[O/T] Help interpreting relay datasheet

[Leandro]

Maybe you guys can help me sort out a major doubt I have about a relay's specs (here's a link to the datasheet).

The datasheet says that the "switching current" of the relay is "2 A max."  My question is if this switching current is:

a. The maximum current I can apply to the coil without damaging it;

or

b. The maximum current which the relay will draw from the power supply when it is switched on (current spike).

Thanks!

[SoundTech]

It appears that he switching voltage and switching current are ratings for the switch, and not the coil.  So, don't pass more than 60VDC or 120VAC at 2A through the contacts.  The coil will be fine as is if you don't apply more than the coil voltage rating.  If you do exceed the coil voltage rating, just use a resistor in series with the coil to drop the voltage to the specified rating.

[R.G.]

Soundtech is correct - that 2A is how much the contacts can stand, not the coil current.

The coil current can't be more than 5v/45ohms, 5v/70ohms, or 5V/120ohms depending on which one of the family you use. As I remember, you were using the 5V relays, correct? That is 111ma, 71ma, and 40 ma respectively. So your switcher power supply needs to supply current for as many relays as you can have on at once times whichever of those relay models you buy.

[Leandro]

SoundTech, R.G., thank you very much!

I was really worried about that.  So, considering that I will be using 5V FRT2 relays (which have a coil resistance of 70 ohms +/- 10%), and that at most I will be switching 10 relays on simultaneously (upgraded from the original eight), the relays alone will warrant a power supply rated for:

10 * (5 V / (70 ohms * 0.9)) = 0.8 A (considering coil resistance error)

Now I just have to factor in the logic IC's and the PIC/AVR/whatever I end up using.

Thanks again!