I tried to make a simple 555 timer circuit which turns on one LED when its output is HIGH and turns on another LED when its output is LOW. I tried connecting two LEDs with single 1k ohm resistor (connection 1). The top LED turns on and the bottom one turns off during LOW state of 555 timer. During HIGH state, top LED just reduces its brightness and bottom LED turns on. Moreover, it spoiled the IC. I initially thought there is some issue with IC and tried another IC. The results were same. Later I realised, both of them were spoiled because of this connection (when I used these ICs for some other project). I searched in the internet and found connection 2 in every search results.
I measured the voltage at pin 3. It was like 2 v lesser than VCC during its on time. My questions are
- Why it spoiled the IC?
- What difference it makes when there are two resistors which make the circuit to work as intended?
Note: R1 and R2 values were high enough to produce visual observation of LED. This image I just took from random site for this question