### PC817
```
VF (IF 20mA) = 1.2V
```

### BC547B

```
hFE = 200-450
IC (max) = 100mA
VBEsat = 0.7V
```

### Finder 30-22 5V
```
UN = 5V
R = 125Ohm
I @ UN = 40mA
```

### Resisitors

#### R1
```
R = (Vin - VF) / IF
R = (3.3V - 1.2V) / 0.02A
R = 105 Ohm
```

#### R2
```
R = (V_RLY - VBEsat) / (I@UN / 10)
R = (5V - 0.7V) / (0.04 / 10)
R = 1075 Ohm
```