Hi,
I would like to control ~100 voltage controlled devices [0..12V] using an Arduino. Any advice on this?
I can ask somebody to have a look at the final design but I would like to have some tips from you for basic information / similar projects / tutorials.
Thanks!
There are loads of ways to control a 12v device, just as lots of ways to control about one hundred devices.
Can you tell us more about your project ?
It probably is a lot easier to answer if you tell us what kind of devices you want to control in what kind of setting.
I want to use Revoltec cold cathode light. At 0V it’s completely dark, going up to 12V you can control how much of it is glowing.
So basically a setup like this one: 64 CCFL on Vimeo
If you want variable levels of brightness, PWM is your first choice. However a Google for "cold cathode pwm" reveals there there PWM behaves a little different and that a variable-voltage or variable-current scheme may give "better" (depending on your definition of "better") results.
You probably just want to start with just PWM and see how that goes before diving into other schemes which are considerably more difficult.
To PWM 12V with an Arduino, you'll need to use an NPN transistor. It looks like current requirements are pretty low, in the milliamp range, so pretty much any random transistor from the junk pile will do unless you've got a monster big cold cathode.
Question: To control 100 of them, do you need to dim them all independently, or can you dim them simultaneously or in a few handfuls of banks?
Thanks for your answer tylernt!
If you want variable levels of brightness, PWM is your first choice. However a Google for "cold cathode pwm" reveals there there PWM behaves a little different and that a variable-voltage or variable-current scheme may give "better" (depending on your definition of "better") results.
I did’n try PWN yet, only voltage modulation using a generator (no Arduino) with 0–12V.
The videos I saw so far seem like PMW controlled cold cathodes behave the same. There is no way to dim the cathodes, they just light up a bit with low voltage and complete with high voltage.
To control 100 of them, do you need to dim them all independently, or can you dim them simultaneously or in a few handfuls of banks?
I need to control every single one of them.
You've got a couple of options. One is inexpensive shift registers and the ShiftPWM library http://www.elcojacobs.com/shiftpwm/ Cheap registers will probably need transistors to help drive your cold cathodes which is inconvenient to wire up. There are upgraded registers that can handle more current to eliminate the transistors, but for the cost of those you might as well use an LED driver IC.
Probably the best option is to use an IC desigend to drive LEDs. The current requirements for cold cathodes is pretty mild so you can probably drive them from the IC itself and not need a transistor. Here is one example of an LED driver IC, there are others: Arduino Playground - HomePage
If shiftPWM works with shift registers via the SPI interface (or fakes it and can do that via the SPI pins) then I offer a board that can sink 150mA per IO from 12V sources for 96 channels with TPIC6B595 shift registers, and has 328P for arduino functionality. Connect an FTDI Basic for programming.
If more current is needed, I also have a board with discrete N-channel MOSFETs for an Amp or so per channel, can be daisychained with 32 channels per board.
http://www.crossroadsfencing.com/BobuinoRev17/
