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Transistor selection — Parallax Forums

Transistor selection

ArchiverArchiver Posts: 46,084
edited 2000-04-28 00:05 in General Discussion
Hi Group,

I am making a motor controller with a BS2 and bought a couple of transistors
from the local NTE dealer. I was hoping someone could give a once over on the
datasheet and let me know if this is suitable to work with the basic stamp.
My motor is 120vdc with .80amps and I plan on using PWM with it.

<A HREF="mailto:basicstamps@egroups.com">http://www.nteinc.com/specs/2300to239
9/NTE2318.html</A>

http://www.nteinc.com/specs/2300to2399/NTE2313.html

Any comments would be appreciated.

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2000-04-21 23:53
    those address's should have come out

    http://www.nteinc.com/specs/2300to2399/NTE2313.html

    and

    http://www.nteinc.com/specs/2300to2399/NTE2318.html
  • ArchiverArchiver Posts: 46,084
    edited 2000-04-23 20:44
    Both transistors are low gain (hfe~10 for the 2313 and 2.25 for the 2318),
    and require lots of base drive. The 2313 would need ~200 ma, and the 2318
    needs ~350 ma. In either case, you need a driver stage between the
    transistors and the stamp, since the stamp should be used at ~10 ma per pin.
    Consider lower voltage transistors, like 300 volt units, because you always
    pay a performance price for higher voltage transistors. You could afford
    darlington transistors with their higher saturation voltage since you are
    operating a 120 Volt system, but remember that the darlingtons are slow to
    turn off when using PWM.

    Consider MOSFETS, but again, do not use higher voltage units than necessary,
    because you pay a price in on-resistance, (and therefore, power loss). I
    have not used MOSFETS in several years, so cannot recommend a part number
    offhand. If the PWM frequency can be kept low, it might be possible to find
    a logic-level device that could be directly driven from the stamp. (You need
    higher drive voltage & current for fast switching).

    Perhaps the best approach would be to search for a ready-to-go H bridge,
    especially if you can find a MOSFET motor driver, where they have
    incorporated necessary spike protection. Someone on this list may be able
    to recommend one. You have an application that can make lots of smoke if
    not done correctly.

    Ray McArthur
    Original Message
    From: <electronguy@a...>
    To: <basicstamps@egroups.com>
    Sent: Friday, April 21, 2000 6:53 PM
    Subject: Re: [noparse][[/noparse]basicstamps] Transistor selection


    > those address's should have come out
    >
    > http://www.nteinc.com/specs/2300to2399/NTE2313.html
    >
    > and
    >
    > http://www.nteinc.com/specs/2300to2399/NTE2318.html
  • ArchiverArchiver Posts: 46,084
    edited 2000-04-23 21:06
    Hello All,

    I wish to use am bs2sx to drive two 12 volt stepper motors. I can do this
    with a uln2003 or uln2803 darlinton transistor array but only for stepper
    motors up to 500mA. Does anyone have any ideas on how to construct a
    driver for a 1 amp stepper motor? I'd be interested in any ideas.

    Regards,
    Jim Szymczak

    N1RYU
    Electrical Engineering
    University of New Hampshire
  • ArchiverArchiver Posts: 46,084
    edited 2000-04-24 12:28
    At 04:06 PM 4/23/00 -0400, you wrote:

    >I wish to use am bs2sx to drive two 12 volt stepper motors. I can do this
    >with a uln2003 or uln2803 darlinton transistor array but only for stepper
    >motors up to 500mA. Does anyone have any ideas on how to construct a
    >driver for a 1 amp stepper motor? I'd be interested in any ideas.

    The TI chip (SN754410NE) often mentioned on the list is a direct
    replacement for the L293D. It can handle an amp (heatsink it). There's a
    tutorial here on how to drive steppers with the L293D, and the TI chip
    works the same:

    http://www.seattlerobotics.org/encoder/may98/steppers.html

    Be sure your stepper really is one amp.

    Best, Duncan
  • ArchiverArchiver Posts: 46,084
    edited 2000-04-28 00:05
    Hi Jim,

    We use N-channel MOSFET's for most loads connected to a stamp. If done
    correctly, no other components are needed. Try using one with a very low
    on-resistance to avoid producing much heat in the MOSFET (under 1 ohm). The
    MOSFET should also have a maximum drain current rating several times that of
    your maximum peak current, a high voltage rating, and have a built-in
    snubber diode connected from the source to the drain.

    Good part numbers are: IRF640, IRF840. Both are made by International
    Rectifier, and cost about $2 when purchased from DigiKey (www.digikey.com).

    We hope this helps you!

    John

    Original Message
    From: Jim Szymczak <szymczak@c...>
    To: basicstamps@egroups.com <basicstamps@egroups.com>
    Date: Sunday, April 23, 2000 4:05 PM
    Subject: Re: [noparse][[/noparse]basicstamps] Transistor selection


    >Hello All,
    >
    >I wish to use am bs2sx to drive two 12 volt stepper motors. I can do this
    >with a uln2003 or uln2803 darlinton transistor array but only for stepper
    >motors up to 500mA. Does anyone have any ideas on how to construct a
    >driver for a 1 amp stepper motor? I'd be interested in any ideas.
    >
    >Regards,
    >Jim Szymczak
    >
    >N1RYU
    >Electrical Engineering
    >University of New Hampshire
    >
    >
    >
    >
    >
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