So, normally the diode does nothing (reverse biased), But if an inductive kickback occurs, the diode is forward biased and "snubs" the spike. the PWM goes to the "off" cycle), the magnetic field collapses and can generate hundreds to thousands of volts in the OPPOSITE direction. So, if you put +12 volts into the motor, when you de-energize it (i.e. Faraday's law basically says that the faster a magnetic field changes, the higher the voltage induced in the wire. When the current is removed, the magnetic field collapses almost instantly. When the motor is energized, a magnetic field forms on the armature. What the diode does is protect the 2N3055 from inductive kickback. The resistors you highlighted are not necessary. What should be the values?Īlso: what is the functionality of the 1N4007 diode next to the motor? And do I need to put another diode from the collector to the emitter of the 3055? I don't know if I need the two green resistors (with question marks), I didn't use them in the test but I saw that some people use them. The circuit works but I'm not sure that is perfectly ok. In the picture you can see that I'm using a 2n2222 that controls a TIP3055 (or a 2N3055). I need to control the speed of a dc motor (0.5 A no load, to 10 A full load).
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