Close, but not quite. As shown, the transistor in the optocoupler will try to supply unlimited current into the base of the rightmost transistor. This will most likely destroy one, or both devices. The rightmost transistor needs a resistor in series with its base lead, something like 470 ohms to limit the current to a reasonable value like 20 mA assuming the rightmost transistor has a beta of around 50 while conducting 1 ampere. Note that the rightmost transistor will need to be a power device with heatsinking possibly.
Things could be simpler is the rightmost transistor was an N-channel MOSFET. The current limiting resistor would not be needed and the power dissipation would likely be much less. Regards, Steve Stallings > -----Original Message----- > From: Viesturs Lacis [mailto:viesturs.la...@gmail.com] > Sent: Thursday, January 19, 2012 5:08 PM > To: Enhanced Machine Controller (EMC) > Subject: [Emc-users] DIY output driver > > Hello, folks! > > I would appreciate some advice or insights, what am I doing wrong. > > What I want to do is to switch on and off a power to laser > engraver diode. > It needs 12 VDC supply and it consumes ~1 A currrent. > > Here is schematics of what I currently have: > http://picpaste.com/DSCF6164-vX7heUEq.jpg > > The problem is that it is not working: > Voltmeter was showing +12 VDC on both leads, going to laser module all > the time, regardless if I had turned the output pin "true" or not. > > First of all I am interested, if the scheme is actually correct. > > Thanks! > > Viesturs > > -------------------------------------------------------------- > ---------------- > Keep Your Developer Skills Current with LearnDevNow! > The most comprehensive online learning library for Microsoft > developers > is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, > CSS3, MVC3, > Metro Style Apps, more. Free future releases when you subscribe now! > http://p.sf.net/sfu/learndevnow-d2d > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
