texts: Programming MSP430 based chips (sans Launchpad)

texts:
I'm wanting to move into working with the full range of MSP430 chips, especially their Ultra Low Power versions.

As I understand it, I'll need the chip I want to program, a JTAG programmer, and the target board in order to do prototyping.

Considering that I want to target the MSP430L092SPWR in particular (to begin with), I'm a bit confused about a couple of the pieces of hardware I need to complete the task (from what is on offer), and would like another opinion before I put money on it (this is purely for enthusiast learning).

So far, I believe I need the MSP-FET to actually program the chip (an aside, is there an alternative to the TI programmer I should consider?), but I'm unsure about the target board. The chip in question has 14 pins, but there are two target boards on offer. One is $20, and the other is $89, but as far as I can tell, they should achieve the same thing.

Can someone confirm/explain this for me? $20 vs. $89 is quite the difference in price, so I'd quite like to know why it is the case. Could someone that has used these before lend a hand?


texts: How to move LTspice transient simulation plot so they don't overlap

texts:
I have a shift register circuit that I want to simulate, and so far, everything seems to work as intended, but I am having a bit of a hard time with the voltage plots. They all overlap, and since the signals are all square waves with either 0V or 5V, it makes it hard to see all the plots at the same time. I have to delete one plot to see the other one, and I want them all shown, but on top of each other. Is there a way to shift the plot of the voltage at a specific signal up and down similar to how you can shift a signal on an oscilloscope up and down or perhaps have ltspice make say X amount of plots, all of them having the same horizontal axis, but each having their own vertical axis. In other words, I want the signals of different nodes to be shown on the oscilloscope in the picture and not overlapping, even though they have the same voltage
.


texts: Why LED street lamp can parallel LED without damage?

texts:
I working on DC LED street light driver using this LED street light look like picture bwelow.

I don't know much about this LED but it use about 30V to drive and I design CC drive for it.
The white LED usually got Vf about 3V. My lamp got 90 LEDs on it, so I assumed the schematic look like this (10 LED in series x9 in parallel). Why we can use LEDs in parallel in this situation?
I remembered we should not parallel the LEDs.

Vf of LEDs can be difference.
Temperature make VI curve changed.

Note: This schematic is just my assumption. If you has real schematic please share.

simulate this circuit – Schematic created using CircuitLab


texts:
Figure 01: This is the circuit I want to use for adding a DC offset with the output of ZMPT101B

Figure 01: Recommended resistor at datasheet
I need to read the output voltage of the potential transformer using a microcontroller (although there are some microcontrollers that provide bipolar ADC, I'm not using them). Suppose my input is 350 volts (peak). Then according to the datasheet, the value of the sampling resistor should be 1.2k ohms for getting an output of 0.51219 volts (peak). Now if I want to add a DC offset like figure 01, will the output of ZMPT101B be 0.51219(AC) + 0.55(DC)? I think it will be changed as a part of the output current of the ZMPT101B will flow through the voltage divider network.
It will be helpful if someone can kindly explain the mathematics for adding a DC offset to the ZMPT101B output.


texts:
I am planning to make some calibration module designs using the ADS8691IPW ADC from TI.
I need 4 channels of separate ADC lines. I am planning to use separate 4 isolated supply channels. I designed schematics for one ADC channel. I used an input isolator before the ADC and an isolator after ADC (for the microcontroller signals.)
I am new to analog design.
Would someone please review the schematics?

Thank you sir for the reply.
If I short every ground together then there would not be any isolation, right?
This is what I am planning:

I am confused about how to isolate each and every section. Is it better to give the separate supply sections?


texts: Adjacent Signal Selectivity: Section 6.1 of ETSI EN 303 372-2 (RED testing). Bad procedure/standard?

texts:
I'm doing pre-certification testing to ETSI EN 303 372-2 V1.1.1 (2016-04), specifically the Adjacent Signal Selectivity test in Section 6.1.

I am a Systems engineer with lots of experience designing and performing equipment testing to DOD, DOE, FAA and FDA standards.  Though I'm not an RF engineer, the test mentioned above makes no sense whatsoever.  Here's the relevant section:

  6.1 Adjacent signal selectivity

  a) Two test signal generators shall be used. Each signal generator shall generate a modulated signal in the IDU input frequency range and thermal noise.

  b) The signal generators shall be connected to the IDU input through a splitter (combiner).

  c) The symbol rate shall be set to the low end of the IDU's range.

  d) The test signal generators shall be set to the frequencies and levels according to table 1. For each row of the
  table:

    a) The IDU shall be set to receiving the signal of the first test signal generator.

    b) The second test signal generator shall be set to output signal off.

    c) The noise level (or signal to noise ratio) of the first test signal generator shall be varied in order to
    determine the threshold for quasi error free reception.

    d) The second signal generator shall be set to output signal on.

    e) The noise level (or signal to noise ratio) of the first test signal generator shall be varied in order to
    determine the threshold for quasi error free reception.

    f) The degradation is equal to the noise level (or signal to noise ratio) determined in step e minus that
    determined in step c.

  e) Repeat from d) with symbol rate set to the high end of the IDU's range.

  f) The result is the highest degradation found.

What makes no sense to me is step e) under d):  There is no limit to how much the SNR of the desired signal can be increased to counter the influence of the interfering signal!

What I believe is needed is to quantify the effect of the interfering signal on the desired signal, and this step actively cancels that out.

What am I missing here?  What aspect of selectivity is this test seeking to measure?

Update:

Based on comments below, my understanding is shifting:

For now, I've decided to take an approach that splits the issue down the middle:

For the "wanted" signal, determine QEF at the receiver, then record both the generator and receiver SNR (they will likely differ by a small amount).
Add 1 dB SNR to the "wanted" generator, and ensure the same step change is seen at the receiver.
Add the interferer signal, and ensure the receiver SNR is reduced by less than 0.4 dB

My hope is this test procedure meets both the letter and spirit of Section 6.1 of ETSI EN 303 372-2 V1.1.1 (2016-04). It keeps the "wanted" signal very close to the receiver's QEF while making the effects of the interferer signal clear and unambiguous.

One minor concern is to not push the receiver below QEF during this test, because SNR measurements below QEF may not be completely reliable.  That is, I don't want to have to fully characterize the receiver SNR value outside of the fully functional state, as it tends to deviate from the generator SNR at both high (>30 dB) and low (below QEF) values when directly connected.

Also, the spec says nothing about the SNR of the interferer signal: I initially chose to make it equal to the SNR of the "wanted" signal, though I am now revisiting that decision as degraded SNR looks like increased roll-off (alpha), so doing any SNR reduction to the interferer would make it differ from what the spec requires.


texts: Building a network of trancievers at long distance

texts:
I have a task to build a wireless network consisting of devices (based on microcontrollers), which transmit data to the main unit.

The devices must be located in an open space on the field with ~2 km between each other, to record and process the data from the sensors and transmit the processed data to the main unit. The devices transmit data when some events take place(very rare) and the size of the data is about 50-150 bytes.

The network must have a mesh topology, so every device should also be a repeater.

So the question is, what technology and protocol are more appropriate for building this network with the specified spacing present between devices?


texts:
I built simple wien oscillator.  How to reduce distortion of the sine wave?
Leads was as short as can be, soldered "Manhattan style".
Tried 2x KD305D power supplies as well as split battery source. This didnt helped.


texts: Preventing Arduino from getting lightning strikes and protecting it

texts:
I want to use an Arduino as a weather station and I want to put it high up in a tree. It should be independent and powered by solar panels. This is where the problem starts.

Lightning strikes occur pretty often in my area, and I assume the lightning would hit the Arduino and its components before it would hit any other tree.

Is there any way I can prevent the lightning from hitting the Arduino? There is a hut nearby (around 40m) which has lightning protectors on it. In case the lightning hit the Arduino, is there any way to prevent damage to it? I plan to use pretty expensive components and I don't want them to be destroyed.


texts: EEPROM Emulation driver does not work when Page Sizes are 2KB

texts: I am trying to implement EEPROM Emulation on an STM32F07x using the driver supplied by ST. Problem is on attempting to initialise the emulated flash, the driver fails and always returns NO_VALID_PAGE. I have changed the defines for the Page Size and the EEPROM start address to match the Reference Manual but it doesn't work.


texts: Is this schematic on the track to create a AC clipper voltage and current regulator?

texts:
Good evening

I'm trying to make a "clipper" circuit for an AC Voltage source that feeds 2 6V light bulbs rated at 10W and 5W.

Problem is that the generator at idle speed produces 4V and at maximum RPM produces from 12V to 14V

My first approach was to put a 1.5mH coil in series in order to raise the inductive reactance as the generator goes to maximum output.

But I also saw the "poor mans square wave generator" using 2 zener diodes and try to come up with this circuit.

Maximum output of the circuit should be limited always at 6V and current no more than 2.5A

The circuit detects the overvoltage when D1 or D2 starts conducting, biasing Q1 or Q2 depending on the stage of the sine wave. This creates a Vdrop of 0.7 on the main line (So V Output= (6.8V (zener)+ 0.7 Zener forward) - 0.7V (Transistor) = 6.8V. The 50 ohm resistors are wrong, the idea is to make 50mA go into the base considering a transistor gain of 50 (so 50 mA x 50 hfe = 2.5A) at 6.8V I need R2 and R3 to be around 136 ohm

This circuit should work as expected or can have mishaps? Also I need to choose a transistor that can handle the reverse voltage when the sine wave it´s opposing the current path of the transistor, if I cannot, I consider putting a 1N4001 diode in the emitter of the NPN and the collector of the PNP, thus lowering another 0.7V at the output (6.1V final).

Any thoughts?


texts:
While I understand the problems trying to demodulate a DSB-SC signal using a direct conversion scheme, mostly the phasing issues arising from the fact that the sidebands are symettric and in quadrature, I still don't get why SSB receivers can't just pass band filter one of the sidebands and reinject the carrier, even if it's not frequency and phase synced with the original.

The scheme I see in most of receivers is an heterodyne approach: downconverting both sidebands, then filtering, and finally reinjecting the BFO. But, doesn't this present the same problems as reinjecting a carrier at an offset so as the desired sideband gets downconverted to audio frequency (after bandpass filtered it)?

Why do the other two major methods (phasing and weaver) need to have phasing syncronism while in heterodyne systems this is not required, but instead you have to downconvert twice?

Thanks and regards :)


texts:
The following picture shows a part of a Gilber-Cell.
The yellow part is a low-pass. The green one the mixer core and the blue one determines the operating point of the transistors.

Actually, my problem is to understand the setup for the operating point.
Lets assume a Vcc of 5V and a voltage drop across RL of 0.4V.
Then we have a collector node voltage at T1 of 4.6V.
Now, the operating point has to be determined via the blue network consisting of base voltage dividers: and here I don't get everything.

What I think: The first diode causes a voltage drop of lets say 0.7V. Then I have a voltage divider. What base node voltage do I have to set up? Obviously it must be smaller than the collector node voltage. So, it must be smaller than 4.6V.
My Question: How much smaller do I need to set up the base node voltage? Is it just necessary that it is smaller than the collector node voltage or must it be -0.7, so the opposite of Ube?


texts: Wireless Communication core concepts based on the NRF24 libary for Arduino

texts:
Well as you may know, there is an amazing libary for arduino called NRF24, used to control Nrf24l01 devices, at the momment I already tried all the examples included, and even made some modifications.

I want to go further but there are some basic concepts I miss, tried on google, in the main site, taking closer look to the examples, but nothing, I just dont understand some things. I really want to go deeper but I feel a good tutorial is missing. Here are some of the things I dont get.

Whats a pipe? How it changes if I want 2 or 6 nodes to speak.

const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };

code extracted from the basic example.

What the numbers mean?

Maybe after the explanation, I will figure how to solve the next issue, but just in case; How do I need to set the pipes if my network is static 6 nodes, one base. The nodes some times send data to the base and then the base answers with some other data back to the emiting node…


texts: CycloneTCP HTTP Web Server Demo For STM32F207 using ATWINC1500 WiFi not working

texts:
I am using STM32F207 Microcontroller for Ethernet and Wifi(ATWINC1500) Interface with ide Keil Uv5, I have installed the CycloneTCP Tcp/Ip stack on top of it and everything compiles fine. CycloneTCP is a free, open-source library that implements a lot of protocols.
However, when I try one of the examples included with CycloneTCP for STM32F207, Compiled Fine, Access Point Successfully Created, also DHCP Server Working fine and I able to connect my lappy to that Access Point. But HTTP Server not Working.
But My Http Server Using LAN Interface(DP83848) Working fine, I am not getting the point where the piece of code misbehave.
Project Directory is under :CycloneTCP_SSL_SSH_CRYPTO_Open_2_0_2\demo\atmel\samg55_xplained_pro\wifi_http_client_demo\keil


texts:
I have an 8 Ω speaker and a Raspberry Pi. To play sound, I can connect the Raspi directly to the speaker, which works, but with very limited volume. I assume this is because of the 3.3 V PWM output by the Raspi which provides up to 20 mA (correct me if I'm wrong).

I therefore decided to test an LM358 OpAmp, which essentially is a voltage multiplier when it operates in closed-loop gain. The Raspi signal is 3.3 V already, so with a 5 V power supply I can at most go to 5 V, corresponding to  Vout/Vin = 1/β = 1.5 (therefore R1 = 1 kΩ and R2 = 2 kΩ).

As the LM358 can provide around 20 mA as well, I would expect the loudspeaker to be slightly louder as it is driven with 5 V instead of 3.3 V, and P = U · I.

The result is that the loudspeaker is indeed a bit louder, but mostly quite distorted and noisy. So not the expected output.

simulate this circuit – Schematic created using CircuitLab

Why do I get such bad output audio? Shouldn’t the OpAmp just do a linear transformation of the signal?

(I probably lack some basic understanding of how OpAmps and speakers are supposed to be used. If so, I’d be happy to get some hints or references to read.)

Edit – WPM measurements

Since knowing the input is important to this question, here some measurements – the first one shows the normal audio waveform, the second one is recorded at higher frequency which shows how the Raspi constructs the waveform. The signal is ± 1 V in these measurements.

I have also found this paper about biasing which provided a nice explanation of scaling and biasing.


texts: Cheapest FPGA PCIe board for Software Acceleration

texts:
This question is somewhat related to an earlier question: Cheapest FPGA's.

I have been searching for a cheap FPGA board with PCI express 2.0 or 3.x support. Such boards can be plugged in one of the compatible PCIe slot on a motherboard, and can be programmed using either HDL entry or OpenCL or C/C++ based HLS tools. In order to facilitate data transfer between CPU DDR and FPGA DDR memory, the board comes with programmable DMA controllers.

There is a company which sells such boards(Nallatech), but the starting board prices are just too high (> 5000 USD). Then there are FPGA PCIe boards sold by Xilinx and Altera with minimum 1300 USD price. But all these are still too expensive for me. Can someone recommend a cheaper FPGA board from Xilinx/Altera with a PCIe 2.0 or 3.x support ?.


texts: PCB antenna: ground plane layers and dimensions?

texts:
I'm using an Inverted-F antenna on a Bluetooth Low Energy peripheral/device I'm designing and I'm not sure how I should design the ground plane.

The ground plane should not be "too big" nor "too small", the recommended dimensions are described on a CSR application note.
However, I have 4 layers, the middle ones are for VDD and for GND, but the outer ones also have a ground plane.

When referring to "antenna ground plane", is it only the ground plane of the inner layer or the overall layers?


texts: What do I need to make a LP-E12 Coupler be powered by either a 18650 or 14500 lition battery?

texts:
So I'm working on a Battery Grip for my Canon M50 Camera which uses an LP-E12 Battery which operates on 7.2V. I found a battery coupler for it that has a 7.4V 2A input requirement. I was thinking of using 18650 3.7V cells to power it or maybe 14500 cells for size constraints. And just as an addon: how about if I were to use NiMH AA Cells from something like Eneloop?
I'm not even going to pretend to know anything about circuits and stuff. I wanna know if I would need anything special or it's just a matter of connecting cables?


texts: 125 kHz RFID Antenna Measurement using CRO - Passive Probe

texts:
I have a coil inductor and a capacitor in parallel set to the resonant frequency of 125 kHz for receiving RFID.  There is no issue with the operation of my circuit but I would like to measure the induced voltage across the inductor.

I only have a digital CRO with a passive probe.  The capacitance of the probe is somewhere between about 80 pF and 150 pF.  Naturally when connecting the probe to the LC combination the resonant frequency changes and I can't measure even a small fraction of the signal.

Can anyone suggest a way of converting my passive probe to an active probe to reduce the input capacitance so as I can make the measurements?


texts: On what condition does Harmonic components of power generated in 50/60 Hz Grid Generators depend on?

texts:
I have power-recording data from 11 countries (USA-60Hz mains frequency / other nation 50Hz). These data were collected using a audio recorder (in a computer) connected directly to the power mains via a step-down transformer. So, the 50hz/60Hz electrical voltage sine wave is basically stored in the computer as a .wav file.

Now if I perform a Fast Fourier Transform on these data, a distinction arises between data collected from one generator (from a grid in a country) to another in the magnitudes of their harmonics. I am including the images after performing the FFT.

  Grid A Here, only the main 60Hz component is prominent.

  Grid B Here, the main 50Hz component is prominent, but the odd multiple components also are present with decreasing significance.

  Grid C  I can't post 3 images due to lower than 10 reps. Thus, Grid C has no image, but the description still holds.

  Here, the main 50Hz component is prominent, but the odd multiple
  components also are present, but not with decreasing significance. The
  3rd component has the most prominence than 1st, 5th or 7th.

My question is what makes this harmonic components arise in the first place (may be some aspect of the generator). What are they dependent upon or are they arbitary? So far, from the large amount of data in my possesion, It seems that this should be a pattern of the generators it self because data from the same grid showcases this trait consistently. Can a grid (including the generators and the load) suddenly stop producing harmonics or alter their magnitudes of different harmonics?

Moreover, I can see that in Grid A, which is from USA, the harmonics are nearly absent. Where as Grid B (Lebanon) and Grid C (Turkey) have significant harmonic components. Could this be because of the better Generator and load control mechanisms of the networks of USA in comparison to those of Lebanon and Turkey?

P.S.
Any information about this would be great. It would also be great if you could point out some relevant literature.


texts: This is a high swing cascode current mirror. My question is what is the significance of the connection from the drain of M3 to the gate of M1 and M2? What would happen if both M3 and M1 were diode connected MOSFETs?


texts:
I'm studying for the best practice to route a switching dc to dc step down regulator. Particularly this TI part.

On page 37 there's a layout example.
I was wonder if it could be any problem to place vias in the whole Vout line and not only after the output capacitors.

I upload a photo.

Due to limited space I've placed the output circuitry both in top and bottom sides of pcb. I hope this won't hurt stability or something.

First, I placed the vias only in the points are necessary. After the inductor to transfer the power at the bottom layer and after the output capacitors to transfer the power at the inner layer.

But, I do not know if the extra vias (these I marked with golden color) in the output line are prefered.

Also, Is there any harm to connect the inner layer (which delivers the 5V output) to the vias at the inductor-capacitors point?

I added one more picture to be more clear of my two considerations.
Red dots are vias

EDIT: I upload one more photo of my final draft layout.
The part I'm still confused is the via placement.
I don't know if the output line 5V must have vias in the whole plane like I did or must be placed only after the output capacitors (see photo 2, A and B).


texts: Can an XBee be programmed with an XBee Shield

texts:
I have an XBee and an XBee Arduino shield.

Can I program my XBee through my Arduino Twenty-Ten and an XBee shield?

Can I do anything with just one XBee?


texts: I want to use MAX14578, I've looked into datasheet (http://datasheets.maximintegrated.com/en/ds/MAX14578AE-MAX14578E.pdf) and found it have an integrated LDO. But I don't need to use this LDO. Since I use BATT pin to power up this IC, can I don't use LDO? If yes, how should I connect this pins? to GND or leave floating?


texts:
Below is my code for ALU which instantiates a 4:1 MUX and a 32 bit squarer modules. The port connections can be seen in module instantiations. However it is important to mention here that input of MUX's are 4 32-bit constants. The output of MUX is connected to input(op1) of squarer through  an internal wire of ALU.

Test bench for ALU contains a clock with T = 20ns, and reset is high only for first 60ns.

The problem is the output of below code is slightly different than it should be which is square of 32 bit number which is there at 1st input of MUX. For example at first input of MUX the number is 32'hABCDEFAB the output I get after simulating ALU is 64'h73440a7554366fe0 whereas it should be 64'h734CC3D82A3EBC39. However squarer is working fine because when i simulate it alone and provide the operand from test bench the result is correct.

If anyone can figure out the issue, would be great.

module ALUUU (
  input         clk,
  input         reset,
  output [63:0] ALU_final_output
);

  wire   [31:0] op_1;
  reg    [63:0] ALU_Out;
  wire   [63:0] Sq_out;
  reg     [2:0] select_ALU_operands;

  MUX__EC_points M1 (
    .select_ALU_operands (select_ALU_operands),
    .operand_for_ALU     (op_1)
  );

  squarer_karatsuba FF_SQR (
    .clk(clk),
    .op1(op_1),
    .square(Sq_out)
  );

  always @(posedge clk) begin
    if (reset) begin
      ALU_Out <= 0;
    end else begin
      select_ALU_operands <= 3'd0;
      ALU_Out <= Sq_out;
    end
  end

  assign  ALU_final_output = ALU_Out;
endmodule

MUX Code:

module MUX__EC_points (
  input   [2:0] select_ALU_operands,
  output [31:0] operand_for_ALU
);

  reg    [31:0] operand;

  parameter BASEPOINT_xp  = 32'habcdefab;
  parameter BASEPOINT_yp  = 32'hcdabefab;
  parameter CONSTANT_b    = 32'hadfecbba;

  always @* begin
    case (select_ALU_operands)
      3'd0: operand <= BASEPOINT_xp;
      3'd1: operand <= BASEPOINT_yp;
      3'd2: operand <= CONSTANT_b;
    endcase
  end

  assign operand_for_ALU = operand;
endmodule


texts: Facing problem with submersible pump (5V)

texts:
I am using a submersible pump (5V) with a power supply 12 volt 1 amps adapter. I know that its operational voltage is 3.3-6 volt that's why I am using IC7805 regulator ic in my circuit. I am facing a problem is that after some time my pump starts to make noisy sound and then stop. I also try to run a pump using 5 volts 2 amps mobile charger but the same issue occurs. I already lost my 10+ pump so can you suggest a circuit with a 12-volt power supply.
Thanks in advance.


texts:
Newbie question:

I have an Arduino board supplying 3.3v.  I'm looking at LEDs.  I've found one which I like, but it has a forward voltage of 4.4v.

Aside from any consideration towards resistors, would this be an optimal setup / would it break either the LED or the board?

I'm unclear as to whether the board would be able to supply enough voltage to power the LED?


texts: voltage regulator capacitor prevent to work of single button on off circuit

texts:
I'm using this circuit to turn on and off the system.

The power supply is 12V.  I use an LM2576 to decrease to 5V.  Here is the circuit:

Firstly I build on-off circuit also I added an LED at the 12V and on-off circuit works well. Then I added the voltage regulator circuit and the on-off circuit stopped working. It just turns on the system at the first push then it always stays turned on. When I remove the voltage regulator capacitors the on-off circuit continues to work.

I would like to know what is the reason of this problem and how can I fix it?

edit: This is my circuit.


texts: Correct circuit element alternative to transistors

texts:
First please see my proteus file to understand what am I trying to do.
http://www.docdroid.net/ru27/yenitasarim.pdf.html

As you see, there is 5 button groups vertical and 5 button groups horizontal.
Each button group has 4 buttons. Assume that each vertical button groups ar signed as A,B,C,D,E and horizontals are 1,2,3,4,5

So, When I want to run the stepper on A1, I'm seting pushed all buttons on A and 1
I can run multiple steppers too, I can simply set pushed the button groups at horizontal and vertical, then concurdend steppers will start to run.

This system works good If I set the buttons manually. But I don't want to use buttons and I don't want to run it manually.

Then I have tried this kind of a design,

As you can see, I have removed buttons and placed transistors. Also there is one transistor that trigs the others. I can send 3.3v to the base of Q5 and make all transitors work.

But, my problem starts here, When I set votage on Q5 base, this voltage flows on all transistors from base to emiter, but as you know, stepper motors drivers generates voltage in a sequence. Flowing voltage from base to emiter corrups the voltage that comes from stepper driver.

Better way to use a relay, it is isolated between vires, but it doesn't work fast.

What is the best solution? I need an element that works as fast as transitors and isolated like relay.

Thanks all.


texts: Trying to drop 13.5 volts to 10 volts in a car

texts: Hi I am in no way an expert or even a mid novice when it comes to electronics so please forgive my ignorance. What I would like to do is in a car drop a 13.5 volt supply from an alternator to a 10 volt supply as a sender instruction to a power steering pump. I am just looking for what resistor / capacitor I would need to achieve this.


texts: What mathematical function do I2C falling edges follow, and why?

texts:
Consider any standard I2C communication : the falling edges, either on SDA or on SCL, will take a certain amount of time to complete.

What mathematical function do these falling edges follow?
Why do they follow this function, from an electronic point of view?


texts:
I have here a winch (ramsey ATV 8), where I would like to add two limit switches and a RF receiver. I already designed a schematic of how I think it could be controlled, but I'm not sure if this will work. If possible, the uC should be supplied by the same battery as the winch, but I'm affraid that the distortion will cause to problems on the uC. Do you think this will work the way I planned? I would appreciate any improvements from your side.

Datasheet:

Schematic:


texts: Which one of these 5 pin 3 phase connectors is more standard?

texts:
Images: http://imgur.com/a/BItbR
One is rated 16A "Dafr-164m" and another is rated 32A "Typ 2"
We have a 16A breaker quite a ways from our house ~50m.
We asked someone and they said they use both.
We have 230v, 380v 50Hz
We have to change the connectors because our house uses the old Soviet connector and... we have no incoming earth! Only 3ph+N because ~50% of the electrical wiring in my town is Soviet-era and there's no earth


texts: How Fourier transform be able to deal with transients?

texts:
Below is what Matt L.said in the thread here.
Could anyone clarify how Fourier transform be able to deal with transitents? Reading that thread many times but I couldn't figure it out.

  Note that it is not true that the Fourier transform cannot deal with
  transients. This is just a misunderstanding which probably comes from
  the fact that we often use the Fourier transform to analyze the
  steady-state behavior of systems by applying sinusoidal input signals
  that are defined for −∞ < t < ∞.


texts: Output AC coupling: upper limit or lower limit?

texts:
I bought a DC2900A board for my project.
In its datasheet it is stated:

The maximum repetition rate of the pulsed laser should be 100kHz. The DC2900A repetition rate is limited by the output AC coupling capacitor and assumes a pulse width of 5ns.

I was questioning why is that so, since LTC6561 chip is 220 MHz amplifier. In my mind 100 kHz should be nothing to this chip. Even APD has 2ns rise time.
Then I emailed about my question to them asking: Why AC coupling capacitor should ever limit the repetition rate, since it acts like a high-pass filter?
I got this response:

The DC2900A upper limit on repetition rate of 100kHz is stated due to the output AC coupling cap (C1, 100pF) used. There will be a slow tail due to AC coupling the output as shown in this slide related to LTC6560.

At 400ns/div, you’ll have 3 divisions (1.2us, LHS waveform) before the waveform settles at the load with a coupling cap of 1nF.

With a 100pF cap, you’d expect this to be faster.

But, that’s the reason that the demo manual states that the repetition rate should not be too high to allow for proper settling before the next pulse comes in.

So, does anybody know why this capacitor is limiting, or am I missing out on basic theory?
.


texts: Taking 5v down to 3.3v with 10k and 5k Ohm resistors

texts:
I'm a beginner in the field, and I'm working in a IoT application, especifically with sensor HCSR-04 and the WiFi module ESP8266.

ESP8266 works with 3.3v in the Vcc pin and HCSR-04 works with 5v, so I need to take down the 5v to 3.3v with a resistor. Searching on Internet I figured out I needed a Voltage Divider Resistor so I found this online calculator, put the values:

Input Voltage : 5v
R1            : X
R2            : 10
Output Voltage: 3.3v

Note that I put in R2 a 10k Ohm resistor, because I only have 5k, 10k, 15k resistors available. So, according to this calculator, X = 5.15k Ohm.

Question:

Is it ok if I use this resistors to take down the 5v input to 3.3v output? Will it work in real life? (not theoretically), or there is something I'm missing?


texts:
I've recently built a temperature sensor and have been testing it against a reference thermometer in several different scenarios/environments/temperature ranges.

My question is, how do I analyse my data to show my sensor is accurate to xdegrees or how good/bad its performance is.
I have a list of reference temperatures readings against my own temperatures readings; I've calculated the difference between the two and calculated the mean difference and standard deviation. Is this enough to say, my sensor is accurate to, for example, 0.2degrees or is there any other data analysis techniques I could use.

Any help is appreciated.


texts: Demerits of oscilloscope performing measurement and math functions on displayed data

texts:
I came across this video on youtube.

Summary of the video: Tektronix uses measurement and maths functions on the acquired data whereas Keysight uses these functions on the displayed data. This leads to a different measurement value when you start zooming in the displayed data on keysight oscilloscope. Tektronix concludes that this is inferior method of measurement. Tek good, keysight bad sort of stuff.

I want to understand whether keysight's method is flawed in practical use cases? If so, why/how will a company do such a blunder? Or is tektronix just blowing it out of proportion?


texts: Inferring number of strands from AWG -> mm

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If there is "16AWG" 1.34mm CSA wire, is it possible to figure out the strand count?

I am thinking it might be possible as AWG is about overall diameter. So 16AWG should have a diameter of 1.291, but if it's 1.34, does this imply a certain arrangement of a certain number of strands?


texts: Difference between Multidrop and daisy chain topology

texts: I want ton know how multidrop differ from daisy chain topology? I am using RS 485 standard and modbus protocol for communication. So which topology is best for my requirement ?


texts: Operating a 12V electric lock with arduino

texts:
I have a similar electric lock-style solenoid like this one.

If we trust the manufacturer it draws between 1.2A and 2A at 12V .I'm currently using a N-Channel MOSFET 60V 30A - FQP30N06L it works just fine but it's probably an overkill for this project but it's what I had in hand, I want to redesign my board with an SMD part but I'm not sure how to properly dimension it. I could go with the SMD equivalent FQD30N06L but any better choice?


texts:
I'm making a safety disconnect for an experimental RC craft.  It will be tethered to the ground, and if it goes out of control the tether will pull a plug disconnecting the power.  I will make the plug from a male Deans connector (pictured below) looped to connect the positive and negative terminals.  The female connector will be in line with the battery.

What's the best material to lubricate this connection?  I would like the plug to disconnect as smoothly as possible when tugged by the tether.  In general, what are the most common connector lubricants that are (a) conductive, (b) will not cause shorts, and (c) not messy?


texts: Do P-channel JFET current go from source to drain?

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For an N-channel JFET transistor, current moves from drain to source. I've read that a P-channel JFET works similarly, but with the voltages reversed. Does this mean that its current travels from source to drain instead?

(The gate current can be neglected)


texts:
I'd like to use a 0.35mm BGA in a new design. If possible, I'd like to do this without resorting to an expensive manufacturing process with microvias. This is possible for my particular application, if I can pull a little trick.

All of the pads I need for my application are around the perimeter of the chip, except one. The other internal pads I don't need. Perhaps I can just miss out the pad that's in the way of my track, and hope that the solder resist prevents a short.

Question: Is this  a sensible thing to do?


texts: Is EN on a switching regulator a suitable for being a main power control?

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I am trying to decide where to put the main power switch on a circuit with a Li cell, charger PMIC, and switching regulator.  The switching regulator I'm considering (ON semi NCP1522B) has an ENable input.  The charger PMIC (MCP73831) is basic, and will only be parallel to Vbat as the Vin on the regulator.

I see in the datasheet that the standby current when EN is low is max 1.5uA.  If I use a simple SPST switch to pull EN high as a power switch, will that be sufficient for the system to not drain the battery much when "off"?  Would it be better to put the power switch in front of Vin, or is there a better way to do this altogether?


texts: Filtering current spikes in photodiode transistor selector

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I am building a circuit for sensing photocurrent from a photodiode. The diodes are manufactured with selection transistors to form an active matrix and below is a model of a single pixel consisting of the selector transistor and the diode that is followed by a simple transimpedance amplifier. Later I plan to and multiplexers to choose the selection transistor on one side and diode anode on the other and this way choose the diode for readout. Note that the transistor is an experimental device in organic material technology, which for the time being is modelled with a LEVEL=3 model:

.model OFET_L2 PMOS (Level = 3, L = 5u, W = 1m, ETA = 0.2649, VTO = 3, NFS = 10, UO = 2, TOX = 20u)

The circuit intends to reach readout speeds of a commercial camera for the whole matrix, so hopefully up to a working frequency of 100kHz (10us per pixel readout). The problem is the capacitance of the photodiode which seems to be causing a current surge the moment the transistor opens. That phenomenon has to be verified experimentally (to what extent is is a real problem and to what extent is it an artefact of the way I chose to model the diode), but I am fairly sure this is an accurate representation of it.

I tried increasing the feedback capacitor on the amplifier to absorb the current, but it results in longer times required to reach steady state.

Selection frequency 33kHz, Iphoto = 100nA, Rrev = 100Mohm, Cf = 5pF

Cd = {0.005pF, 0.05pF, 0.5pF, 5pF)

Making it too small leads to op-amp instability which was the original reason I put it there. Plus, the spike becomes even bigger.

Selection frequency 100kHz, Iphoto = 100nA, Rrev = 100Mohm, Cf = 1pF, Cd = {0.005pF, 0.05pF, 0.5pF, 5pF)

Finally, the problem persists until a fairly large current is provided by the photodiode (much light is incident).

Selection frequency 100kHz, Rrev = 100Mohm, Cf = 5pF, Cd = 5pF

Iphoto = {10nA, 100nA, 1uA, 10uA}

My questions are: is there anything I can do about it other than improve the photodiode? I was thinking of adding a more sophisticated filter after the transimpedance amp, but I need some advice how to go about it and whether it is even possible to tackle the problem this way. I don't want to drown hours into developing a solution that is doomed from the start.

Furthermore, if that speed of switching cannot be achieved then how harmful can such spikes be? Are they likely to cause instability in the circuit when more diodes are hooked up?

I read on possible solutions to similar problems, but they are overwhelmingly concerned with power MOSFETs in motor driving circuits where the spike arises from inductance in the motor and can be mitigated with a parallel diode. It doesn't seem to me like that solution could be implemented here.

Thank you very much for any feedback.


texts: Using 555 to generate square signal with fixed duty cycle / variable frequency

texts:
I am attempting to design a circuit whose output is a square wave with the following properties:

Fixed duty cycle, as high as possible (let's say 99%)
Variable frequency, between 0.2 - 20 Hz (I'm somewhat flexible about this range)

I imagined (naively?) that such a thing would be possible using a 555 timer, wired up in astable configuration.  I began exploring the problem space using an online tool that calculates duty cycle / frequency for given values of R1, R2, and C (see diagram).

It would appear that, at least in theory, I could achieve the desired effect with the following setup:

Some fixed, reasonably high ratio of values for R1:R2 (e.g., R1 = 1 megohm / R2 = 1 kilohm); this sets the duty cycle high
Varying the capacitor between 0.1 and 10 microfarads; this varies the frequency within my desired range without affecting duty cycle

The big problem would be in realizing this circuit with actual components.  At least to my knowledge, there is no such thing as a variable capacitor with that sort of range.

I am left wondering if there is some other way to configure a 555 (besides the typical layout given above), which would provide a more realistic way to tweak frequency while holding duty cycle constant.

Alternatively, I'd be open to any suggestions on how to achieve variable capacitance from 0.1 to 10 microfarads.

Finally, I'm open to any non-555 implementations that achieve my desired result.  The simpler, the better.


texts: 555 square wave generation with frequency feedback

texts:
Knowing that 555's behaviour varies according to temperature, I wondered:

In an astable configuration, is there some way to measure output frequency, compare it with some desired value, and use this to change the resistance in the config? (Basically a feedback loop)

This would be very useful, to create precision square wave generators.

I'm sorry if I couldn't explain myself correctly (the question sounds really bad when I read it but I'm struggling to express it correctly).


texts:
Very related to this question.

While it's already clear that several TP4056 can't be used to charge and discharge several cells, it's not clear to me if it's possible to only charge a battery pack with several cells in series.

The input and output GND pads are connected, but what about the battery terminals? From the TP chip datasheet I fear that B- pad is also connected to GND, and therefore i can't charge a battery pack from it's balance connector, but i'm not that good in diagram reading and understanding and i hope to be proven wrong (maybe thanks to the additional protection chip, dw01 if i'm not wrong).

Thanks for your answer.


texts: What is the definition of Bluetooth peripheral device?

texts:
What is the basic definition of a bluetooth peripheral device, bluetooth master device and a bluetooth slave device, and what are the functions of each of them?
How to define them in a BLE system? Currently I have a BLE development kit. If I want to connect my system in such a way, such that, I have a controller, an Android device, and 3 lights, that I want to connect with the controller. I should be able to control the lights from the mobile, such that, when I send a signal from the Android, it should go to the controller, and then, the controller should accordingly to the lights.


texts: Which type of transistor (MOSFET or BJT) would be better to use for the longest battery life?

texts:
Background

These two circuits will function as a broken loop warning device. Can think of this as a circuit that sets off an alarm when a loop of wire is cut. This cut wire could also represent a sensor that is normally closed and then goes open circuit when some parameter is exceeded. This kind of sensor is normally used because it automatically sets off the alarm if the wires to the sensor get damaged.

There are two circuits shown in the figure that can do this, one based on a BJT and one based on a MOSFET. They both have the same kind of operating principle.

The function of the circuit is to react and let current flow through the alarm when the wire loop is broken. The breaking of the loop is a switching event and the reaction of the transistors is also needs to be a switching event. Therefore, The transistors are modelled as switches that turn on and off.

 Question

If these two circuits were to operate under identical conditions and needed to be battery powered, Which transistor circuit would be better to use over the other for the longest battery life.

My Thoughts

I would choose a MOSFET as a MOSFET is a lot faster than BJT and therefore, it will switch a lot faster than BJT.
Also, aren't MOSFETS more efficient and BJTs consume more power?

Please let me know if I have said anything incorrect or if I could add anything, thaks!


texts: What are the differences between mini, sub-mini, and ultra-mini switches

texts:
Apologies if this isn't the appropriate SE for this question. If not, any pointers to a more appropriate place would be appreciated.

I'm looking to swap out some toggle switches on a R/C controller. I'd like to be able to shop online for the new switches and look at a variety of styles, but I'm confused about the keywords I should use when specifying the size. The switches are the thru-hole panel mount type with with bushing and nut to fasten them.

When looking online some sources don't specify the bushing size, they just specify "miniature", "sub-miniature" or "ultra-miniature" toggle switches. I haven't been able to easily figure out how these classes of switches differ.

I measured a roughly 1/4" hole in my controller, and I've seen a miniature switch say it has a 1/4" bushing, but then a sub-mini switch spec showed a .240" bushing. This seems like such a small difference I'm not sure if that's actually the difference between "mini" and "sub-mini".

So, what do these terms indicate?


texts: Where exactly appears the channel capacitance and Ron when switch on DG442 switches

texts:
I have this switch in a circuit, actually there is 30 switches.

https://www.vishay.com/docs/70053/dg441.pdf

When system is not executing any operation, switches are off. Sx and Dx are not connected. But some system operation will switching them on, connecting Sx and Dx.

In the worst case I have to take into consideration the effects of some associated parameters such as capacitances or intern Rs. I am analyzing the circuit in the worst case and I need to know how to take into account the channel capacity when switch ON. The datasheet tells us that there are 16pF for each channel of the switch.

My question is:

1.- This capacity refers to a capacity between the switch output dx pin and GND? Does it mean that when say "channel"?
It also indicates a Ron = 50Ohms per channel. Is it supposed to be parallel to this channel Capacitor? or is it serial with capacitor?

2.-  Where can it be in the simplest circuit where a signal S1 is switched on with CHA = GND and CHB = signal M is switched on with D1, where M has connected RL = 12K serial with V= 12V? VBA is my Vout as seen here:

I would like to model this circuit adding Ron and Cp. But I'm not sure how to add them to B and A nodes, specially when switching S1 with GND. That would mean S1 != GND?


texts: Stop earth from introducing noise to piezo circuit

texts:
I am currently prototyping a circuit which measures pulses on piezo-electric sensors; however, I seem to be having an issue with noise. When the circuit is battery powered (and therefore floating), there is no noise on the piezo sensor and pulses can be detected easily. However, when the negative terminal of the battery is earthed, the piezo sensor shows about 100mv of 50Hz noise, making it more difficult to detect small pulses. This is a problem as the battery may be earthed in certain conditions (eg an earthed battery charger could be connected).

Why does earthing the negative terminal of the battery introduce this noise? How can I eliminate this noise?

I have considered isolating the entire circuit so that it floats independently of earth, but I'm not sure this would work and the isolation methods I'v come across (isolating buck converters, isolating amplifiers etc) all seem to be inefficient which is not good for this application as it must be low powered.

Another interesting effect to note is that earthing the battery does not always cause this noise. I'm thinking this may be due to certain geographical locations being noisier than others.

Circuit info:
The battery is a 12v lead acid battery, which is reduced to 3.3V using a buck converter.
The piezos are utilised with a charge amplifier which centres there voltage at 1.6v (allowing a positive and negative swing).
The PCB uses an entire layer as a ground plane and is NOT earthed at any point (I'm not sure ground loops are the problem here).

Measurement method:
Currently I am measuring the output of the piezos by connecting the output of the charge amplifier to a logic analyser (which is capable of measuring digital and analogue signals), but eventually the ADC of a microcontroller will be reading this. The logic analyser is connected to a laptop which is also floating (and therefore is NOT earthed).

Any insights would be greatly appreciated.

Thank you!


texts: How to increase range without wasting current if possible

texts:
This is an FM transmitter that I built. I wanted to interface it with a microcontroller.

The enable connection seems to work, but the range is extremely weak (about one inch), even when running off of a 9V battery.

I know I didn't show it in the circuit, but I connected a 22uF capacitor across the 9V battery.

The antenna length I used is 3 inches.

I selected a low value for the grounded base capacitor (470pF) because I wanted to filter out the mains frequency and allow the tone from the 555 to go through.

I do apologize but the bottom transistor is actually 2N3904 and the top one is PN3563, and I used PN3563 for the transmitter because I'm transmitting at a high frequency.

Is there any way I can increase the range without requiring the battery to drain quickly and without requiring a higher voltage source? Do I need different transistors?

What am I doing wrong?


texts: Is it mandatory to include a pulse detector in order to design an edge-triggered JK Flip Flop using logic gates?

texts:
I am trying to design a positive-edge triggered JK-Flip-Flop (using 7400 and 7410 NAND gates) on a breadboard. The circuit diagram is in the picture (I would replace all AND and NOR gates with NAND gates). However, I see that there is a pulse-detector circuit from the clock-pulse input.

My question is:
1) Is it mandatory to include that pulse-detector circuit for proper working of JK?

2) If yes, then can I create the pulse-detector circuit using NAND gates as shown in the 2nd picture? (As usual, I would replace the NOT and AND gates by NAND)


texts: Does Bluetooth 4 or 802.11b/g/n penetrate through walls better?

texts:
I'm thinking of building a signal beacon designed to be used indoors. The transfer speed isn't critical but range and penetrative ability are. Does anyone know if Bluetooth 4 or 802.11b/g/n might be better for this application? In both cases, there won't be an external antenna. I know antenna length affects WiFi signal strength, but how about Bluetooth?

I also know Apple chose Bluetooth for their iBeacons, but I think their decision focused on energy saving instead.

Thanks


texts: Part number for this Molex 4 pin wire-to-board connector (or similar: Foxconn, Wieson, Tyco, etc)

texts:
I'm having a really hard time finding the correct PN for a 4 pin header, used with PWM fans.

The header I'm looking for is a 4 pin one, similar to the Molex 47053-1000, but a right angle one.

I've already spent a couple of hours on Digikey and the Molex website, but I can't find this. I'm only finding a 4 pin connector that has a bigger plastic tab, that won't take the 4 pin PWM fan connectors.

Has anyone worked with this type of connector before that could provide me the PN?

Here is an image of the type of connectors:

Thank you.


texts: what happens when the carry bit is zero in addition/subtraction algo for hardware

texts:
This is the algorithm in flow diagram for addition and subtraction in computers.

A(s)  is the sign bit of A
B(s) is the sign bit of B

//(s) denotes the subscript

E is the register that has a carry  bit
AVF is the register that carries the overflow bit.
A + As is the accumulator register. (A saver !)
Initially the XOR operation is carried that checks if the sign bit of two numbers is same or not.

I understand this algorithm except the circled part. What is happening when E = 0  ? Please explain taking a simple example.


texts: How to make transistor fail protection for light bulb

texts:
In the circuit below I choose an optimal current for the lamp set to 4A (the lamp specs are 12V/5A).

I need to make a safety circuit for the lamp in case transistor Q2 fails.
I add a fuse in the circuit but I'm looking for a better solution, what is the best way to protect the lamp?

This is current regulator circuit:

simulate this circuit – Schematic created using CircuitLab


texts: Will an arduino output pin set low ground a pin on a DFPlayer module

texts:
I have a DFPlayer MP3 module I'm using for a small soundboard project. I have a button that grounds ADKEY1(Pin 12), which triggers playing the next MP3. I'm adding an Arduino into that mix that I want to also be able to trigger ADKEY1. I'm just unsure of how to accomplish this - since the specs are specifically saying to ground the pin, I wouldn't think a digitalWrite LOW would be enough (nor would I think pulling that pin HIGH would be a good thing for the DFPlayer, but I could be wrong. Does this make any sense? Is this the king of thing I'd actually want to use a transistor for?

It's funny, I've done a lot of small Microcontroller projects before, but never had anything where I needed to actually trigger a ground. I feel like the answer is obvious and I'm being an idiot :) Any help is appreciated!


texts: Calculating the gauge of wire required for the secondary in a Tesla Coil

texts:
I am looking to build a small Tesla Coil at home with limited supplies. I am reasonably confident (well.. as confident as a biologist can be!) with my calculations so far, however I have hit a mental wall while trying to work out what gauge wire I should use for my secondary coil.

I would like to know how to calculate the gauge of wire I need to buy. The information I have is the height of the tube I will wrap it around, the diameter of the tube and the number of turns I want.

For my coil specifically the rough plan is to have wire coiled 13.5cm high around a 3cm diameter tube (the tube itself is taller and I have allowed for space to attach it to the other parts) and I am aiming for around 1200 turns, however if when I find out how to do this calculation the wire is too thin I will use fewer turns.

Any help would be greatly appreciated, I can tell this is a simple question, I have over complicated it in my head!


texts: Interoperability between regular and single-wire CAN bus

texts:
Is it possible to connect a regular CAN transceiver (ISO 11898-1) to a single-wire CAN bus (SAE J2411) in a compatible way? By "compatible" I mean that the whole system should support valid J2411 bus topologies and baud rates.

If so, what is the recommended way of doing so? Specifically, should CANL be left floating, connected to ground, or something else?


texts: Determining Electric Field on a Charge Plane

texts:
Question:
A plane \$x+2y=5\$ carries charge \$\rho_s=6nC/m^2\$. Determine electric field at \$(-1,0,1)\$.
My try:
At first, I calculated gradient
Let, \$\phi=x+2y-5\$
\$\begin{align}\\
\vec\nabla\phi&=\frac{\partial\phi}{\partial x}\hat a_x+\frac{\partial\phi}{\partial y}\hat a_y+\frac{\partial\phi}{\partial z}\hat a_z\\
&=\hat a_x+2\hat a_y
\end{align}\\\$
We know, \$\vec E=\frac{\rho_s}{2\epsilon_0}\hat a_n\$, where \$\hat a_n\$ is the normal vector to the surface
Here, \$\hat a_n=\frac{\hat a_x+2\hat a_y}{\sqrt{1^2+2^2}}=\frac{1}{\sqrt{5}}(\hat a_x+2\hat a_y)\$
\$\begin{align}\\
\therefore\vec E&=\frac{6\times 10^{-9}}{2\times\epsilon_0}.\frac{1}{\sqrt{5}}(\hat a_x+2\hat a_y)\\
&=151.53\hat a_x+303.1\hat a_y\\
\end{align}\\\$
But, in my book answer is:\$=-151.53\hat a_x-303.1\hat a_y\$. I can't understand why there is minus sign. Please anyone check this.


texts: Are vacuums tubes suitable for switching high current (~30amps) at high frequencies (~K-Mhz)?

texts:
I was looking to build a system for high currents (say ~30 amps) and a friend suggested vacuum tubes. In theory, vacuum tubes seemed more robust for high current applications, but after looking around, and I found a bunch with relatively low current ratings (~10mA.)

I wanted to avoid mechanical relays if possible because they seemed a poor design for high speeds. I also preferred to use a CMOS type design--my setup is symmetric with respect to p-channel and n-channel MOSFETs (at least in my circuit simulator.)  I noticed some vacuum tubes have a dual gate--which fits perfectly into my design. The question is whether they can handle these currents at high speeds.

My voltage should be quite low ~50V.

EDIT:
I am designing an induction heater, but I am trying a different approach in which I treat the heating element and the object to be heated as a black box, and use the proper switching elements to counter whatever voltage the black box produces. That is the basic idea. There is obviously more to it (e.g. have the switch on only after a threshold voltage, and off beyond another threshold voltage that would damage the circuit.)
Anyway, it was just something I wanted to try, and thus far, it seems like a relatively cheap project considering I can get a lot of parts from old stuff at yard sales, ebay, etc.


texts: Please could I know if the diodes in EESE question “Control speed of Nidec fan” ARE zener diodes (as the symbols sugest) or normal diodes as on another article they had the exactly the same circuit but in the component list the diodes were given as 1N4148 (norma diodes) Thanks.


texts:
Can I pass the signal of a (iepe) vibration sensor over a shielded twisted pair instead of the recommended coax cable?

The signal also needs to travel over 30-meter cable.


texts: CMOS 2-input OR logic gate Circuit (using 4 MOSFET transistors)

texts: I've been trying to find the way to create an OR Logic gate circuit but I can't seem to find anything online. Is there a way to do it with 6 transistors instead?


texts: I have two identical I2C devices that I need to use with a single MCU (arduino nano). I have read here on EE that an I2C multiplexer can be used to switch between multiple I2C buses. But I find them too expensive. A single pca9540 multiplexer costs at least $5, which is too much. (A complete 40pin pic MCU would costs less...) My idea is to use a digital output pin of the mcu to switch between two different scl lines. Would that work? Is it possible to do it with a few transistors? (2n2222 or BC547 etc.) That would keep costs down.


texts: Issues using printf and Serial in Serial Monitor of Platform.io Arduino with STM32

texts:
Has anyone else had issues with using printf and Serial together?
If I do some printfs then a Serial.println() no subsequent printfs show in the serial monitor.
What I discovered was that if I avoid using Serial for writing to the Serial monitor and exlusively use printf then printf works fine.
I guess that's got to be my approach from now on but was wondering if anyone else noticed this and whether there are warnings anywhere telling us to avoid  mixing the two like this?


texts:
I often see silkscreen prints between pads on pcbs. Especially I noticed this on "high voltage" designs (SMPS). What is the reason for that? Maybe it is to

improve automatic inspection
prevent for solder shorts
increase the isolation characteristics (because of an other pollution degree?)

That are all guesses. I'm not sure about that. Maybe you can help?


texts:
The question says "A signal of 40 dBm is passed through the first attenuator. The first attenuator has a gain of 1. The second attenuator has 20 dB output. Find the dBm and watts

This is what I tried doing:

40 dBm = 10*log(Pout/1mWatt)

Pout = 10 W

10 W/Pin = 1 gain

Pin = 10 W

20 = 10*log(Pout2/10 W)

Pout2 = 1000 W

Pout2 = 10*log(1000 W/.001 W) = 60 dBm

is what I did correct?


texts:
I would like to know your perspective on the following:

When measuring 24VDC both the lower test limit (LTL) and the upper test limit (UTL) are defined by either product, safety or 'common' specifications (the latter are chosen limits by company standards). Lets say for example that the 24VDC is tested passed if it measures between 21.6V and 26.4V, i.e. 10% tolerance.

The measured values can be represented by this matrix for 6 measured values at 6 different points in time: [23.2, 22.95, 23.4, 24.0, 23.5, 23.0]

The 'chosen' limits mark one result as FAIL, the 22.95V.

Employee A:

Lower the LTL to 22V, but keep the UTL at 25V to protect the applied product.
Results in asymmetrical limits

Employee B:

Lower the LTL to 22V, but also raise the UTL to 26V to balance the tolerance.
Results in possible product failure (critical limit may be 25V)

Both approaches are approved by the customer. The product using this 24VDC is not known.

How would you deal with this situation?


texts:
I recently bought a second-hand electric scooter for the wife (for those interested it's a Rascal 588XL-S, around 10 years old).
The person I bought it off said the batteries were around 11 months old, and for the first couple of days everything was fine.
More recently after a few trips out it started cutting out going up hills, then on flat. I left it charging for a while and then noticed that the light on the charger was not lighting up and the cooling fan was not spinning.
I don't believe that it has actually charged since we got it, so I bought a multimeter and tested the two batteries. I get 11.8 and 11.3V respectively (they are 2 x 12V) - I don't know a lot about electronics but that leads me to believe that the batteries are in reasonable condition and have simply not been  charged since we brought it home. Does that sound like a reasonable assumption?
I can see no difference to voltage readings when testing with the charger plugged in - the only thing I've not checked properly is the charger itself, though I did take it to a scooter shop and they tried another working charger to no avail, so I'm thinking that somewhere there's a battery controller/circuit that I need to check.
How do I go about testing the charger itself - can I just put my multimeter on the charger pins (it's a 3 pin XLR connector) without blowing myself up/damaging something?


texts: Why do two antennas have to have the same polarization?

texts:
I have a linear horizontally polarized transmitting antenna and a dipole antenna, polarization mismatch losses can be approximated by 20log(cos(x)) where x is the misalignment angle.

What is happening inside the receiving antenna that causes the losses?

My explanation would be the following: the electric field component of the electromagnetic wave causes the free charges inside the receiving antenna to move across it's length (the length of the receiving antenna) inducing a voltage across it. The direction of the electric field is important here because as we misalign the antenna, the free charges move along a different path, with 90° being the worst case as the electrons only move across the diameter of the dipole.

Is this the correct way to think about it?


texts:
I have just begun in the world of microcontrollers, and the first microcontroller. I chose to work with was the PIC from Microchip.  The PIC I am using is the PIC16F877A.  I am using MPLAB IDE and HI-TECH C.  I am trying to make an extremely simple program that turns on an LED. This is the code I am using:

#include<htc.h>
#define _XTAL_FREQ 8000000
__CONFIG(UNPROTECT & PWRTDIS & WDTDIS & HS & LVPDIS);

int main()
{
    TRISB0 = 0;
    RB0 = 1;
    while(1);
}

When I hook up the PIC to my circuit the LED does not turn on. Here is my circuit diagram and a picture of my circuit:

A few other notes about my circuit:

I am using a 9 volt battery hooked up to a 7805 regulator for the power supply.
I have measured the voltage coming from pin RB0 with a multimeter and it measures 0.0 V.
If there is no problem with my circuit I could have programmed the chip wrong.
My capacitors hooked up with my crystal are 22 pf, not 22 µf as in the schematic.
I have put 100 µf capacitors between pins 11 and 12 and between 31 and 32.


texts:
I have a setup like this :

The Power supply is a BK Precision's 1672 model.  I am trying to push 1A through the 1 Ohm/ 10W resistor.  The supply is in CV mode (The current output is set to maximum), and although the Power supply can push up to 3A, I cannot push more than 0.22 A through the power resistor.

The voltage across the resistor does not drop more than 0.3V.

I am sure there is an explanation for this, what is it?


texts:
My friend and I are trying to make sense of this. We have 4 12V batteries, a 48V solar panel charger/controller, but our load needs 12V. The system must be able to support a maximum load of 3000W, peaks of 3500W, but the standard load of less than 200W. The charger will be operational a typical 8-10 hours a day, but always connected. The 200W load will be steady 24/7.

This is what we were thinking:

Connecting the 4 batteries in series. Plugging the charger on the first and the last. This should get the charger operational.
Connect the positive of each battery to a single point (Parrallele connection), but add a 12V 5000W diode on the wire to prevent the current from short circuiting the charger circuit.
Same principal with the negative pole, but with the diode connected in reverse.

This should give us two seperate circuit one in 48V, the other one in 12V.

Here are my questions:

1) Is this circuit operational? Will it work?

2) What is the average energy needed by the diode? On the diodes tech sheet I'm getting for digikey. There is no internal resistance value. I'm wondering if the system itself will require too much power.


texts: What component should I use? H-bridge? Relay?

texts: I am working on a senior design project that involves regulating the noise from headphones to make sure no damage to the ear is done. I have all parts working except the part necessary to switch the unregulated audio input to a regulated one which would turn the sound level down. I have tested Solid state relays, and am currently trying to use a digital potentiometer to automatically increase the resistance of the audio like to decrease the sound. Could I use an H bridge also to switch between two possible outputs (no resistance vs resistance) and if so should I?


texts:
My PCB design software comes with some libraries that include some common components, like chip resistors and capacitors.  I have noticed, however, that the footprint land pattern for the 0805 resistor is not identical to the 0805 capacitor.

I then did some googling, and discovered multiple IPC standards that don't seem to quite agree with each other.

Is there a reason an 0805 resistor would have a different land pattern than an 0805 capacitor?  Is there a "best standard"?  IPC-7351, IPC-SM-782, or what?


texts: Keeping it completely analog, is there a way to high-z an open collector output? An open collector always allows a path to or from a specific voltage potential and this is complicating a rather simple task for me. The only way I can think of to do this is to interject an analog switch IC into the mix, but is there a way to do this with passives? I could use a transistor but then I'd also have to add logic to control the transistor and at that point a switch IC would be just as easy. Thanks much!


texts: ADC EVAL_AD7984_PMDZ voltage source and signal source sharing common ground

texts:
EDIT: (problem definition shortened into 2 sentences)

For anyone using EVAL_AD7984_PMDZ and having troubles to apply -2.5, 0, 7.5 [V] and signal to differential probes, because the voltage source and signal source shares ground (then there is 2.5 [V] difference between the two), check the last comment for solution.

ORIGINAL POST:

I got differential ADC EVAL_AD7984_PMDZ (page 17 connection) on ZedBoard working just fine (from -5 to 5 [V]). It requires not only 3.3 [V] from PMOD connection (logic) but also -2.5, 0, 7.5 [V] from external power source (Laboratory DC Power Supply - 2 adjustable outputs, that I have connected in series, thus I have "ground" on the middle pin, while on the other 2 pins there is -2.5 and 7.5 - relative to my "ground").

And here it comes, when I introduce input from another Laboratory DC Power Supply, the readings are fine within whole range.

But when I introduce signal from AFG-2125 Arbitrary Function Generator, there is offset of 2.5 [V] from both of the ADC input pins and it kind of messes up whole measurement that is below 2.5 [V].

May I get a little bit of insight on that ?

The ground of the ADC probes is the "ground" mentioned above.

Technically I have 3 grounds:

ZedBoard (and thus PMOD connection)(powered from its own power source)
External power source for the ADC (with the "ground")
Signal Generator ground

I am not sure how to resolve that. Would it help if the Signal Generator was battery powered ?

simulate this circuit – Schematic created using CircuitLab

(I am sorry if some electrical engineer finds the above schematic offensive)

Schematics for EVAL_AD7984_PMDZ


texts:
The table in the bottom image is the solution for an exercise based on a NAND SR flip-flop.

"Complete the truth table for the SR flip-flop."

The "initially" row is given, and I was supposed to fill in the q and Q-bar values for the remaining rows.
I don't understand the solution - why does changing S to 0 result in Q switching to 1? And why does switching S and R to 0 result in Q = 1 and Q-bar = 1?

From my very limited understanding so far in this topic, I would have thought that applying 0 to S would leave Q and Q-bar unchanged, as S stands for "set" and we are not applying a current.

Any help much appreciated.

Solution:


texts:
A similar question was asked - What is Copper Thieving and why use it?

And my question originates from the comments of the answer in the linked question.

I have read and understand that to help the etching process, you balance the copper so that it effectively eats away at the board at the same rate. One of the answers/comments makes a note that its for the outer layers.

  Thieving is added to the outer layers in order to help a more balanced chemical process for the plating.

What about the inner layers ?

I have a 8 layer stackup where some of the internal layers routing is not as dense as others. This is a relatively large board (15" x 8" ).

My gut/understanding tells me, that I should be balancing the copper on all layers and not just the outer layers, but I would like to be sure its needed and that my understanding is correct.


texts: I'm trying to use the internal reference of the ADC of an ATMEGA8. I'm trying to use it in proteus simulator coded in codevision. The Full scale reading from the ADC is always 200. I didn't connect anything to AREF or AVCC, there is even nothing mentioned that I should connect anything to it. If I connect 5V to AVCC, I can get a full scale of 1023, I don't know why that behavior happens.


texts:
Below is the schematic of the DC power circuit of a project I'm working on. I'd like to get some feedback on whether I should make any changes/improvements.

The input is from a switching wall-wart at 15VDC, polarity irrelevant.

Specifically, I have 3 questions:

The bidrectional TVS differential diode is used for surge protection, the unidirectional diodes to chassis ground are for ESD. Is this reasonable, and have I wired them in correctly?
Would it be better to place the differential LC L-Filter (L1-C1) before the rectifier and after the CM-choke, then add a second inductor in the com-line, or would this not make a significant difference? The initial benefit I saw of doing it as in the schematic is only one inductor is required, but maybe filtering would be better the other way.
Any other changes/improvements I should make?

Chassis is earth grounded directly with a cable.

Additional Info: This is an audio device used in an FM environment, powered by a CUI SWI6-15-N 15V switching wall-wart @ 25-30kHz. The regulator output is 12V. The circuitry is all analog, no microcontroller. Supply current is around 190mA max for under a minute at a time, otherwise around 30mA.  The choke is a wurth 744235110 (11uH)  was chosen with the caps to filter RF in the FM range specifically, with a minimum around 100MHz from what I simulated (ESL = 1.1nF, ESR 0.23Ohm). The ESD unidirectional TVS's are 400W calculated using human body model, handling an 8kV (330 Ohm source) discharge from VCC or COM over max 100ns. The bidirectional TVS diode is 1500W in case the are any line surges.


texts: LFP Cells - Case to internal thermal resistance

texts: Semiconductors often specify thermal resistance from case to the junction, but LFP battery cells do not seem to specify this.  Instead, they refer only to a generic 'maximum operating temperature'.  Since manufacturers don't seem to respond to the question, does anyone have any insight on how to calculate the cell's internal temperature based on case temperature and power output?


texts: Best way to modify single I/O pin on CANOpen DS 401

texts:
I have a microcontroller with CAN and need to implement a CANOpen master. It needs to toggle a pin I/O on a third party device using CANOpen specification DS 401.

How is the best way to accomplish it?

The problem is that I/O bit can't be accessed individually but only whole 8bits or 16bits register (CANOpen DS 401 - Register address 6200h).

I can see two options:

A)

A.1) Write to "Filter Mask Output" (CANOpen DS 401 - Register address 6308h) with bit mask I want to modify.
A.2) Write to "Write Outputs 16 Bits" (CANOpen DS 401 - Register address 6300H) with desired value
A.3) Reset "Filter Mask Output" (CANOpen DS 401 - Register address 6308h).

B) ("Filter Mask Output" is always set)

B.1) Read "Write Outputs 16 Bits" (CANOpen DS 401 - Register address 6300H)
B.2) Write to "Write Outputs 16 Bits" (CANOpen DS 401 - Register address 6300H) with modified value readen on step B.1

Advantages from A)

More safe

Advantages from B)

Less messages

My environment is a multi master setup, with values from "Write Outputs 16 Bits" always broadcasting as a TPDO.


texts:
Basically, I'm working on a project for a sports team. I want to strap something to each ankle of an athlete (preferrably not much bigger than an oversize wristwatch). These devices should have no connection between them (i.e. allow the athlete to move freely).

If the ankles of the athlete come within approximately 30cm or less of one another, I need an audible sound. The idea is to encourage a "wide stance". I'm not too picky about the accuracy, even an error close to 5-10cm would likely still be alright.

I don't think IR sensors would work because there's no way to keep them "aligned" with each other easily. Would an RF sensor come in this size and allow for this kind of fidelity? I'd basically need something constantly telling difference between two moving points within 1-2 meters of each other, to an accuracy of about within 5cm, and doing so regardless of the orientation of each device (though it's not expected that they will have anything other than possibly the ankles come between them.)

Thank you all for your help/suggestions!


texts: Op amp differential amplifier output level too high

texts:
I'm trying to implement a current limiter for a buck converter charging a 2.7 V super capacitor. The design uses an op amp differential circuit that then feeds a comparator:

I have simulated the approach, implemented the current limiting circuit on strip board, and also tested the circuit in isolation on the prototype PCB. It works perfectly on all of them: the differential stage output is 50 times the shunt current, and the comparator goes high when the diff. amp output reaches 1.25 V, or at roughly 2.5 A. It's not a precision circuit, so I'm not worried about minor differences, as long as I don't overload the supply.
However, when I try to apply the current limiter to the buck converter output, it goes all wonky: the differential stage output DC level rises close to the comparator threshold. For example, this screenshot shows the current limiter when the buck converter is idling with no load. The power supply indicates 0.006 A input current at 12.00 V. The yellow trace is the differential stage output while the cyan trace is the comparator output.
EDIT: In this picture, the yellow trace should be roughly at 0 V instead of 1.16 V.

If I add a 1.0 A (should correspond to 0.5 V diff. amp output, input current is 0.27 A at 12 V) load to Vcap, the traces show some current ripple and the overall DC level is still too high:

Actually, no matter what the load is, the differential stage output DC level always seems to fluctuate to just trigger the comparator. I have already added a 220 uF electrolytic cap in parallel to the existing smallish buck output cap to reduce the ripple due to that. I've also tried adding a cap in parallel to the diff. amp feedback resistor to limit the HF gain. None of these seem to work. I freely admit that I got confused when choosing the op amp. A wide bandwidth op amp shouldn't be necessary, but AFAIU, it shouldn't be a problem either. And it works perfectly when not fed by the buck converter.
EDIT: The comparator is used to make the current limit sharper. The idea was taken from [this YouTube video] (https://youtu.be/8uoo5pAeWZI). It is not part of the question (unless it affects the previous stage output).
EDIT: The question is: the current limiting circuit works perfectly when powered separately and when test current is fed through R304. When the buck converter is powered and sources the current through R304, U303B output DC level is completely wrong and not correlated with the actual current DC level.
What can cause the erroneous DC level of the diff. stage output and what can I do to remedy it?


texts:
I'm trying to use Arduino Leonardo with TVOUT library (the only one that I found to do NTSC modulation).

The problem is that I can't even run the example, I searched in serveral forums without a concrete solution, here is the error:

C:\Users\jepser\Documents\Arduino\libraries\TVout\TVout.cpp: In member function 'void TVout::tone(unsigned int, long unsigned int)':
C:\Users\jepser\Documents\Arduino\libraries\TVout\TVout.cpp:825: error: 'DDR_SND' was not declared in this scope
C:\Users\jepser\Documents\Arduino\libraries\TVout\TVout.cpp:825: error: 'SND_PIN' was not declared in this scope
C:\Users\jepser\Documents\Arduino\libraries\TVout\TVout.cpp: In member function 'void TVout::noTone()':
C:\Users\jepser\Documents\Arduino\libraries\TVout\TVout.cpp:876: error: 'PORT_SND' was not declared in this scope
C:\Users\jepser\Documents\Arduino\libraries\TVout\TVout.cpp:876: error: 'SND_PIN' was not declared in this scope

It would be awesome if anyone can help me, with this.


texts: Directionable parallel in parallel out register

texts: I have this problem. I have 3 devices that use 4bit PIPO registers to transfer each other data. I need to make the controller that select with device to use, so it will connect A with B, AC, BA, BC, CA, CB. The thing is I don't know if I should use a Mux or a Demux or another logic interface? Any ideas how to start? I have to make it in VHDL as well, but I think that will be more easy once I know how to make the circuit.


texts:
I have a problem in the UART communication between NRF52832 and SIM868 module.

The problem is the data sent by NRF doesn't be interpreted by SIM868.

To see that i did tow tests:

First one, I added an Usb to Serial module (TTL) between NRF52832 and SIM868 as shown below in picture

When I send "ATD+phoneNumber" from NRF i got it in the TTL module but the SIM868 doesn't execute the command.

Then i did another test as shown below:

Now i send the same Command form TTL Module directly to SIM868 "ATD+PhoneNumber" and it was executed, and received the response in the NRF and TTL module

I think the problem can be Logic level difference between NRF and SIM868.

could anyone help in this problem?


texts: Current through a short circuit in the Wheatstone Bridge configuration

texts:
The task was to replace part of a circuit with corresponding Norton's generator. To calculate the current of the generator, I had to calculate the current going through the short circuited nodes 1 and 2, pictured below:

There are a couple of things I do not understand.

First, let's look at the node 3. Current I is going in, and currents through R4 and R1 are going out. Then, those two currents are going in nodes 1 and 2, respectively. But if there is a short circuit between 1 and 2, currents have the option to go through the path with the least resistance, short circuit, and avoid R5 and R3 completely. In that case, current through the short circuit will be the difference between them, since they are of opposite direction. Current through R4 and R1 can be calculated by considering a current divider, that is, by combining Kirchoff's Laws. However, according to my textbook, this would not be the solution to the problem.

Another thing that I don't understand is, if currents don't go through R5 and R3 at all, then they must come back where they came from, node 3, but this current would colide with one of the ideal generator. I have a feeling that the ideal current source pushes them to go to R5 and R3 as well and come through the other side, node 4.

My question is: What is the current through short circuited nodes 1 and 2?


texts:
I am now developing a micro-controller based system that detects when a person falls down using Accelerometer. The accelerometer might be placed in the person's cloth pockets. The important thing is to distinguish the signal during a fall from a signal during normal movements. It will be done by a micro-controller. It means that the analog signal from accelerometer must be converted to digital before being given to the controller.

But the digital values are something like 241, 314, 102, etc. I don't know how to fix the signal value which will be generated during a fall i.e., the threshold at which the micro-controller detects the fall. How to do this?


texts: Does DC quiescent current vary with the load applied in an amplifier?

texts:
can you please clarify why the DC quiescent current in an opamp should decrease with load applied?

Is it just a Spice model semplification or is there intrinsic cause?

To me the DC quiescent current (here 6.4 mA, quite correct as per datasheet) need to bias the class AB power stage of the op-amplifier and should stay constant (and not decrease to a min of 4mA) with load applied.


texts:
Find the expression for V0. What would be the nature of V0 When R1 = R2 and C1 = C2?
(Consider the Op-amps to be identical)
---
This circuit seems to be an addition of integrator and differentiator. Now suppose v' is the output voltage of the integrator. v' will be $$V^{\prime}=-\int_{0}^{t} \frac{V_{1}}{R C} d t$$
In the next phase, it will face a differentiator. $$V_{\mathrm{O}}=-R C \frac{d V^{\prime}}{d t}$$
So finally, V0 will be V1.

Edit 1
I have noticed that the opamps are in a non-inverting configuration.Zooming into OP's low-res image u can check inverting inputs are grounded. So this is not just a simple circuit followed by an integrator and differentiator.
HOW to approach?
More over positive-feedback is there so I can't use virtual ground concept here


texts: Connect a 4-pin connector to power supply

texts:
I currently have a fan with a 4-pin connector that I want to power, but I do not have a power supply with a 4 or 8-pin connection. Is it possible to disconnect this connector piece and connect the individual wires directly? (red and black?)

Update: I gave it a shot and removed the connector piece and hooked up the red/black wires to a power supply. This worked.


texts:
I've got few PCB Rules on my project about trace's width restriction and the problem I face is, when I perform "Import changes" from my design, the rules are always appeared on Engineering Change Order dialog as modify action.
I choose "Execute Changes" and "Done" column are checked but when I try to make "Import Changes" again, I don't see something like "There's no differences" but the same dialog is appeared again with the same Rules on the list.


texts: Where I live, one cannot buy an Arduino very cheaply. I figure, if I make one for my own purpose on a pcb then it would be much cheaper and would be much more fun. I cannot find any etchable PDF on the internet so can anyone point me to one?


texts: How to measure the VA rating of a step down transformer

texts: I have an uncased, unlabeled step-down transformer which converts 240 UK voltage to 112v (I have measured this with a meter). It weighs 1.5kg, is 10 x 8 x 10.5cms including the attached 2-pin US socket. How can I determine it's maximum VA rating?


texts: Canon no longer makes CanoScan 8800F AC adapters, help needed to replicate its functionality

texts:
The CanoScan 8800F uses a proprietary 32VDC AC adapter that's no longer manufactured. A Flickr user did the trial and error to find out how to modify another 32VDC AC adapter for use with the 8800f. It seems simple enough. One pin carries the 32VDC of current, and other pin carrying current starts off carrying current through a resistor only to have that resistor shorted after a few seconds so that the full 32VDC of current can be delivered. Could someone advise me what the parts and schematics would be to build "a time delay relay assembly" to "short a 1.5k ohm resistor" "after a few seconds" of the scanner being powered on?

I tried messaging the user to get a more detailed answer, but to no avail. I figure he assumed that if you have more electronics knowledge his solution would be easy to interpret. Here is his original post from Flickr:

"Here is the real deal. I purchased Canon Canoscan 8800F with no power adapter. After extensive testing here is how it works. Looking at the back of the scanner the left pin will be referred to as pin 1, center pin as pin 2 and right pin as pin 3. Now, I had to build a circuit which adds a time delay. Let me tell you how to get your scanner to work. Pin 2 is ground, Pin 3 is 32VDC. Pin 1 wants the same as pin 3 (32VDC) with the following exceptions: when pin 3 receives 32VDC pin 1 will receive the same 32VDC BUT in series must be 1.5k ohms. Then, after a few seconds, the 1.5k ohm resistor must be shorted allowing the full 32VDC to be applied to pin 1. I built a time delay relay assembly to facilitate this function and now the scanner will power on when the power button is pressed. Hope this helps."

https://www.flickr.com/groups/767295@N20/discuss/72157627293403452/72157647465205394

Thanks.


texts: Analyse charging circuit for a small voice recorder

texts:
I'm trying to analyse a miniature MP3 audio voice recorder power/charging circuit.
By examining the PCB I've managed to produce this schematic.
Some of it looks clear to me.

J1 disconnected from USB and SW1 is in position Rec On:

The gate of Q2 (P channel mosfet) is near ground so the LIPO cell is
able to supply IC1 (pin 4) and thus power the rest of the circuit.
IC1_Pin12 is then held high so Q3 then also latches Q2 gate low.

J1 disconnected from USB and SW1 is in position Rec Off:

IC1_Pin11 is pulled low.
Q2 gate is still pulled low via Q3. After X ms, presumably enough
time to  cleanly close down, IC1_pin 12 drops low and the power is
shut off.

Here is not so clear to me:

J1 connected to USB (+5V) and SW1 is in position Rec Off:

The LIPO charges through the Q2 body diode ? Can this be so ?
IC1 then exposes the SD card to the USB connection to allow files to be read via a PC etc.

J1 connected to USB (+5V) and SW1 is in position Rec On:

According to the instructions, you should not do this.
Can this cause a conflict or is it protected against ?

Unfortunately, I have no data sheet for IC1. I can make only some assumptions about its behaviour.

Edit:
A 1M resistor between Q2 S and G is missing from the schematic.


texts: I tried to distinguish about MOSFET statement,,,

texts:
About during studying MOSFET, I was confused about this.
I hope to distinguish about when is triode, cut off, and Active,
umm I think if V0= 5V, then MOSFET is open state, so i guess
cut off states range is  when Vi = V_GS < 0.8V
(0.8 = Vth) that is right...?
I dont know How to distinguish triode and active range...
when  V0= 0V then triode,  when V0 =2.5V then active right? and I hope to get advice about how know Vi range.
V0 = 0V  => triode?? and what range is Vi...

V0 = 5V  => cut off?? and range is Vi<0.8V..?

V0 = 2.5V => active ?? and what range is Vi...

I started semester from March 5th Fri. and learning about MOSFET in this week
so I need to know concept exactly..

simulate this circuit – Schematic created using CircuitLab


texts: Can I use a 12VDC 300mA power supply to run a small 12VDC motor which draws 400mA? Will anything be damaged? Can it start a fire?


texts:
Based on theory when you want to find the output resistance of a circuit with dependent sources you can't turn them off so you have to add another source of known value in the points of interest and just compute the resistance. So far so good.

My issue is with the computation of the input resistance of a BJT transistor, whose equivalent circuit includes a dependent current source as seen below.

Why whenever I see a textbook computing the input resistance of a BJT it always just sums the resistances connected between BE? This is a procedure for when there are only independent sources.

For example in the case of the single transistor illustrated above the input resistance is \$R_{in}=r_{\pi}\$.

In all the other circuits without transistors we have to add a new source as I have mentioned and compute the resistance but in here we just work without caring about the dependent source. Why is that?

Basically if we consider a voltage source of \$1V\$ as an input then the current through BE would be \$i_{be}\$ so it is easily realized, as E is usually grounded, that the input resistance is

$$
R_{in} = \frac{u_{be}}{i_{be}}=r_{\pi}
$$

So is this procedure with the addition of a new source necessary but omitted from the textbooks because it is obvious (as the voltage in the input would be seen in the BE terminals making the resistances connected there easily computable)? Or they actually just add the resistances without caring about the dependent source for some other reason?


texts: uln2003a: Switching ground of device works, however, optional USB function of device doesn't work correctly

texts:
I use the uln2003a to switch a device (with use of a MCU) that is capable doing several things, like fm-radio, bluetooth, playing MP3's etc. It also provides an USB function when it is connected to a computer, it provides an usb soundcard and a SD-card interface. The function is only enabled/started when selected on the device.

The switch works okay, however, when connected to a computer the device is recognized but the computer is unable to communicate with the devices. In Windows there is an exclamation mark present with the comment "Device doesn't start, code 10".

When I bypass the uln2003a switch with a wire, connect ground directly so the uln2003a has no function, all of the devices operates just fine. I tried the following experiment:

Start the device,
Connect point A and B with a wire (see schematic below) to bypass switch,
Select USB mode and working fine.

As soon as I disconnect this wire (ground still connected via uln2003a), devices starts to malfunction in Windows.

Question:

The uln2003a switch the same ground and I don't understand why USB is not working. Can somebody explain what's going on?

Simple schematic to give some idea what's going on:

ULN2003A datasheet:
http://www.ti.com/lit/ds/symlink/uln2003a.pdf


texts:
I am building a H bridge to control a motor in the middle.
As an example, when power is fully removed (24V... 80V in the picture below), there is some back EMF  that will drive the 24V input rail.
What is the most efficient way to prevent the transients on the 24V rail? Are the below even the right options?

Diodes: Where would I place them?

Capacitors? How can I calculate the capacitance required to minimize the transients: Where would I place them (near the motor to gnd?)

thanks,


texts: How to detirmine if I need a gate driver for MOSFET or not?

texts:
I want to design a BLDC motor controller and I am still collecting some info about the components that I will use, of course main components will be MCU and MOSFETs.

I have seen some designs that use gate driver and some doesn't and I really don't know when exactly I would need them and when it would be safe not to use them

I want some guide lines to determine exactly whether or not to use them !


texts:
Could someone explain this finite state machine?

Also is this type of finite state machine Moore or Mealy?
According to my understanding...
The initial state is S0. If the input at this state for u=0 then we will be in the same state and the output will be c=0.
However, if the input is u=1 we will translate to state S1 and the outputs will be inc=1 and c=1.
If we are in state S1 and the input is d=0 then the output will be c=0.
But if d=1 then we will translate to state S0 and the outputs will be dec=1 and c=0.
Is this right?


texts: USB3.x and AC-Coupling Caps on the RX lines

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In the USB3.2 Specification (Sept. 22, 2017) Table 6-18 and Table 6-22 give some characteristics for the TX and RX lines.
Basically, I understand that the TX lines have AC-Coupling capacitors to block DC and let just the AC signals pass. How is the min/max (75nF to 265nF) decided? What if my design has 10nF? Could this somehow effect USB3 enumeration?
The spec also mentions that having AC-Coupling on the RX lines is optional (because the device-side already has series capacitors on its Tx lines, which connect to the Host's Rx lines, so it isn't needed for DC blocking).
But it still states you can have up to ~330nF at the Rx side...I don't really get where this comes from.
This note states:

We recommend 330nF capacitors in order to meet the minimum capacitance
requirement (75nF to 265nF) for RX detection.

I don't understand this note, and how having this capacitance can help with Rx detection...(I am working on a USB3 design where we are seeing some enumeration/fallback issues, and wondering if it might have something to do with these capacitance values)


texts: Why isn't the input impedance mentioned in the datasheet of the AD8597 operational amplifier?

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I am trying to look for a high input impedance op-amp to use as a buffer to prevent source loading.
When I started checking the input impedance value for different op-amps, I noticed that some of the amplifiers mention it and others don't.
For example, the AD8597 datasheet doesn't mention the input impedance value.
In this case, how do I determine the input impedance?


texts: ISO 7637 Supply Transient pulses - Explanation

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I am trying to design an input power supply filter circuit inorder to protect from ISO 7637 pulses.

I am referring this Little fuse app note

There seem to be different pulses. Pulse 1, 2a, 2b and so on.

In page two of the app note, they have given the description of the pulses.

My questions:

Why are some pulses negative and some pulses positive? I just want to understand how some pulses can be positive and can be negative
Can someone explain in simple terms regarding the pulse 1 and pulse 2 description in page 2?
Like please explain "disconnection of the power supply from an
inductive load " and "Interruption of series inductive load"? Any block diagram or explanation with the concept and direction of current and voltage would be very helpful to me.

Quotes phrases are verbatim.

(P.S. I understand when an Inductive load is disconnected, we need to protect DUT with the help of a flyback diode to prevent from heavy voltage build-up. Is this the reason why some voltage pulses are positive and some are negative.)


texts: Help with a multistage NPN BJT audio amplifier

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I am a beginner in electronics.
I have recently learned about BJT amplifiers.
I have designed this simple BJT amplifier on my own.
The book I am following only has theories about various topics but I don't know where to start to build a practical circuit on a breadboard.
I mean how can I find out the values of resistors I should use?
As far as I have learned the Vce of the transistors should be around half of the supply voltage for a distortion-free amplification.
My calculations so far:
Assuming \$I_b\$ to be very small the voltage at the base of \$Q1\$ is \$1.5V\$. \$I_e\$ at \$Q1\$ is approximately \$\frac{1.5V-0.7V}{1k\Omega}=0.8mA\$.
Assuming \$I_c \approx I_e\$ .\$V_{ce}\$ is around \$(9V-0.8\cdot 5k\Omega)-0.8V =4.2V \$ \$r^{'}_e=25mV/I_e \approx 31\Omega\$
The input impedance of \$Q1\$ is around \$31\Omega\$.
The output impedance of Q2 \$(\beta=250)\$ is \$R1||R7||R8||Z_{in(base)} = 1.2\Omega\$.
I think that's the reason I am getting such low output.

Is my calculation upto here correct? - How should I increase the output impedance?
What parameters should I consider for the second transistor?
How should I select the values of the capacitors and resistors for better results?

I always mess up if I try to increase, say, the output impedance as I mentioned cause some other problems like not enough voltage at base.

Note: Resistor R4 is 5k. Sorry for the mistake.
I have chosen the value of capacitors without proper calculations.
I am so confused on how should I select the values of the bypass capacitors as well as the filter capacitors \$C4\$ \$C3\$ and \$C2\$.
I built this circuit but it didn't work as expected. It appeared as though some of the part of audio was cut and filled with distortion.
Since I am beginning to learn electronics I want to start with simple circuits and don't want fancy circuits which use \$LM386\$ amplifiers.
Since I want to get the most out of this circuit type, what rules of thumb should I use to select the resistors and capacitors value?
Calculations regarding these will be very helpful for me.