Relay 12 volt single channel module connections to Arduino

Other Hardware General Electronics
1

Hi,

I have searched the forum before posting and cpould not locate an answer to this even though I am sure it's been posted before.

I have a 12 volt single channel relay module with 3 pins vcc,gnd,in (low switching)

I must be doing something very wrong as I cannot get it to switch from a digital pin.

I connect my 12v supply to vcc and ground and the Arduino to gnd and the digital pin

Whilst I can see the digital pin is going high and low the relay is not switching.

More grey hairs already - what am I doing wrong.

Thanks in advance
Jonathan

2

g6swj:
the Arduino to gnd and the digital pin

WAG in the absence of specifics on the relay module, but the connection may be Arduino digital pin to relay ground and Arduino power to relay VCC like this. (And mind the jumper.)

3

Sorry maybe I did not make the connections clear

Ahh - sorry juma-yetu - just re read your post - will try that

relay module 3 pins

Vcc - to 12 volt postive (battery)
gnd - to 12 volt negative (battery) & Arduino gnd pin - common gnd
in - to Arduino digital pin

Jonathan

4

g6swj:
Sorry maybe I did not make the connections clear

Previous was clear, but it's not clear what connections the relay requires, as distinct from what you have supplied it. You should provide a link to the relay datasheet.

If it's one like in the stackexchange link, the relay's led is cathode to the data pin, and anode to Arduino 5V. That's backwards from what you're supplying, so the led would never be on.

(But I'm guessing: provide details of the relay module.)

5

And it's bad form to edit posts like you did, since it makes my later reply redundant and me look stoopid.

6

Sorry about the edit

This is the module

Relay.png
Relay.png595×625 418 KB

7

I'd probably have connected it same as you.

Presumably the green led, marked SW for switch? is meant to indicate activity- what's it doing?

And is the red on to indicate power to the coil?

8

Yes to led colour indication.

I have used 2/4/8 channels relays without any issue but they have opto isolation and transisitor switching - I can't make out what the components are on the single channel board.

An unsolved mystery....

Thanks

Jonathan

9

Is the green led toggling?

And the module (as opposed to its constituent Tongling relay) is devoid of maker's name and model?

10

These modules are made by the zillion....no manufacturer or data sheet

I have 5v versions and they work fine but I need to power the coil from a 12v source hence the 12v version.

If I power it from 5volts the red led illuminates not very brightly, the green led pulses with the digital pin high/low but the relay coil does not switch as not enough juice as 12v version on 5v supply.

Switch power to 12v and both leds remain illuminated

Take it away from the Arduino totally and power it from 12v to vcc and ground the red led (pwr) illuminates

Ground the "in" pin and the relay triggers and the green led illuminates

Wasted 3 hours on the blighter last night - think I will chuck it and it's 11 mates in the spares box and order a better board

Regards
Jonathan

11

So the implication is that the 12V version not only needs 12V on the coil as expected, but 12V on the signal?

12

Possibly but I don't think so

They are sold as "TTL level control signal" and supposed to be compatible with things like Arduino

I am sure I am missing something obvious but not sure I want to waste too many more brain cells

Thanks for your suggestions

Jonathan

13

I encountered the same problem as i bought same relay module as yours, I think you have to use it along with B547 transistor, as described in this video How to use 12V Relay module with Arduino to control High Voltage Devices | How Relay Module works - YouTube. I still have to try.