Current value for Relays and Solenoid

Any kind of relay (the ones generally sold on ebay) used to control DC or AC devices have 3 pins - the VCC/VIN, COM and SIG

Till now I have only tried using the 5V relays connected to arduino pins. However, I would like to know the following (for which I wasn't able to find the sources)

What is the minimum value of ISIG or the trigger current for a relay?
What is the maximum value of ISIG that can be supplied to a relay?
what happens when the trigger current connected to the relay is higher (higher by 2 or 3 times) than the specified value?

  • The relay busts or
  • The relay accepts only upto a specified value of trigger current as designed by the manufacturer

What is the minimum and maximum driving current value that can be supplied to a relay?

About solenoid, What is the driving current (approximate value) that can be supplied? I know, the question towards solenoid values is insane (differs according to the manufacturer, the size). But, just want to know because I am confused if to use the common npn transistor (max collector current is 500 - 800mA) or the darlington transistor (max collector current is 1A - 10A) or a darlington array (again restricted to 500mA)

Regards

Contact the manufacturer since what you ask without details of the specific relay is the equivalent of asking "how long is a piece of string"

Any relay can consume any ammount of current.
It normally have a working voltage, you supply it that and it will take its required current. You can not supply it with more current unless you increase the voltage. If you do it will get hot, maybe too hot and it will burn out.

@jackrae was thinking the same. I know. However @Grumpy_Mike Cleared my doubt (my main reason behind the question). Thanks @jackrae

Thank you @Grumpy_Mike. But could you please elaborate

You can not supply it with more current unless you increase the voltage. If you do it will get hot, maybe too hot and it will burn out.

Thanks again

Not sure I can say more. The current is determined by the voltage and resistance. The resistance is a property of your relay or solonoide and the voltage is what ever you wire it to so you are in control. The current is then given by working out voltage divided by resistance. Any coil is designed to work at a voltage given in the data sheet. With that voltage you get the right current. If you connect too much voltage you get too much current and the coil gets hotter than it should be. If it gets too hot then it will melt the wires and the coil will go open circuit, the wire acts a bit like a fuse.

Because inside the coil any piece of wire is surrounded by other wire heat builds up faster and it will be much hotter inside a coil than on the outside.

You'd be better off buying the relays on boards made to be driven by arduinos. Making your own driver circuit for relays is not worth the effort.

I think your problem is not the relays but your lack of understanding of Ohms Law.
The previous posters tried to explain it to you but I am not sure you get it.
YOU do not (normally) control the relay coil current if you are operating it at it's rated voltage (which in the
case you cited, is 5V dc). That is because the current is determined by the coil resistance (to which Mike
alluded). You do not set this resistance. It is inherent in the coil design. It is what it is. IF your question
was meant to be:

What if the relay coil current is higher that it SHOULD be (by a factor of 2 or 3) ?
What is wrong ?
Why is it too high ?

If it is a 5V relay and you are running it off 5V (and NOT 12v) , the coil current should be whatever is stated
on the datasheet for the relay. The ITrig you mentioned sounds like a reference to the pull-in
current, the minimum required to engage the contacts. A Google Search of "Relay Trigger Current " yields
references to an automobile horn circuit horn circuit

which seems unrelated.
Please post a link or datasheet for the relay and identify the relay parameters you are referring to.

About solenoid, What is the driving current (approximate value) that can be supplied?

Again, lack of understanding of Ohm's Law. YOU don't supply relay or solenoid current. YOU supply VOLTAGE. The relay or solenoid DRAWS CURRENT (based on it's intrinsic resistance) . IT IS WHAT IT IS.
YOU HAVE NO SAY about how much current it draws ! If you are asking :

"How much current should my solenoid power supply be rated for ? (200 mA, 500mA etc. etc)
then that is a different question.

But, just want to know because I am confused if to use the common npn transistor (max collector current is 500 - 800mA) or the darlington transistor (max collector current is 1A - 10A) or a darlington array (again restricted to 500mA)

This is just crazy. No solenoid is going to draw 1A or 10A (unless it is huge).
You haven't provided ANY SOLENOID SPECIFICATIONS !
Post a link for the solenoid or a datasheet.
The solenoid current is probably going to be closer to 100 mA. (for arduino based circuits).

You could probably use an 2N2222 (metal can) or a TIP120.

Of course , I suppose you could be building a Linear Accelerator in your basement and that's why you
are concerned about solenoid current. ...