How do I simulate this waveform in LTSpice?

I don't care so much about the noise but it would be nice. I can get a pulse to look close but this is a bit more half sinusoidal than a square pulse.

 

How do I simulate this waveform in LTSpice?

I don't care so much about the noise but it would be nice. I can get a pulse to look close but this is a bit more half sinusoidal than a square pulse.


View attachment 119167

I think you could build a PWL file, but it might be a pain.
http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_5.htm
@Alec_t is good at these. Maybe he can help.

 

I think you could build a PWL file, but it might be a pain.
http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_5.htm
@Alec_t is good at these. Maybe he can help.

Yeah this is not that important. If it is going to be that hard I will go with a pulse. I think that will be close enough.

 

This generates half sinewave pulses.
Is that close enough?
Edit: Added noise.

 

How do I simulate this waveform in LTSpice?

I don't care so much about the noise but it would be nice. I can get a pulse to look close but this is a bit more half sinusoidal than a square pulse.


View attachment 119167

Is that the actual output from your sensor?

 

This generates half sinewave pulses.
Is that close enough?
Edit: Added noise.

View attachment 119179

The second graph is the output? Then yes. Wow that is amazing. It even has the noise. It looks just like my waveform. Only difference I see right off is it looks like it goes negative but I guess I can play with it. Thanks!

 

Is that the actual output from your sensor?

Yes. I am using a fan right now with a odd shaped blade. Plus I may not have done such a great job at paining the mark. I think that might be were the noise comes from.

 

Yes. I am using a fan right now with a odd shaped blade. Plus I may not have done such a great job at paining the mark. I think that might be were the noise comes from.

Well, the good news is that a comparitor can turn that Bump into a 5v signal easily. If it is not long enough, you can connect a 555 to the comparitor as a one-shot to extend the duration of the peak, or use a flip-flop to square it up (and cut frequency in half (but that can be corrected in software). Everything is possible.

PS: or connect to a pin that has Interrupt-on-change flag.

 

Well, the good news is that a comparitor can turn that Bump into a 5v signal easily. If it is not long enough, you can connect a 555 to the comparitor as a one-shot to extend the duration of the peak, or use a flip-flop to square it up (and cut frequency in half (but that can be corrected in software). Everything is possible.

PS: or connect to a pin that has Interrupt-on-change flag.

Yeah someone I know that is pretty darn smart suggested I use a comparator to turn that "half sine wave" into a square wave. So I guess I get the bonus of having the noise removed too. And I had already planned to use the interrupt pin.

 

This generates half sinewave pulses.
Is that close enough?
Edit: Added noise.

View attachment 119179

Slick!

 

This generates half sinewave pulses.
Is that close enough?
Edit: Added noise.

View attachment 119179

@crutshow. Would would you mind explaining how your model works? What part does what?

What I am trying to to is figure out how to invert the signal. I got some new sensors in, basically the same wave form as above but inverted.

 

I can get it to go to -2.4. But what I really need is the DC offset at 2.4 and have the half wave peak at 0 volts. So just like this except 0-2.4V

 

Here is the actual wave form.




These TCRT5000s that I got in are really great. Nice strong pulse from several inches away.

http://www.ebay.com/itm/20pcs-TCRT5...744562?hash=item56906549b2:g:fM0AAOSwiDFYKnzw

 

Would would you mind explaining how your model works? What part does what?

What I am trying to to is figure out how to invert the signal. I got some new sensors in, basically the same wave form as above but inverted.

V1 generates a sinewave of the desired frequency, amplitude, and offset.
V2 controls a switch to select the desired part of the sinewave to appear at the OUTput.
B1 generates the random noise, per the equation in the parentheses.
These are summed together by R2 and R3 at OUT.

 

Here's a simulation closer to your actual waveform in post #13: