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# Member #428562

Member Since: April 12, 2013

Country: United States

• RL usually refers to the load, i.e. what you are powering on the A/C side. I’m not sure if that is the case here. But a 3.7V power supply should be plenty. To calculate the value for the resistor connected to Vcc (R1 in the diagram), use V=IR. Datasheet says typical voltage to turn the relay on is 1.2V, and current is 20mA. The purpose of the resistor is to set this current at around 20mA. If supply voltage is 3.7V and the relay needs 1.2V input, the voltage across the resistor should be 2.5V. 2.5V / 20mA gives a resistor value of 125ohms. I don’t think resistors come in 125ohms, but 120ohm or 130ohm should work just fine.

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