texts: Why does the measured potential-difference between two poles of an AA fizzle out after 5 seconds?

texts:
I have some AA and AAA batteries that are sitting on my desk - I decided to test them before throwing them out. Some are Duracell "Duralock" brand, the others are Kendal "Super Heavy Duty - Pile Saline".

I recently bought a Fluke 115 multimeter, so I decided to use that to measure the voltage between the positive and negative poles of the battery.

I set the multimeter to DC V mode; when I attach the probes to the battery (red on the positive terminal, black on the negative terminal) the display reads 1.329 V for about 5-10 seconds, then the number suddenly drops to 0 V over about 2 seconds, then it stays there.

This happens consistently with the other batteries on my desk (the initial voltages are all around 1.3-ish Volts) except one, which stays at 1.329 V and never drops.

What is happening?


texts: Does a Guard Ring around a PLL loop filter make sense?

texts:
Should I guard a PLL loop filter against current leakage with a pour? If so, where can I connect the guard plane?

As an illustration: I use an IC in need of an external PLL-loop-filter connected to the charge pump (a MAX2769). The manufacturer recommends to use a C-R-C-network as follows: (the DNIs are not installed, the installed caps are silver mica type from Cornell Dubilier).

As you can see, there is a 1M (or 100M?) resistor to a net called PLL_FILTER_FENCE. This network is used to pour a plane around the components like this:
This pour is intended to minimize current leakage from the components. As you can see, space does not allow for a plane that also encloses the IC pad. The plane will also introduce an additional filter pole which should not affect PLL performance.

Will this be helpful at all, as there is no low impedance source to connect the guard to?


texts:
I have recently purchased a Halfords 12V calcium battery second hand off facebook. I was told it was about 6 month old ( it does look new ).

The problem is it will not charge using my trickle charger' that works fine for all my other batteries.

Do these new calcium type need some special charger?


texts: Hi, in following circuit how do i calculate value of inductors L1, L2, L3, L4. (Design equations for inductors)

texts: What will be the design equation to calculate values of inductors L1, L2, L3, L4.


texts:
This is an idea I have been toying with for a while and wanted to get an opinion. When I first heard about CAN-FD I thought it was going to be the answer to this problem. However most mid range microcontrollers do not have support for CAN-FD (LPC546 excluded). The STM32H7 does have support, but the cost of that microcontroller is far too high for most applications. There are some devices like the TCAN4550 and the Microchip version which are quite good, but not as flexible.

With an RS-485 transceiver and an iCE40 or other FPGA one can make a custom transceiver system. The idea would be to interface a microcontroller over SPI or UART to the FPGA. The FPGA would handle the actual protocol, which would be similar to CAN.

The advantages of such a system are:

Flexible system speed and cost (up to 48 Mbit/s)
Many settable addresses per device
Option for a multi-cast system
Not restricted to a particular architecture

My questions are:

Is the cost really worth it or am I just trying to reinvent the wheel here?
Can arbitration still occur at high speeds or are very accurate clocks needed?
Is there already a project like this out there that I just missed?

It might make for a great open source protocol that I would certainly be willing to put some effort into developing.


texts: Autonomously-powered (battery-less) wireless pushbutton

texts:
What would be a feasible approach/circuit-design to make a self-powered wireless pushbutton, assuming it is even realistic?

This is what I mean by each of the three terms:

Self-powered: Power derived only from the mechanical action of pressing the pushbutton
Wireless: Pressing the pushbutton makes an RF transmission (let us consider a case with peak current draw of 40 mA during the transmission)
Pushbutton: Any type of pushbutton I can get at a hobbyist store or even build myself, but not a pushbutton where I have to turn a crank to activate the switch ;)

I would like to set up a little "network" project in my home (indoors), with these pushbuttons located at various points, but would like to do away with any battery power source, hence I'm experimenting with the self-powered idea. After all, the pressing of the pushbutton does bring in mechanical energy that could be used, and moreover, the resulting RF transmission event will be the only time the circuit will be alive or need to draw current (of around 40 mA).

My broken thoughts so far:

I am considering using a capacitor/supercap that charges up during the mechanical event.
Perhaps I could use some method of harvesting (piezoelectric, gear-based, etc.) of the mechanical energy from the push.
I've noticed that there is this interesting chip that might be of use here: the LTC3588


texts:
I'm experimenting with waveform generation and I'm using the low-voltage op-amps mcp6002, powered by an arduino due with 3.3V, single supply (3.3V-0V).

The circuit i'm using is similar to this one (the op-amps are replaced with mcp6002, and the circuit is working as I describe)

For the "N-channel enhancement" FET module I use a ZVN420.

Now everything else in the circuit ( i.e. couple of DACS, another oscillator based on the MCP6002 that produces a triangle and a pulse) are very stable and working succesfully. But my two sawtooth oscillators are very sensitive to the ground and power connections. To make the sawtooth rise curve sharp
I have to touch the cables in the circuit. After some tries the waveform is perfect but in general very easily it stops forming the right waveform. (it becomes like a sawtooth - triangle).
Can someone guide me how to counter this situation? I have tried replacing all long cables with very small wires but this does not improved the behaviour. The breadboard is very good. I have tried adding capacitors for voltage buffering but I didn't noticed any difference.


texts: external crystal not working but internal clock worked normaly in PIC18F45K22

texts:
I have designed a PCB based on the PIC18F45K22 microcontroller. I want to use an external crystal (4Mhz crystal with two 22pF capacitors). I can successfully program the code but the PIC won't run. When changing the oscillator mode in the config settings to use the internal clock, it works fine.

The code that I'm trying to test is a simple blink LED code.

note that when the microcontroller didn't run, i couldn't enter to debug mode.

I have tried various values of caps but that didn't help. I noticed that bad soldering actually added some stray capacitance between the OSC1/OSC2 pins and the ground (measured using an RLC meter) so I tried lowering the value of the capacitors to 15pF.

I have tried various crystal (replaced the 4MHz, then tried a 16MHz crystal)  but that didn't help. I also replaced the microcontroller but nothing changed.

I have tried to make the exact same connection on a bread board and it worked normally using external crystal mode. I only poppulated MCLR, VSS, VDD, PGD, PGC and an LED with a series resistance.

I have redesigned the layout of the board, thinking its a layout problem with the crystal but that didn't help.

I have searched about similar problem but i can't find any helpful answer

part number of crystal: ATS040B-E
datasheet of crystal: http://www.mouser.com/ds/2/96/008-0309-0-32667.pdf

I just managed to make this board work... The ground plane that connects the capacitors of the crystal is connected to GND at one point as recommended by many application note... but there is a capacitor 100nF between this plane and +5V for decoupling... this was a mistake by the layout designer. I removed this capacitor and it worked. There is another one between GND and +5V near the PIC's pins as it should be.

still I can't understand why did this solve the problem...

I did test earlier to check if there is any AC voltage between this plane and GND of the PIC... and the AC voltage between this plane and +5V of at the micocontroller. It was about 5mV so I guessed it was OK...

Now the question is how the hell did this 100nF cap messed up the oscillator circuit to prevent it from oscillating!?


texts: Dead groups in 18650 li-ion battery - Negative 62Volt between B13 and B14 BMS wires?

texts:
I have an 18650 battery pack (12p20s) of which 2 parallel groups (12p) recently "died" (their current voltage is 0V or very close to 0 volt (1 of the groups is 0.0v and the other is 0.09v).
The issue was most likely caused by overvolting the cells since I ran the battery without a BMS for many cycles...
The issue: When I measure the 18650's using my multimeter (on the pack) I get 'normal'(expected values) voltages (the two dead cells groups measure 0 and 0.09Volt...the rest of the cells measure approx 3.65V average). Nothing unexpected here...
However, when I measure the voltages at the connector of the BMS's sense wires (the connector to which all wires going to the batteries in the pack, used for balancing/monitoring cells voltages) I get very weird values.
All values appear to be 'normal' apart from the voltage measured between B13 (which should be connected to the positive pole of the 13th series group) and B14 (which should be connected to the positive pole of the 14th series group). When I measure between B13 and B14 the value is Negative 62 Volts?! How can this be? A few days ago the voltage measured between the same two points was approx Negative 57Volts... Weird that it appears to change also...
My first thought was that some of the BMS wires must have shorted with each other or shorted somewhere on the pack... But if that were the case the wires would have gotten hot/insulation and probably wires would have melted away. It has been a few days since the 2 cell groups died and no such thing has happened (all wires cold, all insulation intact).
I have measured using 2 different multimeters, the same exact values.
Is there some way 'dead' cell groups could exhibit characteristics that would result in such measurements on my multimeter to be explainable? If so could you please explain how this weird voltage may be caused?

Here are the voltages I measured:
I measured the voltages on the BMS wires (the voltages of the different cell group and all appear to be approx 3.7volt apart from 3 exceptions:

B1 3.69V (first group connected to B- on one side)
B2 3.7V
B3 3.7V
B4 3.7V
B5 0.00V <-- dead
B6 3.76V
B7 3.7V
B8 3.7V
B9 3.7V
B10 3.7V
B11 3.7V
B12 3.6V
B13 3.6V
B14 -57,4V <-- how can this be so high, how has it not exploded yet?!
B15 3.6V
B16 3.6V
B17 0.09V <-- dead
B18 3.5V
B19 3.6V
B20 3.6V

If I measure from B- to B13 I get 44V
If I measure from B- to B14 I get -17V
Shorting the dead cells (I have only tried 1 by one, not both at the same time) does not significantly change the 'weird' measured values (might change by 0.2 Volt max).
If anyone has an explanation for this or a step in the right direction to finding out the cause I would be very interested. Thank you!


texts:
I have a microcontroller with USB Host, and I need to be able to programmatically power-down the USB peripheral. The reason is that I need to power cycle the USB peripheral to reset it (a necessary evil unfortunately).

The microcontroller simply has D+D- lines for the USB, and power is expected to be supplied by me, which I take from the 5V rail.

I thought I would use some variation of a TIP NPN to simply switch the 5V going to the USB peripheral, and control that with a GPIO from the micro - however, given that USB is designed to never have the data lines connected when the power lines are not - I no longer think this is such a good idea.

Can anyone suggest a simple circuit which would achieve what I'm trying to do? Or if my transistor approach is actually OK.

Thanks!

[EDIT]
This is the Microcontroller http://www.acmesystems.it/arietta
The connected peripheral is a CDC_ACM serial device.


texts:
I know that a Schmitt trigger is used to reduce noise in a circuit, but why does noise need to be reduced.

How does noise effect the overall circuit and what benefits do you achieve by reducing noise using a Schmitt trigger ?


texts: Forcing a Buck Converter IC to behave like a Boost Converter

texts:
I recently thought of a way to force the LM2596-ADJ buck converter IC to behave like a boost converter, just as a fun experiment. Let me explain the idea (I would like to get your opinions before I actually build it.)
This is the schematic block diagram of the LM2596:

Typically, Vin is connected to a fixed input voltage and an LC filter is connected to the switch emitter. If you look at the block diagram, you will see that the switch collector is connected to Vin.  By connecting an inductor to Vin, the output to ground and a diode between Vin and an output capacitor, the buck converter should behave like a boost converter, right?
I went ahead with this idea and simulated it on LTspice. I fed 9V to the circuit and configured the feedback resistors to get 15V:

And sure enough, it worked:

(Blue waveform: voltage across C2, green waveform: voltage across C4)

Then, I realized something about a boost converter and took a look at the voltage at Vin:

As you can see, the voltage at Vin periodically changes between 0V and close to 15V. This this because the switching action of the internal BJT connects one end of the inductor to ground when the switch is on. This also means that Vin, which is not only connected to the switch collector, but is also the input to power the chip itself, is periodically connected to ground. Logically, this should cause the IC to shutdown. In fact, the chip should shut down even before the BJT manages to pull the Vin pin all the way to ground, but that doesn't seem to happen in the simulation. It is as though there is a diode and capacitor at the input that keeps the control circuit powered during the on time of the switch and recharges during the off time.
Please let me know what's going on and what you think would happen if I built it on the breadboard. Will the chip keep cycling? Will it function as a boost converter? Will the chip fail?


texts:
In Xilinx Vivado IP integrator, I want to create a custom building block. The block need to be able to access the memory space (possibly external RAM) by itself.

The target function of the block can be described in the following steps:

I give the AXI-MM slave block two adresses:

0x????_???0: a base memory address, e.g. "0x0000_ABC0".
0x????_???4: an offset memory address, e.g. "0x0000_000D".

The block should will now automatically determine the resulting memory address ("0x0000_ABCD") and fetch the data from that memory location, e.g. "0x0000_0100". This data read represents a new memory address.
The block should now fetch data from that memory location (e.g. "0x0000_0005") and write it to AXI_MM address 0x????_???8.

p.s. I'm using 0x????_???x, as the AXI-MM base address depends on the settings in the IP configurator and on possible other connected blocks.

I haven't found any description of how a custom block should read from the memory. How should I approach this problem?

I'm using Digilent Zybo Zynq-7000 ARM/FPGA SoC Trainer Board.


texts: Effect of Quantisation of a Signal on the Estimated Spectrum

texts:
I have been applying the Welch Estimation technique to a signal in MATLAB to give a Spectral Density plot for frequencies from 0 to 0.5 the sample rate. I have two issues:

I have a peak at 0.25 for all my signals, is this likely a result of the estimation technique at its half the frequency range?
I have noted my signal is digitised, what effect does this have on the spectral estimation?


texts: How to read out a capacitive sensor, (CDC, CVC, TDC)?

texts:
What are the main principles for reading out a capacitive sensor? I read a lot, but I cant figure out what re the different options.
I think that an option is to convert the capacitance into a measurable voltage and the digitalise the voltage value. But what circuits or measurment principles are used as capacitance to voltage converter?
Then there is the option to integrate the capacitance into an oszillator circuit and to detect the frequency which is already done digitally. Is there also another principle to digitalize the capacitive value?
Is it possible to put these methods into categories?
Thanks a lot.


texts:
Using this question as a guide I've been trying to calculate some distances based on RSSI values that I see in our lab. I filled in all the variables with actual data or approximations where necessary (just trying to make sure I understand the math before worrying about having perfect data) and plugging it in to Wolfram Alpha to see if it looks like what I think it should. Here is my Wolfram Alpha equation so far, with values following the exact sequence described in the linked question:

$$d=10^{\Big(\dfrac{-60-(-94)-(-63)-10 \times 2.7 \times \log_{10}2450 + 30 \times 2.7}
              {10 \times 2.7}\Big)}$$

I'm assuming \$P_o=-60\$ based on some graphs in this study, \$Fm=-94\$ based on the "Received Sensitivity (Typical)" stat of the device I'm using to measure the signal, the actual measured \$Pr\$, \$n=2.7\$ (a good, but not perfect, room), and \$f=2450\$ (I picked that value from the range supplied by the aforementioned question, but of all the values it is the one I'm least sure about and not sure at all how much it affects the overall equation).

I hope that makes sense, I only have a distant familiarity with this type of analysis (not being an engineer myself). I know enough math to keep up, just need to be sure I'm putting the right values into the right places.

EDIT: I suppose I should state the actual question. Am I doing this right? The equation above works out to a distance of about \$3 \times 10^{14}\$ units which (unless we're measuring pico-inches or some such tiny amount) doesn't make sense. I assume this is supposed to give me meters.

For reference, here is the equation and explanation of variables from the question linked in the first sentence:

$$d=10^{\Big(\dfrac{P_0-F_m-P_r-10n \log_{10}(f) + 30n - 32.44}{10n}\Big)}$$

Where

\$F_m = \text{Fade Margin}\$
\$N = \text{Path-Loss Exponent}\$
\$P_o = \text{Signal power (dBm) at zero distance}\$
\$P_r = \text{Signal power (dBm) at distance}\$
\$F = \text{signal frequency in MHz}\$


texts: A basic question about output rate and sampling rate in serial communication

texts:
This is a very beginner question. And below is an arbitrary made up example:

Imagine you established communication with a USB device through your PC's USB COM port.

The USB device is measuring the voltage through it's analog input and then converting it to digital by its ADC. And through its port sending the 10-bit serial data to the PC through the USB cable.

Now the device has a sampling rate of 1kHz, i.e it takes 1000 samples of voltage per second.

And when I set the baud rates and the rest by using HyperTerminal and connect to the port, I can see 4 voltage readings per second as incoming lines.

My questions are:

1-) The analog sampling rate of the device was 1kHz, but I receive 4Hz per second. Does that mean the data is averaged? So does each received line in PC correspond to the average of 1000/4 = 250 samples' average?

2-) What is the 4 samples per second received by the PC called in literature? In data-sheets I cannot see a term called "output rate".


texts: How do Free-RTOS and mbed OS handle ethernet?

texts:
Do Free-RTOS and mbed OS poll for incoming data to be received (or use interrupts?)? If so, is there a risk that data to be received while the processor is handling another task (e.g. running a program) risks being missed?

Is received data then stored somewhere in memory, so it can be retrieved when a function such as receive(...) is called? I would imagine that receive(...) is simply returning data which the OS has placed in a particular memory location. Is this the case?


texts: Is this a proper way to connect a piezo speaker to MCU?

texts: Is this a proper way to connect a piezo buzzer to microcontroller pin? Is there anything that could be improved in the sense of robustness and power consumption?  How do i select D1?


texts: What's the use of the marked capacitor (C5 - Y cap 4.7 nF) in this offline switcher circuit? Won't the capacitance induce some ac noise in the DC voltage?


texts: HX711 : Inductor on supply line and feedback

texts:
I'm re-implementing the great HX711 breakout board from Sparkfun (schematics : https://cdn.sparkfun.com/assets/f/5/5/b/c/SparkFun_HX711_Load_Cell.pdf).

I'm trying to understand the exact role of the inductor (I think it removes high frequency noises but an explanation would be great).

The real issue I have with this circuit is:

Why is the feedback of the regulator measured before the inductor and not after?


texts: Wifi/BT on Realtek 8723 - Is FCC, CE certification needed for Wifi if we disable Wifi and use only Bluetooth?

texts:
I'm planning on importing a generic mini pc that comes with an onboard Realtek 8723 for Wifi and Bluetooth. We will need to get it FCC, CE, IC certified before we sell it in North America/EU.

Getting tested for Wifi and BT from a lab costs a several thousand dollars for each system (Wifi and BT). Since we do not intend to use Wifi at all, can I disable the Wifi in Firmware and get certified for Bluetooth only ?

The firmware in commercial product will also have the wireless disabled with no way for user to turn it on.

Thanks in advance


texts: Using analog switches with ultrasonic sensors, what to look for?

texts:
I am designing an anemometer for university project. I intend to use analog switches to switch between ultrasonic sensors. I use this circuit as my first stage - it adds offset to the signal and has high-pass filter. The input signal is centered around 0V I want to know if this could be a problem for the switch I am going to be using the signal not that large (tens of millivolts).

I have also read about charge injection and I learned that it is inversely proportional to the load capacitance I am not really sure if it's going to be a problem or not in this case.

This is the datasheet of the switch I plan to use : http://www.ti.com/lit/ds/symlink/ts3a5018.pdf


texts:
I'm trying to setup Timer0 on an ATTiny45 using the arduino-tiny core. TIM0_COMPA_vect works fine for prescalers 1,8 and 64, but 256 and 1024 cause the ISR to not fire. I am running the chip at 1MHz.

Setup code is as follows:

void setup()
{
  ADCSRA &= ~(1<<ADEN); //Disable ADC
  ACSR = (1<<ACD); //Disable the analog comparator
  DIDR0 = 0x3F; //Disable digital input buffers on all ADC0-ADC5 pins.

  DDRB |= _BV(PINB0); // Set Pin 5 (PB0) as output;
  PORTB &= ~_BV(PINB0); //Set it to low, just to be safe

  //cli();
  TCCR0A |= _BV(WGM01); //CTC Mode
  TCCR0B |= (_BV(CS02) | _BV(CS00)); //Prescale 1024
  TIMSK  |= _BV(OCIE0A); //enable CTC interrupt
  OCR0A = 243;

  sei();
}

fuses are:

low_fuses=0x62
high_fuses=0xD7
extended_fuses=0xFF

Any thoughts on why this might be the case?

Update: Not only do prescalers /256 and /1024 not work for COMPA or COMPB but they do not work for the overflow ISR either.  I don't really get it since according to table 11-6 in the ATTinyx5 datasheet, it supports prescalers /1, /8, /64, /256, and /1024 via the TCCR0B register.


texts: Possible to control a transistor by BC terminals?

texts:
I'm thinking about a strange working mode: the CB part is forward biased and trying to control EC current by CB current.
EB is reversed.
May it work?
Transistor is BJT.


texts: Can cutting electrical steel alter its magnetic properties?

texts:
Please forgive me in advance if this question is not appropriate here. If you think so - let me know and I'll take it down. However I am really hoping someone can share their thoughts!

I want to make an experimental transformer using standard, off-the-shelf U I laminated electrical steel sheets.  As a part of the experiment,  I need to form a gap in the core of a certain specific shape. I want to cut the sheets myself, but I am just wondering if cutting the sheets will stress the electrical steel so that its magnetic properties might be changed, reducing the efficiency of the transformer. Can anyone comment on this?

I was planning on cutting the sheet (0.5mm) with a hacksaw. Very low tech I know, but I don't have the money to get a custom core made...bad idea?


texts: Discrete toggle flip-flop simulation issue

texts:
I always wanted to have some ~100 MHz frequency divider at hand, and since I have some BC548's lying around I ran a quick Simulation with Pspice Student 9.1.

Source: electronics-tutorials.ws/waveforms/bistable.html

A 20 MHz square wave input yields this:

A quick look at the BC548 datasheet says it has a transit frequency of ~100 MHz,
so I'd say it can be done but I don't know why the simulation fails at higher frequencies.

Some analog Gurus know why ?

best,
Chris


texts:
I am designing the simplest form of a camera: an FPGA that interfaces an image sensor and sends the acquired data to the host device via USB 3.0. There is no processing on the FPGA, it is used for sensor control and data acquisition.

By studying various resources online, I observed that typically a DRAM is included in the design to store sequential frames as well as intermediate processing results. At first, my plan was to implement:

Image Sensor ==> FPGA ==> DRAM  (Acquisition)

DRAM==>FPGA==>USB Controller (Transfer to host)

Since no image processing is done, I was wondering if it is safe to omit the DRAM in the design for reducing design complexity. So, the pixel data will go directly from the FPGA to the USB Controller in every cycle, and implementing a small internal RAM as a very small pixel buffer in case there is a temporary stall from the USB controller.

Is that feasible or I will have many frame losses due to transfer bottlenecks?


texts:
I have a small solar panel of the following,

Area = 0.0078 square meter
Rated Power = 1 W

Now, I am interested to calculated the total energy this solar panel can harvest over a day.

I am taking the following parameters,

Annual solar irradiance = 1200 KWh/square meter

Converting this for my solar panel, I get (1200 KWh/365)*0.0078 = 25.6 Wh

Is this 25.6 Wh the total energy it can provide? But I think is is not right as solar panel is only rated to 1 watts, how can it provide so much? Is this right or I am missing something else in my calculation?

I also tried the other way to calculated the total energy it can harvest in a day. This is what I did next.

I find the average sun shine hour from here,
I did the average calculation and got 2.74 hr

Energy = 1 watt * 2.74 = 2.75 Wh, this is the right way to do it?

I didn't use the sun irradiance in my second calculation, is this correct?

Which one of the method is correct to calculate the energy for my solar panel? or there is some other method?


texts: How to use the xprintf function on stm32f429?

texts:
can you help me? I'm a new one. How to use this ''xprintf''? I have connected my uart2, but it's no use. Should I choose the MicroLib in keil? Or rewrite the _wrtie() and _read()? I didn't use the semihostings(use #program to removed the semihostings mode), Thank you.

P.s. My ide is keil5, and use the stm32f429 to do it.
And I downloaded xprintf.c/.h from https://github.com/tmk/elm-chan_xprintf/blob/master/xprintf.c


texts: Calculate total current through a coil using sources of different frequencies?

texts:
I've been presented with this question:

What I've done thus far is:

calculated the current with the 45Hz source
gotten XL with the 45Hz source
calculated the inductance for the 45Hz source
used the ratio of the frequencies to calculate XL and Z for the 60Hz source
calculated the current
used the current and previously calculated XL to get the power
used Z to calculate VA power and then got the power factor

My final answers are I = 6.53 A; P = 426.51 W and PF = 0.18.

I'm pretty sure that what I've done is incorrect. Could anyone assist? Should the values have a complex notation?


texts: Instrumentation Amplifier - circuit analyze

texts:
I found this schematic in LT1014 datasheet:

What the pointed op amp (and the circuitry around it) is for and how it works?
Why do we need to cancel the bias current?
What's the application for such a circuit? just like all other in amps?


texts: Powering 12V device from 5/9/12V powerbank

texts:
I recently bought the Litionite Falcon powerbank that has one of its outs designed for 5/9/12V. The 12V is at 1.5A which I thought would be enough for my 12V/0.8A camera. However, connecting the camera to the charger with a USB to 0.7mm jack doesn't work. Indeed, I can measure only some 5.3V coming through the USB cable which explains why the camera doesn't recognise the power.

How do I get the 12V from the powerbank to charge my camera? Do I need a special USB cable? Do I need one with a step up? Or is it enough to wire the USB differently?


texts: Electro magnetic interference with Arduino Uno and a portable radio

texts: I'm surprised when I'm working with Arduino Uno, by just sitting beside a portable radio, like when I was powered on both Arduino & Radio and when they are close to each other I got some noise issue in the audio of radio, later I tested with my mobile but didn't get that issue . I got to know later it's because of EM interference. Can anyone please share your views, why I got the issue with Arduino and why not with mobile?


texts:
We are using a stepper motor with a Current rating of 0.65A and rated voltage of 4.55V.
We are using a 12v power supply. The current driver chip is limited to supply 0.7A.

Would the power of the motor be equal to Supply Voltage * Rated Current. Or will it be equal to motor rated voltage * rated Current.


texts: How to solve the netIF_SetOption function(IP address changing problem) in CMSIS?

texts:
I am following this

https://www.keil.com/pack/doc/mw/Network/html/network_create_app.html#Runtime%20Configuration

tutorial about the Network library with CMSIS.
I could change the Mac address via

netIF_SetOption (NET_IF_CLASS_ETH | 0, netIF_OptionMAC_Address, buf, NET_ADDR_ETH_LEN);

without any problem but by using the
netIP_aton (ip_addr, NET_ADDR_IP4, buf);
netIF_SetOption (NET_IF_CLASS_ETH | 0, netIF_OptionIP4_Address, buf, NET_ADDR_IP4_LEN);

nothing work. I need to know if changing IP address function has any problem. before calling the above lines my ETH works fine with the default IP address which is set in "Net_Config_ETH_0.h"  (for examples:192.168.120.100) but by using the above lines I could not be successful to change the IP address to 192.168.120.150 or any other values which are not available on my network and I missed the connection ( even the default value 192.168.120.100).
Here is my code:
netInitialize ();
netDHCP_Disable (0);
netIF_SetOption (NET_IF_CLASS_ETH | 0, netIF_OptionMAC_Address, mac_addr, sizeof (mac_addr));
netIP_aton ("192.168.120.150", NET_ADDR_IP4, &buf1[0]);
netIF_SetOption (NET_IF_CLASS_ETH | 0, netIF_OptionIP4_Address, buf1, NET_ADDR_IP4_LEN);
socket = netUDP_GetSocket(udp_cb_func);

if (socket >= 0)
{
    netUDP_Open(socket,4565);
    netUDP_SetOption (socket, netUDP_OptionTTL, 2);
}


texts:
I am experimenting with this guy - http://wiki.seeed.cc/Grove-Piezo_Vibration_Sensor/ and it seems to be quite insensitive. It won't respond to table knocks when I knock it with the piezo bender having some heavy weights (hundreds of grams) on top. Same deal with no weights. I have even tried to tap it directly and no answer. Also adjusted the on-board potentiometer.

The only way this piezo strip gives an answer is by fast bending + fast releasing. I am reading the output with delay(2) to make sure I am not missing anything. From what I have read I should be able to pick fine vibrations with it by just adding a minuscule weight. Maybe mine is broken ?


texts:
Construct an 8k X 32 ROM using 2k X 8 ROM chips and any additional
required components.
Show how the address and data lines of the constructed 8k X 32 ROM are
connected to the 2k X 8 chips.

I tried to solve it but I am not sure if I got the correct answer. Could anyone check my drawing and correct me?


texts: Difference between configurations of unity gain buffer using op-amp

texts: Is there any practical difference as to how a unity gain buffer using an op-amp might be configured? For example, the input signal can be connected to the noninverting input and the feedback to the inverting input; but it can also be configured the other way, with the inverting input as the signal and the noninverting as the feedback. Practically speaking (noise, stability, frequency response, offset error and so on), is there a difference between these configurations?


texts: Beta Multiplier - Not Getting Correct Reference Current

texts:
Solved: The body of M2 needs to be connected to ground and not to source.

I am reading a textbook on CMOS technology and I am having trouble simulating a beta multiplier in NGSPICE. The reference current, mathematically, states the width of M2 should be 4 times the width of M1 to get a reference current of 20uA. In my spice circuit, I created the same circuit. However, I am getting a current of 30 uA. What is wrong with my circuit?

EDIT: Double-checked by CMOS models and they are exactly the same as the authors and the previous poster.

Note: I am using the same model files as the author as it has been tested on every circuit I've done throughout the book.The sizes of the MOSFETs are the same as well as the resistor value.

My Circuit:

*** Baker Figure 20.14 Beta Multiplier Reference No Start Up***

.control
destroy all
run
print all
plot I(VME1) (I(VME2))
.endc

.include /home/babadook/Documents/SPICE/models/MOSFET/NMOS_Baker.mod
.include /home/babadook/Documents/SPICE/models/MOSFET/PMOS_Baker.mod

.option scale=1u
.dc VDD1 0 5.0 0.01

VDD1    DD1 0   DC 5
M3  A   B   DD1 DD1 BPMOS L=2 W=30
M4  B   B   DD1 DD1 BPMOS L=2 W=30
M1  A   A   E   E   BNMOS L=2 W=10
M2  B   A   C   C   BNMOS L=2 W=40
VME1    E   0   DC 0
VME2    C   D   DC 0
R   D   0 6.5k
.end


texts: I have a project to model a transmission line with a reactor. I have searched about it but everywhere it basically says it is an inductor and mostly its application is given to protect the vfds and electrical drives. I have simulated the basic circuit for a line reactor with a Three Phase source, reactor(for which I used inductors), a fault in the line and three phase load, but it isn't sufficient. So please give your suggestions on how to proceed in this project of power system. I have to simulate it with a transmission line model and not with VFDs and drives. Also I want to know which hardware model can I make for this project.


texts: PSPICE Simulation of Cascode Amplifier Not Working

texts:
Can anyone please tell me why I am getting the following "floating node" errors. I have fiddled around with the resistors to see if it affects anything, so these are not the actual values. I have also read a number of post on PSPICE "floating node" errors, but nothing has helped so far. Everything seems to be grounded... I just want to get rid of the simulation errors for now. Thank you.

Here is the schematic:

Here are the errors:


texts: Using a Schmitt-Trigger to transform sine to square wave

texts:
I have a myRIO from NI. I use the FPGA to generate a sine and a cosine digitally for signal processing of a photo acoustical signal. The sine and cosine have the same frequency. I now want to output the sine over the 12 bit DAC and transform it into a square wave with the exact same frequency and 50% duty cycle. The maximum output rate is 345kSPS and the sine has a 5Vpp amplitude (0V to 5V). The square wave can have a high level between 3.33V and 5V, the low level should be 0V with a duty cycle of 50% to control a laser switch. The output Frequency can vary between 1kHz and 35kHz. That is why I also want to implement a low pass filter before the sine enters the Schmitt-Trigger.
The picture shows my try in LTSpice, but although I use this calculator to get the right component values, I only have a DC signal after the LPF. If I try it without the LPF the output of the Schmitt-Trigger has no 50 duty cycle and the high voltage level is too low.
Maybe the comparator is no good choice. I hope you can help me on that.

With LPF (LTC6244HV is uesd from LTSPice) I get this result:

Any comments on the picture and on the low pass filter?


texts: Can Position Sensitive Detectors electrodes be offset? How?

texts:
I've got a prototype board of a light tracking device based on a 2 dimensional PSD, but it suffers from important bias currents on one of the electrodes which could possibly clip the input to the supply rail at any moment. I would like to compensate for that offset in order to be sure the signal is never altered, but is it going to have any effect on the PSD's behaviour? How does that work out really?

What I would like to do in particular, is replace the direct ground connection on the non inverting input of the current-voltage converter by an adjustable voltage divider between 5 and -5V on the following schematic:

 (also in dropbox) - the gain of the tail amplifier is set to 100.

I have tried injecting currents with a 10Mohm resistor to -5V on the electrode but even if the offset is no more, it seems it tempered with the detector somehow because I picked up immediately an important (several Vpp output!) 50Hz noise when it wasn't there before. That noise decreases when the device is obscured, so it really sounds like some kind of imbalance.

In a nutshell, if I offset the potential on one electrode (well, the opamp will do it for me), is it going to change anything else?

Resources: application note of Hamamatsu, datasheet of the detector


texts:
I am having trouble with a circuit:

simulate this circuit – Schematic created using CircuitLab

I must calculate the voltage across R1.My answer is to first compute the current running across R1 and R4 , the two forming a series circuit:

6V/(1k+2k)ohms=0,002A

Then I calculate the voltage drop across R1:

V1=I*R1=0,002*1000=2V

It seems that I am wrong , but I don't understand how to do it in another way.
How must I compute the voltage across R1?


texts: What circuit can be used to match input to output voltage by using an opamp?

texts:
What is the simple way matching an input voltage range to a desired output range.

To be more specific with an example: If I want to convert/match 0V-5V input range to 7V-15V output range linearly, is it possible to do it with an opamp, feedback and a potentiometer ect? I can use a +/-15V dual supply. What should be the topology?


texts: Buck switching regulator based on ATtiny84a -- please critique!

texts:
Here is an attempt at designing a buck regulator based on a ATtiny84a as the PWM controller.
It should go from a 4S LiPo battery (12.8 - 16.8 volts in) to a reasonably regulated 12V output, used to drive servo motors that accept 10-14V inputs. 4S LiPo is slightly too high, and 3S LiPo is slightly too low, especially as I want the rated 12V torque.
The design is intended to deliver 40 amps worst case (stalling out a majority of the motors.)

I can't buy one of these, because as soon as I leave the 10-15A range, all the DC DC converters are designed for industrial use and have heavy cases, are really expensive, require 24V input, or other such mis-matches with my present requirements.

The idea is to use the built-in analog comparator in the AVR to detect over/below target voltage, and generate a pulse of a definite duration when the under is detected.

I would build this on breadboard with 20 gauge wires soldered across the component leads for the high-power paths.

I know about keeping the "switching node" and feedback path as short as possible, when trying to do layout. I would also ground all breadboard traces that are not used, to make for a poor man's ground plane.

I've tried choosing a choke where the saturation current matches my max output current, and a buck inductor where the saturation current is higher than my max output.

The corner frequency of 94 uF and 3.3 uH is about 9 kHz, and I imagine the AVR will run much faster than that. I'm thinking a 5 us pulse each time under-voltage is detected, and then just go back to look for under-voltage again. That gives a max frequency (at close to 100% duty cycle) of 200 kHz.

And here's the schematic:

https://watte.net/switch-converter.png


texts:
I used LM386 to amplify but its minimum 20x gain is to much for me use because my signal is maximum +-0.5v ac , riding 1V dc .

this is my circuit.
I am seeing a signal on scope but I cant hear anything when I connect the speaker [I am measuring without it].
Moreover the scope image is the same as the input image ,no gain !
I can't see what I missed here


texts:
I recently purchased a Corsair TX PSU and when it's on the Y caps are "sending" about 14v to the ground
I'm not sure why this is happening but I already removed Y caps from my surge suppressor to fix this. Sometimes I know it's not possible to remove Y caps (connected between line-ground) but I wonder if this is safe when it comes to computer PSU
P.S: 103 Y caps and above are usually the worst when it comes sending voltage to my earthing system. I notice that between neutral and earth with everything off it's 0volts but when I turn on the PSU it goes above 12V


texts: MOSFET Sizing in Wide-Swing Current Mirror Design Exercise

texts:
TL:DR How do I know how to size transistors?

This is the same problem as this one.

Now knowing that I can change L, I know that my W/L ratio to make Von = 200 mV is roughly 6.75. Also knowing that M5 is supposed to be operating in triode, here's my thought process:

Von > 200 mV; this is set by W/L = 6.75 (math done elsewhere).

Vds (for devices operating in saturation) >  2Von (= 400 mV)

Vd5 = 400 mV

Which means that Vd5 = 800 mV

Which means that Vg5 = 800 mV

Therefore Vth <= (less than or equal to) 600 mV.

Assuming that Vth are relatively similar:

Vgs6 = Vg6 - Vs6 = Von + Vth

Vg6 = Von + Vth + Vs6

Vg6 = 200 mV + 600 mV + 400 mV = 1.2v = Vg8 = Vd8 = Vg7.

The maximum that Vs8 can be is 800 mV for M8 to meet the Vds spec. However, since Vgs7 = 1.2 V and Vth = 0.6 V, then:

Vds7 < Vgs7 - Vth = 600 mV.

And that's where my train of thought stops. The only pertinent equations for MOSFETs that I can think of involve W/L, not one or the other, so I don't know how to set the sizes of these transistors. I was told that M5, M6, and M8 should all be the same size, and the Gray et. al. book Analysis and design of Analog integrated circuits says that W/L7 should be 1/3 of the other W/L's, but I don't know if that's meant for unity gain current mirrors or all current mirrors in this configuration.

If I don't want to keep that ratio that I calculated earlier...then I'm really lost and don't know where to begin.

I'm trying to figure out how to find out as much as possible from hand calculations before I go to simulation. I've got a lot of different knobs to turn: W7, L7, M7, W8 = W5 = W6, L8 = L5 = L6, M8 = M5 = M6 (multiplier factor, not transistors themselves). The smallest number of knobs I can turn (if M8, M5, and M6 are identical and I keep the initial calculated ratio AND if the ratio of M7 is supposed to be 1/3 of the others) is 4; that number quickly gets out of hand if I started changing them relative to each other.

What's the next step? How do I size these transistors?

Edit: Walking through simulations. Will be updated periodically

2018 Feb 18

L1,3,5,6 = 0.35 µm

L2&4 = 0.7 µm

W1&3 = 2.3625 µm

W2&4 = 4.725 µm

W5 = 0.35 µm

W6 = 0.76 µm

M1-2 = 4

M3-6 = 1

V2 = 795.3 mV sets the output current equal to 100 µA, and the bias voltages are as follows:

-------------------------M1 ---- M2 ----- M3 ---- M4 ---- M5 --- M6

Vgs (mV) ---------- 798.3 --- 782.7 --- 798 --- 783 --- 1182 -- 917

Vth (mV) -----------     571 ----- 558 ---- 571 --- 558 ---  385 --- 480

Von(mV) ----------- 227.3 --- 227.8 --- 227 --- 225 --- 797 --- 488.5

Vds (mV) ----------- 399.3 --- 396 ----- 399 --- 399 --- 266 --- 917

Vds % Difference -      -0.17% - -1.01% - -0.25% - -0.25%    -- N/A --  N/A

Ro = 2 M-Ohm (Can't get the Greek letter to display).

Still, no matter what I do, Vd4 is constant at less than 800 mV. What sets this level? Is it M5?


texts: Class A amplifier - Transistor Q-Point calculation

texts:
Reference: http://www.learningaboutelectronics.com/Articles/How-to-find-the-q-point-of-a-transistor-circuit

I am trying to understand this q-point calculation. I recently asked a question about the notation used, however I now understand this.

Consider the line RB=(R1 R2)/(R1 + R2). I understand that this is the calculation of 2 parallel resistors, R1 and R2. However I do not understand what the relevance of this is in the calculation.

I have seen this from other sources, for example the last example at the bottom of this page:

https://www.electronics-tutorials.ws/amplifier/transistor-biasing.html

Again, in this example, I understand everything until the line RB=...

How is this equation derived? I thought it might be obtained from one of Kirchoff's Laws, but if this is the case I can't see which law is used and how.

I copy the relevant diagram and calculation for convenience below.


texts: Will my decimal to binary converter work

texts:
I got into electronics recently and I hope to make a 8 bit ripple carry adder with a decimal input and output.

This input is the first schematic I designed from scratch without a tutorial to go off of and I was wondering if it would work and further, if anyone had any improvements that could be made.

If there's anything wrong with my schematic please comment and I will fix it as fast as possible

Thanks again, stackexchange has been invaluble for my learning electronics

*Edit

A0:  800s
A1:   80s
A2:    8s
A3:  400s
A4:   40s
A5:    4s
A6:  200s
A7:   20s
A8:    2s
A9:  100s
A10:  10s
A11:   1s

and then a binary output

*edit 2, I'm testing the circuit and the clock on a shift register doesn't seem like it can be advanced with a button. Any thoughts?

*edit 3, here's how the switches I'm using work in case that helps


texts:
After soldering my atmega328 tqfp smd chip on my PCB, i can see that my chip is working with a standard blink sketch uploaded earlier
The problem is that i cannot upload a new sketch  using FTDI adapter in my new board, and this is below the schematic:

Is there some tricky stuff to do before trying to upload any sketch ?


texts: What's wrong with my diode SPICE model for the HSMS-2860?

texts:
To be brief, I am as new as they get to creating SPICE models for components so I'm walking blind.
I was trying to create a SPICE model for the HSMS-2860 diode.
HSMS-2860 Schottky Diode Datasheet
Here is the .lib file I wrote for the diode, I got the parameters from the datasheet above.
.MODEL HSMS2860 D
+BV = 7
+CJO = 0.18E-12
+EG = 0.69
+IBV = 1E-5
+IS = 5E-8
+N = 1.08
+RS = 6.0
+VJ = 0.65
+XTI = 2
+M = 0.5

What I noticed is when I import this file into ANSYS Circuit Designer, it doesn't behave like a diode. When I apply a sinusoidal source to it (half-wave rectifier) I still encounter negative peaks on the output even though I have the peak input voltage amplitude below the reverse breakdown voltage of the model.
The goal of modeling this diode is so that I can determine a input impedance at a certain input power so that I can design a matching circuit to match that input impedance to my receiving antenna's impedance.
I'm sure the rabbit hole for SPICE modeling goes deep. I would appreciate some assistance with the matter.


texts: I am currently working on a motor driver that should operate on 100V or higher voltages. I need to implement logic there with 3.3V. I could provide additional, low voltage source but that would give more connections. I Was wondering what is the best and cost/ size efficient way of going from 100V dc to 3.3V dc? I havent found any IC's allowing to do that, most of the dc-dc converters work from a maximum 40V dc input voltage. I would apreciate all help!


texts:
simulate this circuit – Schematic created using CircuitLab

Hi,
Question: In the following, a string of three diodes is used to provide a constant voltage of about 2.1 V. We want to calculate the percentage change in this regulated voltage caused by (a) a ± 10% change in the power-supply voltage and (b) connection of a 1-kΩ load resistance. Assume n = 2.

I had some doubts regarding the small signal analysis to be carried out in part B. After asking here, I got enough help to understand and solve it. But the next passage in the book (Microelectronic Circuits) states that while using small signal analysis we get .

But if we follow the detailed calculations using the exponential model we would get .

I am not able to understand how to derive the answer using the exponential model. What are the steps to find the solution using the exponential model?

Link (to the previously asked question: Diode Modelling)


texts:
Why do computers have clock signals and clock rate, while ordinary machines do not have them?

And why is clock so fundamental in CPU and mainboard?


texts: How to measure the amount of light emitted back from a fiber optic cable?

texts: I would like to build a setup where I use a light source to emit a signal over a fiber optic cable, and then measure the amount of light that is emitted back, e.g. by blocking/opening the other end of the cable with my thumb. How could I build such a system?


texts:
I am having a Lecroy differential probe and trying to measure a LVDS signal. This is the Reference Manual which I am referring to as a guide.
My differential probe tip/lead model number : DX20 - SP/SI/QC. Please see its specification in the table present on the document. I am using the WL-PBUS2 Probus2 cable assembly with the D420-A Differential amplifier.
But can someone tell me what are circled in red items on the differential probe tip/lead assembly?

There seems to be 2 resistors in series with the +ve and the -ve differential line and one resistor across it. I tried to measure their values in multimeter. But it think, there is a layer of coating above those components because of which I am not able to measure their values using multimeter. I did not want to scratch the coating and try fearing it might damage the probe which is very expensive.
Can someone tell me what are the 3 components in the above image? I search and tried to read in the attached manual, but unable to find what those are and how do they help in measuring a differential signal.
Below is my setup :

I am connecting the above differential probe across the vias 1 and 3 to measure the LVDS Signal. I am getting random waveform which I know it is because of the termination mismatch at the probe shown above.
Please guide.


texts:
I've built an ignition timing light, following:
http://citroen.tramontana.co.hu/en/ignition/stroboscopic-timing-light

here the original schematic:

I've changed some components:

Instead of the BD135 BJT, I've used a BD128D.
Instead of R3 (4M) I've used a 3.9M R
as LED1 I've used a  Nichia NFSL757GT LED
as setting current R5, i've used two 220ohm R in parallel
Instead of a 240ohm R (R1) I've used a 220ohm R

Here the schematic as modified:

When I apply it to the spark plug HT lead, the LED flickers as it has to do, but it is barely switched on.

The trigger cable is connected to the spark plug lead insulation via a crocodile clip and it collects the signal via capacitive coupling with the cable.

The cable insulation is made of PVC (dielectric constant 3.19) and is 3mm thick.
The inner cable is made of copper 1mm thick.
The voltage provided by the ignition coil is 14 000 V.
There is about 1000 spark each minute.
The crocodile clip is 5mm wide.

The trigger cable is an audio cable, which I believe is shielded. I've connected the shielding to the battery - pole)

I think that maybe the trigger signal collected is not enough to open the thyristor and the transistor.

Is it possible to calculate the capacitive coupling?

I would like to try to simulate the trigger signal with a Keithley power supply. Which current and voltage do I have to set, in order not to destroy nothing?


texts: help related to frequency of schmitt oscillator

texts:
I have seen the CMOS Schmitt waveform generator circuit (i.e. figure 2nd) from the following link http://www.electronics-tutorials.ws/waveforms/generators.html
I tried to simulate the circuit in MULTISIM using 40106BD to get different frequencies by varying capacitor.
It is given that the formula to calculate the frequency is 1/(1.2*R*C) but I am not getting the frequencies correct using these formula. I am using range of R as 100K and capacitor range 1pf to 1nf . I want to know why I am getting different frequency than calculated. Also how does this circuit works and how do we get the expression for frequency.


texts:
I've been looking around at some power supplies that I am hoping to run a 400W 48V DC motor on. Currently I am looking at this one:

Weidmuller PRO ECO 480W 42V-56V dc 10A

My questions are about the output terminals.

1) Why are there specifically 3 negative terminals and 2 positive terminals?

2) Are the multiple terminal pairs for potentially connecting components in parallel?

3) Are the 13 and 14 terminals (see block diagram in pdf) there to attach a switch if required?

I would be greatful if anyone could help clear up any of those questions.


texts: Measure BJT base voltage cause IC to increase, why?

texts:
simulate this circuit – Schematic created using CircuitLab

When I measure the base voltage, the collect current will increase, why? The only equation that I come up with is $$V_B=5\times \frac{R_{meter}}{R_B+R_{meter}} $$
which tells me that if Rmeter decreases (open circuit to 10's of megaohms) VB will also be decrease. So I was expecting a drop in collector current rather than increase. Can anyone explain this to me, Thanks.


texts: How many AA batteries can I wire in series?

texts:
I'm tinkering with some DC motors, and have been able to drive them with a 1.2A wall wart that produces a variable 3-12v. I want to drive the motors with 24v+. Would I be able to get what I need by soldering together 16 AA batteries in series? Or would internal resistance foil my plans?

Would it be better to hook up three 9v batteries in series?

Some more details: I'm working towards building an autonomous quadcopter with an arduino for the controller and misc surplus parts. At this point I'm just seeing if I can push enough voltage thru the four small motors I've got to even get them to lift their own weight. I found the motors for $1.50 each at a local surplus store. I'm willing to throw $2 of AA at a one-shot feasability test before spending real money on li-po and/or ESC or other 'real' kit.

http://youtu.be/RQKF7VIjHPI


texts: How does R5 bias the zener in this SMPS circuit?

texts:
In the description for the circuit below from this data sheet for TNY268 off-line SMPS switcher, it says

  R5 is used
  to ensure that the Zener diode is biased at its test current and
  R6 centers the output voltage at 5 V.

The Zener current for the BZX79B3V9 is 5mA, the zener voltage is 3.9V and the forward voltage for the opto-coupler TLP181 is 1.0V Min.

How exactly does R6 'center' the output at 5V? How does R5 bias the zener at 5mA? I can't work out the math.


texts: Difference between a controller (e.g PD) and a compensator(e.g Lead)?

texts: Really.What is it?Can't find anything anywhere related to it...Please don't give fancy examples.Just tell me the difference


texts:
I am designing an ADC board for Raspberry Pi using the MCP3004 ADC chip. Please see my circuit below.

This circuit is intended to measure voltages form 0 to 10V, to have overvoltage protection (Vin<=24V), and reverse polarity protection.

According to datasheet BAT54 diode has a voltage drop of 240mV @ If 100uA. When 10V will be applied (Vin) the voltage divider will scale it to ~3V. At this time D2 is blocked (except for leakage current). As Vin will rise D2 will open and the input of op amp will stay close to 3.2V. To supply power to D2, a small 3V LDO will be used. When polarity will be reversed, the non-inverting input will see around -240mV, which is more than Vss-0.3V that is specified in LM358 datasheet, so it should be fine.

Everything went fine in simulation, but will this work in real life? When the polarity will be reversed, will the output of op-amp be stable close to 0V?

I read that op-amps are not happy with capacitive load. MCP3004 is a SAR ADC so it can be approximate as an capacitive load (20pF). For that reason Rx Cx are recommended to be used. My question is: Are they really needed? If yes, based on your experience/knowledge, what will be the optimum values?

Thank you in advance for your answers!


texts: What breadboard simulation software is this?

texts: I'm not familiar with what software is available and cannot recognize the origin of this diagram. Does anyone know what software this is? I'm only guessing that it can perform simulation; it may just be for layout.


texts: How to delay the transistor turning on using a photoresistor?

texts:
I am a beginner in electronics,

my project is the following:
I am trying to build a simple circuit to switch on and off my garden lights according to the brightness level. More to the point, I'd like the lights to turn on when it's dark and off in the morning.

After much thought and some help I came up with this solution which works fine in extreme situations (very very dark and very very bright)

The problems are the following:

1)According to the NPN 2N3904 datasheet, the max current through the collector should be 100mA am I right? However the load of 32 Ohms needs at least 300mA to work properly (375 should be better). Should I change transistor? If yes, what kind should I use?

2)More importantly, using this schematics in LTSpice I noticed that the transistor starts to drive full current (375mA) as soon as the photoresistor hits the 1K Ohms which is obviously too low in order to light up the lights when the sun sets, how can I tune this parameter? Should I change photoresistor as well? Here below is the LTSpice simulation of the current through the load as R changes

In case you need them, here are the datasheets

Photocell (Photoresistor) https://learn.adafruit.com/downloads/pdf/photocells.pdf

NPN 2N3904                https://www.sparkfun.com/datasheets/Components/2N3904.pdf

Thank you


texts:
I'm simply trying to find Vt and W/L for a given practice exam problem shown below:

The solution is given as:

Initially, I was trying to use the equation as shown in line 1 of the solution to develop 2 equations with 2 unknowns and solve for each, but there appears to be a much faster way to arrive at the solution which I'm having trouble understanding. Specifically, I don't understand line 2 of the solution.

What is the logic behind taking the ratio of Id (0.225mA/0.1mA = 2.25)?

The book defines VGT as Vgs-Vt, I don't understand which numbers/logic is used to determine Vgt1/Vgt2 = 1.5. I suspect VGT is not equal to Vgt (lower case), but can't find a formal definition to support my suspicion.

And Finally, how is Vt = 0.6V? The most I can rationalize is that 1.5/2.25 = 0.66667, but doesn't seem right.

I appreciate any help. Thank you.
*This is a practice exam, not hw


texts: How do I go about selecting the resistors for pnp common emitter amplifier?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm expected to design a pnp common emitter amplifier. The gain should be 13 and the output 2Vp-p. Vcc is -13V. The load resistance is 1728 ohms. I've calculated the ac source voltage by using the gain formula Av=Vout/Vin to be 77mV. The other gain formula Av=Rc/RE I used to get an idea of the swamping emitter resistor to get a 13 gain. How do I get the rest of the resistor values if I'm using voltage divider bias? Is my work thus far correct? I've simulated the circuit with arbitrary  values but need to know a the proper design process.


texts: Supplying power to ESP32 from a DC adapter instead of the USB port...is it a bad idea?

texts:
I'm designing this board based on ESP32 which suppose to handle two motor drivers (DRV8874, DRV8840) and a few other modules; a 12V@3A DC adapter seems to suffice powering-up the board according to my calculations. The idea here was to have only one power source to the whole board, even the CP2102A USB_to_UART and ESP32 could both be only powered up via the DC adapter instead of USB port (which a common design in dev-boards is that the 5V on VBUS gate of the MicroUSB goes through a 3.3V voltage-regulator and forms the 3.3V net to eventually supply the VDD on both CP2102A and ESP32 module).
Have I missed anything here? any possible safety issues with the current design? was cutting the power from the MicroUSB's VBUS to the USB_to_UART's VDD and supplying from an external DC source a bad idea?
Thanks.


texts:
I've been measuring low DC-powered devices consumption, by measuring the current at the needed frequency (able to detect the fastest consumption changes).
I can then have the mean, max, min.
To get the mean, i just integrate these measure points over time and multiply the result with the supply voltage.

One collegue of mine told me that this was not correct and, because that the current was not constant, I should use RMS measurement tools like for measuring AC current...

Could you confirm my procedure is correct?


texts:
I am wanting to make a motor driver using a SN754410 Quadruple Half-H Driver IC.

The SN754410 requires external flyback diodes. Here is an example circuit:

My question is, how do I choose which diodes to use? Two popular choices seem to be the 1N5819 and the 1N4007, but I don't know why.

What factors are involved in choosing suitable flyback diodes?

I'll speculate:

Cost
Current rating (motor operating current, or higher?)
Voltage rating (motor operating voltage, or higher?)
Switching time (does this matter with flyback diodes?)


texts: Building a 2-bit adder with a propagation delay of at most 2 gates

texts:
An XOR-gate itself counts as 2 gates, so if I use an XOR-gate the delay would already be 2.

I have no idea how to do this, as a full adder for one bit already contains 2 XOR-gates (or 1 XOR-gate, 1 AND gate and 1 OR gate) so that would already have a delay of 4, while I have to build a 2 bit adder with a delay of at most 2 gates.

Is it actually possible to do this? Otherwise there must be an error in my exercise book.


texts: Questions regarding a comparator circuit coupling to an analog switch

texts:
This is directly related to my previous question, so it requires to first have a look at that. And the below LTspice implementation is based on Andy Aka's answer. The following circuit works in LTspice. But I have some observations and questions before I solder it on a board.

First of all, I would like to mention that since I couldn't find the SPICE model for DG419 (analog SPDT switch IC), I made an ADG419 from an ADG411. I read they use the same components inside. So I just needed to invert one input and tie two outputs and it works and mimics ADG419.

A 10k potentiometer Rth will set the threshold voltage, and another 10k pot Rset will set the pre-set voltage Vset.

(left-click to enlarge the schematics)

Here is the 0-10V DC sweep:

And here is a transient analysis plot for 0-10V in 1 sec (notice the glitch during the comparator action):

And here is the change at Vth during the comparator action (voltage at the node between R2 and Rth):

My questions are:

Is interfacing the comparator LM311 output to the ADG419's input fine this way as in the schematics?
Is that glitch the product of the change in Vth in comparator action? And can that be mitigated? (I don't see the glitch in DC sweep)
Is there any fundamental problem with this circuit or resistor values? Or any peculiarity. For example I'm not sure whether R4 is necessary? (I found it from a circuit I made years ago so I don't remember why it is there.)

Edit:


texts: Full equations for assymetrical stripline

texts: Are there any good sources for nonlimited equations of an asymmetrical stripline impedance. I would like to calculate capacitance, but I cannot get valid results out of the commonly used calculators and published results as the W/H ratio is outside of where the results are anywhere close to accurate.


texts: Does an inverter only draw power from a battery as-needed?

texts:
In other words, does a 1000-watt inverter, draw the same as a 500-watt inverter if they are charging only a laptop? The laptop will draw the same amount and the inverter capacity is really just that, capacity?

i.e. 1000-watt inverter CAN draw UP TO 1000-watts, and the same for 500-watt inverter.

My issue is that I plug in a 1000-watt inverter to a battery, and voltage is dropping to 12.2v. I was informed that I should keep my battery voltage, above 12.4v to keep it healthy and I worry that 12.2v constant (during full solar input) and 11.8v (at night when there is no sun) is killing my battery.

I am currently using a 1000-watt inverter, and now I'm wondering if it is overkill and need to downgrade to a 500-watt inverter to charge a laptop/run cable modem/router (~100-watts/per hour).


texts:
I have been working on raspberry pi, connected to mains power using adapter. But in my area electricity goes again again, so as electricity goes down, inverter in my home takes microseconds to up due to which raspberry pi get shutdown and got re-started. This is mainly due to the microseconds inverter taking to up.
SO I want to avoid these unwanted shutdown. Is there any cheap solution for this problem?
Thanks


texts: Is there a specific rule for a counter to go through states?

texts:
simulate this circuit – Schematic created using CircuitLab

I have the following circuit and I have to tell what the circuit will do?

I determined the state equations as

$$Q1(t+1)=Q1Q2'$$ and $$Q2(t+1)=Q1Q2$$

and the sequence of states I found from state table is 00, 00, 10, 01,

But the answer gven in the book is that
" A controller with a repeated sequence of 00, 01, 10" Which I think I cannot tell from the answer I have found.

So if my method is correct then how can I confirm it
Here is my work I used A and B for FF1 and FF2


texts: ST instruction of avr in microchip stuio (avr studio) nor working as expected

texts:
I am trying to understand indirect addressing in avr and tried the following code :
ldi r31, 0x28
ldi r26, 0x2c
ldi r27, 0x00
st X+, r31

when r26 and r27 are loaded the simulator shows X register as 0x002c and the value in r31 is 0x28 (which is expected). However when the ST instruction is executed the X register and resultingly r26) are updated correctly to 0x2d but the value in data registers location 0x2c is still zero. (as per my understanding it should be 0x28, the value in r31)
what am I doing incorrectly here??
Here is an image of where exactly I am looking at :


texts: Electrostatic discharge on ungrounded components

texts:
My understanding of ESD is that there has to exist a path to ground for static charges to discharge. Take a MOSFET as an example that is vulnerable to ESD and packaged in a way to protect against it, as long as the component is free standing or none of the leads is connected to ground or a lower potential, I should be safe to hold it with my hand without taking any precautious. Essentially my hand and the transistor form an open circuit both sharing the same electric potential with no current.  But it is a fact that touching sensitive components even when they are not powered or just being held by itself can cause damage through static discharge - for that I just can't understand. As if a plane can safely fly through a densely charged cloud (me holding a sensitive component), only until a lightning strikes through the fuselage on its way to reach ground (the component has a path to ground).

[EDIT]

A drawing should help clarify my question. (A) A hand accumulates some static charges (5000V of static charges to ground). Assume the body is not properly grounded and the static charges on the hand have no path to go. A transistor has 0V or no static charges presence. (B) A finger comes in contact with the drain of a transistor. The drain is now 5000V above the source and goes beyond the maximum voltage rating. Thus the transistor is damaged. (C) All three terminals of the transistor come in contact with the hand at the same time. The drain, source and gate go from 0V to 5000V in parallel. There is no potential difference between the terminals and transistor is not damage static discharge.


texts: What is the best transistor for a large RTL (resistor transistor logic) project?

texts:
I've been reading up on older computers like the PDP-1 and TX-0.  I'm fascinated with them and love the idea of making a CPU of my own using discrete resistors and transistors.  Keep in mind, this is an educational project and I will be attempting to create a 4-bit CPU.

It appears the old way was to use multiple voltages.  In several documents, I've noticed that they use -3, +3 and +10.  I find this confusing, but I imagine that those older germanium transistors required a much higher voltage to saturate.

I would like to go with either 5V or possible 3.3 as it seems to be a common standard.

Bottom line, I'm trying to know what transistor values I am looking for.  I have a stock of some 2N2222, but I'm not sure what the "gotchas" are with a project like this.  I've successfully constructed logic gates with these based on some simple examples.  My concern is whether or not they can handle large combinational logic circuits.  I've also read that combining diodes can increase speed.  I realize that this is ancient technology, and that I could simply use 7400' series TTL chips, but this seems fun.

Bear with me as I'm a software engineer, but learn circuits for fun.


texts: Is it true that the average of the product of current and voltage is always real power?

texts:
I’ve had this idea that I recently realized is an assumption. It seemed to me that the average of the instantaneous power (I*V) is always the real power dissipated by the load. However, if you have an AC voltage centered around ground with a resistive load, you’ll get a current waveform with the same shape and phase as the voltage. If you average the product of the current and voltage in this situation, you’d get zero. So here’s my question:

If you have an AC voltage waveform centered around gnd over some complex load that causes distortion/deformation in the current signal so that the current is not purely sinusoidal, how would you measure the power?

What if the AC voltage waveform was slightly offset?


texts: 4 switch Buck-Boost, boost not reaching designed current

texts:
I am working on a power supply that regulates the voltage coming out of a 3S LiPo battery. The buck portion of the circuit works fine and outputs 5+A with acceptable ripple.
The Boost portion instead is giving me some problems.

I require it to work at 20V 5A but it only works up to ~3A, after that it starts making audible noise (even though the switching frequency is 300kHz) and one of the mosfets (HDVR1) instantly overheats.

From the datasheet of the device (LM5175) I know that the HDVR1 switch should be constantly conducting during boost operation and the mosfet that I used is rated well over 3A, so it should not heat as it does.

The diagram of the circuit is pretty much a copy-paste of this schematic from a reference design by Texas Instruments.

I am aware that it is likely to be a routing problem, but I don't know where to start. I did some analysis on the board, but it's not easy because the MOS fries after 4-5 seconds.

The FB signal does not change from buck to boost operation, and the waves on the SW1 and SW2 nodes seem to be ok. The signals on the gates of every mosfet are as predicted and the rest of the board doesn't heat up. During operation under 3A measured efficiency is around 97%. All of that makes me think that there is not a clear and horrible error, but something more subtle must be going on.

I received much help from reading answers to other questions in various situations in the past, but this time I have no idea of how to proceed.

EDIT 1:

On the gate of HDVR1 I get this behaviour during high load condition

@peufeu said that it should be around VIN+7V and at the beginning it's 18V, which is right for a battery partially discharged.

The messy section on the left looks like this

It lasts around 6ms, which doesn't mean anything to me. Also, it oscillates at ~27kHz, which has little to do with the 300kHz working frequency.

While on the right there's more or less this

These are the BOOT1 and BOOT2 signals on no load operation

While there are the same under load

I'm adding here a couple of screenshots from the routing. I'm sorry if they are messy... this was planned to be a prototype.


texts: ATmega168 GND and AVCC not needed when programming?

texts:
I'm reading "MAKE: AVR Programming" and for their "basic LED blinking setup" I noticed in their diagram they don't have the 2nd GND and AVCC (or AREF, which I'm still unsure what it's used for) connected.

I'm using an ATmega328 and everything I read said that BOTH GNDs and AVCC need to be hooked up, but in this picture (and it is indeed the "final" hookup picture) the GND on the right side of the chip and AVCC are not hooked up......is this correct?

If so, can I do the same on my ATmega328? If so, what exactly is the point of the 2nd GND and AVCC?

edit: I also note that a Crystal (with the 2 Ceramic Caps) is not needed here either? Any particular reason? When programming my ATmega328 it would not work at all unless I hooked up the Crystal and 2 caps to Xtal1/Xtal2 (But I pulled my ATmega out of an Arduino, not sure if that matters.)


texts:
I am reading the datasheet for an  ADC. There is no reference as to what to do with unused pins.
I am willing to put some pull-up resistors but..
What would you do?


texts: PSPICE: DC Sweep of zener diode characteristics not working

texts: As you can see, these are my schematic and DC sweep diagrams. Why am I not getting a characteristic zener diode plot?


texts:
I'm just a dabbler in electronic circuits and I'm really still kind of a noob. I am working on a project called the "Atari Punk Console" (Originally known as the "Stepped Tone Generator") but there are some parts of the wiring schematic that I don't understand, specifically the parts with the ground symbol.

Here is the schematic:

See those two ground symbols? I don't understand how to properly connect the circuit to ground at these points. How can I do this and be sure that I did it properly. I don't understand grounding at all so any pointers or clarification is also welcome. Thanks in advance.


texts: I would like to increase the performance of a brushless motor by dividing the frequency of the three hall sensors that detect the speed. is it possible to have a scheme to perform?


texts:
[Taken from Razavi's Design of Analog CMOS IC]

Hi, I'm just wondering, how does he get the 1.25V in 12.21?


texts: In inverting amplifiers, isn't the virtual earth approximation only valid for extremely high gains?

texts:
In this example, at point A, the voltage is +15V, so it is not at all a virtual earth. Then why is it that if we consider an arbitrary inverting amplifier circuit, apply the virtual earth approximation to get Vout / Vin = -R2/R1, and we then choose values of R2/R1 to give a low gain, our results are correct?
I'm finding the argument for point A being at a virtual earth rather circular.
I'd appreciate it if someone could explain this in a clear way. The problem I have with the general argument is that we say if the gain is large, then the formula we derive will be correct. But that formula itself controls the gain..

Another question I have is why do we define the gain of an inverting amplifier to be V output / V in? Should it not be V output / Potential difference between inverting and non-inverting terminals?


texts:
Introduction:
I'm in the alarm industrie and there is something we all do but I never questioned my self if it is good or not. Recently, some guy from the technical support department of honeywell told me that is not good.

What:

We use most of the time a wire 4/22 to do our work.
When we have to "power" our equipment we normally "double" the wire like : "red-yellow" / "Black-green" to drop the resistance.

I know that do not make a bigger wire but it should help.

Situation:
- The power supply is 9vDC
- The manufacturer said : No more than 11' and double wire do not change anything.

The Question:
What are all the real impact of doubling wires in any situation ? (AC and DC, power, communication, etc)

Thanks

15 Décembre 2015

The guy from the manufacturer told me that the method of using 3 wire to match the AWG do not apply because it is in DC ...

It is true that it will not react the same AC / DC ? I know that DC drop faster than AC but how it is accurate in this situation ?


texts: UV intensity behaving oddly with ML8511 UV Sensor

texts:
I am using the ML8511 UV sensor: https://learn.sparkfun.com/tutorials/ml ... -guide/all

The sensor outputs a number that represents UV irradiance (intensity) in mW/(cm squared).

However, whenever I shine a light on the sensor, the number goes down instead of up! And when I cover the sensor with my thumb the number goes down instead of up! This is odd because one would expect the UV intensity to go up when a light si shined on the sensor and down when a thumb is put on top of the sensor.

Why is this odd reverse-behavior occuring?

It is worth noting that I accidentally got a piece of solder on the board which might have something to do with it.

Here are images of the solder on the board:
http://imgur.com/a/CQDv5

Is the solder the reason my board is outputting values in reverse?

Can I remove the solder without damaging the board?


texts: Switch regulator driven by a super capacitor

texts:
I am trying to design a Power Management circuit with some quite tricky (for me at least) requirements. Basically I have a quite high 30-40V (varies) input voltage, with a very low current limit (6mA max in worst case, but it some cases there are more). The goal is to make a circuit which can periodically drive the WiFi of an ESP32 (needs 300mA @ 3.3V) in order to deliver data to a server. (For those of you that have not guessed it, this is an Mbus slave device and the master is guaranteed to support 4UL or more).
My idea is to have the ESP32 run with the radio off when in idle mode. This should be fully possible with a standard Buck converter supply. However, it need a time limited power "boost" for 1-2 seconds when ever I need to turn on the Wifi and send data.
I've designed a switched current limited super capacitor charging circuit. This should insure the capacitor is charged with a constant current, while monitoring the bus voltage to insure we are not overloading it (reducing current further if we do). This is adjustable to any output voltage I would like on the supercap.
The problem is finding a suitable switching regulator that takes the voltage from the Super Capacitor and converts it to a 3.9V @ >300mA (as I need this to supplement the main supply through a diode so it does not interfere with it's feedback). I thought finding something suitable would be easy, but I have not been able to do so. The main problem is that the super capacitor can have a voltage higher (up to 5V) than the output of the regulator, and this really limits the selection of components it seems. I've also looked through a lot of supercapacitor backup supply ICs, but none of them are suitable for the rather special input scenario I am facing. Also, they are typically designed as a back-up, and not as a power boost.
I hope someone have any suggestions on what I should look into (or rethink for that matter), as I am somewhat stuck. I also have to mention I am a DIY beginner in switching regulator design, and my lack of experience may of course be the reason why I am incapable of not finding the solution myself.


texts:
Greetings to everyone,
A few months ago, I started creating electrical circuits. Im trying to produce a control circuit that will control the pragotron clock using the DCF77 module. My circuit also contains a backup power supply that will supply the Arduino NANO in the event of a power failure. This backup will help keep a record of when there was a power failure and how many pulses are needed to reset the clock time properly.
I monitor power failure on the power supply by optocupler (when optocupler stop working, arduino mesure voltage drop) . If this failure occurs, the relay closes, which connects the 9v battery to the circuit. When the arduino is powered by a battery, it switches to power saving mode (~ 4 mA), and the DCF77 module is de-energized. I want to use a solid state relay to close the base circuit, but I have no idea how much mA it can take in the on state. I'm afraid that on state can drain batery realy quickly)
My question is:

Is this circuit designed correctly?
Is there a component that would heat up the backup battery circuit when the emergency power supply fails? Such a relay, on the contrary: if there is current in these "mysterious" component from the mains supply
the contactor is switched off, in the momentwhen the main power fails, the contactor closes and the battery circuit is activated.

Thank you


texts:
I am currently trying to get the configuration bits set up to blink a LED with a 20MHz external crystal. It is operating correctly using the internal oscillator, but does nothing with the crystal, and is "Unable to enter debug mode" after programming. I have tried what seems like an endless variety of configuration bits, and the debug mode issue will not disappear. Also, I have tried disabling the Power-up timer, but it hasn't made a difference. MPLab v8.92. I'm not worried about the speed and therefore PLL values at the moment, I just want to get the thing to blink. Any ideas?

Internal Oscillator:

#include <stdio.h>
#include <stdlib.h>
#include<p18f4550.h>
#include <xc.h>

#pragma config FOSC = 9
#pragma config WDT = OFF
#pragma config LVP = OFF

void delay(unsigned int ticks)
{
    unsigned int i;
    unsigned int loopSize = 10000 * ticks;
    for(i=0;i<loopSize;i++);
}

void main(void)
{
    OSCCON = 0b01110000; // 8 MHz Oscillator

    TRISA = 0; // Set to output

    while(1)
    {
        LATA = 1; // LED on
        delay(100);

        LATA = 0; // LED off
        delay(100);
     }
}

External Oscillator:

#include <stdio.h>
#include <stdlib.h>
#include<p18f4550.h>
#include <xc.h>

#pragma config FOSC = HSPLL_HS
#pragma config WDT = OFF
#pragma config LVP = OFF

void delay(unsigned int ticks)
{
    unsigned int i;
    unsigned int loopSize = 10000 * ticks;
    for(i=0;i<loopSize;i++);
}

void main(void)
 {
    TRISA = 0; // Set to output

    while(1)
    {
        LATA = 1; // LED on
        delay(100);

        LATA = 0; // LED off
        delay(100);
     }
}


texts: Self-charging robot safety considerations

texts:
I have made a 3S5P (18650 Sanyo NCR18650GA 3500mAh with 10A discharge rate) battery pack (about 220 watt hours when fully charged) for a robot.
I'm using a BMS with balance (supports up to 60A continuous discharge) for the pack.

Sense its a self-charging robot the docking station will also have a smart charger that disconnects when the battery is fully charged. The docking station does not have a balance connector because the BMS w/Balance should take care of that.
Is it safe to use the discharging cathode while the robot is charging so I can keep the robot awake?
There will be two cables coming out of the BMS. One connected to the charging cathode that connects to the smart charger, and the other is the discharging cathode that powers the robot. Unfortunately, there is no datasheet for the BMS except these information and the diagram pictured above.
Dimensions : 96 * 45MM
Application: 3 series 12v lithium battery protection board
Type of batteries : lithium cobalt / manganese lithium / ternary materials
Single overcharge protection voltage 4.25V ± 0.05V (4.20-4.35V / / 0.05V per upgrade )
Single overcharge recovery voltage : 4.10-4 .00 V
Single Over-discharge protection voltage : 2.50V ± 0.1V (2.50-3.0V / / every .05 V into the class )
Single Over-discharge recovery voltage : 2.80V ± 0.1V
Protection Current consumption : ≤ 300UA
Short circuit protection current : 120A
Short circuit protection time : 500MS
Temperature protection : 55 / 65 / / 75 degrees
Continuous operating current : 60A
Single balanced voltage : 4.19V ± 0.02V
Single balanced current : ≤ 55MA

The robot also needs a way to determine when it is fully charged so it can continue exploring. Which voltage source should I use to monitor it while its docked?
For added safety, I used a temp sensor to monitor the battery while charging if it overheats the robot will disconnect itself.


texts:
I have a simple question regarding the posted image.

Isn't the potential at point B = 0 or grounded?

In that case both the emitter and base will be effectively at ground and I don't see how the transistor would work then?

What am I missing?


texts: What socket and terminals do I need to buy for this plug?

texts:
I have a "coin mechanism" from a fruit machine that I want to connect up. It has two plugs. One is 17 pins and one is 22 pins. The connections are the 2.54mm connectors and the instructions say I need a "17 Way Molex SIL 6471" connector.

For the 22 pin plug I have the correct socket but don't have the tools or the crimps in order to add any more wires to it.

Here is the correct socket for the 22 pin plug.

And here is the connections from one on of the links inside the plug.

I did a LOT of Googling and also asked on here and managed to find these sockets from RS.

These sockets fit the slot after I snip off the small plastic 'keys' at the edges but I don't think I've bought the correct crimps.

These are the crimps I bought that I thought would be needed.

But these crimps don't seem to suit the socket I've got.

Do you know what socket and terminals/crimps that I need to do this job properly?

A big thank you for any help you can give me and if you need more information please ask.


texts: Measuring crystal drive strength without a current probe

texts:
TL;DR

Is there a means of measuring the crystal drive level reliably using voltage measurements (even with a differential voltage probe)?

Background:

I am attempting to measure the crystal drive strength in order to ensure that it is not exceeding its rated power of 100uW.

Every application note I have read on the subject says to measure with a current probe and calculate from there.

Unfortunately, I don't have a current probe capable of measuring this signal.

Is there any other means of measuring the crystal drive level reliably using voltage measurements (even with a low-capacitance differential voltage probe)?
Coarse accuracy (say 25%) is fine - if I'm not that far below the max drive strength, I would concerns about the design in any case.

For example, would it be valid to measure the voltage across a small "R_Q" (e.g. 1R) on the below diagram?  What pit-falls are there in using a method like this?


texts: What would happen if a neutral wire and a hot wire were vastly different lengths?

texts:
Pretend you had a 120v load, where the hot (ungrounded conductor) was say only 5 feet in length from the source to the load, but the neutral was say, 1000 feet. Excluding things such as voltage drop (we use a thick enough wire, or whatever), what would happen when you turn on that light bulb? Would it pause for a fraction of a second while the electricity passed through the entire circuit traveling on the neutral?

Would it matter if it was a 240v load (ie. a motor). Would it the hurt the motor, pause before turning on, or maybe the motor would turn on despite one phase (say 'ungrounded conductor #1') being 0.1 second behind since the wire was so much longer than the other?


texts: Is the so called kTC noise, that is inherent in an RC filter, dependent on bandwidth?

texts:
An RC filter has intrinsic noise called the kTC noise which is given by the equation
$$
v_\text{noise} = \sqrt{\frac{kT}{C}}.
$$ Does this equation calculate a noise density with units of volts per root hertz? Or does this equation calculate an RMS noise voltage that is not bandwidth dependent?


texts: Where can I find pin mappings for the ATMEGA168?


texts: How to make 95%+ efficiency voltage regulator?

texts:
I need to make an 11 volt voltage regulator.  I would really like this to be step-down, not a linear voltage regulator because I am going to be drawing between 1-2 amps at 11 volts, and if I was using a linear voltage regulator it would get very warm.  The input voltage that I am using is going to be about 12.8 volts.

I know a linear regulator under these circumstances would have 86% efficiency, but they are not reliable when working with voltages close together.

The last option I can think of (which is still linear...) would be to use resistors to lower the voltage, but I don't think that that would be any cheaper than using a step down converter.  Because the resistors would have to "handle" 3.6watts.

There are regulators like this on eBay (which I am bidding on, but only up to $2), should I just buy something like that?  Or would it be cheaper to make it myself?

Even if it is cheaper, I don't know how, and that's why I'm here :)


texts: Identifying bjt amplifier circuits configurations

texts:
how to identify configuration (CE or CB or EF) of this bjt amplifier circuit ?

in complex circuits (bjt amplifier), most  of the times I have this problem of figuring out its configuration.
My approach  to find configuration is

to check which terminal is grounded or common, or
to check  terminals between  which   ac signal is applied  and  terminals between  which load is  applied

and based on that  we can guess its configuration.
I am not sure whether  my approach is correct or not, because  I still  am not able to figure out configuration of complex circuits (as given in figure).
When I try to determine configuration of Circuit(in figure) I follow these steps-
using 1st method that I mentioned no terminal is grounded so I didn't reach to any conclusions
using 2nd method it seems like ac signal is applied between base and emitter but I cannot understand whether load is connected between base and emitter or emitter and Collector and that's it where I got stuck I don't know how to proceed further?
Is there any general rules to  identify configuration of complex amplifier circuits and we can tell its configuration just by looking at it?


texts: STM32 - two errors in turns during programming

texts:
I'm trying to program STM32F107VCT6 via SWD and I'm constantly getting two errors in turns (literally):

Error: Connect failed, check config and cable connection

Error: Flash driver function execute error
Erase: [ 0%]

By "in turns" I mean that when I click "Download Code To Flash" in CooCox CoIDE, I'm getting the first error, and after the second try, I'm getting the second one.
I have a PCB made from the same schematics with this model of STM32 and it works just fine. Changes between the old board and the new one are very insignificant.
I thought the problem may be in connecting NRST line, but everything is fine. I used 10k pull-up resistor, and the connections seem to be OK. Also, the crystal oscillator looked guilty, but I disconnected it to check if I could program STM32 on the internal oscillator, but it didn't help. All signals are connected correctly and all GNDs are connected together.
Could someone point out some possibilities why STM32 could behave like this? I would be grateful for any help.


texts: RGB led weird color behaviour (blue except when touched to skin)

texts:
I have an RGB LED, which I belive to be the diffuse version of this one:
https://www.sparkfun.com/datasheets/Components/YSL-R596CR3G4B5C-C10.pdf, though I am not completely sure, as I bought it some while ago.

I have a 5V power supply (USB), and based on the data sheet I would calculate the needed resistor values as 90 Ohm for green and blue and 150 Ohm for red. I'm using a 100 Ohm resistor for green and blue each and 100+47 Ohm for red, i.e. pin 2, the common ground, connected to ground and each of the other pins connected to 5V through the respective resistor(s).

I am doing my connections on a breadboard.

Now if I connect any of the pins separately, leaving the others disconnected, the LED lights up more or less blue. Except if, after having connected the red pin, I touch the blue pin with a wire which is touching my skin, then it actually lights up red. If I now touch the green pin with the wire it reverts to blue.
By playing with touching and connecting the pins in different orders I manage to get a nice white color, and I have managed yellowish hues and something remsembling violet or pink. I haven't managed to get green and I've even had what I think are mixed colors from just one pin connected.
The blue from the red pin is fainter (because of the larger resistor, would be my guess), but the red is quite bright.

What is happening? I have multiple LEDs of the same type and all the ones I tested show this or similar behaviour.


texts: Is there a common name for scope collar clips?

texts:
I am looking for spare scope collar clips (which attach the ground lead to the scope probe), so that I can make some custom ground attachments for connecting probes to some PCBs. The current crocodile clip damages the PCB and pops off sometimes, but it is still useful for other devices. A lead which is permanently attached to the PCB that could be unclipped at the collar would be more useful.

I am looking for just the clip, which is a flat metal part: I will attach my own wire to it. Does anyone know if such a thing can be bought separately to the probe, if they are standardised or what the canonical name is for such an item?

Edit I found the manufacturer's range of probe accessories: the alligator clip-wire-collar assembly is part #196-3120-01, is named "Clip-on Ground Lead" and costs about $12 (but looks to be hard to get in the UK). The clip by itself does not seem to be part of the range, however.

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texts: Which resistors and capacitors are on this HX711 board?

texts: I have this HX711 board. What model of resistors and capacitors are used here? I need similar the same mounted resistors and surface mount capacitors. I would be grateful if you drop the link to them.


texts: Is there such a thing as a fail-safe, low-power relay?

texts:
Background
Let's say I have a device. I can't give details, but, like many heat-producing devices, it's intended to be used for a limited period of time, but if left on indefinitely can be very dangerous. Let's also assume that:

The device needs mains power.
The device needs to be safe (at least so far as turning itself off) for unattended use.
Using a mechanical timer is not an option. (Maybe as a backup, but not as the primary timer.)

I really want some sort of fail-safe timing mechanism. That rules out most traditional digital timers, and even some mechanical timers. What I'm thinking I'd like to do is use a capacitor to power some sort of NO-relay in a way that makes it as close to impossible as I can manage for the power to stay connected for longer than some period of time. (Basically, using an RC circuit as the timer; the idea being to charge the cap(s), physically disconnect the power supply from the RC circuit, and then drive the relays off the stored charge.)
Question
I'm somewhat familiar with solenoid relays, which would be good due to physically interrupting the circuit; however, IIUC there is some possibility these can weld shut. I'm less familiar with the failure modes of solid-state relays.
Is there a device that can run off of very low current that can switch at least 100 W that could be suitable for such an application? Am I being overly paranoid about using a solenoid relay?
Notes

By "low current"... generally, the lower the better, but let's say ~1 W or less. ~10-100 mW would be better, but 1 mW is probably overkill.
Hazard level: one or a few very angry (or deceased) people, but well short or Fukushima.
I don't have specific regulatory requirements, but I'm also not inclined to cut corners.
This is for a personal/DIY project (or I probably wouldn't need to ask here); I don't have a huge budget to be contracting support agencies or purchasing very expensive components. (Note: $1k is "very expensive", $10 isn't.)
I don't need precise timing. ±50% would be a bit excessive, but ±25% would be very acceptable, and ±1% would be bordering on overkill. Initial operation time is "a few minutes", though eventually I may want to be able to go up to ~8-12 hours.
I don't expect to be dealing with anything higher than US mains (~120V), and probably everything will be running DC.