2012/1/26 Kirk Wallace <kwall...@wallacecompany.com>: > On Wed, 2012-01-25 at 23:43 +0200, Viesturs Lācis wrote: >> 2012/1/25 andy pugh <bodge...@gmail.com>: >> > On 25 January 2012 21:07, Viesturs Lācis <viesturs.la...@gmail.com> wrote: >> > >> >> Kirk, I am getting totally confused... >> >> What is the difference in schematics between both images in Your last >> >> email? I cannot see any... >> > >> > The direction the arrow points in the transistor schematic symbol. >> >> Ok, thanks! >> I do not understand - that is inside the BD139, right? What can I do >> about it, if it is still the same BD139 transistor??? > > If your transistor is a BD139 it will be an NPN. As mentioned in another > message, the pin number depends on the package TO or SOT. >
Based on visual appearance, it is SOT package. >> I finally managed to get at least something working: >> Short-circuiting +5V to 4N25's pin5 turns the laser power on and off >> as required. > > It's jumping the 12 V supply to U1 pin 4 that should turn Q1 ON. If the > 5 Volt supply turns Q1 ON, that means that your 12 Volt and 5 Volt > supplies share the same ground, which is okay unless they need to be > isolated, which is what opto-isolators (U1) allow you to do. My apologies for late-night mistakes - it was 4N25's pin4 that was short-circuited to +5V... Ground is shared on both sides, because 5V and 12V are supplied by PC's PSU. Is there a simple way I can drive that transistor without optoisolator? > The general purpose diode next to R1 can tolerate a much higher reverse > voltage. The opto-isolators internal LED has a reverse voltage tolerance > a little over 5 volts, so hooking up the LED backwards or noise on the > line could burn it out. The general purpose diode prevents the opto LED > from being damaged. In addition, a regular LED can also placed in series > with the general purpose diode, and will light up when the signal is ON. > This can help with trouble shooting, and gives customers something watch > while you are explaining how wonderful your machine is. I checked 3 times - it is connected correctly... Ok, I will take that into account and include in my next design (although I am starting to think that next time I will just acquire7i37 card - it seems that with all my struggle I am getting over the "diy will be cheaper" line and it does not seem that I can easily get it working) I like that point of distracting client's attitude :) 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
