Thank you all for the help I received in my other thread! I've decided to build my own Arduino chip programmer, and then make a PC board to use the chip to run my LED case lighting mod via it's PWM support. It's the only chip I could find that was capable of more than 2 PWM outs.
I was wondering if I could save space on my PC board by neglecting to use a voltage regulator... I may be wrong, but as far as I can tell, normally you'd use two caps with a voltage regulator inbetween to give the chip clean power... I may again be totally wrong... Can someone clarify?
And if that's it's only purpose, is it safe to assume that the 12v rail on my PSU is voltage regulated, or no? It's a standard ATX PSU...
You need 5 volts for an Atmega chip, not 12.
If you have a well regulated 5v power supply, my guess is you could skip the regulator and just put in some caps as an extra measure.
A reg doesn't take up that much space though..especially if you leave it
mounted vertically (TO220 package).
Oh dear... Yeah, the power from my PSU is clean. It had better be too... Spent a small fortune on it!
If I can only power the chip with 5v, how on earth could I use it to control 12v LEDs? Is there a way I can hook those little guys up to a different power source? IE 5v Red wire to power atmega and other bits, then yellow 12v to power the LEDs?
If I can only power the chip with 5v, how on earth could I use it to control 12v LEDs? Is there a way I can hook those little guys up to a different power source? IE 5v Red wire to power atmega and other bits, then yellow 12v to power the LEDs?
You can use relays or transistors. For my project with 12v lighting, I used transistors so that I could dim the lights if I wanted (PWM), plus I didn't want relay contact noise.
Here is a pic of a small "module" that I made with inputs from the arduino and then outputs for the lights. The LEDs on the board were used for troubleshooting, the LED lights when the input from the Arduino has power. It also let me code on the bench without having the lights connected, yet I could see what was going on.
If I remember correctly (how fast it fades), I ran the 12v + straight to the lights, and was switching ground with a TIP-120 transistor. The TIP-120s are overkill for what I needed (they support much more power) but I had them handy and don't need to worry about overheating them!
This method requires one Arduino pin, one transistor and one resistor for each 12v device switched. (The module above supports switching 5 devices) You would need to pick the right transistor based on the power of the 12v device you are switching. I also added the one red LED per output, but you likely wouldn't want the extra light in your project. I chose to do this on a separate board from the rest of my project just to keep things modular, that was my choice given the number of connections in my project and the desire to change it frequently, there is no special need to isolate these devices from the rest of your project.
If I can only power the chip with 5v, how on earth could I use it to control 12v LEDs?
AFAIK, there is no such thing as a 12V LED, unless it has external components added in some package. So dont bother splitting supplies for that reason. I'd only worry about making sure you dont draw to much current from the Arduino's supply. I would control the LED's with transistors if they use much current, that way you can power them with an external 5 or 12 volts. A ULN2003 transistor array or similar (I use ULN2803) makes this very easy to do with a minimum of components.
Back to the question on why your LED's worked on 12V: because you are probably powering them from the Arduino output pins, which means there's actually 5V going to the LED's
The chip on an Arduino is an ATmega168/328, and they like 5.5V or less.
If you are using the PSU in your PC, you may have a spare 5V, so you don't need a voltage regulator (in fact you shouldn't put a 5V regulator on a 5V input voltage, it won't work), but do use capacitors to filter out electrical noise.
You could use a voltage regulator to reduce 12V to 5V. In this case, I'd recommend using an over-specified one (i.e. 2x maximum current) and/or a small heatsink as you'll be converting power to heat in it (heat = power = voltage x current = 7V x Arduino+LEDs)
In your post "Using in a PC case, Powering more than 5v of LEDs" you said you wanted to drive RGB LEDs, which are different animals again, and are not 12V LEDs. Any component colour of an RGB LED can be driven by 5V.
I'll try to make time to post an answer to your question there, but the summary is:
To drive an RGB LED through all available colours, it needs 3 PWM signals. If you want all 10 of your RGB LEDs to be the same colour, you only need those 3 PWMs current-amplified to drive all of the LEDs. You can drive all the RGB LEDs from 5volts, or a higher voltage, using Darlington transistors or FETs.
I'd recommend you build the circuit on veroboard/stripboard before designing and making a PCB. Making a PCB is time consuming, can be relatively costly (more costly than 10 RGB LEDs and an ATmega), and can be awkward to change if you get it wrong.
You do need a PCB if the components are Surface Mount (SMD), but AFAIK, none of the things you want are SMD. So IMHO, try to get the electronics right on veroboard. It may be sufficient to the job, and you never need a PCB.
