I guess the RGB pins of the strip need some kind of voltage, to produce multiple colors instead of just mixing RED, GREEN and BLUE.
QuoteI guess the RGB pins of the strip need some kind of voltage, to produce multiple colors instead of just mixing RED, GREEN and BLUE.No just mixing the R, G B colours at different brightnesses will give you all the colours.That schematic is no good for what you want because that chip can only switch about 650mA of current in total at any one time with each individual buffer being restricted to a maximum of 500mA.
so 0.75A, seperated over 3 channels = 0.25A.
Quoteso 0.75A, seperated over 3 channels = 0.25A.But added together will give 0.75A, which is too much for the chip due to power dissipation. See:-http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.htmlYou could use one chip per colour or a bigger darlington like a BD679 or a logic level FET.
do I have to connect each of the 2-8 PINs on the ULN2003 to GND
Quotedo I have to connect each of the 2-8 PINs on the ULN2003 to GNDYes otherwise there is no path to ground for the current, nor common reference for the transistors.That circuit will work, providing your strip works by grounding the R, G & B signals. But it is a bit of a waste using three arrays only to use one transistor per array.
would this create nice blue-ish color a bright Aqua-blue color
If you are going to do that then you might as well parallel those unused outputs to spread the load. That is wire pins 10 to 16 on each chip together. The data sheet says it is fine to do this.Quotewould this create nice blue-ish color a bright Aqua-blue colorYes.
would this create nice blue-ish color a bright Aqua-blue color Hey I am a bloke, only girls use names like that for colours, I don't know what you would call it, try it and see.
No I mean on each chip connect 15 to 10 together, and also the inputs 1 to 7 together. This makes the current flow through all the transistors for each colour, and so puts less load on the chip.
will be able to mix different levels of blue by using an analogWrite
Quotewill be able to mix different levels of blue by using an analogWrite Yes the intensity of the colour will change with the PWM value you feed it. By mixing different values you will get different colours.For an example of this see the last half of the video in my project:-http://www.thebox.myzen.co.uk/Hardware/Hexome.htmlTake that last circuit. Remove all the black wires that go to ground.Connect pins 1 to 7 together. Do this for all three chips.Connect pins 16 to 10 together. Do this for all three chips.Then wire pin 8 of all chips to ground. Do not connect pin 7 to anything.
but what happens to PIN 9?