texts: How to identify temp setting on a CH-152-35 thermostat

texts:
Pictured is a CH-152-35 thermostat. It is similar but not identical to the one described at http://www.wako-clinac.co.jp/product_en/ch-152-35_en/index.html

I don't have a way to heat this thermostat in a controlled fashion until the switch opens- So I cannot determine its temperature setting by experimentation.

There is more information than just the part number printed on the side of it. I am thinking that perhaps the "195" on the second row of text is the temperature rating - but I cannot find anything via Google that takes my idea from a guess to a fact.

Can someone please tell me if that "195" number is indeed the temperature setting for the thermostat and if the "4131" at bottom is useful information?

As a further help, maybe explain if this is standard marking technique for this type of component and where a reference for these markings might live?


texts: Is there a directory of open source hardware projects?

texts: I would like to print a fairly common circuit. But I don't want to design the PCB myself. Where should I look when searching for PCB layouts?


texts: effect of wheel diameter on line following robot

texts: i am making a line following robot. i have the option of selecting 11cm and 4cm wheels with 1000RPM and 3000RPM respectively. I want to know the advantages and disadvantages of the options. Please help.


texts: Understanding atomic writes to GPIO on different ARM Cortex-M's

texts:
This video succinctly describes why the read/modify/store has potential problems when it comes to interrupts.  Very clear and understandable.

He uses the TI Stelarris Cortex-M4 as a teaching board and in the minute I linked above describes how that board was designed such that one can write to each GPIO bit or a group of bits as it were a single address using 256 different 32-bit registers.

I am following along with a blue-pill STM32F103C8T6 board and page 150 of the reference manual says:

  Note: For atomic bit set/reset, the ODR bits can be individually set
  and cleared by writing to the GPIOx_BSRR register (x = A .. G).

Dave Welche's code does exactly this.  It works exactly as expected and blinks the onboard LED.

My question then: Is there a way to do atomic writes to the blue-pill board in the way that's described in the video? Or is that each manufacturer handles this type of thing differently and in the case of the blue-pill ST has decided to use a single register to handle this?


texts:
I am using an FTDI USB to Serial cable to read the startup log of a board. The FTDI cable is not reading the correct information coming from the board. Here is some of the information that I am seeing when I look at the Tera Term Terminal.

"¿aY'¿3;9!#%='5
5¿-9-!#¿%5%£¿777-5¿777-5#7;!!£%!75%#!#5¿=#7;!!£5'#!
5#!'¿=#7;!!£!9/A5#7!-7¿=#7;!!£!9/A=#5'A-7¿=#7;!!£!9/A35=¿=#7;!!£;!!'!=75£££¥¥3=77;5¿=#7;!!£5-57;!!=5!#15¿¡75¡%%9;')¿¿-åë¹¹¿s'=5#57¿w5-95¿W5¿;'!;¿=¿?åë¿¿¿{!!-#1¿¿1-!#5¿37¿;'!;¿=¿?åë¿¿¿5¿37¿%5%!
     ¿=77¿-
           5åë¿¿¿U-#1¿w5-95¿W5¿-#¿'=95¿=¿?§¿5#7¿?=559åëy½VQÚtÔi)ÓKªÚ4ª:úëåë"

I have checked the baud rate, stop bit and parity bit and all are correct on Tera term and the device manager. I have tried this on both a windows laptop and a Linux laptop and I am having the same result between them. I have updated the drivers of the FTDI cable. I have hooked up the FTDI cable to a USB2ANY from TI using UART and was seeing the same result as above of the data being wrong. I have tested it at different baud rates and the data that is sent is always received as the same wrong data. An example is 0x22 is always received as a "7" across different baud rates. I have tried connecting two FTDI cables together and they can accurately send and receive data at different baud rates. an example being "banana" will be received as "banana". I have tried using minicom, Putty and Tera Term and the results are always the same. Is this something to do with the decoding of the data received? What could be causing this issue?


texts: Want to get a heat gun for SMT - what should I get?

texts:
I need to get a heat gun so I can do some SMT work.  What wattage / heat range should I be looking for?

Obviously it needs to get hot enough to melt the solder (preferably lead-free) yet not fry the components.  I have seen everything from about 1400W up to 3400W with max temperature ranges anywhere from 350 to 650°C

So what wattage / max temperature do I want?


texts: Build electrical characteristic for gas measurament via IR sensor

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I'm building a CO2 measurement unit via Arduino and I'm the phase of choosing the sensors.
I've found out this IR sensor that, thanks to an emitter with WL of 4.26um is able to output a voltage proportional to the concentration in air of CO2.
To calibrate the circuit I must use a titrated gas (% well known) and measure the voltage in output from the sensor.

My problem now is that I can't understand, with this measure done, how associate further measurement with the % of the gas.

Is this linear? Does it depend on the sensor (the distance between the LED and the sensor is fixed)?

I've never used IR or Gas sensors so, this is my first experience with them and I'm pretty disoriented


texts: BLDC control using driver with external MOSFETs

texts:
I would like to be able to control various kinds of sensorless brushless DC motors for robotics. Hobby ESCs are everywhere but I'd like to drive motors with a simple PWM output from a central controller without having to create a servo-like control pulse. First because it's marginally easier to do in software. Second because it would then be possible to replace existing brushed DC motors in existing equipment without modification.

I have found the MTD6501G which looks just fine and I see many people successfully driving dismantled hard drives and fan motors with it. However it can supply only 0.8A.

Another is DRV8301 - more complicated, more expensive, more external components required.

Would it be possible to use the MTD6501G with motors requiring more current by using cheap external drivers like MJE2955 on each of the phase outputs?


texts: Input and output impedance in RC circuits

texts:
As far as I learned, the rule of thumb for the ratio of output impdance to load(input impedance)is 1 to 10.
Thevenin resistance(output resistance) Rth should be very small compred to the load resistance Rload.
Rth/Rload must be small in order to avoid “loading the circuit”. A maximum ratio of 1/10 is often used as a design rule of thumb.

I was trying to understand how this would result in RC circuits.
I came across to the following link which is part of a text book where it explains rule of thumb in RC case (see page 19):

http://sites.fas.harvard.edu/~phys123/classnotes/class2_notes_headerfile_rev_july14.pdf

Basically the text says:

Since impedance of an RC circuit is:

Z = Xc // R = [R * (-j/(w * C))] / [R + (-j/(w * C))]

we have a frequency dependent impedance here and we should  apply the worst case scenario.

To make my question clear I add the following circuit:

In above circuit filter A is driving filter B. Considering the circuit, here is what I understand from his arguments on input and output impedance:

1-) We want ideally Zout (in filter A) to be as low as possible. That means in worst case Zout will be high which happens when frequency is very low. And he approximates filter A to R here.

2-) We want ideally Zin to be as high as possible. That means in worst case Zin will be very low which happens when frequency is very high.
This approximates Filter B to R. I can see that from the Z = Xc // R relation. I can picture this in my mind when I think with "phasor representation". If the frequency goes too high, Xc goes to zero and Z becomes R. This looks more straightforward.

My question is about the first argument above. I will repeat again:

Lets consider Filter A again in above circuit. We want ideally Zout to be as low as possible because we don't want loading. That means in worst case Zout will be too high which happens when frequency is very low.

But when I think with phasor representation. If the frequency is set to too low, Xc goes to infinity and Zout doesn't become R.

Where am I wrong here?

Edit:

Here is how I derive mathematically so far(let me know if agree):

lim[f-->0]: Zout = ?

lim[f-->0]: Xc --> infinity

lim[f-->0]: (-j * R * Xc) / (R - j*Xc) = (-j * R * infinity) / (R - j * infinity)

|Zout| = (R*infinity) / sqrt(R^2 + infinity^2)

|Zout| =  (R*infinity) / infinity

|Zout| = R


texts:
I have something which can measure very high voltages at very high speed. These high voltage can be directly be given to input pins of this ADC without first converting to lower voltages.

Now here is a problem, where can this be used? I mean power electronics do not works in 10s of MHz range (I think so) and these days a high voltage probe can be used with oscilloscope to debug high voltage circuits. Because reducing the least count of this circuit to ~4mV (equivalent to 10 bit ADC) is impossible (as for now) so it can't be used for low voltage signals.
One application that I thought by myself is in mobile tower i.e. we directly connect this ADC to antenna and output is directly given to MCU. But I don't know if it is practical or not. I don't know how the circuits of mobile tower communication works? And where in that circuit would this ADC fits?
Any help/links is appreciated.
Thankyou for you time.


texts: Rotary encoder causing ripple noise on digit potentiometer

texts:
I am using a rotary encoder to control the value of a digital potentiometer, specifically the MCP41HV51. I have a 9V supply feeding a 5V linear regulator. My logic supply for the digit pot is the 5V, and my analog supply (V+) is the 9V (V- is grounded). The encoder goes to a microcontroller which controls the digital pot. I have pull-up resistors on the A and B contacts on the encoder going to 5V. I am using the digital pot as a variable feedback resistor of an op amp used for audio gain control.
I originally thought the noise I was hearing while adjusting the digital pot with the encoder was zipper noise from the digital pot changing values, however I have been able to identify the noise I am hearing is due to the rotary encoder. I have 47uF of capacitance on my 5V supply yet I still hear a popping/zipper noise when moving the encoder. I have been able to verify the sound comes from the encoder by commenting out the code in my microcontroller that sends a new value to the digital potentiometer. I also have a few buttons with pull-ups to 5V that make an audible sound in my gain stage. I'm assuming the popping sound on the 5V supply is making it's way either back to my 9V supply or ground, possibly coupling somehow through the digital pot.
The op amp is a TL072 with V+ at 9V and V- grounded. My reference voltage is 4.5V from a voltage divider.
What should I do to solve this issue? Do I need separate digital and analog grounds? If I do that, how do I couple the grounds together? I'm new to working with both audio and digital in the same circuit.

simulate this circuit – Schematic created using CircuitLab


texts: Is it safe to run and charge a deep cycle battery in an enclosed space like a bedroom?

texts:
I'd like to experiment with running a small server (5.5 watts) / 85AH deep cycle battery / charged via 30 watt solar panel from my bedroom.

I generally keep the window open, but want to make sure it's relatively safe for me to keep the battery inside and out of the sun. I hear the recharge process can release fumes which, if concentrated in a small area, can be toxic, but want to know if discharging also creates fumes and, in either case, if keeping the window open is preventative enough to prevent a build up.

Thanks for your response.


texts:
To understand (and optimize) a circuit for wireless charging a bit better, I tried to simulate the tx/rx coils.

There is a ferrite below/above the tx/rx coil. The peak-peak current is ca. 5A (measured). The tx coil has 5 windings the rx coil has 20 windings.

What I'm primarily interested in is the total current in the rx coil.

Secondarily about the losses in the copper plane close to it (not visible yet)

Is there a reason I could not simulate this with FEMM?

To simulate the rx coil, I tried to follow the idea of the tube example and created a circuit with 0 amps, which allows me to specify the windings. But this leads to a total current of zero amps (I assume I did something wrong). At the moment the rx coil seems to have no influence on the magnetic field (which is expected because the reported current is zero). If anyone could give me a hint where I probably went wrong this would be helpful.

The simulation is axisymmetric (left border is the axis) and the two green squares are just green marked to show where the rx (top) and tx (bottom) coils are.


texts: What does this symbol indicate (line with brackets)?

texts:
I'm modelling a power system, and encountered a few symbols I have never seen before in a single line diagram.

I believe the first one is a switch with three possible position. Closed, open and grounded. Is this correct, or am I wrong?

I haven't got a clue what the second symbol indicates? It must be some sort of feeder, but what is the purpose of the brackets? It doesn't appear in the tables for either IEC or ANSI.

Has anyone seen this symbol before?


texts:
In Thailand we usually use 3 phases (L1, L2, L3) + Neutral (N) + Ground (PE) with 220V.

A machine imported from Taiwan has four connectors: L1, L2, L3 and Ground (connected to the housing).

It uses this mainly for motor controllers (SDB-075A2), some relays and motors.

The technician setting up the machine says there must be 220V between L1 and L2, 220V between L2 and L3 and 220V between L3 and L1.

I was under the impression that if we wire our incoming Y configuration in a delta way (leave out the N), there would be around 380V between the phases.

How would it have to be connected to have 220V between the inputs?


texts: Series pass configuration logic level MOSFET

texts:
I'm trying to create a switch for a negative supply rails -12V/2A using a MOSFET.
I'm not sure how to implement the design in a negative rails,
We want the voltage drop in the NMOS to be less than 0.1V at 2A. So we want Rds(on) to be less than 33mOhm
any help on how to implement the design will be appreciated.
I'm looking for a circuit equivalent to this one but with the changes to operate a -12V negative supply


texts: Simulteneous demultiplexer, multiple relay switch?

texts:
I'm lacking proper terminology here: I have 3 inputs and I would like to route their signals into 3 different pins (on a microcontroller).

But I want to be able to re-route the pins (without physically switching cables).

For example:

              -------
           1 |       |
A  ---->   2 |       |
B  ---->   3 |       |
C  ---->   4 |       |

Then, programmatically switch to this configuration:

              -------
        /->1 |       |
A  ----/   2 |       |
B  ---->   3 |       |
C  ---->   4 |       |

So it's like a set of switches, but very complicated (select k out of n; many possible combinations)

I looked at demultiplexers and they don't do it. I think this must be a frequent (or at least: solved) problem. Is there an IC that could relay the signals as I want?

Edit (to provide more context):

My device has one USB port for a sensor. I want to use different types of sensors (they use different interfaces/protocols: IC2, SPI, PWM ...). The microcontroller has certain pins dedicated to IC2/PWM (and it is not always possible to overwrite them). The physical connection (USB cable) is also fixed. Therefore I'd like to 'rewire' the signal routes programatically.


texts: Resistor in my amp design caught fire, is my design incorrect?

texts:
I'm working on the final stage of my guitar amp. This stage needs to take the line-level signal (~1vpp-~2vpp) from the FX_RCV jack and swing it hard enough to drive the EL34 output tube. This stage of the amplifier is solid state to save on $.

I'm using an LND150 (500v depletion mode MOSFET) to boost the voltage and an IRF820 (500v enhancement mode MOSFET) to supply enough current to drive the output tube (when it goes into saturation).

When I fired the FX loop recovery section up, I had one resistor nearly explode (R29), and another smolder (R28) (Always wear safety glasses around high voltages!).

My wiring appears to be correct :( Is something wrong with my design around the LND150?

EDIT

I figured it out! My wiring is so not correct! The gate on the LND150 is the middle pin, and the gate on the IRF820 is the left pin. This means ALL of my MOSFETs are wired incorrectly. I made the assumption that did not vary from the transistors I've used in the past vs these MOSFETs and the lesson is to RTFM!

http://www.mouser.com/ds/2/268/supertex_lnd150-522923.pdf
http://www.mouser.com/ds/2/427/91059-106635.pdf


texts:
I'm starting to learn about phase-shift oscillators and I'm a little confused at the outset.   Suppose you have an amplifier with a feedback circuit with transfer functions A and β respectively.   My understanding is that the Barkhausen Criterion is a necessary condition for oscillation.  In fact a simple algebraic calculation indicates that in order for there to be oscillation, you must have Aβ = 1 (A and β are complex).   But this condition isn't sufficient is it?
So in the case where Aβ = 1, my questions are:

What additional conditions would guarantee oscillation?
Why is the oscillation sinusoidal?

I'm assuming there must be some 2nd order linear ODE describing the system when Aβ =1, but I don't know how to produce it.
I've been searching on the internet and all the things I've found so far are either naive explanations, which seem to suppose Barkhausen implies oscillation, which it sounds like it doesn't, or research articles in engineering journals which deal with very advanced aspects of topic.
Can someone point me to a reference that might offer some sort of "middle of the road" answer?
Thanks.


texts: How to calculate output resistance in collector circuit?

texts:
Calculate output resistance \$r_a\$.

Here is the solution:

$$ r_a=R_E || \left(\frac{1}{g_m}+r_a'\right) $$

$$ r_a'= \frac{U_e}{-i_c}=\frac{U_e}{-\beta i_B}=\frac{R_G || R_B || R_V}{\beta}$$

I don't understand the solution. What is \$r_a'\$ here? Can I draw \$r_a'\$ as resistor instead of \$1/g_m\$ and \$R_E\$?  Can someone explain this solution?


texts: Interface two Ethernet (10 Base) devices without 4 twisted pairs cable (Common ethernet cable) and 10 Base-T Filter

texts:
I'm autumn and recently working on a project that wants to connect two IC with part: ENC28J60 (that connects microcontrollers (with SPI interface) to Ethernet and LAN Networks) directly in a PCB board (witouth cables and only with cupper tracks in my PCB.

As you know for connecting ENC28J60 (or any 10mbps LAN device) we need a 1:1 filter (it used for CMRR increasing) and you can find lots of schematic for that in google.

for the Ethernet cable (4 twisted pairs cable) we connect the TPIN+, TPIN-, TPOUT+ , TPOUT- pins of ENC28J60 to 10 Base-T Filter and then Connect Ethernet Cable to otherside of the filter. it's common and simple.

But the Question is: How can i connect two 10Base Ethernet Device (Like ENC28J60) without filters in short distance? (like a small PCB) (short distance will not cause noise and we don't need any filter for CMRR and twisted pairs).

Thanks,

Best Regards.


texts: Reason for small-valued feedback resistors in low noise Op Amp

texts:
I am wondering why the feedback resistor values specified in the datasheet of the AD797 are so small. My understanding is that the low feedback resistances keep the noise small, but isn't it also not ideal to have large currents flowing through the feedback network? My understanding was that feedback resistors should be >1k.

Here is a link to the datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad797.pdf

And a picture of an example application:

26.1 ohms seems like far too small a value for feedback resistors.


texts:
I have been given to understand the original crybaby wah schematics. But I can barely understand anything regarding the circuit itself! Any kind of suggestion and help from anyone would be very helpful. If the question needs improvement/clarification.. feel free to comment.

When I applied at input a sine wave of 750Hz, 1Vpk in the multisim, the result I have is: input signal: red  output signal:blue .. I'm not sure what input to apply, so I just used a sine wave. Even if I change the potentiometer, I see no change of the output signal.


texts:
Please consider the schematic:

The MAX1645B is a level 2 battery charger.
My problem is with the P-Channel MOSFETs.
There are two P-Channel MOSFETs in the above circuit.

From the datasheet:

  The source switch P1 is controlled by PDS. This P-channel MOSFET is turned on when CVS rises to 300mV above BATT and turns off when CVS falls to 100mV above BATT. [...]
  Load switch P2 is controlled by PDL. This P-channel MOSFET is turned off when the CVS rises to 100mV below BATT and turns on when CVS falls to 300mV below BATT.

My problem: I think these P-Channel MOSFETs aren't in the correct Source-Drain direction.


texts: I am facing a problem while designing a Schmitt trigger circuit

texts:
I am applying a Schmitt-trigger to the waveform given in the figure below.
.
This is a 3.5 volt signal and I want to perform thresholding so I use 1.58 volts as upper threshold and 1.17 volts as lower threshold for my Schmitt-trigger circuit. My designed Schmitt trigger is given in the image below.

After applying Schmitt-trigger I was expecting a square waveform and it should be. But I got a signal that was not a pure square wave it was rounded from the top. the resulting waveform is as follows:

My question is why it is happening? Why I am not getting a square waveform as an output?


texts: Connect speaker directly to Samsung Galaxy S6. Minimum impedance accepted

texts:
I want to connect an external (passive) speaker (3W/16 ohm) directly to my Samsung Galaxy S6 using the headphone jack. I want to do this on my bicycle using the smallest space possible. Connecting the phone to an active speaker requires extra space (speaker + rechargeable batteries + amplifier pbc) so reusing phone's amplifier will be the optimal solution.

Is the impedance too small? What is the minimum impedance that I can use? Is 16 ohm safe?


texts: How can we interpret the negative side of a double-sided frequency spectrum

texts:
We know that a frequency spectrum includes both positive and negative frequencies. However, how can we explain the negative frequency physically?
For example, in a wireless communication system, suppose the carrier frequency is 2.4GHz. The power carried by this frequency is, say 10uW. In a double-sided spectrum, this carrier frequency can be represented by two tones, one at f = 2.4GHz, another at f = -2.4GHz. Each of these tones carries a power of 5uW.
What I understand is that, the rotations of these two tones are in opposite directions. However, in the carrier signal, what is rotating? Is it related to the propagation of the EM waves?
Could anyone offer some insights?
Thanks.


texts: What is the difference between transistor BC107 and 2N3904

texts: Last week I bought a transistor BC107 for putting it into use in my common emitter class A audio amplifier. The BC107 transistor costed Rs. 15. Yesterday I bought a 2N3904 transistor that costed only Rs. 6 and it gave me almost the same result as the first transistor. Now my question is, what is the difference between the two, that their cost varies this much. Also what would be the different applications of the two transistors?


texts: Is there a good reason to use an SCR based speed controller instead of a TRIAC?

texts:
I tried to purchase a switch for a reciprocating saw with variable speed for my Dewalt DW304. I discovered the part is no longer available.

Instead, I bought a similar switch used on the later model DW304PK. Its electronic, however, baffles me.  The original one has a switch housing a simple DIAC circuit for triggering an external TRIAC, but the new one a more complex SCR circuit.

Below is my shoddy attempt at a schematic. I was able to read values from what I believe to be diodes, capacitors and resistors.  The black strips are resistors.  The two longer ones are slide resistors (?). I was unable to obtain a datasheet for it, but the make is Marquardt and the part number is 2069.0504. The SCR is a TN1215.

I was under the impression that an SCR throws away half of the voltage, whereas a TRIAC uses the full voltage. Is there a good reason why the manufacturer would use a SCR circuit when you are only getting half the power? For machines designed to cut metal, a lower speed is required, but what about torque?

Are the two glass diodes serving to rectify the other AC half, making the SCR behave as a DC speed controller on a universal motor? Perhaps, the circuit is serving the same function as the DIAC circuit by triggering phase angles?

Original Board

New Switch Revealing Circuit Board

Front of New Circuit Board

simulate this circuit – Schematic created using CircuitLab

Poor attempt at creating a schematic


texts:
I am new to this electronics/PCB stuff and was wondering about Dropout Voltages for a Linear Regulator. If I supply a 12V Output Linear Voltage Regulator with 9V, what will happen (firstly if the regulator's dropout voltage is under 9V and secondly if it is not).
Thanks for the help in advance!


texts: How to convert Clock signal to PWM signal?

texts:
Let's say i have a clock signal which i control its frequency making it going from 10Hz to 1000Hz.
And i want to convert this to PWM signal, so that 10Hz gives 0% duty cycle and 1000Hz gives 100% duty cycle.
How can i make such conversion?

Note:
What i'm trying to do in reality is control a DC motor with a Stepper motor driver, The stepper motor driver output Dir and Pulsation signals, and i want to take the pulsation signal (that varies in frequency according to speed) and use it to control the DC motor.


texts: Single chip level shifter from LVCMOS to 12 V

texts:
I'm working on a nixie clock based on a STM32L476RG microcontroller and HV5530 chips. The microcontroller uses 3.3 V logic while the HV5530 really needs 12 V logic, which is a pain to implement. There are buffer ICs that raise the level from 3.3 V to 5 V, but I was unable to find any that works with 12 V. I experimented with a circuit based on the LM339 with a reference voltage of 0.6 V generated with a forward biased diode and pullup resistors to 12 V. It works, but I prefer to use a single chip. I've spent hours online trying to find a chip that does this, but none comply with 12 V output. I looked for both open drain outputs or push pull outputs without success.

Is there a single chip that does 4 channel, one way shifting from 3.3 V to 12 V?


texts: Connecting two Rohm KX224 sensors over I2C

texts:
I would like to connect two identical sensors (slaves) over an I2C bus. The problem is that they have the same address.
The datasheet says the following:

The KX224 Slave Address is comprised of a user programmable part, a factory programmable part, and a fixed part, which allows for connection of multiple accelerometers to the same I2C bus. The Slave Address associated with the KX224 is 00111YX, where the user programmable bit X, is determined by the assignment of ADDR (pin 1) to GND or IO_VDD.

Pin 1 is VDD, not ADDR. Also, there is a diagram:

Multiple KX224 accelerometers on a shared I2C bus
There are assumptions on the diagram about connecting ground or power, which I am not sure about. Here is the link to the datasheet.
Do I just need to invert polarity when connecting one of the sensors to instantiate a different address?
Here is what the sensor looks like:


texts:
This buck converter uses 2 separate grounds. AGND and PGND. Why do we require 2 separate grounds?
I have seen in another schematic which mentions something like track fuse which ties the board ground and the input supply ground.
What is track fuse as it is mentioned below?

Are both (tying AGND & PGND and tying GROUND-GND) the same/same purpose or different?


texts:
I have met with a scalar control algorithm for a permanent magnet synchronous motor. I haven´t heard about it before so I decided to develop a dynamic model to further analyze this control algorithm. Unfortunatelly I haven´t got the Matlab with the SimPowerSystems library so I decided to create this model in Scilab.

I have been using below given equations for PMSM simulation:

\$\frac{\mathrm{d}i_d}{\mathrm{d}t} = \frac{1}{L_d}\cdot(u_d-R\cdot i_q+L_q\cdot\omega_e\cdot i_q), \\
\frac{\mathrm{d}i_q}{\mathrm{d}t} = \frac{1}{L_q}\cdot(u_q-R\cdot i_q-L_d\cdot\omega_e\cdot i_d - \omega_e\cdot\psi_m), \\
\frac{\mathrm{d}\omega_m}{\mathrm{d}t} = \frac{1}{J}\cdot(1.5\cdot p\cdot\psi_m\cdot i_q - T_l),\\
\omega_e = p\cdot\omega_m\$

where \$p\$ is number of pole pairs

The parameters of the model:

\$L_d = 1.365\cdot10^{-3}\,H \\
  L_q = 1.365\cdot10^{-3}\,H \\
    R = 0.416\,\Omega \\
    \psi_m = 0.166\,Wb \\
    p = 2 \\
    J = 3.4\cdot10^{-4}\,kg\cdot m^2 \\
    kF= \frac{3.2}{(2\cdot\pi\cdot\frac{1200}{60})^2}\,\frac{N\cdot m}{(rad\cdot s^{-1})^2}\$

Here is my overall simulation model

The motor is loaded by below given torque

\$T_l = kF\cdot\omega^2\$
which is removed in step wise manner at \$t=0.4\,s\$

The U/f block

The PMSM Model block

The Inverse Park Transform block

The Inverse Clarke Transform block

Ther results are following

Stator currents

Motor torque

Reference and actual mechanical speed

Stator voltage in q axis

I have doubts about correctness of my model due to the fact that the actual motor speed differs from the reference speed. I expected that they will equal because of the modeled machine is a synchronous motor. Does anybody know where I did a mistake? Thanks in advance for any suggestions.


texts: How close can an output transformer be to a preamp tube?

texts:
Imagine a layout for a tube amplifier. The power transformer is on one side, and the output transformer, input jack, and preamp tubes are on the other side. (Take a look at the Soldano SLO for example)

Guitar amps have a huge amount of gain, and the layout is crucial to prevent parasitic oscillations, etc, but I've never seen this question answered.

Exactly how close can the output transformer be to the preamp tubes? Is it better if the end bells are facing the preamp tubes or if the laminations are?

I'm sure it depends on the gain of the amp of course.

What do you recommend?


texts: Consensus on microstrip trace impedance calculations?

texts:
I'm designing a PCB that has a 2.4GHz signal that I'm routing to an SMA jack.  I'm trying to figure out the geometry of the necessary microstrip trace.  This is the first rf PCB I've worked on.

The problem is that if I feed the values into different online calcuators, I get considerably different values!  I don't know which ones to design to.

I'm using a 4-layer PCB, 32-mil thick, FR4. The ground plane is directly under the microstrip, with 5.6-mil of prepreg between them.  The microstrip thickness is 1.35-mil (1oz copper).  I'm assuming a dielectric of 4.2.

The trace is running from a bandpass filter to the antenna jack, and is only 135-long.

Say that I make a 10-mil wide trace. Here are the results:

eeweb.com = 37.1 Ohm.

chemandy.com = 52.2 Ohm using one set of formulas, or 46.85 Ohm using IPC-2121.

If I use formulas from this textbook, I get 42.55 Ohm.

This is a surprising spread.  What is the best practice here?

Thanks!


texts: Symmetric power sockets – design considerations in electrical devices

texts:
There are various single-phase power socket standards in use. Some countries use plugs that can be plugged in the socket only in a specific orientation (for example, the United Kingdom) while other sockets accept the plug in either orientation (for example, Germany).

British plug:

German plug:

Do engineers have to account for this fact when designing electrical devices? Could certain designs be simplified if line and neutral always were clearly defined?


texts: Measuring water level inside a drinking glass

texts:
Background: I am creating an automatic tea brewing machine using an
Arduino and an electric water kettle from Amazon.  My family and I
drink lots of tea and we have many different sizes of glasses.  I was going to use a peristaltic pump to transfer the water from the kettle to the tea glass (mainly because it's food safe and self-priming).
Task at hand: I need a way to know when to stop pumping the boiling
water from the kettle as to not overflow the tea cup.  I was thinking of 3D printing a bracket that will hang over the lip of the cup (like on the side) that will have two wires facing down towards the bottom of the cup.  One wire would be connected to ground and one to an input on the Arduino. That way, as the water fills to the top and eventually touches the exposed ends of the wire, the Arduino would know to stop pumping because the wires are now conducting to Ground.
My question is:  Is my method listed above safe to do in drinking
water (exposing a path to ground in the water for a few seconds), or
is there a better/safer/easier way to accomplish my task?


texts:
I understand how the logic levels of an NMOS work with a pull-up resistor.
1. What would happen though if there was no resistor attached? (What would the logic levels look like and why?)
2. What would happen if there was a pull down resistor instead?


texts:
I am making up a cable for the below diagram, but am slightly confused about the shielding. Does this mean that the red (earth) should shield the yellow, white (earth) shield the orange, etc?

Does the black shield them all?

It is a diagram for an RGBS video cable between two car ECUs.


texts: What certifications are required to sell a home kitchen appliance in the USA?

texts: I have read what the possible answers might be however someone may have had a recent experience dealing in this area.  If I wanted to sell an automatic soup maker in the US (please keep in mind that this unit will use a DC motor not AC motor for blending and it also has an heating element on the bottom) what certifications are need in the USA if any.  The unit will not be used for commercial applications. Thanks


texts:
I am trying to build low side current sense amplifier for my motor drive (1 kW BLDC trapezoidal control.) Before that I get confused with the current waveform of BLDC drive in low side.
My application voltage = 48 V and current =30 A maximum.

I will use 0.002 ohm (2 watts) with op amp to build a low side sensing circuit.
But before that I connect a 0.1 ohm (5 watts) resistor at low side to check the waveform at 2 ampere.
Driving with trapezoid control at a PWM frequency= 15 kHz

Here is the scope image measured in low side with 0.1ohm resistor:

Why is waveform here at 602 Hz? If I increase the voltage or RPM the waveform frequency increases.
Here is the another scope image with 0.002 ohm with op amp added to gain the output. Including PWM signal to compare.

The op amp output = yellow and PWM signal = green
When I observe the op amp output the yellow signal varies like a sine with different frequency.
When I zoom the signal it steps accordingly to the PWM on time.
In motor drive application in order to sense the current, we should sense the ADC in the middle of the PWM on time.

But if I sense likewise then the value be like sinusoidal manner then how would I be able to sense current correctly?
Guide me friends I am bit confused. And my application is not foc. Just to set the current limit for the drive (say 30 A).
EDITED for andy
Op amp circuit simulated:

Scope output:


texts:
I have been doing some project which worked for few months and then MOSFETs started burning. Here is detail of schematic:

So, we are using:

NTD4963MT4G  MOSFET (datasheet)
TLC5940
some 1k and 10k resistors

Microcontroller is Atmel Atmega328(Arduino bootloader, basically Arduino) which communicates with TLC5940 and controls TLC's outputs. Those 16 outputs are connected to MOSFETS.

From output of TLC there in a 1k resistor in series with gate and there is also 10k pull-up transistor on gate(to turn off MOSFET faster).
Source of the transistor is connected to ground.
Drain of transistor is connected to the load.
Positive terminal(+) of load is directly connected to power supply positive terminal.

Riref resistor on TLC is 2k, which equals at 31,5*1,24/2000 = 19mA per channel.

Actual load are LED lights. Power of LED light on each channel is max. 15W.

Behaviour(code at Atmega) is to do various things with outputs, blink, fade etc.

Thanks anyone who puts thier time into resolving this issue.

EDIT: here are more details I, seems to be, forgot:

Vcc is chooseable. It can be 5V, in that case uC and TLC, but LEDs too, are supplied directly from power supply. It can be 12V, also, then via regulator 5V is used for uC and TLC, but on MOSFETs there are 12V.
TLC frequency is default, which is (I think)517,2Hz
Schematic shows FDD8780 just because they have same footprint. NTD4963MT4G  are actually used.


texts: Choosing the proper value for a pulldown resistor in a logic circuit

texts:
I am designing a logic circuit where the inputs are some switches and also some digital inputs are needed, below is an example of the circuit used to enhance the switches as digital inputs.

I am trying to add a pull down resistor for two digital lines which are the remaining inputs for the logic circuit.
Considering that when the digital input signal is not wired, the logic circuit needs to see 0V,  How can I replicate this behavior for a digital input signal?
I thought of a pull down resistor, but as I don't know the output impedance of the circuit driving the input of the logic gate, how can I come up with a good value for the pulldown resistor?


texts: No output voltage at transimpedance amplifier with TL081

texts:
I am trying to build a transimpedance amplifier which has a input of 20uA, square wave with a frequency of 167 Hz.

My diagram looks like below but I couldn't see any output voltage.

simulate this circuit – Schematic created using CircuitLab


texts: Arduino Due precision with function micros

texts:
I read on arduino.cc/en/reference/micros that I can know the number of microseconds since the Arduino began running the program.

On my 16 MHz Arduino Uno board, the function has a resolution of four microseconds and less with a 8 MHz board. I found the Arduino Due and it has a 84 MHz clock speed.

Could I have a better resolution than 4 μs? I would like to have a precision with nano seconds.


texts: Compatibility of trace/conductor clearance standards and SOTA IC packages

texts:
this is one of those questions where one has to pay special attention phrasing it to not get SO-bashed for not being specific enough. However, apart from getting some answers to specific aspects questioned below I'm really interested in real-world experiences and subjective opinions.
Recently I had to dig a bit into a bunch of standards regarding trace (/pad,/conductor, learned that this is luckily differentiated in some of places) clearance for higher voltages. Specifically I was interested in the DC-range of about 24 to 48 V.
One of my personal take-aways is this: All standard texts I encountered (mostly IPC or EN) prescribe huge trace clearances unless conformal coating is in use. To me, this results in the fact that these standards can simply never be respected with some of todays IC packages.
One common example (but really only one of a lot possible ones) are switching regulators or motor drivers. When looking at SOTA (as in: not introduced 10+ years ago) models from big players, there are really neat QFN packages in formats like 24-pin 5x5mm specified for per-line-currents up to a few Amps, some of them for voltages well above >15V (which is a hard line for IPC2221 for example). Now, while assuming TI et al. are doing a great job designing and rating those, we are talking of pad pitches down to 0.20 or even 0.15 mm here.
Long story short: Am I right assuming that no standard out there allows using any "mid-voltage" ICs without conformal coating? I mean yes, using it is an option, I'm just curious because I saw a lot boards (be it provided as-is or while disassembling closed-package devices) that definitely had nothing except solder mask. Is everyone just not even trying to adapt these standards unless you're reaching HV regime, where layouts are huge and more safety-critical anyway? Taking this even further: are dense packages like 0.2 mm pitch QFNs "forbidden" in general because these standards are so conservative and/or slowly updated they're still only having pre-2000 technology in mind?


texts: What is HAL_SPI_TransmitReceive purpose and how it works

texts:
I am trying to understand how does this function works even though there are so many people complaining about it. My questions are these:

1) What is the difference between using this in my code:

HAL_SPI_Transmit (SPI_HandleTypeDef *hspi, uint8_t *pData, uint16_t Size, uint32_t Timeout)
HAL_SPI_Receive (SPI_HandleTypeDef *hspi, uint8_t *pData, uint16_t Size, uint32_t Timeout)

and this:

HAL_SPI_TransmitReceive (SPI_HandleTypeDef *hspi, uint8_t *pTxData, uint8_t *pRxData, uint16_t Size, uint32_t Timeout)

I mean, if I use the Transmit function first and then immediately after it, I use the Receive function what's the difference with using only the TransmitReceive?

The only problem I can think of is that of receiving while sending. For example let's say that I want to send 4 bytes to the Slave and receive from it 7 bytes. Then there are 2 scenarios:

1st Scenario: If my Slave device sends data only after the Master has sent all its data, which means that the Slave is going to wait the Master to send 4 bytes and then it (Slave) will start to send its data then the code that should work is the

HAL_SPI_Transmit(&hspi1,txData,4,TIMEOUTVALUE);
HAL_SPI_Receive(&hspi1,rxData,7,TIMEOUTVALUE);

because as far as I can think of, the TransmitReceive will start to receive from the beginning, so the first 4 receive bytes are going to be trash and the last 3 received are going to be the first 3 transmitted from the Slave?

2nd Scenario: If my Slave device sends data after the Master has sent only the first byte of its data, which means that the Slave is going to wait the Master to send 1 byte and then it (Slave) will start to send its data then the code that should work is the

HAL_SPI_TransmitReceive(&hspi1,txData,rxData,12,TIMEOUTVALUE);

(12 = 4 + 7 + one byte which is the first received byte, which is a dummy one because the Slave starts transmitting after the 1st byte is sent by the Master).

2) How does uint16_t Size variable used in the TransmitReceive function? If I want to send 4 bytes and simultaneously receive 7 am I going to use 11 in the function variable?


texts: Inductance of distributed air gapped core

texts:
I have got two sets of E70/33/32 core of N87 material, one set with centered airgap of 8mm and another set is un-gapped core. I measured the inductance for N number of turns with centered gapped core and also I measured the inductance with 4mm airgap in the each leg (which gives effective airgap of 8mm). But I am getting different inductance value in both cases, for higher number of turns I am getting difference of 1 to 1.5uH.
I am getting more inductance for distributed gapped core. I do not understand the reason behind it. I designed my own coil former(bobbin) just to give 4mm airgap in each leg and also tried putting a plastic of 4mm on each leg and measured it but the inductance is different in both the cases.
I would want to go with distributed air gap because of its advantage. But I would like to know what is the reason to have different inductances in both the case.
If anyone has experienced this please let me know.


texts: Best heating cable for a DYI heating blanket

texts:
I want to make an electric/heating blanket that will work with heating electric cable.

I will use a computer AC adapter that output 19V 3.16A, and this dimmer to regulate the heat and a heating cable sewn in a 1.60x1.20m blanket.

I have some trouble to find out which type of heating cable will be better for my project.

Knowing that the cable could touch my skin, it should not be to hot: the ideal temperature of the cable should be around 40 (45°C/113°F start to burn the skin). I have seen that, at a constant voltage, the heat depends on the current which depends on the resistance of the cable and the length of the cable (I guess I will need between 8 or 9 meters of heating cable).

Since I need a cable that will generate a temperature of about 40°C for 8 meters of cable, which type of cable will be the best?

Carbon fiber flex heater tape is too expensive.
I have seen Kanthal and Nichrome wires, but they don't seem to be coated so
they seem dangerous.
This silved plated copper looks good (Polytetrafluoroethylene PTFE coated).
Also this Carbon Fiber Heating Cable seems great because it's infared heat but I can't find one that will work on a 12V-24V tension.
Do you have any other suggestions?

Since I’m living in Europe, I'll be very grateful if you could advise me on the type of material but also its precise specification (diameter in AWG or mm, Ohms/meter...) to be able to buy the equivalent here in Europe.

Thanks a lot for your help!


texts: Selecting power supply unit for an embedded system

texts:
I am sorry if this is too naive question in this site. I am from non-electrical-engineering major but I am trying to build an embedded system which will be in a real-time imaging system box along with camera. It will be possibly running 24 h/day

Currently, I have a PC/104 motherboard ADLGS45PC with Intel CPU on it, and the system will have 2-3 SSD or SATA HD with USB port to camera. Naturally, I will need to have a power supply unit for the system. But deciding the PSU seems like a complex puzzle to me.

Question 1. What would be right power supply for this system? Choices are

Desktop PSU
PC/104 Power supply unit DC/DC
PC/104 Power supply unit AC/DC

Question 2. What is right way to decide total amount Wattage for the system?

Following is the list of power consumption for each component in the system I got for PSU unit.

Motherboard: 13-20W from motherboard manual
64GB WD sillicondrive A100's power consumption is 5V 0.9W (Active) -> 2W
512 GB Crucial SSD 6Gb/s CT512M4SSD2 ($400): 0.15W (Active) -> 2W
320 GB WD Scorpio Black HD ($62): 1.75W (Active) -> 4W
USB 2.0: 5V x 500mA = 2.5W => 6 x = 15W
Network port: 5W

Totaling above items is about 60W + 20W (for some extension). Is this right way to calculate  wattage for PSU?


texts:
I want to turn on and off both the mosfets at same time and I used IR2110 gate drivers for high and low MOSFETS.

When I try to simulate the circuit, after few seconds it shows error saying time step too small. What is the problem with circuit or simulations?

In the simulation graph,

Green represents the inductor current
Blue represents gate voltage of M1
Pink represents gate voltage of M2


texts: How much will a switching regulator influence my RF transmission?

texts:
Making a project using an ATMega328p and an RFM69W 433mhz radio module.  I want to run the AVR at 3.3v to make interfacing with the RFM69W (which runs at 3.3v) possible without bidirectional logic level translation.  My project has 8 buttons and a PS2-style analog stick.  I'm considering using a switching boost converter to supply a steady 3.3v even as my coin cell batteries fade.

I know that the noise from switching regulators can negatively impact things such as radio transmission and reception.  A linear regulator is obviously an option, but the quiescent current is typically much higher and the efficiency much lower for these.

Is the interference from these switching regulators noticeable?  I don't need a lot of output current, and was planning on sticking to a smaller regulator - for example, the TPS61221 -
 http://www.ti.com/product/tps61221/technicaldocuments?HQS=TI-null-null-octopart-df-pf-null-wwe


texts:
Sorry if this has been asked previously, but I couldn't find anything here or elsewhere on Google (but maybe I'm searching the wrong terms).

I'm trying to design a Type 2 compensator for a PWM chip I'm using. There are two main operating states - a no load state, and a loaded state. The circuit starts in the no load state, and transitions to a loaded state some time later (and never goes back). In order to get loop stability in the loaded state, I need to slow my loop response speed down a lot by lowering the DC gain with the compensator. This, however, causes the response time of the no load state to drop drastically. It's still stable, but it's very slow, and I'd like to speed it up.

I thought about implementing two compensator designs, one for the no load state and one for the loaded state. The way I would switch between these two loops is by changing the input resistance to the compensator (so I can shift the entire gain of the compensator up or down). This could easily be done by an analog switch, which would change the input resistance to either R1 or R1||R1a.

simulate this circuit – Schematic created using CircuitLab

I'm not exactly sure what happens during the transition between the two compensator designs. I can't find any literature about trying this out, though like I said, I might not be searching the right terms. Any insight would be appreciated!


texts: What equivalent series resistance (ESR) capacitor should I replace bad one with?

texts: I've got a bad clock capacitor in my original xbox that I'm trying to replace. It's a 1F 2.5V cap however, I'm not sure what Equivalent Series Resistance (ESR) the new cap should be. I see they sell 1 Ohm, 90 mOhm, 70 mOhm, and 500 mOhm on digikey. Any suggestions? Also how do you feel about the brands Eaton, Taiyo Yuden, or ELNA? Thanks!


texts: How would I calculate the frequency range of this FM radio?

texts:
https://abra-electronics.com/index.php?dispatch=attachments.getfile&attachment_id=599

Here are more clear images of the circuit and it’s diagram

Any contribution to how this radio works mathematically helps!! Thank you


texts: What's the point of vector control for ac machines?

texts:
for what I understood vector control controls the rotor's flux and the torque (both in magnitude) by changing the stator currents in the qd0 reference frame.

let's say we are dealing with direct vector control for simplicity:

in DC machines the rotor magnetic field is always orthogonal to the stator, and this is the goal in PM machines control too (to maximise the torque with using the minimum current, basically the Max torque per Amp problem).

Is this the goal here too? One thing I don't really get is how the flux has a phase if it's a scalar (and this phase seems to be on the D axis, so the same as the rotor's magnetic field), but maybe is an abuse of notation?

I believe my question could be translated in: given a desired torque and speed, will the control drive the rotor flux to be orthogonal (if it even makes sense for fluxes) to the stator's, or this may not be the case since the goal of this type of control is another?


texts: I'm having trouble understanding Johnson Counter self correction. Why is it the lower right box of the k-map that when changed to a 0, results in the desired change of the next state of state 6 being changed from 1 to 0 for digit QB of the specific state??


texts:
I am getting an error in my VHDL code. It says "[Synth 8-27] else clause after check for clock not supported". Why is this?
Below is the code:
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
use work.Data_Sizes_Package.ALL;

entity Encoder_Counter is
  Port (Count_Input_A, Count_Input_B : in std_logic;
        Reset_Counter : in std_logic;
        Counter_Value : out std_logic_vector(Data_width-1 downto 0)
       );
end Encoder_Counter;

 architecture Behavioral of Encoder_Counter is

signal Counter_Value_Temp : std_logic_vector(Data_width-1 downto 0) := (others => '0');

begin

Counter_Value <= Counter_Value_Temp;

    Process (Count_Input_A, Count_Input_B, Reset_Counter)

    begin

      if(rising_edge(Reset_Counter)) then
      Counter_Value_Temp <= (others => '0');

      elsif(rising_edge(Count_Input_A)) then
      Counter_Value_Temp <= Counter_Value_Temp + 1;

      elsif(rising_edge(Count_Input_B)) then
      Counter_Value_Temp <= Counter_Value_Temp + 1;

      end if;

    end Process;

end Behavioral;


texts: What is the circuit size and/or circuit depth complexity of an op-amp?

texts:
What is the circuit size complexity and / or circuit depth complexity of an op-amp?

This is for comparative purposes, so I'm really after a ballpark figure and any op-amp is fine (although the simpler circuit is better, as I guess I'm after a lower bound). My thoughts are that I would either count the transistors (I've found an op-amp design with 4 of them), but I want to know what the convention is. I'm a computer scientist rather than an electronic engineer, so I apologise if this is simple to work out, however I've not managed to find an answer with an internet search.

I'm actually after the circuit size / circuit depth complexity of a current-to-voltage converter (or transimpedence converter which I think will do the job) and that seems to use a resistor and op-amp in parallel, so I think I would count the circuit depth complexity of just the op-amp.

Please help.


texts:
QUESTION

Are interface parameters for a module automatically deducted from the interface instance that is connected to the module instance?

Background

I am designing a System that provides a communication infrastructure with multiple channels. Each channel can be tied to a different module by the user. To separate the user logic from the system I created a module wrapping the infrastructure. This is the setup in (pseudo) code

interface channel_if #(parameter int CHANNELBITS = 8);
     logic dummy;

     modport arbiter(input dummy);
endinterface

module arbiter(
    channel_if.arbiter channel[CHANNELS] //MODPORT defined
);
endmodule

module infrastructure(
    channel_if #(CHANNELBITS=16) channel[CHANNELS] //PARAMETERS defined
);

arbiter channelArbiter(channel);

endmodule

The problem I have is the following: I can either specify the parameters for the interface array OR the modport. I found no way (Vivado 2015.1) to define both, parameters AND modport.

In top the following code would be found:

...
channel_if #(CHANNELBITS=16) channelHarness[CHANNELS];
channel_if channelHarness[CHANNELS]; //either this or previous

infrastructure(.channel(channelHarness.arbiter));
...

While it is no problem to assign InterfaceArray.modport to the infrastructure module, I can not assign InterfaceArray.modport inside infrastructure (We already stripped the interface array down to modports at the infrastructure module boundary).

Questions

Since I can not define the interfaceparameters  for arbiter (only possible if I do not define the modport, which yields inout orts for the interfac,e which I do not want), can I use Interfaces with non defaultparameters?

Are interface parameters for a module automatically deducted from the interface instance that is connected to the modelinstance?


texts: How robust are SMD DC power inlets compared to through-hole?

texts: Normally it takes a reasonable amount of force to push in a (say) 2.5mm DC low voltage plug into a PCB mounted socket. For that reason I have normally only used through hole devices. How do the SMT versions compare? Is there a chance of damaging the board or dismounting the component?


texts:
I have the measurements of the group delay of a filter and  the period of the signal is always smaller than the delay introduced and thus phase (frequency) wrapping is also introduced.
Do you know any particular procedure followed for compensating for that phase wrapping?


texts:
I have a 0-3.3V output that I wish to amplify to 0-10V.

I am using an 8-bit R2R resistor ladder connected to a National Instruments USB-6501 digital I/O device.

The application is to control a linear actuator via a controller that requires a 0-10V command signal therefore I need to amplify the output from the resistor ladder.

Would be grateful for any advice on how this can be achieved, thank you.


texts: Artix-7 FPGA flash configuration without using CS pin

texts:
I have manufactured PCB using Artix-7 FPGA (XC7A200T-2FPG676) and configuration flash (S25FL256S). During layout MOSI and MISO were routed correctly but CS (Chip Select) pin was not routed to the Flash as this version of FPGA has dedicated CS pin. Now I cannot program .mcs file to the flash with Error “Programming Failed” using Xilinx IMPACT 14.5.
Is there any solution, software or technique that I can program my flash while bypass CS pin?
Any help regarding this issue will be highly appreciated. Thanks.


texts: I am looking for a rotating connector over which I can communicate and power devices.  The connector must be able to rotate for a minumum of 1080 degrees.  The scope of what I am trying to do is make a quick release on my racing sim wheel, which has a bunch of buttons and displays on it.  I found some connectors with unlimited degrees of rotation for wind generators, [here], but they don't really support quick release.


texts: nodal analysis - CCCS controlled by current from same node

texts:
From schematics we have:

\$i_1=\frac{v_1-v_2}{3},i_2=\frac{v_1-v_3}{2},i_3=\frac{v_3}{6},i_x=\frac{v_2}{4}\$

for node 1:

\$10 = i_1 + i_2\$

\$5v_1-2v_2-3v_3=60\$ EQ1

for node 2:

\$4i_x + i_1 - i_x = 0\$

\$4v_1+5v_2=0\$ EQ2

for node 3:

\$i_2 - i_3 - 4i_x = 0\$

\$6v_1 - 3v_2 -8v_3 = 0\$ EQ3

from three equations we get

\$v = (\frac{400}{23},\frac{-320}{23},\frac{420}{23})\$

but correct solution is

\$v = (80, -64, 156)\$

Where is problem? My guess is that controlling current \$i_x\$ and dependent source are connected to same node.


texts: Help with inferring max current ratings for these components

texts:
Where is the max output current mentioned for this opamp? What does "Million Min" mean in this context?

And where is the max base current is mentioned for this transistor?


texts: I have built the following circuit for 1 watt power LED lamp. The capacitor C4 (220uf 50v) was heating after a few seconds then it burnt. What is wrong with the circuit? I can remove C4 but reducing brightness.


texts: How to calculate power used by my microphone?

texts:
I want to plug a microphone into my camcorder. The battery from the camcorder will provide the power to both the camcorder and microphone.

The specifications for the battery are as follow: capacity = 1030 mAh, and voltage = 8 VDC.

The specification for the microphone is 3 V. (Unfortunately, that is all the manufacturer tells me).

The model of the microphone is: MOVO VXR10.

The link to this microphone is: https://www.amazon.com/Movo-VXR10-Microphone-Windscreen-Smartphones/dp/B0723D3FVL/ref=sr_1_3?s=electronics&ie=UTF8&qid=1527749498&sr=1-3&keywords=Movo+VXR10

If I use both devices to record a video for one hour, how much power does the microphone use? If possible, please show me the calculations.

PS: Based on the current lack of technical info about the microphone from the manufacturer, many experts say that they can't answer the question. So, I will try to get more info from the manufacturer and will get back with you all ASAP.  However, for now, if you can give me any estimate on the power consumption of this microphone for one hour, I will greatly appreciate.


texts: I am designing a power amplifier using MRFE6VP61K25H at 27.12 MHz with 25watts power output. For that I've calculated the input and output impedance using S-parameter simulation in ADS by importing the model then I have done conjugate matching at both sides of the transistor. Can I get more gain after matching network designing, that is mention in Data Sheet?. The maximum gain mentioned in data sheet is 26dB but i am getting 32 dB gain. is it due to conjugate matching at the input and output end?


texts: How do I fix an Omron d2fc-f-7n microswitch from unwanted clicks?

texts:
Omron d2fc-f-7n microswitches are used in computer mice all around, and they eventually start clicking several times per hit. AFAIK there is a flexible metal plate that wears out due to metal fatigue, so there must be a way to prolong its life.

The obvious solution is to remove the malfunctioning microswitch and replace with a spare, but where I live they aren't available at all.


texts:
In my current design using the T2081, I want to interface both SPI and eMMC card. While reading the datasheet of T2081, I found that SPI_CS0 pin is muxed with sdhc_dat4 which I need for my eMMC interface (page no in datasheet 16-17).
Can anyone tell me that how I can use SPI_CS0 pin for both the cases i.e. Using same pin for SPI CS as well as eMMC DAT 4? Do I need some kind of external circuitry to do the same?
How i can use one pin for two different signal?
Here is the Link of T2081 Datasheet: http://www.farnell.com/datasheets/2618540.pdf


texts:
This is my RC integrator:

From my two different analysises:

$$ V_{out}(s) = V_{in}\dfrac1{sRC} $$

and

$$ V_{out}(t) = \dfrac1{RC}\int V_{in} dt $$

These are of course different as one is in the frequency domain and one in the time domain.

If I understand correctly, \$ \mathcal{L}\{V_{out}(t)\} = V_{out}(s) \$

However, Wolfram Alpha tells me \$ \mathcal{L}\{V_{out}(t)\} = V_{in}\dfrac1{s^2RC} \neq V_{out}(s) \$

What am I doing wrong?


texts: Is there a way to set mili meter as default in Eagle cad? It resets to metric to inches every time I open a board file.


texts: Wich battery configuration I should use to supply raspberry, arduino and stepper motors

texts:
I'm working on a project about a self-stirring robot with sensors to avoid walls.

This project is composed by one Raspberry responsible for all the algorithms, one Arduino to deal with the sensor and the motors, one sensor to measure the distance in front of the car and two motors to make the car walk though the environment.

I need to place everything correctly in such a way that the car moves freely without wires connected to it for not much than 1-2 hours.

What I'm actually doing is powering up the Raspberry with his micro-usb wire then connecting the Arduino to the Raspberry USB port and then connecting the rest to the Arduino power source.

Obviously the Arduino isn't providing the necessary power for the two motors and the sensor although when I was searching I read that the motors need an independent power source because of network distortion they make...

So what kind of battery configuration circuit will I need to keep all this up? Maybe a 12V lithium battery?

Information I've collected about the power needed in:

1 Raspberry (3): Works with 5V/2A
1 Arduino (Uno): Works with 7-12V
1 Sensor (HC-SR04): Works with 5V (normally from Arduino)
2 motors (28BYJ-48 with driver ULN2003): Works with 5-12V


texts: What is the difference between write and flash

texts:
My apologies for my very naive question.
I am trying to get some understanding of the STM32 bootloader,
specifically I am looking at stm32flash
where I read:

write to flash/ram

read from flash/ram

flash from binary file

save flash to binary file

Please I do not understand what is the difference between

write to flash/ram

and

flash from binary file

And what is the difference between:

read from flash/ram

and

save flash to binary file

Thanks!
LISA


texts: RS-485 differential signals won't "cross"?

texts:
I have an issue where a certain controller which uses a RS-485 tranceiver (unknown, due to third party device in epoxy resin) sends data on a bus so that signal levels won't cross.

The signal looks like this (yes, I know, measured on oscilloscope with grounded leads connected to device's GND, each channel on bus's A and B).

First data packet is sent from my tranceivers SN65HVD1781A-Q1,
second is sent from a third party tranceivers (which chip I can't know due to epoxy resin fill)

It looks like, my receiver end won't see the signals 'low enough' to register them correctly. Without this TI tranceiver, I can read the third party controller from a dongle easily.

This picture was generated using a 150 Ohm termination on my tranceiver side. Although third party insisted using no termination resistor - not sure why.
Interesting is that

simulate this circuit – Schematic created using CircuitLab

a) Third party with rs485 USB dongle (no TI's tranceiver) - receive and send works works.

b) SN65HVD1781A tranceiver with Dongle works (no third party)

c) SN65HVD1781A tranceiver with third party (with or w/o dongle) - has this issue.

So either me or the third party might somehow drives the bus at the same time...

How Could I mitigate this anomaly?

Not a direct solution

On test setup I can't access the DE or nRE pins :/, but yes, seems there's some firmware issues. Started to rewrite the send and receive parts, just to confirm, single send or receive parts are working. Currently everything seems to go positively.


texts: Using a 5V LCD screen from a 3.3V Raspberry Pi GPIO pin

texts: I have an LCD screen which expects power from a 5V line, but I want to hook it up to my Raspberry Pi's GPIO pins which only supply 3.3V. What equipment do I need to increase the voltage from 3.3V to 5V?


texts: I want to know why there is a minus sign in the output voltage.


texts:
I came across this question in my book, it says:

  This circuit has three identical bulbs, what will happen to the brightness of the bulb (B), when we close the key (S). (Consider that the internal resistance of the battery is (r)).

The book befoore asked what will happen to the bulb (B) when we close the key (S), but it mentioned that the internal resistance is negligible, so I did some maths and knew that the brightness will not change when the internal resistance is negligible. But in this case when the source has a particular internal resistance (r) I don't know how to know what will happen to the brightness of the bulb (B). So I would appreciate any help here.


texts: PIC24FJ Baud Rate Issues / Crystal Selection

texts:
I'm using a PIC24FJ1024GA606 and I'm using the internal Fast RC Oscillator.

Here is my config:

// FOSCSEL
#pragma config FNOSC = FRCPLL        // Oscillator Source Selection (FRC with PLL module)
#pragma config PLLMODE = PLL96DIV2   // PLL Mode Selection (96 MHz PLL. (8 MHz input))
#pragma config IESO = OFF            // Two-speed Oscillator Start-up Enable bit (Start up with user-selected oscillator source)

// FOSC
#pragma config POSCMD = NONE         // Primary Oscillator Mode Select bits (None)
#pragma config OSCIOFCN = OFF        // OSC2 Pin Function bit (OSC2 is clock output)
#pragma config SOSCSEL = OFF         // SOSC Power Selection Configuration bits (SOSC is not used)
#pragma config PLLSS = PLL_FRC       // PLL Secondary Selection Configuration bit (PLL is fed by the FRC)
#pragma config IOL1WAY = ON          // Peripheral pin select configuration bit (Allow many reconfigurations)
#pragma config FCKSM = CSDCMD        // Clock Switching Mode bits (Both Clock switching and Fail-safe Clock Monitor are disabled)

The issue I'm running into is that 115200 baud UART has a high error rate when sending data sequentially (my bootloader flashes firmware via UART at 115200 baud). From what I've read, the Internal Oscillator isn't really up to the task when it comes to low error rates for high speed UART and I need to use an external crystal.

It should be noted that if I set the baud rate to 111000, where my BRG (currently 8) has a low deviation from the baud rate, everything works fine and there are no errors.

First of all, is this diagnosis of my problem correct?

If yes, what kind of oscillator should I use so that I can effectively use 115200 baud?

If it matters: I'm also using a timer with a 1ms interrupt rate and another timer with a 1us interrupt rate. My FCY is 16,000,000.


texts: What can be inferred from the frequency an op-amp is oscillating at?

texts:
For whatever reason, I seem to create a lot of oscillators in the course of developing circuits involving op-amps.

I'm wondering if the frequency of oscillation, which normally appears to be quite stable, can be used for diagnostic purposes?

For example, could I assume that the open loop gain is 0dB at the oscillation frequency and then back-plot a 40dB/decade line from that point to identify the frequency of a pole I need to compensate out by where it crosses the open loop gain plot from the datasheet?


texts: Why does this rotary switch register multiple positions simultaneously?

texts:
New to electronics, tackling a project that involves a switch matrix.
Having grasped the concept of regular button matrices and modifier keys, it’s time to move on to explore alternative types of switches, such as rotary and slider switches. However, I came across the following issue:

Why does this happen? At first I wondered if this was some sort of manifestation of the ghosting phenomenon that I read about when learning about regular button matrices, but I’m doubtful: if I think about this wiring, if I had hooked up the first legs of button switches to the same Row1, and their second legs individually to Column1 and Column2 respectively, then I would only be getting one registered key press at a time. What makes this rotary switch wiring different?

(I thought I wouldn't need to wire all 11 positions until I get the principle to work with the bare minimum first.)


texts:
I have a simple current controlled op amp based led driver. I pulse the Led with 50khz. Below is a representation of my circuit. (Part numbers are not accurate).

I see the 50 kHz signal nicely on the receiver. However the rise time of my signal is 350nsec and I am trying to reduce this to 50nsec or so. I couldn't achieve this. The led data sheet says I should be able to to turn it on in 5nsec or so. The op amp and the transistor is also very fast.

I measure the rise time using my receiver. My receiver is low gain and low capacitance PD with a high slew rate op amp that has a gain band width product of 450mhz.

When I measure the voltage on the limiting resistor (10ohm) I see a very sharp current increase in a few nsec so the driver is pumping current pretty fast.

I cannot figure out what is the problem. Every component is faster than the required rise time by an order of magnitude. Where I may be going wrong?


texts:
So I'm trying to figure out what GPIO voltage levels on an STM32F4 would if I have my VDD at 1.8V. I'm assuming you just use the minimum values, however the conditions state 2.7V < Vdd < 3.6V, that means either the conditions were only tested for that voltage range OR they only hold for that range. There isn't any other info in the datasheet on Voh and 1.8V

In previous digital devices, I've seen differences between the different voltages (like 2.4v and 3.6V). So for 2.4V it would be Vdd-0.2 and for 3.3V it would be Vdd-0.4.

You can run this chip at 1.8V, that's stated elsewhere in the datasheet. Under table 6.3.1

  VDD: Standard operating voltage 1.7V - 3.6V

What is my minimum Voh and max Vol range for CMOS on an I/O Pin if my Vdd is 1.8?


texts: Issues about driving a high current DC Motor using an H-bridge

texts:
Nowadays, we're trying to replicate a 24V 40A H-bridge as shown in the link:
http://hades.mech.northwestern.edu/index.php/Driving_a_high_current_DC_Motor_using_an_H-bridge

Component   Value/Part#
MOSFETS     STP80NF55-08 (80A 55V)
Half Bridge Driver  IR2109

DC to DC converter  VBSD1-S24-S12-SIP (24V to 12V)
Regulator   78L05 (5V)
Inverters   SN74HC14N
Optoisolator    4N270545K
C_B     0.1 uF
R_G     4.7 Ω
R_PD    2.2 kΩ

Our layout:

Before we start, we comprehend the basic principles of the H bridge. In this design, we have trouble in providing 5V into 4N27 optocoupler and 12V into IR2109 Gate Driver. The voltage converter VBSD1-s24-s12 sparks and burns each trial and we measure 24V voltage applied to IR2109. While this procedure, the motor could not move at all.

Near to VBSD1 converter, we use polar capacitors instead of
nonpolar ones as the datasheet of it. This is true or not?
What can we measure to control this circuit?
What can be the reasons behind the converter burn?

IR2109 datasheet: http://www.infineon.com/dgdl/ir2109.pdf?fileId=5546d462533600a4015355c7e85b1679

Note: The ground terminal is the left hand side of the copper traces


texts: Optoisolator not outputting (DC switching)

texts:
Trying to reset, automatically, an HVAC speed control unit.  The unit has an output pin H8 that goes to 24VDC when tripped, and 0VDC when running.  There is no reliable ground pin (or other ground) that I can use, so I use H5, another output, which is always at 10VDC.  Therefore, the differential between H5 and H8 is 14V when tripped, and -10V when running.

The unit can be reset by shorting H1 and H2 (two more pins on the speed control).  H1 is always 24V.

I picked up an 8 pin Si826x opto isolator and I am having issues getting it to output anything - would like to know if I'm missing anything obvious.

Pin H8 of the HVAC speed controller is connected to a 1k resistor, and then to pin 2 on the optoisolator (anode).  Pin 3 (cathode) of the optoisolator goes to pin H5.

Pin 8 of the optoisolator connected to +5V on an Arduino, and pin 5 of the optoisolator connected to GND on the Arduino.  Am expecting pins 6 and 7 on the optoisolator to be at 5V or 0V depending on whether or not the HVAC speed controller is tripped.  But pins 6 and 7 stubbornly refuse to be anything other than 0V, whether or not the HVAC speed controller is tripped.

I then tried connecting pins 2 and 3 of the optoisolator to more pins on the Arduino, and still no output on 6 and 7.  Then repeated this with a new opto chip, in case I blew something up.  Still nothing.

Am I going mad?


texts: Miscalculation of current for a pure inductive circuit in LTspice

texts:
A 10mH inductor is coupled to a 10V 60Hz AC supply as in the below circuit:

Solution of the current amplitude for this pure inductive circuit is given as:

But when I simulate this circuit in LTspice I'm having the following plot for the current which is twice what it supposed to be:

What am I doing wrong here?

edit: Current supposed to alternate:

Please see here where it explains the pure inductive circuit:
https://books.google.dk/books?id=AE2sCQAAQBAJ&pg=PA76&dq=pure+L+current+inductive&hl=fo&sa=X&redir_esc=y#v=onepage&q&f=false

LTspice and some other simulators plots the current as if it is not alternating. Why?


texts:
When I opened the supply board to the detector (Geiger counter,) I got the above circuit.

The detector uses a gas-filled tube with a central wire at high voltage to collect the ionization (charge) produced by incident radiation.

What is the use of the capacitor-1 (C1) and 2 (C2?)

The detector has only one connection. Both high voltage input and the ionization charge (output) are through this connection.

How is it possible?  I marked the splitting point as X in the picture.

The amplifier is a charge sensitive preamplifier.


texts:
This might be a very stupid question, but I can't seem to figure this out and I'm going nuts thinking about it.

Assuming you are trying to adjust the fixed bias of a tetrode push pull pair in a tube amp. In many amps, for convenience, the cathode will have a 1 ohm resistor connecting it to the ground, so you can easily use a multimeter to measure the voltage and thus the current flowing through the tetrode.

My confusion arises when trying to comprehend how the resistance of the multimeter probes themselves would contribute to this measurement.

I realize the probes are likely not thin enough wire or long enough to make any difference, but assume the resistance of each probe wire is also 1 ohm for this scenario.

Would it make any difference here?


texts: What is value of Reverse Saturation Current (Is) for BC547B NPN transistor

texts: I am trying to evaluate Ebers Moll equation for estimating collector current for a given V_BE at DC conditions. The datasheet of BC547B (which I am using) does not mention the Is (i.e. Reverse Saturation Current). Does someone know value of this Is for BC547B? Yes, I know it is of order 10 (-12 or 13). I need more specific value. Thanks.


texts:
I want to power a device from a battery and be able to plug it in a power source (PC). Will this circuit work?

simulate this circuit – Schematic created using CircuitLab


texts: DC current at input and ouput capacitance of buck

texts:
I'm working on this website

http://www.onmyphd.com/?p=voltage.regulators.buck.step.down.converter

Could someone help me to understand those two statements:

1) "since the DC current of the inductor cannot flow through the output capacitor, then it can only flow to the load."  But I can also read that "It is easy to see that during the off state, the capacitor is charged with current Iin".

My question is why the output DC current can't go inside the output capacitance but the input DC current can go inside input capacitance. I heard so many time that DC current can't go through a capacitance but at the input of buck it's what happen.

2) "That in turn means that only the ripple of the inductor current, centered around zero, flows through the capacitor. Then we have negative portions of the ripple that remove charge from the capacitor and positive portions of the ripple that add charge to the capacitor. Both must transfer the same amount of charge in equilibrium."

What way the decharging current of the output capacitance take. If I don't do any mistake : the only way I see is to decharge via load resistor. But that mean the load current is not so DC.


texts: What is the function of the bulb in a Wien bridge oscillator?

texts:
In this answer it is said that the bulb in a Wien bridge oscillator is for temperature compensation.

Is that true? (I thought it is a kind of AGC to stabilize the output level.)


texts:
I've been thinking of making a database / program to make building analog circuits easier. I wanted to make sure there isn't anything else like this that I can contribute to instead of going through the effort of creating something from scratch. Lets see if I can describe what I am thinking about in my head in words:

With this program or database you would be able to select a type of circuit block and enter the desired specifications of the circuit. The solver would then automatically determine the resistor values, capacitor values and components necessary to meet the specifications set.

How about an example? Let's say that I want to design a BJT common emitter amplifier like the one:

When designing an amplifier like this I really only care about a few things and don't always want to go through and calculate everything every-time. I would input the maximum AC voltage in, the output impedance of the previous stage, the positive and negative rail voltages, and the desired voltage gain / current gain. In turn, it would be able to solve for the resistors & capacitor values needed and if it was REALLY cool, suggest a few transistors that would work for it.

Disclaimer - I'm sure I missed something...

Now with a simple circuit like this you may think, "Is this really necessary?" My answer to this is, not really. But imagine if you could now select these blocks, connect them together and design entire circuits. I have been thinking about using Falstad circuit simulator or circuit lab and some html scripting for this. There are many other things in my head right now about this, but I will keep them to myself to keep this post simple.

So, my overall questions are:
Is there anything else out there like this that I can contribute to? Is this completely impractical? Would anyone else be interested in having a tool like this?


texts:
I would like to understand how the oscillator of this PWM controller works, and what would happen if I do not apply an RC network but directly a PWM signal generated from a microcontroller for example.

It is indicated into the datasheet (https://www.ti.com/lit/ds/symlink/uc3845.pdf?ts=1590914073928) that the capacitor is charged from the reference voltage Vref until the voltage across the capacitor reach an upper threshold and then the capacitor is discharged via an internal current source. Nevertheless the oscillator as showned above generates pulses.

When the capacitor is discharging, we can think that a pulse is generated. It could be the inverse... I would like to know exactly how it works... ie when the pulse is generated ? Is it when the capacitor is discharging or when it is when the capacitor is charging.

Now, if I directly inject a PWM signal into the RT/CT pin, like this :

simulate this circuit – Schematic created using CircuitLab

When the PWM signal which rise (very rapidly as it is a rectangular waveform) to the upper threshold, the controller will draw current (for discharging the capacitor), it will be provided by the microcontroller, then the PWM will be low and the PWM controller will stop to draw current and will wait the the PWM controller rise again to draw again current. So it seems necessary to not insert a resistance as it could insert a voltage drop when the pwm controller draws current and the PWM controller could not able to see the different voltage level of the PWM.

Can anyone know how it is built internally and if what I want to do is possible ?

Thank you very much and have a nice day.


texts: Does signal strength increment mean an increment on data speed?

texts: For a WLAN antenna, if the signal strength is increased, can I expect higher SNR, lower bit error rate(BER) and higher data speed?


texts: Calculate capacitance value and voltage rating in the event of ESD pulses

texts:
I have a input power filter circuit.
It has ESD protection capacitors which help to protect the downstream circuit from ESD pulses.

ESD Capacitors Specifications :
C0001, C0002, C0003, C0004 = 47nF, 100V, 10%, 0805
My ESD Pulse Specifications :

Contact discharge : +/-4kV & 150pF / 330Ohms
Contact discharge : +/-8kV & 150pF / 330Ohms
Air discharge : +/-15kV & 150pF / 330Ohms

Can someone please help me on how to do the calculations so as to justify that my capacitance value and voltage ratings of the capacitors are within the limits designed?
My understanding :
For example, I take the +/-4kV & 330pF spec
Q=CV ;
4kV * 150pF = 600nC
This charge will then get to the input ESD capacitors :
V=Q/C;
600nC / 47nF = 12.76V (And in this step, should I consider the capacitance value for the single cap 47nF or should I consider the equivalent series capacitance value of 23.5nF?)
So, my voltage rating of the capacitor 100V > 12.76V is appropriate for this pulse.
Is my approach correct?
My questions :

The above calculation I have done for only positive 4kV. Can someone help me on how to understand when negative 4kV is applied and how to go about the calculation?

I have justified only for the capacitance voltage rating. How to justify for the capacitance value? Can someone help me with the formula to justify the capacitance value?


texts: Designing a circuit that outputs variable voltage

texts:
Total noob here, I'm looking to implement a circuit to control a fan that has these specifications:

Pin 1 and 3 are DC-
Pin 2 is DC+
Voltage should be from 6 to 16 V
It needs to operate in 70-second cycles

So let's say we're only giving it 6V. For 70 seconds we need to output 6V between pins 1 and 2, then next 70 seconds 6V between pins 3 and 2.
I'm thinking of using simple voltage dividers with resistors for the variable output part, for example 6 resistors and switches for 5 different outputs. Then, using an astable vibrator (relays, capacitors, resistors) for switching the potential from pin 1 to 3.
I'm not sure yet what to use to control the voltage, maybe Arduino but I guess it will come down to switches anyway.
Am I talking nonsense? Is there a right/easier way to do this?


texts: Say I have Atmega8A, I am curious about why its pin arrangement is not in order? For example, pins number 14-19 go for PB0-PB5, and 9 and 10 for PB6 and PB7, respectively. Why is it so? It's not all about this particular IC I have seen this irregular setting quite often in many places. Does it have a particular reason or something?


texts: Solution to unknown function 'v' for a voltage source in LTspice?

texts: I have been getting this strange error. Has anyone else experienced this kind of error beforein LTspice?


texts:
I want to do "RC current shaping circuit" on LED for predistortion,but I don't know how to calculate "R" and "C",because I measure the Voltage waveform across a LED doesn't have this waveform,so I think if I measure current waveform,can I get predistortion waveform like this picture?

and the pulse current and steady current ratio are 1:1,
pulse current is twice steady current.
I see this technology on
https://books.google.com.tw/books?id=0H4bWIpaXb0C&pg=PA400&lpg=PA400&dq=current+shaping+circuit&source=bl&ots=yKHV8xpiY3&sig=2zntNC7TG7mQbAJbEjSdgw2Hq0U&hl=zh-TW&sa=X&ei=gNVuVZz2BYHHmwXYlIKoCg&ved=0CDYQ6AEwAg#v=onepage&q=current%20shaping%20circuit&f=false

Sorry about that,I know how to use "edit" now.
the photo is my connecting to measure current,but the value is zero

enter image description here


texts: Line Tracing robot when sensors are behind the robot

texts:
I am trying to design a robot, a line tracer basically, but the catch is that, instead of the sensors being placed on the front, they are going to be placed on the back.
So I am trying to develop an algorithm, but I haven't had any success so far. The best I can think of is, when a curve comes and the it is sensed by the sensors, then the robot will move back and take the turn.
That is what I can think of.
I tried googling it, but it seems as if no one has thought of this before. So can I get an efficient algorithm?
I use an ATmega 128 microcontroller.


texts: How would the SFP+ transceiver interface (Linear vs Limiting) affect my design?

texts:
On my board, I'd like to replace an RJ45 port with an SFP+ transceiver to increase data rate to 10Gbps.
In choosing an SFP+ module, I have noticed that the only MSA compliant interfaces can be limiting, linear, or both, while I see re-timed interface(existing in XFP and some non-compliant SFP+ modules) is recommended for communicating with some FPGAs.
I'm looking at finisar(FTLX8571D3BCV) and xilinx kintex-7 to communicate with.
Does the lack of CDR module cause problems?

I'm a newbie in these fields, so please let me know if more info in needed to clarify.


texts:
In the below circuit, I have two switches that can turn the light on or off from those two locations. Any 'switch' will turn the lights into the opposite position:

How could a circuit be made to control light from 3 or 4 locations instead of just two?


texts: Help generating a 10Vpp squarewave at 13.56MHz

texts:
I'm working on a test fixture for which I need to generate a 10Vpp square wave, at 13.56MHz, capable of driving 250mA.
My first attempt was a using opamps, but very quickly realized I can't drive 250mA, and line drivers that came close can't support the high slew rate input from the squarewave.
Then, I thought I could use gate driver ICs, to drive a half bridge which would ensure I deliver the full required power to the load.  However, driver ICs don't work at 13.56Mhz.
I also ran into trouble finding FETs that can switch at that speed, but found a few from Onsemi that may work.
Finally, the most promising solution so far (although I don't have it quite working yet) is to use two opamps to drive a FET-based push-pull output stage.  However, I'm running into issues with the op-amps driving the FETs fully on, capable of handling the high sink/source gate currents needed for switching these at high speeds.
I also thought of using an NFC reader IC, since they readily generate a carrier wave driving a >250mA load ( I think) --but these chips do much more than I need and  I'm not ready to be that wasteful (yet).
I'm currently experimenting with these potential solutions with LTSPICE- everything has only been simulated, not built.
Here are some sketches of my initial concepts:

I'm looking for some suggestions.  Is there a better way to do what I'm trying to do?
Thank you.


texts:
I've designed PCB which uses TPS54531 to generate 5v from 12v input. The circuit as below is similar to the reference circuit from TI.

After powered on, the VCC5_TMP read abnormal value 0 instead of expected 5v. Then I measured PH(pin8) as below which is also incorrect.

After that, I measured the VIN(=12v) and EN(>1.25v) which are all good.

After these measurements, I still can't get the reason why 5v can't be generated correctly. The power supply and the EN control are all correct and all the other components are selected as reference circuit suggested. Can someone help me to find the error in this circuit? Thanks.
[Update]
The problem is diode D2 is welded in the wrong direction. After I fixed it, everything is ok now.


texts:
I am trying to make a very compact and lightweight circuit that will cause an IR LED to blink on and off at a constant rate, preferably at least once per second but the flashes can be more spaced out. Due to weight constraints, I would like to use a 3V coin battery to power the circuit. The battery doesn't need to last a long time because it can be easily replaced. I have looked online at LED pulse circuits but I haven't been able to find any that work at 3V. Does anyone know of a way to either reduce the voltage of some pulse circuits by reducing the resistance or a way to make a low resistance pulse circuit? Thank you very much in advance!

Here's a link to one design I have looked at
http://www.instructables.com/id/How-to-Make-an-Led-Pulse-Circuit/


texts: LTSpice transient simulation of LC circuit

texts:
I've a question about the LTSpice simulation of the following simple LC circuit driven by a  DC current source.
The first simulation (A) looks good from point of view of initial conditions for either voltage cap V(n001)=0 and inductor current I(L1)=0. As shown in the first picture the Initial Transient Solution (ITS) for the inductor current looks ok.

Consider now the second simulation (B) in which the initial condition has been set just for the inductor current I(L1)=0. This time, as shown in the second picture, that condition seems to be not honored (the initial inductor current results in 10A)

Can you help me in understanding the reason behind it ? Thanks
Edit: based on comments I've done another simulation (C) without any initial condition. As you can see the solver is able to work out the Initial Transient Solution (ITS) different from the previous two (A & B).

Can you point me to some book (or documentation) about how Spice works under the hood ? Thanks


texts:
I've done a PCB design where I've got a USB3.0 interface using non-standard connectors.
The interface got a hub with 4 USB3.0 data lines and after a intensive tests only one channel runs into instability and communication drops out after a few seconds streaming data, fortunately the other three channels work fine.
I'm into the layout revision process for that 'problematic' channel, and the only difference I found compared to the rest is that the data lines are passing very close to a crystal clock oscillator output, I wonder if this could be the issue....
To make an idea this is a snapshot of the area (the 'bad' channel is routed to J8):

As a first thought, I'm thinking to move/shift the tracks to the right about 2mm.
Does anyone know if this could be the main issue and moving them 2mm could be enough?


texts: Low power Arduino BLE board for HID keyboard

texts:
I am looking for a suitable Arduino board which has the following features:

BLE
Arduino-compatible
LiPo-charger
HID-keyboard compatible
at least one analogue input

I want to build an 8-button remote for a special Android-app with it, so it should just act as a standard BLE-keyboard. I have found several boards capable of this, but some of them require a special software on the receiving client (still don't understand why) and some (ESP32-) boards are really heavy on the battery. I want to at least achieve 20h of runtime with a as-small-as-possible battery.
Thanks for any tips!


texts: Under which possible conditions is measuring with an multimeter a danger to life ?

texts: My knowledge of electrics is very limited, I am planning to buy a Multimeter, but I am confused when it comes to safety. I do not really know what is a danger to life when measuring a circuit with a multimeter. Is it the voltage, current, resistor, capacity, frequenz a combination of some of this or other factors. Could you please explain common conditions in working with an multimeter and when it is safe and when not.


texts: How to read / identify cylindrical ceramic capacitors

texts: as this is my first post I'm not quite sure as to how I should format this question but here goes. I am trying to sort a set of ceramic capacitors and I have come upon a few that I can't identify. When I look up the text on their sides (all the same) nothing if relevance comes up. I think they are 1nF, but I'm not sure. Any help with how to read these would be much appreciated. The tet says "MKT .01 63/K," Images below.


texts: Can this temperature-controlled fan circuit be modified for different input voltage?

texts:
I want to know if this same circuit can be used for 220 or 230 volt input, and if there are any components that need to be modified. C3 has 600V capacity and C1 and C2 have 250 volt.

Link to original circuit diagram.


texts: In VHDL how can I get a clock frequency of 40 MHz if my onboard clock is 50 MHz. I know how to divide the frequency by integers but this case is dividing by 1.25. I am using this for VGA so I think it's important that it is precise. thanks!


texts: Beginner trying to resolve transistor issues

texts:
I have designed a basic transistor circuit with the EveryCircuit simulator.
The idea is that when the switch is open, one LED comes on and when the switch is closed the other LED lights up instead.
It appeared to work fine on the simulator, so I built it on a bread board.
I used an old BFY51 transistor from an old box of bits I have.
It worked great, just as I had intended.
Then I thought I would replace the BFY51 with a more up to date 2N2222., first making sure the B,E & C pins were in the correct slots.
I tested the circuit. Now, with the switch open it still works as it should, but with the switch closed, both LEDS light up rather than just the second one.
I know different transistors can have different operating parameters, but I could really do with some help to make my circuit work as intended with the 2N2222.


texts: Saving a picture to MicroSD while streaming video upon motion detection

texts:
I am using an esp32-cam to stream video.  As it is steaming I want to take a picture and save it to a micro SD card when motion is detected.
Hardware:
ESP8266-12e,
ESP32-CAM,
EKMC2604112K panasonic PIR motion sensor
I am powering the 12e and PIR with a 3.3v regulator with a 10uf smoothing cap.
I am getting the signal from the PIR on pin 13 (INPUT)on the 12e.  I have a 10k ohm pull down resistor on this pin.
When pin 13 goes HIGH it sends a signal to an MQTT server to send a notification of the movement.  Also when pin 13 goes HIGH it triggers Pin 5 (OUTPUT) on the 12e to go HIGH.  When I do a multimeter reading of Pin 5 it reads 3.3v.
I am powering the ESP32 with a 6v regulator with 10uf smoothing cap. which outputs about 5.7v.  I connect Pin 5 of the 12e to Pin 13 (INPUT) of the esp32.  When Pin 5 goes high it should activate Pin 13 which then tells the camera to take a picture and save it to the MicroSD card.
When I power the whole thing up, if I don't have Pin 13 of esp32 connected, the camera streams and takes a picture about every 2 seconds and saves it to the microSD card.
If I then connect Pin 5 (12e OUTPUT) to Pin 13 (esp32 INPUT) when there is movement detected on the PIR the flash on the ESP32 lights up slightly about 500msec apart but when I check no pictures are saved to the MicroSD card.
If I power the whole thing up and I have Pin 5 connected to Pin 13 the MicroSD card is activated but there is no flash of any kind  when there is movement and no pictures are taken.
I have tried an pull down resister of 10k and 20k ohms but there is no change in the outcome.
If I power the ESP32 with a FTDI 5v source with Pin 5 to Pin 13 picture is taken every 500msec. connecting to pull down pin doesn't do anything and disconnecting the pins doesn't have an effect either.
I have attached a drawing of the connections.

I hope this helps.  I am at my wits end as what to do.
If anyone can help me I would greatly appreciate it.


texts:
For those of you that haven't heard of the mbed I'd highly recommend having a look at it for rapid prototyping!

So, the mbed is a 100MHz microprocessor that appears as a usb mass storage device when you plug it into a computer via USB. You can program it by using an online IDE which spits out compiled binary files you can drag-drop into the drive (on any OS) making it a very versatile and very easy to use tool for beginners (like myself!)

As with all of these programmable ICs they have a limited number of IO pins, so if you wanted to drive 150 LEDs individually you'd need to have some kind of intermediatry control device. I'm considering using ATtiny devices to do just that:

Is using ATtiny devices a good way to achieve control over a large number of LEDs? (considering my lack of experience with hardware)
Would it be hard to port the code from the arduino ISP so that I could use my mbed as a programmer for programming ATtiny?
Am I better off using PIC chips?

Many thanks!


texts: Mapping two buttons press as a 3rd button

texts:
I got a cheap controller with only 5 buttons. I thought about soldering a few more in parallel so that pressing any of the additional buttons would trigger some other two buttons simultaneously. Then I would use JoyToKey or LLJoy to map those buttons pressed together as a separate command.

But to make it work, I need one of those buttons to get "pressed" a bit earlier than the other. I guess introducing a delay to one of the connected buttons is the way to do this, but I'm unsure exactly how. Was looking into NE555, but it says you need to power it with 5V or more, and the controller is powered by two AAA batteries. Which is also the reason I wouldn't want to use microcontrollers or really anything that would need its own power supply.

Is there a way to get a small delay with a transistor or optocoupler maybe?