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plotter design

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New Member
hullo there i need to help me with the project of transfering a map from a
paper to the sreen of a cathode ray tube using the principle of converting the picture to co-ordinates then transmitt it through wires , then re-generate it to be displeyed on the cathode ray tube screen. the whole picture should display on the sreen constantly.


Active Member
Hi marronald,

Please explain more clearly
what you want to do.

working with CRTs is dangerous
and should not be attempted by
unskilled persons.

Maybe an LED display would do
what you need.

Regards, John


New Member
no, no wait
from what i understand you want something like a scanner?
and the to display it on a computer screen, or just on a cathode screen from a tv?
that would be DANGEROUSyou need high voltages for the cathode tube, 20Kv, 75Kv, or maybe 150Kv, depends, afrom what i see you need somethinhg like a camera sensor.


New Member
why don't you just use a scanner on the computer. It displays it on the moniter, and it is a CRT. Or are you wanting it to display on like a moniter from a o-scope?

For granted, the voltages are high, but doing it that way would be to complicated and to expensive.


New Member
Hullo there the problem requires me to come up with some mechanical-electronic device that can read co-ordinates in a 2-dimension plane, convert the co-ordinates to electrical signals, then transmitted using the correct procedures with various signal proccessing . The signals representing the co-ordinates are to displayed on to the cathode ray oscilloscope in the electronics lab. that is mainly teh problem. No sensors are required in the design process.


Active Member
Hi there,

I'm still rather confused about this thread.
ive read the two posts from marronald, and i
get the impression that two co-ordinates are
provided from somewhere, and that the poster
wishes to use them to move a point of light
around on a map.

Maybe its a map of his place of employment,
as he says these co-ordinates will also be
displayed on a scope in the electronics lab.

Its difficult to make much sense of this, but
he does say he wants a 'mechanical-electrical'

I suggest that two motors could be used to
move an LED around in two co-ordinates, maybe
behind a paper map.

Personally i dont see whats wrong with a display
on a computer monitor.

Anyone else have any suggestions?



Active Member
Yes a computer display would be much more easier than CRO. And if I am not mistaken he is tyring to plot two points which are marked by a moving Tracer like Arm on the map and pressing the Tracer Pen wherever you want to mark the point. Am I right?


Active Member
Ah, kinjalp,

Yes i think you've sussed it.
After re-reading his posts, i think i have it now.

This is how i now think it goes:

i think he wants to send signals
which represent the two co-ordinates,
these signals are to be reproduced
at the electronics lab on a scope,
presumably as a dot of light
on a screen,
with a map drawn on the screen,
(presumably a removeable tracing)

The way i now read his posts makes a little more sense,

He wants to make an assembly
that would generate these two outputs,
from -as you say- by moving an arm,
probably over a similar picture.

The moving arm having two outputs,
one vertical and one horizontal.

Before diving in to the various ways of making and
sending such signals,

Does that sound like its a correct interpretation ?

Regards, John


Active Member
Hi there,

I recieved a PM from marronald, confirming that kinjalgp
and myself are now going in the same general direction.

i hope he wont mind me reproducing his note here, cos
that would get more people on to it than just me- ok:

Hey there you are on the right track john1 . I have
tried it out by using two variable resistors connected
by movable joints. The output signals from the two
variable resistors represent the 2 co-ordinates. these
signals are to be sent to the cathode ray oscilloscope
in the e-lab so that a single dot is displayed on the
screen for the particular 2 co-ordinates (x&y). As i u
move around the map on paper its picture is retraced on
the screen.
The whole picture should be seen on the screen continously
as we see a pecture on the tv screen. So help me wiz the
signal proccessing techniques.

Still a few questions, but its getting there.



Active Member

Whats this about,

"The whole picture should be seen on the screen
continously as we see a pecture on the tv screen"

I kinda thought it was a moving dot of light,
behind a map on thin paper, or drawn on the scope
screen (if the scope isnt wanted for anything else)

If you want the scope to produce a picture too
then that gets a bit complicated.

If its just a dot,
then things should be easy.
adjust at the scope end for gain and position
of both horizontal and vertical movement to fit.

Your suggestion of two pots to give the two signals
is of course the obvious choice, they come in log
and linear varieties, which is usually written on
the side with the value.
If you keep the values fairly low, and use screened
wire then the hum may not be too bad, it depends a
lot on the environment and the distance.

I cant help wondering if there is more to this than
i have realised, whats this about signal processing ?

I will include a small diagram of a possible layout.
This is just a suggestion,
i may have mis-understood this thread.




New Member
Hey john1 i tried to connect the outputs of the variable resistors to the cathode ray oscilloscope in the e-lab but i didnt get the trace out. Instead i was get two signals one fro horizontal & the other for the vertical sweep. This implies that there are more electronic circutory required in addition to wat u gave me.
I was of the view that if there is any body who can impliment a circuit which can display a character on the C R O screen, then we can buld on his idea.


Active Member
Hi marronald,

turn the timebase off.
switch it to DC.

Horiz feed to ext X.
Vert feed to 'input'

From what you say,
this is what you need,
there is no more circuitry needed.
The scope has all you need.

Except possibly an amp on the X,
that might need stepping up a bit.

kinjalgp ... where are you ...
am i missing something here ??
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