texts: Wall charger\USB vs battery power supply - which will "win" access to the load?

texts:
If both the wall supply/USB (4.4V-5.5V range) and the lipo battery (3.6-4.2V range) are turned on, which one will power the load?   The D1 diode for the wall charger\USB has a 0.6V drop at 500mA and the ideal diode (MAX40200) for the battery has a 45mV drop at 500mA.
Let me guess:  if the wall charger/USB voltage after the D1 diode drop is higher than the battery voltage minus the ideal diode drop, then the wall supply/USB will power the load.
The problem may happen if the wall charger/USB operates at the low end of the supply range at 4.4V - 0.6 Di diode drop = 3.8V and it goes up against the battery's 4.2V.  What is the solution besides using a MOSFET switch?


texts:
I would like to fabricate a slight enhancement over the metal-core PCB's shown here:

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6071

Specifically, my application requires 2 LED's of different wavelengths that can be toggled using a switch or MOSFET.

In principle, the PCB would be a very simple single-layer design which I could mill out from a copper-clad blank -- that is, if it were FRA-core.

However, I'm not sure how to proceed with creating a DIY metal-core PCB. Is it possible? Is there an equivalent "blank" that can be purchased? Are there any tutorials or best-practices published online?


texts: General dimensions and recommendations for a USB dongle

texts:
I'm trying to create a device that connects via USB and sits in a users computers USB socket at all times, and I'm unsure of what the general dimension requirements will be.

Ideally, this device should fit in a USB Type-A receptacle in a scenario where the user plugs it into the following devices - and more:

USB-hubs
Modern computer motherboards and backplates
Raspberry Pi and other Single-Board Computers

The device must not physically interfere with typical consumer products like USB memory sticks, USB bluetooth modules, USB coords, etc.

What would the general dimensional requirements be for the device - and is it standardized somewhere?

Thanks in advance!


texts: what are some dirt cheap, small e-ink displays?

texts:
I'm looking for an e-ink display (pixel-based) that is as cheap as humanly possible, and tiny, yet still a fully pixel-based display that can refresh within a hundred milliseconds.

The "custom display" products from Aveso are almost what I am referring to. But they are immutable displays, ie, not pixel based.

The displays must be very small — 1cm, and ideally they would work with a multi-head controller.


texts: What is (roughly) the ratio of insulation-to-conductor cost in a cable?

texts:
Somewhat related to this question on aluminum vs copper, when making a cable one needs to consider the cost of insulation as well. I suspect there may be significant variance depending on technology, rated voltage, rated temperature, rating for mechanical stresses, and so forth. Are there some rough estimates (even as ranges) of how much the insulation costs relative to the conductor cost?

I'd be perfectly happy with analysis on some commonly used cables, e.g. extension cords for household use (at one end) and, say, metropolitan underground power cables (at the other).

There's not much in the way of cost breakdown analyses for power cables that I could find. One presentation by General Cable briefly mentioned that "Purchases of raw materials account for 75% of total manufacturing costs for most manufacturers." So at least we know that the cost of materials is important in this sector...


texts:
I am attempting to drive a Peltier device using a single MOSFET, controlled by a microcontroller.

I am working with several different peltiers and various MOSFETs, so wont provide component details at the moment, but would like to understand if the general setup is suitable.

I am simply putting a MOSFET in series with the Peltier, and setting the Vgs of the MOSFET to significantly beyond the Vgs(th), the MOSFETs im using claim that this should put their Rds(on) to ~50-100mOhm. At the battery voltage (I'm using a single cell Lipo) of ~3.7v, the Peltier should be trying to take ~2.5A.

Instead of the expected current draw, I am seeing a significantly lower current, ~1.2A, and I seem to be getting a relatively high voltage drop across the MOSFET, as high as 0.85V.

I've ordered some relays and solid state relays, but would like to understand why the system is behaving this way, and if there is a better way to drive a Peltier than this. I am not PWMing the MOSFET, it remains on for several seconds.

Also, sometimes when the MOSFET is powered up, the microcontroller (which is using the same battery) browns out, however I am not observing a noticable voltage drop on my scope, and the uC is heavily decoupled.

Any advice is welcome.

Thanks


texts: ATmega64 needs to be reset after Power Up

texts:
I am using an ATmega64A for my project with ESP8266 and RFM75. But the ATmega64 hangs on power up and I have to pull reset low to make my code work. I'm using an external 8 MHz crystal.

I have connected all VCC and GND pins properly with 0.1 µF capacitors on each VCC PIN. The RESET pin is pulled high with 10 kΩ resistors and 10 µF capacitors are connected between RESET and GND (I have tried 0.1 µF capacitors as well).

I need a some kind of help to get out of this issue. All comments or suggestion will be appreciated.

EDIT 1:
My Schematic attached here.

I have measured voltage level on RESET PIN on power-on condition.

EDIT 2:
Only LED Blinking Code works well on the same hardware, I have checked so many times by switching the supply ON/OFF. I thing Code have some issues.
I'm trying to figure it out.

EDIT 2:
I have flashed Simple LED blinking code on start up before I start ESP8266 or RFM Initialization. I have a Debug option in my code as well. ATmega64 UART1 is used as Debug Terminal. I have tried flashing LED before Debug Initialization. Led Blinking works like charm!
I have a Function in Debug Terminal to print banner on start up. It prints Date time of compile and reboot causes and a version of code. when I have commented the function , my code started working fine. I have tested many time on different boards by the issue disappear from then. here the function which I have removed.

    static void PrintBanner(void)
{
    unsigned char status = MCUCSR;
    unsigned char moreThanOne = 0;

    printf_P(PSTR(CMD_LINE_MSG_WELCOME));
    printf_P(PSTR("Firmware: v%S [Compiled on "__DATE__" "__TIME__"]\r\nBoot cause: "), PSTR(APP_VERSION));

    if(status & (1 << PORF))
    {
        printf_P(PSTR("Power On"));
        MCUCSR &= ~(1 << PORF);
        moreThanOne = 1;
    }
    if(status & (1 << EXTRF))
    {
        if(moreThanOne)
            printf_P(PSTR(", "));
        printf_P(PSTR("External"));
        MCUCSR &= ~(1 << EXTRF);
        moreThanOne = 1;
    }
    if(status & (1 << BORF))
    {
        if(moreThanOne)
            printf_P(PSTR(", "));
        printf_P(PSTR("Brown-out"));
        MCUCSR &= ~(1 << BORF);
        moreThanOne = 1;
    }
    if(status & (1 << WDRF))
    {
        if(moreThanOne)
            printf_P(PSTR(", "));
        printf_P(PSTR("Watchdog"));
        MCUCSR &= ~(1 << WDRF);
        moreThanOne = 1;
    }
    if(status & (1 << JTRF))
    {
        if(moreThanOne)
            printf_P(PSTR(", "));
        printf_P(PSTR("JTAG"));
        MCUCSR &= ~(1 << JTRF);
        moreThanOne = 1;
    }

    printf_P(PSTR(" Reset.\r\n"));
}

What would be the cause for the RESET issue of the ATmega64 with this piece of code?
Does it because of fetching data from program memory to print over UART?
Still I'm trying to go to root cause for this issue.
If anyone have any idea about this kindly throw some light on it.
Thanks.


texts: MOSFET: Cannot control gate signal using Arduino PWM

texts:
I attempted to power a 100mA LED with my Arduino. The power for the LED was provided by a battery (3.0V) - tge Arduino was connected via USB to a computer.
The idea was to use the Arduino PWM to regulate power from the battery to the LED.
Wiring the N-channel Mosfet (IRFZ44N) mostly as shown in the picture (taken from this guide) below (where the power supply is a battery.) For simplicity I connected the gate signal directly to the Arduino pin (without resistors.)

I observed something that I couldn't explain:
The PWM signal (or 3.3V or 5V pin) from the Arduino seemed to have no effect. Connecting the gate wire to either + or - of the 3V battery circuit turns the LED off and on.
My (noob-level) concept so far was that MOSFETs are simply 'voltage controlled switches' and therefore this doesn't make sense to me.
Can someone explain (in layman's terms) why this is happening?


texts:
I had taken this video as a reference to make my own permanent magnet generator: Permanent magnet generator. However, I am not able to understand how the copper coils are wound and outputted.

Nevertheless, I tried making my own model. This was my design for the permanent magnet generator for energy harvesting purposes as shown in the 3D model.

In the bottom spacing I will be placing the neodymium magnets and in the top portion, the copper coils would be wound similar to the video above. However, I have still failed to understand how the copper coil winding should take place in each position whether it should be clockwise or anticlockwise and so on.

On further research I came across this video where they make a brushless DC motor inrunner, and this wiring diagram at 4:52 where four magnets and 12 copper coils are arranged in this manner.

Is this the way it should be arranged? 8 magnets, 8 copper coils or 4 magnets 12 copper coils. For 8 magnets, 8 copper coils, what would be the possible copper coil wiring diagram for 3 phase or single phase output? Any suggestions?


texts: What is the best way to mount a LiPo battery in a project box?

texts:
If you were going to use a LiPo battery such as this one:

. . . and needed to mount it safely and securely inside a project box similar to what is pictured below what best way to achieve that?


texts: What does this op-amp circuit do? (part of an ECG)

texts:
I would like create an ECG circuit based on this schematic (from the AD620AN datasheet):

I don't know this part of the circuit and how it works. I know this is called a right leg driven circuit which is reducing the effect of the noise. But I don't know exactly how negative feedback works in this case. Can someone help me?


texts:
I'm building a small capacitive water level sensor for a reservoir (16cm tall x 10cm x 7cm).

This prototype gives me 10pF on free air and 20~30pF on medium water levels, so its definetively doable (its a piece of wire inside a brass tube).

I'm looking into possibly getting better measurements (as in bigger difference between free air vs with water). So before chopping the rest of the brass tubing I have, I'd like to ask if there are some known recommended geometries.

One that I find online a lot is two tubes, one inside another. I have also considered building a three layer config (wire, tube, tube), with the innermost connected to the outermost (connection not show in this mock-up):

I have tested with one of the armatures not isolated/directly touching the water and I have way bigger difference between free-air vs in water but I need it to be galvanically isolated.

So, again, is there a way to get more contrast between free-air vs on water? Level sensing is nice but detecting an empty reservoir is even more important.


texts: Is there a "common voltage reference point" for all the circuits that connect together?

texts:
Nowadays, the whole world is interconnected. We often say one device communicates with another device through the network. In this context, the 2 devices are viewed as 2 separate entities. But I think a device is no more than a bunch of circuits. And the communication can be expressed/carried out through voltage difference and current exchange.
In the case of voltage difference, I don't view devices communicating to each other as separate entities, instead I prefer to view them as connected circuits as a whole, i.e. they form a giant circuit. And the communications are just state changes within this giant circuit.
If my view is correct, I think there should be a common voltage reference point for this giant circuit. Does it exist? Where is it?


texts: How do I derive the transfer function of this circuit in terms of its corner frequencies?

texts:
How would I derive the transfer function of this circuit in terms of its corner frequencies?

Edit: The solution I am trying to derive is the following


texts: How does this telephone circuit modulate the current?

texts:
I've been reading on how old landline telephones work (POTS, as they call it) and found out it's quite a bit more involved than I had expected.

This circuit comes from the wikipedia article "Telephone", and I have a few questions.

First, what I've got so far. Please tell me if I got anything wrong:

There is a pretty high DC voltage (48 V) between both wires (called tip and ring). I still don't know which one is higher though. Wikipedia says the voltage is negative with respect to earth to avoid corrotion but I don't know which one is connected to ground, if tip or ring.
The voices are modulated on the AC current, not on the voltage. This means that the current along the loop should be i = I_DC + k1 * x1 + k2 * x2. In that equation I_DC is the current resulting from the DC offset on the line, x1 and x2 are the voice signals of each user (they could be air pressure at the microphone) and k1 and k2 are constants to convert to current.

With that in mind, I'm trying to understand how this circuit works. I have a few questions:

At audio frequencies, the impedance of the speaker should be fairly resistive so the fact that it's modulated current makes no difference at all. The current drives the speaker just as well as a R_speaker * i voltage would. Is this correct?
You get feedback on the speaker, right? The microphone signal goes through the transformer, I think I should hear myself but I never payed attention to that, so I don't remember (also it's been a while since I used a landline phone).
Related to the previous questions, Wikipedia mentions that A3 is a hybrid coil, so that the outgoing signal doesn't overpower the incoming signal. What I think this means is that A3 adds up both signals, but since the current from A2 goes into the middle tap, it's level is reduced by the turns ratio on the transformer, since the incoming signal uses the whole coil. Is this correct?
A2 is the microphone, represented as a variable resistance, which I don't understand. My first guess would be that the variable resistance generates AC current due to the DC voltage applied to the resistor. Is this correct? However, most modern phones use electret microphones, which just generate a small voltage proportional to the sound pressure. How is this implemented on a modern phone? Do they feed a current source with the amplified voltage from the mic? And how is it implemented on an old phone? What kind of microphone works as a variable resistance?
What are the typical amplitudes of the AC currents?

These are all the questions I can think of right know. I will update if I think of anything else.


texts: Vias in footprint with no thermal relief?

texts:
I'm making a small board for a PIC18F26K22 microcontroller and the provided footprint in Microchip's Altium Vault is shown below:

I'm assuming the polygon under the IC is a GND pad, but am not 100% sure since I can't seem to find anything confirming this in the datasheet.

My concern is that the vias don't have any thermal reliefs and are untented, so isn't it likely that when the QFN chip is being soldered that the solder will get sucked through the vias as well as the GND pad possibly not getting hot enough?

EDIT: Oh, and the square pad was not named GND (which I just noticed you can see) to start with -- that was me trying to find a way to get the pad to connect to my GND net when routing the board.


texts: What's the automatic equivalent of a variable resistor?

texts:
I have a circuit which controls the volume on a speaker by a wheel which is attached to a variable resistor - I want to reproduce this but instead of using a manually operated variable resistor, I want to use ...something else instead - Ideally something where you can apply a voltage to change the resistance from low to high.

I've done a little research but I think I'm being stumped by not knowing what I'm actually looking for.


texts: How to calculate the lethal amount of current for given amount of output voltage?

texts:
I have some electrical parts that I was planning to reuse, things like laptop chargers and some parts from a printer. I searched google for what's the lethal amount of current and they mention 10ma is lethal. But they didn't mention for what voltage it is lethal. My phone charger outputs 2Amp at 5 volts and I know it's not harmful. So I have these parts that output 24V 0.6Amps and I wanna know if there's a way I can know this will be harmful or not?
In general is there a formula I can use to calculate a threshold amp value for given DC/AC voltage?


texts: How do I hook up an LED across the tx pin on my Atmega328?

texts:
I've built a standalone Arduino and upload sketches via this method From Arduino to a Microcontroller on a Breadboard.  I would like to hook up an LED across TX like on the Arduino board, so I simply wired it to the TX pin with a resistor going to ground.  And it works on a sketch where I am simply sending serial data at a 9200 baudrate.  Both the Arduino TX and my ATmega TX LEDs blink correctly.

However, my application involves a baudrate of 19200, but when I upload this sketch, the TX pin on my ATmega stays on constantly, even if no serial data is being sent.  What's even more interesting is that the Arduino TX led does blink correctly for the same sketch.  Can anyone help?


texts: Laser Data Communication : How it Works General Idea and Concept

texts:
I saw a project that use a laser pointer to point laser to a solar cell and that plays music on the speaker connected to the solar cell.

I am just confused in regards to the general concept behind how this would work. How is a laser light turned into unique sets of data such as music?

link: https://www.youtube.com/watch?v=jvrXXQGXYg4


texts:
I would like to wire a device I'm making with USB-C input for power but I don't need its SuperSpeed capability. The port will only act as a power input (to this device) and USB 2.0 in. Do I need a chip that communicates (over CC) what should be sent or will it automatically receive 5V at 1.5 amps-ish. I have investigated many chips but they always include CC and support higher power standards that I can't use.

All help accepted, please ask me to clarify if I was vague.


texts: Is it possible to use an LDO as an Auxiliary source to a smps?

texts:
My SMPS controller can supply about 250mA and 3.3V output.

There are rare but crucial moments when power demand goes above 250mA, voltage sags below 2.7V, and the MCU brown-out occurs.

The question is: if I add a 3V LDO, will it stay inactive at 3.3V until the droop reaches 3V before it regulates? Or is there some kind of a low side switch that will try to “regulate” the 3.3V down to 3V?

TIA


texts: Anybody see this kind of DC restorer or clamper, would you like to give out the detailed solution for the output waveform

texts:
In the following circuit as shown in Fig-1, assume that the diode is ideal and has a forward voltage of 0.7V. Given RC>>T, Sketch accurately the output waveform for the circuit. I have simulated the circuit with different group of R and C as shown in Fig-2. The interesting thing is that once I keep the two R same , the output( peak value) is almost same, or 8V as shown in Fig-3.  can anyone tell me why the input waveform is shifted down with around 2V?  really appreciate that .

Some symbols are added into Fig-1-x to understand the Eq.2 given out by Jonk.

simulate this circuit – Schematic created using CircuitLab

Based on the solution provided by Jonk, here I give my calculation details:
Eq.2 is derived from Eq.1. Am I right? @Jonk

Here is the derivation details of Vc as below:

What about the solution for Vo in Fig.6?

simulate this circuit


texts: Associating two vault items with a single component in Altium

texts:
In my Altium BomDoc file, I'm trying to associate multiple manufacturers with a single component (to give our manufacturers a few options for sourcing before they have to bug us to approve alternatives). For one of said components, my BomDoc looks like this:

Most of the sourcing solutions come from the details in our Altium Vault. This is good, because these things get updated automatically as our Vault changes. The highlighted solution entry (from Nichicon) was added manually by me, as an alternative. This is bad, because this won't be updated automatically if our Vault changes.

My question is, is anybody aware of a method of associating two Vault entries with a single component? Or, more broadly, is anybody aware of a method of associating more than one supply source from the Vault with a single component?


texts: Safely measuring voltage from solar panels in an experimental research field

texts:
(Note: I asked this on https://engineering.stackexchange.com/ but I was told I should ask this here, so this is what I'm doing.)
I'm installing solar panels (not connected to the grid) in units out in a field for research we're doing, that looks like this (this is an outdated image, but I can't find the updated one unfortunately):

I have to safely measure power output from each unit (and there are 4 units).
Each unit has 9 panels with the following specs:

Maximum Power: 100W
Maximum System Voltage: 600V DC (UL) Optimum
Operating Voltage (Vmp): 18.6V
Open-Circuit Voltage (Voc): 22.3V
Optimum Operating Current (Imp): 5.38A
Short-Circuit Current (Isc): 5.86A
Operating Temperature:-40°F to 176°F
Output Cables: 14 AWG (2 ft long)
Maximum Series Fuse Rating: 15A

(The panels are from Amazon so I'm not sure how accurate the specs are. The link to reference them is at the bottom.)
These panels are going into an agricultural field, so my primary concerns are: 1) Not electrocuting anyone, 2) not starting a fire, 3) being able to accurately measure the power coming from each unit.
This is my main plan so far, which I'd like feedback on:

Wire all 9 panels in series to minimize amperage
Use 14 AWG wire to take the power out of the field (2-12 meters of distance from the field to the load box) to some sort of resistive load to use the power
The unit will be grounded using grounding rods
On the circuit, there will be a 10A circuit breaker, a manual on/off switch
The resistive load will be connected to a GFCI
Power will be measured using some sort of Arduino based module powered by it's own battery

Some notes:

I'm not sure what the best, safest (and if possible, cheapest) way to burn the power from the solar panels is. I was thinking using a space heater since each unit is allegedly only putting out a maximum of 900W and commercial space heaters are rated for 1875W. I know I could ground each unit and not have a load and the power will just discharge, but my understanding is I can't measure that.
On the subject of measurements: Are any of the micro controller compatible power meters I find on Amazon going to be sufficient for this task, or do I need to look for something specific?
I'm a graduate student who has to get this done but I lack expertise in electrical engineering to do this properly.

This has to be done ideally ASAP, but definitely before the end of May. Although, again, my main concern is doing this safely first and foremost. I am willing to hold off on measuring the power as long as there's as the primary concern is discharging power safely then figuring out how to measure power. I imagine that would involve routing power to a grounding rod, but I'm not sure.
Any advice and feedback is greatly appreciated, and I am happy to answer any questions.
Solar panel link: https://www.amazon.com/dp/B07JXYTFF7


texts: Is it possible to acheive a band pass filter with a pass bandwidth sufficient to discriminate AM radio channels, without using an inductor?

texts:
I am wondering if it is possible to make a filter circuit that has a high enough Q/small enough pass bandwidth to discriminate AM channels, which are spaced 10 kHz apart in the ~1000kHz range - so with a pass band bandwidth of <1% of the center frequency - without using an inductor?
I will also note that my goal is not to use such a filter for actually filtering AM radio signals. I am trying to filter non-radio voltage signals at ~1kHz and hoping to be able to achieve similar discrimination as a radio tuner (pass bandwidth ~10Hz), hopefully without using an inductor.
Based on my investigation of high Q active band pass filters, even a 6th order filter seems to have a roughly 10x larger pass bandwidth than what I am looking for.
If this is possible without using dozens of op amps, what is the simplest way to achieve it?


texts: How does a repeater convert light from a fibre-optic cable into binary?

texts:
I'm just starting out in Computer Science and currently learning about transmission of data in fibre-optic cables. I understand fibre-optic attenuation and that a repeater will then take this light and amplify it.
My question is, how is the repeater doing this? What is the process in which the repeater takes light in and converts this to binary code? I completely understand the physical pulses represent 1 and 0, but how is this being read by the repeater?
To my very little understanding, I'm assuming the light is not pulsing any electrical current of any kind to be read by transistors like how they would be in a physical computer.
Thanks.


texts: Why do heaters vary widely in resistance even though they have similar power requirements?

texts:
I have a soldering station equipped with a 24V/60W soldering iron. Its heating element (pins 1-2) resistance measures around 50 ohms. The resistance of the thermocouple (pins 4-5) measures around 2 ohms.

Soldering Iron Pinout

PIN WIRE    PURPOSE
1   Blue    Heating element  ' ~50 ohms
2   Green   Heating element  '
3   Yellow  Case ground
4   Red     Thermocouple     ' ~2 ohms
5   Black   Thermocouple     '

I also have a desoldering gun from a desoldering station with the same power requirements and ratings 24V/80W. The thermocouple resistance measures the same as my soldering iron around ~2 ohms (pins 1-2). The resistance of the heating element (pins 3-4), however, measures only 4 ohms.

Desoldering Gun Pinout

PIN WIRE    PURPOSE
1   Black   Thermocouple      ' ~2 ohms
2   Blue    Thermocouple      '
3   Red     Heater Element    ' ~2 ohms
4   Red     Heater Element    '
5   White   Trigger switch
6   White   Trigger switch
7   CENTER  Vibration sensor

Both instruments are using a ceramic heater.  The temperature range for the desoldering iron is 160℃ - 480℃
I don't understand how the heating element's resistance can be so low.  Am I missing something here?  If I were to connect the heater and thermocouple wires of the gun to my soldering station, wouldn't it overheat? If so, why doesn't it overheat when connected to the desoldering station given the units have very similar power requirements. Is there some other internal circuitry I am not accounting for? Am I misreading something?


texts:
I need to buffer an input signal such that I do not load down the source, which is a 100k resistor. However, I need to buffer at least 6 channels, and for more advanced models I'd like to move to 10 channels (for the more advanced one I'd be okay using multiple chips though.)

I'd rather not use op-amps, because they will take up considerable space - just wiring the inverting or noninverting to the output, for example, uses a lot of space for traces - also, half the pins would be unneeded.

I'm not sure what chip or type of chip to be looking for - all the buffers I've found so far only work for digital logic, not analog signals. The buffer should have very low input bias current (nanoamps to hundreds of picoamps), like a JFET op-amp.


texts: Can I programming Bluetooth module internal registers through UART?

texts:
I have a customized Amicomm A8107 Bluetooth System-in-package (SiP) module for a project in a PCB with a STM32F103Z micro-controller. I have 5 connections between my microcontroller and the BT module:

RF_RST#
WAKEUP
UART_RX
UART_TX
RF_INT

There are 4 further connections between the BT SiP and a 5 pin external interface to the board (which I assume are the JTAG pins?). The in BT SiP datasheet the 4 pins are labelled as:

RF module supply voltage
GPIO/ICE
TTAG_TTDIO/PWM2
TTAG_TTCK/PWM3

A company designed a UART interface of BT SiP for the project; I am not at liberty to disclose the details of that interface. But I looked through it and I could not find any UART commands to either program the BT module registers or to shut it down. The intended design was to control the BT module with the RF_RST# and the WAKEUP pins. Setting RF_RST# (which is connected to pin PA12 in our micro-controller) LOW should put the BT in sleep mode; but we are using the stm32duino backend for our firmware. The backend reserves the PA12 pin high and prevents the firmware from controlling it. We think it is caused by having the -DSERIAL_USB in the build configuration for our microcontroller as described here.

One of my ideas is to turn it off by programming the relevant register in the module (9.2.2 in the datasheet). I have a manual for the module which I used to find the address of the register which I need to program. However, my interface to the module is restricted: I can only access it using UART.

I want to know the following things:

Do you guys it maybe possible to program the register through the UART?
Might it be possible to program the registers through the connections of the module to the external interface pins?

EDIT: Added model of bluetooth and some other details about my hardware platform


texts: We have a circuit in the picture below. What will the phasor diagram look like in case: $$I_C<I_L$$ and $$I_C>>I_L$$ ?


texts: What circuit element is this? Rectangle with diagonal arrow, called G

texts:
What kind of circuit elements are  \$G_\mathrm{Na}\$ and \$G_\mathrm{K}\$ in this circuit diagram?

I understand that \$G_\mathrm{L}\$ is a conductance, but what about the arrows?


texts: What is this schematic symbol (Capsule with two facing arrows)

texts: I came across this symbol in an IEC standard and don't know exactly what it means. From the circuit is appears to be a generic load, but does it have any other significance?


texts: How to measure the voltage drop between 2 points separated by a long distance?

texts:
In the project I am working on today, I need to measure the voltage drop between a portable probe and a fixed reference. The big challenge is these 2 elements could be distant from each other of up to a few miles.

The best solution we found today was to connect a wire to the fixed reference, in order to bring its potential to the probe, where the measurement is performed. But as this probe is constantly moving, this solution is not practical at all.

Do you have any idea of a way to do the job "wirelessly"?


texts:
I am playing with MCSA and Park's Vectors to value motors' health.

As test bed I read currents out of a lathe Spinner TC600, and see something strange: Park's diagram is a snowflake (instead of an approximated circle) and currents are far from sinusoidal waves.

Out of sheer curiosity, is there an "easy" explanation for these graphs? Has it to do with internal inverters? It is not an occasional reading, but what happens when the lathe is on.


texts: Does a load reactor eliminate the need for EMC cabling?

texts:
The company I work with installs ventilators driven by VFD's. To save on cost of EMC cabling we use load reactors at the VFD outputs. (Other considerations for not using EMC cabling have to do with certification issues, the ventilators are used for extracting smoke caused by burning cars).
The overall mentality is: just install a load reactor at the output of the VFD, and all will be fine. I wonder if this reasoning isn't too simplistic. I can for instance imagine the reactance of the load reactor resonating with capacitances in the system, so it could still pass undesired frequencies.

So, in short, is just replacing EMC cabling by a load reactor justified?


texts:
I'm currently doing a project on micro-power harvesting and I wanted to make some practical application but need to modify a circuit I've found. I'm not really sure about all the calculations, so I'd appreciate some help. Here's the circuit:

What I need is voltage output of 5 volts. What other modifications should I make in order to get the circuit work with this constant output of 5V?


texts: Why do temperature-voltage curves of all thermocouple types pass through the origin?

texts:
Notice that the temperature in the graph is in °C, not even in °K.

0°C is the border between temperatures of water and ice under 1 atm pressure. Why do thermocouples give 0V voltage at a temperature of 0°C? Is there any relationship between water and thermocouples, are the thermocouples designed to behave like this, or is this just a coincidence?


texts:
I am trying to make a AC Mains detection circuit with ESD protection. The AC switch is located 30 meters away from the circuit board.

Of the two circuits, which is better for ESD protection & mains isolation?
In Schematic One, is connecting the other end of TVS diode to AC Neutral correct?

Please suggest if there need to be any modification.

TVS Diode: TPD1E10B066   http://www.ti.com/lit/ds/sllseb1d/sllseb1d.pdf

Schematic: One

Schematic:Two

EDIT: Let me explain the scenario in detail.
There are quite a lot of switches to be monitored. Inductive loads are also there. All the switches have very long wires & I am concerned about the excess energy that reach the optocoupler during switching, spikes in the line or by lightning. What is the best way to protect from such occurrences?


texts:
I'm learning embedded programming (I'm not an Electrical Engineer).
Sorry if this is not the right place or I'm asking this question incorrectly, but I had a very tough time trying to figure out a solution.
I'm using a ATMega32 with a GPS module and a 16x2 LCD. I just want to read a NMEA sentence over UART and send the parsed data to the LCD. I read the sentence in a buffer and then spit it out to the display.But I get inconsistent data sometimes..
The GPS is always on and the AVR powers up in the middle and waits for the start of a sentence and then continues on receiving.

My question is: how can two devices sync if one is always sending (GPS sends data at 1 Hz rate) and the other receives at random times.
How is UART synchronization achieved? I know about start and stop bits, but once the UART gets a bad packet (raising a framing error for example) how can it recover and synchronize?

please explain what happens at hardware level also or if you can,point me to some online resource, I can't find what I'm looking for.

Thanks so much!

Luca


texts: Delta Sigma ADC in ADC Pi (MCP3424), how it converts Analog to Digital

texts:
I am studying for ADC Pi, for my Presentation. it uses MCP3424 Chips that uses Delta Sigma ADC.

I know how Successive Approximation ADC Works (on paper).

But how Delta-Sigma ADC Performs the calculation from Analog to Digital.
For instance,

If the input Analog voltage is 5volts and the reference voltage is 2.048volts. And I programmed the ADC Pi for 17-bits (3.75 Samples per Seconds)

How these input 5volts will be encoded into digitized form for this very ADC (Delta Sigma / ADC Pi) ????

for instance, let's take an example of Successive approximation ADC , here is what it does,

If there is a 3-bit ADC then and the Reference Voltage is 2volts, then,

2^3 = 8-bits

Now 2volts will be divided in 8 levels.

8/2 = 0.25volts (each level will represent 0.25 volts

and,

000 = 0 -> 0.25 volts
001 = 0.25 -> 0.50
010 = 0.50 -> 0.75
011 = 0.75 -> 1.00
100 = 1.00 -> 1.25
101 = 1.25 -> 1.50
110 = 1.50 -> 1.75
111 = 1.75 -> 2.00

How would i perform such calculation for ADC Pi (Delta Sigma) which is programmed for 17-bit ?

All that i could think of is,
The bit size is 17.
Reference voltage is 2.048volts
2^17 = 131072

Does that mean there will be 131072 levels ?

So, 2.048/131072 = 0.000007812volts Does that mean each level will represent, 0.0000156 volts ?

Now if the input voltage is 3.3volts the digital output will be,

0.0000156 * X = 3.3volts
X = 211538D
X = 110011101001010010B

Is that right ?

I have tried Googling a lot but couldn't find any basic example for Delta Sigma ADC which is why i eventually posted it here.

Datasheets:
ADC Pi: http://www.abelectronics.co.uk/docs/stock/raspberrypi/adcpi2/Datasheet-ADCPiV2.pdf

MCP3424: http://ww1.microchip.com/downloads/en/DeviceDoc/22088b.pdf

ADC Pi Schematic: http://www.abelectronics.co.uk/docs/stock/raspberrypi/adcpi2/schematic.pdf


texts:
I am making the Arduino Knock lock and the piezo buzzer is making noise. I was wondering if that is normal. Here is the code.
/**
 * @file     knock_lock.ino
 * @author   Phi Luu
 * @date     September 06, 2016
 *
 * @brief    Arduino Projects Book - Project 12: Knock Lock
 *
 * @section  DESCRIPTION
 *
 * Uses the Piezo buzzer to make a secret locking mechanism in order to keep
 * intruders out.
 */

#include <Servo.h>
Servo ServoMotor;

// Required hardware I/O connections
const byte PIEZO_PIN = A0;     // the pin piezo buzzer connected to
const byte SWITCH_PIN = 2;     // the pin switch connected to
const byte YELLOW_LED_PIN = 3; // the pin yellow LED connected to
const byte GREEN_LED_PIN = 4;  // the pin green LED connnected to
const byte RED_LED_PIN = 5;    // the pin red LED connected to
const byte SERVO_PIN = 9;      // the pin servo motor connected to

// Global constants
const unsigned short BAUD_RATE = 9600;
const byte QUIET_KNOCK_VAL = 30;
const byte LOUD_KNOCK_VAL = 50;
const byte MAX_NUM_KNOCK = 5;

// Global variables
byte switch_val;
byte knock_val;
boolean is_locked = false;
byte num_knocks = 0;

void setup() {
    ServoMotor.attach(SERVO_PIN);
    pinMode(SWITCH_PIN, INPUT);
    pinMode(YELLOW_LED_PIN, OUTPUT);
    pinMode(GREEN_LED_PIN, OUTPUT);
    pinMode(RED_LED_PIN, OUTPUT);
    Serial.begin(BAUD_RATE);
    // unlock the box first
    digitalWrite(GREEN_LED_PIN, HIGH);
    ServoMotor.write(0);
    Serial.println("ACCESS GRANTED");
}

void loop() {
    if (is_locked == false) {
        switch_val = digitalRead(SWITCH_PIN);

        if (switch_val == HIGH) {
            LockTheBox();
        }
    } else {
        knock_val = analogRead(PIEZO_PIN);

        // require MAX_NUM_KNOCK valid knocks
        if ((num_knocks < MAX_NUM_KNOCK) && (knock_val > 0)) {
            if (CheckForKnock(knock_val) == true) {
                num_knocks++;
            }
            Serial.print("Need ");
            Serial.print(MAX_NUM_KNOCK - num_knocks);
            Serial.println(" more knock(s)");
        }

        if (num_knocks >= MAX_NUM_KNOCK) {
            UnLockTheBox();
            // reset num_knocks
            num_knocks = 0;
        }
    }
}

/**
 * Changes the LEDs and turn the servo to unlock the box.
 */
void UnLockTheBox(void) {
    // change the is_locked value
    is_locked = false;
    // indicate on LEDs
    digitalWrite(RED_LED_PIN, LOW);
    digitalWrite(GREEN_LED_PIN, HIGH);
    // rotate the servo to 0 degree
    ServoMotor.write(0);
    // print a message on the Serial Monitor
    Serial.println("ACCESS GRANTED");
    // allow time for the servo to completely move
    delay(20);
}

/**
 * Changes the LEDs and turn the servo to lock the box.
 */
void LockTheBox(void) {
    // change is_locked value
    is_locked = true;
    // indicate on LEDs
    digitalWrite(GREEN_LED_PIN, LOW);
    digitalWrite(RED_LED_PIN, HIGH);
    // rotate the servo to 90 degrees
    ServoMotor.write(90); // rotate the servo 90 degrees to lock
    // print a message on the Serial Monitor
    Serial.println("ACCESS DENIED");
    // allow time for the servo to completely move
    delay(20);
}

/**
 * Checks to see if a knock is valid or not.
 *
 * @param   a_knock_val   the loudness of the knock
 *
 * @return                true if a valid knock, false otherwise
 */
boolean CheckForKnock(byte a_knock_val) {
    if ((a_knock_val > QUIET_KNOCK_VAL) && (a_knock_val < LOUD_KNOCK_VAL)) {
        digitalWrite(YELLOW_LED_PIN, HIGH);
        delay(50);
        digitalWrite(YELLOW_LED_PIN, LOW);
        Serial.print("Valid knock value: ");
        Serial.println(a_knock_val);
        return true;
    } else {
        Serial.print("Invalid knock value: ");
        Serial.println(a_knock_val);
        return false;
    }
}


texts: Shorting two pins using a headphone jack

texts:
I've managed to "build" a shutter release for my Canon SLR by shorting two wires connected to the appropriate pins on the Canon connector. I am looking for ways to extend this into an intervalometer using an Android smartphone.

I've already asked this question about how to do this with using the USB jack on the phone, but I'm now wondering if this can be done using the headphone jack on the phone. Essentially, I would be playing a fixed frequency audio sound on the phone so as to not change the voltage and current going through the wire.

Would it be possible to use something like a relay (solid-state or otherwise) to short the pins on demand (i.e., when audio is playing)? I'm asking about the relay because that is what my Google-fu turned up, but other suggestions are welcome too.

The conditions remain the same as the other question, i.e. no hardware mods to the cell phone or camera and the solution has to be cheap ($4-5) without the headphone cables, connector, wires etc. because I can salvage those.


texts: Capturing and replicating IR signals, how to tell frequencies?

texts: I want to capture and replicate IR signals of various electronics.  There are various guides out there.  However, I realize that there are various carrier frequencies, which I dont see discussed.  How do I know what frequency of my target electronics in order to buy the right IR receiver and transmitter?  Thanks.


texts: Connecting center-tapped transformer to earth ground; or, why am I being electrocuted?

texts:
Silly question here.

I've wired up a full-wave rectifier using this dual-secondary transformer. If you want to check my wiring, I connected red-to-orange to "create" the center tap (I assume this is OK?), and use black and yellow to provide +/- 24VAC.  The center-tap is my circuit ground, obviously. See the rough idea below.

This circuit works nicely. Using some filter caps and linear regulators, I get a nice DC voltage. Everything is as expected. I was running some relatively high current through a load (about 1 amp).

After a few hours of use, I noticed I was getting a "tingly" feeling when I accidentally touched the circuit ground. My multimeter says 77VAC between circuit ground and earth mains! Yikes!

I don't understand how it floated so high above earth ground. I understand that when you have two unconnected grounds, you have no right to expect them to not float with respect to each other.

But, in this case, it seems to me there should be no way for current to flow from myself (at earth ground) to the circuit ground--hence there could be no voltage developed between "us". I thought this was entirely the point of isolation transformers: voltage is developed with respect to each lead of the secondary, but not with respect to earth ground--so one is safe when working with high voltages. My transformer claims 4000VAC dielectric resistance between primary and secondary. So, what is going on here--how could there be such a voltage? And, should I connect earth mains to circuit ground here to fix this--or will I blow a fuse?


texts: What are these loops above the tracks at each AirTrain station for?

texts: They seem to be made of plastic conduit. Maybe some sort of inductive sensor that makes 100% sure there is actually a big metal car present before allowing the doors to open?


texts: Why 3 phase and not 1 phase power transmission?

texts:
Why does power transmission use three lines with three different phases? Why not three lines all in the same phase? Does it have to do with the alternators used for generating the power, or is there less loss when the phases of the three lines are all different?

My question is somewhat the reverse of "Why three-phase power? Why not a higher number of phases?" (cf. "Why is three-phase offset by 120 degrees?").


texts:
How can we measure the voltage at the coil of a Slayer Exciter?

We have built a simple 9V Slayer Exciter for a school project. We are examining the conservation of energy at the transformer. The Slayer Exciter works fine: when held in front of it, a TL-light gives light. We use a BD-139 transistor. But we haven’t succeeded at measuring the voltage of the coils.

Measuring with a multimeter give incorrect voltages, like 0V or less than 1V. So, we thought that maybe a voltage divider would work. We connected it to the top of the larger coil and to the ground of the battery. We connect an oscilloscope to the smallest resistor, at the start and at the end of a resistor. It shows a sinus. However, If we put the resistor out of the voltage divider, the oscilloscope shows the same sinus. Without the resistor!
If we put one cable from the oscilloscope to the voltage divider out, it also gives the same result. If we measure with two unconnected cables at the oscilloscope it gives a weaker signal. We believe that the electromagnetic field is causing a problem to the oscilloscope and the multimeter.

Our questions are:

How can we measure the voltage at the coil of a Slayer Exciter, the primary and the secondary?
Why is there no current going through the top of the bigger coil to the voltage divider?
How can we stop the Slayer Exciter from creating an Electromagnetic field?
The transistor creates an AC current, but how can we know what the frequency is of that current? Is it a specific property of the transistor?
We have tested different transistors, all of them NPN. But the BD-139 was the only transistor working. The others got too hot. What are the reasons why they don’t work?

We have built the Slayer Exciter through the following scheme:


texts: How to find out reason for Sonoff SI7021 probe unstable connection?

texts:
In my project I have Sonoff TH10 and Sonoff TH16 - allf lashed with Tasmota 9.4.0 and several pcs of SI7021 probes. Problem is that only one SI7021 probe has stable connection, rest are unstable in terms of reporting measured values, that are sometimes (approx 50%) returning NULL instead of real values. When problem is ocuring log is full of messages:
08:23:37.604 DHT: Timeout waiting for start signal low pulse
08:23:39.574 DHT: Timeout waiting for start signal low pulse
08:23:41.608 DHT: Timeout waiting for start signal low pulse
08:23:43.588 DHT: Timeout waiting for start signal low pulse
08:23:45.567 DHT: Timeout waiting for start signal low pulse
08:23:47.591 DHT: Timeout waiting for start signal low pulse
08:23:49.568 DHT: Timeout waiting for start signal low pulse
08:23:51.610 DHT: Timeout waiting for start signal low pulse
08:23:53.561 DHT: Timeout waiting for start signal low pulse

and
STATUS10 = {"StatusSNS":{"Time":1621865135,"SI7021":{"Temperature":null,"Humidity":null,"DewPoint":null},"TempUnit":"C"}}

Strange thing is that problem seams to be depending on particular probe, not on TH module itself. The probe that is reading fine, works in every TH module, probes that have 50% reliability fails after while in any Sonoff TH module. All probes are same HW version 1.0 and i haven't done any modification in them at all. Only exception is, that the working one was purchased 1.5 year earlier. I have tried to flash earlier Tasmota versions 9.0, 8.0, but there was no difference.
Can it be that new probes are have different firmware or different chip versions, so some of the are working just fine and some of them have 50% failure rate? Can it be something obvious that I have missed.


texts: What are viable approaches to a circuit to detect wet/moist cloth (bed-wetting)?

texts:
Trying to design a circuit that can reliably detect a situation where a child wets their bed. The 3 key requirements are --

Reliability of the approach
Ease of use, i.e. a no-fuss approach
Child's safety (from harm) due to electronics

Can the soil moisture detection technique be used ?
How can I make this easy-to-use given s.t. while changing bed line ? This shouldn't require messing with the device, rewiring etc.


texts: Turn off device when USB power is present

texts:
I have a device I'd like to turn off when power is available via a USB socket. The device that needs to be turned on/off is powered by a 12v DC 0.5 amp adapter. USB sockets should have a max 5v 0.5 amp power output.

Would it be safe to wire this up to a simple spst nc 5v relay such as:

http://uk.farnell.com/omron-electronic-components/g6b2114pus5dc/relay-spst-nc-spst-no-5a-5v/dp/2213823

Coil Resistance:    125ohm
Coil Voltage:   5VDC
Contact Configuration:  SPST-NO, SPST-NC
Contact Current:    5A
Contact Voltage VAC:    250V
Contact Voltage VDC:    30V
Product Range:  OMRON - G6B Series
Relay Mounting:     Through Hole
SVHC:   No SVHC (16-Jun-2014)

Would a usb 2 device to able to provide enough power to trigger the relay?


texts:
I am looking for a simple mini rotating dimmer I can buy for a 5v to 8v circuit.
Can I just connect a potentiometer to the LED and make it work?
Is for 16 parallel 1 watts LEDs powered by 4 AA battery in series or powerbank.
thank you in advance for the help.
best regards
Vasco


texts:
This questions is kind of related to this:

Prevent oscilloscope scrolling

However, now I have a decent signal generator (well still budget, but for my needs more than enough, FeelElec FY6900, 60 MHz signal generator).

And two oscilloscope (one I will not mention in this question, but in a next one). The one I want to use for now is a 10 MHz Philips PM3110 , 10 MHz dual channel scope).

I use a sine signal. At 10 MHz, I get a very nice steady (non scrolling) signal at the oscilloscope using the time (x coordinate) of .5 us/square.

However, when I move down the signal generator to 1 MHz, at any possible x coodinate setting, the display scrolls faster or slower. The only way to make it kind of fixed is to change the inner x-coordinate knob, however, that changes the reading (the width of the signal over the squares, so it's not really useful).

I set the trigger to the correct channel, to LF, and high edge triggering, but actually, it doesn't change a thing.

What am I doing wrong?

(note from the oscilloscope, only the right cable is connected, channel B).

Conclusion (see chat for more info)

The PM3110 oscilloscope's trigger switches do not seem to work well, but the most important is that tapping the side of the case causes (in almost all instances) the beam to be steady, so the encoders/contacts are not conducting well.

Besides fixing (see accepted answer: cleaning/changing caps), some tips (also see chat):

Use another oscilloscope (found out my old PM3253 is working better than expected)
Redirect the output of the signal generator as trigger input for the PM3110.
Change HF/LF (because of video signals there is a 17 KHz switch). I noticed sometimes I have to increase the intensity of the beam to make it visible.
Change trigger level (PM3110 does not have one).


texts: I've got a device that the manufacturer claims uses a 3.81mm pitch connector.  I measured the actual distance between pins, and it appears to be 3.5.  I'm now noticing that some connector manufacturers refer to a "3.5/3.81" connector.  I obviously don't want to buy the wrong one.  If a connector is listed as "3.81mm pitch", is that the same as a 3.5/3.81mm connector?  If it matters, I need these connectors for an NI-USB-6001 DAQ


texts:
I intend to design my first PCB and i am using Orcad suite. So, i built the theoretical circuit and before proceeding to the next step i have to put the footprint values for each part. I have decided what parts i am going to use but i don't know how to find a list with the availlable footprints in Orcad Capture. For example i want to use the IC: CD4007CN which is a through hole 14 pin IC. In the IC's data sheet it says:

  14-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-120, 0.150” Narrow
  Package Number M14A

Do you know which footprint is this? Are you aware of any list with all the possible footprints i could search and match?

Thank you in advance!


texts: Just a simple question, usually we can determine the sign of the mutual inductance M by seeing the position of the dots (as the current enters through it). But if you see the upper picture, we don't have any dots. How to determine if it's -M or +M from the arrows?


texts:
Can somebody tell my what is the value of the resistor with αF SMD resistor coding as shown in figure below?

Thanks in advance


texts:
I have designed PCB for my buck converter.

When designing the PCB I've created, I have made one ground plane as shown.

I received the PCBs and there was noise in the TL494 affecting fixed 5V Vref that feeds into the error op-amp. It came to my attention that the noise is coming from the common ground plane connecting the TL494 ground with the ground of the gate circuitry and the MOSFET and the capacitors at the source of the MOSFET.

My question is how can I fix that? Do I just split the ground plane into two and connect them with a wire and place a decoupling capacitor that connects the two ground planes into Vcc? Just like this

Will this solve the ground noise issue?


texts: Using an inductor and AC source to rise the current of an appliance

texts:
An Arc lamp requires a direct current of 10A and 80V to function. If it is connected to a 220V,50 Hz Ac supply, the series inductor needed for it to work is close to:

To solve this question, we first compute the resistance of the inductor by Ohms law, then write the equation with impedance:
$$ 220= (10A) \sqrt{R^2 + (2\pi fL)^2}$$
i.e: find and L such that the current is 10A
About this , I have two main questions:

Firstly, we no longer give it 80V, so how is it only neccesary condition that appliance receives correct current for it to work properly?
In the AC circuit, the voltage and current is always oscillating as some sinusoid, so wouldn't this oscillation damage the device?


texts:
I have two similar questions regarding the PGA of the ADS1115.

Datasheet

Say I have the PGA set to 2, so the max voltage read is 2.048V. If I apply 3V to AIN0, I assume it will give me the max voltage reading. But will it fry my board?

Also, say I have 4V connected to AIN0 and 3.8V connected to AIN1. Say I wish to take a differential measurement, the answer being 0.2V. To get a precise measurement, should I set the PGA to 1 = 4.096V max, or to 16 = 0.256V max? I do not know if setting it to 16 will give me any result because the individual measurements are much higher than 0.256V, or if it will fry my board.

Thank you very much!


texts:
Given some abstract architecture of CPU:

Note that this CPU has 2-BUS. Why do we need the R_out and R_in? If I use Gra/Grb/Grc then obviousely I will need R_out. The Same for R_in when I use Sra/Srb/Src?

Sorry if the question is not qualified enough. Thanks in advenced.


texts: Curious how does ALU addressing work like in Assembly code?

texts: When writing assembly code, say R1 = R2 + R3, it is pretty easy to understand the addressing procedure because all registers are close to the ALU. But I find it hard to see how does the ALU go to the memory in R2 in instructions like R1 = R1 + M[R2]. It could be very far away, and I don't see it going checking and matching the addresses. How does it even translate the hexadecimal number in R2 into a memory location?


texts: What kind of hall effect sensor IC should I use to convert a frequency measurement in a continuous voltage?

texts: I need to measure the angular speed of a DC motor. My idea is to fix a magnet on the spinning wheel and a hall effect sensor near to the wheel. What I need as output is a continuous voltage proportional to the frequency measured. If there is a practical way to achieve this using an IC could you please explain it to me? Or should I make the encoder myself? this second option feels a bit like re-inventing the wheel to be honest.


texts: Why the delay between transformer failure and power outage?

texts:
A friend witnessed the explosion of the 14th street substation. I believe these transformers, about 1 city block in extent, delivered power to most of lower Manhattan. I am guessing the flood water obstructed cooling, and they overheated and exploded spectacularly.

(there is a 4 stack natural gas generating station next door to where the explosion happened, so -maybe- the explosion was not the transformer, but most reports say transformer)

My friend reported: 'The power flickered, then came back on'.
Some unknown time later the power went out.

So the question is, could power in the grid fed by these transformers stay on for a while after the explosion, and for how long?


texts: What stabilizes the alternators/generators?

texts: I've completed my intern in hydroelectric power plants. I've seen large generators working to maintain voltage in 50Hz. They were turning at 187,5 rpm with 32 poles. But I wondered what stabilizes them? What if water flow makes turbine turn a little bit faster or slower frequency should change, right? When I asked this to them they said, the pipes which turns the turbine are designed to get just enough flow to make turbine turn at 187,5 rpm. But I wonder what if we maintain greater flow or pressure to the turbines, would it produce 55-60-70+ Hz? Are there any electromagnetic force that is holding-back from speeding up?


texts: 12V battery is now 10.5V but still producing a lot of power

texts:
I'd appreciate if someone can advise and give me an idea about the condition of my battery and my overall set-up.

I set-up off grid solar system about 2 years ago, for my parents in my hometown

Below are the following specs

Battery 12V- 180Ah (Sacred Sun Brand)
Solar Panel - 200W ( but was only producing 60W max ever since)
Pure Sine Wave Inverter - 800W (Seldom use)
PWM Charge Controller - 30Amps

I haven't checked this set-up for about 2 years. and just checked it now.

Right now, everything seems to be working perfectly fine since I left except the battery.

My battery seems to be staying at 10.5V when on standby mode. Weird thing is, when I hook my inverter, it is still producing power at around 50W-65W or maybe up to 80W (laptop connected) for around 4-6 hours, and the inverter won't beep for low input voltage. The inverter would previously sets of the alarm when the battery voltage reaches down to 11.5, but now, the inverter will only sets off the alarm if the battery voltage is below 10V (somewhere around 9.9V or 9.8V).

I find it really weird for both my battery and inverter to work like this.

I am also pretty sure the the voltage readings are correct, I use 3 different voltage tester to test the battery voltage.

This is what I notice on my battery.

If there's about 60W from solar panel, battery charge voltage starts at around 10.8V and would climb up to 11.5V or 11.6V
I never notice the battery charges from 11.9V - 12.9V
After few hours with only 30W-60W average charge, the battery voltage reaches around 13.5V up to 15V, and my PWM controller would indicate that the battery is fully charge.
After sun sets. battery voltage would drop back to around 10.5V
During load ( 40W ) battery voltage would drop to around 0.1V or 0.2V Voltage, until it reaches, 9.9V and inverter will sets of the alarm.

Can anybody advise the state of my battery, I'm also curious why my Inverter isn't beeping even when the input voltage is low.

Appreciate any help.

Thanks


texts:
I need to calculate input impedance of an antenna. What I've got is frequency, SWR magnitude, phase, return loss and impedance of transmission line. As far as I know, as a result I should get complex number. I used SiteMaster S331 and my example parameter measurements are:

f[Mhz]    SWR   rho   phase
  450    2,802  0,47  10,4
  841    2,017  0,34  -76,2
  510,1  2,231  0,38  -55,6
  531,4  1,77   0,28  59,8

I'm aware of correlation between input impedance and SWR $$SWR = \frac{Z_{0}}{Z}$$ and $$\rho = \frac{Z - Z_{0}}{Z + Z_{0}}$$but still can't figure this out, how to get the result as complex number. I know I should use phase, but don't know which formula to use.


texts: Vary the integration factor of a opamp integrator

texts:
I am working on a analog PID circuit and I need to make a opamp integrator circuit where I can change the integration factor. Now why do I've to make this circuit (I saw the circuit for example here):

simulate this circuit – Schematic created using CircuitLab

But a 'normal' opamp integrator is a circuit without the variable resistor. Why can I not just vary \$\text{R}_1\$?


texts: Home automation Controller/server needed

texts:
I'm looking for a device that allows me to supervise an existing BTicino home alarm system.  The system can communicate via RS-232 (or USB) interface using an open protocol, Openwebnet.

I need to be able to:

intercept events from the RS-232 communication (known messages coming from the serial port), and then
provide feedback through a GSM network (SMS messages).

The basic requirements I have are:

very low power consumption (<= 5 W),
RS232 or USB interface (communication with the alarm system gateway),
another RS232 or USB interface (communication with a GSM module),
12 V supply (or UPS battery backup), and
programmability (to host the logic for interecept and react to events).

Up until now I have evaluated these solutions:

FIT PC-2

A full computer with very green power supply (5W).
In addition it could host a web server for further connection capability.
Too expensive.

Sheeva Plug / GuruPlug
Telit GM 862
???

Which hardware platform do I need?


texts: Two-core transformer with three windings?

texts:
I am trying to understand how a transformer composed as pictured would function. Basically, two separate cores. Both cores go through the secondary winding. But only one of the cores goes through the primary, and the last winding (lets call it the "control" winding..you know where I am going with this..) goes around the last core.

So yes, ultimately I am wondering if you could manipulate the amount of net flux the secondary winding experiences by driving the control winding with the right phase and magnitude to achieve your goals. Goals being a reduced voltage at the secondary compared to what it would be with the control winding open.

The key benefit here is that the net flux that the secondary experiences is reduced, without reducing the flux the primary generates, and therefore, without reducing the inductance of the primary, which would allow more primary current to flow, and is what would happen if you tried this with a single-core transformer.

I have seen this sort of thing called a "three port magnetic component" with a brief discussion here: https://www.researchgate.net/post/Can_anyone_advise_me_on_how_to_build_a_multicore_transformer

LTSPICE will reject modelling of this component if the coupling constants between the inductors is not physically realizable Unfortunately I do not know what that means beyond a very general idea that some coupling will always occur. I would like to know where I can learn exactly how to calculate the "inductance matrix" and solve this myself, and why it is so at an intuitive level.

So I'm looking for an intuitive and algebraic way to understand why the reality deviates from the ideal here.

It seems to me "magnetic amplifiers/saturable reactors" are not this thing.


texts:
I'm pretty new to stack exchange and I've only just gotten my basic circuit analysis classes done in college. For my school's solar racing team, I've been tasked with designing a constant current load circuit to discharge modules of the battery pack at 20 amps. I've done my research, but am still pretty lost as to what parts to use to design this circuit, and then convert it to a PCB. There are 35 modules, 12 batteries per module, and have voltage of 3.6 volts. The capacity is 36 Ah. Can anyone help me out with designing a constant current load that will discharge the modules at 15-20 amps?

Thanks a bunch,
Alvin


texts: Unity Op amp Question Gain and Resistances

texts:
The Question asks what is the gain in dB and also what are the input and output resistances

I know the gain is 1 so dB that would be equal to 0 dB

But I am confused on how to find the input and output resistances.

I think you have to assume it is an ideal op, so would that mean the input resistance is infinite and output resistance is zero?


texts:
I'm trying to add the MIPS assembly command BGTZ to the following circuit:

I know that BGTZ takes the register value and sees if it's greater than 0. If it's greater it branches to the target. Can I compare the register value to a constant zero with an or gate?

EDIT: corrected BGTZ


texts: How to design a circuit that creates high electric field between two conducting plates?

texts: I need to create an electric field of about ~1500V to move electrically charged particles in a container. I'm trying to convert a 9V DC battery to an AC signal using a crystal oscillator and then amplify the signal using a transformer to about  ~1500V. Here's the circuit I've designed but it looks to simple to work. Should the components be in series or parallel?


texts:
I am looking into constructing a closed and small device with arduino sensors that goes underwater. It has to be submerged into water and back several times, and that is made by someone with a rope attached to it. So it needs a way to communicate to the surface that it reached the bottom, so that the person can start pulling. It is planned for it to go no more than 30 meters under the surface.

So I though that a wireless way to comunicate from underwater to the surface just for that would be nice, and not a big trouble (Like when the pressure stops changing a LED light on in the surface). But I know nothing about eletronics, so I need help. Is there a simple way to do it? What can I use? I would like to keep it small...

And I woudn't like it to have a wire...


texts: Does anyone know the name of this connector?

texts: I have a device that is power by this cable. Now the cable became faulty and I want to replace it. Does anyone know its name? It looks like a 2-pin LED connector, but it is sightly different.


texts:
I want to build the cricuit like on the image below:

V1 - Is a 14S LiPo battery(there would be fuse in real life between
positive battery terminal and "BATTERY+"
M1 - PMOS acting as a load switch
LOAD - Place where the load should be(DC Motor controller)
CTRL - pin turning the LOAD on/off

Q. What would happen if by mistake higher voltage than the battery would be connected where the LOAD is? I assume M1 Body diode would conduct causing overheating and potentialy burn the M1.


texts:
I'm trying to communicate with an I²C device using an STM32F411 Nucleo board.

In standard mode (100 kHz) and fast mode (400 kHz) everything works fine. However, when I try to increase the speed above 400 kHz the connection stops.

I consulted the reference manual of the microcontroller (RM0383) which states as follows:

  It supports the standard mode (Sm, up to 100 kHz) and Fm mode (Fm, up to 400 kHz). The I²C bus frequency can be increased up to 1 MHz. For more details about the complete solution, please contact your local ST sales representative.

I was quite surprised to read this since I have worked with microcontrollers produced by other companies, but in the same range of performance which could go up to 3.4 MHz (e.g. Kinetis K20 chips).

Long story short: Has anyone tried to increase the I²C frequency of a STM32 chip to above 400 kHz? And can explain to me what I have to do in order to get it to work?

I would be glad if I didn't have to contact a sales representative.


texts: switch mode power supply frequency change

texts:
I am relatively new in the field of Switch Mode Power Supplies but I was looking at the Flyback converter with an input voltage of between 30V to 88V DC and an output that would charge a 24V lead acid battery bank. The main reason for deciding on this topology was the power requirements of 720W.

The best transformer that I could find off the shelf is a 250 Watt Wurth Elektronik with part number 760895741 that is designed for 220Vac mains use where the input voltage to the transformer is between 320Vdc and 350Vdc. It has a turns ratio of 27:3:3:2.

My question is this: if I change the input frequency, will this effect the output voltage as higher frequencies in SMPS results in smaller inductors?


texts: bias a signal with DC input coupling, but without attenuation?

texts:
I want to bias the analog signal present on an MCU output pin.  This signal varies between 0v and ≃3V, I need to shift it down to -/+1.5V range.  Most importantly, I need to keep any DC offset potentially present in the MCU output signal, and shift it down with the AC component.

I've been googling DC biasing circuits for a few days and found several circuits to do that; they generally fall into one of two groups:

they have a coupling capacitor which remove DC offset on their input e.g.:

https://electronics.stackexchange.com/a/14416/254310
they attenuate the signal significantly, e.g. in the simplest form:

https://forum.allaboutcircuits.com/threads/add-and-remove-dc-bias-from-a-signal.72479/#post-506668

In the first case, naively removing the cap just shorts the input to the output i.e. no biasing is applied.  I ran SPICE simulations which (I think) confirmed what I'm saying, although I never used SPICE before so I may well have got some or all of it wrong.

Are there circuits that can bias a signal negatively without attenuation, but with DC input coupling?

Note that I'm a Software Engineer by trade and my electronics knowledge is very basic.  Please forgive me for any improper or inaccurate terminology (I'm happy to be kindly corrected), and please provide answers in terms that a novice like myself can understand.


texts: Keeping digital logbooks for individual projects

texts:
I'm trying to improve my workflow, and one of the things I'd like to move away from is hardcopy logbooks.  I find that, when I make a logbook, I never really use it, aside from as a coaster for my mug.  I think the problem is that everything I do, I do on a computer.  It's irritating to work on a computer, then stop and write something down that could as easily be copied from a file.  What I'd like to do is start keeping digital logbooks.

I've used Evernote for this in the past, but I didn't really like keeping everything on a server like that.  What I'd like to do is be able to have a project folder containing a nice hierarchy of directories containing things like design documents, schematics, source code, and the like, as well as one directory containing a project logbook.  In this way, the logbook is integrated with the project the same way a git repository, for example, is integrated with the project.  Does anyone have any recommendations for how I could do this?

Edit:  I should clarify a bit.  The project directory would exist, with or without the logbook.  What I would like to use is something like a wiki or content-rich notebook that can be stored in it's entirety within the project directory.


texts: Which MSC Sub Class is the best for USB 3.0?

texts:
I have been looking at implementing the Media Storage Class on a FX3 from Cypress. There is already a pre-written firmware example using MSC BOT (Bulk Only Transport) and SCSI commands and I was wondering is BOT the best implementation to use in conjunction with e.MMC for my design? I have been looking at UFS as well however I am not able to purchase single chips easily for this prototype and I am lacking the documentation for implementing it.

I have also considered writing a UASP driver from scratch however that doesn't look like a worth-while investment considering the fact only a small selection of motherboards support, or an external piece of hardware would have to be used. So for the only type of hardware I've seen to be capable of this is SATA to UASP, nothing capable of dealing with pure SLC/TLC NAND.


texts: Using Piezo Vibration Sensor with Pull-Down Resistor - Arduino

texts:
I'm using a MEAS piezo sensor (this one: https://www.sparkfun.com/products/9196) to detect very slight vibrations, but I'm having trouble selecting a pull down resistor that allows it to be sensitive, but not so sensitive that it just keeps climbing. I'm currently using a one mega ohm resistor to pull down. It works, and keeps the reading from climbing (also allows it to drop to zero), but moving it a lot only gives me a reading of about 100-200 max (out of 1023).

I have it in the A2 pin, just so you know that I have it in an analog pin.


texts:
I am working on building a keyboard at the moment and I have run into an issue.

I need to power 79 led backlights on the keyboard but I have no idea how to do this given that the power is coming via usb.  I know usb 3 can handle up to 900ma but I want to make this work on all usb.  So I am limited in the assumption that I have 500ma to work with and 5v.

That's 500ma to power two teensy 2.0 ++ and the 79 backlights plus 3 indicator leds.

I cannot find any through-hole leds that are less than roughly 3v and 20ma.  So connecting all the leds in series is pretty much out of the question and since they are 3v I cannot put them in parallel either.

How are commercially made keyboards powering their leds, and they usually have 100+?? How can I power all of these?


texts: Sensing BLDC motor torque using a current sensor

texts:
As it is commonly known, the torque supplied by a motor is directly proportional to the current it draws. So when a motor is under heavy load, the torque required will be more hence it would draw more current

For a BLDC motor, the current is supplied via three phases which are switch by a motor driver. But this motor driver is supplied with a single DC supply.

Can I reliably measure the torque provided by my motor by measuring the current drawn by the driver?

My motor is currently mounted as part of a robotic arm and there is PID control loop for position control.

I only need to get an idea of the current load and detect load anomalies (like an impact i.e. higher load or loss of payload i.e. lower load etc).

Given that I can calculate the nominal load at any position and hence calculate the nominal current drawn, is it a good idea to use current sensing for this kind of load sensing?

Is there any research on this which analyses this method of torque control/load sensing which I can refer to?


texts: Does anyone know the hardware of a Nike+ SportWatch GPS?

texts:
I have one of these devices and I would really love to figure out if it is possible to write and push my own firmware into the device. The software on the watch is pretty limited and I would like to extend it out to give me more capabilities, like being able to choose an activity type of something other than running.

One option that I have thought of is to record the USB activity when the device is being updated but I suspect that it will be downloading an encrypted hex file or something to try and protect the companies IP.  Well that is what I would do if I were them...maybe that is a bad assumption.

Before I go about trying to pry the thing open, I wandered if anyone else had done something similar to find out what processor type it runs on, etc.

Any information would be useful in heading me down the right path before I take a screwdriver to it.

Note: I am not looking for software development knowledge here, I am a programmer and have experience in firmware.  I am just trying to find out the platform so i can work out if there is a toolset available to compile or if the device runs some custom FPGA config or a proprietary processor which would mean the idea is dead in the water to start.


texts: How to disable USB mass-storage in STLink on Nucleo?

texts:
Is it possible to disable the USB Mass Storage option on the STLink hardware of the Nucleo board? I want to prevent mounting the device when I plug it into computers (while keeping the virtual com port).

I am using nucleo-32 and nucleo-64 boards by programming them with OpenOCD and then using STLink's virtual com port to handle USB comms with my target device. In this setup, having the STLink part of my board auto-mount itself every time I plug it is is distracting. In particular, I don't want the user to see the mounted disk to get a warning if it is unplugged without being unmounted.

I am working mostly in linux and there I should be able to make a udev rule to block mounting the USB Mass Storage device, which is my backup plan. However, I would like to disable this on the hardware itself, so that on Windows and Mac no mounting occurs. I guess it might be possible to reverse engineer the STLink firmware and re-flash with the USB Mass Storage device disabled. But I wonder if there is an easier way.

(I am most interested in the Nucleo-64 NUCLEO-F303RE board, but I think the answer will likely be relevant for all Nucleo boards.)


texts:
Where "Rdg"is for reading and "dgt"is for digits.
So, 15,23 * 0,015 = 0,22845.
Rounding to most significant digit it's 0,2.
So is this correct?
 $$15,23 \pm 0,2$$

Since 4dgt is smaller we ignore it. Or am i doing this wrong? I need to find uncertainty in the way I did for a physics lab.


texts:
I'm fiddling with a toy and I found this part. I think its purpose is give feedback to a microcontroller about the angle of the DC motors.
This is the part:

This is how it's placed with the motors:

This is where it goes on the main PCB:

I hope you know this part. I don't know how to search for it so that's why I'm here.


texts: Can I still use this power supply if I clean off the rust from the transformer?

texts:
I have  power supply for a vintage Timex Sinclair. The unit was sealed but the cable felt loose so I pried it open to inspect the connections. There was a knot on the other side so it was just the cable slipping between that and the outside and not on any solder joints themselves. But I also found the transformer to have a lot of rust on it.

Can this be cleaned off with vinegar and a wire brush or will I need to replace the whole thing?


texts: I am working on a silabs C8051 MCU. It has a sleep mode which should be woken up by  a reset. The mcu should start working (wake up from sleep) when the button in connected to Ground (Otherwise it is on the air). What is the easiest way to give a reset signal to the reset pin (or any other way) to restart the MCU?


texts: Inverting Bistable Multivibrator using OpAmp

texts:
I am trying to work on a design project and part of the overall circuit includes an Inverting Bistable Multivibrator using an OpAmp.

I have designed the circuit which is supposed to have a Upper/Lower Trigger point at +/-2 volts. As the circuit contains positive feedback, it is bound to saturate the output at L+/- of OpAmp. However my output seems to follow input with some gain instead of saturating.

Could someone explain what is wrong in the circuit and how can the desired functionality  be achieved. I do not want to use non inverting bistable multivibrator ( and I have verified the saturation using non inverting) so as to keep the overall circuit polarity negative. Any help would be much appreciated if I can get a square wave (Green Trace) instead of triangular wave.

Following is the design schematic and the scope capture.


texts: What is the easiest way for me to measure the amount of "juice" that's left in an alkaline battery?

texts:
This question applies equally to both non-rechargeable batteries and rechargeable batteries.

I want to know if I managed to fully recharge my rechargeable batteries (mine are primitive), and how much battery life is remaining in my non-rechargeable ones.


texts: How to get a steady(ish) 12v output from a varying input voltage

texts: At present, my little atom PC is being powered by an 240V AC to 12V DC PSU which connects to a 12V DC-DC pico PSU. Our home is off grid, so all of our power comes from 12V lead acid batteries. I've tried connecting the 12V batteries directly to the pico PSU to improve efficiency and it works as long as the voltage from the batteries is no greater than 13.5V or so. Unfortunately, while they are being charged, the voltage from the batteries can initially be anything up to 14.5V. Is there a simple way to 'cap' the voltage from the batteries at 12V?


texts: Convert 15 minute kW readings to a monthly kWh total

texts:
I have metering data (kW) in 15 minute intervals that I am trying to get a monthly kWh total for...
I simply summed the entire kW range, then multiplied it by hours in the month 745 (total number of readings 2,981/4). This seemed too simple though and now I'm just confused after looking at it for so long.  Is this correct? Or is there more to it?


texts:
Assume there is an infinite line charge. Therefore, it has an electric field around it. If we calculate the divergence of the electric field \$\mathbf{E}\$ caused by the line charge, what is the sign of \$\operatorname{div}\mathbf{E}\$? Is it positive, negative, or zero?
Since the outflowing electric flux is inversely related to the displacement of the charge, we assume\$\operatorname{div}\mathbf{E}\$ to be negative.
Is this reasoning correct?


texts:
When selecting an X2 safety capacitor what must be taken into consideration. There are only a few types of capacitance ranges and seem to be chosen based on voltage rather than capacitance.

Take mains AC, the cut off frequency is difficult to determine because we don't know the impedance so which capacitance do we pick? Can we assume a low resistance. Also, if the source is an alternator it will change the resistance to.

Is it common to put multiple of them in parallel to get the required range??

Also, will current draw in the circuit affect the value of capacitor? If we have more current flow do we need a bigger cap?

Thanks.

Edit 1:

The Kemet R463R422050M2K is a possible device that could be used.

mouser.ie/datasheet/2/212/KEM_F3095_R46_X2_310_110C-1104274.pdf


texts: "Position measurement diode" identification

texts:
We have a component laying around our lab that we have been using to take some measurements.  Supposedly it reads the position (x/y coordinates) of a laser beam (standard 5 mW red laser pointer) on the central black area.  It has worked well enough for us so far, but we would like to use it to test some flight hardware, so we need a datasheet that will give us figures for linearity and bandwith.  Here is what we know about it:

TP7 is a -15 V supply, TP5 is a +15 V supply, and TP6 is ground.
Outputs are TP1-TP4.  Two of them output positive and negative intensity, the other two output x and y position.  We seem to get better linearity by dividing the x/y channels by the intensity channel.
The two chips are quad opamps.

The board is about 1 1/8" by 1 5/8".

Here is what we would like to know about it:

Bandwith (not so important, just needs to be above ~1 kHz)
Linearity (very important, we need 1% or better)
What do TP8 and TP9 do?  Why did whoever set this up leave these unconnected?


texts:
I'm currently investigating fault recovery in a UAV using MATLAB.
I've been given several variables:

phi = the roll angle
psi = the yaw/heading angle
beta = the side slip
p = roll rate
r = yaw/heading rate
delta_r = angle of the rudder
delta_a = angle of the aileron (the aileron is currently inactive).

My input is the rudder angle.
I've simulated a step fault in the yaw/heading sensor and I'm trying to recover from it.
To detect that there was a fault in the heading sensors: I compared the actual side-slip with the modeled side slip. If there is a difference between the "real' system and the model in heading angle, but no difference in side-slip, then the heading sensor is faulty.
To recover from this fault: I want to reconfigure the side-slip so I can use it to determine the heading/yaw angle. In order to do this I need to multiply the side-slip by the transfer function between side-slip and heading/yaw angle.
We've been given the following equations:

I'm having some trouble coming up with a transfer function between side slip and heading angle.
I figured the best thing to do, as I am using a simulation filled with arrays, is to turn all the derivatives into their discrete equivalent - of course this is means I'm not using a transfer function, but an equation. Taking the equation for the derivative of beta and discretizing it...

When I plug this in, the system doesn't recover.
I even tried doing Laplace transforms, but I get stuck here:

And I'm not sure how I could apply that in MATLAB
Is there a mistake in my logic or approach? How would I turn the discrete system into a transfer function?


texts: MCP2515, CAN bus, and transmission failure

texts:
I'm trying to interface with a GPS device that is intended to connect with a vehicle via the CAN bus. I'm using an MCP2515, driven via SPI by a Parallax Propeller project board. I've successfully been able to capture messages from the CAN bus when connected to a vehicle, but when I try sending messages from the MCP2515 to another device the MCP2515 sets the TXERR bit (it remains set indefinitely) and does not appear to send the message.

The basic wiring I have set up is I'm using a SparkFun CAN bus shield  which has the MCP2515 and the MCP2551 transceiver. CAN-H and CAN-L are connected directly from the transceiver to the appropriate pins on the OBD-II port (CAN-H pin 6 and CAN-L pin 14). Everything has power and a common ground (the CAN bus board, the Parallax Propeller board and pins 4 and 5 of the OBD-II port and the power source all have the grounds connected). I've tried putting a 110 ohm resistor (the closest I had to the recommended 120) between CAN-H and CAN-L, but that doesn't change the behavior.

The exact phenomenon is I'm attempting to transmit and then checking the TXBnCTRL register afterwards, continually, and the transmit bit is still set, but TXERR (bit 4) is now also set, but nothing else (the value of the register is exactly 0x18 - bit 4: TXERR and bit 3: "transmit request").

The data sheet just says  "If the message started to transmit but
encountered an error condition, the TXERR (TXBnCTRL<4>) and MERRF bits (CANINTF<7>) will be set". I'm only seeing the TXERR bit set.

I am just checking if anyone has run into this scenario and knows what I might be missing here.

The topic of terminating the lines with resistors is discussed, among other places, here and here. From my understanding, the diagrams here are showing a big pair of wires, with two or more devices attached to separate points somewhere in the middle, with 120 ohm resistors at each end. But that's not really the scenario that I have. I basically have a device at each end, and I've tried placing the resistors basically wherever it was feasible. I'm running at 500 kHz. That TI documentation says the maximum length is 100 meters, so it's not the cable length. I've included a picture below - the red thing near the middle is the CAN bus shield, which has wires that end up going through that breadboard (which I've tried with and without resistors, no difference) then to the blue Cat 5 cable, then the black ODB splitter thing which I've hacked apart and the blocky thing at the end is the other device (which does get power and lights up, etc.).

I've checked and rechecked all the pins and connections with a multimeter, and as I said if I plug this into my car I do get messages. It seems like it should work. Am I on drugs?


texts: What fuse to set to enable 16MHz clock on the atmega32u4

texts:
It's my first time attempting to program an Atmega32u4, or any microcontroller for that matter, on a custom board I got printed.

avrdude has a weird output when I, for example, run this command: sudo avrdude -c flip1 -p m32u4. This is the output:

avrdude: Warning: USB bDeviceClass = 255 (expected 254)
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e9587 (probably m32u4)
avrdude: Error: "lfuse" memory not accessible using FLIP
avrdude: Error: "lfuse" memory not accessible using FLIP

avrdude: Error: "lfuse" memory not accessible using FLIP
avrdude: Error: "lfuse" memory not accessible using FLIP
avrdude: Error: "lfuse" memory not accessible using FLIP
avrdude: Error: "lfuse" memory not accessible using FLIP
avrdude: safemode: Sorry, reading back fuses was unreliable. I have given up and exited programming mode

avrdude done.  Thank you.

I'm not entirely sure why it can't read the fuse memory, but my plan is to set the fuses correctly. When I went to this website to calculate which fuses I need, I realised there's no option for a 16MHz external crystal frequency. This is an issue, I assume, because my external crystal oscillates at 16MHz.

Could this be the issue when trying to read the microcontroller's memory?

(Sorry if I got any terminology wrong, this is all very new to me)


texts: Salvaged transformer creating a short when connected to 230v in EU

texts:
Probably this is a noob question but i can't find an answer on the web.

I salvaged a transformer from an old radio. I wanted to test it, so i began to wire live to the primary coil and neutral to the other end of the primary. I didn't do anything with the ground wire, should i? I connected my voltmeter to the secondary coil. I plugged it in and... the fuse switched off. The fuse in the meter cupboard, i didn't have any connected to my transformer.

Thanks,


texts: How to Connect USB/Ethernet Shields to Chassis or Digital Grounds

texts:
I have a PCB with a few USB and RJ-45 Ethernet connectors on one side. I'm quite confused as to how exactly I'm supposed to be hooking up the SHIELD pins on them though.

This is for a host device that will interface with peripherals. It is provided regulated 5V 10A power by an external PSU, and is intended to be used inside a vehicle.

I have found this question (Should chassis ground be attached to digital ground?) along with others which helped me somewhat, but I'm still confused. The accepted answer on that says to use mounting holes, but I'm not sure if I understand fully. I'm not sure if the mounting holes connect chassis/digital grounds together directly or if they only connect to the metal enclosure. I assumed the later.

Even more confusing: What if I wanted to use a plastic enclosure? I'd prefer plastic, but I assume metal would protect it better against EMI inside the vehicle.

Here is a (very simplified) example of my current layout.

And the schematic (just in case, not really useful)

The shield pins connect to the CHASSIS plane which is isolated from digital GND. The physical housing for the connectors should also be touching the metal enclosure as well.
The CHASSIS plane is connected to the metal enclosure via the mounting holes/screws.
The power supply GND is connected to the metal enclosure via the lower left mounting hole. This in turn connects GND to CHASSIS via the metal enclosure itself.

Am I overthinking this? Should I just connect the shield pins to GND and call it a day?


texts: How do I get 12V 260mAh from 4x 6V 130mAh solar cell panels?

texts:
I'm trying to figure out how to build a DIY micro irrigation system for my small greenhouse. A part of that task is to figure out how I can charge 8 AA batteries using solar panels.

I've found a set of 4 solar panels with the specification 6V 130mAh. However, if I've understood right I need to have the panels to deliver 12V and 260 mAh if I've got 8 x 1.5V 2600mAh AA batteries. I've read that 10% of 2600mAh is a safe charge rate.

How can I turn these 4 6V 130mAh solar panels into a single array which is capable of delivering 12V 260mAh?


texts: How do I reduce voltage from 5V to 1V using a resistor?

texts:
I'm a beginner at electronics and my knowledge is trying to learn!

I'm trying to make the following humidity sensor work with an Arduino.
http://www.bitsbox.co.uk/data/sensors/humid_sens.pdf

The actual programming of the Arduino I can handle, but I need some advice in order to reduce the 5V supply from the Arduino to 1V which is the rated voltage of the sensor. I know that if I send it 5V I will likely burn the sensor out.

I guess what I'm asking is: What value resistor do I use on my breadboard?


texts: How would you detect vampire/standby power?

texts:
Is it possible to detect when a device is consuming power in a stand-by or nominally off state? For example if I leave my charger plugged in, detect that a small amount of current is being drawn and stop the flow. What about turning it back on? For example, plugging in my phone it could detect the demand and turn the flow back on.

How could you create a device which could turn an outlet on or off depending on the load?


texts: How to calibrate ACS770 upon device startup

texts:
I am using the Allegro ACS770 100A Unidirectional current sensor (datasheet). To measure the output from this sensor I am using the TI ADS1115 (datasheet).

The ACS770 is supposed to output a 0.5V quiescent voltage, and the voltage increases by 40mV every 1A.

The output is ratiometric. The change in quiescent voltage and sensitivity is calculated using the equations below:

ratiometric change in quiescent voltage output (%):

\$\Delta V_{IoutQ(\Delta V)} = \frac{V_{IoutQ(VCC)} \div V_{IoutQ(5V)}}{V_{cc} \div 5V } \times 100\$

ratiometric change in sensitvity (%)

\$\Delta \text{Sens} = \frac{\text{Sens}_{V_{cc}} \div \text{Sens}_{5V}}{V_{cc} \div 5V } \times 100\$

The ACS770 and ADS1115 are being powered by the 5V rail from an Arduino. This is not likely to be constant as power is drawn from the USB connection.

My problem is, how can I get the data required for the above calculations, namely \$V_{cc}\$ and \$\text{Sens}_{V_{cc}}\$ when powering on the Arduino? Is this even possible?

I have considered getting a precision voltage source for the ACS770, but this project is a quick prototype to provide data for another project, so I would like to spend as little money as possible on this.

Please provide ideas on other ways to calibrate at runtime, or some way to get the required values at runtime.


texts:
I'm trying to figure out what's the difference between a master-slave flip flop and a jk flip flop with the clock negated.

Do they behave in the same manner?

can I just say that a master slave flipflop is a flip flop which output id giben in the falling edge but recorded in the rising edge?


texts: What to do with GND of differential mode signals?

texts:
Let us say I have 2 modules. First module gives a differential signal output on a pair of wires while the second module takes the differential signal input.
When I connect the differential signal wires between the modules do I need to connect the GNDs of the two modules together also?


texts:
I have recently taken on a project that involves improving a circuit and there is a couple of instances where there are two capacitors in parallel with each other.

The values of these capacitors are 100nF and 100pF so one is average sized while the other is small. The instances of these capacitors in parallel are placed on input/output signals, one on an output that is readings a battery voltage and the other on a power input to an op-amp. I am a bit confused as to why they are both needed as opposed to one so if anyone can point me in the right direction with regards to that, that would be great.


texts: Do CPLD devices lose non-volatile memory over long periods of time?

texts:
I have devices that use Xilinx XC9572XL CPLDs. They haven't been used (as in: not powered at all) for almost seven years, and symptoms would point to the CPLDs being at fault.

I couldn't find much on the durability of non-volatile storage in CPLDs. Is it possible that storage has deteriorated enough over 7 years to cause problems?

More generally, how long is a CPLD expected to last once programmed?


texts: Ferrite vs. iron powder toroid for buck converters?

texts:
I'm wondering about the difference between small (13 mm outer diameter) ferrite and the yellow white iron powder toroids. Will the ferrite toroids saturate at 5 A current?

I'm planning on using the cores for buck converters (mostly 3 A at probably below 200 kHz).

These are the ones I am looking at:

Ferrite: https://www.ebay.com/itm/Metal-Core-Power-Inductor-Ferrite-Rings-Toroid-Cord-25x10x15mm/310980203521 (also available in 13 mm outer diameter)

Iron powder: https://www.ebay.com/itm/7mm-Inner-Diameter-Ferrite-Ring-Iron-Toroid-Cores-Yellow-White-50PCS-LW/181834403242

Most of the buck converters seem to use the yellow white iron powder toroids, like this: https://www.ebay.com/itm/5Pcs-Toroid-Core-Inductors-Wire-Wind-Wound-mah-100uH-6A-Coil-DIY/221981982278.

From searching on the Internet, the yellow white toroids seem to have a permeability of 75, and the ferrite has a permeability of 2300 or so. Is this important for saturation?

I have some toroids and an LCR meter, and the ferrite toroid needs only a few turns of wire to get a 1 mH inductor, vs. many more turns for the iron powder core. Will this matter if the peak current through the inductor is limited?

I'm guessing the ferrite toroids are great at low currents (0-100 mA) and low frequencies (<100 kHz, as I can get more inductance with fewer turns). But, are they also good for higher currents (like 5-6 A peak)?

(PS: Also another reason I ask, is that at my place, the ferrite cores are half the price of the iron powder cores.)


texts: Multiple induction coils in series (phone charging)

texts:
I'm doing a DIY project of sorts, and I'm trying to create an array of about sixteen coils in series in a sort of square. The goal of this is to make a larger charging surface than just a small pad, and to charge multiple devices. I have bought a wireless charger to use the guts of as part of the project but I am unsure of a few things: (Bear in mind I have little experience in electrical)

Does there need to be more energy flowing through the circuit as the number of coils increases? (i.e. from 1 to 16)
If multiple devices are being charged at once, does there also need to be more electricity flowing through the circuit?
Will the coils in the array interfere with each other?