Actions
Forum Thread Details
  • Replies 7 replies
  • Subscribers 597 subscribers
  • Views 1573 views
  • Users 0 members are here
Related

LTspice for Theremin circuits

FredM

LTspice is available free from http://www.linear.com/

This simulator is superb, and suitable for all designers, from beginners to 'advanced'.. It is well suited to simulation of Theremin circuits.

 

The best tutorial I have found to get you started can be downloaded at

 

This zip file contains a PowerPoint presentation SWCAD.PPT  and running this teaches you all the basics you need start using LTspice.

 

The Full reference manual is here: http://ltspice.linear.com/software/scad3.pdf

A few good guides:

http://web.cecs.pdx.edu/~ssuzuki/engr_notes/ltspice/LTSpice_help.pdf (A good tutorial, particularly on setting up simulation types and creating subcircuits.)

http://pages.suddenlink.net/wa5bdu/ltguide.pdf  (useful tutorial - data on transformers..)

http://home.mindspring.com/~eeweb/ltspicesubckts.pdf (more advanced sub-circuits)

http://denethor.wlu.ca/ltspice/  (Tutorial and lots of good links)
 
LTspice is best for Analogue simulations in my opinion - The digital models are a pain.
 
For anyone having problems downloading LTspice, I have attached it to this message.. Probably not something I should be doing.. but as I am promoting their software, I hope Linear Technology wont object!
Attachments:
LTspiceIV.exe.zip
imagescad3[1].pdf
Parents
  • Some more advice on simulating..

    Work with minimum circuit blocks first.. For example, with a Theremin front-end..

    'Build' ONE oscillator and test it.. usually the oscillators are almost identical.

    'build' the mixer - but instead of using 'actual' oscillators, use sine generators (these can have their frequency and amplitudes set to whatever you want - specify the amplitude you got from your 'real' oscillator, and set one frequency (variable oscillator) at the frequency of your 'real' oscillator, and the other at say 200Hz higher..

    You can now test the mixer quickly - the simulation does not need to compute all the signals to make each oscillator run - there is no delay while DC levels stabilize - the simulation will run at least 1000 times faster!

    When you have tested each block independently, select a time when you wont need to use your PC for severaL HOURS, put all the blocks together, and run the simulation... It is a good idea to do a complete simulation (if possible) once each block has been verified - because you may have missed something... For example, any loading caused by the mixer would not affect signal generators, but may affect 'real' oscillators.. Also (as in the case of the EW simulation) the oscillators may couple to each other via the mixer components (with the EW, coupling is provided through C2 and C6) and this changes the waveshape seen from the mixer (on C23) and can cause the oscillators to pull to the same frequency (giving a DC level, and no difference frequency on C23).

    When running the full simulation, it is a good idea to set the oscillator free-run frequencies to have about 1kHz difference - unless you particularly want to examine oscillator locking.
Reply
  • Some more advice on simulating..

    Work with minimum circuit blocks first.. For example, with a Theremin front-end..

    'Build' ONE oscillator and test it.. usually the oscillators are almost identical.

    'build' the mixer - but instead of using 'actual' oscillators, use sine generators (these can have their frequency and amplitudes set to whatever you want - specify the amplitude you got from your 'real' oscillator, and set one frequency (variable oscillator) at the frequency of your 'real' oscillator, and the other at say 200Hz higher..

    You can now test the mixer quickly - the simulation does not need to compute all the signals to make each oscillator run - there is no delay while DC levels stabilize - the simulation will run at least 1000 times faster!

    When you have tested each block independently, select a time when you wont need to use your PC for severaL HOURS, put all the blocks together, and run the simulation... It is a good idea to do a complete simulation (if possible) once each block has been verified - because you may have missed something... For example, any loading caused by the mixer would not affect signal generators, but may affect 'real' oscillators.. Also (as in the case of the EW simulation) the oscillators may couple to each other via the mixer components (with the EW, coupling is provided through C2 and C6) and this changes the waveshape seen from the mixer (on C23) and can cause the oscillators to pull to the same frequency (giving a DC level, and no difference frequency on C23).

    When running the full simulation, it is a good idea to set the oscillator free-run frequencies to have about 1kHz difference - unless you particularly want to examine oscillator locking.
Children
No Data