texts: Can a BLDC generator power another identical brushless motor?

texts:
To better explain what I am asking in the title, please watch at 18 seconds into this video:
https://www.youtube.com/watch?v=6kgzrXFSDwA

Those are of course brushed DC motors.

I know that BLDC motors require more complex controls to spin up as opposed to just being hooked up to a DC source. However, I am curious if two BLDC motors would behave in the same manner as long as the two motors are identical, thus assumedly having matching phases. Then U would simply be connected to U, V to V, and W to W.

If it is indeed possible, would it also be possible to reverse the direction of the powered motor? How would the U, V, and W terminals need to be reconnected?

To clarify, this is not for any ‘free energy’ purposes, I am fully aware that there would be efficiency losses.

Thank you in advance for any help.


texts: Addition Amplifier equation doesn't seem to work

texts:
In this addition amplifier, when I set V1=5V, V2=5V, R1=3.3kOhm R2=10kOhm, the answer (theoretically) should be -20.15V, but the actual result is -13.04V. Why is this happening? Is the equation for the addition amplifier wrong? Or is something wrong with the amplifier?

The supply voltage was +/-15V, and the equation that I am referring to is

V_0=-(R_2/R_11 v1 + R_2/R_12 v2), where R_2 =10kOhm in this case

Thank you!


texts:
A friend of mine asked me if I could identify a component that keeps causing the flow of current to stop in a 12 V 1 motor system he has increased to 2 motors (perhaps due to overload or heat). He says that when he by-passes this particular component the circuit no longer shuts down, but the wiring starts to get very hot/melt.

The component looks quit old and has some numbers on it but I could not find out anything about it.   I think he uprated the battery to cope with the 2 motors but the extra current is causing this component the shut down the current flow temporarily.   I have added a picture.  Any suggestions?


texts: Real-time measurement of motors' current draw for a mobile robot

texts:
Found an Arduino-compatible Voltage-Current Sensor; it could remove the need for a separate voltage sensor.

Is there a more recommended method to continuously and simultaneously measure the current-draw of each of two DC motors, alongside a battery level/voltage setup or sensor?


texts:
What does this symbol mean in the context of an analog digital converter?

whole circuit:

Steuerung: Control


texts: Capacitor to reduce initial voltage drop when starting winch?

texts:
I have a solar panel charge controller with a load terminal that disconnects when the battery (12V car battery) goes below a certain voltage (9V). I have connected a winch which draws a maximum of 15A to that load terminal. I can start the winch in some instances, but often not.

I assume it is because the winch draws high current when starting, causing a voltage drop below the 9V cutoff and that in turn causes the load terminal to be disconnected from the battery.

Apparently, these load terminals are only meant for small loads like a light. But I wonder if I could just add a capacitor to "support" the battery at winch start to ensure the voltage doesn't drop too much?

Answers to this question suggest this is possible. I also read about inrush current limiters, but I'm not sure if this would be the right application.

If the capacitor approach works, would I put it in the battery circuit or the winch circuit? Is there any risk to damage components? Any hints on how to determine sizing of the capacitor?

I could just connect the winch directly to the battery but there are other loads like lights prewired in that circuit and I would like to take advantage of the automatic disconnect to prevent the battery from discharging too low.


texts:
When selecting a multimeter, what should one look for in terms of safety features and measurement capabilities?

What can you look for in the specifications to tell a good meter from a crappy one (besides price)?

I'm looking at cheaper multimeters for hobby use - so I don't need super high accuracy, and am not planning to measure any higher voltages than normal household power.  But I want something that's a little better than the $10 one I have from Canadian Tire.

I'm not looking for specific product recommendations, just what to look for in choosing a multimeter.


texts: How to connect CPU with RGMII pins to an LTE module that takes only SGMII signals?

texts:
The Hi3519 Hisilicon CPU has RGMII pins. We are trying to connect it to the EC21 LTE Module from Quectel which contains SGMII pins. Would using two Realtek RTL8201F-VB-GG PHY chips with magnetics between them work as shown below?

EC21 (SGMII pins) <--> RTL8211DN PHY <--> MAGNETIC <--> RTL8211DN PHY <--> MAC Hi3559A (RGMII pins)

Can the PMD pins be connected directly without the magnetics? We are very limited in space so we not sure if a transformer can fit with in the design. Are there any other ways to convert between SGMII and RGMII? Thank you in advance for the help.

Edit: I just read up on the Reaktek app note and it suggest ideas on capacitive coupling to go magnetic-less: Youtronics App Note

RTL8208B supports SMII, can I use two of those PHY and connect them as shown below with capacitive coupling instead of using a transformer to save space? The new connections would be:

EC21 (SGMII pins) <--> RTL8208B  PHY <--> capacitive coupling <--> RTL8208B PHY <--> MAC Hi3559A (RGMII pins)


texts: Strategies for using perfboards without pads?

texts:
I'm finding it a little bit cumbersome to work with a gridded perfboard with holes that have no isolated copper soldering pads.  Specifically, I'm finding that I need to make create a big wads of solder on each terminal end just to hold the component in place.  It's big and messy and I'm making lots of mistakes along the way.  I've used perfboards with pads before, and it was really easy to get components to stick and hold in place.  These boards just baffle me for some reason.

Is there any special trick to working with padless perfboards?  How can I get my components to stick to them easily without making a big ball of solder on each terminal end?


texts:
Sorry for the inexperience. This will be quick.

I have two Texas Instrument ICs, one is a device, the other is a hub.

I'm looking at a USB 3.0 device that has the TX and RX lines. When connecting directly to the hub, I should be switching those lines right?

TX (Device) <--> RX (Hub)

RX (Device) <--> TX (Hub)

This breaks down further...

TX+ (Device) <--> RX+ (Hub)
TX- (Device) <--> RX- (Hub)

Is this correct? I'm looking at USB connectors to try and get an idea but it seems like the pinouts that are labeled in pictures match up the TX+ and the TX+ on each side and that doesn't make sense!


texts: Connecting 3 V LED street lamps for a diorama

texts:
I've got fourteen 3 V LED street lamps for a diorama. I need to know what type of resistors I need. The lights could be powered by 3 V batteries.
If possible, I would appreciate a diagram on how to do it.
Thank you for your help.


texts: My understanding of stall torque is that it's the amount of torque produced by the servo when the output is stationary. Suppose the stall torque of a servo was 10kg-cm. It can lift the a 10kg load at 0.9cm but not at 1.1cm. But does it mean it'll actually drop the load at any distance greater than 1cm? That is, it'll drop the load at distances 1.1cm, 1.2cm, 2cm, etc.?


texts: Plot voltage gain in LTspice while ignoring output DC offset

texts: How can I plot voltage gain (Vout/Vin) when Vout can have some DC offset?


texts: How would I have destroyed these photodiodes?

texts:
I was trying to fix a light sensor module and using a diagnostics tool for it found that 1 of the 4 photodiode sensors was faulty (it was reading 0xFF.) As I don't knowwhich photodiode corresponds to what on the board, I took the following steps.

Put a multimeter in diode measuring mode across each photodiode in both polarities. All 4 photodiodes read 0.8V and 0.45V respectively.

I put a multimeter in current measuring mode across each photodiode and shined a light on it. They measured 0mA. Does this mean it's a phototransistor?

I unsoldered the 4 photodiodes, reversed the order of them (i.e. moved the 1st diode to the 4th, 3rd diode to the 2nd) and resoldered them. I used a soldering iron at around 300C and noticed the chip case slightly melting while unsoldering from the pads.

I reconnected the module and now all 4 photodiodes are showing as faulty (0xFF reading.)
At which step would I have destroyed the photodiodes, and next time how to prevent it from happening?


texts: Driving a WS2815 12V LED strip with a CC+CV driver

texts:
I am selecting a driver/PSU to power a string of WS2815 12V LEDs.

  WS2815 datasheet here:
  http://www.world-semi.com/DownLoadFile/138

One option I am looking at to power these strips is the Mean Well HLG-320H-12.

  HLG-320H-12 datasheet here:
  https://www.meanwell-web.com/content/files/pdfs/productPdfs/MW/HLG-320H/HLG-320H-spec.pdf

But, this is a Constant Voltage + Constant Current LED driver.

My question is: will this work?

The WS2815 is digitally dimmable through its data channel (same as the rest of the WS281x family / WS2811, WS2812, WS2813). I have no need for dimming from the PSU side.

I usually power these type of LEDs through a Constant Voltage PSU, but I need more amps than (e.g.) the Mean Well LPV series can offer. Then I found the HLG-320H-12, which suits my Amp-needs, but I'm not sure if CC+CV would work with this strip.


texts:
Sorry if this has been asked before, but I searched for a while and didn't find anything that exactly answered my question.

I would like to sense the "dummy lights"(oil, neutral, etc.) in my motorcycle with my mBed. The bike runs of a 12v battery and the mBed senses at 3.3v. Now I know I can use a step-down to sense the output, but because it's a noisy system don't I want to use a optoisolator?


texts: Can I extend the allowed Vin range of a voltage detector IC with a simple zener shunt regulator?

texts:
I'm trying to solve a particular corner case in the behaviour of a system I designed.

The issue can be boiled down to this: I don't want a particular LDO to operate if it's input voltage is below 4V (give or take, I can accept a 10% tolerance on this).

After some searching, I found that a good way to do this is the following:

simulate this circuit – Schematic created using CircuitLab

(obviously I'm omitting details like decoupling caps and such)

IC1 behaves like this:

when Vin < 4.0V, the OUT pin will be at 0V, disabling the LDO
when Vin > 4.0V, OUT = Vin, enabling the LDO
there's a few % of hysteresis built-in, which I don't care about

Problem

The BD49L40 can only handle Vin up to 10V. The input voltage in my system can go as high as 33V (the LDO is suitable, but IC1 isn't). There are higher-voltage-tolerant voltage detectors, which are several times as expensive, so I'm curious if I can avoid them.

Since the quiescent current of IC1 is 1-2µA, and the Enable pin on IC2 can source or sink 1-2.5µA as well, I need a micropower voltage limiter to the input of IC1 so that I don't kill it when Vin is >10V.

Proposed solution

So I devised this:

simulate this circuit

In this case:

If Vin=3V (for example), the zener does nothing, IC1 is powered through R1;
If Vin=5V, the zener still doesn't conduct, IC1 sees close to 5V on its input pin, puts this on its OUT and enables the LDO;
If Vin=16V, the zener conducts, limiting the voltage that IC1 sees to about 8 (or slightly less) volts. The voltage on the OUT/Enable pins is the same, about 8V. Since IC2 accepts anything above 2.0V as logic high, the discrepancy between IC2's Vin and Enable pins should not cause trouble.

Question

This all seems acceptable, at least in theory. Is there anything I should be worried about? Anything that I may need to add to make it robust?

EDIT

The question is mostly moot. I wasn't aware that the BD49xxx series had Pspice models available. I was able to simulate the thing and am now 99% sure it works as intended. The only non-obvious detail is that a small buffer cap on IC1's input is a must, it cannot function without it. 2-10nF seem to work well.


texts: What part/actuator do you think they used

texts:
At around 2:20 in this video there is an interesting use of electronics. You can watch the video but in short there are these little spoon creatures that pop out from behind a covering. The speed at which they react is proportional to sound. My question is what kind of actuator do you think they used for the movement? Sorry if this is a dumb question, I am not mechanically inclined.

http://www.youtube.com/watch?v=FQdQhV1yjfc


texts:
When using a AC Current Sensing Transformer (5A MAX) what will happen if a current larger than the maximum rating is utilized (like 15A). Will the readings simply be out of range or is there greater risks involved?

Thanks


texts: What does this digital multiplexer (CD54HCT151) output when the selected input is floating?

texts:
I'm not sure if I missed something, or it's omitted from the datasheet, but in any case, I couldn't tell what happens on the output when the selected input is floating. This post seems to imply there is a defined value for (most?) multiplexers.

I'm trying to implement this schema for the reasons in the question, and I'm not sure I would be able to use a digital multiplexer like CD54HCT151.


texts:
I am working on a simple project which involves in supplying a power to couple of loads using battery and Inverter. The capacity of my inverter is 2000W/ 4000W(10sec). I have connected couple of loads to this in which secondary load starts and runs at 1A 110VAC max and the primary load start varies between 2A and 30A 110VAC depending on the setting for less than 1sec and runs at 2A.
   Now my problem is when turning ON the primary load at high setting, (when start power is more than 23A) the secondary load restarts. I am thinking about using a capacitor inline to my primary load for starting it without disturbing the secondary load. I need some advice in what capacitor can I use for this condition.

simulate this circuit – Schematic created using CircuitLab


texts: Schematic Pin Numbers Along With Nets Reasoning?

texts:
I was setting up a Nordic BLE chip to the UART connection from SparkFun and went to the schematics to figure out how to wire the UART up:

https://cdn.sparkfun.com/assets/learn_tutorials/5/4/9/sparkfun-nrf52832-breakout-schematic-v10.pdf

Personally, I was confused if P0.27 is the pin connect to the UART RX or if it was actually "Pin 39" as per the schematic.

I don't layout lots of boards, but for laying out nets I don't leave any numbers like that.  Seems confusing.

I had to monkey around and figure in a project build from Nordic which pins are the UART pins, and spent 15 minutes building and re-building the project till I found it indeed the pin is 27 I needed.

(This is the C code, I needed to guess through a defines list! Is it pin 38/39 or 26/27, UART not working, swap values, check connections and power, blah blah blah, etc.)

#define RX_PIN_NUMBER  26
#define TX_PIN_NUMBER  27

What is the point of the convention with numbers for each net?  Does it go back to the physical pin order?  Is one convention more common than another on this?

For a smaller footprint I can see leaving the numbers for like a SOT, but for a QFN like this is this really typical?


texts: Question about an electronic component which could be a fuse

texts:
i have an old laptop from which i removed the battery in order to repair it. There were 6 cells in total and 2 of them were bad. One of them was leaking cellfluid when i tried charginging and reviving it. The other 4 cells seem fine. I fixed the battery cells and was trying to put the battery back together but there is no voltage coming to the connector of the battery. I saw that there is no voltage coming to the connector and saw this component. Is that a fuse? what kind of fuse is this ans how can i check it?
thanks for every help in advance


texts: Reading ADC value with uV Reference voltage

texts:
I'm trying to improve the accuracy of the ADC by amplifying the signal by 1/256 (i.e. 1/2^8) to make 2 8-bit ADC into 16-bit ADC. My question is can the ADC give good results if the ADC values are from +25uV to -25uV by putting the reference voltage at 50uV.

I'm using ATxmega256A3U. I know that if the microcontroller says 0 to 2.5V then it should be good but I'm worried/curious if this will work. Has anyone tried it before?


texts: Altium: Harness as output of MultiChannel block

texts:
I'm designing a schematic containing a MultiChannel block. I would like to use a Harness with outgoing signals as port.
If I use a single wire, I get a bus at the output. This is clear. But how can I access the different harnesses?

The picture shows the idea, but is not working!

When compiling the design I get the following error:

  Sheet Symbol with duplicate entries Sheet Entry
  MEMS1-MEMS_CNT(Passive)

(Repeated for each entity and harness)


texts:
Update: a practical implementation of this is done in the Tapuino project made by Peter Edwards. Check it out, everything is open sourced: https://github.com/sweetlilmre/tapuino

I'm working on a project where i'm using my Arduino to stream TAP tape data files from my PC to the C64. The software side of the project is going well however i'm still new to electronics and i don't like to fry my Commodore. So i need hardware interfacing help actually.

C64 tapes uses PWM modulation to store program on cassette tape and on reading back the data an opamp + schmitt trigger converts the audio signal into square waves. Every high-low transition triggers an interrupt in the machine and the distance between two interrupts (which is the length of the pulse) represent an atomic part of the stream.

The cassette port's pinout looks like this (the top and the bottom side has the same pins twice):

A-1, GND, Ground

B-2, +5V, 5 Volt DC

C-3, MOTOR, Motor Control, approx. 6 Volt power supply of the motor

D-4, READ, Data Input, read data from datasette

E-5, WRITE, Data Output, write data to datasette

F-6, SENSE, Detection, if one of the keys PLAY, RECORD, F.FWD or REW is pressed

My current idea is the following:

Based on the C64 Interfacing Blue Book (starting from page 29) the machine uses TTL level on READ and WRITE port so i guess i can directly connect a PWM pin from the Arduino to the READ pin.

I also need to interface with the SENSE pin. I think i can directly connect that as well to one of the digital PINs and write digital LOW there when i need to signal pressed button state. Is that correct?

Later i wish to detect the presence of +6V signal on the MOTOR pin. Some loaders stop the dataset in the middle of the loading process so i have to detect that as well to emulate the tape correctly. Should i use some kind of resistor to limit the current there or can i just hook up that directly as well? Maybe i should use a relay there?


texts:
I have a Problem with an LTspice simulation. Specifically, I am designing an 12V bridge amplifier. The Problem in my simulation is that there is an DC offset which partially defies logic as far as I can tell. I attached a screenshot of the schematic for reference. Please Note that this is a first draft!

As you can see, there is an 700 and then some mV DC Offset at the Inputs of the LTC6248 OP amps, behind the decoupling capacitors C1/2 at the outputs of the LT1994, which should not be there as far as I can tell. The capacitor should block all DC parts from U1 and the inputs of U2/3 should not generate a Voltege that large (thinking about the opamps dc offset here...)

The problem occurs with LTspiceIV and XVII,which are very picky as of late (XIIV in general, has anyone else trouble with LTspice as of late?) and also with different opamps and with ideal op`s. All models are from Linear and came with LTspice, no 3rd party libs used. So I am at a loss here and hope that anyone has an Idea where the DC offset comes from.


texts: Is there a free/low-cost bus monitor in VHDL/Verilog for ARM AXI/AXI4 and/or AXI4-Stream protocols?

texts: I am looking for something to log the read and writes on an AXI 4 bus to a file. And similar for AXI4-Stream. For what it is worth, this is for Xilinx. I could roll my own, but I hoped someone else had already solved this problem.


texts: demagnetising a magnet with a high frequency transformer

texts:
This is a theoretical question. Some elements described in the problem may be impossible/impractical, but I am just trying to understand the principles. It is kind of a physics question, but also about electromagnets. If anyone thinks it would be more appropriate in a different section - apologies.

Suppose I have a powerful electromagnet with a C shaped core. In the gap of the C core is a permanent magnet, contained in a box where it may flip freely. When the electromagnet is turned on, it produces a field that is greater than the permanent magnet's coercive force, i.e. a magnetic field that could demagnetize the permanent magnet. In this case however, the magnet can flip in response to the electromagnet's field.

My first question is - if the permanent magnet can flip so that it is aligned to the field produced by the electromagnet, will it be demagnetized by the electromagnet's field, or will the act of flipping mean that it is not demagnetized even though the electromagnet's field is strong enough to demagnetize it?

My second question is - what if the electromagnet is powered by an alternating current, so that the field produced by the electromagnet changes direction each time the current in the electromagnet's coil changes direction? The permanent magnet takes some time to flip in response to the field produced by the electromagnet. If this flip time is longer than the change in direction of the electromagnet's field produced by alternating current, the permanent magnet will still be in mid-flip when the electromagnet's field direction is reversed. If the direction of the permanent magnet's field is opposed to the direction of the electromagnet's field at that point in time, will it be demagnetized?
Will a progressive increase in the electromagnet's frequency at some point potentially demagnetize the permanent magnet?


texts: Chosing R and C values for a given RC filter design

texts:
I'm currently into designing passive LP filters such as RC topology and active filters such as Sallen-Key topology.

I'm fully aware that what matters in the choice of values for the resistors and the capacitors is their product so increasing one will result in decreasing the other in order to keep the same cut-off frequency.

What I have trouble with is knowing whether I should chose my capacitor first and adjust the resistor or the opposite. And for each option, how should I chose the component's value.

I'd like to know if there's any rule of thumb to chose quickly the values for my filters, knowing the impedance of the load or other parameters.

For example, I'm currently designing a filter (active or passive) for a PWM running at around 10kHz and I want my cut-off frequency to be around 1kHz, the load having an impedance of around 100 kOhms.


texts: Optocoupler is failing to isolate circuit

texts:
I have a circuit in which I am trying to use an microcontroller to activate a car horn. I've had a lot of trouble trying to isolate the horn from the rest of the circuit. I have the microcontroller toggling an LED on and off once a second or so, just as a status LED that everything is going good. Then when the horn goes on, the LED stops blinking and just stays on, and the horn isn't being switched off. It's like the microcontroller is being wedged. As I write this maybe the external clock is receiving some feedback somehow? Even if I unplug the 12v car battery from the circuit the microcontroller doesn't recover until I power cycle it. I have tested the circuit with power resistors and everything works as expected. The difficult thing is that I feel like I've done everything possible to isolate the microcontroller from the horn.

I've also tried adding a flyback diode (edit* added to schematic) with no better results (I left it out for this run because one of the guys who helped designed this thing said that a car battery can handle it and a flyback diode isn't needed). I've even tried wrapping the microcontroller board in aluminum foil. That didn't seem to help either.

Any ideas as to what could be going on, or what to try next?

EDIT:

Thanks for all the suggestions. I ended up adding the flyback diode across the coil of the relay and I also simplified a bunch of my arduino code. I then found that if I commented out everything and just had a button as an input to the microcontroller and a single output to the mosfets and horn, then things worked! The problem shows up when I introduce the code that reads from the gyroscope/accelerometer (MPU6050). I think it's over SPI? Anyway, if I include that code in my loop thread, then everything goes awry.

Wire.beginTransmission(MPU_addr);
Wire.write(0x3B);  // starting with register 0x3B (ACCEL_XOUT_H)
Wire.endTransmission(false);
Wire.requestFrom(MPU_addr,6,true);  // request a total of 6 registers
accX=Wire.read()<<8|Wire.read();  // 0x3B (ACCEL_XOUT_H) & 0x3C (ACCEL_XOUT_L)
accY=Wire.read()<<8|Wire.read();  // 0x3D (ACCEL_YOUT_H) & 0x3E (ACCEL_YOUT_L)
accZ=Wire.read()<<8|Wire.read();  // 0x3F (ACCEL_ZOUT_H) & 0x40 (ACCEL_ZOUT_L)

simulate this circuit – Schematic created using CircuitLab


texts:
I am working on impedance matching for one of my projects. After studying different stub matching strategies, I have implemented single and double stub successfully. When I use just a line and a stub (configuration shown in figure 1)
I get very good results. But when I use a T-junction-connector (recommended to use when to connect two micro-strip lines, see figure 2) my results degrade by a significant value. I am using ADS for the design. My questions are:

1) Is it mandatory to use the connector component?
2) If it is mandatory? how to assign dimensions to this component?

Fig1

Fig2

Thank you for the help!


texts: Oscilloscope measuring current that flows a few milliseconds

texts:
Is it possible to measure current that is flowing for 2 or 3 milliseconds inside a circuit through oscilloscope by measuring the voltage drop across a resistor ?

The supply voltage is generated by triboelectricity and it has a peak to peak of around 5 volts, it lasts only for about 3 to 7 milliseconds. I have connected this to two resistors in series, (10 Ohm, 10 Ohm) and i measure the open circuit voltage that is generated by triboelectric impact and the voltage drop across the first resistor to find the current in the circuit. So they are connected to two channels in oscilloscope (Voltage probe, 1x attenuation, probes are compensated)

But, it turns out that i see nothing in the oscilloscope, i cannot measure the the tribo electric voltage as well the voltage drop across first resistor.

When the two resistances are very high, say 100 Kilo Ohms, i see that both the channels in oscilloscope show the same open circuit voltage that is generated by triboelectricity during impact. How can i measure current ?


texts:
I'm trying to make a 3 axis bipolar stepper driver and I think using L293Ds and Arduino is the best cheapest option. I have seen people  using grbl to run their steppers easily  but with grbl they have used expensive Easy drivers or Adafruit motor shield. I can't use them and I want my motors to run from H-bridges only.
What can I do to make grbl compatible with H-bridges or is there any other software ?
I have googled a lot and seems to me it is the most common issue people face since grbl doesn't officially  support H-bridges.


texts: Calculating Battery Life with different working voltages

texts:
I have device that draws 30 uA in current continuously, and it is powered by a Panasonic CR2032 device (240 mAh - continuous standard load current: 0.2 mA ).

There are two components on this device, once is a sensor module and the other is a MCU:

MCU draws: 2 uA (working voltage range from 3v - 1.8v)
Sensor unit draws: 27 uA (working voltage range from 3v - 3.5v)

I calculated my battery life to be 8000 hours (~11 months) - (240 mAh/0.03 mA = 8000 hours) - however I doubt I would get full 11 months if sensor's voltage range is 2.5 v which is discharging ...

How should one think about this, when determining battery life with components of different voltage range? I don't believe I would get 11 months, it must be lower

Would this be an appropriate way to calculate battery life with components of different voltage ranges?

Any reference or thoughts would be helpful.


texts: STM32 usart interface sends data but "128" is added to each sent byte

texts:
I'm using the newest version of stm32cubemx to config my hardware. I'm using a Waveshare STM32H743 dev board and it's completely healthy and uClinux works(I can easily communicate with it using that usart) on it.
so, as I stated, it's not a board or connection specific problem. I guess maybe it's a bug in cube that is configuring the registers in a wrong way. but when I read the registers, I couldn't understand how this is happening.

I tried to change parity, stop bits, baudrate and ... randomly on the receiver(that is my pc) but it wasn't helpful. I think there is a problem with the 7th bit. because 7th bit has the value of "128" and the ascii codes that I receive on my computer are wrong and it seems that 128 is added to them.
my program in while(1) loop:
char h[]="hello";
HAL_UART_Transmit(&huart2, h, 5, HAL_MAX_DELAY);
HAL_Delay(500);


texts: Multiple Open Drain Outputs to one MCU-pin

texts:
i want to use two DRV8844 (http://www.ti.com/lit/ds/symlink/drv8844.pdf) Motor Drivers. It has an Open-Drain output, that indicates an error, when it is LOW (nFault).

What happens, when i connect multiple open-drain outputs together with a pull-up resistor to one pin of a MCU?
If one nFault output of one IC is LOW, what would the MCU read? Still HIGH, because of the pull-up, or LOW, because it is now connected to ground?

My goal is to detect, if one of all connect parts is in fault condition and save pins on the MCU

Thanks for your help.


texts: Why does the cable resistance jump from a low value to high value at a particular frequency?

texts:
I am not well versed with transmission line theory so if you can redirect me to relevant material I'd be grateful. So I used Agilent 4294A to find resistance of a 2 metre long shielded twisted pair cable (BELDEN 3105A E34972 1PR22 SHIELDED) and the resistance across frequency looked something like

with a discontinuity at 5MHz. At 4.99 MHz it was about 2.04 Ohms and 23.5 Ohms at 5.01 MHz. This trend was there in impedance as well. I feel I'm missing something fundamental here.


texts: I bought an electro magnet and i have some questions

texts:
I've just bought a 12V 260mA electromagnet and I have some questions about it

I don't know why, but when I connect electromagnet, my 12V power source (9V and 2 1.5V AA batteries in series) drops to 8V. I suspect that this is because of the protection of the 9V battery, because the 9V battery drops to 5V whereas voltage drop of 2 1.5V AA batteries is negligible, and when I try different 9V battery, it keeps and slowly drops to 2V.

When I disconnect the electromagnet, it seems that it sends reverse voltage, Before I disconnect, my multimeter connected in reverse reads around -8V, but when I disconnect it, it reads around 2V. Since I'm gonna switch electromagnet using transistor, would this reverse voltage be harmful? If so, just connecting the diode would prevent this?

My original plan is using 2 9V batteries in series to create 18V and using a voltage divider to divide it into 6V and 12V, and using 6V to power the rest of the circuit. If the voltage drop stated in 1 is actually caused by the protection of 9V batteries, is there any way to bypass it?


texts: DC-DC converter from low voltage at high current, to high voltage at low current

texts:
I want to build a DC to DC converter with:

25 V input side
400 V output side
4000 watts of continuous rating

That means (obviously) 160 amps on the input side and 10 amps on the output. I can’t find anything remotely close, that has such a high voltage gap with such a high wattage rating.

Is this feasible? I can’t see why not.
What would be the best way to go about this, or a reference design somewhere that I can scale up? I don’t mind spending the money on quality products, but I prefer to DIY it so I can make changes etc.

I have an adequate voltage source for the input side that can handle the current so that’s not the issue, but I’m failing to find more info and even big companies like Vicor, Lambda, etc. all have 400-600 max rated units. Therefore I have to build it.


texts: How to implement wear leveling for Elm Chan's FAT FS

texts:
I have a working AT45DB and SST26VF driver I made and successfully implemented it for elm chan's FAT-FS. But as you know a NOR or NAND flash will wear out after 100,000 write cycles, so I have to include wear leveling to increase it "lifetime".
Do you know of any open source middleware wear leveling block?
I found Spiff, which is a file system with wear leveling included. But I was hoping to use Chan's FS as it is well maintained and quite robust.


texts: Differing voltages with the same ground?

texts:
I have a battery powered radio controlled aircraft.  The aircraft runs at 16v.

I want to add a video transmitter that is built for 12v.  I plan to use this regulator to supply the 12v.

+16v-------->|  D24V5F12  |+12v---------> Video
 GND---------|  V. Reg.   | GND---------- Trans

The 16v side also drives a camera and telemetry equipment built for 12-24v. That subsystem outputs a video signal.  I have 2 questions..

I have this notion that subsystems running at different voltages must be isolated form one another, say, by a transformer.  But I think the voltage regulator gets wired with a common ground, so it seems I am incorrect.  Can subsystems running at differing voltages safely share a common ground?

Am I safe simply connecting the video out from a 16v subsystem to the video in of a
transmitter running at 12v?  The final wiring would be:

+16v-------->|  D24V5F12  |+12v--------->Video
 GND-------------------------------------Trans
Vsig------------------------------------>Vsig


texts: How does LTSpice model reverse recovery time?

texts:
Hello everyone,

I am working on the prediction of the reverse recovery losses in a Buck converter. I have the following schematic:

You can see below a zoom on the turning-off time of the diode:

I am using the following models for the MOS and the diode:

.model diode d(Is=1f n=1 tt=200p)
.model pmos pmos Vto=-0.4 Kp=40u lambda=0.05 tox=5n Cgdo=0.207n Cgso=0.207n LD=30n

Can someone explain me how does SPICE (I am using the latest version of LTSPICE) model reverse recovery time? I am looking for equations, aka a way to predict tRR. In their book Microelectronic Circuit Design (5th Edition), R. Jaeger and T. Blalock speak a little bit about it, p91-92-93-94 and p128-129. They give an expression for the storage time, but with this expression, I can’t predict what SPICE shows.

Can the reverse recovery time can be seen as the time required to empty QD = iDtT the charges stored in the diode? If yes, tRR should be the integral of the negative peak current flowing through the diode right? When I calculate this integral, it doesn’t match QD.

I am not looking for information from a datasheet, I would like to understand how LTSpice is doing its calculation and ultimately, I would like to be able to predict what it is doing.

I haven’t defined parameters CJ (junction capacitance), and RS (series resistance). But still, SPICE does model a reverse recovery effect. How and why?


texts: Powering a 12 V Relay and a 3.3 V Microcontroller with one Power Supply

texts:
I'm trying to power the LN298 motor driver in order to use a 12V linear actuator. This motor driver comes with a 5V voltage regulator, so you can power a microcontroller with one power supply. The problem is that there is a 2V drop (if I supply 12V to the motor driver, only 10V is sent to the linear actuator) which makes the actuator move slower than I want it to move.
If I supply more than 12 V to the motor driver (rated for much more than 12V) the voltage regulator shuts off, so now I need another way to power my microcontroller.
I have looked into other voltage regulators, but I assume a voltage drop from 14V to 5V might create a lot of heat. I am currently learning about SEPICs and trying to find some that work for my application, which seems like the best solution I can come up with. Are there any better solutions out there?
Thank you so much!
Edit: The microcontroller I'm using is an Arduino Nano 33 BLE and I suspect the current draw to be around 25-100mA.


texts:
I have build a simple motor control for a brushed DC motor for my robotic mower. The motor is feed with a PWM signal and when the cutter should stop you just pull the PWM signal low to stop the motor and pull a Brake-signal high to short the motor terminals for a quicker stop. It's working but it's a bit crude and I guess I should put a resistor in serial with the braking MOSFET to limit the heat build-up in the cutter-motor during braking. The circuit looks like this:

The downside is that it requires an additional brake-pin on my microcontroller and you must make sure, in the software, that the brake and PWM-pins never are High at the same time, because that would short-circuit everything.

So the question is if it would be possible to have it automatically brake if there where no PWM-signal available? Could this circuit do it?

Normally Q7 will be actively braking since R8 pulls gate High.
When there is a PWM signal then R7 activate Q6 pulling gate on Q7 low to disabling brake.
The problem is that it's a PWM-signal, if the motor was only supposed to be On or Off then I guess this circuit could work. But since the motor speed is adjusted by turning the driving MOSFET on and off quickly then the brake would kick in everytime the PWM-signal goes low, I only want the brake to kick-in if the PWM-signal is less than 1% duty cycle. That is the reason for C1, to keep base of Q6 high for the short periods when PWM-signal is low.

Is these correct assumptions? And how do I calculate the values of R7 and C1? I guess it depends on the PWM-frequency?

Thanks!


texts: Getting frustrated because I don't understand what this -4dB thing is in the circuit and I can't figure out how to wire it correctly or even if I have the right part. I have a 3.5mm mono audio jack but I'm not sure what -4dB means. I've tried looking up some videos on how to build this circuit but the ones I've found were pretty poorly made and didn't clearly show how this was supposed to get wired. The audio jack I'm using has 3 prongs. The wiring diagram only shows one connection. Where do I connect the other prongs?


texts: Voltage variations with N Channel MOSFET and flyback diode

texts:
simulate this circuit – Schematic created using CircuitLab

I have a circuit that uses an LM338K adjustable power regulator to supply 14V to a electromagnetic loop coil for producing a pulsed square wave signal under 500Hz.  The coil has approximately 10.5 ohms resistance and about 6.25 Henries.

The switching to generate the pulse is produced by a raspberry pi GPIO pin driving an N-Channel MOSFET (NTE2980).  I have a flyback diode across the coil outputs to kill the ringing in the square wave.

Here's the problem I'm experiencing and I'm hoping someone can explain this observation and offer an option on how to correct it:

With the flyback diode in place, I get a variation of voltage coming out of the regulator (when the MOSFET is off).  That voltage measures around 16.2 V and the regulator becomes only nominally adjustable.  When I remove the flyback diode, the voltage returns to the 14V the regulator is set at.  Of course, the diode is also protecting the MOSFET, which if the diode is removed, gets hot fairly quickly (~20 seconds).

So, why would the flyback diode be causing the power fluctuation and what is the right solution to fix it?

Here's a text representation of the circuit:

14V positive supply connected to one side of the
electromagnetic loop.
Other side of the loop connected to the drain
of the mosfet
MOSFET source connected to ground.
PI GPIO driving gate of MOSFET
Diode placed directly across the loop coil terminals.


texts:
The MP1584EN datasheet says: Absolute maximum ratings section: All other pin: -0.3V to 6V max. Figure 3 shows the 1.8V typical application. On the picture, there is a voltage divider: between GND and EN: 59k and between EN and VIN 100k.
If the input voltage is high, for example 28V, between GND and EN approximately 10V appears. It's not a problem? The 10V is higher than 6V.


texts: I want to use the L293D to control 2 motors forward/backward. My question is if I set all inputs (A) high, do I have a short circuit? Because the driver gets really really hot.


texts: What is this white stuff inside this circuit board?

texts:
I'm having problem getting any output from this universal adapter for my older laptop, so I opened it up to see this rubber-like white substance inside, on top of the big 68uF 400V capacitor.

A closeup:

If it is glue, why would they use it? It fits well without it, with the leads of that capacitor bent as they are.


texts: Math to predict current in circuit with different voltages in parallel

texts:
I was playing around with my voltmeter and I came across something I don't know how to work the math of.

The circuit built was the one below, the right power supply was a 9V battery and the left was a six volt. Both resistors R1 and R2 are 1K ohms.

What is the math to determine how much current will go through (certain points on the circuit) R2 and D1?


texts:
I'm having a hard time trying to understand some basic sound engineering concepts.

From https://en.wikipedia.org/wiki/Original_Chip_Set#Paula:

  Paula has four DMA-driven 8-bit PCM sample sound channels. Two sound
  channels are mixed into the left audio output, and the other two are
  mixed into the right output, producing stereo audio output. The only
  supported hardware sample format is signed linear 8-bit two's
  complement. Each sound channel has an independent frequency and a
  6-bit volume control (64 levels). Internally, the audio hardware is
  implemented by four state machines, each having eight different
  states.

How can these 4 input channels be translated into the modern DSP world? The only reference I can find when trying to google some modern DACs, is that they can support > 2 output channels (5.1 sound and so on). From what I understand, today the mixing is mostly done in software, and the combined result is then fed to the CODEC/DAC. Are there any analog mixer chips with multichannel support and how would they work?


texts: doubt when Arduino connects to multiple i2c devices

texts:
I am using Arduino nano to drive multiple i2c devices, actually, they are premade modules which are available on eBay.
ads1115 ADC, ds3231 RTC, 20x4 character LCD i2c module, at24c02 EEPROM module

all these modules have I2C SDA & SCL pull-up resistors in the module, please correct me if I am wrong.

doubt -
if I connect these all devices to same SDA and SCl i2c bus what will happen to pullup resistances? according to the theory, since they are configured in parallel resistances will go low isn't it? means pull up resistance will go low?

how this will affect to my end device?

Is there a specified distance between SDA/SCL pins and pull up resistor?


texts: Heat vs derating power resistor Lithium battery discharge load tester

texts:
I am making a Lithium battery discharger/tester to test some 18650 batteries that I found in some old laptop cells because I am too poor to buy some brand new battery which cost more than 5 USD each. Using Two 20 ohm 1 w 2512 chip resistors, it gives me a sweet little tiny 10 ohm 2W resistor. A lithium battery at full charge is 4.2v. With my calculation, the maximum current should be less than 4.2v/10 ohm = 420mA; or With Power <=RI^2= 10 0.42^2= 1.76 watt. So a 2w resistor should be able to deal with a 1.76w load. Unfortunate, it's not the case. My resistors are extremely hot to touch (hot glue melting kind of hot). After running for a hour or so, even the other side of the PCB is burning hot to touch. But to my release, other than being super hot (oh boy, I wish my gf is that hot too), I don't find any problem. First of all, the current for my testing battery is constant at 360ma, so this really tells me that the resistance is not changing much. Second of all, nothing is burning and after removing the load and read the value of those 1% accuracy resistors, they still read 10 ohm.

Here we go, after my boring story, my first question, can heat really kill resistors (especially this kind of resistor) when operated below its rated wattage? To my own understanding, heat does kill the resistor eventually, but it should last pretty long time? Third question, what is an ideal load for discharging a 4.2v lithium battery @ about 500ma?

After soldering a huge nail to one size of the pad as a heat-sink as others have suggested, this helps a little if not at all. The resistors themselves are still super hot, while the whole nail is hot to touch. So My conclusion is that huge PCB trace is simply not enough to dissipate the heat generated by these two tiny resistors.


texts: Motor Control - Counter design for the control circuit

texts:
I want to design a Johnson/ring counter circuit for control of my sr motor. Until now I have got this information, which I have tabulated in the following waveforms I am attaching for the reference:-

Now, I want to be able to run the motor at low speeds of Not more than 200-300 RPM. I was hoping to control the motor via johnson/ring counter circuitry by generating control pulses to the power circuit. For the power circuit, I am using a DC split link based converter topology to energize each phase. Thus, each phase needs just one MOSFET switch to be energized. I have drawn the expected pulses duration for each phase in the above waveform template.
Also, the position sensor outputs and their complements I have drawn. Low level is 0 Volts while the High level is 5 Volts for the sensor output.

All for a conduction from 0-180 (mechanical), the rest 180-360 is also the same.

So, my question is:-

From the above waveforms templates:
Given the output of the position sensor of the motor(optical type slotted photo-interrupter), and the expected pulses for each of the given phase (Which have to be synchronized either with falling or rising inductance of each phase); How I might be able to generate the output control switching pulses (each of 20 degrees duration) from a sequential circuit(Johnson/ ring counter) for each of the four phase MOSFET switches to drive my motor at a particular low speed?

Any kind of help will be appreciated.

I have tried making a logic with the ring counter which should go like: 1000 => 0100 => 0010 => 0001 and then repeat.

But, it dosen't seems quite right.

So please give your inputs, suggestions or directions to help me


texts: Why are rectifiers-inverters used to drive AC motors instead of using the rectified current to drive DC motors?

texts: I understand the advantages of using a rectifier-inverter system to drive an AC motor instead of simply plugging it into mains power, as it allows much better control of its speed and performance; but what I don't understand is: since the original AC power has to be converted to DC in order to feed the inverter circuit, why is this DC not directly sent to a DC motor, instead of converting it back to AC and then sending it to an AC motor?


texts: LTSpice .MEAS Command: Measuring Mag and Phase Data

texts:
I got a real stumper of a LTSpice question for y'all. I'm do an AC analysis to calculate input impedance by setting the input to AC 1V and then adding the trace "1 / I(v1)" (where V1 is the source).

To automate the process, I'm using the following code:

.
.
.

.MEAS AC zi_freq1 FIND 1/I(v1) AT=10
.MEAS AC zi_freq2 FIND 1/I(v1) AT=100
.MEAS AC zi_freq3 FIND 1/I(v1) AT=1000
.MEAS AC zi_freq4 FIND 1/I(v1) AT=10000
.MEAS AC zi_freq5 FIND 1/I(v1) AT=100000
.MEAS AC zi_freq6 FIND 1/I(v1) AT=1000000
.MEAS AC zi_freq7 FIND 1/I(v1) AT=10000000

.
.
.

The code is giving me magnitude values that line up with what I'm seeing in the plot. However, the phase values don't exceed -180deg even though the plot clearly shows that from approximately 10kHz to 1MHz the phase is greater than -180deg. What am I doing wrong here? The faulty data seems like an anomaly to me but I want to make sure I'm not making any common errors when writing my .meas commands that I'm overlooking.

Here's the circuit btw:


texts: Integrator circuit RC time constant and integration time

texts:
I have hardware which performs current to voltage conversion.
Hardware is design is Transimpedence amplifier, opamp integrator, adc for digital conversion.
Transimpedence amplifier supports two gain modes.
Integrator rc tine constant is 10us.
I have to write firmware to read adc. There are some question I would like to get calrified.

What would be the integration time to read adc. Trigger the conversion, wait for the integration time to elapse, then read adc.
What is the relation between rc time constant and integration time? Integration time must always higher that the rc time constant?
What is the relation between Transimpedence amplifier gain modes and integration time? How to find out optimal integration time for different gain?


texts: can a female A USB port be used on an OTG host?

texts:
I'm designing a USB device that will act as a host all the time. Instead of using a mini-AB OTG receptacle i'd like to use a classic female A receptacle on the PCB. Is this allowed and can this potentially cause problems?

Clarification: I'm asking this question because I have a device where I would like to use the OTG functionality, i.e. give the user the possibility to hook it up to the computer OR to a peripheral, but I can't use the mini/micro OTG connectors and want to use classic USB A and B connectors. Ideally I would want the OTG port to be able to communicate both as a device and a host but that is probably impossible (?) so if I can find a way to allow the user to EITHER connect the device as a host or as a device using ONE of the two ports, that would be enough.

Clarification #2: I primarily want to use the OTG port as a host port, but if I can use it as a device port as well that is an extra feature on the device I'm working on which will make it more attractive. However, I do not want to use mini or micro connectors. I get that they are the new trend and all that and that they are great for smartphones and tablets but for the application I'm working on we can't and don't want to use them. I'd like to thank all who answered already whether I can use a type A host port. Any hints on how I could add a B port as well connected to the same OTG port, and let the user connect the product as a host or as a device, but not at the same time, but using a type A and B connector rather than a single micro or mini USB connector are very welcome. Confusion for the user is not an issue here since we can make that perfectly clear in the manual (e.g. you can use the host or device port but not at the same time - if you use the host port then the device port won't work or the other way around). Hope this makes it clear.


texts: Does Kicad (pcbnew) allow dragging nodes — i.e. junctions between track segments?

texts:
I am starting to use Kicad and am used to gEDA suite. The latter allows dragging anything in pcb: tracks, track segment ends, footprints, selected objects... For instance, you can drag the end of a track segment in gEDA pcb by clicking one end with a left click and drag it so only that very end is dragged while the other stays in place.

I just couldn't figure out how to do that in Kicad; all I could do was drag the clicked/selected segment. On the other end I tried myself at grab-and-drag a whole track while conforming to the DRC rules, keeping the net connected, which feature gEDA doesn't have. That said I find this feature very convenient.

So is it possible to drag track segment ends in Kicad or do I have to change paradigm? I didn't find any info on that very topic so either it's too trivial to be mentioned (you can all me dumb) or it's not implemented because something more useful is in place...


texts: PSpice Error subcircuit internal node floating

texts:
I am trying to simulate a circuit with a variable capacitor in PSpice.
The circuit is a simple test circuit like this:

And the VARICAP model description is this:

*PSpice Model Editor - Version 16.6.0

*$

.SUBCKT VARICAP 1 2 CTRL

R1 1 3 1u

VC 3 4

EC 4 2 Value = { (1/v(ctrl))*v(int) }

GINT 0 INT Value = { I(VC) }

CINT INT 0 1

.ENDS

*$

Running the simulation gives me this error ("ERROR(ORPSIM-15142): Node X_U1.int is floating"), which indicates that the internal node INT in the VARICAP component is floating. Usually this error shows up when a node does not have a DC path to GND. How is this possible to fix in the subcircuit description?

PS: The theory behind the circuit is described here: VARICAP


texts: Back-to-basic question regarding OpAmp, its input and output information

texts:
I am doing literature research about Transimpedance Amplifier (TIA) architecture and designs.
What I know for sure are its input is current, its output is voltage and it has low input and output impedance.
But I found some publications that use OTA+Resistive feedback to form a TIA.
It makes me question some fundamentals understanding that I have so far.

Questions:

Is the topology like this VCVS(Opamp) or VCCS(OTA)?
There is this discussion as well but it did not give a conclusion.

Razavi also referred the following Cascode Op Amp circuit as OTA.

If I have Current Amp and I dump this current into a resistor, does it make the circuit to become TIA? I do not think so, because we need to consider the impedance also at the input and output port.


texts: Can I simply add a 240V Neutral to SONOFF TH10 when replacing wall thermostat

texts:
So, I have purchased a SONOFF TH10 wanting to use it to replace my wall mounted thermostat.

The thermostat has 2 connections: Always-Live and Switched-Live (which is activated of course by the position of the temperature dial in relation to the room temperature).  This then returns to the central heating control.

The SONOFF however, has a Live-in, a Switched Live-out, Earth and and also needs a Neutral mains connection (I assume for its own internal power.) It also has a temperature sensor input.

So, in order for me to use the SONOFF to replace my wall thermostat, I need to run the following connections:

Neutral cable from mains supply to the SONOFF
Earth cable from mains supply to the SONOFF
Thermostat Always-Live -> SONOFF Live-in
Thermostat Switched-Live -> SONOFF Switched Live-out

In principle, is this the correct way to wire it, folks...?

I am happy with mains cabling, and I fully understand the dangers of 240V mains wiring, but I have also learned it is never a bad idea to seek confirmation from others.

Many thanks.


texts:
I have noticed that in PCB design, usually placing Capacitors next to the IC's on the power lane, are more favorable than placing Inductors.

I was given different resoaning that why RC is more favorable than RL.

I know that usually Inductors are bigger than Capacitors and that is one of the reasons that RC are being used more on PCB than inductors.

However, I was also told that RC circuit provide protection against power supply sagging, when an IC draws current abruptly. And, I can see why.

I was also told that on the contrary, LC will not be so good, because Inductros tend to prevent transient current changes, and this is no good, because IC tends to draw transient current.

However, I read different articles explaining that both RC and RL circuits behave very similarly. Eg: http://zone.ni.com/devzone/cda/ph/p/id/217

By reading the above article (figure 7.6), I think that those two circuits behave similalry, and they can be used interchangably. Is this correct?

Because, for example, I can see that the inductor, in the RL circuit, will prevent current change inside the inductor, if let's say an IC is connected to it on the right (figure 7.6).
But, this will result in a transient voltage change on the right side of the inductor, which means that transient current will be provided to the IC via the Resistor (R) path instead of the inductor (L) paht, correct?

Which will imply that both RC and RL circuit will behave the same way when connected to an IC that draws transient current, correct?

I would appreciate some help,

Thanks,
R.B.


texts: LC circuit: can it act as an "AC battery"?

texts:
I am curious about a resonant LC circuit. Assuming a perfect inductor and capacitor, would it be possible to tap off the energy in the oscillations to use it as a battery? Literally, it would be an AC battery. With a bridge rectifier and filter cap would this act as a DC battery?

(This is just theoretical stuff - I doubt you could get useful energy from an LC circuit as it would dissipate too quickly due to losses in the inductor and capacitor, plus to store any reasonable amount of energy would probably require a massive inductor and capacitor.)


texts:
I'm trying to code an exponential function for use on a PWM signal.

My question is, does anyone know how to do a power function on an ARM cortex-M (STM32F4 in this case, which has an FPU) microcontroller. Or would a taylor series approximation do the trick better.

I know this is question is very much programming related but as its related to microcontrollers I thought it would be ok to post here(?), plus it seems questions on stackoverflow get lost very quickly.


texts: Consequence of uncomplimentary MOSFETs in Hbridge

texts:
I am constructing my own H-Bridge to control a high current motor (24V at 25A), as such I was looking to use high current MOSFETs for each quadrant of the H-bridge. My go too MOSFETs for these applications is the IRF1405 unfortunately the manufacture for these MOSFETs do not offer a complementary P-channel equivalent. What will be the consequences of using a P-channel MOSFET  which is not exactly complement to the N-channel MOSFETS in my bridge.
Also does anyone have a suggestion for a complementary MOSFET pair which has similar specifications as the IRF1405? (RDS = 5.3mOhm ID= 169A)

The P-channel replacment I am considering is the IPB120P04P4L.
I have attached an image of my proposed H-Bridge for your reference.


texts:
Question:
How can I safely control a homemade solenoid that draws around 90A at 12v with a relay that has a hard limit of 10 amps?

Background:
First of all let me start off by saying that I know enough to be dangerous and try to approach things carefully.  I try to research as much as possible, but in this circumstance I cannot figure it out on my own and would like some guidance.

I have seen many small solenoids that I can buy and use much less current to drive the solenoid.  However, I generally like to try to build things first before usually being forced to break down and buy it anyway.  I guess I should state that it is my assumption that current (amps) is the driving force that draws the bolt into the solenoid and that the larger the weight of the bolt in the solenoid = higher amperage required.

I took my solenoid to a local battery supply store and I got to talking with the service tech. I convinced him to attach my solenoid to a battery and some kind of large expensive looking tester that is able to variably apply current to the attached item.  My thought was to find out at 12V what amperage will the bolt be drawn into the solenoid. Then with this information I will at least know what I am dealing with.  Well it turns out that magical number was 90~ amps at 12V.  The battery service tech told me that even if I bought a 5Ah battery it will still produce several hundred amps upon shorting it as I am doing.

I have been reading online and I know that I need a diode to handle the inductive load.  However, where I get confused is possibly adding in a resistor to handle the difference between what is required to draw the solenoid and what my relay can handle. Is there a way that I can place resistors into my circuit to make it work?

What role does the gauge of the wire play in making a solenoid?

Background on the control circuit:
I have an arduino attached to a relay board, the relays are rated 10A 28-30V DC... up to 250V 10A. I have no issues programming the arduino or interfacing the relay board.  My only question is how can I safely control the solenoid and still be able to use my homemade solenoid.

Here is the relay board:
http://www.amazon.com/SainSmart-8-CH-8-Channel-Relay-Module/dp/B0057OC5WK/ref=sr_1_1?ie=UTF8&qid=1442459317&sr=8-1&keywords=8+channel+relay+card


texts: Word or phrase to describe how frequently a value is measured

texts:
When writing software for instrumentation, it is often required to specify a small gap of time between taking measurements. Say for example that 250 voltage measurements must be taken, and they must be 1ms apart.

Is there a word or phrase in electrical engineering that describes that 1ms interval that takes place between the voltage measurements?


texts:
This board is a prototype for the project and is for testing. It is missing the soldermask and silkscreen layers, so correcting mistakes is very possible. The board was printed correctly, but somehow I missed one via (grr) from the top layer of copper to the bottom, and the software I used (ExpressPCB) of course doesn't have any checks for things like this.

I would like to know how to add my own via. There is no ground plane on this board because I used the bottom layer for traces to lower the size of the board. It is a basic 2 layer "prototype PCB".

Below you can find a picture of the portion of the board front and back with the trace ends circled. They are lined up directly over/under each other. I need to connect those two.

Top

Bottom

The two solutions I'd imagine would work:

Use a tiny drill bit or mill and drill a hole through, and make sure solder is filling the whole and touching both traces
Just solder a wire to the top trace, wrap it around, and solder it to the bottom trace.


texts: Reading 16 voltages accurately with three decimals on Arduino

texts:
I need to monitor 16 LiFePO4 cells.
Their Voltage during operation measures from 3.0 to 3.7V which I would like to measure accurately with 3 decimals.
I was thinking of using a 16 port multiplexer like the 74HC4067, and connect its output to an LTC2400, a Linear Technology’s LTC2400 24 Bit Analog to Digital Converter, and then data log the voltages with the Arduino.
While this conceptually work, I lack the experience to make a judgement, whether this works in practice, or if there are more things to consider. In particular the accuracy of the Voltage... I would like 3 digits after the decimal to me as precise as possible.


texts: What is the explanation for the shape of the Zener avalanche effect?

texts:
The following diagram is a trace of a Zener diode in avalanche. I can understand the explanations behind shapes A - D, but what causes shape E?

A is the accumulating charge within the junction's capacitance, and thus follows the common exponential form.  But no charge seems to accumulate immediately following breakdown (shape B).

And from my own experiment, this time with a 24V diode at 30V:-

My theory is the electrons are cascading so fast that they're exceeding the current flow through the 100k resistor, spurred on by impact ionisation. So no charge can build. The avalanche gradually stops between ~26.4V and ~28V, and only then does charge rebuild > 28V.

Is this correct?


texts: Can we send a file through Half Duplex connection?

texts:
I am working on a boot loader design for a kinetis controller. I am using this Terminal application ( https://sites.google.com/site/terminalbpp/ ) . I am able to send texts like, " Hello world" through my serial port, by debugging the code using Segger's J link debugger into my board.

But When I try to send the application file after programming the Board with my boot loader code, The terminal is unresponsive.

Is it because my Serial Connection is half duplex (RS 485) or is it because there is some error in my code ?

I don't know whether half-duplex connection would be a reason. I wanted to know whether that would be a reason. If my question sounds dumb to you, please explain me the logic.

Thanks for helping

Update:

This code provides the output successfully as shown in the image.

for(;;) {
      GPIO_PDD_TogglePortDataOutputMask(GPIOA_BASE_PTR, GPIO_PDD_PIN_21);
      CLS1_SendStr("Hello World!\r\n", CLS1_GetStdio()->stdOut);
      WAIT1_Waitms(1000);
      CLS1_SendStr("Welcome Ganesh!\r\n", CLS1_GetStdio()->stdOut);
}
But this code

`    static void ReadText(void) {
          uint8_t buffer[32], ch, i;

      for(;;) {
        GPIO_PDD_TogglePortDataOutputMask(GPIOA_BASE_PTR, GPIO_PDD_PIN_21);
        CLS1_SendStr("Enter some text: ", CLS1_GetStdio()->stdOut);
        GPIO_PDD_TogglePortDataOutputMask(GPIOA_BASE_PTR, GPIO_PDD_PIN_21);
        buffer[0] = '\0';
        i = 0;
        do {
          if (CLS1_KeyPressed()) {
            CLS1_ReadChar(&ch); /* read the character */
            if (ch!='\0') { /* received a character */
              buffer[i++] = ch; /* store in buffer */
              if (i>=sizeof(buffer)) { /* reached end of buffer? */
                buffer[i] = '\0'; /* terminate string */
                break; /* leave loop */
              }
              if (ch=='\n') { /* line end? */
                buffer[i] = '\0'; /* terminate string */
                break; /* leave loop */
              }
            }
          }
        } while(1);
        GPIO_PDD_TogglePortDataOutputMask(GPIOA_BASE_PTR, GPIO_PDD_PIN_21);
        CLS1_SendStr("You entered: ", CLS1_GetStdio()->stdOut);
        CLS1_SendStr(buffer, CLS1_GetStdio()->stdOut);
        CLS1_SendStr("\r\n", CLS1_GetStdio()->stdOut);
      }
    }`

It gets debugged into the board without any errors but the in the terminal application there is no change.
GPIO_PDD_TogglePortDataOutputMask(GPIOA_BASE_PTR, GPIO_PDD_PIN_21);
This piece of code enables and disables the Transmitter while sending and receiving respectively.
Am I doing any mistake in usage of this piece of code ?


texts:
I have a soldering station which came with a 3.5mm jack socket and a power prong as in the following photo:

The manual only mentions the following about the usage for the 3.5mm jack in their manual as:

What is the need for this? I never saw this in previous stations. Does anybody have experience with such wiring? Which one is safe in my case? Do I really have to earth this?
I couldn't find any information in the manual.


texts:
The MIPI I3C Basic standard describes an I2C-like bus with different timing requirements.   In particular, that document describes a measure, tSCO, that describes a slave device's clock-in to data-out responsiveness.
The maximum standard tSCO is 12 ns, but normally it is only 8 ns   per Table 59.   Both seems quite hard to implement in programmable synchronous logic, but I guess it makes sense for the I3C standard data rate of 12.5 MHz where the clock period gets down near 80 ns.
I3C can operate at slower clock speeds.  My question is does it make sense that tSCO should scale with the clock speed?


texts: Can signals be used directly in conditional statements in lieu of comparison to 0/1?

texts:
Can a signal (of type std_logic) be used directly as the condition in an 'if' statement? For example, can I write
if (A and not B) then
instead of
if (A = '1' and B = '0') then ?
I realize something wonky may happen if the signals take other values like 'Z', but aside from that sort of thing, is this syntactically valid? The first one seems much briefer, especially for more complicated logical expressions.
Addendum: What worries me is whether the argument of the "if" is of the right type, if that matters. I'm from a programming (C++) background, so I routinely use things like if( my_int ) instead of if( my_int != 0 ) where my_int is implicitly cast to a bool. Just wasn't sure if the same thing is really going on here. I presume the result of the VHDL comparison A = '1' is an abstract logical value ("true" or "false") and not some concrete std_logic value.


texts:
I have a headphone amplifier that is afflicted by mains hum 50 Hz and upper harmonics, below is an FFT of the spectrum with nothing connected to its inputs.

In headphones you can clearly hear a buzz-drone sound, volume pot doesn't change its level either. Is this to do with the rectifier, single ground planes or something else? I tried two different transformers one R-core, and the other a novatel sealed one. No effect, changed out caps,  still with this noise in the spectrum present.


texts: What gauge wire do I need to connect a 3.7V 750 mAh LiPo battery?

texts:
I originally thought that I could use any type of thin wire, but after some research,  it seems that different voltages and milliamps require different size wire. Am I correct with this?

My question is, what type of wire is recommended to use with that type of battery?

Thanks!


texts: changing 2000 honda civic domelight from incandescent bulb to LED panel- smoothing out PWM "dimming" with capacitor circuit

texts:
My 2000 honda civic has an incandescent dome light that has PWM controlled "dimming".  It takes a period of about 6 or 7 seconds when the domelight goes from full bright (not pulsed) to a pulsed duty cycle so the bulb dims slowly.  I took some measurements with my scope when it is doing this.

The frequency is a constant 63.7hz.  When it goes into this PWM controlled dimming it starts at about 60% on-time duty cycle.  It reduces the "on time" and ends up going from this 60% to about 5% over a period of about 6 or 7 seconds.

The problem with this 63.7hz, is that it is not a super fast pulsing and I can see it with my naked eyes when I connect an LED strip to it.  The goal of this project is to prevent the visible flicker when it dims with an LED circuit instead of a bulb.

I drew up an LED circuit with 27 LEDs- (9 parallel strings of 3 LED in series- each string has its own current limiting resistor) it will draw about 470ma total when connected to 14v.  It has an effective resistance of 20 ohm.

The factory bulb that is in there draws about 600ma when it heats up (I measured on the bench).  This means at steady state when everything is working the LEDs will draw about 130ma LESS than the original incandescent stuff.

I want to use a capacitor so that it will smooth out this dimming while it is PWM.  The problem I am having is that I can't find a way to be sure on what capacitor value to buy.  I want to get the smallest capacitor I can, and still do the job.  Since my circuit draws 130ma less than factory, I can use a resistor to slow the charging of the capacitor (14v divided by 130ma is about 100 ohms in front of the capacitor- this way I will not ever draw more than the original 600ma that it draws from the factory with the bulb fully warmed up- this should protect the driver that controls the circuit in the car)

I was also thinking i should "diode isolate" the charging and discharging of the capacitor so that the discharging does not have to go through the charging resistor.  The LEDs and the resistors on the output side should take care of this right?  I assume it will see this as a 20 ohm load.

Here is a video of the entire system working when I was playing around with it first understanding how it works better.  (sorry this video is sideways!)
https://drive.google.com/open?id=149BNC7PA8Fv81TNguBFgFEfnkXbPAcyn

I do not mind a delay of about .5 seconds while the capacitor charges.  I just don't want to draw too much current over the driver in the car.  I do not mind if it changes the 'fade duration', I just want to hide the visible 'flickering' that I see because the frequency is too low.


texts: Problems with 16Mhz SPI clock on PIC 18F25K22

texts:
I am using the MSSP module of a PIC 18F25K22 (datasheet) for SPI.  This works successfully except for when I try to use the maximum SPI clock rate of 16Mhz.

The target device is an SD card and the symptoms described below happen with a selection of different cards, tested with 6 cards from different manufacturers.

The microcontroller clock is the internal 16Mhz oscillator with 4x PLL, setup as shown below.

// Internal 64Mhz oscillator
IRCF2 = 1;
IRCF1 = 1;
IRCF0 = 1;
PLLEN = 1;

Circuit diagram

The relevant portion of the circuit is shown below, connections go directly to the PIC (note I used 47k resistors when assembling the PCB).

There are some right angles on the PCB where I broke out the SPI pins for debugging.  On the top layer the traces go to the debug header, on the bottom to the PIC.  I include this in case signal integrity might be relevant.

What works

Any speed below the theoretical maximum works successfully.

The following setup should produce an 8Mhz SPI clock from the formula 64000000 / (4 * 2).

// SPI clock = Fosc / (4 * (SSPADD + 1))
SSPCON1bits.SSPM = 0b1010;
SSP1ADD = 1;
SSPSTATbits.CKE = 1; // Work around known silicon bug, see errata
SSPCON1bits.SSPEN = 1;

Data is written using the most basic method, no interrupts are used:

unsigned char spi_byte(uint8_t data) {
    SSPBUF = data;
    // Wait for the buffer to fill with incoming data
    while (!SSPSTATbits.BF);

    data = SSPBUF;
    return data;
}

When tested with a logic analyser there's a decent 8Mhz clock and my code works fine:

What doesn't work

I'd like to use the fastest clock possible, the datasheet shows two ways to do this:

I should be able to:

Set the clock rate directly to Fosc / 4
Set SSPxADD = 0 for the same effect - Fosc / (4 * (SSPxADD + 1)) = Fosc / 4 * 1

With my 64Mhz clock this should give a theoretical SPI clock speed of 16Mhz from the MSSP module.

SD initialisation requires a slow speed, below this can be seen marked by the red "1".

This phase is successful.  Therefore I should be able to speed up, so I tested with SSP1ADD set to zero (this happens around marker "A1").  The faster clock should be present in the period marked by a red "2".

SSPCON1bits.SSPEN = 0;
SSP1ADD = 0; // BUG: Set to 1 to make this work, 0 gives unstable clock?
SSPCON1bits.SSPEN = 1;

However this does not work and produces a very unstable clock of about 82Khz, shown below (this is a zoom of the period marked "2" above).

The first three bytes here have a slightly faster clock but it's still only ~400Khz (far below 16Mhz) and the duty cycle is nowhere near 50%.  Then the clock rate mysteriously changes to ~82Khz during the fourth byte and is more like a series of pulses than a clock.

The 18F25K22 does have slew rate control, which has an impact.  The above traces were taken with the default settings, slew rate control enabled.  When disabled the above settings give a SPI clock of 400Khz (which is more stable and does work), but is far slower what it should be.

Notes

There is nothing relevant in the Microchip errata (I have a revision 5 chip)
I work around the one MSSP bug which still affects revision 5 by setting CKE = 1, though this isn't relevant to the problem here.
I can take scope traces if required, but don't have it with me right now.
I found this unanswered question which is similar, but I can't switch to MSSP2.

Question

Does anybody know if I should be able to use an SPI clock of 16Mhz, or am I missing something from the datasheet?


texts: What is that rubbery white substance in switching power supplies?

texts:
There is often some rubbery white substance (looks kind of like some hot-glue) in switching power supplies.

In this example it's on the right side between those electrolytic capacitors.
What is it; what is it called like? And what is it's purpose?


texts:
Ive come across this

(source: rapidonline.com)

its a 4PDT switch, Im not sure of the symbol or the purpose of pins 13 and 14

Any ideas ?


texts: Can you turn off usb protocol and use the USB port as a regular serial port?

texts: I am trying to make my pic16f84a micro controller communicate directly to my computer without a uart to usb bridge but I have been told that the way usb is handled wouldn’t allow me to do that with such a slow micro controller. Is there any way to turn the USB port into a regular serial port so that I could bypass that restriction?


texts:
Some one posed a question about current ratings in a capacitor and the replies basically came across as a non-issue except for what might be induced due to  ripple in various power supplies.  But what about one in RF service, where voltages may be low, but RF current passing though them can be 5 amps and up?  A typical circuit may have a 470 pF, 2 kV DC ceramic in line with a low Z load and have only a couple hundred volts across it, but passing several hundred watts of RF from VLF on up.

Where is that breaking point on the basic round, radial lead ceramic?


texts: Is an ungrounded earth wire worse than no earth wire?

texts:
The electrical installation in my house is old and have no earth wire, with the outlets having only two holes. However, the new equipment come with three pins plugs, so I installed some new three hole outlets without any earth wire connected.

The problem is that if I measure the voltage between neutral and the chassi of a device that has a three pins plug, I get almost 60V. I think this voltage is being induced by the nearby live wire inside the power cord.

In such a situation, would it be better to disconnect the earth wire inside the equipment, so the induced voltage coming from the earth wire doesn't energize the chassi?

I know this is all far from ideal, but I'm just trying to figure out what would cause less harm.


texts:
I found this design idea (Fast-settling-synchronous-PWM-DAC-filter-has-almost-no-ripple) on EDN where an RC integrator and a sample/hold amplifier are used to filter PWM signals into stable DC values.

From the schematics given in figure1 and results in figure2, it is clear that PT0 is the PWM signal to be recovered. What is PT1? not very clear. I think it is the time base for sample-&-hold. Is my thinking correct? And if so, then what is the relation between PT0 and PT1. The current schematic shows PT1 to be 50% duty. Does that need to change if PT0's duty goes beyond 50%?

Also, why does the author say that this DAC settling will take 0.1sec, when actually it should settle in 1 PWM cycle, so if my PWM frequency is 10KHz, the output should settle in 100us.

The chip used for analog switching is CD4053. This chip selection inputs S1, S2, S3 are active high, but the schematic in figure1 shows these inputs to be active low. Can we simply swap the signal inputs and achieve the same result?

Please enlighten me.


texts:
A practical differentiator has two cut-off frequency but can no longer perform differentiaiton after first cut-off. After first cut-off there is a 20db per decade gain reduction but why does this affect the mathematical function itself. The DC equation still remains
$$
V_{out}=-R_fC_f \frac{dV_{in}}{dt}.
$$
In a low-pass filter the signal just attenuates and does not change mathematically, is something different here.
Is it just that it is still differentiating but for some reason my output is distorted or is there a mathematical explanation behind this. I am using a standard practical differentiator as shown below and I am sure the values I have are correct.


texts: Rotary encoder Grayhill SERIES 26 pinout

texts:
I can't figure out how this rotary encoder works. What's the Vcc and GND?
The technical sheet is attached here but it does not say anything about how to wire it

http://www.grayhill.com/assets/1/7/Mech_Encoder_26.pdf


texts: Application of Fourier Series in Circuit

texts:
I am trying to find \$v_o(t)\$ in the circuit below, where
$$v_s(t) = 3 - \frac{6}{\pi}\sum_{n=1}^{\infty}\frac{1}{n}\sin2\pi n t$$
The correct answer is $$v_o(t) = \frac{3}{2} - \frac{3}{\pi}\sum_{n=1}^{\infty}\frac{\sin(2\pi n t - \tan^{-1}4n\pi)}{n\sqrt{1 + 16n^2\pi^2}}$$
but I got
$$v_o(t) = \frac{3}{2} - \frac{6}{\pi}\sum_{n=1}^{\infty}\frac{\sin(2\pi n t - \tan^{-1}4n\pi)}{n\sqrt{1 + 16n^2\pi^2}}$$

What is my mistake?


texts:
I'm not an engineer, but my monitor stopped working yesterday (it just wouldn't display anything but still gets power) so I figured I'd like to take it apart and see what went wrong.  At the very least I'd get to see what the inside of a monitor looks like :).  Anyway, I took it apart, and also read around about my issue and it seems the capacitors have gone bad, at least some of them.  However, I also noticed some white elastic stuff all over the board.  Some of them are sticking two capacitors together and to the board, but I also see some from where power socket connects to the board.

My question is, what is the white stuff?  Should I replace all capacitors that have white stuff around it, and should I also replace the power socket part?  Or should I just replace the bulging capacitors and leave it at that?

UPDATE:


texts: Parallel->Series switches for capacitor bank, only one charges

texts:
Here's my goal: To create a capacitor bank to dump a load in to a load resistor/inductor, pulsed, without using switches and keeping it as isolated as I can from myself.

Here is what I have so far:

VG2 a square wave simply at around 10Hz, J1 being a net.

My thoughts (I tried with PNP and NPN with 10k Rs at base at first): Have the capacitors charge at full voltage in parallel, the control voltage (VG2) allowing this by opening a path for both to charge side by side.

When the control voltage goes to zero, the N channel fets will turn off (C2's path to ground) and also the diode's (ignore why it is there for now, but to prevent it from recharging C1 during discharge phase I believe) and connect the two in series to make the intended C1+C2=~240V on the load.

What I simulated:

C1 seems to be fine, but does not discharge.
C2 starts at negative (going down slightly)
Load seems to continuously have a voltage (no path to flow?)

I wonder if the fets or BJTs last time simply do not switch or work as I suspect, would they perform as I intend? Is there a more straightforward way of doing this parallel->series switching to isolate myself a little better?


texts:
I have a single cell, ~2100mAh rated Li-Ion battery. Something like 18650, I have taken it out from a laptop battery pack. I want to make a simple charging circuitry for it since I will use it in the heart rate monitor that I am trying to build.

I am going to supply power to the battery via the USB port. Whenever the USB cable is connected to the device to communicate with PC using MCP2200 USB-to-Serial converter, it will also charge the Li-Ion battery which is the main power source of the device.

Below is the circuit I am using:

Here is how it works:

V_BUS is the 5 V power from the USB bus. C15 is the bulk capacitor, I did not want to violate the standard, so I put a 4.7 uF capacitor. Also, since I did not want to violate the current limit of the standard, I have put a current limiter in the charger circuit; D5  and D6 limit the voltage that is dropped on R22 + (Vbe of Q2).

The way the charging circuit works is simple; Q2 is current limited, but to limit also the voltage, TL431 is configured to control the base of Q2 with respect to the voltage on node A.

Also, there are some other circuitry after node B, that is powered up from the battery BT2. Here is some of it shown:

Now, I thought there is no way the battery can supply current to Vbus since Q2, D5 and D6 will be reverse biased, but it seems like I am wrong at some points. At certain voltages of the battery, for example at about 3.8V, MCP2200 cannot enumerate and Windows does not recognize it as a virtual serial port. Whenever I remove the battery, this problem is solved, USB enumerates successfully every single time.

Also, I have inserted a diode between node A and node B with a polarity that is shown in the schematic, and this worked, too. I know that I have to connect R28 to node B again to compensate for the voltage drop of the added diode.

That makes me come to the conclusion that battery feeds the circuitry on the left of it and messes up with the voltage or current levels of USB standard and it cannot enumerate. However, I cannot give a logical explanation.

Edit: When the battery voltage is 3.8 V, I measure 4.3 V on the V_BUS node when the USB cable is not connected and there is a diode between Node A and Node B.

Edit: It seems like V_BUS was getting fed by Rx pin of MCP2200, through the protecting diode inside of MCP2200. Madmanguruman said it right, I have to include full schematic and here it goes; Page 1 and Page 2 of the full schematic. I have edited the code to idle this pin at 0 V instead of 5 V, and the problem seems to be solved now.

What is the reason this USB battery charge circuit will not work without a diode?


texts: I am looking for a solution to step-down the 12V 82A from a server power supply to charge a 3S2P supercapacitor to 8.1V. Not sure which buck converter to go or if there are any specific limitation to them. Would a LTC3824. Based on the datsheet I calculated 198nH at 90A but can't seem to find a suitable inductor. Where am going wrong?


texts:
For a small project I'm working on, I am trying to decide the best route to take for the power connection to the device. It will be running on 5V and, in its current iteration, draws less than 100mA so it would be viable to power it off of USB.

The project will be a kit that needs to be assembled so I need to stick with through-hole parts that could be soldered by a relative novice. The usual go-to power connector for these projects seems to be the 2.1mm barrel connector but I really don't like those for a lot of reasons. Partly because it takes up a lot of board space (and my board will have little to spare) but mainly because that means I would also have to provide barrel connector wall adapters with the kit. This adds extra cost and parts I have to handle.

A microUSB connection would be fantastic since almost everyone has at least a few of those cables around and you could power it from a wall adapter or directly from a computer. However, I have yet to find any microUSB female sockets that are in any way easy to solder.

I've found things like this USB to 2.1mm barrel cable, but that seems like a cop-out.

Any other options that I'm missing?


texts:
In this schematic it shows the smbus as a separate unit, what im wanting to know is this a seperate ic that i have to integrate in or is it just simple as a usb port?

(source: www.ti.com)


texts:
In power systems, there are rules and regulations stating what levels of harmonic distortion is acceptable. One example I've seen for voltage distortion is: THD < 8%, single component harmonic <5%. These values are (hopefully) not random numbers.
From Schneider Electric:

Harmonics are unwanted currents that overload wiring and transformers,
creating heat and, in extreme cases, fire. These currents are harmful
to equipment. They weaken the reliability and shorten the life
expectancy of equipment exposed to the distortion

For induction machines, negative sequence harmonic currents will also cause a negative torque, which of course isn't good.
My question is: How bad is it, really? What can the consequences be if the total harmonic voltage distortion is 10% instead of 8%, if the 7th harmonic is 6% or if the negative 5th harmonic current is 10%. The reason why I ask is: Reducing harmonics does not come for free, is it really worth it in all cases? I know I have to adhere to the regulations, but assuming there were no regulations, what then?
Does anyone have any experience in this area?
Update
I forgot to mention the following in the question: The system I'm studying is not connected to the main grid. It has its own generators, UPS-system and all other necessary infrastructure. The operator and the owner of the system is the same company. The specific regulations I'm mentioning are for such isolated systems, not systems connected to the main grid (could for instance be a vessel).
Update 2
If you have your own power grid, and all the equipment is your own (thus you would need to take all the costs of installation, maintenance etc), then why are there limits and not guidelines when it comes to harmonics? I understand why there are rules regarding for instance short-circuit levels, arc-flash hazard etc. etc.
I also understand regulations regarding voltage drops, as this may lead to motors stalling, loss of excitation and more, I just don't get why there are strict regulations when it comes to harmonics.
How much damage can it do?


texts:
The block diagram below is for a simple use of a solar array in conjunction with a battery, in a battery tied bus format. The diagram is simple and straightforward excepting the capacitor configuration.

One possible use of this configuration (usually) is to create a specific value of non standard capacitance using standard capacitors. This is clearly not the case as they are all equal and the equivalent capacitance is simply 100uF.

The configuration looks like it is acting as a filter in case of any sudden spikes in voltage, is this why it exists?

Could this configuration exist as some sort of redundancy?

simulate this circuit – Schematic created using CircuitLab


texts:
Referring to the Infineon ICE2A365 datasheet.

In the datasheet, the thermal resistance from junction to ambient is 90 K/W.

What is K? Is it kelvin or degrees C.

If it is kelvin than changing it to degrees centigrade will be approx -183C/W, which does not make any sense.


texts: Nodal Analysis with current and voltage source

texts:
Would the following be the correct approach? I am a bit concerned with node C as it introduces another unknown. Do I need to write a constraint for this problem?
$$A:  ((A-Ref)/4000) + ((A-B)/2000) - .002A = 0$$
$$B:  ((B-A)/2000) + ((B-Ref)/2000) + ((B-C)/2000) = 0$$
$$C:  ((C-B)/2000) - I(source) + .002A = 0$$


texts: TDA7262 Audio Amplfier's SVR/MUTING pin (pin3)

texts:
What exactly is the SVR/MUTING pin on the TDA7262?

I've done my research on it but I cant find much. I found something that said its to eliminate the thump the speaker gives off when power is applied or removed to and from the amplifier. I must design a pcb with datasheet specifications but I don't understand pin 3 and the 0.45V.

Circuit attached.


texts: Can the GND pin of the Arduino UNO be used as a ground instead of the negative terminal of a battery while using a battery as the power source? If no, do we have the liberty to choose our ground for the circuit OR DOES THE NEGATIVE TERMINAL ALWAYS HAVE TO BE THE GROUND WHEN WE USE A BATTERY AS A POWER SOURCE?


texts:
I seem to have burned out this chip on my Hobby King ESC (see picture). I am not able to read the component part number. The ESC is no longer available to buy. What is the part number (so that I may fix it)?
It's this one, BTW. https://hobbyking.com/en_us/hobbyking-40a-2-6s-esc-w-ubec-4a.html?___store=en_us


texts:
Could you give me more info on these capacitors?
My guess is
Top = 50pF
Bottom = 15000pF = 15nF
Correct?
What is the meaning of remaining char?
Thank you!


texts:
I tried an example of code to display serial output on an array of LEDs.

#define F_CPU 1000000UL
#define BAUD 9600UL

#include <avr/io.h>
#include <util/delay.h>
#include <USART.h>
#include <pinDefines.h>

int main(void) {
    char serialCharacter;
    LED_DDR = 0xff;
    initUSART();
    printString("Connection Successful\r\n");

    while (1) {
        serialCharacter = receiveByte();
        transmitByte(serialCharacter);
        PORTB = serialCharacter;
    }
    return 0;
}

The code for the serial connection:

#ifndef BAUD
#define BAUD  9600
#endif

#define   USART_HAS_DATA   bit_is_set(UCSR0A, RXC0)
#define   USART_READY      bit_is_set(UCSR0A, UDRE0)

#include <avr/io.h>
#include <util/setbaud.h>

void initUSART(void) {

    #define BAUDRATE ((F_CPU) / (BAUD * 8UL)-1) // Set Baud Rate Value for UBRR

    // Set register
    UBRR0H = (BAUDRATE >> 8);
    UBRR0L = BAUDRATE;
    UCSR0A |= (1 << U2X0);
    // Enable USART transmitter and receiver
    UCSR0B = (1 << TXEN0) | (1 << RXEN0);
    // Set 8 data bits and 1 stop bit
    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
}

void transmitByte(uint8_t data) {
    // Wait for empty transmit buffer
    loop_until_bit_is_set(UCSR0A, UDRE0);
    UDR0 = data;
}

uint8_t receiveByte(void) {
    // Wait for incoming data
    loop_until_bit_is_set(UCSR0A, RXC0);
    return UDR0;
}

void printString(const char myString[]) {
    uint8_t i = 0;
    while (myString[i]) {
        transmitByte(myString[i]);
        i++;
    }
}

The connection works well and the data I key in will be displayed on a serial terminal as expected. Though the display on the LED array is odd. No matter what I key in, I get the output on LEDS of 00001010 (8 LEDs each representing one bit) on PORTB of the ATMEGA328p.

Always the same 2 LEDs light up. When I press a key to be transmitted I get a short flicker of the LEDs and then going back to lighting up Bit 2 and 4. How can I fix this?


texts: How does a GSM device (ME) decides which tower/base station (BTS) it should connect to

texts:
I'm looking for an article or specification that explains how a GSM device (ME) decides which tower/base stations (BTS) it should connect to.

I'm looking for info specifically on the registration phase and NOT the hand-over phase.

From my understanding, and this is just a very basic explanation for a complex process, the ME scans for nearby towers (typically only the ones from its designated MNO). During this process it will gather info about these towers such as signal strength. Once the scanning process has completed, it will try an attached to the tower with the highest signal strength.

I will appreciate your comments, but I really need a reliable or at least somewhat reliable source as a reference. Unfortunately a forum post will not be sufficient.

Anyone out there knows where I can find this info?


texts: User power supply current limit to avoid current limiting resistors for LED

texts:
everyone!

I would like to know if I can avoid to use current limiting resistors by pushing my power supply to its limits (it already sounds not like a good idea... btw...).

Say I have a 3.3V power supply with 200mA current limit.

Question 1: is it safe to suppose that connecting 10 LED in parallel with no resistors (positive to 3V3, negative to ground) each one gets 20mA of current? (200mA/10)

Question 2: how much can I trust the power supply limit?

Question 3: pushing a power supply to its limit for a long time can cause any issue?

Thanks!


texts: How to detect if a high voltage fuse is blown

texts:
I have a 150A fuse on a 100A @ 400V nominal battery pack. There are 5 service relays and 2 isolation relays (one on each pole) in this battery pack. I'd like to make sure that none of these relays can be opened if the fuse is blown (so some kind of interlock would be wired in series with the emergency stop buttons, and the fuse blowing would trigger the same re-startup routine).

What's the best way to do this, or is there a type of fuse with an interlock which can be used?

I must not make an electrical connection between the pack and the interlock/fuse checking circuit.


texts: Calculation of noise in Non inverting Op-amp circuit

texts:
I have this non inverting op-amp circuit:

I would like to calculate the output with the Op-amp noise impact.
I can easily find the voltage output, but only if I assume there is no noise.

How to do it with noise Op-amp (assuming others components are "perfect")?

We will use a TI OPA141 Op-amp:
http://www.ti.com/lit/ds/symlink/opa141.pdf

Input is signal frequency is 100Hz.
I want to use the 6.5nV/sqrt(Hz) but it seems to be a spectral density, and I can't add it to a voltage.

I wanted to use the square of this to find a value in RMS, but it failed and I want a voltage value, not a RMS value.
We should have 42.25V^2/Hz

How can I find the noise from the opamp?


texts: Create new component based on existing one in Eagle 9

texts:
How can I create a new component in Eagle 9 based on an already existing one?

It used to be a relatively straightforward endeavor in all the previous versions prior to v9.0 but the process seems to have changed. There are plenty of tutorials explaining how to create a component from scratch, but so far I've found none that walks through the process of creating a new component based on an existing one.


texts: Node voltage equation with weird solutions

texts:
I recently had an exam with the following multiple choice problem:

Consider the circuit below:

The node voltage equation for node A is which of the following?:

\$ \frac{V_A-kV_a}{R_1}+ \frac{V_A-V_3}{R_2} + \frac{V_A-V_B}{R_6} = 0 \$

\$ \frac{V_A+kV_A}{R_1} + \frac{V_A-V_3}{R_2} + \frac{V_A-V_B}{R_6} = 0 \$

\$ \frac{V_A-kV_A}{R_1} + \frac{V_A+V_3}{R_2} + \frac{V_A+V_B}{R_6} = 0 \$

\$ \frac{V_A+kV_A}{R_1} + \frac{V_A+V_3}{R_2} + \frac{V_A+V_B}{R_6} = 0 \$

\$ \frac{2V_A}{R_1} + \frac{V_A+V_3}{R_2} + \frac{V_A+V_B}{R_6} = 0\$

\$ \frac{V_A-V_3}{R_2} + \frac{V_A-V_B}{R_6} = 0\$

My attempt
This is how I would make the node voltage equation for node A:
\$ \frac{V_A}{R_1} + \frac{V_A-V_3}{R_2} + \frac{V_A-V_B}{R_6} + ki_1 = 0 \$
But as you can see, it doesn't match any of the options above and I can't figure out how I'm supposed to reach on of those solutions.
Can somebody help me out?


texts:
Is there a way to save and use a parameter set (title, author..) on all schematics in a document or another document?

Thank you


texts: Can fields generated by an antenna damage an iPhone?

texts:
I am currently attending a radio technology course. We continuously work on radio sets that are sometimes used as manpacks by the Army. In order to learn how to operate them we work in close proximity to the sets and their antennas.

The antennas are generally whip type or long rods. Such as these :

The radio sets generally output around 25-50W in the 30-90MHz frequency range. Can that possibly cause damage to my iPhone?