oscilloscopes and microcontrollers

[naimead]

Hello all,

I have a question regarding the conversion of an analog oscilloscope to a digital one by using a microcontroller.Has anyone tried that?I have done a little research but no one seems to have performed such a task.

I am relatively new to electronics so in my mind seems a relatively easy task.I am finding the analogic X-Y outputs from the oscilloscope(before or after amplification?) and connect them to a microcontroller.Then I use its in-build analog to digital converter and that's it.

Can someone give me any clues if I am right or wrong?

They have been able to construct a whole digital osciilloscope by using microcontrollers so it seems to be strange why there aren't any descriptions for just a conversion.

thank you,

naimead

 

[poor mystic]

Seems reasonable to me. Of course the digital scope you end up with won't have very high specifications - microcontrollers aren't optimally designed for such work. Special digital signal processors (DSP's) are used for the real ones.
I can see you learning a lot about electronics in this project.

PS the reason people don't do this more often is probably that after all the work you don't wind up with a better scope.

 

[naimead]

Thank you for your reply poor mystic!

The microcontroller I have in mind has 8 10bit ADC output with a sampling rate of 6kHz.
So these specifications I believe cover my completely basic needs(about 4.9mV steps).

The job is to construct an electrocardiograph(for experimental use only of course), but they gave me an old machine which is just analog thus I can't have the signal digitized so I can work with.

The main problem of this project I thought is that most microcontrollers take as input 5V the most, so anything larger than that would fry it.

But hypothetically speaking what would you try to use as input from an analog oscilloscope to a micro?

Also I am not very experienced with DSPs but would be very hard to program such a thing to do the job?

thank you,

naimead

 

[poor mystic]

But hypothetically speaking what would you try to use as input from an analog oscilloscope to a micro?

Hi Naimead
I don't understand this question - I thought the micro was to be the source of a signal which would be displayed by the scope.
Maybe that's not all I got wrong (I'm good at getting things wrong I've discovered).

It sounds like you want to build a digital electrocardiograph out of an analogue electrocardiograph. Is that so? The microcontroller sounds ideal for the job at that low sampling rate. The inputs can be filtered and conditioned using instrumentation amplifiers to handle any voltage.

I can't tell you about DSP's except that I believe they're mostly programmed in C and that they're not easy to get, especially the ones in the National Data Books. Hopefully you can get information on the controller you already have.

As for how easy it is to do this and that, everybody is different. Some people find the most arcane things quite simple and unmysterious. You'll just have to try yourself out on a few things and see what you like doing.

 

[naimead]

Exactly poor mystic!The only thing I am trying to do is to use a microcontroller as an analog to digital convertor.

I have the schematics of the oscilloscope so I was thinking of connecting the micro to the Y-amplifier's input.I can program the micro in C but I still have a few newbie questions as for example shall I also connect my microcontroller to a common ground with the amplifier?(I guess yes but I am not quite sure)

thank you,

naimead

 

[poor mystic]

Naimead
For the meantime a common ground for the signal and the microcontroller sounds fine.

I sure hope you don't plan to let anybody get "measured" with this thing with these ghastly common grounds getting stuck on people's bodies, but I guess those who gave you the instrument have told you about that pretty convincingly?

Now that that's cleared up, there are lots of ways to deal with inputs including differential inputs, AC inputs, filtered inputs and there are plenty of other sorts. Building these inputs will be a marvellous way for you to learn electronics - all you need is enough information to get you started.

You need The Book, which is "The Art of Electronics" by Horowitz & Hill. You'll think it's great. It *is* great. Get a copy immediately, and don't waste time with other approaches.

Once you understand what that book is telling you, you'll be able to make decisions about how to connect the microcontroller for yourself.
You'll soon dream up plenty of questions I know, and I hope you bring them back to the forum.