This who right stuff is going on too long here Jon you have posted links that show the same thing. When it comes to posting something on this forum it always looks like you have to have the last word. And you always post peoples ideas about what they think is right.
I posting mine and there not about right or wrong I only post things that have been fully tested and work as is. I started this road in the late 1970's and I have read more books then and papers then there are days. Like that old saying there more then one way to skin a cat it's true.
The name of this forum is digital-diy it was started to share ideas not bang the poster for there ideas. If you want support for the ideas that's good and well.
If i post my idea that because I tested it and it work that how electronics's
got started people tried ideas based on what they want to happen and it worked some
write up the how's and why's. I don't have the time to be a writer.
And I'm not going to do all the work for ever one just to post something and and see
a book reader post I'm wrong and never test my Idea...
Jon Hope you can see the point here seeing you posted this
. I'm beginning to feel the same way with this topic! It would have been far easier just to do it, and maybe or maybe not share the final results.
One of Dave's comments sums it up really well to me]
You posted a circuit with an unusual transistor configuration. Freely admitting that I don't have a lot of experience in using transistors as switches, I posted a reply questioning the placement of the transistor.
This was your chance to explain how the circuit worked, or to cite a reference so that I and the other readers here could learn and understand the logic behind the circuit. Instead, you reply "It works either way" and plagiarize a picture which doesn't explain anything.
Since your circuit is unusual, and searching on "transistor switches" yields at least 99 out of 100 links showing the standard arrangement, I posted a couple links showing how to use transistors as switches and explaining the pertinent parameters and calculations. I posted these links so that the readers here can learn and have a reference to explain how to use a transistor switch. Nothing here is my opinion, except that the references I quoted are clear and understandable.
In the second reference (which is in our links collection here by the way), Microcontroller Interfacing- Section 8: High Side PNP Transistor Switching, Gary Sutcliffe says that the high-side NPN switch may not work properly in all cases because the transistor may not have enough gain to be fully driven into saturation (meaning the transistor is not fully on).
So there are two links showing the common arrangement and showing the required calculations so that everybody here can make effective use of transistor switches, including one that says a high side switch may not always work vs:
One of the greatest electronic minds of all times put that in a book about 20 years ago
Maybe your circuit works beautifully. But you haven't offered any explanation or reference so that we can make use of it. I'm not saying and I haven't said it won't work. What I have said is it's not the usual method and provided some references so people can understand the usual way of using transistor switches.
You're more than welcome to explain how to use a transistor in the way you have shown.
I actually asked Jon about this in a PM when it was posted on the other topic. I asked because in reading the things I have read so far, I have yet to see an NPN used to source current, it's always done with a PNP. I have seen it done using an NPN/PNP pair so that HIGH = ON. (to quote my PM to Jon) But never as was stated by Burt. This doesn't mean it's not POSSIBLE, obviously...
However, let's think for a moment about the facts here, disregarding calculations. As near as I can tell from some research, the BJT has been around since 1948, giving people some 62 years to experiment with them. I guess I didn't suppose nobody had ever thought of trying to place an NPN on the high side, given how convenient that arrangement would be for a great many circuits. This leads someone like myself to wonder "why?" Then I see someone post saying that it's possible to do that. I thought maybe I'd just overlooked something since I hadn't seen that configuration yet.
I'm all for messing around to see what works... I've done most of my learning that way. However, at some point in time, it's nice to know the "WHY" so that someone can move beyond the basics. Right now, I don't know WHY I need a resistor prior to the base on a transistor, but I know if you don't have one it gets hot as hell and can blow. (don't bother trying to explain that, I'd rather look it up at this point)
The point I am trying to make is that just because something works with one circuit doesn't mean it works with everything and it doesn't mean it's "right." Right can mean a lot of things including the difference between a transistor or maybe the PIC connected to it lasting 5 days or 5 minutes instead of 5 years. You don't just "hook shit together" and move on... I've learned that the hard way, the same as many others.
Jon as a moderator here has some responsibility to read into things a little more closely, as he did on that topic. We aren't talking about using a 10k resistor when people might normally use a 4.7k. We're talking about something that for most readers is either new or goes against what we've read about a subject that's been studied and examined for the more than 60 years. Maybe you want to pick a fight with Jon, I don't know. However, given the circumstances, his question didn't seem out of line. You simply seem annoyed that he didn't take what you said at face value. I don't know about you, but I wouldn't take the word of "some guy" on a website as gospel. Not even Jon, and I know him fairly well.
And dammit, it's "WHO'S RIGHT?" I'm sorry but I personally tire of lazy writers. You're capable, please help the readers.