Practical considerations when using transformer
I basically love doing LED experiments and i was replacing many of the night lamps and stuff with simple LED circuits i made. Now i have few questions:
1) I generally use transformers to power them (230v/12v). Now apart from primary and secondary voltages and currents, are there any other ratings which i should consider?
2) I have made a portable night lamp with blue LED's. It has 4 arms in parallel and each arm consists of 3 LED's in series. All the arms are connected finally to a single 100 ohm resistor. Now as at most the whole setup might draw about 50mA of current. I had a transformer rated for about 500mA of secondary current, and so i used it with the setup. Will i have any issues using this? (Although i am sure i won't, but just in case anyway)
3) Also, the transformer gets hot. How much temperature is in safe operating zone? The setup i used, after an hour, got pretty hot. I could barely hold it for a few seconds and i had to let go. Is it okay if it gets that hot?