Get a copy of Ian Getreu's "Modeling the Bipolar Transistor." Link below. About half the book is on how to measure various BJT modeling parameters and the rest is about what they mean and why they are as they are. The two versions shown at Amazon are nearly identical, so either works very well. (One is a recent reprint that I was involved in helping produce, but have no financial interest in, at all.)
Use a NPN transistor with the emitter linked to floor, the collector to the detrimental part (if the solenoid is polarized) of the solenoid, and the bottom of the transistor linked to the easy stamp with a 470 ohm resistor, this can reduce the present via 10 mA. If the solenoid does no longer require more advantageous than 100 milliamps a 2N2222 transistor must be used. If the solenoid calls for added modern you've gotten to detect a a probability transistor. The transistor will act as an inverter the common sense a million from the easy stamp will turn the solenoid on. If the solenoid is polarized it has an internally linked diode to suppress the back emf even as the solenoid is grew to grow to be off. If the solenoid isn't polarized, you'll opt to connect a diode which contain a 1N4001 in the course of the relay. The anode of this diode is linked to the collector - solenoid junction, and the cathode to the +12 volts.
Which value do you want? Transistors are complicated. Their performance is described by a whole bunch of different parameters. They're not like resistors and capacitors where there's one well-defined number that says what its behavior is.
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Get a copy of Ian Getreu's "Modeling the Bipolar Transistor." Link below. About half the book is on how to measure various BJT modeling parameters and the rest is about what they mean and why they are as they are. The two versions shown at Amazon are nearly identical, so either works very well. (One is a recent reprint that I was involved in helping produce, but have no financial interest in, at all.)
Use a NPN transistor with the emitter linked to floor, the collector to the detrimental part (if the solenoid is polarized) of the solenoid, and the bottom of the transistor linked to the easy stamp with a 470 ohm resistor, this can reduce the present via 10 mA. If the solenoid does no longer require more advantageous than 100 milliamps a 2N2222 transistor must be used. If the solenoid calls for added modern you've gotten to detect a a probability transistor. The transistor will act as an inverter the common sense a million from the easy stamp will turn the solenoid on. If the solenoid is polarized it has an internally linked diode to suppress the back emf even as the solenoid is grew to grow to be off. If the solenoid isn't polarized, you'll opt to connect a diode which contain a 1N4001 in the course of the relay. The anode of this diode is linked to the collector - solenoid junction, and the cathode to the +12 volts.
Which value do you want? Transistors are complicated. Their performance is described by a whole bunch of different parameters. They're not like resistors and capacitors where there's one well-defined number that says what its behavior is.