Ramp/Sweep Generator

[Tronikid]

Can anyone please help me with the design of a linear Ramp/Sweep Generator to drive the X input of X-Y Plotters in the Time domain?

I prefer analogue circuits, using op-amps if possible, with switched capacitor timing ranges from 1 minute to 24 hours.

I am an electonics newbie, keen to learn.

Many thanks.

 

[williB]

have you got a working plotter
you want to plot a circuit..?
you want to plot the graph of a time domain output of a circuit..?
i am not sure what you are asking.

 

[Tronikid]

Sorry, my apologies for not being clear (it's my first time doing anything like this).

Yes I have several X-Y Plotters, two of them do have Time/Sweep in the horizontal plane. What I want is to provide a Ramp signal for all the Plotters, so that the pens can be made to travel from left to right, over a period of time, switchable from one minute to 24 hours, to monitor long-term activity.

The Ramp signal should be just one shot, with a switch to start the sweep, and a switch to reset to zero.

Pen lift does not need to be included.

Hope that this explains it a little bit better.

 

[williB]

Sorry, my apologies for not being clear (it's my first time doing anything like this).

Yes I have several X-Y Plotters, two of them do have Time/Sweep in the horizontal plane. What I want is to provide a Ramp signal for all the Plotters, so that the pens can be made to travel from left to right, over a period of time, switchable from one minute to 24 hours, to monitor long-term activity.

The Ramp signal should be just one shot, with a switch to start the sweep, and a switch to reset to zero.

Pen lift does not need to be included.

Hope that this explains it a little bit better.

ok what plotter are you using ..HP ?-- model number..?
because it would all depend on the type of interface that the plotter has on it..some if not most have centronix parallel ..some have serial..
others have analog inputs..(granted not many)...

 

[Roff]

Due to current leakage, it is difficult to get a linear ramp by charging a capacitor if the time is more than a few minutes. For long time constants, you need large capacitor values. Kemet (a major cap mfr) specs X7R-dielectric caps with a worst-case leakage time constant of 1000 seconds. In other words, if you were to charge one of these caps with a constant current, the cap could reach a steady-state voltage in as little as 5000 seconds (5 time constants). Now, the cap might actually be 10 times as good as worst-case, but that's still only 50,000 seconds, or less than 14 hours, so the useful linear portion of that charging waveform (depending on what you can tolerate) might only be an hour or so.
If you really need long ramps, you need a high-resolution D/A converter, a high-stability voltage reference, and a counter driven by a variable-frequency clock pulse. The simplest solution would probably involve a microcontroller. I guess your plotters don't have a stepping motor for the X-axis drive. This seems like the best solution, but if your plotters don't have this...