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  • dgogate07 commented on dgogate07's forum topic My 555 IC overheats

    Hi,I checked current through the relay and it is just 30mA and hence it works very well.but if I increase the delay, it creates problem.

    Hi,here are the values of resistors and capacitor:R1 = 470KR2/R4/R5 = 1kR3 = 2.2KC1 = 4700μf

    Hi,yes, it is 4700uF and not 4700mF, sorry for that typo.

    Hi,It was connected to 12v DC supply which actually delivers 13 Volts.my relay is a 12 volts relay but the pick up voltage of its coil is 9 VoltsHence I bought another power supply of 9 volts which actually delivers 9.95 Volts. Now my IC and relay both were working on 9 Volts but still the same, The IC burns as soon as it triggers the relay.Looks like the relay was a culprit, even after connecting a fly back diode, my IC was burning. I tried running it without the relay and it works well without the relay.now I am considering to use a PNP transistor instead of 2 NPN transistors. but I need a PNP transistor which can support 1Amp. current.

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  • dgogate07 commented on dgogate07's forum topic My 555 IC overheats

    Hello,here are the component details:R1 = 235K (2 470K resistors in parallel)R2/R4/R5 = 1KR3 = 2.2KC1 = 4700μFThis gives me High Time of about 13 min. and Low Time of about 3 seconds.As a test, I also tried one more combination, I replaced both R1 and R1 with 1K resisters keeping the capacitor the same, this gave me a High Time of about 7 seconds and Low Time of about 3.5 seconds. and then even if I connect the Relay directly between +Vcc and Pin-3 of the IC, it works fine without any issue.But if I increase the delay, it breaks the IC.

    Hi,this time I connected the "flyback diode" as well, but still result was the same. it burnt the IC.

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