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Topic: Help making a high powered RGB Lighting system for my highschool (Read 14247 times)previous topic - next topic

neurostar

EDIT: And what is the maximum input voltage for driver? A 48V input would work great for my needs.

As in data sheet PVIN max is 45V. If you use same power for VIN, you are limited to use 30V.

charliehorse55

#46
Mar 14, 2011, 03:59 amLast Edit: Mar 14, 2011, 04:01 am by charliehorse55 Reason: 1
Okay, I guess I'm stuck with the slightly more expensive 36V/300W PSU.

I assume the actual driver IC doesn't use much power so I can simply use two 200m ohm resistors to make a voltage divider for it to run it off the +36V?

EDIT: That won't work, but possibly with higher ohm resistors? I doubt the IC draws more than 2-3W of power anyways.

neurostar

There are reasons why people don't use a simple voltage divider as a voltage regulator. It is not matter of efficiency. If you use high ohm resistors to reduce the resistor power dissipation, there are high voltage drop across the resistor depending on current draw. When LT3496 draw varying current especially during PWM, you will have huge fluctuations on VIN.

charliehorse55

Right, so a 12V VRM is a better idea.

neurostar

Why 12v? You want to use as low as possible, If you are going to use switching voltage regulator. Linear voltage regulator won't work, because of high voltage difference between In and out. I think you can use 5V from Arduino, anyway you need to power Arduino with lower than 12V.

charliehorse55

I was going to power the arduino through the USB interface. The only thing I'm going to be doing is driving 6 PWM outputs and 6 digital outs, no LEDs or other devices. The 2.5W a USB connection can draw should be enough for that right?

Unless the driver IC uses <0.25W each, I won't be able to run them off the Arduino because I will be using 6-8 of them.

neurostar

USB power may not enough. Computer USB supply normally 500mA max, and LT3496 need 80mA max based on my measurement. You can just buy 3.3 or 5V power adapter.

charliehorse55

Okay, I have done a major re-work of my driver board.

I am going to use the same LT3496 driver, but in boost configuration so that I can use a +12V input. This will also negate the need for a separate 5V power supply as the LT3496 can be run from 12V without issue.

I have also decided to switch to an I2C interface. I'm trying to find a chip like the ATTINY85, but runs from 12V. If that's not possible I can always power the chip from the Arduino as it takes <3mA at full load, but it would be much neater and easier to use a chip that can be run from the main +12V connector (that comes from a computer powersupply).

charliehorse55

#53
Mar 30, 2011, 11:12 pmLast Edit: Mar 30, 2011, 11:23 pm by charliehorse55 Reason: 1
I have now figured out that I will need a 5V source for that ATTINY85 so I have decided to use the +5V rail from the powersupply and power each board with a molex connector.

Should I power the LT3496 with +12V or +5V? I have access to both on the board.

Also, is there a way to flash the board so that when it is not plugged into a computer it executes some simple code? I am going to attach some 10k pots to the analog inputs and I would like the board to automatically read those values and run the lights accordingly if no computer is plugged into to control them.

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