I am thinking of using a couple of relays that I had laying around for a project, but I'm worried about drawing too much current from the Arduino. The model of the relay is stated in the subject line. I have provided a link to the datasheet.
I see in the coil specs on the datasheet that power consumption is 0.9W at all voltages. Correct me if I'm wrong, but doing a quick calculation indicates that the coil will draw 180mA. Obviously the Arduino can't handle this so I'm wondering if I can just add a resistor in series with the relay coil to drop the current and if anyone can tell me if this will hinder the operation of the coil?
If using this relay is not possible then I will try to find others, but I have 4 available so if they can be used that would be great.
LiquidBoarder:
....5 volts from the Arduino isn't going to be enough to drive it.
Keep in mind you need more than volts to drive a relay. You're going to need a driver circuit. This is one of my favorite articles that explains it all.
I had to use waybackmachine to show it to you because at the moment ermicro.com is having an outage.
You can also get a relay module that has the driver circuitry built in, and those are popular for Arduino use. Have a look at this recent post where it is discussed.
And there's a whole YouTube video all about easy-to-use relay modules right here.
Yes, Ok that's one of mine but this question does tend to repeat itself quite a bit here, so now we have one (more) guide to using relay modules (with a gotcha pointed out in the link to the other thread).
Ralph_S_Bacon:
And there's a whole YouTube video all about easy-to-use relay modules right here.
Well, there's a lesson here in itself. Always check your links in the "Preview" (but don't use "iurl" for links or the post will be lost ).
Good tutorial. I liked it (though it was a trifle tedious for me). Covered all the bases nicely, including the cost diversity.
Didn't realise it was March already!
Also liked your use of a suitably coloured piece of Dupont connector ribbon. Now servo cable must be a specially made ribbon - black-red-white - but brown-red-orange is commonly used.
Does this mean there is a whole heap of yellow-green-blue-violet-grey-white ribbon and loose black wire floating around somewhere (in China)?
LiquidBoarder:
I see in the coil specs on the datasheet that power consumption is 0.9W at all voltages. Correct me if I'm wrong, but doing a quick calculation indicates that the coil will draw 180mA.
Yes, correct reasoning. The same solenoid or relay can have different windings for different voltages,
but they will all have the same number of amp-turns and same power dissipation
Obviously the Arduino can't handle this so I'm wondering if I can just add a resistor in series with the relay coil to drop the current and if anyone can tell me if this will hinder the operation of the coil?
No, the current is needed to switch the relay - you always have to boost a logic signal to
control devices using significant power like a solenoid.
Thanks for all the insights! I did know that its really the current that drives the relay coil. When I said the 5V won't drive it I misspoke.
When I posted this I was quite certain I knew that this would not work for some of the reasons mentioned. I was just hoping I had missed something and someone would point out how I could make them work without having to use separate circuitry.
Guess I will have to work on finding some more components!
).
Covered all the bases nicely, including the cost diversity.