2x8 VU Meter Design Question?

I am trying to work out the design of a VU Meter Project I would like to build. I have Googled lots and I wouldn’t say I am a complete noob, but compared to some here on this forum I know nothing :stuck_out_tongue:

I have included a Diagram that IS NOT 100% Tested! But it should give a rough idea on what I want to do.
I have a 2x8 matrix of LEDs and each 2 are in parallel as they fit on the breadboard nicer that way and if one LED is on the other one should be on too as it’s a VU meter.

My main question is power. From what I have read on the forum the Arduino Shiftout Tutorial is wrong in that it cannot provide enough power to power all 8 LEDs at once or in my case 16(roughly 16 x 15ma = 160).

Can I use Multiplexing to Loop Over all 16 LEDs 2 at a time therefor only using 30ma(15ma per LED x 2) of power to power the LEDs at any one time, but loop so fast it looks like they are all on at once?? Also would this theory hold if I want to expand this to a 2x10-16 matrix?
Or do I have to look into using a LED Driver and NPN transistors?
Thanks for any help
Chris

Hi,
I know that lots of people like to use Arduino in projects whether they need to or not, but there are lots of inexpensive ways of building vu meters using opamps or even purpose built vu meter ics. The purpose built ic can be chained together or large arrays of leds. I will post some parts for you to look up in a moment.

Edit - part number lm3916

Duane B

rcarduino.blogspot.com

Thanks for the Info Duane. Its funny you mention the LM3916, I was about to pick up the LM3914 tomorrow at my Electronics store. I dont think they carry the LM3916 tho. I wasnt sure what the difference was between them from reading the datasheet. However I found this link on Google http://groups.yahoo.com/group/Electronics_101/message/1171 that seems to explain the diff pretty well and I think the LM3914 should work in my case.

Thanks Chris

Hi,

Thanks for the link, I was aware of the three, but not sure of the difference myself.

thanks

Duane B

rcarduino.blogspot.com

I was aware of the three, but not sure of the difference myself.

???LM3916 - for VU meters LM3914 - for a linear response LM3915 - for a logarithmic response