KITT Voicebox style VU Meter (6x10 segment led bar graph)

[system]

Hi All

This is my first post here, so I'm quickly going to introduce myself

I've been playing around with an Arduino Uno since quite a while now, hacked a couple of toys to make useless but fun stuff. I would still consider myself a complete newbie though since I never deeply dived into the world of electronics.

I know bits and stuff here and there and am able to put together and code some very basic stuff, but I decided to work on a (hopefully) simple project I want to keep rather than use for a day and get rid of again almost immediately

So here's the plan:

I want to build a knight-rider style Voicebox using 6x 10 segment LED graph bars which react to a soundsource (pretty much like a simple VU meter really). I might even hook up a small speaker and an amp (already build that stuff, should be easy to include).

What I have found so far:
6x10 segment LED bar graph: http://shop.boxtec.ch/segment-led-bar-graph-rot-p-41877.html
I have not found orange ones, so I'll go with red...

LM3914 or LM3916 LED Driver > Dot/Bar Display Driver Hookup Guide - SparkFun Learn

...And some resistors

And that's where the questions already start..

I think I can use the LM3914 or LM3916 to apply a technique similiar to the LED Cube's where you don' t need a lot of pins to switch on/off individual led's. I have however never used an LED driver.. Is my assumption correct that I'll need to have resistors hooked up to every single LED? I will have to go through some tutorials to figure out how to use the LM3914, but any help here is highly appreciated Also, I'm not sure how the difference between the LM3914 and LM3916 has (if at all) an impact on the project.. Any hints?

Another thing I'm not quite sure about: How do I acchieve the "LED dimm effect" (see this video > - YouTube).

I'll probably find out how to get the LED's to behave like a VU meter by finding some sketches and following tutorials. However I'm not sure how to achieve the dimming effect. The LED's are not simply on/off, they also seem to be more dimmed at the higher / lower section (and also left/right section, see video above). Is this achievable with PWM for 60 led's? I guess I'm asking because I'm still not sure how that LED Driver works.

So hopefully I'll be able to put this together with the help of you guys

Thanks for any help!
Carl

[Paul_B]

OK then, you have a decision to make here.

Does an Arduino have anything at all to do with this project?

You can approach it in either of two ways; analog, or digital.

The analog approach has nothing to do with an Arduino; you use the LM3914 or LM3916 (which is an actual "VU" meter variant) to drive the LEDs according to your audio input level. This gives you a display which is simply a "blob" of light which expands vertically and the side displays are simply an echo of the wider sections of the vertical display.

There are a couple of tricks to this; one is that if you use a 12V (or more) supply, you can wire four (red) LEDs in series to each output of the LM3914 and if you organise the connections right, you can do the whole job with two LM3914 ICs. You would set the driving current to 20 mA.

As to the "soft edge" effect, that is rather simple - you just apply (add) an AC voltage to the input of the LM3914, which can be generated by a simple oscillator using a 74HC40106 or a dual op-amp (just look for a "triangle wave oscillator" design). This blurs the display and in fact, works better at a low frequency of the order of 15 Hz. A good area of experimentation.

Your other option is to do this totally digitally. 64 LEDs can be driven easily by a MAX7219 driver using only one current-defining resistor (just like the LM3914) - and a couple of bypass capacitors. Your Arduino code is then responsible for all the processing of groups of LEDs, analog input, blur and such. It's not trivial, but very effective and makes for a very simple circuit as far as the LEDs go.

[system]

Hi Paul

First of all, apologies for the late reply. Been kinda busy, but finally had a chance to look into it and buy some parts Many thanks for your reply below!

I decided to do it the analog way, and I found a schematic which I will try to follow (probably a hard task for a noob like me...) Butusing an Arduino for a fancy VU Meter seems to be a bit of an overkill..

The circuit I will try to build is this one > Knight Technologies
Unfortunately I'm a bit of a breadboard / Fritzing guy, so schematics are quite hard to read for me, but hey... I'll have to learn

As you can see, it uses an LM3915, so that's the one I bought.

However, just to start working on this and understand how the LM works, I decided to build a very simple VU Meter based on this instructables > http://www.instructables.com/id/LM3915LM3916-VU-Meter/step2/Wire-the-LM3916-Circuit/

As far as I can tell, I built it the same way, but that's where the trouble already starts I can't get it to work. The LED's just light up even with no audio source. I have attached a picture of the circuit. I did it on Fritzing, looks a bit messy, but should do the job I hope.

When powering the thing, grom left to right, the first 2 LED's are a bit dimmed, LED's 3-5 are full on, 6 and 7 are again dimmed, 8 is full on and 9-10 are dimmed again.. no idea why. Adding an audio source doesnt change anything.

I have also done a fritzing diagram, maybe someone can tell me what the hell I'm doing wrong here

many thanks again!
the noob

PS
If anyone is bored and wants to translate the circuit from the knight rider page to a Fritzing schematic.. Feel free to do so! That would make not only my day, probably my entire year

LM3915 Sketch.fzz (14.7 KB)

[system]

Greetings. I am new to arduino. I strated playing around with it last year. I want to make a Knight Rider Style VU meter using the 6, 10 segment Red LED bargraphs I have from a left over kit. I also have a MAX7219 from a DOT matrix that came with my Arduino starter kit.

I haven't found any online schematics or threads for how to get started with this project using an Arduino.

I'm looking for help. I've been told it's simple but haven't found where to get started.

Thanks cummunity
Rivers

[PaulRB]

Hi Rivers,

Its not a great idea to ressurect an old thread like this. Better to start a new thread and include a link to other similar old threads that you found.

It would be unusual to find intructions or schematics that exactly match a project you want to do. You must find projects that include parts that are similar to parts of your own, and work to combine them.

The wiring for your 60 leds will be quite laborious I'm afraid. You will need to group sets of 8 leds together, 8 from the first display, the remaining 2 plus 6 from the next display and so on. Connect the 8 anodes in each group together. Connect cathode 1 from each of the 8 groups together and so on.

Paul