Shop OBEX P1 Docs P2 Docs Learn Events
pwmpal and 2n7000 — Parallax Forums

pwmpal and 2n7000

mikeyhzmikeyhz Posts: 16
edited 2010-09-09 21:19 in BASIC Stamp
hi there everyone,
i am currently playing around with a bs2e on a boe trying to switch a motor with a 2n7000 mosfet.i have used the schematic in the pwmpal documentation and i cannot get the motor to work.the debug window shows the speed increasing but the motor wont go...have turned the mosfet around incase i got it the wrong way but its still the same.the motor is from a little toy car and i am using a 9v rectangular battery(motor supply).i realise i must have killed a few mosfets by now.any ideas on what im doing wrong? or does anyone have a pic of this circuit on a breadboard to check mine against??? i dont have a camera so i cant post pics of my setup.any help would be very much appreciated.

Comments

  • dandreaedandreae Posts: 1,375
    edited 2010-09-08 06:30
    Can you verify that the motor still works? Do you have access to an oscilloscope?

    Dave
  • mikeyhzmikeyhz Posts: 16
    edited 2010-09-08 15:00
    no i do not have an oscilloscope and the motor does work when i connect it straight to the battery.
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2010-09-08 19:36
    The first step is to not panic, at school or at home. So, don't plug stuff in "backwards, just in case." How does that make sense anyway?

    I'm familiar with this circuit, I believe. In addition to the schematic, I've rendered the circuit in a sort of point-to-point fashion, too.
    fetmotor.jpg
    800 x 387 - 28K
  • mikeyhzmikeyhz Posts: 16
    edited 2010-09-08 20:32
    thank you for your reply pj.i shall check my set up against your diagram.i thought i may have had my source and drain mixed up,round the wrong way...cheers.
  • LeonLeon Posts: 7,620
    edited 2010-09-08 22:44
    That doesn't matter with some FETs, they are symmetrical. I'm not sure about the 2N7000, though.
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2010-09-09 05:36
    Drain-Source "symmetry" is only with JFETs, Leon, not with (these) MOSFETs/HEXFETs.
  • mikeyhzmikeyhz Posts: 16
    edited 2010-09-09 21:19
    thank you all for your replies.it turns out everything was ok i just had really bad connections in my breadboard so i bought a couple new ones.soooo sorry for wasting your time and thanks again for your input.cheers,mike.
Sign In or Register to comment.