texts:
This is a snippet of the data sheet of the BJT transistor 2SC828A.

What do they mean by Q R and S classifications?
I know that 2 in the code means transistor. What do the other numbers and letters mean (SC828A)?

Link to the data sheet:

2SC828A data sheet


texts: Transformers confusion with output voltage and number of iron cores used

texts:
I have been wondering about an experiment which can help me observe that the output voltage of a transformer increases as we increase the number of cylindrical iron cores to an experimental transformer in normal high school labs. So I have indeed conducted this experiment, and I notice that as I put more and more iron cores, the output voltage seems to go up given that I do not change the number of turns of the coils, and I keep the input voltage the same.

My question is why does it does it do this?

My thoughts: If we increase the number of iron cores, then this establishes a stronger magnetic field when the primary current enters the coils. A stronger magnetic field means a greater change in magnetic flux, and therefore the greater emf induced on the secondary coils (how about primary coils)?

There was a suggestion from other stack exchange sites that greater iron cores inserted implies a stronger current, but I do not understand why this is the case. For instance I would argue that:

$$\frac{I_s}{I_p}=\frac{V_p}{V_s}$$

Since, Ip increases (under the assumption that current increases, although I am not sure if primary current or secondary current increases), Is will get smaller over time as there will be some losses as it is moving through the iron core, then it means given Vp remains constant, Vs will therefore increase?

(Is = secondary current, Ip = primary current, Vs= secondary voltage, Vp = primary voltage).

My confusions:

i) Why do I observe an increase in output voltage when I add more iron cores to my transformer? How do I explain this using the laws of physics?

ii) Is there a relationship between the number of iron cores used, and the output voltage in the transformer?

I would appreciate the clarification as I am genuinely very confused with transformers at the moment.


texts: If I drive a piezo sensor with switched DC, will I get back over-voltage?

texts:
I have a built a vibration detection circuit based on an op-amp to trigger high speed photography of balloons popping.

(I'm using this circuit)

(From this blog - not my image)

It works well. It includes a 5 volt zener diode to bleed off the potentially high voltages that it can give from strong shocks. (well, a 5.2 zener, since that's what I had)

I have found that the pictures look really good if I put some cornstarch in the balloons before shooting. It gives a spun cotton look to the air inside, but the cornstarch needs to be suspended in the air to get the best effect. Thus I have to shake the balloon, put it in my rig, and quickly turn everything on and pop the balloon, triggering the photo.

It occurred to me that since I already have a piezo element touching the base of the balloon, I could drive a moderate frequency tone through the transducer to create a loud base buzz that would kick the cornstarch into the air inside the balloon.

To do that I would drive the piezo element directly from an output pin on my Arduino (or perhaps run it through a transistor if I need more current, but I doubt if I will. I get pretty loud tones with a current limiting resistor in place that keeps the current well below the 40mA limit on an Arduino output pin...)

Anyway, my question is, will a piezo element being driven as a speaker generate echo voltage that's higher than the input voltage, sort of like the boost effect you get from an induction coil?

And can I be confident that my (5.2 volt, what I have on hand) zener, wired across the terminals of my piezo, will protect my Arduino input line from damaging voltages when I bump the sensor and generate big spikes of voltage from the transducer?

EDIT: Some  person deleted the paragraph on why I put cornstarch in the balloon, and why I need it to be suspended in the balloon. I've put it back. Please don't delete it - my question does not make sense without that background info included.

EDIT #1: One of the posters asked for me to post pictures. Here is one:

There's a gallery of images at http://www.pbase.com/duncanc/popping_balloons&page=all


texts: Why use a capacitor instead of just a wire?

texts:
https://youtu.be/30rPt802n1k

In this video an arduino is used as a programmer. So its reset and ground should be connected. However, the guy prefers to use a capacitor instead of just using a piece of wire. I am wondering what is the purpose of the cap here.


texts:
I am playing with BJT push-pull circuit from a previous question (there are 3 push-pulls with various speedup tricks for comparison):

I've recently realized, that's it's voltage follower, so it's not supposed to show rise/fall times shorter than ones of input signal.

Is it possible to modify it somehow to have more 'steep' output? I don't expect it to be like Schmidt trigger, just want it to have more than 1 voltage amplification near 0.5*VCC.

Is that possible? Probably some fancy level shifting, diodes...

Updated circuit which gave me somewhat desired results. 150 Ohm resistors on the right are load.


texts:
Will this circuit work to connect an lapel mic mic (expecting ~2.5v plugin/bias power) to an XLR input providing phantom power (I have a choice of 12 to 48v).

I assume the lav mic has a typical electret capsule / JFET type arrangement. It's got a TRS plug, though T&R seem to be shorted.

EDIT: the mic claims to have an impedance of 2.2KΩ Max.

Question

EDIT: the circuit works, using 12v phantom, with a 100nF cap and a 10k resistor.

What disadvantages does it have compared to a more complex design such as those at http://www.epanorama.net/circuits/microphone_powering.html, and are there any simple alterations to improve it? Any rough suggestions for component values?

I'm expecting the resistor to limit the current/voltage to the mic, and attenuate any audio signal going to the ground. The capacitor would prevent the phantom power on cold being shorted to ground, whilst allowing audio to pass.

Background

I'm trying to connect a cheap ($1 ebay special) electret mic to an XLR mic input, and power it with phantom power. I'm using a Zoom H5, so have a choice of 12-48v phantom. (I don't want to use a battery)

The mic works fine with the Zoom's plugin-power input (2.5v), giving a surprisingly good signal with very little noise, but I want to connect several to the H5, so need to use the XLR inputs (also want to use an H5 capsule, which the plugin-power socket disables). I'm aware I can buy XLR->Plugin Power adaptors, but they're pricy, as are lapel mics designed to plug into phantom.
Also, I kinda want to see if there's a simple solution...!

Updated Circuit

In my final circuit, I've adjusted the resistor choices to account for the voltage drop on the phantom supply when under load. These values give about 3.5v on the mic, which gives a stronger signal than 2.5v, improving SNR, whilst keeping the DC resistance high enough that the supply doesn't drop too much.

50nF ceramic caps seemed to work best from the selection I had.

The circuit is still small enough that both the circuit and a 3.5mm socket will fit into the tail of an XLR plug.

The sound quality is great; it actually seems to out-perform the Zoom's built in plugin-power input, probably because the higher voltage increases the SNR.

simulate this circuit – Schematic created using CircuitLab


texts: Msg about opencore in Quartus programmer

texts:
I did some changes to a design in Quartus and in Qsys. Now when I load the design to my FPGA with Quartus programmer then I get a message about opencores and that there is unlimited time. The msg was not there with the original design.

Why does it appear and what are the limitations the msg is mentioning?


texts: Calibrate for an inaccurate 50 ohm load in a DIY Vector Network Analyser (VNA) based on a VSWR RF bridge

texts:
I have built a "DIY VNA" using a frequency generator, an SDR receiver, a RF Reflection Bridge and a 50 ohm load. This is used to measure "VSWR values" of antennas to see what frequencies they are matched to.
My reference for the build is https://medium.com/home-wireless/testing-antennas-with-the-limesdr-mini-98b59b99c8b9

I am not sure how accurate the results are. I have some doubt in the results. I have measured the 50 ohm load that I have with a multi meter and it shows 52 ohm rather than 50 ohm. Is this something that will have an effect on the power loss measurements vs base values that I am doing? Does this affect where the antenna will have its measured maximum power loss vs the true value?

Can I compensate for this error or calibrate the results to be true while using the 52 ohm value that I have? Can I estimate the error on frequency based on the error in the load resistance?


texts: How to find the step and impulse response of a circuit with a diode

texts:
I have a circuit similar to the following:

simulate this circuit – Schematic created using CircuitLab

I am trying to find the impulse and step response mathematically.  I know I can split the responses up from the time the left part of the circuit switches from positive to negative.  Is that the proper way to do it?  Also, I am wondering how to find the Laplace Transform of an if statement.

I have the formula from node voltage for the response when the diode is turned on (assuming the diode drops .7V).  Problem is when the diode is turned off the stored voltage in C2 determines the output.  If this was a function of time, this would be simple, but it is a function of when the diode turns off which is tied to the voltage of the input.

Diode turned on:
    $$V_o = -1.4V + 0.7(sC_1/(1/R+sC_2))+V_i$$

I'm not sure how to go about finding the response when the diode is turned off.

Update:
The input would be a decaying sine wave.


texts:
I have to work on a magnetic regenerative braking system, I already designed the magnetic brake and it works, now I need to regen the braking force (Lorentz force). What kind of motor and circuit should i use.
PS: The model i designed is an aluminium wheel rotating on a magnetic flux.


texts: Will 14.4 volts from my solar charge controller damage my 12v equipment?

texts:
My charge controller is set to recharge my battery bank and begin a float charge at 14.4 volts.
If I use some of my 12 volt components during the day while the batteries are charging, will this high voltage damage my diaphragm pumps and Arduino etc.?
I thought of adjusting the float charge level at the controller but someone told me that doing so will be bad for my sealed lead acid batteries.
I'm thinking of using XL4015 or XL4016 buck converters, but I want to maximize the power before reaching the 11.1V load disconnect..
And advice and correction will be highly appreciated.
Thank you so much!


texts: Hybrid Model - Why differential of voltage equals AC component voltage?

texts:
In the derivation Hybrid Model (Equivalent Circuit) of transistor, there is a step that replace differential \$dV_1\$ with AC component \$v_1\$. However, to the best of my knowledge, voltage equals sum of DC component and AC component, that is \$V_1(t)=V_{DC}+v_1(t)\$. If take derivatives on both side respect to time, as \$V_{DC}\$ is a constant, we get \$\frac{dV_1}{dt}=0+\frac{dv_1}{dt}\$ which simplifies to \$dV_1 = dv_1\$. So, I feel quite confused about this replacement.

Also, I think \$dV_1\$ means change (approximately) in voltage from time \$t\$ to \$t+\Delta{t}\$ while \$v_1\$ means the value of AC component voltage at time \$t\$, that seems to be quite different. Thus why shall we replace \$dV_1\$ by \$v_1\$ but not \$dv_1\$? Could anyone give me some hint? Thanks.


texts: MSP430 programming under Linux - mspdebug fails to connect to programmer

texts:
I am trying to program the MSP430 (on an MSP-EXP430F5438 evaluation board) under Linux using gcc-msp430 (I eventually will do code larger than the 16k that the free version of the Code Composer allows).

As a debugger, it is recommended to use mspdebug, but when I try to use it, it doesn't connect to the FET430UIF.

~$ sudo mspdebug uif
MSPDebug version 0.19 - debugging tool for MSP430 MCUs
Copyright (C) 2009-2012 Daniel Beer <dlbeer@gmail.com>
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

TI3410 device is in boot config, setting active
Initializing FET...
FET protocol version is 20408002
Configured for Spy-Bi-Wire
ti3410: usb_bulk_read: No error
warning: fet: set VCC failed
ti3410: can't send data: No such device
fet: command C_IDENT1 failed
fet: identify failed
Trying again...
Initializing FET...
ti3410: can't send data: No such device
fet: open failed
ti3410: warning: TI_CLOSE_PORT failed: No such device

The same device works correctly with Code Composer running on a Windows virtual machine or on a physical Windows system, so I know it is working.

I tried on Ubuntu 12.04 and on Arch Linux and got the same errors.

As recommended in an answer, I tried with -d and got further, but didn't work:

~$ sudo mspdebug uif -d /dev/ttyUSB0
[sudo] password for renan:
MSPDebug version 0.19 - debugging tool for MSP430 MCUs
Copyright (C) 2009-2012 Daniel Beer <dlbeer@gmail.com>
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Trying to open UIF on /dev/ttyUSB0...
Initializing FET...
FET protocol version is 20408002
Configured for Spy-Bi-Wire
Set Vcc: 3000 mV
Device ID: 0x0580
Device: MSP430F5438A
Code memory starts at 0x5c00
Number of breakpoints: 8

uif: read error: Connection timed out
fet: warning: message C_IDENT3 failed
uif: read error: Connection timed out
fet: message C_IDENT2 failed
fet: identify failed
Trying again...
Initializing FET...
uif: read error: Connection timed out
fet: open failed

What is wrong?


texts:
I am trying to simulate this circuit I saw here:

However, when I simulate it, the "mid-point" does not behave like the blue line in the above picture. You can check the simulation here:

Is the original picture wrong? Am I missing something?


texts: What could be meant by "Open output" in this context?

texts:
Regarding this transducer what could be meant by "Open output"?:

The transducer is set to output 0..10V voltage.

And if the transducer sees 10V at its output through 220k resistor is it a problem for the transducer?

The reason Im asking in the circuit below there's a similar situation where 10V at node R4/R5 applies:


texts: Trying to simulate a simple micro inverter, Cant connect scope

texts:
I am trying to simulate a simple Micro inverter. Below is my Simulink Model :-

But somehow i am unable to connect Voltage Sensor to a scope. Even if i used a DC Source instead of Solar Cell.

What i have done is  :-

Connected two capacitors in parallel with the Solar Cell/ DC Voltage Source to distribute the voltage.
Using two Thyristors each with antiParallel diode and using Resistive Load, I am trying to measure Voltage and Current of the Load Branch.

Issue : -

Voltage Sensor and The Current Sensor i am using is from Simscape/Electrical Sensor Library, but i am unable to connect it to a Scope or a MUX. How do i read my load outputs?

I am fairly new to EE SE & Simulink, so if any additional info is needed, Please drop a comment.

Thanks..


texts: Using an ATS interface to remotely start a generator

texts:
I am trying to use the ATS (automatic transfer switch) interface of a generator to set up a remote start system using a microcontroller with a cell phone modem and relay bank (for a rural microgrid application in India).

The ATS interface connection is shown below:

In the circuit diagram, the five pins are labeled as follows. Based on the labels I'm inferring inputs vs outputs, and guessing at what GC and MC stand for.

INPUT?   1. Auto start switch
OUTPUT?  2. GC relay            generator contacter?
         3. MC relay            mains contacter?
         4. BAT+                12V lead acid battery
         5. BAT-

Can I use this interface to start the generator? If so, how, and what is each pin for? Also, what is this type of connection called, so I can order the appropriate cable?

The manual for the generator does not include any detail. However, it's my understanding that the 12V+/- supply power to the ATS, GC and MC are to allow the genset to drive contacters, and the auto start switch should short to ground to start the generator, then open circuit to stop it. Is this correct?


texts: 2 way 0.1" jumper sockets - which way up?

texts:
Simple question. This is a typical 2 way jumper socket:

Which way is up? [I suspect in practice it doesn't matter, but still curious]


texts: Single voltage replacement for 741 opamp

texts: I am working on a project that recreates the cassette-in port on an Apple II for use in an Apple IIGS. The original circuit used the LM741. The location where I am interfacing my circuit only has +5V and GND. The audio is decoded using a zero crossing detector. Would a single supply opamp like an LM358 be a suitable replacement?


texts: How many physical lines does an AXI4 bus require? How do signals described in the standard map to physical lines?


texts: I have a 12 volt AC 300 watt plug in transformer used for outdoor landscape lighting. I would like to control individual lights with switches, however the transformer manufacturer insists no load side switching is allowed.  They indicated to control lights, each group has to be on its own transformer with switches on the input side. Why would this be?  Certainly a 120 volt AC switch should be able to handle 12 volts AC. Is there something unique about the transformer that makes it unsafe? Any insight is appreciated.


texts:
I have a question concerning a power adapter.
I bought a weather station from US but I live in Sweden with   EU electric plug 220V.

The original power adaptor has the following spec.

Input : 120V AC 60HZ 6VA.
Output : 5V DC 100mA.

Which option is the best ?
Step down ?
Can I use a 5V output voltage adaptor with my 220V input ?

Thanks in advance.


texts: Eagle V7 - Add via while routing without changing layer

texts:
I am using Eagle 7.6 to route a four layer board. While routing a trace, I would like to either add a via at the end of a trace or place a via mid-trace without changing the the current layer. I believe this is done with the spacebar in V8 but I don't have that.

The application is to 'pin' ground and power traces to the inner planes without a lot of futzing about. For example, all components (SMT) with a ground pad would have a little trace coming out and going straight to a via for ground.

I know I can lave the stub traces and go and drop the vias on top afterwards but this can fail if the grid changes or I am a bit clumsy.


texts: Using an arduino to control whether or not a phone is charging or not

texts:
I am working on building a circuit that is controlled with an Arduino Pro Micro. It is being fed by a 3.7V 5000mAh battery which is also going to be used to charge the phone, but only when the Arduino program tells it to. That battery is hooked up to a charging board with variable voltage output (basically a DC-DC step up module built in to the battery charging module. I have it set at an even 5V of output). That 5V supply is used to power everything in my circuit.

The easiest option for this scenario would be to use a Relay switch, but a normal relay switch is big, noisy, and unnecessary (as long as I can do without it), and I don't have any solid state relays designed for DC power.

Instead, I want the arduino to switch a transistor on and off to send the phone 5V @ ~1 Amp, which my battery can handle (when I wire the phone directly to the battery, the current reads just over 1 amp at 5 volts).

The problem is, I don't know enough about transistors and general electronics to get this to work. The circuit that I have right now is pictured below:

(There are some details in this circuit that aren't important to my question, for example, don't worry about the SPDT, its just there to control whether the phone is charged by the battery or from the charging input to the circuit. Again, don't worry about this).

This circuit does not work right now. It works if I am testing the load with an LED to simulate the phone being charged, but when I actually connect the usb charging cord to the phone itself the circuit fails to switch on and off and instead just powers the phone constantly (I think, I could be wrong. If these details are important I can do more testing).

I am hoping someone here who knows more about electronics, specifically transistors, can help me figure out what my problem is, or offer suggestions as to how they would do it. Thanks for any help!


texts: LDO selection based on power dissipation

texts:
Perhaps You could help me confirm my thermal discussion on choosing appropriate LDO?

MIC5225, a 16Vin and 150mA output current quaranteed LDO.
So, parameter-wise I would guess that I could use this SOT23-5 package and get it to run from f.i 14Vin to 3.3Vout and 100mA output.

I checked some relevant Q/As about the 'LDO power dissipation' topics:

(can't provide links, since not enough rep)

"LDO selection in Thermal point of view"
"SOT-223 Thermal Pad and Vias" (many references also)

According to a potentiometer model [http://www.ti.com/lit/an/slva118a/slva118a.pdf], the power dissipated is equivalent to the input and output voltage difference and output current. So

(14Vin - 3.3Vout) * 100mAout = 1.1W. (getting suspicious)

Based on my readings, SOT23-5 (with 235C/W of thermal ambient resistance) can't handle it with such input voltage.

(125C - 25C)/235[C/W] = 0.426 W (So when ambient is 25C, the package could dissipate 426mW) no-airflow

I conclude that it's false to expect the regulator to work up to 16Vin and 3V3, 150mA, even though it's advertised as such (Couldn't find any other package for this either). Why false advertise xD?

I then chose LD1117S33TR with SOT-223 which should manage 1.1W with some heat sinking. Space is also quite scarce. Package thermal resistance is ~110C/W. So perhaps package-only could dissipate:

(125C-25C)/110[C/W] = 0.91W

and with some heatsinking on PCB and airflow it should be fine?
I wonder if this train-of-thought is correct?


texts: Can I use FET input capacitance to store a charge for some time?

texts:
I am new to EE but I see that FETs such as the FQP30N06L have an input capacitance of 800pF. Can that be used to store a charge for some time?

The goal is to push a momentary button to power on a Raspberry Pi and after about 60 seconds detect on a Pi GPIO input that the power button was pushed. And because it is solar-powered, a requirement is to minimize the current in use when the Pi is not powered. Power on events could be hours apart.

The circuit powers on a power control latch via a FET gate. This latch starts the Pi booting. The circuit also feeds voltage into the gate of another FET which would start current flowing. After the Pi is booted, I want it to read the state on the second FET to determine if the power button was pressed. (The Pi could be started via other means so I need to be able to determine what started it.)

Is this doable? Is there a better FET for the job? Is there a better way to meet the goal?

It doesn't work on Falstad, but I'm not sure if that's because of a limitation there; they don't have a parameter on FETs for input capacitance.

simulate this circuit – Schematic created using CircuitLab


texts:
How do you predict how long it will take a battery to discharge? I thought it was simply t = C/I, but I'm experiencing a very fast discharge rate.

I bought this 3000mAh 7.4V lipo battery, and my multimeter says my circuit (containing a switching 5V regulator) draws a fairly constant 680mA. So I would have expected to get around 3/0.68 = 4.4 hours of run time. However, I'm finding my battery's voltage drops below the usable 5V mark in about 10 minutes, after which the battery is effectively dead.

What am I missing? Why is my battery discharging so quickly?

Edit: The only other thing I think could be a factor is that I've wired this lipo protection board between the battery and my circuit, to protect it from dropping to a voltage that would permanently damage the battery. My current measurements from the battery are after this board. I haven't measured the current leaving the battery before this board.


texts:
I'm trying to read out the analog differential pressure sensor MPX2100DP. In my first approach I used an oscilloscope to visualize the change of voltage. My basic setup was only the sensor connected to +9V and GND. The other pins were connected to the oscilloscope. The tube to produce pressure by blowing in is connected to the pressure side of the sensor. I think I connected everything correctly like mentioned in the data sheet (http://cache.freescale.com/files/sensors/doc/data_sheet/MPX2100.pdf). My setup is shown in this image:

The first strange thing is that the sensor shows max voltage difference (55 mV) when both inlets of the sensor are free (no pressure). I didn't expect it this way. When I increase pressure in the tube the sensor does nothing. When I'm doing a depression in contrast I can see a change of voltage as shown in the second image. Does anyone of you guys have an idea what could be wrong?

idle state here Idle state here

with depression in tupe


texts: In schematics Design two buses having different names then how their pins can be connected together?

texts: I am referring one schematics design of silicon labs in that at page number 3 page title "EFR32 I/O Port Connections". Pin of bus RADIO_PA[5..0] and WSTK_P[45..0] are connected together how it can be possible when both buses are with different names.Here is the schematics Design link "EFR32MG1"


texts: What happens if you draw too much current from a 12 volt sealed lead acid battery?

texts:
We all know the Michael Bay-esque excitement you get if you misuse lithium-based cells, but I've heard lead acid batteries are a lot more durable. The datasheet for my sealed lead acid battery says it can deliver 65 amps safely for 5 seconds. What if I draw more? What if I draw 65 amps continuously? Or what if I short out the terminals and draw the theoretical 300 amps it can deliver (40 mohm ESR)?

I haven't found much information on this. I've only seen the effects of deep discharging, over charging, and very briefly shorting lead acid batteries (rather than continously). None of which are what I'm talking about.


texts:
I've built a DC signal mixer that doesn't quite work as expected. The supply voltage is 9V, virtual ground at 4.5V and the mixer uses a TL074 quad op amp. While the input voltage is 0-9V, the output voltage is 1.3-9V. How can I remove that 1.3V offset? I tried biasing the input and the output with no success so far.

Any ideas why? I need my signal to 'sit'at 0V at minimum.

https://www.circuitlab.com/circuit/wvu5n3/dc-mixer/


texts:
simulate this circuit – Schematic created using CircuitLab

I designed this as it would pass frequencies between 400-600 Hz. But it passes every single frequency anyway. What is the problem?


texts:
So I solved this using current division and KVL to find \$V_s\$, but I wonder if there is a simpler way to find \$V_s\$ in this circuit.

(This is a textbook example, not homework; the given answer is \$V_s = 9\text{V}\$).

Will someone verify my procedure and let me know if there is a better way to do this problem?

Labels:  \$R_1 = 20\text{k}\Omega\$, \$R_2 = 60\text{k}\Omega\$, \$R_3 = 120\text{k}\Omega\$

 Step 1:  Using current division, I_R2 = 0.1mA = (120k/180k)*I_R1
          The unknown here is I_R1.  So, that gives I_R1 = 0.0001 A * (3/2) = 0.00015A.
 Step 2:   V_R1 = 0.00015A * 20k ohms = 3V
 Step 3:   V_R2 = 0.0001A * 60k = 6V
 Step 4:   Setup KVL around the left loop:   -Vs + 3V + 6V = 0
 Step 5:   Isolate Vs and simplify the KVL equation:   Vs = 9V

So, that's correct, but, did I get the answer correct by chance, or did I find the correct procedure?  Also, what could I have done to simplify the process?


texts:
I am attempting to get two probes through a sealed case to detect the pH of a fluid like water.

My thought was to get two header pins and seal them with a custom 2mm diameter seal. However it looks like most header pins are square. Are there round ones? Or something similar not called a header pin? I trust sealing on a round surface better than a square surface.


texts: Why do we have single ended DQ and differential DQS in DDRIO?

texts: if differential can reduce cross talks, why do we use single ended DQ? And we know DQS is differential from DDR2


texts: How to use three CCP modules in compare mode simultaneously in PIC16F?

texts:
I need to use the three available CCP modules (CCP1, CCP2, CCP7) in compare mode simultaneously. They all use Timer1 as reference to compare.

My goal is the following: on every match, for each of them, I want to update the target value and reset Timer1. However, each of them will have a different target.

How can I achieve this? Is it possible to change the comparing Timer?

Any help is very appreciated.

I am working with PIC16F1773 : datasheet


texts: Partial Differential Equations to Describe Electric Current

texts: I am a newbie in PDE. I know that Navier-Stokes equations are used to describe the motion of viscous fluid substances, what are the equivalent partial differential equations that are used to describe the motion of electric current in wires?


texts:
I am trying to write a simple simulation of a Resistor / Capacitor network. I need to calculate the voltage across the capacitor as the input moves up and down.
The problem is that there is two formula to calculate Vc. One when its charging and a second when it's discharging.

When charging:

When discharging:

Is there a single formula or technique I can use to simulate Vc when the source Vs is moving up and down?


texts: Benchtop power supply current limit on MC34063 switched-mode power supply

texts:
I'm currently building a power supply using a MC34063 IC. I have used an external n-channel MOSFET for switching the high current used to drive an LED pair.

simulate this circuit – Schematic created using CircuitLab

The switch operates on a fixed duty cycle of about 6:1, frequency 40kHz. I have modified the circuit to run current mode, using a ZXCT1109 current sense amplifier and sense resistor. Gain is controlled by R1: whenever voltage at the INPUT node exceeds 1.25V, the internal comparator outputs low and the emitter output (i.e. gate voltage) stays low until the sense voltage drops below this threshold. Current is maintained via C3 decoupling capacitors.

At low currents (i.e. when current gain is high), the circuit operates fine:  the switch correctly shuts down whenever current is above threshold. Decreasing gain while the circuit is operating leads to an increasing in gain, and the output stays stable. However, whenever I turn on the circuit again at this higher current, current feedback no longer works correctly, and the switch always turns on during its on cycle. Naturally this leads to an overcurrent condition and if I left the circuit on for more than a few seconds the MOSFET would fry. The LEDs continue to light up in the overcurrent, but at reduced intensity. Oscilloscope readings show the comparator input node voltage just reaching 1.25V at its peak before rapidly falling off. Non-fault readings have this voltage exceeding ~2V before slowly falling off as expected.

I strongly suspect this is due to current latchup as described here. The input steady state current threshold above which this occurs is around 1A. My benchtop power supply has a maximum current limit of 2A. This overcurrent problem does not occur whenever I use Li-ion batteries to power it.

I can understand why this is occurring on a very rough basis: the current limiting is preventing effective IC startup. However, I don't understand the effect any further than this. Why does the voltage at the comparator input node never go above threshold even though the current is definitely high enough to trigger it? Why would the current limit affect the circuit this much and prevent the trigger threshold voltage ever being reached?

The article suggests using a soft start measure to fix this. I know this works (since I did it manually via changing current after the circuit was already online), but the MC34063 lacks an internal soft start function. Is there any way to implement this in a relatively simple fashion?

I have not included oscilloscope readings but I can provide them if requested.


texts: Why is the voltage drop over my MOSFET so large?

texts:
I am trying to use an NCV8403B N-channel power MOSFET to control the power for my circuit.
The schematic itself is quite simple:

The MOSFET is controlled by an SPST switch. When in the ON position, Vds and Vgs will be between 7V and 8.4V, depending on how charged the batteries are.
The Vgd is well above the Vgs(th)(gate threshold) of 1.0V-2.2V.
A Vgd of 7V - 8.4V should also give a Rds(on) value of about 40mOhms. With a current, Id, of 3A, that should equal a voltage drop of 0.12V, but when I test the circuit I get a voltage drop of 1.8V over the MOSFET.
Why is this happening, and what can I do to stop it?


texts: Sum of two 4-bit and a 5-bit number with 74181 ALU any advice?

texts:
I was designing a medium logic circuit and when trying to figure out this equation with 74181 ALU, I couldn't really find anything about how to make this work with a 4 bit ALU.
equation F= 2A + B while A is 4 bit binary number, B is a 5bit binary number.
I tried use another 74LS83 to do sum but I think there is a short way, any help?


texts:
I'm trying to design an audio mux based on a MAX49XX

There is input capacitor on audio lines but not any tip to find the value and technology. I suppose that's a high pass filter to block DC signal but how should I compute the value?

I read that ceramic capacitors are not recommended for audio purpose, what type of (small) capacitor can I use?


texts:
I'm trying to understand how data is going to fill up a 64bit cacheline with x4 DDR4 DIMM.
x4 DDR4 has 16 Banks, 4 Banks each in 4 Bank Groups and each bank is having 4 memory arrays. Burst size is 8.my understanding is column width is the no. of memory arrays within the Bank.
Now my question is when i requested any data how is it fetched i mean whether all the 4 memory arrays provide 8 bits of data to fill the cacheline? how x4 relate with burst size 8?


texts: Calculating the input current that can be taken by an Operational amplifier

texts: Is there a way to  calculate the input current that can be taken by an Operational amplifier, if we know its input Bias and input offset current?


texts: How do I convert a Eb/No from a dB value to a linear value

texts: So for example how would I convert an Eb/No value of 2dB into a linear value?


texts:
I'm using the IRF7422 (P Mosfet - warning opens a *.pdf) FETKY and I'm experiencing a strange issue.

I am pulling the gate high to +5V which should theoretically cause the source-drain channel to stop conducting. However, if I subsequently measure the voltage present at the source I get 4.5 V. It seems whatever voltage is present at the drain node is fed back to the source with a 0.5V drop. Is this to be expected? There is nothing else connected to the source node.


texts: AC Simulation in Power supply simulators

texts:
I would like to design a boost converter using LM3481 from texas instruments. To de the job, I have selected TINA TI circuit simulator, where the average model of LM3481 is given. So I have used this model to get the open loop bode plot of the power stage without the compensator.My objective is to get a plot that will help me to decide where to put poles and zeros of the compensator. The circuit is given bellow with (L=6uH, Rsense=20m, Fsw=227kHz)

My probleme is that I do not know how to built a circuit for AC simulation, for exmample, I do not know how to isolate the COMPENSATION PIN or where to connect it.

*If I connect it the compensator circuit, I will not get the open loop graphs, but I will get the closed ones, am I right ?

*If I connect it to the ground, I get a strange graphs that are not convinient to me.

What are the techniques that I should use to get the bode plot of the power stage without the compensator?


texts: Why arc only happens when circuit on load?

texts:
I'm preparing research about high voltage electric distribution for my university but I don't understand why the arc only happen when current is flowing.

I made my internship in an electric distribution company and they told me you can't use disconnectors when a circuit is on load; you have to use high voltage circuit breakers first and they will extinguish arc and then you can use disconnectors to cut off voltage.

First I thought that happens because of capacitive & inductive loads but if that's true it shouldn't happen when load is ohmic but basically short circuits are ohmic load (phase to earth short circuit) and they cause arc too.

Also electric company's voltage values : 31.5 kV and 154kV .
Load current 100-300A , short circuit current 400-1000A and they use 10 ohm resistor for earth.

They use SF6 gassed circuit breakers and I remember something about "arc extinguish when phase angle is 180" (V=0) and something about current voltage phase difference.


texts: How to use zvs driver to power tesla coil's primary

texts:
So, i am thinking about making my own crude tesla coil which would work upto 30volts. I got a zvs driver for that purpose. The zvs driver has 3 output lines( 1 positive and other 2 ground). Most of the tesla projects i see have no center tap on the primary of tesla coil. So would it be okay to use a cenre tapped primary for tesla coil? If not what is the possible solution for it?
 Note that zvs driver is basically an oscillator circuit which generates high frequencies necessary for mutual induction.


texts: Can a 125mw dual gang pot handle 10w audio output?

texts:
I want to build balance control for two audio amplifier circuits, and I want to use dual gang pot.

I want to know if I connected it directly to the outputs of the two audio amplifiers circuit then to the speakers if the the resistance go to about 0 ohm will it be ok for 10W output.


texts: AC vs. DC in Low Speed, High Torque application

texts:
My club is building a 1/4 scale utility tractor (around 800 lbs) and for the past couple of years we have been using an electric hybrid drivetrain. Our system has been a 32 hp gas motor powering a DC generator which we convert to 3 phase AC to power our independent wheel motors with an operating voltage of 72V AC. My question is would we be better off using a DC motor considering we don't require high speeds but need very high torque for our pulling competition.

The motors we are currently using are rated at around 40 ft*lbs at 5,000 RPM and go through a 31:1 gear reduction which we thought was plenty but when they start seeing a high load, the current spikes and faults out our controllers.

The first year we ran this system the controllers faulted out because we didn't limit the amount of current the motors could have, we changed the system this year to have a current limit so the controllers wouldn't fault out and it basically shut our motors off under a high load, I guess the question isn't necessarily which is better but is one more efficient under high load to make the most out of the current we can generate.

RPM: Our final drives have a 31:1 ratio so anywhere between 3000 to 5000 RPM, HP our gas motor is 32 hp so we sized our current motors to be 15 hp peak per motor so we could equal the power capability of the gas motor, Budget is hard to gauge, we have a decent amount of funding but sometimes companies sponser us or give discounts, Torque: we initially thought 1200 ft*lbs per wheel was plenty but now it is looking like we would need more around 2000 ft lbs per wheel to be able to compete with the other teams at our competition. The pull lasts maybe a minute or two maximum so we are pulling peak current that whole time but we have long rest cycles between pulls and events so the motor doesn't see prolonged current draw. We have a .66 F Capacitor in our system to smooth the DC current we provide to our controllers.

Links: Motor Controller


texts: I want to build me an electric longboard, and I was planning to run it off of 4 or 5 11.1 volt laptop batteries... I want to wire them in parallel (The sets of 11.1 volt), and charge it as one big battery with only 2 wires... (If it's possible.) I have a TRITON Electrifly computerized charger/discharger wit one three pinned thermal probe, for Li-Ion, Lead Acid, NiCad, And NiMH batteries. I need to know how to wire the batteries (If it isn't just straight forward + to + and - to -) and what my settings should be on my charger. If there is any information that you need, just ask, and I'll try my best to get it to you. Thanks!


texts: What is this resister can't find its code

texts: Buned out resistor can tell if that's silver or yellow as the multiplier.  But neither correspond to a resistor I can find to replace it.


texts: Household appliances frequency conversion

texts: I'm curious as to how household appliances are able to convert frequency, obviously they can change voltage through transformers. If anyone could just tell me what devices change frequency and I can do some research myself, just having trouble getting started on the topic! I'm no engineer, just an electrical apprentice who is curious, none of my tradesman have looked into it before. Thanks!


texts:
Please see attached image. I'm struggling to understand how the book went from line 2 to line 3; it doesnt seem obvious how they did the differential.

Thanks


texts: Calculating base-emitter current of a BJT, with emitter connected to ground (no resistor)

texts:
Much like the circuit above, most BJT amplifiers use an emitter degeneration resistor to stabilise the bias. It's relatively straightforward to calculate the base and collector quiescent currents. I have been looking at schematics, where a diode provides a voltage on the base of an NPN.

But, is there a rule of thumb to calculate the base-emitter current when no emitter resistor is used? I've been going through the equations for the intrinsic emitter and base resistances, (\$r_e = 26mV / I_E\$), etc, but can't seem to find an answer. The internal emitter resistance seems to be a function of the emitter current. Would you just use the Ebers-Moll equation?

\$I_E = I_S (\exp(V_{BE}/{VT}) - 1)\$


texts: Stiff, straight wire similar to LED legs

texts:
I'm planning on building another LED cube. I've built ones before using tinned 0.6mm copper wire which looked OK, however the wire bent easily and was never quite straight in the first place.

I spent a long time searching for some sort of stiff, straight wire to use for the structure of the cube, however couldn't find anything suitable (somewhere around 1mm in diameter and at least 250mm long). I realise this may be off topic, but is there a specific type of wire I can find that is pre-straightened and (shiny) silver in colour, that's solderable using conventional methods?

The type of wire I'm looking for is similar to LED leads like this (but stiffer):

The makers of the Hypnocube suggest using 22 AWG straightened galvanized soft steel wire in their build instructions, however long searches on the internet and eBay revealed nothing.


texts:
I'm wondering if there is any publicly available documents or research papers that cover GDDR power estimation?

Micron provides very nice documentation and calculators for DDR up to DDR4, however I cannot find anything for GDDR.

I understand that GDDR is based on DDR, but how similar are they when it comes to calculating power?

GPUWattch Publication


texts: What is wrong with my circuit and how can I fix it?

texts:
This circuit used to work before I soldered it. When I initially soldered it, I used a 6V battery and it was oscillating, but the speaker was very quiet. I went with a 9V battery and I re-soldered some other parts because the speaker would still not produce any sound. As well, the LED would have a voltage of around 8V on its turn while the speaker would only have around 0.03V on its turn (this stayed the same even after I switched their places and even replaced them). Right now, the speaker makes no sound and the LED (which previously flashed up with each oscillation) no longer flashed either. I checked with a voltmeter and voltage was still there across the circuit and across the loads. I can assure you that no soldered part is touching another (I know this cuz I've spent a day looking at them).
I don't know what to do make the circuit function and for the speaker to make sound, please help.


texts:
I am having a problem replicating some lab results in the PSPICE/capture CIS program for an assignment. I have this circuit right here:

which is an oscillator using the uA741 op-amp which is supposed to output an oscillation through its output pin(pin 6). After doing this experiment in the lab i found out that oscillations begin at about 220 ohms but after doing a parametric sweep for r between the values of 10 and 300, with an increment of 10, i am getting only a stable voltage of a few mV and not an oscillation of any kind. Is there any mistake i'm not seeing?


texts: How to interface LDR with microcontroller?

texts:
I need to interface an LDR with a microcontroller.

While searching for some circuit ideas on the internet, I came across two different ideas:

One was using a voltage divider circuit with another resistor and input that into the ADC port of a microcontroller.
Another was to couple the LDR to ground via small capacitor and connect the other end directly to a microcontroller. (I am not sure how this works?)

For example:

Image source: Measuring Light on a PIC 16F62x from Robot Builder

  The PIC 16F62X series is a pin-compatible upgrade to the old F84 offering lots of extra internal goodies such as timers, a USART and a couple of comparators. There are no analogue to digital converters (ADC) as such but it is a simple job to use a comparator, a timer and a few lines of software to make one.

Which one is more accurate?


texts: Is my SparkFun RS232 Shifter SMD faulty?

texts:
Product Link

I am connecting this to an Arduino. (once Arduino programmed I removed the USB connector as it shares the serial comms with Pin0&1)

RS232<->Arduino
VCC <-> 5V
GND <-> GND
TX <->Pin0(RX)
RX <->Pin1(TX)

Seems simple enough. However when I connected the DB9 port to the actual serial device I could clearly see the serial data being sent to the RS232 (RedRX LED was active) but nothing was coming back from the actual device I was connecting to.

So...

I then connected the device to my laptop & hyper-terminal to test I could communicate with it. Sent the same commands as I was getting the Arduino to do... And yes I was getting the correct responses from the device.

I then connected the Arduino+SparkFun RS232 to Hyper-Terminal and loaded up a basic program into Arduino that a) sends a welcome message and then b) sends a message each time it receives a character via the serial interface (one of the example sketches of the Arduino). The result I am getting is the welcome message only, the SparkFun RS232 is not seeing anything I send back from Hyper-Terminal.

Is it faulty or am I missing a vital trick to getting it working properly?

Thank you for any help.

edit: I should also add that this morning I tested pins 0 & 1 with a simple LED blink sketch to prove the arduino pins were functioning (which they were).

This is Kellenjb- I am having a hard time easily seeing what cases are working versus not working. Rather than writing a long and hard to follow comment or an answer that isn't an answer, I am going to add it here and have the OP or someone else correct me if I have understood wrong.

Arduino Sparkfun Shifter -> Serial Device (No Go)
Serial Device -> Arduino Sparkfun Shifter (Go)

Serial Device -> Laptop (Go)
Laptop -> Serial Device (Go)

Arduino Sparkfun Shifter -> Laptop (Go)
Laptop -> Arduino Sparkfun Shift (No Go)


texts: Will replacing MOSFET with a MOSFET with lower rds(on) reduce the thermal characteristics?

texts: I want to replace a MOSFET in a legacy product. The MOSFET is a P-channel Power MOSFET that is used for PWM switching purposes (VGS @ -12V, PWM is 20% @ 200us). The FET is switching in to a 200uH, 10ohm load (see image, 5 and 6 are a coil of 5ohms 200uH @ 10KHz). The FET has quite a large heatsink attached due to it getting hot. I'm wondering if the RDS(on) of 1.5 ohms may be the culprit as this is fairly high resistance in saturation mode? Would it be worth looking at alternatives with similar characteristics but with lower RDS(on) (in the milli-ohm range)? Or is the issue potentially more complicated / caused by the load? Any help would be great.


texts: Avoiding multiple defines by using side effect of PIC banking

texts:
This is more a question of style than anything else and might strike some as a bad thing to do. If I have a serial port pin on RC4, say, I can make some defines to help out:

#define TXSER_PIN   LATC, RC4

What I realise then is that you can do this:

banksel     LATC
bsf         TXSER_PIN
banksel     ANSELC
bcf         TXSER_PIN
banksel     TRISC
bcf         TXSER_PIN
banksel     INLVLC
bsf         TXSER_PIN

I'm using the same define all the way down even though, theoretically, I suppose it's wrong to do so. The point is that I can change LATC, RC4 to LATB, RB7 and (after also changing APFCON0 to move the TX function) that's all that changes.

On this PIC I'm using, TRISA = 0x8C and LATA = 0x10C. But only the BANKSEL causes them to be distinguishable - TRISA, LATA, ANSELA, WPUA are really all the same 0x0C offset from the start of the bank and, as compiling the instruction implicitly does an "operand & 0xFF", they can be used interchangeably.

(In fact, that can be quite annoying if you use pairs of operands incorrectly. Something like bsf   EEADRL, RC5 will not flag an error even though the compiler could easily do so. I wrote some awk to catch this...)

Can I run into trouble doing this or is it just bad form? Sure makes for less #defines though.


texts: Motor PWM Controllers Too Good to be True

texts: I am working on a project which involves driving 2 high power 60amp stall 12v motors from an arduino.  I had been browsing available drivers, and everything on the market seems to be quite expensive (examples: this, this).  However, I was browsing on Ebay and came across this generic board.   It seems to have the correct specs to control one of my motors.  Granted it doesn't have current sensing or anything else fancy like that, but does that really warrant an extra $150?  If there is something wrong with that board, could you recommend me a cheaper alternative to either of the examples above?  Thank you.


texts: The PCB has a pulse oximeter mounted on the surface, and it's tolerance is 0.6mm. The problem is the pulse oximeter needs to touch the bottom case at all times. How to best mount the PCB in the case without putting too much stress on the pulse oximeter? Will screws with flexible washers be all right? Sadly separating pulse oximeter from main PCB is not an option.


texts:
Ok here's the problem. I have a power antenna in my car. The antenna goes up when a voltage is supplied to the voltage sensor in the antenna and goes down when the voltage is removed. I used this fact to install a switch allowing me to listen to CD's without deploying the antenna.

The problem is: Whenever I start the car when the radio is on, the voltage drop is enough so the sensor registers a loss of signal and begins to withdraw the antenna into the car only to redeploy three seconds later when the car is running and the voltage returns to normal. This is hell on the gears and the torque switch. My plan is to install a capacitor in the signal circuit so that the voltage sensor no longer registers a temporary loss of signal when the car is started but will still withdraw the antenna (after a bleed time ) when the car is off or the switch is turned off.

Two questions: Since I need about a 10 second bleed time how big a cap do I need? And  I install the cap in parallel across the signal leads, correct?

\$Update\$

Got it done tested, soldered, boxed and installed it works great!!!  Thanks to  @Davetweed AND @RedGrittybrick for your help and insight.


texts: Reverse-engineer pinout of capacitive touchscreen

texts:
I'm interested in reusing the capacitive touchscreen of my old iPad. (As a learning experience -- I'm aware that this project will cost me more than just buying a new capacitive touchscreen would.)
The digitizer has a ribbon cable: (Picture from the iFixit teardown)

This connects to two 51-pin FPC connectors, seen in the bottom right of this picture, also from the iFixit teardown:
My understanding of capacitive touchscreens is that they have a set of conductors going horizontally across the screen, and a set of conductors going vertically across the screen, called the X lines and Y lines. These then connect to a controller, which measures mutual capacitance between each pair of (X, Y) lines, and does some algorithmic magic to turn that into touch events.
Since this connector has so many pins (more than just a serial interface), I'm assuming it brings the X and Y lines to the logic board, where it will connect to a touchscreen controller.
Without destroying anything, how do I determine the pinout of this connector?


texts: Ziplock Bags: OK for electronics project storage?

texts:
Are plastic "ZipLock" bags OK for short-term storage of projects?

Context: beginner's Arduino class, carrying Arduino, breadboard, and wiring.


texts:
An AD ADA4622-1 with LFCSP8 Package shows as Thermal Specification a "2 Layer Board with 2x2 Vias".

What do this exactly means?

It is a pcb for the exposed pad pin with 4 vias distributed as a 2x2 square array, in a 2 layer board?

Anyway, where are those "Layer JEDEC Boards" drawings or specs?


texts: Pspice error: voltage source and/or inductor loop

texts:
I'm trying to simulate the above circuit in Pspice, but I am getting the error:

Voltage source and/or inductor loop involving V_V5

I looked it up and it says this will happen if the voltage source (V5) gets a short circuited or connected to an inductor, but it is not!

The netlist:

* Schematics Netlist *

I_I1         $N_0001 $N_0002 DC 3A
R_R1         $N_0002 $N_0003  1
R_R3         $N_0001 $N_0002  4
R_R4         0 $N_0001  2
R_R5         0 $N_0002  2
I_I2         0 $N_0002 DC 5A
V_V2         $N_0001 0 5V
V_V5         $N_0003 $N_0003
R_R2         $N_0001 $N_0003  1


texts: Can I change the battery connector on this model aircraft safely?

texts:
I am working on a project, and am required to build an autonomous glider (no propulsion).

Weight is limited to 9oz, and we are using the Pixhawk 4 mini for flight controls. The power management board (PMB) that came with the package only has XT60 plug, so it does not fit with the small batteries that I have.

Any recommendations on what I can do? I am considering de-soldering the XT60 plug on the PMB and solder a red JST plug. Is this safe to do?


texts: Can electronic devices be installed on the pillar of UHV towers such as 345kV?

texts:
Can electronic devices be installed on the pillar of UHV towers such as 345 kV? Because I have an idea to install a remote automatic control electronic device on the tower to control the rotation and extension of the water pipe.
I know there must be a magnetic field problem because of the transmission line, I would like to ask if a signal is transmitted from the ground to this electronic device, which is located at a height of 60 meters, will the signal be seriously disturbed by the electromagnetic field?
Also is there any energy harvesting application in this situation? Because I want to use this technology to solve the power problem of this electronic device.
I am not good in this field, but I can survey some paper about this, so if you have any answer or reference, please tell me. You can just provide the reference rather than explaining it to me.


texts: H-Bridge Motor Controller High Side Strange Behavior

texts:
I am working with a "tried and true" H-Bridge MOSFET driver circuit. I have used this design 2 times before with no problems. Now I am having an issue that I cannot seem to solve. The only difference in the current iteration over the others is that my gate driver is 1.5" away from the MOSFET as opposed to 0.25" away. To compensate for this distance I am only running my PWM period at 16kHz instead of my usual 60-100kHz.

I am seeing a strange waveform on my high-side gate signal. After changing the capacitance of the bootstrap caps a higher value the period of the on-off problem goes up. A smaller value speeds up the period. My actual PWM duty and period are correct during this "on" time. It appears that the bootstrap caps are slowly loosing charge until the high side turns off to recharge and the process starts over. Aprox (800mV)
However if I use a super small capacitance the on-off pattern continues only to disrupt the actual PWM. I have check all of the microcontroller signals and they are perfectly clean and consistent.

Any suggestions of where to go from here?

Thanks!


texts: Carrying your circuits in a bag without bending/messing up parts?

texts:
In my circuits lab classes, I might sometimes be working on two breadboards at once. I'll stick a breadboard or two in a plastic bag inside of a messenger bag to carry with me.

Short leg components will often fall out because they weren't really deep in the breadboard to begin with. One time we were given some very short leg potentiometers in our kit for a lab and this happened.

Long legs can also be problematic for obvious reasons when a breadboard is put in a bag. Also one time we were only given one certain inductor to be used for several labs- I was very hesitant to snip the legs.

What are your tips for carrying around a bunch of breadboards in bags and keep the elements in place? One idea I had was taping the potentially loose components but that is a bit of a hassle and when you remove the tape you could accidentally dislodge some elements

"well just hold the circuits upright" Sometimes it rains, sometimes you need to ride your bicycle. So say sometimes you need to put the breadboards in a bag sideways. Know anyone who might have some tips?


texts: Programming STM32: JTAG/SWD vs bootloader

texts:
I'm making a PCB for a personal project using the STM32L031K6T7 microcontroller. It looks like this uC has a bootloader that can be used to reprogram the flash program mem through UART or SPI. It also has SWD pins.

So, does that mean I have two entirely separate but equally valid methods to program this uC if I want? I understand I'm able to interface to SWD using my j-link debugger, but how would I interface to the bootloader method?

My guess is that I'd need a device to interface between my computer's USB and the UART or SPI bus of the uC, but I'm not 100% sure. And then I'm wondering if I have to worry about what would happen if I had the SPI bus populated with other devices, and then I tried the bootloader method to program it. Wouldn't the programmer device need to be the SPI master in order to start communications with the uC as a slave?


texts:
I have recently been looking at the datasheets for the 74HC139 IC in order to see if it was suitable for my project, and have come across the following logic diagram which strikes me as a little bit odd:

simulate this circuit – Schematic created using CircuitLab

For each of the inputs Yn, there are two NOT gates after the triple-input NAND gate; I don't understand why this is necessary as simple boolean logic tells us:

$$\overline{\overline{A}}\equiv A\qquad \forall A \in \{\text{TRUE}, \text{FALSE}\}$$

Therefore I am assuming there is some electronic based reason why there are two inverters before the output? I have heard not gates called Inverting buffers before, and these supposedly isolate the circuit before and after, however, I cannot claim to understand the use of this so I'd appreciate any enlightenment!


texts:
I went through an assembly program of the PIC16F88 downloaded from microchip and saw something that I have ever seen before

; eeprom definitions

    org 0x2100
    de  LOW(IREF_ZERO), HIGH(IREF_ZERO)
    de  LOW(MAX_BATTERY_VOLTAGE), HIGH(MAX_BATTERY_VOLTAGE)

********End of the program****

The de does not appear in the set of the instruction the PIC, what does the instructioin de do in the program ?


texts: Can I charge a 12V 2A NiCd battery with 18V 14.6A?

texts:
I have a 12V 2A NiCd battery which I want to charge. I have a power unit that puts out 18V 14.6A. Can I use it to charge it?  Would the battery just draw the current it needs or would it always put out 14.6A?
The battery will be used to power a fan I want to install in the car for my dogs :).. get that AC air in the back seats

Picture of battery and power unit here:


texts: Source voltage and voltage across inductor waveform

texts:
I did an RL circuit experiment. It is a series circuit with a potentiometer, inductor, and a DC source.

Here is the resulting waveform at 2 different resistances (ch 1 is source voltage and ch 2 is voltage across the inductor.)

Why does the voltage across inductor on the first picture have 'jumps' and why does it curve like that in the second picture?

I am also confused as to why the source voltage is affected on the second picture.


texts: Use of tristates vs multiplexers in a RAM

texts:
Why are tristates favored over multiplexers to select the output from RAM? The explanation that I've heard of is that the RAM is too large for using a multiplexer but I need more details.

A theory we've come up with is that using a multiplexer would necessitate a tree of OR-gates to select the output which would dramatically increase the propagation time of the signal to the bus whereas with tristates, no matter the size of the RAM, the propagation delay would be constant.

Is that correct?

Thanks


texts:
I've got a normally closed momentary push button switch that I would like to make behave as normally open.

E.g. I press the button and 12V is supplied to the solenoid. I understand that it would be easy to do with the NO push button switch but I've got a very specific push button that I'd like to use and it happens to be NC.

Can this be done? How? Thank you for any ideas.


texts: How to measure or estimate the phase delay between two analog input channels of this board?

texts:
There is a 16-bit data acquisition board with +/-10V range which multiplexes analog inputs and buffers the data to the PC. Specifications are given here (DAS6036 is the model in question).

Now I need to quantify by measuring or estimating the phase delay between two analog inputs of two channels. The board seems like have one A/D converter which is multiplexed between channels because under the key features sampling is mentioned as multiplexed. More detail for the board is given here.

First I wanted to measure the delay at 100Hz sampling between Ch0 Ch7 and Ch13. To do that I set the function generator to a 1Hz sine wave and splitted the the function generator's output to three by using three same length coax cables and coupled them to Ch0, Ch7 and Ch13.

Below shows 5 seconds of logged data:

And here if we zoom it we can observe the delay between the channels:

Now the function generator output is set to 1Hz triangular wave and sampling frequency is again 100Hz(we cans still observe the delay):

But now keeping the same input if I increase the sampling rate to 4kHz I cannot observe that delay anymore:

By increasing the sampling rate I was hoping to observe the delay is being reduced. But as you see the the delay is kind of buried in noise.

Here are the questions I couldn't figure out:

What could be happening here which makes us impossible to observe
the phase delay? Is there a better setup or method to measure such
delay at higher sampling frequencies?
If we cannot measure, is it enough to estimate the phase delay by
using the specs? Here is an excerpt from this site:

How can I conclude the board in question is Pseudo Simultaneous or Evenly Spaced?


texts: Why does overshooting occur when probe's adjustable capacitor is under-value

texts:
I can't wrap my head around how overshooting (the spike) happens when the 10X probe capacitor trimmer (Cp) is under-tuned (i.e. adjustable capacitor's value is not high enough). There are countless of tutorials online but none I found explains how the shape takes its form. I've been staring at the simulation and played with the values, but can't figure intuitively as in where these spikes and dips come from, other than knowing I'm compensating the capacitor divider to achieve the same ratio as the 9:1 voltage divider so I measure the right voltage when the signal increases in frequency.
Mathematically, the RC rise or fall time is \$ V = V_{0}(1 - e^{\frac{-1}{RC}}) \$ so no where in time should \$V\$ "shoots" above or "dips" below \$V_{0}\$. The scope input voltage is essentially the voltage drop across \$Cp\$ - the smaller the capacitance, the earlier the capacitor hits the target voltage (i.e. a smaller rounded corner); vice versa, a larger capacitor takes longer to settle to its target voltage (i.e. a bigger rounded corner).  But both my oscilloscope and the simulation contradicts my reasoning, and I'm not sure where I'm thinking this wrong.


texts:
I have been trying to figure this out, kinda a amateur question actually! Looking at the above circuit diagram am wondering why there is no voltage drop across the resistor R1? A part of voltage should be dropped out by the R1 isn't it?

But the simulation in Proteus shows that the Voltage across both R1 and R2 remains the same. Can anyone help me out on this one please?


texts: Linear accelerometer on a rotating platform

texts:
I want to measure the linear speed of a vehicle putting the accelerometer on its wheel. Assume the vehicle is moving at a velocity 70 KMPH and its wheel has a radius (R = Radius) 30 CM. I made this analogy, If the accelerometer will be placed on the wheel at position R/2 whose Z axis is now orthogonal to the wheel and let us assume there is no tilt in X and Y axis.

The Accelerometer reading in X and Y should give the net accelerometer which is a_translational + a_rotational + TIGA = (R/2)alpha + (R/2) omega ^2 + TIGA where aplha is the angular accelartion and omega is the angular velocity and TIGA is the Tilt induced gravitational accelarion.

If my above observation is correct, how can i calculate TIGA factor? Will it change with the rotation degrees? How to balance it?

For calculating the speed (to correlate with 70 KMPH) i should integrate the accelration value in that period. In this case? Which accelration value from the accelrometer data should be considered? Should the a_rotational and TIGA factor must be removed from the data before integration?


texts: What are the issues with using multiple inductors for a DC/DC converter?

texts:
I'm going to be designing a Buck Converter that will supply a max of 10A of current to an LED Strip (9V to 20V in, 5V out). Since I want to minimize the amount of EMI in the circuit, I want to use shielded inductors rated for around 26uH. But since the inductor would have to be rated for at least 10A (preferably 15A or higher), there aren't a lot of options to chose from. So instead, I was thinking of using two 13uH inductors in series so that I would have a larger variety of parts.
I understand that the math works out to where 13uH + 13uH = 26uH. But are there any real world issues that comes with using multiple inductors in a DC/DC converter?


texts: Preparing a 100 Ohm resistor for use as a PT100 standard

texts:
I need to connect a precision 100 Ohm resistor to my boards to calibrate the zero Centigrade point offsets for my PT100 circuit (the only other way being a water triple point cell AFAIK). So, I have selected a through hole mount precision resistor of 0.005% accuracy with a 2ppm temperature coefficient. This is specified at around 25 degC. The rated power is 600mW, but I will only be putting about 500uA through it at most.

The questions are:

Is this good enough? On paper it looks like it could calibrate to 13 milliKelvin equivalent accuracy.

How do I mount such a resistor? I intend to put it into a sealed box with terminal connections for the 4 wire PT100 and keep it in an enclosure that is temperature controlled to within a tenth of a degree. I am planning to have it hanging in the air with the two ends soldered to the terminals of the current carrying wires, and soldering connections for the sense wires close to the body. Any special precautions or advice on this? Has anyone done anything similar?


texts:
I'm trying to simulate simple BJT circuits to verify my hand calculations. Following is my circuit,

I'm just trying to get the calculated DC collector current with the shown voltages and parameters. Using the following equation for the collector current,

$$ I_c = I_s e^{V_{be}/V_T}$$

Ignoring Early effect, this should approximate to 1mA at 17C temperature. But this is the result I get

What am I doing wrong?

Edit: changing TNOM parameter upon @jonk's suggestion, I get the "correct" results. Hope this helps other fellow engineering students in the future.


texts:
How to decide the operating region of given transistor as shown in the figure?
I mean is it possible to decide the operating region of bjt without knowing the Load(Assuming pure resistor and supply voltage of opamp +15 and -15) value.


texts: Can't get GPIOH pins to work as output on STM32F4 Discovery

texts:
I'm using 4 LEDs connected to different pins on STM32F4 Discovery: PA6, PD8, PH0, PD1. All of these pins have been configured as output with same function:

void initPins(uint32_t ahb_gpio, GPIO_TypeDef * gpio, uint16_t gpio_pin)
{
    GPIO_InitTypeDef GPIO_InitDef;
    RCC_AHB1PeriphClockCmd(ahb_gpio, ENABLE);
    GPIO_InitDef.GPIO_Pin = gpio_pin;
    GPIO_InitDef.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitDef.GPIO_OType = GPIO_OType_PP;
    GPIO_InitDef.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitDef.GPIO_Speed = GPIO_Speed_100MHz;
    //Initialize pins
    GPIO_Init(gpio, &GPIO_InitDef);
}

...

initPins(RCC_AHB1Periph_GPIOA, GPIOA, GPIO_Pin_6);
initPins(RCC_AHB1Periph_GPIOD, GPIOD, GPIO_Pin_8);
initPins(RCC_AHB1Periph_GPIOH, GPIOH, GPIO_Pin_0);
initPins(RCC_AHB1Periph_GPIOD, GPIOD, GPIO_Pin_1);

The three pins on GPIOA and GPIOD work as they should, but I can't get pin on GPIOH to work. I tried also connecting 5th LED to PH1 and configuring it as output but it's no use, it won't work either. I also tried using TM GPIO library to configure pins:

TM_GPIO_Init(
    GPIOH,
    GPIO_Pin_0 | GPIO_Pin_1,
    TM_GPIO_Mode_OUT,
    TM_GPIO_OType_PP,
    TM_GPIO_PuPd_NOPULL,
    TM_GPIO_Speed_High
    );

but it won't work either. I see these two pins can be used also for oscillator. Is that interfering with their configuration? Does anybody know why these pins are not working?


texts: I'm attempting to design a basic FSK transceiver (architecture shown below) using only discrete components (transistors, diodes, resistors, etc). My idea was to separate the two binary frequency components via band-pass filters but I'm having trouble figuring out how to get such a high-Q (i.e. narrow-band) effect. Most filter calculators suggest capacitor values in the femto-farad range, which is not possible for SMT MLCC's. Any thoughts would be appreciated.


texts: Switches for PCB: Mounting and hole questions

texts:
I'm designing a pcb board and encountered a problem for switches. Is it common to follow the schematic and create square holes for mounting the switches?

Please help. Thank you.


texts:
I have a 1W push-pull guitar amp circuit where the 9V power supply deliberately sags to ~8V when strumming the guitar. Believe it or not this is important to the sound - it modifies the otherwise snappy pick attack transients.

However, I now want to add another low-load op amp based "preamp" circuit to the same supply but I don't want it's supply to sag. So I'm wondering if there is a way to load the transformer so that the push-pull supply sags as desired but the op amp circuit gets a steady voltage.

Any ideas?

If I add a second rectifier and coupling cap will that suffice?

Or would I just have to go with a separate transformer?

Or perhaps I can use a bigger transformer and then add series resistance to the push-pull supply? But would a resistor act the same? I tried using my bench supply with ~30 ohms in series and got sag but it didn't look the same on the scope. It seems the transformer sag is limited. It seems as the amp pulls harder, the transformer keeps up better whereas with the resistor it just follows ohms law.


texts: How to switch dummy load circuit on/off with pwm?

texts:
I built pretty much the simplest dummy load for testing batteries I found on youtube (EEVBlog #102) , but I modified it little bit. I used 0R1 resistor, because I needed bigger currents from battery (expecting little bit over 2A max). I also use rail-to-rail operational amplifier TS912. I use voltage on sense resistor for feedback to have more control over the current. Also, I use my ATMega32 to control this circuit. It works perfectly in these two "modes":

Constant current: I set voltage on DAC and it sets the current
Constant load: I check battery voltage to calculate DAC output, therefore current to maintain constant load

I need to add PWM switching, switching on/off with ATMega32 and I am desperate to make it work. I tried adding N-channel MOSFET and connecting PWM to it directly, but it did not work. Then I read that I need bigger Vgs voltage and there was this "switching circuit" to make it work- see image. But it can´t possibly work, since PWM is only 0/5V. With 12V supply, P-channel MOSFET is on all the time. Only workaround here would be to find some P-channel MOSFET with Vgs(th) like -8V, but I can´t find any. I could also lower supply voltage, but I am not sure if it works.

I already ordered parts to test it, but in the meantime I still think about it. There is probably different solution to that problem. Can you please help me? What do I use to just simply switch this circuit on/off with PWM?

Thank you,

Jakub

Edit - So I have been thinking about it and what if I just did not include that "switching circuit" at all, I would just set voltage on DAC with the same frequency as I wanted with that N-MOS. I guess I will definitely try this and the other answer recomendation.


texts: Potential of a wire grounded through a resistor

texts:
I'm reading a paper that uses a simple setup to measure the zeta potential of liquid-air interfaces (that's not really important). Their method/apparatus is given in this picture

In the paper itself they write: Initially, the detection electrode is exposed to air and thus has an electrical potential of V0 (relative to the earth). When the electrode contacts the electrolyte solution–air interface which has a zeta potential of xi, the difference of the electrical potentials of these two surfaces (one is the electrode–air surface, the other is the electrolyte solution–air interface) generates an electrical current through the measurement circuit.

Here's my question - when the electrode is grounded like that through a resistor and it's in air (i.e. there's virtually no current), doesn't its potential equal the potential of earth?


texts: How do I prevent output of opamp summing amplifier taking negative values?

texts:
I want this circuit to give \$V_{out}\$ satisfying

\$
V_{out} = \begin{cases}
-\dfrac{R_f}{R_1}V_{s1}-\dfrac{R_f}{R_2}V_{s2}; \quad \text{if} \quad \left(-\dfrac{R_f}{R_1}V_{s1}-\dfrac{R_f}{R_2}V_{s2}\right) > 0 \\
0; \quad \text{if} \quad \left(-\dfrac{R_f}{R_1}V_{s1}-\dfrac{R_f}{R_2}V_{s2}\right) \le 0
\end{cases}
\$

How do I do it?

I considered adding a diode at the output like in the image below, but I'm not sure whether it will work or not, or even if it works, it is the best way of doing it or there is a better way.


texts: Adding USB Tracks Directly on PCB with gold finish and contact lifetime

texts:
We are making a USB device but with the USB tracks on the PCB itself, something like this -

My concern is regarding the life of such a product. How can I make it last as long as it would if I were to add a 'normal' USB connector to the PCB.

The copper thickness we have used is 60 um and Gold thickness on the USB tracks is about 0.5 um. Will this suffice?


texts: Copper side diagram vs component side diagram

texts: I have to draw a simple circuit using a copper side diagram and a component side diagram. I can’t find any examples online.


texts: T - Flip Flop Using D Flip Flop (Verilog)

texts:
I am trying to implement t flop  using d flip flop in veilog
for which my d flip flop code is like this :

module dff(D, CLK, RESET, Q, QOUT);
input D, CLK, RESET;    // Inputs to flip flop
output Q, QOUT;     // Output of flip flops

reg Q, QOUT;            // Flip Flops need to store the previous value, therefore using reg

always @ (posedge CLK or posedge RESET) begin   // This block executes every time at rising edge of clk or reset
if(RESET)                           // If reset is high
begin
    Q <= 1'b0;
    QOUT <= 1'b1;
end
else
begin
      Q <= D;
     QOUT <= ~D;
    end
end

endmodule

And i am using this dff in my t flip flop module which looks like this

module tff(T, CLK, RESET, Q, QOUT);

input T, CLK, RESET;
output Q, QOUT;

wire out1;
wire out2;
assign out1 = T ^ out2;

dff uut(out1, CLK, RESET, Q, QOUT);

assign Q = out2;

endmodule

But on compiling the code i am getting an error which is
Xst:528 - Multi-source in Unit tff on signal Q; this signal is connected to multiple drivers.

Please help me where i am wrong in my code


texts:
I am trying to put a custom message on a "sound box" in a stuffed animal. I asked this at the Reverse Engineering SE and they pointed me here. Here is a picture of the circuit board:

The blue wires lead are connected to the speaker. The bottom holders are where two batteries go. I am thinking that those pads coming out of the chip that are not connected to anything might be used to put a new message on there. This board was in an "animal" and was not originally supposed to be modified so there is no microphone. Would this be possible? Any ideas on how I would do it?


texts:
I'm working on a senior design project that is using three 20-30 gauge wires that are going into a detachable box.

The idea is that the box has three wires coming out of it, and the three wires that need to go into it are going to get connected to the three wires coming out of the box.

What I am looking for is 3 male and female wire connectors that are threaded to allow some sort of water resistance. Does anyone know of a good idea or plan here? I'm open to any suggestions.

Thanks

Edit: Here is a picture, the wires on the left are going into my system.


texts: What additional components/boards are needed to use CAN with an STM32?

texts:
I have a STM32F103C8T6 (later I want to more to STM32F407VET6). Both have support for CAN. But what does this mean?

I bought (not received yet) an MCP2551 CAN Controller.
Do I need this or is this functionality already built in my STM?

And I think I also need a CAN transceiver like TJA1050?

According to this Example circuit both are used and the input of the MCP2551 but that has a SPI as input and the STM has RX/TX as CAN input/output which is similar as the 'connectors' for MCP2551. But I think this example circuit is not meant for STM32 (since SPI is not used for CAN on STM32).

(I want to make a CAN bus of a few meters, just two, later maybe 3 devices, with preferably 1 mbps speed).


texts: New (for me) wire range syntax [(1)-1:0] in Verilog

texts:
I think this is quick question and assume the range of the wire is 1, but I wonder why they used the following syntax, maybe I am missing something else and would like to know your thoughts.
...
input wire [(1)-1:0]  p1;
output wire [(1)-1:0]  p2;
...


texts: Select power source with a mosfet and no voltage drop

texts:
I've 'designed' this power source selecting circuit.

VIN is the output of the circuit.
VBAT will have a voltage of 3-4.2V when connected.
VUSB will have a voltage of 5V when connected.

The idea is for VUSB to provide all of the power when it is connected, and VBAT to supply power when VUSB isn't connected.

Will this design work as intended? Do I need any diodes to prevent power to go from VUSB->VBAT?
Will I have a >0.1V voltage drop when either VUSB or VBAT is used as a source?

If not, is there a better or more proper way to achieve these goals?


texts: Troubleshooting communication with ESP-12e

texts:
I have an ESP-12e and set it up like here with the exception that I am using FT232RL chip. The problem is I can't receive anything from the module despite the command I send. When I try to connect the REST pin to ground for a second I get garbage on putty.

What I tried:

Different baud rates.
Connecting REST pin to ground for a second.
Used CR after LF and vice-versa in Putty.
Used ESPlorer software.
Powering it from a standalone 3.3V line from an ATX power supply instead of using a 3.3 voltage regulator.

If I'm not mistaken I have seen that some are using capacitors with the 3.3V line going to the module (Which I am not using). Anything we can do before concluding the chip is broken? Because I haven't run it in a like a year.


texts: Why is there no current flowing through another parallel wire in this video?

texts:
In his video Making logic gates from transistors Ben Eater draws a following scheme

simulate this circuit – Schematic created using CircuitLab

When the switch is on, the LED stops emitting light (to demonstrate that there is no current on the wire the LED is connected to). I wonder why there is no current on the LED wire. In theory, there should be at least SOME current flowing through LED.

Is it assumed that the resistance of wire going through the transistor is negligible as compared to a huge resistance that is provided by LED and therefore the current going through LED is negligible too?


texts: Comsol simulation for electrochemical impedance spectroscopy

texts:
I am new to Comsol and did not know where else to seek help, so posting here.
I am trying to analyse how finger-like interdigital electrodes made of gold can be used to detect concentration of nitrates in drinking water. I am simulating this on Comsol version 5.5 with gold electrodes on a glass (quartz) substrate (model attached). I want to first try and see what the response is like in Air. The frequencies I am looking at is between 10 KHz to 1 MHz at 1V peak-to-peak.
How to go about simulating this to determine impedance change with varying frequencies?


texts:
I have the question " The instantaneous values of two alternating currents are given by i1 = 20sinwt amperes and
i2 = 10sin(wt + pi/3) amperes. By plotting i1 and i2 on the same axes, using the same scale, over one cycle, and adding ordinates at intervals, obtain a sinusoidal expression for i1 + i2."

The graph for the question is:

The answer for the sinusoidal expression is:

I understand everything except for the 19 degrees. The solutions say that the resultant waveform leads the curve i1 = 20sinwt by 19 degrees which is 0.332 rads, however I do not understand where the 19 degrees came from.


texts: What does it mean to have a complex signal?

texts:
I've been told that complex signals are a "notational convenience for easily making two signals orthogonal so that they can go on the same wire." Is this accurate/what does this mean?

Is there a physical meaning to complex signals? Is multiplying by j actually shorthand for multiplying the real part and imaginary part by orthogonal carriers? (is that the way this would be observed in real life?)


texts:
Confusion about the rated voltage of a Permanent magnet synchronous motor.

I’m currently trying to do a motor control experiment and I’m really confused by a term called “rated voltage” from the motor specifications.

Below is my Simulation scheme for the speed control of a PMSM (with sinusoidal back-emf).

Under experiment circumstance, it would be something like this.

The outputs of the inverter are Vao, Vbo, and Vco.  The line-to-neutral voltages would be
VaN=(1/3)(2*Vao-Vbo-Vco)
VbN=(1/3)(2*Vbo-Vao-Vco)
VcN=(1/3)(2*Vco-Vao-Vbo)

And the line-to-line voltage would be
Vab=Vao-Vbo
Vbc=Vbo-Vco
Vca=Vco-Vao

My question is, when we mean rated voltage of a PMSM. Does this value refer to the RMS value of line-to-line voltage, the RMS value of the line-to-neutral voltage, or simply the DC bus voltage of the inverter?
I want to clarify this confusion because I know that to drive a motor, the DC bus voltage for an inverter should be 1.414 times larger than the AC RMS line voltage of the Motor.

Assume that the rated voltage of a PMSM is 24V.  If this rated voltage means the RMS value of the line-to-line voltage, then the required DC bus voltage (Vdc) should simply be 1.414*24=34V.  If this rated voltage mean the RMS value of the line-to-neutral voltage, for a three-phase PMSM, the line-to-line voltage will be 1.732*24=41.5V.  And the required DC bus voltage for the inverter will be 59V.  If this rated voltage refer to the DC bus voltage of the inverter, then the DC bus voltage for the inverter will simply be 24V.  And the line-to-line voltage of this PMSM under rated condition will be 24/1.414 = 17V.

Can anyone clarify this for me?

Thanks.

@ Bruce Abbott

Based on the datasheet I provided in the comment.  I picked the part number DN42040S24-026 and used the following motor specs:

Stator phase resistance: 0.75ohm;
Lds & Lqs: 0.0021H;
Flux linkage established by PM: 0.00477564V.s;
Inertia: 2.4e-06;
Pole pairs:4.

I have no idea about calculating the viscous damping based on the datasheet, so I assumed the viscous damping to be 0.0001N.m.s.  I tried to simulate the motor’s performance at rated condition in Simulink.  I initially supplied the motor with 800/3Hz three phase sinusoidal voltage inputs as (let’s call this group 1)
Vao=24*1.414*cos[2*pi*(800/3)*t];
Vbo=24*1.414*cos[2*pi*(800/3)*t-2/3*pi];
Vco=24*1.414*cos[2*pi*(800/3)*t-4/3*pi].

The motor speed is around -5000rpm and have large amplitude oscillations.  But when I change the supply voltage to (let’s call this group 2)
Vao=24*1.414*cos[2*pi*(800/3)*t];
Vbo=24*1.414*cos[2*pi*(800/3)*t+2/3*pi];
Vco=24*1.414*cos[2*pi*(800/3)*t+4/3*pi].

The motor speed reaches a steady-state of -4000rpm.  I’m confused here because I think I should have the same speed response with either group.  Also, I don’t understand why I get a negative speed response at -4000rpm rather than +4000rpm.  I tried to switch the phase sequences of group 2, but I get the same speed response as group 1: -5000rpm with large oscillations.  I do not know what the problem is here.  Any suggestions?  Thank you.


texts: why could Darlington circuit protect Load Dump at automotive?

texts:
I just took over a project from EX co-worker and not understand a circuit (Darlington circuit) designed to against load dump(5b) at automotive. in my previous experience, TVS usually is used for protecting load dump at automotive, not Darlington
here is test requirement of load dump and the circuit.

According to my ex co-worker explanation, the designed Darlington can suppress load dump to 33V that is safety voltage input buck DC/DC
Normal operation
input voltage from Battery=24V at circuit (DC+)
operation current measured from Battery=200mA
My question

Is it correct at this Darlington application for load dump?
If it could , how Darlington is activated when load dump is occurring ?


texts: What device can I use as a load to calibrate a power meter accurately?

texts:
In old times calibrating a power meter was as easy as connecting 1x, 2x, 3x high power halogen bulbs to get realistic data, free of reactive power or strange waveforms with strong harmonics.
Nowadays simple heaters are not common (I have no electrical room heaters, for example) and light bulbs with LEDs produce harmonics which may affect the accuracy of a power meter, not to mention that calibrating a 2+ kW meter with 5-15 W is unrealistic.
I read online that motors are not suitable for the calibration, therefore hairdryers don't work.
What can I use, easily available in households in 2020 and which power I can accurately estimate with other means, to calibrate my power meter based on (according to Tasmota codes) "HLWBL Energy Monitoring" and "BL0937 Single Phase Energy Monitor"?
Concerning the tools, I have a multimeter which I can use to measure resistance, voltage and current values.
Concerning the devices, besides normal household ones, I also have more unusual devices like an about 80 W terrarium heating cable and a 750 W silicone heater for 3D printer, which however, contrary to the terrarium heater, is not meant to be operated without temperature control (it is meant to be overpowered).


texts: Interpretation of rating of the primary voltage of a real transformer

texts:
The rating of a real transformer is 15 kVA , 2300/230-V then can we say that the primary rms is 2300 V or can we say that the secondary rms is 230 V or both.

To clarify further, suppose to solve for certain characteristics of this transformer like primary current and secondary current i use the equivalent circuit equation of the transformer referred to the primary side as:

Vp = aVs + Req*Ip + jXeq*Ip

Then what should i use for Vp or Vs in the above equation looking at the rating of the transformer.

In the above equation looking at the rating data given above is Vp= 2300 or Vs = 230 ?As mentioned earlier the transformer is mentioned to be real.


texts: Will cutting only the Power Lines damage the Data Lines or the Device?

texts:
A USB 2.0 Cable should have 4 cables.
They are the Vcc, Data+, Data- and Ground.

Will only disconnecting the Vcc OR Ground Wires damage the Connected Device or the Data Wires?

I currently have a USB SD Card reader that I like to Disconnect and Connect. The reader is mounted on the table, so to disconnect the reader, I would plug off the USB Cable connecting the reader and the computer.

To solve this problem, I would like to place a switch in the power lines, but I wonder if this will break the device since the Data cables are still connected but the power lines are disconnected.

Any answer will be Appreciated. Thanks in Advanced


texts: Battery charger with load sharing for portable Raspberry Pi 3

texts:
i'm doing portable Rasberry Pi 3 and i need help choosing the right battery power system requiered for the project.

The project has:

Raspberry Pi 3. Normal power consumtion around 700 mA with peaks of 1 A.
TFT screen. Power consumtion 100-500 mA
Speakers: 10-100mA
4.2 V lipo battery.

So the battery power system must be capable of supply 1.5-1.6 A of current at 5 V. The 5 V must be very stable because the RPI is sensitive to input voltage vriations and can cause reset of the device.

The requirements for the system are:

Output 5 V and max output current >1.6 A in all the range of the batery charge level (from 3V to 4.2 V).
Load sharing/power path (i don't know the exact name), to alow a 5 V wall  adapter to power the system at the same time it charges the battery.
If the adapter can't support the system current the battery must suply the extra current needed by the system.
If the sysetm if working and the baterry is low, and the adapter is pluged while runing, the system must be capable of mantain the stability of the output in the transient to avoid reseting in the raspberry.
Smaller ic and pasives  as posible (tring avoid BGA packages). It is a portable system, i have a limited space.
Cheaper as posbile.

I have two solutions in mind. In one hand a 1 cell battery charger ic with load sharing and input current >= 2 A plus a DC/DC boost converter to output the 5V to the system. The charger ic must be capable of support 1.6A at the input plus the eficiency of the converter ( ~2A input). For example, i used this device for previus versions of the rasoberry pi which consume less power. It uses the TPS61090 as boost converter, but i think, looking at the graphs of the datasheet that i can't use this converter because at low battery levels (3V) it can't support the 1.5 A. A boost converter with this requirement if easy to find, but i din't find a ic charger with this characteristics.
In the other hand i also searched for ICs for power banks, that are capable of charging battery and suply 5V output directly in one single package, but i didn' find one that alows being conected to a wall adapter (charing the baterry) and supply 5V at the same time.

I need guidance in witch system may be better for my requirements and if you know about some IC that have this characteristics.

Thanks


texts:
When driving an NPN transistor using the GPIO output on a raspberry pi I assume no protection is needed on the GPIO side of the circuit?

So nothing would really be needed beyond this to drive the LED as seen below?


texts:
I am trying to simulate a voltage clamp using two Schottky diodes.

I am trying to recreate the case when a resistor (R1) shorts (0 ohms)...  I would expect to have around 3.3v at out port.  Without adding the series resistance PS, I got 12V.   Adding I got around 7.9v.

So I am suspecting I have to set some parameters to have a better simulation.  any idea?


texts: Feedthrough capacitors as capacitors with low inductance

texts: Can a feedthrough capacitor be considered (and used) as a capacitor with a very low equivalent series inductance?


texts: Measuring small (and small changes in) capacitance

texts: I would like to measure the capacitance between two random pieces of metal. Also, I would like to monitor the changes in such capacitance as people walk by those metal objects.  Can a cheap off-the-shelf meter do this?


texts: MCP73831: design a lithium battery charging circuit

texts:
I am trying to design a charging circuit for a lithium polymer battery with 2200 mAh capacity and 3.7 V nominal voltage. The integrated circuit for the control of the charge of the battery is the MCP73831  and as a power supply a solar panel of 6.2 Voc and Isc =175 mA is used (I do not have more information about the solar panel). The atmega328p is used as a microcontroller. On the one hand, I want to detect the three states of the tri-state output (pin 1 MCP73831). For this, I used the solution proposed in (How can I read a tristate output with microcontroller? by @Wouter van Ooijen), with the voltage divider connect to microcontroller ADC but I would also like to add a LED connected to pin 1 (STAT) so that it only lights when STAT is a low (not in high impedance). I mainly have two questions (if you see any more mistakes or improvements, I would appreciate it if you told me).

I have put a zener diode (BZT52H-C5V6) with a Vz = 6 V to ensure that the maximum voltage allowed on pin 4 (MCP73831) is not exceeded. It is right? It is not necessary?
Would both the led (TLMS1000 red) and the voltage divider work to detect the three states?

simulate this circuit – Schematic created using CircuitLab

Thanks in advance.
Best regards.


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Using STM32F103RBT6 chip (Specifcally Olimex STM32- H103 Board), Keil u5. Communicating with AS5311 magnetic sensor

SPI peripheral is setup in master mode uni-directional rx only. CPHA = 1 and CPOL = 1. The clock pin is set as alternate function push pull. initialisation of SPI is below:

  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_MASTER;
  hspi1.Init.Direction = SPI_DIRECTION_2LINES_RXONLY;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;
  hspi1.Init.CLKPhase = SPI_PHASE_2EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLED;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLED;
  hspi1.Init.CRCPolynomial = 10;
  HAL_SPI_Init(&hspi1);

I then enter a loop with the following code simply on a constant receive mode

while (1)
{
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_1, GPIO_PIN_RESET);
  HAL_SPI_Receive(&hspi1, (uint8_t *)Rx_Buffer, 3, HAL_MAX_DELAY);
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_1, GPIO_PIN_SET);
  HAL_Delay(1);
}

I've checked the polarity and phase in the perihperhal viewer and can see the registers are set as 1 for both CPOL and CPHA. However when using a saleae logic analyser i can see that after transfer of data the clock does not idle high.

In terms of hardware the clock is directly connected with no pull up/down resistors.

Any ideas why the clock wont idle high?


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Does anyone know what kind of connector this is? It is used in a battery pack of a car to connect can-bus wires with each other.

The connector has 2 rows with 22 pins in total.
Dimensions of female wire harness: 30mm x 14mm x 19mm


texts: Multiple slaves with identical address on multi-master I2C bus

texts:
I'm planning a hardware design, where I have a main board and multiple peripheral boards. On each of these boards is a microcontroller with I2C, which is the communication bus for the boards. The same kind of a peripheral board can be attached multiple times to the bus.

The microcontroller (will be an ARM, not specified yet) supports dual address.

My idea now is, to set one address to an unique address (with switches for example) and the second to a "group" address, which will be the same for one kind of peripheral.

Is it possible to send commands from my main board to the peripheral, as long it doesn't need a "read back" (only master -> slave)?

For me, it looks like the same functionality as for the general call with address 0x00 except it allows me to make "grouped" general call. But I don't know for sure, if this will work.


texts: What are "Bulk" conditions in a semiconductor?

texts: What is meant by "Bulk condition" in a semiconductor?