Electronics > Beginners

Single shot 555 timer getting hot!!

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Unordung:

--- Quote from: Hero999 on July 28, 2018, 01:25:56 pm ---Perhaps the 555 or MOSFET are bad?


--- End quote ---

I have tested the mosfet in a tester and everything seems within spec, I may have got a bad batch of 555's as they were an eBay purchase.....


--- Quote from: Hero999 on July 28, 2018, 01:25:56 pm ---How much current does the relay's coil need? Can it be powered directly off the 555 timer?


--- End quote ---

The datasheet says 200mA, whilst it's highly likely the coil will draw less than this I want the added confidence of the mosfet.


--- Quote from: Hero999 on July 28, 2018, 01:25:56 pm ---The relay's coil will need a back-EMF suppression diode in reverse parallel with it.



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Yeah It will have a flyback / catch diode once the relay is delivered.

I will give the circuit you provided a go and see if it produces better results, thanks for your help.

sourcecharge:
I think your discharge pin 7 is connected somehow to Vcc pin 8.

Pick the chip out, inspect the legs to make sure there is no damage, then check under that yellow wire that crosses where pin 7 and 8 were for a single row wire bridge hidden underneath it, and if there isn't one, check the resistance between the two rows on the bread board for a short to see if there is a problem with the bread board.


alsetalokin4017:
It's frightening to contemplate that anyone would actually fake a 555, but this chip sure looks suspicious to me.

Maybe it's just the light, I dunno.

exe:

--- Quote from: alsetalokin4017 on July 29, 2018, 11:20:20 am ---It's frightening to contemplate that anyone would actually fake a 555, but this chip sure looks suspicious to me.

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Actually, there are fake 555: https://zeptobars.com/en/read/Ti-555-NE555-real-vs-face-china-chinese . But may be the IC was abused and damaged, I'd try swapping it...

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