texts: Band stop filter RLC circuit frequency response

texts:
Assume we have an $ RLC $ circuit as described in the picture

This should be a Band-stop filter. But somethings bother me in my calculations. This is my calculations for the frequency response:
Using the impedance of the inductor and the capacitor, and using voltage divider, we conclude:
$$ V_{out}=\frac{\frac{1}{j\omega C}}{\left(j\omega L+\frac{1}{j\omega C}+R\right)}V_{in}=\frac{1}{\left(1-\omega^{2}LC\right)+R}V_{in} $$
Where $$ V_{out},V_{in} $$
represents phasors.
So now the amplitude given by:
$$ |\frac{V_{out}}{V_{in}}|=\frac{1}{\sqrt{\left(1-\omega^{2}LC\right)^{2}+\left(\omega RC\right)^{2}}}=\frac{1}{\sqrt{\left(1-4\pi^{2}LCf^{2}\right)^{2}+\left(2\pi RCf\right)^{2}}}$$
And now if I'll try to plot the graph of the amplitude of the frequency response for, say $$ \begin{cases}
R=300\varOmega\\
L=84mH\\
C=8.3nF
\end{cases} $$
This is what I get by desmos:

Which does not seem like a Band Stop Filter, as we can see here for example: (photo that I found online)

What am I doing wrong?
Thanks in advance. This is very appreciated.


texts: Will the capacitor stop receiving more voltage when max is reached

texts:
I'm trying to understand how capacitors acts in different situations.

Let say i have a constant power input source that is rated 5v and my capacitor that is 100uf 25v is receiving this voltage.

If the power input is always running and the capacitor is keep receiving it without without passing it over to any component. will the capacitor keep storing the voltage until it reach 25v and fail/explode if it exceed that limit or will it just stop accepting more until the power have been used ?


texts: Can I mix new and old batteries in a parallel circuit?

texts:
I mean non rechargeable alkaline batteries like energizer's, some full, some half empty. I know I cannot do that in series, I forgot why, but what about parallel?
I found answers for rechargeable batteries only.


texts:
I have an in-house board with a microcontroller (Microchip dsPIC33E) and an RS485 driver (Analog Devices ADM2587E) that I'm trying to connect to a desktop PC using an FTDI (USB-RS485-WE-1800-BT) USB to RS485 converter cable.  The in-house board receives data packets from the FTDI correctly and responds.  However the PC will frequently, usually within the first fives bytes, but sometimes later and sometimes sooner, see bit errors in the data received by the FTDI.

The picture below is a typical trace captured from an oscilloscope, showing:

The DE input to the ADM2586E in yellow (1)
The Data- (B) signal of the FTDI in cyan (2)
The Data+ (A) signal of the FTDI in purple (3)
The GND signal of both the FTDI and ADM258E in green (4)

The scope has been set so that the '0 V' level of signals 2, 3 and 4 are all aligned and marked by the position of signal 4 - the green line.

The first burst of data (on the left) is a Modbus Request Server ID packet, sent at 19200 bps, 8 data bits, 1 stop bit and even parity.  This is recognised by the in-house board, as seen by it asserting the Driver Enable of the ADM2587E and responding with the second burst of data (on the right).  The FTDI sends USB data that includes a bit error in the 6th (in this instance) received byte.  Note: I cannot be certain of which byte contains the bit error, as the USB driver does not retain very much in the way of timing information, but this is not particularly relevant to my question anyway.  Also, the delays either side of the DE transitions have been deliberately inserted in the in-house board software; I originally used the UART RTS simplex mode to reduce them to the width of a single data bit, but this had the same effect.

I suspect that the problem is due to the voltage levels of the received signals being misinterpreted by the FTDI.  The in-house board includes a 360 Ohm fail-safe bias resistor between A+ and VOUT and between A- and GND2 on the ADM2587E, plus a 120 Ohm terminating resistor between A+ and B- lines, as per the Analog Devices application note for this RS485 driver IC.  (I've also tried 1 kOhm and 10k Ohm bias resistors, but with very little difference.)  The trace above was taken with a Keterex USB Isolator between the PC and the FTDI, although this makes no difference.

The output from the in-house board is as I would expect to see a half-duplex, two-wire RS485 signal, with the B- and A+ signals balanced around the mean of their idle levels.  The output from the FTDI looks odd to me, with the B- and A+ signals both elevated relative to the mean of the idle levels.  If the FTDI is expecting the received data to conform to this 'elevated' signal, that would explain the bit errors and leads me to my question.

Why does the output of the FTDI appear to be elevated, relative to both the ground and idle mean voltage levels?

Edit

The answer marked as correct below indicates that there is nothing wrong with the FTDI levels, which is the closest thing to a correct answer: it doesn't matter that they are elevated since they are within spec.

As an aside, the problem I'm seeing actually appears, on much closer examination of the scope traces, to be due to the output from the ADM258E, and nothing to do with the FTDI at all.


texts:
I'm interfacing a 23LC1024 SPI Serial SRAM with a PIC18, using the C18 compiler and the built-in functions from <spi.h> as described in the Compiler Libraries, section 2.8:

  OpenSPI1 - Initialize the SSPx module.

void OpenSPI1(
    unsigned char sync_mode,
    unsigned char bus_mode,
    unsigned char smp_phase);

For bus_mode, I can choose one of the following modes:

MODE_00 - data is read on the clock's rising edge (idle to active clock state)
MODE_01 - data is read on the clock's falling edge (active to idle clock state)
MODE_10 - data is read on the clock's falling edge (idle to active clock state)
MODE_11 - data is read on the clock's rising edge (active to idle clock state)

I can't find in the datasheet of the 23LC1024 what mode I should use. Doesn't it matter? Or is there a standard assumed?


texts:
I'm designing a data recorder application which uses an 8-bit AVR microcontroller. It uses the TWI and SPI interfaces with the microcontroller being the master. There is one SPI device, a microSD card, and one TWI device, the MMA8452 accelerometer. The accelerometer is going to be sampled at 400~800 Hz, and I plan on storing relatively large amounts of data so there will be semi-frequent writes to the microSD card as the uC's memory gets filled.

My question is what is the recommended workflow for enabling/disabling the interfaces. Can I keep the SS for the SPI interface asserted low throughout my application, or should I only keep it active when I'm interfacing with the microSD card?

Also, can I keep the TWI/SPI master interfaces enabled, or should I enable them only when the interface is required?

ex. code (for TWI, similar for SPI):

// enable/disable during each operation
twi_master_enable(&TWIC);
// ... TWI-related operations
twi_master_disable(&TWIC);

Or, is this better:

// initialization/wake-up code
twi_master_enable(&TWIC);

// .. somewhere else in the code, perform TWI operations

// power-down/sleep code
twi_master_disable(&TWIC);


texts: Building "AND" and "OR" gates from tri-state drivers & inverters

texts:
I'm working on a digital circuits assignment which asks me to prove that if you have tri-state buffers and inverters, you can build any combinational logic circuit.

My attempt at doing so would be to create an "and" gate and an "or" gate, because "and", "or", and "not" are logically complete, if I'm correct.

My design for an "and" gate was to have two tri-state drivers, with two inputs (A and B) and they would come together with one output (C).  "A" would be the selector for driver two and "B" would be the selector for driver one, then "A" would be the input for driver one and "B" would be the input for driver two, then the outputs of those drivers would come together at "C".

My concern is that this design leaves a "Hi-Z" in the truth table:

A  |  B  |  C

1  |  1  |  1

1  |  0  |  0

0  |  1  |  0

0  |  0  |  Hi-Z

How would I go about fixing this? Or do I need a new design entirely?


texts: does impedance limit the current in a transformer?

texts: high frequency is suitable for small transformers with Ferrite core, but that cause high impedance, my question is: can we use that impedance to limit the current in a transformer of 1:1 ratio to 1 A without overheating or dissipation of energy?


texts:
Ok, long time reader first time asker on this parcticulair stack-exchange.
I am rather new to electronics, I've done some simple projects like Blinking Lights, alarms that go on when its dark and a Joystick Gamepad (with Arduino).

However, I am experianced in system programming, I've written a bootloader (x86) for fun, read assembler language for a living and have hacked some code for kernel modules.

For my most recent projects I got rid of the arduino and used a breadboard to build the entire board (same setup as the arduino though). I've created a project, got the breadboard prototype to work and now I am ordering a number of PCBs (seeedstudio) to get the real prototype going.

While I am waiting for these boards and the components to arrive I've started a project with the RaspberryPI, created a embedded linux for it and I've been playing with the GPIO. Now I wonder, how hard is it (and what is required) to breadboard a raspberrypi so I can eventually also get my own boards created for beefier projects.

TL;DR)
What should I learn about before I can assemble a RaspberryPi on my Breadboard? As I can't imagine it is as easy as breading the Arduino

Note: I've read, http://arduino.cc/en/Main/Standalone


texts:
Question "a" says "find the base potential Vb", and I can't do it :(. All the resistors are given above (you don't need to understand french, don't worry)
Could someone help me please, I would appreciate it !!!


texts: I'm building a quadrocopter and would like to prevent drift using a down facing camera. To do this properly, I need to get the height of the drone from the ground. Obviously the ground can vary, so maybe something like radar would be an idea, but I was wondering... how accurate are altimeters (electronic) these days?


texts: What does this vertical bar in an equation mean?

texts: I'd like to know what the vertical line followed by an E represents in this image. I would Google it, but I don't know what to type in to Google.


texts: What to do when I have energy loss due to distance

texts:
I have to connect a total of 15 12 V, 2 A motors in parallel.

They are all going to be connected to a battery and I’m trying to bring a line to connect all 15 of them. The distance between them is 25 meters. What can I do to reduce the energy loss due to the distance?


texts:
hi i am planning to install two small white light LED on my car as parking lights.

so basically i am using the reflector along woth LEDs from a torch that uses 3 AA cells(4.5v), the power of LED in manual is 3.2 V and the 1/2or .5W,
as we know

V=I*R which Implies I=V/R and R=V/I

and P=V*I, by following these equations i get 154ohm resistance to be used but i used two individual resistors of 60 ohms with each LED, so my question is will it work (well ofcourse its working as of now but for longer durations like 2-3 hours continous working and also with charging system engaged, i guess the power source will change from 12v to 13.5 V.

any help will be appreciated.


texts:
I'm working with an 80C51 derivative, the P89C668HFA.  At the moment, I'm trying to get some very basic functionality out of it- I just want to 1) disable ALE toggling and 2) get the I/O ports to toggle.  I wrote a little bit of code to accomplish this:

    MOV 08EH,#003H ; set lowest bit of AUXR low to disable ALE toggling
START:
    MOV 080H,#000H ; Port 0
    MOV 090H,#000H ; Port 1
    MOV 0A0H,#000H ; Port 2
    MOV 0B0H,#000H ; Port 3
    MOV 080H,#0FFH
    MOV 090H,#0FFH
    MOV 0A0H,#0FFH
    MOV 0B0H,#0FFH
    SJMP START
END

The output of my assembler matches the hand-crafted binary that I started with.  When I take the device out of reset, the ALE pin is still toggling, but not PSEN#, and the I/O port pins are all high.  Given that information, and the fact that I am able to successfully program the device and verify that the program is correct, I believe that the device is working correctly, but it seems that the code is not being executed correctly (if at all).

I'd appreciate any thoughts on the topic, threads I could pull on, etc.  Thanks.


texts:
I'm trying to design a circuit which takes an RGB888 signal from another board and deinterlaces/scan doubles using the Averlogic AL250 to send to an RTD2660H. The AL250 "only accepts RGB565" but it has a section in the datasheet that has a mapping for RGB888 (section 7.1).

What I want to know is, am I understanding correctly that I can use the pins it's described from the RGB888 signal and just ground/vcc the unused RGB888 signals or is there a way/IC to convert from 888 to 565 before it gets to the Averlogic?

Here is a link to the Averlogic AL250 datasheet.


texts: Am I able to burn a bootloader and program with an AVR ISP?

texts:
I have considered purchasing some ATMega chips as to create simple realizations of projects without sacrificing a dev board (i.e. Arduino)

Now I understand the bootloader is required to read from a usb-to-serial device. The AVR ISP (or equivalent) burns the bootloader, then people often either use a usb-to-serial or the Arduino itself to program the chip.

What on earth does the AVR ISP actually do? If it can burn a bootloader (is it stored within, a generic one for all the AVRs it supports?) why can it not also program the device (as people seem to never instruct, even if that makes it simple)

Why does the ISP also allow you to connect to a computer via USB, for power? for custom boot loaders? Can it even "program" a compiled program in to flash via something such as avr-gcc (assuming the arduino IDE does things that required the bootloader)

I just cannot wrap heads or tails around what is required. I am aiming for a "program the new chip, plug it in to socket, and go" kind of approach without multiple burns or programming.


texts:
I am designing a four layer stack up PCB having nrf52832 SoC with chip antenna (2450AT18B100 Johanson Technology).It is BLE Board (2.45 GHz). This is the first time I have been designing a PCB with an antenna. I am using kicad EDA Software. The stackup of my design is:

Signal and RF traces with ground copper fill (Green Colour in Picture below)
Ground Plane
3.3V Plane
Bottom Plane (Basically Solid Ground Plane) (Red colour in Picture below)

I am going to add many vias (at 1/12 of RF frequency which will be 2.45 GHz). The antenna part is not completed yet because I am yet to receive some specification from my PCB fabrication house. I will change the width and shape of antenna feed considering the distance between signal plane and ground plane. I have one question regarding the calculation of width of antenna feed line. Since, I have four layers, Can I use formula of coplanar waveguide with bottom ground plane? Won't power plane and bottom layer will effect the impedance of coplanar waveguide? Do I need to take into account presence of power layer and bottom layer (actually solid ground plane).

NOTE: The other sensor in the left part of my layout is a CCD (TCD1304) which is basically a linear image sensor.

What I want from the community is suggestion on the pcb and review my design for RF. Since, this is the first time I have designed such a board, I don't want to design a PCB which won't work or work with very short range. The pictures of my PCB are given below:

Picture 1:

Picture 2:

Picture3:

After reviewing the datasheet of my chip antenna and suggestions from Johanson Technology, I can see they have suggested a large ground plane for which I don't have space.You can check pictures of my layout above as I have marked area for antenna (7mm X 23mm).

The picture below are taken from Johanson Technology's layout suggestion:

EDIT:
I got specification from my fabrication house (See Picture below:)

I have updated my layout after calculating width for 50 ohm antenna feed line (which happens to be 21 mils). The pictures of updated layout are:


texts: Help with datasheet for isolated DC-DC converter

texts:
Currently writing a bachelors thesis of a power distribution system.

Have been checking websites like mouser.com for DC-DC converters to test before making my final decision which kind I am going to choose. I'm having a slight problem understanding the information provided on the website and/or datasheet.

How can I figure out what kind of isolated converter I'm currently looking at?

And, for the DPA423-426 from mouser.com. What does it mean the converter is both forward and flyback?

https://www.mouser.com/ProductDetail/Power-Integrations/DPA423PN?qs=sGAEpiMZZMu6TJb8E8Cjr3sTIccEzm0g

Thank you for your answers.


texts: Relay Controlled Gain for Microcontroller

texts:
I'm thinking about controlling analog circuits with a micro controller and lots of tiny relays (Omron G6L). For signal routing this is fine but gain control is troubling.

Obviously I could do something like this:

But this requires a relay for each step. I'm thinking there has to be a better way.

Is there a clever resistor network arrangement that can yield the voltage dividers found in inverting and non-inverting op amp circuits, panning controls, etc?

More specifically, is there a parallel and / or series network of relay controlled resistors that can yield the ratios necessary to control gain in op amp circuits (both inverting and non-inverting), pan controls, etc?

With 2 relays that is 4 possible ideally. With 3 relays that's 2 x 2 x 2 = 8 steps. With 8 steps of 3dB each that would give me a 21dB range from say -9 to +12 or whatever. As the gain is increased or decreased, the microcontroller would just iterate through a predefined sequence of binary codes.

Surely this has been studied before but I'm not an EE (I'm just doing this for fun) so any pointers would be greatly appreciated.


texts:
I know there were some changes applied to voltage amplification formula of BJT when "Ce" (emitter bypass capacitor) was connected to the circuit. How is it with JFET (MOSFET too) and its bypass capacitor? I haven't seen any formulas for JFET considering bypass capacitors when equations were discussed. Can anyone suggest how solve this kind of  "problem"? Maybe explain it a bit.

Here is a schematic

Here are some equations (probably refering to different models) for Au:

*Also from one of my sources (from the one with pink coloured formulas) it says that source bypass capacitor increases gain magnitude!


texts: Problems with the antenna module sim800l

texts:
Good day!

There is a problem with the sim800l module. I tried to connect sim800l to the network, but it does not connect. The LED should flash 3 times per second, but it slowly flashes 9 times, then turns off, then 7 times, then turns off again, the cycle repeats ... The power source that I use is 4 VDC. Current 2A. I connected a capacitor to the power pins.

GND and NET are short-circuited, is this normal? I tried to unsolder an external antenna connector and cut the wire, but it did not help.

I got a new module, but the problem remains. Could the party be defective?

Thank you for your attention!


texts: Ungenerated Voltage across the DMM and random spikes across the Oscilloscope

texts:
I am working with piezoelectric material known as PZT-P-43 MY PZT datasheet
(please look at the red outlined).

So far I have been trying to find the Energy that is being delivered to my 100uF capacitor, but I am facing few unprecedented issues. My circuit that I have built is

simulate this circuit – Schematic created using CircuitLab

I am using 100uF capacitor with a Voltage buffer supplied by +10V and -10V across the rails. Now, my issues are:

1) Across the oscilloscope I can observe Random spikes of around the range from 15mV to 50mV without generating any taps on the Piezomaterial. The waveform of these spikes are shown below:

2) Very interestingly, My DMM shows a maximum voltage of 340mV (charges slowly to this value) without ANY TAPPING on the Piezomaterial, at 340mV if I start tapping it increases very slowly but it discharges back to 340mV. So at 340mV it does not charge or discharge automatically.

Note: 1) I found out that if I just touch (bare handed) my Piezomaterial at 340mV it Discharges and once I remove  my touch it Recharges to 340mV. Does this indicate that current is flowing back to the Piezoelectric element through the Bridge rectifier? and yes my bridge rectifier works absolutely fine.

2) There exists a continuous amount of mV (3-5mV) without tapping the piezomaterial.

3) Really looking for a RIGHT way to calculate the Energy being stored inside the capacitor and How much energy is produced by a single tap.


texts: High side switch using complementary MOSFET: pull up/down calculation

texts:
For a battery powered ultra low consumption application I designed a classical high side switch using the complementary MOSFET FDMA1032CZ. this is the schematic:

The idea is simple:

before shipping, the circuit consumption is nearly 0[A] (only MOSFET and battery leaks),
then the user powers on the circuit using switch S1,
the microcontroller starts running and activates Q1-N and Q1-P via "PWR_ON" signal,
the circuit is then continuously powered on by the battery through the mosfet switch.

I need assistance to calculate the optimal value for both pull-up and pull-down resistors (R1 and R2). For reminder, those 2 resistors are mandatory to set voltage level when circuit is powered on.

In my opinion those resistors must be :

as large as possible to minimize current when the 2 mosfets are on,
but not too big to make sure the 2 mosfets can switch fully on.

When looking at datasheet, it appears that the maximum MOSFET gate body leakage IGSS_max = +/-10[uA] and the minimum gate threshold voltage VGSth_min = +/-0.6[V].

According to previous point 2), the resistor value should NOT be greater than R_max = VGSth_min/IGSS_max = 0.6/10e-6 = 60[kohm].

For a battery voltage of 3V, this would result in a total consumption through the resistors of: I = 2x V_BAT/R = 2x 3/60e3 = 100[uA], which is far too big...

I would appreciate if someone could confirm and/or correct my calculation.


texts: Water level sensor for a coffee machine boiler

texts:
I made a simple water level sensor with an Arduino. A digital pin  supplies 5V to a probe in a coffee machine boiler. Boiler chassis is connected to AC ground (earth) and the ground to an analog IO pin on Arduino. A pull down resistor is between the analog pin and GND pin on Arduino. If there's water in the boiler, the analog pin detects the voltage, if there's not, it reads zero.

The digital pin is turned on every 1s to slow down corrosion of the probe.

Now, a lot of things are connected to the AC ground - the pump, boiler heater, power supply etc. Should I do anything to protect the Arduino in case anything goes wrong? Is there a better design for this?

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: DC - High Voltage DC converter that acts like a sink

texts:
Anyone knows of any DC DC converter that can produce at least 200V and act as a sink? If it is comes in  DIP package, its better.

Right now I am using EMCOs DC-DC converter. But it cannot really act as a sink.

Datasheet here:
http://www.emcohighvoltage.com/pdfs/qseries.pdf

Edit: When I say sink, I mean an electron (negative current) sink. The application I am working on floats a collector plate to a high negative voltage. ( - 80 V to - 100V) range


texts:
I was just wondering if someone could tell me if I am doing this right, because I don't really have any sample problems but just want to be prepared for anything. If we wanted to find the output voltage of this system could we find:

The gain by Rf/Rs
Then multiply Va*Gain?

simulate this circuit – Schematic created using CircuitLab

*It would not be square rather just a 5v source.

So gain would be: 36k/12k or 3; so Va*3 would be the output?


texts: How to calculate Snubber for different load value

texts: We are doing home automation project in that we need snubber for both resistive  and inductive load. If we connect less than 5W load(Bulb) it is keep on glowing without switch on. Whether i need to design a snubber for Low Watts? If so, Please Suggest the corresponding formula for design a snubber for different value of loads. Thanks.


texts: Why or when does battery capacity matter in a series circuit?

texts:
I have 3 sets of doubled 18650 cells from a laptop battery, and I gather that it can be dangerous to use cells of different capacities in series. This question is more about the theory than practice.

I have tested each set of cells at 1amp continuous draw and as usual there is a minor differences in capacity; one lasts for 3h where as the other two last closer to 2h and 50m, if my math is correct that is 3000mah vs approximately 2860mah?

These functioned in the laptop without issue and I'm assuming over time cell capacity diminishes and not exactly at the same rate per cell, this is obviously not dangerous, what is the difference between the results from these factory matched cells and unmatched or differently used ones that makes this safe?

If I were to put these cells into a different laptop battery harness with their difference of capacity how would it differ from the original?


texts: The reason why the output waveform of gate voltage boost is not almost the straight line?

texts:
I read paper,about gate voltage boost,recently,and i found the output is not almost the straight line,the more gate voltage boost circuit is in series, the more pronounced the output is tilted ,as the second picture shown

Because it use the precharge and discharge of capacitor (\$C_{B1} \$,\$C_{B2}\$...\$C_{BN}\$) to boost every stage output voltage,so is it,the precharge and discharge of capacitor,the reason why the more gate voltage boost circuit is in series, the more pronounced the output is tilted?


texts: Undescriptive capacitor and inductor values in audio-amp datasheet

texts: I was learning about audio amplifiers and came across the STA516B IC. To my surprise, the example circuits feature some values for capacitors and inductors which seem a bit high for me. So I wanted to ask if I was missing something or if these components are somehow special and are really meant to have such high values. Thank you for your answers]1


texts: How to step down the voltage efficiently

texts:
I need to power three devices/loads from a single DC source (a 48V at 200A battery). The buck converter used is this.
The three loads are:

RFID reader (24V DC @ 2.1A)
Rasberry Pi 4 (5V DC @ 3A)
DC fan (5V @ 800mA)

Which option is more efficient in terms of power?
Option 1:

Option 2:

Block Diagram of power supply:


texts: How does the power efficiency of an appliance compare using 12V DC or 240V AC with an inverter?

texts:
With an off-grid system, if an appliance supports powering via both 12V DC and 240V AC, is there any difference with the power efficiency of either method excluding the draw of an inverter used to power via 240V AC?

And how does the power efficiency compare when the draw of an inverter is taken into account?


texts: Smart Light Switch power supply solution for 2-wire (without neutral) scenarios

texts:
Considering a smart switch based on a power greedy WiFi ESP8266 (800mA spikes and 100mA on idle, @ 3.3V), there is the common situation to have the neutral wire missing from the wall switch box (left with 2 hot wires, maybe some earth wire that I don't want to consider in any way). Powering the electronics in the smart switch from the 2 hot wires will draw current through the light bulbs, making them either flash or light up (maybe except for some incandescent ones, but I can't rely on the light bulb type in any way; all usual types ranging from 1W to 100W, 110/230VAC should be considered).

At this point you might have already guessed the problem: what kind of smart switch design can bypass this issue?
Some suggestions I read were to use an extra capacitor in parallel with the light bulb so that the current drawn by the switch won't get through it. Although I'm a beginner with electronics and I don't fully understand how exactly should that work, or how to scale the capacitor (maybe someone could explain me), I only wonder why didn't the LED/CFL bulbs manufacturers just include this feature in their products, since this seems to be an universal issue. Are there any reliable solutions to this problem?


texts: ICEO, ICBO physical interpretation in BJT

texts:
I am stuck with the equation:

ICEO = (1+β) ICBO

My questions are:

What is the physical interpretation of this equation?
Will both the currents exist simultaneously?
Are any of the reverse currents getting amplified?


texts: How can Arduino send an RF signal at 433 MHz?

texts:
I am asking this question primarily to learn.

I have learned that Hz is the number of cycles in one second.

Taking that into consideration I have tried the following examples.

Example 1

void loop() {
  digitalWrite(3,HIGH); // make pin 3 have a voltage of ~ 5V
  delay(500); // wait 0.5 seconds
  digitalWrite(3,LOW); // make pin 3 have a voltage of ~ 0V
  delay(500); // wait 0.5 seconds
}

This code has a frequency of 1 Hz because voltage is .5 seconds up and .5 down. My voltmeter shows .99999 Hz

The duty cycle is 50% because the voltage is half of the time up and half of the time down.

Example 2

void loop() {
  digitalWrite(3,HIGH); // make pin 3 have a voltage of ~ 5V
  delay(90); // wait 0.09 seconds
  digitalWrite(3,LOW); // make pin 3 have a voltage of ~ 0V
  delay(10); // wait 0.01 seconds
}

This code has a frequency of 10 Hz because every cycle is .1 seconds (90 ms + 10 ms). In 10 cycles you will reach 1 second. The duty cycle of this code is 10%.

The following examples are basically the question:

Example 3

void loop() {
  digitalWrite(3,HIGH); // make pin 3 have a voltage of ~ 5V
  // Do not delay
  digitalWrite(3,LOW); // make pin 3 have a voltage of ~ 0V
  // Do not delay
}

If I run this code, my voltmeter shows a frequency of 112,000 Hz or 112 kHz:

I believe that is the highest frequency I can get. I am not delaying in between cycles. Why is it that when I google the frequency of Arduino Uno it says:

Example 4

Google is probably correct and the frequency is 16 MHz for Arduino. If that is true, then how can an Arduino send a 433 MHz frequency? I want to buy this:

When I now set delay as in Example 3, the highest frequency I could obtain was 112 kHz (with a k). How is it possible to send a 433 MHz frequency (with an M)?


texts:
It seems that I fried my 74LS181N ALU, though I'm operating on 4.95v and have a 1k resistor (plus LED) on all output pins.  I was sure it could handle those 5mA, but the datasheet suggests an output current of max 0.1 mA.

Im I misreading the datasheet, is it realistic that the ALUs limit is 0.1 mA?

For those who care, for testing I have the pins Vcc and input A0 tied to 5v, the output pins 14-17 floating, and all other on ground.

EDIT: Oh yeah, the chip gets hot.


texts:
I have a weak AC signal which I amplify about 25k times. (Frequency of my signal is from 1kHz to 30kHz. )

However in certain cases this gain become more than enough and saturate at the input of adc.

What is the correct way to do AGC ?

Currently the only ideas are digitally controlled resistors, which I believe would be noisy or at least I don't find this solution elegant. Alternative is to use multiple ADCs where I sample the signal at different locations in the signal chain. But this may get expensive especially if I use expensive ADCs.

Looking for ICs or more elegant solutions.


texts: Why can you not combine resistors in series when there is a voltage or current source between them?

texts:
Combining resistors in series with a voltage source in between

The answer says no, but I don't understand how it alters the circuit at all. If there is a current source between two circuits, the end result is current flowing and a voltage difference encompassing the three elements.


texts: High Frequency Start Arc Generator For Pulse Arc Welder

texts:
A little back story - I'm a network security engineer turned bench jeweler. I built a capacitive discharge spot welder. It's an awesome unit, and works great, but it's not exactly what I need it to be. It's a resistance welder, which means that the resistance of the workpiece generates the weld heat. Gold and silver (the metals I work in), are very very conductive to both heat and electricity. I need to convert the unit to a pulse arc welder. For reference look at the Orion welder line by Sunstone Engineering, the PUK line by Lampert, or the Pulse Arc line by ABI.

http://www.orionwelders.com/
http://www.abiusa.net/Pulse.htm

To convert the unit to pulse arc, all I need to do (in theory) is boost the voltage above the breakdown voltage of air. It has a 3 farad main bank at 25 volts making it's an 800Ws welder when charged to it's safe max. The main bank can be charged to anything from 0 to 25, with 2 output pulses anywhere from 0ms to 35ms each. The breakdown voltage of air is about 370 volts.

The unit has a main control board that interfaces with a mosfet switching board that uses 18 75v @ 209A mosfets. Basically, it just takes 5v pulses from the control board and turns the mosfets on and off accordingly.
I'd like to build a daughterboard that will sit in between the two, and switch a high frequency source on then "pass" the 5v control pulses along to the mosfet board.

This should create an ionized plasma channel through which the weld energy will then travel.

So, two questions.

1) How do I create that high frequency source? I could use the tried-but-true automotive ignition coil method. But that seems... crude. There's got to be a better way.

2) How do I protect the rest of the circuitry from being fried to bits by the high frequency addition?


texts:
I want to sense whether 14V Power input is on or not and send it to the GPIO Pin of my micro controller.The micro controller accepts any voltage greater than 2V as Logic High.Based on that ,I designed my below circuit without considering the GPIO input impedance as I could not find the information on the datasheet.Do i really to need to consider the input impedance in my case?

Added:
Here is the link for the datasheet.
http://cache.nxp.com/documents/data_sheet/LPC2131_32_34_36_38.pdf?pspll=1


texts: Power consumptions of the following 2 LED driving circuits

texts:
I have simulated the following two circuits that can drive and pulse the LEDs.The transient result is shown on the right.

The thing I am not sure is that which circuit consumes more power? My idea is circuit 1 (left) because the current flowing through the top transistor never goes to zero. Am I right?

Btw, can anyone explain why some spikes occur in current lled2? Is it because of the charge injection?

Thank you.


texts: How to correctly document wireless network choice for a project?

texts:
Disclaimer: I have limited wireless knowledge at the moment, I'm currently following the Certified Wireless Network Administrator study guide.

I'm working on an RC car and have the following network requirements:

I'm in the planning phase and wish to properly document my wireless network choices and I'm not sure how to proceed. I'm under the impression that I should take a linear approach in determining the wireless standard and the wireless module while not making concrete assumptions about the next stage:

Network requirements > Wireless standard > Wireless module/controller

I was thinking that an approach of going from requirements to choosing the wireless standard is to first delimit candidates for each function based on the minimum required channel bandwidth to support the required payload rate, using the Nyquist bit rate formula. But the formula refers to a noiseless channel and makes assumptions about modulation and Shannon's capacity requires SNR, which would make assumptions about the wireless module.

I'm not even sure of the proper way to estimate the payload rate because in reality there's a protocol overhead as well and it depends on the chosen wireless standard, that's why I want to use the payload rate and not bit rate.

To recap:

What is the correct way to determine candidate wireless standards and wireless modules based on network requirements?
How to estimate speed requirements for different functions?


texts: Why do magnet door/window alarms use always-on switches?

texts:
I am looking at door/window alarm designs, and they all use overcomplicated circuits with an always on switch, where the piezo is triggered when the switch is off.
If the switch was always off, it would be simpler, cheaper, and would consume 0 Watts at idle because the circuit would always be off unless triggered.
Why don't they use simple always off switches in between the piezo and the battery?


texts: DC isolation fault circuit breaker feasibility - design review

texts:
So I was wondering what the best way is to interrupt ground faults in ground isolated DC circuits. After some research, I found out about isolation fault detectors and was wondering if one could use a circuit like the one below to achieve the same functionality.
The circuit basically works by weakly pulling the PE to half the supply voltage. The voltage of the PE line in reference to the circuit GND is then monitored for much lower/higher than half of the supply voltage.

The circuit is supposed to go in between a solar array and an isolated 230V grid tied inverter. Its only job is to detect ground faults in the DC wiring (short to earth -> cable insulation defective -> possible danger for unlucky homo sap.)


texts: When adding binary numbers, how do you just ignore the overflow?

texts:
So lets say I used 2's complement to put -17 in binary and then I added it to +27, e.g.:

  +27    0001 1011b
+ -17    1110 1111b
-------------------
  +10    0000 1010b

This calculation here should have an overflow of 1. Where did this overflow of 1 go? How can you possibly just disregard it when it would completely change the whole calculation?

When you add 2's complement numbers, does it just always mean you have to work in a predefined number of bits, and if so, why?

Also, does 2's complement have -0 value and a +0 or only one 0 value?


texts: Is this the correct AC analysis of the following circuit?

texts:
If I have the following circuit

simulate this circuit – Schematic created using CircuitLab

Is this AC analysis correct? I am not sure if I should add the R4 resistor in series with the re resistor or not?

simulate this circuit


texts: single phase 120V convert to 3 phase 208V

texts:
Can you convert 1-phase 120V into 3-phase 208V?
If yes, whats the simplest way to do that?


texts: Is it possible to have multiple wave windows in ModelSim?

texts:
Is it possible to have multiple Wave windows opened in ModelSim simultaneously?

I know it is possible to add multiple "Window panes" in a single Wave window but it's so buggy and un-flexible that is barely useful or productive (or even usable). I need to fit all signals of two instances in the screen but I don't want constant access to both of them, so "Window Pane" is not the best option anyway.

I'm using ModelSim Altera 10.0c, rev. 2011.09


texts: dsPIC33, SPI slave, and Timer1 interrupts. What happens?

texts:
I have an interesting problem with the dsPIC33FJ128GP802.
I have it configured as a slave SPI device connected to an Arduino acting as the master.
Timer1 is set up to trigger an interrupt at specific times in a certain sequence.
One of the sequences of interrupts takes about 50µs to execute.  Yes, I know it's not "good practice" to have in interrupt routine lasting that long, but there is only the one interrupt being used in the system, and timing restraints mean that it has to take that long.
Now, it's all working - the SPI is running and receiving commands from the Arduino.  The Timer1 is triggering the interrupt at just the right times, and everything is looking good.
Except, I am seeing corruption on the SPI.  I can only assume that it is due to the interrupt for Timer1 firing during the SPI transfer.  If I disable the timer and its interrupt I get no problems with the SPI transfer at all.
From what I understand of interrupts, all the registers etc are supposed to be in exactly the same state when the ISR returns as they were when the interrupt was triggered.  That is certainly what the C30 user manual claims.
I have tried re-writing my C code for the SPI reception in assembly, but the problem still persists.
Here is a snippet of my C code:
while(PORTAbits.RA3==1);     // Wait for a transfer to be requested
SPI1STATbits.SPIEN=1;        // Enable the SPI module
SPI1BUF=0x0;                 // Prime the buffer to start a transfer
LATAbits.LATA1=0;            // Signal to the master it may transfer
while(PORTAbits.RA3==0);     // Wait for the master to signal it has transferred
in = SPI1BUF;                // Store the resultant word
SPI1STATbits.SPIEN=0;        // Turn off the SPI module
               ... perform operations depending on SPI command received ...
LATAbits.LATA1=1;            // Signal to the master the command has finished and it may transfer again.

RA3 is the Slave Select pin for the SPI
LATA4 is reverse handshaking back from the slave to the master

Both are active-low.
As you can see I am using more handshaking than normal SPI, as I need to feed back from the slave to the master when it is safe to start transferring another SPI command.
My ISR is defined as:
void __attribute__((__interrupt__,no_auto_psv)) _T1Interrupt(void)

I have tried adding the __shadow__ attribute to use the shadow registers, but it has had no effect.
So what actually happens to the SPI in this chip when a timer interrupt is triggered?  As it's clocked independently from the main CPU, and just shifts bits in/out of a shift register, surely it should be unaffected by interrupts.
It's doing my nut, so any pointers would be most welcome.


texts:
I am getting my head around the process of multiplying two Qm.n numbers, and producing an answer of the same width.

As an example, I will pretend I have an 8 bit Q2.5 number. I understand that this format can represent a number in the range -4 to 3.96875.

I understand that multiplying two 8 bit SLVs results in a 16 bit SLV, I'm just not sure what each bit means in this 16 bit result.

Here is my algorithm:

multiply the two 8 bit SLVs, to get one 16 bit result
shift the result left by the number of fractional bits, 5 in this case
assign the lower 8 bits as the result

Is there anything more to it than this? Why do the number of integer bits not come into it? Here is a function I've written to try do this:

function qmult(a : signed; b : signed; n : integer)
return signed is
    variable tmp0 : signed(a'length * 2 - 1 downto 0);
    variable tmp1 : signed(a'length * 2 - 1 downto 0);
    variable ret_val : signed(a'length - 1 downto 0);

begin
    tmp0 := a * b;
    tmp1 := tmp0 srl n;
    ret_val := tmp1(a'length - 1 downto 0);
    return ret_val;
end qmult;

Two main questions to conclude:

Why is there no such function in numeric_std if it is this simple?
From my understanding, if you are unsure of the Q format of two numbers, then is is impossible to get a proper multiplication result (you don't know the fractional bits, so step [2] of the above algorithm won't work) or is there a hole in my understanding?


texts: How do I calculate how large my battery's voltage needs to be to power my robot?

texts:
I'm building a robot and need to select a battery. I will be powering 3 12 V motors, a 5 V infrared sensor, an Arduino (input voltage of 5 V), and a couple of other electronic devices ranging from 3.5 to 7 V. How do I calculate how much voltage my battery needs? I'm not too familiar with how electricity works so I'm clueless.

Do I need to only get a battery with a voltage as high as my robot's highest voltage component?


texts: Input inductor ripple current of the buck regulator?

texts:
This is a buck converter circuit I am analyzing:

Here the input voltage is 5 V and output 3.3 V.
I am interested to calculate following parameter,

  Input Inductor peak current

I know the basic equation for inductor ripple current is:

Q1) Can I use this formula for calculating input ripple current?

Q2) What will be the case if the input inductor is replaced with ferrite baed? I mean how can calculate the input ripple current?


texts: Why can you feel voltage when ungrounded

texts: I regularly test for voltage with my fingers. When wearing boots and touching nothing but the live wire, Why can I feel tingling on a live wire. It's not a shock, as I'm not grounded. I used to touch thumb to ground and finger to wire to test it. (Do not try this at home!!)That is until I figured out they tingle, when live, and I'm ungrounded. I still do it. It's easier than getting the meter. I've never been shocked this way other than through finger and thumb method. Please no safety lectures. Been doing it for 30 years. Never been shocked except for the finger thumb method (that is the point of that one. to direct the current from finger to thumb)


texts:
The fuse of this guitar amplifier blows.
Changing the output transistors had the amp working for a while, but then after a while the fuse blew again.
The output transistors that were changed are new.  The configuration based on the schematic here seems to be a Darlington style push pull B class amp output (correct me if that is wrong) and that all seems to be okay.
From what I understand this problem with the fuse blowing could also be the zener diodes, is that correct?  If so while I am at it, is it recommended to change the filter capacitors as well?
One other thing. For draining the filter capacitors, is the cement type 2k ohm, 10 watt resistor on the terminals necessary, or is that needed for only tube guitar amplifiers?


texts: How do I measure material specific(volumentric) capacitance

texts:
I'd like to test electric capacitance of different powders pressed into solids.
I want to know if my procedure is correct.
First I connect a wire between the material and a ground (ex. radiator) to discharge the material. Then I disconnect the wire and connect red terminal of the multimeter to the material and the other (black) to the ground (radiater).
I repeat the discharging procedure before every measurement.
Is this the correct and required procedure to follow?


texts: Why DDRx I/O bus frequency is half effective frequency?

texts:
I've already known that I/O buffer transfers data on both the rising and falling edges of the clock signal.

But it really confused me why I/O bus frequency is half of effective frequency.

For example, in DDR2-800.

Basic memory clock is 200 MHz.

Use 4n-prefetch technology.

So the effective frequency equals 200MHz*4 = 800MHz from the processor (CPU)'s perspective.

Here's the point.

Since I/O buffer transfers data 800M times per second on both rising and falling edge, we can infer that, each time when it works, I/O buffer transfers 400M times on one single edge.

Thus the work frequency = 400 M times / 0.5 second = 800 MHz.

By this equation, I/O bus frequency should be equal to effective frequency, both 800 MHz.

But on Wiki page DDR its said to be 400 MHz.

How to explain this?


texts: RS485 network failing on replacing SP485 chip with MAX485

texts:
I have created an RS485 communication network as shown below.

{PC}->[FT232->RS485](120 ohm)<----twisted pair(2 wires)------>(120 ohm)[RS485 -> MSP430]

Here PC acts as Master and sends the data towards MSP430.Data is a single 8 bit character.
I am using CBUS pins to put the RS485 chips in Receive mode and transmit mode by using the CBUS bitbang mode. After which I just send the character in serial format.

PC puts the RS485 chip in Transmit mode and sends the data.

On the MSP430 side, MSP430 puts the chip in Receive mode and waits for the character to receive.

On both sides I am using 120R termination resistor.

Now if I am using SP485 chip from EXAR (similar to MAX485) on both sides system works beautifully. No issues.

{PC}->[FT232->SP485](120 ohm)<----twisted pair(2 wires)------>(120 ohm)[SP485 -> MSP430]

Transmission of the character happens fine.

On the other hand
if I am using SP485 on the PC side and MAX485 on the MSP430 side, the system just fails to receive the character.

{PC}->[FT232->SP485](120 ohm)<----twisted pair(2 wires)------>(120 ohm)[MAX485 -> MSP430]

Please note that I haven't changed the circuit a bit , I have just dropped in MAX485 instead of SP485. The length of the transmission line is about 1.5 meters and I'm using termination resistors of 120 ohm on both sides.
I don't have any oscilloscope so I have connected an LED to the RO pin of MAX485 on the MSP430 side to check for reception of character.
When I send the character from the PC side the LED on the RO pin lights up indicating some data is coming but microcontroller refuses to acknowledge it.
I have also changed the MAX485 chip twice to check wheter it is the ic's problem.

Does any body have a solution for this ?


texts:
Is it normal for exposed (no solder mask) FR-4 to blacken during reflow? We're using a fairly ordinary profile with a max at 233C,  about 5 minutes total and only about 60 seconds above 200C. I realize FR-4 has a max temp of 130C+/- long term but I thought it should be able to take a reflow cycle.

It turns from bright green to almost black. It's darker in areas exposed on both sides, not quite so bad over large copper floods. Electrically everything is fine and the boards are functional, and the solder looks great down to 20 mil pitch QFNs.  The gold connectors and traces aren't discolored so I don't think it's something else on the board or in the oven fuming off, and there was no smoke.

Are we doing something wrong, or is solder mask simply mandatory for reflow on FR-4?

Edit:

The SMA connectors were hand soldered on after the fact and the white stuff is rosin from that (doesn't clean well off the blackened surface).


texts: How does risetime affect transmissionline effects?

texts:
How do rise and fall times affect reflection in a transmission line?

Reflection will occur with shorter lengths as rise times becomes shorter, does this mean risetime effects the wavelength of a signal?


texts: Why do we use a current source to relax tradeoff between voltage gain and voltage headroom?

texts: My textbook [Fundamentals of Microelectronics: B. Razavi] claims that in order to relax the tradeoff between voltage gain and voltage headroom, we use a current source in place of the load resistor. I don't understand the reasoning behind it, and neither has it been mentioned in the book.


texts: Why am I getting only 1.5V across the two terminals of the Load even though the Input voltage is 12V?

texts:
I have asked this question previously:
Why this pair of IGBT's died silently?

Some of those genius people advised me for not playing with high voltages, so I am here with another question with low voltages.

Please take a look at the circuit diagram below:

simulate this circuit – Schematic created using CircuitLab

Here is the Arduino code for turning ON and OFF the transistors to create an AC like signal.

int Phase1TransistorA = 3;
int Phase1TransistorB = 5;
int Phase2TransistorA = 6;
int Phase2TransistorB = 9;

int t = 50; //frequency
int p = 7; // pulse width
float GateDischargeTime = 0.000090f;

void setup()
{
  pinMode(Phase1TransistorA, OUTPUT);
  pinMode(Phase1TransistorB, OUTPUT);
  pinMode(Phase2TransistorA, OUTPUT);
  pinMode(Phase2TransistorB, OUTPUT);

}

void loop()
{
  for (int i = 1; i <= p - 1; i++)
  {
    digitalWrite(Phase1TransistorA, HIGH);
    digitalWrite(Phase2TransistorB, HIGH);
    delay(1000 / (4 * t * p * (256 - i)));
    digitalWrite(Phase1TransistorA, LOW);
    digitalWrite(Phase2TransistorB, LOW);
    delay((1000 / (4 * t * p)) - (1000 / (4 * t * p * (256 - i))));
  }

  for (int i = p - 1; i >= 1; i--)
  {
    digitalWrite(Phase1TransistorA, HIGH);
    digitalWrite(Phase2TransistorB, HIGH);
    delay(1000 / (4 * t * p * i));
    digitalWrite(Phase1TransistorA, LOW);
    digitalWrite(Phase2TransistorB, LOW);
    delay((1000 / (4 * t * p)) - (1000 / (4 * t * p * i)));
  }

  delay(GateDischargeTime);

  for (int i = 1; i <= p - 1; i++)
  {
    digitalWrite(Phase2TransistorA, HIGH);
    digitalWrite(Phase1TransistorB, HIGH);
    delay(1000 / (4 * t * p * (256 - i)));
    digitalWrite(Phase2TransistorA, LOW);
    digitalWrite(Phase1TransistorB, LOW);
    delay((1000 / (4 * t * p)) - (1000 / (4 * t * p * (256 - i))));
  }

  for (int i = p - 1; i >= 1; i--)
  {
    digitalWrite(Phase2TransistorA, HIGH);
    digitalWrite(Phase1TransistorB, HIGH);
    delay(1000 / (4 * t * p * i));
    digitalWrite(Phase2TransistorA, LOW);
    digitalWrite(Phase1TransistorB, LOW);
    delay((1000 / (4 * t * p)) - (1000 / (4 * t * p * i)));
  }
  delay(GateDischargeTime);
}

When I power up my Arduino and the Transformer, I thought, I should get LED strip working. But it doesn't. So, I checked the voltage across the two terminals of LED strip & I surprisingly got 1.5V instead of 12V. But just after the Rectifier circuit, I always get 12V. Then why am I not getting the required voltage across the two terminals of load??


texts: what is the voltage at the emitter of optocoupler 4N25?

texts:
simulate this circuit – Schematic created using CircuitLab

I am using the emitter voltage to drive another transistor. But voltage is zero.


texts: Basic common emitter circuit: voltage reduction at the output

texts:
I have a basic circuit for converting the 3.3V signal of a microcontroller board to a 24V constant voltage needed to control a device switched by voltage.

When I measure voltage at the output while the transistor is on, it's 0V, and when it's off I get 24V, as expected. The problem is, whenever I connect the output to the device while the transistor is off, the voltage drops to 14.8V. The voltage I'm getting seems to be dependent on the load resistor, smaller resistor gives less voltage drop, but increases current when the transistor is closed.

So the question - what causes the voltage drop and how can I avoid it? In my eyes, the resistor appears to be causing the voltage drop, but why is it not the case while the external circuit is disconnected? Is the only way to avoid this using less resistance at the emitter? Thank you.


texts: Should a piezoelectric sensor be modeled as a voltage or current source?

texts:
I know that one can do source transformation between current and voltage source. But take a DC power supply, and we usually model it as a voltage source because the voltage is constant even the load current varies. One could model it as a current source though using norton equivalent but that doesn’t represent the battery as a first degree model imao.

So in reality is a piezoelectric sensor by its nature more close to a current or voltage source?


texts: AC-coupling capacitors for high-speed differential interfaces

texts:
Can you explain me why and where I should put AC-coupling capacitors (usually around 0.1uF) on high-speed (1...5 GHz) differential serial interfaces (like SerDes for Gigabit Ethernet SFP modules)?

From what I have read, the caps should be placed as close to receiver pins as possible. Any legit references are welcome.

[CHIP1 RX+]--||-------------[CHIP2 TX+]
[CHIP1 RX-]--||-------------[CHIP2 TX-]
            0.1uF

[CHIP1 TX+]-------------||--[CHIP2 RX+]
[CHIP1 TX-]-------------||--[CHIP2 RX-]
                       0.1uF

Thank you in advance

UPDATE:

Got a reply from the IC manufacturer and it advised me to put the caps closer to the transmitter. So it seems that the actual place depends on how the particular IC works. A while ago, there was a completely opposite advise from another manufacturer.


texts: ICL7660 - Cannot provide stable negative voltage for audio amplifier

texts:
I built this audio amplifier mainly with UA741, ICL7660 etc. The VCC is 5 volt from USB.

But I found that the -VCC is quite unstable and this caused noise from speaker, which can hear even when music was played. And here is what my scope picked when nothing is played on computer from output (pin 6) of the Op Amp on the left.

And I picked the working frequency from pin 2 of ICL7660.

They lined up so nicely that's why I think it is the ICL7660 IC that caused the audible noise. Also, when music is played I found the -VCC become less negative significantly while VCC stays really stable.

So, can I improve this to get rid of that noise or must I make some other approach to fetch -VCC?


texts: Gray code usage in modulation constellations

texts:
When mapping symbols of various modulation constellations, Gray code is used such that - each adjacent symbol only differs by one bit.
Why do we want small physical changes in the signal to correspond to small changes in the symbol ?
Why not use binary mapping ?


texts: OLA adder and signed digit vhdl design problem

texts:
I have implemented the following online adder for signed digit using vhdl code
and I have simulated my design according to the example table shown in the figure attached
the problem is I am not getting the first result which is "10" for Z+ and Z+ and at some point a combination of XX and YY gives different ZZ

I also did not understand the happening operation since if I normally add the given bits
I do not obtain the same result

Is there a special conversion happening?!

an example of 11111111 - 11111111 to check whether the result is satisfying but I did not get a 0000 0000 result in the simulation, although I got the table result by simulating the same input values in the figure

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_textio.all;
use IEEE.std_logic_arith.all;
use IEEE.numeric_bit.all;
use IEEE.numeric_std.all;
use IEEE.std_logic_signed.all;
use IEEE.std_logic_unsigned.all;
use IEEE.math_real.all;
use IEEE.math_complex.all;

entity sD_adder is
port ( clk,rst : in std_logic;
         x_p,x_m,y_p,y_m : in std_logic;
         z_p,z_m : out std_logic
        );
end sD_adder;

architecture cSadd of sD_adder is
signal sig_xm : std_logic;
signal sig_zp, sig_zm : std_logic;
signal n_sig_xm, n_sig_ym, n_sig_w2m,n_sig_g2p : std_logic;
signal sig_g3, sig_h2, sig_w2m : std_logic;
signal sig_g2p, sig_g2m, sig_w2p : std_logic;
signal sig_z2p,sig_z2m : std_logic;

begin

    n_sig_xm <= not(x_m);

    FA_add1: entity work.add_sig
    port map( a => x_p,
                 b => n_sig_xm,
                 cin => y_p,
                 sum => sig_g3,
                 cout => sig_h2);

    reg_ff1: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>y_m,
                 q=>sig_g2p
                );

    reg_ff2: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>sig_g3,
                 q=>sig_g2m
                );

    n_sig_g2p <= not(sig_g2p);

    FA_add2: entity work.add_sig
    port map( a => sig_g2m,
                 b => n_sig_g2p,
                 cin => sig_h2,
                 sum => sig_w2p,
                 cout => sig_w2m);

    n_sig_w2m <= not(sig_w2m);

    reg_ff3: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>sig_w2p,
                 q=>sig_z2p
                );

    reg_ff4: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>sig_z2p,
                 q=>z_p
                );

    reg_ff5: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>n_sig_w2m,
                 q=>z_m
                );
end cSadd;


texts:
I see home sound systems rated at 300w, etc. but a 50w guitar amp is massively louder.
I assume that the first one is some useless marketing rating, but how are the two figures calculated to be so different?


texts: Can anyone make sense of my electronics instructor's common emitter design?

texts:
I think that I need to give a little back story, but I will try to make it short enough as possible. I have a 2 year degree that I describe as half hardware/ half software. What I mean by that is half electronics design and half programming and controls. I work in a field that uses the programming and controls skills, but try to keep up with the hardware side via hobbies. Anyway, I am going through some old notes and refreshing myself on them (this class was roughly 2 years ago). When I get to the section of analog amplifiers, I am lost on how my instructor came up with the design. He taught us what he calls the "Quick and Dirty" method of CE design. This uses some odd values such as "r`e" and "re", neither of which are RE (emitter resistance.) I am including screen shots of a spreadsheet that I made of the formulas that we were given in class to design CE amplifiers, a close up of the formulas that I can't understand where they came from, and a schematic that I made in gschem from the values given by running the formulas in the spreadsheet.

I found an old test in which I gave these answers and got 100% on it. So in his opinion, this is correct. We also did physically build these in class. I have the components to build this now, but no oscilloscope to verify.

So my questions are.

What are the "r`e" and "re" values and does anyone have any idea where they came from? I tried Duckduckgoing these and the only thing that I could find is emitter resistance (which as I said is neither of these values.)
Does anyone have any critiques or criticisms of this design method?
Can anyone recommend an excellent resource for learning proper CE and other analog circuit design?


texts: Why is the 74hc595 shift register causing a few pins to be lower voltage than others?

texts:
I've wired up two 74HC595s to a Photon from Particle. I followed this guide here for Arduino in how I wired it. The only place I deviated is to not put a capacitor on the latch pin.

It all appears to work. I can shift in two bytes in a row and they show up on my leds. My problem is one or two LEDS don't go as high as the others. Most of them measure at about 2.8 volts, but the few dim ones are at 1.8 volts. When I make all the pins low then the voltage is basically zero. So it seems like its trying to work but for some reason not giving full voltage.

I googled the 74HC595 and low voltage on pin and wasn't really seeing anything. This is happening on four different chips that I've tried so it must be some thing I'm doing wrong.

Below is a sample of the code I'm using:

#define bitSet(value, bit) ((value) |= (1UL << (bit)))

int dataPin = D6;
int clockPin = D4;
int latchPin = D5;

byte leds = 0;
byte leds2 = 0;

void setup()
{
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
}

void loop()
{

    leds = 0;
    leds2 = 255;
    updateShiftRegister();
}

void updateShiftRegister()
{
   digitalWrite(latchPin, LOW);
   shiftOut(dataPin, clockPin, LSBFIRST, leds2);
   shiftOut(dataPin, clockPin, LSBFIRST, leds);
   digitalWrite(latchPin, HIGH);
}


texts: How to find Base, Emitter, and Collector Voltage of a Circuit Demonstrating Miller Effect


texts:
Does anyone knows anything about -include_all_with_leaf switch of report_power command in the Synopsys Prime Time PX?
Someone suggested me it can be used to report dynamic power of separate nets and module inside a bigger module however my prime time have not this options. It is Prime Time 2016.


texts: Measuring and conditioning ignition coil secondary signal

texts:
I would like to measure and log the ignition advance timing angle of a vintage (70s) car. That is, mechanical distributor points (Kettering system), no electronic ignition, no RPM sensor.

For this, amongst other things, I need to monitor the signal that is sent from the ignition coil via the distributor points to spark plug #1, which determines the start of the ignition event for my purposes.

This signal is coming from the secondary side of the coil, and it's a periodic pulse signal in the order of kV. A single period looks like this:

Essentially, I want to convert the burn line region on the picture to a square signal of TTL level, which I can then read with a microcontroller.

This question and its answer explain a way how to do that for the primary side of the coil. As the secondary side mirrors the primary side, the concept of how to condition the input signal is the same: add low pass filtering, clamp the maximum and minimum voltage with diodes, buffer and convert to square wave with a Schmitt trigger.

However, the main difference here is that while the primary magnitudes are in the order of tenths of volts, the secondary ones are in the order of kilo Volts.

This brings a whole new set of considerations: obviously if not managed safely, it can pose a risk to the signal conditioning electronics, or more importantly, to the person handling them.

My experience is with lower voltage signals, and I'm assuming that there has to be more thought put into it than simply adding more attenuation (or optoisolation) to the signal going into the microcontroller.

This "Testing your ignition with an oscilloscope" document (coincidentally, the same vintage as the car) describes part of what I'm trying to do. On page 5, section Connecting the scope, a homemade pick up capacitor is coupled to the ignition wire. I'd like to think technology has advanced since the 70s and there is a more refined way of doing it. Furthermore, I do not often drive with tin foil wrapped around engine wires :)

How would I best go about:

Measuring the signal with a scope for testing/prototyping? Using a capacitive or inductive probe with built-in attenuation?
Permanently connecting, i.e. interfacing the signal to a microcontroller for monitoring purposes? I'm not asking for an actual circuit (*), rather a recommendation on the best way to physically connect the signal from the ignition cable to the stage that would condition it before going into the microcontroller, which would sit in a box in the engine compartment. Would that be the same answer as the oscilloscope question? I. e. capacitive/inductive probe? Or a regular resistive attenuator?

Thanks.

(*) although suggestions are welcome.


texts:
I am using an LM35 temperature sensor, which produces an output of 10.0 mV/°C. My circuit will handle temperatures up to around 90C

What can I do to check the LM35 output, and maybe fine tune it for accuracy? Are there any non hazardous easy to obtain chemicals that boil below 100C?

Or if I am forced to change the circuit to handle temperatures up to 100C would sticking the suitably waterproofed sensor in a pan of boiling water be sufficient to calibrate it?

Note

I am not looking for 0.1C accuracy, 0.5 will do.

Update

All interesting answers, thanks, but the simplest solution seems to be changing the circuit to allow 100C as a close enough calibration point


texts: Software Driver for custom AXI-stream IP in Xilinx SDK

texts:
I created an IP (say 'myip') using HLS with AXI-stream input and output. After connecting the IP to Zynq and exporting the bitstream to SDK, header file xmyip.h got generated which had functions like "Xmyip_LookupConfig", "Xmyip_CfgInitialize" etc with which I was able to initialize my IP 'myip' and use the function "XAxiDma_SimpleTransfer" to send AXI-stream input data to/from PL/PS.

But if I create any custom-IP (not HLS, but using Create and Package New-IP under tools), in the same name ('myip'), headerfile myip.h (not xmyip.h like in case of HLS) got generated. And also it has the following functions only

#define MYIP2_mReadReg(BaseAddress, RegOffset) \
Xil_In32((BaseAddress) + (RegOffset))

#define MYIP2_mWriteReg(BaseAddress, RegOffset, Data) \
Xil_Out32((BaseAddress) + (RegOffset), (u32)(Data))

There are no util/wrapper functions ("Xmyip_LookupConfig", "Xmyip_CfgInitialize") like in the case of HLS IP to initialize my IP core. How do I proceed in this case?

Regards


texts: How do I know what power supply to use with a circuit?

texts:
I've bought this tiny microcontroller called a Photon. It comes with a micro USB connector for powering the device (which I am connecting to my computer). I've read somewhere that the maximum voltage that can be applied to the pins of the device is 3.3V.

I'm an electronics newbie. The Photon did not ship with a power adapter. I want to connect it to a wall socket so that it is always on. I'm thinking of using a 5V 1A iPhone adapter, but how can I be sure this will not destroy the circuit?

In general, is there any way I can know what adapter is safe to use with a circuit?

Here is an image of my device:


texts: How to connect two buses with an offset in Proteus?

texts:
I am working with Proteus and learned how to use buses on this way for example:

I have successfully used buses on this way. But now I want to connect two buses, lets say I have bus A[0..31] and bus B[0..31] both of 32 bit, I want to connect bus A with bus B but with an offset, for example, connect bit 0 of bus A to bit 2 of bus B and so on. Is that possible?


texts:
I am (for educational and research purposes) trying to replace diodes with MOSFETs in a rectifier of a conventional automotive alternator (12V).

Before I proceed with hardware implementation, I would like to learn as much as possible about rectification itself and also synchronous rectification. I would like to know which parameters (hardware and software) affect parameters like efficiency and similar. I would also like to study how different MOSFET timing affects the rectification.

Can somebody suggest a good simulation software for a start? Also any advanced literature would be welcomed.


texts: Lossless Transmission Line Length vs Rise Time

texts:
I am trying to answer the question - Does a signal's rise time increase with the length of a lossless transmission line? - using LTspice simulation. Some references say that lossless transmission line does not degrade the signal. Does it mean the rise time remains the same? Intuitively, it seems to me that the rise time should increase as the length increases.

I tried two cases. Case-1 is with LTspice T-Line model and Case-2 is with distributed LC model. In each case, I simulated with four cascaded T-Line models, each having 250ps delay, to give a total of 1ns delay. In Case-2, each "T_100" component has 100 LC segments (L = 0.125nH and C = 0.05pF). Rise time was set to 10ps.

Case-1 results in signal being delayed by 250ps per T-line with no appreciable change in rise time. While Case-2 results in significant increase in rise time along with 250ps delay per T-line.

I can't seem to figure out which one is correct. Attached are the LTspice schematics I used.


texts: Data transmission through the human body

texts: As we all know, data can be transferred through cables using electrical pulses transferred into binary codes. My question is, is it possible to transfer data in a similar manner but through the human body? Basically, can we act as a cable? The answer I am looking for is if it is theoretically possible or not?


texts: I need to provide uniform intensity or uniform spread of light using this LED in a particular area(Small region). I have read about diffusers such as engineered diffuser, ground glass diffuser, Light shaping diffuser etc. Which is good for my project? Which diffuser can provide highest efficiency?Small region means the dimensions are length x width x height : 5cm x 5cm x 3cm(rectangular box). Sample is placed at the bottom centre of the box and led is placed 2.7cm away from my sample at the height of 1.5cm


texts: Bias Input Current Compensation for Instrumentation Amplifier

texts:
What is the motivation to choose R1=R5=5k6 Ohm?
If they are for bias current compensation and both OP Amps have same Bias input current, 10k should be taken in my opinion to eliminate common mode offset at the output...LTSpice Simulation gives same result. So why 5,6k ?


texts: How PCI Express Hardware Interface communicate with device core?

texts:
I'm currently reading the book which name is "PCI Express System Architecture" and i need some answers;

1.)How PCI Express Interface sends TLPs(transaction layer packets) to device core(suppose that device is GPU)?Does PCI Express Interface raises a hardware interrupt?

2.)How Pci express device core interpret these packets?

3.)How long time needed for the next packet transmission?How the receiver and transmitter agree when to transmit and receive packets?


texts: Is it a good choice to use mbrb1545ct schottky for the 5 MHz signal clipper?

texts:
For my application, I need to clip 5 MHz(max) signal to stay within ±0.5 V. I selected two of mbrb1545ct Schottky to clip my signal. I selected Schottky because I think they are faster to turn on and has faster recovery time so they would be really good for clipping highspeed signal.So, far in the simulation this diode clips ±6 down to approx. ±0.5V successfully.  However, I am not sure if the selection of this particular diode is overrated or underrated for my application.

If this diode selection is overrated then what is the best diode type I should go for. If not then what is the best diode I should use.

mbrb1545ct datasheet:
http://www.vishay.com/docs/88670/br15xxct.pdf


texts: Why resistance of load resistor determines gain of common emitter amplifier?

texts:
Most schematics I saw take output signal from collector, not from load resistor. So why we are calculating gain by dividing load resistor by emitter stabilizer resistor (or re - equivalent dynamic emitter resistance)? My logic tells me that the bigger load resistor would be, the more voltage it will steal from transistor itself, and this way will decreases gain in voltage. But in reality totally opposite thing happens.

This confuses me greatly and inhibits my attempts at understanding how amplifiers work.


texts:
JLCPCB 4 layer pcb stack mentions a copper core as the image attached.
Is this a error or the layer 2 and 3 are wittingly in short?
This image makes no sense...
Taken from: https://cart.jlcpcb.com/impedance?_ga=2.35895136.1315427483.1592868937-1547839306.1592059153


texts: Mathematics in selection of RC time constant for an envelope detector for AM

texts:
Let the capacitor be charged to voltage \$ V(t_0) \$ at \$ t=t_0 \$ and then start discharging. At time \$ t(>t_0 )\$, the delayed capacitor voltage is $$ v(t)=V(t_0)e^{(- \frac{t-t_0}{RC})} \tag 1$$

  The rate of change of \$ v(t) \$ AT \$ t=t_0 \$ is
  $$\frac{dv}{d(t-t_0)}|_{t=t_0}=-\frac{V(t_0)}{RC} \tag 2$$

My doubts:

When they are saying rate of change of \$v(t)\$ , why have they
differentiated \$ v(t) \$ with respect to \$ (t-t_0)\$, why haven't they differentiated with respect to \$t\$ and then subtituted \$ t \$ with \$ t_0 \$ , which gives the same answer as shown: $$\frac{dv}{dt}=V(t_0)e^{\frac{t_0}{R_C}}\frac{d}{dt}(e^{-\frac{t}{RC}})$$

$$=V(t_0)e^{\frac{t_0}{RC}}e^{-\frac{t}{RC}}(-\frac{1}{RC})$$

$$=>\frac{dv}{dt}|_{t=t_0}=-\frac{V(t_0)}{RC} $$
How to differentiate \$ v(t)\$ w.r.t \$ (t-t_0)\$. I am particularly confused about this because of the component \$ V(t_0) \$ of eq \$ (1) \$. Should I consider it a constant or should I consider it a variable as I am differentiating \$ v(t) \$ with respect to \$ (t-t_0)\$. In other words how to do this differentiation?


texts: Connect 5V straight to resistor straight to ground

texts:
I'm very new to electrical engineering in general and picked up an Arduino recently.  I have a couple questions:

What will happen if I short 5V/3.3V/Digital pin output directly to ground?  Will it damage the board or does the Arduino board have protection against it?
If the above causes damage to the board or is bad practice, can I put a resistor between the power and ground to fix it?  If so, how many ohms should the resistor be?


texts: I mixed VDD and VSS plane in a 4 layer PCB - Does it matter?

texts:
I made a 4 layer PCB according to a recommendation from this datasheet

https://www.ti.com/lit/ds/symlink/dp83848-ep.pdf?ts=1613467684339

Signal
Ground
3.3v
Singal

But instead, when I notice how the PCB was actully made, it was:

Signal
3.3v
Ground
Singal

Is this OK, does it matter? I mean, signal is signal, right? The ethernet Phy will not get noise from the 3.3v signal? I'm using both the bottom layer and top layer for signals, but most top layer.


texts: Help Identifying this socket / connector FFC / FPC

texts:
I am trying to identify this socket connector for an FFC / FPC. Ideally, I'm trying to get a breakout board, because I want to utilize the existing routed flat cable and connector on one end, and break it out on the other end to a custom board.
It is a 41 pin locking connector, pitch appears to be 0.5 (0.4878 is as close as I could measure). Cable is a 20706 AWM 105C 60V VW-1.
The breakout board is functionally, what I'm really trying to get at here. I appreciate the help!


texts: Problem calculating winding temperature in a brushed DC motor

texts:
I'm building a rig for measuring pull out torque for stepper motors, and am looking at dynamic braking and plugging of a permanent magnet DC motor which will be used to apply a variable braking torque.

My first step has been to go through the maths to be certain I understand the relationship between torque, speed, power temperature etc. correctly. So, I found a decent motor datasheet:

https://www.maxongroup.com/medias/sys_master/root/8833416495134/19-EN-136.pdf

And set about trying to replicate the torque vs speed at 150 W, and safe continous operation boundary (red area adjoining white area) lines shown below, using the figures given in the datasheet for this motor (Maxon P/N 148877) and the equations I know for these things.

I had no trouble creating the 150 W assigned power rating line, my result matched the line in the datasheet. However, I cannot do the same for the continous operation boundary line so there must be a gap in my understanding somewhere.

What I expected was that any point along the red/white boundary represents a torque and RPM condition which would calculate out to a winding temperature of 155 degC given an ambient temperature of 25 degC

Here's my working so far:

1) Chose a convenient point on the graph where the red area on the left meets the white area on the right. Measured RPM and torque at that point.

Torque (T) = 150 mNm, RPM (N) = 12000

2) Calculate the motor current, Im:

Kt = 60.3 mNm (from datasheet)

Im = T/Kt
Im = 150/60.3 = 2.49A

3) Calculate power dissipated in motor resistance:

Rm = 1.13 ohms (winding resistance, from datasheet)

P = I^2R = 2.49^2 * 1.13 = 7 W

4) Calculate temperature rise in winding

Rth1 = 1.9 K/W (Winding to motor case, from datasheet)

Rth2 = 4.7 K/W (Case to ambient, from datasheet)

Temperature rise = (Rth1 + Rth2) * P

= (1.9 + 4.7) * 7 W = 46.2 degC.

Add on the 25 degC ambient to get 71.2 degC

Problem! My result is 71.2 degC, when I expected 155 degC.
What did I do wrong?

I tried another approach...

Um = (I * R) + E

Where Um is motor terminal voltage, I and R are current and motor resistance, and E is back EMF.

Where E = RPM/Kv, where Kv is the Speed constant, in this case 158 rpm/V

E = 12000/158 = 75.95 V

So

Um = (2.49 * 1.13) + 75.95 = 78.76 V

And Ptotal = I * V = 2.49 * 78.76 = 196.2 W

Pmech (mechanical power to load) = Torque * (2pi/60) * RPM = 0.150 * (2pi/60) * 12000 = 188.5 W

Power dissipation I then make as Ptotal - Pmech = 196.2 - 188.5 = 7.7 W (oddly, slightly higher than previous calc, but why?)

Making winding temperature rise (1.9 + 4.7) * 7.7 = 50.82 degC + 25 degC ambient = 75.82 degC. Prety much the same, still a long way off 155 degC!


texts:
I've gone through two of my text books and consulted my teacher but nothing seems to clarify my doubts.

The two versions of race which I've been taught are -

When the S and R inputs of an SR flipflop is at logical 1, then the output becomes unstable and it is known as race condition.
When the S and R inputs of an SR flipflop is at logical 1 and then the input is changed to any other condition, then the output becomes unpredictable and this is called the race condition.

Which one is right? Or, are both of them wrong, if so, what is actually race?


texts:
I am using PCB soldered relay to switch 8-10A 220V appliance. Out of curiosity, I tried to visualize the EMI being radiated from arc sparking. I attached the GND to Neutral pole of proble and kept the measure tip of 10x probe near the body of relay. I used arduino to switch on/off the relay. On for 200 ms and Off for 800 ms and it continued.

Here are the graphs I received:

In second one, I am getting peak to peak of around 1V. Should I be worried? This relay will be on the same board as a microcontroller (Atmega328P). I have a nice ground plane on the PCB and in real case, I won't be switching as frequently.

One more question - If I have freedom to choose thin traces (10-16 mils) or wide traces (20-30 mils), what should I go for in order to improve noise resistance of my circuit?

A while back, I got an idea (which might be useless). How about making metal casings the size of relay and cover the relay with that and ultimately ground the metal casing. It should block majority of EMI which might disturb the micro-controller. Alternatively the micro-controller can be covered with a metal casing in the same way.


texts: Discretization Using ZOH, FOH and Tustis bilinear Transformation

texts:
I am very new to this forum, so excuse me if i do not write the equations properly. And I'm pretty new to DSP too, so this might be very basics for most of you, but it's pretty complicated to me.

I need to discretize a PT1 filter:

\$T\frac{dy(t)}{dt} + y(t) = u(t)\$

I need to discrtize this using ZOH, FOH and Tustins bilinear transformation.
I need to apply this filter to my signal, using a for loop( yes i have Fc, Wn).
I know this can be easily done in Matlab. but i wanna understand how it's done by hand.I could not understand anything from google.

Any leads would help me.

Edit1 @JonRB: Matlab Script:

% define a continuous-time first order low-pass filter in state-space
% notation. differential equation of the filter:
%  T * y'(t) + y(t) = u(t)
% -> State-space notation:
%  x'(t) = -1/T * x + 1/T * u
  % -3dB cutoff frequency: 100 Hz => omega_c = 2 * pi * 100 rad/s
% => T = 1 / omega_c
f_c = 10;
T = 1 / 2 / pi / f_c;
filt_cont = ss(-1/T, 1/T, 1, 0);
enter code here
% sampling period
Ts=
% discretization of the filter
filt_discr_zoh = c2d(filt_cont, Ts, 'zoh');
filt_discr_foh = c2d(filt_cont, Ts, 'foh');
filt_discr_tustin = c2d(filt_cont, Ts, 'tustin');


texts: Interfacing 3-5V power source with 3.3V SD-card

texts:
I'm trying to find a reliable way to connect my nRF52840 BLE-module to a 3.3V SD-card. The application is going to run on a lithium-ion battery and power is extremely budgeted.
The nRF52840 module can be powered in high-voltage mode by a supply between 2.5V and 5V and internally down-regulate that, BUT there is a 0.3V voltage drop. This means that the 3.3V will start drooping when the lithium-ion battery reaches 3.6 volts.
There is a solar-charging IC in my circuit (bq25570) which has a built-in configurable buck-regulator but that too has a voltage-drop of 0.2V, so the 3.3V will only be maintained until 3.5V.
I've been looking into buck/boost converters to regulate the voltage of BLE-module and SD-card to 3.3V, but seeing the poor efficiency at low currents (the nRF52840 consumes about 10uA when sleeping) I'm afraid battery-life will take a huge hit. I could only connect the buck-converter to the SD-card but when the battery is almost empty, the nRF52's SPI-lines will only be able to deliver up to 2.7V. What would be the most straightforward way around this?


texts: So I want to build a little "setup" with a led strip, using an arduino and a seperate psu to power the led strip. The psu outputs 12v 5A dc. Before I start connecting anything and might hurt myself, is the output of the psu deadly? I want to connect the the psu to the led strip through one of these: http://www.gearbest.com/diy-parts-components/pp_530107.html?. Any help would be highly appreciated. (Not very known with electricity)


texts: Adjusting voltage to non-dimmable LED lamps

texts:
Some commercially available LED lamps are considered non-dimmable.   Traditional phase-control dimmers don't work well with them.
Would the behavior of such lamps be different if a full sine wave AC power source, at a lower voltage, were supplied? I.e. could dimming be accomplished using a variac?


texts:
I have a Piezo buzzer that has an internal transducer so is able to take 24VDC and work. This one has a continuous sound. Just a beeeeeeeeeeeeeeeeeeeeeeeee...

I have a 24V output that needs to power an alarm sound (has to be piezo). The alarm has to be On/Off, a beep beep beep. Not particularly concerned about the exact frequency, or sound, or even how long the beep and pause is for. Just has to be a beep, and preferably customizable if required.

I thought of using an ATTiny but then I need a switching regulator to provide 5V to the microcontroller, and then another power transistor to run the buzzer. That makes 3 fairly large components (footprint is important) and the price goes over £10. I thought of 555 but definitely, the footprint is too large because even the 555 won't take 24V.

I cannot for the life of me figure out how to make the buzzer switch on and off, like a slow flip-flop, or PWM maybe, without using a microcontroller.

By the way, THIS and THIS is exactly what I am talking about. I will definitely use these for my application, but I need to figure out how to make a continuous one pulse. Or even better, how to take just a regular Piezo element (without internal transducer) and get any frequency I want out of it, with as few components as possible. I can do it with an ATTiny as mentioned above, but running it 24V introduces two additional components.

I highly appreciate any help I can get.


texts: Why do we calculate input/output resistance?

texts: I am learning about MOSFETS and one thing keeps me troubled. Why do we calculate input/output resistance of a mosfet when we try to amplify signals and construct small signal models. It seems pretty useless thing to do. I do not see any point in doing that. Can you explain why we do this and what does it mean that let's say that the transistor has low output resistance? Thanks in advance.


texts: Physics behind signal reflections and series termination

texts:
I have been looking for cause of signal reflections in transmission lines. Everywhere it is concluded that the reason is impedance mismatch. I can understand if the impedance changes in the path of the signal travels, then reflection will occur, but what I could not understand is the physics behind it.

How does including a series resistor of the characteristic impedance suppress the reflections, since the direction of reflected voltage is opposite? Does it mean the point at which the impedance changes becomes high in potential or anything else?
Can anyone give directions to understand the physics behind this?


texts: Decoding an unknown serial bitstream that does not fit 8-N-1

texts:
I am looking at an RS-485 signal using a scope and an analyzer (saleae). This is running a mystery bus (see below for more information). I would like to know how to fix my frame errors. I can't begin to decode the protocol until I am reading the bits correctly.

7-E-1, LSB first

8-N-1, LSB first

Manchester 7bit

I have tried 40 or so combinations and nothing comes out without frame errors.

Other Information
The alcom bus runs at 62.5kbps over RS-485 and supports up to 112 or 113 nodes. The master is always sending out packets over the bus to the slaves. The slaves node address is set with dip switches.

The physical layer is 2 wires with 150 ohm terminating resistors. This bus is used with the DeLaval Alpro system. The vendor is not helpful and provides no information. I have looked at the slave node boards. The chips all have varnish on them, so are very difficult to decode.

The packets all start with OxAA (or 0x55, depending on frame errors issue). I then assume there is a node addressing, data, and checksum.

Because of the bit rate I initially thought it was Profibus DP, telegram format does not seem to match.

People in the past have tried to figure out this same problem in 2010 and 2015.

Alcom is a Netherlands based company that seems to work with CAN Bus, etc. So maybe they initially designed the bus, hence the name.

My motivation for doing this is I want to read one specific node's telegrams. This node is an RFID reader and I want to see if the node is miss reading RFID tags (I highly suspect this to be true).


texts:
While reading through this page I came across following info:

"For accurate reconstruction using sin (x)/x interpolation, your oscilloscope should have a sample rate at least 2.5 times the highest frequency component of your signal. Using linear interpolation, the sample rate should be at least 10 times the highest frequency signal component."

I could not understand why is there so big difference in sampling rate if the interpolation type is changed from one to the other?


texts:
I was trying to design a simple 3rd order low pass filter by cascading 3 first order low pass filters along with an amplifier at the end. The transfer function is straightforward:

$$
H(j\omega )=4\bigg(\frac{1}{j\big(\frac{\omega}{\omega_c}\big)+1}\bigg)^3
$$

where $$\omega_c=\frac{1}{C_f10k\Omega}$$ is the cut-of frequency. Thus when I want to make the filter have a cut off frequency at 1KHz I simply replace values and figure out Cf:

$$
C_f=\frac{1}{2\pi\times f_c\times10k\Omega}=\frac{1}{2\pi\times10^3\times10\times10^3}\approx16nF
$$

However the circuit below when simulated gives me a cut-off frequency of 500Hz. What am I getting wrong?

simulate this circuit – Schematic created using CircuitLab


texts:
Inspired by the idea to minimize the return path, I am thinking about the two possible improvements of the design, how to connect the signal source to consumer. In short, there are lots of high frequency lines going from the source to consumer and then sharing the return path into the ground. I have produced a separate example because my original circuit is too complex. Let's assume we need the following connectivity:

The source that is an IC chip puts the VCC voltage in pulses at high frequency into consumer. The consumer that is the LED array passes the current through into the ground. I assume, the ground should be the return path for the signals.
Seeking to minimize the length of the loop, the two ideas come to mind:

Put large copper area into the second layer that is now ground only. I have seen multiple recommendations in the literature to do so. However I am not sure about the exact shape of the "return path" of my signals. If they choose to go the shortest way right to the ground pin of the chip, this will not be the smallest area covered by the signal loop.

Provide individual ground routing for the signals in the parallel layer. In this way I hope that the return path would largely match the signal path on the opposite layer. However it cannot go all way together because they still have the different destination.

Here is the routing of the three possible designs (left - the current version, middle - ground plane, right - individual ground that still obviously must join somewhere).
Which of these designs (left, middle, right) would provide the least inference?


texts: How does a switch mode power supply without a control IC work?

texts:
I have a very old computer (1987) that all of a sudden shut down, followed by a bang (blown fuse) a couple of seconds after that.
Here's a look at the PSU

Upon opening the PSU I noticed the following

Fuse blown violently
Power transistor completely shorted (all 3 legs)
Schottky diode shorted (package with 2 diodes , one diode shorted)
An NPN transistor with surface damage (and also not passing the multimeter-diode test)

After replacing all those parts the fuse is no longer blowing, but I am getting zero DC output on all rails.
I'm not really comfortable with doing measurements on the AC side of the PSU when it is switched on, so I am wondering what other kind of diagnostics I can do.
I read that a violently blown fuse most likely results in lots of failed components (see above) and further diagnostics include :

Checking the transistor
Checking the bridge rectifier and other diodes on the PCB
Checking some resistor values
Checking capacitors
Checking control IC

Not visible in the picture above but beneath the heatsink of the power transistor is a 2SD667A NPN transistor that had some damage. I replaced that one with a BD139 (due to the lack of a proper replacement)
Here's a better view of what is beneath that heatsink (removed the bulk caps)

However I could not find a controller IC to drive the power transistor on this PSU.
I guess I always (wrongly) assumed there would be a control IC to turn on / off the transistor. Not knowing too much about how this could be achieved using discrete components, can somebody help me understand how such a circuit would look like and how this could have been implemented in this PSU ?


texts: Making a 1m sized 16x24 screen so that the picture is recognizable

texts:
I'm thinking about making a flexible LED screen with 16x24 LEDs.
I want the screen to be 1m wide so it will have big gaps between the LEDs.

Because of the big gaps I think the image may be unrecognizable.

How do I solve this problem? Use bigger LEDs? some kind of diffusers with small LEDs?


texts:
I am trying to understand memory transfer rate while working with DDR3. I am getting different numbers.

For example, in Wikipedia https://en.wikipedia.org/wiki/DDR3_SDRAM DRAM has peak transfer rate from 6400 MB/s to 17066MB/s depending on the clock.

While looking at different FPGA development boards I see data in Mbps and it is completely different from the ones in Wikipedia. For example this product offers 1050Mbps at https://store.digilentinc.com/zybo-zynq-7000-arm-fpga-soc-trainer-board/.

For me, 1050Mbps is 131MB/s. Where is the error?


texts: Regarding the design of a basic voltage divider

texts:
I've just entered the fabulous world of circuitry and was wondering about the design of voltage dividers. I understand their function and formula quit well, but was wondering about the actual structure of the voltage divider.

In the picture below, there are two resistors and Vout is between R1 and R2.
I was wondering why Vout is placed exactly there as opposed to after R2 and if the placement would actually make any difference in Vout?


texts: How to properly remove an op-amp from this signal amplifier circuit?

texts:
This is a pulse shaping circuit, that has three amplifiers: U1, U2, and U3. The shaping amplifier is the 8pin component far right. Both U1 and U2 serve as "coarse gain," which are activated by the switch in the bottom left of the diagram. U3 controls the polarity of the input signal, and is also activated by the switch in bottom left. I would like to remove U3 as I have no need for polarity switching.
U3 is connected to another switch, U7, which is boxed in blue along with U3. My first thought is to simply bypass the blue-outlined portion of the circuit. I would do this by connecting the output of U2 to the R7 and shaping amp input, both boxed in black. I imagine this is not the "proper" way, and would require a few components to properly deliver the output of U2 to the shaping amp input.


texts: Ethernet communication between 2 controllers

texts:
I'm working on establishing communication via ethernet between 2 microcontrollers.

Its a stand alone system. Controller1 will interface with the user via a keypad. Controller2 will be interface with a couple of motors(via drivers).
When Controller1 receives keypad presses it will request controller2 to carry out certain motion tasks.

The block diagram will be(standard circuit):
    Controller(with an in built MAC) --- PHY --- transformer -- RJ45 and the same repeated on the other controller board.

What I'm trying to understand(from the firmware perspective) is whether I really need to get into all the abstraction layers (upto http), will my controllers need an i/p assigned, etc.

Assume that these are the only 2 devices interacting. Is it sufficient to have the code working up to only the data link layer. i.e I configure the MAC registers, each controller having its own MAC address and the communication is done via the ethernet frames with no higher level layers involved.

Working with ethernet for the first time so apologies if there are any basic errors in the query. All the forums mention using tcp/ip stacks, ip addresses but its not clear to me why that is needed.


texts:
I want to use the following dual diode for the return path with a fuse.

The diode is dual with each diode rated 25A, the cathode is the same, which means I have to connect it like in the figure? Do I have to add something more?

EDIT 1

The purpose is to protect a motor controller as explained in this datasheet, pp 10.

simulate this circuit – Schematic created using CircuitLab


texts: Is it logical to use pull-up resistor on SPI Clock line

texts:
I am just wondering that for Master SPI-CLK line is Output line while for Slave device it's input, is it logical or necessary to put the pull-up resistor on the SPI CLK line. What happens if we don't put pull up ? I am using 8-bit Microcontroller of PIC series and using spi interface for communication.

I am sorry for such basic question but i need to clear my doubt. Thanks


texts:
I have a 16 V lithium battery with 60 Ah.
How much energy can this battery store?

My home specifications are: 220 V mains and I have a contracted power of 6.9 kVA.


texts: Are some mechanical relays sensitive to their orientation?

texts: I've heard several cases where individuals burned out their motor start windings on inductor start induction motors. In almost every case, they've had their switch assemblies positioned upside down or in an odd orientation. Is it possible for an mechanical relay to stay open or closed due to gravity?  What else could cause the relay to fail to open or close?


texts: Identification: what type of connector does the pictured socket take?

texts:
The picture was taken off an equipment we are trying to connect to. Unfortunately the connector type was not specified in user manual.

The closest one I can find based on shape is molex 4 pin female connector, or 4 pin peripheral connector used to send power to CD/hard drive in desktops.The difference is, molex connectors have flat sides, while the socket in picture has curves around each pin.

Could anyone offer some clue?