![]() The datasheet states that the Base-Emitter saturation voltage is 1.2V when the current at the collector is 150mA but what about a current of 20mA at the collector? Furthermore, the DC Current Gain is 75 for Vce = 10V, Ic = 10mA and 100 for Vce = 10V, Ic = 150mA, but i have a Vce of 5V and a Ic of 20mA. BJTs can be used to amplify analog signals, but they can be used as switches as well. The fading effect can be done by replacing the 470ohm resistor wiyh a lower value. Watch on The 2N2222 is an NPN bipolar junction transistor (BJT). It could be made more complex by adding more components but I'm talking about a simple 2 led flasher. ![]() Then if i understand right R1 = (5-0.3)/0.02 = 235 Ohm ?įor the base i am completely lost. If you want to add more leds remove the 470 ohm resistors from each side and replace with one led each and also replace the 1uf capacitor to 10uf. The datasheet states that the Collector-Emitter saturation voltage is 0.3V when the current at the collector is 150mA and 1V for a current of 500mA so i assume that for 20mA is even less than 0.3V? LED Pattern-Flasher Using 555 Timer, 4017 Counter and 2N2222A Transistors With Variable Resistance Varying at 0-5KSelf Explanatory, Animated Electronic Circ. If this image is taken as a basis, i am struggling to calculate the correct values for R1 and R2:Īs with the image, the voltage across the collector is 5V and the current through the Led should be 20mA. Driving IR led from 3.3V GPIO using 2N2222 transistor. I recently started in the world of electronics and i am trying to make myself comfortable with various parts before starting to build real projects. Experiment with different led colours and models to control base current.
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