texts: I keep zapping mosfet and I don't know why

texts:
After asking collagues, trying a few variations and spending days on research, I figured out I could ask there as I am running out of ideas.

The most similar discussion I have found is: mosfet is always on despite a pull-down.

Point is, as far as I can tell, I have this circuit...

simulate this circuit – Schematic created using CircuitLab

...differently from the linked Q, it is my understanding the negative is already wired to the source (it is my understanding in the picture the Source is the lowest M1 pin, drain is the top).

This is usually on a PCB (taking 8 of those each) but the problem has been ongoing so long I have breadboarded a single specimen and the problem does reproduce.

I am pretty sure I had burnt some mosfets during experiments yet I am using fresh ones from the reel for the breadboard. Most mosfets (say 7 out of 10) behave incorrectly.

Expected behaviour

When CTRL is undriven, D1 is OFF.
When CTRL is driven GND, D1 is OFF.
When CTRL is driven +5, D1 is ON.
(true target: when CTRL is driven +3.3, D1 is ON).

Observed behaviour

CTRL = undriven. Led is on, albeit not fully. 6.8mA current M1.source-to-gnd. BAD.
CTRL = undriven. Different pull-downs (or ups) make no difference.
CTRL = undriven. Disconnecting source shuts down led. OK
CTRL = driven GND. Led is almost Off. About 2mA are flowing out of the gate to the GND! BAD
CTRL = driven +5V. LED is fully ON. OK

In general, this behaviour is coherent with most tests. That is ON state is always good, while OFF state is usually bad.

At work I dealt with this mosfet several times with no issues but I figured out something was different at home. I speculated I could be frying them by static discharge so I did the whole thing again while grounding myself. Same outcome.

I'm pretty sure I have managed to assemble a case which worked perfectly for perhaps a second. I'm not sure what happened but I suspect I have touched one of the wires (I was not grounded at all back then).

I do not know where to look for anymore.

Update 2019-08-09

Thank you for your insights.

As far as I can tell the diode on this mosfet goes source-to-drain (i.e.: in the picture it is the opposite of D1). This seems correct to me.

I do not have a scope at home.

I hope 3.3 will do but I'm ready to respin the whole design for other reasons as well.

After some googling I sorta know what "esd clamping" more or less means (I might have a clue about electronics but I am a software developer). I will keep in mind.

Fasten your seatbelts. Today I have managed to assemble two perfectly working specimen. Differences:

I now use a cheap no-name solder (I think it is leaded, but I don't really know).
I have been using my el cheapo ZD-98 (eew).
Restored capacitors on V1.

This last point requires some more elaborations.
The +5 supply is not a supply at all. The whole supply chain is 220VAC -> 24DC, 24DC -> 5V. The first is a boxed supply from a well known brand while the other is a small PCB for LDO replacement (I'm not sure I can name specific brands).

In the original tests from PCB, the DCDC module was populated with its capacitors. Yet the issue emerged. So I am inclined to believe the problem lies in the soldering tool. I will perform further tests.


texts: Measuring Signal Strength with a RF Circuit

texts:
Note: I'm primarly a 4th year Computer Science student, but I have also interest in electronics but I have very limited knowlege.

Is it possible to measure the signal quality or level of a RF transmitter with a RF reciever (like this: https://www.sparkfun.com/products/10533)? I need to know if I am getting close to the source. I mean is it possible to use these RF transmitter/recievers for not data transfer but signal level calculation?


texts:
I am trying to read an analog signal using the Analog.Read() function and output 1 or 0 depending on the value of the analog signal. While testing using a serial monitor, I always get the symbol for 'phi'instead of 0 and the 'square box with question mark'instead of 1. Please help.

    const int analogInPin = A3;
    int inputValue=0;
    int ch1=1,ch2=0;
    void setup()
   {

     pinMode(A0, INPUT);
     Serial.begin(9600);
    }

    void loop()
    {
      inputValue = analogRead(analogInPin);
      if(inputValue>240)
      Serial.print('1');
      else
      Serial.print('0');
      delay(10);
    }


texts:
I am using a 555 timer in astable mode to clock a 4017, for some reason, the first output to become high is Q1, not Q0. Do I have a faulty chip? It's definitely wired up correctly, which checked numerous times.
Here is a video of it: https://www.youtube.com/watch?v=9wveTqKnOH8


texts:
I have previously entered a competition called "robocup juinor australia" for a few year now with increasingly good performance each year, this year we have been sponsored for over 15k which is a big deal considering all of our previous robots were built for approximately $250. anyway this year we are trying to implement a bluetooth system were each robot knows exactly were the other robot is on the field, we are struggling to come up with an idea to do it considering we cant rely on motor rotations or ultrasonic sensors because of other robots blocking/pushing/interfering with our robots. do you guys have any ideas how we could do this?

link to example game for reference: https://www.youtube.com/watch?v=YlVk7OHae2M


texts: The electric and magnetic components of far field EMR and shielding thereof

texts:
This is a newbie question.  I'm pretty sure of the answer, but I would like confirmation. I found this thread in this forum that came close to what I was looking for, but I think my question is different.
I want to shield against ingress of far field electromagnetic radiation. The material I'm working with provides good attenuation of electric fields at the required frequencies, but no magnetic shielding. I've been trying to determine if I need to incorporate magnetic shielding into my design. I'm pretty sure that because there's a fixed relationship between the electric and magnetic fields in a plane wave in free space (E/H = 377 ohm), if the electric field is attenuated, the magnetic field is also equally attenuated, and no magnetic shielding is needed. Do I have this right?


texts: How to isolate the microcontroller from power source?

texts:
I'm fairly inexperienced in electrical engineer so forgive the simple question. Using a microcontroller (Netduino) and two 8bit shift register (serial in, parallel out) I'm controlling 16 LEDs.

The logic works fine, I was expecting the shift register and lights not to work when I don't plug in the auxiliary power source and just fired up the microcontroller. Right now, the microcontroller is powering all the LEDs and I don't want that.

Even though the schematic isn't perfect, here is my circuit:
The resistances are 220 ohms +/- 10%. The shift registers are SN74HC595s.

I know I could add NPN transistors on each of the shift register outputs, but that would require quite some transistors, and most importantly, the microcontroller would still power the shift register.

I did try to use transistors on Pins 1-3 from the microcontroller but the LEDs were still powering on without the external source of power.

As a secondary point, I know I should add one/some capacitors, but I'm not exactly sure where beside maybe a large one around the power source.

Edit: Here is the adapted schematic, in which the outputs triggers a transistor for each LEDs. I didn't replicate the transistor for every LEDs, but it's assumed that from Qa to Qh on both shift register, it's the same:


texts:
I recently purchased this signal relay board.

When Input 1 and Input 2 are at 3.3VDC, both D1 and D2 illuminate.

Here is my set up,

+3.3VDC for IN1 as well as a separate +3.3VDC for IN2. For VCC we are feeding with +5VDC. Each +3.3VDC input line has more than 20 mA of drive strength, but the relays do not trigger as expected.  If we apply +5VDC to to IN1 or IN2 for the relays which do not work with +3.3VDC, the relay triggers as expected.

Can someone review on my set-up and confirm that both relays should indeed be working as it's set up like this?


texts: Circuit to control a magnetic field, using a laminated core

texts:
I need to produce a magnetic field that goes from 0 - 80 kA/m (0 - 100 mT), which I can control the amplitude of, and change its polarity.
The diagram below outlines a couple of pieces of laminated transformer core I was given (blue), with a winding (red) and the green is where I need to place what I want to measure. This was apparently used by someone before to do the same things, but the rest of the set up is lost.

I am hoping somebody could advise me as to what to use to drive the coil to reach the the field I need and to control reasonable steps (5-10 kA/m) of the field, or any other set up or modifications that I could make to improve things.

I put 4 amps through the coil and measure 8 kA/m (10 mT) in the gap. This is the limit of the power supply I have, and the coil heated up quite a bit. I have some worry of the coil heating up and the limits. If I assumed a relatively linear increase that would require 40A, which seems like a lot.

There is a gap between the cores under the coil, and the calculation I have come across for these setups usually there is only one gap placed opposite the coils.

Any advice would be greatly appreciated, even if it is an alternative set up.


texts: ALTIUM Setting all parts of a schematic to pcb library "Any"

texts:
I have a schematic with different part in i. I have imported this schematic from another design and the parts are linked to a library I don't have access directly.

I need to set up all the parts in the schematics to be setted with their pcb library to point to any library. I can edit manually the pcb library where the part should point to any after what it found out the proper library automatically. However I would like to apply this to every part of my schematic.

I have tried to use the SCH inspector and change the Library parameters to Any but its seems it doesnt work.

Does anybody got idea ?


texts: Connecting a positive voltage to an Arduino OUTPUT pin

texts:
Basically I want to turn on a computer power supply using my Arduino. I know that to turn it on you have to sink pin 14 on the ATX connector (PS_ON) to gnd. My idea is to connect that pin to a digital output pin on the Arduino, set to high, then when I want to turn it on, set it to low. My question is, since the PS_ON pin does carry current, will there be any problem connecting it to an OUTPUT pin set to high? From my understanding the PS_ON pin had a maximum of 5.25V in open circuit, but the information in this post might be more useful:

https://electronics.stackexchange.com/a/97308


texts: What device has high inductance? For example >1000mH (for 220Vrms 50-60Hz output)

texts:
What devices have high inductance values (for example >1000mH?)
What I found in a real device (for example induction motor) datasheet is just near <1000mH (on rotor and stator.)
Is there anything that has high inductance value besides filters and chokes?


texts:
Currently working on an elevator circuit. I am using 4-bits to represent the floor that the elevator is on, and I need a way of comparing this value to the floor that the user wants to get to.  I am currently trying to use a 4-bit comparator to solve this, but I can't figure out how to connect the 4 floor bits into the comparator without getting an improper width error. I feel like there must be an easy way to do this, but I am new to Logisim and not totally sure how to make this connection. To clarify, the four bits representing the floor are not directly compatible with the comparator because I used 4 different registers with 1-bit outputs.

If there is no other way I can just make a comparator from gates but obviously that is less than ideal.


texts: What is the relationship between dark current and the contribution of dark noise in a photodiode?

texts:
For example, if I have a datasheet for a photodiode that lists a dark current of 1000nA. I have a transimpedance amplifier with 1kohm transimpedance and 1 mV voltage output voltage noise.

Presumably the specified dark current is the current mean value.  Clearly the dark current will result in a mean output of 1000ohms*1000nA = 1mV.  Dark current is also Poisson distributed, but does that mean that the noise variance also 1 mV such that the voltage noise from the amp and photodiode are equal?  Or is the relationship more complicated?


texts: AM Radio gets static when driving near PV arrays, but not FM

texts: My school has PV arrays that act as shades in the parking lot. Whenever I'm within 10ft of them, I get overpowering, humming AM static, but the FM signal is clear as day. Why?


texts: Understanding the resistance readings between PCB connectors

texts:
Based on a question I asked earlier today, I am trying to verify that there's not short caused by my bad soldering.

Luckily I had bought two of these modules.  To make a baseline, I started looking at the module that I had not done anything to.

Using this Multimeter (on a disconnected module -- it has no solder and no wires in/out), I am pressing the black lead again the MOSI pin (see diagram below) and moving the red lead one pin down, one pin at a time.

However, I am not entirely sure what I am looking at, for example:

With black on MISO and red on MOSI, or SCK, the reading is 350+K Ohms.

With the black on MISO and read on RESET, the reading is 150+K Ohms.

With black on MISO and red on DIO5, the reading is 1.05K Ohms and red on GND shows 0.5K Ohms.

When I compare that with this video for example, his reading stays at 1 across pin changes.

Again, this is an untouched board, direct from the seller.  So is my understanding not correct (i.e. the readings are fine and I don't know what they mean)?  Or is it a bad module?


texts:
Unijunction transistor is a semiconductor device that can be represented as shown:

It forms a voltage divider with a diode pointing towards middle of divider marked as \$\eta V_{BB}\$ (where \$\eta\$ is voltage divider ratio, I assume).
If a circuit is built with discrete components, using two resistors and a diode, then the behavior of such circuit becomes fairly similar to UJT.

But what kind of function should such transistor perform? Not as an amplifier, that is for sure. Since major current flow comes from emitter node and emitter is control node (something like base/gate in conventional BJT of MOSFET), while either of base nodes provides with minority current flow. What is that useful for anyway? Where would one use its behavior as something useful?

Also, it doesn't seem as a switch to me. Since, again, major current flow comes from emitter and emitter should be the controlling node in this case. While base provides with minor current flow.

From experimenting with such transistor on breadboard I saw that increasing emitter voltage \$V_E\$ increases \$I_{b2}\$ slightly but increases \$I_{b1}\$ greatly. And with emitter-open, there is a current very little current flow (compared to emitter current) between B2 and B1, since there is no junction between those two but rather semi-conducting path.

Also, how does UJT achieve negative resistance? With \$V_E\$ increased beyond threshold of UJT, the emitter current injected into the base is increased and \$R_{B1}\$ is decreased. But although it is decreased, the current through it still increases. If there would be a negative resistance, then the current through B1 would decrease as \$V_E\$ would increase.

I am mainly wondering, whether this kind of transistor is worth of troubling and dealing with.


texts: Extracting 25W from a pair of 18650 li-ion in series

texts:
If I have 2 bats of li-ion in series. 8.4V full charged and 6V full discharged. What should be their minimum mAh capacity, if they are 18650 size, and considering a constant load of 25W.

25W/6V = 4.16A?

Would they heat much at that power?


texts:
I have been reading a textbook on Embedded systems called An Embedded software primer by David E Simon (great book btw). I am trying to answer questions after each chapter, I got through first 2 chapters, in chapter 3 there is a question

  Why can't you use microprocessor I/O pins as chip enable pins for ROM and RAM?

You normally Encode Address pins to do this.
 Which also got me thinking, can you use Data pins and address pins as I/O pins for a processor (Like I/O pins you can write certain bits of data pins HIGH), if not what is the difference between them, do I/O pins have more current driving capability?


texts: Purpose of Pullup Resistor for Active low pins in EEPROM

texts:
I am working with a 25LC640A EEPROM, which is having active low control Pins like CS,Hold,wp (Write Protect). I have Connected Pull up Resistor for CS only alone. Its working fine. Please refer the Circuit.

As per the application notes which is from microchip, they are advised to connect Pull-up resistor for all active low pins.

My Doubt: What is the necessity of Pull up resistor in active low pin where as it can directly connected to vfc  . If it is not connected what will be the impact on EEPROM performance?


texts:
I want to design a cheap but safe, low-wattage, always-on heater to keep a small space above freezing.  (A small underground tunnel that the water pipe for an automatic horse waterer goes through.)
I've got NiChrome wire for the element, and I need a cheap way to step down 120V AC to about 50V AC @ 2.3A.  (or 25V @ 4.6A or 17V * 6.9A , etc.) I will use a half-bridge rectifier for low-power and a full bridge rectifier for high-power if the pipe freezes and needs to be thawed.  I figure a simple wrap-wires-around-a-bolt transformer should work for the job.  Efficiency doesn't matter much -- it is supposed to generate heat.
My guess-work assumption is that I need to make the primary coil with enough turns so that its reactance will prevent the primary from burning up.  (It is, after all, a wire connecting hot to neutral)  Is it solely based on the inductance/reactance of the primary?  Reactance + resistance?  Reactance * resistance?
What factor must I design to ensure that:  1)  The transformer won't burn itself up, 2) The transformer won't be absurdly inefficient or dangerous, and 3) this is a reasonable use of a cheap, DIY transformer.  (IOW, if keeping this safe isn't realistic, I can either find a pre-built transformer for this or figure out a different way to provide power to the heating wire.  This sounds fun to design, but I'm not too proud to be told not to do it.)
NOTE:  For safety, assume that the heating coil powered by the secondary will eventually burn out and become an open circuit.  And assume that this will happen but not be noticed for >2 weeks.


texts: How to troubleshoot a boost converter (ADP1613)?

texts:
I have attempted to put together a schematic utilizing the ADP1613 boost converter, and I am having no luck at all. I don't have a good understanding of how this device really works, so I don't know how to troubleshoot it.

I lifted the schematic directly from the datasheet (page 16), replacing a couple of values, b/c I did not have the exact parts. The changes in values are very small and within the ranges specified in the datasheet:

Here's what the physical circuit looks like:

I am applying a 5V battery to Vin, and I am getting 40V at Vout, whereas what I configured the booster for is 5V output: 1.235V × (1 + 37.4/12.4) = 4.96V. This measurement was taken with no load attached to Vout.

I tried to examine the Switching Output pin with a 10X oscilloscope probe, but the chip heated up very quickly and I had to unplug it.

If I supply a load that draws 410mA, Vout drops to 8.5V.

What am I doing wrong here? What is the correct way to troubleshoot a device like this?

EDIT 1: Could the problem be that I am running the regulator w/o a load? If the chip was not capable of 0% duty cycle, wouldn't the voltage continue building to the maximum the inductor can handle, until something blows? Just guessing...


texts: How do I test how many amps a transformer actually puts out

texts:
I have a 120v <-> 9v ac transformer rated at 3.34 amps, but my multimeter suggests that (after running it through a diode bridge), I can get 7+ amps out of it @ 9.4 volts ac.

Can I?

I have a device that draws 4 amps DC at 6-10 volts,a nd I'd like to power it from this device.


texts: Transfering audio data between two DSP's, clock sync problem

texts:
I have a system with two DSP modules. The audio is routed from DSP1 to DSP2 and then back to DSP1, which in turn immediately sends it to DAC. It's a high-quality stereo sound at 44.1KHz.

This is a requirement, there should be two DSPs and routing can't be changed.

The problem is the clocks. Each DSP module has its own internal clock, which can't be ideally synchronised. I set the rate numerically on both, but the result is that I get a slightly glitchy sound, for obvious reasons.

One solution would be, of course, to feed the clock from one DSP to the other, but at this time this is a bit problematic for me.

Is there another way around this? E.g. a relatively simple algorithm that can compensate little differences between clocks? Any other ideas?

Edit: the connection between the DSPs is I2S. Either module can operate in master mode, but it doesn't help.


texts: Is it possible to design an amplifier with a given gain from a random discrete JFET?

texts:
A few weeks ago, I played around with a discrete JFET bass preamp design I found online (http://www.albertkreuzer.com/preamp.htm).

One thing I realized from analyzing the circuit, running simulations and eventually building the amplifier was that performance, and even actual operation in some cases, relied heavily on the characteristics of the specific transistors used.

In my research, I found that all JFET manufacturers provide only crude tolerances for specs like VgsOff or Isat. As an exercise, I tried to come up with an amplifier design that would deliver a specific gain over the whole range of spec, but failed. JFETs just vary too much, and a given circuit could very likely break if a specific transistor had to be replaced. In my case, I ended up having to test several transistors and adapt the design to the resulting specific specs.

A good production design wouldn't require this kind of cherry picking. Have I missed anything ? Is there a good way to design a circuit with transistors that have big tolerance on key specs ?


texts:
I have arduino nano + HC-05 bluetooth module.

I have used following pins D9, D10, D11 for HC-05 KEY, TX, RX and this works for data communication without any problems.

D9 pin is set to output pin HIGH (5v).

However, I want to be able to run AT commands to change default bluetooth configuration, for example to change a name.

I followed this tutorial for example just to make sure that I'm doing everything right but I wasn't able to run any of these commands.

I tried to use different speeds but without luck.

I also tried to connect KEY pin when VCC is disconnected (I read on some forum that this will change speed for programming to 38400) but same thing, nothing changed.

Any idea what else I can try?

But for some reason, this is what I'm getting as response from the code from that tutorial:

  Starting config

  Done!


texts: Routing power and HDMI signal into usb type-c for DIY computer monitor

texts: I am starting a project to build a DIY monitor. I have a spare lcd panel (model # LP156WF6) taken out of a laptop. I plan on buying a controller board for it and building it into a homemade enclosure. The controller board has an HDMI input and a 12V/4A barrel connector for powering the display. I would like to wire both the HDMI port and the barrel connector into the same USB Type-C plug and use the same USB Type-C cable to power the monitor and send it its signal from the thunderbolt port on my laptop. Is this even possible? I know HDMI over USB Type-C protocols have existed for a while now, so I imagine buying a USB Type-C pinout PCB and soldering a split HDMI cable to it should be relatively simple as long as I can find the wiring diagram. For the power, is it possible to simply wire a small power regulation board in-between the barrel connector and the Type-C pinout? It seems there are many products out there that support power and signal through the same Type-C cable, so this seems possible, but I'm afraid I'm greatly oversimplifying the procedure. I would greatly appreciate any advice anyone out there may have on the subject.


texts: Systemverilog - class inside package synthesis error

texts:
In Systemverilog - I declare a package, a class and a function as follows:
package package_functions_general ;

    class class_one_hot_to_binary

    #
    (
        parameter WIDTH_ONE_HOT = 16
    ) ;

    localparam WIDTH_BINARY = $clog2 ( WIDTH_ONE_HOT ) ;

        static function logic [ WIDTH_BINARY - 1 : 0 ] one_hot_to_binary
        (
            logic [ WIDTH_ONE_HOT - 1 : 0 ] one_hot
        ) ;

        automatic logic [ WIDTH_BINARY - 1 : 0 ] binary = 0 ;
            foreach ( one_hot [ index ] )
            begin
                if ( one_hot [ index ] == 1'b1 ) begin
                    binary = binary | index ;
                end
            end
            return binary ;

        endfunction

    endclass

endpackage

When I tried to synthesize it using Synopsis DC (2019.3) - I got the following error:
"Syntax Error at or near token 'class'. (VER-294)"
The error points to the line "class class_one_hot_to_binary"
At first I thought it has to do with the DC lack of synthesis support for classes in Systemverilog,
But it worked when I declared the class in a module (not a package) as follows:
module foo ;

class class_one_hot_to_binary

#
(
    parameter WIDTH_ONEHOT = 16
) ;

localparam WIDTH_BIN = $clog2 ( WIDTH_ONEHOT ) ;

    static function logic [ WIDTH_BIN - 1 : 0 ] one_hot_to_binary
    (
        logic [ WIDTH_ONEHOT - 1 : 0 ] one_hot
    ) ;

    automatic logic [ WIDTH_BIN - 1 : 0 ] binary = 0 ;
        foreach ( one_hot [ index ] )
        begin
            if ( one_hot [ index ] == 1'b1 ) begin
                binary = binary | index ;
            end
        end
        return binary ;
    endfunction

endclass

endmodule

What am I doing wrong ?


texts: How to define a false path using design entities

texts:
I'm trying to do a timing analysis on a design I wrote in VHDL.
The design looks like this:

And the mux's are only activated in a way that the path is either:

in -> circuit1 -> circuit2 -> out

in -> circuit2 -> circuit3 -> out

Is there a way to 'tell' this to vivado so that the timing and implementation will take this in to account when determining if I meet the timing constraints?

I assume this will be done by 'setting false path'. But I'm not sure how exactly choose 'trough' what this path goes, since after synthethisation vivado 'joins' these entities (I'm using the 'rebuilt' setting during synthesis).

I have the circuits in separate entities, so I'm wondering if there is a way to use the 'set false path -trough' constraint with vhdl design entities.

Kind regards,

Michael


texts: connecting a LED to a PC case fan header

texts:
On my motherboard (ASRock B150M Pro4S/D3) i have an unused 3-pin case fan header.

Can i use it to drive a single LED with only a resistor in series?

The fan can be configured in the BIOS to change speed according to the CPU temperature, so would like to use the LED as a visual indicator for that.

(I expect the LED to blink faster as the CPU temperature increases.)


texts:
The below circuit is an attempt at having 3 isolated bipolar switches able to handle +/-20A. Voltage is below 10V when "conducting/enabled" and below 200V when not.
IA1212 is an isolated DC/DC converter with 12V output.
Mosfet Datasheet

While it "works", Q12 burns as the current increases. ~6A for a few seconds destroys Q12.
I'm not really sure why because Vs on Q12 would be 0V + Q13 reverse diode voltage, about 1.2V at 20A, which means the +12V - 1.2V => Vgs 11.8V which is way beyond the safe Vgs threshold of ~8V at 20A.

The goal of this circuit is to measure the current through different shunt resistors, as different ranges depending on the input current. The system needs to be bi-directionnal and controlled from 3V3.

simulate this circuit – Schematic created using CircuitLab
Any ideas are welcome, additionally, there is perhaps a better implementation than this?


texts: Having trouble reading serial data from ADC chip with FPGA

texts:
I am trying to read serial data from an ADC chip (AD7476A) that converts 0 to 3.3V into 12 bits, with an FPGA development board (Nexys A7-100T).
I use 12 LEDs on the FPGA board to display the 12 bits sampled and a 4 digit seven segment display to display the decimal equivalent to the 12 bits. The signal interface between FPGA and ADC chip is SDATA (12 bit output from ADC), CS (enables ADC conversion) and SCLK (controls the bit output timing). I can provide more information about the signal timing and can show scope waveforms if required.
Now the AD7476A is a surface mount chip and it is soldered onto a through hole adaptor, and is plugged into a breadboard. The 3 wires between FPGA and breadboard are around 30cm long with push in connections on both FPGA and breadboard obviously. The datasheet recommends 680nF de-coupling capacitor on ADC chip, but I won't have one until tomorrow, so I have shown on the diagram at the bottom what ceramic caps I have stuck in.
A 10K potentiometer is used with an LM358AP op amp operating as a voltage follower to vary 0 to 3.3V to ADC input voltage (Vin). I have electrolytic caps as shown on the diagram as well. Now the whole system is noisy as I can touch wires and the value will change erratically. As I am new to this I am unsure as to what accuracy I can expect, but I think it should be better than it is now.
5V is used to power the FPGA and the op amp, to allow some head room for voltage follower. The 3.3V is used to power up the ADC chip and to supply the common for the potentiometer. The negatives are tied together.
With the pot screwed fully down (~0V to ADC input) the value fluctuates between roughly 66, 135 and 160.
With the pot screwed fully up (~3.3V to ADC input) the value fluctuates between roughly 3960 and 3977.
I don't have another variable power supply to input a fixed voltage so when I connect the ADC input to 3.3V, I get 4095 perfect, and when I ground the ADC input, it flicks between sometimes 33 and 40, sometimes between 66 and 80, and sometimes 132 and 134. Currently as I look at it now, it is flickering between 33 and 40.
I am unsure as to whether this is a problem with the noisy poor setup or the signal serial interface between FPGA and ADC chip, or probably both.
I am unsure as to what my next step should be as when the input is grounded, the shouldn't be any ones coming from ADC chip, I should be reading zero. Maybe the grounding is so poor, there is still noise on the ground which the ADC chip is picking up and converting?
Any advice as to what I should try? Forgive my lack of knowledge on this, but it is a university project and I cannot get much help due to covid.
Thanks everyone!
Data sheet for the AD7476A ADC chip
EDIT 1
From rdtsc's comment, I measured the output voltage from the op amp and there is up to 20mV peak of ripple.
EDIT 2
The circuit now has a 330 ohm series resistor between op amp output and the ADC input, with a 22uF cap between the ADC input and ground.
EDIT 3
I have scoped the CS and SCLK signal from the FPGA. At the time of these images, the CS and SCLK are not connected to the ADC. The SCLK frequency is at 16.7MHz and the CS frequency is around 877kHz.
CS pulls low at the same time as SCLK goes high. There are then 17 clock cycles of SCLK when CS is low. On the rising edge of the SCLK, I have a shift register that shifts the ADC data in. On the falling edge of the 17th SCLK clock cycle (I think its the 17th), I store the shift value register into another register.
This image shows both the CS and SCLK with SCLK frequency.

This image shows both the CS and SCLK with CS frequency.

The image below shows the hardware circuit. There has been a modification so see edit 2 for details.


texts: passing Synplify options from Lattice Diamond TCL code

texts:
I would like to pass, from the TCL file that is commanding the Diamond tool of Lattice, some options to the Synplify synthesis tool.

E.g.: It is possible to set a value of the VHDL generic at toplevel in the GUI.
https://www.doulos.com/knowhow/fpga/Setting_Generics_Parameters_for_Synthesis/

But when saving this project in TCL (save_script test.tcl), this option is not exported to TCL.

Adding the Synplify TCL code in the Lattice TCL file isn't helping.

set_option -hdl_param -set BUILD_VERSION {x"01"}

pnmainc diamond.tcl
invalid command name "set_option"
    while executing
"set_option -hdl_param -set BUILD_VERSION x"01""
    (file "diamond.tcl" line 3)

And the manual not the help in Lattice/TCL isn't revealing anything.

I would like to avoid having another TCL file just for Synplify in my repo.


texts: Looking for linear solenoid actuators less than 2 cm in length

texts:
Do such parts exist?  Are they cheap?

I want to take a sheet of plastic and cover both sides with solenoids, some aligned in the X  direction and some aligned in the Y direction.  With at least a 10x10 grid, I can selectively turn the solenoids on and off to flex the sheet into millions of unique shapes.


texts: Relay with arduino/microcontroller, diode needed?

texts:
I know that you have to place a diode in parallel with a relay to use with i/o on microcontroller. Would you have to do the same with a relay board such as......

http://www.sainsmart.com/module/acce...-pro-mini.html
http://www.sainsmart.com/module/acce...p-arduino.html


texts:
I need some help in this circuit!

How can I connect LED-driver (BJT) in this circuit? Then what is the valus of RB and RC  that meet the requirements, so that the LED driver works properly.

Hopefully get help

Online circuit: https://www.circuitlab.com/editor/#?id=f5rq8hvpj63d


texts: SLEEP or busy-waiting. Which would service an interrupt faster?

texts:
I'm programming a PIC microcontroller to service two events via interrupts on a very time constrained environment.

PIC microcontrollers allow a SLEEP mode which wakes the PCU on any external interrupt (INTn) but has a wake delay depending on the selected oscillator mode.

I want to know which option would start servicing the interrupts faster. A main loop like this:

//CPU never goes to sleep, keeps executing a jump
void main(){
    while(1){}
}

or a main loop like this:

//CPU goes to sleep (idle), waits for INTn interrupts.
void main(){
    while(1){
     asm SLEEP;
    }
}

Waking from idle sleep seems to take 2 cycles according to the PIC18F4XK22 whereas a jump instruction (of an infinite while loop may take longer and may or may not be interruptible halfway into the execution of the jump.


texts: Should I consider the current source for this circuit?

texts:
I am making an analysis for this circuit and I want to make a KVL at mesh 1 (in red), but should I take the current source as it is or does it have another voltage equivalent since I am working with voltages.

This is the equation I got: KVL @ mesh 1: (RB x IB) + (VBE) + I + VEE = 0

Note that I want to find the current IB and I am solving using expressions and not values.

Thank you in advance.

This what I am asked to do. I guess it is necessary to find the expressions in DC mode so I use these in the AC mode.


texts:
I would like to add an EMI filter to a high power LED driver. The datasheet of the driver suggests an LC filter for the power line as shown below. However I would like to use more than one driver connected to the same power line, how would I properly combine these?

Should I use a single inductor - capacitor combination for all drivers? Does the inductance and capacitance multiply, or does it stay the same for any number of drivers? Or perhaps separate filters for each driver is the way to go? In this case adding the inductors is clear - one for each driver's Vin, but what about the capacitors? One common capacitor for all inductors?

As you probably already see, noise filtering is quite new for me, so any help will be appreciated!

EDIT: It's step-down DC constant current driver.


texts: Button press on espresso machine suddenly activates wrong solenoid

texts:
I am trying my hand at fixing a La Cimbali M28 Select, which is a professional espresso machine.

The remaining issue is that, when I press the 'hot water dispenser button' it does not dispense hot water but it pulls an espresso shot from the left group (meaning, the left coffee dispenser unit). When I push the button, the solenoid of the left group is activated now instead of the hot water solenoid.

This seems to me like an electrical issue. Why?

The boiler is directly connected to the hot water dispenser via a solenoid that is activated by that button. When I put the machine in 'maintenance mode' it dispenses hot water just fine, meaning the solenoid is working fine and the pipes aren't clogged. I should also mention it was dispensing hot water in 'regular mode' just fine a day ago without changes that could possibly affect it (unseizing the pump, fixing the gauge, ..).

In the schematics, pushing the button (PA) should activate the hot water solenoid (Eac), and should trigger the water tank fill solenoid (Evc) and its indication light (L2). None of which is happening. Instead it triggers the left coffee group solenoid (G1).

My DMM is broken and I cannot get a quick replacement due to COVID. I used a buzzer as a continuity tester. I used my working steam dispenser, with a near identical set-up, as a reference.

Having connected the buzzer to the two opposite pins - to be more precise, to the incoming wires that are connected to these pins - of the 3-pin solenoid (leaving out GND), I hear a very loud beep when pressing the button. When doing the same with the hot water dispenser, I hear soft crackling when the button isn't pressed and soft crackling when the button is pressed. Surely that is not right? The only difference is that the steam button is activated upon pressing, but the hot water button you need to press and release to activate and press and release to disactivate.

The only thing I can think of, is that I needed to disassemble the machine to reach parts. Some of the machine housing has a GND wire connected to it. I left this untouched, but removed the panels from the machine. Putting everything back together is a lot of work, so I touched the GND wires to the inner machine casing but that didn't make a difference.

EDIT: Completely rebuild the machine and it didn't solve the issue. I did find a GND plug-in on one of the metal sheets that doesn't have a corresponding green-yellow wire. Can this kind of behaviour ever originate from not all GND terminals being connected?

Any insights are more than welcome!


texts: How to determine the input resistance of a bootstrapped emitter follower

texts:
I've used bootstrapping several times, either to boost the input impedance of an amplifier or to increase its gain. However most of the times I can see the beneficial effects of bootstrapping without actually knowing what's the actual input impedance of an amp due to bootstrapping.

Consider the following emitter follower stage which I got from a textbook.

simulate this circuit – Schematic created using CircuitLab

According to the book from which I got that circuit, the input impedance without the 10kΩ load (\$R_2\$) is 500kΩ and the input impedance with the load is 350kΩ. However the book doesn't provide any formulas or explain how any of those values were derived. So I'm trying to figure it out. This is what I've got:

Just to compare, suppose there is no bootstrap capacitor C2, transistor MPSA42 has a beta of 70, so the input impedance would be roughly \$\beta (R_2\parallel R_1) \parallel R_3\$ (I didn't consider R4 for the calculation since \$R_4 << R_3\$), substituting values results in an input impedance of 77.7kΩ.

Now consider what happens when the bootstrap capacitor is in:

The emitter current of the transistor is approx. \$\frac{24-0.7}{\frac{R_3+R_4}{\beta}+R_1}=2.01mA\$

Which results in an incremental emitter resistor of \$r_e=\frac{V_T}{I_C}=12.93\Omega\$

The voltage gain of the CC stage is roughly:

$$A=\frac{R_1 \parallel R_2 \parallel R_4 }{R_1 \parallel R_2 \parallel R_4 +r_e}=0.996$$

Now suppose that 1V is applied to the input. That would mean that the current through \$R_3\$ is \$ \frac{1-0.996}{100k}=40 nA \$ which, compared to the current through the 100kΩ resistor without bootstrap is \$\frac{40nA}{1/100k}=4x10^{-3}\$ times the current without bootstrap. This means  the resistance of 100kΩ actually looks like a resistor of \$\frac{1/100k}{40nA}=250\$ times greater value, or \$100k\times 250=25M\Omega\$. This will be in parallel with the resistance reflected from the emitter to the base, which is roughly \$\beta (R_1 \parallel R_2 \parallel R_4)=233k\Omega\$, that in parallel with the 25MΩ resistor gives 230kΩ, as opposed to the 350kΩ mentioned in the book. I checked with a simulator and the input impedance is indeed close to 350kΩ.

What am I doing wrong, is my line of reasoning correct?


texts:
Since i started my training about design of DCDC I'm really confuse with control part.

At school i learned that DutyDycle=Vout/Vin for Buck,  and that's it.

But now, i see that, Duty cycle  is set by the output of error Amplifier and can indeed change from 0 to 100 according the output Voltage state. Is not at all a constant :/.

My second confusion and is my main question is about the picture joined.

If the result of EA is 0V (Line i drawn in red). What happen? duty cycle will be zero? This is not a problem ? because we should also have  DutyDycle=Vout/Vin.
Is there any constant  define for the PWM modul for exemple if EA is 0V -> give a fixe dutycycle ?

I'm so sorry my question is not totally clear because is not clear in my mind too.
If someone could give me a clear view about this part it will be a big party for me.


texts: How does the back-power protection of the pi function?

texts:
The Raspberry Pi HAT design guide states that it is important to build in protection should the user want to back-power the pi via GPIO. I believe I understand its function (to stop current flowing from the Pi to the HAT) but I would like to understand how.
My questions:

How does the back-power protection work?
Is it also enough for back-powering a Jetson Nano, which could pull at most 6A at 5V?

The design I'll be using is this one:
Its origin lies in the KiCad Template for Pi 40 pin HATS, probably derived from this schematic. The left side is the Jetson Nano GPIO side, right side (P5V_HAT) is the side that the power is supposed to come from.


texts:
I designed a current source circuit for driving LEDs. This circuit works fine and supplies constant 2.5A. I wonder if this circuit is linear or not.

simulate this circuit – Schematic created using CircuitLab

1-) If this circuit is linear;

VLOAD = 9VDC and Vin = 16VDC and VDS-M1 = 6VDC. The Power dissipated by MOSFET would be as:
P = 6 * 2.5 => 15W
Rth = 62 °C/W so MOSFET temperature should increase by 62.5 * 15 = 938°C but it only increased by 50°C. So I think this circuit is not linear.

Also I scoped the gate voltage using an oscilloscope and there is a switching:

2-) If this circuit is not linear;

If this circuit is not linear, Iin and Iout should not be equal but they are totally equal.

Am I wrong? How can we characterize this circuit?


texts:
To play a joke on this question, we came up with the following image on the Super User Chat.

Of course this will not work, but now my question is:

What happens if you charge a laptop using it's USB power?

Assume there is a fully charged battery in the laptop to begin with. ;)

I see three possibilities:

A short circuit happens, the cable might map - on + and vice versa.
Nothing happens, like you were to connect the + and - of a battery to itself.
Power goes around in a circle and you lose faster than usual due to heat.

But I can't see which one of those would really happen...


texts: Choosing a microcontroller for a project

texts:
Possible Duplicate:
  How to choose a MCU platform?

I'm designing my first project that could possibly go in to production(as a university project) but I am now stuck on choosing a microcontroller for it. My main experience is with Atmel AVR so im tempted with choosing an AVR, however I don't feel that it would be future proof. What characteristics should I look for when choosing a microcontroller? How should  I decide between a 8- (Atmel AVR), 16- (MSP430) or 32-bit(ARM Cortex M3) microcontroller?


texts:
I have a motherboard, that requires a DC input. The manual has this:

I'm trying to find a power brick, but all bricks I can find usually have +12V/-12V on pins or shell and no ground.

Can I use them? Or can I modify them?


texts:
I want to drive around 80 LEDs from an Arduino with 10 8-bit shift registers.  (Some will be RGB LEDs; I count those as 3.)  I know of the TPIC6B595 high power shift register but it's expensive: 1.75 USD from DigiKey and Mouser.  I would prefer to do this cheaper.

I can get 74HC595 low power shift registers for 50 cents and ULN2803A Darlington arrays for 65 cents from Futurlec.  That is a total of 1.15, so I'd save $6 on the whole setup.

But the ULN2803A is way overpowered for LED's - each pin can sink 500 mA! Is there anything similar to the ULN2803A, but lower power and even cheaper?


texts: Creating an low current negative voltage

texts:
Good evening,
This is my first post on this forum, so if I'm doing something wrong don't hesitate to tell me.
Now to my question; I need 2aa batteries or an LiPo battery(3v-3v7) to be boosted to 5v(Done), boosted to 13.6v and inverted boosted to -15v. As you can see in the schematic below, I've got 2 boost converters to make the 5v and 13.6v. But since the current consumption on the 13.6v and -15v 5mA is. It's an waste of money to get an Buck boost converter for the 13.6v.

But this doesn't include the solution for the -15v. So what would be best, cheapest and most efficient way(can be 3 different methods ;) ) to make large negative voltage out of an small positive voltage?
These are some simulations I ran (The load resistor is currently simulating an 10times bigger load then needed. But changing it didn't effect the outcome, it did speed up the simulation..)

all voltages dropped below the input voltage:13.6v. I got tired of waiting, so don't look at the output voltages
I was planning on using the charge pump method on the SW pin on the 13.6v regulator. But after some wishfull thinking I figured out that you can't get an higher voltage then the input voltage on the charge pump method.(to be honest, it took me to long to figure out..)
The least efficient method I could figure out myself would be to get an Boost converter to generate, lets say, 20v. Inverting that voltage to -15v, stepping it down using an level shifter or zener diode to 13.6v and using an regulator to make 5v out of it. Ow and last but not least, it has to fit on an 17mm*20mm PCB(components single sided)


texts: How to improve and add frequency adjustment function to my DIY wave generator?

texts:
Introduction
I want to build a wave generator. I chose wien bridge oscillator(WBO) as my oscillator and I obtain other waveforms by filtering the sine wave I get from WBO. I managed to get a fairly decent wave forms when the switch is at position 1 but nothing near that other combinations. I am looking for ways to improve my design and make it work since it doesnt work as intended.
Design Intentions

Adjustable frequency (15 or MHz to 15 Hz)
Adjustable output peak voltage
Can be powered with 220V AC city electricity (by transforming to -15/0/15 or -12/0/12 volt outputs)
Preferably should use WOS as oscillator

Design and Circuitry Explanation

I power all the opAmps with 15/-15 volts
I used:

TL071 OpAmp
2 x 1nF capacitors
3 x 100k resistors
1 x 210k resistor
2 x back to back diodes

To build the oscillator. I get a nice sine wave with this setup, which is actually one of the reasons I chose WOS. Even though the signal was clear, the magnitude of output was pretty low (around 750mV) and I wanted to amplify it.
I used:

UA741 OpAmp
1 x 100k resistor
1 x 10k resistor

To build an amplifying component with gain 10. Now my sine wave was nice and around acceptable magnitudes. Then I wanted to filter and amplify it again by using an integrator OpAmp to gain a square wave.
I used:

TL071
1 x 1k resistor
1 x 1nF capacitor

I preffered TL071 here again to get rid of the slope of the square wave. TL071 has a higher slew rate around 10V/us as I remember. As you will see the square wave is pretty neat too.
To acquire the triangle wave I used the same circuitry I used to filter the sine wave. At first I tried to use an UA741 but it just gave me the same square wave, I dont know why. Later I just used a low pass filter
using

1m resistor
1nF capacitor

which gave me a rough triangle wave it had peak voltage near to none. So I used TL071 instead of UA741 to apply the same filter I used on sine wave, to the square wave. This gave me a decent triangle wave with a little plateau.

outputs with oscillator having 1nF capacitors and 100k ohm resistors
In the end, I had a nice sine wave (around 6.5/-6.5 peak voltage), a nice square wave (around 12.5/-12.5 peak voltage) and an acceptable triangle wave (around 12.5/-12.5 peak voltage). To implement the adjustable output peak voltage I thought about using a potentiometer to change the gain of first OpAmp which amplifies the sine wave. To implement the adjustable frequency I thought about putting some capacitors with trimmers. Since for the sake of oscillation C2 should be equal to C1 and I couldnt find a way to change both capacitance exactly the same (like a ganged up potentiometer) while adjusting the frequency, so I abandoned this idea.
I thought maybe using a rotary switch I can switch between frequency mods, which turned out to be a huge dissapointment. In the schematic above you can see the final implementation. when switch is at first position everything is fine. As I switch problem begins.

You can see the switch time exactly. Plot of before and after the switch

Close up
There were even times that I get 0 output from every wave form. I need suggestions to:

Implement adjustable voltage and frequency
Fix the plateau at triangle wave
Any opportunity for improvement you see

Thank you.


texts: Safely detecting lead-acid battey charger output?

texts:
How can I safely detect output of a car battery charger?

It has a OS/MP switch and for output it lists 12 V and 10.1 A. Unfortunately I have no idea what OS/MP means and I of course have no manual. The charger also has a single 5x20 glass slow fuse rated at 2 A and a 10 A standard household circuit breaker.

I'm hoping to use the charger as a power supply for a project. Either constant current or constant voltage would be OK, but I can't determine right now which one the charger is. It looks low-tech, so I doubt that it has both output types.

On the equipment front, I have two multimeters and I could easily obtain various 5 W and 11 W ceramic resistors. I have several 10 $\Omega$ resistors available right now.


texts:
I’m setting up a little self-service laundry mat (in Spain) composed of 3 washers and 2 dryers all having 3 phase motors running at 380V.

The washers consume 1,5kw 2kw and 2,5kw while both dryers consume 0,8kw each.
The rest of appliances, UPS, lights, fans, AC outlets, etc., run on 220V off of one of the 3 phases.

The electrical technician has suggested installing a 3 phase capacitor bank to compensate for the “Reactive power” produced by the motors because if not, I may be penalized economically by the local electrical company.

I doubt the 5 motors will be running all at the same time but, just in case they will, should I really be worried about the possible reactive power? Because if so, I’ll take steps to prevent any problems caused by said motors.

Thank you in advanced.

John


texts: How to create large inductors (1H) for audio use?

texts:
I am building a tube amplifier, and have decided to add a 5ch EQ to it. Historically, the ones used in guitar amplifiers were all passive RLC filter style systems, with large inductances of 0.5 - 2H for the 80Hz channel.

I know now days it would be smaller to use an active op-amp style, but I am doing this as a hobby and want to try making a passive one. I was slightly surprised to find Digikey does not carry any small inductors over ~100mH.
My guess is this is because no one uses them for small current applications anymore with the advent of DSP or active capacitor based filters.

Any advice for creating large 1H inductors with <1mA of current that does not involve winding 300 turns through a 1" torroid?

Or does anyone know how they were historically made, really fine wire i would guess with many turns?


texts: TA says in the solution of this question that Va=v1-((v1-30)/20)*10 , how did he get this?


texts:
My Chinese phone usb charger has gone.

I opened the lid to repair it, and this is how it looks like (picture below).
Actually how it looked like after I removed Q1 for testing.

I suppose it has been gone. I checked with the multimeter and all pin combinations are open. And since both transistors were named as Q1 so I removed the second transistor and ensure it's a actually what I think (NPN transistor). But the problem is these two transistors are not identical in their label. I think originally this was designed as identical but later customized it in a later review.

So is it safe to assume that it's also NPN transistor?

This is the transistor that needs to be replaced. And it's a 13001 S 8D, and the second transistor is , S9014 C331.

What I want to figure out is an alternative.

This transistor is available on ebay.

Could somebody please recommend me a equivalent transistor for this?
Possibly a 1250 mW 600 V one.

If I just put some of those C945 what will happen?

There are no schematics available on this.

--Thanks in advance--


texts: If I am charging a super capacitor with buck converter, that is a 1 amp, 1-18 volt output, and the capacitor is rated for 2.5 volts, how do I stop the buck converter from feeding it more than 2.5 volts? When I attach the capacitor to my digital power supply, it starts charging, and the voltage slowly increase to be more than 2.5 volts, at which point I turn it off. I was wondering will it draw more than 2.5 volts from my buck converter? If so how do I stop it?


texts: How were the voltages/frequencies of mains defined?

texts: In other words, are there any historical reasons that set mains supply voltage to 120, 127, 220, 240Vrms per phase, and 50/60Hz? These are the most common voltages/frequencies, there are many others, depending on country. Here in Brazil a single phase is always 127Vrms/60Hz.


texts: Differences between notch filter designs - use of op-amps

texts:
I have a question about notch filter designs using op-amps and I hope that you can help.

Following this tutorial https://www.electronics-tutorials.ws/filter/band-stop-filter.html, they give examples of different notch filter designs. I'm interested in the designs using 1 and 2 op-amps:

Circuit 1:

Circuit 2:

Besides the fact that values for the resistors and capacitors have been introduced in circuit 2, what is the difference between having one and two op-amps connected in this fashion? What does A2 add to the circuit? It has something to do with the feedback, but I'm not sure how it's affecting the circuit.

As a note, I'd like to know more about these circuit elements and be able to figure these things out on my own. So if you have any litterature suggestions, please feel free to share :).


texts: Problem while simulating a 12 bit counter using 3x 4bit 74163 counters

texts:
I have attached a circuit which includes three counters which are the IC 74163. This specific IC is a 4 bit counter. I want to make a bigger counter which will be able to count 752 steps with an input frequency of 20 MHz. The fact is that my counter does not work at all and I would like to know what do I make a wrong. Is there something that I do not see? In this case the preset is 4095 - 1 - 752 (steps) = 110100001110. Unfortunately the system does not count correctly and I am sure that there something wrong with my design. Could please someone give me advice?

The input signal is 26.6 kHz and the frequency of the system is 20 MHz. Also the reason for doing something like that is because I am trying to use an external PLL in cooperation with my FPGA design and the circuit below is used to make the division which is needed fout = N * fin and theoretically I want to make a division of 752 so I need 752 steps. The system does not work well but with another preset value it worked. Despite the fact that I get the 20 MHz I need digitally I want to understand completely why the counter that I have designed does not work properly.

The reason for which I do not get a bigger counter is that I have to simulate the system using parts available from my FPGA's software library. Is there a possibility of overflow or something like that, which I cannot see?


texts: How is the voltage supply and peak-to-peak voltage of a rectifier found in this example?

texts:
I'm struggling with rectifier calculations, and below is an example my teacher uploaded in my blackboard. How did he find the frequency of the voltage supply and what is the calculation of the peak rectifier voltage?

From what I thought, you need Vrms x 1.414 = Vp, or am I wrong?


texts: Cooling the IC on a board printed by hand

texts:
I'm building a battery charger circuit with BQ24278. The battery draws 500mA minimum and 2.5A maximum current; therefore, I must prevent IC from overheating. I printed the board onto single sided copper plate with ironing method and unfortunately there is no opportunity to drill the copper plate since I don't have a proper drill equipment. So, considering my restriction, is there a practical way to cool down the chip? I already have DC fan and heatsink for TO-92 package; however, since I have burned out 2 ICs already, I would like to apply a solution by getting ideas of other people.
I connected AGND and PGND under the bq24278, and put as much copper as I can. I attach the datasheet and the circuit diagram.
Thanks.
the circuit:

datasheet:   http://www.ti.com/lit/ds/symlink/bq24278.pdf


texts: Building a personal RF anechoic chamber in a large walk-in closet?

texts:
What would one need (besides many foam absorbers) to build an in-home small anechoic chamber for transmissions in the UHF to L-bands (specifically 500Mhz - 2 Ghz), and what resources would you point them towards?

Also does anything specific need to be under the foam absorbers?

For example, if a closet is 'unfinished' and only consists of wooden boards and some insulation between each board, could the absorbers go right on, what do you suggest?


texts:
I want to design microstrip antenna for UHF RFID. The chip I'm using is SL3S1013FTB0. I found some demo kits and found some antenna examples. One of them has small antenna that I'm especially interested in and it looks like this:

But there is no information about this design and to be honest I'm having a hard time understaing how it works. What is more, when I checked the gerbers it seems to be shorted to ground!

Can anyone explain how it works or recommend any book/article that explains it?


texts: High pass filter Using Inductor or a capacitor?

texts: So I was thinking about making a basic Highpass filter. I was wondering if there was any reason to use an RL configuration as opposed to a CR configuration.


texts: Is it possible to switch relay above the power spec?

texts:
I am planning to use a DC drived SPST reed relay. Below I include the spec for voltage, current and power ratings.

Contact Rating: 200W
Carry Current: 5A
Switching Current: 3A
Switching Voltage: 3500V

I want to use this relay for 2000V - 3 Amp power source switching. I know it makes 6000W which is out of spec for contact rating.

However, my question is if I turn off the power before switching off the relay and turn on the power after I switch on the the relay can I use this relay with this voltage and current?

This is the spec link of the relay I want to use (model 5503 more precisely). Here, another one similar to it.


texts: What is the easiest way to increase the Voltage output of this power supply?

texts:
I have this power supply which is part of an energy meter design already on PCB, and undergoing some tests. It passed all tests except the one that requires it to run at 60% or rated voltage, 240V, which gives us 144V

The AC supplies 240, the transformer output gives 6V, and the LDO gives me 3.3V.
HOwever, at 144V, the input of the LDO is just about 3V, giving me no output.

I want to know the easiest way to make this work.

Thanks.


texts:
I'm creating a set of modules that can be daisy chained and hooked up to a master controller unit. I'd like to have a display on the master that shows the combined current draw of the modules in realtime.

Is there an IC that you can pass the circuit through and then query (through I2C for example) for the current load?

This is a 5V project and the current will be in the range of 0 to 2 amps at most.


texts:
I'm implementing a WM8804 S/PDIF transmitter in a project I'm working on. The datasheet states that clocks from 10MHz - 27MHz are supported.

What crystal oscillator frequency should I look for in order to support 44.1kHz I2S output given a an input of 44.1kHz S/PDIF?

Edit:

It looks like 12MHz would work fine, given the info below:

Is this correct?


texts: Electrophysiology amplifier problems (electrode design help)

texts:
I have been working on a small differential amplifier that will ultimately be used for whole nerve recording from lobster connectives.  Throughout the process I've been testing the amplifier using tongue EMG signals (taking the two input electrodes, putting them on my tongue).

Recently I discovered that the amplifier only seems to work properly when I use two identical electrodes.  In this case either two fine silver wire electrodes, or two wired alligator clips.

When identical electrodes, I get an amplified tongue EMG signal and everything appears to work great.  BUT, when I mix different wires for electrodes (using a fine silver wire and an alligator clip), I briefly get the signal before the amplifier goes silent.  Once the amplifier goes silent, the individual electrodes stop reacting to touch unless I touch the wires together.

I initially thought electrode wire resistance may have been the issue (the silver wire electrodes seem to have a resistance of ~1 Ohm, while the alligator clips register at 0 Ohms), but I've been told a difference that small should be negligible.

Is it possible that the differences in surface area of what is touching my tongue (larger piece of metal vs. fine wire) is causing the problem?  The lab I work in traditionally uses alligator clips as grounds, so I hadn't expected this to be an issue.

In general I'm curious how differences between the electrodes being used could cause an amplifier to go silent and/or not function properly.  I appreciate any advice someone has on the matter.


texts: Raspberry pi not getting any data from hx711

texts:
I'm trying to combine two boards into one: SparkFun Load Sensor Combinator(basically just a wheatstone bridge) and SparkFun Load Cell Amplifier. The data will be transmitted to a Raspberry Pi 3 so there is a connector on the board specifically to communicate with the raspberry. My problem that nothing is comming out the HX711. Nothing comes out of DATA nor CLOCK. Here is the schematics i've done:

I've tested the transistor to make sure it's saturated because i thought that may be the wheatstone bridge was not correctly powered but it's ok. Any idea what the problem might be?


texts: I'm hooking up and old  HC-05 BT module and it powers even if vcc is disconnected, (if TX is high and is key is high), is it likely i fried something and it's broken?


texts: Why build very similar diesel-electric engines in both AC and DC traction versions?

texts:
I'm reading Wikipedia on GE Evolution Series diesel-electric engines. The series includes ES44AC and ES44DC models. Looks like they are very similar but one uses AC traction and another uses DC traction. They are being built in parallel - it's not like one version is "old and boring" and the other is "newer and brighter".

These are not catenary powered engines - they don't need to be compatible with railroad electrification parameters. They just burn diesel fuel and run the onboard generators and use generated electric power to run the traction motors.

AFAIK it's usually "what combination of generator, controller and traction motor can be made most maintainable and cheap" consideration that affects the choice of generator-motors combination. However this time the manufacturer decided to build both versions at the same time.

Why build both versions in the same series of diesel-electric engines?


texts:
By Ohm's Law, V = RI.

I am learning about impedance, reactance, etc.

One question: can Ohm's law be extended to impedance?

I mean if V = RI, will
V = ZI?

Suppose this circuit:

Suppose this R/C represents an amplifier and I am injecting audio to it, from 20 to 20Khz.

The reactance of the capacitor will decrease with frequency. If AB represents the output of that circuit, what will happen to the voltage between A and B as the frequency increases from 20 to 20 kHz?

How to I plot that curve of Voltage AB with frequency?

Please answer these 2 questions. Thanks.


texts: Safety switch to latch when power turns off till reset

texts:
So I currently have a drive run by a PSU. I have a thermal controller that will cut power to the drive when it runs over temperature but it doesn't latch off, so as soon as the drive cools a little it just turns back on. So I am trying to make a latching reset but I keep running into problems with the latch because the drive voltage needs to be 0 to 20 V. I have a crude diagram below.

I have looked up multiple latching switches using BJTs tried a relay with a push button and a 12 volt rectifier leeching off the thermal controller. Most fail when using the drive at low voltage sub 3 volts and burnt a few parts when going over the 20v.

Again I currently have it cutting the output to the PSU when it goes over temperature but I want it to stay off until manually reset in case I am not watching it or so it wont restart if I try to change something after it over-temperatures.

I am using a temperature controller model SlB4848-R2 and TDK-Lambda model UP36-6 power supply I would prefer to use those since I have. I also have access to a wide array of other common parts.

Thank you in advance for any of your advice I can post previous attempts I had if desired.

So I found a higher output op amp used as a compactor as the latch with a push button to trigger the relay. Would not have figured this out without user Transistor showing me CircuitLab made so much easier. The voltage divider is meant to both limit current and stop the input voltage from exceeding the op amp output.


texts: Generating Asymmetric AC PWM with MOSFETs

texts:
I have a tricky project that requires -10 V low, +40 V high, duty<0.5%, 2 kHz PWM.

Load: 50Ohm resistive (forward),backward is probably in MOhm range. max power 1W (only works with very low duty).

The most straightforward way I can think of: MCU driven dual supply complimentary MOSFET:

simulate this circuit – Schematic created using CircuitLab

However, the VDD+ and VDD- is so much greater than logic level, I wonder if this will blow up the MCU.

Is there better way to do this? I also checked half-bridge with 2 NMOS, but all schematic I found does not support dual supply (the low side is always grounded).

This is an isolated half-bridge driver I came up with. I don't know if it works:

simulate this circuit

Since VDD+ and VDD- are different, H-bridge is out of question.
Highly integrated solution is preferable.


texts: Altium 2019 - "PLACE" option is not highlighted/showing

texts: I've recently downloaded Altium 2019 (version 20). When I was searching for the components using the manufacturer part number, I was not able to place the searched part as the "PLACE" option was not highlighted. What should I do?


texts:
I am using a 74F283PC 4 bit adder, and I am not sure why, but the LEDs are not working, like they will not change at all. I have no idea why it's not working, and I could use any help.

This is the schematic, its connected to 5V and there are 1k resistors at every input, and LEDs to every output except carry out, which is connected straight to ground. When I change an input, the output does not change. Thank you in advance

Datasheet : http://eelinux.ee.usm.maine.edu/courses/ele172/docs/74F283.pdf


texts: Confusion regarding root locus. Open loop or close loop?

texts:
Which transfer function ,open loop or close loop do we use/need as a pre req to perform root locus analysis?

I have also attached a snapshot of the relevant webpage of university of Michigan.

I have also highlighted in my snapshot both contradictory terms used in the webpage article.


texts: Converting a DPS800 server PSU into a standalone 12V PSU

texts:
I recently got my hands on 2 server PSUs from a HP Proliant DL380-G5.
HP model DPS-800GB A REV 06M Series HSTNS-PD05
Partno: 379123-001
(They appear to be made by Delta, going from the logo on the internal PCB.)

These can output a whopping 82A max at 12V (with 240V input), which would be very nice to power some LIPO battery chargers.

I know it is possible with the closely related DPS-700 and DPS-750 PSUs that use a very similar internal PCB.

Does anyone know how to convert/modify these DPS-800 units to function as standalone 12V power-supplies ?


texts:
Noob alert.

I'm about to build a pretty simple PSU for my modular synth project. I'm looking at a few schematics from popular sites and I've previously built a simple wall-wart one based on this from MusicFromOuterSpace, http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY using LM7912 and LM7812.

There are also lots of kits with these 7812/7912 pairs like https://www.banggood.com/DIY-LM7812LM7912-Dual-Voltage-Regulator-Rectifier-Bridge-Power-Supply-Module-5V-12V-Kit-p-1363569.html?gmcCountry=SE&currency=SEK&createTmp=1&utm_source=googleshopping&utm_medium=cpc_union&utm_content=2zou&utm_campaign=pla-all2-se-en-pc&gclid=Cj0KCQiArqPgBRCRARIsAPwlHoXE9RgOOi3wlJ44WgDhjwz376YPlV3aI21Tsu0PF-d2THapEru2bzUaAqCAEALw_wcB&ID=557391&cur_warehouse=CN

But then I watched this video on capacitance multipliers:

https://www.youtube.com/watch?v=wopmEyZKnYo

and just don't understand why this isn't used everywhere? I guess I'm missing something.

What I mean is, it seems to be a really big thing to really reduce ripple on power for synth applications. The schematics I'm looking at are sticking really really big electrolytics in there to do that - it's like that's probably the big material cost for these PSU's. Like 10kuF or so. Wouldn't it be a very simple win to just use a mosfet capacitance multiplier just before the voltage regulator?


texts: Sending an audio signal using piezoelectric sender and receiver - strange electrical behavior

texts:
I'm building a rudimentary sonar using piezoelectric discs and I wanted to test it to see if a receiving disc could hear a sending disc. I have the sender hooked up to a ATTiny85 that is sending a pulse train (yellow on the oscilloscope output), and I watch the purple (received) signal. On some other questions here, people suggested I put a 1 megaohm resistor across the receiving disc. When I look at the scope output, it gives a very strange sinusoid while it's clamped in my little testing rig (4 arm soldering helping hand thing). If I take the receiving disc and put it on a table instead, the waveform looks more normal like the 3rd image.
Is the 2nd image a result of a capacitive effect while my helping-hand is gripping the disc? The metal of the claw is encased in some plastic so the metal doesn't touch the disc directly.
My final image is the disc itself with some added wires to it. I did an abysmal job soldering because I'm not that good at it. My question here is, can bad soldering like this introduce capacitive effects of it's own?
My final question: if I wanted to use the signal from one of the images, should I use an op amp to amplify the signal before I send it into an Arduino or some chip with an analog input? I'm thinking of doing that but wanted some quick feedback. The scale on the scope for the purple signal is 5mV per square.


texts: How do I find out about the technical details of an LED if I don't have the fact sheet?

texts:
I have bought a bunch of LEDs from the rummage table of my local electronics store. Now, I don't have a fact sheet, neither I do know the vendor and / or the article number.

How do I find out about the desired voltage and current of the LEDs (without doing it trial-and-error)?


texts: Why a source which has high source impedance modeled in general as current source?

texts: Is there a practical example by using a circuit where a source better modelled as a current source if it has a high output impedance? I have been hesitating to ask here but couldnt figure out myself. Im trying to grasp the logic behind it.


texts: Unused battery life in electronic device?

texts: Why do batteries in an unused device die out in time? Is it because, even if the circuit is open, - terminal is in touch/connected with a metal inside the device? Or, is it due to chemicals, since sometimes they melt, but only in devices.


texts: Something I was wondering about: Why is one still using transformers for vacuum tubes? I know that they need higher voltages than usual, but do they really need AC voltages? Or can't one simply use DC/DC converters to generate this high voltage? That would remove those ugly transformers, and just leave the tubes on the outside.


texts: Sensing when micro USB power cable is unplugged from a smartphone (or other device)

texts: I am looking to create a charging device that can provide 5v power to charge a smartphone (or other consumer electronics device) via micro USB. How would I go about making this charging device "aware" of when it is plugged into the smartphone or not? It would need to be able to detect a simple "unplugging" of its micro USB male end from the smartphones's micro USB female end. It would need to be able to detect the "unplugging event" regardless of whether the smartphone is charging or not (i.e., it should not be affected by whether or not it is charging).


texts: What is the well-known mechanism to make sure the grounding connection always works?

texts:
I want to put high-voltage machines or devices on potentially hazardous working places such as kitchens, washing areas, etc.

Is there any well-know mechanism to make sure the grounding connection always works? I meant, when the grounding cable is accidentally cut, current from the electric outlet cannot flow to the device automatically.


texts: Making LED flash from steady-state signal

texts:
I am looking to design a simple circuit that detect objects placed in a spot. So far, the circuit uses simple IR LED and photodiode to detect the object placed between them.  The voltage developed in the junction of photodiode is fed to inverting input and Vref to the non inverting input of an opamp. The circuit works as expected, detecting the object placed with some adjustments in the pot.

simulate this circuit – Schematic created using CircuitLab

My intention is to make an LED blink (not shown in the schematic) continuously (like driving using square waveform or some sort) whenever the object placed in between the IR LED and photodiode is removed. Well so far the op amp gives a steady output which is enough to light up the LED, but not blink.

I have considered the options of using a monostable multivibrator in the next stage using the opamp output as trigger, but unfortunately when the object is removed, the opamp gives high output until the object is placed back, which again will make the multivibrator to stay in a single logic state and again will not be enough to make the LED blink continuously.

I am looking to implement this without the use of any microcontroller. But right now, I am clueless on how to proceed and what to use to achieve the continuous LED blink as output.

Any help or any leads will be very much appreciated.


texts: SparkFun Power Driver Shield Kit for controlling 60 V input

texts:
I just bought SparkFun Power Driver Shield Kit. I read in the specifications that it was possible to control up to 60 V using PWM. I have got a project where I need to control 60 V with the PWM so I bought this card but got a bit confused when I got it. I thought it simply would be possible to connect my 60 V output into the card and controlling the output with PWM. but I got confused where it says 12 V and 5 V.
Is it not possible to use higher voltage then 12 V with the card? My idea was to use it basically as a dimmer, controlling voltage between 0 - 60 V with the help of PWM.
Did I misunderstand something about the concept?


texts: STM32L4R5xx Different Pins Same Function

texts:
I am working with a STM32L4R5LQFP144 microprocessor right now. I'm trying to use the SPI1 with several sensors. I understand that the SCK on the slave needs to be connected to SPI1_SCK pin on the microprocessor, but there are several different pins that all say SPI1_SCK on the microprocessor.

Do I connect the slave's SCK pin to all of the SPI1_SCK pins on the microprocessor? Or do I pick a single master pin?

Thanks in advance.


texts:
On the technical sheet of a motor controller integrating two BTS7960B (picture below), the description of the 8 PINs on the board is as follows:

  RPWM: Forward level or PWM signal input, active HIGH

  LPWM: Reverse level or PWM signal input, active HIGH

  R_EN: Forward drive enable input, HIGH enable, LOW Close

  L_EN: Reverse drive enable input, HIGH enable, LOW Close

  R_IS: Forward drive - side current alarm output

  L_IS: Reverse drive - side current alarm output

  VCC: 5V power input

  GND: Ground

I tried to search for "side current alarm" and "side current" but all I found was about "high/low-side current sensing". Being a newbie in electronics, I'm not sure what is the connection between all those terms.

What is a "side current alarm"? How is it used?


texts:
I am doing a benchmark between 2 EDGE devices: Google Coral and Jetson Tx2.
I have planned to overclock the TPU and GPU respectively.
So far I have overclocked the TPU, from 250MHz (STD) to 500 MHz (MAX). But I do not see any difference.
The "stress" test was doing inference 70000 times in a classification task (AI). I used 1 image, because I do not want to measure the latency between the CPU and TPU (the CPU does the image preprocessing). everything took around 2 hours.
I do not know what else to try. Maybe I should overclock the CPU too as the TPU is a coprocessor? I have no idea.
Please any comments or suggestions are welcomed.
Here is the plot that I made. It displays the variation in temperature. Unfortunately it is the same for STD and MAX frequencies.


texts: Calculation of the lower cut-off frequency of an amplifier with only one transistor

texts:
I need to calculate the lower cut-off frequency of an amplifier with a transistor BJT. I have to analyze in isolation the Thevenin equivalents seen by each capacitor C1, C2 and C3.

The model for small signals (with C1, C2 and C3) is given by:

For C1:
\$R_{Th1}=R_1//R_2//r\pi+R_6=\Big(\frac{1}{2,7\times 10^3}+\frac{1}{22\times 10^3}+\frac{1}{3869,97}\Big)^{-1}+2,2\times 10^3=3683,18\,\Omega\$

\$f_1=\frac{1}{2\pi RC}=\frac{1}{2\pi\times 3683,18\times 10\times 10^{-6}}=4,32\,Hz\$

For C2:

\$R_{Th2}=r_0//R_4+R_5=\Big(\frac{1}{30\times 10^3}+\frac{1}{2,2\times 10^3}\Big)^{-1}+10\times 10^3=12049,69\,\Omega\$

\$f_2=\frac{1}{2\pi RC}=\frac{1}{2\pi\times 12049,69\times 2,2\times 10^{-6}}=6,00\,Hz\$

For C3:

\$R_{Th3}=\bigg(\frac{R_6//R_1//R_2//r_{\pi}}{\beta}\bigg)//R_3=\bigg(\frac{\Big(\frac{1}{2,2\times 10^3}+\frac{1}{2,7\times 10^3}+\frac{1}{22\times 10^3}+\frac{1}{3869,97}\Big)^{-1}}{500}+\frac{1}{220}\bigg)^{-1}=0,56\,\Omega\$

\$f_3=\frac{1}{2\pi RC}=\frac{1}{2\pi\times 0,56\times 470\times 10^{-6}}=604,69\,Hz\$

So, the lower cut-off frequency of this amplifier is approximately
the frequency of C3 = 604,69 Hz.

Could you please confirm if my calculations are correct? And if I calculated the Thevenin well?


texts: How to find the nodal voltage when there is a voltage source across two nodes?

texts:
How to find the nodal voltage when there is a 40V across Node 1 & 3?
V1= 22.4 V
V2= 65.6V
V3= 62.4 V
My Nodal Analysis
Node 1 (SuperNode):

-V1/4 - V1-V2/3 + V2-V3/2 - V3/6 = 0

Node 2

V1-V2/3 + 16 - V2-V3/2 = 0

Constraint Equation

V1-V3 = 40

Any help is greatly appreciated!


texts: How can I dim 50 high-power LEDs in series with an Arduino?

texts:
What I'm trying to do is to use an Arduino to control the brightness of two series of 50 high-power LEDs independently.

Each series has an independent LED driver, and each LED has a foward voltage and current of 2V and 700mA respectively.

What I want to do is to be able to vary the brightness of each series from 0% (OFF) to 100% (full brightness) with 0.5% or 1% steps using my PC or my smartphone (with a BT module) and an Arduino.

I've searched on the internet about how to do this, and I found that maybe I could use an n-MOSFET to control the current provided by the LED Driver using an analog output of the Arduino (as far as I know controlling the current I can control the brightness which is the main point), but I saw that those MOSFET can get very hot (and I don't want this) and the current doesn't change linearly, so I'm afraid of not being able to precisely control the brightness. So now I'm completely lost on this problem, if someone could help me I would be extremely grateful.

OBS: I'm a complete noob in electronics and with Arduino, so if it's not asking too much, please explain exactly how I should build this circuit to get it to work.


texts: How to amplify 3.3V to 10V by using an NPN transistor? How to select resistor based on current, how does the amplification happen?

texts:
I have basic knowledge about NPN transistors and I know how they work: for current gain based on the small input current in the base we are able to drive large amount of current in between collector and emitter.

In my circuit I need to amplify 3.3V of my stm32 micro controller input to 10 V output to drive a Mosfet switch.

I want to give 10V input to the gate of the MOSFET to get very low Rds. I am using STM32 micro controller for controlling. Its maximum output voltage is 3.3V but I need 10V so I planned to use an NPN transistor in common emitter configuration so that I can amplify 3.3V to 10V and then I can give that to the gate of the MOSFET.

I understood that the amount of voltage we give in input to the base we will get as large voltage between collector and emitter based on the resistors. I also understood the voltage gain based on Rc and RE for example if Rc = 1k and Re = 100 ohm the gain is 10.
But I cant understand how to choose a resistor and how much current should I use how much current to amplify to amplify the voltage, and how much voltage to give to get 10V as output. How this entire thing works based on voltage amplification based on my circuit.

I have searched on google but I can't 100% understand it.


texts: Using an LM331 as a frequency to voltage converter, how to set frequency FSR?

texts:
I'm trying to use an LM331 in a frequency to voltage converter configuration.

LM331 block diagram:

I'm trying to implement this circuit from the datasheet for a supply voltage of 5V and an input frequency of 0-100 Hz.

Given my input signal frequency range, I'm trying to figure out how to set the full scale range of the frequency measurement. Is it as simple as setting the resistor values such that Vout = 5V at 100Hz, or do I need to do something else with the RC timing circuit?


texts: Inverting negative voltage back to positive with LM324

texts:
To be able to measure the value with an Arduino Nano I want to convert the negative rail voltage to positive. I tried to build a simple inverting amplifier with unity gain using LM324. The supply is +/- 10V.

The voltage is converted but scaled down. When I measure the voltages on the pins I see the values noted in below pic with red. It seems that the inverting pin can't be pulled to pin non-inverting pin value.

For the test purposes I didn't attach any output load to the circuit.


texts: Connect gesture control to media player of the car

texts:
I am very new to design and implementation of embedded systems. I have designed and implemented the gesture detector like in BMW. There are many open source projects to implement this project. My question is imagine that we have simple media controller like pioneer media player for car, how to connect it with our Arduino micro-controller, like up volume of the sound.
Is there anyway to connect them with some particular modules which send signal?


texts:
I'm currently setting up a STM32F407 to evaluate a display module which utilizes  a Renesas R61526A Displaycontroller.

I was able to set up the  project using CubeMX no problem, and the FSMC seems to be working.

However I noticed that the output data word was big endian, yet im pretty sure all STM32 are little endian (uint16_t 0x51ab as variable becomes 0xab51 when monitoring D0-16 output with the scope). I did not expect the FSMC to change the byte order on the output.

#define LCDADDRESS 0x63FFF00F
const LCDmemorymapping LCDRWregisteraccess = (uint16_t*) LCDADDRESS;
static void writetoLCD(uint16_t dataword)
{
    *LCDRWregisteraccess= (uint16_t) dataword;
}

static uint16_t readfromLCD(uint16_t unused)
{
    return  (uint16_t) *LCDRWregisteraccess;
}

/* FSMC initialization function */
static void MX_FSMC_Init(void)
{
  FSMC_NORSRAM_TimingTypeDef Timing;

  /** Perform the SRAM1 memory initialization sequence
  */
  hsram1.Instance = FSMC_NORSRAM_DEVICE;
  hsram1.Extended = FSMC_NORSRAM_EXTENDED_DEVICE;
  /* hsram1.Init */
  hsram1.Init.NSBank = FSMC_NORSRAM_BANK1;
  hsram1.Init.DataAddressMux = FSMC_DATA_ADDRESS_MUX_DISABLE;
  hsram1.Init.MemoryType = FSMC_MEMORY_TYPE_SRAM;
  hsram1.Init.MemoryDataWidth = FSMC_NORSRAM_MEM_BUS_WIDTH_16;
  hsram1.Init.BurstAccessMode = FSMC_BURST_ACCESS_MODE_DISABLE;
  hsram1.Init.WaitSignalPolarity = FSMC_WAIT_SIGNAL_POLARITY_LOW;
  hsram1.Init.WrapMode = FSMC_WRAP_MODE_DISABLE;
  hsram1.Init.WaitSignalActive = FSMC_WAIT_TIMING_BEFORE_WS;
  hsram1.Init.WriteOperation = FSMC_WRITE_OPERATION_ENABLE;
  hsram1.Init.WaitSignal = FSMC_WAIT_SIGNAL_DISABLE;
  hsram1.Init.ExtendedMode = FSMC_EXTENDED_MODE_DISABLE;
  hsram1.Init.AsynchronousWait = FSMC_ASYNCHRONOUS_WAIT_DISABLE;
  hsram1.Init.WriteBurst = FSMC_WRITE_BURST_DISABLE;
  hsram1.Init.PageSize = FSMC_PAGE_SIZE_NONE;
  /* Timing */
  Timing.AddressSetupTime = 3;
  Timing.AddressHoldTime = 15;
  Timing.DataSetupTime = 8;
  Timing.BusTurnAroundDuration = 3;
  Timing.CLKDivision = 16;
  Timing.DataLatency = 17;
  Timing.AccessMode = FSMC_ACCESS_MODE_A;
  /* ExtTiming */

  if (HAL_SRAM_Init(&hsram1, &Timing, NULL) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

I would like the output to be little-endian as well, so am I doing something obviously wrong ?
The obvious solution would be to read/write the data as

*LCDRWregisteraccess= (uint16_t)((0xff00&dataword)>>8)|(0x00ff&dataword<<8));

or to just use the REV16 instruction but I was wondering whether there is a configuration within the FSMC that I'm missing or something else I'm doing wrong.

Also this is my first stack exchange question, so if I didn't formulate the question correctly, please feel free to point it out :)

Many thanks in advance!


texts:
I'm trying to create a circuit that will make the output go high some amount of time after a 5V control signal goes high. That delay time may vary by application, so I'll use a potentiometer in place of the 249k resistor. I'm thinking of using a 555 timer in monostable with a 5V power supply. Below is the circuit I came up with, and I think it will work, it just seems like I might be coming up with something that's overly complicated because I'm a n00b. Is this a good approach, or is there a simpler/more effective way to do it?
EDIT:
One other requirement that I neglected to mention. I want the delayed output to go high after some time, but I also want it to go back low immediately after the input goes low. I feel like that might cause a problem with using an RC filter.


texts: Car Tail light - why the extra components?

texts:
I'm replacing the LED in a car tail-light. Naturally, it will run off 12V (battery) but the circuit I have uses just an LED and a 0.6w (440ohm) resistor. But the existing circuit includes two, larger resistors (the power ratings, that is, I assume are higher) and a diode. Can anyone tell me what functions these play in the circuit?

Is the diode for protecting from reverse current, as I'd assume? (not for voltage drop or anything like that), if so, why would there be a risk of this?

And why are the resistors so much larger, when the LED I put in should easily run from a 0.6 resistor? Would the existing LED be a higher wattage LED; It's just the same looking led, there's no heat-sink or anything.


texts: Transmission of a digital signal over a medium

texts:
A digital signal is said to have a infinite bandwidth. If a transmission medium cannot have infinite bandwidth then how can a digital signal be transmitted over such mediums?

Please correct me if I am wrong in my understanding.


texts: Can you stack voltage regs for higher voltage?

texts:
Can I stack these on top of each other http://www.ti.com/product/TPS7A47/datasheet without degrading AC performance? Will the output impedance of the lower ones affect the output impedance of the higher ones since they are serving as the new ground connection or does it not matter because it is an active circuit?
Like this


texts:
In figure 8.21 $$ R_1 = 50 , R_2 = 200 , L = 2 H$$
Voltage is given by $$ V_{in}(t) = V_{s1}u(-t) + V_{s2}u(t) $$ where $$V_{S1} = -10 V , V_{S2} = 20 V$$

a) Find  $$ I_L(0^+)  $$ and $$  I_L(t)$$ for t > 0

So far, I haven't done anything because I don't know what to do first. Some hints would appreciated.


texts:
We need to measure +-50Amps of current (PWM) on a PCB. We need the measurement to be isolated, so I thought of using an ACS758, and feeding its output to an ADC. However, this hall effect sensor is "limited" to 120Khz bandwidth and in our application, we need around 200Khz of bandwidth.

I suppose another option is to use a shunt resistor and an op-amp feeding an ADC. Aside from an isolation problem, at 50Amps, assuming a shunt resistor value of even 1mohms, that's 2.5Watts dissipated on the poor resistor. Just another thing to cool on the board.

What are other possible solutions, if any?


texts: From where does State space model equations come from?

texts:
I have a good basic understanding on classical control theory. Now I am studying modern control theory.I encountered the following equations as seen below.

Online I have only been able to find representation of differential equations in the form on these equations.
Im more interested in the background (or derivation) of these equations themselves or atleast some background on from where these equations came about, I dont want to accept them as is.
If my question too rudimentary, please know im just starting out in this subject. Thanks!


texts: How to solve this diode resistor circuit?

texts:
Here is the problem:

The assignment asks to calculate various voltages and currents in this circuit.

Here is the diode current-voltage characteristic:

Here is my thought process and what I tried:

The capacitor is per assignment fully charged, so I think no current should flow there.

Also the diode has an ideal current-voltage characteristic where it lets through any current if the voltage is above \$0.7 V\$

\$I_2\$ is per my best knowledge \$I_2=0A\$ since the capacitor is fully charged and no more current can flow into it.

\$I_1\$ is the current flowing through \$R_1\$ which should be easy to calculate: \$I_1 = 3.5 V :280 \Omega = 0.0125 A \$

\$ U_1 \$ should also be \$3.5 V\$ since there is nothing lowering the voltage, am I right in my assumption ?

Also I think the only part of this circuit where the voltage gets changed is after the diode at \$U_3\$ and/or \$U_4\$ because of Kirchhoffs circuit laws.

Here is my problem:

I don't know how to "resolve" the diode in parallel with the resistor, since our voltage across the whole circuit is \$3.5 V\$ I don't think any current is going to flow through \$R_4\$, because why would the current go the resistor when the diode is "faster", but per Kirchhoff's circuit laws
both voltages should be equal, right ?

I don't know how to calculate: \$I_5\$, since I don't know how to treat \$R_4\$.

Also, I don't even have an approach on how to calculate \$I_0\$ since I don't how to calculate the \$R_4+R_1\$ resistance, to clarify, I don't know if that is the correct way.

Update: here is the marked solution


texts: Can I shorten a length of C9 Christmas lights?

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I have a string of 25 C9 LED Christmas lights, and I'd like to shorten the string.  After untangling the string, they seem to be wired like this...

simulate this circuit – Schematic created using CircuitLab

I've removed a few of the lights between D4 and D23, but when I plug the string in D2 explodes. Is it possible to shorten the string of lights?  Do I have to add a resistor if I remove too many lights? If so, how do I know what size resistor to put in the circuit?


texts:
I am having a bit of confusion regarding the use of AC ammeters in a battery charger circuit. The electronics shop guys told that they have been using it successfully in their chargers. Can this be used as such ? My assumption is the diagram shown below

Leaving apart the charging process, is this OK from a DC/AC point of view ? Or it possible to connect the ammeter to the centre tap line ? I am more inclined to use DC ammeter in the circuit, but here they have only these AC types at stock .


texts:
I am trying to model a wireless energy transmitter as a transformer equivalent circuit with a large air gap. Because of the large air gap I’m assuming that for a realistic model fringing fluxes would have to be taken into account, I can’t find an easy to understand equivalent circuit that allows me to model the effect of a large air gap (or other mediums e.g concrete+air) by some formula for the coupling coefficient (I think?) that allows for a large air gap because most seem to assume the air gap is small.

Any help would be greatly appreciated.


texts:
I am building a simple water level indicator (approx like the circuit below) for my tank.

However, I am wondering about the wiring, for I suppose copper cables corrode in water and produce toxic result. Looking for a robust non-toxic solution the same.

What wiring is generally used under water?


texts: Can capacitors be used to make a low-impedance ECL termination voltage?

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I am trying to develop a circuit in which an RF sinusoid is put into the input of the ADCMP552 PECL output comparator and then the PECL output (square wave ish) is input to the MC100EP140 phase frequency detector, ideally as LV negative ECL.  I have two questions:

In general, can I use the ADCMP552 as negative LVECL (even though it's only specced for positive ECL)?
If I need to go from PECL to NECL or vice versa, I would use a blocking cap and need a 50 ohm termination to Vtt= Vcc-2V.  Could I use something like the following circuit as a proper 50 ohm termination?  As far as I can tell, the DC level is determined by the resistors and the high frequency impedance is only the 50 ohm resistor.

simulate this circuit – Schematic created using CircuitLab


texts: The type of wire used in walkie talkie earphone

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I have some Motorola Walkie Talkie TKLR T7 (seems only available in Hong Kong, cannot search much information), was trying to connect a pair of them to a relay. Not that I did not succeed, but I encountered some strange problem.

The earphone jack is 3 parts 2.5mm diameter 14mm length (Motorola M2 standard?), it is connected to the Speaker, PTT/mic, ground. When I cut open the wire, there is four separate wire of four colours (it was found out later that 2 actually connected to the same ground of the jack, so it is still 3 connections). Not knowing which wire is which, with the jack plugged in, I tried to short exhaustive combinations of 2 wires, by twisting them together or by using crocodile clamps, to init the push to talk signal, but the icon never showed up on the walkie screen.

Desperate, I actually peeled all plastic off a jack, and directly soldered some plastic coated copper wire to the 3 connection points, and then when I short 2 of them (ground and PTT), the push to talk icon is showing on the walkie.

So I can conclude that when I was using the 4 coloured wires, I did not make them connect, So I thought the coloured coating might be cloth like insulators. I tried to unwind the threads, only to find out that the coating seemed to be very thin metallic wires twisted around some transparent rip cord like threads. And again no matter how I try to short the metallic like wires or the rip cord like thread, I cannot get the push to talk signal nor the icon on the walkie screen.

So can someone tell me what kind of wires are these? and where is the conducting metal part? is it the coloured thread or the transparent thread in the middle? if it is the coloured threads, how did they prevent themselves from shortcircuiting each other in the long wire? was there some filler that was destroyed when I rip the wire apart? Or was there some simple physics I have missed? And why did I fail to short circuit them?


texts: Is it ok to power an Arduino Duemilanove with 15 V?

texts:
The documentation says 12V is the max tension recommended to power a Arduino Duemilanove, however the "limit" is 20V (see: http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove).

Will the Arduino Duemilanove be OK if I power it with a 15V battery? I am using a shield on top of it, maybe it will be worse because of the heating?

Additionnal information: I will use the VIN pin to provide current to motors (up to 2A). I think there is no impact on the Arduino (because I will not draw power from the Arduino, but from the VIN that is directly connected to the battery), but I'm not sure of that.