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IRF510 to control from Pic?

Discussion in 'General Electronics Chat' started by RogerTango, Nov 26, 2008.

  1. RogerTango

    RogerTango New Member

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    I am using a Picaxe, lets just call it a Pic chip.

    From a pin, I am alternating high then low to the gate of an IRF510, and the Pic(axe) ground to the Source.

    Between the Drive and the Source I applied 12vdc.

    There is no resistor between the Pic(axe) pin and the IRF510.

    The circuit works... for small loads. I can flash a 12v marker light that has a small bulb, but when I hook up something like a brake light, the filament is really dim.

    Can I make the IRF510 work? (Read my sig... sigh.)

    The Picaxe manual (#3) shows an IRF530 being used, I have ordered a few of them but wonder if the 510 will work?

    What about a TIP31? I can get that at the RatShack.

    I am wanting to run 12vdc devices at about 10-15 amps without using a relay, if that is possible.

    Thanks,
    Andrew
     
  2. Eclipsed

    Eclipsed New Member

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    The ~5 volts from the pic isn't fully turning on the irf510.You need a logic level mosfet or a mosfet driver.
     
    Last edited: Nov 26, 2008
  3. RogerTango

    RogerTango New Member

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    Ahhhh! That makes sense! I got the 510 because I didnt know any better. Well, we live and we learn!!

    So I take it, without extra circuits the 510 will not work.

    I am going to look at the data sheet on the 510, the 530 and the TIP31. What symbol am I looking at that will tell me it will work with 5v/TTL levels??

    Thanks-
    Andrew
     
    Last edited: Nov 26, 2008
  4. dave

    Dave New Member

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  5. RogerTango

    RogerTango New Member

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    Well, Im confused looking at the datasheets. I really need someone close by that could mentor me on some of this stuff.

    I am all self taught, which translates into I know enough to be dangerous. :(

    Andrew
     
  6. Eclipsed

    Eclipsed New Member

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    I don't know any specific part numbers off hand, but I believe some have an "L", like IRFLxxx.I suppose since you're not switching at high speed, you could just use a general purpose transistor to drive the mosfet with your 12 volt supply.
     
  7. eblc1388

    eblc1388 Active Member

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    Do not look at the value of threshold voltage.

    Look for Vgs=?? for lowest RDS or device rated current and that would give you an idea of what voltage you should apply to the gate to get that current.
     

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  8. Mikebits

    Mikebits Well-Known Member

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  9. audioguru

    audioguru Well-Known Member Most Helpful Member

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    An IRF3711Z logic-level N-channel Mosfet (and hundreds of others) is spec'd to have a max on-resistance of 0.0073 ohms when its gate is only 4.5V and its current is 12A. Then its max dissipation is only 1W. With a heatsink it can conduct much more current.

    A low value resistor (22 ohms) should be connected in series with the gate pin mounted at the pin to stop the Mosfet from oscillating at a very high frequency.
     
  10. RogerTango

    RogerTango New Member

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    Thank you all for very helpful information! Happy Thanksgiving!

    Andrew
     
  11. Roff

    Roff Well-Known Member

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    IRF530 is no better than IRF510 for your application. Shame on Revolution Education, or Picaxe, or whoever created manual 3. A search for "logic level MOSFET" will yield some more places to look.
     
  12. RogerTango

    RogerTango New Member

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    I just ordered a few FDB603AL LL MOSFETs, Ill see how these do! Will post back with results, thanks again.

    Andrew
     
  13. Mikebits

    Mikebits Well-Known Member

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    That should work nicely. :)
     
  14. RogerTango

    RogerTango New Member

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    I hope so!

    What Ive got going on right now, and I am perplexed, is a 2N2222 switching a small 5v relay, that appears to be working fine. However, when I put ANOTHER relay on the NO contacts of the small relay, the small relay starts acting erratic! The 12vdc that is going through the small relay is from a totally different power source (battery) than what is powering the xisiter/relay board.

    Ill just wait on the MOSFETs before I do much more, Im about to pull my hair out. The ones I ordered are SMT (its what was on ebay at the time), so Ill have to try that one on Pad2Pad, not done SMT on PCB layouts yet, but it should be easy enough.

    Cheers,
    Andrew
     
  15. RogerTango

    RogerTango New Member

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    THEY CAME IN THE MAIL TODAY!

    SMT was no problem, laid it out in Pad2Pad, board etched nicely, MOSFET works 100% PERFECT! LL +5 direct from Pic(axe) to MOSFET, switches a turn signal bulb at 12v without a hitch!

    Thanks much for your help everyone-
    Andrew
     
  16. RogerTango

    RogerTango New Member

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    I also got the 530s in, but have yet had a chance to work with them.

    Ill post more when I get to fiddle with them.

    Andrew
     

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