Almost agree.... having the 10K to ground is still not a bad idea as it will bleed off any leakage from the opto. Note that in your example you assume a beta of 20 and in my example I assumed a beta of 50.
Steve > -----Original Message----- > From: Przemek Klosowski [mailto:[email protected]] > Sent: Thursday, January 19, 2012 5:33 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] DIY output driver > > On Thu, Jan 19, 2012 at 5:08 PM, Viesturs Lacis > <[email protected]>wrote: > > > 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. > > > > > What is the voltage of the 'low' state? could it light up the LED? > > As Steve said, your resistor is in the wrong place. I'd put it on the > collector of the phototransistor.; then, the base current of > your power > transistor would be (12V-0.7V-0.7V)/R; assuming the power > transistor beta > is 20, you'd need 50mA, i.e. the resistor must be 200 ohm. > -------------------------------------------------------------- > ---------------- > 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 > [email protected] > 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
