Suggestions for RGB LED Ambient Lighting with MSGEQ7

Hello all,

First off: I'm a noob. I am totally new to the Arduino hardware, software, etc. I've only played with Arduino for about 45 minutes in my whole life, lol. However, I have done a little bit of tinkering with electronics and built a few really basic things like turn signals for my bike, and a portable iPhone charger.

My goal is to build an ambient lighting system for my car that pulses/flashes/changes color based on the frequency. Here's what I know so far:

  • My Arduino of choice is the Uno
  • I'll be using an MSGEQ7 chip for analyzing the audio frequencies
  • I want to use this program, but possibly slightly modified to include more red than blue (as it is now)
  • I want to power it using the car battery
  • I'll use 12V RGB LED strips

My main question is about powering the setup from the car battery. I'm pretty sure the Uno has a built-in voltage regulator for knocking the 12v down to 5v, but I read somewhere about filtering the power because it could damage the board. Also, I'm not sure about powering the LED strips; are they powered directly from the board, or do I need a separate +12v line for them? Or do I need to use some sort of external LED driver? I'm not trying to control them individually, I just want to control a total of around 2-4 meters of LED.

Thanks in advance for any help, regarding the power solution or any other suggestions about the project. All help is very much appreciated!
-Adam

The big concern on power is that automotive power is notoriously noisy, and swings between 10v and 15v depending on the state of the battery and what the car is doing. I'm not sure if the 12v LED strips are okay with taking 15v, but if they can't, you'll need a converter.

You may want/need a DC/DC converter just to get a stable 12v out of it (you can get DC/DC converters on eBay for dirt cheap. Get a couple, so you can afford to trash one, and even if you don't, you'll use it later). A step-down converter (ones that go up and down are bulkier and more expensive) is probably fine - it'll give you 12v when voltage is over 12v, and the input voltage (approx) when it's not on the ground that the LED strip will work if it's a little under 12v, and if it's so far under that it won't work, you're in a ditch on the side of the road. Make sure it can handle the current that the LED strip will draw.

Thanks for the quick reply! I found some step-down converters on eBay, but that kinda confused me more; what kind do I need? I saw a 12V to 9V converter but that would cause the voltage to always bee too low for the strips. Do I need like a 24V to 12V converter?

PS - Did you mean the "ditch on the side of the rode" figuratively or literally? I don't want to draw too much current from the car battery and literally end up on the side of the road. Lol.

You need a converter that regulates to 12 V but can take an input of at least 15V.

Grumpy_Mike:
You need a converter that regulates to 12 V but can take an input of at least 15V.

Thanks! So if I got this:

http://www.ebay.com/itm/Waterproof-DC-DC-Converter-Regulator-24V-12-40V-Step-down-to-12V-60W-5A-/181007852150?pt=LH_DefaultDomain_0&hash=item2a24e8a276

and used it to power the Arduino, do I need anything separate for powering my LED strips? Or can they draw all the power they need from the Arduino itself?

can they draw all the power they need from the Arduino itself?

No the Arduino's regulator has a limit of 1A, but because of thermal issues this is more like half an amp. But why do you need to, you said:-

I'll use 12V RGB LED strips

Unless you are thinking of connecting them to the Vin pin with you putting the 12V into the Arduino with the power jack. Then you have the series diode with a 1A rating to consider.
Do you know how much current you are going to draw with the LED strips?

So because the Arduino's regulator has a limit of ~.5A, I couldn't use the converter linked above (step-down to 12V 5A)?

I actually don't know the current draw.. I want to use these but the current isn't listed anywhere. I did read somewhere that most use about .2A per meter, though:
http://www.lightingever.com/12v-led-strip-non-waterproof-4100059-rgb-nf.html

I thought about powering the Arduino via USB using one of those DC to 5V 1A USB converters. But then how do the LED strips get power?

In this example, Adafruit connected the +12V on the LED strip to the Vin on the Arduino. Can I instead connect the LED strips directly to the + car battery and ground on Arduino? See the Fritzing sketch attached; nothing is wired except for power of course, but would something like this work?

Screen Shot 2015-02-05 at 12.20.40 PM.png

Yes you can. Still need transistors to sink current from the individual cathodes.

Awesome, thanks! Can you take a quick look at this circuit to see if it will work? I found it on Instructables (I know some people despise Instructables, but sometimes it’s pretty good). Of course, mine will have the power change mentioned in my last post.

I hate fritzing. Looking at a bunch of black boxes with no clue as to their IO functionality.
Have to look up each unlabeled part to see what it does.
A real schematic tells all. Try creating one & post that.

I couldn’t use the converter linked above (step-down to 12V 5A)?

Why ever not?

The current rating of a power supply is only what it can provide not what it will provide. But you knew that didn’t you. :wink:

I found it on Instructables (I know some people despise Instructables, but sometimes it’s pretty good).

Oh come on I have never seen a good one yet.

Grumpy_Mike:
The current rating of a power supply is only what it can provide not what it will provide. But you knew that didn’t you. :wink:

Oh come on I have never seen a good one yet.

Yes, silly me. Of course I knew that :wink:

If you’ve never seen a good Instructable, you’ve never seen my Instructables. Hehehe.

CrossRoads:
I hate fritzing. Looking at a bunch of black boxes with no clue as to their IO functionality.
Have to look up each unlabeled part to see what it does.
A real schematic tells all. Try creating one & post that.

Sorry. The IC chip is the MSGEQ7 and the three transistors at the top are the N-channel MOSFET's. The green/black plug is a 3.5mm audio jack. I'd create a schematic but don't have the time right now :frowning:

adambowker98:
If you've never seen a good Instructable, you've never seen my Instructables. Hehehe.

Post a link, I am always up for something new.

Grumpy_Mike:
Post a link, I am always up for something new.

If you insist :wink:

Here’s one of my favorite projects, but please don’t pay attention to the wire joints. Lol.
LED Bike Turn Signals

These two have nothing to do with electronics, but I think they’re pretty good :stuck_out_tongue:
DIY Etched Glasses
Adjustable Paracord Bracelets
EDIT: I forgot the Sweet ‘n’ Tangy Wings!

PS - Can you take a peek at the Fritzing diagram I posted and see what you think of it?

-Adam

If you insist :wink:
Here's one of my favorite projects, but please don't pay attention to the wire joints.

Sorry but it is well up to the standard of electronics instruciables. It is crap.

You have LEDs in parallel and a single common current limiting resistor.
LEDs in parallel will not share current so in time one LED will take more current than the rest and so burn out early. Using a 10 Ohm resistor for a 2.6V LED on a 9V battery is plain stupid. This means that the total current through the resistor will be 640mA. Assuming that they all share current equally that means you have 128mA per LED. Are they rated at that?
I think not.

I think the only reason the whole thing did not melt is that you used a crappy PP3 square battery that has very limited current, that is it has a high output impedance.

Sorry I don't do Fritzing.

Grumpy_Mike:
Sorry but it is well up to the standard of electronics instruciables. It is crap.

You have LEDs in parallel and a single common current limiting resistor.
LEDs in parallel will not share current so in time one LED will take more current than the rest and so burn out early. Using a 10 Ohm resistor for a 2.6V LED on a 9V battery is plain stupid. This means that the total current through the resistor will be 640mA. Assuming that they all share current equally that means you have 128mA per LED. Are they rated at that?
I think not.

I think the only reason the whole thing did not melt is that you used a crappy PP3 square battery that has very limited current, that is it has a high output impedance.

Sorry I don't do Fritzing.

Oh, wow. That was unexpected but probably deserved, haha. To be fair I did do that about 2 years ago, and I know much more now than I did back then. But I'm still by no means very good. I do thank you for your input though :slight_smile:

Since no one around here seems to like Fritizing, I'll see what I can do about drawing up a schematic with my plans.

That was unexpected but probably deserved,

Amazed you take it like that, well done.
I made all my growing up mistakes in private because there was no internet then. But it also meant that I had to work everything out for myself.

Despite what you might think you never stop learning, most days I learn something new. Keep plugging away and you will get there.
Cheers