Help on I2C question

@bobcroft

     I could use SPI interface from what you show. Researching that angle. Would like something elegant/simple to do...

@Michael Oldfield

     Need to check this one out too because transistors should be rather inexpensive. MCP23008 could be the key to switching these. About how fast do you think this can occur (the switching).

Thanks to all,

Clem

The MCP23008 according to the datasheet MCP23008 - Interface- Serial Peripherals can switch at 100kHz, 400kHz and 1.7MHz I²C with the transistors depends on which ones you use but normally very fast and to save on pins you could do a 7x7 matrix and it should only use 8 pins i think if you have a common ground but that would only be 49 transistors. if you where going to use SPI the 595 series shift register at 20mhz could be a cheap option http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf but can use a lot of memory and you would still need transistors but like i say it is hard to offer solutions without knowing more like how many amps at 12v, what type of load the more info the better.

Looking at 300 LED's at 20 mA each for a total around 6 A if all on with white! Really hope not to do this... I plan on feeding this with old 120V-> 20 volt/6 A laptop regulator rated at 90 watt's into a buck DC to DC down to 12 Volts. Am I crazy? LOL

Oh I plan on dividing these into groups of 3-6 LED's per cup...

If you have all that stuff already then no, not crazy at all

I would do the same

Peter

i can help with what your planning i had a feeling it was going to be leds and i had to do something similar in a limousine. Their is some great IC`s out their for just this kind of thing but if you are a masochist take a look at http://en.wikipedia.org/wiki/Charlieplexing i dont have much time at the moment but i will help more tomorrow and try and put all i know about controlling large arrays of leds but if they are RGB leds then you will need to triple the current because it is 20ma per colour so 60ma with all three colours on to produce white but if they are being PWM`ed then it is unlikely that you will every reach the full 18A also if you connect some in series you can lower the current but will need to raise the voltage.

PS its not crazy sometimes you just have to climb the mountain because it is there

i can help with what your planning i had a feeling it was going to be leds and i had to do something similar in a limousine. Their is some great IC`s out their for just this kind of thing but if you are a masochist take a look at http://en.wikipedia.org/wiki/Charlieplexing i dont have much time at the moment but i will help more tomorrow and try and put all i know about controlling large arrays of leds but if they are RGB leds then you will need to triple the current because it is 20ma per colour so 60ma with all three colours on to produce white but if they are being PWM`ed then it is unlikely that you will every reach the full 18A also if you connect some in series you can lower the current but will need to raise the voltage.

PS its not crazy sometimes you just have to climb the mountain because it is there