistor puts the relay outside manufacturers guaranteed operating range and would be definitely unreliable.
  3. Connect VCC to RPi 3.3V. This will ensure the opto LED is definitely OFF.

There is info re this board with text describing the link function and other variations here

Cheers Bob
Another solution
The opto couplers might be happier and more reliable with 5V.
Leave the link in place. Use a logic level shifter to up the GIO outputs to 5V. This would ensure that the opto couplers are OFF when the GPIO pins are HIGH. This will use the relay 5V supply for the optos in which the relay supply ground and the RPi Ground must be connected.
If you don’t want to connect the grounds remove the link and connect VCC to RPi 5V output…DO NOT connect RPi Ground.

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Your not gonna beleave this i feel so dumb. Turns out they just got stuck on first trigger. Unpluged the load and knocked them with back of screwdriver while rapidily changing state once it was unstuck i just cycled the relay for like 20-30 times then pluged load back on and its working well now.

Thank you so much for your time and to respond so promtly. This is why i shop here absolulty fabulous service top knotch!

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Not so dumb. I wouldn’t have expected that to happen. If it was me that unit would be in the bin and I would find another brand. But that is me.

Even if you are satisfied the problem is fixed I would still have a read of above and investigate carefully how the 5V and 3.3V are used. If there is any chance at all of the opto couplers staying on, even a faint glimmer you could not regard the system as reliable. If those relays stuck mechanically once they will do it again and personally I would not trust them.

Problems with this sort of board came up some time ago and I had occasion to search. There is one brand of board at least which uses OMRON relays which are a proven and trusted brand. I personally have never heard of this SONGLE brand until I started reading posts on this forum.
Cheers Bob

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