display design

[marronald]

hey there i would like to help me wiz the necesary circuit design to help me have a continous display of a picture like a general layout of a map onto the screen of a cathode ray oscilloscope in the electronics lab.
I have the signals representing the map on to wires. One x-co-ordiate and the other y- co-ordinate. every time i change the co-ordinates i get different positions of the dot on the screen. Myb problem is to have all the dots joined together to have the whole map seen on the screen at a particular time. so help me do that pliz.

 

[mechie]

Writing on a CRO Screen

Vector Graphics !

You have obviously got a data set (the X and Y co-ordinates) you want to plot and are inputting these values as voltages into your 'scope's X and Y channels ('scope set to X-Y rather than the usual Y-t).

How are you generating the data set ? (two twiddly pots?)
How fast can you step through all the values?
I suspect that each set of co-ordinates represents a corner on your map and the values are organised in a logical sequence?

If you cycle through the data set at a sensible speed (fast enough for the CRT persistence to "maintain the dots" between updates, slow enough for the 'scope to keep up) then all that is left is to slow down the transition between dots such that each change in co-ordinates produces a line rather than an abrupt 'switch'.

For the best display you need to compare each co-ordinate pair with its predecessors and integrate each at a rate that will allow for both to complete simultaneously, if one completes ahead of the other there will be a sudden change in direction during this line-draw.
Ideally the co-ordinate pairs will be equal distances apart such that the whole outline is drawn at a fairly constant speed , this evens the image brightness and simplifies the integration task.