Calcul transistor of the relay :
-J'ai utilisé 1 relais donc la résistance de la bobine est de 27.8 ohms.
- 1 diode 1N4007.
- 1 transistor
2N2222.
- 1 resistor 240 ohms.
The relay coil amperage is (3.3 volts / 25 ohms = 0.132 amperes) (is the intensity of the collector of transistor IC)
There are 2 operation for to find the value of the resistance between the transistor and the digital pin of Arduino.
// the intensity of the base of transistor is (IB) = IC / gain saturation.
Collector--Emitter Saturation Voltage (Note 1) VCE(sat) =0,3V (IC = 150 mAdc, IB = 15 mAdc)
gain saturation = 150/15=10
IB = 0.132 / 10 = 0.0132 amperes.
// The resistance = 3.3 volts / IB.
R = 3.3 / 0.0132 = 250 ohms (Me i use a 240 Ohms resistance)