texts: Find the differential equation for Vo (RLC circuit)

texts:
Find the differential equation for Vo

My attempt at a solution:
Node V1:

$$\frac{V_1-V_{in}}{R_1} + \frac{1}{L}\int_{0}^{t}(V_1-V_2) = 0$$

Node V2:

$$\frac{1}{L}\int_{0}^{t}(V_2-V_1)+C*\dot{V_2}+\frac{V_2}{R_2}=0$$

Am I doing this correctly? How would I solve for V2? V2 is equal to Vo, correct? If the input (Vin) is a square wave, how would I find the transient and forced responses (assuming I'm given numerical values for R1, R2, L1, C1)?


texts: How do I refer an impedance from the delta side of a transformer to the WYE side?

texts:
My question is regarding the simple arrangement below:

It is simply a three phase source feeding a load through Z1, followed by an ideal WYE DELTA transformer, followed by Z2.

My question is how do I refer the impedance Z2 to the left hand side?


texts: Can I use an op-amp in voltage follower configuration as variable voltage power supply?

texts:
I see that this works in theory, but I my gut feeling says there is a drawback or caveat of which I'm not aware. Basically what I want to achieve is described best by the circuit diagram below.

simulate this circuit – Schematic created using CircuitLab

I have a power supply (2A @ 12VDC) that I want to use to make a variable voltage power supply. In the voltage follower configuration, whatever is on the non-inverting terminal on the op-amp is present on the output terminal. The extra current at the output terminal needed to keep the voltage up is provided by the op-amp's supply. Since I'm using a linear pot as a voltage divider to set the input voltage to the op-amp, will this work as an effective variable power supply from 0V to almost 12V? If not, why can this configuration not be used this way?


texts:
In an assignment I was asked to improve the power factor of a certain circuit to 1. The supply is 240V peak-to-peak @ 60Hz. Rs = 58 ohm, Rl = 2 ohm and L = 8 mH. Below are my calculations but I can't seem to get the right answer. Indicating where I am going wrong would be a huge help :)

\$X_L = 2 \pi  f  L = 3.0159j\Omega\$
\$Z = 60 + 3.0159j = 60.0758 \angle 2.8776 \$
\$I = \Large{\frac{240}{60.0758}} = \normalsize 3.995 A\$
True Power = \$I^2 * R = 15.9596 * 60 = 957.576 W\$
Reactive Power = \$I^2 * X = 15.9596 * 3.0159 = 48.1326 VAR\$
Apparent Power = \$I^2 * Z = 15.9596 * 60.0758 = 958.7857 VA\$

Then for the capacitor:

\$X_C = \Large\frac{V^2}{Q} = \frac{57600 }{ 48.1326 }= \normalsize1196.6941 \Omega\$
\$C = \Large\frac{1}{ 2  \pi  f  X_C} = \frac{1 }{  2  \pi * 60 * 1196.6941} = \normalsize2.3557 nF\$

But this value for the capacitor seems way too small :/
Thanks for any help!


texts: How to make a solder paste more liquid-like

texts:
I recently purchased Kester EP256 solder paste. This is the first time I am working with it, and placing it on the PCB is very difficult. I do not know how viscous it should be, but it seems to be too dry - it virtually does not stick to the board, or the components. It almost looks like a fine wet send - it sticks to itself, but not to anything else. I was expecting it to be more like a toothpaste.

I know, it is difficult to judge the quality of the paste by my description, but how is the paste supposed to be? Also, is there a way to dissolve it, or rather, make it more sticky?


texts: Infrared High Intensity LED with two anodes?

texts:
I got an infrared led emitter, with model ""L1I0-0850060000000" and the datasheet is plenty of technical data but I can`t find why it has three terminals - 2 anodes and 1 catode. Usually it's used for data transmittion.

Datasheet: https://www.lumileds.com/uploads/685/DS191-pdf

Here is the datasheet showing the three terminals:

I don't have many experience with light data links, but I know that some common leds have three terminals to allow switching the color. As far as I understand, this model is made for one specific infrared radiation - I could be wrong.

Has someone any idea on how to figure out this? I tried looking on google but cound't find a solid answer. I plan to use this for digital transmission.


texts: Selectable Voltage Divider Optimal Switching Point

texts:
I've built a circuit to measure an unknown resistance (over a large range) which is basically the following:

simulate this circuit – Schematic created using CircuitLab

Range_Select_1 and Range_Select_2 can be set to GND or High-Impedance by a microcontroller. When set to GND, they effectively short circuit the voltage divider and remove resistors below the node. So In the circuit above.

Range_Select_1 = GND  => Low Side Resistance = 1 kOhm
Range_Select_1 = Z, Range_Select_2 = GND => Low Side Resistance = 11 kOhm
Range_Select_1 = Z, Range_Select_2 = Z => Low Side Resistance = 111 kOhm

Is there an optimal way to select the Range_Select_1 and Range_Select_2 settings to get the best results in measuring Rx?

I figure I will get 3 ADC readings (one for each range selection) and choose one of them as my best choice. How do I choose which one without knowing the true value of Rx ahead of time (which would defeat the purpose of doing the measurement in the first place).


texts: Ethernet Interface PCB layout requirement (if any)

texts:
I am doing Ethernet communication to/from an MCU.

I got it working great with an ENC28J60 development module:
https://www.digikey.com/product-detail/en/olimex-ltd/ENC28J60-H/1188-1044-ND/3471433

I recreated the module layout w/ DIP components on breadboard. It works pretty good though not as reliable, the obvious reason being that im using a birds nest of wires vs a module.

Now I am going recreate this interface circuit on a PCB. Are they any trace width/ length recommendation I should use?

I found this:
http://ftp1.digi.com/support/documentation/022-0137_F.pdf

It says I should the keep the trace impedance below 50ohm for signal traces... But since Ethernet operates at different frequencies do i need to know ahead of time what frequency I'm transmitting at?

Should the Tx/Rx pairs be routed side by side or above/below on different sides of the PCB.

I am going to be using basic 1oz Copper, 2 layer board. I probably wont be able to keep the traces all on one side... Meaning the ground plane wont be flawless.
How big of deal in this? I mean I did get it working on breadboard w/ jumper wire.

Thanks
Tony


texts: Difference between push pull and half bridge

texts: I don't understand well the difference between push-pull and half bridge. Someone told me it was totally different but as I understand it, half bridge is a generic name where we have 2 switches and a load connected in the middle. So I guessed that push-pull circuit is just a kind of half-bridge. Is that correct?


texts: What is the meaning of standard discharge current mentioned on the datasheet of lithium batteries. Does it represent the maximum current load can take or it represent the instantaneous current battery can provide


texts:
I'd like to use the Micrel MIC2606 boost converter for a 36 volt circuit I'm working on. The datasheet gives a formula for calculating the RHP zero based on output voltage, current, and inductor value.

I'm also using the TI app report discussing feedback loop analysis for boost converters here:

What is the D in the formula?
Does it have to do with the size of the loop between Vin and the SW node?
Out of habit, I was planning on keeping that loop as small as possible and away from sensitive circuits but are there any other general guidelines I should use when developing this circuit?


texts:
I'd like to use a slide switch to switch an output between one of three inputs. However, I'm having trouble understanding which pin is the pole and which pins are the throws. Here's a link to the switch I'm planning to use, and here's the drawing datasheet. This is an on-on-on switch, which I believe means that at any given time, the switch connects the pole to one throw and leaves the other two open. Here's an image of the switch:

My guess is that the 3 gold-colored pins to the right are the throws and the single pin on the left is the pole. However, this is based purely on the fact that these three pins are grouped together and separated from the fourth pin. Additionally, I'm guessing that the black slide switch is positioned (relatively) above the throw shorted to the pole. I use relatively here because the plastic sliding piece seems to be centered (not above the throws). So, the leftmost position (as in the picture) would indicate shorting between the pole and leftmost of the 3 rightmost pins.
Unfortunately, I can't find confirmation of this on the linked datasheet. There's also a product guide, but I didn't see an indication there either. Is my assessment correct? Did I miss something on the datasheet, or is there a standard here that I'm not aware of?


texts: MOSFET N-channel as switches in an AND gate

texts:
I thought I could use two BS170 transistors working as switches in series, to create logical AND functionality. My circuit is switching an LED with 1.5V of forward voltage and 10mA current set by a resistor. The positive voltage is supplied by an LM7812 regulator and not the battery as the diagram shows.
A problem I didn't expect is that when only the left switch is closed, the circuit is conducting enough current through the LED to activate a transoptor of which this LED is a part. This problem is not present on the simulation as shown in the picture. The simulation behaves as I would imagine.
I didn't spend too much time on this when making a quick prototype, but IIRC on the right transistor, I could measure 0.3V of drop between drain and gate and 2.33V between gate and GND. This made me think that it conducts the current of the LED, but why?

I solved it ultimately by using NPN transistors in the same configuration, but initially I wanted to save some base current by using MOSFETs. Now I would like to know the reason why the initial solution behaved this way.


texts: Trouble initiating I2C communication with MSP430g2553

texts:
I am having difficulty getting I2C communication going on the MSP430g2553. After working on this for a couple of days I finally stripped down the code to what I thought should be the bare bones needed just to send the start pattern and the slave address, but even that does not seem to work.

I have an oscilloscope hooked up to pins 1.6 and 1.7 but haven't been able to capture anything at all. In addition, I turn on an LED while the start pattern has not been sent and attempt to turn it off afterwards, but it never turns off.

Here is stripped down code. Can anyone throw some light on this?

#include <legacymsp430.h>
#include <msp430g2553.h>

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

  // Set up the DCO
  BCSCTL1 = CALBC1_1MHZ;
  DCOCTL = CALDCO_1MHZ;

  P1SEL |= BIT6 + BIT7;                   // Assign I2C pins to USCI_B0
  P1SEL2|= BIT6 + BIT7;                   // Assign I2C pins to USCI_B0
  P1REN |= BIT6 + BIT7;

  P1DIR |= 0x01;                          // For the LED
  P1OUT &= ~BIT0;                         // Make sure it's off

  UCB0CTL1 |= UCSWRST;                    // Enable SW reset
  UCB0CTL0 |= UCMST + UCMODE_3 + UCSYNC;  // I2C Master, synchronous mode
  UCB0CTL1 |= UCSSEL_2 + UCSWRST;         // Use SMCLK, keep SW reset
  UCB0BR0 = 10;                           // SMCLK/10
  UCB0BR1 = 0;
  UCB0I2COA = 0;                          // Master own address
  UCB0CTL1 &= ~UCSWRST;                   // Clear SW reset, resume operation

  UCB0I2CSA = 0x78;                       // Slave Address
  UCB0CTL1 |= UCTXSTT;                    // Send start and slave address
  while(UCB0CTL1 & UCTXSTT){
    P1OUT |= BIT0;                        // Turn on the LED while the start has not been sent.
  }

  P1OUT &= ~BIT0;  // This never gets executed.

  LPM0;

  return 0;
}


texts: Low-Side Switch MOSFET Drain Voltage Drop in OFF state?

texts:
I'm trying to replace a normally open switch with a low-side switch mosfet. The drain of the mosfet is connected to an input pin of a non-modifiable 3.3V MCU.

Prior to my changes to the setup the HIGH side of the switch measured around 3.3V since it's a LOW = TRUE logic input.

After I added a 5v long-period square wave (~5V high, 0.070V low) to the gate of the mosfet the voltage changed drastically at the drain side of the mosfet.

MOSFET ON - V_ds = 0V with V_gs = 5V as desired.
MOSFET OFF- V_ds = 1.7V with V_gs = 0.070V - HALF of what it should be with the mosfet switch open.

Anyone have any insight as to why this would be? From what I can tell I'm utilizing the 2N7000 well within spec.

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to understand the theory of operation of a time domain reflectometer (TDR).

TDR is a time domain instrument with measurement the impedance versus the distance. If with a VNA one can measure s-parameters, then with TDR one measures impedance.

Why would TDR be called S-parameters measurement method?

Ok, if I know the impedances, then I can create matrix U= Z I, where Z and I are matrices. But How I can use TDR for S-parameter measurement?

I have found the some slides (enter link description here)

pictures from this pdf:


texts:
I was wondering about what's the best storage method to save files to in order to save it from natural dynamics like earthquakes, tsunamis, or just to keep them along times...

We all know that there are several of storaging types such as:

HDD, SDD
Memory cards (SD,MMC)
Flash drives (like USB, RAM and ROM)
EEPROMs (well, that's for pretty sure not for a large amount of data)
Magnetic tapes

Note that for storage method I mean actually archiving some files, without needing the possibility to actually have access to them, excpect in case we grab the storage device out of his safe place.

Also note that they actually should be powered off. So a RAM-like storage solution is not effective at all, cause it will loose its content once powered off.

I'm not planning any anti-catastrophe method to save my files ( lol ), I'm just asking it because actually I don't know which is the best one for archiving files in long time.


texts:
I am hacking a vacuum cleaner robot by trying to control the motors with an Arduino.

I have then two 8V motors, each one needing from 50mA (when the wheel is turning free) to more than 1A (when the wheel is blocked).

The robot battery provides 16V (and I know it can provide enough current for the motors because that is the original battery).

Now, how can I connect the battery to the motor ?

I guess once that is done I can just add a transistor to control it with my Arduino.

Thanks


texts: AMS1117-3.3 over-heating and blow up way below max current

texts:
I am designing a circuit for my home automation system. To give a gist, I have a 12V 3.5A supply. I need to operate multiple loads off it.
One of the Loads is a ESp12E module.

Esp12e module ----- Max current pull = 350mA. Voltage = 3.3V.

For this purpose, I am using a regulator AMS1117-3.3
Following is my circuit diagram:

My Problem is, with this connection, the AMS1117-3.3 regulator is heating up and hence blowing up. I have read the datasheet and it says "Max output current = 1A"

What can be the problem?


texts:
I am working with an RF transformer. I would like to understand the voltage rating of this transformer. How can I do that. The only voltage related information ios the inter winding isolation of 300V. What does that signify please ?
The part number is AE458RFW01B1SZ and the screen-shot of the datasheet is as shown below -

The other thing could be the derivation of voltage from the wattage.Wattage is 0.254W rating and a current rating of 250mAmps. This makes the max voltage as 1V, which is ridiculous.


texts: How can I scroll through all colors of an RGB LED using an Arduino microcontroller and a single Potentiometer?

texts: The RGB LED is supposed to be controlled by PWM, how can I map the position of a potentiometer to a color combination?


texts: How can we multiply two 2-digit BCD numbers?

texts: I am designing a PIC18F4520 microcontroller based system. By using this system I want to multiply two numbers. Each number is a 2-digit BCD number. Such as 73*27 and I want to see results as 2715 at a 4 digit seven segment display. I have a problem creating algorithms while multiplying those numbers. How can we multiply those numbers?


texts: Generating exact frequency of vibration with motors

texts:
I measured the frequency of motors with an accelerometer (ADXL335), but the frequency from my measurement is a lot different from the frequency specified in the product page.

I tested with two motors.

1) http://www.adafruit.com/product/1201
I got 220-250 Hz with 5V, but the product page shows that the frequency should be around 180Hz

2) https://catalog.precisionmicrodrives.com/order-parts/product/303-100-3mm-vibration-motor-8mm-type
I got 170~180Hz with 3.6V, but the datasheet shows that it should be around 280Hz.

The vibration frequency in the datasheet has tolerance, and the frequency may vary with different mounted materials. I thought that my measurement is showing different frequencies because my measurement setup (mounted material, variation in the motor) would be different from what manufacturers used.

Therefore, I want to make sure that my measurement is correct by generating the exact frequency and measuring it again with the accelerometer.

Can you suggest any way to generate exact frequency? The frequency should not be higher than around 1 kHz because the accelerometer has limited sampling rate.


texts: Converting a 10A supply into a 16A appliance

texts:
Is it possible to insert a converter between regular 10A 240V mains supply that would be capable of running a tool rated at 16A, 3500W?

Obviously, the tool won't run to it's full capacity but could it work for a portion of its capacity?


texts: Regarding edge triggering and level triggering in flip flops

texts:
After reading different books,I have understood what is edge triggering and level triggering.But I fail to understand in edge triggering how input is only taken during the falling edge or the rising edge of the clock and why input is not taken by the circuit when the clock is actually staying high?As when clock is high,the flip flop should be enabled ,so it should take the input when it is high as well,but it only takes input when it is rising or falling.
How does the circuit understand when to take the input?


texts: Verilog Generate statements: Syntax error near "<=": unexpected <=

texts:
I am very new to Verilog, and I found the need to use "generate loops" to instantiate multiple hardware blocks. In this case, I am instantiating multiple "pe" blocks, a block which performs some simple arithmetic.

Code is shown below:

// intermediate signals
reg init_temp;
reg [D_W-1:0] in_a_temp;
reg [D_W-1:0] in_b_temp;
reg valid_D_in_temp;

genvar i, j;
generate
        for (i=0; i<N; i=i+1) begin : pe_generate_i
                for (j=0; j<N; j=j+1) begin : pe_generate_j
                        if ((i == 0) & (j == 0)) begin
                                valid_D_in_temp <= (pixel_cntr_A == M-1);
                                init_temp <= (pixel_cntr_A == M-1);
                                in_a_temp <= A[0];
                                in_b_temp <= B[0];
                        end else if (j == 0) begin
                                in_a_temp <= A[i];
                                valid_D_in_temp <= valid_D[i-1][j];
                        end else if (i == 0) begin
                                in_b_temp <= B[j];
                        end else begin
                                valid_D_in_temp <= valid_D[i][j-1];
                                init_temp <= gg;
                        end

                        pe pe_inst (
                            .clk(clk),
                            .rst(rst),
                            .init(init_temp),
                            .in_a(in_a_temp),
                            .in_b(in_b_temp),
                            .valid_D_in(valid_D_in_temp),
                            .out_sum(),
                            .out_b(),
                            .out_a(),
                            .valid_D(),
                            .init_out()
                        );
                end
        end
endgenerate

A syntax error arises in the first non-blocking statement:
valid_D_in_temp <= (pixel_cntr_A == M-1);

Error:

# ** Error: (vlog-13069) systolic.sv(37): near "<=": syntax error, unexpected <=.
# ** Error: systolic.sv(37): (vlog-13205) Syntax error found in the scope following 'valid_D_in_temp'. Is there a missing '::'?

Can anybody suggest what the problem might be?

Thanks in Advance


texts: CE amplifier circuit gives output voltage that is not completely out of phase

texts:
This is the circuit that I have constructed

But it fails to give the output voltage that is completely inverted (out of phase)
Can anyone show me whats wrong with the circuit?


texts: Does this sensor measure electrical or magnetic fields (with oscilloscope)

texts:
I want to measure electrical and magnetic fields of the frequency 50Hz to 1MHz with my oscilloscope.
For electrical fields I learned that any bunch of metal will work.
For magnetic field derivation with respect to time I learned that a search coil will do.

So I took a 30x wounded up bell wire, skinned the endings and clamped it between the tip and the ground clip of my passive oscilloscope probe.

Now I have a search coil which obviously is also a bunch of metal.
What do I measure? Electrical or magnetic fields?


texts: Could you tell me how I can make the black screen like this in proteus so that it look like more interesting simulation :)


texts: Strange substance in PCB soldering (corrosion?)

texts:
After about 8 month since the electronic components were soldered to a PCB using Pb-free tin, a strange substance appeared in some of the contacts (see attached image)

.

The PCB may have been exposed (OR NOT) to some humidity but not to other substances during its working time

What could such substance be? Would it cause short-circuit between the component pins?

It looks like some mold. But why there?


texts: Is a MPPT controller basically a buck converter with a feedback geared towards power?

texts:
Conceptually, is a MPPT controller for charging (simple) batteries with energy from solar panels basically a buck converter whose feedback loop (which influences the PWM duty cycle) is geared toward maintaining the maximum power point rather than a stable voltage?

Can it be only a buck converter or does it need to be a buck/boost one?


texts: Flash ADC with TL074 & 74LS148: encoder inputs always high?

texts:
I am attempting to build a 3-bit 0-5V flash ADC using two TL074 quad op amps and a 74LS148 active-low priority encoder.

The circuit is fairly simple. 8 100K resistors are connected in series between 0V and +5V, with each node between connected to the inverting input of one of 7 op amps, providing 7 reference voltages for the comparators, equally spread between the supply rails. The input is connected to the non-inverting inputs of all 7 op amps. The op amps are also supplied from the 0V and +5V. Each op amp's output sits at about +1.4V until the input goes above its respective reference voltage, at which point it snaps up to about +3.6V.

My thought was that these could then directly drive the 74LS148 inputs (1 - 7, in reverse order, with input 0 grounded). If I interpret the voltages by hand according to the 74LS148's function table, I should get the (active-high) output I want. However, it seems that the inputs from the op amps are always being seen as high, even when they are at the low +1.4V state. (I do see occasional glitches where the outputs jump to a state other than all high.)

Is that +1.4V simply above or too near the logic threshold for the 74LS family? Research suggests not, but maybe I read something wrong? Or, are the output pins of the TL07x perhaps unable to sink enough current to drive the 74LS inputs low? Or is it something else?

Note that I also have -12V and +12V supplies available in this circuit, in case the op amp supply rails need to be changed.


texts: hold time violation during FPGA post place and route simulation in modelsim

texts:
I am designing a simple encryption circuit on Xilinx Virtex-5 FPGA. I have given the timing constraint in the UCF as below:

NET "clk" TNM_NET = clk;
TIMESPEC TS_clk = PERIOD "clk" 25 ns HIGH 50%;

My design does not have any errors in static timing analysis report after place and route. Part of the report is shown below:

Timing errors: 0  Score: 0

Constraints cover 191219 paths, 0 nets, and 38438 connections

Design statistics:
   Minimum period:   9.954ns{1}   (Maximum frequency: 100.462MHz)

However, when I run a post place and route timing simulation in modelsim. It gives me this error and the design does not generate the proper result in the simulation.

# ** Error: /home/rex/opt/Xilinx/10.1/ISE/verilog/mti_se/simprims_ver/simprims_ver_source.v(121020): $hold( posedge CLK:650974 ps, negedge I &&& (in_clk_enable1 != 0):651125 ps, 153 ps );
#    Time: 651125 ps  Iteration: 0  Instance: /tb/aes_wrapper_0/\aes_fwd_0/aes_fwd_core_inst/CIPHER_RND_1_ARK_ROW_1_4_ARK_COL_1_3_xor_itm_1_sg1
# ** Error: /home/rex/opt/Xilinx/10.1/ISE/verilog/mti_se/simprims_ver/simprims_ver_source.v(121020): $hold( posedge CLK:650974 ps, negedge I &&& (in_clk_enable1 != 0):651125 ps, 153 ps );
#    Time: 651125 ps  Iteration: 0  Instance: /tb/aes_wrapper_0/\aes_fwd_0/aes_fwd_core_inst/CIPHER_RND_1_ARK_ROW_1_4_ARK_COL_1_2_xor_itm_1_sg3_0
# ** Error: /home/rex/opt/Xilinx/10.1/ISE/verilog/mti_se/simprims_ver/simprims_ver_source.v(121020): $hold( posedge CLK:650974 ps, negedge I &&& (in_clk_enable1 != 0):651125 ps, 153 ps );
#    Time: 651125 ps  Iteration: 0  Instance: /tb/aes_wrapper_0/\aes_fwd_0/aes_fwd_core_inst/CIPHER_RND_1_ARK_ROW_1_4_ARK_COL_1_3_xor_itm_1_sg3_0
# ** Error: /home/rex/opt/Xilinx/10.1/ISE/verilog/mti_se/simprims_ver/simprims_ver_source.v(121019): $hold( posedge CLK:650974 ps, posedge I &&& (in_clk_enable1 != 0):651125 ps, 153 ps );
#    Time: 651125 ps  Iteration: 0  Instance: /tb/aes_wrapper_0/\aes_fwd_0/aes_fwd_core_inst/CIPHER_RND_1_ARK_ROW_1_4_ARK_COL_1_2_xor_itm_1_sg3_2
# ** Error: /home/rex/opt/Xilinx/10.1/ISE/verilog/mti_se/simprims_ver/simprims_ver_source.v(121020): $hold( posedge CLK:650974 ps, negedge I &&& (in_clk_enable1 != 0):651125 ps, 153 ps );
#    Time: 651125 ps  Iteration: 0  Instance: /tb/aes_wrapper_0/\aes_fwd_0/aes_fwd_core_inst/CIPHER_RND_1_ARK_ROW_1_4_ARK_COL_1_3_xor_itm_3

I only know this is a hold time violation. How do I interpret this error information more precisely? How to solve this problem?

Updates:
I tracked the signals that cause the hold time violation. The input pad is connected to some combinational logic before it goes to the DFF which has hold time violation. I assume adding OFFSET IN constraint will solve this problem. How do I determine the right value (??ns) in the OFFSET IN constraint?

OFFSET = IN ??ns BEFORE "clk";


texts: What is meant by "zerø-crossover" in the OPAx365 datasheet? And why the "ø"?

texts:
TI's OPAx365 seems to be a fairly ordinary op-amp after you dig through all the marketing buzzwords. But one thing sticks out: the datasheet repeatedly mentions having a "zerø-crossover" topology.

I initially thought the use of ø instead of o was a typo, but it doesn't seem to be as the term is used, including the ø, repeatedly throughout the datasheet. Is this some form of branding for their proprietary technology, or is there some actual reason for this spelling?


texts: Where do I find models for various common op amps for use in LTSpice

texts:
I have just started using LTSpice. I need to simulate a circuit with op amps, where the parasitic elements of the op amp may effect performance. So I need to try different 'real' op amps to see which on is best.

Is there a source of commonly available op amp models like TL074 or LM324


texts: maximum voltage that a colpit oscillator can withstand

texts:
I am working on a wireless power transfer project using, I need to design an oscillator. I need a frequency of over 2MHz and I need it for a high power application.

So my question is what is the maximum value of voltage I can apply as \$V_{CC}\$.
Does it depend on what the oscillator uses, i.e BJT, MOSFET, or an op amp?

Any suggestions and solutions are welcome.


texts: Bus Bar voltage calculations for renewable integration to grid

texts:
I am confused on the problem bellow

I started off by use P=IV = V^2/Z --> V=sqrt(P*Z)
Assume at each bus bar the power from the PV is being given to the grid with +6KW from knowning that the PV produces 10KW but the load PL uses 4KW
We know that z = 0.2
Thus, V = sqrt(6 *10^3 *0.2) = 34.64 V. This means that the voltage level at each bus bar is 230+34.64
Thus the voltage at each bus bar is 264?
This is because each bus bar outputs 6KW to grid i think.
Thus in P.U V = 264/230 = 1.15 ??
Wrong! :""( i am soo confused as to how to approach this problem.
The notes only say general stuff like if PL == Ppv then voltage == 1 p.u
Please help me understand this simple problem


texts: Power old Nokia phone from Bench Power Supply

texts:
I have an old Nokia Mobile that has a dead battery.  I am trying to power it up to see if it works without having to purchase a replacement battery.

I have a bench power supply but am confused as to what the 4 battery terminals are doing, do you think I would be able to power up the phone using my bench supply or is their some other circuitry involved?

UPDATE

I have tried powering up with my bench supply by connecting to VBat+ and GND at 3.6v.  When the power button is pressed it draws current for a second and then nothing.  I am wondering if the BSI pin and BTemp provide some sort of signal that is required before it will power on


texts: Reed switch passive interupt for garage heater when door is open (using NC switch)?

texts:
I'm trying to prevent my garage heater from running while the garage door is open to prevent it from attempting to heat the entire neighborhood if/when the door is accidentally left open.

I have a wireless garage door sensor (Honeywell 5816MN) wired to an external magnetic reed switch already installed for the alarm system that triggers whenever the garage door is opened.  I was hoping to re-use the same equipment if possible, since it's already mounted to the door for monitoring.

What I'd like to do is interrupt the heating wire from the thermostat to the heater whenever the door is opened.

The problem is the magnetic reed switch already uses the Normally Open terminals as the wireless sensor identifies an alarm state when continuity is interrupted.

Requirements:

1) When door is closed, heater can run, when door is open, heater cannot run

2) Must either use the NC terminal of magnetic switch, or coexist on NO terminal with the existing alarm wireless sensor

3) No power available for active electronic components (relays, etc)

Is this possible?


texts: What does "bolt-on" mean in this Arrow Electronics' job posting?

texts:
I came across of Arrow Electronics job posting, and wondering what term "bolt-on" means. While I can find generic description of this term, I can not understand how it relates to the electronics and duties of the job holder. I found subsection "bolt-on (chassis)" at Digikey website, does this "bolt-on" have any relation to electronics / component product line being sold? Or it is a property of the candidate they are looking for? Please advise.

  CLEAR CATEGORY: Sales w/ Sales bolt-on’s

...

  Manage all resources to grow the business with Field Application Engineers, Field Marketing, Asset, Business Process Excellence (BPE), Assignees, customers, suppliers (bolt-on for CE), Customer satisfaction (bolt-on for SE)

...

  Support the company credit policy (bolt-on for SE)

Update: if you have an urge to press close question button, consider this before doing so  -

This question, while is not about electrons, chip and op-amps, is about entity, playing role in EE and which has, most probably, influence on you and your life;
This question is NOT about job, but about probably industry-specific term;
Prove that this term bolt-on has no specific meaning in EE / electronics manufacturing / electronics business. I have never seen this term before anywhere, and I am not a native English speaker;
Last, but now least. Think about your fellow EE colleagues who may be also looking at such masterpieces from Arrow. By closing this question, thus not allowing giving (more) answers and replies to it, you may give disservice to them.

I am waiting for answer from the agency, it seems they will refer to Arrow's HR (the only contact for them), as they appeared also not having idea what it is.

Update (as a response to Jeanne): let me explain the history of why I asked this question. I have got JD from agency, and the target job is located in the country with English being non-primary language, while used to be taught in the schools. The link to JD in UK I posted in the question above is reference for you how it looks like in my JD (mine is not online). I have classical British business education, but this "bolt-on" got me stuck, and stuck just at the top of the document.

My first thought was that it is sales of something relating to bolts or bolting. So the first link to the heat sinks and product lines related to parts being bolted. This was the time I decided to ask this question.

Next thought was about "bolt-on" as idiom, meaning "additional". If considering JD this way, I would say it is about sales person sitting on at least 3 chairs (self, some SE and some CE), which is business nonsense, and must have been explained differently.

As I did not see this idiom anywhere else, I still think it has to do with business Arrow Electronics is in, or to culture of this company in particular.

And by the way, there're some idioms even Brits and native English speakers are not able to get without solid context.

Update: it seems we have a consensus here that "bolt-on" is not related to EE (product line, some specific EE business term or business technique). Let me get response from the agency (if they will ever provide one).

Final update: agency got stuck, and they did not go to Arrow for clarification. Both answers should be correct ones, and the best reply is by @JRaefield (below the question, he did not make it an answer). Thus I choose @pipe answer as best one (he has answered first and has the lowest score at the time of assignment).

Thanks everyone for the participation, and my apologies for being EE off-topic.


texts:
I disassembled a dynamo-fuelled torch and I found this set-up.
Now, what I know is that the led should be lighted up by the electromagnetic force generated by the time-varying flux within the coil. Thus I wonder how can the rotation of the magnet (which is the thing I hold in my hand in the second and the third picture) generate a time-varying flux within the coil?

I don't understand how could the magnetic fields' lines be, however, as far as I can see, the rotation of the magnet shouldn't change the flux within the coil!

I think it has to do with the "metallic teeth" arranged over and under the coil  (there are four over and four under it)... But I don't know how.

PS: From the picture I took it can't be seen but the coil is NOT inside the magnet. In fact, the magnet just leans on the "teeth structure" and all of the teeth are inside a cavity in the magnet (which can be seen in the photos).


texts:
What is a multiplexed network?

Multiplexing means many to one and sending the result over the network. As far as I know, Control Area Network (CAN) supports multiplexing. How?

CAN is said to support multicast, one to many (kind of de-multiplexing).
Then what is multiplexing and a multiplexed network?


texts: How to set power when given fixed supply voltage?

texts:
WARNING: noob question!

If given a supply of voltage V, how do I "set" to have a load that dissipates P amount of heat? I think i have a mental block here:

Since R is the only variable I can play with, I thought a higher resistance would give more heat since \$P = I^2 \cdot R\$. But, then wouldn't higher resistance also reduce the current that passes since open circuit = infinite resistance?!! Also, \$P = \dfrac{V^2}{R}\$ !?

Thanks in advance!

PS: I am a software programmer who is tasked to reverse engineer an electrical design software that was written with excel formulas and VBA. I need to know some of this to know if the formulas are correct in the first place.


texts: RF - sma pth connector impedance matching to cpw

texts:
I am designing a 4-Layer PCB with an SMT GPS/GNSS receiver (1575.42 MHz), where it connects to an external antenna through an SMA Connector. I have already done all the calculations of CPWG using Saturn PCB Toolkit to match the 50 Ohm required impedance.

My stack up is like:
- TOP
- GROUND
- POWER/SIGNALS
- BOTTOM

As the RF trace is on top the Conductor Height(H) is 7mil (0,178mm). This value I got from the PCB manufacturer.

My final layout can be seen in the image below:

The image is zoomed and on the left, you can see the GPS Receiver PADs, on the middle is the RF SMA connector and on the right is an M3 mounting hole.

Question: What is the influence of PTH VIA of the SMA connector on the RF trace? Does it matter on "low" Frequencies of 1575.42 MHz or like 868-928 MHz or even 2.4GHz?
I know that VIAs adds inductance/capacitance to the circuit and it is strongly recommended to avoid them on RF traces, but what about in this case?
Is there any consideration about the gap of the VIA pad and the ground plane of CPWG?
I have searched for CPWG to SMA Connector transition but everything that I found is saying about the board edge mount connector, but nothing explicit explaining about the PTH connector or saying something about VIA influence (always to avoid using VIA on RF Trace).


texts: How to interpret packaging information in Datasheet

texts:
I'm trying to create a part for Fritzing and I am struggling to interpret the packaging size in the datasheet.

In the notes it is said that the sizes are in mm, ok with that, but how should these numbers be interpreted? A division or max/min does not make sense.


texts:
I disassembled a LED lamp and it's circuit. My intention is to rebuild that circuit within EveryCircuit app, to understand how it is working.

On this circuit I found two elements that are rising questions to me.

A) I couldn't find a reference for “CY40(0|D)474JE“ To me it looks like a capacitor but it have no idea about the numbers to use?

B) I also found a so-called varistor. I understand that as a variable resistor? But the data sheet that I found did not specify any ohms.

The lamp was driven by 230V AC. The lamp's circuit did drive 30 LEDs in series. From my measures I saw 300V DC coming out of the circuit and going to the LEDs.

Thanks


texts: Will electricity flow in a perfectly conductive medium?

texts: I was just wondering that since resistance is required for a potential difference to build up, what happens when we have a perfectly conducting wire, 0 resistance? Will current still flow through the medium? Or am I getting something wrong?


texts: Can I use SMPS to power 12V DC water pump

texts:
I'm looking to use a 12V 60W DC water pump in my project, and I'm trying to find a suitable way to supply power for the pump. I'm wary about using the brick-like power adapters as I think they are not reliable. I see that SMPS is more reliable. Can I use a 12V 10A SMPS unit to power the pump ? One concern is that I read that a DC motor could draw upto 3 times more current while starting. So the SMPS could cut-off supply due to overload. Please note, I will be turning the pump on/off many times in day using arduino/relay control.

Water pump -
http://www.ebay.in/itm/12V-High-Pressure-Auto-Diaphragm-Water-Pump-5L-min-100-PSI-Pressure-Switch-/222221212173?

SMPS -
http://www.ebay.in/itm/12V-10A-120-Watt-DC-Switch-Mode-Power-Supply-Driver-Transformer-CCTV-Led-Strips-/322280796678?hash=item4b096eb206:g:aqwAAOSw6n5Xwt4s


texts: Need Help: Wiring LEDs with 2 source voltages

texts:
I have a series of LEDs I would like to have display at 2 brightness levels and am confused how to properly wire this. This is for additional running lights/brake lights on my bike.

LEDs - Typical Voltage 2.2V, Max Voltage 2.6V, Forward Current 150ma

simulate this circuit – Schematic created using CircuitLab

Source voltage 1 (running lights): 11.5V

Source voltage 2 (brake lights): 0.5V at all times, 11.7V when brake is engaged

When using the series LED calculator I believe for the Source voltage 1 I should set the forward voltage to 1.1V and 75ma (half of typical voltage and half of forward current) and then set the Source Voltage 2 to 1.1V and 75ma (the other half of voltage and forward current). That in my eyes would result 2.2V and 150ma. http://led.linear1.org/led.wiz

Is this right or should I be approaching this wiring different?


texts:
I'm using NODEMCU and SSR modules to turn on / off the lamps with WiFi. Nodemcu uses I = 80mA and V = 5v as its input current and voltage (Vin pin). It worked without any problems with a single lamp on my desk. When I implemented the whole device behind a light switch and connected the ac wires to the SSR module, there were some problems. The WiFi switch works fine alone and also, I can control it via WiFi. But when I hit another switch next to it which is not WiFi enabled, it affects the WiFi switch.

For example, when I want to turn on a lamp and hit its switch (which is not WiFi enabled), the lamp turns on and subsequently, the lamp which has a WiFi enabled switch turns off and on randomly. I think because nodemcu needs 80mA current, it's sensitive to power swing. and I can't use sleep mode because if I use it, WiFi will be disabled and as I want my device to be in station mode, it would cause problems.

I tried different capacitors for Vin pin from 0.1 uF to 470 uF !! but none of them helped and still, when I turn on some other lamp, it has a bad effect on my device.

What is the problem and how can I solve it?


texts: Currently I am doing a project on a voltage regulator. Can you tell me some advantages of MOSFETs over BJT? Apart from a higher power loss, I can not find much. In control engineering it is much more difficult to deal with them. Would be great if you could tell me a few.


texts: How to derive receiver noise figure/input noise floor

texts: When calculating the noise figure for a receiver, assuming the IF bandwidth is narrower than the input RF bandwidth, do you use the narrower IF bandwidth to derive the receiver noise figure?  Also, when calculating the input noise floor power level at the receiver input, do you use the wider input RF bandwidth in said calculation, or the narrower IF bandwidth since that is what the receiver ultimately outputs?  If you use the IF bandwidth for said noise floor calculation, would that imply that your noise floor power level will drop after the RF bandwidth is reduced by filtering, at least due to the contribution of B in kTB? (Assume a lossless filter)


texts:
Hello everyone!

I am trying to test this circuit, but actually I have some issues with LDO power supply!

Actually the problem is that, the two LDO: LDO_circuit and DLDO are working fine. I mean that if the power supply is 3.3 V they put on output 2.6 V and if the power supply is 5 V on the LDOs'output there is 3.3 V.
Instead, on LDO_uC I have always on output very few mV even if I checked that on input I have the given power supply.
Someone have ideas to suggest?

Thank you very much in advance!


texts: feeding scaled down voltage to XADC (Xilinx)

texts:
simulate this circuit – Schematic created using CircuitLab

I have XADC (Xilinx) with single ended voltage range of 0-1V. To regulate the output of a DC/DC converter let's say 15V i feed the XADC with 15V scaled down by ratio of 1/16, So using 150K(1%) and 10K(0.01%) resistor. The worst case error would be around 0.103%. That looks very small. Now lets say i want to maintain the regulation to 15V +/-5%. I wanted to understand how would the scaling down of voltage for feedback would affect the voltage regulation in DC converter? What would be better option either to scale down and feedback or to use separate ADC with higher input range ? What else to consider ? Thanks


texts: How to measure power consumption of Arduino Uno onboard ADC module?

texts:
For a project, I am using Arduino Uno onboard SAR ADC module. I want to calculate the power consumption by the ADC module. The way I am thinking to calculate it is AVCC*ICC. Here, AVCC is the supply voltage for the ADC module and ICC is the current drawn from the power supply. Now, if my clock is 16MHz then at active mode I'll consider the ICC is 9.2mA according to table 28.3 (attached) from the datasheet. My confusion is

If I set the ADC module reference voltage at 1.1 V (Typical) then should my AVCC will be 1.1 V or still 5V?
For 1.1 V internal reference voltage, will the ICC be 9.2mA at 16MHz clock?
Is there any way to experimentally measure the power consumption by this ADC module?
I am adding the ADC characteristics table 28.9 from the datasheet as well.

Thanks!


texts:
I am trying to get a cable solution to output 80Gbps of data. My FPGA is trying to input/output data. It has QSFP-DD cages. Fiber SFP+ cables (50um and multimode) need to interface to this. From my search online, it doesn't appear anything fiber can breakout from QSFP-DD to 8x 10G, but if I use a MPO/MTP, it seems like I can breakout from QSFP-DD to 8x 25G.
If I specify my FPGA to output 10G (which is can. Its the ADM-PCIE-9V5), can I make a custom cable of a QSFP-DD MPO/MTP to 8X 10G and does the fiber cable automatically convert to that?
It seems like I may need a MPO/MTP cassette, but I couldn't find any that breakout to 16 ports. Only 12 and 24.
Thanks
EDIT: More context: I am thinking of using a QSFP-DD SR8 with a fiber breakout cable to 8x 10G SFP+ TRXs/Modules. The QSFP-DD is rated up to 400G, but I am curious if it can "do" 80G if the FPGA and data is sending it at that rate.
Essentially this QSFP-DD connector with this SFP+ TRX. Connected by this cable


texts: Manufacturers' recommendations for ground plane for GPS patch antennas

texts:
I see requirements for specific ground plane sizes in many GPS antenna datasheets, but I also see many devices that ship with significantly smaller ground planes. Do these integrators know something that the GPS vendor doesn't, or am I missing something about the requirements?

As an example, u-blox SAM-M8Q Hardware Integration Manual specifies a 50mm x 50mm gp, but all off-the-shelf PCBs I see on the Web look much smaller (for scale, the M8Q patch is 15mm x 15mm).

  SAM‑M8Q GNSS patch antenna module is intended to be placed in the middle of 50 x 50 mm GND size board,
  but a larger or smaller ground plane can be used. When using smaller than 40 x 40 mm ground plane, the
  performance may get decreased significantly.


texts: Can I use a microcontroller to control the output voltage of a switching powersupply?

texts:
I am attempting to control a switching power supply from my microcontroller. I am using a LT1377 from linear.

In the diagrams in the datasheet, a voltage divider is used to drive the feedback pin. Is it possible to replace that with a signal from my microcontroller?

EDIT: Thanks for the answers. I am waiting for parts to come in to be able to test the different solutions.


texts: How to compare a magnetic loop antenna to a conventional antenna

texts:
I want to build a compact 1 MHz receive coil (antenna for very near field). For that I need to make a choice on whether to build a simple RF coil only consisting of wire and capacitors or using a coil with a ferrite core. I found materials that have a high real permeability and very low imaginary permeability even at 1 MHz. For example, this NiZn ferrite material.
How do I compare the sensitivity of the magnetic core antenna to the sensitivity of the antenna without the core. Does the core introduce noise beyond what is described with the complex and real permeability?


texts: Circuit for driving 24V VF-Display with Arduino MC. Does this work?

texts:
I am trying to operate an IVL2-7/5 vacuum-fluoresecence-display with an Arduino Uno.
It is a multiplexed 4 digit clock display that requires a cathode voltage of 2.4V and an anode and grid voltage of 24V. The 24V will be supplied by a seperate voltage source, the Arduino shall simply switch this voltage. (I know that VFD driver ICs exist but I want to try to do this with discrete components)

I have created this circuit, a high side-switch from two MOSFETS, but am unsure weither it's suitable.

My question is basically: Is this circuit a working switch and would it work to switch the 24V supply of a single anode element?

Also: what resistances should I select for R1 and R2? Do I need another resistor between Arduino and M1?
I am very inexperienced in electronics, but I vaguely recall that a MOSFET's gate acts kind of like a capacitor and can pull strong currents if switched quickly.
I'd like to utilise stronger resistors for R1 and R2 to minimize the current they "consume", but don't know if that will still allow fast enough switching for multiplexing of the VFD.


texts: What is the voltage of LED string when not conducting?

texts:
Simply put, what's the voltage at the end of an LED string if the low side MOSFET is switched off. In other words, what must the FET voltage rating be. Note that I'm not asking on exact answer on this particular type of LED and voltage/current in that schematic. It's just to demonstrate the idea.

In my actual circuit I'm driving 20x high power white LEDs at 40mA. Vf=6V. Mosfet leakage current is 0.1µA at 25C and 1µA at 125C.

So when I switch off the bottom MOSFET, is it going to see

zero volts
120 volts
something in-between like 120V - 20 x 3v
    (effective zero current forward voltage) = 60V?

Conclusion
I performed a simple test using 60Vbr Mosfet with 2k2 resistor in series with source and the gate tied to GND.

The voltage will rise to the MOSFET breakdown voltage presuming it's less than the LED bar input voltage. However the current flow is practically zero as no avalanche can develop as the LEDs are firmly below any sensible threshold voltage. Regarding if this can damage the FET or not, I'd hazard the answer is "no", presuming the Vbr is large enough that the LEDs will not conduct meaningful current at the remaining voltage.


texts: MOSFET small signal model output resistance

texts:
I am wondering what is the output resistance of the circuit below. I found that it depends on the gate voltage:

$$
\begin{aligned}
R_{out} &= \frac{V_{out}}{I_{out}}
\end{aligned}
$$

$$
\begin{aligned}
I_{out} &= I_{out_1} + I_{out_2} \\
        &= \frac{V_{out}}{R_3} + I_{out_2}
\end{aligned}
$$

I convert the parallel current source in a series voltage source to find \$I_{out_2}\$:

$$
\begin{aligned}
I_{out_2} &= \frac{V_{out} + g_m V_{gs} r_d}{r_d + R_4} \\
&= \frac{V_{out} + g_m(V_g - R_4 I_{out_2}) r_d}{r_d + R_4} \\
&= \frac{V_{out} + g_m V_g r_d}{rd + R_4 + g_m R_4 r_d} \\
&= \frac{V_{out} + g_m V_{in} r_d}{rd + R_4 + g_m R_4 r_d}
\end{aligned}
$$

I am wondering if my reasoning is correct. The problem sets solution is $$R_{out} = R_3 // (R_4 + r_d)$$ but I don’t understand how \$R_4\$ and \$r_d\$ can be in series because the current going through them doesn't seem to be the same according to the model.


texts:
I am doing a course in Communication Engineering and on reading Amplitude Modulation in my textbook I found that a typical AM is defined by the following equation;

$$ s(t) = (1+k_{a}m(t))A_{m}cos(\omega t) $$
The reasoning which the book gives is that $$-1<k_{a}m(t)<1$$, so that $$1+k_{a}m(t) > 0$$ But why do this and instead just make $$0<k_{a}m(t)<1$$, because including a 1 would only make things worst by increasing transmission power and it also does not supress the carrier.


texts: How can I calibrate my sound card based oscilloscope?

texts:
I'm using Soundcard Oscilloscope software that presents as below

You'll notice that the display has a grid, and in the example is set for 100mV/div.  Since it's using the sound card integral to my motherboard, there is no calibration of this display or the line in socket, so the divisions could actually be anything.

I have a digital multimeter as well that can measure AC style voltages in the 10 - 400 Hz range. How can I calibrate it, at least roughly?  My only thought was to build a sine wave oscillator to produce 100 Hz @ 1 V RMS.  That way I can confirm the amplitude with my multimeter, feed it though line in to the software and then adjust for the reading.

Is this likely to work, or is there some other way of calibrating PC based soft oscilloscopes?

EDIT:

Following some comments, I tested my multi meter against a range of sine wave frequencies.  These were line outs generated via Audacity software, with the TONE command set to a volume of 0.8.  The red dot is @ 50Hz, so this should be ideal for the meter and forms a baseline voltage reading.  The response seems reasonable over 10Hz - 10KHz.  Even better across 50Hz - 1KHz.


texts:
assuming the below circuit is functional. Can you tell me how soft-start part is working? Would the same setup be valid for Vin=~3V and Vo =~1.3V, or would I need to change the C1 and R3. Also how can I increase the soft-starting time? Thanks in advance.

Edit: The image is from onsemi LM317 datasheet, I found no explanations.


texts: How to make polygon inside orphan of another polygon?

texts:
After manual routing a PCB in the Eagle CAD I widen ground net by putting a polygon on the whole PCB and naming it "GND". I disable the "orphans" options, so I have some free orphan areas on the PCB.

Now I want to use this free areas for widening the power net. For this, I create another polygon on the whole PCB with name "+5V" with greater (weaker) rank than "GND". But when I do ratsnest, power net are not widened, because orphans are not really free: they are in ground polygon, so power polygon can't use it.

But if I make the rank of the power and ground polygons same, both polygons connected without spacing (because Eagle can't determine boundaries between them).

How to make polygon inside orphan of another polygon with spacing?


texts: I need a simple exponential converter that with 9V and allows me to control a VCO. I've tried the one the schematics below but it needs bipolar power supply and just doesn't work. I have plenty of transistors and op amps, a simple circuit would be appreciated!


texts:
Is a microwave oven considered an inductive load?

I have a battery back-up and uninterrupted power supply system that I would like to connect to the microwave oven. But the UPS manufacturer cautions not to connect to inductive loads. So how much of an inductive load is a microwave oven?


texts: Photocurrent in photodiode smaller than expected

texts:
I have a question regarding the usage of the phototransistor SFH 203 P, which I want to use for a project, where I need a small fall- and rise-time. The data sheet (I think) implies that if I use the photodiode as follows (in reverse bias) I should get a photocurrent of about 800µA (see page 3 under "Rise and fall time of the photocurrent").

simulate this circuit – Schematic created using CircuitLab
But unfortunately I only measure 2.3µA with bright room lighting. Did I misinterpret the datasheet, use the wrong circuit or is my photodiode maybe broken?


texts: Why does the volatge drop is huge once a load is connected to a generator?

texts: At no load condition the generated voltage at transformer secondary output is 140 V ac. When a 60W resistive load is connected the voltage drops to 27 V ac. The pmg generator rating is 1 KW 415 V and transformer rating is 415/230 Vac 1 Kva. Why does the voltage drops so much and what would be the reason behind this scenario?


texts: KiCad Bus on multiple sheets - Are labels the right way to go?

texts:
I want to connect bus-lines via several-sheets in KiCAD 5.0 But I don't know whether I got that right. Please consider the following design:

Shown in Figure 1 you can see my connection from the chips output to the signal-bus. I added hierarchical labels to each bus. Those were added with the following function:

Figure 2 shows the parent-sheet in which the network-logic- and the plug-sheet live. There I then added the hierarchical pin with the following function:

I added the label and the bus on the plug side the same way, as shown in picture below.

Question:

Is my bus now connected correctly, or am I using the idea of labels wrong?
Do labels work with busses the same way the do with single wires?
Is it correct, that every line from a bus that has the same name,
will be connected in the net-list?


texts: Accelerometers and transient acceleration

texts:
I'm trying to understand the notion of transient acceleration threshold. I'm working with the popular MMA8452 and the way I understand transient acceleration is that it represents the dynamic component of acceleration.

The issue is that when I set the transient threshold to 1g or less, I'd get interrupts fired even when the device is stationary. If the transient acceleration is simply the second derivative of velocity, the device shouldn't fire off interrupts when stationary even with a 0g threshold - right?

If it's because of noise, 1g of noise would be terrible.

Am I missing something obvious?

Thanks

EDIT

These are the registers I've set:

writeRegister(TRANSIENT_CFG, 0x1F);
writeRegister(TRANSIENT_THS, 0x0F);
writeRegister(TRANSIENT_COUNT, 0x00);

writeRegister(CTRL_REG4, 0x2B);


texts: I have to transfer signals over around five meters. My input signals are I2C or SPI-compatible, but unfortunately it is no good idea to transmit them over such a long distance. Therefore I was thinking of converting the I2C- or SPI-signal to a CAN-signal (and back). What is the best approach of converting these signals into each other without having to use (too much) external components? My first approach was to use a MCP2515, but there I already need an external clock. Is there a cheaper way to do that?


texts: Using a PNP instead of an NPN in a circuit

texts:
The figure shows my circuit.

The transistor I am currently using is a MJH6287 (PNP) as opposed to whats shown in the figure (MJH6284 - NPN)

The circuit with the PNP transistor worked just once in turning the LED on and off, Would it make a difference if I replace the NPN transistor with a PNP, if the circuit is designed for an NPN?


texts: How in-depth is the IPC "Introduction to Printed Circuit Design" course?

texts:
I'm looking into courses to progress from autodidactic hobby-level PCB design. IPC is offering an "Introduction to PCB design" course.

How well does the course cover the standards? IPC-222x, IPC-7x51, library conventions, something else?

Is it

"from introductory, never touched Altium/KiCAD to able to draft a basic audio amplifier, with only tidbits of standards thrown in"

or

"You'll still learn a lot about how to do things RIGHT even if you've done stuff before"?

The curriculum is at https://www.ipc.org/ContentPage.aspx?pageid=Introduction-to-Printed-Circuit-Board-Design. It doesn't fully answer my question.

I'm most interested about the documentation aspect: What must/should/must not be in the package of documents going to the manufacturer/assembler, what are good practices to avoid common mistakes etc, according to IPC/IEC/ISO standards.

Hoping to hear from someone who has actually taken the course.


texts: Is there any formula to get number of windings for a 50W voice coil of a speaker?

texts:
Is there any formula to calculate number of windings to get a 50 Watts voice coil of a speaker?

let's say, I want to wind a 20mm diameter voice coil for a speaker. And my coil is made out of copper wire which is 1 mm thick (diameter) and has a resistance of 13 ohms per 1000 meters. And I want the voice coil to use 50 Watts. How do I calculate the number of windings required?

P.S: I'm developing a new speaker design, so, I'll experiment with overheating issues. Just ignore all other parameters and let me understand the relationships between given parameters to initially wind the voice coil. I'm stuck in finding out the number of windings to experiment with, so if some formula gives 50 turns, I'll initially wind it and experiment with all other parameters one by one (eg: overheating).


texts: Can anyone help identify this part? I've tried googling the numbers in various combinations and found nothing. This is something I bought a long time ago, recently found, and can't remember what it was for. Thanks.


texts: Intermittent control signal injection clock sync

texts:
I have a big challenge in my design to overcome:

I need clock frequency accuracy of <0.2ppm with incredibly low power consumption.

What we are doing currently is, using a 3G transceiver' baseband output, we are using a PLL using the baseband as the control signal, and frequency multiplying from there, and achieving incredible results (<1ppb!!!), however the power consumption is too high, and this level of accuracy is not needed. The transceiver's current is around 26mA.

I am thinking, is there any form of clock synchronization technique that does not need a constant control signal? Could a control signal of some kind be intermittently 'injected' into the system so re-synchronize the clock at set intervals? I'm thinking of powering on and off the transceiver at a low duty cycle (5% on, 95% off type of thing), to reduce power consumption in this way.

My understanding is a little limited, but from what I already know this would be difficult (impossible) using PLLs due to the lack of a constant control signal.

I'm thinking what if the control signal input could be switched from the PLLs output itself and the baseband output of the 3G transceiver?

The basic concept of what I need is shown below:
Please ignore where it says 'OCXO'. It should say '3G Tranceiver Baseband'.

Any constructive suggestions are welcome; no "it can't be done" replies please.

Crystal oscillators are not really an option due to at least one or a variation of power consumption, size and device cost.


texts: Graphing an N-channel MOSFET's characteristic curve in LTSpice: Am I doing it wrong?

texts:
I was trying to replicate the characteristic curve of an N-channel MOSFET in LTSpice. I wanted to achieve something like this:

but I end up getting this graph instead:

in which the drain current are in the negatives. I am not really that familiar with SPICE syntax so pointing out where I did get it wrong would be a great help.
The SPICE Directive I've constructed:
MOS   100 1 0 0 MOS
Vbias 1 0 DC 1.5
Vd    110 0 DC 1.5
Vid   110 100 DC 0

.MODEL MOS NMOS

.DC Vd 0 12 .0001 Vbias 0 5 1
.PROBE          DC I(Vd)
*.PRINT DC  V(1,XIS.2) V(XIS.2,0) V(XIS.23) V(XIS.46) V(1)I(Vid)
.OP
.END

Was it the circuit I've constructed, or was it my syntax/semantics that was wrong? I was pretty sure I used an N-type enhancement mode MOSFET.


texts: How to implement step-up DC-DC converter with reverse current capability

texts:
I am trying to step up voltage from 24V to 36V using a boost converter, specifically the PI3740-00-LGIZ by Vicor, in order to power a motor. However, I want to be able to do regenerative braking with the motor, which would require reverse current through the step-up converter. Can I simply connect a Zener diode in reverse in parallel with the boost converter, which breaks down at some voltage above 36V, e.g. 37V? If not, how can I achieve this?

Edit: The data sheet for the converter is here: http://www.vicorpower.com/documents/datasheets/ds_pi3740-00.pdf

I am looking to return about 100 watts for 1/4 of a second, once every second.

Thanks!

Edit 2:
Thanks everyone for the posts. After looking through all the answers, I think the easiest thing to do is use the LT8708 controller from Analog Devices, and build a circuit around that. https://www.analog.com/media/en/technical-documentation/data-sheets/LT8708.pdf


texts: PWM + LC filter - voltage value non linear with duty cycle

texts:
I'm experimenting with PWM and LC filter and I think it works correctly when it comes to smoothing signal, but for some reason voltage on the output is not linear with duty cycle. I use 56uH inductor and 220uF capacitor (from 1 / (2 * PI * sqrt(L * C)) it's 1433Hz). The PWM signal has 20kHz frequency. Smoothing looks like that on the oscilloscope with 50mV/div:

The problem is that the voltage doesn't raise linearly with duty cycle. I use 5V output from arduino with a 1k resistor with an LED, which gives me a little less than 2V going through the LED. After connecting an inductor and a capacitor, the voltage on 100% duty cycle is still little less than 2V and it correctly drops to 0 for 0%. But what happens in between is unexpected. The voltage is almost maximum at about 33% duty cycle and changes only a little when going up to 100%.

Is it something normal? If that's correct, how do I calculate voltage based on duty cycle? If that's not expected, what should I look for in my circuit?

Here is a schematic:

And also an overview of how I connect it to arduino, just in case:


texts:
I'm trying to get the VGS of DMHC4035PMOS. Based on the simulation, I'm supposed to get -5.53V but I'm getting -8.2V on my PCB. Is there anything wrong with the design? What is the collector voltage of the current mirror on Q1 supposed to be?
DMHC4035 - H-bridge - https://www.diodes.com/assets/Datasheets/DMHC4035LSD.pdf
DMMT3904 - current mirror - https://www.diodes.com/assets/Datasheets/ds30311.pdf


texts: Interfacing a microcontroller digital IO

texts:
I'm working with some microcontrollers, and I'm quite confused about how to interface the digital I/O. I've already see some projects with opto-couplers on outputs, other ones with buffers, so I'm kinda confused. When should I use each? When should I not use anything?

For me, that is the way that I thought that would be the "safest" mode:

(SOMETHING OUT) -->Buffer -->Opto -->(Microcontroller)-->Buffer --> Opto-->(OUT)

But, I do not think it's the most efficient way. Can someone help?


texts: What is the reason to use an isolation amplifier?

texts:
A PC is connected to a data acquisition card which has single ended channels. One of the channels is outputting a constant DC voltage which can be controlled by a user via a program in the PC.

The output voltage is feeding a VFD. The VFD takes the voltage value and controls the frequency of the AC motor depending on the voltage applied.

There is an isolation amplifier between DAQ analog output and the VFD as in the figure.
When I measure the analog output of the DAQ and the output of the isolation amplifier with a voltmeter I see the same value.

What might be the reason then for the isolation amplifier?


texts: DALLAS DS1220AB Non-volatile SRAM from 20 years ago --- reusable?

texts:
The DALLAS DS1220ABs that I have were mostly manufactured in 1992 and 1993, I have a bunch of pulls.  The datasheet speaks of a "lithium" battery inside (not "lithium-ion").  Do people here think that applying GND and VCC would recharge the "lithium" battery inside to make these chips quite usable, or is that just not the way it works?

(for e.g.  http://cgi.ebay.com/Dallas-DS1220AB-200-16K-NonVolatile-SRAM-/170576839051)


texts: LMR33630A, my built circuit doesn't match the expected output

texts:
Using TI's "power designer", I've taken their 33630A and designed it for a 5v output. My actual circuit has a slightly different value for the divider to raise the voltage up to about 5.2v, otherwise it matches this design:

..and here's my design. I've reviewed it a few times.

My circuit, and the PCB from it, are on easyeda. After assembling the circuit, my output is right around 1 volt and the chip is overheating. I can't figure out why! I've checked for short circuits, and I've done in-circuit tests to ensure the passives are approximately correct.

As a wanna-be-EE, I don't know where to go next. I have a low-end 'scope and a high-end meter. I'm not using this attached to anything (e.g., it isn't actually connected to a Raspberry Pi), and I'm supplying it with 12-16v. I also removed LED1 so I could rule that part of the circuit out.


texts: Period for this astable multivibrator (nor gates with limiting diodes)

texts:
I was able to find the period without the diodes which was T=2RCln(3)

But I am unable to find the expression when we connect the two diodes. (Our course says it is :
T= RCln( (VDD+Vd)  /vt).
I am unable to find out how we obtained this expression)

This is the circuit:

Please explain how to get the expression of the period of this circuit, and thank you.


texts: I have to design a project that uses an LED to transmit data and a LDR to receive the data or signal from the LED. But the problem is I have to use two Arduino UNO boards, one for LED transmit and another for LDR to receive. I know we can just use one Arduino board, but in my condition, my project is to have another advanced application that requires using two Arduino boards and have to separate the LED and LDR .So, how can the led transmit data? For example speed of car, so that LDR can receive data and display at the LCD? How to connect between the two Arduino?


texts: Set STD_LOGIC_VECTOR with constant integer

texts:
Is it possible to set a STD_LOGIC_VECTOR(6 DOWNTO 0) with a constant like so:

signal s1: std_logic_vector(6 downto 0);
s1 <= 12;

Or do I have to define it as a set of bits?


texts: Question about FTDI USB-to-Serial Evaluation board

texts:
The evaluation board

I am talking about the FTDI EVAL232R evaluation board which can be found at the bottom of this page. It employs a FT232RL IC.

What I want to do

I would like to connect a USB joystick to the board´s USB port, then connect the RS232 interface to my PC, move the joystick and check out the incoming stream of information.

What I tried

I know that those converters usually are used to program a microcontroller over USB and similar things. There the USB port connects to the PC and the RS232 interface to the chip. In the datasheet I can not find any clues as to which extent a reversed flow of information (from joystick to PC) is possible.

Is the above board the right one? If not, could you please point out a device that would better suit my needs?

Edit: I rephrased the title to make it more general.


texts: Silicon controlled rectifier P-type gate connection and layer doping

texts:
1). In SCR the gate terminal is connected to the P type semiconductor layer. Can it be connected to N type SC layer?

2). The outer most two layers of the SCR should be highly doped as compared to the inner two layers. What is the reason behind it?


texts: How can I design a 4-to-16 decoder using two 3-to-8 decoders and 16 two-input AND gates?

texts:
I have an idea of how to get started, but not sure where to go from there.

Since I am using two 3-8 decoders to develop a 4-to-16 decoder, I want to use 4 inputs out of the two 3-8 decoders.  So I'll use all three of the first and the first of the second, and connect the last two inputs to ground, since they won't be used.

Any pointers on where to go from here are appreciated.


texts:
I have a problem and some of the components I think I need to solve the problem but I do not have the knowledge or understanding to put it all together and what I read online is just not connecting the dots for me.

Ultimately what I need to have happen is a PIR sensor detects movement and triggers a string of LEDs. Which seems like it should be simple enough. I can get the PIR sensor to light an individual LED but anything beyond that and the PIR is to weak.

The LEDs I am trying to light are in a ribbon format and I want them to run off of bare minimum 12v but preferably 18vdc as this is when they are at their absolute brightest. At 18vdc they draw about 2 amps of current.

The PIR is powered off of 6Vdc and outputs 3.3VDC with around 300uA.

I want to use a relay that I have which the coil can be pulled in at a little under 3 volts but needs around 100mA of current and the contacts could handle the 18vdc and 2 amps I want to run my lights.

My problem is how can I get more current from the output of my PIR to trigger the relay, being that I can't increase the voltage coming out of the sensor?

I have some transistors to work with but I don't have enough understanding to connect a proper circuit up and I believe I have been burning out some components needlessly just playing around with stuff.

My PIR is an HC-Sr501, my Relay is a JQC-3F (T73), the LEDs are a 12V RGB ribbon style, and I have available some standard NPN and PNP transistors BC547, BC557, 2N2222, and 2N3904. I also have a variety of common resistors and other standard components. Either a circuit somebody has already created or just some specific instructions of how the connections should be made in order to accomplish my goal would be appreciated.

I don't have a data sheet for the LEDs. This is what they are and all the specs I could get on them.
SUPERNIGHT (TM) 16.4FT 5M SMD 5050 Waterproof 300LEDs RGB Color Changing Flexible LED Strip Light
Voltage 12 volts
Wattage 60 watts
I don't have a problem running them at 12v if I have to and I understand it would be a better idea.
here is a data sheet to my PIR sensor http://www.datasheet-pdf.info/entry/HC-SR501-Datasheet-PDF .
Although it isn't marked as an HC-sr501 when I purchased it from a chinese supplier this is
what they claimed it to be.

I know you need real information from data sheets but I don't have much of that stuff.

I know what I can read from my DMM. The sensor puts out 3.3 volts as expected when triggered but the current is only 300 micro amps. my relay coil will react at about 2.8 volts but draws about 100 milliamps in order to do so. The LEDs are designed to operate on 12 volts but when I crank it up to 18 volts they are bright and although they will eventually burn out I have run them at 18volts for more than 24 continuous hours without fail, that doesn't matter so much to me anyways, even if I only supplied them with 12 volts that would be ok. I just can't get my PIR to trigger my relay to turn my leds on in the first place. There isn't enough current coming out of my PIR output to activate the coil.


texts: Can someone explain what each pin does on an LM3914 dot/bar graph chip?

texts:
I got an LM3914 chip to control a ten segment bar graph, but I am confused on how to wire it. The data sheet is not helping me with what pins do what and how to wire it.

I need to know how it works and please don't be hyper technical I am still new to electronics.


texts: Can a rechargable dash cam battery be replaced with a dc-dc converter in-place?

texts:
While reading this question, where a user is having difficulties with his dashboard camera battery, I noticed that one of the answers suggests (or seems to suggest) to replace the existing battery with a converter attached to the car battery.

  Another way is to use the un-switched (i.e. always-on) 12V from your car, regulate it to 3V, and put this into your cam. But make sure you do not drain the battery and also use fuses, as there's a lot of power behind the 12V in a car.

This seems like a good idea - why bother replacing the battery with a capacitor (or another battery) if you have a huge one just laying there - the car battery. I happen to have the same dash camera at hand (G1W) and also have a 12V to 3V DC-DC converter just lying around.

Hence, the question. Can the replacement be done in-place or would an additional circuit be required to prevent the device attempting to charge the car battery through the converter. This is what happens during normal camera operation when attached to switched-on 12V car power supply - it only uses the battery to shut down safely and maintain its memory for settings. The original battery is a 150mAh 3.7V rechargeable battery.


texts: Determining the gain of a circuit with multiple op-amps

texts:
say I would need to find the gain (Vo/Vi) for a given circuit like this one with multiple op-amps.
I know how to find the gain for a simple circuit with a single op-amp, like an inverting circuit circuit would be -(R2/R1)Vin
But I can find the gain in those situations only because I know the gain formulas for those specific op-amps circuits. How can I determine the gain for unique circuits like this one?
I know for a start that the first op-amp is a voltage follower, so its output equals Vi, but that is about it... I am lost afterwards. I don't recognize any op-amp circuit on the right stage.
I am basically looking for a universal approach to calculating gain of op amps circuits

Thank you for your help!!


texts: What Determines the Noise Bandwidth of a DC Voltmeter?

texts:
Say I have a 1000 Ohm resistor. At room temperature, this has 4 nV/rtHz of Johnson Noise.  That means that a measurement with a bandwidth of 100 Hz would see 40 nV of RMS noise.

If I were to connect the resistor to a preamplifier, run the output of the preamplifier through a bandpass filter with 100 Hz bandwidth (say 2950 Hz to 3050 Hz), and then run the output to an oscilloscope sampling at more than 7100 Hz, I would see around 40 nV of RMS noise from the resistor (multiplied by the gain of the preamplifier) plus whatever noise is added by the amplifier.

That case is simple, and easy to understand because a bandpass filter sets the bandwidth.  How could I calculate the amount of RMS noise generated by the sample, when I am measuring with, say, the DC Voltmeter setting of a Keithley 2000 Multimeter? In this case, there is no bandpass filter (correct?). I do not have a good understanding of how voltmeters actually work.

Thank you!


texts: Homemade DC generator isn't outputting much voltage

texts:
I'm new to electronics and I've made a permanent magnet brushed DC generator, but when I spin it (using a drill to get high RPM) I get an output of less than 1 volt.

I've used it as a motor and it runs perfectly fine. I'm wondering if maybe it's the size of the magnets?


texts: 33883 H-Bridge Driver IC Intermittent Switching

texts:
I am using a NXP (freescale) 33883 H-Bridge gate driver IC to drive a simple H4 bridge circuit which is connected identically to that in the application schematic in the datasheet:

I am switching at 25kHz using bipolar modulation and maintaining a duty cycle of 50 as it is being switched over a transformer. I am controlling the input signals with a STM32F4Discovery, which have an amplitude of 3V, which is sufficient according to the datasheet. Here are screenshots of both the input and output signals to HS1:

25kHz HS1 input signal at 3V

GATE_HS1 output signal

GATE_HS1 output signal zoomed

You can see that it switches at the desired 25kHz for a short period of time before falling to zero and not switching again for another 3ms. I have used electrolytic capacitors for Clr_out and Ccp_out, but Ccp is a surface mount ceramic 33nF. Is there not enough charge stored in the capacitors to switch at the desired frequency? Is the 12VDC power supply which is rated at 1W not providing enough power to switch (33883 max power is 1.25W)?

Any help or suggestions would be greatly appreciated.

NB. Please ignore the pk-pk values on the oscilloscope, they are proportional to one another but not correct in amplitude.


texts: Issue with n channel mosfet switching with an isolated gate drive

texts:
I am trying to make a n-channel mosfet switch a load from a high voltage (250V). I am using the n channel C2M0280120D mosfet. the circuit looks something like below:

simulate this circuit – Schematic created using CircuitLab
so in this configuration, when ever the uC pulse rises (uC generating pwm between 5V and 0V), the Vgs on M1 would rise too. I measured the Vgs on M1 and its a pulse at 5V peak for 250ns. the datasheet states that maximum threshold voltage is 4V, so one would assume this would be sufficient, but when I measured the source of M1 (node S2) against power ground (pgnd), it is a pulse but with a peak of only 30 odd volts, instead of 250V.
I thougt it might be the case that the mosfet is not properly overdriven and it still is in its linear region, so I tried chopping a 15V supply to make the gate signal with a higher amplitude, this time my Vgs is a pulse with 10V peak. The circuit is shown below:

simulate this circuit
I also put a 1uF cap (as it is in the first schematic) just before the trasnformer, but I still get less voltage than expected on node S2. (waay less for that matter.)
so if this is not for the larg resistance between drain and source (since it is turned on properly) what else could be the issue?
Thank you in advance for your time.


texts:
I have a long single strand aluminum  wire. I want to use it with a microcontroller to detect water in the tank. I'll be putting one end of the wire inside water tank. Other end of the wire will be connected to a microcontroller to make decision if the first end of wire has come in contact with water. I know two wires can do this job fairly easily (by using one wire as Ground and the other for signalling) but I want to know how can I use a single wire to do the same job. Is it even theoretically possible? I want to detect just a 'zero' or 'one' corresponding to situations: wire 'is' and 'is not' in contact with water!

Edit: The tank and pipe are made of cement and stand on the ground.


texts: I have a portable mortor mixer that came with a on/off switch.  My mixing time is consistantly 3 minutes long.  I would like to know if it is possible to buy/make a toggle/rocker switch along with a timer that when the switch is thrown, the mixer will run for 3 minutes and then shut off and then the timer reset for the next mixing. This would help me from continously having to look at my watch while working durning batch mixes and help eliminate under/over mixing times.  The material I am working with is a bit messy so a timer with a turn knob would not last long after it got coated with material off my hands.  The motor on my mixer has a rating of 0.55kw,  absorbed current 9.2A, 115 volts, and frequency of 60 Hz.


texts: Interfacing two ICs with different thresholds

texts:
I'm trying to using an ADuM1251 (http://www.analog.com/media/en/technical-documentation/data-sheets/ADUM1250_1251.pdf) with an ATxmega32A4U (http://www.atmel.com/images/Atmel-8387-8-and16-bit-AVR-Microcontroller-XMEGA-A4U_Datasheet.pdf).

ADuM1251 (on side 1) has a voltage for low-level output of max 900 mV
ATxmega32A4U recognize as low-level a voltage of max 800 mV (@ 3.3V).

Of course they can't communicate each other!

I would be simple if the data line was unidirectional, but unfortunately I'm talking about the SDA signal that is bidirectional. Hence I cannot use a buffer.

I would use this solution, what do you think about?

simulate this circuit – Schematic created using CircuitLab

Does the side where I put the ICs matter?


texts: How can/does a mobile phone provide power to pen drive?

texts:
Mobile phones with USB OTG are not uncommon today. I am wondering that how can a battery operated device like mobile phone power a pen drive? From what I know, the power consumption of pen drive on 5V VBUS is around 100mA. The 5V can be derived from the battery voltage using boost converters, but are these converters so efficient and offer such a high current?

This question came to my mind when I came across a topic "connecting a pen drive to my android phone" when browsing for USB OTG.

Any thoughts?

Thank you.


texts: Why are these resistors between different nodes assumed to be parallel

texts:
I am given a circuit to simplify, and because I got stuck I looked at the solution, but it confuses me.
The circuit is the following:

simulate this circuit – Schematic created using CircuitLab
In the solution, the first step that is done is to combine \$R1, R3, R6\$ into an equivalent resistance \$Ra\$. The solution states the following:
$$ R_a = R_3 + \frac{R_1R_6}{R_1+R_6} $$
This means that \$R_1\$ and \$R_6\$ are assumed to be parallel.
Now I see that \$R_1\$ and \$R_6\$ indeed share the common node \$C\$, but \$R_1\$ lies between \$O\$ and \$C\$, while \$R_6\$ lies between \$C\$ and \$B\$.
At my knowledge-level, I would only assume these resistors to be in parallel if they shared common nodes on both sides, in this case if \$O\$ would equal \$B\$.
This is clearly not the case here. I guess I am missing some theory about resistors in parallel, or I am having some wrong assumptions.
How can it be explained that these two resistors \$R_1\$ and \$R_6\$ can be treated as parallel in this case? Any explanation, as well as references to some related theory is highly welcome.


texts: Current splitter/divider in nA/pA range possibilities

texts:
My objective is to realize a current splitter which could split current from a wire A in the range of pA, nA equally to wire B,C.

I was initially sure what this type of circuit would be called, but google redirected me to Current Conveyors page - https://en.wikipedia.org/wiki/Current_conveyor. (please correct if I am wrong here).

A CC-1 circuit is shown below:

I could correlate (X=A,Y=B,Z=C). However, I am not sure if it would support low currents (pA,nA).

Voltage Range: (0-3.3V)
Frequency Range: 1-100 kHz.
Loads: Current sensing amplifiers, each on B and C. (Assume Input is a gate capacitor of MOS and hence high impedance)
Reason on why I am doing this: To compare results of 2 current sensing amplifiers.

Any hint/guide on above will be helpful.


texts: How to measure high frequency with an oscilloscope without loading circuit down too much?

texts:
I am experimenting with building a high frequency common emitter circuit shown here. It operates at 144MHz and it should have around a gain of 4.
Here is the simulated circuit. I do not have any load resistor attached yet (knowing of course this will also divide up the gain.) I wanted to purely see what the circuit gain was without a load. Looks to be near 4 in the simulation. This would make sense since I have no emitter bypass and my RC/RE is around 4 - and the transistor Ft of this transistor should be able to go up to a gain of 6 at 144MHz, so my gain is within limits.

When I built this circuit in real life however, I think I had trouble measuring it. When I measure the output with  my oscilloscope the signal is actually attenuated and not showing gain. I suspect the problem isn't my circuit but my method of measuring.
I'm using a passive 200Mhz scope probe with a Siglent 200Mhz digital oscilloscope, with the probe set to 10x mode. I was also using the "short stub" ground "spring pin" and not the long, high inductance ground clip. But the signal measured on the output was showing an attenuation of almost .5x.
Someone had mentioned that my probe capacitance was probably loading the circuit down too much. My probe says in 10X mode it is around 18pf capacitance (if I'm reading it correctly.)
I was told that this capacitance will be across the load. Now, if I simulate that, you can see it does kill the output pretty hard.
Example in the simulation:

Notice now the red signal is the OUTPUT and it's actually attenuating! Losing gain. This is because the 18pf is loading down the collector. This looks almost exactly like what I was seeing in real life when I built the circuit.
Is there any other way I can attempt to measure the gain of this amplifier without loading it down too much? Should I just use a loop of wire on the scope probe and bring it near the base/collector?
I thought perhaps if I built an impedance transformer to connect to a 50ohm load, this still may not help if the scope is also acting like too much of a load, it will again cut the signal "in half."
Measuring the input and the output with the same probe also doesn't work to "compensate" for the loading because the input has a source resistance of 50ohms, (so it would at most divide voltage in two on the scope) whereas the collector output resistance is 500ohms - the loading effect will be much greater on the collector, giving me inaccurate results entirely.
Would an active probe help much? I think they can get down to 2pf but even that is around 2K or so impedance.  It seems you need special techniques to get accurate amplitude measurements at these higher frequencies - is there maybe some methods that I don't understand yet?
I know I saw an article where the author just uses a RG58 cable, strips it, puts on a resistor on the center lead to use as the probe "tip", and then uses a 50ohm tee on the scope side. I can't recall if it was a 50ohm resistor or a high megohm resistor they put on the tip.
I don't actually care about the voltage value being accurate since I'm measuring relative - I will be comparing output to input. I just need a way for the scope to not load down the circuit too much and I think my probe is doing that. (If the probe doesn't load down too hard that a relative measurement should actually be accurate.)
Any other ideas on how to possibly measure the output of this circuit "in real life" and know if it's working correctly?


texts: Explain how this LED driver circuit will work - is there any way to turn on the LED?

texts: Is there any way to turn on the LED in the below figure? You can apply different voltages at the diode input:


texts: Why shouldn't two AC sources be connected in parallel?

texts:
In data centers, servers usually have redundant power supplies, which makes it possible to plug them to two different UPS units. This way, the server continues to function correctly if one of the PSU goes down, or if one of the UPS units is shut down for replacement.

Some servers don't have redundant power supplies. In order to be able to still connect them to two UPS units (in order to be able to replace one unit without shutting down the server first), special devices called transfer switches are used: they can receive input from multiple sources, and provide power for single-corded equipment. A transfer switch is usually expensive and contains lots of electronics inside. Basically, automated transfer switches provide power from one source, and when they sense that the source is down, they fallback to another source.

What makes it impossible to have just a cable which would plug into two sources on one side, and to one server on another side? In other words, something like that:

but the other way around, i.e. not a cable with one male and two female connectors, but a cable with two male and one female connectors?

In other words, why is it possible to wire two DC power sources in parallel, but one cannot (or shouldn't) wire two AC sources in parallel? Is it because the waves may not be synchronized and could then cancel out each other? Or something else?

simulate this circuit – Schematic created using CircuitLab


texts: Mazzilli flyback driver mosfets keep failing

texts:
I've been trying to build a high voltage generator consisting of a high-voltage transformer and a Cockroft-Walton multiplier.

I have actually tried several different drivers to drive a high-voltage flyback transformer with no luck. My earlier attempts consisted of using an IRF2153 in a push-pull to drive the transformer like an SMPS.

I had minimal success with it but it seemed that I could not get the multiplier to increase the voltage to what I wanted.

I had planned on 15 kilovolts out of the transformer with a 5x multiplier but ended up with only 1.5 kilovolts after the multiplier. This was at about 20 kilohertz or so if I remember correctly. Anyway, I put it away for a while and gave it a rest.

I picked it up again and decided maybe I would go the resonant frequency route and try to drive the transformer with a Mazzilli driver.

I first tested it with a 12-volt 30 amp power supply for the entire source. At first, I had a little better luck with this and got probably a 15 kilovolt arc directly out of the transformer without the multiplier.

But when I connected the multiplier it didn't increase the voltage. I measured the voltage with it connected to the multiplier and apparently, it would draw too much current as the supply voltage would drop off.

So I decided to upgrade my DC supply.

I stripped an old microwave and rebuilt the high-voltage transformer into a step down transformer and rectified the output to 100-volt direct current.

For the gate voltage source, I have the hundred volt split with resistors for a gate-source voltage of 15.5 volts and a maximum output of 1.2 amps.

At first, I was following a schematic that I had found on the internet for the Mazzilli driver. But since I upped the input voltage to 100 volts I made a few changes.

I wanted to aim for a resonant frequency around 10 to 30 kilohertz. So I decreased the series inductance of L1 and the primary coil and also decreased the resonating capacitor down past the recommended .68 microfarad of the schematic to .5 microfarads in hopes that I could get the frequency a bit higher.

I also decreased the pull-down resistors from 10-kilo-ohms to 1 kilo-ohm because I wasn't sure if the voltage would drop off the gate fast enough at 20-30 kilohertz with the given parameters of the gate capacitance, gate resistors, and the 15.5 Supply voltage.

I've been smoking mosfet after mosfet with it in this configuration.

At first, I thought maybe I was overshooting Ids of the IRF460s I had, so I dropped the bucks on a pair of 500 volt 48 amp mosfet ( the numbers are on the schematic I'm going to include).

By my calculations and measurement estimates, I'm pretty sure I wasn't getting more than 48 amps out of regular household 15 amp breaker 120 VAC mains outlet stepped down to the RMS of whatever 100 Volt peak to peak VAC is.

From an earlier revision, I had the mosfet sandwiched between two peltier devices connected to respective fanned heatsinks because I thought the heat might be killing them.

So my question is this I suppose:

Even if my calculations of the resonant LC circuit or something is off and I have just straight current running through one of the MOSFETs in full-on shouldn't it still survive with a max Ids of 48 amps? Or do I have some sort of weird thermal problem in which the peltiers I have on there are actually transferring heat slower than the mosfets being directly connected to the heat sinks or something of that nature? ( Or am I missing something else completely?)


texts: Understanding a circuit for reading current passing through human bodies

texts:
I found on Instructables this circuit that is used to detect when two conductive pads are touched at the same time by a person (or, in that particular example, a chain of people).

Used in conjunction with this Arduino sketch it works perfectly, producing a stable value when the two pads are not being touched and different values proportional to the amount of contact when being touched:

void setup() {
  Serial.begin(9600);
}

void loop() {
  int r = analogRead(A0);
  Serial.println(r);
  delay(200);
}

It works perfectly for me but I don't understand what is the principle behind it and the article doesn't explain it.

Normally I would expect to have a voltage source present on one pad, and pull down resistor on the other pad, and the person completing the circuit.
However in this case there's no voltage source and one of the pads is connected to the analog reference pin instead.


texts:
I have seen in some text books that power converters produce harmonics in power systems.

How do power converters inject harmonics in a power system?


texts: Is Induction Wattmeter ,Energy Meter and Watt Hour Meter the same thing

texts:
I have a topic to study regarding Energy Meters. In the Syllabus it says Energy Meter, in the textbook it says Induction Wattmeter and one online reference  by IIT, says WattHour Meter/Induction Type Energy Meter.

Are all these things the same?


texts: Why does this crystal oscillator have a window?

texts:
I came across this device just now, and I can't think of any reason for it to have the window that it has.

This isn't just a cutaway display image, either; the datasheet specifically mentions that you should avoid getting glue under it to avoid cracking the glass:

So, what is the purpose of this window? Surely it increases the cost of manufacture, so it wouldn't be there without some good purpose, right?

I can't see it being for trimming, either, as what seems to be exactly the same part is also offered in a different package that doesn't have a window.


texts: Adding polarity protection to this circuit

texts: Anyone know the best way to add polarity protection to this circuit?


texts: If three identical charged capacitors get connected in series to each other (there is no battery). How would the charge distributes itself among them? Are they in series? Or two capacitors are connected in series and connected to the third one in parallel?


texts: Using the same potentiometer for two 555 timers

texts:
simulate this circuit – Schematic created using CircuitLab

I have two 555 timers hooked up and I want them their duty cycle to be controlled by the same potentiometer.

The second one has twice capacitance on pin 2 so I want to be able to get the second one exactly twice slower than the first one.

If you need clarifications just let me know and I'll try to do my best to help you understand my situation.


texts: Non-inverting UA741 opamp simulation on QUCS

texts:
According with instructions provided here https://www.youtube.com/watch?v=dBY1k5qK2w4 (in Spanish), I tried to simulate an inverting opamp configuration, but I couldn't figure out the right vout behavior, as reported in the second graph of the following figure.

Output results with a high DC term which is not supposed to be in the YouTube video, nor in the well known theory. Furthermore I expect an out of phase behavior of the output signal, as compared to the input one.
Is there anyone who could find out what's wrong here?

I did a second attempt
.
By the way, changing the opamp I've got this

That could mean the 741-opamp (TI) simulation software is not properly working on my QUCS.
With this other opamp the simulator seems to work reasonably well, but still there is an issue: I don't understand why there is a downward saturation on the output signal.


texts:
I'm trying to do some soldering on a PCB with a 20 watt iron and 1.2 mm 63/37 solder.  From what I can understand, I'm supposed to touch the iron (has been tinned) to the point and heat it up then touch the solder to the point and it should start melting.  But it takes like 20 seconds for it to heat up enough to melt that way instead of like 5 seconds in the videos I see.  I end up having to touch the solder to the iron and try to let it flow on to the board.

Would 0.8 mm solder work better?