I want to make temperature controller using Arduino and the circuit which can simply turn on and off AC bulb within some range of temperatures. As a switch for AC current I want to use moc3021, BC547 and BT136. I use 160 Ohm resistor in collector circuit, 3.3kOhm resistor in base circuit of BC547. From pin 4 of moc3021 to the Gate of BT136 is resistor of 510Ohm. The only difference from the circuit which i used is that I connect A1 of the BT136 to the pin 6 of moc3021 and A2 of BT136 to the AC source. The bulb does not turned on when I give 5v to the base of BC547. When I connect Gate and A2 of BT136 with 10kOhm resistor it turns on. What may be the reason. May the problem is that I did not connect A1 and A2 as it shown in the scheme?