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Topic: 12V door strike and the 5V arduino uno  (Read 438 times) previous topic - next topic


Aug 21, 2017, 12:12 pm Last Edit: Aug 21, 2017, 12:19 pm by mumbus12
Hi everyone,
I currently have a 12VDC fail safe door strike which i would like to wire to my arduino. From my research i require a 12v relay but i have no idea how to set this sort of circuit up with another 12v power source to power the doorstrike. Could anyone help me with this? and maybe draw a schematic for the circuit which I could follow?

Any help is appreciated. Regards,

More info on my project: I would like to control my door strike remotely via Bluetooth modules (HC-05 and HC-06) I am connecting the doorstrike to the HC-06 Module which is set up as below:


Aug 21, 2017, 12:39 pm Last Edit: Aug 21, 2017, 12:41 pm by groundFungus
You could, probably, activate the door strike with just a logic level MOSFET, a diode, and a couple of resistors.  No need for a relay.

Door strike is the load.  Size the MOSFET for the current requirement of the door strike.


I am really new to arduino and have no idea what this means. I can understand more simpler cirucits, so this might need a little bit more expaining. Thanks for taking time out to help me.



A MOSFET uses a small signal of voltage to change the state of the device.
by sending a 5 volt signal to the GATE, you allow the device to pass power.

as shown, the FET  is an 'N' channel which means it MUST be between your device and ground.
your device gets connected to the 12 DC + connection.
your device 12V - connectes to the FET
the FET connects to ground.

the MOSFET is a DC only device, never AC

if you were to use a LOGIC LEVEL device such as a IRL540  (the L stands for logic level)

You could put a voltage from a pin to the GATE.

you need to get a device, read the data sheet and connect as per the data sheet and the above schematic.

Note that the diode can be any diode but is required.

The resistors laid out are good, you could get away with a 100 ohm or a 330 ohm or some such.
remember, 2 resistors of 330 ohm with ends twisted together (parallel) would deliver half of the listed resistance.

you could use a Transistor, but would need a slightly different circuit.


How would this circuit look when made? I know you might not have a door strike but i would just like to see something i can folllow. And for the MOSFET does it have to have an L? The only one my local electrical store sells is IRF540N, would this suffice or do I need to look elsewhere.

Thank you so much for your help! :)  :)


Yes, the "L" is necessary. You may get the "N" version to work adequately well, but it won't be reliable and may be burned out the first time you use it.

Start looking for online stores. The variety of electronic components available is much larger than any physical store can hold.
"The problem is in the code you didn't post."


If I am not able to purchase the correct mosfet, could someone help me in setting up a 12v relay for the doorstrike?


This might be what you're looking for (see attached)


whats under the purple line??? And thanks for the diagram it helped me heaps!!!


Please don't introduce newbies to Fritzing diagrams - PLEASE !
When posting - use the toolbar and read the stickies if you're not sure!


Aug 22, 2017, 12:09 pm Last Edit: Aug 22, 2017, 12:10 pm by TomGeorge
@sylki image..

Why are you supplying 12V to the control side of the relay PCB, when clearly it has 5V coil relays?

Where do you set the jumpers in the lower right corner of the relay PCB?

Tom..... :o :o :o
Everything runs on smoke, let the smoke out, it stops running....


+12 on the control side of the relay board will almost certainly have damaged the output side of the opto-couplers on the trigger inputs.
Fingers crossed they are over-rated, and current listed within spec.
The 5v relays woukd have given a mighty 'click' when they pull in!
When posting - use the toolbar and read the stickies if you're not sure!


Are you guys saying this diagram is wrong???


Yes, the diagram is wrong. Either you have the incorrect connections or you have a different module to the one in the diagram.
"The problem is in the code you didn't post."


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