texts:
I have a Verilog module that is able to make my FPGA blink its LEDs at frequencies according to certain variables/constants I've set within the code.  However, I would like to change these variables externally, so that I can alter the blink pattern on the fly without having to reprogram the FPGA every time.  That's why I've considered trying to figure out how to transfer data to the FPGA board perhaps via the Ethernet port.

The FPGA board I have is the Digilent Nexys 3 with the Spartan-6 FPGA.  I am using the Xilinx ISE with Webpack license to do designing and programming.

I've read some of the documentation, but a lot of it is hard to understand.  From what I understand, I need to use create an Ethernet IP core.  I did that on ISE by adding an IP Core as a source and selecting "Ethernet 1000BASE-X PCS/PMA or SGMII."  Doing so created an .xco file in the design hierarchy.  I clicked "View HDL Functional Model" and saw that there is a module defined along with many ports.  The ports don't seem to match the pins listed in the Nexys 3 reference manual though.  The Ethernet on the Nexys 3 board has the SMCS part number LAN8710.

Another method I've considered is using the Digilent Adept software to write data into the registers on the Register I/O tab.  Apparently the range of values that can be input for the addresses is from 0 to 255 (8 bits).  The problem is I don't know how to map these Registers onto the variables within the module (if that's even possible).

This is the first time I've been working with FPGA's (been at it for about a month), with little to no digital electronics background (I'm an undergraduate Physics Major), though I do have some programming experience as well as computer hardware and networking experience (CompTIA N+ certified).  Anything info you can give to help a newbie along would be appreciated.


texts: When I connect 2 motors to a battery do the motors share volts or amps?

texts: That is, when I have an 8.4 v 3000 mAh battery connected to two of the same (DC) motor, is each motor getting 4.2 volts, 1500 mAh or both? Or am I just super confused?


texts: Short Circuit Protection for Low Power Circuits without using a fuse

texts:
For low power circuits (24V, 250mA, approx. 6W), what is a good method to provide short circuit protection without using a fuse or a PTC re-settable fuse.

As far as I know, those are the two main methods and the oracle (google) has failed me in terms of finding any alternative approaches so I figured i would ask stackexchange.

Does anyone have any experience with providing short circuit protection without the use of fuses (for low power circuits).

Thanks


texts: Fixing Setup and hold timing violations in FPGA's and ASIC designs

texts:
I have basic knowledge in static timing analysis. I understand concepts about setup and hold time of bistables and that failure to meet these two timing constraints can lead to metastability where output of such bistables can become unpredictable (as transients have not died).

What are different techniques to address issues of setup and hold time violations for FPGA's and ASIC designs ?


texts: Leds blink with a different power supply

texts:
I made a led circuit in parallel with a power supply of 12v 2a.

But there is the problem, I’ve changed the power supply. Still the same value of 12v 2a but my circuit doesn’t work. I’ve tried a lot of power supply with the same value but still the same.

The leds blink on and off quickly. I don’t understand why?

R1 to R20 : 27ohm resistors

Leds : https://www.digikey.fr/products/fr?keywords=1214-1616-1-ND


texts:
I am designing a signal conditioning circuit which reads in data from 20 sensors and output it to the ADC of a microcontroller. My problem is I don't really understand how to connect these signals into the microcontroller due to the limited number of pins available (8 pins because the microcontroller comes with a 8 channel analog MUX).

Currently, my idea is to group the sensors into 5 groups, each containing 5,4,4,4,3 sensors respectively. Then, use connect each group of sensors to one pin of the 8-channel ADC. I'm not sure if this idea is feasible nor am I aware of the hardware available to do so. Please advice!

Some basic information of the microcontroller is listed below for your reference:

12-bit
Sampling frequency: 200 ksamples/s
Clock speed: 24MHz
Conversion time: 50 clock cycles


texts: N-FET not working (leaking at drain-source while gate is at GND)

texts:
Trying to use N-FET 2N7002 but I am unable to make it work.

I would like to control N-FET (control LED) so when I put 3.3V at gate it turns on and when I put 0 (GND) at gate that it turns off.

What I am getting is that my LED is dimming (light glow) when my gate voltage is 0V (GND).

Also measuring at drain-source I get voltage drop of 1.8V.

I tried to replace 330Ω with 100Ω, also tried to remove 100Ω at the gate, all of that didn't work.

Just to add that when connecting 3.3V to gate LED turns on (works).

Circuit is as in diagram below:


texts: True near field distance for a short monopole antenna

texts:
Antenna properties:

Height x Diameter = 3.3 inches x 1.4 inches
Test Frequency: 900 MHz
(Wavelength = 33 cm or 13 inches)

I see some conflicting formulas to calculate the near field distance for an antenna w.r.t. the frequency of interest.

Method 1: (multiple sources)

  Reactive Field <= 0.63 x sqrt(Height^3/Wavelength) ===> 2.6 cm or 1.02 inches

Method 2:

  Reactive Field <= Wavelength ===> 33 cm or 13 inches

Which one applies here accurately.


texts:
So I had a look into the pinout of a mPCIe Connector (and the pinout described in the PCIE 2.0 Base Specification).
But I am not sure which signals are really mandatory to be used as declared by the description of the "standard" pinout and which pins of the mPCIe Module can just be used for any other signal - while still beeing "compliant" to the mPCIe specification?

In other terms: From a Mini PCIe Card I assume that it uses PCIe as the communication "type" (i.e. PCIe physical layer, data link layer and so on...).But have look at this board (just to have an example):

https://www.codico.com/shop/media/datasheets/Quectel_UC15_Mini_PCIe_Hardware_Design_V1.0.pdf

They claim to be mPCIe standard compliant, but acutally don´t use any PCIe signaling? For example they use UART signals on the lines dedicated for differential transmit pair of PCIe. ?

Can anyone assign any function to egde card of a Mini PCIe Modul and claim that it is standard compliant?

EDIT: I found the follwing phrase in the standard:
Two primary data interfaces are defined for PCI Express Mini Card: PCI Express and USB System designers may optionally choose to implement slots that support only one of these interfaces and still be compliant to this specification.

--> So If i interpret this correctly, I have answered my question and was a bit too quick in asking here. But to be sure: That means as long as I use USB signals on the mPCIe connector, I am conform to the PCIe standard, although I don´t use PCIe?


texts:
Could a customs x-ray corrupt sram data? Programming RTC on one side of the world, then transporting to the other side has worked fine in the past. The majority of a recent batch all had corrupted memory https://www.maximintegrated.com/en/products/digital/real-time-clocks/DS1500.html
Thanks. BW.


texts:
Anyone know of a SOC (System on Chip) that you could use for your own router? There probably many types of SOC, I'm looking for something that would run Linux (i.e. isolinux).

Looking for something with a low power consumption.

Some of the answer are suggestion using a existing router and replace the firmware. Sound great! I have a DLINK 825 and, for example, i like to add BOOTP to my router, so i can setup a bootable image (on a different server) but being served the dhcp of my router?


texts:
I want to get rid of the measurement label in the PCB (the double arrow showing the dimension) but I am not able to delete it. It is showing overlap errors with the bottom traces. How do I delete this? I am using Eagle 7.7.

Things I have tried:

Hit the Delete button and tried to delete the arrows as well as other parts.
Hit the Ripup button and tried deleting at multiple points.


texts:
In a simple model of a renewable energy system, I have a residential inverer and Lithium ion battery system with a round-trip efficiency (for inverter and battery, i.e. ac to ac) of 89% (at 25 degrees and a given charge / discharge power). The model needs to calculate the SOC of the battery (to determine when it's fully charged, etc.) which requires me to distinguish between charging and discharging efficiencies. Some studies assume the inefficiency is in charging, so SOC = 89% of charging energy, but this seems unlikely. Is it reasonable to assume that the losses for charging and discharging are approximately equal, so the charge and discharge efficiencies would both be  approximately 94.3% (square root of 89%) or is there some other rule of thumb?

To clarify: this is a techno-economic model and is only concerned with energy flows in the system.
If n(charge) is the charging efficiency and n(discharge) the discharge efficiency, all I know (from the manufacturer) is n(cycle) = n(charge) * n(discharge) = 0.89

For example, in time period t1, energy delta(E) is sent to the battery-inverter system and - if the battery has unused capacity - increases the energy stored in the battery by delta(E) * n(charge). The change in the state of charge is then:

delta(SOC) = delta(E) * n(charge) / usable capacity

I need to estimate SOC to know whether the battery has capacity to take delta(E).


texts:
I have been wokring on a circuit,  where I am amplifying a signal to a high voltage(around 100V) with a frequency of 20kHz but with fast edges. `

The op-amp shown below is used as inverting amplfier thus for the feedback loop.
I am using the AD712.

I want to make sure I get the PCB layout correct, so I have been spending a lot of time on reading application regarding PCB layout.
There is one point I stumbled on ; In this article https://medium.com/@Altium/designing-operational-amplifiers-pcb-layout-tips-to-reduce-the-noise-e4900a7d7fc5
it is stated that having a ground near the input pins causes stray capacitance which can lead to instability.
On the other hand, I know also that it is not good practice to break the ground plane.

so, what is the best way to go about this?Should I break the ground plane close to the inputs of the op-amp?
Does someone have experience with this?


texts: Electronicaly switching parallel LC circuit components

texts:
Let's say I have mentioned circuit and I want to be able enable/disable one of the 1uF capacitors to change the frequency of the LC circuit.

I would like to do this electronically with a micro-controller.

I know a relay is ideal for this but is bulky and mechanical.
Another option could be a an "analog switch ic" but they have a relative high internal resistance, and a low max current. The low max current is a problem for a parallel LC circuit because the current can go quite high.

Are there other solutions to do this?

Thank you in advance

EDIT

bigger picture:
This is just a picture from the interwebs, but what I would like to make is very close to this, the inductor will be a large solenoid for vehicle detection. If the inductance changes (because of the presence of a car) the resonant frequency will change. The comporator will convert this attenuated oscillation in a block wave, the microcontroller can than determine the frequency of the block wave and so detect any changes (traffic).


texts: Optimum location of the most positive/negative spots of a battery pack

texts:
Which design would be better for the following batteries the most positive/negative connector? The reason i am asking is my original design is the one on the left, but someone told me the one on the right is better because the current is evenly distributed. Is that true?

simulate this circuit – Schematic created using CircuitLab


texts: What is the minimal capacitor (capitor type/size/capacity) needed to fool a capacitive touch screen?

texts:
Say I want to provide a device (completely batteryless of course, and detached from any human touch) the capability to immitate a touch on a capacitive screen (Galaxy S6 here). I know I just need some kind of a capacitor to touch the screen. I managed to register a touch by folding a piece of metal snack wrap (an inch square of it), put it on a piece of plastic, to escape my body's capacitiveness, and touch the screen with it.
So, would I be able to do the same by connecting, let's say, an copper/aluminum foil to a capacitor, then touch the other side of that foil (or wires?) on the screen to register a touch?

I am asking about a capacitor, because I guess this would be the best/smallest solution to mimic our body's (connected to the finger) capcitiy. If I am totally wrong, and you have any other idea, welcome to suggest ;)

To make the question more clear: I want to mimic a finger (or multi touch) press, with the smallest/flattest possible (electrical?) device. I asked about a capacitor because it is small, and from my tiny knowledge in electronics, it "should do". So, this is not a general question like been asked before. I want to try and get to the specifics of how to mimic.

Thanks


texts: Where can I learn about how to create homemade electronics

texts:
Unfortunately, all I've learnt so far are concepts. I do not know where to start, but I have made a commitment to practically build some electronics. I want to ask where can I learn and acquires the skill. One of the thing that bother me a lot is how those builder could analyze an electric circuit and describe its purpose. What I usually see is a whole set of capacitor, resistor, and some ICs. All I can do with my skill is finding out the Volt, Amp, and all the numbers, but still I cannot define the purpose behind that set of circuit.

What I really want to have is the skill to understand the circuit, in the same way as how my programming skill works. As a programmer, I learn more from browsing source code and actually programming an application than listening in a class lecture. Therefore, I wish for the same experience with electronics.


texts: Digital means of varying frequency or voltage to a blower motor

texts:
I am working on updating an existing product which uses a resistor network (with one potentiometer) and a phase controller (PHS230A6) to vary the speed of a blower. My goal in this redesign is to make it a more digital operation which would allow me to use one potentiometer (digital incremental encoder) to allow adjustment to the blower speed as well as other things (adjust settings on a display).

I have done a lot of research and have looked into PWM options which the lead engineer has ruled out due to the complexity of the snubber design and the fact that the existing PHS230A6 and resistor network have many years of trouble free experience.

Does anyone have any other ideas or suggestions on digital blower speed control? I have contacted the MFG of the PHS230A6 and they have no suggestions.


texts:
I need to check the integrity of 40+ custom cables.  Each cable is meant to be the same, and is meant to have 19 ways.

I bought an enclosure, some mating connectors, some LEDS and a bunch of resistors and diodes.  My first and second attempts at building  tester circuits were unable to catch the three conditions I want to check for:

short circuits
open connections
cross wiring

So now I'm back at the computer.  I have searched the internet, and I have found a CAT5 tester circuit here.

I recreated part of this circuit using the awesome tool at Falstad,

Here is the result:

Only when each adjacent LED pair lights when the switch is flipped, can the cable be considered good.

I’m somewhat confident I can extend the circuit so that it can test each way in my cable, but can anyone offer improvements or advice before I start my third implementation?  I have a nagging suspicion I am overlooking something, or there might be a really simple way to do this!


texts: How does the impedance that voltage "sees" while traveling down a tranmission line affect how the current move down the line?

texts:
It is well known that the voltage sees different impedances while traveling down a tramission line, and this impedance is a function of the intrinsic impedance of the line Zo and tangent of wave frequency and the length away from the load according to:

But my question is, since the voltage sees different impedances at different position along the line, why is it that power is always delivered to the load (i.e. an AC line that spans many Kms)? If voltage source truly sees different impedances down the line, then why would it deliver any power to the load at all since eventually somewhere on the line the impedance would be infinity?


texts: Why Flash memories have less P/E (Program / Erase) cycles (e.g. 100K) compared to EEPROM (e.g. 1000K)?

texts:
As per datasheet of EEPROM: CAT24C02 (On Semiconductors) - P/E Cycle count is > 1000k whereas as per datasheet of NAND Flash: MX30LF2G18AC-TI (MXIC) - P/E Cycle count is > 100k

I would like to know why there is such high difference in P/E cycle count because as per my understanding from internet websites; EEPROM & Flash memories are similar types of programmable memories.


texts:
I have a scooter ignition lock that i got from ebay and i was planning on retrofitting it on a 1980 motorcycle. The thing that i need to make this work is that the ignition lock needs to be closed (let eletricity pass through) when the key is turned and opened (not letting power pass through) when key isn't turned, but it does the opposite. Is there any way to reverse it? (I didn't find any way to do it on the switch and i can't open it)!

link for the switch

The motorcycle has a button that when pressed connects a wire coming from the engine to ground (frame in this case). i would remove the button and connect the wire directly to the ground and put the ignition switch in between so that it acts as a switch and not let the motor start.

(i barely understand english. I live in europe in a small country so i never got a chance to learn english properly and the terminology is correctly said in my launguange but i wrongly translated it)


texts: Switching device connections to MCU based on power source

texts:
Sorry for the vague title, I wasn't quite sure how to word this.

I'm designing a circuit that will have an AVR, an RF module, and a keyboard matrix, powered by battery. The problem is this will use all available GPIO pins on the largest DIP package MCU...

I'd like to also add USB capability (make the device able to be powered by usb, as well as communicate with host instead of using the RF module IF it is plugged in to the usb.) This would also mean I need 2 more pins for D+ and D- which I don't have.

I was thinking I could use a DPDT relay to disconnect the RF module if power comes in from the usb connection, and connect d+ and d- to two of those pins, or if usb is not connected, disconnect d+/d- and connect the RF module.

This seems kind of clunky (no relay pun intended) and I was wondering if something like this could be done with transistors or some strange IC I don't know about.

Is this even doable or am I crazy? Worst case scenario I guess I'll have to learn how to solder those darn surface mount chips with tiny pins that have more GPIO pins... but I'd prefer not to have to do that if at all possible.

Any nudges in the right direction would be greatly appreciated!

Thanks!

EDIT:

Ok I think I've settled on a solution. Atmega328p as master connected to RF module (SPI) and Atmega1284p (also via SPI). 1284p is connected to the 8/16 matrix and leds. Whole thing powered by li-on battery with charge controller. Charge controller can be plugged into usb to charge battery. usb data lines go to 328P. This solves the need to deal with multiple power sources.

The 328p can detect if usb vbus is connected by checking d- since it is pulled up to vbus, and vbus is isolated by a diode so the battery can't power it. Then its a simple matter of if d- is pulled high, usb must be connected, disable radio and send over usb. Else, use radio.


texts: Origin of increased noise in BF862/OP27 charge amplifier

texts:
For the amplification of piezoelectric sensor signals I am currently building a charge amplifier with a low noise JFET frontend utilizing an NXP BF862. The amplifier design is based on application notes from Linear Technology/Analog Devices (Design Note 254 and Design Note 308). My schematics and PCB layout are as follows:

My problem is that the measured noise is too high. For a capacitive test source (just a capacitor) of 264 pF I need an output referred noise floor below 100 nV/rtHz for frequencies between 800 Hz and 900 Hz. According to my LTspice simulation this should be achievable, the overall noise floor at 850 Hz is 52 nV/rtHz:

However, after producing the PCB several times with different layouts and measuring the noise floor at the amplifier output the result was always the same: Approx. 250 nV/rtHz at 850 Hz. Referred to the input that means approx. 9.5 nV/rtHz, which I think is much too high. I am doing these measurements in a faraday cage with a SR785 FFT analyzer whose input noise is well below 10 nV/rtHz. I changed the BF862 several times and I also increased the feedback resistance to up to 50 GOhm. But the noise floor always kept exactly the same. The amplifier was powered via two lead acid batteries. So, the simulated noise (52 nV/rtHz) is roughly a factor of five lower.

Does anybody have an idea what the problem could be, i.e. where the noise is coming from? Is it possible that the simulation is wrong? Or could it be that one of my components is not behaving like expected? For example I thought that maybe the feedback resistance (or the source/drain resistances) adds some kind of additional 1/f noise? I also checked all the DC operating points, but they are correct, i.e. like in the simulation. What would you try next?

Thank you very much for your help!


texts:
I would like to use a pull switch as a trigger for an alarm that I'm building.  When the switch is triggered it will turn on a siren and potentially a strobe light.  I've found plenty of options out there, but the prices are a bit staggering.

Take this one for example, it's $238.  I was thinking $20 would be expensive!  My alarm isn't going to be used in an industrial environment and the items I'm securing aren't worth enough to justify spending that kind of money for a switch.

I think a simple pull type light switch would be sufficient, but I need the cable to break away from the switch when activated and not damage it in the process.

I guess I have two questions:

Why is this switch so expensive?
What other options are there for a N.O. pull cable switch that stays closed after being activated? I'm open to ideas of building my own switch.


texts: Powering BLDC motors using a Li-Po battery

texts:
I'm building a self balancing cube using 3 reaction wheels much like the Cubli but smaller. I'm a mechanical engineering student with not a lot of electronics experience other than the basics.
The project will consist of 3 EC 45 flat 30W BLDC motors from Maxon and a controller also from Maxon (link to datasheet of controller: https://www.maxongroup.com/maxon/view/product/367661)
I'm planning on using a Li-Po battery because of their high output current. The motors are 2A nominal each and I estimated the total maximum current to be 8A including electronics.
The controllers can handle a voltage between 8 and 24 VDC. The motors are 12 V so I am guessing the controller contains some buck-boost converter. The datasheet does not say anything about this.
My questions are:

Would this require any other components like converters between the battery and the controllers? Or will it be sufficient to just wire the battery directly to the controllers with maybe a fuse?
I selected a 3s1p Li-Po battery with 11.1 V. would it be better to get more cells for a higher voltage since the motors are 12 V?


texts:
I am trying to select an n-channel MOSFET to switch a 12 V power rail. The use case here is to switch on/off a couple of LEDs which are wired in series. The LEDs (datasheet) can draw a maximum of 700 mA. I want to control the MOSFET via a microcontroller (3.3 V logic level).
I am now struggling to choose a suitable MOSFET, mostly because I do not understand some of their characteristics.
What I know so far is:

MOSFET needs an SMD package for my application
Vcgs(th) should be smaller than my 3.3 V logic level
FET type should be n-channel

What I don’t know:

What does Continuous Drain Current (Id) mean? What is important here?

What does Drain to Source Resistance mean? What is important here?

How important is the Maximum Power Dissipation?

For more information on the circuit, you can look at my original question here.

An example circuit.

This MOSFET may be suitable for the use case.


texts: Can 12v dc circuit spark and start a fire?

texts:
I'm new to electronics and electricity. I have the following scenario:

I am wiring a LED light switch and mounting it into wooden cladding. My concern is, can the wires spark unexpectedly and start a fire?

We are talking about 12V DC, with three, 2W LEDs. The circuit is properly fused.


texts: Why power transmission lines voltage regulation is referenced to the receiving voltage not the sending voltage?

texts:
Why power transmission lines voltage regulation is referenced to the receiving end voltage not the sending end voltage?

It's more logical to divide the difference between the sending and receiving end voltages by the sending voltage since it's held constant, right?


texts: Simplyfing a circuit by replacing two nodes with a voltage source and removing a connection between resistors

texts:
I am given the first circuit (A) and I have to find the voltage across R4. Since the potential at node C is independent (V2), I was thinking about a possible transformation to circuit B. However, I am not sure if it is valid or affects the currents within the circuit, since I remove the connection between R1 and R4. Are the two circuits equivalent regarding the voltage across R4?

Any help would be appreciated, thanks!


texts: How can I tell if my current is continuous in a first order DC circuit with a switch

texts:
Assuming this circuit has been running for a long time (switch SW1 is closed), and in t=0 the switch (SW1) opens, and I'm being asked about the current that runs through the inductor L1.

I know that in DC circuit the inductor acts as short and after a very few calculations I came with the current that runs through the inductor to be: 10A.

So I know that for a brief second before the switch opens the current is 10A, how can I make sure or check or explain that the current running through the inductor shortly after the switch opens is still 10A? That there is no "discontinuities" in the current function...

simulate this circuit – Schematic created using CircuitLab


texts: There is a rectangle around the outside of my OrCAD footprint (pointed to with the blue arrow), and it is on the no-probe-top layer. I googled it but I couldn't find any explanation of what that layer is.


texts:
With this question I would like to clarify an understanding of resistors.
I have built these two schematics and performed a test.
Lighting the particular LED I use in this experiment directly with 1.5V produces no light at all, and lighting it directly with 3V lights it well.

I conclude the LED does not light with 1.5V for that is not enough voltage to open the diode's 'gate' at all,  yet the LED in "Schematic 2" is very dimly lit.
Measuring voltage between point A and B in "Schematic 1" reads 1.5V. Some may say by Kirchhoff's laws that is the voltage dropped by the resistor.
If the resistors actually 'drop' voltage this way, why does the LED light?
Is it safe to conclude the resistors only reduce current to the LED in this fashion and do not effect voltage to the LED?
Is 3V provided to the LED in "Schematic 2"?

I have created another one of these experiments.
Now, with a 10K and a 1M resistor, this LED (the green portion of an RGB) remains lit.
This LED still will not light on a single 1.5V AA.

I think using the classic needle voltmeter is giving an invalid reading.
Using an oscilloscope on difference mode at 1V a division,
I measure 2V on the LED (between B and C) no matter what resistors I use.
Measuring the resistors (between A and B, C and D) the sum of their voltage is about 1V, in the case of the photo, the 1M drops most of the 1V.
On the other schematic with the 1K's, both dropped about 0.5V

Do resistors drop a constant voltage upon completing a circuit and then only drop current from then on as resistance is increased?

The only voltage drop here to me seems directly caused by the diode.


texts: Diagnosing water heater error - Need help with diagram

texts: I'm diagnosing an error in a water heater. The error code indicates that the error is related to the connectors X2. Between both connectors X2 there is this Symbol "/" with the number 5. I have marked it with slight yellow. What does this symbol indicate?


texts: Can I can control an RC servo using only a 5VDC and GND signal?

texts: I'm working on an application where I want a servo to open and close a hatch. Because I only need the servo to operate in two positions, I'm curious if I can forgo the PWM aspect and just supply a 5VDC and GND signal to toggle between two positions.


texts: Best board-to-board low latency protocol/interface

texts:
I've been asking similar question which received some downvotes, so I'm reformulating my task (hopes this one gives more clarity).

I'm planning to establish a high-speed (3 Gpbs full duplex) serial connection between two fpga boards (distance between the chips < 15 cm, including the connectors), more precisely between spartan 6 and artix 7 devices (these are not absolute requirements, but appear to be the cheapest ones having integrated transceivers inside).

I'm not sure about what protocol should I pick. I've been digging into RapidIO specs lately, but it looks like I have to use a switch chip to connect devices, but switches are pretty expensive (~ $150/piece) and introduce at least 100 ns delay, as well as 10+ layers PCB requirement (example).

PCIExpress is not an option (though connector is nice), since it introduces around 500ns delay, and ideally I'm looking into sub 100ns transmit latency (from parallel stream inside one fpga to parallel stream inside another). Due to high latency 10Gb Ethernet is also not an option.

There's also an Aurora protocol from Xilinx (link), but I cannot find any PHY layer definitions and delay numbers. More of that, despite all high-speed serdes applications advertise low pin counts, all dev boards with embedded transceivers use either SMC, optical or cryptic mezzanine card connectors with 400 pins. Is there any other option? Like, ~50 pin connector or less. So, to sum this up, questions are:

Is it possible to achive sub 100ns delay between two chips using
serdes?
Are there any PHY specs/examples for Aurora?
Will it be simpler to throw wide BLVDS interface and use high-clock parallel bus?

Any suggestion is greatly appreciated!


texts: How to disable charging of a battery while still powering my application?

texts:
I have a battery-powered circuit which uses a Li-Ion battery which can be charged over USB using an MCP73831 charging controller. The battery has built-in deep-discharge protection, so disabling discharging is not required. However, Li-Ion batteries shouldn’t be charged below 0°C or above 60°C, which is why I want to be able to disable charging while still powering my circuit over the charging controller (which is why I don’t want to simply turn off the charging controller).

Would the following circuit with Q1 in an unusual, reversed direction work? The CHARGING_ENABLE wire is connected to a microcontroller in the 2.1V domain.


texts:
I need to attenuate a signal which outputs from a function generator.
The minimum amplitude of the signal from the function generator is 1mV. What would be the best method to attenuate the signal from 1mV to 1uV without adding noise to the system? Are there any attenuators available?
The signal of interest is sine wave, frequency being 1Hz to 100Hz.
I am new to this and would be obliged if someone helps me for the same.


texts: What type of MUX to most effectively connect both sets of resistors at once?

texts:
The following circuit is used PER CHANNEL, and I have 4 channels, to according scale the gain for our input signals on each channel.

However, each channel, has to be able to switch between 4 resistors top and bottom, in order for the gain to be effective for the input.

What type of analog MUX would you guys recommend for this to be able to avoid using tons of physical switches? I plan on using a teensy 4.0 MCU to program this.

Thanks in advance!


texts: Rectifier, Flyback vs Transformer, Rectifier, Buck

texts:
I've just finished doing my first off-line flyback, which proved a success. A simple block diagram is as follows:

I know this topology seems common now, for example it is used in Apple USB Charger wall bricks (that video discusses cheap-knock offs, but the principal is still the same).

The problem is, flybacks are very complex beasts to tame. So I started thinking why isn't the following topology just used instead more commonly:

For the record, I have never designed a power supply using this method (particularly, using a high-voltage buck). But on paper I can't seem to see any problem with it.

Is there any reason one might be preferred over the other?

Both provide the same level of isolation, and depending on the parts used, potentially the same efficiency.

From the block diagram you can say the first process has "less steps", but that doesn't necessarily mean less parts, lower cost, or easier to design by any means.


texts: Communication between STM32 as host and Arduino as device via USB otg_FS

texts: Is it possible to send data from USB via STM32F4 OTG FS to another MCU (Arduino, for example)? I tried STM32_USB_Host_Library and it didn't work.


texts: Moving two elements from series to parallel

texts:
I got a small pizza oven with two elements (top and bottom), they are rated 115V 600W and they are connected in series, as we have 230V in Europe.

Everything works fine, but I would like to control those two elements independently (so I will need to connect them in parallel), unfortunately that is not going to work with 230V, what is the best solution, in your opinion, to connect them in parallel and still have them operate within their rated conditions?


texts:
Having a conversation where a colleague asked another to pass the charger, only to find out a cable was handed over.

Decided to wonder whether a USB cable really qualifies as a charger, since we are used to plugging it into an adapter (the charger) which connects to the power outlet.

However, you have USB ports built into power outlets nowadays and also USB ports in computers which serve the function of a 'power outlet'.

So is it technically correct to call a USB cable a charger?


texts:
I'm trying to rid my speakers of the typical buzz from my iPhone. I get poor reception in my apartment and so it's constantly trying to find a signal, meaning I get a near-constant buzzing when the phone's anywhere near it. Airplane Mode works, but it's a pain to keep switching it on or off.

I use reference monitors as opposed to ordinary speakers, and each has an audio output cable (XLR, balanced), and a mains output (i.e. each speaker is powered independently). Do I need cores for all four cables, just the audio output, just the mains? If so, do they need to wrap TIGHTLY around the cables, or if they're loose and I secure them with tape, is it the presence of the cables that suppresses the noise?


texts: I am not electrical engineer by profession. So, accept my apology if my question sounds stupid. I am simulating a situation on computer where electric power is being send from one point to another through transmission lines (500kv). The total length of transmission line is 1600 km. Could any one help me after how many kilometres typically a step-up transformer is used to boost up the power? Also what is the total fraction (approximately) of power being lost during this process?


texts: Creating atime based heat exchanger simulation in OpenAi gym and MATLAB for the purposes of temperature control regulated flow rate in

texts:
Apparatus:
Crossflow Tube and fin HX. (liquid-to-air Intercooler),
Hot Side: Tube side, gas flowing internally
Cold Side: fin side, water flowing in crossflow
Goal:
Generate an environment in "OpenAI gym" where the agents actions:
are moving the valve (1),(0) fully open, fully closed on the inlet stream.
Observation:
outflow temperature
The concept was as follows:
derive the TF for the HX system,
generate a block diagram of the feedback loop system,
allow the agent to play with flow rate, which would cause a non instantanious change at the outlet temperature. This would be used to train the RL algorithm for this PID control system.
Problem:
Generate a formula for the change in
$$\Delta{\dot V in} = \Delta{Tout}$$
where:
$$\Delta{\dot V in}$$ is the flow rate inside the tube &
$$\Delta{Tout}$$ is the temperature out of the tube.
Its understood that this is one of the most common process control problems:
feedback or feedforward valve that controls inlet flowrate to regulate outlet temperature. Temperature is sensed by a thermocouple.
Understanding:
Mass balance:
F-F = 0
Energy balance:
$$V \cdot \rho\cdot c_p \cdot \frac{dT_{out}}{dt} = F \cdot \rho \cdot c_p \cdot T_{out} - F \cdot \rho \cdot c_p \cdot T_{in}$$
This can be rearranged to make $$T(out)=f(T(in))$$ Its further understood that the change in Tin can be proportional to the pressure or height change at the valve.
Im looking for a solution that ties this whole process together. Better yet if someone knows a textbook (process control, instrumentation engineering, Linear models etc.) where this problem similar to this is solved and the logic is stepped out would be even better. Thank you all for your time.


texts:
I have a retired stoplight - with real lightbulbs.  I am looking for a simple way to wire it to have it automatically move RED-GREEN-YELLOW cycle just as the ones on the street.  I have manually switched it but was looking for something more "automatic" that I can put together as a learning project with my 15 year old.

I saw this answer: Most Simple Stoplight circuit

But I am not sure about the power requirements for the circuts - the bulbs are actual bulbs as used and are 120V and I think 100 watt.

Ideas or suggestions?


texts:
There are three types of package in specification: SMA, Folded SMA and Clip SMA.
The link for datasheet: SK32A

What is the differences between them ???

I suspect, that Folded SMA it is SMAF, but I am not sure.

The SMA and SMAF drawings:


texts: Relay VS Push Button: blind test (how to tell the difference)

texts:
I have a classic push button that closes the circuit when pressed down.
This push button was replaced by a simple relay, the relay is activated when 3V goes through its trigger points, and the circuit is closed.
The result is the same, the circuit is being closed.

Now, if I was on the other side of a wall and someone was to replace the push button with the relay (case 2), how can I tell the difference from my side? I do not see anything, so I don't know when the other person pushes the button or when he triggers the 3V for the relay.
If I have access to an oscilloscope would I be able to see a different when the circuit is closed in case 1 VS case 2? Is there any simpler test?

See my beautiful drawing:


texts:
I have an question for which I could not get an answer, even from google.
What is location transformation for parasitic?
How do people deal with it?
And what is the significance of it in whole vlsi flow?
Hi Admin,
Please help to tag the right tags.


texts: Is it possible to convert radio waves to some small DC power?

texts: Is it possible to generate a small DC power from Radio waves?If yes then how?


texts: Resistor power rating and circuit stability

texts:
I've read the following excerpt from a book (Passive Circuit Analysis with LTSpice by Colin May page 96) but am not sure what that means (with no relevant explanation before nor after):

On Fixed Resistors: a useful point to consider if good stability and
reliability are essential is to derate the resistor so that its
temperature is far less than the operating maximum. Thus, if the
actual power is 1/10W, instead of a 1/8W resistor, use 1/2W.

Resistance of a resistor increases with temperature. So if the temperature is far less than the operating maximum, we're lowering the specified resistance of the resistor, and as a result the resistor (under lower temperature) will load itself with a higher current. Under such condition (same voltage and higher current) the resistor dissipates more power - hence it makes sense to choose a resistor with higher Wattage rating (1/2W instead of 1/10W).  I don't see any meaning to it other than reminding us to change higher rated resistor when temperature gone low.
How does choosing a resistor with a higher rating (1/2W) has anything to do with testing the stability or reliability of a circuit? And why is it considered "derating" when you switch to 1/2W resistor as you lower the temperature?


texts:
I am trying to understand how exactly to tune the Superhet receiver. In my simulations, I have attached to the initial frequency mixer---> A local oscillator and an AC signal source to model the incoming frequency.

Now my question is how will this wanted frequency reach the mixer from the antenna ( Since antenna is exposed to all frequencies ) ?

Do i need to add an additional tuning circuit or will this be sufficient ?

If an additional tuning circuit is needed, how will I co-ordinate the oscillators attached to them ( since both of them will require different frequency).

I believe gang capacitors come into this play ( not sure) but I have only this piece available ( nothing else) :

http://www.petervis.com/electronics/tuning-capacitor/tuning-capacitor.html


texts: Is the SSM2019 an appropriate IC for a optical sound solar cell preamplifier?

texts:
I am restoring a 35mm film projectors from the 1930s, which at some point had a Kelmar optical sound head added onto it. The solar cell outputs a balanced signal through an XLR jack that is very weak (around 60-70 mV). If I run the XLR straight into a mic input of a mixer I can get some recognizable audio if I crank the gain way up but it is extremely muddy. Here is a image of an oscilloscope reading of the output signal:

I would like to build a preamp circuit to get this signal up to line level. I am very new to electronics (more comfortable with the mechanical aspects of this project) and would like to design a circuit based around the SSM2019 IC. I tried to replicate a mic preamp schematic with poor results and ultimately I somehow fried the IC experimenting with it.

Before I order another one I want to see if I am on the right track at all.

Specific questions:

Is the SSM2019 an appropriate IC for this project?
Do I need to correct for the DC bias of my input signal or is that
insignificant?
Can I/How can I design this circuit to run on DC
power?
How does the impedance of the solar cell affect my circuit
design?
If I measure across the outputs of the solar cell I read
its 34k ohm resistance. Is that the same as the solar cell's output
impedance?


texts: Traco DC DC Can I connect -Vin and -Vout

texts:
I'm using Tracopower TEL 5-1211.
Can I connect both -Vin and -Vout to gnd of my design?

Thanks


texts: Switchover between two power supplies using FETs

texts:
Trying to create a switch-over with two p-channel MOSFETS using arduino. I need to switch between 2 sources with a GPIO pin from my arduino. I've looked into ideal diodes such as the LTC4414 and the LTC4415 but its hard to get them with my local supplier and I want to see if this is possible using FETs. I've seen some solutions using just diodes but I am not really interested in the inefficency they introduce.

The purpose is to do a power switchover e.g. source 1 dies, source 2 switches on.

Source 1: 11.4v, 1300mah nimh

Source 2: 12 DC wall adapter

The circuit it powers will sometimes require somwhere between 2-4 amps peak.

Would the following circuit work?? I don't have any p-channel mosfets to test it out (side note: recommendations welcome). I'm trying to keep everything through-hole (yes I know ... relic of the past) but I don't have the necessary gear to solder small stuff.


texts: What is important in computer clocks' signal: signal edges or intervals when signal is stable? Will multiple value propagation occur?

texts:
I am trying to figure out some basics of digital electronics. We have all seen the squared graph of the computer clock signal:

I have read multiple articles on the Internet and still can't figure out whether the moment of signal value switch (I guess on the graph only approximated as point) is important. It would mean it represents the interval when a circuit gets feeds from the inputs and is expected to propagate the values to the outputs, during the interval and the periods of the stable signal are used for something else?

Or the edges are not important but the periods of the stable signal are and the clock signal could be considered as only one additional circuit input, with high or low voltage set? It would mean the circuit starts e.g. reacting on other inputs when the clock signal is set to 1 and it is expected to get values on the outputs somewhere in that clock cycle - when the clock signal is 1 or 0 right after that?

Only the second option seems logical to me but internet authors regularly write that something is expected to happen on the rising edge, and that a circuit should get its outputs in the interval? That is only a term for saying that signal is set to high now?

If the other option I favour is true look at, for example, a counter register made of a single JK flip flop with its inverted output feeding its J input. It is expected to toggle from 0 to 1 in every cycle. If the circuit should start reacting on its inputs when the clock signal becomes 1, what if the result propagates to the outputs while the clock signal is still 1 and there is enough time to propagate values through the whole circuit once more while the clock signal is still 1 in the same cycle, and toggle the counter once more? I see nothing in the circuit that should stop multiple same-clock-cycle propagations if the circuit is fast enough?


texts: Independent watchdog timer is not accurate as expected

texts:
Here is my source code:
  void CLOCK(void){

    RCC_DeInit();

    RCC_LSICmd(ENABLE);

    RCC_HSEConfig(RCC_HSE_ON);
    while(RCC_WaitForHSEStartUp()==ERROR);

    FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
    FLASH_SetLatency(FLASH_Latency_2);

    RCC_PLL2Cmd(DISABLE);

    RCC_PLLCmd(DISABLE);
    RCC_PREDIV1Config(RCC_PREDIV1_Source_HSE,RCC_PREDIV1_Div1);
    RCC_PLLConfig(RCC_PLLSource_PREDIV1,RCC_PLLMul_8);
    RCC_PLLCmd(ENABLE);

    while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY)!=SET);

    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

    RCC_HCLKConfig(RCC_SYSCLK_Div1);
    RCC_PCLK1Config(RCC_HCLK_Div2);
    RCC_PCLK2Config(RCC_HCLK_Div1);

    while (RCC_GetSYSCLKSource() != 0x08){}

}

int main(){
    unsigned long int counter;
    CLOCK();
    GPIOS();

        IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable);
        IWDG_SetPrescaler(IWDG_Prescaler_32);
        IWDG_SetReload(500);
        IWDG_Enable();

    while(1)
        {
            counter=counter+1;
            Print(counter);
            if(counter>6553500){counter=0;}
            IWDG_ReloadCounter();
        }

}

I have set my watchdog counter to 309( 1 second)(Stm32f107, LSI=40Khz,Prescale=32 ). By ignoring the "IWDG_ReloadCounter(); " (I commented //IWDG_ReloadCounter();) , this watchdog resets my MCU after about 3 seconds instead of 1 seconds. I need what my problem is.


texts: Comparator with hysteresis for bus-powered communication

texts:
I have a circuit that, supposedly, converts a current-modulation signal to a digital signal. This is basically the receiver end of a bus-powered, bi-directional serial communication device (master).

There can be any number of slaves on the bus that normally draw up to 1.5mA each. Slave-to-master communication happens as a slave draws a variable current (I'm not quite sure about the details).

This is realised with a comparator in hysteresis configuration.

simulate this circuit – Schematic created using CircuitLab

Without the capacitor C it's not hard to analyse, V- is always above V+, so Vout=0. This makes sense, as it's unknown how many slaves are drawing current the 'baseline' current I is unknown. (I use the abstraction that zero current goes into the comparator at - and +.)

Now, including the capacitor C, the intuition is, I think, that at higher frequencies the capacitor begins to short V- to ground, so at some point the comparator flips to Vcc as V- dips below V+.

And this is as far as I get. I'm not sure at all how to analyse this circuit and determine the values of the resistors and the capacitor. Is this whole setup even a good solution?


texts: Why place an inductor between Vin and Vdda (AVDD)

texts:
So I know this must be a filter of some sort, just like you place caps in on power supplies as close as possible to the IC's that you're working with. But I'd like to know a bit more in detail about the function of an inductor between Vin and the AVDD pin of a IC (such as the STM32F303RET6).
In another stack this example was given that shows an inductor just like I mean.

Now, I'm making a PCB with the STM32... and the datasheet does not show typical applications with such a inductor, but a schematic I got from some source with the STM32 does have an inductor between +3v3 and AVDD of the chip but does not have an inductor between +3v3 and VDD. Why is that?
Please excuse me for the maybe basic question but I'm trying to obtain some more common knowledge on the matter. This is why I'd very much like detailed explenations and tips/tricks for future designs.
What are the rules of thumb on this matter?


texts: how to clear an UART interrupt flag manually?

texts:
I'm using an  ATmega32. I have ISR(USART_RXC_vect) as follows

ISR(USART_RXC_vect)
{
    char ReceivedChar ;
    ReceivedChar = UDR; // Fetch the received byte value into the variable "ReceivedChar"

    if(ReceivedChar == '\n'){
        RxBuffer[RxPos] = '\0' ;
        RxReady=0;
        USART_Cmd_Eval();
    }
    else{
        RxBuffer[RxPos] = ReceivedChar;
        RxPos++;
    }
}

After triggering the ISR, it calls the following function to define which command is received from the PC.

void USART_Cmd_Eval(void)
{
            strcpy(RxCommand,RxBuffer);

            if(strcmp(RxCommand, "c") == 0){
                    RxReady = 1;
                    ADC_measure();
            }
}

For each command, the relative function will be called. Like following:

void ADC_measure(void)
{
        while(RxReady ==1)
        {
                _delay_ms(50);
                // Measrung ADC values and send them to USART
        }
}

The problem is: I can't send another command because it is stuck in the ADC_measure function. Basically, it doesn't want to receive another command though ISR, I think it will continue open. Therefore, I think I should clear the interrupt flag before calling ADC_measure. Right? How can do this?


texts: Designing custom solenoid with feedback for measuring force

texts:
I am contemplating the construction of a very small tensile force sensor based on the following principle:
1) Use positional feedback to a linear solenoid to maintain a fixed position when the plunger is under tension -- e.g., automatically vary the PWM input to the solenoid as needed to exactly balance that tension.
2) Determine the tensile force based on the required input to the solenoid.

First, let me know if there's any problem with the above concept that I might be overlooking. I realize there probably has to be some kind of damping to control oscillations and to optimize the frequency response of the sensor, but that's for another day.

Now for the main question.  I haven't been able to locate a commercial linear solenoid of the size that I think I need, so I'm contemplating fabricating one from scratch. This would be a continuous duty cycle solenoid, and I want to minimize the power draw required to maintain a particular steady state force (order 0.01 to 0.1 N).

My thinking so far:

1) For a given coil radius, solenoid force F is proportional to the number of turns and thus to L*I, where L is the length of the conductor and I is the current.

2) For a given coil volume (excluding the empty interior), the length L is inversely proportional to the square of the conductor diameter D.

3) The resistance R of the conductor is proportional to L/D^2 and thus to 1/D^4 (from 2).

4) The current flow is V/R, proportional to V*D^4.

5) Combining (4) with (1) and (2) gives F proportional to V*D^2

6) Using (4), steady state dissipation of power is proportional to V^2 * D^4.

What (5) and (6) seem to tell me is that, for a given voltage, I can maximize solenoid force AND minimize power consumption by using the thinnest possible conductor (e.g., 44 AWG) and thus the largest possible number of windings in a given volume.

I realize that the inductance goes up with more windings and thus the time response to changes of input, but this strikes me as likely to be important only if one is trying to measure very rapid changes in force.


texts: Time to charge a capacitor with a power limiting supply and ideally no resistance

texts:
So I have a capacitor being charged by a solar cell which has a varying (but readable) power output. This is being fed directly into a 10 farad cap with a solar panel voltage of about \$2.8V\$. For the sake of this question let's assume the output of the panel is \$5mW\$. Also, at the time of calculation, the voltage on the cap is known.

I would like to calculate the amount of time it would take to reach a voltage on the cap from some starting voltage on the cap (as a function).

Using a bit of algebra I've figured

$$t = CR \cdot \ln(1-V_C/V_S) $$

where \$V_S\$ is the open circuit voltage of the solar cell and \$V_C\$ is the voltage on the cap. And the resistance is

$$R = P_S/({V_C}^2) $$

where \$P_S\$ is the power output of the solar panel.

but the current and voltage vary based on the power output and charge and therefore the apparent resistance also changes (well I would assume). I'm a bit rusty on my calculus and am having a hard time coming up with an equation to express this relation.


texts: Current across high speed mechanical switch contact even if it can’t be measured?

texts:
If I am cycling a mechanical switch at a frequency higher than the bandwidth of a current amplifier and biased using a DC source, is current actually flowing across the contact? The following describes the scenario in more detail.

I am performing contact reliability tests on piezoelectric micromechanical switches to observe degradation of the electrical interfaces after millions of hot-switched contact cycles. I use a home-built logarithmic current amplifier to detect current, which allows me to track contact resistance as a function of cycles. This works beautifully if I am actuating the switch slowly – up to tens of Hz. However, I would like to speed up the actuation frequency of the switch beyond the bandwidth (kHz) of the current amplifier. I have tried high frequency cycling and, unsurprisingly, did not detect any current across the source and drain of the switch using the logarithmic amplifier. Does this mean that [A] no (or potentially some fraction of) current is flowing across the contact or [B] current is flowing across the contact but I just can’t detect it given the bandwidth of the amplifier?

My signal chain is: Instrumentation controller with DC source → BNC cable → logarithmic current amplifier → wire to switch → mechanical switch with metal electrical contacts → wire to ground

Actuation of the mechanical switch is achieved with a separate signal generator and isolated from the source, drain, and source-drain leads of the switch.

I am just so confused with the electrical theory behind current/DC voltage in this scenario. I’m not sure if this would be characterized as an AC or DC phenomena. If AC, it seems that no (or some) current might be flowing across the contact and that I would need to calculate the effect of the impedance and inductance of the instrumentation controller, BNC, log IV amplifier, and switch contact to estimate current flow during a switching event. Or, I may be overcomplicating things and it’s as simple as the current is flowing (i.e. it is hot-switching) but I just can’t see it.

Overall, I want to hot-switch at high frequency and can slow down actuation periodically to measure current/contact resistance with high fidelity. Thus, I am not looking for a method to accurately measure current at high speed, but want to know if current would be flowing even if not observed.

Thank you for any perspective you can provide. This question has been keeping me up for weeks and the electrical engineers I have spoken with in person haven’t been confident of their answers.


texts: Does it ever make sense to have more precision than accuracy? E.g. if you had a variable resistor which you could control with a resolution of 0.01 ohms but your multimeter only had 1% accuracy, then that extra resolution would be pretty useless wouldn't it?


texts: I've been trying to connect 3 HDMI sources to one endpoint. When using analog muxes it takes about a second for the devices currently connected together to reinitialise communication after switch. Unfortunately it's too much for my design. Is there any other way? I'm trying to avoid FPGA, as the deadline for the project approaches. For now I was unable to find anything resembling active HDMI switch. Ideal would be some ice with buffer inside and switchable input source.


texts: Working of Hex Schmitt−Trigger Inverter as a Sawtooth and Square Wave Producer

texts: Can someone explain how a Schmitt Inverter can behave as a Sawtooth (on pin 1) and a Square wave (on pin 2) as produced in a circuit where we have a Capacitor between pin 1 and GND, and a resistor between pin 1 & 2.


texts: What is pv cut off for 100amp(12v) lead acid battery?

texts:
I have 100 A lead acid battery and it charged with solor controller charger, the charger remains on after crossing 14.4V. Is this harmful for battery life? If it is dangerous, what is PV cut to charge 100 A battery fully?

Battery Picture:
(https://i.stack.imgur.com/103Ly.jpg)

Solor Charger picture:
(https://i.stack.imgur.com/lSjm9.jpg)


texts: Can I lower flash power consumption by pre-flashing all values to high?

texts:
I am designing an embedded system that will use either embedded flash memory or an SD card.
The system must survive without much power and the estimated 30mA draw of an SD card sounds too high for me.
My idea is to prepare the SD card before it is deployed by writing 1's to every single flash cell then formatting the card.
When being used in the application, the controller will never need to charge the flash cells with the battery, and will instead discharge them, perhaps lowering power draw further by acting as a micro power supply.
Is this reasonable, or will I not notice any power savings?


texts: LTspice modelling for the end terminal side

texts:
So I have this model. I am trying to build a current/voltage converter circuit for a bus carrying current to the other end of the bus, because I need to give this voltage output from the amplifier to a ADC of a micro controller to read the voltage data. I have the circuit below.

So here, the R5 is my shunt resistor across which my I need to identify the voltage. And R6 is the actual end terminal of the wire.

The question here is, I don't know what kind of internal circuitry is on the end terminal, is there a way to put a module or component on the simulation circuit, which will allow me to only read the data appropriate to the real circuit? Every time I change the value of the considered R6, the output changes. So I am trying to understand what is the best approach to simulate the circuit without the other end circuitry?

The max current from the current source is 40mA.

How do I simulate the shunt resistance part without the data of the other end?


texts:
I have an OEM touchpad I want to connect to a PC. The drivers for this touchpad are widely available. I asked the manufacturer for the original datasheet, and it says there, that the touchpad interface/protocol is PS2/SMBus.

On the device there is an 8 pin connector - of which 7 pins are used. They are laid out as follows:

I do know however that a PS/2 connector has only 6 pins (7 incl. the shield, but is it used at all?), and not 8. I can't see how this connector is compatible with PS/2.

FWIW, this is what the spec had to say about interface:

  Interface

  PS2

  Refer to IBM PS2 specification. Internal pull-up resistors (5k
  typical) are provided on DATA and CLOCK lines.

  All the commands specified by IBM are implemented, except for the
  following:

  "Scaling" and "Set Resolution" commands generate an "ACK" response from the touchpad, but leave the touchpad resolution unchanged.

  SMBus

  Refer to the System Management Bus (SMBus) Specification. Version 2.0.

That's it.

So am I looking here at something that is technically possible?


texts: What is the proper methodology to create portable FPGA designs?

texts:
FPGA designs may contain RTL along with IP blocks. These IP blocks most likely shall be from the vendor of the FPGA. Examples of such IP blocks are instantiating dual clock FIFOs, floating point and fixed point maths blocks so we can precisely set the latency e.t.c, low level primitives e.g device I/O buffers e.t.c. Such things cannot be inferred from the RTL code.

It may happen that development is usually carried out on a certain platform e.g Altera Quartus targetting Cyclone V. However, it may be that the final design for whatever reason has to be implemented in a completely different device e.g Microsemi Igloo 2.

What is the proper method to create portable designs in this case?

In theory the proper method will require:

A design where files exist for the two versions of IP blocks from the two vendors. A wrapper can be used to instantiate one of the two IP blocks during simulation and synthesis.
The synthesis tool to determine which files to use and which to exclude as it synthesizes the design. Thus, Quartus shall only use files that are relevant to it and Libero only use those relevant to it.
The simulation tool can be set to compile and simulate design using one of the two vendors' IP.

An assumption made here is IP blocks with similar functions exist from both vendors.


texts:
Does the Arduino Uno supply AC or DC power when connected to the computer via USB?

Can we specify is we want AC or DC?

I am trying to build a circuit that has a transistor but I don't currently have an external battery power supply for the DC current (see pic) and thus was wondering if I could just use the Arduino for that... (I am already using the Arduino for the AC power supply because up until now I assumed it supplies AC current...)


texts: Here you can see the schematic of an LC oscillator. When I change the value of C3 it changes whether I have oscillations or not. For example if C3=10u there are not stable oscillations, and if C3=1000p then I have oscillations.


texts: Can a resistor of known value be used to induce a predictable current, in accordance with Ohm's law?

texts:
CONTEXT

I have a 100A shunt and an opamp, which I'm going to use for measuring current through a battery bank.

But in order to calibrate it, I need to know the actual current flowing through the circuit. I don't have a 100A (or even 50A) capable meter. I could use my 10A-capable multimeter, but I wouldn't be able to measure at the higher current levels.

METHOD

Can I place a known resistor over a known voltage, and then use Ohm's law to reliably calculate the current?

simulate this circuit – Schematic created using CircuitLab

E.g. if I measure the resistance of a dummy load with a multimeter, and then measure the voltage drop over the resistor, can I then reliably calculate the current?

Also, since my cheap voltmeter can measure up to 10A, I'm thinking to test it with an adjustable power supply, by gradually increasing the voltage until the current reaches maybe 5.00A, and then measure the voltage with a separate voltmeter (so that the circuit remains constant), and then use this to calculate the resistance more accurately.

Is this a stupid way to approach it?


texts: How good is to use this zener diode for reverse polarity protection?

texts:
In the following circuit how does the zener diode D1 provide reverse polarity protection?

Lets say V+=12V and V-=-12V and the zener is 36V zener.

It means for correct polarity zener will not pass any current since it sees 24V across itself.

But in case of reverse polarity, the zener will short the opamp maybe protecting it, but wouldn't that also mean it will short the power supply? Is this a good reverse polarity protection?


texts: Replacing 18650 cells in laptop battery with greater capacity ones

texts:
My laptop battery died and I can't find a replacement (old laptop) so I'm going to need to replace myself the 18650 cells it has.

It is an 8-cell battery (a series of 4 banks of 2), making the whole package 14.8V and 4Ah.
So each individual 18650 cell is the typical 3.7V and 2Ah.

As a possible replacement I found these:
http://www.ebay.com/itm/2-x-3-7V-4000-mAH-18650-Protected-Lithium-Based-Rechargeable-Battery-Flashlight-/131347594474

Which are 4Ah (twice the capacity of my current ones) and also they are protected.
My current battery cells don't have any marking that indicates whether they are protected or not but I have the impression they are not since the battery charging circuit should provide such protection.

Also, the physical dimensions of the cells are exactly the same as my current ones.

My question is:
Would there be any problem that the new cells have twice as much capacity?
Also, does it affect in any way that the new cells are protected and the old ones are not?


texts:
I am trying to design a circuit that will completely turn off the Adafruit Powerboost 500 (by connecting the ground and EN pins) automatically. As part of this, I have come up with the attached circuit. I have very little experience with electronics, but my reasoning is as follows:

When the battery is first connected, the EN pin will be grounded and the powerboost will be off. Upon pressing the button, current will begin to flow and the transistor will be inhibited, so the device will continue to operate.

If this circuit works as I expect, I will add a microcontroller between the transistor and 5V pins, allowing me to cut power automatically when a certain event is triggered. This will require pressing the button again to turn on the circuit.

Powerboost manual: https://learn.adafruit.com/downloads/pdf/adafruit-powerboost.pdf

Thank you.


texts:
I am trying to figure out the GPIO Pins that are used for ADC input looking at the following ADC Initialization code for STM32L476RG.

      // DMA for ADC1
  RCC->AHB1ENR |= RCC_AHB1ENR_DMA1EN; // DMA1
  // Wait a bit
  nop(); nop(); nop(); nop(); nop(); nop();
  DMA1_Channel1->CPAR = (uint32_t)&(ADC123_COMMON->CDR);
  DMA1_Channel1->CMAR = (uint32_t)&adc_data;
  DMA1_Channel1->CNDTR = 2;
  DMA1_Channel1->CCR = DMA_CCR_MSIZE_1 | DMA_CCR_PSIZE_1 | DMA_CCR_MINC |
                       DMA_CCR_CIRC | DMA_CCR_TCIE | DMA_CCR_EN;

  // ADC123
  RCC->AHB2ENR |= RCC_AHB2ENR_ADCEN;
  // Connect to system clock
  RCC->CCIPR |= RCC_CCIPR_ADCSEL_0 | RCC_CCIPR_ADCSEL_1;
  // Divide clock (/8)
  ADC123_COMMON->CCR |= ADC_CCR_PRESC_2;
  // Dual mode
  ADC123_COMMON->CCR |= ADC_CCR_DUAL_1 | ADC_CCR_DUAL_2;
  // MDMA
  ADC123_COMMON->CCR |= ADC_CCR_MDMA_1;

  // ADC1+2+3
  // Disable DEEPPWD, enable ADVREGEN
  ADC1->CR = ADC_CR_ADVREGEN;
  ADC2->CR = ADC_CR_ADVREGEN;

  // Wait a bit
  int n; for(n=0;n<100000;n++) nop();

  // Calibrate
  ADC1->CR |= ADC_CR_ADCAL;
  ADC2->CR |= ADC_CR_ADCAL;
  while(ADC1->CR & ADC_CR_ADCAL);
  while(ADC2->CR & ADC_CR_ADCAL);
  // Wait a bit
  for(n=0;n<100000;n++) nop();

  // Enable procedure
  ADC1->ISR |= ADC_ISR_ADRDY;
  ADC1->CR |= ADC_CR_ADEN;
  ADC2->ISR |= ADC_ISR_ADRDY;
  ADC2->CR |= ADC_CR_ADEN;
  while(!(ADC1->ISR & ADC_ISR_ADRDY));
  while(!(ADC2->ISR & ADC_ISR_ADRDY));

  // Sequence
  ADC1->SQR1 = (1<<6) | (3<<12) | 1;
  ADC2->SQR1 = (2<<6) | (4<<12) | 1;

  // Oversampling (16x)
  ADC1->CFGR2 = (3<<2) | 1;
  ADC2->CFGR2 = (3<<2) | 1;

I expect 3 input channels but cannot find out which are those.


texts: I don't understand how the resistor between GND and the source in a common-source amplifier stabilizes it

texts:
See this circuit:

Applying KVL around the gate-source-GND-gate loop, I get Id = (Vg - Vgs)/Rs. I know the typical argument begins with, if Id increases then Vs increases, but I am not sure of how it continues.

There is something else I don't understand. The reasoning is based on the previous KVL equation, but it can be further simplified down to Id = Vs/Rs since Vgs = Vg - Vs.
Well, if we examine Id = Vs/Rs, an increase in Id corresponds to an increase in Vs, and that's all there is to it. No negative feedback. Usually the argument is based on the non-simplified equation Id = (Vg - Vgs)/Rs, I am not sure why since in reality Vg cancels out.

How does Rs stabilize the amplifier?


texts: I am trying to design a comparator using a 741 IC, with a single supply of 12V. I have set the reference to 2V and I require the output to toggle between 12V to 0V. but the problem I am facing is the output is only going to 11V max and min of 2V. What is the reason behind the output saturation?


texts: AVR. How to configure as output just one pin?

texts:
In AVR C code, if you want to declare some port as ouput, you just have to to do this:

DDRB = 0xFF;

But how can I do if I want to declare as ouput just one pin. For example, I want to declare has output Arduino's pin 13, which corresponds to PB5.

I know I can declare that in binary format:

DDRB = b11111111;

But, I don't know which bit position corresponds to PB5.

Thanks in advance, I could not find this answer in Google.


texts:
I've the following kown values:

Switching on loss is \$\text{E}_\text{on}\space\text{J}\$ in \$t_\text{on}=\tau_\text{on}\space\text{s}\$
Switching off loss is \$\text{E}_\text{off}\space\text{J}\$ in \$t_\text{off}=\tau_\text{off}\space\text{s}\$
In the pass state we have \$\text{P}_\text{pass}\space\text{W}\$
In the blocking state we have \$\text{P}_\text{block}\space\text{W}\$
The chopperfrequency is equal to \$\text{f}_\text{c}\$ hertz

  Question: Find the maximum duty cyle, when the heat sink on the thyristor can handle \$\text{P}_\text{hs}\$ watts of power?

My work (I use total energy per period):

$$\text{E}_\text{on}+\text{P}_\text{pass}\cdot\left\{\frac{\text{d}}{\text{f}_\text{c}}-\tau_\text{on}\right\}+\text{E}_\text{off}+\text{P}_\text{block}\cdot\left\{\frac{1-\text{d}}{\text{f}_\text{c}}-\tau_\text{off}\right\}\le\frac{\text{P}_\text{hs}}{\text{f}_\text{c}}$$

Now, solving \$\text{d}\$ will give me the answer.

  Question: Can I do this also using power instead of energy?

$$\color{red}{\text{d}\cdot\left(\text{P}_\text{pass}-\frac{\text{E}_\text{on}}{\tau_\text{on}}\right)+\left(1-\text{d}\right)\cdot\left(\text{P}_\text{block}-\frac{\text{E}_\text{off}}{\tau_\text{off}}\right)=\text{P}_\text{hs}-\text{f}_\text{c}\cdot\left(\text{E}_\text{on}+\text{E}_\text{off}\right)}$$


texts: Drive stepper motor with a battery efficiently

texts: I bought a bipolar stepper motor (Mercury SM-42BYG011, 12V, 0.33A) and an LN293 H-bridge. I drive the motor with a 9V alkaline battery. Unfortunately the stepper motor empties the battery very quickly. I don't need a lot of torque, and I don't need high accuracy (the motor turns 1/10 of a turn every few minutes). How could I drive the motor using as little battery as possible? Would some driving sequence, hardware implementation (resistor, capacitor...), or something else help saving battery? Does turning off the motor after each turn be enough not to use battery when static (or should I get the 9V battery with a transistor or something)? I should add that I control the motor with a raspberry pi.


texts:
I'm using an LM7805 regulator in my circuit to supply power for my microcontroller (Attiny 13) and another module.

I have to decrease 5V voltage to 3.3V for the microcontroller so I use two resistors (1k & 2k) to decrease the voltage from 5V to 3.3V
but sometimes the microcontroller does not work well (noise occures in GPIO)
I measure voltage between VCC and GND of the micro , It's about 3.0V
It means I have a 0.3V voltage drop by the microcontroller

I want to know how can I calculate the maximum resistors value (minumum current) to supply the micro ? Of course we have a voltage drop with any value of resistors, but which paramater of the microcontroller tell us how much voltage drop is acceptable for it ? Is there any standard parameter for It ?


texts: Temporary connection between two individual very small wires

texts:
I've separated a bunch of phone wire to connect a bunch of small devices (small motors, switches, buttons, electromagnets, etc all embedded in Lego blocks) and I need a way to temporarily connect them. I have some connectors like this:

But they're far too big and bulky, I need something tiny, it doesn't have to fit very tightly or be insulated, it would be nice if there was only one kind (so any two could connect together). Maybe some kind of micro alligator clip? Magnetic connections? Maybe little jewellery clasps? Or like this?

Surely instead of making my own I can go buy a bag of something, right? How do most hobbyists handle this?


texts: Connecting two DC sources in parallel using diodes

texts:
In the following circuit two DC sources with different voltage and current are connected in parallel using diodes. Can I assume that the load works fine if either of the source is available (S1 or S2) and when both sources are available, then power is supplied from S1(15V) source and S2(12V) remains idle?
When S1 alone is available, considering D1 drops 0.51V and Regulator giving 75% efficiency, I would still get 3.3V, 400mA output from regulator (i.e 15 - 0.51 = 14.49V, P = 14.49 * 0.133 * 75% = 1.44W, Regulator Output = 1.44/3.3 = 0.436A). Is this calculation correct?

simulate this circuit – Schematic created using CircuitLab


texts: Sensitivity list for clock edge and state change

texts:
Not sure if this is correct implementation, although it works so far. I output the data on the rising edge of the FETCH signal (this is not a clock). The data should only be out in the OUTP state. This also counts how many words were output so far, and the state machine (not shown) transitions to a different state if the word count reaches some value.

always @(posedge FETCH)
    case(state)
        OUTP:   begin
                OUT_DATA <= DATA[WordCounter];
                WordCounter <= WordCounter + 1 ;
                end
        default:WordCounter <= 6'd0;
    endcase

The problem is that to reset the WordCounter, I must pulse FETCH signal when not in the OUTP state. Is there a better way to rewrite this code, so I can fetch the data on the edge, but the WordCounter can be reset in any state other than OUTP not requiring a rising edge?


texts: Drive DC Motor with H Bridge(H Bridge turns off too slow and problem with current monitor)

texts:
I have two questions about my circuit, drving DC Motor with H Bridge. The picture below shows my design and how I drive it with signals.

For example, when I make the motor rotate forward, I give 'S1' PWM signal and give 'S4' always 1. Then I find a problem that the signal 'T1' shows like the picture up, which means the H bridge turns off two slow!(Which will cause problem when I want to make the motor move slowly). I have change the value of R1 and R2 so as to make U1B and U2B turn off as quick as possible, but it doesn't change much for the signal of 'T1'. Then I analysis the induction electromotive force. Maybe like the picture below,

So could you give me some advice to improve the signal of 'T1'  so as to make the H Bridge turn off quickly.

Moreover, I have another problem with current monitor and I have drawn the similar signal of 'T2' in the picture 2(Sometimes it has positive burr voltage, sometimes it has negative burr voltage, like a discontinuous sinusoidal). Any advice about improve my current monitor circuit?(I add comparator after 'T2', but I want to improve the signal of 'T2'). Thanks for your suggestion!

Here is one more picture to descrbe my problem. I want to make the time of red rectangle short.


texts: How to measure 6S LIPO battery juice in percentage from Raspberry Pi?

texts:
I've got a Raspberry Pi and I want to use it to measure the percentage of charge which a 6S LIPO battery pack has left which I then send to a server over the internet. I assumed there would be easy ready made sensors for this, but the closest things I found were

this Sparkfun LiPo Fuel Gauge which I think is only for one cell LiPo batteries
things like this HobbyKing battery monitor which I think only display the voltage and cannot output it using a I2C port.

After some more searching I found this Texas Instruments Gas Gauge and Battery Management Controller which seems to be able to read out 6 cell LiPo batteries and output the charge over I2C.

So I wonder three things:

Am I missing or overlooking something? Isn't there an easy way to measure the percentage of my battery pack from a Raspberry Pi? Aren't there any ready made boards with example code (preferably Python)? I suppose I'm not the first one wanting to do this..
If the answer to 1 is "No" I guess I need to build it myself; am I correct that the TI thing I found is something I can use to achieve what I want?
I'm a programmer, but an early beginner in electronics. Considering this, how hard is it to use the TI chip to achieve what I want?

Note that I don't need an exact figure. An approximation would be fine.

All tips are welcome!


texts: High Frequency Capacitors in Differential Amplifier

texts:
I am curious about the function of two capacitors near differential transistor pair amplifier. The circuit picture is cut out of one of Pioneer's audio amplifiers. This amplifier is basically complementary differential pair that drives VAS and Emitter Follower.

I am interested in the functions of capacitor C133 (47 pF) and C141 (470 pF) - what is their purpose in such circuit? The function of C132 is the dominant pole compensation, which I understand, but the other two (red squares) seems to me like another high frequency bypass capacitor, according to their values.


texts: How does the settling time affect the frequency components to be measured?

texts:
There is a physical transducer which measures wind-pressure by simply performing an A/D conversion and send the data to serial port. Since there is no data in the data-sheet I contacted the company for more info.

They say: "the device has an impulse response time constant of 20ms suggesting that the instrument might attenuate wind variations by about 25% at 4Hz."

Does that mean the settling time of the ADC is 20ms and the transducer cannot resolve frequencies more than 4Hz? Why?


texts:
I am trying to work out how to specify the transconductance value or Kn for LTspice. I have a part I can't find a suitable model for so I'll need to create one. I've tried this before and got values that ended up being entirely wrong. So I'm trying to figure out what went wrong there so as not to make the same mistake.
The part number I tried this on before was the CD4007UBE npn/pnp transistor chip. I worked out the Kn value by wiring up the first circuit below, replacing Vcc with a variable voltage source. I cranked the voltage just a little bit at a time until current began to flow. I found the value to be 650m. The scribbled values are those measured from my multimeter. I then hooked up the 2nd circuit to measure Kn. Knowing that 8.3V is much higher than the threshold voltage, I can be sure that the transistor is in saturation.
I then solved the system of equations below for Kn. I ended up with a value of 154m (work). I used this value for my ltspice simulation and it gave me improper values for my Qpoint when I built my circuit. The value that provided the correct Qpoint was something closer to 0.6m, which is what most of the pre-built models for this chip have as well. I can't find a prebuilt model for the chip I am using now, so I need to know where I went wrong, and what LTspice is expecting for the transconductance value Kn.
EDIT
I used the following definition in ltspice after obtaining the values.
.MODEL myNMOS AKO: NMOS (VTO=650e-3, KP=.154e-3)
$$k_n = k_n'\left(\frac{W}{L}\right)$$
$$I_D = \frac{1}{2}K_n(V_{GS} - V_{TH})^2$$
$$7.4\text{m} = \frac{1}{2}K_n(960\text{m} - 650\text{m})^2$$


texts: Operating a 60 hz Induction motor at 50 hz

texts:
If i had an Induction motor that runs on 460 volts ,35 amps , develops a power of 35 hp at a speed of ~1800 RPM ( data acquired from a nameplate )

How is it possible to calculate the same parameters if i wanted to run this motor at 50 hz instead ? what equations should i use ? , all i know is that power would decrease as well as RPM (obviously).


texts: Solder 4 switches off postive pole + fuse

texts:
simulate this circuit – Schematic created using CircuitLab

I have a basic circuit diagram: 12V system, 4 lights, (bike lighting).

Anyhow, I dont have experience with soldering multiple wires together.

My question is do I just solder 4 switches and the positive lead together. (i.e. how do I solder 5 wires together?)

I know there are terminal blocks, but its just a bunch of lights... er how do I solder 5 wires together?

Just twist all 5 wires together and apply some solder?  It seems like a mess to deal with if something goes wrong, (but quite easy to put together initially).

Also there is the fuse.  Can I just now twist 6 wires together and solder them together?  Seems the fuse should be first off the battery, but given there is only 1 positive pole/1 negative pole... does that distinction even apply?  In a 1 pole system, are all components the same distance from battery? Conceptually, they are, but how about in real-world situation.

Again, I don't have practical experience with soldering circuits.  Further I've misplaced my breadboard so cannot do a quick mock-up make sure lights turn on off, and battery doesn't overheat, etc. and that is adding to my hesitation.

One last question, why are the switch and light wires so thin (high gauge).  I calculated, that with total watt approx. 60W @ 12V, puts it at 5A running a few feet, 18G would suffice.  Can the wires in the switch-box be higher-gauge (thinner)?  Dealing with thick 18G wire will be a pain if it turns out I cant just wire everything off one pole.

Anyhow, sorry for naive questions (I have bread-boarded 8-bit adders in years past... er but am new to soldering...)

All advice is welcome.


texts: DC motor efficiency which formula to use?

texts:
I'm doing a lab report for a shunt DC motor evaluation. I seem to be stuck on the efficiency vs torque of the motor.

I have plotted a graph of measured \$\frac{P_{out}}{P_{in}}\cdot 100\%\$, which shows that the motor becomes less effcient with more load. (Increments from 0.1Nm to 1.1Nm then stalls.)

This is fine as it shows me that the motor is running aroud 50% efficiency at 0.1Nm and 18% at 1Nm.

My issue is when I try to use some more involved formulas the graph seem to flip around using the recorded values and shows that the motor is most efficient just before stall condition up to 95% so I'm unsure which to use.

The formulas I have been given are

$$ P_{out}= 2\pi T \frac{N}{60} \\P_{in} = V_f I_f + V_a I_a$$

Calculate these then put into the previous formula \$\frac{P_{out}}{P_{in}}\cdot 100\%\$.

Any ideas why the results are flipping?

To add here are my results from the Lab I have calculated the Pin and Pout using Ohms law V.I from the armature values Pin and Field values Pout i have also added the equation 5,6,7 calculations on the right hand side

Here are my calculations using the Eq 5,6,7 from above excell doing the calculations

Hopefully this all makes sense thanks


texts:
How would I need to set my fuse bits on a ATMega328p  to use a 16MHz crystal?  I tried this on my own and killed the last atmega I had.  I'd like some advice this time.

The crystal I am using is this one

I am assuming this is a "Full Swing Crystal Oscillator" as listed in the datasheet, so CKSEL3..1 should be 011

Then I need to set the startup time.  I'm assuming the "Crystal Oscillator, slowly
rising power" is the safer option so CKSEL0 should be 1 and SUT1..0 should be 11.

I don't want to divide the clock by 8 so CKDIV8 should be 1

CKOUT I will leave at the default of 1

If my assumptions are correct (and how do I verify that?) my lfuse bit settings will be 0xf7.

Am I doing this right?

This didn't work.  See here


texts:
In my current project, I'm trying to implement a smart card reader using LPC1788 which has a built-in smart card interface. Smart cards use the ISO7816-3 standard to communicate with the outside world. Smart cards need clocks which must be between 1MHz to 5MHz. This clock will be used to generate a baudrate with a fraction that is implemented in the card as default. ISO7816 states that if I connect a 3.58MHz signal to the card, the baudrate will be 9600.

On the other hand, the LPC1788 datasheet states that:

  If the smart card to be communicated with requires (or may require) a clock, program one IOCON register for the UART SCLK function. The UART will use it as an output.

Then it states:

  Enable the UART clock and set up UART clocking for an initial UART frequency of 3.58 MHz.

So I'm confused! If I set the baudrate to 9600 and program UART SCLK , will I get 3.58 MHz?

What does it mean by: "set up UART clocking for an initial UART frequency of 3.58 MHz"?

How can I do that?


texts: How to connect external switches to this circuit board

texts:
I am circuit bending a walkie-talkie to move some of the switches around and embed it in a shoe.

One part I'm not sure about is how to replace some momentary switches on the front with external switches I bought. I will be hand soldering this, and I don't want to fry the circuit board.

Here's the front of the circuit board.

One can peel up the white film that adheres to the board to reveal the leads.

The back of the circuit board is quite dense, and I'm not sure where to find the leads from those switches on the front.

Here is the momentary switch that I want to connect in place of the white film stuck on the front.


texts:
I am trying to implement Square Law Device on Virtex 5 Family FPGA but before burning it to the FPGA I was trying to simulate it in the Xilinx ISE kit. I am not sure whether the code is correct or not but here is the procedure I followed:

Created the schematic
Generated and Instatiated the IP Cores for Binary Counter (just for simulation purpose) and Sine Wave Generator using Cordic
Inserted a Verilog Test Fixture.

But I was not successful in simulating it. I am inserting the code for the Verilog Test Fixture.

// Verilog test fixture created from schematic F:\Xilinx\demod\demod\schema.sch - Wed May 01 19:16:25 2013

`timescale 1ns / 1ps

module schema_schema_sch_tb();

// Inputs
   reg clk;

// Output
   wire [35:0] outp;

// Bidirs

// Instantiate the UUT
    schema UUT (
    .outp(outp),
    .clk(clk)
   );

// Initialize Inputs
   `ifdef auto_init
         initial begin
             clk = 0;
                 repeat(100) begin
                     #10 clk = 1;
                     #10 clk = 0;
                 end
         end
   `endif
endmodule

Also I am copying the schematic of the project.

Where am I wrong?

Edit: The multiplier element is red just because it got selected while taking snapshot. I tried removing the instiantion of IP cores and I got some output but not the correct one. After that I replaced the always begin loop with repeat(16) begin loop, but it shows an error near repeat.


texts: How to get RSSI of Bluetooth, specfically HC-05

texts: We purchased a Bluetooth device EGBT-045MS in hope that we will be able to get its RSSI. Do you have any idea how to do this?


texts: how LTspice integrates Laplace in the time domain?

texts:
I modeled two different PID controllers with Laplace and with the same control parameters in LTspice, but the results show me the same behavior of the two PID controllers in .AC and different behavior in .TRAN. As in the picture.
My question would be:

Why do I get the same behavior in the .AC, but not in the .TRAN?
How does LTspice mathematically integrate Laplace in the .TRAN?
Where does this go wrong?


texts: Looking for tools or technique to design circuits on PCB prototype boards

texts:
Once I test my prototypes on a breadboard, I have a hard time to migrate the breadboard circuit to a double-sided PCB prototype board like this:

I am looking for a design tool (similar to thinkercad circuits) that helps me to place (draw) my components on a double-sided PCB prototype board and add connector wires. The drawing helps me to print and implement my circuit easier on such PCB prototype boards.

I know there are many free online tools to draw and design PCB board. Is there a similar drawing tool for double-sided PCB prototype boards as well?


texts: Pulldown resistor value for an NPN transistor to switch a solid state relay

texts:
I've got a basic setup which allows me to control 230V AC by switching a solid state relay on/off.
I'm using a Raspberry Pi's GPIO output pin and a general-purpose NPN transistor (BC547B) to allow a current to flow through the relay, here's my schematic:

Resistor R1 allows me to limit the current flowing through the SSR (The SSR accepts 4-32V, max 15mA). Assuming the transistor has a 150x voltage gain, this should be about 10mA.
(Is this right?)
Resistor R2 acts as a pulldown resistor so that the transistor stays closed when the GPIO pin is turned off/disconnected. However, I don't know what value to choose for this resistor.
After some research I found out that the resistor's value should be between 10kOhm and 100kOhm but does it have to be greater than R1? If so, what happens if the resistance is too great?
So my question is: Does R1's value make any sense and if so, does R2's value depend on it?
Additional information:
Here's a link to the SSR datasheet (The LED-indicated, random-on 240VAC relay).


texts: Establishing transfer function for s = f(e)

texts:
I'm preparing for a test this Wednesday and I'm stuck on this exercise:

Ud1 = voltage across D1; Ud2 = voltage across D2; e = in voltage; s = out voltage

I need to study 4 cases:

Both are blocked
Neither are blocked
D1 is not blocked, D2 is blocked
D1 is blocked, D2 is not

As you can see I started with D1 is not blocked, D2 is blocked, but I have no idea where to start. I tried representing D1 and D2 accordingly (Vt = 0.6V), but what should I do next? Thank you in advance for your help.


texts: Does the voltage of a solar panel have to be greater than that of a battery pack to charge it?

texts: I have a 6 volt solar panel and a 4.8 v battery pack(4 AA nimh). Will I be able to charge the pack? The solar panel is 100 milliamps and batteries 2300 mah.The solar panel is like the one here: http://www.ebay.com/itm/301018398863?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT


texts:
INTRODUCTION

I'm trying to program a custom board I designed, featuring a SAME54N20 MCU. My programming probe is a J-Link EDU (version 10.1), connected to my board using a Olimex adapter with a 10 pin connector.

PROBLEM

I can't get to "connect" to the MCU using the  J-Link Commander software (JLink.exe, Version:"V633f" ) despite having followed the Segger troubleshooting guide.

This is my J-Link Commander log:

 SEGGER J-Link Commander V6.33f (Compiled Jun 13 2018 17:12:50)
 DLL version V6.33f, compiled Jun 13 2018 17:11:37

 Connecting to J-Link via USB...O.K.
 Firmware: J-Link V10 compiled Jun 13 2018 16:23:32
 Hardware version: V10.10
 S/N: 260107390
 License(s): FlashBP, GDB
 OEM: SEGGER-EDU
 VTref=3.315V

 Type "connect" to establish a target connection, '?' for help
 J-Link>connect
 Please specify device / core. <Default>: ATSAME54N20
 Type '?' for selection dialog
 Device>
 Please specify target interface:
   J) JTAG (Default)
   S) SWD
 TIF>S
 Specify target interface speed [kHz]. <Default>: 4000 kHz
 Speed>100
 Device "ATSAME54N20" selected.

 Connecting to target via SWD
 InitTarget()
 Secured Atmel SAMD device detected.
 For debugger connection the device needs to be unsecured.
 Note: Unsecuring will trigger a mass erase of the internal flash.
 Executing default behavior previously saved in the registry.
 Device will be unsecured now.
 Mass erase done!
 Mass erase done!
 Mass erase done!
 Mass erase done!
 Mass erase done!
 ... (and about 420 "Mass erase done!" afterwards) ...
 Mass erase done!
 Cannot connect to target.
 J-Link>

ADITIONAL INFORMATION

Sorry if any obvious information is missing, I'll edit my post accordingly if asked to do so!

The prove and software does work with an Aruino Due (SAM3X8E) board.
I haven't got any SAME54N20 based or similar Demo boards available.
This is the SWD interface schematic:

This is the SWD interface board layout:

Poligons are shelved, but GND runs on the bottom layer of the 1.6mm thick two layered board, and 3.3V the top layer.
The reset trace continuing "outside the picture" goes to the actual Reset switch and series resistor, without any nearby routed signals.
The SWD header middle key faces the silkscreen adjacent line.

When I press the board Reset button the Segger J-Link LED turns red and stays green the rest of the time.
Each time a "Mass erase done!" message is displayed, the J-Link LED blinks in a red color with green color in between.
I haven't got an oscilloscope.

QUESTIONS

Has someone experienced a similar behaviour in the past and knows how to fix it?
What troubleshooting recommendations can you suggest?


texts: Beaglebone black gets shutdown signal when I move rc motors

texts: I have a beaglebone black that I tucked inside an rc truck.  I removed the radio control chip.  Everywhere it had 3.9 volt logic I put in a 3.3v gpio control from the beaglebone. It works great I'm able to control everything from the beaglebone via WiFi.  The clencher is I put in a 5v regulator and power to the beaglebone and now whenever I fire the motors  Linux begins shutting down,  it shuts down safely and while it's shutting down I can still control it until it powers off.  I tossed in a diode between ground and positive going into the beaglebone incase it was getting a voltage spike,  no success.  Now I'm thinking maybe it's a brief voltage drop,  however I'm still unable to successfully power the beaglebone and rc car from my own custom made battery. I tried li-ion and ni-mh I went ni-mh because it seemed to do better providing the amperage the rc car needed. Do I need a cap to store energy for possible microsecond lapses in power? If anyone has an idea what's going on please let me know.  Also,  whatever it is it's  not coming over the ground because I can share ground,  it's only an issue when I add in the positive for voltage regulation.


texts: 50 Volts on the Neutral (180 Volts on the Live) bad or safe?

texts:
We have an off-grid UK home on occasion powered by a generator (MOSA GE 6000 SX/GS).

Due to the design of the generator, it has two modes: centre-tapped-earth 110 V, and 230 V.  When running in 230 V mode, the two windings in the generator are connected in series; in 110 V mode, the windings are operated in parallel.

The result is that when the house is powered (generator operating in 230 V mode) there is 50 volts between the neutral and earth, and 180 volts between the live and earth.

I am told by an electrician that the neutral should be 0V (tied to earth) while the manufacturers of the generator unsurprisingly say that 50 volts on the neutral is fine.

Which is correct?

System Diagram

Note: Generator is connected to earth by an earth stake connected to the case.

Portion of internal circuit diagram of generator:

Note 1: BL=Neutral (230V), BR=Live (230V).
Note 2: The manufacturer added that the two windings are: connected in series when the generator is in 230 V mode, and connected in parallel when in 110 V mode.


texts: Is current flowing backwards a bad thing?

texts:
In the circuit below:

I find it awkward that the direction of the current on the 2V power supply is running opposite to the direction of the current on the 5V power supply. In the 5V power supply the current flows from - to + but in the 2V power power supply the current flows from + to -.

Mathematically, it all works out and the numbers add up but I am having a little bit of a hard time gaining some intuition regarding what is going on with this "backwards" current.

Here are a couple of questions:

If the 2V power supply was a battery, would this mean that the battery would be charging? If that was the case, would the battery eventually explode due to overcharging?
If the 2V power supply was a regular power supply (connected to the wall) why is the power supply not breaking? The power supply is not a battery, right? So there should be no such thing as "charging" a power supply so why do I not see smoke coming out of the power supply given that I am going against the natural flow of electrons?


texts:
I want to measure the EMC radiated by a circuit board, not very accurate, but just to give me a hint of how much is radiated.

The frequency of interest is 30MHz to 1GHz.

My idea was to place an antenna in the far-field, and simple terminate the antenna with the correct termination load.

Then measure the voltage across the load (using my 250MHz oscilloscope with spectrum analysator), and from this voltage calculate the dBm, dBuV/m and ect.

(Yes I know my 250MHz oscilloscope, will only give me the spectrum up to 125MHz).

Now for the questions:
1) Is it possible to get an estimate of the radiated EMC in this way?
2) What antenna design to use?