How to use Arduino with Audio Shield & LM3915 for driving high power LED's

Hi guys,

I just wanted to know how can I use my Arduino with an Audio shield I bought from SparkFun to drive High power LED's.

I am using TIP122 for driving the high power LED's. But i dont know how to use a LM3915 in coordination with the arduino outputs to drive the LED's according to the sound levels from the audio shield.

If anyone could provide some help, it would be great!!!

If anyone could provide some help, it would be great!!!

Yes it would be great if we had an idea of what you have and what you want to do.

Audio shield I bought from SparkFun

What shield, link please.

But i dont know how to use a LM3915 in coordination with the arduino outputs

The LM3915 is very much a stand alone chip. You feed a DC level into it and it lights up the LEDs connected directly to it. So where does the TIP22 come in and how high power are your high power LEDs?

hey Grumpy_Mike,

I need to build a VU meter with High Power LED's.

So the LED's im using are 60ma Leds Each, so to drive those I was using a TIP122.

The shield: https://www.sparkfun.com/products/10306

Ive tried to feed the output from the arduino to the LM3915. it didnt seem to work!

Could you suggest a schematic?

And i Was using the Audio Shield to get the Audio signals split into different frequencies, So that i could build a separate VU meter for each wavelength/band..

Well the LM3915 data sheet says:-

Output current programmable from 1 mA to 30 mA

So your 60mA is too much. However, 60mA is not a high power LED and so is quite easily controlled using a resistor.

You can still use the LM3915 but replace the LEDs with resistors. Then connect the outputs to a 74LS04 inverting buffer ( 6 in one IC ). Then run the output through a resistor and on to the base of a transistor. The emitter to ground and the collector to the current limiting resistor. The other end of that to the cathode of the LED and the anode to the +ve supply.

The transistor only needs to be a small one and the TIP122 is way over the top for this. Any NPN transistor can cope with 100mA and you need only 60mA so get the cheapest one available at your local supplier.

Alternatively the TPIC6B595 power shift register can power these LEDs directly