This is a placeholder topic for “5V 2 Channel Relay Module 10A” comments.
A versatile relay board with opt-isolated inputs. Each channel can drive up to 10A @28VDC
Read moreHi, does this work with 3.3v logic if powered by 5v? wanting to use with esp32
does the 5V 2 Channel Relay Module 10A work with 3.3V control logic (with 5V VCC)? I would like to use it with an esp32
Hi Daniel
Text on this one is delightfully vague isn’t it. No schematic to help, does not even indicate whether operation is active high or active low. I personally would not touch this with a barge pole (as the saying goes) unless that sort of information is made available.
But getting back to your question, being opto isolated it probably would work IK. You are doing the right thing though by operating the relay at 5V. it is fairly obvious that this option is available which is good.
Cheers Bb
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I’ve just tested a unit from out shelf stock, I was able to make the relay fire with 3.3V logic while VCC was connected to both 5V and again the 3v3 rail.
I’ve updated the product page to reflect this new information, which will be live in a few hours.
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Hi Dan
That still does not say if it is active high or active low input.
Although
sounds like active high. But that is still only a guess.
Cheers Bob
This has been brought up many times but operating the relay at 3.3V is well outside manufacturers specs which from memory is 3.75V. Some or even most will probably work albeit a bit slower but there are others that have been reported to not operate at 3.3V.
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Awesome, thanks for the help guys
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Hi, me back with another dumb newbie question…
- I assume that the symbols on the screw terminals represent COMmon in the middle, and I guess that the bent line for COM indicates that the right terminal is its default, normally connected (NC) position ? Which makes it NO - COM - NC ?
- I assume also that if there in no In1 or In2 signal (eg the ESP32 is in deep_sleep) that the relay goes to its default NC position ?
- Similarly if there is no VCC (eg the battery has gone totally flat) the relay also reverts to NC ?
Assuming 2. is correct, I am thinking that I will need to distinguish between deep_sleep and flat battery. I guess that’s a latching relay, so it stays in the open or closed position it was last set to even when power is off ? If so, is DFR0996 - Gravity: Magnetic Latching Relay for ESP32 / Arduino the only/best latching relay to switch 5V DC load ?
Hi Donald
Items 1, 2 and 3. All correct.
As for the last paragraph depends what you actually want to do. I just had a look at the text for that latching relay. Says it is something new developed over the last few years.
What a load of crap.
They have been around for the proverbial donkeys. That little board might be something new. If it is the same as the old ones you apply a voltage to the coil in one direction to operate and in reverse to release. I think that on board IC takes care of this. Not enough information available to know for sure. Others had 2 coils, one to operate and one to release. So the self latching relay is nothing new.
It is common to wire a DPDT relay to self latch but this will still release when power is removed.
The text also says that the latching relay is quiet and the non latching type hums. With DC ??? that statement can join the other one as crap. Probably a 5V relay operating at 3.3V and not being able to make up its mind whether to operate or not. THAT would probably seem to hum.
Cheers Bob
Add on: I just had a hunt around to try to find out about when latching relays came into use. I did not have any luck here but Wikipedia has a good article on relays in general and a section on different types of latching devices, but no development dates. It seems that this principle evolved over quite a time and was mainly driven by necessity. I do know that they were around quite a while before I finished full time work and that was 25 years ago.
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Thanks Robert for confirming my assumptions before I dive down another rabbit hole 
What surprised me most is that a search for “latching relay” or just “latching” on Core returns plenty of latching switches, but only the one relay product and an Adafruit feather. Like you, I thought they had been around a loooong time.
A google search finds plenty of latching relays for automotive and industrial use … so maybe there is just not much in the hobby / breakout board market segment. Yep, Adafruit only have the Feather board which frankly scares me with all those header pins.
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Hi Donald
I KNOW they have been around a loooong time.
I would think that Element 14 and RS Components would have lots as they cater mostly for professional and industrial user.
You had linked the Gravity one above, that is where I got those statements from. I checked the DFR web site and the statements seem to be a direct copy from there. I could not find a circuit so hard to tell what type it is.
Just looked up the data sheet for the relay used. It is a single coil latching type. The Core and DFR text says a 2mSec pulse is required to operate but the relay data sheet says 100mSec. Maybe the on board smarts stretches the pulse. There is no circuit available that I can find so don’t know what they are doing here.
Can’t make out much about the Adafruit offering. There is a circuit of sorts but does not say much. Can’t work out how it works and I am not really going to bother much.
Cheers Bob
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Hi Donald
I had another look at the circuit for that “Feather” board. The circuit indicates 2 different boards. the non latching and latching, both are depicted on the circuit drawing.
The one on that Core page is latching and would appear to be the 2 coil type. The circuit shows 2 relays but if you look carefully the relay pins are different so I believe there is only 1 actual relay with 2 coils.
I haven’t bothered to look any further.
Cheers Bob
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Hi there, I’m using a 5V 2‑Channel Relay Module (10A) to control two 220V / 4.5A water pumps. When the relays are triggered, the relays don’t always activate unless I tap or shake the relay module. I’ve already checked all the wiring and connections.
Any suggestions on what might be causing this?
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Hi Farhad
It would be a BIG help if there was more info.
Which relay board have you got, there are several around.
How are you driving it.
What voltages are involved.
A schematic or even a block diagram would be a help also.
At a guess I would think you are using 3.3V. Some of these relay board descriptions say the 5V relays will work at 3.3V but my personal belief is that this is too marginal for reliability.
The symptoms you describe are pretty much what I would expect if your 5V relay device was powered by 3.3V
Cheers Bob
Sorry, there is an SKU in the title. Is this the one you have.
But as usual there is virtually no information on the Core web site. You might get some more info if you purchase one but I am not about to do that.
I think someone reversed engineered this device some time ago and produced a schematic but I would have to search for it.
Hey there, @Farhad164597, and welcome to the forum, glad to have you here.
Can I clarify that your water pump is actually 220V?
If so, I would insist that you stop at once. Anything over 50V is well outside the domain of us hobbyists and becomes the job of a licensed electrician.
If you’re using this relay from the forum page, please note that while the actual relay is rated for 250V, the board it is attached to is not. The unit is only rated to 10A @28VDC. At the voltages you’re using, you are playing with fire.
Please hire a licensed electrician to do this work.
Hi Jane
I certainly agree with and I completely missed that.
But. In fairness to Farhad. The text says 10A @ 28VDC it DOES NOT state the rating placed on the board for ACV. This is on the Relay as 230VAC and I suppose he could be excused for thinking this applied to the unit as a whole.
You (and I should) know this as it has cropped up before with other products using these relays but if this is a first time use of this type of product I think he could be excused.
Just one other observation. I think (and I could be quite wrong) that previously the operating voltage was stated as 3.3 - 5V. There was quite a lot of discussion about this for some appreciable time but I note the absence of any reference to 3.3V now. This is good as there was a lot of debate on this issue and now that has been cleared up. I think there are similar units fitted with 3V relays now so this issue has been catered for.
Cheers Bob
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I have drawn a circuit of it. This shows the input and relay are separated by an opto Isolator which allows 3.3v to drive the 5v relay. I hope that helps.
Relay2pcb.pdf (131.0 KB)
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Hi Andrew
Thanks for going to this trouble. I don’t need one of these so this is interest only. I don’t see why Core could not have published this in the first place.
I could make some comment though. I don’t see the reason for any indicator LED (do you??) as it only tells you you want the relay to operate, not that it has actually done so.
Secondly the Opto LED is quoted as a forward drop of 1.2V. By the time you add the drop across the extra diode there is not much left of a 3.3V starting voltage. With a 1kΩ resistor in series the opto current would be lucky to be 1mA. Hardly enough to operate the Opto coupler reliably. Would stand a bit of chance at 5V.
That alone would put me off buying this item unless I was using at least 5V.
Thanks again for your effort
Cheers Bob
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Hi Bob, indeed 1mA is what the Sharp datasheet says is the minimum requirement for the opto coupler to function. The series status LED is quite bright at 1mA. I bought a few of them, it saved me doing a PCB and so far they always operate reliably at 3.3 volts. I wondered if they could be jumpered for active high. Tracing out a circuit let me understand what I have actually got.
Andrew
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Hi Andrew
Not easy as it looks like the series resistors (R1) are common to 3.3V VCC. If they were separate all you would have to do is connect the “IN” (signal in) pin to ground and connect the High signal to the 3.3V VCC point.
You will just have to make your sketch or whatever suit the relay module.
All too close to not working for this little black duck.
Each to their own ideas about “headroom”.
Cheers Bob
I would think seriously about fitting another 1kΩ resistor on top of the existing ones (to make 500Ω) to provide that little bit more LED current.
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