2012/1/20 Kirk Wallace <kwall...@wallacecompany.com>: > On Thu, 2012-01-19 at 17:32 -0500, Przemek Klosowski wrote: >> On Thu, Jan 19, 2012 at 5:08 PM, Viesturs Lācis >> <viesturs.la...@gmail.com>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. > > Just to add my two cent's worth, see attached (if it makes it):
Thank You, guys! Kirk, I repasted Your scheme here: http://picpaste.com/scheme-3V0w43QM.png Do I understand that includes also Steve's and Przemek's sugestions, if R2 is 200 ohm? The optoisolator is 4N25, the transistor is BD139. Gene, I think that I have spare 330 or 470 ohm resistors to replace the 1K ohm R1, I will try to test it. 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
