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How does a transistor work as a switch?
You can use a transistor as a switch here. So when the GPIO is low or zero then the transistor would be in cutoff region and the green LED glows and when the GPIO is 3.3 V the red LED glows since the transistor goes in saturation state the Green LED would be switched off. The resistors values are so chosen that the transistor work as a switch.
Can a transistor handle four LEDs at a time?
As you say, the transistor in the first circuit needs to be able to handle the combined LED current. For four normal indicator LEDs, that is not much of a limitation. Depending on the voltage of the LEDs, you might be able to drive two at a time in series with a single resistor.
Can you use two LEDs at the same time?
Doing that gets you the same LEDs lit with the same brightness, but with half the current used. Green LEDs with 2.1 V drop are on the edge, but can work doubled up. Two LEDs would drop 4.2 V. Again, figuring 200 mV for the saturated transistor, that still leaves 600 mV for the current limiting resistor.
Can a NPN transistor be used to control multiple LEDs?
The first circuit is entirely adequate unless you value independent control of each LED. The second circuit has the advantage that if desired you can turn individual LEDs on or off independently and the (obvious) disadvantage of requiring more components. Almost any NPN transistor will work. If the LEDs are white they will have ABOUT 3v on voltage.
The maximum current can flow through the collector to emitter according to the rating capacity of the transistor. We provide forward biased voltage between base and emitter terminal. It works like a short-circuit between collector and emitter. The biasing voltage is usually greater than 0.7 volt.
What are the names of the two way switches?
The three terminals are usually named COM, L1 and L2, but sometimes the terms COM, 1 Way and 2 Way are also used. In one position, the COM and L1 terminals are connected, while in the second position, the COM and L2 terminals are connected.
How does a two way light switch work?
All the switches perform simple task of either interrupting the flow of electric current or divert the flow of current. They essentially ‘make’ or ‘break’ the circuit. All the switches we use regularly to turn on or off lights, fans, etc. are two terminal devices.
How does a Darlington transistor work as a switch?
Darlington Transistors simply contain two individual bipolar NPN or PNP type transistors connected together so that the current gain of the first transistor is multiplied with that of the current gain of the second transistor to produce a device which acts like a single transistor with a very high current gain for a much smaller Base current.