Connecting 6VDC relay with Arduino?

I bought a bunch of Relays that i want to connect with Arduino UNO they have an Operating value of 6VDC and switching capability of 240 VAC and having 5 connector’s as in the Picture:

I wanted to know how can i connect it to arduino and as its 6VDC will it be able to work with arduino’s 5 VDC or not or i have to provide external power source?

The picture is so unsharp it could be anything - my car seen from space ?. You have to come up with a better picture. If there is a typenumber on the relay you can google for "typenumber datasheet" to find more info about the relays.

As the relays are 6V you better drive them with a transistor and external powersupply. see -

Nishant, you have to be taking the piss with that photo :)

With 5 connectors it's probably a SPDT relay, two if them will be the coil and they will almost certainly be seperate from the other 3, get a 6v battery and briefly touch these two if you can identify them. When I say briefly I mean hold GND on one pin and brush past the other pin with the 6v wire. If the relay clicks your done, if you get a flash you've found common and NC.

If the two aren't obvious just try different pairs until the relay clicks.

Having found the coil the other 3 are probably C, NC and NO.


Thank you to you both sir's. its like i had a weak camera (VGA) and the info. you gave was really worthit!

What point i have to connect with my Arduino UNO so that Relay could be controlled by it?

What point i have to connect with my Arduino UNO so that Relay could be controlled by it?

Have you identified the coil connections yet?


Here is a basic drawing of a typical Arduino to relay interface:


Most likely, looking at the very blurry picture, the three terminals on the right, from top-to-bottom are "coil 1", "COM", "coil 2", while the other two on the left are "NO" and "NC" contacts (from "COM"). This is how most SPDT relays are set up, with the common center pole between the two coil connections. Use a multimeter set to 1K ohm or lower range, and check the connections; the coil will register with a resistance, whereas everything else will either be infinite resistance (open/no continuity) or zero resistance (closed/shorted). If those two aren't the coil, then they'll be the contacts on either side of "COM", and the other two on the left will be the coil.

To hook it up to the Arduino, see here:

Just use a 6 VDC supply across the coil to energize the relay; make sure your ground is connected with the Arduino's ground. DO NOT leave out the resistor -OR- the diode, they are important!

i have found the connection's , The 3 on the right side have the COIL points at the extreme corner's and in between it is the COM and the other 2 points at the extreme(left side of the pic) are the NO and NC, Now which point you think i should give into the arduino?

Also i have operated it at 5 VDC and It clicks with it too! my dad is telling me that 1 VDC is not that much of a difference it can be operated from arduino? , What you people think?

I have Uploaded A NEW NICER! PICTURE please! take a look

Firstly, your camera problem isn't that it's a vga. You are too close for it the focus setting. I have a simple VGA camera that is capable of excellent focus down to less than a centimetre. Does it have a rotating lens assembly that can be used to adjust close-up focus.

Tell your dad that operating a 6 volt relay at 5 volts via a transistor driver results in the relay operating at around 4.3 volts. That is 72% of it's designed rating ( ie 28% short) so 1 missing volt is indeed relevant. Yes it might work but not with 100% assurity.


The 3 on the right side have the COIL points at the extreme corner's

Does this part have any identifying marks on it? Post that information.

You may be able to make it click with 5V, but without knowing how much current it takes you are at risk of damaging the arduino pin you connect to.

Do you have a multimeter that can measure milliamps? If you have a milliamp setting on your multimeter, then put your meter in series with the 5v supply, the relay coils, and ground and see how much current is flowing. It it's 25-30-35 mA, then you're asking the arduino to work hard to drive it. If it's over 40mA, then you're looking at damaged pins. Hence the transistor in the schematic examples that were posted.

why not just use the mini relays form radio shack i saw them 1.88 cheap

The OP started the post by saying a bunch of them had been purchased.

@Crossroads Sir, There have been no marking over the RELAY but i have checked it with 5 VDC supplied to it with a Voltage regulator/adjuster and it Clicked perfectly! and stayed at that state,Yes i have a multimeter that can measure miliamps ?,

No markings. Odd.
Well, check the coil current when you have 5V turning it on, see how much current it is using to make the contacts change.

5V+ to Meter+,
meter- to coil+,
coil- to power supply ground.

Better still, measure the coil resistance and maybe some of our more experienced users can make an informed guess as to what the voltage rating is

Are you sure there are no markings, absolutely nothing at all ?


Hello, its BAD news relay takes 60 mA calculated by measuring the ohms at the coil points (w/o giving them power just multimeter)and used the formula I=v/r so I = 6V/100 ohms gives I=0.06 i.e. 60 mA.

Arduino pins can handle MAX 40mA , Now what to do?

Look on the bright side - you didn't damage your arduino, and you have a chance to learn something new. Now you get to play with some new parts - a transistor, resister, and diode. There has been plenty discussion here the last few days about driving relays. Do a little search, then pick up a 2N2222 transistor, 330 ohm resister, and a 1N1004 diode:

Or several of each if you plan to use several of the relays.

Consensus is that you can parallel up transistors for more current drive. Connect the collectors together to go to you relay. Connect the bases together with a 560 ohm resister from the arduino. Put a small resister from the emitter of each transistor to ground. With each resister dropping 30 mA, a 5 ohm resister should work (or 2 10 ohm resisters in parallel).

Sir,What about the diode ? ,do i need to duplicate it too or use one or not required?

Yes, you need a diode across the relay. This will help protect your transistor as the relay coil changes state going from on to off and creates a voltage spike (something inductors do when the current suddenly stops flowing). 1N4004 or similar (I may have mistyped some other numbers before). Doesn't have to be very big with 60mA of current. But definitely put one across the relay coils, with anode towards the transistor.

i got 4007 diodes(its similar to 4004 which is dis-continued in our market briefly due to being similar in many respects) and i’m putting a BC 547 ,can you tell me the resistance that i had to link from arduino?

I think 6000 ohm would suffice as in following:(fact that BC548 ~ BC547)