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Topic: Help with picking what product to use! (Read 397 times) previous topic - next topic


Okay I just got some nano's in last night and soldered one up in my excitement and all the pins are on the same side as the reset button so I can mount it easier and well because I was having fun soldering it..  I've spent a few hours reading stuff on the internet and this is what I'm trying to do.

Picture 5 triangles with bases forming a pentagon (aka a star).  I guess I'd probably need something like a MSGEQ7 and at the moment I have 5 nano's sitting around.  I figured a 5 point star as I have 5 colors of LEDs (probably 11 LEDs per triangle is my guess) and each triangle would be a different color and only the outline of each triangle would be made up of LEDs.  I currently have a car radio hooked up to two 6.5" speakers and I can get an analog signal off the rear speaker outputs or there is a line out signal wire for each channel. 

Either that or I already have some high sensitivity sound microphone sensors (which I thought I could just hook up to and power a couple LEDs but they don't have the power on their own I have realized) that I could use with something like a PCA9685 16 Channel 12 Bit PWM Servo Driver and just have the triangles flash to the music that the mic picks up.

The MSGEQ7 would be nice but it's $30
The PCA9685 is around $12 but would it work to pulse the LEDs?

FYI this is for a busy board for my 16 month old girl.  I'm wanting to integrate switches and I could probably put a switch between each of the triangles and whatever is supplying power so she could turn each on or off with various switches.

Any thoughts or ideas to make something like this happen is appreciated!!


You can get ws2812 strands to form the triangle, then you can control each pixel individually...
A creaking creeping shadow
stiff against the freezing fog
glares at a tickless watch.

Time has failed him -- all things shall pass.


I would use fewer but brighter LEDs and hide them behind some diffusion material. Make the whole section a button per. Make each cycle colors per press.

Pulsing to music- msgeq7 may be overkill. A simple sound sensor that pulses to ambient noise could be enough. You said you're making a busy board, not a spectrum analyzer.


Aug 12, 2017, 02:34 pm Last Edit: Aug 12, 2017, 02:36 pm by Grumpy_Mike
The MSGEQ7 would be nice but it's $30

As to LED triangles see this
LED triangle strips.


Nice, I have a microphone sensor but it and a nano aren't going to be able to drive much for LEDs.  Nano doesn't have many outputs and according to the pinout they say not to exceed 200Ma for the entire package.  Though not sure how much an LED draws but I have some whites reds blues yellows and greens and three draw over 4 volts.  Speaking of that what does a nano put out for volts on the digital outs?  Does it depend on Vin volts or can that be programmed in for output volts?  Because of that I was thinking then of this to power the LEDs

SunFounder PCA9685 16 Channel 12 Bit PWM Servo Driver for Arduino Link: http://a.co/iUu7peu

Interesting looking stuff there Grumpy, I have a piece of plexi already cut (with the plywood already cut and recessed for it) that I was going to have the LEDs mounted in, all I have to do is drill some holes and stuff them in there so really I can do any design but I have 5 colors of LEDs so figured a star would fit some of each.  And the LED kit came with 10 each of RGB and flashing RGB and UV so I might put a few flashers in the center of the star.

Right now this whole thing is powered by 10 rechargeable C batteries to get around 13 volts (for car radio) with a DROK DC Car Power Supply Voltage Regulator Buck Converter 8A/100W 12A Max DC 5-40V to 1.2-36V Step Down Volt Convert Module set to 5 volts out to power LEDs/nano/microphone sensor and whatever else.  Though if those c batteries die fast I have an old desktop pc psu that has 12v and 5v out that I can hook up to it.

This is what happens when my wife wants something simple and I get carried away SMH but it's fun at least for me!


That is the problem with single LEDs they take up a lot of pins.
An Arduino's output voltage is the voltage you power the chip with their is no way to control the output voltage. Vin pins normally have a regulator to cut down the voltage before it is applied to the chip. With a single LED you need a resistor on each pin.

Addressable LED strips on the other hand can be very long and only take one or two outputs depending on the strip type what ever the choice you need 5V to drive them. Each LED can be any colour you want.

Most LEDs can be driven at 20mA per colour, although the current you drive them at is your choice. Some LEDs are far too bright at the 20mA maximum.


I was going to have each color soldered up in parallel so that should require only one pin on the nano, I did order two of the PCA9685 that I found for cheap just in case I need them as well as I have a couple extra nanos in case I fry one :D 


Parallel LEDs are a bad idea. Putting multiple LEDs to an I/O is an even worse idea.
The pins are 40mA max. Each LED should be given 15-20mA.

Loose 5mm bulb type LEDs are for learning and indicator lights mostly. For any project aimed toward significant light output, using SMD style LEDs is the correct route. They are about 5 times brighter. With smart ones, you'd be replacing 10 components and 15 solder points with 1 component and 3 solder points per 5 bulb LEDs, and you gain RGB functionality. 15 solder points jumps to 35 for equivalent rgb bulb LEDs.

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