Poor mans scope

[Mikebits]

I was just surfing the net and ran across this article.

A poorman's oscilloscope

It just seemed unfair not to share this with you. I have no need for a scope as I already have a tek, but for those that don't have a scope, you might find this handy. The author supplies schematics, source code, and everything. Looks like you could build this in less than a day.

Well thats all, hope some may have use for this

 

[dknguyen]

I have no need for a scope as I already have a tek, but for those that don't have a scope, you might find this handy.

...show off.

 

[Externet]

...show off.

I had seven : until last week, I just sold 3Tek. Left only with a pen size, a pocket size, a Hitachi and a Tek2465.

 

[Boncuk]

here is another one:

eOscope

Really nice, but requires reverse engineering. No signals labelled within three buses!

 

[Mikebits]

Geez, I just thought this thing might be cool to some, not trying to show off. With some modifications on the input, you could have a handy device.

 

[dknguyen]

Geez, I just thought this thing might be cool to some, not trying to show off. With some modifications on the input, you could have a handy device.

It was a joke hence the smiley face.

 

[Mikebits]

I know, it is all good.

 

[joshua17ss2]

Google Image Result for https://cybertopo.com/img/md_scope.jpg
i dunno if anyone has seen this scope but it seems to be faily cheap and easy to build

 

[Mikebits]

What would be cool is that someone tweaks this design for a LCD.

 

[Nigel Goodwin]

Well it's damn impressive, even down to using a tiny 8 pin PIC!

I might have to throw one together, just for a laugh.

If you want an LCD version, there's an example using a graphic LCD on Bill's Unicorn board - probably a higher spec than this version, but not as clever!.

 

[blueroomelectronics]

It is pretty neat, I've not looked at the code is it NTSC or PAL?
Something to consider the 27MHz is outside the 12F675 spec, it may or maynot work with your 12F675

 

[ericgibbs]

It is pretty neat, I've not looked at the code is it NTSC or PAL?
Something to consider the 27MHz is outside the 12F675 spec, it may or maynot work with your 12F675

hi Bill,
Its PAL 625.
Would be easy to convert program to a 18Fxxxx.

The 27MHz is a IIRC a radio control freq xtal.?

 

[blueroomelectronics]

I was working on a dsPIC video generator for NTSC, this PIC can run at 120MHz (8x PLL)

 

[Nigel Goodwin]

hi Bill,
Its PAL 625.

As there's no colour it's not PAL or NTSC, it's 625 line B&W

Would be easy to convert program to a 18Fxxxx.

The 27MHz is a IIRC a radio control freq xtal.?

More likely to be 27.something, not just 27MHz, for radio control. It's a value used in many TV sets, for either teletext/processor main clock or on the NICAM board (again for a processor clock). I might even have them in stock at work?, as it's a value which does tend to fail - I replaced one a few weeks back, for no teletext.

 

[blueroomelectronics]

I noticed the LC tank to detune the crystal. Speaking of Teletext that's what I was hoping to build with the dsPIC... Maybe add an SPI SRAM...

 

[Nigel Goodwin]

I noticed the LC tank to detune the crystal. Speaking of Teletext that's what I was hoping to build with the dsPIC... Maybe add an SPI SRAM...

Well teletext will be discontinued over the next few years, it's part of the old analogue TV, and digital TV uses a completely different method.

I had to debug and connect to a TV one of the original Wireless World teletext decoder kits - it used all TTL chips (pre-CMOS), and had edge switches to select the text pages. It took a LOT of getting working, particularly as the only scope we had at work was an incredibly old antique, and it's spec was so low it wasn't true (it wasn't even triggered, it was synced).

But I got it all working, and fitted it in a Bush A823 based colour TV - we used it as a demonstration in the shop, the first teletext in the area (by a long way!).

The first actual teletext TV we saw was also a Bush, using a TIFAX module, and I actually had the set at home for a number of years, when it came back off rental. It predated IR remote controls, and was the most complex ultrasonic remote I've ever seen.

 

[ericgibbs]

As there's no colour it's not PAL or NTSC, it's 625 line B&W

hi,
Just quoting the designers text.? ala PAL not NTSC.

Is that flyover finished yet.?

 

[Pommie]

The code that that chip uses is very clever, to get that sort of resolution out of a 9MHz instruction clock is just amazing.

To do the same on a GLCD would be really trivial by comparison.

Mike.

 

[Nigel Goodwin]

Is that flyover finished yet.?

Would that be the new junction 29A?.

It said on the radio that the official opening was Friday (I think?), but while it was officially 'opened' it wasn't going to be useable until 6:00am the next morning - seems a strange 'opening' to me!

 

[Nigel Goodwin]

I noticed the LC tank to detune the crystal. Speaking of Teletext that's what I was hoping to build with the dsPIC... Maybe add an SPI SRAM...

I've had a quick read of the article, the coil isn't to detune the crystal, it's to prevent the 3rd overtone crystal (most 27MHz are 3rd overtone) from oscillating at 9MHz instead of 27MHz.

I've just checked my crystals at work, and I used the last 27MHz one the other week but I've had a search around some teletext boards, and found one on a board. It's actually connected to a Philips SAA5246P teletext IC.

Looking at the circuit from the TV, there's a 4.7uH choke in series with the crystal, which is connected in a fairly strange way - presumably this is because it's an overtone crystal as well?.