Hello,
I want to redesign a relay circuit (thru hole to SMT) and I found this existing schematic (attached). The relay coil is energized by switching on a 3904 NPN transistor. I've used similar circuits before, but I've only used a single resistor at the base of the transistor. I'm curious why there is this extra circuitry (D1, R1, & C1), and why those particular component values were used. I'm assuming the reason for this extra circuitry is for protection, but I'm wondering if this would be absolutely necessary when I hook up my own circuit. If this protection is deemed valuable, I would like to know if there is any insight as to why the particular component values (R1 & C1) were used.
Also, what's the worst that could happen if I remove D1, R1, & C1?