Programmable unijunction transistor oscillator circuit problem

Discussion in 'The Projects Forum' started by mdalieren, Jul 22, 2016.

  1. mdalieren

    Thread Starter New Member

    Apr 17, 2016
    7
    0
    Hello,
    I tried to make a slow speed speed oscillation with a PUT but it doesn't work. Just, as soon as I gave the power (6V DC), LED flushes weakly and then light gone. Capacitor reaches 5.9 volt and it doesn't discharge. I don't find out why. Could you check the circuit and tell why it doesn't work? Thanks...
    (All components work well individually and transistor is 2N6027)

    1-800x597.jpg

    2-800x597.jpg
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    My simulation of your circuit did not work either until I reduced the 330kΩ resistor to 300kΩ (or less), so you might try that.
     
  3. mdalieren

    Thread Starter New Member

    Apr 17, 2016
    7
    0
    I reduced it to 300kΩ and also 200kΩ but it did not work again. So, I can not proceed in my project.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,776
    1,103
    Are you sure you have the pinout of the PUT correct? The cap should connect to the emitter. The anode should connect to the programming resistors.
     
  5. mdalieren

    Thread Starter New Member

    Apr 17, 2016
    7
    0
    I think all pinouts are correct. I've attached my circuit on breadboard.
     
  6. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    Try increasing the value of the two gate resistors from 10kΩ and 20kΩ to about 100kΩ and 200kΩ.
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,776
    1,103
    On the breadboard you have the gate connected to the programming resistors instead of to the cap.
     
  8. mdalieren

    Thread Starter New Member

    Apr 17, 2016
    7
    0
    It doesn't work either. It works as in the video I have attached. I have tried varied resistors as well but It never worked. Should I calculate value of Rg (R2*R3 / (R2+R3) and then do it again?
     
  9. mdalieren

    Thread Starter New Member

    Apr 17, 2016
    7
    0
    Gate is already connected to the programming resistors. Cap is connected to the anod.
     
  10. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,776
    1,103
    Can't open .rar files :(.
    Precisely. It should be the other way round.
     
  11. mdalieren

    Thread Starter New Member

    Apr 17, 2016
    7
    0
    I did circuit by the reference of make electronics book as below. I guess my circuit is same except resistor values. Could you please show your advice on picture. I am sorry I couldn't get how to replace cap the other way round.

    upload_2016-7-23_22-30-25.png
     
  12. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    I'm confused. :confused:
    That's the way it should be (gate to programming resistors and capacitor to anode) as shown below.

    upload_2016-7-23_12-48-42.png
     
  13. mdalieren

    Thread Starter New Member

    Apr 17, 2016
    7
    0
    I am also confused and exhausted to try it :( Now, I am going to try this circuit.
     
  14. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    Below is my LTspice simulation of the circuit working.
    Of course that's no guarantee that the real circuit will work with the same values.

    Try increasing the power supply voltage to see if that makes a difference.

    upload_2016-7-23_13-24-51.png
     
  15. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,776
    1,103
    Oops. My bad. :oops:
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    Try shunting D1 with 1K so that cap. can almost fully discharge.
     
Loading...