Article View: sci.electronics
Article #20376Re: Variable speed motor control ... need help.
From: Richard S D'Ippolito
Date: Tue, 10 Jan 1989 20:01
Date: Tue, 10 Jan 1989 20:01
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In article <15880003@hpficad.HP.COM> stu@hpficad.HP.COM (Stu Bell) writes: >I use the circuit below for model trains (I have left out the direction >switches): > > [deleted] > >Make sure you heat sink the PNP transistor -- If you are pulling a couple of >amps through the motor at ~10 volts, the PNP will be dissipating 20 Watts! >This is plenty enough to get (VERY!) warm. Nope. The motor will -- the transistor sees only the difference between the supply voltage and the motor voltage. Maximum dissipation occurs when both the motor and transistor see v_supply/2. Rich -- --------------------------------------------------------------------------- You can lead a horse to water, RSD@sei.cmu.edu but you can't make him fish. ---------------------------------------------------------------------------
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arc1-ca.pugleaf.net!utzoo!attcan!uunet!lll-winken!ames!ncar!tank!uxc!iuvax!rutgers!rochester!pt.cs.cmu.edu!sei!sei.cmu.edu!rsdReferences:
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!lll-winken!ames!ncar!tank!uxc!iuvax!rutgers!rochester!pt.cs.cmu.edu!sei!sei.cmu.edu!rsd From: rsd@sei.cmu.edu (Richard S D'Ippolito) Newsgroups: sci.electronics Subject: Re: Variable speed motor control ... need help. Message-ID: <8165@aw.sei.cmu.edu> Date: 10 Jan 89 20:01:59 GMT References: <288@heurikon.UUCP> <15880003@hpficad.HP.COM> Sender: netnews@sei.cmu.edu Reply-To: rsd@ae.sei.cmu.edu.UUCP (Rich D'Ippolito) Organization: Carnegie-Mellon University, SEI, Pgh, Pa Lines: 23