I am currently using 150R series resistors to limit the current to each segment in a 7 segment display. I picked 150R because all the online "led resistor calculators" suggest this value. The power supply is 5v/2.5A.
The datasheet for these displays (Kingbright SC52-11EWA) says the LED's have a forward voltage of 2.0 (2.5 max).
For testing, I've currently just got one segment wired up with a resistor. For some reason, after a few minutes the resistor gets quite warm/hot. The displays themselves do not heat up.
When I use a 330R resistor, it is still slightly warm but a tiny bit cooler than 150R. However, the display is then noticeably dimmer, especially when viewed during the day.
I've never had problems with resistors heating up when lighting LED's.
- What am I doing wrong?
- What value resistors should I be using?
I've attached a picture of the breadboard, if that's relevant (The display is much brighter than this, the flash just makes it look dim).