I bought a cheap LED strip and a 12V 5A power supply unit on Aliexpress. After testing it I realised that the LEDs closer to the PSU end get quite hot (around 55°C) while the ones at the other end of the strip don't get hot at all. I'm a bit worried that continuous exposure to this kind of temperatures might change the colour of the paint on the wall over time.
I measured the open circut voltage output of the PSU and it turned out to be slightly higher than it should be (12.2V), so I thought I could lower the voltage a bit by adding a couple of diodes in series with the strip.
I went to the local electronic parts shop and they sold me FR302 diodes which are rated at 100V 3A. I added 2 in series and indeed all the LEDs now are now cold to touch without noticeably losing in brightness. I measured the voltage drop and it turned out to be 0.8V across each diode, and the current drawn by the strip dropped from 1.1A to 0.9A, but here comes a new problem: the diodes get really hot (79°C according to my multimeter).
I can't find much in the diode's datasheet about how hot it should get in these conditions. I can see that it can operate in the -65..+150 range, but my question is: is it normal for the diodes to get this hot in these conditions? Can I avoid it by using a different type of diode? Should I use a different method of lowering the voltage altogether?
I'm also worried that some of my measurements might be wrong, because according to the description on Aliexpress:
Power Consumption (W/m): 7.36W/m
Which I thought should mean that the strip draws
7.36 W/m / 12V * 5m = 3A, whereas I can only see 1.1A on my mulitmeter. Am I wrong in my calculations?