The motor was then connected to the positive and negative leads of the batteries, and it begins to spin. The 2N3906 transistor allowed enough positive current to go to the base of the TIP31 transistor to switch it.īecause the positive lead of the motor is attached to the positive lead of the battery holder, when the TIP31 transistor switched, it allowed negative current to go from the battery case to the motor. The phototransistor allowed enough negative current to go to the base of the PNP transistor, so that positive current could flow from emitter to the collector. To allow more current to go, I used a PNP transistor. However, the phototransistor didn't allow quite enough current to switch the TIP31 transistor. To do that, I needed a transistor that allowed more current through, like a TIP31. However, when I tried that with a 2N3904 (an NPN transistor), I found that the transistor didn't allow enough current through to power my motor. Common transistor pinouts Last edited just now by Farooqkz. When the positive current goes to base, it allows current to pass from the emitter to the collector or from the collector to the emitter (it depends on whether or not the transistor is NPN or PNP). A transistor is a semiconductor device used to amplify or switch electrical signals and. Transistors can be used as switches when a little positive current is passed to base (in the case of an NPN transistor). However, it can't handle enough current for a motor. A phototransistor allows electricity to flow through it when light is shining on it.
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