The reason you can drive it the same way is quite simple: in the usual NPN circuit, the relay is driven by a 3.3 V or a 5 V logic level GPIO, and for small signal FETs, that is well within Vgs.

The only problem is that the circuit was expecting a low signal as the trigger and the PIR sensor outputs a high signal. [brmarcum] resolved this problem with an NPN BJT to invert the signal.

Fig 1 shows a 2nd optocoupler driving an NPN transistor. The components indicated should be able to source or sink 500mA with a voltage drop of about 1V. I was able to test mine at 100mA. At 100mA, ...

This is a simple flashing led circuit with 2 leds and 2 NPN transistors. It illustrates the behavior of transistors and capacitors and if you use an. ... Two flashing LED circuit diagram. Components ...

The system is an interface circuit that connects the motor to the PC using a 4-bit binary counter (a 74LS193), three current- limiting resistors, three npn transistors, three 5-V relays, and two ...

Voltage across components in a series circuit; Parallel circuits; ... Npn transistor. The transistor is on, when the input voltage is greater than or equal to \(0.7 V\).