Electrical question concerning led and relay?
In a circuit, my power source is 5 volts, and I have an led that operates on 2.2 volts (capacity of .02 amps). If I connect a 3 volt relay in series with the 2.2 volt relay, would the circuit operate properly or not?
If not, what kind of relay would I need? I did some calculations and the total voltage from the relay and led is 5.2 volts
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It's not safe as the relay produces back emf .
Take 4 silicon diodes they each have a voltage drop of 0.7 volts and total drop is 2.8 volts
Connecting a relay across this will activate the relay
The diodes will protect a led connected after this from back emf
Connecting the led in series with the other diodes but outside the parallel relay will light the led .
If your objective is to indicate the relay is active this circuit will only show enough voltage is there to turn on the relay
I kind of don't get what you want to do. Light the led with 5 volts? If so, calculate the value of the series current limiting resistor and be done with it.
Resistor value = (5v - 2.2v)/0.02 a = 140 ohms.
The voltage of the relay is generally refers to the coil operating voltage, as the relay contacts can handle much more voltage (and current) than the coil. You won't find a 2.2 volt relay anywhere, as it is not a standard coil voltage. So basically, two low voltage relays with the relay contacts in series will deliver the same voltage at the output as the input as long as both relay coils are energized (n.o. contacts that is).