Simple triggered sweep.

Nov 23, 2005 4 Replies

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Steven Swift 20 years ago

Greetings.

A short while ago, I posted a request for links to simple triggered sweeps for older recurrent timebase oscilloscopes. I spent a fair amount of time looking in old magazines and circuit handbooks, but didn't find what I thought I was looking for.

So I decided to cobble-up a homebrew of my own. This circuit probably has been done before, but it met my criterion of being really simple. I used already on-hand parts, so the design is far from optimum. It works fine on an Eico 460 up to about 1MHz. No attempt was made to make a calibrated sweep. You could use a 5v rail and an HC4538 to make a nice high speed triggered sweep.

Have a look at:

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Thank you to all of you who sent me emails and posted comments on these boards.

Steve. Seattle,WA.

Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com NOVATECH INSTRUMENTS, INC. P.O. Box 55997 206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA

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John Popelish 20 years ago

I think you could use an LM361 comparator in place of the front opamp. It produces high going and low going digital outputs that you can enable separately, so you can choose whether you want to sync on positive going or negative going edges, without changing the switching threshold.

It will also clock the flip flop a lot faster than an opamp will.

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Steven Swift 20 years ago

Yup, good call! I actually have a 361 based circuit I built a long time ago. It works to about 50MHz. It is overkill for this purpose, but would be the right choice, along with an HC4538, if someone wanted to modify this and go to higher frequencies. You actually have to move some pins around on the 4538 to make it non-retriggerable.

On the 361 board, I use long-tailed pair miller integrators to get near perfect sweeps. But that was a complete homebrew scope I designed in 1978 or so.

Thanks.

Steve

Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com NOVATECH INSTRUMENTS, INC. P.O. Box 55997 206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA

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Yukio YANO 20 years ago

It would seem to me relatively easy to replace the horizontal sweep oscillator with a 555 chip ! and trigger it with a sample of the vertical Amp. signal !

Yukio YANO

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Michael Black 20 years ago

And as I pointed out in the previous thread, that wave thirty years ago of adding triggered sweep to older scopes did all use 555s for the ramp generator.

I cleared off the scanner, and

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is the scan out of Howard Berlin's "The 555 Timer Applications Sourcebook with Experiments" from 1976. The actual circuit was originally in Electronics magazine for October 11, 1973, which I likely do have (at least the part with the circuit) somewhere but can't be bothered looking.

And as I said, this basic circuit did seem to be the basis of all those "add triggered sweep to your oscilliscope" articles from thirty years ago. As I recall, they were all basically like this one.

Michael VE2BVW

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