SS 3.9!!!

Hi Skfir,

Yes, the sweep begins and ends on zero crossings, as shown below (with no scope handy, I recorded the 1701's output with Audacity):

And yes, you'll hear clicks. I hear them as well. They are mathematically inescapable whenever a tone is started or stopped abruptly, even at zero crossings! The math is beyond me (it has something to do with Laplace transforms), but we can demonstrate it with the spectrum analysis tool in Audacity:

Here's a 1 KHz tone, with a selection made carefully at zero crossings. The tone is continuous throughout the selection interval.

Plotting the spectrum of this tone, it appears as expected -- a peak at 1000 Hz, with little energy elsewhere (and virtually none at low frequencies approaching DC):

Now I select a section that has half tone, and half silence to analyze. The tone still begins and ends at zero crossings:

The spectrum of this section is quite different -- there's lots of stuff away from 1000Hz, including a flat run down towards DC. This we hear as a click:

So an audible click does not necessarily indicate nonzero switching. In your application you probably need the resolution of a sharp "on-off" transition between segments more than click reduction -- which as you know, could be had with slewing.

SigmaStudio's programming manager monitors this space; perhaps he's in a position to comment on your question about a linear sweep.

Bob

Thanks Bob!

Now I understand.

Bless you god good man!

Hi Skfir,

Thanks, it's a pleasure to help with your applications since you're always so appreciative. Actually I'm quite ordinary.

Bob

Thanks, Bob!

Hi Coleman, so what is about the linear sweep? Is it planned for implementation? Or there will be just the logarithmic one?

Hi Skfir:

You can easily generate a linear sweep with a counter and a VCO, Could you try this and let us know your results.

Hope this helps.

Miguel

I will for sure, thank you.

Just in order to clarify a bit, if I want a stopwatch to count in bigger increments, I should use a multiplier block right?

Ok, I have tried and it works fine, but unfortunately in my application, where it is needed to produce regular sweeps, controlled by pulses (it is a device for helping disabled people) the whole thing becomes way too heavy and I simply do not have enough horse power to run everything. Of course if there was just a single vc linear sweep block it would make things much easier and less horse power consuming. Guys I know that you are very busy and have lots of things to do, but if once you could just make the same VC sweep block you already have now, but just make it linear it would be more than just great. It would solve all the problems at once. Because now to implement the same thing I need to use many blocks and a linear vc sweep could really help many visually impaired people, for whom I have been building this thing. So guys once you have such a possibility, could you please implement such a block?

Hi Miguel,

Skfir's ultrasonic blind assist device operates at fs = 192KHz, thus the need to conserve instructions. ADI's log sweep generator uses 75 instructions. So far, the best I can do for a homemade linear-step sweep generator uses 84. If I can get it below 75 I'll post the results, but for now a linear version of your sweep generator would help.

Bob

Hi Bob!

Thank you for you concern also. Here is what I made so far. The idea is this linear sweep is interlaced, the 1st sweep is from 80 to 55khz, and the second from 55 to 22 approximately. Such a thing eats 89 points. Also there are lots of constants, which make any adjustment really painful. Let alone sweep triggering frequency control, which requires changing almost all the constants. So if a linear triggerable sweep block existed it would make everything very easy to control and easy to implement and most probably economized some precious horse power.

Hi Skfir,

ADI's log sweep generator makes discrete tones that change frequency abruptly -- that's why Miguel suggested having a counter drive the VCO to make a similar but linear sweep. I tried your circuit above, inserting a (1/100) attenuator before the VCO to render the frequency audible. I heard both abrupt (from the pulse generator) and smooth (sawtooth) features. Thus I'm not sure what sort of output would serve your application the best.

This present topic which started about SigmaStudio 3.9 is getting long in the tooth. I suggest you start a new post that begins with your desired sweep characteristics. That might help evoke a solution.

Best regards,

Bob

Oops... Sorry Bob I made one silly mistake, if you please change the value of the DC, connected to input D of the logic gate to zero, instead of one, it will work fine.

I am afraid that the only solution here can be just one block, I will pray for it to happen one day

Thank you again Bob!!