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analogdesign said:It is comprehensive, easy to understand, and goes step-by-step with easy to understand explanations and design procedures. It was my go-to book when I designed an integrated PLL a few years ago.
anstxfw said:If I change C18 from 0.1uF to 10uF, PLL cann't lock phase,the VCOin is always 5V,How to select C18/R5/R6 of the filter.
jim hardy said:Well slowing the loop filter reduces capture range.
View attachment 106144
I don't quite understand what you are up to.
Are you shifting the pll center frequency and trying to lock that to output of whatever is (U1 divided by U3) ?
anstxfw said:I don't understand why this voltage could fluctuate? (PS:my AC power is 50 HZ).
anstxfw said:It is strange that if I put the ground of the machine to the earth(the real ground),no any changes,the PLL can lock again,put it off the earth,unlock again.
Of course, we're looking for cause-effect.anstxfw said:I don't have 500pf,is it ok to use 200pf?
No, for this experiment it's to alter the value of R3 or R19&R20anstxfw said:I can't see your point.Is the probe capacitance to be C10?
First connect probe at pin R1 so that when wetted it decreases resistance from that pin to common, as if value of R3 were changedanstxfw said:what's the meaning of "in turn".
Is that sensor plate coated with plastic insulation? If not, it will be sensitive to R as well as C. Is it a pin or a plate?anstxfw said:When the needles are filled with ionized water,
it may be better to connect the sensor across the timing capacitor C18,you mean connect the neddle to the C18? what is the sensor?NascentOxygen said:Is that sensor plate coated with plastic insulation? If not, it will be sensitive to R as well as C. Is it a pin or a plate?
Is your connection of the sensor plate directly to the IC pin correct? This evades any filtering; it may be better to connect the sensor across the timing capacitor C18.
Sorry, I misinterpreted your diagram.anstxfw said:it may be better to connect the sensor across the timing capacitor C18,you mean connect the neddle to the C18? what is the sensor?
anstxfw said:Figure 5.2,the figure 5.2 shows that the waveform of VCOin before and after touching the liquid level.But the response time will be longer.This will cause the needle to overshoot at the level of the liquid.Now solved a problem and lead to another problem.I am going to crash.
no,i don't solve my problem.using 0.1uf (C18) ,the VCOin can not be stable, the frequency of the hash is 50HZ,you can watch the figure 4 at 3# where I posted.If using 1uf,the VCOin have no hash,but the rising time will be 5 times before. It is unacceptable.Looks to me like you've solved your problem. It appears to never lose lock ? Fig 5.3 also locks . I am unable to read what is the time per division on your 'scope
It looks like Figure a,attached in the annex.If you measure at capacitor C18, other side of R5, you'll see DC without the hash. Then you'll be able to reduce C18 for faster loop response.
To change the circuit will have a little bit of trouble,so I want to know why to do this?I hope you'll try wiring your needle to R3 and R19 , just to see what happens.
anstxfw said:no,i don't solve my problem.using 0.1uf (C18) ,the VCOin can not be stable, the frequency of the hash is 50HZ,
anstxfw said:Sorry about that,because i put the ground of the machine to the earth.
i think that means you'll have to decouple your beaker from Earth and connect it instead to signal common. See post 11.anstxfw said:If the power supply systems of some customers don't connect to the earth,it can be an problem.
I try 200pf,but the PLL can unlock.the VCOin is 5V.jim hardy said:Did you try that small capacitor in series with the needle ?
no, an honest question is never impolite.anstxfw said:And Impolite to ask a question,why to Series a capacitor,i don't understand.
Hmmm . It unlocks ? Have you a 'scope trace of that ?anstxfw said:I try 200pf,but the PLL can unlock.the VCOin is 5V.
I think you're exactly right !anstxfw said:I think the wire bypass the interference
A PLL, or phase-locked loop, is an electronic circuit used to generate stable and precise frequencies. It is crucial to select the right parameters for a PLL in order to ensure its proper functioning and achieve the desired frequency output.
The parameters for a PLL depend on the specific application and the desired frequency output. Factors such as input frequency range, output frequency range, phase noise requirements, and power consumption should be considered when selecting parameters.
The loop filter is a key component in a PLL that helps to determine its stability and response time. The parameters of the loop filter, such as its bandwidth and damping factor, should be carefully selected to prevent instability and achieve the desired frequency response.
While some PLLs may come with default parameter settings, it is important to carefully consider and adjust these parameters for your specific application. Using default parameters may not provide the best performance and could result in instability or inaccurate frequency output.
Once the parameters have been selected, it is important to test and verify their performance. This can be done through simulations and measurements, comparing the output frequency and phase noise to the desired specifications. Adjustments to the parameters may need to be made in order to achieve the desired performance.