Interesting Oscillator

[MAURICE]

Hi to all.
I have been investigating this oscillator with LT spice for some time now and wondered if it may not be a candidate for some of the projects like IGSL. It is the whites oscillator with some small changes from original. Now I have been told and understand that a spice simulator is not the most ideal way of checking oscillators in particular regarding start-up.I did get assistance from a friend and mentor on this circuit ( he has a Rf and dev.background). The oscillator seems adaptable to most coil values by changing the feedback capacitor ( c1 in attachment ). IT also has a clean out put spectrum when viewed with LT spice. Perhaps some of the Guru's on the forum would like to comment on this oscillator. PS LT spice asc.
Regards Maurice.

[golfnut]

Hi Maurice,

It looks ok - 14.5kHz.

It does take a little time to cough into life but no problem. You can slash the starup time by a factor of 10 by increasing the feedback cap from 150p to 470p.

The ac current thru the 6mH coil is your 'Tx power' in this case it is only 15mA peak

I run my IGSL oscillator from the 12v (not 8v) rail to get 45mA peak thru my coil.

I get air tests up to 30cm on various coins.
Saying that I rarely find small stuff in wet clay deeper than 5 inches !

Steve

[MAURICE]

Hi Steve. Thanks to your quick reply and valued comments on oscillator. I will now re-run simulation and adjust values to get current up through coil. The the interesting thing about keeping the feedback capacitor low is the harmonic products are low. I use the fft function to view this and products are in some cases 25-30db down,this may not be essential but it something to note.
Regards Maurice

[golfnut]

Hi mine is similar to this

[golfnut]

this time

[kliner]

Sorry, what prog do I need to open an .ASC file?

[golfnut]

LT Spice

http://www.linear.com/designtools/software/

[golfnut]

there are lots of demo circuits here


http://www.linear.com/designtools/so...o_circuits.php

[porkluvr]

Hi to all.
Perhaps some of the Guru's on the forum would like to comment on this oscillator. PS LT spice asc.
Regards Maurice.

I don't mean to sound crabby, but your question would appeal to more readers if you posted a picture of the oscillator schematic in question. That way, we would not have to download your zip file and open it in LTspice before it could be viewed.

You know, not everybody wants to have LTspice installed on their machine. There are other circuit simulators in use.

(Yes, I know I'm crabby.)

[golfnut]

HI Maurice, I have been working on a Tx osc buffer amp that uses 2 coincident poles in a bridge config.

Take a look.

The Tx coil current would be a few hundred mA.

It is not practical for MP as it is too sensitive to some component tolerances - parts would have to be blueprinted for each unit.

Steve

[golfnut]

Here we are porky - heres maurice osc, knock yourself out.

[MAURICE]

Hi ALL
Sorry about not posting schematic in visible format I am computer challenged, I will have to learn how to save asc.file in JPEG ,bmp ect. Steve I have just opened this post and Iwill look at your colpitts oscillator shortly. I have just re-run simulation using 1.3mH Inductor 100nF capacitor and 1nF for feedback. Peak current now 100mA harmonics down-30db. This may be a good option. Seems like this oscillator more suited to inductors in the 1mH range.Thanks for all the input from members and posting the Schematic. I attach circuit with new values.
Regards Maurice

[porkluvr]

Hi ALL
Sorry about not posting schematic in visible format I am computer challenged, I will have to learn how to save asc.file in JPEG ,bmp ect.
Regards Maurice

I can't get LTspice to give me a usable jpg or bmp file either. What I do is press CTL+PRINTSCREEN and that copies my viewscreen to the Windows clipboard, then CTL+V will paste it into a program like PaintShop Pro which lets me crop and resize the image, and save it in a variety of formats.

Even the Paint program that comes with windows will let you paste the screen shot and save, but unfortunately you can't crop with it.

By the way, Ivconic already implemented that Whites oscillator as an option for the IGSL. R values are different and his original RC values tuned to around 9KHz, but same topology used. It does look very clean.

If you have a slowly starting oscillator simulation you can usually speed it up with an "Initial Conditions" statement; something like ".ic iLtx=1u". Really low value of coil current is all that is needed.

[golfnut]

Hi Maurice, how do you do the harmonic measurement?



Attached is the highest power I can get from it, I imagine the harmonics are ave at best as I can see the sinusoid is a little scratchy.

250mA peak to peak - this would freshen up a weak target signal vs the original 15mA !

Steve

[golfnut]

sorry maurice heres the model