texts:
I'm looking for an adjustable or fixed 6V regulator, performing up to 6A peak current. The continuous consumption will be much smaller. It needs to be a LDO regulator, since I will be powering the regulator from a 2S LiPo batery (7.4V nominal). The drop-out would need to be about 1V or so.

Could I use a switching regulator for this kind of thing? I'm afraid of noise on the power rail that would be bad for the motors and would make it harder to control them. They will be used on a robot for robocup rescue B. I'm using a 9.7:1 Metal Gearmotor motor with a DRV8432 motor driver.

I will be driving 4 motors, so I'll probably get a separate regulator for each one.


texts: By data processing inequality, by processing we are losing information. So why do we process the data?

texts: From data processing inequality(DPI) we know that if \$Z=f(Y)\$, then \$I(X;Z)\leq I(X;Y)\$. However, in the application, we process the data. For example, we pass the received signal via a matched filter to maximize the SNR. Isn't it in contradiction with the DPI?


texts: What is the purpose of this capacitor in the SA602A circuit and how do I choose its value?

texts:
I'm trying to use the SA602A mixer and I'm not sure what the capacitor between the emitter and the base does. I'm using this mixer because I've seen it being used in the Norcal40. However in the Norcal schematics it's a trim pot, which leads me to believe it's part of the LC tank?

I'm working at 7 MHz, the tank has two 30 pF caps and the inductor is 33 uH. The decoupling capacitor is 0.1 uF. How do I pick the last cap?


texts:
I have a question about a differential transceiver.
In my application I am using a MCU to generate PWM signals for a gate driver board (CGD1200HB2P-BM2). This board, however, needs a diffierential PWM signal.
I checked the circuit and the gate driver board is using a differential transceiver (SN65C1167).
Unfortunately, I never worked with this type of PWM signal before, which is why I am a bit confused: do I really need a differential PWM signal with +5V level and -5V level or would it work if I have a PWM signal with +5V and GND
See picture of PWM signals:


texts: Class A single transistor amplifier with 2N3904

texts:
I made a simple little transistor amplifier using the 2N3904 (basic class A amplifier):

\begin{align*}
R_1 &= 2.2\, k\Omega \\
R_2 &= 1\, k\Omega \\
R_L &= 22\, \Omega \\
R_E &= \text{potentiometer} \\
C_1 &= 2.2\, \mu F \\
C_2 &= 20\, \mu F
\end{align*}

It works fine, but if I leave it on for a little too long it gets really hot.

I have 2 different types of transistors that I can mount to a heatsink. TIP31A and TIP41C. But when I put them in they don't work. Could someone explain why they don't?


texts: Signals from optical sensors to count the number of people entering/leaving a room

texts:
The Problem

Suppose I have two optical sensors attached to a room's door.

When a person enters the room, these are the signals from the sensors:

When a person leaves the room, these are the signals:

Using these signals, I need to implement a counter that will tell me how many people are in the room.

Assume up to 25 people may be in the room at any time. Assume any other signal pattern will not happen, only one person will leave/enter at a time, and there are no other exits.

What I have tried

I have tried using two 74LS190, connecting A to the clock, and B to the up/down switch. Like this:

However, I have run into some bugs when cascading: an enter signal when we have 9 people sends the count to 10 then to 20. This happens because of rc's specification.


texts: Why some vias have solder mask and others do not?

texts:
Here's an area of a commercial PCB.

I'd like to know if the "missing" solder mask is a deliberate choice made by the PCB designer, and if so, why?

edit: changed graphic to highlight representative vias.
Blue circle - solder mask (gold-colored)
Red circle - no mask (silver colored)


texts: What does the term 'min' mean in AAA Rechargeable cell current capacity?

texts:
While checking the specification of rechargable AAA Ni-MH cells, the specification shows 2 parameters Voltage say 1.2v and Current Capacity  say 630 mAh.

However the current capacity is preceded by 'min'
For example 1.2v  Min 630mAh.

What is the meaning of 'min' here? If I understand the basic Ohms law the load shall only draw the current it needs at a specified voltage. So ideally if I use 630mAh cell or 830mAh cell at 1.2 volts the load shall only draw same amount of current. I hope I am correct.

So indeed what does 'min' specify in such a specification.

Below picture courtesy of Amazon Website.

Thanks.


texts:
I am looking at a reference design for the allwinner H6 SoC. My question is pretty straightforward. Why does pin B3 need to be powered if the EPHY pins are unused. Additionally, pin B4 is being pulled down through the use of a 6k ohm resistor(incorrect assumption). [These have been answered]

What would you do regarding EPHY pins? Follow the design reference, include 50-150k Ohm Pu resistors, or include 50 Ohm pu resistors in the EPHY pins like Passerby recommends here.


texts:
I am designing a two layer PCB. Two part schematic is shown in attached figures.

In the circuit, I am getting four gate signals from FPGA of 3.3V and and error signal, also of 3.3V as inputs and I need to step up the gate signals to 5V while ensuring that signals are  turned off in case if error persist (ERR is active low). So I  use a digital isolator/level shifter to step the input signals upto 5V and an AND gate to ensure signal turn off in case of an error.

The next part is to generate the voltage levels. I am getting 3.3V as an input from other PCBs and I need to generate 5V for the level shifter and my AND gate. To do that, I use two Traco dc-dc converter to first step down voltage from 24V( from floating lab power supply) to 15 V and another TRACO to get 5V from 15V.

Now as can be seen in schematic, I have four isolated grounds on my PCB
: For 24V, 15V , 5V and two signals of 3.3V. I would want them to remain isolated. I have following queries:

Do I really need to isolate grounds of 15V and 5V( although TRACO ensures it)
Which ground level should I choose for ground plane
Should I use different ground planes for my digital signals (eg5V)and my same voltage level power ground and connect them at one point or  should I rather use one ground  plane for digital and analog signal of a particular voltage level (eg : 5V power supply ground and 5V digital IC ground)
PS: My gate signals are 40kHz and TRACo dc-dc converter switches at 400kHz

Thanks


texts: Approximating the dirac delta function on LTspice to find the impulse response of a high pass filter

texts:
I have an assignment which requires me to find the impulse response of a high pass filter on LTspice. In order to do this the question suggest feeding a Dirac delta function as an input to a simple high pass filter circuit consisting of 100R resistor and 1uF Capacitor. Now I've tried a triangular pulse and square pulse with a high voltage and minimal rise and fall times but I don't quite get the expectedthe frequency response (the general frequency response of a high pass filter) when I take an FFT of the output voltage.
It would be brilliant if someone could show me the best way to approximate a Dirac delta function on LTspice. Any and all help is appreciated, thanks in advance.
High pass filter with simulation parameters for a square wave input:


texts: Switching in parallel high-capacity LiFePo4 battery packs during discharge cycle

texts:
I have two, possibly three 48V-nominal 50Ah Lithium Iron Phosphate battery packs used for E-bikes (16S cells, 2.5kWh capacity each).  The packs have BMS circuitry which limits discharge to 50A (through the 10Ga output leads) and also limits charging to 5A (via the thinner 18Ga leads).

I wish to discharge two or three of these packs in parallel to power a 48V sinewave inverter which would then charge my plug-in Prius car at a continuous maximum rate of 1350W (120VAC) for up to 5 hours.  The Prius battery pack accepts a charge of about 6kWh when fully depleted.

Question:  Is there any danger/concern in paralleling these packs for a full discharge cycle?  If I only parallel two packs instead of three the combined capacity of the pair will not be enough to fully charge the car, so one pack's BMS will shutdown first, leaving the other pack to supply the full current of roughly 30A to the inverter.  The question is, will the remaining active pack backfeed current into the one that's shut down?  I plan to test this with a much lower-current load to start out...


texts: Is it okay to make a loop of LED strips?

texts:
I have 10 m of RGB LED strips (common anode) and want to put it around my room. I realized on testing that the "far of" LED s were very dim compared to those that were "electrically" near the driver circuit. Would it be okay to loop back the common positive and ground to the starting point. Basically loop back the power and ground rails? Is there any problem if I am driving them with a PWM signal of around 1 KHz?
edit 1: I asked the last part because a loop would might create some EMI due to the 1KHz PWM signal running through it.


texts: Why so different lumen efficiencies between mains and 22V halogen?

texts:
I was looking for data about halogen reflectors I just bought. They are 50W, 230V.

On the package I read 320 lumen and that looked ridiculous to me, then I found this document by GE: Halogen Lamps Spectrum Catalog.

It states on page 100 that MR16 Start (normal reflectors, 12V) at 50W emit about 680 lumen, while MR16 GU10 (mains voltage) emit at 50W about 340 lumen.

Seriously? 7 lumen per watt?

Now I wonder why this big difference in the emitted light. Maybe because mains are sinusoidal and the lamp absorbs power even when the voltage is low, but maybe the temperature of the filament gets too low to emit properly. Still, this explanation seems odd to me, because thermal inertia should be enough to smooth the \$P=I^2\$ enough.


texts: How to use a subcircuit in capture / spice

texts:
I am wondering how to add an IGBT .subckt file to a schematic in Orcad Capture. I already found out that if you have an '.NIGBT' model, you can use the Breakout library.
But I cannot find out how to use models that are provided via a .subckt such as the one below from International Rectifier:

.SUBCKT irg4ph50ud  1 2 3
**************************************
*      Model Generated by MODPEX     *
*Copyright(c) Symmetry Design Systems*
*         All Rights Reserved        *
*    UNPUBLISHED LICENSED SOFTWARE   *
*   Contains Proprietary Information *
*      Which is The Property of      *
*     SYMMETRY OR ITS LICENSORS      *
*Commercial Use or Resale Restricted *
*   by Symmetry License Agreement    *
**************************************
*Model generated on Dec  2, 97
* MODEL FORMAT: SPICE3
*Symmetry IGBT Model (Version 1.0)
*External Node Designations
*Node 1 -> C
*Node 2 -> G
*Node 3 -> E
M1 9 6 8 8 MSUB L=100u W=100u
* Default values used in MSUB:
* The voltage-dependent capacitances are
* not included. Other default values are:
*   RD=0 RS=0 LD=0 CBD=0 CBS=0 CGBO=0
.MODEL MSUB NMOS LEVEL=1
+VTO=4 KP=0.5 LAMBDA=0 CGSO=3.65971e-05
RD 7 9 0.001
RS 4 8 0.001
D1 3 1 d4ph50u
.MODEL d4ph50u d
+IS=3.82367e-11 RS=0.105288 N=2 EG=1.19013
+XTI=0.5 BV=1200 IBV=0.00025 CJO=1e-11
+VJ=0.7 M=0.5 FC=0.5 TT=1e-09
+KF=0 AF=1
Q1 4 7 1 QSUB OFF
.MODEL QSUB PNP
+IS=1e-16 BF=10 NF=1 VAF=100
+IKF=1000 ISE=1e-11 NE=2 BR=1
+NR=1 VAR=100 IKR=1000 ISC=1e-11
+NC=2 RB=0.1 IRB=1000 RBM=0.01
+RE=0.001 RC=0.001 XTB=0 XTI=3
+EG=1.16989 CJC=3.64714e-09 VJC=0.878241 MJC=0.9
+CJE=7.29428e-08 VJE=0.4 MJE=0.9 TF=3.04597e-11
RDS 7 4 1e8
RER 4 3 0.01
RG 6 2 6.18923
RL 10 11 1
D2 12 11 DCAP
* Default values used in DCAP:
*   RS=0 EG=1.11 XTI=3.0 TT=0
*   BV=infinite IBV=1mA
.MODEL DCAP D IS=1e-32 N=50
+CJO=5.60567e-09 VJ=0.4 M=0.9 FC=0.5
D3 0 11 DL
* Default values used in DL:
*   EG=1.11 XTI=3.0 TT=0 CJO=0
*   RS=0 BV=infinite IBV=1mA
.MODEL DL D IS=1e-10 N=0.4
VFI2 12 0 0
FI2 6 7 VFI2 -1
EV 10 0 7 6 1
CAP 10 13 6.81948e-09
RCAP 10 14 1
D4 0 14 DL
VFI1 13 14 0
FI1 6 7 VFI1 -1
.ENDS irg4ph50ud


texts: Would a suitably placed inductor stop audio feedback whine?

texts:
To give some context, I am designing a cosplay armor costume that somewhat muffles everything that is spoken while wearing it.   I have a simple low power audio amp that I was intending to use to amplify my voice and place a small (3") speaker on the outside of the armor, theoretically enabling me to be easily heard outside the outfit without needing to really raise my voice.  However, because of the restricted possible range between the mic and the speaker, by the time the volume of audio from the speaker is at acceptable levels, it is evidently picked up again by the mic inside the costume, and produces an annoying squeal from the speaker that rapidly increases in loudness until the amp's volume is turned down, at which point the level of audio from the speaker is undesirably low.  The amp is a physically separate device from both the speaker and the (suitably biased) microphone, so I could potentially add some custom electronics to either location.  I cannot change any of the properties of the amplifier itself, which takes a line-in, and can directly drive a speaker.
Yes, I know there are commercial stormtrooper amps that likely do most of what I am wanting to accomplish here, but I'd like to see if I can work a solution out myself, and hopefully not have to splurge more than a hundred dollars on what amounts to nothing more than a voice amplifier.
And to that end, I was thinking of possibly using an inductor that coupled with the impedance of either the mic or speaker, depending on inductor placement, would have an L/Z time constant such that the cutoff frequency would be approximately 1.5khz, which is far enough above normal spoken communication that I am hoping it should not interfere with normal voice communication, and still below the frequencies of the squeals produced, which according to the decibel meter that I used to check, peak at well over 2khz.
But I am not sure if that will actually work, nor am I sure whether it would be better to place it on the input or output even if it did.


texts: I'm working on a computer-controlled indoor waterfall. One of the requirements is to be able to change the water pressure via computer interface. I've googled all day long and can't seem to find a valve that can be controlled via computer. Anybody happen to know of such a device and where I could find one?


texts: Effects of rapidly pulsing DC inductive load on solid state relays

texts:
I'd like to use some solid state relays to turn on and off a high voltage, low current DC inductive circuit (120-150VDC, 20-60ma). The SSR would only be switched on and off at a maximum of once every few minutes-- it would not be used for signaling.

-

(EDIT: Details about the SSR added below)

The specific SSR itself is a Fotek SSR-25 DD-- the DC 25A model sold here, rated between 5-220VDC and up to 25 amps. It's definitely a counterfeit, however, so it can only be trusted at up to around 10 amps according to my research (AC counterfeit versions were reviewed well here and here; I'd expect the DC version to have similar results, but I haven't found reviews for the DC version specifically). I can't seem to find a datasheet even for the "real" component, perhaps because Fotek never manufactured one named SSR-25 DD. The Fotek DC to DC SSR datasheet is here, rated up to 10 amps load for the 220VDC version.

Since I have such a low current requirement (60ma max), I felt comfortable enough to test these out for how inexpensive they are and spent $10 on a few after I originally asked this question. I will post results of my tests for posterity later.

-

The load is inductive. I've read about inductive AC loads potentially having issues with SSRs depending on the type of SSR, but I don't see anything about inductive DC loads thus far. This leads me to believe the issue must only be with AC circuits due to AC modulation, but I'd like to be sure.

1. The first question is simple-- would an inductive DC load have any issues running through an SSR?

The second and third questions are in regards to the signaling that will pass through the load side of the SSR after it is switched on. The circuit will pulse off and on at a speed of up to 45 modulations per second (45 baud, or up to about 1 modulation per 22ms; also remember that this signaling is being reliably generated by another component on the circuit, not the SSR).

2. If an SSR is rated to operate a load between certain voltages (5-220VDC in this case), when the circuit modulates between 0 and n volts, would the SSR effectively turn off and on even though the control circuit has never turned off, thus introducing a delay in each signal modulation?

3. Would an SSR having an inductive DC load modulating at a frequency like this cause any problems, particularly a delay or distortion in signaling?


texts:
I have a large shelf (like 5-10meters, or 15-30 feet long) which I want to put an LED in at every level. Thing like a positional system for a mini-library.
I have a litte problem to efficiently drive the LED's. So I figured wiring every LED to the main board would be a waste of cable.

I think that I could make a mini LED-driver board per self part, and then daisy chain these drivers and let them be controlled from the main board.

LED - Main Board --- LED-Self-Driver1 --- LED-Shelf-Driver2 --- ...
                     |- Shelf1, Row1      |- Shelf2, Row1       ...
                     |- Shelf1, Row2      |- Shelf2, Row2       ...
                     |- ...               |-  ...

A - or | should indicate the cable connection in the 'diagram' above. That would save me a lot of cable. :)

My question: What would be a good way to daisy chain these Arduino's? The space between the shelf parts (and the drivers) would be at most one meter and the chain connection should include the powering of the drivers. The connection speed should be around 1kbit's.

Would SPI do it? Maybe a Software SPI with slower frequency? How would you do it? Or is the connection scheme a stupid idea?

Thanks for reading and happy X-Mas :)


texts:
I'm having a problem in DipTrace. I'm trying to change the shape of the pads on the bottom layer. I have successfully created and had etched a similar PCB in DipTrace yesterday, and have followed the same rules today, but it just doesn't want to change.

On my previous PCB, changing pad properties changes both top and bottom layers shape etc, but this project, it seems that the shaped is locked on the bottom layer. No matter what pad property I change, the change is only reflected on the top layer.

Can someone point me in the right direction please?

Thanks


texts: Baud rate for Square Wave data signal via UART if frequency is given

texts:
I was trying to solve the 2013 paper set by ISRO for electrical engineers. Question no 13 made me confused.

So since Idle in UART is usually high and start bit is low, we can find the 8 bit data to be \$1010 1010 = (AA)_{Hex}\$ since it ends with a high stop bit, and because we observed a square wave we know the bits are alternating.

But when I tried to find the baud rate, which is same as the bit rate in this case since we have 1 bit for 1 symbol. I am getting 19200 baud, there is no option for this.

We see the square wave has frequency 9600 Hz, so we have 2 bits being send (2 symbol changes) happening in one cycle or in one time period.

$$ \text{Baud rate} = \frac{2}{\frac{1}{9600}} = 19200 \ \text{baud} $$

So I was wondering how I got this wrong. Can UART have high as the start bit? If so option B is the answer. Maybe I am counting the bits being sent incorrectly, is D the answer?

This is how I saw 2 bits being transmitted in one time period. We are sending the 8 data bits in \$ \frac{4}{9600} secs\$

I was also wondering why the data bits cannot be \$ 11001100 \$. I mean that is also a square wave right?


texts: Ground fault protection for fault on delta side of a wye-delta step down.

texts:
I have a distribution circuit with a primary 4-wire 21 kV and secondary 3-wire 12 kV circuit. The two winding transformer is a (grounded) Wye-(closed) Delta transformer. I know that if I have a ground fault on the secondary side of the transformer, I will not have a path for ground. I am requesting to add a grounding transformer to provide a source of ground fault current during line to ground faults.

My question is, would a ground fault on the secondary side be seen on the primary side of the circuit (after adding grnd transformer)? That is, will my breaker ground relay on the 21 kV side see a ground fault on that occurred 12 kV side?

Thank you!


texts: How to analyze this opamp circuit with logic gates, Zener diodes and transistors?

texts:
This is the circuit with this values:
 $$\text{Logic gate of CMOS,VTH=2.5v,VCC=5v,Vz=3.3v,Vd=0.7,VBE=0.7}$$:

The left
side is working like a SR FF , and the right side Schmitt trigger
comparator and I did calculate the VT1 and VT2 correct .

What is
unclear for me is:

how does the PNP and NPN transistor work?
where is the base resistor?
what is the state of transistor Q1 and Q2(saturation, active, off )?

In addition, I'd like to know

how the capacitor charging and discarging and why?
The target of the
circuit is to output triangle wave what is unclear for me is why the
capacitor will charge and discarge with constant current.


texts: How can a CPU deliver more than one instruction per cycle?

texts:
Wikipedia's Instructions per second page says that an i7 3630QM deliver ~110,000 MIPS at a frequency of 3.2 GHz; it would be (110/3.2 instructions) / 4 core = ~8.6 instructions per cycle per core?!
How can a single core deliver more than one instruction per cycle?

To my understanding a pipeline should only be able to deliver one result per clock.

These are my thoughts:

Internal frequency is actually higher than 3.2 GHz
Some parts of the CPU are asynchronous in a way a humble human like myself cannot understand
There are multiple concurrent pipelines per core
A pipeline can deliver more than result per clock, an instruction can skip pipeline stages and there are multiple prefetcher to keep up
I am missing something


texts: Find the transmission parameter A the circuit

texts:
My work:

I am trying this from hours by all method I am getting answer 1.5.But answer given is option (A).

Please help me whats the mistak I am doing?

  Method 1

Method 2


texts: What is the name of the mentioned component?

texts:
I have a pair of GRDE GL019 earbuds. One of those cheap ones, but fits me really well and has a great sound , hence i am taking so much pain to repair it.
I want to replace the mentioned/marked connectors in the picture, but dont know what are those called, and where can i find them online. These points are for contact charging the buds. BAsically, when i close the box the buds charge. So my guess is, there is some kind of spring mechanism inside those connectors whcih dont work anymore.. I can only see J1 and J2 (guessing those are just codes for connectors).
Any help would be really appreciated.
Thank you.
enter image description here


texts:
I found this video where a technician with a lot of experience seems to clean his PCBs using water, and then he just puts it in the sun so it can dry. I was just amazed to see the circuit keeps working as intended, he says he keeps doing this all the time and several times, however I doubt this is normal.

Which leave me some questions:

What are the recommended methods to clean huge PCBs like the one in the video?
What happens to charged capacitors when water shorts them out?
Solder joints do not get any kind of corrosion?
Is the antisolder mask waterproof?


texts: Whats the effect of a resistor inside the feedback of an active low-pass filter?

texts:
I'm working on the bias driver of an EEG system to remove the common mode signals from the channels. The output stage consists in a active inverting low-pass filter (I used an AD8606). Due to international medical standards it's mandatory apply a protection resistor to limit the current flowing through the body in case of fault. Depending of specific system and its stability requirements, this resistor can be placed inside or outside the feedback of the active filter (or also split).

In my case the system can work without stability problem either with the resistor inside and outside. But I have a strange behavior. If I keep the resistor inside the feedback most of the common signals disappear except for the 50Hz component, also improving the filter gain.

The first image shows the power spectrum of channels with a filter's gain equal to 1, with all the common signal present:

In the next image the effect of filter with a gain of 10 but the 50Hz component again present

But if I move the resistor on the outside (the red arrow in the schematic above describe the change) the 50Hz component disappear.

I know that maybe the context is too specific, but I'm wondering what are the consequences of putting the resistance inside the filter' feedback on its behavior? I know that there are no difference except for change the output impedance of filter.

Any suggestion on what's happening?

EDIT

Just to be clear, in the following figure you can see the model of the system applied on the user. All the parallel RC couples represent the skin/electrode interface and the circuitry on the left of the BODY block is the model of the EM interference which is the source of common signals.


texts: Voltage drop when connecting DC-DC booster XL6009 to my solar panel generating 10V constant

texts:
I have connected my solar panel (rated 6 V 3 W,) but it is generating approximately 10V.
This 10V is fed to an XL6009 to generate ~15-166, which is further fed to a 4S BMS to charge.
I checked that the open circuit voltage is 10 V and when I connect it to the XL6009, the 10 V input it drops to 3 V.
Please suggest and advise.


texts: How do I EM-Extract a subcircuit and define a different em/drawing-layer than the original circuit in AWR?

texts:
I have a 4-layer project in AWR/MWOffice and have built a parameterized microstrip inductor schematic (named "spiral") with a "Line Type" of layer1 that I wish to reuse on another schematic as a subcircuit (SUBCKT) on layers 1,2,4.
When I place "spiral" as a subcircuit on another schematic ("sch1") and assign that SUBCKT shape's "Line Type" to be different than "spiral" was drawn, EM extraction puts it on the layer where "spiral" was drawn, not where the SUBCKT is drawn.
(By "drawn" I mean right-click the shape in Layout View, select Shape Properties, and select the "Line Type" in the "Layout" tab; I know my EM layer mappings are correct because I can change the line type of "spiral" and EM extraction puts it in that em-layer, but let me know if there is an LPF trick I should try since I can't get multiple SUBCKT's to extract into different layers).
Strangely, the drawing shape color/pattern that I assigned for layer1 always shows in "sch1" even though the SUBCKT element line-types are set to layers 1,2,4. However, if I right-click on each SUBCKT's shape properties, each SUBCKT's "Line Type" is shown correctly. Here are the details:

The microstrip schematic ("spiral") layout is all drawn on layer1
Another schematic ("sch1") has the following subcircuits:

SUBCKT S1: NET="spiral", shape layer=layer1
SUBCKT S2: NET="spiral", shape layer=layer2
SUBCKT S3: NET="spiral", shape layer=layer4

Is there a way to reuse my "spiral" subcircuit on different drawing layers so that it shows correctly both in the "Layout View" and is placed correctly in the EM extraction?
Let me know if there is anything else you might need to help troubleshoot.
Thank you for your help!
-Eric


texts:
I have a quite powerful DSO, MSO2024 from Tektronix with SPI interpreter on board.
Any idea to convert USB line levels to SPI so I can watch them with this scope?


texts: In VHDL 2008, can a type from a package with generics be used for a port signal?

texts:
So I can define a package with a generic - in this case, the package takes a size as a generic and defines a vector type of that size:

library ieee;
use ieee.std_logic_1164.all;

package vector_package is
    generic (
        size : integer);

    subtype vector_t is std_logic_vector (size - 1 downto 0);
end package;

Now I can instantiate that package within an architecture to create a signal of that vector type:

entity foo is
end entity;

architecture rtl of foo is
    package vp_4 is new work.vector_package generic map (size => 4);
    signal vector : vp_4.vector_t;
begin
end architecture;

But what I want is to use the vector type for a port signal. I would have expected to be able to do something like this, but it does not appear to be valid VHDL 2008:

package vp_4 is new work.vector_package generic map (size => 4);

entity bar is
    port (
        signal vector : out vp_4.vector_t);
end entity;

This is rejected by ModelSim 10.2c with the message (vcom-1136) Unknown identifier "vp_4". in the line containing signal vector : ....

Is there a way to use the type from the package for a port signal? I am aware of unconstrained types as an alternative, but they do not fit my requirements in the actual use case.


texts: Reduce BOM Lines or reduce BOM cost? How to make production cheaper?

texts:
We are designing a product that will hopefully sell many thousand units, and now I am at the stage of specifying what parts to use.

We require three inter-board connectors, one with 10contacts and two with 4 contacts. Instead of using two different sizes, we can just use three of the ten contact connectors. The ten contact connectors cost 30% more than the four contact connectors at volume. So the obvious choice is to spec for two different parts on the BOM.

But more BOM lines increases the PCBA assembly cost, and increases the inventory of components we have to hold.

What has the greater effect on unit cost, reduced BOM lines, or reduce BOM cost?


texts:
I want to connect chips that use SPI protocol to communicate (To be specific those chips are ws2801) the distance may reach 100 meters.

How can I solve this issue? After a few days of searching I've come up with two solutions:

Using RS485 conversion IC's.
Shifting the voltage to 12V so that it's more immune to noise. I'm not sure how much delay the conversion makes.

Is there any other practical solution?


texts: What is the limiting factor for a CAN bus to exceed 1Mbps bandwidth?

texts: Why can't CAN baud rate increase beyond 1Mbps


texts:
I've implemented the low lever drivers of the fatfs. I tried to write some txt file to  an SDHC card, but I can never initialize the card. MCU is STM32F103C8T6. I'm using CubeMX with HAL libraries and using SPI to communicate. I've debugged to find out that during wait_ready(), the card is supposed to return 0xFF to indicate it's ready, but in my case it returns 0x00, no matter how long I wait. If I omit the the wait_ready() and send the IDLE command(CMD0), I still get 0x00 as a response. I enabled the internal pull-up for the MISO pin, didn't help. The interesting part is that, when I probed the MISO pin right after its initialization, I noticed it was at 0.01 volts. It seems to me that it was not being pulled high. I also made sure that SPI clock speed was in between 100khz-400khz range.

I managed to write to the card by connecting it to my computer. Also managed to write with an arduino. Following are the relevant parts of my code. You can ignore the timeout implementations.

static BYTE wait_ready(void) {
Timer2 = 255;
rcvr_spi();
do
    res = rcvr_spi();
while ((res != 0xFF) && Timer2--);

return (res == 0xFF) ? 1 : 0;
}

void deselect()
{
    HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_SET);
    xmit_spi(0xFF);
}

uint8_t select()
{
HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_RESET);

xmit_spi(0xFF);
if(wait_ready()) return 1;
deselect();

return 0;
}

DSTATUS USER_initialize (
BYTE pdrv           /* Physical drive nmuber to identify the drive */
)
{
  BYTE n, ty, ocr[4];

if (pdrv)
    return STA_NOINIT; /* Supports only single drive */
if (Stat & STA_NODISK)
    return Stat; /* No card in the socket */

deselect();

//send_initial_clock_train();
for (int i = 0; i < 10; i++)
    xmit_spi(0xFF);

HAL_Delay(10);

ty = 0;
uint32_t tick = HAL_GetTick();

if (send_cmd(CMD0, 0) == 1) { /* Enter Idle state */
    Timer1 = 100; /* Initialization timeout of 1000 msec */
    if (send_cmd(CMD8, 0x1AA) == 1) { /* SDC Ver2+ */
        for (n = 0; n < 4; n++)
            ocr[n] = rcvr_spi();
        if (ocr[2] == 0x01 && ocr[3] == 0xAA) { /* The card can work at vdd range of 2.7-3.6V */
            do {
                if (send_cmd(CMD55, 0) <= 1
                        && send_cmd(CMD41, 1UL << 30) == 0)
                    break; /* ACMD41 with HCS bit */
            } while (Timer1);
            if (Timer1 && send_cmd(CMD58, 0) == 0) { /* Check CCS bit */
                for (n = 0; n < 4; n++)
                    ocr[n] = rcvr_spi();
                ty = (ocr[0] & 0x40) ? 6 : 2;
            }
        }
    } else { /* SDC Ver1 or MMC */
        ty = (send_cmd(CMD55, 0) <= 1 && send_cmd(CMD41, 0) <= 1) ? 2 : 1; /* SDC : MMC */
        do {
            if (ty == 2) {
                if (send_cmd(CMD55, 0) <= 1 && send_cmd(CMD41, 0) == 0)
                    break; /* ACMD41 */
            } else {
                if (send_cmd(CMD1, 0) == 0)
                    break; /* CMD1 */
            }
        } while (Timer1);
        if (!Timer1 || send_cmd(CMD16, 512) != 0) /* Select R/W block length */
            ty = 0;
    }
}
CardType = ty;
deselect(); /* CS = H */
rcvr_spi(); /* Idle (Release DO) */

if (ty) /* Initialization succeded */
    Stat &= ~STA_NOINIT; /* Clear STA_NOINIT */

return Stat;
}

static void xmit_spi(BYTE Data)
{
 while (HAL_SPI_GetState(&hspi1) != HAL_SPI_STATE_READY);
 HAL_SPI_Transmit(&hspi1, &Data, 1, 5000);
}

static BYTE rcvr_spi(void)
{
 unsigned char Dummy, Data;
 Dummy = 0xFF;
 Data = 0;
 while ((HAL_SPI_GetState(&hspi1) != HAL_SPI_STATE_READY));

 HAL_SPI_TransmitReceive(&hspi1, &Dummy, &Data, 1, 5000);

 return Data;
}

What am I doing wrong?


texts: Does a resistor in an AC circuit produce the same heat as in a DC circuit?

texts: Does a 1k ohm resistor produce the same heat in a AC circuit which has an rms voltage of 10 volts (60 hz.) as it would in a 10 volt DC circuit?


texts: What role does a FET play when working with GPIO pins on a Raspberry Pi?

texts:
I recently asked this question where I'm trying to wire up this momentary switch to my Raspberry Pi 1 Model A such that:

The switch is normally open; and
When pushed down: it closes the circuit, lights up and fires a HIGH signal to a GPIO input pin (GPIO 04 in my case); and
If needed, I can make the GPIO 07 pin an output pin and make it available to help run the light/LED inside the switch, but not sure if that's needed

The answerer to that question provided the following solution:

simulate this circuit – Schematic created using CircuitLab

I'm just wondering what function this M1 Logic Level FET is performing in the circuit (e.g. why is it there?! why is it needed if I can control signals in/out of the GPIO pins?), as well as confirmation that I could (or can't!!!) use this one to get the job done.


texts: Recommendation for low cost RFID receiver (approx 0.5 meter range)

texts:
I am looking to build a low power, short distance identification system. The distance would be around 0.5 meters. I've been looking at RFID, and it looks like the perfect solution. I've been playing around with this device.

It works great, except I only get a few inches of range. I am wanting to increase this range to about 0.5 meters. What would be the best next step to take? I've been reading about increasing the power of the RFID receiver, but I'm not sure how best to do this.

This system uses the 13.56 MHz frequency, and I would like to keep using it. Eventually, I want to use these RFID tags.

If anybody can at least point me in the right direction, that would be greatly appreciated!


texts:
Is there some rigorous treatment of convergence issues in transient analysis?
I am using LTSpice. In transient analysis with maximum time-step is used. Fundamental oscillatory frequency of analysed circuit is under 100MHz.
I undestand that implicit trapezoidal integration can produce nonphysical ringing. On the other hand Gear algorithm of a given order introduce damping which is also nonphysical. So I tried Gear, trapezoidal and modified trapezoidal implicit integration schemes implemented in LTSpice.
But none of the methods can eliminate these micro-transients.
they look like this

and also note, that they start to showing up after some time.
But I have suspect these are not real oscillations. With Gear I got less of these events.
It is quite simple model of circuit with ideal components (low damping). Its unlikely that real-world circuit will have similar properties, but since I am processing large amount of such transients in Matlab, I need to be sure that I can remove these (using wavelet transform reconstruction for example) as they have no significant effect and are purely numerical product.
What is your rule of thumb for situations like this? Whenever modeled circuit contains LC tanks with much lower frequency than its artefact?
EDIT

Using equivalent series resitance of 0.1 ohm for shunt capacitances still produce these transients. One can be spotted right on the startup


texts: Powering two 5v 1amp devices from one battery

texts:
I'm looking to power a rPi Zero W and a tomoko 87 mechanical keyboard both of which take 5v power (I know the rPi needs 1amp, not sure about the tomoko 87 as the description simply says "5v DC"). I'm thinking of using the Powerboost 1000 charger/recharger from adafruit and a Lithium Ion Polymer Battery - 3.7v 2500mAh to power them. Do I need to use 2 batteries? Or must I use 2 Powerboosts? Or do I need to use two batteries and two Powerboosts?

Thanks!


texts: The simplest way to keep n-channel mosfet saturated by positive feedback

texts:
Actully it will be one way switch for a lamp based on photo-resistor input:

To keep the mosfet saturated in the moment it turns on I need positive feedback. How to get it in the simplest way? I can think only about this option below, but is it the simplest solution?


texts: China bluetooth modules and RS232c with RTS/CTS

texts:
I've been having a lot of fun (mostly using other people's instructions) with some of those cheap bluetooth modules (via ebay specials) from China. I'm just getting my feet wet learning the actual 'design' aspects of electronics, however.

I'm wondering how to take full advantage of the CTS and RTS lines on these modules and if anything needs to be done to make them compatible with older devices expecting an RS232c standard. The bluetooth modules seem to conform to the UART standard and voltages (3.3v vs 5v)

I note in the specs they give you, that they use a modified darlington style circuit off the TX line, presumably to hop the 'high' voltage on the TX line up to the 5v that the RS232 side expects.  What I'm wondering is if I need to do something similar on the CTS and RTS lines if I wish to use those as well?  One of the devices I am trying to connect to claims in it's instructions to use both of these connections.


texts: Charging batteries directly from 117 volt wall socket

texts:
It has occurred to me that almost no battery charger would be required if the battery pack was of the same voltage as grid supplied power.

I build electric bikes, and the voltage on these has been ever increasing for obvious reasons (smaller diameter cables and connectors vs high current, over volting motors for additional speed, lower current mosfets required in the speed controls Etc.).

90 volt systems have now become fairly common.

Now I was pondering, if we were to increase the battery pack up to, say, 32 LifePo4 cells (3.6 volts constant voltage charging) couldn't I just rectify the 117 volt grid power and charge directly from that?
I know voltage will shift with the rectification, but I don't know the specifics. In either event the number of cells charging could be adjusted to the closest match of what was coming out of the wall.
Yes the final constant current phase of charging would be skipped, but this is a negligible amount of power anyway.
Am I missing something?
Is there a reason this won't work?


texts: Which push button ratings should be considered due to its data-sheet

texts:
I'm planning to use the following normally on push-button switch: http://uk.rs-online.com/web/p/push-button-switches/1336473/
According to the following data-sheet: http://uk.rs-online.com/webdocs/137f/0900766b8137f3b1.pdf it says:

Contact Current Rating: 650 mA @ 30 V dc

But in my application the button will be pushed less than a second where the voltage across it will be 48V and the current through it will be 48mA for less than a second.

Should I look at the power (P = I*V = 30*0.65) in this case, or I shouldn't use it since it says 30V in its ratings?

Edit:

Push-button controls 48V supply and is normally open. Here is the part of the circuit where the switch is in LTspice(I didn't check this in scope):

Points A and B represents the terminals of the push-button.
Below green plot is the potential difference across the switch terminals A and B:

And the blue plot below is the current through the switch:

And finally, I zoom to see both the voltage across the switch and the current through the switch:

What I understand from the above plots, the switch is exposed to 48V whenever it remains open. The moment the switch is closed, the potential difference drops quickly in nano-seconds to zero volts and micro-ampere level current passes through it.

What I understand from the first answeers is that, the problem with the following push button: http://uk.rs-online.com/webdocs/137f/0900766b8137f3b1.pdf is that if I use them in my circuit, they will be exposed to 48V all the time when the switch is normally open. So the real problem does not occur the moment I push the button but it occurs when the push button is not pushed at all.

Is that correct?


texts:
I got a handful of these chips at my job when they were being thrown away. They are Programmable Logic Devices. I found a datasheet online from 1997 that says that xilinx bought the ip for a similar chip, but the website is dataman.com and I don't know if it is a reliable source, and the information is 20 years old.

I've done a little bit of hobby fpga programming with verilog and I wonder how similar this procedure is, if it is similar at all.

I've found atmel, academic, wikipedia, hackaday, and instructablestutorials but they are all about either chips that come on a board with some sort of serial port or else they are circuit diagrams and I think they expect someone with a different education than mine to take the next step.

update:
found one two three videos on youtube and skimming them shows some talk about the circuit diagrams. Ill come back if I find an answer and maybe answer this question myself.


texts: Transformer Inductance not taken into account?

texts:
When modelling an ideal transformer, why do we not consider the inductance of the primary and secondary windings of the transformer. Wouldn't this inductance affect the current pulled from the source?

(By ideal, I mean no leakage reactance, winding resistance, iron/copper losses, no magnetizing current.)

Why do we model the ideal transformer with no magnetic properties (i.e. inductance)?


texts:
Hi, I saw this online and I'm a bit confused why they chose B as the correct answer.

My answer was:
The DC voltage gain is 20dB, so -3dB frequency will occur at 17dB gain. 17dB in normal gain is 7.07945.

GBP = (Gain)(BW)

BW = GBP/Gain

BW = 1MHz/7.07945 = 141253.7545Hz

This is option D.


texts: Calculating bits/sample from a digital MEMS microphone

texts:
I'm thinking of using a digital MEMS microphone in a project - looks like it would save on some parts: no need for an amplifier and ADC. The output from the microphone is PDM and I'd need to convert it PCM for any useful processing.

Say I'd like to work with 16-bit, 48 kHz audio. Seems like the answer is to oversample 64x by clocking the microphone at 3.072 MHz, then low-pass filter and decimate the output. What's the effective number of bits (ENOB) I get out of this?

If the microphone datasheet claims 60 dB SNR (just less than 10 bits), and 64x oversampling gives me 2.5 bits (1 bit for every 4x oversampling), then I'm only getting in the neighborhood of 12-13 bits. Is this calculation right?

FWIW, the parts I was considering are http://www.mouser.com/ds/2/720/DS45-1.01%20AKU240%20Family%20Datasheet-552987.pdf or http://www.mouser.com/ds/2/389/DM00121815-524679.pdf. They seem fairly close in specs.


texts: Characteristic Impedance without transmission lines

texts:
let's consider this three port power divider:

I saw somewhere that the reflection coefficient Г11 can be calculated with the formula Г11 = (Zin - Z0)/(Zin + Z0), where Z0 = 50 Ohm.

Now my questions are:

1) What is Z0? There are no transmission lines here. I thought that maybe Z0 is like a reference value, which can be used in any kind of network. But I need a confirmation.

2) If the previous hypothesis is true, how can the entity of wave reflection (represented by the value of Г11), which is something physical, depend on the arbitrary choice of the value of Z0?


texts: Pi Filter Design / Realization with 915MHz u.Fl

texts:
I'm putting a u.Fl connector into a new LoRaWAN design (915MHz). Apologies ahead of time if the scope of my questions are too wide for one post, but I think it's all closely related.

I'm going to locate the connector quite close to the antenna pin of the module I will be using; maybe a trace length of 250mil at worst. I'm looking around the web it seems like a good practice to include a π-filter in series with the antenna trace. I've gleaned that it's a CYA-strategy if you find a problem during certification testing to have an out that you can tune the filter if your emissions are failing; and it seems like generally you just DNP the capacitors in the filter as a first pass. So I have a couple of practical questions about this implementation.

How much does this matter for 915 MHz / should I even put it in at all?
The guidance I've seen is pretty wishy-washy about component values, but, this calculator seems to think about 5nH is what the inductor value should be for 50-ohm characteristic impedance in and out at 915MHz. Not sure what Q-factor is there so just accepted the default of three. Does that pass the sniff test?
Should the filter be located closer to the transmitter or should it be closer to the antenna, or (it would seem unlikely to me but) somewhere in between? At the total distance I need to travel, it seems like it's probably irrelevant, but I thought I'd ask.
How much does the physical form factor of the components in the filter matter? Is it OK to use 0805 parts? 0603? 0402? In my mind bigger is better for reliability in manufacturing, but I can imagine parasitic inductance or whatever being a factor with bigger geometries. Again, is this something to be concerned about at 915MHz?
As far as the trace to the u.Fl connector goes, I could make a microstrip co-planar waveguide for 50-ohms. Using this calculator I came up with 18mil (0.4572mm) width, 10mil (0.254mm) gap, using relative dielectric constant of 3.9, and a dielectric thickness of 9mil (0.23mm) for this 4-layer design with a ground plane directly below the antenna feed trace. put ground stitching vias around the feed trace, and cutout the ground (and other) plane directly under the u.Fl connector "slot" where the coax connects as shown in below recommendation I found. Again, just wondering if I'm overthinking it.

ref * note, I'm treating this as a generic reference, not a specific part I'm using.

Update #1

I went ahead and routed a feed line through a Pi-filter, using 0603 parts, here's what it looks like:


texts:
I'm trying to build Sparkfun's sound sensor and testing the first stage only. Here's the first stage:

If I scope before C2 and at Pin 1, I get the following when I scream at it:

where Ch1 is the mic input and Ch2 is the opamp output. As you can see, the gain is just 1x where it should actually be 100x.

Here's my breadboard:

Am I missing something here? Shouldn't I get a 100x gain? I'm using a LM324 (with 5V) rather than a LMV324, but I think they're essentially the same.

Thanks


texts: which kinds of electrical equipment need a pure sine wave inverter to work correctly?

texts:
I am planning to purchase a good inverter, and pure sine wave inverters cost about 3 times as much as modified sine wave ones of the same power. I am thinking about a 2000W continuous/4000W peak inverter 12/24VDC -> 230VAC.

Which commonly used equipment requires a pure sine wave, and what kind of equipment will be equally fine with a modified sine wave?

I am especially wondering about compressor and absorption refrigerators, dehumidifiers, electric drills, fans, microwave ovens, common power tools and kitchen tools. Purely electronic, computer and lighting equipment will not be used through this inverter, as these will have dedicated low-voltage DC-DC converters straight from the battery.

Are pure sine wave inverters any more efficient then much cheaper modified sine wave ones, in terms of input battery consumption per 230VAC output power?

Do there exist inverters which can accept a wide range of input DC voltage, for example will work on all of: 12V, 24V and 48V DC?


texts: Measure a power supply voltage with floating ground

texts:
I'd like to measure the output voltage on a power supply with a ADC and a micro-controller. The ADC is powered from a different source and the grounds of the power supplies are not connected. How can safely I measure the differential output voltage of the power supply? I'm sorry if this is a standard question, but I can't find a simple solution.

Edit in response to the comments:
The voltages I want to measure range between 0 and 14V. Precision is not important (a few percent). Frequency of measurements is low (about 1Hz). No high frequency components present.


texts: I need help getting my computer to talk to my Arduino Uno

texts:
I've recently jumped on the Arduino bandwagon and am attempting to upload my very first sketch to my Arduino Uno installed on COM port 3. However, I get errors that another device is using COM port 3 and I need to disable that device.

Specs:
Win XP, all current SPs.
Arduino drivers 1.0.3, dated 12/10/2012, downloaded 12/25/2012.
Drivers installed successfully without error messages.
Windows Device Manager shows Arduino Uno as the device on COM3.
The Uno is connected via USB.
The status bar at the bottom of the Arduino Software window indicates Uno @ COM port 3.
The Arduino software preferences are set to Arduino Uno (as opposed to one of the other form factors...Duemilanove, etc.).

I can write and compile sketches just fine. When I try to upload, compilation happens fine, but it'll eventually crap out telling that COM3 is in use by a device, and I need to stop that device and try again.

I feel like I'm travelling back to the early 90s and need to manually fix contentious COM ports...a phase of reality I never wanted to go back to...and have been spoiled by plug-n-play to the point where I've forgotten most of what I know about configuring ports from the command line...what is what I suspect I may need to do.

I've not found solutions in Arduino's help, Arduino's forums, or LadyAda.net's troubleshooting guides.

Anyone ever encounter this situation before or have any advice on how to counter it? This MAY be a more appropriate conversation for SuperUser...so if an admin wants to move it...


texts:
I am trying to stop power feedback on a 12volt car lighting circuit,
actually the 2 indicators that feedback from one side of flasher unit.
My question is what DIODE do I need for this, I have 1N4001's but I think the
1A rating won't work for long as 1 indicator bulb is 21watts which is 1.75A,
so 2 would = 3.5A is this correct? Thanks!


texts: Can I use a mosfet to discharge quickly a capacitor without resistor?

texts: I have to monitor a PV cell with a capacitor and to discharge I was thinking about using a mosfet whithout resistor to do it, whithout time constant. This, produce a short circuit when the discharge is on. Could I do that? What happen with the energy ?


texts: How to store 8 bit character in 32 bit Data Flash memory?

texts:
Is it possible to store 8 bit character to 32 bit Internal Data Flash in the Microcontroller by just using only 8 bit of space for each bytes?,by using a combination of 4 bytes which can be also recovered as individual bytes later.
I'm using Nuc240 (ARM-M0) Microcontoller with 32 bit Data Flash and 512 bytes erase limit,read write limit is 32 bit.
Please explain a code template if possible.


texts: Is it safe to sleep in the same room with a car battery?

texts:
I sleep in the same room with 2 car batteries. I'm not a battery person so I don't know what type they are. I tried looking for voltage but didn't find it printed on the battery. They're standard acid batteries, I use them to power LED lights and charge a phone/laptop.

I've been told they emit dangerous chemicals and it's not safe to sleep in the same room, is this true?

I only found one other thread similar to this, but it was about deep cycle batteries, I don't think those are the same as car batteries.


texts:
I am trying to use an LM2596-adjustable to make an inverting Buck-Boost power supply as per below:

The circuit requires a voltage divider that is used to adjust the output voltage. In the diagram, the resistors R4 and R3 somehow adjust the output.

In my application I have not used C1 or R2; the ON/OFF pin is just connected to the output.

If I do not connect any resisters, just connect the feedback pin to ground, I get -1.23v output, as expected.

My question is what values to use for R3 and R4 to get -5v output.

Thanks for any ideas.
Bob


texts: If I need to access memory cell by cell, should I shift or index?

texts:
I have a piece of memory which I need to access cell by cell:

parameter RAM_LENGTH = 1024;
reg [7:0] mem [RAM_LENGTH - 1:0];

I need to iterate cells sequentially. It looks like there are at least two ways to do this. The first approach is to index memory as if it were C array of bytes:

reg [7:0] ram_addr = 0;
reg [7:0] current;

and then

current = mem[ram_addr];
ram_addr = ram_addr + 1;

This is cheap for CPU. But what if Verilog builder will attempt to build a 1024 channel 8 byte width multiplexer for me? This would be a digital circuit of tremendous size that this memory may not deserve. Or is the Verilog builder smart enough to implement access by index more reasonably?

The alternative approach would be to shift the cells every time the value is needed:

current <= mem[0];
for (i = 1; i < RAM_LENGTH; i++)
  mem[i] <= mem[i-1];

in this case, I would hope from the builder to generate a shift register rather than overgrown multiplexer, as all values that define the loop are constants.

Which approach is more reasonable and would be typically used by an experienced Verlilog developer?


texts: Why do different resistors of the same power rating burn out / not burn out?

texts:
I have a circuit board for a small LED light, which comes with an annoying strobe mode. To disable this I have found that I can wire a resistor from a pin on a chip
to ground and the LED will stay in the always-on mode that I want. I'm trying to find the lowest resistance that the circuit board will tolerate (if it is too low, the LED turns blue and dims, and chips begin to smoke)

I started with a 1K 1/4W resistor and that worked but was much dimmer than I wanted. I tried a bunch of other resistors (all 1/4W) down to < 50 ohms.

Some resistors, or combinations of resistors, smoke and turn black (although they keep working) such as:

1x 47 ohms
1x 22 ohms
1x 22 ohms, 1x 10 ohms (wired in series)

However, some resistor combinations work fine e.g. 2x 22 Ohms. I don't understand this as I thought the reason the resistors are burning out is due to their power rating being too low, but if that were the case any combination of resistor would burn out as they are all 1/4W.

So I measured the voltage from the pin to ground at 7V (makes sense as the power source is 11-12V) and I measured the current at 2A (with my multimeter in 10A mode and my probe in the 10A port). But that comes out to 14 watts which should instantly blow any resistor I wired in.

It is of note here that, when I measured the current using my multimeter, the circuit board didn't tolerate it (as described at the beginning) presumably because the multimeter offered little resistance in current measuring mode.

Could someone please clarify what I'm missing here as my observations don't seem to match my measurements at all. Sorry for any obvious or stupid oversights as I do not yet understand how the different mechanisms of electricity work.

Here is a picture of the board I am working on:

The resistor in that picture is 47 ohms (though it measures 1.1K when the board is powered). The voltage across the resistor is 7V giving me a calculated current of 140mA and power of just under 1 watt.


texts:
Since I've started electronics I'm using this kind of board for permanent projects:

But sometimes it's a bit annoying, especially when I need a line going from the top to bottom of the board.  I've seen this kind of board:

My question is, how can I cut the strips?

By cutting the strip I don't mean cutting the board itself, just the copper strip. I've tried with a precision knife but I'm not sure about the method, the blade gets damaged really quickly and it's really hard to cut the copper.


texts: I understand the difference between a VIA in a pad and Breakout VIA but why not just use VIA in a pad since it saves space?


texts: Reading a CT with burden resistor and voltmeter, why am I getting this reading?

texts:
So I have hooked up a 50:5A CT, with only the hot wire going through its center. I put a 1 Ohm burden resister between the legs of the CT and then measured the voltage on each side of that resistor.

The primary is 120V @ 60Hz.

Since I used a 1 Ohm resistor, the voltage reading should be roughly equal the the current across the CT. I read 183mV, so I would expect ~180mA, which equates to about 1.8A on the primary wire going through the CT.

Two separate clamp-on amp probes both read 3.3A on the primary. I'm confused as to why my voltage reading is not more like 330mV. What am I doing wrong here?

Note: My meter says that the actual resistance value of the resistor is 1.1 Ohm.


texts: What is the minimum sampling rate for QPSK or what is the bandwidth of QPSK signal?

texts:
Consider  we have created a QPSK signal with a carrier frequency 100kHz. Before applying matched filter or demodulation we need to take sampls from the received signal. So what is the minimum sampling rate we must have? Cosider that somehow we have perfect synchronization and there is no drift of the carrier.

Any help would be apreciated.

I have asked this question (for more attention) in

https://dsp.stackexchange.com/questions/59003/what-is-the-minimum-sampling-rate-for-qpsk-or-what-is-the-bandwidth-of-qpsk-sign


texts: A question about inductive kick and the current voltage equation

texts:
In the book The Art of Electronics the author writes the following when trying to explain the inductive kick:

And then he mentions when the switch is opened abruptly, the inductor tries
to keep current flowing and damages the switch if no flyback diode is used. And that differential equation formula shows that large peak in voltage.

So far I understand his point. But the same logic applies when the switch is closed because dI/dt again can be large.

It seems like something is missing here to differ between what happens to dI/dt in case of switch being closed comparing to the switch being opened. How can we have a more clear insight about this? Why theres is no large voltage in case of the switch is being closed? How can the difference between opening and closing be mathematically demonstrated?


texts: Removing noise from ADC for STM8S 8-bit microcontroller

texts:
I have implemented ADC for STM8S1003, but looking for a way to reduce the noise on he signal.
There's no offset but the ADC varies 50 digital levels for each analog voltage input.
I'm reading a DC voltage from a wearable biosensor, the input ranges from 0-5V with sampling frequency of 444 kHz. I'm mearing the digital output.
What are the most efficient ways to reduce such an error?


texts: What is the reason that the value "47" is so popular in electrical engineering?

texts:
We often see component values of 4.7K Ohm, 470uF, or 0.47uH.  For example, digikey has millions of 4.7uF ceramic capacitors, and not a single 4.8uF or 4.6uF and only 1 listed for 4.5uF (specialty product).

What's so special about the value 4.7 that sets so far apart from say 4.6 or 4.8 or even 4.4 since in the 3.. series we usually 3.3,33, etc.  How did these numbers come to be so entrenched?  Perhaps a historical reason?


texts: How to implement a dirac delta as input signal for this system

texts:
y[n] = b0x[n] +b1x[n-1]

I have this MA filter in matlab as following

 load handel;
 x = y;

 b0 = 0.5;
 b1 = 0.5;

 N = length(x); % Length of input signal
 y = zeros(1,20); % Allocate space for output

 y(1) = b0*x(1); % First sample, assuming x(0) = 0
  for n=2:N % Remaining samples
    y(n) = b0*x(n) + b1*x(n-1);

  end;

 soundsc(y,Fs);

I was asked to create an input signal x[n] = dirac[n] where i save the x[n] for n = 0...19 in a vector and plot both signals in the same window for axis ([-1 20 ,0 1.5]).

I have tried so far that the new signal should look like this y1(n) = b0*dirac(n) + b1*dirac(n-1) but not sure if this is the right way or I maybe just not understood something?


texts:
Using LTSpice I'd like to simulate a L-C parallel resonant circuit; I'd like to check its .tran behavior, but I don't know how to simulate a frequency variable voltage source similar to a Frequency Signal Generator in which I turn the frequency value to look for the tuning value.
How can I do ? Is it an example I could use to do it?


texts: What is "trunc" in VHDL: numerical example

texts:
What does it mean ?
integer(trunc(log2(maximum(coeffs))));

I have found it in a filte implementation here. It is given some description:

-- Determine the optimum power of two scaling for filter coefficients
-- to make the fixed point representation with minimum leading zeros

let say, the part log2(maximum(coeffs)) = 4,856  , what will VHDL give as trunc(4,856)?


texts: Adding more LEDs to a current regulating circuit

texts:
I am modifying a current regulating circuit that was designed to power three LED lights (see figure below). The circuit is designed to maintain current through the LEDs at 1A. The LEDs should be off when no PWM signals are input (the PWM signals are sent by an Arduino Mega). In the diagram, SJ1 SJ2 and SJ3 are regular BJTs and BJ1 is a power BJT.

I now want to power six LEDs instead of three. Is it as simple as adding three more LEDs in series with the original three? Or do I need to modify components of the circuit?


texts: What's the simplest way to calibrate a thermistor?

texts:
As a hobbyist who don't have access to lab equipment, it really seems impossible to me to be able to calibrate the thermistor that i have.

Of course there are calibrated temperature sensors like DS18B20, but thermistors specially on slow MCUs like Aruino UNO (compared to new MCUs) are snappier.

What options do we have for calibrating a thermistor without using lab equipment?


texts:
In this article the author dissects a radio-controlled clock that syncs with the NIST transmitter, WWVB, in Colorado.  The radio receiver seems to be a single integrated unit:

Of special note is that the author is able to get a binary signal out of the little Temic U4226B IC, which could presumably be processed by a microcontroller.

I have seen this (or something very similar) for sale at Sparkfun but they are no longer available.  In particular, the ferrite-core wound antenna is common between the two setups.

What is required to receive the signal that WWVB broadcasts?  In other words, what is the circuit doing to pull the signal out of the air and convert it to binary logic?  In particular, what is special about the antenna (number of windings, materials, etc) that tune it to the 60kHz signal?


texts: RFID (13.56MHz) tag properties depending on read distance

texts:
In a reader design i experiencing some problems with RFID tags. I've evaluated the different tags, and they all are made equally - the tag size, tag chip type, antenna and antenna geometry are perfectly identically, so no problem of dis-alignment or obvious visually identifiable problem with the tags. In a bag of 1000 Tags, the quality is very mixed, ranging from not working at all to medium performance and exceptional performance
The following test fixture was made:

NXP CLRC663 reference design board (to exclude problems with the custom reader)
printed holder for the reference board with alignment posts for a slid-able tag holder (to ensure same position over reader)
printed distance plates to rise tag holder from reader antenna
testing a large number of finished tags (key fob like), as well as bare antenna coils with tags

All tags reading 8mm or more were accepted as "working". There are around 60% working. The other 40% are reading below 8mm down to zero. The tags deviate in readability distance, for example tags that read >8mm range from some that read to 8.5mm, and some that read to 16mm. Same goes for the below 8mm ones.
Since the reader has designated pins for analog debug, i checked them with a scope, and it clearly can be seen that the less readable tags have a lower voltage signal on the receiver path of the reader. For example a very bad signal is 250mV, and a very strong one is 550mV. Attached is a screenshot of a oscilloscope. The yellow trace is used as a trigger, and is "transmit active" from the reader. The green trace is the correlation result. The dotted cursor line, marks the approx. level of a "bad" tag. The green trace shows the result of a very strong tag (16mm reading distance)
My question now is, what factors, else than physical changes (antenna shape or size, tag coating material etc), can influence the readability of RFID tags. Second i would like to know if there is any reliable option for checking the tag quality before they are coated into a key fob like item.


texts:
After (mentally) banging my head at the wall wondering why my own circuit is glitchy after the PC communicates with it, I read some posts, and noticed others had very similar problems. All because the charge-pump action of the Max232 IC causes noise in the high millivolt range.

My source of info is here: https://e2e.ti.com/support/interface/f/138/t/151543#pi320995=1

I already considered the two-transistor circuits in place of Max232 but they aren't meant to be very reliable.

The speed I'm trying to work with is 38400bps and I want to be able to send and receive any set of characters over the serial port.

I thought of a replacement circuit but I don't know how well it works, but if it has hope, I'll add capacitors at the input and output of each regulator and between each VCC and GND pin.

Since much of my circuitry runs on 5V, the idea here is to use 2 pairs of inverters with 12VDC for VCC (might have to try CMOS IC) then the conversion takes place in the inverters themselves, then after conversion, the signals are sent to and from microcontroller (AT89C2051 in this example) via 5VDC only. The "SerialIn" and "SerialOut" are connected directly to the PC's serial port's TX and RX respectively.

Would such an idea work? If not, then what is a better alternative to Max232 that's commonly available and that doesn't make noise?


texts: What pull-up or pull-down resistors to use in CMOS logic circuits

texts:
I use a lot of "wired or" circuits where rather than using a logic gate in an IC package I simply use diodes (eg. 1n4148) into a destination gate that has a pull-up or pull-down resistor on its input (depending on the logical function I need).  I have found this quite reliable and have used as many as 5 diodes (so far) to make such a logical function.
With CMOS circuits I have been delighted that I can do this with very high valued resistors.  Where I might use something in the 1K to 5K range in a TTL circuit, I am using up to 100K with CMOS circuits. This of course helps keep current draw down.
My question is "what problems might such an approach expose my circuits to?"  Using very high value pull-up/down resistors is something I want to do, but I read one article (from TI) that suggests the 1K to 10K range even for CMOS logic. That seemed counter-intuitive to me.  Are there any nasty suprises that may lay in wait for me by using high-valued resistors?


texts: Capacitor DC Bias Characteristic question

texts:
If ceramic capacitors lose their capacitance values quickly with increasing voltage (for example most capacitors I looked at from Murata and TDK have a curve like this)

how do IC manufacturers specify what capacitances to use? For example if they say to use a 10uF capacitor - does that mean I should a find a capacitor that will give me 10uF at the voltage I'm operating at ? Or do they say this knowing that the 10uF cap I use will be lower to some extent?

Thanks in advance!


texts: Charging circuit for automatically 'switching' between 1A and 2.4A?

texts:
Does anyone know of a charging circuit that could automatically switch between 1A and 2.4A depending on what the device accepts? Suppose the power source is 3.6V which till be stepped up. For instance, older phones would take 1A but the iPhone 6 takes 2.4A. I heard that there's a chip for this.

Thanks


texts: Can I hook up a water pump directly to DC-DC converter after solar panel?

texts:
I have a 20W/24V solar panel, a module like this: http://www.ebay.com/itm/DC-DC-Converter-Automatic-Step-Up-Step-Down-Module-3-5V-28V-to-1-25V-26V/361283328807 (step up/down module) and a 5W/12V water pump (in transit to me: http://eu.banggood.com/Wholesale-Warehouse-Mini-DC12V-3M-Micro-Quiet-Brushless-Motor-Submersible-Water-Pump-wp-Eu-932046.html).

The question is: Can I hook them up directly, given that the step-up/down is of course set to output 12V?

The whole thing is needed to fill up a 1000 liter tank of water from a small river which will then be used to water our small greenhouse. The water tank has at the top a float switch which will have its wires between the solar panel + wire and the step up/down module.


texts: Are there any RF remote control circuits without any ICs?

texts: I'm currently trying to make a simple 3 channels RF remote control circuit but without any ICs or micro-controller. I'm Googling but it seems to not populate (useful results). Does anyone have ideas?


texts: Where do I solder the shield wire on my USB C breakout?

texts:
First of all, I'm new to all this so I most probably won't understand complicated explanations.
I'm planning to solder a USB-C breakout to my old keyboard's wires, but I'm not entirely sure where to solder the shield cable. I know where I should solder the first 4 cables from checking different posts though.
I've got 4 choices I guess:

don't connect the shield to anything
remove it entirely by cutting the wire from the base
solder it together with the ground
solder it to the metal case of the USB C breakout

Could I have some advice for this?


texts: E.V. Motor Driver (DC). How to protect parallel MOSFETs and the driver?

texts:
Overview:
I have an electric quad that I have heavily modified. The motor will need to be replaced every now and then because I am driving a 48 volt motor with a 72 volt supply that can give extremely high currents (6 12V motorcycle batteries) . This is no problem as I dont mind getting a new motor periodically. I am looking to exploit the limits of this small vehicle!

(components below linked to Mouser datasheets)

Gate driving Problem:
I am using a microcontroller to drive a Gate Driver to drive a MOSFET that powers a DC motor (with Flyback Diode of course). There are two power supplies; one to power the motor (72V) and the other one powers the control circuitry (including Gate Driver) (12V). MOSFET Gate is pulled to ground with a 5W 220ohm resistor (probably too low/unnecessary resistance). Everything shares a common "star" ground.

Every time I try to test this circuit I notice 3 things happen:
(1) The circuit seems fine initially at very low throttle before the motor even start to turn (I can hear the 500HZ PWM signal hum). (2) When throttle is increased slightly more to rotate the motor, the Gate Driver]1 BLOWS UP! (3) The MOSFETs are then ruined as Gate and Drain are shorted. As well as Source and Drain.

I have a large toggle switch to shut off the circuit in an emergency. The switch connects the Source on the MOSFET to Ground (turning it off breaks the motor circuit mechanically and reliably in an emergency event).

Instinctive Solution?: Add a Diode between Source and Drain on the MOSFET? Increase PWM frequency? Reduce the Gate-Source resistor to 10K. Add a 220ohm resistor between the Gate Driver output and MOSFET? All the above?


texts: Prickling sensation in feet while near electric cables - should I worry about this?

texts:
I noticed that I have a prickling sensation in one of my feet near one of my power cables. This doesn't seems to happen next to other cables.

If it matters: 2 computer and 2 screens take their power from that cable.

Should I worry about this or brush it of as maybe sitting in the wrong way?


texts: Error when running parametric analysis in Cadence

texts:
I have set up a formula in Calculator in Cadence Virtuoso. When I did the transient analysis in ADE L, there was no evaluation error. But when I used Parametric analysis to evalutate the formula for different parameter values, the following error appeared.

Could anyone advise how I can clear this error? Thanks.


texts:
How would one design a component that allows heat to flow freely in one direction only, while preventing heat conductivity in the reverse direction?

I imagine such device might be thought of as a "Heat-flow Diode" or "Thermal Gate", that would, eg, allow neighboring appliances with vastly different heat dissipation requirements and tolerances to share a common heat sink, preventing heat from entering any appliance via heat sink backflow.


texts: Effect of 0 Hz setting on VFD with continuously spinning fan

texts:
As part of a HVAC system we have a supply fan and extract fan running on independent VFD1. With the current configuration we usually don't need to run the return fan as the supply fan pressurises the room adequately to force air out through the return duct and room is at the required pressure. So far, so good.

The control system ramps down the return fan speed to control room pressure and so we're mostly running the return fan at 0 Hz. We are wondering what effect this will have on the drive.

Variable Frequency Drive outline schematic thanks to Stephen Collings.

We know that in normal VFD braking the normal commutation of the output transistors and generation from the motor result in a rise in DC bus voltage. If this exceeds a preset level the drive will bleed off power into a braking resistor (not shown on the schematic).

Questions:

Q1. What typically happens at 0 Hz? Will the drive hold the three motor phases at a particular DC levels (by PWM2)? Or will the output transistors turn off completely.

Q2. Is this a bad thing? (I have experience of servo motor brake resistor burn-out. The resistor turned out to be more like a toaster element and I repaired the drive by connecting to an external high-wattage heater cartridge of the same resistance.)

I'm going to check the DC bus voltage and motor current readings and will update the question. Is there anything else I should read from the drive?

Update after inspection

I visited the drives and recorded the following data. Both are ABB ACS550 series.

╔═════════╦════════════════╦════════════════╗
║         ║     Supply     ║    Extract     ║
╠═════════╬════════════════╬════════════════╣
║ Model   ║ ACS550-01-059A ║ ACS550-01-023A ║
║ Rating  ║ 30 kW          ║ 11 kW          ║
║ DC bus  ║ 555 V          ║ 564 V          ║
║ Power   ║ 12.4 kW        ║ 0 kW           ║
║ Current ║ 30 A           ║ 11 A  <--- !   ║
║ Torque  ║ 44%            ║ -4% to +10%    ║
║ Speed   ║ 900 RPM        ║ 0 RPM          ║
║ Temp    ║ 30°C           ║ 30°C           ║
╚═════════╩════════════════╩════════════════╝

The only thing that looks odd is the 11 A on the idle return fan. It could be that the voltage and current are 90° out of phase or that the motor voltage is zero.

1 VFD = variable frequency drive for AC induction motor.

2 PWM = pulse width modulation.


texts: I have a direct mapped cache of size S with the line size L. The cache is physically indexed and tagged. The physical address is 50 bits, numbered from 0 to 49 (with 0 being the least significant bit). The machine has a word size of 4 bits and the memory is byte-addressable. Which bits of the 50 bits are used to select a word from the line? Is it as many bits as it takes to point of a word in the line size L e.g. if line size is 8 byte then 2 bits are needed? Is it some logarithm again that must be used?


texts: Solar panel array interference with DVB-T reception

texts:
We are looking to get solar panels installed, and also currently use DVB-T to get TV via antennas in our attic space.

The solar company has suggested that the EMF from the panels/cabling will make reception hard, if not non-existent, even though we have arranged them leaving a space on the roof where PVC pipes currently poke through the roof, and our antennas are point out via.

How far would the EMF field travel from ~300 watt panels/cabling right behind them that is routed "around" the area of the antennas, emanate?

Is it realistic to have panels sitting on either side of a ~3 foot gap that has antennas behind looking out through that gap, causing so much interference that even with an amplifier a decent quality+strength of TV signal won't be able to be received?


texts: I have voltage source of 7v 250mA. Question is, when I apply it to regulator do I get 5v and 1.5A on the output of regulator?Or do I need 1.5A for a linear regulator ?   How much current would I need to get 1.5A out when using a buck regulator?


texts: MOSFET-based ring oscillator not oscillating (but oscillate in simulator)

texts:
I created the following ring oscillator:

In the LTspice simulator, it is supposed to oscillate at ~3Hz (LTspice source) given the 47nF caps and 680kΩ resistors:

I then built this design on a PCB using 2N7002LT1G from ON Semiconductor, but it doesn't oscillate. All LEDs stay off unless I touch some part of the circuit (e.g. touching R2 will slightly brighten D2).

Is there something wrong with this design? Should I use another MOSFET part?

Edit: when ramping the voltage up, all LEDs start to turn on without oscillating. At around 5-6V, all LEDs are mostly on (brightness is inconsistent). Even at 15V the design does not oscillate.


texts: Possible thermistor identification found in thermal conductivity cell

texts:
I have a component (I believe it is a thermistor, can you confirm?) de-soldered from a device. Could somebody help me identify the type of thermistor and suggest a method/procedure to identify the resistance?

Also on close examination, I found that there are two thermistors connected in series with each other. Could somebody guide me to find the values?
On one thermistor is written "151" and on other "52 56".


texts: Cannot predict closed-loop gain of this amplifier

texts:
This is the circuit I am currently analyzing: (link to LTSpice file)

I am trying to predict each stage closed loop gain and overall gain (with all loops closed).

First thing I did is calculate DC conditions in circuit for given parameters and then started dealing with feedback of each circuit. Also, at beginning, I connected each sub-circuit separately to a source, to make things easier.

simulate this circuit – Schematic created using CircuitLab

FIGURE A:

\$r_e = 43\Omega\$, \$\beta = 250\$, \$I_c = 600 \mu A\$, \$r_\pi = 10.8k\Omega\$, \$A_{ol} = 387\$

\$r_e = 26mV/I_e\$, \$r_\pi = r_e *(\beta + 1)\$, \$A_{ol} = \frac{(R_2 + R_1||R_\pi)||R_3}{r_e}\$ (NFB loading included)

I defined closed loop equation from KCL $$ \frac{V_{IN}-V_B}{R_1} - \frac{V_{OUT}-V_B}{R_2} - \frac{V_B}{r_\pi} = 0 $$ and got

$$ A_{CL(Q1)} = \frac{V_{OUT}}{V_{IN}} = \frac{R_2}{R_1} - \frac{V_B R_2(R_2 r_\pi - R_1 r_\pi + R_1 R_2)}{V_{IN}R_1 R_2 r_\pi} = 30.4 $$

In LTSpice I measured \$ \frac{V_{OUT}}{V_{IN}} = 30.3 \$, so I got pretty close with upper equation.

FIGURE B:

\$r_e = 43\Omega\$, \$\beta = 250\$, \$I_c = 592 \mu A\$, \$r_\pi = 66.2k\Omega\$, \$A_{ol} = 63 \$

\$r_e = 26mV/I_e\$, \$r_\pi = (R_9+r_e) *(\beta + 1)\$, \$A_{ol} = \frac{(R_7 + R_1||R_\pi)||R_5}{(R_9+r_e)}\$ (NFB loading included)

I defined closed loop equation from KCL $$ \frac{V_{IN}-V_B}{R_1} - \frac{V_{OUT}-V_B}{R_7} - \frac{V_B}{r_\pi} = 0 $$ and got

$$ A_{CL(Q2)} = \frac{V_{OUT}}{V_{IN}} = \frac{R_7}{R_1} - \frac{V_B R_7(R_7 r_\pi - R_1 r_\pi + R_1 R_7)}{V_{IN}R_1 R_7 r_\pi} = 22.4 $$

In LTSpice I measured \$ \frac{V_{OUT}}{V_{IN}} = 21.3 \$. Not so close to calculated value as for Figure A, but close enough for me.

FIGURE C: (here things aren't as they should be - as was measured from LTSpice)

Main thing here was to predict overall gain of circuit from Figure C. I thought I would achieve this by multiplying each sub-circuits closed loop (active) gain and also multiplying each sub-circuit's input gain (passive - smaller than 1), which comes into place due to finite input resistance and non-zero output resistance of each BJT. Like so:

$$ A_{CL(OVERALL)} = A_{P(Q1)} * A_{CL(Q1)} * A_{P(Q2)} * A_{CL(Q2)} = 354 $$

where

$$ A_{P(Q1)} = \frac {r_{\pi(Q1)}}{R1+r_{\pi(Q1)}} = 0.65 $$ $$ A_{P(Q2)} = \frac {r_{\pi(Q2)}}{((R_2 + R1||r_{\pi(Q1)})||R3)+r_{\pi(Q2)}} = 0.80 $$

In LTSpice, I measured \$ A_{CL(OVERALL)} = 1135 \$. As you can see, measured value is at least 3x bigger compared to what I calculated! This is a huge difference that cannot be accepted. So, when both sub-circuits are combined, something happens that I didn't manage to predict. Something must greatly be wrong with my calculations, otherwise such enormous error wouldn't take place in this example.

Can anyone tell/explain me, where did I go wrong, when analyzing this specific circuit? Can anyone spot the mistake(s) I have made?


texts: 555 timer not working in monostable mode

texts:
I am a newbie electronics learner and trying my hands on 555 timer to get it running in the monostable mode. Am trying the circuit as in the attached diagram. I am just unable to get the LED blink. I have tried the following troubleshooting steps:

Tried with different LEDs. Made sure they work.
Made sure replacing C1 capacitor with different values to ensure the capacitor is not faulty.
Removing and replacing ceramic capacitor at pin 5 to make sure its not causing any issues.
Trying various resistor and capacitor combinations; making sure that the pulse is not too short to be visible.
Tried with 5 different 555 timers to eliminate the possibility of a faulty chip. Though they were all bought from the same vendor at the same time.

Given the reputation of the 555 timers and their proven history, most likely I am doing something wrong here. Can some one please suggest what could be missing? Ignore the spiral at the bottom of the picture, my two year old is learning with me how to draw electronic circuits.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
EDIT 1:
Adding the pictures of my setup on breadboard. Battery is 9V, R1 - the resistor on PIN 7 is 96 K Ohms and the cylindrical capacitor is 1000 micro farads. There are 3 LEDs on the board. The two lighted LEDs on the power rails show that both the rails have power. The third one, connected to the output, has its negative terminal connected to ground power rail and positive terminal connected to pin 3 (output) of the timer for pulse. This LED is OFF in pictures and is not getting getting ON; but I have successfully tested it before and after taking the pictures; so it's a working LED. You can also see some other 555 timers at the bottom which I am trying alternatively.
I have tried it two ways.
Picture 1 and 2 (zoomed) show the setup where I am using a button to trigger the pin 2 of the timer.
Picture 3 shows the second way where instead of using a button, I am manually inserting the grey wire on pin 2 into the negative power rail for a brief time period to create the trigger.
Picture 4 just shows that the cylindrical capacitor's negative terminal is connected to the negative power rail.
Picture 1: Using a switch to generate trigger:

Picture 2: Using a switch to generate trigger - Zoomed:

Picture 3: Using a loose wire to generate trigger:

Picture 4: Capacitor's negative terminal:


texts:
How will we have a current through a pure inductive coil connected with ac power supply? I am confused because the induced emf will be equal to the applied voltage but opposite in direction,

\$emf = -L\frac{di}{dt} = -vsin({\omega}t)\$

then how we will have a current through the inductor?


texts:
I'm a newbie to electronics even though I have been working on them for a few years in mostly a hobbyist setting. I'm posting here for the first time so please be gentle.

The problem I'm having with my old car is that the headlight switch's contacts are getting eaten away (it's apparently a common problem with my model). I'm not sure if a relay is being used on the circuit or not, I will have to check, but I assume the lights are being driven directly.

I have a 12 V to 15 V power supply (car voltage) driving 2 headlights (65 W * 2). So if I test the Load I should be getting around 9 amp draw (still have to test). If this is true, this will create a big spark that will eat away the contacts.

I read on the Internet that a possible solution is to attach a Snubber Network Over the Switch to reduce arcing.

So my questions are:

What values would I use, and how do I calculate it
Can I use something like high voltage home appliance electronics components to do it relatively safely?
Would polarity be a issue? Eg. the order in which the capacitor and resistor is connected in reverence to the positive and negative terminals.

Here is an image I made with some of the values that I expect to have on hand.

I would like to know how to calculate the values, even if you suggest other options, just to be able to protect simple switches and relays in the future against arching in DC circuits.

I see other uses for a Snubber Network would be in AC circuits and across MOSFETs and inductors. If you want, you can also explain the calculations for these because I read that they have more to do with the frequencies of circuits that these can produce, and this information could be helpful to me and others looking for it.


texts:
I am working on a project using Atmel SAMD20 microcontroller (anyway, my question is in a general aspect, so I think this should not affect the answer)

I use an USART to connect my board to the serial port for debugging purposes, TX and RX lines are directly connect to CP2102 RX and TX respectively and I send debug information through the serial port during the whole execution of the program.

When developing stage is over and the product is in use, these pins are no longer used and are left floating.

Everything was fine until I detected that putting noise (just touching BOTH lines with my hands) cause a hardware reset in the uC and the program stop working at all. I suspect that the uC is interpreting that noise as a signal and causing infinity USART interrupts.

What can I do to ignore signal on these pins when the CP2102 is not connected?

What I've tried:

Setting a pull down in RX pin. Didnt work.

What I definitely CANT do:

Have two different boards, one for developing and another without those pins when the product is finished.

What I could do:

Have two different firmwares. One for developing and another for production removing all code related to that USART, avoid it's initialization and sending information through it. But is this the best solution??

Is there any hardware or software change I could do to avoid this problem using just one firmware?

Many thanks!


texts: Powering a project from a car cigarette outlet

texts:
In my car boot there is a cigarette style power socket, I have a one of these:

https://www.amazon.co.uk/gp/product/B077D71HXY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

I also have an Arduino Uno R3:

https://en.wikipedia.org/wiki/Arduino_Uno

A CAN Crocodile:

https://www.jv-technoton.com/products/cancrocodile/

Finally a neopixel strip:

https://www.adafruit.com/product/1138?length=1

I want to power all of these from the car supply, the neopixel strip is configured in 3 rows of 62 pixels.  The CAN Crocodile requires 12v.

How can I power all of this from the car's outlet and ensure that I have 5v for the Arduino, 12v for the CAN crocodile and enough current to run the Neopixel strip without causing damage to either the car or the components?


texts: Don't bypass caps result in high currents?

texts:
Standard disclaimer: I'm not an EE, just a hobbyist. I could be missing some fundamental concept here.
Though not limited to regulators this is how this question started for me. When looking at linear regulator datasheets you always see something like this (values and regulator model are just for show):

I get the point of the capacitors is to bypass: filter high frequency noise and provide fast response to spikes (with larger caps). I will restrict the thread to the first question I have.
Regarding CIN, it's supposed to shunt high frequency noise. I know it works but I don't understand how this setup actually doesn't cause issues. If Zcin = 1/(2*pi*f*Cin) and f = 10khz and Cin = 220uF then Zcin = 0.07 ohms (ignoring ESR). I'm not sure if there's an integration trick to calculate the noise current but simplistically I'm thinking if the amplitude of the noise is 100mv then I = 1.38A. That's a ton to draw, no?
I must be thinking about this wrong because I've also tried another experiment. I connected a signal generator with a sine wave with an amplitude of 0.1V on top of a DC 1V offset to the power rails of a breadboard. I placed a 47uF cap on the rails as well and the scope showed an almost fully attenuated signal. However if the logic I applied above was sound I would have burnt out the scope/generater but I didn't. Someone please explain this to me and put me out of my misery :)
Thanks!


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In the figure below I think that the Purple wave leads the pink by 135 degrees. The reason is that at the zero crossing the purple wave crossed the x-axis to be in the positive y-axis whereas the pink is in the negative y-axis.
Right?


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Need to modulate a 200 mW laser diode to 2 Gbps.
The diode has typical threshold of 50mA and typical forward current of 500mA.

Chips such as: ADN2871 by Analog devices;  SY882322 by Micrel;  and M02067 by Mindset Tech.
can provide as much as 80mA bias and 100 mA of drive current for modulation anywhere from 2 to 4 Gbps. Is there a simple way to supply the additional current (e.g. through a bias tee) to achieve full output power from the laser and full modulation to 2 Gbps?  Thanks.


texts: Gain due to Input Voltage Offset in op amp

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For a lab, I need to calculate the gain due to the input voltage offset of an op amp. This is the circuit below:

This looks like an inverting op amp to me; so I was thinking the gain would be -1M/100K. But does the R3 resistor have an effect? I also wasn't sure if the fact that both terminals (V+ and V-) are grounded has an effect; I believe this is just to establish an input voltage of 0V.

Thanks for your help.


texts: Automating Filling of Humidifier - Logical OR Gate

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I have an Ultrasonic Humidifier that I use to humidify my shop. I have to fill its 2-gallon tank daily which is becoming a nuisance. Rather than connecting it to a larger tank, I have opted to automate  the process.

I have two liquid level switches (seen here) which can be set up for NO or NC operation depending on whether it is facing up or down.

I have installed one switch at the top of the humidifier's tank and the other switch at the bottom. I am looking to construct a logical gate using transistors that will signal the water solenoid valve to open when the water level drops below the bottom liquid level switch and close the water solenoid valve when the level rises above the upper liquid level switch.

Based on my limited knowledge and the research I have done, I need to construct a logical OR gate using transistors (like this one.)

Am I on the right track so far?


texts: I don't understand the text about LED's type and power consumption

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On my web-surfing, I found some information about LED's type and power consumption.

I don't understand below (Red-lines.)

Why 'common cathode' power consumption is lower than 'common anode'?

Please explain exactly.


texts: Understanding the NE5532's opamp input impedance

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So I was reading the datasheet of TI's NE5532 and I noticed something that I don't quite understand:

Chapter 7.5 (page 5) says that the NE5532 has an input resistance (I guess input impedance?) of 30kOhm to 300kOhm.
I don't really understand the internals of opamps but my initial thought was that this input resistance seems rather low for an opamp (most ones I've seen are 1MOhm - 1GOhm). From what I know opamps usually have a relatively high input impedance so that they do not affect the input signal by very much.

Chapter 9.1 (page 8) then shows an example circuit of a single ended to balanced converter (with bias) that looks like this:

As far as I understand 9.1.2.2 (page 9) then mentions that this particular circuit used 36kOhm (+-2%) resistors (R1-R4).

I have to questions which relate to that:

Doesn't the low input resistance of the NE5532 totally screw up the "voltage dividers" that are used to create the inverter and the bias voltage with these particular resistor values? The opamp's input resistance isn't even 10 times as large as the input impedance.
What exactly does input resistance mean? I understand how resistor networks and Kirchhoff's law work, but if I look at the opamp's schematic in 8.2 I don't really understand anything: What is this (possibly virtual) input resistor connected to? How does it affect my circuit and how can circuits like above work properly with such low input resistance? If the opamp would have a an input resistance, which is a magnitude higher than the impedance of the input signal, I wouldn't worry, but like that I totally don't know how things work.


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I have this exact motor starter on my AC braking motor (FLA 3.5A).

The starting current is 12.1 A however and keeps tripping the relay after approximately ten minutes of use.

The motor operates by raising and lowering a diverter. When raising it turns 180 degrees and likewise when lowering. It raises and stays for 30s then lowers and stays there for 30s.

Why does this motor trip after a while?

Keep in mind the temperature of the motor is 42 degrees C when tripped.


texts: Need help with 16F887 and Microchips 44-pin demo board

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I need some help using a PIC16F887 and the provided 44-pin demo board from Microchip. Its being programmed with a PicKit2.

On this demo board, there is a push button connected to RB0 in such a way so that the level at the pin is high all the time, and pressing the button drops the level low. The purpose of the push button is to simulate an external interrupt signal. I am trying to experiment with interrupts on this chip but cannot read any status change on this pin.

I have a simple piece of code which tests the status of RB0 and sets RD0 accordingly. However, nothing happens whether or not the button is pressed.

Can anyone see something wrong here? I know the IC itself is fine as I can run other programs that dont use this input pin.

Here is a PDF on the demo board if anyones interested.
http://ww1.microchip.com/downloads/en/devicedoc/41296b.pdf

#include <pic16f887.h>
#include <htc.h>

__CONFIG (0x20E4);
__CONFIG (0x2EFF);

void main(void){

 int i;
 int k;
     TRISB = 0xff; //set PORTB as inputs
     TRISD = 0x00;        // Set PORTD as an Output
     while(1)
 {
    RD0=RB0;
 }

I made the following changes as per the solution by Dave below with no change.

void main(void){

 int i;
 TRISB = 0xff; //set PORTB as inputs
 TRISD = 0x00;        // Set PORTD as an Output
 while(1)
 {
     i=PORTB;
     PORTD=i;
 }

}


texts: What will be this CMOS logic circuit's Truth Table?

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I encountered with this MOSFET logic circuit and asked to find which logic gate it represent.

simulate this circuit – Schematic created using CircuitLab
As far as I understand , When \$V_{x1}\$ is  high then COMS with input \$V_{x2}\$ became active and transmission gate became OFF . So we get output \$V_{x2}'\$

But when \$V_{x1}\$ is low , then CMOS inverter is deactivated. Transmission gate's PMOS and NMOS have LOW and HIGH as input. But it confusing me that sources of PMOS and NMOS of the transmission gate are both connected with input \$V_{x2}\$ . How that will affect output \$V_f\$  ?
How can I calculate it's logic output value \$ V_f \$ ?
forgive me if this is a very silly question, I'm new at this.


texts: Transformer winding tap switch without relay

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I have a transformer with four taps and I use two relays to switch between them:

simulate this circuit – Schematic created using CircuitLab

When both relays are energized, they consume ~60 mA which really is a waste. I want to switch between taps of transformer with something that draws less current.

I was thinking to use four logic-level mosfets but mosfets have an internal diode which will do unwanted half bridge rectification...

What options do I have other than relays and mosfet to switch between taps of transformer?

Edit:

12 V Relays are on the secondary side of transformer, relays and controller (MCU) are powered from another winding of same transformer which is independent from this four tap winding.