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Picture of Use Your Laptop as Oscilloscope
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Oscilloscope is an electronic test instrument that allows projection of voltage signals to be displayed and learned. A specific circuit in the oscilloscope creates repeated moving signals from left to right. This repetition creates non-repeating waveforms that can be learned.

Oscilloscopes are commonly used to observe the exact wave shape of an electrical signal. In addition to signal amplitude, oscilloscopes can show time distortion between two events (such as pulse width, period, or rise time) and relative timing of two related signals

Below is a picture of common Oscilloscope.

Today, Oscilloscope uses LCD color display, displaying better graphics
 
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Step 1: Make Your Own Oscilloscope Using Your Laptop Computer

Picture of Make Your Own Oscilloscope Using Your Laptop Computer
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Once I need an oscilloscope to see the electrical voltage ripple in the car. Ignition systems, alternator rotation, high-beam lights flicker, and others are generally emit noise or voltage ripples, Well, this is what I want to know, size of the noises, etc.

Oscilloscopes are very expensive tools, and generally are only used in electronics / electrical laboratory.
Finally, I found an application that could use laptop computer / PC as Oscilloscope by adding some components as interface.
Those components are simple and quite cheap!

The necessary components:
• Two 22K ohm Resistors
• Two 82K ohm Resistors
• One 50K Linear Potentiometer + Tuning Knob
• One meter Shield Stereo cable
• One 3.5mm Stereo Jack
• Tester Terminal

Step 2: Electronic scheme

Picture of Electronic scheme
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Remarks:
• The 22K Resistor serves as voltage safety limit into laptop soundcard.
• The Potentiometer serves as input voltage resistor. If the voltage is above 5volt, adjust the potentiometer necessarily to prevent the soundcard from being damaged by excessive voltage input.
• Use shield audio cable to prevent induction around the cable.

Step 3: The Probes

Picture of The Probes
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Attach the probes

ajoyraman25 days ago

The M-Audio Revo 5.1 is basically a high performance PC add-on audio card. The main feature is a sampling rate of 196 kHz compared to 96 kHz of most other cards. This means that the maximum signal frequency that can be seen clearly while using it as an oscilloscope would be around 20 kHz. The audio input levels would be typically +/- 1.4V which would also be capicatively coupled. This Instructable provides a simple resistor network to attenuate larger voltages. It also uses a Sound-Card oscilloscope software.

Regarding the probes: The frequency response of probes determine the max-frequency that the probe passes but finally frequency limit is from the card which is much lower. Also probes are used with active input circuits with typically 1 MOhm impedance which not be met by the simple pot-divider scheme presented here.

Overall this may not be a suitable scheme for observing high frequency signals.

JanM526 days ago

I'm trying to build somehow functional oscilloscope (best bang for buck ratio). Got second-hand M-Audio Revo 5.1 which has 24-bit 96kHz ADC, AKM 5365 (http://www.akm.com/akm/en/file/datasheet/AK5365VQ....). At some point I'll consider active circuitry, but right now I'd like to test and play with it using passive interface. By any chance would you be able to advise best Vmax for the input? I've read that it has "Auto Level Control (ALC) Circuit", but I'm not very smart about it. And "ANALOG CHARACTERISTICS" table in the datasheet is just overwhelming for me :( One last thing which would help a lot, there are many passive oscilloscope probes out there, most confusing for me is frequency and capacitance (I have some idea what resistance means there :)). Does it mean I'll have to buy multiple probes in order to have some reasonable range of the freq. specter or is there some way to choose one suitable for sampling rate of the card. Target is to be able to see various digital signals (e.g. DHT11, FHT8V, IrDA, nRF24L01+), so some flexibility would be great.

Any suggestions are welcomed!

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hubble072 months ago

Hi, I wish to build this circuit. However, I don't know if the pot used is a dual gang pot (stereo pot) or linear pot. I have got one which has 3 pins. Can I use that? Please forgive me if I am being ignorant.

I believe it's dual gang as you'd want to keep signals A and B proportional controlled by the same knob.

>signals A and B proportional controlled by the same knob.

And kept separate.

What is the purpose of the voltage divider (i.e. 2 82k resistors) connected to ground?

paulieux8 months ago

What should you do if you want to use it as a sound detector? What modifications should be done, like you will use microphone to detect the sound and find out its wave form in the software?

kf4nxs paulieux2 months ago

what you need is a spectrum analyzer

pffm12 paulieux8 months ago

Hello.

You don't need to build nor modify anything for that purpose. Connect the microphone to the computer, open the software and there you go. You'll see the wave on the screen.

paulieux pffm128 months ago

Thank you, but what if the microphone has a big stereo jack which is not compatible to be inserted in the soundcard?

pffm12 paulieux8 months ago

Use an adapter.

http://www.paprinka.com/productos/imagenes/img_418_0f248579a4ddfb5182794b2f4ee7c9c3_1.jpg

ColbyH4 months ago

Urane,

You may look closely at your headphone port, it might have a picture of the headphones symbol as well as the microphone symbol.

References:

My laptop has a single port that does both.

DavidP134 months ago

Hi, what is the wattage on your resistors and the 50K pot? I went to purchase the necessary components, and found that the wattage varies from 1/8 watt to 1/2 watt (and possibly more that I didn't see). Good job, btw.

urane5 months ago
My lapptop has no mic i/p....it has inbuilt mic
pffm129 months ago

Hello,

I am finding trouble with this. If you plan to use this project to see noises or similar, like the author, it's OK, but if you want to use it like a real oscilloscope, if you want to see the waves shapes this is not going to work (I reckon).

I've made some measurement in 2 computers with crappy built-in souncards (which I hope are better than USB chinese ones). I've measured the maximum voltage you can put straight in them (in mic input as well as line) without distort the perfect sine wave I used.

The results are:

For a Realtek, Mic: 10 mV, Line: 100 mV

For a Sygmatel, Mic and line: 125 mV

You can put 1 or 2 volts directly and it won't break, but the pure wave gets cut, or distorted if you pass the very low voltage levels I indicated. As an example, on the Realtek, if you put it just 0.5 V, the sine wave looks almost perfectly square because of the cuts.

The problem is, if you want to solve that with a voltage divider, it'll have to be massive. I don't think this project is viable for other purpose than see noise.

fdhrubo9 months ago

what software can i use??? I need a freeware.

pffm12 fdhrubo9 months ago

This is by far the best oscilloscope software, and it's free for educational and non-commercial uses. Anyway, another fully free soft is 'BIP Electronics Labs 3.0 - Oscilloscope'.

ajoyraman1 year ago
Great minimum component interface ! For safety/protection I suggest you add a couple of back-to-back 2 X signal diodes across the 82K resistors which would restrict the sound card input voltage to approx 1.4 V.

  
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fdhrubo ajoyraman9 months ago

is it fully safe now? if I add the 4 resistors? i am trying to build 1. And what software can I use for this?

ajoyraman fdhrubo9 months ago
It is quite safe as long as you remember that the ground of the PC is not isolated and so we should avoid measuring the AC mains or other circuits not isolated from the AC mains.

The software you can use is:
http://www.zeitnitz.de/Christian/scope_en

This instructable uses passive components and the impedance of the sound-card may attenuate the voltage inputs.

You can also see my instructable which uses active components:
http://www.instructables.com/id/PC-SOUND-CARD-SCOPE-INTERFACE-FACILITATES-DC-RESTO/
phmanzano1 year ago

By ignorance (or laziness or cut-the-corners mentality), I tried the free JOszi (der-frickler.net, java) without anything but an audio cable plugged in my laptop.

Reading this instructable and all you comments I guess I was lucky because I didn't fry a thing. Here is the kind of result I got.

I wonder if a cheap USB soundcard can act as "breaker"?

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wyatt87401 year ago
I'd definitely add a 5.1 volt zener diode and a 3 or 2 ampere fuse. This would protect against overvoltage relatively well. I'd also use an external, powered USB hub. This would further prevent damage to your computer from excess voltage.
When you don't know the voltage you are about to measure, test with a multimeter, and if it is too high for a 22Kohm resistor, add a bigger one to it until it is a safe level.
true the cheap usb sound card should in theory burn b4 yr laptop does.
rombi1 year ago
super
padbravo1 year ago
Great!...

Let give it a try... thanks!
I have never tried this I have oscilloscopes.

Can you expand the signal for easier reading?

That looks like you could have a duel trace Oscilloscope if you could expand the signal.

Have you seen my Instructable, Building a Digital Oscilloscope from a DIY Kit?

http://www.instructables.com/id/Building-a-Digital-Oscilloscope-from-a-DIY-Kit/
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