Need an oscilloscope that can be connected to a TV

hi all!


I dunno if someone else posted this already but...anyone got schems/plans for a simple?? oscilloscope that can be connected to a TV??

love to have one...

Re: Scope using TV

I don't think the generation of composite video signals is a simple task.

Re: Scope using TV

hi!

let me re-state the prob... a circuit that is like a scope (external)... even with a single input will do.... and will use TV as the "viewer" of signals... hope this clears up a bit..

Re: Scope using TV

Please type "osciloscope+TV" and search this forum.

Re: Scope using TV

Try these:

http://www.electronic-projects.net/Electronic-Projects/projects/telescope/index.shtml

http://www.dansworkshop.com/Homebuilt oscilloscope.shtml

Also, Circuit Cellar issue 161 (Dec 2003) have a project based on an ATMega32 and very little else.

FoxyRick.

Re: Scope using TV

hi foxyrick,


tnx for the links... btw, regarding those, the first link looks good but bandwidth limited to 20khz only..

the third link, using MCUs was much simpler.. but i dunno where i could get those chip..

any other??

Scope using TV

Sounds like you have some price/performance goals in mind that you haven't mentioned.

Are you doing this as a fun learning project, or because you want an inexpensive oscilloscope, or because you really need video output (such as a classroom large-screen projector)?

Re: Scope using TV

hi echo47,

"as a fun learning project, or because you want an inexpensive oscilloscope" is my main goal... if only this could be done easily.. i know it is really hard .... asme goes for PICs and programmable IC... wish there was a way of using "analog" parts..

Re: Scope using TV

I see! (I'm looking back at myself about 25 years ago.) You want a fun project *and* a useful scope.

If it were me, I would separate those two goals. First buy myself and old but working analog scope for very little money (eBay). Then I would use it to help me design and build my digital scope. Forget all those construction project magazines, I'm building it *my* way. If it belches smoke and fire, it's going to be *my* smoke and fire. The video output looks like the hard part, so I'll take a temporary shortcut. Just build the input amplifier, D/A converter, sample clock, some sort of start trigger circuit, and a really big FIFO. I'll connect that to my Windows computer parallel port, write some software and bang! I now have a useful scope with maybe 20 MHz bandwidth and full color 1280x1024 graphics. Hey wait a minute, I can drop in a simple FFT function and Bang! It's now a spectrum analyzer. Oh this is fun. Way more fun than low-resolution TV video output. If I were 20 years old again, I'd make some cool "skins" and sound effects to make it totally awesome. I'm now spending my time writing fancy display software, building better anti-alias filters, higher sample rates, two or four channels, interleave sampling, ...

Stop me! Stop me! I have work to do.

Companies such as Tektronix and LeCroy have done basically the same thing, changed their oscilloscope products into Windows computers with D/A inputs.

Re: Scope using TV

Hello rx5,

Echo47 has a good idea there. The problem with trying to build an oscilloscope is that you tend to need an oscilloscope to find the bugs in it!

I bought a really cheap one (not working) from eBay a few years ago just to play with - I am still fiddling with it, trying my own input circuits etc. If you get one with the HV section working and just faulty input amps or timebase, it can be good fun making your own bits for it. But as I said, you really need another 'scope to test your bits.

Building one from a TV can be done in two ways:

1. Force the TV into "oscilloscope" mode, making the beam scan the screen and draw your input. This is quite easily done (there are several circuits on the web, all similar). This will suffer from very low bandwidth as the TV tube is simply not intended for this type of use.

2. Use the TV (or monitor) simply as a monitor and make a circuit that takes a signal, digitises it, buffers in a frame memory and outputs frames to the monitor. This can be much better as an oscilloscope (as echo47 said, it's what a digital 'scope does) but is more complicated to make.

Personally, if I wanted to try making a 'scope and did not want to buy one to test it with, I would use a PC soundcard and oscilloscope software (search the web). This should have similar or better bandwidth than an analogue-TV 'scope and is a lot easier to get!

My final advice (for what it's worth ) is:

First: buy a cheap, working 'scope or use a PC soundcard and software

Then: if you still want to experiment with 'scope building, buy a non-working basic 'scope (hopefully with a working beam so you know the tube and HV are OK) and design your own timebase and input circuits. I'm sure I have seen such circuits on the web, but I can't find the links. Try searching.
Ideally, get a service manual for the 'scope so you know what is what inside it. You might even find somewhere that will give you a junk scope for nothing.

Whatever you do:- enjoy it, learn, ask here when you get stuck, and don't get zapped by the HV (it hurts!!!)

FoxyRick.

Re: Scope using TV

He-he,
this returns me back about a decade ago.
Back then I made a digital scope (7MS/s) and connected it to my PC (8-bit , 1MHz).The PC was connected to the TV because it was that kind of PC.Everithing still works,I wrote a BASIC program with a lot of assembler modules and the scope was able to do FFT ,filter freq.response etc.
Now if I had to do it I would do it either as a PC-connected board or as a stand-alone LCD scope,or maybe both.
I myself have been thinking lately of using a TV-set as a cheap screen but gave up.It is not worth the effort.
So....If you want a cheap scope to play with,do as the others suggested: buy an old scope and try to improve it a bit.