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How to wire this setup?
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Youkai:
Oh I didn't notice you posted an image in your second post. I looked at it and yours is definitely organized better but I think they basically show the same thing. Or at least your image and mine are the same thing in my mind. I'm just using the 12V+ as the "12 volt rail" in your image. so it splits to the transistor and buck converter.

I think your image basically confirms I was on the right track. Also it gives me a better idea of how to structure these diagrams. Thank you.
KL27x:
Ahh..

A little triangle is commonly used to denote ground, but it conventionally points down. An arrow pointing up usually denotes a power rail. Even despite this, I still see some minor errors in the schematic. Or maybe it's just too confusing for me.

 
--- Quote ---Either way the transistor's collector and emitter has to be in series with the LED strip and run from + to ground, right?
--- End quote ---
Yeah. If you are trying to switch on the high side, with a transistor between the 12V rail and the LED strip, then you are going to have a problem. If you are using an NPN, then you will need to put something higher than 12V on the base to get a base-emitter current going, and the Arduino will output only 5V. If you are using a PNP on the high side, the Arduino pin will be exposed to 12V, and the ESD protection diode on the input pin will pull the base down to 5.3V. The Arduino will be unable to turn the PNP off. There is no way you can control the LED on the high side with only a single transistor without adding parts. (Or using a common positive rail and having -5 and a -12V rails.)

The easiest way to do it is to switch it on the low side, like I have shown, using an NPN transistor or an NFET.

The easiest way to switch it on the high side in this case, if that were necessary for some other reason, is to use a PFET or PNP transistor and switch that with an NFET or NPN transistor. And connect your Arduino to the base/gate of the N transistor.
Youkai:
The LED strip has a 12v pin and separate RGB pins. So the transistor would need to go on the low side to control each separately. I just drew my initial diagram bad. It will go on the low side.
Brumby:

--- Quote from: Youkai on May 10, 2018, 04:12:25 am ---Oh I didn't notice you posted an image in your second post. I looked at it and yours is definitely organized better but I think they basically show the same thing. Or at least your image and mine are the same thing in my mind. I'm just using the 12V+ as the "12 volt rail" in your image. so it splits to the transistor and buck converter.

I think your image basically confirms I was on the right track. Also it gives me a better idea of how to structure these diagrams. Thank you.

--- End quote ---

It took me a while to make sense of your original circuit - because layout conventions guide our thinking.

The general structure is something like this:  Power rails tend to be horizontal lines, with potential (usually) defining their height: +V at the top, 0V at the bottom.  If you have a split rail supply, then it will (usually) be +V at the top, 0V in the middle and -V at the bottom.  Inputs from the left, as are power supplies (frequently); Outputs to the right;  Feedback paths go wherever they need to go.  Also pay attention to earth and chassis connections as well as off-page connections.

Of course there are many circuits where you can't follow this 100% - but if you get the major logical process flow to run from left to right, you will have something easier to read.
Youkai:
Ah. Cool beans. I'll follow that in the future. Thanks
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