Blinking leds with NE555-IRFZ44 mosfet

Discussion in 'General Electronics Chat' started by VI ASI 1, Dec 24, 2018.

  1. VI ASI 1

    Thread Starter New Member

    Dec 24, 2018
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    Hello everyone !
    I have a problem with my circuit, in the simulation it seems normal, but when i wired everything , the blinking speed went up when i added the mosfet, for exemple when i use only the NE555 directly to the led, the led blinks once every 3 secondes , but when i use the mosfet, i had like 1-2 blinks/seconde, i tried removing/replacing the 1M ohm resistor but the same problem,i then tried putting a resistor between the NE555 and irf (pin 3 to gate) but then i had another problem... the led doesn't light up directly but there is a "transition phase" where the led starts lightening slowly first and then it lights up,i'm looking for a solution if anyone can help ^^ (sorry for my english btw).
     
  2. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    What is the value of VR1?

    ak
     
  3. VI ASI 1

    Thread Starter New Member

    Dec 24, 2018
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    50K
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Is the circuit on a breadboard? If so, there may be a poor connection to the FET.
    Did you confirm the FET pinout is correct?
    1meg seems much too high for R5. Try, say, 10k.
     
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  5. VI ASI 1

    Thread Starter New Member

    Dec 24, 2018
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    The connection is correct, i'm connecting everything on a breadboard before soldering , as for the R5 i tried 1K, 100 ohm, 4.7k, and a potentiometer 50K (i tested it from 0 -> 50K )
     
  6. LesJones

    Well-Known Member

    Jan 8, 2017
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    Try adding some decoupling capacitors. I suggest a 100 nF CLOSE to the 555 and a 47 uF. Also adding a resistor (Say 47 ohms ) between pin 3 of the 555 anf the gate of the mosfet. The current pulse when the 555 tries to charge the gate source capacitance of the mosfet it could be putting a negative pulse on the supply line. You could also try adding a decoupling capacitor to pin 5 of the 555 (Between 10 and 100 nF.)

    Les.
     
    VI ASI 1 likes this.
  7. dl324

    AAC Fanatic!

    Mar 30, 2015
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    Shouldn't make any difference.

    If English is difficult for you, write in your native language, using correct grammar, and run it through a translator.
     
  8. VI ASI 1

    Thread Starter New Member

    Dec 24, 2018
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    Thanks everyone, it seems like adding a 100ohm resistor between the NE555 and irfz44 was enough!
     
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