texts: Which power converter topology has higher benefit of EMI/EMC?

texts:
Which power converter topology can be best suited for EMC compliance for small power converter to be used in LED lighting products. In my context I'm using a 5W non-isolated AC-DC converter which is not complying as per EN-55015 standard.
Any suggestion to use isolated Flpyback topology for the same application if this can yield better EMI performance ove non-isolated buck.


texts: Multiple boost converter voltage pulled down

texts: I need to make a simulation of multiple boost converter design for different load ratios. I have designed 2 boost converter both of them have same duty cycle and same L and C values. Voltage input is 12V and with 50% duty cycle I expect to see 24V output from each of them. If I connect them in series I should get arround 48V total output, but for some reason, the top boost converter voltage is pulled down and not giving 24V. Can someone notice my mistake ot give me some tips? thank you


texts:
I'm trying to add the MIPS command SRA to the following one cycle CPU:
If I knew how many bits needed to be shifted I could easily replace the lower bits with 0's, but that's never a known till the instruction is being executed. What would be a way to implement this so it doesn't matter how far the bits need to be shifted?


texts: Bulging capacitor - already leaked? replace urgently?

texts:
I spotted a bulging capacitor through the top vent of my stereo amplifier, with white goo around the base (at top of first picture). The amplifier seems to work fine, though it has been in storage for many years and probably a wide range of temperatures (sub freezing winter to 30+ degree C summers - not ideal, I know). I pulled the cover off to get a better look at the problem. It seems that the white goo might be glue applied to the base of the capacitor, from comparing to other large capacitors in the amplifier (second picture). I poked it, and it seems quite hard. The top of capacitor is definitely bulging, and I am worried that if it has not burst already it will soon.

My questions are:

is the white goop indeed just glue?
if it is glue: what is its purpose?
does the capacitor need to be removed urgently?


texts: How to understand this simple voice-over-laser circuit

texts:
The Sci-Toys project A simple laser communicator shows a surprisingly simple way to send an audio signal over a laser pointer.

A transformer AC-couples an audio signal directly into the DC supply to the laser diode, with it's high-impedance end in series with the battery.

I'm confused by the back-to-back diodes shown in the symbol for the laser diode. Is that standard?

I think that the basic idea here is that amplifying the audio to directly drive the laser without the DC supply would result in second harmonic generation and garbled audio, whereas the small signal addition to the DC supply would result in closer to linear modulation of the light intensity; a small signal on top of mostly bias.

Is there any chance that the DC current would be partially saturating the transformer's core? I seem to remember something about a very early design of an audio amplifier (before valves/tubes) based on modulated permeability. Is that an essential part of the function here, or just a red herring?

All images Sci-Toys

  The battery clip is attached to a 4.5 volt battery pack (not a 9 volt battery!). Since I didn't have a pack that takes 3 cells, I used one that takes 4 AA batteries, and I replaced one of the four batteries with a straight piece of bare wire.


texts:
I am using a reference design that modulates a 8Mhz carrier DC square wave in simple on-off keying at 10bps.

I wanted to change the carrier to 125kHz. I took out the 56pF capacitor in C4 and soldered in a 330nF capacitor hoping it would resonate at 125khz. Instead a 7.6Mhz signal showed up inside the pulse of my 125kHz square wave. You can see it start to appear when I go below 1Mhz modulation in the photo. (This is 900kHz)

Where does it come from and how do I get rid of it? The PIC uC is running at 8Mhz so I thought it was coupling, but the reference design companion board runs at 125kHz modulation and doesn't have this problem.

Here is my simulation in LTSpice. This is what I thought would happen. I soldered in a .33uF cap but measured .45uF with my multimeter.


texts:
I have here this continuous transfer function:

$$\frac{Y(s)}{U(s)} = \frac{s+3}{s^3 + 12 s^2 + 39 s + 28}$$

Passing this tf to discrete domaing like this:

T = 0.01;
sys_discrete = c2d(sys, T);

I got this:

$$\frac{Y(z)}{U(z)} = \frac{4.853.10^{-5} z^2 + 1.57.10^{-11} z - 4.57.10^{-5}}{z^3 - 2.883 z^2 + 2.77 z - 0.8869}$$

Considering this:

$$\frac{Y(z)}{U(z)} = \frac{a_0 z^2 + a_1 z + a_2}{b_0 z^3 +b_1 z^2 + b_2 z + b_3}$$

and doing the inverse Z transform, I got this:

$$y(k) = \frac{a_0}{b_3}u(k-2) + \frac{a_1}{b_3}u(k-1) + \frac{a_2}{b_3}u(k) - \frac{b_0}{b_3}y(k-3) - \frac{b_1}{b_3}y(k-2) - \frac{b_2}{b_3}y(k-1) \\
y(k) = \begin{bmatrix}u(k-2) & u(k-1) & u(k) & y(k-3) & y(k-2) & y(k-1)\end{bmatrix}.\begin{bmatrix} a_0/b_3 \\ a_1/b_3 \\ a_2/b_3 \\ -b_0/b_3 \\ -b_1/b_3 \\ -b_2/b_3 \end{bmatrix}
$$

Renaming these guys:

$$ \begin{bmatrix} a_0/b_3 \\ a_1/b_3 \\ a_2/b_3 \\ -b_0/b_3 \\ -b_1/b_3 \\ -b_2/b_3 \end{bmatrix} = \begin{bmatrix} c_1 \\ c_2 \\ c_3 \\ c_4 \\ c_5 \\ c_6 \end{bmatrix} $$

So when I find this C vector, I will back in this way (just replacing back):

$$\frac{Y(z)}{U(z)} = \frac{c_1 z^2 + c_2 z +c_3}{-c_4 z^3 -c_5 z^2 -c_6 z + 1}$$

So what I'm trying is to find C:

$$Y = A.C \\ A^T.Y = A^T.A.C \\ (A^T.A)^{-1}.(A^T.Y) = (A^T.A)^{-1}.(A^T.A).C \\ (A^T.A)^{-1}.(A^T.Y) = I.C \\ (A^T.A)^{-1}.(A^T.Y) = C$$

That's how I'm doing this at MATLAB:

t = 0:T:10; %time vector
u = wgn(length(t), 1, 1); %input vector
[y, t] = lsim(sys, u, t); %output vector applied to sys

%[u(k-2) u(k-1) u(k) y(k-3) y(k-2) y(k-1)]
A = [u(2:end-2) u(3:end-1) u(4:end) y(1:end-3) y(2:end-2) y(3:end-1)]; %doing the right shifts here, no problem about losing data...
Y = y(4:end);
C=(A'*A)\(A'*Y); %finding C
c1 = C(1); c2 = C(2); c3 = C(3);
c4 = C(4); c5 = C(5); c6 = C(6);
sys_ls = tf([c1 c2 c3], [-c4 -c5 -c6 1], T);

When I step(sys, sys_ls), that's what I'm getting:

I was hoping to find something very very similar... What am I missing to get this system fit right?


texts: What rules or guidance should be followed assigning busses to I/O banks in Xilinx Spartan FPGAs?

texts:
I am modifying a Spartan 6 project to upgrade several external interfaces from 16 to 32 bit data paths. I have it in mind that all signals in a data or address bus should be assigned to one I/O bank (but different busses can be on different banks). I have searched (mostly the Xilinx documentation) for guidance on this question, but failed to find a suitable answer. Please advise which of these applies, and why.

All signals in a bus should be on one I/O bank
Split address or data busses across more that one bank to reduce simultaneous switching loads
It doesn't matter, as long as the voltages are compatible.

In my case, all the I/O is the same voltage and no differential drivers or receivers are required.

I am expecting to be guided to the first answer to use a local common clock for all signals in the bus, but I cannot find any information to justify that expectation.


texts:
Background

I am designing a basic IIoT device. When the sensor detects the parameter of interest, it transmits a message using an LTE modem. The modem is capable of Cat-M1 and NB-IoT, and I want to use NB-IoT because I read that it uses less power. Data rate has no importance. The bands I have available are 2, 4, and 12. This is based on my module's hardware, its IC (Industry Canada) modular certification, and my service provider. Here's a map of the coverage in my region with my provider, Rogers:

I am currently selecting the antenna for the device. In my research I found that antennas which support all those bands are too expensive. Therefore I will select an antenna to only support one or two of the bands. I can select the band
in my modem through software using the command AT+CBAND.

I couldn't find too much information on characteristics of the bands on Google. I found that lower bandwidth is generally better for penetrating buildings, and higher bandwidth is better for fast data.

Question

For which LTE band(s), out of 2, 4, and 12, should I get an antenna? A constraint is the best reliability possible. Criteria are that I would like to have good penetration into buildings and use less power. I'm also interested in other parameters you think are relevant.


texts: How to choose cutoff frequency of an LC filter for an isolated voltage converter?

texts:
The manual of B0505S states: "It should also be noted that the inductance and the frequency of the LC filtering network should be staggered with the DC/DC frequency to avoid mutual interference."
The switching freq is 100 kHz (typical). Do I aim at 100 kHz or do I avoid 100 kHz? Or what freq is good?


texts:
I would like to build a security alarm that just buzzes when a door opens.

My question is can I use a speaker to generate a loud buzzing noise or I need something else like a piezo buzzer?

If I can use the speaker in what way do I have to connect it?


texts:
I've got a project BOM costed out and I know my PCB costs. Without sending my project out for quote I'd like to be able to estimate the assembly cost by number of SMT components placed and  the number of through holes (for connectors) requiring hand soldering. Assume these are assembled in the US. Assume I know the fixed costs for stencils, pick and place programming, etc.

Anybody have some ballpark figures which might help here?


texts:
I am working on a project that includes the W5500 circuit, this is the first time i had the opportunity to layout Ethernet Interface circuits.

Schematic:

Whole board and W5500 Module Layout Pictures Here

My questions are :

In general does it matter if i not calibrate the differential pair impedance 100 ohm for the pair and 50 ohm for the individual signals if the traces are very short and crowded with termination resistors and other components as shown in the schematic below ? if yes, which part exactly should i implement ( before / after the 33 ohm or after the TVS diode if that is any different.
I am aware of the original chip manufacturer's HW Guide lines here but in order to implement proper impedance on a 2 layer board then it is going to be very thin and thus mechanically unsuitable for the entire board 20 x 10 cm ( i hope i'm wrong ). The original chip manufacturer is selling an open source W5500 Ethernet shield here has eagle source files, i checked it and as far as i understand it may not follow the strict impedance control guidelines ( maybe things are a bit forgiving ? maybe i'm wrong ).
I have added TVS diodes (IC2, IC4) USBLC6-2SC6 in the differential pair path as shown in the schematics below, any notes on the selection of this unit or any notes on the layout would be very much appreciated.
As shown in the layout screenshots below, I made a separation on top layer (red) between the differential pair and the ground plane. and left the bottom ground plane as clear as i can get for now, any suggestions or comments are welcome.
Under the TVS diode at the differential pair path, i needed to connect a 3.3VA and that trace runs under the IC which is passing through it the differential pair, i’ve attached a picture here to further explain my question, is this a real problem or not ?.
Does the center tap connections need to have any impedance controlled value ?
This may be off topic , but any ideas on how to connect the RJ45 Metal shield to the ground plane , the board will be enclosed in a metal box, how can i connect them ( System ground ----- RJ45 Metal Chassis ------ Metal Enclosure ), I've searched around a bit in this site and there are several methods and apparently there is a debate on to implement it, i think i'd go with "Short them together directly via the mounting holes on the PCB" answered by user3624, where i got the idea.

Some useful notes :

I am using this RJ45 Straight Connector MFG Part no. 74990101210 from Wurth Electronics.
I found this Wiznet Wiki HW Guidelines page to do the layout here
The trace width of the differential pair is 10 mils and the distance between the pair is 10 mils, I'm working on a 2oz copper weight PCB, the fab house i'm working with offers the limit of 10 mils trace width and clearance 10 mils.Also i'm currently using Eagle v6.6
I'm using this tool to figure out the differential pair/trace impedance characteristics.

I would appreciate any feedback. Thanks in advance !

Regards

Sultan


texts:
In Memory-mapped I/O, how does device allocation and address ranges are decided? For instance like, EPROM has control over address bus for address from > 0x0000 and <0x4000, RAM1 from 0x4000 to 0x8000
Especially curious about partial address decoding methods


texts: Single supply op amp that can swing -0.3v and output -0.6v

texts:
I'm limited to a single +5v rail and ground and so could anyone recommend an op amp which could swing atleast 0.3v below its negative rail and that would be able to amplify by atleast 2 (capable of -0.6v output). I will be using this to amplify a video signal which has a negative sync.

Would the LT1006 be able to do this?

Basically I will use the op amp to drive a 75ohm video line. So the + input will be the video line and the negative line will be connected to the output of the op amp


texts: What is inside a General Purpose Operational Amplifier

texts:
I am trying to analyze the building blocks of an operational amplifier and for that purpose I have chosen, probably one of the most famous and earliest op-amps built, ua741.

I have figured out most of the building blocks, such as differential pairs, push-pulls, current sources, class AB op amps etc, however there are still some parts that I don't have any explains yet. One of which the highlighted line below for the class AB amp which I was expecting to be connected to Vcc-.

What is the function of the yellow line?


texts: Does anyone know where to find the datasheet for an Electrocraft Model E19-2 motor?

texts:
More details from the motor casing:

Electrocraft
Model: E19-2
Serial: A01314
Part #: 0643-08-013

It looks like it was made by Robbins Myers Motor & Control Systems Division.

In case anyone is wondering, this motor comes from inside of a PUMA 560 robotic arm.

It also has an encoder/potentiometer attached to it which I am interested in getting datasheets for as well:

esoline (? it's actually kind of hard to read the first character on the label) encoder.
Type: P.4201717
S. No.: 70754086
7223C30903

Any help in finding datasheets, or at the very least pinouts for either of these would be much appreciated.


texts:
I'm looking to change my breadboard design of an amplifier into a PCB. This is the first PCB I've designed and I'm not sure what sort of components to get.

My original  full wave rectifier is made of a tl072 and diodes/resistors but I was wondering is there a surface mount component that incorporates all of these? I'm working with small bio-signals so the current won't be that large.

Thanks


texts:
I am building a light bulb with an integrated neodymium magnet for an art piece. I have successfully integrated the magnet into a LED bulb model that suited my needs so it works but now I want to lower the brightness and it does not support dimming.

I have therefor decided to try to lower the brightness with a resistor but I don't want to break it so I want to ask about the best place to position it and what strength/type of resistor to use for it to not overheat or otherwise damage the circuit.

I tried doing this with an earlier model of the same kind and it worked but the next morning when I switched it back on it burnt out a LED diode. That time I put a 10K Ohm (or 1M Ohm resistor.. one of them gave me a good dampening of the light) between the LED circuit and the power going in (the gray cable marked B in the image). I am not sure if this was because I accidentally short circuited it or if current had been building up over the night and then it released it all at once.

So I would like to ask for some advice on the questions marked in bold above (placement and recommended resistor) or perhaps you will get back to me telling me not to do it that way, any valuable input is welcome. Below is an image of the finished bulb and the LED driver inside.

All help or advice is greatly appreciated, many thanks in advance


texts: What determines the speed of a brushless DC motor

texts: When driving a brushless DC motor, which parameters control the speed.  Is it the current in the windings, the voltage, or both?  What determines the maximum speed?  If you drive the windings with PWM, that controls the winding current, correct?


texts: Can a triphase current regulator be used with just two phases?

texts:
My house is located somewhere with power problems, these have been going on for 15 years and will probably never be fixed. Family lives next door and I want to regulate the power to both my house and theirs with a pure sinus wave power regulator. I was thinking of getting a 15kva/9000W triphase 380V and only use two phases, one for my house and one for theirs.

Our power lines run on 220V. Would this work?! Or do I need to get two single phase 15kva/9000w 220V units.

BRAUN GROUP ES-SVC 15KVA

Unit spec:
BRAUN GROUP ES-SVC 15KVA , Triphase

Main Features:

Three phase compensation servo motor technology
Wide AC input voltage range 276-450V
100% unbalanced loading capability between three phases
Digital display for voltage and current
Isolated manual bypass switch
Full protections such as over voltage, under voltage, overload, overheat, etc
Selectable 6s/180s output delay
Optional surge/spike protection (replaceable SPD)
Optional output isolation transformer
Optional RS232/RS485  Typical Applications:
Multi-color printing machines
Air compressors
CNC machines
Punching machines
Laser cutting machines
Welding machines
    Specifications:

INPUT
Rated Input Voltage
380V (400V/415V Optional)
InputVoltageRange
276-450V
Input Frequency
45-65Hz
Power Factor
0.98

OUTPUT
Rated Output Voltage
380V (400V/415V Optional)
Output Precision
±3% (±1% Optional)
Response Time
<1s, against 10% variation of input voltage
Efficiency
over 96%

DIGITAL DISPLAY
Input Voltage
Line Voltage: AB, BC, CA          Phase Voltage: A, B, C
Output Voltage
Line Voltage: AB, BC, CA          Phase Voltage: A, B, C
Output Current
Phase Current: A, B, C

PROTECTION
Output Under Voltage
Output cutoff by contactor + "L" in display + Buzzer beeping
Output Over Voltage
Output cutoff by contactor + "H" in display + Buzzer beeping
Overload
Output cutoff by contactor + "F" in display + Buzzer beeping
Overheat
Output cutoff by contactor + "C" in display + Buzzer beeping
Phase Failure
Output cutoff by contactor + Buzzer beeping
Wrong Phase Sequence
Can't switch on regulator
Short Circuit
Input cutoff by air breaker
Bypass
Isolated Manual Bypass Switch (Automatic Bypass Optional)
Output Delay Time
6s/180s Selectable
Surge Spike Optional
Replaceable SPD
RS232/RS485 Optional

SAFETY
Insulation Voltage  2,000V / 60s
Insulation Resistance   >5MΩ
Creepage Distance   >8mm
Grounding Resistance    <0.1mΩ
Insulation Class of Coil    Class F (155?)
Cooling Mode    Cooling Fan
IP Level    IP20
Audible Noise

OPERATING CONDITIONS
Operating Temperature   -5°C - +45°C
Operating Humidity  10%-90%, non-condesing
Operating Altitude  <1,000m

MODEL AVAILABLE:
Model No.
15KVA
Capacity
15kVA/9kW
Machine Size
D600 x W520 x H1080 mm
N.W.
78kgs
Packing Size
D610 x W530 x H1200 mm
G.W.
88kgs


texts: Additional current source for large LED-7-segment-display

texts:
I have two sets of LED-7-segs.
Each with 4 Digits, all 4 inch tall.
One set CC, the other CA.

Combined they consume some smooth 1.68A / 1.4A according to the data sheets.

That is manifold the current the driver can provide, let alone that the driver is fulled by an Arduino (I'll change that as well).

My question is: What components could I use to supply additional current to the digits?

Basically it seems like I am looking for a certain type of transistor:
Controlled by the driver, it forwards current from a seperate 'unlimited' supply.
At the same time it has to be quite fast, to keep pace with the driver.
I don't want to build this myself, as time matters more than cost,
so out of the box solutions are highly appreciated.

Also I am pretty sure the thing I'm looking for exists,
but I can neither find an example part nor the name of such a component.

Datasheets:
Drivers: ICM7218 (A Version for CA LEDs, B Version for CC)
CC LED: Kingbright SA40-18EWA
CA LED: Kingbright SA40-19SGWA


texts: In op-amp, how do they remove Quiescent votage (bias voltage of a bjt) from the output?

texts:
We use a coupling capacitor to remove the dc component from the output in simple ac amplifier circuits.

In below base biased CE amplifier, the voltage at collector node is not ac, it is pulsating dc with an average value of 15V. After coupling capacitor it becomes ac with average value of 0V.

How do they manage this in an op-amp ? Since op-amp works for dc inputs too, wouldn't a coupling capacitor block both the input and the quiescent bias voltages ?

For ex : As far as this question is concerned, I hope we can assume op-amp is just a two transistor differential amplifier with single ended output and let the gain be 1000; then putting 1mV dc at input gives 1V dc at ouput, but this floats above the already existing quiescent bias voltage of the transistor. If I use a coupling capacitor, it blocks both the quiescent bias voltage and the amplified input voltage. But we want to block only the quiescent bias voltage, not the amplified input voltage. Capacitor blocks all the dc, it doesn't know what is bias and what is input, so I feel we cannot use a capacitor here.

In above circuit \$V_1\$ is dc input and the output is \$V_{out} = V_{CE} + 1000*V_1\$, where \$V_{CE}\$ is the quiescent voltage of Q2 transistor. But we want to remove \$V_{CE}\$ from the output in practical circuits right ?


texts: Fine-grained sensing of distance between two permanent magnets

texts:
(disclaimer: bit of an electronics newbie here)

I have a bunch of little magnet ball-bearings that I was playing around with the other day. I formed them into a strand, then fixed both ends leaving a small gap in the middle of the "string" allowing it to vibrate when plucked:

My ultimate goal is to be able to pluck this strand like a string and be able to convert the subtle (I would presume) changes in the magnetic field as the string oscillates into an analogous oscillation in voltage/current which I can supply to an arduino where weird sounds shall be produced.

This question about making a magnetic field sensor was helpful and pointed me to the Allegro A1301 IC and the Hall effect, which might be what I'm looking for but I suspect won't work for me here.

I also wondered whether I could use inductance here in a way similar but sort of opposite to the inductive phone tap here.


texts:
Before, I asked some ways to solve the EMI problem and I got some useful answer from here:
Really occasional malfunction of the Schmitt-trigger input - Really occasional malfunction of the Schmitt-trigger input
However, another problem has risen.

My board has some adjacent LEDs near the 'trouble making area', and I revealed that sometimes they are powered off by my hand(Of course, I didn't touch the LEDs, I just brought my hand near the lights). For the 74HC14 problem, I added some capacitors to reduce the effect of the EMI and that was really successful. But, what can I do for these LEDs? LEDs are just connected by the MCU output pin, series connection with a resistor. For example, the part of the LED circuit will be MCU PIN->Resistor->LED->GND.

Ironically, this output pin indicates whether the network is on or off and even if the LED is off, the WiFi chip keeps connected to the server. So I think it is just output-related issue.

Would just adding some capacitors near the output pin going to GND be okay? If this is applicable, could I apply to similar situation?

This is the part of the circuit. The board is perforated and there are so many adjacent connections(especially for 74HC14, near the LED).

These are somewhat more general circuit(showing nearly located circuits).


texts: Which type of Ethernet magnetics should I choose for PoE?

texts:
I'm trying to find a suitable PoE MagJack for use with my Phy, KSZ8051MNL. The problem is that I can't find one with the same suggested magnetics topology. The closest one I can find has one extra inductor.

Suggested magnetics on the left. Available magnetics on the right.

The available jacks with integrated PoE magnetics don't have the centre tap on the network side of the transformer. Instead they have the centre tap on an extra coil which is obviously for the common mode power. However, I really don't need that as I am going to use the two spare pairs for power.

Is this extra coil likely to be a problem?

Additional information: I do not intend to implement IEEE 802.3af standard, as this application is not intended to be compatible with any other PoE device. It will be running over cables no longer than 2m.

Added: Here's a few of the Jacks with integrated PoE magnetics I can find:

MagJack SI-52008-F
Bel 0813-1X1T-57-F
Wurth 7499210121A

These are just a representative sample. I can find quite a few, but all of them seem to have some difference to the suggested ones.


texts: Should Passive LPF/HPF Component Selection Depend on Ability of Input to Source Current?

texts:
When choosing R and C for a passive LPF or HPF, should you take into account the input's ability to source current? I'm currently working on a passive HPF for an input that can supply up to 10 mA @ 3.3 V. The input will be PWM. Should this be a factor in choosing R, for example?

Side note: The output of the HPF will go through an op amp buffer.


texts: How to connect a load combinator to a load amplifier for load cells

texts:
I would like to link 4 load cells sensors to an arduino. I am trying to follow this tutorial. I am using this load combinator

and I need to connect it to this load amplifier

The combinator has E+ E- A- A+ SLD outputs
The amplifier has E+ E- A- A+ B- B+

How do I connect the 2 boards?


texts:
It is my understanding that a square wave can be converted to a smooth analog signal via passive low pass filter. However, this low pass filter acts like an integrator which ideally achieves the same result.
For the application of a DAC using PWM in the neighborhood of 1MHz, would an integrator or a low pass filter give me better results in terms of the quality of the analog output? Are there advantages/disadvantages to each method?
Would an integrator cause issues by relying on the capabilities of the OP amp used?


texts:
Can anyone explain a little more about watchdogs, specifically in the circuitry level?

If there is some kind of problem in the chip, how can I guarantee that it will be kept running? It is implemented in a different silicon and later attached to the main chip circuit to avoid temperature problems? Which kind of interface circuit it is commonly used to avoid counting/resetting errors? It is common to implement any kind of redundancy?


texts: How to substitute something modern for the TDA2003?

texts:
Application
pocket radio, ham-radio transceiver.
It has to connect standard microphone with speaker which couldn't be powered through differential pair of wires.

Minimal specs

single ended output (must have!)
4.5-14V supply voltage
at least 1W on 4Ω load of power when powered from 5V
analog input
should be capable withstand shorts & hanging output

Ideally class D amp with low quiescent current and stand by mode.
Design problem
I found many great amplifiers but all of them are BTL. I spent several hours on many ICs vendors and had no luck. All modern power efficient amps are BTL.
Initially, tried to use TS4962 in single-ended configuration but it died right away. Also, doesn't tolerate shorts and opens. I killed several ICs and stopped my experiments. TBH, it is amazing IC and when all connections are soldered as BTL provides really good performance.
After I tried to use LM386 but was not happy by its internal noise level.
Then I tried SSM2211 (in a SE configuration) which did work well but seemed having less gain. When I tried to make it more sensitive I ran into stability problem.
TDA2003 seems like ideal amplifier but it is very outdated, consumes too much current, makes too much heat.
Disclaimer: I understand rules, this is not website for recommendations but I did my homework there and I am stuck therefore I am looking for help of the community.


texts:
Apologies if this has already been asked, but I couldn't easily find an answer.

So - We all know the basic design of a buck converter: Closed-loop clocked PWM into a low-pass filter.

But my question is... Is the clocking part of it necessary? Could someone make a buck converter by closing the switch when the output voltage meets a certain "low level" and then opening the switch when the output voltage hits a certain "high level"?

So basically, an unclocked feedback loop with hysteresis to prevent ringing.


texts: STM32-H407 write program with USB mini cable (USB-OTG)

texts: I have Olimex STM32-H407.  Manual says you require JTAG/SWD cable.  Until I get JTAG/SWD cable, I am trying to write program on the board with USB mini cable.  Is it possible?  My PC or IDE (crossworks) do not seem to recognize STM32-H407 when USB cable is connected.


texts: Why is processing power and memory in smartcards so limited?

texts:
Why is it that common smartcards like the SLE5528 are almost always limited to <16K of available memory, and a very slow 8 bit processor?  What is the limiting factor that makes it technologically/economically infeasible to raise these limits?

EDIT: Maybe I should give some more background on why I'm asking this question.  For a customer at work we had to integrate a smartcard module which basically acted as a keystore (similar to the ones you can use in high-level programming libraries like PKCS11).  We were constantly hitting the limits of this device (can't store more than a few keys, can't store any key larger than 1k, have to wait at least 5 seconds before fetching the key list, etc.).  The only person at our supplier's end I could reach was a vendor that gave me the "That's the way smartcards work" answer.  It's not like there is no real market for storing RSA keys of size >4K on a card.  I'd love to know the real reason behind this.


texts: A laser driver (MLD203P1) with an external Bias-Tee for modulation

texts:
As the title says, I would like to add an external Bias tee to modulate a high frequency signal into a laser diode, because the laser driver I have chosen does not have a built-in modulation circuit. I have bought the MLD203P1 laser diode driver from Thorlabs. This laser driver does not have the modulation circuit, so I decided to add an external bias-tee to it. The typical application of the MLD203P1 is seen below.

What I know so far is that a bias-tee consists of an inductor and a capacitor, which is in parallel and with one DC-input, one AC-input and one AC+DC output. So I think this should be the solution. This is seen below.

I just only need a modulation range of 10 kHz to 20 MHz. I have also read the datasheet of the MLD203P1 and don't see a problem if I attach the external bias to the LDA (Laser diode Anode). Although, I will add a current limit resistor between the LDA and the DC input of the Bias Tee.
So I wonder if this is working or has anyone tried it with another laser driver? And is this the right path I am following, to get a modulation signal of the laser diode?
Datasheet of MLD2031P1: https://www.thorlabs.com/drawings/8c0acf99c70bcbeb-392580F3-E400-B9B9-C9E56C95CCB14E62/MLD203P1-DataSheet.pdf


texts:
I am trying to sum three audio signals using a non-inverting summing amplifier as shown below. If I want to bypass one of those signals, what is the correct way of doing that (let's say with a switch)? Connecting the route to ground as shown?

I assume just disconnecting the signal from the circuit would affect the amplification of the other two, right?

simulate this circuit – Schematic created using CircuitLab


texts: How to provide 3 options (pull-up, pull down and Open) in an IC

texts:
I have MAX9278 Deserializer IC.
I have 2 doubts.
Doubts :

I am performing the schematic now. Below, I need to provide options for both 24-bit, 27-bit and 32-bit.

How to provide the provision for all three modes? Pull-up, Pull-down and Open?

What should do with unused pins?


texts:
I have been reading up a lot on how oscilloscopes work and how to best attenuate signals and figured the best way to learn is to create my own simple oscilloscope. My design goals are quite modest compared to an actual product but I aim for accuracy and quality as well as understanding.

Design criteria:
DC - 1MHz bandwidth
1Mohm and <= 25pF input impedance
Settings electronically controlled
+/- 10% variance from input Z (Less is better but absolutely no more!)

I have read quite a few pages online as well as books. This Question was handy and basics like probe internals are good to know but the actual act of design is a daunting task.

I have selected Omron relays High End / Low End as they have great ratings and are somewhat reasonable in price. These will select AC/DC input and choose between the attenuation levels. I chose double throw relays as I will put the attenuation network in series so the fail safe mode is max attenuation and you will opt out attenuation networks by powering a relay and completely isolating the attenuator branch. (DPST on each side of the filter).

The main issue I am having is that I can not get a remotely stable input Z across DC - 1MHz, in fact I have 80.6% variance at some freq which make my setup useless. I have considered using a JFET input buffer instead of Diodes for input voltage protection but even before the protection stage my Z is all over the place.

Can anybody give me a crash course or some pointers on how the heck you attain a stable input impedance across frequencies??


texts:
Is there a standard convention for marking an inverted signal using only text? The package currently being used does not support having a bar over the signal in all instances.

IE: NOT_Reset or Reset_Bar etc? when you can't use \$ \overline{Reset}\$


texts: ESP8266 sleep current is higher than it should be

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In short:

Despite setting my datalogger IMU to SLEEP and going to deepSleep(0) on the ESP without any other IC peripherals besides the buck converter and 2 deactivated LEDs, I still measure 2.5mA current draw while the data sheets predict 108uA. What could be the cause?

Detailed version:

I am using an ESP12F/ESP12S as a small data logger. Connected to the module are a Renesas ISL85415 buck regulator set to 3.3V output (Connected to a LiIon Battery), an MPU9250 IMU (Over I2C) and 2 LEDs (Active HIGH) with their respective ~300 Ohm resistors. I have a set of pullup/pulldown resistors, namely 10k PUs on the reset, CH_PD, GPIO0 and GPIO2 pins, two 4.7k PUs on the I2C lines, and a 10k PD on GPIO15.

I am using Arduino-ESP to program the chip.

After power-up, the ESP sets the LED pins to OUTPUT LOW, tries to initialize the IMU, collects some data, connects to a WiFi AP, sends some UDP messages, sets the IMU to sleep using the SLEEP bit in its PWR_MGMT_1 register, and goes to Deep Sleep.

According to the data sheets, the buck converter should draw 80uA quiescent current (In light load operation mode), the ESP should draw 20uA, and the IMU 8uA. With a cheap multimeter I get 2.5mA (2.4 and 2.8 with other versions of the same circuit), and the battery runtime suggests a draw of ~2mA.

I measure a difference of ~2.5mA when the IMU is in sleep mode vs. not, so I am pretty sure the IMU is really going to sleep. Where does this additional draw come from?

I have seen This similar question but it is not answered as of right now.

EDIT:

This is my schematic:

I was able to reproduce the issue with following minimal code:

  #include <Wire.h>

  void setup()
  {
     //Init I2C
    Wire.begin(4,5);
    delay(10000); // For initial multimeter measurements

    sleepMPU9250();

    ESP.deepSleep(0);
  }

  void loop()
  {
  }

  // Set the IMU to sleep mode, hopefully reducing current draw
  void sleepMPU9250()
  {
    writeByte(0x68, 0x6B, 0x40); // Put MPU9250 to sleep
    delay(100); // Wait for all registers to reset
  }

  void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
  {
    Wire.beginTransmission(address);  // Initialize the Tx buffer
    Wire.write(subAddress);           // Put slave register address in Tx buffer
    Wire.write(data);                 // Put data in Tx buffer
    Wire.endTransmission();           // Send the Tx buffer
  }

I also measured the ESP12 pin voltages during deep sleep as recommended:
RST, CH_PD, GPIO16, VCC(duh), SDA, SCL, GPIO0 and GPIO2 have VCC, ADC is at 1V when VBAT = 4.1V, and all other pins are at zero.

The ESP12S schematic is found here at page 13, but I didn't find anything out of the ordinary. According to this(with SparkFun ESP8266 Thing) and especially this (With ESP12F) it is quite possible to run the Chip+Breakout at 77-78uA.


texts:
I am modifying an old 90s keyboard (CTK-450 by CASIO) to make it a MIDI controller. I'm going for an Arduino that goes over the matrix layout of the keyboard.

The issue I have is with debouncing. Now I know the best idea would be to add some small capacitors in there to make sure there are no issues with bouncing switches, but I'm wondering whether I could just ignore the problem. My reasoning is as follows:

I don't really care if I get bogus input, as it's a MIDI controller. It isn't some button that deals with menu scrolling or what not.
The RC circuit on the original PCB for the keyboard is R = 1kOhm, C = 1nF or 0.1 nF depending on the exact circuit, which gives me a time constant t <= 1µs. I'm going to be polling the keystates at a much slower rate to start with (Arduino digitalRead() takes 1-4 µs, and I have to go over around 60 keys plus some overhead), and it's extremely unlikely that the reading will happen exactly at the time the key is in a bouncing state.
Even if I manage to sometimes read the key while the signal is bouncing, it shouldn't really matter. If I read logical low when I just pressed the key, by the time I go through all the keys again, the bouncing will have stopped and I will have a solid digital high to read, and vice versa.

I think the key to this is the fact that the time constant for the RC debouncing filter is so small. Is it really believable that the switches in the keys will have such a short bouncing time? I understand the bouncing time doesn't necessarily have to be the exact same as the time constant, but even if it happened to be a bit bigger, assuming it's around that order of magnitude, arguments 1 and 3 still hold, I would assume.

Thus, can I completely avoid putting those debouncing caps into the circuit, even if in principle, it isn't a good idea for every situation?


texts: Why is the output from this astable 555 the reverse of it's simulation?

texts:
The simulator in LTSpice looked OK ... so I moved to the breadboard with an LED (eventually replaced the LED with a buzzer) at pin 3. One more difference in the assembled circuit is the condenser at pin 5 is not electrolytic.

The supply is a retired AT SMPS from my old computer.

The waveform in LT Spice is initially LOW, and subsequently HIGH after a few hundred seconds. The assembled prototype however begins with the buzzer audible.

My impression is, therefore, that cycle has somehow got inverted in assembly. Is this impression correct? What need be done to have the output on the prototype behave as designed?


texts: How much voltage multiplication can boost converter produce?

texts:
I want to make a PWM based inverter for my college project to convert 12V DC to 220V AC.

But as the PWM output is not exactly sine wave, it can not be stepped up using a transformer. So I need to convert 12V DC to 300V DC first, before feeding it to the H bridge for PWM.

But my question is "Is it possible to convert 12V DC to 300V DC using a boost converter?"

Because I have read that in commercial inverters, they first convert 12V DC to high frequency AC, step it up to 220V AC and then rectify it to get 300V DC. Why so much hassle when you can use a boost converter instead, which will be much simpler solution? Are there any technical difficulties in boost converter which prevents their use?

Also, is it possible to connect multiple boost converter available commercially in a cascade connection to get output voltage higher that what they are specified for?


texts: What is this sealed electrical component?

texts:
This thing, pictured below, is part of a mower's safety electronics (the mower is a bunton model "forty eight"). All the switches to make sure you can not start the mower with the blades engaged, or in gear, and you are holding the handles run through this thing.
The only markings on it are 1200-18B and 88210 (second picture). Google has been no help with those numbers.

Here is a crude wiring diagram.

simulate this circuit – Schematic created using CircuitLab

What is this, and what does it do?


texts: I am looking at programming an AVR chip as a possible avenue due to some problems I'm having with 555 circuitry, but I need to be able to adjust the frequency on the fly with a pot.  Is it possible to setup an AVR chip with variable frequency so that the program execution speed can be adjusted right on the board with a simple pot and without having to go back and reprogram the chip?:


texts: Speed Control for a 12v DC PC Fan for Magnetic Stirrer

texts:
I working on mini project to create a magnetic drink stirrer out of an old PC Case Fan.

(For those that don't know, a magnetic stirrer is basically a spinning magnet under your glass and a magnetic bar in the glass that spins with it and mixes the drink.)

The Fan I'm using is a old 12V DC PC Fan, one of the two wire types, I tried connecting it to a 5V connection and it span but was too slow to mix the drink properly and so I'm now using a 12V power supply but that spins too quickly for the magnets.

I tried connecting a 100K B Potentiometer as a variable resistor to the circuit to adjust the speed but all that does is has the fan off for 95% of the pots range and then full speed for the last bit.
Is there any way I can adjust the circuit easily to control the fan speed?

I don't want to replace the fan with a 3 or 4 wire type and I ideally want to keep using the 12V supply, I'm looking for a solution that will allow me to do this with only one or two component additions or changes such as a different or additional potentiometer etc.
I'm pretty new to electronics so don't know if I'm doing something stupid here.


texts: What was the motivation for making behavioral descriptions such a big part of Verilog?

texts:
I don't use Verilog for anything serious, but I use it in my classes, and I'm starting to think I must be missing something about the appeal of behavioral hardware description.

When I write Verilog I feel like behavioral description is solving the easy problem, namely making a structural description of the hardware; and I'm not really sure if it makes it much easier. But I do find myself spending a lot of time checking and rechecking my ifs and cases to make sure they're really combinatorial when I want them to be.

Maybe I'm just not designing the right kind of hardware to make always blocks convenient?


texts:
I am designing a board which converts DisplayPort to LVDS, in order to drive cheap panels from older notebooks or off ebay. DP is free of charge, compared to HDMI, and a simple converter IC is available using the PTN 3460.
My first draft used a full size DP connector. Pins 15+17 for aux, pins 10+12 for lane0 and 7+9 for lane1. It is the sink-sided pinout of the DP specification, as wikipedia states:
https://en.wikipedia.org/wiki/DisplayPort
It works... kind of... The mechanical tolerances of DP plugs seem to be pretty bad, or I bought a bad series. I really have to press the connector in, with a lot of force and I need both hands to achieve a stable image. I couldn't take a picture because of that :)
Thats why I removed the DP and added an mDP receptacle. Saves some space as well, so why not.
Again I used a pinout from the web, e.g. wiki egain:
https://en.wikipedia.org/wiki/Mini_DisplayPort
The lanes are again crossed, I just did a continuity test. The mDP is connected to my board, and I am probing into the open end (full size DP) I unplugged from my notebook:
Pins 1+3 end up on the PTN's lane0 input, pins 4+6 on lane1 and aux on pins 15+17. Ground, config1 and config2 and hot plug are also connected correctly.
But: nothing. The board is not even getting recognized. Where can I start to search for the the problem? The only thing I did was replace a dp receptacle with the mini dp version of it. I also tried several cables, no change.
I also attached two images, showing both board versions from the top. Blue is top layer, green is the third layer and red is the bottom one. The resolution is 1600x1200 for my test panel.


texts: DC voltage measured on an AC to AC wall wart - why and how?

texts:
I have a wall wart that says it is Input 110/230V AC and Output 3.5V AC.

I put voltmeter on it without switching it from DC to AC (forgot to) and measured 8V DC.

I have Googled the subject generally and on this site and found some info saying that it CAN happen but the DC voltage isn't useful as it's not controlled by a regulator - but I cannot find a layman's explanation of why it is happening.

Anyone want to clue me in? (This is my first post here.)


texts: How do I find a "pin readout" equivalent for this omnivision cameracube?

texts:
I need to know how to connect this omnivision cameracube to a pcb but I don't know what any of the connections on the bottom of the camera correspond to. How can I figure this out?

http://www.digikey.com/product-detail/en/OVM7690-R20A/884-1019-1-ND/2123272


texts: Does the electron beam go towards the deflection plate with the higher, or the lower voltage?

texts:
So I've started tearing apart an old CRT scope to learn everything about them, and right now looking at the voltages on the deflection plates. When the trace goes down, my vertical plates read (a)193v, and (b)130v. When the trace is all the way up, A is 106v, and B is 188v. When trace is in the middle, both read around 157v.

So I can tell that giving the two plates different voltages is causing the electron beam to gravitate towards one (or push away from the other.) Which way does it go? Is it being attracted towards the higher voltage, or the lower one? I can't tell which is which because I cannot see inside the tube, because of that annoying black coating inside. I really wish I could see those deflection plates.


texts: Difference between 1-bit, 4-bit and 8-bit SDIO

texts:
Please help me understand the significance of 8-bit SDIO over 1-bit and 4-bit SDIO. Let me know the pros and cons of each type.

Wiki or SDIO specification document does not discuss this.


texts: Should I ground PCB to an aluminum enclosure when using in car?

texts:
I have been working on a bluetooth audio adapter for car, and I plan to put it in a metal enclosure when it is finished.

The bluetooth adapter is very low power and I'm powering it directly from the car's battery. Antenna connector have it's shield/chassis connected to ground, which means unless I use a grommet or something similar, the enclosure would be electrically connected to ground (the enclosure would never be intentionally used as a ground conductor, however). Could this cause any issues?


texts:
As I'm reading about switch-mode power supplies (SMPS) I keep coming across the term clamped inductive load.

You'd think there would be a clear definition that would pop up as the first Google hit, but no such luck (for me anyway :).

What exactly is a clamped inductive load? And in particular what is being clamped? and what is doing the clamping?

I get that something like this probably counts as one:

.. but I have only the vaguest idea what makes it so.

It seems to be something that crops up over and over in an SMPS context (re:switching MOSFETs, snubbers, etc.), so I'd like to have a clear idea how to distinguish one and what makes it important :)


texts:
I made this standard LM317 voltage regulator circuit:

It worked as expected, but then I tried connecting a TDA2005 audio amplifier. I connected the LM317 to my audio amplifier as a power supply and because I am new to electronics I had some problems with my amplifier. Trying to fix the problems, I probably shorted my circuit accidentally (not sure about it). My LM317 potentiometer burned down with pretty bad smoke.

I was wondering whether could this happen because of shorting the output of the LM317.


texts: MCP2210 (Microchip) has delays between chip select to data, data to data

texts:
I am using MCP2210 in my project to communicate with a processor (TMS320F28377D from TI).

For tests, I use SPI Terminal programm from microchip. However there are some issues.

There are some settings for delays, CS-to-Data, Data-to-Data, LastData-to-CS delay. I set everything to zero, although there are always delays if I use high speed SPI for example 1MBit/s.

I attach screenshoots and osci picture.

This is SPI Terminal screenshoot. I send zeros just for testing. I use 32 Byte transfer and as you can see, all delays are set to zero.

This is MCP2210 Utility programm. I read back the configurations, they are set correctly.

If I send data, there are huge delays between Cs-to-Data, Data-to-Data and LastData-to-CS (not shown in picture).

Green is SPI clock

Yellow is Chip Select

Light blue is MOSI (MCP2210 is Master)

Purple is MISO (TMS processor is Slave)

Why is it so?

Thanks.


texts:
I was just introduced to the concept of Amplitude Modulation and how it was used for transmitting information between radios.
What modulation technique is used for communication between mobile cell phones and why is AM not used? Also, if newer techniques save more power, why is it still used for radio transmissions?


texts: WolframAlpha results for logic statement input

texts:
I was trying to simplify the following Boolean logic equation using wolframalpha.com.

  (not (A) and B and C) or (A and (not(B)) and C) or (A and B and not (C)) or (A and B and C)

When I entered it into the box, it spat out the following.
Image is a link.

After showing me some simplifications of the logical statement, Wolf showed me something called truth density, which I am guessing is the ratio of true outputs to false inputs. I am mostly confused with the last two categories/results. What is a Boolean operator number, and why does the number 232 match my equation?


texts: Paralleling Multibit current DAC: Improving Accuracy by Averaging

texts:
No doubt that if I put in parallel n DACs, multibit (i.e. 16 bit) current output R2R ladder chips, I get n-times higher current at the summing node and the output impedance is also reduced by "n".

But what about linearity and precision at low signal levels? Can we apply the general law for "uncorrelated events", for which in summing configuration noise and tolerance (and, hence, DAC linearity and LSB -least significant bit- precision) may improve by SQRT(n) times?


texts:
This is  my fist time working with a "bigger" micro controller, ATmega128. So far I've worked with ATmega328, ATmega8 etc.

Reading through the datasheet, I didn't understand couple of points

That AVR instruction set can support a maximum of 64 I/O locations. Why is that? Does the AVR instruction set take in 6 bits for an I/O location?
To accommodate the extended I/O in ATmega128 (160 extra ones), these 160 locations have been mapped to the internal SRAM right after the 64 existing ones. So in effect out of the 4KB SRAM that ATmega128 provides, 160 is taken up by these extended I/O locations. What happens if the ATmega103 compatibility fuse set (programmed by default)? Do I have access to these 160 locations then?
How exactly do I access these extended locations? The datasheet asks to use LD/LDS/LDD and ST/STS/STD. Any examples to this as I've never used assembly before. I am kind of confused how this wold integrate into my C code workflow? Let's say I need to access DDRF and PORTF. Would I need to know their address(in SRAM) in advance or is there some macro in avr-gcc?

Any code samples or links to read and understand above would be great!


texts:
As I'm reading the Mastering STM32 Book, I came across this graphic describing the memory map

So what I'm trying to figure out is whether my understanding of memory is wrong, or if the graphic is. It is my understanding that in the figure on the right, the 5th variable (a byte) should be at address 0x20000008. The memory addresses increase from right to left, and top to bottom. So the 1st variable would have bits 7 to 0 at 0x20000000, bits 15 to 8 at 0x20000001, so on so forth. Could someone point me in the right direction if I'm incorrect?


texts: Does the STM32F103C8T6 blue pill chip require external resonators?

texts:
I am designing a custom PCB with the bluepill MCU, which I want to program over ST link and SWD, which external resonators are a must?
In the standard version, it comes with 32kHz and 8MHz:
https://easyeda.com/r3bers/STM32F103C8T6-Test-Board
EDIT: I only want to use SWD programming (so no USB) and read an ADC signal each min.
More references on this question are provided here:
Link1
Link2


texts:
For my final project in my electronics course this semester, I need to design an amplifier with a specific set of parameters. Specifically, it needs to have a gain of 100, a voltage swing of at least 10 Volts peak-to-peak, an input resistance of 75 kilo-Ohms or greater and an output resistance of 100 Ohms or less. After designing a common-emitter amp with a gain of 100 and a voltage swing of at least 10 Volts, I calculated the input and output resistance, and determined that I needed common-source/common-drain buffers in order to get the input and output resistance that I need. After designing buffers that fulfil these requirements, I put them all into MultiSim for simulation. Each stage worked as expected, so I connected them all together. However, the gain of the overall amplifier was far, far less than expected. I checked the voltage being outputted by each stage, and I found that the first stage, a MOSFET common-drain amplifier, was outputting a signal of 2 mV when a 50 mV signal is applied. When I detached it from the rest of circuit, however, it began to output a 50 mV signal, as desired. The stages are coupled with capacitors to simplify the DC bias calculations.

Is there any reason why an amplifier would have a lower gain when coupled? What can I do to fix it?


texts: Switching between 2 power supplies without outage

texts:
I have two in voltage about equal power sources, a built in 12V and an external solar+battery backed up stable 12V source.

I looking for a simple solution to switch immediately to the other one because my circuit contains a raspberry pi 2 as well what I would not like to reboot.

There can be only 2 situations for my circuit:

1, Solar power source comes on (the main is force switched off)

2, Solar power goes out (the circuit is switching back to main)

Also I would like to completely turn off the main adapter with a relay when the device operates from solar not to waste power.

I realize this is possible by using a simple 12V relay in default close position connected to the solar input only and using 2 reverse current protections on both lines but would a big cap on the supply end be sufficient enough to keep the device operation for a second when the power switching happens?


texts: How to determine the Solar-panel power requirement battery

texts:
I'm having a problem calculating the rated power requirement for my solar panel project. The panel will charge a battery that will power a 'micro' water pump.

The power requirement for the pump is .827 Watts (very small, I know, it's in the project requirements).

Can I use a deep cycle battery with this size?

My motor consumes 1 watt at 40rpm 6v, based in Ireland (weather and sunlight hours).


texts: Paralleling output of multiple BLDC motors used as generators

texts:
First of all, I apologize for anything stupid I say as I am not yet well versed in the proper technical terms and schematics.

I wish to use several identical BLDC motors that will be spun at the same speed (chain driven off same source) and used as generators rectified to DC power.
I am curious if there is a simple way to safely parallel their output (combine their output current).

Since the motors are identical and spun at the same speed, I may potentially get away by using identical three phase bridge rectifiers for each motor and then paralleling the output of the rectifiers. However, I know that is not a reliable solution as manufacturing tolerances and other variables will still mean that the output from each rectifier will not be 100% equal, thus possibly causing a catastrophic situation.

If anyone has any advice on how to do this properly, I will greatly appreciate it.
Or is it even possible?

Thank you.


texts:
I am trying to make my own core rope rom, according to the link.  I have 15mm ferrite cores, which I wound about 30 times with 1mm magnet wire.  I thread the primary ( also 1mm wire) through one of the cores (once) to test it.  That was connected to a diy dc pulse generator based around the 555 timer, which is fed 9v.  When I first tested it, I barely got any voltage from the secondary, about 1mv according to my multimeter set to dc (my ac 200v range which is the lowest picks up nothing).  I also tried connecting a low power led, which did not light up.  I figured the dc was not being pulsed at a high enough frequency (7.5hz ish) so I changed the circuit for the dc pulser so that it puts out at about 45hz.  However, I’m still having the exact same problem.  Can anyone think of anything i might be doing wrong?  At this point, I’m assuming i am not using the correct frequency.  If so, is there a way I can calculate this? Any help would be much appreciated.

http://qrp.gr/coreROM/


texts:
First and foremost I have a question regarding the MMF distribution in a Motor produced by a single coil. I found a picture here:
Why does the MMF not start at 0 at 0°? When I apply the $$NI=\int{H \mathrm{d}l}$$ with a curve with a small angle opening around the 0 point (horizontal arrow), I'd get 0.

And my second question is the following: What's the easiest explanation why the fundamental of the permanent magnet flux should be perpendicular to the fundamental MMF to produce the maximum possible torque from a PMSM (without saliency)?
Edit: I'd really prefer a mathematical derivation of the torque equation to understand the behaviour.


texts: Best way to group power pins on a connector?

texts:
I am designing a little mezzanine PCB that uses Hirose DF12 connectors to connect to the motherboard.

Four different voltages are delivered to this PCB: ±10v, 3.3v, 48v (and ground). They go through one of the DF12 connectors.

Which of these two ways is the preferred way to lay out the power and ground connections on the connector?

First way: Each power has its own ground.

Second way: Single set of ground shared by all power.


texts: Can batteries connected in series be treated as separate voltage sources?

texts:
I'm working on a project where one module will run on 6V and another on max 5V. As voltage source, I use 4xAA batteries (so 6V in total). My initial idea was to use a zener diode to limit the voltage to the 5V module, as in the figure below.
Then I had another idea of looking at the batteries as separate voltage sources and using only three of the batteries (4.5V) for the 5V module, and all 4 batteries for the 6V module. See figure below

Would this cause any problems or be "bad practice", or would it work just as well as the first solution?


texts: Supercap backup power - delayed power on

texts:
I'm trying to figure out how to make a backup power that will allow my SBCs to safely power down in case of power outage. What I thought to use are supercaps (2 in series for 5.5V) that will first charge before sending power to SBC.

Idea is that on power connected to 5V rail FET is turned off and capacitors will charge through shunt resistor R1. R2 and R3 create a voltage divider that is used by opamp to detect when charging current drops below set level. Since I don't need perfect values, pins 1 and 5 of LM741 are NC. So when charing with high current, source voltage will drop charing at 2A then when it hits 5V it will charge with CV until current drops to around 100-100mA. Then opamp output switches to low pulling Q1 gate low and turning on FET. This in turn turns on Q2 which will keep Q1 gate to ground until voltage drops to very low level.

Now I think it should work, but I'm not sure about R4 R5 and R6 values, also, not really sure what FET and transistor to use. I also wonder what will be the best way to check if we are running from that 5V supply or from caps.


texts: Positive input terminal - Basic Circuit Analysis

texts: I am trying to do some basic analysis over some circuits, however, I am unsure how to deal with the non-inverting input. I already found Vin/20 and -Vout/100 based on the other 2 resistors, I am stuck on the third one. We were using 0 for V- so I was guessing V+ would be 1, but I could not find any information on the matter. Assume ideal op amps


texts: What resistor values should I use with this boost DC-DC converter IC?

texts: I'm trying to use a STOD1317BTPUR DC-DC Boost converter to drive a 12v OLED Display from a 1-cell lipo (~ 3v - 4.5v). The thing is that in the application circuit provided in the datasheet the values for the resistors R1 and R2 are not detailed, neither a formula to obtain them. I've looked for different application circuits from other parts but what confuses me about this one is Vout and Vo_set. I don't understand the difference between them. (I know it has something to do with the LDO it has on the output, but I don't know if this changes something in the formula of the voltage divider).


texts:
Ref : Is making a D flip flop with asynchronous level triggered reset possible?

My code :

always @ ( posedge clock, posedge rst)
begin
if(rst) q = 1'b0 ;
else q = d ;
end

Waveform :

Error :

Between 100 and 150 ns, the output followed the d input although there was no clock edge. In other words, it behaved like a latch.

I wanted to make a positive edge triggered d flip flop with asynchronous positive level triggered reset, which I succeeded after examining the reference link above.

Prior to this, I was using the code given above. As you can see, the only difference is that I have used blocking assignment while the reference uses non blocking assignment.

Now I know that non blocking assignment schedules the values in contrast to blocking assignment. However I am not able to understand how is this affecting my design ?
In other words, can someone explain step by step or in little detail why changing non blocking to blocking is resulting in incorrect design.

Additionally, I also tried this code :

always @ ( posedge clock, rst)
begin
if(rst) q = 1'b0 ;
else q = d ;
end

which also resulted in erroneous design. But why, I wasnt able to understand.

Thank you.


texts: convert falling / rising edge to pulses with minimal components

texts:
I have a signal that changes from high state to low every few minutes, after changing state it will remain constant, all level changes are clean.

I'm looking for the smallest possible circuit that can detect a rising edge and falling edge (could be two different circuits) and will output a pulse when the the edge is detected.

Ideally, I'm looking for a single circuit that will output a positive pulse when one type of edge is detected and a negative pulse when the other type is detected.


texts: Minimum value I2C-pull up resistor for arduino

texts:
I'm trying to determine the minimum value of pull resistor for Arduino Uno

The datasheets says; 0,4 Vol for 20 mA Iol. Let's assume VDD = 5V

For formula is:  Rmin=Vcc−0.4V/20mA =  4,6V / 20mA = 230 ohms.

But I saw that people use 0,4V for 3mA. Than the minimal value is 1,6K ohms.

So whats the minimum value of pull-up for arduino?


texts: Can I split a USB cable's male end, add a second male plug, and draw 10V from 2 ports instead of 5V from one port for a single device?

texts:
Say I have a device that accepts 10V @ 2A, and I have a wall-wart with two USB plugs that both output 5V @ 2A. Can I add a second male connector, connect both connectors to the wall-wart's two ports, and draw a cumulative 10V @ 2A?

This question's answer indicates that this would cause havoc for motherboards or other electronic devices, but there's a lot more going on with a motherboard than with a power block. Does this answer still apply?


texts: A variable in microcontroller RAM changes 50 times/second. Does that degrade the memory location of the MCU in long run? If so, how long is the memory location expected to be active?


texts: Instrumentation amp not measuring voltage across capacitor, piezo energy harvester

texts:
I have made a simple piezo-energy harvester.
The piezo strip is connected to a full-wave bridge rectifier, then into a capacitor for storage. The voltage across the capacitor increases as expected, when measured with a multimeter - however drops rapidly due to the allowed current flow.

I then connected an INA126 single instrumentation-amp to allow the reading of the capacitors' voltage without current flow.
A voltage-divider from 9V source supplies the opamps' V+ of 5V, and V- is ground, the same ground as the battery, as are the opamps. The voltage-divider has a capacitor in parallel to ground, and the Vout runs into an OP07CP precision opamp as a unity-feedback buffer for voltage regulation.

My problem is the voltage measured from Vout of the instrumentation-amp and ground, is an inaccurate reading of the capacitor to a direct reading across the capacitors terminals.

For example, the capacitor currently has a voltage of 1V, and the output of the IA126 with ref. to ground is a stable 3.6V.. And the voltage-divider output is roughly 5V.

PS There is no Rg resistor, to add gain over 5..


texts: Path analysis D-FLIP-FLOP - what is SET?

texts:
I have to calculate the clock paths in a circuit and I have a 2 dual positive-edge-triggered D-TYPE FLIP-FLOP with clear and reset called DFF1 and DFF2.

Data sheet: http://www.ti.com/lit/ds/symlink/sn74lvc74a-q1.pdf

what does it mean: the CLR and SET pins of the two flip-flops are set such that {DFF1,DFF2} are reset to {1,0}?

Thanks!


texts:
I am confused in my understanding in implementation of voice guide for one of the instrument. I am trying to implement voice guide while operating one instrument. Audio data will be saved in memory ( No mic provision since data will be saved hard coded )

Hardware consists of DAC connected to controller and DAC's has inbuilt amplifier ( Please refer TLV320DAC Texas IC )
http://www.ti.com/product/TLV320DAC3100?keyMatch=TLV320DAC&tisearch=Search-EN-Everything

So, my question is how to get audio signal in digital format to save in memory?
Can we connect controller without DSP support to this DAC?

Please someone explain.
Thank you.


texts: ESP8266 Wake from deep sleep with an interrupt

texts:
I have an ESP8266, and a MCP23008 I2C GPIO expander.

The GPIO expander has the ability to trigger an interrupt when a pin changes - this is handy, as it means we can do something when an input pin changes (in my case, when a doorbell button is pressed or the door is opened and a reed switch activates).

The ESP8266 has 'deep-sleep' mode, which normally you wake from by the RTC activating the RESET pin by wiring the two pins together (through GPIO16).  Sleep is probably an optimistic word, as actually it's more like shutting the chip down entirely - when you hit the RESET, you boot from scratch.

My thought was to hook up the INT output of the IO expander to the RESET pin - in order to wake from sleep when something happens.  However, the INT pin remains active until the register is read - if I am holding the ESP8266 in reset, that'll never happen!

Would a valid solution that works with the vagaries of the ESP8266 be to make a basic one-shot MOSFET monostable circuit to fire when the INT pin is active?


texts:
I got a doubt about an interrupt grouping in stm32f103. In programming manual of microcontroller I found 5 ways to configure it.

But, while debugging, I found 8 ways.
How is it possible to get extra 3 ways, when only 4 bits of Interrupt Priority Registers are implemented?


texts: How to calculate frequency for PWM design

texts:
I would like to create a PWM controller for an open loop galvo-mirror. The similar questions involve motors and I can not directly use that approach to galvo-mirror which only deflects, not rotates.

It should deflect at +-1023 discrete angles, where the |1023| value would represent the maximum deflection. A particular period would start from -1023, -1022 ...0 ... 1022, 1023, 1022... -1023. So, the angular rotation would look like a triangular wave.

If I understand correctly, for a particular deflection angle I must have pulses of particular length. Thus, for 1023 angles there should be 1023 pulse width variations.

Now, the time between two successive consecutive positions is 100us. How to calculate the number of pulses within the 100us period (PWM frequency, switching) necessary to maintain that particular deflection angle, so the mirror does not jitter?

If I use the suggestion f>R/L from this question, then the minimum switching frequency is 1400Hz. But that does not look right, since I must have at least 10kHz switching frequency. In the 10kHz case, there will be only 1 pulse to support a 100us period deflection. What am I missing here?


texts: Is my IIR implementation (in C) correct for this difference equation?

texts:
I recently started developing a digital regulator for a DCM boost (Digital regulator for DCM Boost - How does it relate to duty cycle?) And I've implemented the difference the following controller in C:

$$ G_{Z} = \frac{1.39 z^{-1} - 1.332z^{-2} }{2 - 2.002{z^{-1}} + 0.002031z^{-2}} $$

in terms of a difference equation:

$$ y[n] = 1.001\cdot y[n-1] - 0.0010155 \cdot y[n-2] + 0.695\cdot x[n-1] - 0.666 \cdot x[n-2] $$

My code is as follows:

// Digi Reg Coeffs
const float a1 = 1.001;
const float a2 = -0.0010155;

const float b0 = 0.0;
const float b1 = 0.6975;
const float b2 = -0.666;

typedef struct
{

    float y0;   // new reg value
    float y1;   // last reg value
    float y2;   // last^2 reg value

    float x0;   // latest sample
    float x1;   // last sample
    float x2;   // last^2 sample

} voltage_control;

uint16_t DigitalRegulator(float error) {

    float duty = 0;

    voltage_control.x2 = voltage_control.x1;
    voltage_control.x1 = voltage_control.x0;
    voltage_control.x0 = error;   /// this is the new sample

    voltage_control.y2 = voltage_control.y1;
    voltage_control.y1 = voltage_control.y0;

    //calc new y0
    voltage_control.y0 = (a1 * voltage_control.y1) + (a2 * voltage_control.y2) + (b0 * voltage_control.x0) + (b1 * voltage_control.x1) + (b2 * voltage_control.x2);

    // new value for PWM
    duty = (voltage_control.y0 / PWM_GAIN) * PERIOD_VALUE;

    return duty;

}

Is this the correct way to implement a difference equation? I'm asking because the resulting controller seems unstable, and I'd like to know if it's my implementation or something else.


texts:
1) Why there is no multi-bit synchronization problem for slow clock domain ? it is obvious that the pointers could increment by more than one.
Screenshot from sunburst asynchronous FIFO paper page 12

2) According to FIFO depth consideration , why "The depth of the FIFO is therefore required to be at least 10 cycles, 5 in each direction for updating the pointer" ?

3) Why is the asynchronous FIFO driven with wclk clock from write domain ? and why rinc does not "AND" with !rempty ?

Screenshot extracted from sunburst asynchronous FIFO paper page 9

There is alternative version that does not require the AND gate to generate the signal wclken. Could anyone elaborate ?

Screenshot extracted from sunburst asynchronous FIFO paper page 5


texts: Shunt Resistor Color Code wrong or different

texts:
For a project, I was tasked with identifying some components. To identify all the resistors, I use the digikey calculator which so far gave me correct values. However, with that specific resistor shown in the picture, no table was able to correctly guess the correct value.

It is a shunt resistor and the value must be less than 1 Ohm. It also has a higher precision.
At first reading the values from right to left seemed logical, and I intepreted the middle silver band as white. In the end, I received a value of 690 Ohm, which cannot be.

I am currently thinking that the bands are to be read from left to right with the trailing black band to be ignored. That gives me the more likely result of 0.51 Ohm 0.25%.

My questions are:

Is my assumption correct.
What is the reason for using a different color code.

Thanks

EDIT: I added a second picture of a resistor with the same problem. Would be really fantastic if you could help me out.
Thanks


texts: Converting a 12V pulse to a shorter 24V pulse?

texts:
I have a bunch of Point-of-Sale printers which can emit a ca. 1 second long 12V pulse in order to open the attached cash-drawer.

Because of a procurement SNAFU, I now also have a bunch of cash drawers which would like a 24V pulse to activate the solenoid and open the drawer.

In spite of this, the 12V pulse USUALLY works. But not always.

So, my question is: is there a way to convert the 12V, 1 second pulse to e.g. a 24V, 0.5 second pulse, using only basic electronics which would NOT require an additional power source?


texts:
I am designing a software for a microcontroller that transmits and receive data from various UARTs in a loop every 15ms.
I am using UART interrupts to send and receive data. UART interrupt copy bytes to/from the UART TX/RX registers into the circular(a.k.a. ring) FIFO buffer.
I have read that the RX and TX circular buffer should be larger than data bytes and number is in power of two like 4,8,16,64,256 etc

So my question is what is the efficient size of the circular buffer? How can I calculate it?

I was reading about some queuing models. Can we use them to find the buffer size? What will be its arrival and service rate? Do these rates depend upon the baud rate or periodic system cycle?


texts: How to get the difference between two currents by using only analogue circuitry?

texts:
If I have two current sources, producing currents I1 and I2, respectively, getting the sum of the two currents is easy—just connect both sources to one end of a wire and the currents will be forced to go through it in the same direction, meaning that they sum up to I1 + I2. But is there some way to instead get the difference between the two currents to flow through the wire, i.e., I1 - I2, without involving AD and DA converters and digital electronics?

If of any interest, the way I1 and I2 are generated is by connecting a node with electric potential V to two conductors, with conductances C1 and C2, respectively, where I1 = V * C1 and I2 = V * C2. There is then a node with the potential 0 that can be used to create the voltage V over the two conductors, but which doesn't have to be connected directly to the conductors.


texts:
I have a microcontroller powered at 1.8V and I break out V_target, SWD, SWCLK, nRST, and GND from it.

Question: If I provide V_target from the microcontroller to the J-Link Plus, does that mean the I/O voltage levels on the serial wire debug pins are reduced to 1.8V?

I'm looking at this (arguably overpriced for what it is) V_target adapter, and trying to understand the real benefit I get from it: https://www.segger.com/products/debug-probes/j-link/accessories/adapters/supply-adapter/

It appears that it would just allow me to not require an additional wire for V_target coming out of my device.

J-Link Plus product page: https://www.segger.com/products/debug-probes/j-link/models/j-link-plus/


texts: Why is there often a metal clip around a dc motor

texts:
I have seen many DC motors with a piece of sheet metal that is bent and snaps onto the motor casing.

What is its purpose?
Is it an additional cooling body?
Or maybe to concentrate the magnetic field better? It covers the whole area where the permanent magnets are on the inside.
picture of such a motor with clip


texts:
Studying an IC component's datasheet, somewhere you meet electrical characteristics for the device. Device is tested under specific conditions (e.g. Vs).

How electrical characteristics are affected when conditions are different? How can I specify the new values?

In the case of H-bridge L6205N (PowerDIP20), what about values of V-IL, V-IH, I-IL, I-IH, when Vs isn't 48 V but 9V?


texts:
I am interested in developing an idea using CMOS sensors, and I was wondering if I could get some pointers (I don't know much about image sensors)

First, my understanding is that CMOS image sensors can (in theory) access pixels one at a time -- like simplified 2d ram there is a vertical line and horizontal line select -- this is different than CCDs which typically have to read out chunks of pixels at a time. Please correct me if I am wrong.

If I am correct is it possible to get a raw CMOS sensor that let's me read out pixels in what ever order and timing I feel like (so I specifically do not want an easy to use, standardized video format, and I am willing to do the various downstream DSP and error correcting myself.)

At this stage of my project, I don't need a high resolution, low noise setup -- something simple would be fine, I just want complete control over how I read out the pixels.  (However, if the system came with simple optics and shutter that would be great)

Does anyone know of such a setup?  Are all CMOS sensors available in raw format, or is what I'm asking for very odd?


texts: If I put 12 volts across a 1 ohm resistor, will it pull 144 watts?

texts: I would think putting 12 volts across a 1 ohm resistor would pull 12 amps of current, and since watts=volts*amps the resistor would be dissipating 144 watts of heat,  all of this assuming the source could supply it.  Am I correct?


texts: What should be the watts of solar panel and battery size

texts:
I want to light one 70watt bulb for 12 hours at night time. I want to know what should be the Watts of the solar panel and how much Ah battery will I require?

I searched many of the questions here and found this one relevant. But the question is how will I know the volts which you assumed here to be 12 V?

Powering 10watt light bulb for 24 hours using solar power

May I know if I have done the right calculation as below

Panel Watts req = 70 * 32 / 10

Sunshine hours=10

Assumed 12V, Battery Ah= 70W / 12V * 12h = 70Ah


texts:
I'm working on STM32F303VC. How does the heap allocation work?

When I declare the arrays outside main() it allocates them on the heap - SRAM - 0x2000000 and forth in this MCU. But what determines the size of the heap? (And hence its overflow.)

There are two options:

In the 'startup_stm32f30x.s' file I see that:

Heap_Size       EQU     0x00000200 // Which is only 1K!

[See here: [http://www.keil.com/support/man/docs/armlib/armlib_chr1358938939461.htm. Anyway, I just used the default file from STM's library]
But on the target configurations options, the R/W memory area is declared to be a size of 0x8000 (which is 32K).

So I checked this in the debugger:

uint16_t _xValH[5000];
uint16_t _xValL[5000];
uint16_t _xVal[5000];
//3*5000*2 bytes each = 30 kilobytes

int main(void) {

    _xValH[4999] = 0x4;
    _xValL[4999] = 0x5;
    _xVal[4999] = 0x6;
}

This didn't throw an exception - which means that it is the second option of the above. But furthermore, even if I go above the 32K - say:

uint16_t _xValH[6000];
uint16_t _xValL[6000];
uint16_t _xVal[6000];
//3*6000*2 bytes each = 36 kilobytes

int main(void) {

    _xValH[5999] = 0x4;
    _xValL[5999] = 0x5;
    _xVal[5999] = 0x6;
}

It's still working! The only time it throws me to exception is when I surpass the 40K - which is the limit of the SRAM (0x20009FFF).

So, what is the meaning of the A line code? And the meaning of the size I enter in B?


texts:
I have what is probably a really stupid question, so please don't laugh at me. Say I have a circuit with a microcontroller and an LED. This circuit is powered by two AAA batteries in series for a total supply voltage of 3V. If the LED has a forward voltage of 2V, does that mean that it could starve the MCU of voltage and cause it to reset?

My thinking is that 3V - 2V = 1V, which wouldn't be enough to run the MCU. What am I missing?

Clarification: I'm not connecting the LED in series before the MCU Vcc pin of course. The LED is driven by one of the output pins of the MCU.


texts:
I need to convert from 4 to 3.3V. So I was thinking of a diode, or voltage regulator. Voltage regulators, I know that it uses about 5mA to do the job.

How much current a diode uses ? I cant find this information...

[sorry I deleted the former question, was wrong 3.3 not 4.4]


texts: Small size ultra short waves (UKW) emitter

texts:
I want to create a small battery-powered device that can emit a few bytes per day to as far as possible (100 km?).

While discussing with someone working on sensors placed outside (even in the countryside), he said that they use ~170 Mhz (ultra short waves), with a device such that the battery can last 10 years without any human intervention.

This looks too good to be true, is this really possible? I mean:

battery-powered (Lithium Cell Battery CR2032 3V)?
long range (100+ km)
no GSM signal required, using ultra short waves instead

and let's add (to make it completely incredible):

small PCB possible (< 5 x 5 cm), and cheap


texts: Slayer exciter (mini Tesla coil) not working with IRFZ44N

texts:
I made a Tesla coil using the circuit from this video.
The MOSFET seems to be getting hot and current passes through the primary but I get no response from the secondary.

Here are the dimensions of the coil:

Secondary winding: 1.5 inch 670 turns
Primary winding: 3 turns
MOSFET: IRFZ44N (fresh)
Capacitor: 3.3uf 50v
Power supply: 15V @2000mA

Please help me with this project as I am an amateur in electronics.


texts:
How important are the specific termination values used for PoE pairs (pins 4&5, 7&8)?

Below is the recommended Ethernet front end for Micrel’s KSZ8841/42.

http://www.micrel.com/_PDF/Ethernet/app-notes/an-139.pdf

Would it be acceptable to use 49.9 ohm resistors in place of the 51ohm resistors? Why did they specify 49.9 on one side, and 51 ohms on the other? I’d like to make them the same in order to reduce the number of component types. This would not only help drive down the price of the 49.9 resistors but also mean there is one less component type to manage in inventory and load into the pick n place machine.

There must be a good reason for specifying slightly different resistor. I'm sure they didn't do it just for fun. How critical are the terminations of the PoE pairs? In my mind they are not critical because there is no data being transmitted over them, but I’m not sure how much their termination influences the characteristics of the cable for the other conductors.


texts: Will a diode conduct if one side is floating and one side has voltage applied to it?

texts:
I have a circuit that has a battery output voltage of about 7V and can also have a charger input that when plugged in will output around 9V.  The battery/charger power a microcontroller (regulated down through an LDO) as well as a motor driver (simply shown here as a current limited transistor).

The battery charging is taken care of separately through a multi-cell PMIC, but I need to isolate the battery positive output from the charger input when the charger gets plugged in.  I figured I could use a transistor switch to control this, but I thought that an easier way to separate the supplies would be to simply put a Schottky diode from the lower voltage to the junction where they connect.  I want to confirm the behavior of the diode and if this design seems reasonable (assuming the diode can handle the load current and that it is low turn on voltage).

I know that when the charger is plugged in, the diode will not conduct b/c it will be reverse biased; however, I am not quite sure on the behavior when the charger is not plugged in.  It would seem that the cathode side does not have a defined voltage, so I am not sure if it would be considered forward biased or not in this case.  I would imagine the diode would conduct but would like a more rigorous answer.

Also, do not assume the driver (represented by Q1) is turned on.

simulate this circuit – Schematic created using CircuitLab


texts: Calculate total impedance in circuit with series RL in parallel with C and R

texts:
Hi im trying to find the total impedance in this circuit but im having troubles figuring it out. I have calculated the individual impedance for each branch like following:
Xc = 46.8 ohm at -90 degrees
Xl = 46.8 ohm at 90 degrees

ZR = 1000 + j0

Zc = 0 - j46.8

ZRsL = 10 + j46.8 => (47.8 ∠ 77.93)

So now when i try to find the total impedance the first thing i tried was ZT = 1/((1/ZR)+(1/Zc)+(1/ZRsL)) which i get to be 23.1 ohm. Which is wrong. Any help would be appreciated.

EDIT: So i get how do do it from the comments below but i dont know what numbers to use. Like with (ZT=(Z1⋅Z2⋅Z3)/(Z1⋅Z2+Z1⋅Z3+Z2⋅Z3)) What do i actually put as Z1, Z2 etc. I cant take (10 + j46.8)( 0 - j46.8) can i? In my mind that is 56.8-46.8. I know it isnt but i cant figure out how to do it


texts:
I need to write to a register from 2 sources.. in this case, a pci host
and a microcontroller.  The 2 will never access the register at the same time (basically once the PCI is done , it hands it over the other host, which will then have exclusive access until it's finished).

Since the clock domains are different, I can't just have multiple
processes writing to the same register..

always @(posedge pciclk or negedge nrst)
   if pci_wr & pci_addr == 0
        cntl_reg = pci_data

always @(posedge mcclk or negedge nrst)
   if mc_wr & mc_addr == 0
        cntl_reg = mc_data

So how is this typically done?  Not sure if this a fundamental architectural question, or just a syntax question on how to write the sensitivity list.


texts:
I am trying to use Spartan 3E kit to generate 50 MHz clock. The kit comes along with a 50 MHz crystal which I am trying to use.

So, I wrote a simple code to output the clock from the FPGA to the SMA connector. The code is as follows:

module clock (in_clock, out_clock);

input in_clock;
output out_clock;

wire in_clock;
reg out_clock;

always @in_clock
out_clock = in_clock;

endmodule

The UCF file which mentions the pin configuration is as follows:

NET "in_clock" LOC = C9;
NET "out_clock" LOC = A10;

The output waveform of the 50 MHz clock looks like the following. The waveform is of 50 MHz but I do not get square pulses. In addition to that, the voltage level is too small (<10 mV). Can someone please tell me where the problem could be?
50 MHz clock http://www.ee.iitb.ac.in/student/~neelsmehta/2012-02-23%2011.08.20.jpg


texts: Debouncing : Can we use only one capacitor for multiple Key?

texts:
In my project, I've to use more than 5 keys to be interfaced with Micro-controller. We can use sufficiently large capacitor to reduce debouncing of key. My question is: can I use one single capacitor for all the five keys or should I use separate capacitors for each key.

if No, what would happen we try to use one capacitor for all keys.


texts: Why is String Conversion Necessary to LCD

texts:
So I got this code up and running and it works fine but I don't understand just why and what it is the code concerning the ldc display string is doing. I know it has something to do with different type of microcontrollers and the string needs to be converted to like an unsigned 8 bit integer in this case to work?
Below is the code.this is on a L476VG Discovery Board with an STM32L476 arm microcontroller


texts: KVL in the capacitor during transient analysis

texts:
I can see that this topic has been discussed many times in this site. But I still can't figure out why I am still not getting my correct equation applying the KVL.
Consider a circuit as shown:

simulate this circuit – Schematic created using CircuitLab

I figured out that the capacitor charges to 6V at t<0. For t>0, there is discharging of the capacitor through the resistor and inductor. The direction of discharge is as shown by the red arrow. So I applied the KVL in this loop and the equation is

.

I am writing -ve value for the instantaneous voltage across the capacitor because the current I have supposed is discharging the capacitor. But my teacher told the equation I wrote was wrong but couldn't convince me why exactly I was wrong. I don't have any kind of problem with the further math involved in finding the expression for transient current. I just want to know what is the correct equation and why it is correct.


texts: How information is collected from a photographic sensor

texts:
For example, you have a sensor measuring temperature, light intensity or anything else.
You have microcontroller reading your data and a sd card to save your data.
I can understand how you can collected data from 1(one) point. But the plate is a mass of points.
Pixel separation happens after transfer, doesn't it?
How can I transfer all of this information on a wire ?
Where can I read about this part of electronics?...
Thanks.


texts:
I'm using a low-power PIC16LF1554 together with an nRF24l01+ 2.4GHz transceiver.

During power-up, the PIC will try to initialise the RF module before the supply has reached the required minimum and will fail unless I insert a delay. Something like this

void main()
{
    // 4x PLL, 8MHz internal oscillator = 32MHz clock
    OSCCON = 0xF0;

    // wait for HFINTOSC to stabilise
    while (OSCSTATbits.HFIOFR == 0);
    while (OSCSTATbits.HFIOFS == 0);

    // configure TRIS, APFCON etc.
    // (removed for clarity)

    // **** necessary delay ****
    __delay_ms(500);

    // initialise RF transceiver
    NRF_Setup();

    // main loop
    while (1)
    {
        // ... whatever ...
    }
}

I don't quite understand why this is so because the RF has a minimum requirement of 1.9V and, according to the datasheet, the PIC requires 2.5V for the HFINTOSC to stabilise, so I thought it should be ok. (The nRF24l01+ is on a separate breakout board, which has other supporting components so maybe that affects things).

So, while this works fine and obviously the delay has no impact on the end application, I still don't like the idea of having to code an arbitrary delay and my gut feeling would be to try something a bit more deterministic. The 500ms is probably overkill and I could empirically find something shorter, but that doesn't feel like a robust approach.

So, is there some easy way to measure what the VDD is as it ramps during power-up, either in code or with external components, in the absence of a known voltage reference? Or perhaps that's not the problem I'm seeing and the delay is necessary for another reason?

EDIT In case it's relevant, these are the CONFIG settings

// CONFIG1
#pragma config FOSC = INTOSC    // Oscillator Selection Bits (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE = OFF       // Watchdog Timer Enable (WDT disabled. SWDTEN bit is ignored.)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = OFF      // MCLR Pin Function Select (MCLR/VPP pin function is digital input)
#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable (Brown-out Reset disabled. SBOREN bit is ignored.)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)

// CONFIG2
#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write protection off)
#pragma config STVREN = OFF     // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will not cause a Reset)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), 1.9V trip point selected.)
#pragma config LPBOR = OFF      // Low-Power Brown Out Reset (Low-Power BOR is disabled)
#pragma config LVP = OFF        // Low-Voltage Programming Enable (High-voltage on MCLR/VPP must be used for programming)


texts: Does Registers and RAM are same kind of memory?

texts:
Recently, I found out a YT channel of a man who build a 8-bit computer and explain how.

In his video on the registers, he uses a D flip-flop, and in his other video on the ram, I understood that he says he'll use the same system as the registers, and that's called 'Static RAM', and the 'Dynamic RAM' is faster.

But I think that the registers are faster than RAM, so if dynamic ram is faster than static ram, which uses the same kind of system than the registers to store, they are slower than dynamic ram...

Did I not understand the videos or something else?


texts: Oval solder spots on universal pcb boards

texts:
I’ve searched as much as I could...

For the double-sided tinned universal pcb prototyping boards...

They have a bunch of oval solder spots on each end of the board (see pic).

What is the use case for those?


texts:
I have been working in some homemade raspberry project, using node.js to control a relay for some lamps.
I am using:

raspbery PI  Zero W
6 channel relay HL-56S v1.0 (https://www.ptrobotics.com/modulos-de-reles/7671-6-channel-12v-relay-module.html)

Connections:

Vcc => 5V (pin 2);
GND => Gnd (pin 6);
1In => GPIO 20 (pin 38);

I'm not familiar with the international system so it's hard for me to explain with a correct scheme.
Can you help me with photos?

The only problem you have is that with the connections of the images the lamp is always on regardless of the relay status.
You can see that in one photo the relay is off and in the other one it is already on and still the lamp is always on.
Are you finding any problems?
Here's my relevant code:
app.post('/relay(38/on', function(req, res){
  gpio.write(38, false, function(err) {
      if (err) throw err;
      console.log('Written True to pin 38');
      console.log(path.join(__dirname, 'public'));
      return res.render('index', {status: 'Relay 38 is On'});
  });

//RELAY OFF
app.post('/relay/38/off', function(req, res){
  gpio.write(38, true, function(err) {
    if (err) throw err;
    console.log('Written False to pin 38');
    console.log(path.join(__dirname, 'public'));
      return res.render('index',{status: 'Relay 38 is Off'});
  });
});
});

I hope that's enough.


texts: Sonar single transducer element SNR vs array SNR

texts:
Background:

I'm taking a flexible learning unit on radar and sonar systems in a vocational college for an assoc. degree level course. The teacher has given us a reading assignment: "Chapter 15 Underwater Acoustics", source unknown, and we are to answer the end-of-chapter questions. I have searched online and off, unsuccessfully, for the source reference, and there are no texts on sonar systems in the college library system in my state.

My question is a general systems engineering design question, I believe:

Given a single sonar transducer element SNR (signal to noise ratio in dB) of X dB, what would be the SNR of an array of  M elements?

My question relates to calculation of the array gain, AG,
where, stated in the reading material,

$$
AG = 10~ log ~{ \left \lbrace {{(S/N)_{array}} \over {(S/N)_{element}}} \right \rbrace }.
$$

I've been given the element SNR, but I have no information on the array SNR.

In the absence of any information on multiple SNR elements, I've gone ahead and guessed a possible answer.

In the problem I'm trying to solve, \$ ~ SNR_{element} = 40 ~dB  \$ $$ \therefore decimal  ~ratio ~ (S/N)_{element} = 10^{40 dB ~/~ 20} = 100 $$

Question now is, to get the  \$ ~SNR_{array} \$, do I add or do I multiply? Taking the RMS doesn't make sense, since it is implicit.

Given M = 25 elements in the array. Raising \$ (S/N)_{element} \$ to the 25th power, i.e. \$ ~100^{25} \$ doesn't make sense.

But adding together: \$ {~(S/N)_{array} = (S/N)_{element} \times M = 100 \times 25 ~ elements = 2500 ~} \$ puts the answer in the realms of possibility:

$$ So, ~ AG = 10 ~log {2500 \over 100} = 10 ~log~ 25 = 14 dB $$

Am I close? A reference would be appreciated.

@drfried, the problem is assuming an ideal solution. The book problem is originally stated as:

If an element of an array has a signal to noise ratio of 40dB, what would be the array gain of 25 similar elements in such an array?

No further information or diagram is given.

@Andy, From the response you've provided, and a response I received on the linkedin.com "Antenna Solutions" group, https://www.linkedin.com/grp/post/2232865-6001739735423270914 , without source reference, I'll see if I understand you correctly. The answer I've been given there is \$ SNR_{array} ~=~ 10~log~M ~+~ X ~ [dB] \$. Let's see if they coincide. Apologies for the mathematical massacre that follows.

Firstly, let's replace the subscript "array" with \$ a \$ , and the subscript "element" with \$ e \$.

If I understand @Andy correctly, we can write his statements as,

$$
(S/N)_a ~=~ { {\sum\limits_{i = 1}^M S_{ei} } \over {\left( \sum\limits_{i=1}^M N_{ei} ^2 \right )^{ 1 \over 2 } } }
$$

where, for my problem,  \$ S_{ei} ~=~ S_{ej} ~=~ 100~ units ~(ie~ \mu V,~ mV, ~etc.) \$ and \$ N_{ei} ~=~ N_{ej} ~=~ 1~ unit ~(ie~ \mu V, ~mV,~ etc.) \$.

$$
\therefore ~~~ SNR_a ~=~ 20~ log ~ \left \lbrace {M S_e} \over { ( M ~ N_e^2 )^{1 \over 2} } \right \rbrace
$$

$$
=~ 20~ log ~ \left \lbrace {M S_e} \over { M^{1 \over 2}~ N_e } \right \rbrace
$$

$$
=~ 20~ log ~ M^{1 \over 2} (S / N)_e
$$

$$
=~ 10~ log ~ M ~+~ 20 ~log ~(S / N)_e
$$

$$
=~ 10~ log ~ M ~+~ X ~[dB]
$$

Looks like both responses coincide. I'm inclined to accept @Andy's reasoning and experience, so I think my question may have been answered.

To finish the whole problem for posterity, as stated above, M = 25 elements and X = 40 dB.

So, \$ (S/N)_a \$ = 14 + 40 = 54 dB.

$$
\therefore ~~~~AG ~=~ 10~ log  \left \lbrace {(S/N)_a} \over { (S/N)_e } \right \rbrace ~=~ 10~ log  \left \lbrace {10^{54~dB ~/~ 20}} \over { 10^{40~dB ~/~ 20} } \right \rbrace ~=~ 10~log~(10^{(2.7 ~-~ 2) }) ~=~  7dB
$$

Don't even need a calculator!!!

Thanks to all who helped.