Slightly warm (5–10°C above ambient) is normal. If it’s hot to the touch (>50°C), you have a defective module or are running >6V.

If you are experiencing the sensor getting physically hot or if you are interested in thermal IR:

If you’ve ever searched for you’re not alone. Maybe you touched the back of the comparator chip or the voltage regulator and thought, “Is this supposed to feel like a hand warmer?”

By following this comprehensive guide, you'll be well on your way to understanding the FC-51 IR sensor datasheet and using this versatile sensor in your projects.