texts:
I just received the following breadboard in a electronics starter pack I purchased.

I am a little confused in how I would go about prototyping on this board, all the tutorials I have read state that the breadboard should have a positive and negative  input on it. But it appears this one doesn't.

Could anyone help clear my confusion?


texts: How to design a transimpedance amplifier that can adjust to large voltage swings?

texts:
I am making a photodiode sensor based on one show in the image below which I got from this research article. The problem I run into with my photodiode sensor is that variations in sunlight create amplitude swings that are too large. The circuit shown claims to be able to solve this issue.

How does this sunlight adjustment work, and what is this type of circuit called?


texts:
In Induction motor theory the term slip is used as normalized relative speed of the rotor to the synchronous speed and it depends on the physical rotational speed of the rotor.

Is there any special benefit of not using the physical observable rotational speed in the formulas and instead invent another special term 'slip' to be used in the motor modeling formulas?

Will i lose any generalization if i convert the formulas from the 'slip' parameter to the rotational speed parameter?


texts: How to easily make a ground plane in Altium 19.1

texts: Does anyone have any ideas on how to make a ground plane in Altium 19.1? I have seen some guides but they appear to be in an older version of altium. I am also very new to PCB design and I know next to nothing. Any help is greatly appreciated.


texts: Nios II system generated by Qsys looks awful (All pin are at one side). Can we make it look better?

texts:
I have tried Quartus 16.0 and 14.1.
Both of them generate Nios II system that looks very awful as shown in the figure below.

Is there any way to make it look better like the previous version as shown below.


texts: Why isn't there a potential difference across a disconnected diode?

texts:
I know this question sounds silly, as if there was a potential difference a current would be created when the terminals are connected together and this would mean energy has come from somewhere.

The reason I ask this though is that from my understanding of the depletion region and built in potential of a diode it seems like if you connected a voltmeter across the whole diode it would show the value of the built in potential.

This is explained in the image below:

At first, electrons flow from the n type to the p type because there are a higher concentration in the n type, and holes do vise versa. This is called the diffusion current. The first electrons and holes to cross the pn boundary are the ones which are closest to it; these carriers recombine when they meet each other and are then no longer a carrier. This means there is a depletion region of no carriers near the pn boundary. because electrons have left the n type material, and holes have left the p type material, there is a surplus of positive and negative charge on the n and p side of the pn boundary respectively. This causes an electric field that opposes the diffusion current, and so no more electrons or holes cross the boundary and combine. In short, only the electrons and holes near the boundary combine, because after they have done that an electric field is formed that prevents any more carriers from crossing. The current due to this electric field is called drift current, and when in equilibrium this will equal the diffusion current. Because there is an electric field at the boundary (pointing from the positive charge to the negative charge) there is an associated voltage. This is called the built in potential.

If you sample the electric field at each point along the diode from left to right, you would start with 0 in the p region because there are an equal number of protons and electrons. As you approach the depletion region you would see a small electric field pointing back towards the p region, caused by acceptor impurities which now have an extra electron (due to recombination) and therefore now have a net negative charge. This electric field would increase in strength as you get closer to the boundary, and then die away as you get further away.

This electric field means there is a voltage, as shown in graph (d). The p side is at an arbitrary potential, and the n side is at a potential higher than this because there is an electric field between them. This means there is a potential difference across the depletion region; this is known as the built-in potential.

But why when I connect a volt-meter across the whole diode will I not see this built in potential?


texts:
I know that a NOT gate always inverts its input.

When the input is "ON" I can imagine the gate stopping the flow of current.

But how does the gate generates flow of current when the input is OFF?

Please could you explain how this happens as simply as possible, I'm new to electronics ;)


texts: Lead acid battery boiling during charging: this is bad, right?

texts:
I'm an electrical engineer who could use some help understanding lead acid batteries.

I recently bought an old motorcycle and charged the battery on my trusty automotive style battery charger after it lost charge. After several hours, the water was boiling inside the battery. I'm fairly certain the battery is relatively new and the water level was correct the last time I checked. I didn't have my multimeter at the time so I didn't take any measurements, but the battery is 12V and charger was set to 10A.

Is it normal for the water to be boiling?
Is my charging current set too high?
Can permanent damage result from boiling?
Is this the reason they must be topped off with water from time to time?

Thanks!


texts: Can I connect two outputs to supply more voltage to speaker?

texts:
http://ruggedcircuits.com/html/ancp01.html

I have a very basic electrical question.

I cant use two Outputs and have 10 volts?I am trying to figure out how to put out different voltages to a basic speaker to make noise.


texts: v-usb with default arduino bootloader on ATMega328

texts:
I've been trying to figure out how to use v-usb on an ATMega328P but pretty much all the tutorials I've found are for ATTiny or use the ATMega328P but use a modified bootloader. I don't actually care at all about being able to program the chip over this USB connection and would rather just use the FTDI connection. I just want to have USB HID capability once the sketch starts.

Does anyone know how to use v-usb and still have complete compatibility with Arduino and use its default bootloader??

Edit: The bootloader issue may be moot. It may just work with the default. In that case, great. But I would still love to be pointed to something that shows exactly how to setup the hardware and firmware to get v-usb working on an ATMega.


texts: Schematic Critique - ATMEGA328P & VS1063

texts:
My knowledge in PCB design is very limited, so I've been trying to learn as much as I can on my own. Some feedback on my first design would be incredibly helpful!

Description

ATMEGA328P "A" is supposed to receive serial commands via USB, output RGB LED data through the two LED ports and send commands to ATMEGA328P "B" via I2C.

ATMEGA328P "B" is supposed to read MP3 files from an SD card via SPI, and send data to VS1063 to decode which plays audio through AUX jack to external speaker/headphones.

Both ATMEGAs are TQFP. Connected RGB LED strips are 5V.

Questions

Can pins like CS, BSYNC, and DREQ on VS1063 be connected to any GPIO?
Do I need the linear voltage regulators for 3V3 and 1V8? Or just voltage dividers?
Can ATMEGA328P “B” read MP3 from SD then send data to VS1063 on the same SPI line?
Can I leave unused pins floating? Do I connect them to ground?
Can I connect I2C lines of ATMEGAs directly?
What should I keep in mind when designing the PCB?

Any additional feedback is greatly appreciated!

Datasheets

ATMEGA328P Datasheet
VS1063 Datasheet
FT232RL Datasheet


texts:
There are two horizontal connectors in this illustration, one with four pins  and one with six pins.

What are these connectors called?


texts:
I am designing a basic 100kHz active bandpass filter using opamps (LF353). I am only interested in receiving the 100kHz frequency (might drift a few kHz) from my input signal. I have used a basic Fliege bandpass filter, because it has low component count, simple, uses only 2 opamps and has adjustable frequency and Q control.

Parameters:
V(in) = 2v(p-p) sine wave 100kHz (for testing)
Bandwidth: 20kHz
f1 = 90kHz
f2 = 110kHz

Any suggestions for improvement or new designs?
I have no restrictions except that I would like to use no more than 2 opamps, preferably LF353.

This is my design:

And the Bode plot:


texts: MC34063 9v to 5v doesn't give expected voltage

texts:
I'm trying to make a 9v to 5v step-down voltage regulator using MC34063
I used an online calculator for the values and assembled this schematic for stepdown config:

The calculator gave me these values (for Vin=9, Vout=5, Iout=750, Vripple=1, Fmin=100):

Ct=257 pF
Ipk=1500 mA
Rsc=0.2 Ohm
Lmin=13 uH
Co=1875 uF
R1=1k R2=3k (5V)

I used a 1800uF capacitor and 10mH inductor but on the output I'm measuring 0.8V instead of 5v with voltmeter
What I'm doing wrong?


texts: Why doesn't this diode conduct in a boost converter?

texts: It seems like current should pass through the diode even in the "on state" because the current is flowing in the right direction. Is it because the current will be too low because of the closed switch "stealing" too much?


texts: Step-down DC/DC converters 0 V output voltage

texts:
My friend designed a 6V to 3.3V power supply using XC9235 Datasheet
But It didn't work, he gets 0 V at the output of the DC-DC converter. I thought the problem in CE pin but I couldn't explain why. (I usually use a voltage divider not a pull-up resistor in analog circuits)


texts: Neon-lamp type tester glows on gooseneck lamp adjustable shaft

texts:
I have bought several adjustable gooseneck shafts with the intent of creating lamps of my own. I have put a brand new 2x0.75mm^2 cable through it and attached a simple E27 light fixture. I have noticed, however, that when I plug the cable to the socket and test if there is a potential difference on the adjustable shaft, the neon lamp inside the tester does light up. This is concerning, because the tester neon lamp has a declared range of 100V ... 500V AC.

An old-type analog multimeter seems to show millivolts of RMS on the shaft, while a relative of mine tested it using an oscilloscope and got peaks of around 30-40 volts.

What is the phenomenon that I have encountered, and is it dangerous to a so-called end user?


texts: USB devices not working if I solder them through wires

texts:
When I'm trying to connect a USB device like a USB WiFi dongle or Pendrive with a homegrown USB breakout by soldering 4 wires to them, it's just not working.

I'm running Ubuntu and getting errors like this,

hub 1-1:1.0: unable to enumerate USB device on port 3

Above line is not the exact same error message, I can post them if needed.

But low speed USB devices like a USB AVR programmer is working fine.

The ehci-pci kernel driver is being used for both high-speed and low-speed USB devices.

So what's the problem with high-speed devices ? Is there any way to fix this problem ? Probably extra capacitance and inductance from the DIY breakout is violating high-speed USB specification, am I right ?


texts: Why is serial output from shift register offset from others?

texts:
I was debugging my circuit that uses TI SN74HC595 shift registers, which I daisy chained. I transfer data to she first shift register using an Arduino, and SPI library as it is faster than bit-banging.

Here is what I have on the input of the first shift register :

Channel 1 (yellow) is the CLK pin of the Arduino, going to the SRCLK pin of the shift register
Channel 2 (blue) is the MOSI pin of the Arduino, going to the SER pin of the shift register

Using SPIMODE0, ie. data is read on the rising edge of the clock, we can see this picture seems correct.

When daisy chaining, I connect the Serial output Qh' from the first shift register to the SER pin of the second shift register, the CLK remains the same, and is connected to both shift registers.

Here is what I have for the inputs of the second shift register, fed from the Serial output of the first shift register :

Now we can see it's all offset and it seems data is now read on the falling edge of the clock. I've checked the datasheet and it seems it is a normal behaviour, as shown on the timing diagram below (Qh' is slightly offset):

Now the most confusing part, is that it works, and the second shift registers has the correct data. I don't get why, so I would appreciate any explanation on why Qh' has been designed to output data which is offset from the clock, but nevertheless works when daisy-chaining.


texts:
I have a quartz crystal and I am connecting it to a microcontroller's EXTAL and XTAL pins.

Can I connect it anyway?
Do the crystals have polarity?
In EXTAL and XTAL, which is input and which is output pins?


texts:
I have 3.3V switching power supply. I want to power 3W RGB LED.

Forward voltages are: 2.2~2.8V(Red), 3.0~3.8V(Green), 3.0~3.8V(Blue)
Current: ~350mA

Should I use current limiting resistors? As I understand, for Red I need to drop 3.3V to under 2.8V and the resistor is necessary, but how to be with Green and Blue? Can I connect them directly?

Please explain.

Thanks.


texts: I'm trying to evaluate the quality of an 8b/10b encoded data stream (Gigabit Ethernet, 1.25 gigabits/sec). Without doing clock recovery from the data stream, I want to measure jitter (et al) with a plain oscilliscope. Is there any 8b data stream I can send which ends up as a regular square wave in 10b format? I don't care it's divided or uneven duty cycle, as long as it's a regular grouping of 0's and 1's.


texts: Can wireless radios be joined by direct wire connection?

texts:
I have an off the shelf device that uses 802.11 wireless for connectivity and nothing else. My system makes heavy use of wireless communications and I would like to incorporate this device into my system without further degrading the RF environment.

Is it possible to create a wired connection between the antenna connector of my device and the antenna connector of another device, and avoid poluting the RF environment with the communications between these two devices?

If so what are the requirements (line impedance or shielding, etc)?


texts: Can current be drawn from ground in a SWER transmission setup?

texts:
I am almost certain that this is a ridiculous question, but cannot figure out why it wouldn't work.

From what I understand, current from the electrical station is distributed to houses through power lines, then, to complete the circuit, returns to the station through the earth. Is there anything stopping someone from burying two electrodes of a simple,  low-impedance element deep enough into the ground that the current will travel through it in its path back to the power station?

Low impedance bulb

 |---@@@@---|
 |          |
 | gnd      | gnd
_|_        _|_
 _          _
 -          -


texts: Desoldering speaker cable in order to replace with fresh and longer wire

texts:
I have the following speaker crack oppened and showing its guts:

What I want to do it is to place a fresh wires for audio IO becasuse in these wires exist a 3.5mm audio jack as audio IO.

My problem is on how I can desolder the Audio ΙΟ wire without desoldering the rest of the wiring. For desoldering I will use desoldering braid. (Seemed easier for me instead of solder sucker.)

Also the soldering wire will also be 0.3mm with flux.


texts:
The master slave D flip-flop, is it used to prevent glitches in the data signal?
Say, when there is a transition between LOW -> HIGH or HIGH -> LOW in the data signal when clock signal is at level ?


texts: Best way to reduce initial current drawn by fan?

texts:
I need to kinda soft-start an array of fans, all connected to one reference PWM. The problem is our fans at top speed can roughly draw 2.5 times as much power as our DC-source can handle (on-board custom PCG for an inverter not easily replaceable). And of course, they also draw a lot of power during start-up.
We got 4-wire fans, so I plan to use a PWM to control their speed, this works fine after start-up, but during the start-up the fans will draw a lot more power even when setting the duty-cycle to 10%. Are there any tricks I can use? Does the PWM frequency affect the start-up? Due to small differences between the fans (6 in total) they also won’t start synchronous, this affects changes in the duty cycle too, their speed will vary for a couple of seconds (also shows in power consumption).
Fan details:
PWM 10-100% (Max for our dc-source is around 55%)
Fan-PWM-Frequency: 1-30kHz
So basically what is better in such a case a high or low frequency PWM? Also have you any recommendations at how fast I should change between duty-cycle levels?


texts:
I am using stm32f103 and TI's TCA9539 and TCA6408A Port extender.Both of them support 400-kHz(I2C Fastmode) and 100-KHz (I2C standard mode) clock frequencies. I use 3 TCA9539 and 1 TCA6408A;here is my Schematic diagram:
I use STM32CubeMX and here is the configuration and code:

I tested both 400kHz mode and 100kHz mode.

HAL_GPIO_WritePin(TS0_RESET_GPIO_Port,TS0_RESET_Pin,GPIO_PIN_SET);
HAL_GPIO_WritePin(TS1_RESET_GPIO_Port,TS1_RESET_Pin,GPIO_PIN_SET);
HAL_GPIO_WritePin(TS2_RESET_GPIO_Port,TS2_RESET_Pin,GPIO_PIN_SET);
HAL_GPIO_WritePin(TS3_RESET_GPIO_Port,TS3_RESET_Pin,GPIO_PIN_SET);

//...
while(1){
  uint8_t test_data[3] = {0x08,0,0};
  HAL_I2C_Master_Transmit(&hi2c1, 0X75<<1, test_data, 2,10);
  HAL_I2C_Master_Transmit(&hi2c1, 0X20<<1, test_data, 2,10);
}
//...

According the datasheet,since I connect the address pin of TCA6408A,the address of it should be 0x20(7 bits);and three TCA9539 's addresses should be 0x74,0x75 and 0x77. So I sent the test data in the above code.

However,only the TCA6408A responses(ACK),and the TCA9539 doesn't.I change the different addresses but it doesn't work.Here is the wave.

TCA6408:

TCA9539:

They are all similar devices of TI. I think the only difference between them is that they have different GPIO bits, so I wonder why they have different situations.


texts:
For a pet project of mine, I like to generate power from a rotational motion. (similar to bicycle tire turn). I want to build the system without a battery where as the tire turns I generate enough electricity to turn an LED. It is ok if the LED is dim in slower speeds, my application will only cover the high speed cases.

What is the best approach to this?

I do not want a magnetic coupled system, this should be one piece.

update
The device is for bicycle, it is an active reflector. I wanted to use the rotation of the bicycle and light an led from the generated energy. T I didn't want a two point solution where I put a magnet somewhere and use that to generate energy. Just use the rotational motion. Some piezo material that would accumulate energy and use to pulse a led for a few msec every second.


texts: What should be the output resistance of this source with series diode?

texts:
Below shows three sources with open terminals:

simulate this circuit – Schematic created using CircuitLab

In Figure 1 if we want to calculate the output resistance, according to the linear circuit theory we short the voltage source V1 and look into the source and calculate the Thévenin equivalent. Hence for Figure 1 the output impedance is simply 100 Ohm.

What should be the way of thinking for the output impedance/resistance for Figure 2? If we know the current-voltage characteristic and the dynamic resistance of the diode D1 what does that indicate? Because if we short V2 and apply voltage to its terminals, because it is reverse biased the current will be close to zero and we will experience almost infinite resistance.

Does that mean in Figure 2 the output resistance is infinity? Or it is the dynamic resistance? How should be the way of thinking to derive the output impedance/resistance for the Figure 2 source?


texts: How to compute voltage limits in n-MOS transistor?

texts:
I have come across two different ways of computing the \$V_d\$:

In the first one, the DC bias point is considered to not be affected by AC, so by superposition, $$V_d = V_{d;V_{AC}=0} + V_{d;V_{DC}=0} $$, where $$ V_{d;V_{AC}=0} = V_{dd} - I_{d;DC}\times R_d$$ and $$ V_{d;V_{DC}=0} =  -2k(V_{gs}-V_{t}) \times V_{gs; {AC}}\times R_d $$
In the second one, first the maximum and minimum values of the sensor's voltage is computed, and then the maximum and minimum \$V_d's\$ are computed as $$ V_{d} = V_{dd} - I_{d;DC}\times R_d$$, where $$I_{d;DC}= k(V_{gs}-V_{t})^2$$

Both methods give slightly different results. Which is more correct?


texts: Function to describe alkaline battery voltage under constant current / load

texts:
Introduction

Commonly used alkaline batteries (Duracell etc) have a pretty interesting discharge curve. For example, an AA duracell has the following voltage characteristics under constant load,

and constant current:

(http://www.procell.nl/pc1500.pdf)

The battery voltage is also affected by temperature. For example, from some of my recent tests the fluctuations correspond roughly to the time of day (temperature) they were measured. If the batteries were hotter, they measured a higher voltage.

Question

Before I try to do this myself, does anyone know a mathematical function to describe the voltage of an alkaline cell under constant current and/or constant load? An added bonus would be a function that takes temperature as a parameter. Of course a linear approximation often suffices, but I'm after a better fit.

The purpose is to fit the curve (representing the function) to battery voltage readings taken from a device under test. This will enable predictions of battery life, and battery life at different temperatures.


texts: CMSIS - Peripheral Definitions - Structs With Unions Syntax?

texts:
I've moving over from 8 bit bare-metal registers, and having to learn some new C Kungfu to wrap my head around the CMSIS Core approach.

I have a snippet of code here from a Peripheral Access Layer from a ARM Cortex M vendor. They create this SN_WDT_TYPE structure, which you can use to set watch-dog timer registers using their notation.

Why do they use the unions? I haven't seen this kind of syntax before.

If you use unions to create structures like that, do you they go several layers deep with pointers? Memory management with the unions? Is there some C syntax thing I'm missing here?

This might be CMSIS specific, does anyone know what the ": 1" is doing in those struct declarations...? I know the __IO ties back to some CMSIS definition of read/write.

ARM'S CMSCIS PERIPHERAL NAMING CONVENTION -- This example code doesn't seem to confirm too gracefully...

/* ================================================================================ */
/* ================                     SN_WDT                     ================ */
/* ================================================================================ */

/**
  * @brief Watchdog Timer (SN_WDT)
  */

typedef struct {                                    /*!< SN_WDT Structure                                                      */

  union {
    __IO uint32_t  CFG;                             /*!< Offset:0x00 WDT Configuration Register                                */

    struct {
      __IO uint32_t  WDTEN      :  1;               /*!< WDT enable                                                            */
      __IO uint32_t  WDTIE      :  1;               /*!< WDT interrupt enable                                                  */
      __IO uint32_t  WDTINT     :  1;               /*!< WDT interrupt flag                                                    */
           uint32_t             : 13;
      __O  uint32_t  WDKEY      : 16;               /*!< Watchdog register key                                                 */
    } CFG_b;                                        /*!< BitSize                                                               */
  };

  union {
    __IO uint32_t  CLKSOURCE;                       /*!< Offset:0x04 WDT Clock Source Register                                 */

    struct {
      __IO uint32_t  CLKSOURCE  :  2;               /*!< WDT clock source                                                      */
           uint32_t             : 14;
      __O  uint32_t  WDKEY      : 16;               /*!< Watchdog register key                                                 */
    } CLKSOURCE_b;                                  /*!< BitSize                                                               */
  };

  union {
    __IO uint32_t  TC;                              /*!< Offset:0x08 WDT Timer Constant Register                               */

    struct {
      __IO uint32_t  TC         :  8;               /*!< Watchdog timer constant reload value                                  */
           uint32_t             :  8;
      __O  uint32_t  WDKEY      : 16;               /*!< Watchdog register key                                                 */
    } TC_b;                                         /*!< BitSize                                                               */
  };

  union {
    __O  uint32_t  FEED;                            /*!< Offset:0x0C WDT Feed Register                                         */

    struct {
      __O  uint32_t  FV         : 16;               /*!< Watchdog feed value                                                   */
      __O  uint32_t  WDKEY      : 16;               /*!< Watchdog register key                                                 */
    } FEED_b;                                       /*!< BitSize                                                               */
  };
} SN_WDT_Type;


texts: How Verilog decides upon simultaneous events

texts:
Say we have a function, simple as f(x) = x. Say we have a clock that ticks every 20 nanoseconds, and say we change x as we wish.

Say there is a clock tick to come, at t = 20ns exactly (whatever that means). Say x had been 0 from the t = 0ns since, and we somehow change the x into 1 at again exactly t = 20ns.

Now describe this scenario in Verilog. The question is, what would f be at t = 21ns?

Here are the Verilog codes I had written, along with the screenshot from Xilinx ISim simulation window.

The circuit.v

module circuit(f, x, clk, rst);

    output f;
    input x, clk, rst;

    wire d, q;

    d_flip_flop flipper (q, d, clk, rst);

    assign f = q;
    assign d = x;

endmodule

The d_flip_flop.v

module d_flip_flop(q, d, clk, rst);

    output reg q;
    input d, clk, rst;

    always @(posedge clk, posedge rst)
    begin
        if (rst)
            q <= 1'b0;
        else
            q <= d;
    end

endmodule

And I test these with this tester.v

module tester;

    reg x, clk, rst;
    wire f;

    circuit uut (f, x, clk, rst);

    initial clk <= 0;
    always #10 clk <= ~clk;

    initial
    begin
        x <= 0;
        rst <= 0;

        rst <= #2 1;
        rst <= #4 0;

        #10 x <= 1;
    end

endmodule

And here's the waveform I get:

Is this a defined behaviour of Verilog to perform so? If yes, how does it decide upon what should come first in such circumstances?

I have been told by the assistants of the course that what I should really be seeing is actually the opposite, for sure, and I must be doing something wrong if I am seeing otherwise. I would like to know what I am doing wrong, I need help, and they don't provide me this particular help. Could anybody here maybe help?


texts: Convert MP3 recording of data casette to serial data

texts:
I have a retro EMCO F1P CNC machine with a matching M1 controller that comes with mini data cassettes containing the "Machine State Data" which must be fed into registers of the controller before operation.

Unfortunately my cassette is missing, but I have managed to find this MP3 recording of it online.

The machine also supports RS232 input of this data. So my question is thus, is the format of the audio in the mp3 recognizable, and would it be possible to deduct simply by looking at the audio in the MP3 to determine how to format the equivalent RS232 data?

Some hints are to be found on page 9 in the service manual of the machine:

  RS232c interface (V24 and 20mA), 150 - 2400 bd tape recorder (Phillips
  MDCR) 600 signs/sec. (corresponds to 6 kbaud)

This way I would avoid having to find equipment to record the MP3 to a cassette, instead I could simply craft a binary file to send over TTY from my laptop, and even better, write a small software that would craft this file on the fly based on parameters selectable from an UI.

EDIT: Here is a picture of the cassette player:


texts:
I got tlp test data and found that the current at vertical line means leakage current.

But I don't understand the method how does the tlp-test measure the leakage current.

I tried to search the method, but I failed.


texts: Any ideas on how to implement a USB man in the middle circuit?

texts:
I'm looking for an easy way to get in between of a HID USB communication.
Can it work by multiplexing a single usb port on an AVR?

Thanks!


texts:
Is it possible to test the pins of a transformer using the resistance part of the multi-meter?  I was testing a 6 pin transformer, and resistances measured

4.1 Ohms between two pins connected to a copper winding
4.2 Ohms between two pins I think are connected to each other
952 Ohms between a pin in the bottom of the transformer, and a stray wire

The bottom pins, closest to the table are connected to the copper winding.  The two pins closest to the magnet  are connected to each other.  The black stray wire is connected to the lonely wire in the bottom.  Why is there since a huge resistance in the output of the transformer?


texts: Mq4 sensor doesnt detect natural gas but detects cigarette lighter gas only!

texts:
I am working on a project for detecting natural gas of cooking stoves, I have tested several sensors but the mq4 sensor was the one that worked fine.

Now after about one month of using the sensor i bought, it is no more detecting natural gas from the stove and only detects the cigarette lighter gas!

I have two and they both showed the same problem after more than month period.
I have tried changing the potentiometer several times after this error occurred,unfortunately they didn't respond.

What is the problem?
Thanks in advance.


texts: Is this a good explanation for a start/stop/retain relay circuit?

texts: The control circuit is in series with the coil of the motor and the motor works when the start button on the control circuit is closed. The start button is in series with the pilot coil meaning when the start button is closed the current goes through the pilot coil so that the contact closes and the motor starts. When the start button is not pressed the motor stops.


texts: Unknown resistive disk in parallel with AC motor capacitor

texts:
This assembly is the motor connector for a Grundfos U15-38SPA circulating pump, which interfaces to the capacitor (2uF) and power supply (220VAC).

Between the two brown wires leading to the cap is a black plastic holder with IDC spikes to connect a 1N4007 rectifier and unknown disk of 166 ohms resistance in series across the leads.  (The leads have been removed from the spikes, and the holder top is set aside.)

What is this disk all about?

Best I can figure is some sort of thermal device.  Perhaps its resistance goes up (or down) after current flows for a bit.

Finally, note that the black plastic carrier is a stand-alone unit that can be snapped in place over any leaded capacitor.


texts: Measuring RMS power output from audio amplifier channel

texts:
I am looking for a simple way for getting the RMS power output of an amplifier channel set to some arbitrary gain. I want this in order to find the maximum level I can safely set the amplifier at for a speaker with a given continuous power rating.
Edit to add more context:
I often don't get to choose the gear I work with, so there are often mismatches between amplifier power and speaker maximum power handling. I want to find the maximum I can set the amplifier gain at without blowing speakers.
The volume control will be at signal source. I want to know that even if the signal gain is set to 0dB, the amplifier's volume will ensure the speakers will not be blown. If it helps, think of it as a theoretical exercise.
I came across this youtube video  that suggests that by measuring the resistance of the disconnected speaker, and AC voltage across speaker terminals (while outputting to speaker), you can calculate RMS power from the equation \$=\frac{^2}{}\$, but all the other articles and videos I found suggested using a clamp meter to measure current, plus a regular multimeter to measure V, and calculate P from: \$P=IV\$
My question: Are both methods equally reliable? Are there practical considerations besides the fact that method 1 requires disconnecting the speaker and method 2 requires an extra measurement device?


texts: Altium bug: White trace outlines on layer wont go away

texts:
My PCB in altium is presenting with a "ghost" of previous traces. They occur only on the one layer. Deleting the surrounding traces does not remove them - moving the components does not move or remove them.

How can i get rid of these glitches? Also where did they come from??

Last thing i need is these ghost traces impacting exported gerbers!


texts: Reverse polarity protection and enable function

texts:
The purpose of the schematic is, on the one hand, to provide reverse polarity protection. On the other hand, the switch has the function of enabling the flow of current to the load.
These are the characteristics in a summarized way:

Battery: 1 cell 3.7V (4.2 to 2.7V)
Maximum current: 1.5 A
Q1: DMG2302UK-7
Q2: SI2399DS-T1-GE3

Would this schematic work? If so, how could it be improved?

simulate this circuit – Schematic created using CircuitLab


texts: Large voltage spikes on charge pump output

texts:
I'm prototyping a small charge pump out of a NE555 timer. However, I'm getting some spikes on the output along the rising and falling edges of the timer.

Channel 1 is the output signal with AC-coupling. Channel 2 is the output from the NE555 chip.

Here is the basic schematic I'm using. I've left out the 555 schematic and simplified it with a square wave generator in the schematic. The diodes are both 1N5819s. I'm not driving a load.

What could be the root cause of this issue? The spikes seem to be pretty significant being about 100mV.

I initially used 1N4004G diodes and thought that it could be reverse currents from the diode recovering from the change in current direction but switching them to 1N5819s didn't seem to help.

Are the large spikes caused by the fact that this whole thing is being set up on a breadboard at the moment? If I shortened the leads and built this on a prototyping board, would it help?


texts: Difference between .MACRO and .SUBCKT in SPICE

texts: What is the difference between .MACRO and .SUBCKT in SPICE simulators, such as HSPICE?


texts: In my dc to dc buck converter(0 to 17V - 12v), when i connect a load ,converter output voltage decreases to 1V

texts:
I try a buck converter of variable input(0 to 17) to 12V. when i connect a load with very small resistance , voltage decreases.if load increases , converter voltage looks constant.

what happens if i connet a battery in real time ?


texts: Need help interpreting a Energy Meter datasheet

texts:
I am reading this datasheet for an energy meter, to start understanding how this market works.

A friend of mine wants to make a test in a small office building to see if it pays having one of these and he asked for my help, and finally I have an excuse to get to know this kind of devices.

I am leaning towards that meter, good price (around 170eur ~ 200USD), but I don't know what CT clamp to buy for it.

I want one clamp for 100A, 200A and around 600A or more.

But looking at the datasheet:

I am not able to tell which CTs to buy. So far the meters I've studied they have something like primary coil 100A -> 5A secondary or primary coil 100A -> 1A secondary, primary coil 100A -> 0.333A secondary, primary coil 500A -> 10A secondary, and so on. But this one is different...

For this meter I am not being able to interpret what's the maximum secondary coil current it can handle, and consequently nor the primary.

Can you help me with some examples covering their ratios (1.0 to 99.9/ 100 to 999 / 1.00k to 6.00k etc.?

Thanks!

PS: I know the dangers of high voltages and current, and no, I am not going to handle the installation of these devices, nor touch electric boards, etc.


texts:
A signal that swings between -1V and +1V must be amplified with a gain of 2 using MCP602 and then biased by +2.5V, so it eventually swings between 0.5V and 4.5V.

The amplifier only connected to 5V, GND and an input of 2.000V gives an output of 4.034V which is OK. However when it's VDD and VSS pins are connected to 5V and the middle of the voltage divider (+2.5V when not connected to opamp), its output becomes 3.611V and the middle of the voltage divider becomes 3.609.

Is the opamp being biased the incorrect way? If not, how can the circuit be changed?


texts: Proper way of connecting logic GND / power GND on MOSFET driver

texts:
I am tring to build half bridge using IR21844 mosfet driver, i have read datasheet and design tips and some of the topics in this forum. The one thing i still cannot get is the separate GND pins between logic and power.

I Qoute from an article:"The IR21844 has two different grounds, one for logic and one for power. Hypothetically, they are allowed to float 5 volts apart, providing some semblance of isolation between logic and power."

I have also confirmed this by looking into deisgn tip 97-3 page 2 paragraph 4 called Vs undershoot.
Design tip 97-3

I get that the 2 pins Vss and Com are should be connected ( becuase this is a non isolated driver) but how and where ?

My proposal now to is not to connect them at the PCB under the IC instead connect the Vss pin to micro controller logic GND and Com pin to lower Mosfet Source and let the 2 GNDs meet at the battery.

I am attaching my sample circuit schematic which is simplified to the maximum to show only the necessary items please provide your insight and correct me if i am wrong.

I also have doubt if a capacitor should be required between pin 7 (15v) and pin 3 (Vss) as the datasheet show but doesnot explain.

IR21844 dataheet

thanks in advance


texts: INA126P gain is exactly double what it should be

texts:
I'm using an INA126P, 8-dip chip on a breadboard.  I'm using +/- 15V supply, and the input I'm trying to amplify is a voltage divided input.  In the diagram below (sorry for the terrible quality), V1 = 0.3V (from a DC power supply), R = 47K.  No matter what I use for my gain resistor, the gain is actually double.  For example, my input voltage should be approximately 0.3mV and, without a gain resistor at all, I should see a gain of 5 to get me 1.5mV.  However, I see 3mV.  When I set the gain to, say, 13, using a 1K resistor, I expect to see 3.9mV but instead see 7.8.  I have tried a second INA126P and the same issue arises.

What might be going on?


texts:
I have designed a board and it can be supplied by USB and/or D-Sub connector. The board gets the 5V from USB or another board via D-Sub connector.

I have placed 2 schottky diodes to prevent reverse voltage between these 2 connectors in case of they are both connected.

This is the circuit:

USB 5V and connector 5V both enter diodes and they get connected as 5V on the cathode side of diodes. My first question is, does this circuit make sense?

I have supplied the board via USB and checked the D-Sub diodes anode voltage. It was same as cathode. Don't the diodes block the voltage? I placed them for this purpose.

I assumed there is a mistake on my PCB and tried the circuit on a breadboard.

This is the first circuit I have tried:

I have read 4.9V on the cathode of diode.

This is the second circuit I have tried.

I have supplied 5V from the cathode of diode to check does it allow reverse voltage. I have read 5V on the probe.

After that I have reversed the diode to see what happens.

I do not understand why it behaves this way. This is the datasheet of the diode.

What I was expecting was when I applied the 5V to the anode, I would see 4.9-4.8V on the cathode. This part is ok. If I apply 5V to the cathode, I should read 0V since diode won't allow any voltage/current to that way. Is there something wrong with my circuit or did I misunderstand the behaviour of the diode?


texts: Take the voltage out of a voltage divider with no distortion

texts:
In the (simplified) schematics below, I would like to measure the voltage at point A with an instrument that I have to plug at point B.

The problem is that if I simply add a wire between A and B, the voltage divider will change (from V/1000 -> V/100000). Is there a way to do that ? (a component, ...)

On the schematic, I drew everything I can't change (no control on), but else I am "free" to do whatever it needs.

EDIT Answers to a few questions :

I don't "manually plug" something to B. There is some sort of analog to digital converter circuit that is always there and a microcontroller that talks with it
V is 220V alternative (electricity "directly from the wall")
the real schematic is VERY BIG, and this is a simplified case that I also have been struggling with in other projects


texts: PLC to act as or simulate 4-20 mA transducer

texts:
I have a PLC Control system that measures a few 4-20 mA pressure sensors. Today we test these with loop calibrators on each channel.

I want to set up a PLC that simulates these pressure sensors so I can program a complete test, or simulation if you will, of the system.

The PLC system has these 4-20 mA modules:
http://www.bartec.de/homepage/eng/20_produkte/130_automatisierung/s_20_130_90_10.asp?ProdID=204#Docu

If I understand current loops correctly I need a passive 4-20mA output module (and of course I need zener barriers for the Ex/IS).

Question is that I havent seen any passive 4-20 mA output modules, at least not with Profibus or K-bus, and that makes me think that this might be a flawed idea. Anyone care to help me along?


texts: What does SWR and reflected power mean in terms of power actually dissipated in a load?

texts:
I'm struggling to understand the "meaning" of VSWR in the context of power delivered to a load.
Say I have a transmitter operating at 10MHz, a short (~1m) piece of assumed-lossless transmission line, and a load whose impedance is not well-matched to the line.
If I measure forward and reflected power at the transmitter, I'll see some reflected power due to the impedance mismatch. But I understand this gets reflected "again" at the transmitter back to the load and is eventually transferred to the load (it does not get dissipated in the transmitter). So for a lossless transmission line, what measurement is the power dissipated by the load? It is simply the forward power? It would seem like it's not the (forward minus reflected) power, so does that quantity (forward minus reflected) have any physical meaning?
Ultimately, I'm trying to measure the power delivered to this load at 10MHz, and don't quite understand  if I can just measure voltage and current and multiply them (accounting for any phase shift), of it I need to account for SWR and/or reflected power in some way...


texts: High and Low Side Driver vs. Half-Bridge Driver

texts:
Please excuse me for what I am about to say as this type of area is all completely new to me.

I am currently attempting to construct an H-bridge (which is a primer to my attempt in constructing a 3-phase bridge) using N-channel MOSFETs and a corresponding gate-driver to control the MOSFETs.  For the gate-driver ICs I was looking through the inventory of drivers that International Rectifier provides.  One thing that I can not seem to find adequate information is the difference between their High and Low Side Drivers and Half-bridge Drivers.

Based on what I know on how an H-bridge works, the source of the hide side MOSFET in one of the half-bridges is connected to the drain of the low side MOSFET.  In between is the connection to the load.

Following is an image of a typical connection of one of the High and Low Side Drivers from the IRS2106/21064 datasheet  and after that is an image of a typical connection of one of the Half-Bridge Drivers from the IRS2108/21084 datasheet.

From the High and Low Side Driver, the source and drain of the MOSFETs are not connected whereas in the Half-Bridge Driver the source and drain are in fact connected.  Besides the majority of the layout of the IC/pin connections between the High and Low Side Driver and the Half-Bridge Driver are pretty much the same, the connection from the high side MOSFET and the low side MOSFET is the only difference between the two.  From reasons obvious of motor control, the half-bridge driver is more ideal for this situation.

My questions are:

Is it possible to utilize a High and Low Side Driver in a half-bridge configuration?
If not, what sort of applications are High and Low Side Drivers used?


texts: Difference between TRIACs holding and Latching current

texts: I am reading wikipedia page of TRIAC. While reading, I got struck with holding and latching current definition. They look similar to me but the wiki says they are different. Find the wiki screenshot below:


texts:
Having this circuit and chronogram:

I have to complete the chronogram for Z1 and Z2.

This is what I have done:

I'm a bit confused about ini being 1... I thought that it meant that Z2 would reset, but apparently it's incorrect.

What am I doing wrong?

Thank you.


texts: Significant differences between CAN and RS485 regarding the physical layer

texts:
In comparing the physical layer of CAN and RS485, I am trying to find the advantages of either one over the other. I found out that they are quite similar. Both are good in terms of common mode rejection and both need protection against ESD and overvoltage. I found just one significant advantage of CAN over RS485 (regarding the physical layer) in which CAN has a fault tolerant mode which enables it to maintain the connection between CANbus nodes through just 1 data wire even though there is one data wire shorted or opened or both data wires are shorted together.

Away from collision avoidance and the message priority system that CAN has,

1. Does RS485 have the same fault tolerant mechanism?

2. Are there any other important advantages or differences between CAN and RS485 regarding the physical layer?


texts: How does a DC motor drive control the motor?

texts:
AC motor drives are pretty well documented; topologies, inverters, frequency control, volts-per-hertz, space vector modulation. It's all out there in a dozen places.

But what is a DC motor drive, and how does it control the motor?


texts: How can I cover PCB burn marks to identify burns later?

texts:
I'm repairing a receiver from the 1990s that has a few burn marks on the PCB where a few transistors overheated.  After replacing them and any other offending circuitry I'd like to be able to know if the issue has been resolved -- i.e. I'd like to know if the PCB burns again.

I don't have access to a thermal camera and I don't feel like using the back of my fingers to test for overheating.  Is there some way to cover up or clean the PCB so that I'll retain this indication?


texts: Are Verilog if blocks executed sequentially or concurrently?

texts:
I'm learning Verilog with some background in VHDL and C. I would like to know if Verilog if blocks are executed concurrently or not, and if this is IDE- or vendor-dependent.

For example, are the following always equivalent or never equivalent, or sometimes equivalent, depending on something I'm not aware of?

always @ (posedge clk)
begin
    if (x == 1'b1) begin
        // do something
    end

    // possibly other code

    if (y == 1'b1) begin
        // do something else
    end

    // possibly other code
end

versus

always @ (posedge clk)
begin
    if (y == 1'b1) begin
        // do something else
    end

    // possibly other code

    if (x == 1'b1) begin
        // do something
    end

    // possibly other code
end

The if blocks and the "// possibly other code" chunks of code always execute sequentially, correct? My understanding is that the two blocks above should never be the same in Verilog because the line-by-line sequence is different.

I've read that "statements in procedural blocks are executed sequentially", implying that the code should be synthesized to execute in hardware line-by-line. However it is unclear to me if the blocks themselves are processed sequentially, and simulating with just one behavioral simulator doesn't address the question of how universal Verilog synthesis is supposed to be.


texts: How does a neutral wire add any protection from near-by lightning strike

texts: As an amateur radio operator for 60 years now I have been aware that a major worry vis-a-vis lightning is not so much the very rare "direct hit" that blows up the house, but the far more common "near miss" in which a very large electromagnetic pulse will spread at the speed of light whenever lightning strikes nearby. I have been taught that this pulse (EMP) will induce a substantial voltage on antenna structures but also on power lines coming into the house.  In this context, how does having the neutral wire (grounded at the home's AC service panel) provide ANY protection against a voltage surge on the AC supply going into the  house? I am confused about this despite much reading on this great web site.


texts:
I was just wondering if an integrated circuit exists that would do the following:

Has around 10 inputs (8 for 8 bits of data, 1 for output selection and one for output enable) and 16 outputs
Will output the inputted data through one half of the output pins depending on whether the output selection pin is high or low
Output bits On are high if (An&(!S)&E)
Output bits On+8 are high if (An&S&E)
Where On+x = Output bit (n + x), An = Input bit n, S = Selection bit, E = Enable output

Any ideas?


texts:
I am wanting to use an inverter based TIG welder as a constant current power source for anodizing aluminum.

The main hurdle I suspect I will be facing is that the amperage of the welder may be difficult to control at low amperage settings. The current required for anodizing one of the parts is 6A the lowest I suspect I can set on the welder is 15......
If I add in a small stove element as a resistor (guessing at about 10A load) in series I can just set 16A on the welder and have 6A flowing to the part......
Is my thinking flawed?


texts: How do I interrupt an ISR with a higher-priority ISR on an STM32F105?

texts:
I have two external interrupt sources coming into an STM32F105. I want one of them (call it "IRQHigh") to pre-empt the other ("IRQLow"). Currently, if IRQHigh is triggered during the IRQLow ISR, the program flow waits until I clear the IRQLow ITPending bit before it branches into the IRQHigh ISR.

The STM32F105 is a Cortex-M3-based microcontroller. It supports nested interrupts. My application is written in C, using GCC (arm-none-eabi-gcc) in Eclipse, with the STM32F1 Standard Peripheral Library.

I think I have the priorities configured correctly but I must be missing something.

Here is the corresponding initialization code.  I have stripped out AFB clock commands, GPIO config, etc, since each subsystem seems to work fine by itself:

#define IRQHIGH_EXTI_PORT  GPIO_PortSourceGPIOA
#define IRQHIGH_EXTI_PIN   GPIO_PinSource3
#define IRQHIGH_EXTI_LINE  EXTI_Line3
#define IRQHIGH_EXTI_IRQn  EXTI3_IRQn

#define IRQLOW_EXTI_PORT   GPIO_PortSourceGPIOC
#define IRQLOW_EXTI_PIN    GPIO_PinSource11
#define IRQLOW_EXTI_LINE   EXTI_Line11
#define IRQLOW_EXTI_IRQn   EXTI15_10_IRQn

NVIC_InitTypeDef NVIC_InitStructure;
EXTI_InitTypeDef EXTI_InitStructure;

// Sixteen levels of pre-emption priority, no subpriorities
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_4);

// IRQHigh

    // Connect EXTI Line to GPIO Pin
    GPIO_EXTILineConfig(IRQHIGH_EXTI_PORT, IRQHIGH_EXTI_PIN);

    // Configure EXTI line
    EXTI_InitStructure.EXTI_Line = IRQHIGH_EXTI_LINE;
    EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
    EXTI_InitStructure.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStructure);

    // Configure and enable EXTI Interrupt
    NVIC_InitStructure.NVIC_IRQChannel = IRQHIGH_EXTI_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

// IRQLow

    // Connect EXTI Line to GPIO Pin
    GPIO_EXTILineConfig(IRQLOW_EXTI_PORT, IRQLOW_EXTI_PIN);

    // Configure EXTI line
    EXTI_InitStructure.EXTI_Line = IRQLOW_EXTI_LINE;
    EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
    EXTI_InitStructure.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStructure);

    // Configure, but do not enable, EXTI Interrupt
    NVIC_InitStructure.NVIC_IRQChannel = IRQLOW_EXTI_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 5;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = DISABLE;
    NVIC_Init(&NVIC_InitStructure);

The IRQ handlers are set up as so:

void EXTI3_IRQHandler(void)
{
    IRQHigh();
    EXTI_ClearITPendingBit(IRQHIGH_EXTI_LINE);
}

void EXTI15_10_IRQHandler(void)
{
    if (EXTI_GetITStatus(IRQLOW_EXTI_LINE) == SET)
    {
        if (IRQLow()) // This returns a non-zero value if an overflow happened
        {
            CleanUpOverflow();
        }

        // Clear interrupt bit.
        EXTI_ClearITPendingBit(IRQLOW_EXTI_LINE);
    }
    else // unknown EXTI source
    {
        ErrorHandler(ERR_UNKNOWN_EXTI15_10_IRQ); // This never happens
    }
}

A few things of note:

IRQHigh() and IRQLow() each take significant time to complete (which is why I want one to interrupt the other)
IRQLow is not initially enabled, but is enabled down the line with NVIC_EnableIRQ(IRQLOW_EXTI_IRQn);
Within EXTI15_10_IRQHandler(), I'm getting a return value from IRQLow().
I have declared the xxx_IRQHandler() functions with and without __attribute__ ((interrupt ("IRQ"))).  I understand that this attribute isn't necessary with Cortex-M3, but I tried anyway (and got the same results).

What am I doing wrong?

Update: With help from a comment by @Jeroen3, I've discovered that IRQLow is interrupting IRQHigh. Now I need to find out why...


texts: Does an over voltage, over current and reverse polarity protection IC exist?

texts:
I'm designing a circuit that has the following protection requirements:

Reverse polarity
Over voltage (60v max)
Over current (approx 1A)

There's quite a large input voltage range, 10v to 60v.

48v is nominal, drawing about 150mA. At 10vin, it draws rougly 750mA.

I made and tested the following circuit to satisfy the conditions: (Values are working but not proved optimal)

M1 was my starting point for reverse polarity, then the zener, divider & M2 were added for over voltage.

I found that D1 was needed when I breadboarded it, much to my annoyance as I wanted to avoid much voltage drop. (I smell redundancy...)

The fuse is the most frustrating element. I don't want to have to replace any components if there is a fault (even a fuse in a housing), so I was working with a PTC resettable fuse. Not only does this have an horrific tripping time (~4 seconds!), it also has a large footprint on the PCB; much too large for me I'm afraid  :(

I decided it is more beneficial to me to monitor the current and turn off a FET for example, than to crowbar the circuit if such a fault should occur.

My question is...

A) Is there an IC that can take care of these three elements? I've been looking at battery charger protection ICs but I haven't found anything yet.

B) Does anyone have a suggestion about incorporating the over current requirement in my circuit without a fuse? My initial thoughts were to use a sense resistor, comparator and another FET, but I can't help but think the whole circuit could then be simplified a great deal.

Thanks for looking.


texts: Does it matter if I replace germanium transistors with silicon?

texts: I found computer gold today with this amazing article - it details construction of a 400 germanium transistor-based digital bit-serial computer, circa 1967. Before I get my hopes up of spending about $120 to construct it, I noticed it specifies germanium transistors for construction. I was considering using these as a replacement - but I'm not entirely sure this would be suitable. Are there voltage differences or other electrical issues that would arise, or can I take it straight for face value? thanks for the help!


texts: MOSFET as a switch to control 12 solenoid valves using arduino

texts:
I am working on a project that requires me to control 12 solenoid valves using arduino. I find out that I can use MOSFET as a switch to turn on or off my solenoid valves. I have minimal experiance in EE field and wanted to ask if the diagram I made is a correct one for my application.
Just for completeness, here is the link to the solenoid valve that I am using.

Here is the diagram

So this diagram shows only 1 solenoid valve, but in my application there will be 12 of them. Is this a viable method for controlling my valves ?

Also if I can use MOSFET for my application, which type of MOSFET should I use ?

Thank you.


texts: Steady State Error: why we use a negative feedback rather than a single gain to reduce the error?

texts:
I'm studying signal analysis, and we reached a topic of correcting and enhancing a system with the following transfer function :

$$
\frac{Y(s)}{U(s)} = \frac{2}{s^2 + 5s + 6}
$$

with \$U(s) = \frac{1}{s}\$ (unit step input)

When we calculated the steady state error (ess) we obtained 67 % >> 5 %. With 5% being the maximum acceptable value.

In order to reduce the error we used a unity negative feedback with an amplification k (amplifies after the summing point of the feedback).

Therefore,
$$
\frac{Y(s)}{R(s)} = \frac{2k}{s^2 + 5s + 6 + 2k}
$$

Where \$R(s)\$ is the new input but still a unit step.

Why we are using negative feedback, while (mathematically) we could only use an amplifier k which will simplifies the analysis ? Is it impractical ?


texts: Does circular motion of electron perpendicular to the magnetic field experiences a force?

texts: If i am moving a charged particle in a circular motion and then applying the magnetic field perpendicular to this circular motion ,will the charge experience a force. Note that magnetic line produced by charge and the applied magnetic field are in the same direction.


texts: Which load resistor value for amplifier?

texts:
I have build this circuit succesfully but I need more volume. This is an audio chip with animal sounds.

I tried to remove the transistor and connect the out pin to a class d amplifier breakout. I get only a very low volume then.

My idea is to amplify the sound first with the S8050 transistor, and then connect to the amplifier. When I remove the speaker from the circuit from the spec sheet I need to replace that with a load resistor. I have however no idea which value to pick. The output will then be between the load resistor and the transistor (right?)

I use a 8 ohm speaker.


texts: Eneloop rechargable batteries for mouse?

texts:
I have a Apple Mighty Mouse, and I want to use rechargeable batteries, but I read somewhere on such a device I should only use Eneloop rechargeable batteries as they hold a charge when the device is not in use.

Is this a correct statement? I don't understand how one battery can hold a charge when the device is not in use, and another one cannot.


texts:
I have a signal, which can vary from  400 to 7000 Hz approximately. It is a kind of pwm signal and has the time of high level, Ton, 30 times longer than the time of low level, Toff.  The shape of the wave is not so relevant, allowing some level of distortion without major problems. High level is 12 and low level is 0V.

I know that when we have a square signal and Ton = Toff, we can use a capacitor in series to stop the DC level, in other words, perform AC coupling only.  This makes the signal approximately symmetrical, positively and negatively.

However, for case in question, Ton is  greater than Toff, as I mentioned, and the capacitor  is not working, I used 10nF and 100nF capacitors, none of them worked.  I would like it swings from - 6V to 6V, aproximatelly.

Does someone has a simple  idea of how to do it? About source voltage, I just have positive ones, of 12 and 5 volts.

EDITED:

I tried the following circuit:

I had the following results of nodes 1, 2 and 3, respectively:


texts: There are different tracks in proteus ARES like T15, T40 etc. What is their unit? How do I decide which track mode to use for different ampere ratings?


texts:
For some test equipment I have an LVDS line running at 100 Mbps. I would like to make an Arduino Due (because I use this for other monitoring in the test) detect activity on the LVDS line.

Using a (bad, slow) scope I can see that the voltage swings at one of the differential inputs on the LVDS receiver is ~100 mV. It is probably higher (it should be according to the LVDS spec) but my scope or probe is probably just not fast enough to catch it.

Can someone suggest a small circuit I can put on either one or both of the differential inputs in order to monitor the activity? It does not need to be production quality, and it's ok if some tuning is required, as it is only for test purposes.

I was thinking about something along the lines of an capacitor (to block common mode DC) followed by a voltage biased high-speed Schottky diode to rectify the signal onto a small capactor from where I could read the voltage using the Arduino. But honestly I have no idea if this would even work...


texts: Help understanding the behavior of an RLC circuit

texts: I am trying to generate a transient pulse (time to peak T1 = 6us; time to fall to 50% of peak T2 = 70us)  with an RLC circuit. The cap is first charged and then discharged through an LR circuit. I noticed that T1 increases when L1 is increased, and T2 increases when I increase R1. Why is that? Are T1 and T2 independent of each other? I expected T1 and T2 to both increase as I increment either R1 or L1. Is the time constant governed by RL or the RC circuit? Finally, how do I "soothen" out the waveform so it doesn't have those sharp turns as seen in pic 2.


texts: Converting passive USB Hub to powered USB Hub, by adding regulated wall-wart as power supply?

texts:
From a quick price-check on ebay,

Passive (bus-powered) USB Hubs - ~ $2-$5
Powered (externally) USB Hubs - ~ $15-$20

My use-case is to expand the no. of USB ports on a ARM-based SBC, and to embed the hub in the same enclosure, so I was wondering, if it is possible to just add a regulated (7805 based) wall-wart power adapter, to supply extra current to the devices.

Is there some per-port and up-stream protection circuit required ?
Does it make a difference if the host-port is USB1.0 / USB1.1 / USB2.0 (from the point of view of converting the hub to a powered one) ?
Are there some gotcha's with this approach, which I might be missing ?

BTW, if someone is aware of an existing "embeddable" USB hub circuit schematic, which isn't more expensive (BOM-wise) than the ebay consumer devices, would appreciate a pointer.


texts: Error when using debugging under Atollic TrueStudio / STM32

texts:
I'm using

STM32F103C8T6
Atollic TrueStudio
STLink2.1

Error I get when debugging:

Debug configuration set in TrueStudio:

What worked before was in SW4STM32/Eclipse, with the following settings. I always had to change the reset mode from Connect under Reset to Software System Reset. However, this option is not available in the debug configuration of True Studio.

What can I do to use debugging successfully with STLink2.1 on Atollic TrueStudio?


texts:
I am a software developer trying to understand how computers work at a lower level.

I understand that there is a difference between an Integrated Circuit, a MicroProcessor and a MicroController.  A Microcontroller is an integrated circuit but an IC is not necessarily a Microcontroller.

I have had a look through my book, which shows lots of examples of logic gates used in IC's.  Is there a one to one relationship between a logic gate and an IC? The IC's I have looked at suggest that there is not, but the circuit diagrams suggest that there is i.e. on the circuit diagram, the IC is replaced by a single logic gate.

Also, I read somewhere that a NOR gate has four Transistors.  A Microcontroller has a billion Transistors, so based on this logic; does a microcontroller have millions of logic gates?


texts: How to test if my circuit is affected by noise?

texts:
I have a PCB I designed for a project and I'm testing it. In general, it has some analog channels and a MCU to handle all the logic and the communications. I used an isolated DC-DC converter since this will be connected to a rather noisy power supply.

Anyway, I have left it connected working and communicating to the PC for long periods of time to test its stability and sometimes it can work for days and sometimes it stops working. It's being difficult for me to see what's going on because is more the time that it works correctly than the times it just stops working. I think that external EM noise could be the problem (nearby radios, motors, other switching supplies, etc) but I'm not sure.

My specific question is: What can I use to generate high amounts of noise and test my device to see if it can survive?

I thought of just putting a radio antenna near to it and hit the transmit button but I'm not sure if this would be as bad as possible. I need a way of generating some serious noise, the more the better.

UPDATE:
Also I'm using galvanically isolated RS2232 IC from maxim and galvanically isolated SPI IC to comunicate with the ADCs (since I'm not using the MCU ADC) and I have 4 layer PCB with 4 different isolated power and ground planes (one for each stage) without slots or current return interruptions. The only common ground points I have is at the voltage regulators because nevertheless I have separated LDOs for every stage (4 in total), they all have to have a common ground point at the main supply. I'm still not completely sure if I'm completely noise-free. As per the comments before I think the may be a coding issue but I still want to noise-test the system to be completely sure is not a hardware issue.

Any suggestions?

Thanks!!


texts: What are the cases where one should avoid using a breadboard? e.g. high frequency, noise prone circuits etc.


texts: Connecting power source to Arduino's 5V pin

texts:
I have an Arduino board connected to a Neopixel Ring. This Ring draws more than 0.5 Ampere, so it needs its own power supply (not drawing power via the Arduino board)

I found this schematic that connects a Neopixel and an Arduino to a single power adapter. To my surprise, the power adapter connects its power straight to the 5V pin of the Arduino board.

Arduino seems to advice against this, so my question is: is this the correct way to separately power a device AND an Arduino from one adapter?


texts: How to replace electrolytic capacitors with non-electrolytic ones?

texts:
guys

I've a little project and want to make a PCB for it, as small and thin as possible, but the electrolytic SMD ones are bigger than I wanted. With that I faced a small problem that led me to a question that can help future projects.

I know that I can replace an electrolytic capacitor by a ceramic one, but how to do it correctly?

Assume I have a 100uF 16V electrolytic one, what would be the equivalent for ceramic ones? If I reach the 100uF wanted with N capacitors rated X Farad in parallel, how do I match the 16V that I want?
Are there any considerations when doing it? Are there do's and don't's?

Thanks.


texts: Are special antennas required for 802.11n connection?

texts: I'm looking for a chip or a PCB antenna to add to a module. I would like if there's difference between antennas that make some suitable for 802.11n WiFi connection and some to 802.11b/g.


texts: PLL Loop Filter and its influence on speed

texts:
I was doing some research on Phase Locked Loops (PLLs). Now what I understand is, that the Loop Filter is first necessary to suppress unwanted signals on the VCO, so the tuning is controlled by the DC value of the Phase-Freqency-Detector (PFD). So the loop filter is a low pass filter and of course you want a low cutoff frequency \$f_c\$ for this reason.

Now to the second influence of the Loop Filter: If \$f_c\$ is low, the PLL will take longer to lock. But I don't understand this, how can the bandwidth determine the lock speed?


texts:
Just a theoretical question more than anything. Does the clock signal have to have the same width between peeks and troughs?

A normal clock signal with data (below):

A random clock signal with data (the data is still in sync with the clock) (below):

Would the chip (any chip in general, but as an example, a serial in parallel out shift register) still behave normally with a more random clock? If not, why not?

Again, not that I am planning to do this, but theoretically is there any reason that I could not use a standard ouput pin on the Raspberry Pi/Arduino as the clock and another pin as the data?

Example pseudo code:

fakeClockPin = 1;
dataPin = 2;

setPin(dataPin, HIGH);
setPin(fakeClockPin, HIGH);
sleep(1); //1ms
setPin(fakeClockPin, LOW);
sleep(1); //1ms

setPin(dataPin, LOW);
setPin(fakeClockPin, HIGH);
sleep(1); //1ms
setPin(fakeClockPin, LOW);
sleep(1); //1ms

setPin(dataPin, HIGH);
setPin(fakeClockPin, HIGH);
sleep(1); //1ms
setPin(fakeClockPin, LOW);
sleep(1); //1ms

setPin(dataPin, LOW);
setPin(fakeClockPin, HIGH);
sleep(1); //1ms
setPin(fakeClockPin, LOW);
sleep(1); //1ms


texts:
I'm currently working on this circuit and I ran into 2 questions that I'm not sure I understood them correctly  ( I have U1 = 15V , URE = 2 V , β = 180 , UCE = 5V and a constant current I = 2mA )

These are my calculations for this circuit
$$U_{R1} = 15 – 2.7
         = 12.3 V$$
$$R_1 = U_{R1} / I_B = 12.3 / 2 mA
                  =  6.15 kΩ$$
$$U_{RL} = U_2 – U_{CE} – U_{RE} = 15 – 5 - 2 = 8 V$$
$$R_L =  U_{RL} / I_C
   = 4kΩ$$
$$R_E =  U_{RE} / I_C
      = 1kΩ$$
In which range of UCE is current control possible? When UCE is between 0 and 15V ?
How do we determine the internal resistance of the current source? Is R1 supposed to be the internal resistance here ?


texts: SD Card formatting in FAT 32 file system

texts:
I am using NXP Micro for interfacing microSD card with FAT32 file system.

for implementation I am using drivers located at below link.

https://embedded-code.com/source-code/memory/secure-digital-mmc-memory-cards/secure-digital-mmc-memory-card-fat16-fat32-driver

the original driver is not configured for HCS12X compiler. I have done those changes and I am able to read data from SD Card using SPI.

my issue is when I format the SD card using PC in FAT 32 mode I am unable to read THE BOOT RECORD from SD card.

I have successfully read MBR section of card, but after MBR check in SD card initialization- it checks THE BOOT RECORD and i am getting all zeros at that section.

thus the card init is failing as it is not receiving data from THE BOOT RECORD read..

Do i need to follow some specific pattern while formatting  card??
Does all SD cards have THE BOOT RECORD section right next to MBR (as a 1st partition)


texts: DC motor as a generator as a torque limiter?

texts:
Is it possible to use a DC motor as a generator to regulate applied mechanical torque?  A hypothetical situation:

I have a DC motor acting as a generator attached to the ceiling.  The motor shaft has a pulley with a cord wound round it.  The free end of the cord is attached to a weight.  How can I regulate the speed at which the weight will fall to the floor? How can I adjust the system for differing weights?

My initial thoughts are that I could simply attach a potentiometer across the leads of the motor.  Varying resistance will limit the output current of the generator and thus limit the speed at which it unwinds.  Is there anything wrong with this assumption?

Thanks in advance!


texts: How to go about sensing AC power in existing wiring

texts:
Is there a practical way to sense 60Hz AC power in a pair of wires? Measuring the exact power or even current isn't necessary; it would be sufficient to know whether the load is pulling more than, say 5 amps, or not. For example, suppose you have a well pump wired directly into the house distribution panel, and you only want to monitor when it turns on and off.

This would be a piece of cake if it were possible to separate the conductors and get a regular AC current probe around one of them, but cutting into the romex is unsatisfactory. Finding a place where the conductors are already separate is an obvious angle of attack, but let's leave taking the face off the distribution panel for last resort.

Ideally there are already commercial sensors for this, but it's proving to be an awkward thing to google for. Seems like 8 or 10 amps through two conductors 3/8" or so apart should give off enough stray field to at least tell the difference between on and off.


texts:
I bought this small cheap transformer for my nest hello smart bell, it has 3 input options "4 wires" if i use 220v input wires it gives me 30 volt output without load of course.
If i use the 440 input wires it gives me 15 volt output, also without load.
My question is:
Is it safe to use the 440 input wires with my 230v outlet socket?

3:


texts: Alternative to ZIF socket and alligator clips

texts:
As we know ZIF socket holds ICs and enables us to add or remove easily.

Is there anything for axial elements such as resistor or diodes for holding them without bending those elements?

The problem of ZIF is bending the element

The problem of alligator clips is that the clip is not tight to PCB and it is messy.

My purpose is to test an axial element by a circuit without damaging the pins of it.


texts: What are coupling and decoupling capacitors?

texts:
I have come through many places stating capacitors as coupling and decoupling capacitors, but I can't understand what is meant by coupling and de-coupling capacitors?

Can anyone explain me what they are and how do they differ from normal capacitors??


texts: Is it possible to toggle a pin between "ground" and "not connected"?

texts:
I am trying to control a pump (ismatec ecoline V380) from a microcontroller (xmc4300, infineon) using an analog interface.

The pump takes several inputs, most importantly: the speed (from a current loop, 4-20mA.) But also, using another pin, you can determine the pump direction. According to the instructions of the pump, if this pin is in an "open position", the pump operates clockwise, whereas when conneted to ground, it pumps counter-clockwise.

Now my question is, if there is a possibility to implement this direction control using a digital output pin of my microcontroller?

I tried to toggle the output to high and low, but the pump only pumps in one direction. Therefore, the "high" state is not similar to "open," is it?


texts: Is there a standard DC power jack that prevents devices from being damaged by the wrong voltage?

texts:
USB is by far the most widely used serial bus by consumers. Plugging any device in any USB port is safe from hardware point of view.

On the other hand, the common DC power jack . For example this guy is quite common, but without regard for the output voltage shape or size:

I recently ruined an expensive device by plugging a 12VDC power supply into it, instead of 5VDC (I was using two devices, that need different voltages, but have the same connector).

Is there a standard that prevents connecting a device with a power supply of the wrong voltage? E.g. square plugs for 5V, triangle for 12V etc. Or PC-like molex connector with the not needed voltages hallow?


texts: Why phase is the position of the waveform relative to time 0

texts:
I was reading a book which says:

Phase  describes  the  position of the waveform  relative  to  time 0. It indicates the status of the first cycle.
and below is a picture

I am a little bit confused. According to the picture, at time 0, the waveform is just a point. Later it starts to form a waveform shape, so how come a waveform is relative to a point at time 0?


texts: Powering AC Guitar effects processor with a batteries

texts:
I am not a tech...so I must ask before burning up my equipment...

1) Can I power my AC effects processor with batteries? (Line6 Amplifi TT)
The power jack says DC 3A min. The power adapter also rates at 3A

2)if so...Would I need a 3A battery or would one with higher amps be safe? last longer?

I need it to last at least 5 hours so which option would work best? one 12v sealed lead acid or a custom made Nimh battery pack like the one seen here:

http://www.batteryspace.com/custom-nimh-battery-12v-4500mah-flat-pack.aspx

I am trying to stay small and light as possible because this will be used for street performances where ac power will be scarce.


texts: What's the definition of "signal to ground capacitance" of a coaxial cable? What's the difference between it and normal capacitance?

texts: What is the definition of "signal to ground capacitance" of a coaxial cable. I know what capacitance is, but I'm not sure whether it is just the same thing.


texts: Master-Slave D-FF vs Edge triggered: timing issues, simulation shoot-through

texts:
There is a thing that bugs me about flipflops: usually, the edge-triggered flops are used, which sample D and update their Q on the posedge, i.e. master latch has inverted clock and slave latch has positive clock, like this:

On the other hand, "usual" master slave flops have master on positive clock and slave on the negative clock, meaning they sample D on posedge and update their Q on negedge, like this one:

Question: why such flops are not the default flops that are used? Most CMOS libraries and designs are using posedge flops.

But, there are several advantages to master-flip flops that update their Q on negedge:
1. No headaches with hold timings, as D won't trigger on the posedge together with clock, making timing analysis simpler
2. No simulation shoot-through. If your design has clocking path longer than D path (for instance, there are clock gates), then the next stage will properly sample "previous" D value, instead of "currently updated" new one.
The only disadvantage I see is that you lose half a period of time for your combinational logic to settle.
Is there something else that I am missing?


texts: How the Cerebras across the reticle limits to produce the largest chip,WSE?

texts: How are the connections made on wafer-scale circuits (50,000 mm2 and up), given that the imaging reticle limits are around 600 to 800 mm2?


texts:
I'm having a little problem with a circuit and I want to tell you my adventures with it.

A few months ago I found a 125 KHz RFID tag reading circuit on the internet and decided to work with it to learn how these circuits work and to learn more about electronics in general.

The circuit is this:

All information about the circuit is on the author's website.

The circuit is supplied with 12V, but I decided to eliminate the power circuit and supply it with 5V, from a power supply.

In addition, I decided to improve it a bit (according to my limited knowledge in electronics), and I added decoupling capacitors (C2, C3, C6 and C7) and a pull down resistor (R3) on the digital output that produces the 125KHz wave which makes resonate the circuit. This pull-down resistor was added to eliminate any noise or fluctuation that could occur at that output.

The resultant circuit remains as follows:

I sent it to manufacture at https://www.elecrow.com/ and after soldering it was like this:

I tested it with PVC cards and it worked perfectly. Then I tried it with key fobs and wristbands and it did not work.

I have another reader (a Chinese one, the RDM6300) and all my cards, key fobs and wristbands are read perfectly by this Chinese reader.

Then, I used my logic analyzer and the PulseView software. This software is an open source tool for logic analyzers that has a decoder for the EM4100 protocol (the protocol used by all my RFID tags.) I did this to make sure the digital signal to which goes to the microcontroller is good.

I discovered that the PVC card is decoded perfectly, but the signal of the key fobs and the wristbands did not. So the problem is in the analog signal that comes to my circuit. Specifically, that signal reaches my antenna (air core coil) from the antenna of the RFID tag in question (card, key fob or bracelet).

The problem is that a PVC card has a much larger antenna than a key fob or a wristband.

The antenna of the key fob or the wristbands is a very small antenna, and therefore does not produce an electromagnetic field large enough to generate signals of large amplitudes in the receiver.

To solve this, I must increase the gain in the amplifiers, with a corresponding factor, to be able to increase the signals received.

The Chinese reader (which is a different circuit, schematic) amplifies the signals enough to be able to read the RFID tags of anything: cards, key fobs, wristbands, ...

I would like somebody to help me to solve this problem or at least give me guidance on how to increase the gain in the amplifiers in order to increase the signals received.


texts: How to generate PWM with different frequencies and duty cycles?

texts: I am going to use TMS320F28027 for PWM generation. I have to generate 5 different frequencies of PWM with different duty cycles at a same time. How it could be implemented? Can I use a single PWM signal from HRPWM of that controller and using it with timers and DAC I can generate other frequencies. Is that possible?


texts:
I'm trying to receive some data via USART on Atmel SAMD20. I use usart_read_wait() and usart_read_buffer_wait() but they return with error: the first with STATUS_BUSY and the second with STATUS_ERR_TIMEOUT. Sending works great, I get all the bytes in Putty or minicom. Here is my code:

#include <asf.h>

static struct usart_config usart_conf;
static struct usart_module usart_mod;

int
main (void)
{
  system_init();
  usart_get_config_defaults (&usart_conf);
  usart_conf.pinmux_pad0 = PINMUX_UNUSED;
  usart_conf.pinmux_pad1 = PINMUX_UNUSED;
  usart_conf.pinmux_pad2 = PINMUX_PA20D_SERCOM3_PAD2;
  usart_conf.pinmux_pad3 = PINMUX_PA21D_SERCOM3_PAD3;
  usart_init (&usart_mod, SERCOM3, &usart_conf);
  usart_enable (&usart_mod);
  stdio_serial_init (&usart_mod, SERCOM3, &usart_conf);

  uint8_t buf[8];
  enum status_code st = usart_read_buffer_wait (&usart_mod, buf, sizeof (buf));
  printf ("Code: %d\r\n", st);
}

The uC is connected to the PC via USB-to-TTL serial adapter.
I suspect that I did the pinmux configuration the wrong way. I don't really understand what pinmuxes and pads are. So how could I send some data to the uC?


texts:
Hello I am creating a little device, which has a total number of 30 tactile switches arranged in a matrix with 3 rows and 10 columns. My problem is, that I have only left 5 IO pins on my AVR micro-controller. For normal, I would scan my switch matrix, with enabling only one of the 10 columns at a time, and than read the input from the three rows. This is, how I determine the pressed switch, but this would need 13 IO pins.

My first approach, to find a solution was using a ring counter, but I was a little bit confused, on what it actually does, and how it works. I could also find only so called Johnson counters in my preferred electronics store. Can anyone help me out with this?

EDIT: Sorry I forgot to mention, that I also need to detect, if multiple keys are pressed. I am using diodes on each switch to prevent shorting(hope I can call it like this, not so experienced in english).


texts: combining large oscillation with quick damping possible?

texts:
I have a question about a sensing circuit for two frequency bands, in the form of the figure below

I would like the voltage oscillation to be as large as possible, but also would like damping to happen fast between bit transitions. When I add the resistors in, a lot of power is discipated in the resistor and I can no longer obtain a good range for sensing.
I was wondering if anyone can point me to some resources on the trade-offs between ringing and damping (I understand critically-damped is a sweet spot for this perhaps), and whether a more advanced circuit can be used to only add damping at certain times (like at transitions)?


texts: I know my question is a bit broad, but I haven't found the answer to this question. As a work for university , i am asked to use an oscillator that produces a triangle wave and after that use two active filters (one band-pass and one second order low pass) so that the triangle waves becomes a sine wave . I haven't quite understood , why would two filters be needed and not only one that can do the same job and that question is in general not only for my circuit . I am going to be posting some photos of the schematic just for reference (Ι have highlighted the parts that my question is based upon)


texts:
I've developing an LED fixture for my aquarium to grow plants. To do so, I've selected several high powered LED's. I'm currently considering driving them with LM317's because I know how to use those and they're simple. I'm not the most skilled with electronics. What is the ideal way to drive high current LEDs?

The LED's I've picked out are these specs:

2 (in parallel) 700mA @ 33V Luxeon K LED 12UP Warm White
3 (in series) 1.2A @ 8.55V Cree XTE 3UP Royal Blue, 25.65V total
2 (in series) 700mA @7.2V Luxeon Rebel 3UP Deep Red, 14.4V total


texts: Help me to identify this transistor (PIC inside)

texts:
Hi @can you help me to indentify this transistor of my old EVGA X58 SLI (132-BL-E758-E1)?

It's something related to the system temp sensor, because the "system temp" sensor its faulty. The transistor its broken and its expensive to send this out waranty mobo to the RMA.
Can you help me?


texts: Cutting off AC current to motor with thermistor

texts:
I have an AC single phase motor (120V/60Hz) connected to mains (plus a power resistor in series, and capacitor and voltage controlled resistor in parallel) The motor has a NTC thermistor attached to it. I'd like to know how to design a circuit that uses the thermistor to cut off the AC current when the motor gets too hot.

In my research I've read different things about using relays or BJT's but haven't been able to come to a definite solution. My best guess is that I use the thermistor to divide the voltage from a DC source and use that to control a relay. I read here (Relay control of AC motors, handling turn-off kickback) about some problems with just having the relay. So I'd like to know what you'd suggest.

I'd like this solution to fit on a proto board if possible, if that helps with scope.

If it helps, I found that the thermistor is about 8 kOhms when the motor is at room temperature and about 4 kOhms when the motor gets too hot to handle. I don't need you to design the circuit for me but an arrow in the right direction would be grand.

Thank you!


texts: Why does my multimeter always show a value of 1 for resistance?

texts:
I have a brand new multimeter, but any time I set it to resistance mode (any setting) according to the user manual, it shows 1 in the leftmost digit, and the decimal point will move around based on which setting I chose (but the remaining digits will never set to 0.

I've connected the positive lead to the VΩmA jack and the negative to COM. The output does not change when I connect the leads to opposite ends of a resistor.

Am I doing it wrong, or is my meter defective?


texts: Eagle - outlines/placeholder for smd (0603)

texts: I'm a bit new in this area, trying to make a PCB for my little project and cannot find how to make placeholders for smd components in Eagle 9.2.2. Is it possible to have/create outlines for smd (resistors, capacitors etc) in the cam processor/silkscreen? Cannot find how. Would be great if there's an option to have different outlines types. Thank you.


texts: How does a transistor make a signal copy?

texts:
I am very new here and almost just as new at learning about electronics. I am a musician and sound engineer first and foremost and I just recently have caught the circuits bug. My first big task has been to learn how a transistor amplifier works. I understand the concepts surrounding current and voltage gain, and I think I understand the basics around biasing the base and collector terminals.

What I just can't seem to grasp (and this may just be a very silly question so go easy on me) is how the transistor makes an amplified copy of the base AC signal. From what I can tell, the current never actually flows from the base to the output of a simple Class A transistor circuit. Maybe I just don't understand the concept of current and voltage well enough, but it seems crazy to me that the output has an amplified version of the complex AC input signal, when the current to the output really only flows from the DC bias, down through a resistor, to the output of the circuit and collector! It just seems like magic.

To be clear, I understand mathematically how it all works. I understand that if there is a negative current from the collector to the output junction, there is a gain in voltage.
I guess I just don't understand the amplification process intuitively and I would love someone to break it down for me like the noob I am. Maybe I also am struggling with a lack of knowledge of how an AC signal flows through a circuit.

Thank you !!


texts:
In this schematic, if the T5 transistor is off and the T4 is on, what would be the incremental resistances ri3 , ro3.

my guess is that:

ri3 is :

rPi4 + RE5 + Rspeaker.

and ro3 is :

RE5*(B+1) + rPi4

Is this correct?


texts: Is length matching is necessary on I2C, UART signals, and SPI?

texts: I am currently designing a board where there is a UART, as well as SPI and I2C, should I length match or take care of differential pairs on those interfaces?


texts: Trying to understand why op amp voltage follower goes high when fed negative input

texts:
I have a project where I want to take the positive and negative outputs of a passive differentiator and produce only positive pulses. E.g. when the switch feeding the differentiator is closed I get a positive pulse which I want to merely pass along; when the switch is opened I get a negative pulse which I want to invert and also pass along as a positive pulse. I got this to work by feeding the output into an active rectifier circuit. But the interesting thing is that while experimenting with Ltspice I found that I could achieve the same result with the voltage follower configuration shown below, and sure enough it worked on the breadboard, too.
I understand that when you exceed the ratings for a particular device you can get bad or unexpected results. (In this case my negative going pulses approach minus nine volts whereas the LM358 VICR is -.3V to 32 volts.) Still, if anyone can explain exactly why this works, I would be glad to know.
Also, is the op amp being damaged? Is abusing an op amp in this way a bad practice?

simulate this circuit – Schematic created using CircuitLab


texts:
The Wikipedia link quoted below refers to incorrect termination on USB-C cables.  Please could you suggest a way (with basic equipment) to test a USB-C cable to see if the correct pullup has been used?

Thanks

  Power issues

  Some non-compliant cables with a USB-C connector on one end and a legacy USB-A plug or Micro-B receptacle on the other end incorrectly terminate the Configuration Channel (CC) with a 10kΩ pullup to VBUS instead of the specification mandated 56 kΩ pullup, causing a device connected to the cable to incorrectly determine the amount of power it is permitted to draw from the cable. Cables with this issue may not work properly with certain products, including Apple and Google products, and may even damage power sources such as chargers, hubs, or PC USB ports.

(Source - Wikipedia USB-C)


texts: Raspberry Pi 3 B+ can't be powered by battery using regulator 7805 and LM2596, requires higher current. Help!

texts:
I want to power my Raspberry Pi 3 model B+ using a battery. It turned on and worked perfectly with:

1) a 5V 1A powerbank or adapters

2) and a 5.5V(4.2+1.3) battery connected directly.

However, i was not lucky in getting it to work with two lithium ion batteries in series 8.4V by either linear and switch regulator of 5V output. For linear regulator, i used 7805 and for switching regulator i used LM2596.

i have tried many variations of the 7805 linear regulator circuits and using different components and testing with multimeter but it did not work with raspberry pi. The same results with the LM2596. I tried both by powering using the USB micro port and the two 5V and GND pins The micro USB cable is perfectly fine as i tried it with powerbank and adapters which worked.

Everything in my project worked fine with these regulators, arduino, lights, motors, sensors except raspberry pi. I tried to make it work separately, i thought maybe the other components are intefering with it, but it still not working. Either power it directly using 5V batteries, or use powerbank or adapters. Its a dilemma because i tried everything i could think of.

Many people recommended this online and it worked for them. Could it be because of the new raspberry pi 3 B+ which has some changes. Please help, i will appreciate it very much.

In the commments, i was told that there could be not enough current being supplied by the regulators. That is true, not enough current is supplied. Thank you for letting me know. I tried the circuit below in an effort to solve my problem. Here i used a TIP142 transistor and a zener diode of 5.6V. I got a voltage of around 5.5V across the emitter capacitor. It worked! It powered the raspberry pi and got the remote desktop and shut it down.

However, i saw a white smoke, i thought im hallucinating, maybe a signal from my brain to take a smoke break, but the zener diode was getting hot. And to be honest the potentionmeter could be replaced with a tiny ohm resistor, cause i spinned it all the way to almost zero resistance. Thats how i got the maximum current. Please can you advice me on how to improve this circuit, so that the zener diode cannot get very hot. Or if you know a way to get high current, please do share. Thank you very much for your time.


texts:
A while ago I had some trouble with a TPS73633 (see Troubleshooting handsoldered TPS73633 SOT-23 LDO whose output is unexpectedly high) . I didn't get the 3.3v output voltage that I was expecting, whatever I tried. Since I wan't sure whether the error was in my board design or somewhere else, and I wanted to get to the bottom of it, I designed a new board specifically for testing the TPS73633.

My final goal would be to use the TPS73633 to power a ESP8266.

My testing board looks like this:

it follows the "typical application circuit" design in the datasheet (http://www.ti.com/lit/ds/symlink/tps73633-ep.pdf). The board design looks like this:

Unfortunately, I do not get 3.3v out of it when I hook it up to one of these batteries:

At first I thought the problem was that I bought these ldo's cheaply in China, so I bought another batch to see if it woukld make any difference, and then I aven bought some from farnell, so I would be sure I had the real deal, but whatever I tried, I never got a output voltage of 3.3v. What I did get was 2v, 4v and 0.2v:

I even bought a few TPS73733DCQ ldo's, wich are basically the same thing in a SOT-223-6 package, but even those gave me 0.2v as output. So after all this testing I'm a bit lost at why I don't get a simple LDO to do what it should do.

I did all my tests while a load was attached ans with fully charged batteries. I also measured all connections and it doesn't seem like the problem is in my soldering skills.

The only other thing I could think of is that I either soldered at a too high temperature (300 c) or that there's something wrong with these batteries.

Does anyone have a clue what I'm doing wrong here?

Update 19-03

As suggested by peufeu I removed all capacitors. That actually did the trick for most of the ldo's, i finally got 3.3v out of it (except for the Chinese ones from the first batch, I expect them to be counterfeits, they just give a output voltage that is the same as the input voltage).

After that discovery, I started adding capacitors again, since the datasheet suggest doing so, in this diagram:

In my original design I was using capacitors of 1uf, 0.22uf and 0.01uf. To be honest, I don't remember why I chose those values.

In the datasheet I only found this information:

  Although an input capacitor is not required for stability, it is good
  analog design practice to connect a 0.1-µF to 1-µF low ESR capacitor
  across the input

it doesn't say anything about the value of the other 2 optional capacitors. I tried using a 1uf capacitor for all three capacitors, and that seems to work fine. Is there some standard rule as to what values you would use in a case like this?


texts: Anyone familiar with this power solution?

texts:
I'm studying a server schematics and found something interesting.
It uses a power solution, to transform 48V to CPU core power (~1V)

http://www.vicorpower.com/zh-tw/industries-computing/48v-direct-to-cpu

I don't quiet understand about this design.
It uses a so called "ZVS" module, but the input and out of this module are both 48VDC??  What's the purpose?

And the VTM seems to be a a transformer, so that means this modules transform DC to AC, through a transformer, and then from AC to DC?

Here are more info: http://www.vicorpower.com/documents/datasheets/Picor/ds_pi3751-02.pdf
http://www.vicorpower.com/documents/datasheets/VTM48E_040_050B00.pdf


texts: I'm asking this in reference to multiplexers where there are multiple inputs to the final OR gate. Say I have two different signals to an OR gate. One is at 4V and the other at 5V. So if I'm letting both them signals pass at the same time what should be the reading of OR gates' output? Will it be 4.5V or simple 5V?