Phillips PM3256 Oscilliscope - How to make Lissajous figures ? - help please

[teutonic]

Hi

I could use a little help. I love my ebay sourced scope ( Phillips PM3256 ) but the trigger control switches are baffling me when I try to create lissajous figures.

Can any gurus guide me. ? The scope does'nt have a XY button, it has a XDEFL button which I think does a similar thing but I'm getting bogged down with all the button choices. Heres a pic of the buttons. Can anyone tell me what to choose for Lissajous figures generating ?

And I just put 'sinewave a' in ch1 and 'sinewave b' in ch2 I think. ? Should I be using the 'hold off' or an external trigger when I try this ? Also is a 'huntron' any good to me ? I made one but not sure why lol

Thanks for any help with the buttons I'm grappling with.

**broken link removed**

 

[Nigel Goodwin]

There is no trgiggering as there's no timebase for doing lissajous figures, I would imagine you probably press the button 'xdefl' to make CH2 the X input?.

 

[Reloadron]

There is no trgiggering as there's no timebase for doing lissajous figures, I would imagine you probably press the button 'xdefl' to make CH2 the X input?.

I agree with Nigel as I don't see an XY or an external Horiz (X) input?

I also suggest you give this a read and start getting an understanding of what the pattern is all about other than an interesting image on a scope. Start working with your scope and getting a handle on oscilloscope basics.

<EDIT>Ah wait a moment, I see it. You use the Exrternal Trigger input. You hit X DEFL and run your X axis into the external trigger BNC. Where it says Trig or X Defl. </EDIT>

Ron

 

[teutonic]

There is no trgiggering as there's no timebase for doing lissajous figures, I would imagine you probably press the button 'xdefl' to make CH2 the X input?.

Thanks <blush> yes I realised it'd be a V/V graph ( not V/t ) so. All those triggering switches bottom right of pic. Shall I leave the whole lot 'out' or off ?
I'll fire it all up in a bit see how I get on

 

[teutonic]

I agree with Nigel as I don't see an XY or an external Horiz (X) input?

I also suggest you give this a read and start getting an understanding of what the pattern is all about other than an interesting image on a scope. Start working with your scope and getting a handle on oscilloscope basics.

Ron

I've got the basics down to a fine art lol. Its the tricky stuff I need a bit of help with Cheers for the link though - i've scoured google - cant even find a phillips scope manual to buy, never mind download lol

checked the link. nice math, nothin practical there. even the bottom links are for java pretties n' stuff. I need the real thing >

 

[Reloadron]

If you see my edit you will see how to set it up. Your Y axis will be a vertical channel and your X axis will be fed into the external trigger BNC. Use the X DEFL button. Rhat should get you going.

Ron

 

[ericgibbs]

checked the link. nice math, nothin practical there. even the bottom links are for java pretties n' stuff. I need the real thing >

hi,
Just dug out my old scope Phillips PM3256 and sig gen.

Look at the image.

 

[teutonic]

thats fantastic thanks fellas. I played for ages, switched it all off, checked here, theres the info !

I shall endeavour to apply this info tomorrow evening after work, its a little late here now. Thanks again

As an aside the best 'general' info I could find for understanding lissajous figures after scouring google many times was this fine guide:
Lissajous Figures
regards

 

[teutonic]

Could'nt wait til tonite - I have an hour before work so ...Well thanks to your help I managed to get my lissajous trace - this is a 1khz and 2khz ( approx ) sine waves input.

https://www.youtube.com/watch?v=4bYAzZATVpY

Next query. I cannot get the trace to 'stay still'. Is there anyway I can do that ? Or is it always going to drift about, nice eye candy but unable to study the waveform ?

 

[Mikebits]

I think the two signals have to be in phase to get a stable non moving waveform.

 

[ericgibbs]

Could'nt wait til tonite - I have an hour before work so ...Well thanks to your help I managed to get my lissajous trace - this is a 1khz and 2khz ( approx ) sine waves input.

YouTube - VID 00006-20100416-0730.3GP

Next query. I cannot get the trace to 'stay still'. Is there anyway I can do that ? Or is it always going to drift about, nice eye candy but unable to study the waveform ?

hi.
Look at this pdf, make up the 'shifter circuits.

 

[teutonic]

hi.
Look at this pdf, make up the 'shifter circuits.

Thanks again Eric ! I was googling around for phase shift circuits last night without much success but this looks great - and easy ! I shall fire up the soldering iron tonight !

 

[ericgibbs]

Thanks again Eric ! I was googling around for phase shift circuits last night without much success but this looks great - and easy ! I shall fire up the soldering iron tonight !

hi,
Give me a few minutes and will post a handy little phase shifter circuit.

EDIT:
Look at these images.

φ= 2 * tan^-1* [R3/Xc1]

Where Xc1= 1/[2Π f C1]


The image showing the circuit is with R3=10k and the smaller image with R3=2K

 

[Mikebits]

If you can lock the two signal sources to a common reference this would put the phase in line. ie. two sig gens with same external ref.

 

[teutonic]

thanks so much again. I have my 'homework' for the weekend now
By the way 54 yr old tech level service engineer here. Great with DC, got me 224's, licenced ham since '87 ( g0ier ) but not so hot with phase shift and AC theory - but enjoying these insights

I need a wee drinky first now we've reached the weekend but I will be back !

If you can lock the two signal sources to a common reference this would put the phase in line. ie. two sig gens with same external ref.

Ahh. now your tantalising me as a scope newby ! Yes I was using the 1000 Hz ( fixed ) output from my lovely old Heathkit RF Oscillator ( Model IG 5280 ) as sinewave A and a 2 khz sinewave from my shiny new Pintek FG30 sweep gen as Sinewave B.

I just about barely grasp its the initial trigger or measure point that needs 'locking' . I have no idea how to do such a thing. Glad I posted though - learning a heap

 

[teutonic]

hi.
Look at this pdf, make up the 'shifter circuits.

hi again Up with the larks, I whipped together the passive RC Phase shift network in the link.

I 'matched' the resistors and caps for closest accuracy. The resistors came in about 994 ohms and the C at 112 nF

This was the result:
**broken link removed**

A nice stable 1:1 lissajous. ( as expected ) My only dissapointment is it is an oval shape rather than full circle. Adjusting the signal amplitude and juggling the volts/div ch1 will not create a perfect circle.

I am clear on what I want to do next thanks to these experiments ( thanks for the assists ). I want to make a sinewave generator with 'multi' frequency outputs.

My first idea was a frequency divider circuit, where I can 'tap' into the frequency divisons. So I might have a 10 MHz oscillator with a frequency divider network giving outputs at 9/8/7 MHz and so on, right down to say 1 MHz.

Is such a circuit feasible ?


oh and ...

hi,
Give me a few minutes and will post a handy little phase shifter circuit.

EDIT:
Look at these images.

φ= 2 * tan^-1* [R3/Xc1]

Where Xc1= 1/[2Π f C1]


The image showing the circuit is with R3=10k and the smaller image with R3=2K
View attachment 41688View attachment 41689

**broken link removed**
This is a really nice easy looking phase shifter circuit thanks eric


regards all

 

[ericgibbs]

hi again Up with the larks, I whipped together the passive RC Phase shift network in the link.

I 'matched' the resistors and caps for closest accuracy. The resistors came in about 994 ohms and the C at 112 nF

This was the result:


A nice stable 1:1 lissajous. ( as expected ) My only dissapointment is it is an oval shape rather than full circle. Adjusting the signal amplitude and juggling the volts/div ch1 will not create a perfect circle.

I am clear on what I want to do next thanks to these experiments ( thanks for the assists ). I want to make a sinewave generator with 'multi' frequency outputs.

My first idea was a frequency divider circuit, where I can 'tap' into the frequency divisons. So I might have a 10 MHz oscillator with a frequency divider network giving outputs at 9/8/7 MHz and so on, right down to say 1 MHz.

Is such a circuit feasible ?


oh and ...

This is a really nice easy looking phase shifter circuit thanks eric
regards all

hi,
You are becoming a techno nerd...

The problem with the freq divider is that it will be a square wave output.!!

Look up Wien oscillators. , also there are IC's which make good Function generators.

Ref the waveforms,,, turn the Y amp switch CW , so that the trace is oval, with its major axis vertical and then adjust the 'blue' CAL knob on the Y amp until you get a round waveform.

Lets know how it goes...

BTW: always set the CAL knob to CAL when you do any serious measurements.

Use the 1.2V sig cal pin as a quick Y amp check.

 

[teutonic]

hi,
You are becoming a techno nerd...

Thanks ! I was praying I would'nt be the only one Eric, when I sought a forum, joined and posted my puzzlement ! Looks like you're the answers to my prayers haha!

The problem with the freq divider is that it will be a square wave output.!!

Look up Wien oscillators. , also there are IC's which make good Function generators.

Interesting. Very interesting. In fact I've been image googling 'frequency dividers' and see there is a dearth of square/pulse wave dividers out there. Dividing sine wave frequencies is another matter entirely by the look of it. But I came across this most interesting sine wave divider circuitry :
**broken link removed**. My initial thought was cobble summat up with mpf102's or 2n2819's and some ceramic resonators I have. But it propbably would'nt work.

Ref the waveforms,,, turn the Y amp switch CW , so that the trace is oval, with its major axis vertical and then adjust the 'blue' CAL knob on the Y amp until you get a round waveform.

Lets know how it goes...

BTW: always set the CAL knob to CAL when you do any serious measurements.

Use the 1.2V sig cal pin as a quick Y amp check.

The scope's resting at the mo but as soon as I get my next techno-urge I will pay some attention to your CAL button advice, thanks.


Oh Eric - my PM3256 'cal' signal output appears to be 2.33 kHz graticule calculated and 2.35 kHz measured on a Phillips PM6667 freq counter. I sort of expected a 1kHz cal signal. Could you confirm to me the manual quoted value ? ( I reckon it'll be 2.4 kHz )
regards

 

[ericgibbs]

hi,
This is a early version of the function generator IC, I understand they are still around also I believe there is a 'newer' version.


EDIT:
I have/had a manual somewhere!
I will look, but dont hold your breath.

EDIT2:
Unable to find the manual at this time, look at this link, scroll down linked page for a manual

**broken link removed**

 

[teutonic]

Ah interesting. He's selling CD's with manuals on. I've emailed asked him if he's doing the phillips ones again sometime.

I have found an interesting 'two tone' oscillator here:
http://home.alphalink.com.au/~parkerp/projects/twotone.gif

I was thinking this would be two sine waves with a guaranteed same trigger / reference point ?