I work with max. 18V DC current, amateur. I thought the max. thing you can do is to mess up your multimeter, but I saw some capacitors exploding pretty big even on 9V on Youtube. As an utter beginner and with no mentor I would like to know about what to avoid to be safe. I am using max: 18Vs, but better safe than sorry right? My equipment: multimeter, a breadboard, diodes, capacitors (electrolytic), transistors, thyristors, triacs, LEDs (I destroyed one so far with 9V), resistors, integrated circuit... As a bonus you an can also say tips regarding AC (220V here), but the only thing I dared with it was measuring it's 230V with a multimeter, and 50-60 Hz frequency, but I do not plan to experiment much/at all with high voltage.