I have a transducer that creates a step voltage (0 to 4.5V) with a proximity stimulus, However I would like to put this step input into an op amp where the output of the op amp will follow the step input but with a controlled amount of ringing (both amplitude and settling time). This is essentially a controlled under-damped system.
What is the best op amp configuration for this? Has anyone tried this before?
Thanks,
That's a somewhat odd request - some context might be helpful here. What are you intending to do with this? Is this something that would be better simulated in software and output on an DAC?
I agree with DrAzzy about simulating it in software, maybe with a Due or Teensy 3.1/3.2 with their 12 bit DACs.
Otherwise, an op amp active filter with a normally undesirable peak response at the cut off frequency? Kind of hard to control the amplitude and settling time, especially if you want it adjustable after it is built.
hairbair:
I have a transducer that creates a step voltage (0 to 4.5V) with a proximity stimulus, However I would like to put this step input into an op amp where the output of the op amp will follow the step input but with a controlled amount of ringing (both amplitude and settling time). This is essentially a controlled under-damped system.What is the best op amp configuration for this? Has anyone tried this before?
Thanks,
A low pass filter. The filter Q determines the damping. But the mind does boggle at the request. It sounds like an XY problem.
Sounds like a Chebyshev low-pass filter is wanted, or an LC circuit (or its gyrator equivalent)?
Perhaps some numbers are in order - resonant frequency and Q...
Post a link for the transducer and state the reason for the request.
aarg:
A low pass filter. The filter Q determines the damping. But the mind does boggle at the request. It sounds like an XY problem.
Funny. The OP WANTS what most op-amp designers try very hard to AVOID.
Can you tell us why you want to do this?
Are you trying to create a drum machine? (and if so why didn't you tell us?)
A lot of replies for a single post that was 48 hours ago!
I figure either the OP comes back to explain, or forget it!
But it's fun considering solutions to a poorly-stated problem. No solution proposed can ever be wrong!
My solution would be to have a long transmission line, like a hundred feet of cable with no termination resistor. That may be what he wants to simulate but a loop of cable is not expensive to buy so you can test on the real thing. For really long lengths, buy ribbon cable and connect the ends just one step over. Instant kilometers of wire and you don't even take it out of the cardboard box except to find the ends.
you could maybe leverage something out of this .The shorted turns tester described here rings a coil and then counts the rings
Well , yes, but if you want ringing you would be shopping for a coil anyway right ? But then what do you use for damping to control the ringing ?
once you have some ringing happening a phase synchronised adjustable low impedance could be applied to a secondary winding to dampen the oscillation as/when required . the initial specs are wide open to interpretation
phase synchronised adjustable low impedance could be applied to a secondary winding to dampen the oscillation as/when required
And what (component/circuit) would that be ?
mosfet
A Sallen-Key active low pass filter worked well for me when I wanted that. Since we're still having fun.
It must be the 5 minute rule. He only has 14 posts, you know. 8)
This may come as a surprise but I don't know what the 5 minute rule is
5 minutes between posts.
raschemmel:
Just as well. The OP's post was worded like a homework assignment. Think about it. He says he "has a transducer.." . He doesn't say "I have THIS transducer . He doesn't say WHAT he doing. He doesn't say WHY he wants ringing. He says he wants to use an op amp but obviously does not know ANYTHING about op amps. Does not even know what a Voltage Follower is because he describes one to a T but not by name. He describes an LPF but not by name. Instead of saying " Can I use an op amp to generate such and such an output from a [ sensor name] input ?" he starts out by asking "what op amp configuration follows the voltage of it's input ?" (is that a trick question?)
Obviously he's never used an op amp.. He asks for an " under damped controlled system but doesn't know the first thing about Control Systems (like PID parameters for starters).
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Hello,
I am back now. Sorry that my question seems to have offended you so much! This was not a homework assignment, and thanks to the people who gave helpful answers my memory was jogged and I remembered the Sallen Key filter topology and I have now implemented this into a Spice model and the results are great!
My transducer (since you seem keen to know) is a microphone and pre-amplifier which I made myself, therefore there is no "link". And by the way I know what a "voltage follower" is.
What I was after was a low-pass-filter topology which would allow me to chose the components easily so that I can control the time reponse of the second order system. Hence allowing me to chose the overshoot, damping, settling time etc.
The Sallen Key transfer function allows me to select the resistances/capacitances so that I know what the response will be. Thanks to those that mentioned this. And by the way, anyone who possesses any real knowledge and experience should be happy to share it, not to mock and belittle others whilst reeling phrases like "he doesn't even know..." or "he has never heard of...".