Positron BASIC Community

Has anybody ever used a PIC to read two analogue signals and then display them on a screen like an oscilloscope? The old 'scope we use to show Colossus paper tape reader output is on its last legs. I'm sure somebody has done this before?

Charlie

Hi Charlie,

what would be the rise/fall times for the Colossus tape reader signals?

I would have thought that the easiest solution would be to use one of those handheld battery oscilloscopes, low bandwidth ones are really inexpensive on Amazon etc.

Of course you might want to roll your own, in which case I can't help, sorry.

John

Hi John

Thanks for replying. I hadn't thought of that: the cheap hand-held jobbies. I'll look into it.
The risetimes are around 20uS. There is no need for it to be real-time, a few mS delay wouldn't be noticed. It was one of our engineers (ex Post Office Eng) who suggested that I might be able to use an old flat-screen telly.

I wouldn't be surprised if Les has something?

Best regards
Charlie

These days, it is not worth taking the time to create a low spec LCD oscilloscope, when they are available from china, for less money than the components cost. For example, on ebay:

DSO 152 Handheld Oscilloscope

The above LCD scope is very basic, but good enough for most testing, and it only costs £23.59, or £28.99 for a higher spec one.

It will take a week or two to arrive from china, but it is free postage!

If a CRT one is required, they can be bought from ebay for around £50, and that is usually the 5MHz types from the 1970s, and as you know, they were excellent, and still are. For example:

Vintage Dynamco D7100 Oscilloscope

Regards
Les

Thanks Les, the first one you mentioned DSO 152 looks OK. I think that I secretly wanted to design and make something but I can probably use my time better. This will become part of the Colossus machine, showing two signals from the tape reader. We will of course point out that it wasn't part of the machine originally!

Best regards
Charlie

Hi Charlie,
If it is from the tape reader would a logic analyser work. I think I had a play at doing something like that ages ago. I could see if I can find it if that would work.

Regards,
Bob

You can always do what I did as a young-un, for an oscilloscope Charlie. i.e. Convert a black and white television into one.

Back then (mid 1970s), me and dad used to get people's old black and white televisions given, instead of them throwing them out, and they were great fun to repair and work on, being either all valve, or hybrids.

So I repaired a 20 inch ITT (mains dropper resistor), and disconnected the scan coils, and made a dummy coil for the line/EHT generator, so it would still oscillate and create the EHT. Then built a simple sawtooth generator and an amplifier for the X axis scan coil (with a simple sync), and an amplifier for the Y axis coil.

It worked a treat, and for a young teen, I thought I was a genius for doing it at the time. :-) So much so, I still remember the TV make and size, and can actually see it in my mind, sitting on the bench in the back garden hut with the squiggles on the screen when I talked into a microphone connected to it. "Testing, Testing... One, Two, One, Two... Mary had a little lamb... Testing One... Testing One, Two, three" :-)

It should be fast enough for electronics back then, and look more authentic.

You can get the 5" B/W portables now for a few quid at car boot sales, and they are excellent to work on.

Best regards
Les