I was using my old routers power supply to light up an led strip with a simple LDR based night detector. When I was assembling the setup, I felt a strong tingling sensation when I touched the power supply. I took a multimeter and found out that it measured 10.2V in DC setting and about 15V in the AC setting. Troubled by this reading I switched to a cheap LED strip PSU and this too measured about 12VDC and about 20VAC.
My question is whether this is a normal behaviour or something going wrong?
Interestingly my 2n2222 based night detector worked for one day and stopped working from the next time I turned it on. Could the AC voltage destroy it? I'm thinking of adding a relay to output the power to leds rather than a direct connection from the transistor. Should I try building a low pass filter before the input to the transistor?