DIY Waveform Monitor

[jishnudg]

Is it possible to build one's own waveform monitor ? Basically I'm thinking of building a really stripped down oscilloscope - no controls or anything, just maybe a few trimpots to set the operating frequencies within reasonable limits to get good visual readings from stompbox outputs. Can it be done with an LCD/ microcontroller/ arduino -ish arrangement? Or even an analog solution? Have trawled the net for this but most of the results I'm getting are too complex for my needs - I'd be satisfied with a just simple screen showing me a roughly accurate waveform.
Any ideas?

[Mark Hammer]

In the 1970's, you'd see construction projects in the electronics mags for things like this.  Generally, it would involve:
a) a matrix of LEDs
b) a bar-graph chip like an LM3914 or similar
c) a series of counter chips
d) a clock to step the counter through its paces

So, imagine a column of LEDs, and a series of such columns. The bar-graph chip (or chips) convert the current voltage into a column (or simply one, with appropriate logic) of light, whose height represents the voltage at that moment.  A given moment later, the input voltage is resampled bar the bar-graph chip, and the counter, havng moved a step, enables the next LED column over to light up in similar fashion.  Much a moving movie marquee, the moving display, when harnessed to the magic of persistence of vision in the human retina, creates an image on the matrix of LEDs that could function as a crude oscilloscope.

[duck_arse]

I dimmly remember elektor magazine doing something similar, with leds, sometime in the 90's. but don't quote me.

on anything.

[caldersm]

Why build one from scratch, when they have this Device.....the Xprotolab......only $49 plus shipping..!!

http://www.gabotronics.com/development-boards/xmega-xprotolab.htm

Some Pictures are below....it looks really Slick....am going to buy one like it myself.  They are selling one with a case in May....for $98.


http://www.gabotronics.com/components/com_virtuemart/shop_image/product/xprotolab-meter.jpg

Hope this helps you...
Steve

[wookie]

There's an android app that will let you use your phone as a control surface for the xprotolab.

https://play.google.com/store/apps/details?id=com.nfx.noscpro&hl=en

It will let you use the microphone input of your phone as a signal source as well...but that's probably not the best idea in my opinion.  I'd rather loose a $50 module than a $600 phone.

[PRR]

> a really stripped down oscilloscope - no controls

You need controls. Even for "pedal only". Same reasons you have more than one string and several volume knobs on your rig. "Pedal level" varies 0.02V to 4V, frequency 80Hz to 8KHz. A single sweep rate is only suited for a couple octaves of frequency, and much the same for gain.

Anyway it isn't the knobs that are the "problem"....

> imagine a column of LEDs, and a series of such columns

I've built a 10*8 LED array (octave spectrum analyzer). It is a lot of work. It's fairly poor resolution, hardly something for "waveform". This was before bargraph arrays, but the matrix wiring is not really reduced with 10-bar chips.

I have an LCD 'scope with 128*64 resolution. It's sufficient for waveform, but just barely. Eight thousand LEDs is beyond my comfort zone.

Design of such a contraption is non-trivial.

> Why build one from scratch, when they have this Device.....

Indeed. The selection of decent audio quality "oscilloscopes" has exploded in the last decade and the last few years. A factory-made LCD array beats heck out of hand-soldering hundreds or thousands of LEDS. Modern PIC and similar chips beat wiring ADCs and multiplexers. The PIC can also put numbers on that, and do waveform generation (bench signal generator) in its spare time.

[FiveseveN]

Another solution would be using your sound card for ADC and one of the many software scopes.

[gritz]

Another solution would be using your sound card for ADC and one of the many software scopes.

+1 on this.

[J0K3RX]

http://www.seeedstudio.com/depot/digital-storage-oscilloscope-with-panels-p-514.html?cPath=174



$50.00

[J0K3RX]

Has any body ever used a Huntron Tracker? Build your own using your O-scope...

Cool tool!!

[artifus]

Poor Man's Oscilloscope

A Preamplifier for Smartphone Oscilloscopes

Visual Analyser

DSSF3

In the 1970's...

7400 Oscilloscope !!!

*also* google around for arduino and msp430 oscilloscopes too - there are a few projects online.

[Jdansti]

Has any body ever used a Huntron Tracker? Build your own using your O-scope...

Cool tool!!

Good video!

[chromesphere]

I just bought an owon 6062.  $300 aud.  I know, its a lot of $, but I consider it a good investment.  I bought it as a bday present this week to cushion the expense

If your after an oscilloscope to learn, or to fault diagnose...or design...or....or....get one!  The owon is really good.  I'd heard of a few bugs with the firmware (haven't seen anything yet) but it has surpassed my expectations.  I'll be uploading a few videos about it / with me using it, so sub to my youtube channel if your interested in seeing it in action.
You could get away with an analogue oscilloscope, but unfortunately in my neck of the woods, their aren't too many 'cheap' oscilloscopes around.  YMMV.
Good luck in your search!
Paul

[duck_arse]

 

Eight thousand LEDs is beyond my comfort zone.

this made me think of those roadside signs, the box-trailers with the solar power and the panel of orange leds, you know, "slow down police ahead".

that would make an impressive signal display.

[Mac Walker]

Forrest Mimms - 5 x 7 LED matrix scope

http://books.google.com/books?id=STzitya5iwgC&pg=PA65&lpg=PA65&dq=forrest+mims+oscilloscope&source=bl&ots=Le6pNCfLsN&sig=aFx2AIqcsSpi5sacssMFGjGDrR4&hl=en&sa=X&ei=ljNoUeKyFcnC2wXfhoH4Dw&ved=0CC0Q6AEwAA#v=onepage&q=forrest%20mims%20oscilloscope&f=false

I'd buy the $50 JYE Tech scope if I didn't already have an analog scope, the space savings would be nice, although it is a single trace scope.....

[fuzzo]

http://www.seeedstudio.com/depot/digital-storage-oscilloscope-with-panels-p-514.html?cPath=174



$50.00

is it good ?

I considered it few times ago but didn't make the step to buy it.

[GGBB]

Another solution would be using your sound card for ADC and one of the many software scopes.

+1 on this.

Along those lines ... got recording software?  If it supports VSTs, there are probably more than one but here's this first I came across: http://bram.smartelectronix.com/plugins.php?id=4.

[Seljer]

A recomendation for using your PC as an audio frequency scope:

build yourself a high impedance buffer with an opamp so you can stick the probe (almost) anywhere in the circuit without changing the way it behaves (and maybe even add a BNC connector so you can use actual probes!). Possibly add a second channel so you can view the waveform before+after  You can calibrate it reasonably well with a run of the mill multimeter on the AC voltage settings, use your comptuer to generate a ~60hz sinewave and measure it's amplitude with the multimeter. If you feel like spending some extra time add some preset gain stages (and attenuation too maybe...I'd also reccomend some output voltage protection, maybe even just two back to back LEDs to clip it before it goes to the PC's audio in).