texts:
I have a setup with 12 buttons. 10 of them connected to the arduino pins 0, 1, 6, 7, 8, 9 and analog 0, 1, 2, and 3 (these are all configured with pinMode as inputs in the setup-part of the sketch). button 11 and 12 are connected to an I/O expander (mcp23016) which I read from through the i2c bus on analog pin 4 and 5.

Each button is connected as this:
side 1: directly to 5v
side 2: to GND through a 10k resistor AND also to an input-pin (one pin for each button)

The first issue I had was with pin 0 (the RX pin). It was acting as though it wasn't connected, although it was indeed connected. So I ended up replacing its 10kohm resistor (to GND) with a 220ohm, and then it worked fine.

I don't know why this specific pin would need a smaller resistor in order to get connection, but everything seemed to work fine now.

When I had put all my components inside my casing, suddenly the same issue started happening with other buttons as well.

So my question to you is:
what possible reasons could there be for this issue?
Is it my 10k resistors that are too much resistance, thus leaving the input pins as not-connected?
And if so; how can I measure impedance of my buttons, wires etc, and how would I find out which resistor would work?
Is this a plausible reason or is it more likely that it's a soldering somewhere?
I'm using screw connectors which are screw very tide together - but could this have anything to say?

I must admit I'm quite stranded on this one.

When I measure with my multimeter on the input pin that stays high, it gives me just below 5v reading.
I tried momentarily connecting the faulty input pin directly to GND (without any effect) and also tried connecting it to GND through a 1k and a 220ohm.. no luck.
So my best guess would be that there's a broke connection somewhere, but I really have a hard time finding it. All looks fine.

Any advise is very much appreciated.


texts: How to find the gain K at break-in and breakaway points of a Root Locus Plot on MATLAB

texts:
I would like to know how to find the break-in and breakaway points of a transfer function using root locus on MATLAB.

MATLAB Code:

f = tf(poly([4 3]),poly([-1 -2]))
rlocus(f)

But how to get the K value where the break happens?


texts:
In New Induction Appliances When you lift the pan from surface of furnace they automatically switch off the power of furnace

so  my question is

How Induction Cooking Appliances Can Know The Difference Between Furnace With Pan And Without Pan ?


texts: How much hold current is consumed when there is no load?

texts:
Given a 24V 1A motor with no actual load connected (just a piece of orange tape so we can see the shaft moving).  How much current will the motor use if I configure the driver board for 2A maximum hold current?

This is the scenario:

We have a breadboard that is configured for 2 motors at 24V 2A.  However, we only have 1 motor and axis configured for now.  So until we get the second motor, I asked for just any motor to be connected to the second channel so that I can see that the software is working.  The project EE found a 1A motor and connected that.  The EE then warned me to reduce the maximum hold current to 1A.  I was told that the driver board would "push" 2A of current to the motor.

This is where I get confused:

I don't understand how the motor could draw 2A when there is no load, even if there was no current limit at all.
I thought that the "maximum hold current" was the current limit.  Not that the board would push 2A to the motor.  At 24V, supposing that the motor was drawing say 200mA just sitting there idle, wouldn't the driver board have to supply 24V x 2000mA/200mA = 240V to get 2A of current into the motor?


texts:
We know when use switch easy for us to state input logic.
Logic 1 means input connected to positive terminal.
Logic 0 means input connected to negative terminal.
How about unconnected input from anywires?
It will be problem when use pushbutton as input.
I want when unpushed button the state input will be 0.
When button pushed, the state input will be 1.
But the problem is when button unpushed, the input state will "unconnected to any wires" which we can't say it as 0 state due to 0 state means connected to ground


texts: How do utilities calculate transmission lines impedance?

texts:
I'm an electrical engineering student getting into Transmission Circuit Analysis, and a question came out to me: How do utilities measure their transmission lines impedance?

Do they use special meters?
Or just mathematical calculations?

Similarly, I'm studying Distance Relays, where knowing the impedance of a specific transmission line is essential to set them up.

So, what do you think, people?

Regards!

F. Alvarez.


texts: Compact Fluorescent Lamp Load Calculations

texts:
I help build/wire up large illuminated carnival/parade floats, and in the past we have used around 11,000 40w/60w GLS BC light bulbs in festoon sockets, powered by a 800KVA 3 phase diesel generator. However, these are becoming more and more difficult to buy, and so we have started to use energy saving compact fluorescent lamps.

The float uses normally around 80% of the capacity of the generator. My question is, as I start to replace more and more of the old incandesant bulbs with compact fluorescent lamps, what considerations do I need to apply when calculating the load that I'm putting on the generator? I'm concerned that as the load is becoming more inductive and less resistive. I've read that at some point power factor correction will be needed, but I'm not sure how to calculate this, and how to apply this on this scale.

For example, before I would have had:

4000 x 60w = 240kW
7000 x 40w = 280kW

but now I have:

3000 x 60w = 180kW
6000 x 40w = 240kW
2000 x 11w = 22kW   (11w energy saver bulbs)

All this runs ok, the generator isn't overloaded, everything runs smoothly, the phases are near perfectly balanced, and nothing gets warm!

As I increase the ratio of inductive to resistive load, what will happen? How do I calculate how much inductive load the generator can take?

UPDATE:
I found some information about a Synchronous Condenser on Wikipedia, which appears to do what I need by just connecting an unloaded motor to the supply, but it lacks details about how to do the calculations. Can anyone help with that?


texts:
I'm using LDO regulator MCP1700 @ 3.3V -  LDO Low Quiescent Current

Dropout voltage is ~180mV. So below 3.3V + 180mV regulator should be in dropout zone with constant Rds at min value.

But if I test it, below 3.3V Vds ~ 0V, and there is no cutoff zone. I cannot explain it from functional diagram in datasheet p2.
Can anyone explain it?


texts: How to connect MCU input pin with LED and Button?

texts: I want to connect a LED and Push button on the GPIO input pin of a MCU, STM32F103 so that when the push button is pressed then the state of LED indicates the button is pressed. Is it possible to connect a LED and Push button on the input pin?


texts: Microcontroller Newbe here. LED color pattern controller for arcade machine

texts:
I am building an arcade machine and I want to make a cool led light display for the marquee.

You can see pictures of what I'm talking about here.

I want to light up each one of those holes with an LED, and make it so I can program the LED's to create different effects.

I have no experience with micro controllers, but I do have some programing experience (PHP, javaScript) and good soldering skills.

I don't have a clue where to start though. I'm looking for some advice and guidance.


texts:
I am wondering about catch diodes in the context of switching power supplies. I have read all the books that are the norm in designing a SMPS, but all of them don't or barely touch the subject. My question is about how do you select it's current and voltage rating.

From a buck converter standpoint I have reached the (maybe bad) conclusion, that the current rating of the diode must be equal or larger than the current flowing through the load, since the inductor stores energy then it returns it to the load through the diode. But in an SMPS with a transformer, which ideally only transfers energy, the diode selection would be based on the leakage inductance. If so, how do you select the ratings?


texts: Op-amp circuit has lower gain at low frequencies

texts:
I'm trying to design an amplifier, which amplifies line level audio to 5 Vpp, so I can sample it with a microcontroller. My plan is to do this in two steps: amplify the signal to 5 Vpp and then add a 2.5 V offset. I'm stuck at the first step.

I put together a simple inverting amplifier like so:

I'm using the LM324N op-amp. I'm powering it using a PC power supply (-12 V for negative rail and 12 V for positive rail). Ground, pictured in the circuit is 0 V.

I'm testing the setup with a sine wave (from my phone) as input. The amplifier works normally at higher frequencies, but the gain starts dropping at around 300 Hz. At 20 Hz, the gain is basically 1. For example:

1000 Hz:

40 Hz:

What am I doing wrong? Is this normal behaviour for this op-amp? As I understand, op-amps start behaving abnormally at high frequencies, not at low. Is something wrong with my input?


texts: What methods are used to protect floating devices against ESD

texts:
In conventional circuits you'd like to divert your strike to ground and through a path that diverts the current safely to a grounded chassis or output. That is not possible in hand held devices for example, i'd like to know what methods are chosen for these kind of floating hand held or otherwise devices. Do we prefer dumping charges into our ground plane or the power plane for an example?.

Hints on material related to this for further reading also appreciated.


texts:
My group and I have been working on a Torque Sensor project using the PIC18F2431 chip, and we managed to write the code for each individual aspect on MPLAB for the Quadrature, ADC and LCD. Our concern right now is how to get the ADC value to display on the LCD.

Basically, we need to take our ADC values into decimal, but we are having trouble finding a suitable method for this. (We want to take a pot and adjust the values and see it real time on the LCD)


texts: What is the best battery configuration for a solar powered electric fence setup?

texts:
I have two solar panels: SunWize SW-85P; 85W max power, 5.1A, 16.7V.

I have a charge controller: SOLAR BOOST 2000E.

I have four 12V batteries: two Interstate SRM-24 (couple years old), two CarQuest DP27M (new).

I have a fence energizer: Speedrite 3000 w/ 12V DC power adapter.

What is the best arrangement of batteries for this system?  Since the batteries are 12V and the fence energizer requires 12V input, I believe that there is no series arrangement of batteries that is possible.  However, what parallel arrangement is best?  And in particular, which specific battery terminals should be connected to what?

Thanks.


texts: Wiring up an LCD display with unknown controller

texts:
I found an old LCD in my pile of trunk. I would like to be able to use it. However, someone (possibly / probably me) sawed off the part of the PCB with the series code, so I can't know what the controller chip is. I'm trying to figure it out.

My analysis so far:

The display has backlight. There are 16 pins, so HD44780 would be my first guess (3 power pins, 11 data pins and 2 for backlight). The three pins that are wired up could be power, looking at the traces, and the last two LED anode and cathode. So I tried to wire it up with pin 1 to 0V, pin 2 to 5V, and pin 3 (probably contrast) to 0V. I got this result:

This looks like HD44780 to me, with a 2x16 screen.

But I've got a few questions about this:

Are there other (not HD44780-compatible) displays that would give this display when only power is supplied (but no controls), or is this specific for HD44780?
The pinout I have used up to now for all LCDs with HD44780 I've used so far (as far as I can remember) had a pinout like this:

Power (Vss, Vdd, Vcontrast)
Control (RS (register select, command or data), R/W (read / not write), E (enable)
Data (DB0 - DB7)
Possibly backlight (Anode, Cathode)

But is this a standard? Can I assume that this uses the same pins for the same functions? And, if not, is it safe to just try it, or could things go wrong? If it could go wrong, is there a way to say judging by the PCB traces what lines would be data, probably?

I don't think it's important, but in the end I intend to use this chip with a PIC. I have used HD44780 displays with PIC before, so I have working code to try out (and also other displays with HD44780 (or ~compatible) to check the code and setup).


texts: Artix - 7 Voltage Specification I/O standard

texts:
I want to design a PCB for FPGA prototyping. Please help me understand if I need to supply these voltages and why?

Vref
Vrefp
Vin

These voltages are from the Artix-7 Datasheet.
http://www.xilinx.com/support/docume...Data_Sheet.pdf
I'm using the Artix - 7 236 pin BGA FPGA.
I'm only using the FPGA board I'm laying out on Altium for gigabit ethernet purpose,
no LCD screen,
no USB,
no SRAM,
no DRAM,
no memory,
no microcontroller,
no other peripherals except JTAG/SPI configuration of the FPGA.

Kindly inform what is meant by Select IO standards.
Which standard should I use for gigabit ethernet?
Here is the document I referred
http://www.xilinx.com/support/docume...s_SelectIO.pdf

Your help is much appreciated.


texts: Does magnetism affect the likelihood of an electrical arc occurring?

texts: Would magnetism affect the likelihood of an  electrical arc occurring?


texts:
You have a 500kVA load with a power factor of 0.6 lag. You add an additional synchronous motor with an input of 80kW and max power factor of 0.8 leading.
Determine the reactive power and the overall power factor.

Can anyone help me with this question? I don't even know where to start. I don't think my teacher even knows how to do it.

Thanks.

Is this correct?

Existing installation

$$P=S\cdot pf = 500\cdot 0.6 = 300\text{ kW}$$

$$Q=\sqrt{500^2-300^2} = 400\text{ KVAR}$$

$$S=500\text{ kVA}$$

New synchronous motor

$$P=80\text{ kW}$$

$$Q=\sqrt{100^2 - 80^2} = 60\text{ KVAR}$$

$$S=\frac{80}{0.8} = 100\text{ kVA}$$

Added together

$$P= 80\text{ kW} + 300\text{ kW} = 380\text{ kW}$$

$$Q= 400\text{ KVAR} - 60\text{ KVAR} = 340\text{ KVAR}$$

$$S= \sqrt{380^2+340^2} = 509.9\text{ kVA}$$

Overall power factor = \$\frac{P}{S} = \frac{380}{509.9} = 0.75\$ lagging.

So reactive power = 340 kVAR and pf = 0.75 lagging.


texts:
I wanted to verify the following or get some helpful pointers.

So, I have a gate driver which can supply a maximum current of 0.5 A , and I am driving a MOSFET Vgs of 15 V, based on these two specifications I should be selecting a gate resistance of at least 30 ohm (preferably even higher). This way the gate driver doesn't get damaged when the MOSFET is switched ON and its Cgs is charged up.

The peak power that the resistance should be able to handle is

\$ 15 W \cdot 0.5 = 7.5 W \$.

So while selecting the SMT resistance, I was looking for something like a R~50 ohm, P=10 W and guess what, its hard to come by something like that (in a 1210 package size or similar), and not to mention they are pretty expensive (highest I found was 3.5 W for $ 3!)

So, instead of considering peak power, I assume we should consider avg. power?

\$P_{\text{avg}} = \frac{V_{\text{rms}}^2}{R} \$

While considering Pavg in LTSpice, it came to around 0.5 W (when Vgs was charged to around 80%)

So, is it fine to use a resistor of 1 W rating in this scenario?

Any other pointers would be much appreciated.


texts: I2C Interface is not working on STNRG388A

texts:
I am trying to communicate with MAX30205 using STLUX385/STNRG388A.
I'm using STM8S standard peripheral libraries to communicate with I2C bus.
For STNRG388A device drivers, I'm using STLUX385 drivers provided by ST.
I can read/write GPIOs, UART communication successfully.
But when i tried the I2C bus communication, it's not working as expected.
My main.c code is below, rest of the task is in the stlux_it.c in INTERRUPT_HANDLER(I2C_IRQHandler,19)

void main ( void )
{
    // work with HSI at maximum frequency
    CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV1);
    // enable PLL - Used by the SMED
    CLK_PLLCmd(ENABLE);
    while((CLK->PLLR & CLK_PLLR_LOCKP) == 0);

    // initialize the GPIO registers
    GPIO_Init(GPIO1, GPIO_PIN_6, GPIO_MODE_OUT_PP_HIGH_FAST);
    GPIO_Init(GPIO1, GPIO_PIN_7, GPIO_MODE_OUT_PP_HIGH_FAST);

    I2C_DeInit();
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_I2C, ENABLE);
    I2C_Cmd(ENABLE);
    I2C_Init(I2C_SPEED, SLAVE_ADDRESS, I2C_DUTYCYCLE_2, I2C_ACK_CURR, I2C_ADDMODE_7BIT,16);// (CLK_GetClockFreq()/1000000));
    I2C_ITConfig((I2C_IT_TypeDef)(I2C_IT_EVT | I2C_IT_BUF), ENABLE);
    rim();
    /* TXBuffer initialization */
    for (i = 0; i < BUFFERSIZE; i++)
        TxBuffer[i] = i;
    I2C_GenerateSTART(ENABLE);
    while (NumOfBytes);
    while (I2C_GetFlagStatus(I2C_FLAG_BUSBUSY));
    /* Add a delay to be sure that communication is finished */
    Delay(0xFFFF);

    while(1);
}

I have checked the MAX30205 with arduino and it's working fine.
Waiting for any positive response.
Thanks in advance.
Regards


texts: Help with a DC motor speed controller circuit

texts:
I have a circuit which i'm trying to rebuild because the original stopped working due to a short-circuit (mechanical caused)

First i copied exactly how the circuit was made, with no modifications and i made this sketch (i'm kind of new to electronics, sorry if some symbol is incorrect) . With that circuit the motor works but i can't regulate the speed.
So i made a small modification, i connected POT pin 1 to ground with a 300ohm resistor (because i have that available, i didn't calculate anything i'm an electronic amateur/enthusiast) and cutted the interconnector (red) cable (which i can figure out it function).

That worked and then i could control motor speed. But after a while (less than a minute) d3 and d4 burned out.
I think what's happening is: when i connected POT pin 1 to ground then it started working (didn't worked before) but now that it works (and so the transistors) the current is "out of the bounds" and the diodes can't handle it. I would appreciate if you can suggest a correction to make it work correctly. Thank you.

Update:

Hello again!
I modified as you suggested, with the new arrangement and placing the motor in the new place. The good news it that nothing gets burned now (the POT gets a little bit hot), but the motor only works at full speed or stops.
It seems to me the POT can't regulate the speed. Its working full speed approx. between 0-90% of the POT range (rotating clockwise). And in the final 10% range (max. POT resistance) the motor stops. I noticed that lets say... "between range of 89% and 91% there is a point when the motor speed gets affected". But i'm regulating by hand and i'm not sure if is only a -wrong- perception or truly there's a regulation possible in that range. Trying a couple of times i reached that spot where the motor speed was slower, and i start/stopped it several times to confirm that wasn't just some accident/coincidence.

My conclusion is:
Maybe i need to try with a different range POT with less resistance (1K/5K p.e.)?
And/Or should eliminate R2 (or replace for smaller resistance) from the IN of the POT?

PD: I don't know if is important but my C1 value is 1000 µF and the POT is 10K ohms (in your draw C1 reads as 1µF and POT 1K ohms, the rest of the components values are OK).


texts:
Is there a charging cable which splits into two?
One of the split cable will have DC 12v 3a with a male coaxial 5.5mm x 9.5mm
The other split cable will have DC 5v 3a with a USB Micro.

Does this exist? If so, where can I buy one?
If it doesn't exist, how can I make one?


texts: How this 9 LED Knight Rider Circuit Works Properly?

texts: I have recently started working on 9 LED Knight Rider Circuit on a breadboard. All the connections have been done according to the circuit diagram given in this article. But I am having a problem with it - The light is running only one way instead of coming back and forth. Can anybody identify the problem and suggest me the modifications to be done to this circuit arrangement?


texts: 100BASE-TX (MLT-3) to 100BASE-FX (NRZ-I) conversion

texts: Is there a way to convert 100BASE-TX packet to 100BASE-FX packet only by use of MLT-3 to NRZ-I coding scheme convertion by means of simple logic ICs such as some trigger ICs (wichout the use of FPGA or ASIC)?


texts: RF Design - Microstrip vs. Lumped Components

texts:
I currently working on a RF design, with frequencies up to about 2GHz.

What is the "rule of thumb" for when to stop using lumped components (Capacitors, Inductors, Resistors), and start using microstrips ect. ?

P.S. I can see that lumped components are available up to about 10GHz, but they are pretty expensive.

Edit: What about decoupling capacitors, on supply lines to pll's ect., should they always be associated with RF Chokes to work probably (at 2GHz) ?


texts: Does the LPC1343 MCU need an external clock for USB operation?

texts:
I am trying to design a board using the LPC1343: http://www.nxp.com/documents/data_sheet/LPC1311_13_42_43.pdf

I would like to be able to use its on-board USB bootloader to program it. My question is whether or not my board requires an external 12 MHz oscillator. I am confused because in the user manual (http://www.nxp.com/documents/user_manual/UM10462.pdf) it seems that there is an internal 12 MHz:

"12 MHz Internal high-frequency RC oscillator (IRC) that can optionally be used as
a system clock" (page 7)

Does my design need an external clock to work with the USB programming? Ideally I'd like to use it as a USB mass storage device to drag-and-drop .bin files to program it. Thanks.


texts: Can I supply a device rated for 1A with 15A power supply?

texts: I'm talking about a big difference between output current of the power supply and rated current of the device here. Would it burn up?


texts:
I've spent a very long time trying to work this out, but some websites seem to conflict the information - or I'm completely missing the point.

I have a rechargeable battery:
2600mAh
4.2V max charge voltage
9.62Wh energy

It is to charge from a vehicle 12V or 24V (battery runs through a circuit board...it's designed for vehicle tracking).

What I'm trying to work out is:
The A - is it 2.6A? Is this the same as Ah? Meaning it will only last about the 2.5 hour mark before running out of juice.
The approximate charge time. I was using 12V but then read the max charge voltage on the side of the battery

I have one of the batteries connected to a PSU, but the current needle flips up a few bars, then drops straight back down. The battery was flat, so I'm not really sure what's happening.
Appreciate any help understanding this.


texts: Auto Audio Gain Control IC for normalized audio from line level input

texts:
The problem I am having is like this:
I am using an aux cord line level output from a smartphone to a MSGEQ7 chip which samples the frequencies and splits it into 7 channels which can be seen as an analog voltage from 0V to Vin based on that frequencies strength. 63Hz, 160Hz, 400Hz, 1kHz, 2.5kHz, 6.25kHz and 16kHz. (Sparkfun info) I am using an Arduino to then take the output and display it on  7 bar graphs.

Now the problem... Unless the output is at around 80% volume, any song playing will either not be strong enough to be displayed, or too far over and will be clipping the top of each bar graph. Unfortunately I don't own an oscilloscope so I can't give the peak to peak voltage. This would be ok if I could always leave the volume at 80% but in this case its much easier to turn down the voltage on my phone rather than going over to the speakers and turning down or up the preamp knob. Ideally at any input volume the signal would be either boosted or decreased to the sweet spot.

I've researched a bunch of different solutions from diode/npn circuits to multi op-amp circuits, to Compandor (compressor/expander) chips like the NE570 (but far too expensive), but I'm not sure what would actually work for my solution. I don't need high fidelity, but I also don't want to lose sensitivity for high and low frequencies. (Is this normalization or dynamic range compression?) I have used the Adafruit auto-gain microphone which uses a MAX9814 which offers an output of 2V peak to peak and a DC offset of 1.25V and it works great, but I'd also like to be able to use an aux cord in.

Thanks ahead for your answer


texts: What is a safe amperage limit for a homemade lead pencil resistor? I made a 25 ohm resistor with a regular wood pencil and would like to know what current it will take without getting hot to the touch. Anyone play with this and know?


texts: Why do I get warnings for all my voltage supply connections in Eagle CAD?

texts:
Take a look at the following list of ERC errors:

Why is Eagle CAD showing Warnings for the voltage supply connections? For example:

  POWER pin U1 VIN connected to VBUS

I know these pins are connected to the correct supply voltage, so do I just approve them?


texts:
In the attached circuit, with input of 30mV at 40kHz, the reference DC voltage at pin 2 of the comparator exhibits noise at the same frequency as the input.

At low input amplitude (4mV p-p) the noise does not appear.

A scope shot of the reference signal is shown below.

What might be causing this noise?


texts: Does an ungrounded shielded cable shield at all?

texts: Does a shielded cable provide any shielding if the shield isn't grounded?  Would it be practically different than an unshielded cable?


texts: Output Characteristics : Common Base vs Common Emitter

texts:
In output characteristics graph of common emitter transistor the current and voltage are both 0 when one of them is 0 as shown.

But in output characteristics graph of common base configuration it is not so.Why?

I just started learning transistors yesterday and I'm feeling very confused already.Please explain in as simple language as possible.Thanks!


texts: What type of plug is this? It belongs to a 7.2V 1600mAh RC car battery (NiMH I guess, 6*1.2V). Scanning the internet and comparing plug pictures, I came across similar plugs that go by "M-Plug" or "Mini 7.2 Connector" but I wasn't able to confirm this.


texts:
I am looking at the Altera Stratix V overview Table 1. In it, they distinguish two types of memories:

M20K memory blocks
Memory logic array blocks (MLAB)

What are the differences between the two types of memories?


texts:
Could anyone help me identify these male and female connectors? They're smd mount, I would guess molex, but Farnell shows way too many results to sift through.
Any lead is much appreciated!
I am also interested in what kind of crimps are used on the female side.


texts:
I am currently working on the FFT example using MAX32660. The toolchain that I am using is ARM Cortex Toolchain. It uses Eclipse for the compiling and bugging purpose. I imported the example code and when I debugged the code I get this error.

The point is this path does not exist in my system. I checked the Compiler and the linker path, they appear to be correct. Can I someone tell me what is throwing this error.


texts:
I've got a device with a 12V input requirement like this:

But I've got no idea what the name of this input type is, and after searching for the correct supply (needs to be powered from a 240V mains socket) found this:

It meets all the spec requirments for the device, so is it a simple matter of stripping the connector off of the power supply, stipping the wires and wiring them into the device?

Or have I missed something obvious, is there a name for the type of connector I need?

Thanks
Matt


texts:
I am interfacing DS1307 RTC with PIC32MX795F512L. I am using I2C1 for DS1307 RTC and then using UART2 to send the RTC value to the terminal. I have written the code but don't know why I am not getting data.

In my code I am using

OpenI2C2 to open the i2c channel.
StartI2C2() to start the communication
StopI2C2() to stop the communication
MasterWriteI2C() to write the data
MasterReadI2C() to read the data

These are included in plib.h file.

Updated CODE:

OpenI2C2(I2C_EN, 163); // I2C channel Configuration

StartI2C2();
IdleI2C2();
n = MasterWriteI2C2(0xD0);  //device address
IdleI2C2();
MasterWriteI2C2(0x07);
IdleI2C2();
MasterWriteI2C2(0x00);
IdleI2C2();
StopI2C2();

StartI2C2();
IdleI2C2();
MasterWriteI2C2(0xD0);
IdleI2C2();
MasterWriteI2C2(0x01);
IdleI2C2();
MasterWriteI2C2(0b00010011);
IdleI2C2();
StopI2C2();

StartI2C2();
IdleI2C2();
MasterWriteI2C2(0xD0);
IdleI2C2();
MasterWriteI2C2(0x01);
IdleI2C2();
StopI2C2();

StartI2C2();
IdleI2C2();
MasterWriteI2C2(0xD1);
IdleI2C2();
**res = MasterReadI2C2();**
IdleI2C2();
NotAckI2C2();
IdleI2C2();
StopI2C2();

I am using 163 ((33000000/2/100000)-2)as BRG value for I2C communication. I am debugging the code and can see all the values in I2C registers are correct but at res = MasterReadI2C2(), nothing shows up in I2C2RCV register which holds  the received value and even nothing showing up in the res variable. I also used a variable n to check if the values are actually transmitting or not. So I received 0x00 as the value of n and according to document, 0 means transmission successful.

I don't know where I am missing the point.


texts:
I am testing a circuit which is used in a synchronous motor rotor excitation.

I am testing the part when the rotor is stationary and the motor stator has a rotating magnetic field, in that case it will be inducing an AC voltage and this test is basically to test that behaviour.

So I connected a single phase AC supply at F1 F2 and got the below waveform on the scope.

So far so good the diodes are working and only the positive half cycle is visible on the scope.

On increasing the voltage from the variac the SCR is turned on I suppose and then I was expecting to see the other half of the AC wave, but I am getting the below waveform on scope

I don't understand where the diode half cycle part gone.

The scope is connected here:


texts: Will I need diode if I add button to this schematic?

texts:
Here is some pre-story. I removed ignition switch in my car which had five wires connected to it (accessories, ignition, starter, +12V for ACC&IGN, +12 for STARTER), and connected the wires to the relays. Relays are controlled by arduino board. The arduino board is controlled by phone over bluetooth. Everything works great, just like I wanted it to be. However, I noticed that in some cases I might want to have a button to control starter relay without arduino. This might be useful if I stall the car and have to re-start the car. In this case I wouldn't want to reach for the phone, but just use starter button. So I bought 3A@125VAC/1.5A@250VAC pushbutton just for that.

Now I have three options of connecting this pushbutton.

Put it between 5V and resistor that goes before transistor.
Put it between ground and relay coil wire
Connect the button to arduino. Read the input on arduino and then set the output for +5 control pin.

Here is the picture of schematic. "Digital pin" is some digital pin on arduino board that send +5V. On the top "+-12V" is just a sing +12V wire. And finally RLY1 is the relay.

I kinda see why and how I would want to have a diode for case 1 and 2 so that the current doesnt flow to the collector side of transistor. Or similarly have diode so that current doesnt go to the digital output pin on arduino.

Does this make any sense?


texts: Simplest way to switch inductive load with arduino?

texts:
I'm trying to switch (just on/off) a 3.7V motor (coil resistance 2.2 Ohm) and a 6V motor (coil resistance 8 Ohm)  with an arduino mini. And I have trouble finding an universal way to do so. What I know so far:

there has to be a fly-back diode (D1 on schema)
There are 4 possibilities for the switch

a) relay (simplest, Arduino Uno with 12V pump: transistor or optocoupler+12V relay?)

b) NPN transtor https://electronicsclub.info/transistorcircuits.htm

c)(low gate voltage) MOSFET How to drive low impedance load with arduino and transistor

d) optocoupler (see the relay link)
A Low side switch is better than high side switch. High side switch and Low side switch
All grounds have to be connected together (unless using an optocoupler) Does signal ground have to be connected to actual ground?

I would like to keep the component count and price to a minimum. Relays are big and expensive so I hoped a transistor would do.

Questions:

What components I can safely remove from the schema?
What is the most important thing to get right?

I understand I need R1 to prevent a floating pin What does pulldown resistor from Arduino's output pin to ground do? Is it necessary?

I'm trying different motors to see which one works best.

Edit:

In the end (after reading replies) have built the following schema:

So the morale is points 3 and 4 are extremely important


texts: How protect analog input connected to thermistor through long wires

texts:
I'm developing a data acquisition board for 8 thermistors hooked up through 3 feet wires. The board is gonna be installed inside a package unit air conditioning.
In there, we have compressors, fan motors and contactor generating EMI.
I was wondering how to protect those analog inputs without degradation the thermistor resistance the microcontroller's ADC is measuring.
I saw here and in other forums some alternatives based in 100-ohm resistor and TVS diodes. Also I took a look at the ADG5412xx, but it is for voltages higher than 3.3 v which is the MCU operation voltage.
I would appreciate very much some help with that.


texts:
I'm looking to add a controlled amount of delay to some 75 ohm impedance RGB lines. The signal will be an AC sginal. I'm looking for about 30 ns so would something like the Maxim DS1135 be a good chip for doing this? Also do I need to terminate the line with 75 ohm resistors to ground before inputting to the delay IC? Correct me if I'm wrong but a signal with an impedance of 75 ohms and a peak to peak voltage of 1 means the signal is 13.333 mA correct?

(Edit) I need a chip because I will be using a PCB design. I will be doing some processing on one of the RGB lines which will put it 30ns behind, and so I need a 30 nanosecond delay.


texts: Using DC-DC converter with input voltage same the specified output voltage

texts:
I have a circuit board with a full bridge PWM motor control. The full bridge component (HIP4081A) needs 12VDC input voltage but can be used to switch 24VDC voltage motors. I want to use the same circuit board for both 12VDC and 24VDC systems.
I use a 24-to-12V DC-DC converter (tsr 0.5-2412) to get 12VDC to the full bridge. This works fine when the input voltage is 24V but when input voltage is 12VDC the DC-DC component (tsr 0.5-2412) gets an input voltage that is lower than specified minimum input voltage which is 15VDC.
When the input voltage to the 24-to-12V DC-DC converter (tsr 0.5-2412) is 12V the output will be about 1V lower. Is it ok to use the DC-DC converter outside the specified input range or is there a risk that I destroy the dc-dc converter?
Is it a good idea to short circuit the input and output of the DC-DC converter e.q via MOSFET when voltage drops below 15V? Or is there a better way to solve this problem?


texts: having trouble finding phase angle on Pspice

texts:
The only issues I can see is that my circuit contains a parameter called AC from the AC voltage supply, whereas the one in the example does not ! I don't know how it would work without AC voltage though.

I have used this method of testing for phase angle before, using the total current at the start of the first resistor, and using v+ and V- measurements of the source, in order to compare the two. So I can't see how it is not working this time !

Please if someone could shed some light on this and give me some insights into how to do this is would be very grateful as I have spent a long long time trying to complete this question and others with no avail !

EDIT

Here is the information I have been using :

I have been asked to use time domain (transient) in order to make the analysis, so have been following the instruction to the letter as far as I'm aware, but can't seem to solve the issue, thank you for already explaining that the AC Parameter will not make a difference.


texts: Circuit for model railroad building lighting control

texts: The building has 10 separate rooms. Want the circuit to turn on LEDS to light each room sequentially. Another words you turn the circuit on, a 555 timer pulses and turns on room one. About 5 seconds later, the clock pulses again and turns on a second room while the 1st stays on. this continues until all 10 rooms are finally lighted. Than they reverse and start to go out one by one. Than the cycle keeps repeating. I want to build this using the CD4000 family.


texts:
I have a 14-bit ADC. However, looking at the datasheet (see table 2 on page 5), the effective number of bits (ENOB) is always less than 12 bits.

Why is my the DAC claiming to be a 14-bit ADC when it only has 12-bit accuracy? What is the point of having two extra bits if they are meaningless?


texts: What are Hall sensors used for in a brushless DC motor?

texts:
I'm trying to buy a brushless DC motor for a hobby project, and I found a nice one, which lists the information table I pasted at the bottom of this message.

As you can see at the top of the table you can choose between one with, and one without a Hall sensor. So I was reading up on Hall sensors, and I read that Hall sensors can measure the strength and direction of an electromagnetic force. And (as far as I understand) this can be used for measuring the position and speed of rotation within a Brushless DC motor.

My questions are:

Am I correct in what I say above?
I also need a rotary encoder for my motor. Can a Hall sensor be used for the same purpose as a rotary encoder?
Can a motor with a Hall sensor be reversed or does that have nothing to do with it?
Or am I wrong here and is the Hall sensor used for something completely different?


texts: RS-485, 5Vdc and 24Vdc over a single Ethernet cable

texts:
I recently started to work on a project that involves motor drivers and microcontrollers in a network topology. This is rather a theoretical question, just something that I was thinking about. The microcontrollers run on 5Vdc, the motors run on 24Vdc and the microcontrollers need to communicate with each other. The microcontrollers control the motors locally with pwm signals using the 24V supply. This is now solved with many cables.
So my question is the following: since RS-485 would only use up 2 wires, 4 wires would still remain in an Ethernet cable, so would it be possible to use these remaining wires to provide both the 5V and the 24V voltage levels, so that only one cable is used?
I am asking this more from a noise point of view. The 24V network has motors on it driven by pwm signals, I can imagine that this could cause some noise, the RS-485 would also add to that, and then there is the 5V for the microcontrollers and sensors. But on the other hand the point of a twisted pair should be noise reduction. We are talking about 3m wires maximum.


texts: What should be the distance between the object and the sensor (TCRT5000L), for sensor to be able to detect it? I foun in datasheet operating distance is 0.2 to 0.15mm, but it seems little to me.


texts: understanding DRC errors in ares proteus

texts: i'm new to PCB and this my first printed circuit , i cannot understand what the DRC error is telling me , could you help to better read the error log and also help me with this error


texts: How to find out whether serial standard is RS232 or TTL when stated as "serial(RS232/TTL)"

texts:
I am recently moving from C programming into automation engineering. I have learned about RS232 and TTL standards, and I understand that they are based on the same concept of serial communication, however TTL uses logic voltages (3.3 V or 5.0 V) to be compatible with microcontrollers, while RS232 uses higher voltages for historic reasons (signal-to-noise-enhancement).

To start connecting to the "real world", I planned on using a simple printer to start practicing sending bits via the COM-Port. Here is a link to an example: https://de.aliexpress.com/item/JP-QR203-58mm-Micro-Receipt-Thermal-Printer-RS232-TTL-USB-Panel-Compatible-with-EML203/32693670343.html

This device seems suitable for my needs, however, some questions remain, as I am very eager to learn, but still a newbie in electrical engineering:

The interface is stated as "Serial (RS-232,TTL)" - Is there any way to find out which standard is implemented on the PCB exactly, RS232 or TTL?

Another suitable device seems to be this one here:
https://www.amazon.de/WELQUIC-Thermodrucker-Bondrucker-Bluetooth-Standard-Art-1/dp/B075GG7VJT/ref=sr_1_2?ie=UTF8&qid=1533543476&sr=8-2&keywords=welquic+printer

Again, how can I figure out whether RS232 or TTL is implemented?
This device seems to feature a Mini-USB port for USB-communication and another Mini-USB port for RS-232/TTL communication... Which cables would be needed? Is there something like a serial/Mini-USB adapter cable? As I understand, USB standard has to be converted to RS232 or TTL - So my second question basically is, how can there be a port in Mini-USB-format for RS232/TTL?


texts:
CAN Transceiver Transmit Mode

I try to understand the transmit functionality of a CAN transceiver. I found this post a good starting point, but it doesn't completely answer my question.

Block Diagram

Let's say we have the following CAN transceiver block diagram (VDD = 5 V / VSS = GND = 0 V).

(CAN Physical Layer Discussion p. 5)

CAN Bus Basics

In my understanding there are a few simple basics for an ISO-11898-4 "complient" CAN-Bus.

In the recessive state: CANH and CANL should be at the same voltage level (≈ 2.5 V).
=> CANH ≈ 2.5 V & CANL ≈ 2.5 V
In the dominant state: CANH and CANL should have a high voltage difference (≈ 2 V).
=> CANH ≈ 3.5 V & CANL ≈ 1.5 V
There must be at least one termination resistor of ≈ 120 Ω.
A logical TxD LOW or 0 bit is transformed to a dominant state.
A logical TxD HIGH or 1 bit is transformed to a recessive state.

This should be enough for the first understanding!

Functional Description

Recessive state

CANH and CANL output transistors are open (high impedant).
The recessive voltage level of CANH and CANL = VDD / 2 ≈ 2.5 V is created by the following circuit part.

Dominant state

CANH and CANL output transistors are closed.
Let's say:
Transistor (collector emitter voltage): Uce = 0.1 V
Didode (diode drop voltage) UD = 0.5 V.
=> CANH = VDD - (Uce + UD) = 5 V - (0.1 V + 0.5 V) = 4.4 V.
=> CANL = Uce + UD = 0.1 V + 0.5 V = 0.6 V.
=> UT (Rtermination voltage) = VDD - (2 * (Uce + UD)) = 5 V - (2 * (0.1 V + 0.5 V)) = 3.8 V.
=> IT (Rtermination current) = UT / 120 Ω = 3.8 V / 120 Ω ≈ 32 mA

QUESTIONS

Did I miss something or is my calculation valid (just for basic understanding :) )?
Can anyone explain how the recessive voltage generator in picture 2 works in detail? How big are the resistors to CANH and CANL?
Will Itermination double if there is a second termination resistor?


texts: Higher spec LED near the center of the wafer?

texts:
Does anyone know if it is true that chip tolerances are tighter towards the center of the wafer?

There is a vendor that claims that "we pick our LEDs from the center of the wafer".

Because of inherent production variation, LED manufacturers sort the LEDs so you get parts with similar color rank or Vf. But does this have anything to do with where the die is positioned on the wafer?


texts: What is the purpose of this resistor between BJT Base and Emitter?

texts: Can someone please explain to me what the purpose of this resistor is?


texts: What is the purpose of the Vref in this opamp comparator circuit?

texts: I am designing a simple circuit for a sensork, and this was an example circuit given by the manufacturer. The sensor is a magnetic sensor in a standard wheatstone bridge arrangement. I was wondering what the purpose of the Vref is. Why not just input the Vout+ directly to the opamp?


texts: Using an electrical transformer for simple project

texts: I have an electrical transformer with 4 wires.. an orange pair and a black pair.. I have measured the resistance across the black pair, and it is significantly higher than the resistance in the orange pair.. I plan to connect this transformer to my mains and see if it steps down the voltage.. also I plan to build a rectifier circuit to convert my voltage into DC.. I am however a bit scared of connecting the transformer to the mains because this is 220/240 volts and might be harmful to me... just seeking an experts opinion please.. thanks for reading


texts: 50Hz noise affecting my oscilloscope and i want to know how to stop it

texts:
I need help my oscilloscope keeps showing 50HZ 40mV Noise when the probe is not connected to any circuit,
I think The probe is working as an antenna for the 50hz from the power line !
How can i stop this because im trying to measure low voltages and frequencies!
My oscilloscope is Hantek Dso5102p 50hz/220V


texts: Subtracting Audio Signal from Ambient Noise Signal

texts:
So I'm pretty well-versed in the software world, and my buddy and I decided to tackle a hack idea to get into hardware hacking but we're trying to figure out whether our implementation will actually be feasible the way we're thinking about it.

The basic gist is this:

Some audio is playing through a car's speaker system. We have direct access to that digital audio stream. We also will be capturing the ambient sound, which is a mix of the audio song, any white noise, and conversation between the passengers in the cabin. We would like to take the latter (ambient) signal and subtract out the song's signal as much as possible to detect (roughly) whether or not a conversation is happening past a certain volume threshold (the resulting output for this measure can be 0 or 1 or analog).

Our proposed solution is to feed both signals into a differential amplifier and then capture the output and make meaning of it. We're not entirely sure whether this is the correct rabbit hole to jump down. We do know that this is possible via software with Least Mean Squares Filtering (or Finite Impulse Response filtering - although it doesn't bode too well in real time), but, again, we would like to try to get this done through hardware for the fun of it.

An issue we were thinking about is that the audio signals may be out-of-phase, but, since we're both noobs, we're not entirely sure how much of an issue this is in practicality.

Please excuse my ignorance if this is a dumb question. I tried looking for a similar question in the group but couldn't find anything that I perceived as close.


texts:
I have got an old camera that runs on 7.2V (2 cell li-ion). I only have a 4 cell li-ion battery. Is it possible to divide the voltage without using a DC-AC converter and a transformer?

I have looked up "Voltage divider", but this will not work as I don't know the resistance of the camera, which probably isn't constant either.

Is it possible to do this?


texts: Why is data delayed by 1 clk cycle in AHB write transfer?

texts:
Here is image showing a basic write transfer:

The HWDATA comes 1 clk cycle after the control signals and the address. Why is this so?
What will happen if the HWDATA is put on the bus at the same time as the address and control signals and kept there?
Is it true that the address, control signals, and the HWDATA must be kept on bus for only 1 clk cycle and then be reset to zeros?


texts: Operating region for NMOS transistor - Can someone check my work?

texts:
Given: Vtn = 0.4V

NMOS1
Vgs = Vg - Vs = 1.9V
Vgd = Vg - Vd = -0.6V
Vgd < Vtn and Vgs > Vtn
My answer is Saturation Region

NMOS2
Vgs = Vg - Vs = 2.2 - (-2.3) = 4.5V
Vgd = 2.2 - 0.5 = 1.7V
Vgd > Vtn and Vgs > Vtn
My answer is Triode/Linear/Ohmic region

NMOS3
Vgs = 0.9 - (-2.5) = 3.4V
Vgd = 0.9-0.5 = 0.4V
What region is the NMOS operating in if Vgd is equal to Vtn?

I have attempted to answer 1 and 2 as highlighted above but am unsure. As for number 3, my book only has cases for Vgd>Vtn and Vgd


texts:
I think it is a very simple test to perform, but I do not know the correct equipment for this.

I just have a basic LED circuit, resistor before LED, but I want to test a short in parallel with the whole circuit. I was able to test this with a normal Voltage power source but after sometime it burned. During this test the Voltage went down to almost 0 V, and current went as high as the source was able to supply.

Is there some sort of equipment to test short conditions?
I am intending to test current(mA) against temperature.

Any help will be appreciated. Thanks in advance.


texts: How to fake an encoder signal with one function generator?

texts:
I wish to be able to have a encoder quadrature signal that I could set the frequency to some specified values (from 10 to 60 Hz). I have a function gen that fulfills the freq requirements but it has only one output.
So the question: is there some kind of circuit (analog or IC) that I could use to add 90 degrees of phase to a signal generated by a function gen, and then use both as they were the outputs of the encoder. It means that the gain should be unitary as well.


texts:
I need an active probe for use with a spectrum analyzer and oscilloscope. My scope has contacts around the BNC connector for powering a compatible probe. The spectrum analyzer is a different story. There is no port for powering a probe.

Looking around I see that the Tek 6201 seems fairly generic with a lead to be attached to power. Something generic is preferable as I want to use this with both of my instruments. Would this suffice? If so, how do I power it? Specifically, what voltage/current requirements and interface?

My scope is a Tek MSO2024 and my spectrum analyzer is a Rigol DSA815.


texts: Why would a modern digital clock rely on mains frequency?

texts:
I am in the military, stationed in Djibouti, Africa.  We generate 240V/50Hz power on base, but some buildings also have 120V outlets, which I assume is transformed somewhere else on base, probably at the diesel generating station.  I also assume that it is 50Hz as well (see below).

We just received a new coffee pot with a 120V plug and a clock/timer:

After two days of setting the clock, hoping for hot coffee when we arrive at work, and finding that the time on the display was incorrect, I realized that the clock is probably 5/6 slow due to the fact that the power is 120V/50Hz instead of 60Hz.  A bit of timing confirmed that the clock is, indeed, ten minutes slow every hour.

I would have thought that the internal clock would be a simple quartz clock running off rectified DC, but that wouldn't (I assume) affect the frequency of the crystal.  I'm guessing, then, that the clock is a different A/C circuit.

Is there a reason (cost?) that the clock relies on a 60Hz signal?


texts: What are the critical characteristics of an op-amp for buffering reference voltages?

texts:
So, let's say I have a precision voltage reference with the output fed to a voltage divider which is tapped at two places for voltages A and B. I've made sure to use precision resistors (or calibrate) and the divider doesn't overload the voltage reference. So at this point, I have maintained line regulation up to the taps but significantly degraded load regulation there by using a voltage divider for A and B but I thought that the best thing to do now is to use an op-amp voltage follower to buffer each of A and B. The characteristics that I've identified so far are that the input impedance should be very high, the input offset voltage should be as low as possible, low input offset voltage temperature drift and the input and output ranges should match. It seems like CMRR wouldn't matter in this application. On top of that, I'm not sure what else to look at. Noise should be low but how low and relative to what exactly?

To give a couple of examples, if I use the LM4040 4.096 Grade A then I should have, at worst, 14mV of error due to temperature drift and load, right? So how do I make sure that my buffer doesn't make that worse? What about something like the REF3240 where the error might only be in the tens of μV? Isn't it the case that something like the OPA340 would work fine in the first case but might not be quite good enough (just because of the input offset voltage and its temperature drift) for the second?


texts:
In this case the Led blinks,

In this case the led just glows

I've committed some terrible mistake, please educate me.


texts: Can somebody explain to me, someone who has no idea of EE, what a unipolar inductor is? Im trying to understand the process by which the rotational energy of a black hole is converted into energy to power relativistic jets. In the book i read (https://1lib.eu/book/2339827/854387  [pages 157, 158, 159]) it is said that the black hole in the magnetic field of the surrounding gas behaves like a spinning conductor in a magnetic field, therefore like a unipolar inductor (apparently). I already asked this on the physics site but that has for now been left unanswered, so I thought I`d ask here about the analogy the book uses.


texts: using 1.8V, max 40mA to switch a 12V, 70mA load (MOSFET data sheets?)

texts:
I recently asked a question about controlling a magnetic relay with a solid state relay.

The reason is that I'm controlling the circuit with a MCU that has a max ouput of 40mA per output pin and the coil on the relay draws 70mA. Also, the MCU is operating at 1.8V and the relay coil is 12V (as is the external load).

It was suggested that I use a MOSFET rather than a solid state relay.
While researching that I have become very confused trying to iron out the information on the MOSFET data sheets.

Can anyone give me some tips to make it more understandable for a newbie hobbyist?

EDIT - what I think will work to see if I'm totally confused:

gate source threshold voltage - 1.2V (MOSFET will "turn off" under 1.2V?)

gate source voltage - 1.8V (MOSFET is designed to be fully "turned on" at 1.8V?)

continuous drain current - 2A (MOSFET is designed to handle switching up to a 2A load?)

drain source breakdown voltage - 40V (MOSFET is designed to switch up to a 40V load?)

drain source resistance - 260 mOhms (using ohm's law to calculate the load that will be placed on the MCU output pin, this is way below 40mA?)

Am I reading all of this correctly?


texts: What happens to a generator when we rotate it in open circuit(no load)? Let's say we have an old bicycle's dynamo without regulators, capacitors and battery. What happens if we remove the lamp and turn the wheels? Do we transform mechanical energy into electrical energy? And then what happens to this energy?


texts: Precision Current Sink for LED Modulation

texts:
I one of my first designs, I am attempting to simulate a high precision optical transmitter using an LED by varying the brightness in linearly with the incoming signal. The input signal is BFSK, either 30kHz or 50kHz, and ranges from 0V to 5V.
The LED's brightness varies linearly with forward current. For this purpose, my goal is to have 20mA forward current when the input is 0V an 80mA forward current when the input is 5V.
To do this, I've referenced this guide for higher current LED modulation:Linear Current Modulators for high-power LEDs. My circuit implements the same precision current sink. My circuit is shown below:

To get the value of R5, I chose that the resting LED current (2.5V input) should be at 50mA (between 20mA and 80mA). Therefore,
2.5V=(0.050A)R_5 -> R_5= 50 Ohms
This brings me to my first question: At 5V, the forward current, using a 50 Ohm resistor, would be 100mA, not the desired 80mA. How can I properly set the 20mA-80mA range using only R_5?
I believe that, theoretically, the input voltage (green) and forward current through the LED (blue) should both resemble a sine wave since the input is AC. However, the output I get is different as shown below:

It looks like the forward current does not rise above the designed 50mA. Looking at the opamp's noninverting input (blue) vs. the opamp's output (green), the output gets limited at 3.5V:

This overall operation of this circuit deviates from what I expected since the output gets limited instead of varying linearly. What can I add or change about this design to achieve linearity?


texts: How to simulate PCIe to debug my FPGA endpoint

texts:
I'm working on an FPGA controller connected through PCIe. The only way I can debug the hardware is using chipscope. So I execute commands through my driver and check out the signals from the FPGA.

The problem is that it takes a lot of time to build the project and load it to the FPGA every time I want to check a signal to debug the project.

Is there an easier way to debug an FPGA connected to PCIe?

Is there a way I can simulate all the PCIe signals and not have to run the FPGA at all?

To be more specific, I would like some kind of infrastructure that I can write a command through the linux driver (writeq) and TLP packets would be sent to my verilog design..


texts:
Excuse the simpleton schematic, but I don't understand how I should use/wire a P or N channel MOSFET to disconnect a load.

I am using this MOSFET, this solar charger, this PV solar panel and this LED driver.

During daytime, a PV solar panel shall charge a battery (works). During nighttime, the battery shall power an LED driver (works). I assumed I can use a P channel MOSFET as shown to automatically disconnect the LED driver during daytime and only be powered at nighttime. What would I have to do to do it right?

Edit: No matter what the insolation (0-7V output by the solar panel - covered, indoor, in full sun), the LED remains off at all times (the driver receives near zero voltage). I checked the MOSFET and tried it with another of the same type.


texts: NRF52 Debug Connection - GndDetect and VTRef

texts:
I'm currently in the process of laying out a debug connector for an nRF52 chip. I'm planning on using the IDAP-Link. Most of the pins are pretty straight forward to connect (ie: for SWDIO I simply route that pin on the nRF52 uC to pin 2 on the debug connector). However I'm having trouble figuring out where to connect VTRef and Gnd Detect. With VTRef do I simply connect it to the same power source for my chip? I'm pretty sure this is the correct answer but I just want to confirm as this is my first time laying out a debug connector.

Secondly for the GndDetect pin, the documentation I've been able to find isn't very helpful. ARM's info center states that it can be used by the target system for debugger presence detection, but I can't find anything in the nRF52 documentation about where to connect it (I'd include a link but I'm limited to two due to my current reputation). Does the fact that VTref and GndDetect aren't in bold on the ARM infocenter mean that they're optional and don't have to be connected?


texts: What is the highest frequency possible to be generated with electronic circuits

texts: First, its sound oscillators for low-frequency audio waves. Then Radio wave oscillators varying from low frequency AM to high frequency Cell-phones. Then microwave oscillators in the giga hertz. What is the highest frequency that electronics can generate and what are the uses?


texts: sim800 restarts on battery but works fine on power supply

texts: I am using SIM800L with PIC18F66J94 , but issue is that SIM800L keeps on restarting when powered by battery but works fine when powered by power supply . I have changed some battery to verify the issue but still sim800l restarts on battery .


texts: Basic question about diode voltage drop and resistor position

texts:
I'm new here and also new to electrical engineering so no fancy stuff yet, still tinkering with basic components such as resistor, led, caps and batteries. I think I caught up with the bad side of conventional + and - so I'd like to impose a few question.

I was reading this book "All New Electronics Self-Teaching Guide, 3rd Ed" by Kybett and Boysen to remembers bits what I've learnt so far. On Ch 2 about diode, I stumbled on the idea of the voltage drop in diode. In a series of resistors, it's pretty straight forward, it's a ratio of resistors' value, higher value drops more voltage, etc.

But when a diode is introduced after the resistors, you have to decrease the source voltage with the voltage drop of the diode first before you can measure the new voltage drop of each resistor. Why is this happening? Is it pretty bizarre to count backward first as the current move from + to -.

Also I've seen several examples where a resistor is introduced before anode, which I think is logical and introduced after cathode which is plenty weird as resistor is used to limit the current going into the led but in actual reality, both do just fine(I tried both ways). Is this because of positive charge and negative charge? Because P-N junction, holes and p stuff?

Update (request by Anindo) :
Here is the page of the book in googlebook

Previous pages explaining in simple series are gone.
For full book you can see it on page 47 (or 71/450, ch 2 starts at 59/450) here
(Please edit this, if it's against the law)


texts: What is the equation for "beff", i.e., "Gain Factor in Saturation" in BSIM4?

texts:
Using the device parameter list in Cadence, I found out that ID follows this equation exactly:
ID = 1/2 * beff * vgt**2

I also found out that beff is not linear, as expected.
I checked the BSIM4 documentation but either I cannot find the equation or I do not know the name(s) used to describe this parameter.
I need the equation because one analytical formula that describes my circuit has this term
$$
\mu_{0}C_{ox}\frac{W}{L}
$$
So, I would appreciate it if anyone can point me where to look.


texts:
I was readings this article and extracted from it that "The maximum efficiency of a Full Wave Rectifier is 81.2%". Is that true, or alternatively is there some other fundamental limit on AC/DC conversion efficiency?

Since FWR is the canonical stage in converting AC to DC, does it stand to reason that any DC-operating electronics that are not run from battery power intrinsically wastes at least 18.8% of the energy delivered to it by the grid? That sounds crazy to me, what am I missing?


texts: Coefficients and harmonics of a PWM signal

texts:
I have been doing some research into the fourier analysis of square wave signals for my project which involves filtering of PWM signals. Just a few things online that I have found which don't make sense to me which hopefully somebody could clear up. First off this document by Texas instruments discusses the Fourier coefficients of a PWM signal with duty cycle pT. The image of the signal in the example is shown here:

And so the text goes on to to discussing the derivation of the Fourier coefficients of this signal using first principles.The formulas along with their results are shown in the next image:

The problem I am having here is that I cannot evaluate the highlighted integral and get the same expression for the A sub n terms. When I do it taking the limits from \$\frac{-pT}{2}\$ to \$\frac{pT}{2}\$ I get \$\frac{K}{n\pi}[\sin n\pi p]\$. Could somebody evaluate this integral and show me how they got this.

Here is my attempt to evaluate it:

Also this document says that the fourier series is a sequence of higher end frequencies stretching out on both sides of the fundamental frequencies which are integer multiples of the fundamental frequency. The coefficients are the amplitudes of these frequencies on the frequency spectrum. I cannot find any formula that explains why these harmonics are integer multiples of the carrier frequency.

This online tutorial for example I can't get my head around. Here is the image of the square wave upon which a fourier transform is performed:

As you can see the frequency of this square wave is 100KHz. But then when the Fourier transform is performed you get given this image of the signal in the frequency domain:

Could somebody explain/show why this signal has frequency components at what I believe are 200kHz, 400kHz, 600KHz, and 800KHz. I understand its central DC component of 1.65V but other than that I don't get this.

Thanks in advance,

Simon.


texts: How to use nodal analysis in resistive circuits

texts:
I am trying to solve a question in a text book of resistive circuit using KVL. The circuit is as follows :

I have to calculate the voltage through each resistor. What I have got is:

V1 = 24V
V2 = 18V
V3 = 18V
I1 = -3A
I2 = 3A

The actual values are (on the answers sheet)

V1 = 24v
V2 = 6V
V3 = 6V

An answer with proper calculations will be highly appreciated.


texts: Finding output of the operational amplifier with diode at inverting pin

texts:
My question is about solving the output of the op-amp.

The input 'x' is a fluctuating (AC) signal. The output is piecewise function but I lost track of solving it.
I know that Vb = 0. So
(vb-Vout)/150k=(-Vout)/150k
Applying nodal analysis at Va, I get
(Va-x)/10k+(Va-(-15))/68k+(-Vout)/150k=0
(Va-x)/10k+(Va+15)/68k=Vout/150k
Please let me know how to solve it. The op-amp can be of any family including LM741 and diode can be any diode.


texts: Learning videos for electronic concepts?

texts:
Are there any interesting and graphical videos for learning electronic concepts, like basic principles of capacitor, inductor, resistor, transistor and other advanced concepts like digital electronics?

I am mostly looking for animated videos which would teach me concepts and possibly their practical applications. I have been reading books but haven't made much progress.


texts: Assignment compatiblity error in verilog

texts:
//Universal shift register..32 bit
// en_out=1 serial out..
//en_out=0..parallel out
module Uni_shft_reg(data_out,
data_in,
s1,s0,
lft_shf,
ryt_shf,
en_out,load,
clk,reset);
output reg [31:0]data_out;
input [31:0]data_in;
input s1,s0,clk,reset,lft_shf,ryt_shf,en_out,load;

reg temp1[31:0],temp2 [31:0],temp3[31:0];
reg f1,f2;

always @(posedge clk or negedge reset)

begin
 if (!reset)
  begin data_out <= 32'd0; end
 else
  begin
   case ({s1,s0})
    2'b00 : data_out <= data_out;
    2'b01 :begin
            if(en_out==1)
             data_out <= {ryt_shf,data_out[31:1]};
            else begin
                     temp1[31] <= ryt_shf;
                     data_out <= temp1;
                     temp1 <= {temp1[30:0],1'b0};
               end

           end
    2'b10 :begin
            case(en_out)
           1'b1: data_out <= {data_out[30:0],lft_shf};

            1'b0: begin
                     temp2[0] <= lft_shf ;
                     data_out <= temp2;

                     temp2 <= {temp2[30:0],1'b0};
 end
             endcase
           end

    2'b11 : begin
            if(en_out==0)
             data_out<=data_in;
            else
                begin
                 if (load)
                 temp3 <= data_in;
                 else
                begin  data_out<= temp3[31];
                 temp3 <= {temp3[30:0],1'b0};end
               end
            endcase
            end
   endcase
  end
end
endmodule

this is the code which I have written for universal shift register..
On compiling...I am having an error which I am not able to fix.Please help me out..
thanks.

ERROR : Assignment compatible type required for assignment.

errors in the line
line 33 , 34 44 46 58 61 63


texts:
Let the open loop transfer function of a positive feedback closed loop system be K(s−3)/(s^2+3s+2), where K is a non-negative real valued parameter.
Consider the corresponding locus of closed loop poles. Which one of the following statements is TRUE?
a)The region (-∞, -2) lies on the root locus
b)The region (-∞, -1) lies on the root locus
c) The region (-2, -1) lies on the root locus
d) The region (-1, 3) lies on the root locus
I drew the root locus of the transfer function but there are two region on real axis
(-infinity,-2) and (-1,3) . But only one option is correct. What option should I choose?


texts: What is this black tape on my laptop's keyboard?

texts:
I am trying to replace the keyboard on my 2019 Samsung Notebook 9 Pro. I had to pull off a layer of black tape on the old one to get it out. The tape was glued to the bottom of the keyboard, right above the motherboard. It ripped a little bit as I pulled it off and I can see that it looks metallic on the adhesive side.
What is this? An electrical insulator? Heat conductor? Do I need to replace it, and if so with what? I attached pictures of the old keyboard in process of trying to remove the tape, and the new one without the tape.
Pictures:
https://imgur.com/a/VJHTdP3
Edit:
Here is a rough outline of where the layer was glued down. There were two pieces, the one on bottom is almost entirely pulled off in the pic, while the top one remains intact and glued to the keyboard.
Here is a picture of the keyboard area with the tape still applied, pulled from a parts supplier website: https://www.impactcomputers.com/image/cache/data/products/2/974577-800x800.jpg
My Pictures of Old and New Keyboard:


texts: how to adjust drain bias to keep power dissipation constant (HEMT)

texts:
I am reading a chapter in a thesis about using HEMT (high electron mobility transistor) as a cryogenic amplifier. The measurement scheme is to use the gate voltage fluctuation's influence on the drain source current.

In order to use a HEMT as an amplifier, it is necessary to find out what the gain factor is going to be, for a given circuit.  To that end, the paper shows plots of \$I_D\$ as a function of \$V_{DS}\$(image a) and as a function of \$V_{GS}\$(image b)  for fixed power dissipation values \$100\mu \$w,  \$10\mu \$w, and \$1\mu \$w.

My question is about plot (b).  The gain factor from the fitting of plot (b) is only valid, to my knowledge, if you can somehow adjust the drain voltage bias such that, throughout the operation of the HEMT, \$100\mu \$w \$= I_D V_{DS}\$.

Based on the plot, it appears that if you can somehow adjust the drain voltage bias to keep the power dissipation of the HEMT constant, you have a nice well defined gain factor over the entire range of the gate source voltage.

It is difficult for me to imagine a feedback circuit where the drain voltage bias does change to keep the power dissipation constant though.  Based on the circuit shown below, it doesn't seem to have such a feature.

My question is, given the fact that you are measuring the drain voltage and the drain current has to come from the source of drain voltage bias, is there a scheme to change the drain bias voltage to keep the power dissipation constant?

.


texts: what is the frequency spectrum mean in real life ? , if we said x(t) , we mean that each time we have an output which is represented by x(t) , also it can represent decaying ,growing of an object , it can represent the power of an object accroding to it's time . but how can i understand the X(f) , if we say that X(f) represent a power according to it's frequency , it's not make sense , because frequency is not an abstract thing that can we deal in real life , like time , we can not "feel" it , to give better understand for my question , let's say that x(f) is zero at f=5 , how this reflect in the time domaine ? , I  know that my question is a kind of 'philosphy' rather than 'electrical' :)


texts: Startup current for buck converter controller

texts:
In this Reference Design, a buck converter was designed using the UCC28881 controller.

According to the datasheet, the HVIN pin is a current source, with an internal supply current of 58 uA typically. Also, the minimum voltage at this pin is 30V.

In the design above, the HVIN pin is connected to the VIN net, which is the cathode of diode D6+D7, after the string of resistors R6-R15. The design says the minimum input DC voltage is 235 VDC.

My question is:
If I want the design to operate with lower DC voltage, that is, 100 VDC, what modification would I need to do? Would that string of resistors allow enough current for the HVIN pin at the minimum voltage? The diodes comes into play when bus voltage is >500V, so below 500V, the voltage at HVIN pin is the same as the bus voltage, right?

I'd appreciate any guidance to further understand the input side of this circuit.


texts: Charging batteries while powering device

texts:
This may be somewhat of a common question although there are some specific challenges in this one.

I have a bluetooth speaker which no longer charges its internal Li-ion cell. Using a new cell I can power the speaker's circuits from the cell although the circuit no longer charges the battery when connected to its 5v DC source. I therefore want to add a new charging circuit to fix this. Excuse the rudimentary circuit diagram:

simulate this circuit – Schematic created using CircuitLab

From reading up on many questions here I understand that it is not ideal to charge the battery and run the device from the battery at the same time? Assuming this is correct I need a way to disconnect the battery from the device's load when the external power is running. The charging board I have does not have separate pins/connectors for power out while charging.

My knowledge of circuits and electronics is very limited. How would I go about connecting the new charging board and having it work flawlessly?


texts: Converting a high frequency ac signal into square wave without creating a low pass filter by accident

texts:
I've been building an induction heater for a while now and wanted to get the frequency tracking to work properly. I need to convert the up to 600V ~100khz sine wave signal into a square wave, I've currently been doing it by using a 300kohm resistor and then clamping the voltage by using 2 back to back diodes.

The problem is that even very low capacitances of like those in a breadboard (~2pF) create a low pass filter which imposes a phase shift which makes tracking phase kind of hard.

How would I go about properly clipping the voltage without causing a phase shift?


texts: figuring out what is displaying on four digits led seven segment display

texts:
I'm trying to control portable highlight range using arduino. I've done automate switch easily using 4N35 because it is simple touch switch.

And next, I'd like to know current state from its display(on or off and strength)

range uses its own microcontroller so I couldnt find about.

is it possible to know what is showing from the display and how?


texts: What limits the number of MOSFETs/IGBTs in Series / Parallel

texts:
I was looking at HVDC systems out of curiosity and I have a question that I have not exactly found an answer for.

In HVDC converter, because of the high voltage (Tens/Hundreds of kV) they have to use so-called IGBT valves, which is multiple devices in series in order to increase the voltage blocking capability. My question is why is there a limit to how many devices can be used in series? Is it because the conduction losses are too great? Is this also why they can't use let's say 10 MOSFETs in series instead of a big IGBT?

I would also like to know how the parallelism is affected in this case. I know that for MOSFETs this isn't a big problem, as they conduct less at a higher temperature, thus no positive feedback leading to the destruction of the device. I'm not necessarily looking for a straight answer, I am happy to research this myself if I am pointed in the right direction.


texts: In the given circuit would CY2 connect the grounds leading to non isolated circuits?

texts:
Here's the datasheet for the part being used
https://www.cui.com/product/resource/pdqe10-d.pdf
I'm using this part to isolate different parts of a circuit.
The schematic above is the recommended EMC circuit.
Would CY2 non cancel out the isolation parts of the circuit because it would be connecting the grounds?


texts: How can I troubleshoot an active short circuit?

texts:
What are some effective methods of diagnosing an active short circuit? By this I mean a short circuit that presents itself only after a PCB is powered on.

tl;dr

I have a design in the prototype phase.  17 of my 20 boards work great.  The other 3 all have a short circuit on a 3.3V rail.  This only shows up after the board is powered on.  After removing most of the components on the rail, I tracked it down to an Ethernet PHY.  If I lift the IC off, my rail is rock-solid at 3.3V.  When I put it back on (also tried 2 new ICs), my rail is overloaded again and it drops out.

I have thoroughly visually inspected, and probed the board for shorts, but cannot find one.  I have lifted off pretty much everything around the IC (crystal, series resistors, ferrite beads, etc.) but still get the same behaviour.  I've also tried holding the chip in reset, but that doesn't help.
 I lifted individual pins on the IC (VDDIO) and that fixed it, but doesn't offer a real diagnosis.  I'm starting to wonder if there's an issue with the PCB fab, but not totally sure how it would cause this.  They claim to do 100% E-test.  Any advice will be appreciated!


texts: Confusion regarding the term"locking" in PLL

texts:
I am trying to learn PLL from a website

https://www.allaboutcircuits.com/technical-articles/what-exactly-is-a-phase-locked-loop-anyways/

]1

I came across a sentence containin[g the term "lock" twice ,1st for frequency and then for phase as shown highlight in attached photo

What is the simple meaning of "lock" in both these scenarios of phase and frequency?


texts:
I need to generate a pulse train with 12 bit resolution, controlled by an MCU.

The duty cycle can be in the range of 30 - 40%, while the frequency (0.5 - 32 kHz) is what needs controlling with 12-bit resolution.

The pulse train is to be used to control a Yaskawa Inverter which appears to operate under these parameters.

I think I have several options:

Find a chip that will generate this for me (controlled via SPI, I2C, etc).
Use a pulse generator like the 555, and find someway to vary the frequency using an output from the MCU - perhaps using the output from a DAC.

What is best way to do this?


texts: Arduino Fails to Program Custom NRF52, But Has Worked In Past

texts:
Background:

I have a custom board that consists of two PCBs connected via a 100mm Picoblade connector. The "Aux" board has a USB port, and CP2102N Serial=>USB converter. The "Main" board has an NRF52 moduel (MDBT42Q by Raytac).

I have 5 boards that I successfully flashed with the boot-loader via a JLink programmer. One board after flashing the boot-loader I was able to program ~5 times via USB with Arduino.

Come back a week later, I can not program the original board, nor can I program any of the other 4 boards. My friend is also unable to program the boards using both a Mac and PC.

Investigation:
For anyone familiar with this boot-loader, it expects a "softdevice" to be programmed, if one is not found, such as after burning the boot-loader, it starts up in DFU mode, which can be identified by a flashing LED. The "MODE" led on my board is flashing thus indicating the boot-loader is working.

Examining the physical signals on the board, it looks like the RX line is not being pulled to 0V, more like ~1V on a 3.3V logic level. There does appear to be some serial data on it though. Arduino is giving an error:

"Failed to upgrade target. Error is: No data received on serial port. Not able to proceed."

So this seems like it is realistically being caused by the NRF52 not driving the RX line low fully. I tried placing a 22k pull-down resistor from the RX line to ground, and then the CP2102N/NRF52 faults out upon communication and the RX line sits forever at ~1V.

The most frustrating thing is that I have programed one of these board multiple times, and "magically" it no longer works. Since I have 5 boards with the same issue, I find it hard to believe it is local damage like ESD etc.

Any ideas would be much appreciated.

Schematic:


texts: what is the best power management system (DC -DC)?

texts:
I would like to create a low-power management system (DC-DC Boost converter)to power up to two systems. The power management system will take a power input that changes from time to time and make sure the output is always steady at 3V (Boost voltage and lower current).
System 1: Temperature sensor circuit
System 2: Bluetooth chip (Connected to the sensor circuit)
Is it better to have one power management system that takes one input and release two outputs or two separate power management system where each is one input to one output?


texts: Help analyzing this BJT LED driver circuit

texts:
My usual focus is in digital electronics, and my BJT knowledge is fuzzy.  I'm working on a design using the Intersil ICM7245 16-segment display driver.  It recommends this circuit to drive the led segments with a higher drive current.

I'm having trouble figuring out exactly how this works, namely, so I can choose compatible BJTs for both the high and low sides, assuming my LEDs are Vf = 2v, If = 20mA.

2N2219 = NPN.
2N6034 = PNP Darlington

I duplicated it in Orcad/Pspice, and the results don't seem like it should work.  I think I can just choose some BJTs that match, but I want to make sure before I get the PCBs ordered.

Thanks!

Edit: To clarify my question, I understand that each transistor has a gain (hFE) of ~100, hence 1mA->100mA, and 14mA->1.4A.  I'm just not clear on how they made sure the bases would have those currents, and how much I can change the 14ohm resistor to keep my LEDs at ~20mA.


texts:
I have a PCB that controls some doors and gates at a facility. I need to determine the status of said doors/gates. There are no I/O ports at the PCB to read from, and soldering some probes to it is not an option. But there are SMD LEDs on the board for each door status. I had an idea that I could attach some photo sensitive elements on the LEDs to determine the current state with light.
What elements should I use to easily read the data with a simple I/O microcontroller? Light resistors? Maybe there is something already in the market for exactly this kind of application? There are multiple locations I would need to install this and I'm looking for a simple "plug and play" solution if that is even possible.


texts: Is there a theoretical limit to power supply transformation efficiency?

texts:
As I'm looking at some resistive-load applications I'm wondering whether there are any rules that put an upper-limit on supply-matching efficiency.  Because if a load isn't matched to the power supply in terms of voltage, current, and waveform (typically AC vs. DC) then we have to add all sorts of components, and depending on how mismatched the supply and the load are we may end up cooking off a lot of waste power to bring them into alignment.  To what extent is this just for design simplicity, and to what extent is it unavoidable?

Is there some minimum waste power cost involved in stepping voltage up or down?  My understanding is that in the AC realm it is negligible even in practice with transformers, as it is in the DC realm with multipliers.  But are these limited to cases where the input and output are multiples, and it gets more expensive in terms of waste power to hit a specific voltage that isn't an integer (AC) or binary (DC) multiple of the input?
Current seems to be an efficiency killer.  I.e., once current in a circuit becomes significant it seems like there's no way to control it without generating a lot of waste.  What theoretical constraints are there are on current throttling efficiency, and on what variables do they depend?


texts:
Given this circuit:

vs is small signal voltage.

I calculated the Operation Point and got that Vout must be equal to 0.
Now let us say I want to put a capacitor in series with R2.

Does this change my operation point?

I still get that Vout must be equal to 0.

The upper and lower Voltages of the Amplifier are 5 and -5.


texts: Is it just me, or is charging via usb not as good as using an outlet?

texts:
I used to charge my phone during the day at work with a USB cable (plugged into my workstation). Obviously USB doesn't provide the same amount of juice as an outlet so it took all day to charge but after the charge I noticed that the battery life was very low, maybe 2-3 hours.

When charging using an outlet, obviously it only takes about an hour to charge, but afterwards it seems that my battery life is much longer about 5-6 hours.

Both tests were performed playing MP3s all day, nothing that would cause a serious difference between the two tests.

Is it just me?

Edit: My question is about charging methods vs battery run time, not the charging methods. "Faster" in this case doesnt mean modified charging, it means using OEM charger with a power outlet.


texts: Hardware debouncing using 74LS14 - inverter input does not drop below 800 mV

texts:
I just recently started dabbling with electronics, so probably I just made some beginner's mistake. Here's my problem: I want to debounce a switch in hardware. During my internet research, I found this circuit in several variations; but pretty much all of them have in common, that they make use of 2 resistors, a capacitor and an inverting Schmitt trigger. So I built one using 2 10k resistors, a 0.1 uF capacitor and a 74LS14N (see the attached schema). My problem is, that the input of the Schmitt trigger only drops to exactly 800mV when the button is pressed, and the inverter's output stays low.
I am desperate to know where those 800mV come from.
It is also possible that something went wrong during my wiring (I built this on a breadboard with jumper cables); but there's only so many ways you can mess it up, and I tried many times already, even on different boards, with different cables and different ICs - nothing helped.


texts: Consume less energy by slowing down a 1 HP 220v pool pump motor

texts:
I would like to know if and how I could have my pool pump motor consume less energy. It is a 1 HP motor that works on 220v.  It is my assumption that if the motor runs slower, then it will consume less energy, such as a fan with different settings for the fan speed.  Does anyone know how to easily do this?

The volume of water that the pool really needs is a lot less than what is coming out and less gallons per minute through the pool pump that feeds the pool would not effect the final outcome which is to recirculate the water.


texts: What size resistor to light 3.3V LEDs from a 3.3V circuit?

texts:
I have some blue LEDs that are listed at having a Vf of 3.3V @ 20mA.  If I want to drive them from a 3.3V source,  do I need a dropper resistor?  Methinks I do, but R = (3.3 - 3.3) / 0.02 = 0 Ohms!

I know that LEDs can be finicky about how they're driven, so is there a rule of thumb? (There's no data sheet as they're unbranded.)


texts: What is the definition of absolute maximum ratings?

texts: What is the definition absolute maximum ratings? Does it vary from manufacturer to manufacturer?


texts: LM324 Difference / Instrmentation Amp 1mV Signals

texts:
I need to amplify 1mV signal from a wheatstone bridge (no DS available). 5kg max weight; output is 1mV/Kg @ 5V. The resistances are 880+880 and 749+749.

Currently I only have LM324 and LM358. And can procure quickly OP177 (others will take a week, which I dont have)

I have tried a standard difference amp (gain 470, 100 and then 1). I have tried the 02 op amp difference amp and finally an instrumentation amp all constructed from a single LM324 chip. The op-amp configurations are from TI SLOA034 http://www.ti.com/lit/an/sloa034/sloa034.pdf. I have used 10k 1% resistors (for unity gain) and 470K, 1K as and when required.

Simulation on Proteus (below) (and the feedback on LM324 on stackexchange) leads me to the conclusion that that it is the opamp that can't perform.

My questions are:

Have I understood the problem correctly (op-amp to blame)?
What parameter limits the the performance of LM324 in such applications?
What is the theory behind the problem?
What is the eventual solution?
Can I use OP177 to fix the problem?

Thanks.

EDIT:

The problem is depicted below in the picture (on the real circuit it behaves almost similar - the o/p volts are in the range of 0.3 - 0.5V the i/p difference is 1 - 2 mV).
In words it is as follows:

The S- input is at 2.500V. The o/p of the amp is reasonably correct +17mV.
The S+ input is at 2.515V. The o/p of the amp is reasonably correct -13mV.
The input at the non-inv pin of the final amp is 1.266V. [Correct]
The input at the inv pin of the final amp is 1.488V. [Incorrect - since both inv and non-inv should be at the same potential, op-amp golden rule. Meaning the o/p is not correct]
The output of the final amp is at 0.4896V. Incorrect, as per the eqn of an instrumentation amp it should be 03 times the i/p difference i.e 3 x 15mV = 45mV.

Hope it is all clear now.


texts: Does it make sense to use a clock input for combinational logic?

texts:
Today, I came across this problem on QuickSilicon's RTL Hackathon. It was to design an Endian converter.
The requirements were

The output should be available in the same cycle
The module should produce an output every cycle.
All flip-flops, if any, should be triggered on the rising edge of the clock and resets should be asynchronous.

The only way this would work (i.e output is provided on the same cycle as the input is seen) if there are no flip-flops in the module.
module big_endian_converter #(
  parameter DATA_W = 32
)(
  input   wire              clk,
  input   wire              reset,

  input   wire [DATA_W-1:0] le_data_i,

  output  wire [DATA_W-1:0] be_data_o

);

  // Write your logic here
  logic [DATA_W-1:0] be_data;
  always_comb begin
        // convert endian
  end

  assign be_data_o = /* code for reset */;

endmodule

That would imply that the design is combinational and the clock signal is not really used. Is this possible for a signal in the module is not used? Can this unused signal still be useful? If yes, how can it be useful?
Is it common to include a clock input for non-sequential logic?


texts: How to send ADC results over USB to my PC

texts:
I'm a beginner in STM32F4 and I want to design a data-acquiring system to send ADC results over USB to my PC. But I'm completely confused with the STM32 USB library. My questions are:

Which USB Class should I choose? Assert I have 16 or 24 ADC channels, 12 bits and the sample rate is not less than 9600 Hz. That needs a 2~3 Mbps speed.
Which function in the USB library should I call to send data?


texts: Switch resistor with n-channel MOSFET not working

texts:
So I try to amplify a photodiode signal with an operational amplifier.

As I want to amplify two signals (1 for a high-intensity light and 1 for a low-intensity light) I sort of need to design a switch for the feedback line. Currently, I'm doing it manually, but that's not good solution. :-)

To demonstrate my idea I have made the following schematic:

simulate this circuit – Schematic created using CircuitLab

Basically, I want to automatically be able to switch R1 to a lower resistor value (From 1MΩ to 180kΩ).
 - I tried achieving it with the 2N7000 Mosfet and an "extended" circuit, but for some reason, the transistor consumes a lot of the current.

What solution am I looking for here?


texts: Unplugging a router from the wall socket

texts:
When the internet appears to have crashed, the service provider invariably gives this advice as a first line remedy: unplug the router from the wall socket, then wait 5 minutes, then plug it back in.  Many times this remedy works.

Question: Why does the router care if it's been unplugged from the wall versus simply turning it off?  And more interestingly, what happens during the 5 minute interval that the router is unplugged; if it has no electricity, is it not merely in a deadened state?


texts: ARM startup file attributes vs GCC command line arguments

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The startup files for STM32 Cortex-M MCU's, for most GCC toolchains, often bundle the Atollic TrueStudio startup assembly files with HAL libraries, like for example in my case, STM32CubeF4.

I'm looking at startup_stm32f407xx.s, and it starts with a section looking as follows

.syntax unified
.cpu cortex-m4
.fpu softvfp
.thumb

I want to rewrite the assembler startup script to C, as part of learning the Cortex-M startup process.

When compiling with the GCC ARM Toolchain, or perhaps any other GCC based toolchain, does that mean I have to transfer these arguments, found in the assembly startup file, to command line arguments for arm-none-eabi-gcc:

arm-none-eabi-gcc -mcpu=cortex-m4 --mfpu=softvfp --mthumbz ...

Do these assembler lines correlate to the respective GCC arguments, or are they used for something entirely different?


texts: Why is the output impedance of a non-inverting op amp zero?

texts: Also is it actually zero or just very low?


texts: Making conductive traces for capacitive touchscreens

texts:
This is a follow-up to this question I asked years ago.

A short summary:

I'm using a head pointer (see my linked question for a photo) with a tip made of plastic,  thus non-conductive. The shaft is metal, and conducts well enough for a smartphone touchscreen. My goal was/is to make the tip effectively conductive so I can operate devices with capacitive touchscreens

My experiment

As my initial attempt I chose something as non-invasive as possible (as opposed to crafting a new tip) and decided to draw conductive traces on the existing tip. I chose this CircuitWriter pen to draw several traces connecting the very tip (i.e. the surface that comes in contact with the keys/the touchscreen) and the metal shaft of the head pointer, hoping the resulting path(s) would be conductive enough be registered by touchscreen.  Well, disappointingly, it was not the case. As to why that  is, I am lost.

Here is a picture of the result:

It shows one path going up to metallic shaft, but there actually three one. The tip of the tip is fully coated with the conductive polymer. Basically, all that is (light)-grey are CircuitWriter traces.

After applying it, I let cure at 15cm from 40W light bulb for 2h+, tested it carefully, re-applied, cured and left overnight.

My attempts at fixing it

When at first it not work (no reaction neither by an iPhone nor by a Sony Xperia), I suspected one path to the metal shaft was not enough and drew two more paths.  Still did not help.

Another guess: there wasn't enough contact betwen the plastic tip and the metal shaft. I wrapped the critical region with tinfoil to guarantee a conductive path. Still, did not work.

Do I need to apply yet  more of  the stuff? Why doesn't it conduct?

UPDATE 27 June 2016 - I solved my issue. Posting my finding for others as information.

I had no luck with the CircuitWriter, so a different approarch was attempted, which does work. The reliability of it (in regard of beeing registered by a touchscreen) depends highly on the "craftsmanship", but not so complicated that it could not be done by average people with average tools&materials.

So, a piece of conductive foam was used, the kind that comes with graphic cards and such nowadays. The foam was rolled tighly (or in my case I wrapped it around a Q-tip with the help of a thread to add stability) and connected with simple copper wire (for capacitance) and the whole thing was placed into the stick, thanks to it beeing hollow. That looks a bit ugly and primitive, but is working.
Here are the photos

Still I am  not completely satisfied. This construction is not very robust and the first incarnation failed after about 2 weeks due to the foam wearing out from typing. The positive aspect is that it is soft, so there is no chance of you scratching the screen.

The next approach I will try will be some adhesive copper tape, as suggested by HighInBC and Dmitriy Grigoryev. Should I post the results then?


texts: I am a newbie. I have a power bank which gives 5 v output from a USB. Now I need to step down the 5v into 1.5v to run a small motor. I have searched a lot to find any readymade IC... But unable to find. Can anyone help me, how to convert 5v to 1.5v ?


texts: What type of socket is needed if the documentation states "17 Way Molex SIL 6471"

texts:
I have a coin validator (for a fruit/slot machine). The main connector on the board has 4 pins then a space and then 12 pins (see picture).

The manual states the following "Connector types used:- 15 Way Molex SIL 6471 or 17 Way Molex SIL 6471"

I've Googled "17 way Molex SIL 6471" and not managed to find any.

I wondered if I could use a 4-way and a 12-way side by side so I looked for those and found references on eBay to a "MX-6471-121 Plug wire-board KK 254" which looked promising but then I also saw a "MX-6471-131 Plug wire-board KK 254" and a "MX-6471-141 Plug wire-board KK 254"?

At that point I stopped and came here to ask. Can anyone help point me in the right direction of what socket I need for this?

The plug is approximately 48mm long, 5mm wide.


texts: Current Sense circuit with digitally programmable gain

texts:
I'm designing a precision source meter and I wanted to put a couple ideas out to the community. One thing I will note is that this device has 32 channels, so I need to be very cognizant about both component cost, and component size.
Current sense circuit
You can see the current sense circuit below. The dynamic range of this circuit is pretty big. It needs to measure up to 125 mA and down 100 nA. The load voltage is +/- 10 V. I was thinking about using an instrumentation amplifier with a digital potentiometer as the gain resistor. I set the reference pin to 2.5 V to give the output a 2.5 V offset. There's also an output buffer to clamp the ADC input to
0 to 5 V. Regarding the potentiometer, I would then select three resistor values to give me the gains that I desire, and then calibrate them in software.
To calibrate this I will basically store gain and offset values in the firmware to satisfy V = Gain*V_adc+offset. I understand that these are temperature dependent, and depending on how much time I can dedicate to this, I will add a polynomial factor in as well.
My concern about this design is error. Is this idea propose at any greater risk of injecting noise due to the digital signal? What about any other noise sources. I understand that temperature variation will always be a factor, is this particularly at risk of this?
I'm interested in your thoughts. Do you have any other ideas? I'll post the voltage sense circuit tomorrow.
Thank you!
FYI, I know I need caps on the power rails for the op amps and digipot. I made this schematic quickly and didn't put them in, but they'll be there in the prototype.


texts: What is affected by DC/DC converter frequency selection?

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I planning to use the LMR33640 DC/DC converter which exists in 400kHz and 1MHz switching frequency versions. I know that the 1MHz version allows to use a smaller inductors. But I think that the 1MHz version has higher EMI emissions as a drawback (not sure)?

What other PROs and CONs do exist with switching converters concerning switching frequency selection?