Thanks be80be for the reply, this helps IMMENSELY!
I think, based on my multimeter readings that it is definitely going high to low, correct? I.E, I see the current when testing 2 pins w/o a button press, and it goes away when holding the button down.
Keeping in mind my noob status, how did I determine which side where the button connects is high versus ground? Once I can figure that out, I think I'm good to go with your instructions!
Originally you said to put a 1k resistor between the base of the NPN and the digital i/o on the arduino. But in the most recent reply you said I shouldn't need a resistor on the collector...?
And I'm still hoping for some guidance on understanding which is high side side versus ground side on the remote board.
So, to confirm, in your diagram, your positive from the board is connected to the NPN collector.
Ground from the board goes to the NPN emitter.
1k resistor between base and digital i/o of arduino.
What about ground from board to arduino? I'm realizing in your original reply you mentioned "tie ground of remote to ground of arduino", but you also mentioned "solder emitter to ground side". I don't see this in the drawing.
Sorry for so many questions. Just want to make sure I actually understand what I'm doing before I do it
EDIT: Attached, for your reference, is a photo of the remote board with the 4 pins for the momentary button circled.
Yours is a lot easier to figure out then My board you can see thee parts. lol
Just place the NPN pins collector and emitter to ground and hook the base to the arduino with a resistor 1k or higher and you should be able to make it work just as the button did.
Your button is easy if you test it one side is high and one side should be ground just solder the collector to the high side of the button and solder the emitter to the low side of the button and you'll be good to go
Okay, I've essentially re-drawn on my own board what you provided previously, but I'm just covering my bases here.
Here's my proposed setup:
If I hold the board to the light, I can see the red lead headed to the bottom right pin in the photo above, so this should tell me (even w/o a multimeter, which I've tested as well), that this is my "high" and therefore, my solder point for the NPN collector.
One of the other pins that doesn't read out any volts is going to be my low (ground), and the NPN Emitter gets soldered to it.
NPN base is getting connected to one of the Arduino I/O's with a resistor between.
All good so far, right (hopefully)?
Under such a setup, I'm not using the Arduino itself to supply any power (I think where some of my initial confusion came from between us), and as such, the 9V battery remains in my setup to supply the needed power. Correct?
So, looking at the PDF for the 4N25, I would just use connectors 4,5,6, with 6, base, going to my Arduino I/O. Do I still need a resistor between base and the Arduino?
Thanks. I'm getting there. Bear with me, I'm very "green" with the electronics side.
In this setup, then, I was clearly off on my thinking, as pin 6 is unused. I'm good, per your reply on 4 & 5.
The only thing that confused me in your statement is that pins 1 AND 2 are for the LED. Is that 1 for the I/O slot, the other for ground from the Arduino? And, the resistor is between the Arduino I/O slot and Pin 1, right?
Assuming I'm on the same page, it would seem to make sense to just go with the PC817, since it has just the 4 pins I need and nothing else.
Look in the PDF that is linked on the ArduinoInfo.info WIKI. Pin 1 is marked.
Pin numbers go Counter-Clockwise from pin 1. As seen from the TOP.
This is because people are used to going clockwise with pin numbers. On vacuum tubes. From the BOTTOM of the socket. Inside the chassis where you are soldering the filament transformer wires etc etc. In 1949. Everybody knows that 8)
be80be:
What I don't under stand is why you changed from transistor to Logic Output Optoisolators
If you think it works better you can still hook it up backward and 2 I showed you clearly how this worked with a transistor.
Actually, I'll probably try it both ways just to learn. I like the simplicity of the opt-isolator though, as it appears I don't have to worry but any other ground connections, etc. It just seems simpler to me. Certainly appreciate your help as well. I already have 2 NPN transistors (1 for backup, lol), so they will probably get first shot.
So, I decided to breadboard out my setup for testing, by seeing if I could toggle the remote board via momentary button connected to the Arduino and breadboard, and have the state of that button change the I/O on the Arduino to High for the pin I connected the NPN base to, whose collector and emitter are connected to the remote board HIGH and LOW in the location where the remote's momentary button is connected (see below):
And, I'm proud to say, it works like a charm! Yes! Ignore my solder job, I'm still trying to perfect it.
Gonna try optos next, just for fun, but I'm ready to package this up and integrate it with the rest of my setup, and into my Android app now.
Thanks for those who helped assist / clarify my understanding.