Power Supply Needs

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GatorGnet

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This may be a obvious answer but one of our current projects uses 4 relays with a 360ma rating on the coil, 2-4 20ma LEDs, a PIC, a MAX232, and some other minor components. Should I provide a power supply for the total current needs or could I get away with less? My main concern is the relays. I would like to make sure they can all be on at the same time if needed.
 

hi gator,
If all the 360mA relays are on at the same time, thats 4 * 0.36A =1.44A.

Say 4 LED's at 20mA thats only 80mA, plus the PIC say 100mA max!

Gives a total of 1.62A.

The relays seem to be very high current coils at 360mA each. ???
What is their voltage rating.?
 
I think you are looking at the relay coil power which is 360 mW. The coil currents are much, much less.

5 Volt Coil = 72 mA
6 Volt Coil = 60 mA
9 Volt Coil = 40 mA
12 Volt Coil = 30 mA

See the coil section of your link for the coil currents in that relay family.

Ron
 
I guess I didn't read enough into it. Thanks for the help! Also, am I reading it right that even though it states 6v for the coil, it would pickup at only 4.2v?
 
Last edited:
Yes, but remember the Pick Up and Drop Out voltages are approximations and shouldn't really be counted on. Meaning if you have a 6 volt relay coil it "should" pull in at 4.2 and should drop out at .6 volts but don't design or build around those numbers.

Ron
 
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