Simple triggered sweep.

[Steven Swift]

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:

http://novatech-instr.com/Fun/trig.pdf

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

Steve.
Seattle,WA.

 

[John Popelish]

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:

http://novatech-instr.com/Fun/trig.pdf

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

Steve.
Seattle,WA.

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.

http://www.national.com/ds.cgi/LM/LM161.pdf

 

[Steven Swift]

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.

http://www.national.com/ds.cgi/LM/LM161.pdf

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

 

[Yukio YANO]

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:

http://novatech-instr.com/Fun/trig.pdf

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

Steve.
Seattle,WA.

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

 

[Michael Black]

Pretty good. Did a similar thing using 3 555s. One was used as a
threshold detector, one for the Onshot (with a FET constant current
source) and one for the retrigger holdoff oneshot. Worked to well
to beyond the 5mhz scope it was used with.

Allison

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
http://www.cam.org/~blackm00/ramp.jpg
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