texts: How could a charger "cut out" when charging is complete?

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Possible Duplicate:
  Why is it so problematic to have close to zero standby power consumption?
  How would you detect vampire/standby power?

This article discusses why cell phone users have to unplug the cell phone charger once charging is complete to avoid unnecessary consumption of energy when the charger goes into standby mode and why the charger itself couldn't somehow shut off.

First they explain that ay kind of electrical switch would need some standby power and so zero consumption is impossible. Then they say they

  could make a charger that cuts out when the phone is full

but that would require a lot of extra components that complicate charger production and that offsets all the benefits.

What do they mean saying "cuts out" and how can that be implemented?


texts: Wired vs SMD resistor on 230V optocoupler input

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For circuits similar to the one below, we used large wire resistors with proper power rating in our past designs.

The question came up, if it would be a good idea to replace the resistor with SMD chip resistors (lower cost, less space, easier assembly).

Most 2512 SMD resistors for example are rated for 200V (mainly thick film material). So using two of those in series should work with respect to the voltage.

You can get wired resistors with guaranteed failure mode "open" and non-flammable. Is there some equivalent SMD resistor type available? What material/technology would I look for?

Creepage distance shouldn't be a problem, since the opto coupler properly isolates the rest of the electronic.

Are there any other considerations I missed?


texts:
I'm designing a simple 15V to 5V DC voltage feadback mode non SMPS regulator.

I'm using E13007E2 power NPN switch mode transistor. And to drive that transistor
I'm using C945 another transistor.

This is my schematic diagram of the circuit.

It gives 4.5V output when it's not loaded. But when it's loaded and after some
time the C945 had gone. It's 2 junctions are open now.  c945 is to shunt just only
6mA. Why it can't handle 6mA?

Any idea how could I calculate the operating points precisely?


texts: Signal modulation at 38kHz using a 16-1 mux w/ 4bit counter

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A little back story to what I am trying to achieve: I want to be able to control the bit pattern using DIP switches to send a controlled IR signal at 38kHz. I want to create a "game" where each IR transmitter can be easily programmed to a different signal and "activated" on a server back-end to allow that signal to be received by my receiver on an ESP32. The problem I seem to have is that I cant get a consistent 38kHz signal, the more DIP switches i activate the higher the signal frequency gets, is there some way to limit this so it always sends at 38kHz?

Attached is my schematic:

Any ideas would be great!
Thanks


texts: Does the Ebers-Moll BJT model support multivibrators?

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I'm developing a circuit simulator and tried to create an ideal astable multivibrator (I set some values not to be completely symmetric for the correct startup).
The simulation usually stuck in equilibrium states.
Then I put capacitors between the emitter and base on both BJTs. This fixed the simulation , everything worked fine.
Is it possible that EB capacitors/delay effects are necessary in the BJT model to create a multivibrator?


texts: Comparison of wireless communication technologies: bluetooth vs wifi

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I would like to build a simple battery-powered board with temperature and humidity sensors. It should be able to be placed in different rooms of an appartment, and I want to be able to read the values remotely. Eventually I would like to equip all rooms with such board.

I haven't chosen any hardware yet, but I was thinking to connect the sensor(s) with a low-powered microcontroller, and some wireless interface. But considering the somewhat low distance (not more than 10m), the likely presence of wall, I am hesitating on the technology I should use for the wireless communication.

I considered the following technologies

WiFi,
Bluetooth.

Could anyone summarise the pros and cons of those three technologies? Or point me to a good review, which would help me choose the best for my needs?

Of course, if I am missing a very crucial technology, do not hesitate to point it out. Radio RF?

PS. I know that there are commercially available products for exactly such needs, but I would like to do it myself, for the experience it would bring me, and also because of possible extensions I could implement.


texts: Implementing a safety lockout through ladder logic

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The family fireworks show has become my soon-to-be brother in law's and my "thing" over the last couple of years. We have some ideas to make the show better next year, my part is spinning up some automation hardware.

SW1 will serve as a master power switch for the entire system. The digital parts of the system will pull their power from right after SW1. SW2 is the ARM/FIRE switch. I do not want SW1 to close and power the circuit unless SW2 is open.

simulate this circuit – Schematic created using CircuitLab

It's been a long time since I've done ladder logic. This was my first thought. It satisfies my requirement of not powering on unless SW2 is open. The problem is, flipping SW2 from ARM to FIRE will shut down everything. Adding a transistor driven from a spare GPIO pin would solve that problem. I don't particularly like this solution because it puts something safety critical in the hands of software, and safety critical software is not what I do. What do I need to change to make this work with switches and relays?

simulate this circuit


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I am trying to understand better the characteristics I need to look at when choosing an extension lead (i.e. an extension cord that plugs into a socket, and gives me multiple sockets on the other end).

I know it is best to avoid using these, but I have to as I do not have enough sockets.

I have budgeted for expensive extension leads, as I want it to be as safe as possible, so the issue is how to get the best possible.

Is the only risk overheating ?
As far as I understand, the thicker the extension lead, the safer it is because it is less likely to over heat. Is there any downside in getting the largest found cable?
Some have a fuse, is it useful ?
Can I use extension lead bought in a country where Volts are 220V, in a country where Volts are 230V ?

Any other tip is much appreciated, thanks!


texts: Can somebody please tell me why do we have those tiny random spikes on the output signal? And why does the input wave behave like in the picture when we reduce the frequency of the noise source to 1kHz?


texts: Can I get the NOT of 3 inputs using as many and/or gates but only 2 NOT gates?

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Came across this question in an online course. I think it belongs to electronics and logic alike.

EDIT: To clarify, if I have A, B, C as inputs, I need ~A, ~B, ~C as outputs, separately.

EDIT-2: So what I did was constructing a XOR off the inputs A and B. When either one of them is set as 1, then the other one is automatically reversed. But won't be able to get simultaneous results.


texts: How to halve a frequency with analog circuitry while preserving signal integrity?

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The question is simple, the answer I'm not sure...

How could I pick up an analog audio signal, divide it's frequency by 2 (one octave lower) and send it back on it's way?

I could do this by sampling the input signal and generating an output signal that is half of it, but the generated signal would be a digital signal, not an analog, and when we speak of audio, tone means a lot, and the less differences there is between the input and output signal (besides the fact that the output is an octave lower, obviously...), the better...

Is this possible in anyway?

There can be digital circuitry, e.g. for sampling, but the least, the better.


texts: Replacing capacitor with a battery as a filter/buffer in a 6V circuit - is it a viable idea?

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I have a circuit in my bicycle where I get the variable voltage, variable frequency AC from a hub dynamo, rectify it with a bridge, regulate it with a 6V zener, and filter it with a 6800 uF capacitor.

While I am moving, the voltage gets quite stable and I can successfully power some 20 leds (around 400mA max), but as soon as I stop, lights turn off.

Now that I want to add an Arduino to the circuit (with a LM2940 LDO to step down from 6 to 5V), I need something that holds more charge - even if it is only part of the Arduino subcircuit - because otherwise the Arduino will keep resetting.

Since the capacitor is "just" something that holds charge at a given voltage range (after it's been regulated by the zener), I wonder:

  Could I replace a Zener + capacitor regulator/filter in an intermitent charge/discharge circuit with a battery pack? What should I take into consideration? Would I need a dedicated power-path circuit, or is there a "pure dumb battery" way of doing it?

My goal is not even to have the leds on all the time, I actually would only want some juice to prevent Arduino resets at stop lights (2 minutes max). All the leds would be driven by Mosfets, so the Arduino path consumption should be quite low.


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I'm trying to get a better understanding of how this 1.5v pulsing transmitter works.  I found it on Youtube and modeled it up with some success.
https://www.youtube.com/watch?v=aLS9DsF2ilg
The schematic is as such.

My questions are:
1. Does the LC tank circuit need to be tuned to the crystal freq?  When I insert a 40Mhz crystal I can see it on the spectrum analyzer but tuning the tank circuit capacitor doesn't seem to effect anything.

In the video the guy mentions moving the tank capacitor to ground instead of the power rail?  Any ideas?
How does the pulsing action work?  Is it a side effect of 1.5v, the 220k resistor and the NPN choice?
Lastly, when I insert a 10nf cap across V+ and V-  the oscillation stops.

Thanks in advance to anyone who has ideas on this.


texts:
I'm on the market for a car subwoofer system, and it occurred to me that there were many amplifiers capable of producing 1000W+ of output. However, even with a 1-ohm speaker, the power equation \$P=V^2/R\$ seems to dictate that even with a car battery voltage of 16V, the amplifier would not be able to drive more than 250W into the load.

So how do they do it? Is some kind of voltage conversion done inside the amplifier?


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What kind of capacitors should I use to couple audio? I'm dealing with line level 1Vp-p audio, with a 1V dc offset (typ.) I want to convert this into 1Vp-p AC, at up to 20 kHz. My first version used ceramic 10u 10V caps - a simulation showed attenuation by about 15% at 20 kHz.

Update: I eventually went for 10u 6.3V. I did not need Hi-Fi quality and the fact that 10u 6.3V caps were available in 0603 packages was useful for me.


texts: PCB: digital at one side and analog at another

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Due to layout restrictions I may have to have digital signal at one side of the board, and analog signal at the other side. I used to separate them dedicating parts of the board for each, but not this time.

Board thickness: 1.6 mm
Layers: 2
Digital signal: 3.3/2.5/1.2 V LVTTL, up to ~30 MHz
Analog signal: audio ±1.5 V (output of op-amps in voltage follower mode powered from ±12 V), mostly human ear hearing band

I am worried if quality or integrity of one signal will be negatively affected by the signal on another side of the board.

Are my apprehensions having a reason to exist, or I am over-complicating things? Should I make 4-layer board with ground layer as "padding" between digital and analog?

In general, what should I be aware of if I will decide to continue with such design?

@MichaelKaras: Not possible to separate at this time, that's why I ask this question. I have to place audio jack in the middle of digital logic because putting it in other places of PCB will simply make it not accessible outside of chassis. Audio signal will be fed to the jack through airwires, thus in general there will be just several pads of analog signal, but there're digital wires at another board's side which I afraid may suffer.


texts: Internal or external Oscillator on STM32F072CBT6

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Whats the benefits between internal and external Oscillator?
I'm using a STM32F072CBT6 and I tried both with internal and external. Dont see any differents.
Can someone explain why I maybe should use an external Oscillator?


texts: Unexpected saturation with the rail to rail instrumental amplifier AD623

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I'm trying to use the rail-to-rail instrumental amplifier AD623. Here the datasheet.

simulate this circuit – Schematic created using CircuitLab

First experiment:
AD623 set as a voltage follower. Gain = 1 obtained by removing  the Rg resistance between Rg-  and Rg+ pin.

Everything goes right until I reach 4.3 V (read with VM1 and VM2)
4.3 V is the maximum amplifier output even when the difference between inputs is 5V.
But this is a rail-to-rail amplifier...

Second experiment:
AD623 set with gain = 2 (using a 100K resistor in according to datasheet).

Everything goes right until I reach 2 V of difference between inputs.(read with VM1)
In this case 4.0 V is the maximum amplifier output.

Under this value the amplifier works good (if in input I have 1V in output I read 2V)

Other information:

+Vs = +5V
-Vs = GND
REF = GND

How is it possible?

Can anyone help me?

Thanks for help (and sorry for my poor english)


texts: How can I find the equivalent resistance of this circuit?

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I'm trying to find the Norton Equivalent circuit using Norton's Theorem for the circuit below. Since I need to find the Norton Resistance, I removed all the sources from the circuit. The problem is, I can't find the equivalent resistance because I don't know what to do with the 10kΩ resistance. I would appreciate it if I can get an explanation on what I should do. Also, what should come to mind when trying to find equivalent resistance of complicated circuits? Thanks.
Circuit for Finding Norton Equivalent

Circuit for Finding Norton Resistance


texts:
I have a question on lag compensators in general.

Why do they increase both the rise time and the settling time? Is it due to the introduction of a slow pole?

Much thanks!


texts: Is it necessary to have a 50 Ω impedance track after the matching circuit and the antenna for a space constrained RF mcu(MKW21Z) design?

texts:
I have followed quite a few RF MCU based designs from Texas Instruments like CC3200, CC2650 etc and in all of them I did not have to worry about the trace impedance between the MCU pins and the antenna.

Their application notes mentioned that as long as the antenna is not far away from the MCU, there is no need to bother with impedance matching.

However now I am designing a RF (2.4GHz) based MCU from NXP, MKW21 to be precise. If you look at the hardware design guidelines, they mention that the trace impedance should be 50 Ω (page 6ff). Here is the pdf link .

Now, my design is space constrained, so the antenna will be kept as close as possible to the MCU. In this case do I still need to monitor the impedance of the track between the tuning circuit and the antenna ?


texts: why sometimes we need to use Broadband Transmission (Using Modulation)?

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I was reading a textbook which says:
Baseband transmission requires that we have a low-pass channel, a channel with a bandwidth that starts from zero. This is the case if we have a dedicated medium(such as coaxial or fiber optic cable) with a bandwidth constituting only one channel. For example, the entire bandwidth of a cable connecting two computers is one single channel.
I'm a little bit confused, if dedicated medium means low-pass channel, why we still need Broadband Transmission (Using Modulation) to have bandpass channel—a channel with a bandwidth that does not start from zero and we need to convert the digital signal to an analog signal before transmission. Because for example, broadband transmission using modulation is the sending of computer data througha telephone subscriber line, the line connecting a resident to the central telephone office.
Isn't the subscriber line also a dedicated medium, connecting a user and telephone office?


texts: Can the ADS1118 ADC converter accurately read a voltage close to GND?

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1. About the ADS1118 ADC converter

I'm using the ADS1118 ADC converter from Texas instruments to measure a voltage. You can find the datasheet here:
http://www.ti.com/lit/ds/symlink/ads1118-q1.pdf
The converter has four analog inputs. You can configure them to be four independent single-ended inputs, or two differential inputs.

2. Single-ended mode

If configured as single-ended inputs, my setup could look like this (simplified):

3. Differential mode

In differential mode, I can measure Vsig better because I can compensate for the resistance (and possible noise pickup) from the cable going to the unit producing Vsig.

I expect to see AIN0 and AIN1 signals like this:

What bothers me is AIN0 being so close to GND (Obviously, it actually is GND measured from a little distance). In my experience with OPAMPS, input signals should always stay away from the positive or negative rails. Some rail-to-rail OPAMPS can deal with such inputs, but even then you usually should keep at least a few mV distance.
OPAMPS perform best if you keep the inputs close to mid-rail. In other words, you keep the common mode of your differential input pair close to mid-rail.

4. What says the datasheet?

I've searched in the ADS1118 datasheet, but couldn't find any figure relating the signal's closeness to the GND or Vdd rails to reading errors.
The only figure that could be useful is this one:

But the figure isn't entirely clear to me. It looks like the x-axis represents the differential input, being for example Vdiff = AIN1 - AIN0. If that's the case, then this figure is useless for my case, because it doesn't say anything about the common mode of this differential signal.

5. What if it doesn't matter?

What if the common mode of the differential signal doesn't matter? Then the following two cases should give exactly the same results:

I feel like the situation on the right (SITUATION TWO) will give much better readings than the situation on the left (SITUATION ONE). But I can't find anywhere proof of that in the datasheet.

6. My question

So my question is:

Will SITUATION TWO from the last figure give better results (lower error) compared to SITUATION ONE?
If yes, can the error difference be quantified (some formula/graph)?
Where do you find this info in the datasheet?

Thank you very much ^_^


texts:
I have got a problem with an USART module I wrote in C for PIC12F1822, related to USART transmission.

Everything happens to be fine when I debug in MPLAB with PICKIT3 (TXREG changes value and every register is updated correctly as I defined it).

But the PIC won't send anything to the TX port, as there is no signal at all observed at the oscilloscope.

I followed the steps in the datasheet found here (see page 287 for USART setup)

Here is my code :

            #include <stdio.h>
            #include <htc.h>

            void init_ports(void);
            void enable_transmitter(void);
            void enable_receiver(void);
            void write_USART(unsigned char);
            unsigned char read_USART(void);

            int main(){
                unsigned char i = 0;
                init_ports();
                enable_transmitter();
                while(1){
                    write_USART(i);
                    i++;
                }
            return 0;
            }

            void init_ports(){
                //RA0 = TX/CK and RA1 = RX/DT
                TXCKSEL = 0;
                RXDTSEL = 0;

                //Baud rate configuration - clock @ 1*4(PLL) MHz, refer to p.300 datasheet
                BRGH   = 1;
                BRG16  = 0;
                SPBRGL = 0x31;
                SPBRGH = 0x00;

                //Disabling eventual analog I/O function
                ANSA0  = 0;
                ANSA1  = 0;
            }

            void enable_transmitter(){
                SPEN   = 1; //enables the EUSART and automatically configures the TX/CK I/O pin as an output
                SYNC   = 0; //configures the EUSART for asynchronous operation
                TX9    = 0; //8-bits transmission
                TXEN   = 1; //enables the transmitter circuitry of the EUSART
                TRISA0 = 0; //TX on RA0 = OUTPUT
            }

            void enable_receiver(){
                SPEN   = 1; //enables the EUSART
                SYNC   = 0; //configures the EUSART for asynchronous operation
                RX9    = 0; //8-bits transmission
                CREN   = 1; //enables the transmitter circuitry of the EUSART
                TRISA1 = 1; //RX on RA1 = INPUT
            }

            void write_USART(unsigned char input){
                while(!TXIF) //interrupt flag - buffer not ready
                    continue;
                TXREG = input;
            }

            unsigned char read_USART(){
                while(!RCIF) //interrupt flag - buffer not ready
                    continue;
                return RCREG;
            }


texts:
In my application there is a signal from 0-10V. The signal gets into 4 different OPAMPs with different gains which are supplied from +- 5V.
I would like to limit the input voltage to the OPAMP to 0-2.5V, so that when the signal reaches 2.5V, it will stay at 2.5V (a resistor divider is not an option).
I thought about a zener diode with a VZ of 2.5V. The problem with it is, that for a very low VZ, there could be a large tolerance at different temperatures and different currents.
If the VZ was 15V for example, it would be a good solution.
I hope to hear some ideas.
Accuracy is very important, so the solution must minimize the effect on the signal when it is in the permitted range.


texts: How to make a circuit to run DFRobot with a Netduino

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So I ordered a DF Robot kit and got some help to put it together.

I want to control the wheels with my netduino.

What I want to do is simple. Press the netduino's button, and start the 4 wheels in the same direction, full power.

When I try to make it run with one wheel plugged in my breadboard, it works, the wheel move.

But when I add a second wheel, nothing happens. It seems that I don't have enough power to make the wheels move.

The netduino is powered by a 9volt battery. When I press the button, the netduino let the big power source ( 5 AA batteries , as suggested in the kit)  flow in the motors. (this is how I see it correct me if I'm wrong.)

 ( note that I removed the resistor)

Basically, I'm doing the exact same thing with my df-robot kit.

The motors negative wires are all lined up in the #5 pin of the 4n35 transistor.
The 4 positive wires are all lined up with the positive power source positive wire. (5 new AA batteries)

I'm using the 4n35 transistor that came with my netduino kit I ordered.

But before I go on and buy something along the lines of a motor shield, is there a way to get it working with my current setup ?


texts:
I have written a verilog code for a circuit (test.v) and a testbench (testd_tb.v). I use these commands for generating the power using cadence encounter RTL compiler.
I have made 3 folders. Work, RTL(where all .v files are stored), Library (which has slow_normal.lib).
In the work folder I type these commands :

rc -gui (to invoke the encounter tool)
set_attribute lib_search_path ../library
set_attribute hdl_search_path ../rtl
set_attribute library slow_normal.lib
read {test.v}
elaborate
synthesize -to_mapped
report power

The above commands help me to generate the power for the design but I am unable to get test bench specific power output. Kindly do suggest me the changes that can be made in this code.


texts:
I'm unable to come to terms with something I think is a paradoxical situation relating to the virtual ground of an Operational Amplifier.Please pardon me if this is a really stupid question.

When the 'Negative Feedback' in an Op-Amp (Ideal) makes the difference between its input terminals equal to 'Zero'. Shouldn't the output become zero too because the Op-Amp is fundamentally a Differential Amplifier and according to the equation:

Vo = (Open loop gain)*(Differential voltage b/w the inputs)

The Explanations I've come up with so far are:-

1) The Op-Amp Output is indeed zero and it is the External Circuitry
 (consisting of resistors Rf and Rin) that create the voltage, which adds up to the Op-Amp output voltage (in this case Zero) at point B to create the actual output of the system.

2) The virtual ground is not perfect and there exists a very very small differential voltage at the input which gets multiplied by the very high gain and produces the output.

I'm fundamentally unable to understand how the actual definition of Op-Amp behavior is consistent with the virtual ground phenomenon without making the output zero.   Please Help!


texts: Introduce delay on a single bit signal w.r.t. input clock

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I have seen this question and removed the "#.." part of my code to introduce delay, since my code will ultimately run on hardware.

Anyway, I am trying with counters and not able to introduce the required delay of n clock cycles.  Here is my code:

`timescale 1ns / 1ps

module SyncDelay( clk_27,vsync,vsync_o);
 input clk_27;
 input wire vsync;
 output reg vsync_o;

 reg[2:0] cnt=0;

 always @ (clk_27)
 begin

    if(cnt > 3'd4)
    begin
        vsync_o = vsync;

    end
    else
    begin
        cnt = cnt + 1;
    end

 end //always

endmodule

This is what I'm getting:

vsync and vsync_o have the same values at all instances. Instead, I want vsync_o to lag with a delay of n clock cycles.

EDIT:

With the code:

  `timescale 1ns / 1ps

  module SyncDelay( clk_27,vsync,vsync_o);
   input clk_27;
   input wire vsync;
   output reg vsync_o;

   reg[2:0] cnt = 0;

   always @ (clk_27)
   begin

      if(cnt > 3'd4)
      begin
          vsync_o = vsync;
          cnt = 0;

      end
      else
      begin
          cnt = cnt + 1;
      end

   end //always

  endmodule

I get:


texts: How can a crossed dipole (turnstile) antenna be omnidirectional in 3D?

texts:
A crossed dipole or Turnstile antenna is said to not only be omnidirectional in the plane of the two dipoles, but its pattern is roughly spherical, there's no null along the axial (boresight) direction.
There are no monopole waves; in order to couple to plane waves in the far field an antenna must have a dipole moment, but a dipole field will always have a null somewhere.
Question: How does this actually work? What's the "secret sauce" for getting a spherical radiation pattern from a couple of dipoles?
I'm wondering if there is magic involved somehow. The author of the following does mention having a tool that can make wires longer after cutting them too short though at the time of writing it had been "misplaced" ;-)

With the initial dimensions, best return loss was at 1.14 GHz, so I pruned the dipoles proportionally to move it up to 1296 MHz. As can be seen in Figure 3, I trimmed a bit too much, so it ended up tuned to 1340, but the Return Loss is still a very good 22 dB at 1296 MHz. I couldn’t find my tool for putting stuff back on, so I figured this is good enough.

cf. Quick and Cheap Omni Antenna for 1296 MHz from W1GHZ.org found at http://www.w1ghz.org


texts: Honeywell sensor protocol True IAQ system

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Does anyone know the protocol of the Honeywell DG115EZIAQ TrueIAQ sensor system. This is an outdoor temperature/humidity sensor control system. It has a two wire sensor with 24VDC across the pair and a pulsed waveform superimposed upon the DC. I added this question to clarify my needs of my first post "Protocol Analyzer in software?". Thanks in advance.

EDIT:
The data is updated once each ~1second. I assume it is a response from the sensor only, however that is just a guess.


texts: Slow down rs232, 9600 (locked) to 300 for vintage printer

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I have an old GE terminal (late 70s) that I'm trying to use and an old serial printer. The RS-232 port is locked at 9600 baud but my TI Silent 700 (late 70s) is 300 baud max. I've tried to Google printer buffer ideas but came up with nothing.
I was thinking I might be able to make a buffer using an Arduino but figured before I pursuing Arduino shields I'd ask for ideas.


texts: What is all properties of orthogonal axis (dq) axis?

texts: We know about the transformation between abc three phase to dq0 axis which is orthogonal. BUT I am confused about What is the added value and all properties of orthogonality for dq0 axis that help in analysis?


texts:
Ok, I know the basic function of an optocoupler is "turn on irLED, triggering a phototransistor and allowing current to flow"; an optical off then on switch.

Is there a reverse optocoupler, i.e. "turn on irLED, unknown component is triggered and stops/blocks current flow", an optical on then off switch?

Circuit A does something that includes a charging function then activates Circuit B.
As long as Circuit B has [enough] power, Circuit A is removed from it's power source (turned off) by a signal from Circuit B.  When Circuit B's power is gone/too low, signal is removed and Circuit A's power is returned and starts process over again.

I know how optical relays work (Circuit A on, Circuit B off, trigger on, Circuit A off, Circuit B on, trigger off, original condition).  A standard optocoupler is essentially one half of this.  I am wanting the other half.


texts:
I saw this display on Adafruit.

They describe it as a mix of an e-ink (the low power consumption) and an LCD (the fast response time). And further as "a matt silver background, and pixels show up as little mirrors for a silver-reflective display".

Does anyone know what this display technology is called?


texts: Muxed pin of Analog To Digital Converter,ADS8548 - Interface Issue

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I am trying to interface TI's ADS8548 ADC with Xilinx XC3S700AN FPGA to get the coordinates from an accelerometer.

When I went trough the spec of the ADC, I found that pin20 is a muxed pin for DB11/REFBUFEN.

The DB11 is for parallel interface (which I prefer in my application), but it's been mentioned in the datasheet that REFBUFEN should be kept low if Internal Reference Voltage is to be used.

Yes I want to make use of both the parallel interface for output and the internal reference voltage that can be enabled using the REFEN pin. Is that possible?

If I pull the REFBUFEN down hardwired, does it affect the digital output through parallel interface from the ADC in anyways?

Or if it can be done only by configuring the register named CONFIG, please explain in detail the interface needed to access the register from FPGA or any host in general. I went through the datasheet, but was not able to find any details on this.

I prefer this ADC because I want to do simultaneous sampling on all eight channels at relatively small sampling rate of 600 ksps.

Please let me know if the details I have provided are not sufficient for you guys to help.


texts: Surface mount capacitor value confirmation

texts:
I was just checking for some bad caps on my TV as I get a large distortion for a few minutes at power up.
The power board looked fine but I noticed some aluminium surface mount caps were bulging slightly on the control board (image attached ) so thought I would try to replace them.

Just wanted to confirm that these are 220 uF and I could just replace with through hole.

Thanks


texts: Is this a voltage subtractor switching the position of Q1 with Rc1 and Q2 with Rc2 ?Also if we want current to flow from the + sign to the - sign how many times bigger resistor than Rc2 and Rc1 do we need?


texts: Flow of preemptive multitasking execution of program

texts:
I am reading this article about preemptive multitasking and I didn't understand few things in the article:

The explanation says

  Figure 1 shows the execution timeline for two tasks and an ISR. First, the ISR preempts the lower-priority task. But that ISR's execution makes the higher-priority task ready to use the processor again. So the scheduler selects that task to run after the ISR, further delaying the return to the preempted task. Note that the processor considers the lowest-priority interrupt in a system more important than its highest-priority task.

Figure 1:

,

My questions are :

Shouldn't the exit from high-priority task be done by returning back to the ISR and then returning back to the low-priority task?
How is the lowest-priority interrupt in a system more important than its highest-priority task?


texts:
I have tried to solve this problem for a very long time and keep getting the wrong answer but am absolutely baffled at this point what I have wrong.

simulate this circuit – Schematic created using CircuitLab

My equations are as follows.

vcvs1 = (I2-I1)(-j300)

Loop1: 9+600-j300)I1+j300I2 = 0

Loop2: 2(I2-I1)(-j300)+(-j300)I2+300I2-300I3+j300I1 = 0

Loop3: -1+300I3 - 300I2 = 0

Then (-1)/I3 = Rth

The answer should be 247angle(-16 degree)

But this does not work out to that at all it's something around 90.

Am I just getting something simple wrong?


texts:
I'm looking at this data sheet: T67M-512Mb-Mobile-Lpddr-Sdram (targeting speed grade -75) and trying to understand the timing requirements for performing a read, specifically when to sample the DQ input data lines. It gives a formula on page 27 for Data valid output window (DVW) being tQH - tDQSQ

Writing down the min and max values as <min,max> in unit of nanoseconds, I find tDQSQ on page 26 as <-,0.6> . I assume if the minimum is not stated, the worst case is 0?

A formula is given for tQH on page 27 as tHP-tQHS. tQHS is on page 27 and given as <-,0.75> while yet another formula is given for tHP as tCH,tCL. Not sure what a comma means here.

tCH and tCL are both found on page 26 with values of <0.45,0.55>

Plugging in all my values, I get a final formula of:

(<0.45, 0.55> - <0.0, 0.75>) - <0.0, 0.6>

This formula confuses me as there are values within the ranges that can result in an overall valid window time of zero, or even a negative value.

Am I calculating/interpreting this correct? Do these values means that there are no gaurantees that the output data will be valid?


texts: Techniques for driving inductive load, e.g DC motor, with PWM and constant current

texts:
I'm having trouble getting full torque out of a DC motor at anything other than full speed with a PWM driving circuit.

Assuming the problem is inductance of the coils, what can be done besides decrease the driving frequency?

What is usually done? Nothing? If something, what?

I was thinking of using a constant current source, but at the beginning of each pulse, this would apply a voltage across the coils higher than the rated voltage. So, two questions:

Is applying a higher voltage OK? Or would it have to be a constant power source, rather than a constant current source? Or despite the counter-emf of the coil, is any voltage applied beyond specs going to reduce life or safety of the motor? And would the additional circuits have to be active, or would some clever passive circuit increase the voltage when each pulse energises the coils, without even needing a higher voltage power supply?


texts:
i am working on very low amplitude signals and sensors. I have recorded one hour data. And i am looking its FFT graph. You can see FFT image. My question is that, what can cause the spikes in FFT graph? And how can i filter it?

I should not see any spikes. Normal FFT plot should be like this:


texts: How soft-switching works in these circuit?

texts:
I read that one of the major power losses of an IGBT circuit is its switching losses.In order to overcome it, soft-switching is used. The book gave an example with the circuit diagram:

  This is know as "soft switching". The voltage or current applied to the switching circuit can be made approximately zero by using the resonance created by the LC resonant circuit and the anti-parallel diode across the collector to emitter of the IGBT. Gate switch control from the MCU has the voltage of the switching circuit VCE set to zero right before the circuit is turned on (ZVS) and having the IGBT current fl ow close to zero (ZCS) right before turning it off.

I understood that how ZVS and ZCS work in order to avoid power losses but I cannot understand how the given circuit above uses the LC resonant circuit to delay(?) the current before turning on the IGBT or delay(?) the voltage before turning off IGBT. It will also help me if you can give other circuit example(that is not too complex) having soft-switching. Circuit above is a resonant inverter with induction cooking


texts:
I am asking this question in hopes to get a solid answer from anyone who has direct experience dealing with the most recent RF as well as Bluetooth 4.0/LE developments.

What I am essentially trying to understand is why so many devices such as keyboards, mice and remote controls seem to always opt for using RF verses using Bluetooth.

More specifically - my understanding is that the new 4.0 specs of Bluetooth and the LE (low energy) variations would be the ideal protocol to use while not requiring a dongle.

My thought was that there must be something I am not aware of which you electrical/RF engineers do know.

In my view these reasons my be related to one or more of the following:

RF interference
Higher battery usage
Increase Latency
Company Policy decisions (like with Logitech that seems to always force the use of their own dongle)

Can someone enlighten me on the pros/cons based on their direct experience using both. Please provide any supporting facts to convince me that Bluetooth 4.0 or Bluetooth LE is the wrong wireless protocol to use for example as the wireless technology for a small handheld (apple style) remote control which does not need to be charged every week (other than the distance factor)?


texts:
I want to monitor traffic on a SERCOS bus that is controlled by a Schneider/ELAU C600 PACDRIVE
I have a profibus port on the C600 but don't want to impact scan time.
Is there a device/Gateway that I can install on the bus that will monitor traffic.
If there is, does it need a node address and does that address have to be registered in the PACDRIVE? It is SERCOS  2  (2MBaud)


texts: Approximate Gain vs Frequency Curve for an RC circuit

texts:
I'm trying to draw an approximate gain vs frequency curve for this RC circuit:

I can solve for specific points, i.e. when \$\omega=\frac{1}{RC}\$ the Gain scale will be at -3dB but I'm not sure what values to plug in for R & C since I have two resistors and two capacitors in this circuit. Am I just allowed to treat them like they're in series and use \$ C=C_1C_2\div(C_1+C_2)\$ and \$R=R_1+R_2\$


texts: Jumper wire solution for short header pins /

texts: I installed header pins that fit into a feather microcontroller, but since they are not double sided header pins, the top side is too short to attach normal jumper wires to. Is there some clean, non-permanent solution to this where I can still attach jumper wires, but not solder or desolder any existing pins?


texts: Do 9-pin LCD modules have a standard interface?

texts:
I bought some text LCD modules without spec sheets or obvious part numbers. They all have a series of connector pins, unlabelled other than a 1 to indicate pin 1. I was able to get the one with a Hitachi driver and 16 pins to work fine, and now I'm trying to get a 9-pin lcd to work.

Is there a standard pinout for most 9-pin LCDs?

Pin 8 is clearly A for anode, possibly for backlight. Pin 9 is K for cathode, again possibly for backlight. The other 7 pins are unlabelled besides the 1 and 9 indicating pin numbering.

There is a sticker on the back that reads:

UC164904
-GLHTX-A
97051306

And another that says 847845740. There is a Samsung logo as well. The controller circuit is covered with that hard black protective material that I typically see on cheap devices, so I can't see the controller at all.

If the faint outline I can see on the screen is right, it looks like its 16 columns x 4 rows.


texts: Need to add blinker module to relay trigger

texts:
simulate this circuit – Schematic created using CircuitLab

I have a simple light controller box. I have a 2 channel relay that controls a red and green light by magnetic switch. so we can tell from a distance if the door is open or closed. i have the switch part working great, but people are not gentle in my warehouse so the magnetic switches have been broken a few times. now i have a dpst switch installed on each unit and it was originally set to ground out both led's so they would make yellow. this is not working for us. I am now trying to add a basic motorcycle blinker to my design so we can make the relay constantly alternate red and green until the magnet gets fixed. the blinker wont blink. is there an inexpensive and safe way to make the blinker alternate the voltage on the switch of the relay so i can get this better. The supplier said to add a 5w load to it. Can i just add a 1ohm 5w resistor to the mix? When the magnet is down it could be two days of run time before I can get in and fix the issue. Any help would be much appriciated. I have also added a diagram of how I wired the unit. Feel free to let me know of changes that are needed. FYI I can not change the relay to run + instead of - because we also have strip rgb leds on the other side of the door that have constant positive and ground out each color needed.  Thank you for your time.!


texts:
I need some help with a circuit that will accept a digital input (0V-5V) and output 5V at 40mA for 200ms when the input goes high (5V), then drop to 20mA until the input drops low (0V.)

I had thought about using a capacitor to provide the 40mA that would discharge in the 200ms with a resistor that would then limit the current to 20mA, but I have no idea how to do that, or even where to start to make it work.

The load for this is an electromagnet that attracts a neodymium magnet. There are three in a row that makes a wheel turn as part of a clock. Basically a very slow motor.

For testing, I have used a pair of resistors where one provides 5V 40mA and the other provides 5V 20mA, then manually connected them to a coil. The 40mA moves the wheel, and the 20ms holds it in place. In testing, I tried many variations before settling on these values.

I had thought about using a larger set of shift registers so I would have two pins per electromagnet, but was hoping for a more elegant (at least electronic-wise) design.

This is way over my head design-wise, so any help would be greatly appreciated.


texts: Can both internal and external pullup resistor be used on an MCU pin?

texts:
I am taking a microcontroller class in university and have the following problem:

(Sorry for the poor image quality)

Its fairly simple but here is my problem: In my solution I set the internal pullup resistors on the input pins. I realise you don't need to because of the presence of the external pullups but I though it would be safe to do nonetheless.  From my perspective, enabling the the internal pullups does not affect the operation of the circuit, however apparently the correct answer is that the internal pullups should be disabled and I'm not sure why. Isn't it a good idea to have the internal pullups enabled for redundancy so in case something happens to the external pullups the input pins still have a defined state?


texts:
I want to take an old laptop fan that I have and connect it to a battery so it could run just on its own.
Can you just connect a TX3 connector to a battery?


texts: Powering EL Wire from a PoE power source

texts:
I'm checking out some EL wire through the simplest means I've found: using the EL Escudo shield. I have connected it to an EtherTen microcontroller, and following the instructions in the EL Escudo manual, it all goes swimmingly. That's until I don't use a power adapter directly.

I'm assuming that using USB to power the EL wire doesn't give the inverter enough juice on its own: the inverter makes a tiny little squealing noise (normal for the inverted I'm told), but no light in the wire.

What I'm a bit confused about is trying to run the shield with power over ethernet (the EtherTen has PoE). If I plug the ethernet lead into the device, I get the same result as trying to power with USB: not much. But if I plug the device directly into the power adapter which was running the PoE (I'm using this midspan injector), it seems to run without any problem. I've been using PoE for other small projects and haven't had a problem yet.

So I'm wondering if there's something specific about direct power source (as opposed to PoE) that an inverter or EL wire needs?


texts:
First I apologize if this is the wrong place for this question.

Recently my sub-woofer/amplifier stopped working, and I would like to know what is broken. I opened the case and didn't find any physical damage, and was wonder how I should proceed to discover what the defect is.

I am electronics novice, but would like to use this as an opportunity to learn more. What is the general procedure in a case like this? Should I use multimeter to find where the current is blocked?

Any help would be greatly appreciated.


texts:
I have a 16 bit signal, for me only the last 4 bits are important and the first 12 bits are always "0", so I'm doing nothing with the first 12 bits and in the end it goes out of my component to next component like this :

my16bitsignal <= x"000"& my4bitsignal;

In my VHDL component I do lots of operations etc. with my4bitsignal but in the end when I synthesize Xilinx gives me these warnings:

WARNING:Xst:1710 - FF/Latch <my16bitsignal_4> (without init value) has a constant value of 0 in block <MYCOMPONENT>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <my16bitsignal_5> (without init value) has a constant value of 0 in block <MYCOMPONENT>. This FF/Latch will be trimmed during the optimization process.
.
.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch <my16bitsignal_15> (without init value) has a constant value of 0 in block <MYCOMPONENT>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:2404 -  FFs/Latches <my16bitsignal<15:4>> (without init value) have a constant value of 0 in block <MYCOMPONENT>.

How can I avoid these warnings? Create a temporary 12 bit signal with zeros and then assign it to first 12 bits? This solution seems very lame to me, is there another way?


texts: When i try to connect xbee s1 to computer using xbee regulated explorer, xctu is not seeing it

texts:
So I have an Xbee regulated explorer with an Xbee and I am connecting

DIN - RX
DOUT - TX
GND - GND
5V - 5V

but X-CTU(old version) is not seeing the Xbee when I click test/query. It goes and then says "Action Required unable to communicate with modem." I have the right com port and I tried connecting RESET - GND on my arduino and I tryed removing the chip entirely but nothing works. Please Help. Thanks!


texts: IR2110 getting really hot in this high-side gate driver configuration

texts:
I've constructed the following circuit:

From this blog:
Tahmid's Blog

I put an LED in series with a 330 ohm resistor at the OUT terminal.
I have the 5 V being supplied by an Arduino and the 12 V from a lead acid battery. The arduino is not programmed, I'm just using it for its output, and I am manually moving HIN from ground to +5V to test the circuit.

When I connect the lead-acid battery, the IR2110 gets really hot. I've measured the voltage between 3 and 5 and it is about 1.5 V, when HIN is at ground. This doesn't change when I move it to +5.
The LED turns on brightly then dims when I connect the 12V and HIN is at ground. It turns off if HIN is moved to +5V. I am using the IRF540N for the MOSFET.

I have 5V at the drain of the MOSFET.

Please help. I don't know what could be wrong.

Oh and all the grounds are common.


texts: How battery level is indicated in power bank

texts: was actually trying to build a battery level indicator. looking at fuel gauge they all come with I2C interface. However is there anyway that battery level can be assessed directly and led indication can be provided on the battery level.


texts: DAC controlled LDO as current source - Pt.2

texts:
This is a follow-up question which references to "DAC controlled LDO as current source.". I am now trying to use the recommended LTC6363-0.5 as seen in the schematics. This is a fully differential OP amp and it does not work the way I connected it to the LT3083. The OP amp does in fact produce an output voltage of 0.5 * input (DAC) voltage, but only if not connected to the LDO.

I think the problem is that the output voltage levels of "SET" and "OUT" are about a few 100mV and the LDO - in the way I need it to work - needs an output voltage level at several volts. I think the key is the VOCM input but I have no clue how to connect it correctly.

I admit I do not understand OP amps well, especially this one, as I have never seen a differential OP amp before. Is it even possible for the LTC6363 to drive the LDO as a current source or do I need a non-differential OP amp? As a side note, the latter already works for me, but I have already bought several LTC6363 and I would like to use them if possible.

Furthermore, this OP amp can only be driven with a source of +/-5.5V max and the voltage level at the 1R resistor (referenced to GND) is usually about 6..7V which seems to be a problem already.


texts: cigarette lighter power plug; how to wire?

texts:
The part
https://www.digikey.com/en/products/detail/mpd-memory-protection-devices/ZA1030/2439603?s=N4IgTCBcDaIF4EMCMAGAzCgtAOwCYgF0BfIA
and the drawing
https://www.memoryprotectiondevices.com/datasheets/ZA1030-datasheet.pdf
How do you wire this plug?  Is there an additional set of ferrules/supporting parts or crimping tools needed?  Solder wets fine, but will cold work.


texts: Will A Logarithmic Potentiometer Linearise A Capacitor Charge Curve?

texts:
I want to use a rising voltage on a capacitor to set more than one trigger points for events via comparators; that is when the voltage reaches a certain level, the comparator goes high. For ease I want to set the trigger points with simple potential dividers for now. The problem is that a capacitor charge curve isn't linear. So I'm trying to figure out if the use of a log pot will "cancel" that out, since my maths frankly isn't up to analysing the two curves against one another. The intention is to get a roughly linear scale on the pot rather than having all the values bunched up at one end of the pot's rotation.

If this does work, will it get messed up by having fixed resistors in series with the pot to limit the voltage range?


texts:
I am currently working on a scientific hobby project about computing the error detection capabilities of CRCs. Unfortunately the C++ code used for such computations has up to years of run time on normal x64 CPUs, even on multi core systems. Also the power consumption of such systems is a pain.

It came to my mind that the common way of x64 brute-force-searching isn't the best. I would like to move the algorithm to an FPGA. Alas I have worked very little with FPGAs and I lost the minimal knowledge after working in C/C++ software engineering for decades. So I need a little help about the feasibility of my idea before burying myself into the technology.

The algorithm I want to run in hardware is a specialized ~1000 line C++ code that could easily be ported to C. No floating point operations. No standard libraries required. High frequent loops. Lots of basic 64 bit integer arithmetic. Even more binary operations (shift, or, xor, bit-counting, etc.) and some array operations. A few kB of RAM and ROM should be sufficient. No peripherals required. Very few memory allocations are used that could be removed by adapting the code. The computation results can be easily filtered internally so a serial interface should be enough to pass the results to a PC.

I would like to compile the C++ or C code into VHDL code and let it run on a FPGA as fast as possible. Also, since this is a hobby project, the FPGA (including software and a developer board) should be affordable.

My questions:

Can I expect a significant speedup? By which order of magnitude?
Is there a C/C++ compiler suited for the purpose?
Which FPGAs are suitable?


texts: What material can I use as a dielectric in my own high voltage capacitors?

texts:
I need capacitors rated for 50 kV. Buying them is an option but the ones with appropriate voltage rating I have seen cost more than 50€ which is far too much.

That's why I want to make caps on my own but the simple aluminium foil - plastic foil - aluminium foil trick won't do it. Such caps can barely resist voltages higher than 5 kV. I plan to stick to aluminium (good idea?) for the plates but I need a much stronger dielectric.

I have heard about several materials to use as a dielectric for voltages that high:

Distilled water: It has a breakdown voltage of 65 to 70 MV/m (Wikipedia). The problem is the forming of ions within microseconds after applying the voltage which lead to an immediate breakdown. This can be prevented by keeping the water flowing and deionizing it somehow. Thats rather complicated though as I would need a pump, a filter and a water circuit.
Waxed paper: It has a breakdown voltage of 40 to 60 MV/m (Wikipedia). Waxed paper is, as far as I know, basically the same as baking paper. It would be a lot easier to use than water but it comes in thicknesses of about 0.1 mm. Assuming a dielectric strength of 40 MV/m (=40 000 V/mm) it would need to be at least 1 mm thick. I don't think that folding it/putting several sheets on top of each other does the trick.

Do you have an idea on how to achieve my goal?  Wikipedia lists a lot of chemical substances with crycptic names that have a high dielectric strength. Maybe one of those is easy to get/produce an can be used by an amateur like me? Hopefully someone is more experienced in this topic than I am.

I need the capacitors for a Marx Generator powered by a flyback transformer which supplies approximately 50kV. Capacitance isn't too important but the higher the better.


texts: How to flash a bootloader onto the STM32WLE

texts:
I am currently designing a custom PCB with this board:
https://www.st.com/en/microcontrollers-microprocessors/stm32wle5jb.html
I cannot find any mentioning that it comes with a factory installed bootloader. I would like to program it over SWD.
Do I need to flash and if yes, how?
These seem to be good ressources for me:
https://www.electronicshub.org/how-to-upload-stm32f103c8t6-usb-bootloader/


texts:
I'm trying to make a small trimming in polygon pour in Altium Designer.
I upload a photo.

How can I cut these edges and make it more flat?


texts:
Anyone can tell me (or preferably, point me to a source that explicitly shows) the pinout of the 4-pin current-sense resistors?

I'm seeing the datasheets for three different models (including Rideon's FHR 4-2321, the Powertron FHR 4-2321,and the PBV-R005-F1-0.5) and I simply cannot believe that neither one of them shows the actual pinout !!!  (the Powertron datasheet does say "Standard Contact S", but a Google search for that shows nothing concrete)

This page gives a very good explanation of the intended use.  Except that they talk about terminal 1, 2, 3, and 4.  They do not explicitly relate T1,T2,T3,T4 to pin numbers (and their drawing doesn't look like Terminal N maps to pin N --- in any case, if we read the pins 1,2,3,4 from left to right)


texts: Are the ratings on a bench supply absolute or do they imply total power output?

texts:
If a bench supply is rated as "30V, 5A", does that does that imply a 150W total output (meaning it could supply say, 10A at 15V), or does it mean that 5A is the maximum it can supply at any voltage in its 0-30V range?

If the latter, what will typically happen if I try to draw more than 5A?


texts: Calculating different rated power from the rated parameters for a delta AC motor

texts:
A delta connected motor in the following link:
http://www.vanbodegraven.nl/en/products/ac-motors/asea-mbg-200-m-60-6/

has rated current 47A, voltage 380V

Here is the rated values. Cos(fi) = 0.8 on the label.

So the power I calculate is = sqrt(3)*380*47*cos(fi) = 24747 is around 25kw

But AS YOU SEE the label stated rated power 22kw

Why my calculation does not match the rated power?


texts:
1- Am I correct in my schematic if I want to connect L298N to arduino to drive 2 motors ?
2- are the resistors of 0.5 ohm mandatory ? (I saw them in datasheet)
3- Am I missing components in my scheme ?
Motors consume 24 volt and max current of 300 mA
L298N allow me to change the sense of rotation or motors
Diodes are 1N5819
thank you

simulate this circuit – Schematic created using CircuitLab


texts: How to decouple a negative feedback loop in DC?

texts:
My question is open ended, but I provided an example to explain the question better. R19 and R8 in the middle of the pic form a negative feedback loop. They set the gain of the amplifier.

I need to decouple the NFL in DC, in order not to fry the circuit, but if I add capacitor, Q2 will not be powered on.

My first idea was to add a voltage divider to bias Q2 to it's value, but that doesn't work, because it screws up all the calculations for the NFL.

I actually need to build this and our professor said it's probably to hard to do, but I'm asking to see if anyone has any ideas.

EDIT: Added a pic without the currents and voltages.


texts: DC motor, confusion in specification about Current

texts:
So, I am trying to build a little robot mower, and getting all parts. So I recently buyed two DC 12V motors, here is the specs:

Now I am trying to calculate how big or which battery should I use, and here is my confusion:
Why unload current is way bigger than rated current inside specs?
And which one should I use in calculation for a battery?
Thanks in advance!


texts:
I'm trying to understand this table, which specifies the operating ranges for a dataflash memory I am trying to use.

The one part that I don't understand is where it says Fr under conditions. What does that mean? Why are there two numbers? Can that be measured by a multimeter?

The datasheet is here.


texts: Let us say I have a DAC that gives out differential signal and I want to amplify it. How can I do that?


texts: Solving a circuit using Thevenin's theorem and superposition

texts:
I have the following circuit in an example problem from a book, where it shows you how to find the Rth and the Vth. The Vth has to be found via superposition.

The Rth solution is Rth = 103/77R, which I can find correctly and I do understand how to get. The problem comes at the time of getting the Vth. When the end result of getting a sub Vth isn't a typical voltage divisor circuit, the resolution book uses these formulas without explaining where they come from.

I would like to understand how these formulas work.


texts: 3 port matching of a directional coupler

texts:
My goal is to apply resistive matching (L-pads/attenuators) to the ports of a Mini-Circuits ADC-10-4 directional coupler. I have a 3x3 impedance matrix derived from the available 3 port S-parameters. Within the context of the solution provided by Sven B:

Calculating input impedance of 3 port network

can  "Z11 + Re(Z11)" and "Z22 + Re(Z22)" be substituted for "Z11 + ZL1" and "Z22 + ZL2," respectively, to obtain an expression for Zin under a matched condition and could this expression be adapted to provide a system of 3 equations, 3 unknowns to solve for matching load impedances ZL1, ZL2, and ZL3?


texts: What is the maximum voltage that silicon can handle?

texts:
Today, in a race for efficiency, we have moved from transformers to switching power supplies. Almost all PSUs were designed for single-phase low-voltage operation (220Vac/310Vdc in my country). I've never ever seen 380V 3-phase 3+ kW ATX PSUs for PCs despite their efficiency and lower ripple noise. They would be very useful for stacks of GPUs. I think that it is mainly because electrolytic capacitors cannot survive rectified 660Vdc.

And it could be even better to rectify a 10kV medium voltage line, as it usually comes to the village transformer. But what is the voltage limit silicon devices (MOSFETs) can survive without breaking down?


texts: Is it possible to connect an embedded device to the internet through a USB internet Dongle?

texts:
In my country (Nigeria) we have very few wireless hotspots,
most people connect to the internet via private USB dongles.

I was wondering if it is possible to use these dongles to allow an embedded system connect to the internet.

I know that involves knowing some form of USB protocol with which these devices communicate with a system, but I don't know if there is some standard for that or something to make it generic.


texts: Detecting when an illuminated AC doorbell is pushed

texts:
I have an 8VAC (can be switched to 12VAC if required) pushbutton bell which is in series with two "ding dong" chimes. The button is illuminated with an incandescent bulb, also in series. Pushing the bell "short circuits" (and so puts out) the bulb, causing the chime hammers to pull back for a ding - releasing the button swings them back for the dong.

I want to smarten this system. To make it as flexible as possible, the idea is to split the sensing of the button from the firing of the chime (controlled with an esp32 or whatever), ie keep the two circuits separate and link them via software as required. I have been advised to use triacs and drivers to control the AC chime circuit and am exploring that idea separately.

Detecting the illuminated button seems a little trickier to do. A similar question on this site suggests using a current sensor which seems an elegant solution, however the circuit there is a regular open/closed one, with the chimes still in series:

Doorbell Press for MCU

Since my button circuit is always closed (for the bulb to illuminate), current is always flowing. Can such a sensor be made to work here? Even though there is always current flowing, I presume the current changes when the button is pushed and that's what I would aim to detect with the sensor.
I understand that that chimes are necessary in the original circuit to provide some load. Since they're no longer in series with the button, would I need to replace them with resistors or something?
If we assume the micro-controller can provide 5V, would it be a better idea to convert the button circuit to a DC one connected to a GPIO pin? I'll still have a closed circuit at all times, so I'm not sure this actually solves anything - unless the low current when the button isn't pressed can be made to be seen as a LOW on the pin somehow? The ESP32 for instance has an ADC pin that can read varying voltages along with this: http://www.vwlowen.co.uk/arduino/current/current.htm


texts:
I was following this tutorial: http://highlowtech.org/?p=1695 and by mistake I uploaded code with 8 MHz External clock settings.
The tutorial says

Warning: make sure you select “internal” not “external” or your microcontroller will stop working (until you connect an external clock to it)

Is it possible to unlock it without external crystal clock? If not, what crystal do I need to unlock it?

Thank you :)


texts: How to build a simple LED transmitter and receiver

texts: I'd like the distance to be about 1/10th of a mile; less distance will be fine if that's easier to build. What tools and parts may I need for this? I have plenty of LEDs lying around and I have breadboards. I should add I've been working with electronics on and off for about a year so I just need directions and a tools list.


texts: What does the attenuation setting do in an RF spectrum analyzer?

texts:
I have to make measurements of the RF power which a circuit is delivering, and I am using an RF spectrum analyzer for that purpose. I am a beginner in this topic, so I apologize if the question is too silly.

So, I am using a 30dB attenuator before the Spectrum Analyzer input in order to ensure that the power levels entering the instrument is well within the design limits of the device.

When I obtained the RF power spectrum, I noticed that there was a setting in the Spectrum analyzer called 'Attenuation', which I could change by using the various knobs provided in the control. When I made the measurement, the 'Attenuation' setting was on 10dB.

So, my question is, have I done a mistake by using the 10dB attenuation setting when I was actually using a 30dB attenuator externally? Or does the attenuation setting mean that an additional 10dB of attenuation is provided inside the spectrum analyzer?

To sum it up: So, using my current setup, with a 30dB external attenuator and a 10dB 'Attenuation' setting in the oscilloscope, if I read a power level of 'x' at a frequency of interest, what is the actual absolute power which is being measured? Is it x+20dB? Or x+40dB?

Also, can you please explain what the attenuation setting in a Spectrum Analyzer does?


texts: Series 2 Charger Module to Charge 2Cell Li-ion Battery

texts:
So for a portable project, I will be using two lithium ion 2200mah 3.7v batteries in series to give me 7.4v. I have two 3.7v Lithium Ion charger found here https://www.adafruit.com/products/1905 .
The question is can I series my charger modules to charge my 2 cell battery?


texts: Inductive Charging 2 layer coil transfer to 1 layer receiver. Any issues?

texts:
I am looking to incorporate a inductive charging mechanism into a project I’m working on. On the receiving side I only have room for a single layer coil design. For my transfer side I have more spatial freedom. What I’ve found online thus far is that by aligning my coils (Same ID, OD, # of turns) and adding  ferrite reflector to both sides I will have the greatest efficiency. If I continue to add layers of coils ( one article mentioned having a layer of coil separated by a soft iron core then the second coil layer) will I be able to increase my magnetic field strength and thus increase efficiency?, granted I keep the resonant frequency the same for each coil?

All the studies I've seen have had identical double layer coil designs. Will the efficiency still increase if the transfer side is a double layer but the receiver is a single layer? What are risks associated with this mismatch?


texts: does anyone know if it's possible to DMA a constant value using the STM32F103? I've scrutinized the datasheet but can't see anything obvious and nothing via Google either. Could do a single word in circular mode of course but it would be nice to avoid the bus access.


texts: What is the difference between pulse-skipping mode and burst-mode in power converters?

texts:
I have been looking at methods to regulate a resonant converter which switches from full load to zero load at rates anywhere from 100Hz to 100kHz. I am looking online at some journal/conference papers and two methods seem to be the use of "burst-mode" and "pulse-skipping" to regulate the output voltage when there is little to no-load current.

What is the difference between these two? What are the advantages of one over the other, and when exactly is it best to use them, respectively?

EDIT: I am most interested in these techniques in a resonant converter design of mine which I am struggling to control at no load conditions after a load pulse transient occurs.


texts: What design considerations need to be made to accurately measure current flowing through a BLDC motor due to a 20khz PWM control?

texts:
My early attempts to incorporate current sensing onboard a BLDC motor drive operating at 20khz involved the MAX40201FAUA differential amplifier (50V/V) IC and a 0.001ohm shunt resistor. Results were, at best marginal and at worst non-linear and useless. At low PWM dutycycle, the short ON pulses seemed to excite a particularly high response into the diff amplifier (to the tune of it thought it was seeing 20A when only 2.5Arms was flowing).

I need to redesign this section and I need it to be able to accurately (+/- 0.01A) measure from 0 - 30A on the VCC side of the upper level MOSFET switches. Could you guys point me in the direction of a time tested differential amplifier IC that seems suited to this application or even a modular solution that incorporates amplification and measurement into a single package, to be interfaced with over I2C, serial or even PWM (I have no idea if such a solution even exists in a PCB mountable package)?

Thank you


texts: For an Op-amp with a single power supply, how do you get negative voltage

texts:
In my design, I am connecting an LM324 op-amp in the inverting mode and thus the output voltage would be negative of the input multiplied by th gain. But I am using a 5v and 0V power supply. So how is it possible to get a negative output when my power supply cannot have negative value. Do I need a dual power supply to achieve this?

The frequency range of both bandpass filters is from 0.7 hertz to 2.5 hertz.  Both op amps should provide enough gain to raise my weak signal (+-0.3v) up to the TTL logic level of my microcontroller I.e around 4.7 v , if not I would add a comparator to do that.


texts: setting an initial directory for the NGSPICE

texts:
After one launches NGSPICE, I want NGSPICE path, or current directory to be setup by me. How is that done?
I.e., instead of (for example):

cd:\Users\NGSPICE\lv
source in.sp

Just run:

source in.sp


texts: How to improve this analog interface for only counting pulses through audio port

texts:
I want to count pulses through sound-card of a PC or a smartphone's audio port.
Two different pulses will originate from two LM331 and I can scale them to 1V or any amplitude.

I want to feed these pulses to the audio port of a sound card's channels. Then the rest is to software to count the pulses.

So far I plan to use this analog interface between the pulses and the audio jack and sound-card:

Do you think the topology is correct? How can I improve this interface for the noise? I am only interested to count pulses not to view any other signal.

Edit:
R1 R2 sets the voltage at X.


texts: Arduino Controllable Digital Pot for Motor Controller

texts:
I have an analog motor controller that has a B10K potentiometer on it. I'd like to be able to swap out the analog potentiometer for a digital one, but I'm not exactly sure what voltage is being sent to the original potentiometer as I don't have the spec sheets for it.

My current specifications, which work as a prototype, are:

- Power supply: 48V 4A transformer, connected to...
- Variable speed DC PWM Motor Controller which controls...
- A 130V 1A max DC motor.

I'm fine with the power and speed that 48V gives me, but do I need to specifically look for a digital potentiometer that can handle high voltages, or would a standard 10K digital pot work?


texts: Connect MIDI input shield connection to ground with capacitor. What voltage / kind?

texts:
The midi specification mentions optional capacitors between connector shield and ground for a midi input:

Neither the type of capacitor nor the voltage rating is specified.
I would think that the voltage on this capacitor could be quite high if both the sending appliance and the receiving appliance grounds are "floating". What kind of capacitor would be appopriate here?


texts: What happens if we take out two diodes from diode bridge?

texts:
In all textbooks diode bridge that transforms AC to DC is drawn as having 4 diodes like this

simulate this circuit – Schematic created using CircuitLab

I wonder, what would happen if we replace, for example, D1 and D4 with usual wires? In order for current to flow, the circuit has to be closed. However, the diodes D2 and D3 should stop the current from flowing through the lamp in the wrong direction.

Nowhere could I find full explanation of why isn't that so and in fact all four diodes are needed.


texts: Was the Intel 186 chip commonly used anywhere? Was it only found in industrial computers? Why not PCs?

texts: I don't think the Intel 186 was in any "home computers" or PCs, but I see other people referencing it as a common chip. Also, I've heard that NEC V20s had the 186 instruction set in addition to 8088, etc. That's about the only reference I have to it actually being used. What happened to it and why did the IBM PC and all its clones jump to the 286 chip for a CPU from the 8086?


texts:
I have a project where I need to interface with a machine that was never built to be interfaced with.

I basically want to programatically press physical buttons on the machine(critical) and also sense(optional) when they have been pressed.

The circuit below shows a circuit that I've been thinking of (blue represents existing circuitry):

To press the button, I was thinking of simply adding a solid state (or normal) relay in parralel with the switch (press button).

My question is about sensing that the physical button was pressed.

Option 1 in the image above shows that I would have to cut into the circuit and insert a relay in series.

Is option 2 possible? Can I coil a wire around the existing wire and so induce a voltage/current in the coil that I could read from a MicroController? I don't yet know what voltage or current will be running through that cable. Not sure if it's going to be 5V or 35v, but it would probably be DC though. How many turns would be required if the MicroController is runnning on 5v or 3.3v?

I've seen this type of sensing on some taredown videos online of high end lab equipment, but never tried it myself.

I'm trying to leave as much of the existing circuitry in place as possible so as to (ideally) fully preserve any warranties that come with the machine.

Assumption

The switches will be low current micro swicthes as this is a high-end consumer device.
The in existing circuit VCC will not be at the same voltage as my MicroController


texts: part number of switching regulator component

texts:
Can somebody help me to read this component part number?
i think its switching regulator.
thank you.


texts: share eletromechanical buzzer between 2 mcu's?

texts:
I'm trying to 'share' a buzzer between 2 separate mcu's, one is on a multirotor flight controller (STM32 or Atmega328), the other is a module I'm adding that needs to use the same buzzer.

diagram: left side is flight controller (cannot change), right side is my module simplified.

The issue I'm having is that the buzzer driver circuit varies on flight controllers, some use a low-side switch (see diagram), but some use a high-side switch.  I'm trying to come up with a solution that will work in both situations, which I think means I need to supply my own v+ and gnd to the buzzer.

Can anyone refine my circuit (I'm not sure it would work), or offer something better?

thanks!


texts: How to use a current source with current control pin of LM13700

texts:
I am trying to bias the lm13700 Input amplitude bias current pin with a current source rather than using a voltage source and current limiting resistor as shown in all the data sheet schematics, but cannot figure out how to connect a current source up to the pin.  Seems like it should be simple, but I am getting confused with how to connect The IABC pin as the "load" of the current source.

Here is a forum post where Andy aka describes the op amp/NPN transistor combination voltage to current converter I am trying to use:  forum post on voltage to current conversion

As a shortcut, here is an image of the current source circuit:

If I were to use this current source to drive LEDs, it seems straight forward: put all the LEDs in series between Vcc and the collector of the NPN transistor.  Each of those components have a positive and negative side and together they all become the load.  How would I use this current source though to connect up to the IABC pin though of the LM13700?  Unlike an LED, the pin appears to have just one node and no obvious way to complete the "load".

Here is a link to the LM13700 data sheet: LM13700 data sheet

Thanks,
Dave

______Additional information below on questions including visuals from LTSpice______

I didn’t realize that my initial circuit was actually a current sink rather than a current source.  I took the circuit provided by Spehro and modeled it as best I could into LTSpice with the LM13700.  It appears to be working (somewhat), but I discovered some more unexpected things that I’m hoping you or someone else may be able to shed some light on.  Figure 1 is a picture of the entire LTSpice schematic to test the Voltage Controlled Current Source (VCCS).  I’ve also labeled a few key nodes used to plot output signals.

Ultimate Goal:  I’d like to modulate the amplitude of the Carrier (V2) using the the LM13700.  To do this, I’d like to establish a linear VCCS where the input at V1 (Modulator) goes between the limits of 0v and +5v, and the output of the VCCS, which for purpose of this post I have been measuring through Ix(U1:Ibias), would be between 0mA and 1mA respectively.  I used the value 5k for R5 to make this relationship work.  I got something wrong in here though because my voltage readings are unexpected in the LTSpice simulation.  My application uses a dual rail supply.

Question 1: (Reference Figure 2 below)  How come the following test voltages at V1 are yielding unexpected current outputs when measuring current at Ix(U1:Ibias)?  I think the equation for this VCCS would be Ic(Q1)=V1/R5.  I suspect that the PN junction in the Q1(2N3906) might be causing some of my issues, though I am not sure.

Test 1: V1 = 0V; I would expect the current leaving the VCCS to be 0mA, but I am measuring 1.8mA going into Ix(U1:Ibias).
Test 2: V1 = 5V; , I would expect the current leaving the VCCS to be 1mA, but I am measuring 800uA or .8mA going into Ix(U1:Ibias).
Test 3: V1 = 2.5V;  I would expect the current leaving the VCCS to be .5mA going into Ix(U1:Ibias), but instead it is 1.3mA.

Question 2: (Reference Figure 2 above) How come the current at Ic(Q1) is the opposite polarity of Ie(Q1)?

Question 3: (Reference Figure 3 below) How come the current at Ic(Q1) is the opposite polarity of Ix(U1:Ibias)?  I would think that they would be exactly the same as they are connected by a wire.

I think that’s everything.  Many thanks for taking the time to look at this.  If you’re into LTSpice, here is a link to the SPICE files required to view this simulation using LTSpice 4.23e.  Just keep all files together in one folder when running the schematic.  I used my LTSpice base folder with the executable.


texts:
I am a bit confused. I want to buy a miniature solar panel like this. The problem is that all the miniature solar panels online in their specifications they give the peak voltage and peak current. Thats fine but I dont understand in which irradiance does the panel give those values. This is my first question.

My second question is why there is no datasheet? I guess that depending on the type of panel (for example polycrystaline) the I-V curves are same for every panel. Am I right?

And when giving the dimensions they give the device's dimension, how can we know the total panel area to calculate how much power it will produce?


texts: Data Path Routing or Switching for AFE circuit

texts:
Currently i am making the PCB (for analog front end) for the digitization of some sensors(electro-chemical and photo-ionizations).

To simply the things this sensors are giving output in Milli volt(photo-ionizations sensors) and uA current(electro-chemical sensors).

I have BOTH(independent) the circuit ready which are taking input and giving digital output.
(one circuit is based on the trans-impedance amplifier while another is based on the operational amplifier)
Now the thing is i want to make a single channel PCB which works for both the sensor(one at a time) at same input terminal. All the sensors have the 3 leads.
Probably i required the programmable switch (decoder demultiplexer) so that MCU can switch the routing path of that 3 leads when user gives input to the MCU. (when sensor(uA output) is connected then he will press the switch-A and vice versa for the sensor(mv output) with switch-B).

Please let me know suggestion that it will work or not for that lower inputs (i mean very low current and voltage).Any suggestion of the IC will be great help.

Added below details
lead terminal of sensor Info :-
 - 1:- GND
 - 2:- Current Output/Voltage Output
 - 3:- Not Used in most of cases.

Range of mills volt :- 1mv to 500mv
Current output sensor are just floating photo sensors.

Speed for switching is not concern i can adjust with lower speed also. And isolation is also not required for ground of both sensor.(however isolation will not be in picture as at a time only any one sensor get connected)

Thanks,
Bhautik

Added Photo to simplify things more. As from picture "solution should select the Path A or Path B" based on the input signal to it.


texts:
I'm building a solar powered light. The idea of this light is that its output is proportional to the brightness of the sun. At night, no light. During daylight, full light. So it's basically as simple as attaching my 12v 0.5A LED setup to a 12v 6w solar panel.

But not so fast. The 12V 6w panel won't produce enough voltage at lower sunlight levels - I want the LEDs to be brighter in the AM than a 6w panel will drive them. So I want to use a 12V 10W panel. In full sunlight, however, I fear it'll overdrive the LEDs. So I need to cap the output at 12V 0.5A. Below that, the output should just follow the output of the panel.

I assume I'll need a zener diode circuit, but am not sure how to make the circuit. Please help me design one with the correct values for my system.

EDIT: I'm hacking an existing LED strip that runs off of a 12V .5A wall wart to operate from a hobbyist-type panel.  This isn't a pre-existing system.

EDIT: like this http://www.amazon.com/Solaro-Energy-SD1000-Daylight-Simulator/dp/B0053AL5LA only not $600

EDIT: so-called "12V" panels are actually >12V because the typical use is to charge a 12V battery.  Both models available (the 5W and 10W) actually have nominal voltage of ~18V in full sun and OCV of ~21V in full sun.  I can limit the amount of sun to prevent the voltage from peaking so high, but that kinda defeats the purpose of having an efficient system that will drive the LEDs fairly brightly at lower sunlight levels.


texts:
For VB2 = 7.5V and VB1 = 2.5V we get:

simulate this circuit – Schematic created using CircuitLab
Assume Q1 operates in the linear region(forward active) , Q2 operates in the linear region
IE1 = VB1-VBE/R1 = 1.9/100 = 19mA
IC1 = β/β+1IE1 = 18mA
VR2 = IC1*R2 = 1.8V
VE2 = VB2-0.6 = 6.9V VC1E1 = VE2-VR2-VE1 = 6.9-1.8-1.9 = 3.2V>VCEsat(Q1)->Q1 is operating in the linear region(forward active).
Holding VB1 costant(2.5V)which is the lowest voltage VB2 before Q1 enters saturation?And which is the lowest voltage VB2 before Q2 stops conducting current?


texts:
I have recently used a H bridge to control a small stepper motor obtained from a DVD drive and now want to look into controlling something larger, for example large Nema 23 steppers. From reading online I found that H bridges cannot be used for controlling such a motor and instead a "chopper circuit" is to be used such as the EasyDriver. This raises the first question:

Why can ordinary H bridge circuits not be used for larger steppers?

I kept reading about this to find an answer and then saw that many people are using drivers such as TB6600 instead of an EasyDriver. From what I can see, EasyDrivers cost around £1 whereas the TB6600 controllers are almost 10 times that! Why is there such a big difference, do they not just do the same thing? Why do so many people use these when there is such a large price difference?


texts:
I need to make sure I understand perfectly the high-Z state and its relation to voltage.I intend to explain what I have understood based on three example, is there something wrong ?

Let's consider the three following examples :

If the LED is red, the point 1 will approximatively be at 1.3 V because the voltage drop across a RED LED is approximatively 2 V.
Point 4 is at high-Z so we do not know its voltage. Can we assume it is near 1.3 V, or can it really be anything ? If I measure it with a voltmeter I would get around 1.3 V, but it is because the voltmeter is injecting a small current resulting in measuring the LED's resistor value ?
Point 3 is at high-Z as well. But is point 2 considered at high-Z ? It is not really an unconnected wire as it is connected to a resistor. More generally, if we replace the resistor with any other passive component, would 2 be at high-Z or no ?


texts:
I'm using the following BLDC motor as part of a project to generate power:

http://www.rcdude.com/Cobra-C-3520-18-Brushless-Motor-p/c-3520-18.htm

I'm able to spin this motor to about 3000 RPMS which gives me about 5 Volts. This is to be expected given that the motor is rated at 550 KVs. I'm using a three-phase rectifier with a smoothing cap to convert this to DC power. What I don't understand is the current produced. I'm getting about 33mA which is to low for my application. Essentially I would like to spin a small PC fan with this power. I'm able to do it but at a very low speed given that there isn't enough current flowing from the generator. What I would like to understand is why there is so little current flowing at those RPMS. I would at least expect it to be 100mA or 200mA, but this is just speculation on my part. Apologies for my noobness. Any help is appreciated. Thanks.


texts: How to handle excess MW of a generation plant, required to deliver constant 100MW, when its 100MW load decreased to 50MW

texts:
What is the best method to handle the excess load of coal generation plant, required to deliver its full capacity to a portion of a distribution utility's load, when almost 50% of the said is out? The coal generation is embedded to the distribution utility. I need to prevent the coal generation to export power to the national Grid. I have thought of ways to handle this excess power, but I still need suggestions. Thank you!

Use Dump load, and convert excess power to heat.
Use Large-scale electricity storage for future use.


texts: Proteus Simulation examples for ATMEL AVR Controller

texts:
I am looking for some examples for simulating AVR controller based designs in Proteus.
Currently I do not have any board and Proteus look promising.

Is there any authentic reference?  Can some one give a link for the same ?

Thanks


texts: Has there ever been a case of overvoltage in a power grid?

texts: Every now and again we read about blackouts, where the voltage of the power grid drops and the infrastructure is paralyzed. But have there ever been cases where the power grid experienced a massive overvoltage? What kind of damage would that do?


texts: Help understand 3-phase generator load in amps in a mixed single and 3-phase grid

texts:
I have a 140 kVA, 440 V 3-phase 50 Hz generator running an aquaculture farm in Indonesia.  There are 100 staff on site with the usual loads like freezers, light bulbs, TVs and water heaters etc.
Also there are a number of 3-phase pumps that run more or less continuously.
I am running well over 100 amps on all phases on a normal day. I thought this was very close to overloading the generator, but I then discovered that there is a difference in kVA calculation from amps depending on whether it is line-to-line or line-to-neutral.  I would like to make sure I understand this distinction.
If I understand correctly, I can calculate the load in amps for the single-phase gear as "line-to-neutral" as follows:
I(A) = 1000 × S(kVA) / (3 × VL-N(V) )
And the 3-phase loads as line-to-line:
I(A) = 1000 × S(kVA) / (√3 × VL-L(V) )
The product of each can be added to give the total load, correct?
And the reason I am not overloading the genset is because although the amperage for line-to-neutral would be too much, I have line-to-line loads as well, correct?


texts: HJS-480-0-24 Power Supply begins smelling like burning plastic after 30 seconds of running

texts:
I recently purchased a HJS-480-0-24 power supply off Banggood and I tested it out by running a 150 watt heater. After 30 seconds the power supply began to smell like burning plastic, so I immediately turned it off.

According to the seller, the cooling fan does not turn on until the device is at 40°C. I tested the fan and it works if I power it externally, but I havent seen it turn on yet by its self (which makes sense as the power supply probably isnt reaching 40°C in 30 seconds).

I opened it up and not a single component looks to be damaged. As best as I could tell, either the big capacitors or the inductors seemed to be the smelly culprits, but again they showed no sign of damage or swelling. The fuse is intact and the supply still fully works, but I'm just paranoid that something will catch fire or explode if I run it for more than 30 seconds. Is this normal for a new power supply to smell bad during the first while of use? What should my next steps be here?


texts: Can I multiplex a thermocouple (using a MPC507) without losing significant accuracy?

texts: I would like to reduce the number of thermocouple to digital converters (MAX31856) needed on my board for the sake of space. One approach that I have considered is multiplexing the eight different thermocouple inputs using a differential multiplexer (MPC507). Is this possible with thermocouple voltages (10s of milli volts) without significant measurement distortion?


texts:
I have purchased two lots of ZY12PDN modules and from day one they have been problematic. When I Program them to negotiate 12V (green), they stay green for about 3 seconds when initially connected, but then the light switches to flashing blue, with a frequency of about 3 blink per second. What is strange is that initially I managed to make it output 12v after fiddling with it for a while. but then it went back to flashing blue when I left it to charge my battery overnight. I have no idea what I did to make it work or to stop working again. I am using it to charge a robot I have made. so when I charge the robot, ZY12pdn is connected to the battery and a couple of other voltage regulators. what does the blue flashing light mean? I have not been able to find an answer or a datasheet for this module which explains that. My charger is USB PD and outputs up to 12 volts.
I have also tried it without connecting the module to anything and still the same.
the following is a diagram of how components are connected to each other


texts:
I am working on a project where I have to power a 5 meter long LED strip (https://www.sparkfun.com/products/12022) and 54 3.4V 20mA LEDs and control them all from an Arduino.  My current idea was to have one 12V source for everything, direct power to the strip in parallel with a voltage regulator to 3.4 volts to power the LEDs.  After that stage, everything would be controlled from the Arduino through transistors.

According to the datasheet, the strip is 300 20mA LED assemblies at 12V, bringing total power necessary to 6 amps to power it.  The individual LEDs are 20mA each, and with 54 of them the power draw would be 1.08A.  This would bring total consumption to 7.08A.  Do I really need a +7.08A 12V power supply, or am I doing something wrong?


texts: What are the essential layers in the design of a MOM capacitor in Cadence?

texts:
I need to design a custom-designed MOM capacitor.
I have looked into the layout of a MOM capacitor in 65nm CMOS technology, and I am a bit confused. There are many layers that I don't understand the purpose of them (except for metal layers which I am sure about their functionality). Could you please explain which layers are necessary for the design of a MOM capacitor?
Thanks


texts:
What's so special about NAND & NOR(apart from being universal gates) that most books on digital design try to emphasize design using these gates?

Is it easy to manufacture or something?


texts:
Here is a screenshot of a cache benchmark:

In the benchmark the L1 cache read speed is about 186 GB/s, with the latency being about 3-4 clock cycles. How is such a speed even achieved?

Consider the memory here: the theoretical maximum speed is
665 MHz (memory frequency) x 2 (double data rate) x 64 bit (bus width)
which is about 10.6 GB/s, which is closer to the benchmark value of 9.6 GB/s.

But with the L1 cache, even if we could read at every cycle with the processor at its maximum frequency (3 GHz), we would need about 496 data lines to achieve such a throughput which sounds unrealistic. This applies to other caches as well.

What am I missing? How do we calculate the throughput of a cache from its parameters?


texts: Old Variac -- chassis ground? is it safe?

texts:
I've got an old (vintage!) GenRad Variac (below) that has two prong plug and two prong socket. I want to modify it to add a safety earth pin to both input and output. In doing so, I opened it up and have realized the circuit runs through the metal chassis itself, and I'm confused about what I'm looking at and would love to get a bit more clarity.
Have done a bunch of googling about chassis ground and hot chassis radios and such and I suspect this is just an old design, but I'm confused about why it appears in a Variac. Photos below showing the internal configuration, but the circuit is simple and as expected-- a 2PDT on-off switch connects both incoming lines to the transformer taps, and the other side of that is the output socket with a circuit breaker. The transformer mounting core and wiper mechanism is not isolated from the chassis (they are in contact at the front panel), so there's (multimeter-verified) continuity between the outer chassis and all taps of the transformer, the outputs and (when switched on) the inputs. (Pic showing continuity measurement added below.)
When I set the output to e.g. 50V, the potential between the outputs is 50V-- ie the Variac seems to work. When I measure the potential between each output and the chassis screws, one is ~50V and one is ~110V.
When I measure the potential from the chassis screws to real earth (wall socket), it's very low, < 1V, and when I touch the switch/case it doesn't shock me.

This isn't a radio or TV, so there should be no RF interference concern here, so why isn't the circuit totally isolated from the chassis in the first place? Is this a form of safety intent? IS this design safe?

I can replace the plug and socket with 3 prongs and connect the earth pins directly. I obviously would like to "ground" the chassis properly but I obviously can't here since that will allow current to flow to earth in normal operation and trip the GFCI-- right?

I'm trying to make sure I (a) understand what I'm looking at (b) it's working as designed and is, in fact, safe and (c) that I shouldn't mess with the chassis grounding when adding the third pin connection.
Thanks for insight or pointers.


texts:
I've seen lots of useful threads here over the years but this is my first post.

I'm building a little box to switch an output based on RPM's watching the ground of an the primary ignition coil on an old car with points. I built an input circuit and it seems to work.... until the supply voltage gets too high.

Here's the whole thing:

I believe most of it is working ok - though I'm open to any and all suggestions - for completeness, my regulator is actually 9V not 8, but I don't think it is relevant.

My problem: The resistor (highlighted yellow in the simplified circuit below) seems to effect where my circuit works. My "function generator" spits out a 0-3.3V square wave and is input at "SIMULATED Tach-In". The real input isn't used here, but in the application this will look at the car's ignition coil.

The input to the NPN drops to ~1V if I keep turning up the supply voltage ("+12V"), and I don't know why. In fact, the output ("circuit output to CPU") stops switching after I reach a cut-off voltage which depends on the yellow resistor. See chart "Ohms/CutOff"

Does anyone have any idea why this is happening? I keep dropping the value, but I'm already using a 1/2W resistor and this seems overkill.

Please let me know if there's anything else I can provide to help with this.

THANKS!
              -Abe.

EDIT: More complete schematic added at (remove the space) abefm.smugmug. com/MegaSquirt-Stuff/Random-MS-Questions/i-sG85Vjc/A , not enough 'reputation' to post it here. Sorry for the remote link.
The short version - there's a 470R resistor on my board, and a line which goes to the generator's CPU. (A "Jim-Stim" from the Megasquirt world, if you're familiar)

The good news is I got the pull up working on THAT board, so I now have a nice +12V signal which demonstrated my real input works fine.

Note: This was solved. For those interested in project, my next issue is discussed here: Mysterious Noise Issue in Automotive Ignition Coil Application, Arduino


texts:
I am verifying a memory interface to MIG IP from Xilinx.
The MIG IP is connected to a ddr3 SDRAM from Micron. I have a ddr3 model from Micron that I included in my testbench.
I waited until the initialization of the SDRAM is done by MIG and then I started reading.
I assumed that the SDRAM content after initialization is zero for all addresses but when I send a read command to the memory, I am getting random data read back from memory.
Is the SDRAM after initialization empty or have some random data?


texts: Stray-inductance and capacitance of non-isolated heat-sink

texts:
I read an application-note that says the heat-sink (when not electrically isolated), is one of major source of EMI. Well I think this can be corrected at some point by good EMI filters and a good case to prevent EMI/RFI.

But what about stray inductance and capacitance?

This presuming that:

IGBTs, with the case electrically common to the collector.
Individual heat sink for each IGBT.

Update:

Although EMI is a concern, as my question states, my concern too is to add stray
inductance / capacitance to the circuit, increase the miller effect (even thought the IGBTs are being driven with negative gate bias, etc).
It does not need to meet Class A emissions, so at some point the EMI can be reduced to
acceptable levels with good case and line filtering.


texts: How is the gate trigger resistor value calculated for a triac

texts:
As per the application notes of bta08-600cw, to control a three phase induction motor, for triggering the triac gate, the value of resistor is shown as 510 ohm. How is this value arrived at? What would be the resistor wattage?

From the
From the data sheet, which quadrant to be considered to know the gate trigger current?

Also for three phase supply, how is the voltage shown as 220v instead of 440v(in the schematic diagram)?

Can the gate be triggered with either AC or DC? If so what is the impact of calculating the resistor value in both these cases?