Communities

tag:snake search within a tag
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
created:<1w created < 1 week ago
post_type:xxxx type of post

Activity for TonyStewart‭

Type On... Excerpt Status Date
Edit Post #287969 Post edited:
11 days ago
Edit Post #287969 Post edited:
11 days ago
Edit Post #287969 Post edited:
11 days ago
Edit Post #287969 Initial revision 11 days ago
Answer A: What does it mean for a signal to have impedance?
$$Z = R + jX$$ R is a real resistance that stores energy as heat and temperature rise which depends on the thermodynamic property of thermal resistance which is impacted by an enclosure to get hotter or cooler by forced airflow. Everything has some real resistance, even insulators with an elec...
(more)
11 days ago
Edit Post #287952 Initial revision 19 days ago
Answer A: Testing instrumentation amplifier with differential signal
It is important to realize that an ECG signal is high impedance and this easily picks up line voltage E-fields. Using a 50 Ohm sig.gen. is a poor simulation of the use of this circuit and also negates any common mode rejection using it as a single-ended amplifier with one input grounded. Ground by ...
(more)
19 days ago
Edit Post #287524 Post edited:
4 months ago
Edit Post #287524 Initial revision 4 months ago
Answer A: What is the difference between rise/fall time and Turn-On/off Delay Time?
To understand the timing, you must understand the cause. Delay is the time from input to output It is measured from +10% of input to 90% of output ( or a 10% change in output), unlike logic chips where the same voltage is used for input and output so delay is measured at Vdd/2 or 50% from input to...
(more)
4 months ago
Edit Post #287523 Initial revision 4 months ago
The problem with cable emissions from HS data and SMPS noise is very common even with UTP and ribbon cable with adjacent grounds on differential signals. I have seen this frequently on HDD testing at EMC sites, whereas the HDD emits nothing of interest. The problem is due to the imbalance of the...
(more)
4 months ago
Edit Post #287326 Initial revision 5 months ago
If "base voltage isn't applied" then Ib=0 & dIb=0 then the proposed formula with Ib is not logical.
(more)
5 months ago
Comment Post #286900 If I understand what you said refers to my description of a differential amp (DA) with 3 NPN's , " There is a negative feedback in this common-base (CB) stage driven by an input current " then I cannot agree. The emitters are "common" to input and output so it is not a CB but rather differenti...
(more)
5 months ago
Comment Post #287265 You would need a spectrum analyzer to determine the signal from line noise due to SMPS , motor starts and Triac dimmers in order to determine the Noise rejection required. But yes you should expect interference with the wider -40 and -60dB BW unless it was at least 6 to 8th order.
(more)
6 months ago
Comment Post #287257 It seems you still use the single-ended topology but integrate current offset error with Hall, Rs or dual CT sensors to correct for the asymmetric current in each supply.
(more)
6 months ago
Edit Post #287265 Post edited:
more details
6 months ago
Edit Post #287265 Post edited:
6 months ago
Edit Post #287265 Post edited:
6 months ago
Edit Post #287265 Initial revision 6 months ago
Answer A: Ceramic filter vs ceramic resonator
A resonator cannot replace a filter because the filter has multiple resonances to extend the bandwidth. For AM carrier modulation using a narrow band resonator with 0.5% tolerance of 6MHz or +/-30 kHz with a Q of 10k and its narrow -3dB BW can be as high as a crystal resonator but > 100 worse tol...
(more)
6 months ago
Comment Post #286900 The simple ideas behind the differential amplifier are to ; - eliminate the Vbe diode voltage offset from the input and choose any reference voltage for 0 output. - use Ie to modulate gain when required - choose either output for inverting or non-inverting gain or use both.
(more)
6 months ago
Comment Post #287257 Does that mean you want it direct coupled but behave like a transformer AC coupled? Then the PFM or PWM drivers must have error feedback for the integral sum of current sensed from each to null the DC current and voltage feedback to null the error from the input voltage. So the answer lies in the ...
(more)
6 months ago
Edit Post #287244 Post edited:
so what
6 months ago
Edit Post #287244 Post edited:
plot
6 months ago
Edit Post #287244 Initial revision 6 months ago
Answer A: Low-pass filter after the output DAC in CD players
The oversampling is said to simplify the LPF yet the better reason is that it improves the SNR. Lower noise comes from better image rejection, lower filter ringing, and significantly lower group delay distortion in the audio band as the band edge is moved up. The majority of phase shift trav...
(more)
6 months ago
Comment Post #285107 >Why does the collector current depend linearly on the base current? When emitter resistance to supply rail is much greater than the base-emitter resistance re=26/Ie [mA] the voltage applied to the base is conducted to the base with Vbe drop. Thus there must be some relatively constant current g...
(more)
6 months ago
Edit Post #287072 Post edited:
6 months ago
Edit Post #287072 Post edited:
6 months ago
Edit Post #287072 Initial revision 6 months ago
Answer A: pH Electrode Buffer - Offset when solution grounded
DC offsets in hundreds of mV from different grounds may be coming from either the floating ground or the PE earth. The latter may be from rectified AC line filter noise shunted to PE. The former might be caused by front-end ESD protection diode rectification with DC bias and a CM signal large enough...
(more)
6 months ago
Comment Post #287027 Conductance = S=siemens (Volume) Conductivity, σ is "siemens per metre" (S/m) is the length/surface area Resistivity (rho) = "ohm-metre" = area/ length
(more)
6 months ago
Comment Post #286900 "Common" refers to input and output references that are shared. Vce and Vbe depend on the external resistors. While "e" is common to both.
(more)
7 months ago
Comment Post #286900 The differential BJT amplifier is well-defined in simpler terms. Av=Rc/(re+Re)=Rc/(26/Ie+Re)
(more)
7 months ago
Comment Post #285107 We know Ic is precisely controlled by the exponential function of Vbe and current gain is very inaccurate. This means every device has a wide range of Ic/Ib in the linear range and exceptionally wide variation in the nonlinear range down to 10% of the maximum current gain at Vce=Vce(sat) or usually r...
(more)
7 months ago
Comment Post #286900 The common terminal is not the least important, perhaps it is often ignored how important it is.
(more)
7 months ago
Comment Post #281971 I expect your measurements are accurate enough, but now you realize how reflections within 10 wavelengths or so can affect your results.
(more)
7 months ago
Edit Post #287007 Post edited:
7 months ago
Edit Post #287007 Initial revision 7 months ago
Answer A: Can confusing the plugs for earphones and microphones do any damage?
If you mean electret microphone, no damage to JFET buffer. Microphone input won't damage a headset with it's current limited pullup resistor for electret Mics.
(more)
7 months ago
Comment Post #286950 A bipolar switch rated for high Vceo seems to be all you need to protect the driver. Either high side PNP or low side NPN. >100V is easy to find. Your 1st plot is not to scale.
(more)
7 months ago
Comment Post #286944 The ideal conditions are almost never achieved in ordinary ground communications, due to obstructions, reflections from buildings, and most importantly reflections from the ground out of phase. This fading can cancel up to all of the signal. So it is more important you define the path and all refle...
(more)
7 months ago
Comment Post #286215 "across it" or it's own voltage is merely a value indicating the state of charge at some time. The actual charge Q = CV(t) for the capacitor's voltage. Your question is just about the semantics of a single test point (with an assumed common test point of 0V) or differential "across"
(more)
8 months ago
Comment Post #281971 What have you learnt?
(more)
8 months ago
Edit Post #282053 Post edited:
8 months ago
Comment Post #286868 interesting analysis +1, close enuf for gov't work.
(more)
8 months ago
Edit Post #282053 Post edited:
8 months ago
Edit Post #286867 Post edited:
8 months ago
Edit Post #286867 Initial revision 8 months ago
Answer A: Design high -pass filter with 2 points of the bode plot
Filter design 101 - 1. given hypothetical high-pass (HPF) filter -3dB gain HPF at fc 2. attenuation of -8dB at fc/2 3. Assumptions gain = 0 dB at f>> fc 4. Ripple between -3dB and 0 dB is unknown but assume 0dB max for simpler case. 5. steepness of skirts << fc is unknown but we know 1s...
(more)
8 months ago
Edit Post #282053 Post edited:
8 months ago
Edit Post #282053 Post edited:
8 months ago
Comment Post #282053 @#8176 The reality is your results of variations are real and certainly affected up to 10 or more wavelengths from reflections. The other reality is s21 is also affected by these reflections with multipath, so the net effect is to measure RSSI where possible in your receiver and test the variation...
(more)
8 months ago
Comment Post #286211 Anti-aliasing filters are always needed when the spectrum above the Nyquist rate fs/2 will degrade SNR with the resulting difference frequency output. Thus dynamic range and spectral values ought to be estimated with desired SNR. Typically a sampling rate might be 3x the upper frequency is the sp...
(more)
8 months ago
Comment Post #286215 **Is this interesting?** All voltages are relative to some reference. The local ground is defined as zero volts, just like Protective Earth PE ground. So if one side of the cap. is 0V then the voltage drop is the same as "the voltage" (relative to 0V.) **What is reactance, really?** It is ...
(more)
8 months ago
Edit Post #286866 Post edited:
8 months ago
Edit Post #286866 Post edited:
8 months ago
Edit Post #286866 Initial revision 8 months ago
Answer A: Circuit which create ac sine wave from dc pulsed signal
This is about as simple an analog inverter that I can simulate, but warning, not for the beginner with resonance issues. The bridge diodes are 2f multipliers reduced to logic level with divide by 2 FF, then complementary inversion switches with a center tapped transformer with the tap having the i...
(more)
8 months ago
Edit Post #286862 Post edited:
8 months ago
Edit Post #286862 Post edited:
8 months ago
Edit Post #286862 Post edited:
8 months ago
Edit Post #286862 Post edited:
8 months ago
Comment Post #286862 Thanks Olin, I added details to explain for others to understand why it is 180 + 180, with the assumption he knows there exists a frequency point at which -180 deg occurs from 3rd order (x90deg) phase shift) from 2L's and 1 C in a Pi filter. This is a slight change, from the Hartley.
(more)
8 months ago
Edit Post #286862 Post edited:
8 months ago
Edit Post #286862 Post edited:
8 months ago
Edit Post #286862 Post edited:
8 months ago
Edit Post #286862 Post edited:
8 months ago
Edit Post #286862 Initial revision 8 months ago
Answer A: Results of analysis of Hartley oscillator dont make sense
This LC circuit depends on several criteria for stable linear oscillation; - 180 deg phase shift ( with 3rd order LC network) plus 180 degree inversion to achieve the oscillation criteria of 0 or 360 deg at gain >=1 Thus each reactance affects fo. - adequate bias current and impedance ratios with...
(more)
8 months ago
Comment Post #286859 Not precisely, but you can filter the harmonic content of a broadband pulse to pass a narrow BW filter. Or you can phase modulate a square wave and filter any harmonic or fundamental.
(more)
8 months ago
Edit Post #286215 Initial revision 12 months ago
Answer A: What reactance actually is?
Reactance is the lossless part of impedance that stores and releases energy E=1/2 LI^2 or 1/2CV^2 . Much like a spring stores energy when compressed or expanded. L is a conductor that stores current with charges flowing. Q=LI. C is an insulator with some dielectric constant , Dk, relative to a...
(more)
12 months ago
Edit Post #286211 Post edited:
12 months ago
Edit Post #286211 Initial revision 12 months ago
Answer A: When do I need to put anti-aliasing filter in front of SAR ADC?
Anti-Aliasing filter depends on the following parameters; 1. Signal BW 2. Sampling Rate 3. Sampling duration and thus BW of sample 4. LPF attenuation of alias spectrum above 1. From your SNR spec or dynamic range desired for resolution When sampling rates of 64x are used, ofte...
(more)
12 months ago
Comment Post #286209 Level shifting can be accomodated with >10k resistors to limit ESD diode current rating specified.
(more)
12 months ago
Comment Post #286209 IF you want to detect tri-states, you need to specify the condition for the high-Zstate such as back driving with a 10k resistor 1/0 and detect that.
(more)
12 months ago
Edit Post #282054 Post edited:
almost 2 years ago
Edit Post #282054 Initial revision almost 2 years ago
Answer A: Capacitor ESR vs. Impedance
Capacitors are lossless with 0 ESR and rise in temperature and become less reliable by 50% for every 10’C rise due to I^2ESR=Pd losses. However the current spectrum must be known with the ESR frequency graph in order to estimate losses. The ultimate goal is to attenuate ripple voltage by the imp...
(more)
almost 2 years ago
Edit Post #282053 Initial revision almost 2 years ago
Answer A: Is there a way to reliably measure antenna return loss outside a lab?
The RSSI detector in the receiver is the best field tool. In Windows I had a tool (Wifi Radar?) that read the Broadcom IC RSSI and displayed a time plot of the results as I changed laptop orientation a couple of degrees and the results might change from -74 to -84 dBm and result in occasional errors ...
(more)
almost 2 years ago
Edit Post #281598 Post edited:
almost 2 years ago
Edit Post #281598 Post edited:
almost 2 years ago
Edit Post #281598 Initial revision almost 2 years ago
Corners and chambers that are a small fraction of a wavelength are not significant in the <4Ghz band. More significant is the tolerance and loss tangent on the substrate. They would hardly be measureable even with a 2 ps TDR. Emissions are not significantly different. WHAT COUNTS is the RL and lo...
(more)
almost 2 years ago
Edit Post #279302 Post edited:
almost 2 years ago
Comment Post #281444 But we only wore tinfoil hats when I bought a Lingren EMI proof chamber. In the 90’s.
(more)
almost 2 years ago
Edit Post #281597 Post edited:
almost 2 years ago
Edit Post #281597 Post edited:
almost 2 years ago
Edit Post #281597 Initial revision almost 2 years ago
Answer A: Estimating the input capacitance of an BLDC motor controller
To answer some of your questions: Cable inductance: - - approx 1uH/m +/-50% depends slightly on l/d ratio , while cable impedance from sqrt(L/C) depends on twists/ft 50pF/m while coax is 100pF/m Bulk storage Cap - - C value should store Energy Ec for load power x sag time between puls...
(more)
almost 2 years ago
Comment Post #279493 I remember when Qmodem would compute the bit rate differently, and shown higher than output expected. On dialup using 56k modems in high speed mode with a faster serial port, they would count the start and stop bits in the transfer rate, which then of course got translated into , I forget 64 levels ...
(more)
almost 2 years ago
Comment Post #279493 Can you give an example where Baud Rate is higher than Bit Rate?
(more)
over 2 years ago
Comment Post #279493 ... So don't byte me for saying your Byte rate example is not related to bit rate vs baud rate or symbol rate. but does affect character rate. characters are not symbols in this sense yet are symbols in language.
(more)
over 2 years ago
Comment Post #279493 There are many types of Baud Symbols that compress bits in time, frequency, phase or time in many combinations by sending many per unit of a bit. such as 9600 modems using 1200+2400 Hz tones with multiple levels to get 8 bits per Baud symbol in a 2400~3000 Hz bandwidth. ( I think, I forget)
(more)
over 2 years ago
Comment Post #279493 Dear Olin, I think you are using bit rate efficiency with overhead to define effective data rate, both which have nothing to do with the bit/s baud compression technology Symbols can stuff more bits per symbol such as the Baud symbol in a modem after Émile Baudot who invented the Baudot code (Bodo...
(more)
over 2 years ago
Edit Post #279442 Post edited:
over 2 years ago
Edit Post #279442 Post edited:
over 2 years ago
Edit Post #279442 Post edited:
over 2 years ago
Edit Post #279442 Post edited:
over 2 years ago
Edit Post #279442 Post edited:
over 2 years ago
Edit Post #279442 Post edited:
over 2 years ago
Edit Post #279442 Post edited:
over 2 years ago
Edit Post #279442 Initial revision over 2 years ago
Answer A: How to estimate time of completion while developing an electronic product?
In my 15 yrs of intense deadline R&D for new state-of-the-art design in my 45yrs experience, estimation of time is inversely proportional to the number of mini failures from bad assumptions from which you learn to expand your understanding of everything. You don’t have to be brilliant, that helps imm...
(more)
over 2 years ago
Comment Post #279010 The cap must be low ESR type as there is also an R ratio from arc negative resistance to cap ESR voltage divider. The. Common mode series R and TVS diodes provide secondary clamping with current limiting R chosen for 1kV to TVS Rs. The arc -ve Rs was proven by Faraday to be inverse to current densi...
(more)
over 2 years ago
Comment Post #279010 Erhm When the resistor arcs it will become a capacitance transformer, 200pF/100nF = 0.2% of 15kV so move the caps to the shunt R and make the current loop small and close to the injection PT. The cap must be low ESR type as there is also an R ratio from arc negative resistance to cap ESR voltage di...
(more)
over 2 years ago
Comment Post #279010 With 0 tolerance parts this amplifier acts with open loop gain as the feedbacks are equal and cancel. Olin is correct, and the tolerance stack up would make this an unpredictable outcome. This design fails because of unstated assumptions for designs specs, yet intuition and experience tells it won’t ...
(more)
over 2 years ago
Edit Post #279413 Post edited:
over 2 years ago
Edit Post #279413 Initial revision over 2 years ago
Answer A: How to plot the I-V curve of a tunnel diode?
How to test a Tunnel diode in 25 words or less. - With DC bias = 490mV with fine tuning and a small signal swing of 60mV you can generate a IV negative slope of -16 Ohms.
(more)
over 2 years ago
Comment Post #279280 Don’t take down vote personally, it means some jerk thinks you made a bad assumption or statement. If they give no feedback or value added comment , ignore those trolls who have communication issues. You seem competent enough to make intelligent questions, but watch out for unstated assumptions.
(more)
over 2 years ago
Edit Post #279388 Post edited:
over 2 years ago
Edit Post #279388 Initial revision over 2 years ago
Answer A: Using FET based followers and design rules
Allow me to address the MOSFET only as a source follower. - this has very unpredictable linear use without voltage = current feedback as the RdsOn at threshold has a wide tolerance.(>20%) (Many wider than the next example). However it is extremely popular in dual N ch. designs for a Half Bridge ...
(more)
over 2 years ago
Comment Post #279228 That’s the spec on the tightening of the connectors to achieve desired low loss without removal of excessive gold plating.
(more)
over 2 years ago
Comment Post #279302 @Lundin. Low value added readers who fail to communicate and downvote are called Trolls
(more)
over 2 years ago
Comment Post #279016 have fun learning.. maybe I'll make a Youtube or Zoom or any forum to train a group if there is interest. But I need motivation to do this.
(more)
over 2 years ago
Comment Post #279016 This article has value to share your method that works for you. I learned 45 yrs ago when we had no tools except paper and pencil and experiments. So it worked for me too. But now I can do so much more using Falstad's simulators, that its amazing as long as you know to make ideal parts real C+ESR,...
(more)
over 2 years ago
Edit Post #279302 Post edited:
over 2 years ago
Comment Post #278856 @Olin's assertion to resonant frequency is totally bogus. Water has absorptive properties over many decades of f without this resonance. http://www1.lsbu.ac.uk/water/microwave_water.html#loss This is a good reference but fails to discuss the ionic behaviors of contaminants.
(more)
over 2 years ago
Comment Post #279302 IF you are an experienced EE and down vote this without comments you are in contempt of your own ego issue and have no business here.
(more)
over 2 years ago
Comment Post #278856 false assumption on resonant frequency of water. -1
(more)
over 2 years ago
Edit Post #279302 Post edited:
over 2 years ago
Edit Post #279302 Post edited:
over 2 years ago
Edit Post #279302 Initial revision over 2 years ago
Answer A: Microwave oven interfering with WiFi on the 2.4GHz band
Microwave Materials, Spectrum then EMI effects on SNR of WiFi, BT. There are a lot of measurable parameters in microwave dielectrics which affect; - Dielectric Constant , Dk between conductors and thus Impedance , Zo - scattering parameters in a transmission path from mismatch and losses ...
(more)
over 2 years ago
Comment Post #279016 For professional development, it is important to define the performance and assumptions desired before starting the design. I have some doubts on this design but then there are missing assumed values
(more)
over 2 years ago
Comment Post #279016 TL;DR but very well-prepared WTG and image readability can be improved with Irfanview/Gimp with contrast+brightness
(more)
over 2 years ago
Comment Post #279228 Then s21 losses in the connector threads of 0.1dB is good 0.5dB is bad, so calibrated torque is important.
(more)
over 2 years ago
Comment Post #279228 Now that you grasp the basics, the geometry is a big factor moving towards 5% of the wavelength and beyond. Although video SA's are 75 Ohms the std versions are 50 Ohms. But the only difference in coax is the ratio of the conductor radius for outer/inner. In your example the small solder gap add...
(more)
over 2 years ago