texts: Inductance value of PI-filter connectors?

texts:
I find myself in the situation of being forced to use filter connectors to solve an EMC issue very late in the project. Normally, this should of course be solved in circuit design, but as projects and schedules go, this is where we are. Now, to simulate the influence of the filter parasitics onto the main circuit, I'm turning to the manufacturer data sheet to get the capacitance and inductance values for the different filter topologies (C, PI):

Source: Glenair EMI/EMP filter connectors (PDF)

To my amazement, Glenair is not listing the inductance values of the PI-filter. Could it be because the inductive element is so small (coil or ferrite bead for each pin), that the filter response is dominated by the capacitive elements anyway? Then why make a PI filter in the first place?

Any insight here is much appreciated.


texts:
I'm experimenting with a linear-mode fast-charge circuit for NiMH batteries. I was surprised to find that the voltage measured across the battery terminals while fast-charging is higher than the theoretical series cell voltage. By that, I mean rechargeable cells are theoretically 1.2V each (as opposed to non-rechargeable cells that are 1.5V each).  Charging four AA NiMH cells in series I measured a voltage of around 6V across the pack, rather than 4.8V.

What is the explanation for this higher voltage while charging? Can I predict the maximum voltage, V, I will measure while charging N cells in series with a current of J mA?


texts: Does a ground fault compromise the whole circuit?

texts:
(this image taken from http://www.allaboutcircuits.com/vol_1/chpt_3/3.html)

Based on this picture, would a tree across the bottom wire of the circuit (the solid wire, not the dashed wire representing earth) cause the person to be electrocuted? Am I correct in thinking the tree would cause a voltage drop?

EDIT: To clarify, what would happen if a resistor was added to the bottom, solid wire?


texts:
My goal is to extrapolate (or estimate) the future prices of FPGAs and/or ASICs.

Does anyone know of the price history of FPGAs or ASICs?  I am looking for a source of information.

I know that today FPGA's can be categorized into three basic categories (High end, mid range, and low end FPGA).  I'm much more interested in the High end product range, but any information is helpful.

Are there any academic or business journals that study the prices of FPGA or ASICs?

Any input on this topic is welcomed.

Thanks.


texts:
Hi In this circuit below:

What role is the LC Low Pass filter playing?

The switch is switching ON-OFF alternatively, at a frequency which determines the Duty cycle, and we get an average output at the point before L. Now why do we need to hook up an LC Low Pass filter for that signal?

I did understand that L would prevent Sudden current change and C would prevent Voltage change, but what exactly is the role as a filter?
And how does switching frequency effect that?


texts: Paper in oil (PIO) capacitors: what is special?

texts: Many audio circuits use PIO capacitors. What are the electrical Characteristics of PIO caps that make them special (i.e. justify the cost)? Which parts of an amplifier circuit benefit most from the use of PIO caps?


texts: Beginner question about OP AMP as "DC differential amplifier". Does switching inputs between + and - make any difference?

texts:
I'm just starting to learn about OP-AMPS used to control current through a mosfet and I have a few basic questions about the general concept of the schematic below, taken from this thread: op amp+mosfet = current source.Why do we need a feedback resistor?

I'm only asking about the general concept, not about the miller caps and 10k feedback resitors as discussed in that thread.
In the schematic above, is that what's called a "DC differential amplifier"? Are there other names for this type of op amp circuit?
Would it make any difference at all if I switched the inputs around, having the control voltage VC go into the - input on the op amp, and having current sense resistor voltage drop go to the + input? As the op amp regulates it's output to ensure + and - have the same voltage, my assumption is that switching inputs around as I described should make no difference at all. Could that be right?
Could that op amp circuit (with mosfet removed) be used to "convert" a voltage controlled boost IC into a current controlled circuit by replacing the "standard" boost IC feedback divider with the output from the op amp?
Edit: Attempting to clarify this last question. The TPS63020's output is controlled by what voltage is sees on the FB pin.

I'm asking if I can remove that R1 and R2 divider and using an op amp somewhat like in the first schematic instead:


texts: Set ground reference of a 5v DC power supply to the middle of a 24v DC power supply

texts:
I have 2 isolated AC/DC power supplies. one generates a regulated 5 volt power supply and other generates a 24 volt power supply as you can see in the picture below:

I also have designed a circuit (the blue PCB above) that has analog parts that works with 24v and digital part that works with 5v. The analog part are some op-amps that I use for audio amplification so I need the GND reference of my audio (on my circuit) to be in the middle of the 24v. this reference GND is also used to be the GND of my digital circuit. so my main question is what is the best approach to set the GND of both 24v and 5v power supplies to be at exact middle of 24v rail. in other word, i have 2 pair of  isolated 5v and 24v cables and I want to have these signals: GND(0),-12,+12,+5

you can see the main question in the picture below:

simulate this circuit – Schematic created using CircuitLab

now the approches that I currently have in my mind is as follows:

use an op-amp:

simulate this circuit

use a 12 volt regulator (7812)

simulate this circuit

I wanted to know that if my approaches are OK? and if yes, which one is better? If there is a better way of doing this I would really appreciate any suggestions! :)


texts: Is this potentiometer linear or logarithmic?

texts:
I have old potentiometer Alps 902B-250KBX2 in my amplifier.

I need to replace it, but I don't know is linear or logarithmic?

It should be linear, because it has letter B in mark. But one my friend said that though it has letter B in mark, that it is not necessary that old pot is linear? Do you have information on how Alps labeled their pots in past?


texts: How to turn a DIP switch into an array of logical values

texts:
Is there a better way to turn a open/closed switch into a logical value (capable or sinking or sourcing current) other than:

simulate this circuit – Schematic created using CircuitLab

I'm playing with 8 bit DIP switches and I was wondering if there was something better than 8 resistors.

Note: I could swap the positions of the switch and resistor, but I think this arrangement is better as the voltage-required-to-register-a-high is usually further beneath Vcc than the voltage-required-to-register-a-low is above GND, allowing a larger resistor and therefore less leakage.


texts: A confusion about error components in a data acquisition system

texts:
My question is related to my previous question:Accuracy of a data acquisition hardware

In a data acquisition system absolute accuracy is defined as measure of all error sources as following:

Abs. accuracy = error from Gain(Span error) + error from Offset + (error from Noise + Quantization)

Here in the following data sheet at page 30 and 31:

http://www.mccdaq.com/pdfs/manuals/PCI-DAS6034-35-36.pdf

"absoulte accuracy" is  defined.

My question is about interpreting these parameters.

Lets say I take five samples by applying precisely known 5V reference voltages to a channel as:

I apply 5V and daq-board reads 5.004V

I apply 5V and daq-board reads 5.002V

I apply 5V and daq-board reads 5.001V

I apply 5V and daq-board reads 5.003V

I apply 5V and daq-board reads 5.002V

Now the readings above are different than the 5V true value applied.

So the readings above includes gain error + offset error + noise error

Noise error is statistical in nature and wont effect the mean value but the disperse.

As far as I understand, What effects the mean value here is the "gain error" and the "offset error" (systematic errors).

My question is: Are the gain and offset errors in the data-sheet fixed values or are they maximum values and also statistical or indicate a range?

For example, if data sheet says offset error is x, and my mean reading is A; should then I correct my reading as A-x ? or x is not constant?

I'm asking because if lets say offset error is fixed and knwon for all measurements why don't they compensate it before sending the data to sthe erial port instead of documenting?

Or if it is not fixed should I measure offset before each measurement?


texts: How to know what is the safety standard to apply to a PCB design?

texts:
I want to design a PCB with some points at some KV during certain times, less than 10KV and no more than 30mA of current. After dealing with concepts and getting the main idea about my circuit needs, I was thinking about protection PCB boxes too. The box will limit maximum PCB area. And I would like to reduce the spacing and the distances within the board, to choose the correct box case material, etc.. but I prefer doing it ensuring safety standards, due to it having interface wire connectors being accessed by a user. Ideally, they only must access them before powering on, and after powering off.

So, I would like to know how to know what IEC standards I must to apply to the board design, especially for human safety.

UL/IEC 60950
I have seen how some engineers are often referring to IEC 60664 but it deals with low voltage.
IEC 61010 is also one of the standards commonly mentioned.

Questions:

Is it enough following only one of the two standards UL/IEC 60950 or IEC 61010?
I don't know if they are talking about different electronic tips, but I wonder what happens if this was the case which of them has priority? As e.g. (seeing index): IEC60950 and IEC61010 when talks about safety and protection against hazard chapters.
Furthermore, I guess I must put human error prevention in my design in case someone is close to the connectors after powering on. Is it?


texts:
Edited my last question in order to contain the work I've done.

I have to find the output voltage Vo related to the input voltage Vi knowing that the input values range from 0V to 50V. All diodes are ideal.

I started by assuming that D3 is reversed biased. This means that D1 is forward biased and D2 is reversed biased if I am not mistaken.

So, I found VA= 3V (6V/2) using the voltage divider of the 2 5kΩ resistances. I made all this process in order to be able to define the range in which D3 conducts.

So, knowing that VA=3V, when D3 is OFF, I can say that D3 conducts when Ui>3V.

Then I got the range [3V,6V] where D3 and D1 are ON and D2 is OFF and found the output voltage related to the input voltage using the Millman's theorem.

Then I got the range [6V,20V], in which only D3 is ON , so again using a voltage divider on the simplified circuit with the 2,5kΩ and the 5kΩ resistances I found Vo=(2/3)Vi.

Finally I got the range [20V,50V] where both D3 and D2 are ON and D1 is OFF and again using a Millman's theorem found the output voltage.

However I don't know if this is the right way to approach this problem and i am not sure if my process is right. Any help is appreciated! Thanks in advance!


texts:
I am currently working with a current transformer (CT) to measure the load current of a system. I am connecting the CT with a pic16f877a microcontroller using a basic circuit I found on the internet. I have implemented this circuit pictured below and connected the CT but it did not work. The value is not being changed by CT. Please suggest any changes in the diagram below or provide help regarding how to connect CT with the PIC. I have provided pics of the specific CT as well.

I need to measure AC Current. actually am software engineer by profession and don't know much electronics but are learning and implementing things. My purpose is to measure load on three phases of our company which is provided to us from Grid. So I will pass AC wires from CT to measure load on every phase. Can you help me to provide solution as I can read ADC value from pic because I have measures temperature successfully using LM35 but don't know how to connect CT with Pic, neither any manual or data sheet is provided by CT supplier. Can you help me to connect CT with pic16F877a.


texts: Is this a 'proper' way to represent a circuit schematic?

texts:
Is this a reasonable way to do a wiring diagramme. What are the common practices when making this sort of thing?

Basically I am a compleat beginner and would love to know if this is a proper neat way to represent a circuit schematic.


texts: Microchip documentation does not label CAN buss pins on micro controller pinout diagram

texts:
Link to the data sheet

I want to use Microchips DSPIC33FJ128GP802 in a new project and want to use the ECAN buss.

The problem I'm facing is that in the Controller families list at the top of the data sheet it says that device DSPIC33FJ128GP802 has one ECAN port as Remappable Peripheral:

When I go down to the Pinout descriptions table and look for the ECAN pin labels it says that they are C1RX and C1TX:

Until this point everything is perfect, I now know that this chip has a CAN buss somewhere and I know what the pins are called but now when I go to the pinout diagram for the chip:

There are no pins that have the label C1RX or C1TX. So what am I supposed to to? should I guess where the CAN pins are or am I missing something here?

All help is appreciated XD


texts: Assemble Peltier Cooler to Li-poly Rc Battery

texts:
I have procured a thermoelectric cooler (TEC, this one) and my purpose of the TEC is to produce current for the Li-poly RC battery to increase its battery life. The Li-poly RC battery has 7.4V stated on the battery itself.

Am I supposed to get a DC DC converter?
And how to go about assembling the TEC to the battery?


texts: How do I use a USB OTG cable to read a USB thumbdrive on Arduino Uno?

texts: Is is possible to use a USB OTG (On-The-Go) cable hooked to the Arduino Uno's (or similar) USB connector to read a thumb drive or other device?  If it is possible, what software would be needed?


texts: How to model this scenario/circuit with 50Hz interference?

texts:
There is an industrial amplifier for force transducers. It amplifies strain gauge outputs and outputs voltage. Lets call this as a voltage source Vtrans. Its output is around 50 Ohm.

I measure it with a data-acquisition board as follows:

The max interest of signal component is 200Hz and the sampling rate is 500Hz.

The thing is there was 50Hz noise in the sampled data if wired as above.
But when I put a 1uF resistor across the terminals A and B, the 50Hz interference disappeared. But if it was a low pass filter it would also remove anything around 50Hz but no. This cap gets rid of only 50Hz, not the signal component.

This 50Hz appears in FFT and affects standard deviation if 1uF cap is not added. And more interestingly it even exists even I power the amplifier with battery but not a power supply.So I dont know where it comes from.

What kind of inference is this(common mode?) and how can you model it to simulate so that 50Hz is removed but any other Vtrans signal almost perfectly passes when a 1uF added across A and B? I mean how can I modify the above circuit to mimic the real scansion?

EDIT:

Below plots show the output in time and FFT without any capacitor for 500Hz and 24kHz sampling rates:

Sampled with 500Hz:

Sampled with 24kHz:

And below sampled at 666Hz (see FFT peak shifted comparing to 500Hz sampling rate)):


texts:
I have some problems on understanding this equivalent circuit for a photodiode (picture taken from this article):

The author states that:

The equivalent circuit for a photodiode is shown in Fig. 1, where \$I_P\$ is
light generated photocurrent, \$I_N\$ is noise current, \$R_{SH}\$ is the shunt resistance, \$R_S\$ is the series resistance,
CJ is the junction capacitance, and \$R_L\$ is an external load resistance connected to the photodiode.

I have some questions about it:

I do not see any biasing network. I think it has been omitted for simplicity. How would it have been connected to the photodiode terminals?

I do not understand why the ideal diode has been inserted in this circuit. Which is the ideal behaviour of a photodiode? I'd say that it is simply a current source Ip, without diodes in parallel.

Which is the cause of Rsh? Is it quite high or low?


texts: [solved]Resistors used in LM386 amplifier

texts: I have found a circuit to bass bump headphone amplifier. In the parts list most of the resistors are 1/8 W, but I have only found 1/4W resistors. Will this effect the functioning of the amplifier? Should I increase the battery voltage now?


texts: How exactly do I null my metal detector coils?

texts:
I've finally started work on my metal detector project and after a fair start, I'm a bit stuck.

The circuit is based almost entirely on the buccaneer VLF circuit to be found here.
I've made some alterations, I've upped the voltage to 9V and made the necessary adjustments to account for that.  I've also increased the coil diameter to 20cm (the original was 11cm), but I've kept the inductances more or less the same (my coils measure 2.9mH, whereas the original was somewhere in the region of 2.3mH).  With the Tx and Rx circuit built (on the breadboard - yes, I know it's not the best, but I didn't want to commit to a full build just yet) and the Tx oscillator up and running, I tried nulling the Rx coil.  I must have spent hours trying to get near where I thought I should be at (millivolt level) without much success.

In the screenshots below, I set the p-p Tx voltage at about 40V by trimming R6.  This is considerably less than the expected output of the original circuit (80V on my simulations) and yet the Rx coild is showing just over 2V p-p (1.8Vrms), which is certainly a far cry from the millivolt level I was expecting.

The give away here, is that in the original circuit the pre-amp gain is set to be roughly 10.  When I tried that kind of gain, my signal railed badly, so I reduced the gain to 5 but it's still clipping.

So, my first question is this:  just exactly what should I expect when I "null" my coils and do my results look normal?

Secondly, I wasn't expecting a perfect induced signal but the Rx coil has these annoying witches hats that appear at twice the operating frequency.  If you look really closely at the Tx signal you can just make out the glitch that may be coupled into the Rx coil, but I'm not sure.  What can be causing this?  One thing to note is that the "hats" move around the signal as I squeeze the coils to try to null them.  It's really screwing up my Rx signal.

I know there's a lot to take in here and if you need more info I'll post that up.

UPDATE: Incidentally, for those who'd like to know more about the Tx Oscillator, see this post


texts: Need help with identifying diodes in a 1970s automotive circuit

texts:
I have an old ignition module from a 1978 W116 model Mercedes-Benz, and I'm trying to "reverse engineer" it. The original circuit diagram is not available to mere mortals, so I have made one based on the PCB itself. I believe it is, beside being ugly, electrically correct. Thus far I have identified all resistors, caps and transistors (bar one). What I have a huge problem with are the diodes, and any help would be appreciated.
Schematic:

PCB Layout:

The known diodes are:
ZD1 - 6.8V Zener (5 Watt?)
ZD2 - 2.7V Zener
ZD3 - 27V Zener
ZD4, ZD5, D1 to D8 are unknown. ZD4/ZD5 are not shorted, but I'm getting nowhere with these with my 30V power supply, so they're probably rated above >30V. D3, D5 and D6 are fried.
D4 is just beside R4. The two left-most black diodes are D1 and D8 (both marked "703"), the one underneath them is D7 (marked "1849" and "714"). The missing T5 transistor is a TO3 packaged power transistor marked "1120008" and "7/32". I haven't cracked this one myself, but have been told a BU426A is a direct replacement for it. T1 to T3 are BCY58IX, T4 is a BSV15-16K.
The power supply is a standard 12V car battery.
Edit:  The entire ignition circuit looks like this:    (higher resolution)


texts: I have an issue with designing a Real Time Clock by using Transformerless power supply. I don't use RTC IC but I use Microchip PIC instead and 32kHz clock. I use battery of 3.3V for backup supply. The problem is when I cut off the AC power, then PIC is reset. However when I tested with cutting off DC supply no reset occur. My project is working on 5V powering and 12V for controlling a relay. Overall current is about 20mA when I test it with DC supply, so in transformerless power supply, I use X-rate cap 0.47uF in Full Bridge configuration. Could you please give me any idea what my problem is? Thanks,


texts:
I have a question about relays used by an arduino.
I know how to wire them and they work fine for the most of the time.

But sometimes the relays doesn't correctly switch on or off.
I can clearly see that the LED on the relay is in the correct state.
I can also hear a faint "click" sound. But the relay is not really switching.

Even funnier, then I physically hit/punch the relay with i.e. screwdriver it starts to switch to the desired state...

Usually the problems start when the arduino is running for a few days.

I have also tried completely different relays and have the same issue with them.

Does anybody know what can cause such issues?

Edit:

I am using an SRD-05VDC-SL-C relay with an Arduino Nano.
I have also tried different arduino compatible relays. Same issue.
I use it to power a light which uses ~250W.
Usually powering off works fine. But powering on needs a "physical hit" on the box of the relay.

I will try to measure the output tomorrow 7 o'clock when the relay is supposed to switch on again (just before I hit the relay box to force it to switch on)

Thanks!


texts:
I have been trying to amplify the output of this near field LC receiver with different OP AMP types and configurations.
All the circuits I've tried have either had a really high offset at the output, and don't amplify the signal, or just give completely wrong outputs (several orders of magnitude above supply voltage).
How would you go about designing an amplifier for this circuit ? I don't want to dampen the Q of the circuit much at all while amplifying the voltage across the capacitor, setting the gain with a potentiometer. Rail-to-rail operation would be nice too, since I only need the positive portion of the signal.


texts: How to safely use RPi GPIO to detect if computer is on

texts:
simulate this circuit – Schematic created using CircuitLab

I have a Raspberry Pi that I want to use to detect if my desktop computer is on, by detecting if the 5V rail is powered. I have in the past used optocouplers to short pins on the motherboard together with the RPi, but when I tried to use my pc817 optocouplers for this purpose, they kept releasing magic smoke.

Am I doing something wrong? I was directly connecting one end of the optocoupler to the 5V wires in a USB cable I took apart and the other end of the optocoupler to the GPIO.

Thanks in advance! Neil


texts:
In 3 phase machines have L1,L2,L3,N and PE(Protective earth).some time Neutral wire is not connected to the power supply.But,Machine have a neutral wire.What will happen if not connect neutral wire?what is the usage of neutral wire for machines?
In the installation neutral wire is note connected.Is it good idea?


texts: SPI clock synchronization issue and inconsistency with data output

texts:
I have got the spi active and have tested the working of SCLK, MOSI and CS w.r.t  the program with TI CC3200 LP Rev 3.2. While testing, I noticed some of the following issues such as:

The data bits clocked out from MOSI are not matching with the actual data byte being sent
Sometimes, the data out is clocked out even before the start of the clock signal and I was wondering how can this be possible.

SPI configured for Bit Rate of : 100 KHz

SPI Sub Mode : 0 i.e. If I have understood it right -- The data is sampled on the rising edge of the clock signal and the data bit is clocked out during the falling edge of clock signal

SPI  Mode: MASTER

The FIG(1) below shows the DSO output that addresses the issue (1) relevant data mismatch. The Blue line is data line and Yellow one is clock signal.

In FIG (1), I have transmitted a character "A" i.e 0x0A. The expected data output bits supposed to be (MSB) 0000 1010 (LSB) in binary w.r.t the eight clock cycles shown above. However, form my perception of the signals, I  am getting some other data at the output and not 0x0A. Please let me know if the data out what I am getting is actually wrong or I have interpreted the signals in a wrong way. This same issue applies to FIG (2) below as well when I transmit a character "B" i.e. 0x0B.

Just for more information, I am also attaching an image below with FIG(3), which show the transmission of 5 bytes i.e. "ABCDE".

The FIG(4) below shows the DSO output that addresses the issue (2) relevant data being generated even before the start of the clock signal. The Blue line is data line and Yellow one is clock signal.

In FIG (4), I have transmitted a character "F" i.e 0x0F. The expected data output bits supposed to be (MSB) 0000 1111 (LSB) in binary w.r.t the eight clock cycles shown above.  Here too, I am getting some other data as well as , it can be seen that the data out is clocked out before the clock signal and there is not sync between the clock and the data.

Below is the software/program I used while performing these tests in master mode, which is a slight modification of the actual spi_demo example in the SDK :

  #define MASTER_MODE      1

  #define SPI_IF_BIT_RATE  100000
   #define TR_BUFF_SIZE     100

    //Default start strings
   #define MASTER_MSG       "ABCDEFGHIJ"
    #define SLAVE_MSG        ""

   void MasterMain()
 {

int i;
    int bytecount = 1;
    unsigned long ulUserData;
    unsigned long ulDummy;

    memcpy(g_ucTxBuff,MASTER_MSG,sizeof(MASTER_MSG));

    ucTxBuffNdx = 0;
    ucRxBuffNdx = 0;

    MAP_SPIReset(GSPI_BASE);

    MAP_SPIConfigSetExpClk(GSPI_BASE,MAP_PRCMPeripheralClockGet(PRCM_GSPI),
                     SPI_IF_BIT_RATE,SPI_MODE_MASTER,SPI_SUB_MODE_0,
                     (SPI_SW_CTRL_CS |
                     SPI_4PIN_MODE |
                     SPI_TURBO_OFF |
                     SPI_CS_ACTIVELOW |
                     SPI_WL_8));

    MAP_SPIEnable(GSPI_BASE);

    Message("Enabled SPI Interface in Master Mode\n\r");
    Report("Press any key to transmit data....");

    while(1)
    {
        ulUserData = MAP_UARTCharGet(UARTA0_BASE);

        MAP_SPITransfer(GSPI_BASE,g_ucTxBuff,0,bytecount,
                SPI_CS_ENABLE|SPI_CS_DISABLE);

        Report("\r\n\nSending:");
        for(i = 0; i < size; i++)
        {
            Report("%c", g_ucTxBuff[i]);
        }
        Report(":");

        Report("\r\nReceived:%s:",g_ucRxBuff);
        for(i = 0; i < size; i++)
        {
            Report("%02X, ", g_ucRxBuff[i]);
        }
        Report(":\r\n");

    }
}

Any help, information or advise on changes to be made regarding this would be appreciated. Thanks in advance.

Regards

~VD


texts:
My boiler is connected to a sun-water-heating system. After the sun goes down this system start to draw heat from my boiler.
Today I'm manually closing the valve connecting my boiler to the system.

I'll like to build system based in Arduino that will operate a solenoid that will open and close the valve.

The solenoid will probable by normally-closed and I'll open it only when sun is up which is a few hours every day.

I remember reading somewhere that solenoid should be operate for short time, is that true?
Can I leave the current on for say 6 hours to keep the solenoid open?
Is there a better way?


texts:
I wanted to sniff communication between two RS232 devices. This link presents a simple solution but I want to make sure that my 'sniffer' does not load the communication link.
To that effect, I was wondering if I could use a MAX-232 as a 'looping' buffer:
RS232 in -->TTL out-->TTL in-->Rs232 out
The MAX-232 will be powered by an external 5v. Is this a fool proof way of sniffing without loading the line? Does the MAX232 even act as a buffer in this configuration? If not. are there inexpensive RS232 buffer ICs available? All the 74xx range of buffer ICs seem to work only at TTL levels.
My communication link is only half duplex.
UPDATE: I think I was not clear with my description. Please see the image:

Both my devices already are on RS232 levels. I simply wanted to read the data using a COM port of the PC, but thought a MAX-232 in between (the loop buffer that I was talking about) might serve as a buffer. But then again, even the PC's COM port per se might have a MAX-232 inside it...
P.S: I have not indicated the capacitors etc for the max232 in the above figure.


texts: As far as I know, a computer sends currents through address lines and each address in memory is accessed by a unique combination of currents and as a pulse is sent into a flipflop the data in it is read(in the form of a voltage pulse).But how does the CPU generate the unique combination of currents?Please correct me if I am wrong


texts:
My vehicle's ignition barrel has given up the ghost, and instead of replacing it, i want to go with a push to start system. I have already sourced a start button and only released after chucking the slip that it pulled to ground. Can you guys help me?

Relay 1:

Pin 30: 12v From Battery with SW1 closed
Pin 85: SW2 From Per 12v + LED(positive) on Button
Pin 86: Goes to Relay 2 + Accessory 12v + LED(positive) on Button
Pin 87: Goes to Ground

Relay 2:

Pin 30: 12v From Relay 1 with SW1+SW2 Closed
Pin 85: Needs 12v
Pin 86: Goes to Starting Circuit
Pin 87: Goes to Ground

Normally the ground of the STRT pin on Button (which is push to make) will supply the 12v to Pin 86 on Relay 2 to send 12v to the starting circuit.

simulate this circuit – Schematic created using CircuitLab


texts:
I've just bought Waveshare rotation sensor.

I connected it to Logic Analyzer and made some tests. As expected the sensor sends two low-level signals moved in phase.

But when you zoom in it you can see many noise while changing level from high to low or from low to high as long as voltage will not get stable. Here is an example.

The noise continues for several microseconds so it is a problem because if I want to register user action from sensor in microcontroller it register falling-edge (as expected) but often (not always) also the noise. As a result I get a few interrupts instead of real one.

1. Is this noise natural behaviour while shaking the rotation shovel?

2. Is any way to eliminate this noise because communication with the microcontroller?


texts: Circuit with switching MOSFET not working

texts:
I have this circuit built (updated to remove short-circuit):

I'm experiencing some weird behavior though that I don't understand.
1. When I close the switch, nothing happens. No current flows through the MOSFET, according to the Ammeter.
2. If I disconnect the ground of the Arduino from the negative terminal of the power supply, current flows through the MOSFET, even when the switch isn't closed!

Have I hooked this up incorrectly? Why is the MOSFET letting current through? Any ideas?

Note: Data Sheet for MOSFET
Note 2: When I use this exact setup but replace the 12V power supply with a battery, and the component with a resistor and an LED, it works fine.


texts: What is this power supply connector and why was it likely chosen over a 12V DC?

texts: This is from a 3.5" hard drive enclosure that I am tempted to throw away since I don't have a plug. What likely influenced the design choice to use this sort of plug? The hard drive itself likely takes 12V DC as that is what a computer has.


texts: Driving parallel arrays of LEDs from a single constant current supply

texts:
I'm looking at using a single constant current, DC-DC boost converter to power several (6 - 8) parallel strings of 3 LEDs, like the drawing below. This is powered by a single li-ion battery.

To control each string of LEDs, I'm proposing using a MOSFET like in the diagram below.

Each MOSFET would be driven by a separate microcontroller pin either high or low.

As I understand it, provided the set current is high enough to drive all of the strings simultaneously this will work but might have some side effects:

When disabling any string, the current will be shared by the remaining enabled strings, i.e. the remaining strings will increase in brightness. This means when only one string is enabled, it must be capable of being driven at the full current (8 x the current in the above diagram).
If I used the MOSFETs to dim each string individually using PWM, it may be a significant source of EMI as these will be driven by non-slew rate controlled ON signals.
Dimming using PWM would be less efficient than other methods but would offer better chromacity and intensity control.
The LEDs used in the feedback circuit will need to be illuminated and can't be switched on / off, unless the whole DC-DC converter is disabled.

My questions are:

Are my assumptions correct above?
Are there any other disadvantages to this approach?
Could the three LEDs used in the feedback circuit be substituted with a zener diode and resistor? The feedback voltage for this driver IC is ~100mV.

Any other thoughts on this, or other potential solutions would be appreciated.


texts: Which microcontroller should be master / slave?

texts:
I'm design an alarm to wake me up the morning. The system is composed of 3 subsystems :

(S1) RGB seven segments management. Composed of 5µCs, one for each digit and one for ":". The high number of µC is due to the fact that I don't use IC for RGB led, only transistors.
(S2) Sensor and input management. One µC that manage the distance sensor for set alarm and current time; and switches for configuration.
(S3) Communication and audio file. One µC that communicate with a bluetooth module in UART for further project, got a RTC crystal to have an accurate clock and manage audio playing. (I didn't work on the audio yet)

During normal execution, S2 reading the input and send it to S3 for processing. then S3 send to S1 what has to display.

I want to make all these subsystem communicate together, I then choose to use the I2C bus. But here come my question :

Which µC has to be the master?

In the first hand, S3 is the center of the system but in the other hand, S2 may send more message than S3. That's why I'm undecided about who gonna be master / slave.

Is there a rule to determine who will be slave / master? What question should I ask myself to make the good choice? (in general, not for this specific system)


texts: Characteristics of a Laser Diode Below Threshold

texts:
This question is related to that one:
Can laser diode be operated with lower than specified voltage?

I am driving a laser diode in a current controlled fashion. What actually happens below the lasing threshold?

In experiments, I can clearly observe some "fluorescence". The fluorescence intensity makes up for only ~0.2% of electrical power. Even more interestingly, the fluorescence intensity stagnates at a nearly constant level, independently of current. Also the voltage remains at a constant level.

Can one theoretically predict some sort of curve for the I / V - characteristics of a Laser Diode below threshold? Similar to the shockley equation for ideal diodes?


texts: Programmable DS1077 Oscillator: Cannot set the DIV register

texts: I am trying to run a Maxim DS1077 programmable oscillator through the I2C bus from an Arduino Uno development platform. I am able to run the oscillator at the different pre-scaler values 1,2,4, and 8. My oscilloscope shows that the changes in Out 1 are appropriate. However, I cannot set the divider DIV register. It always seems to be set to N=1, i.e. it is as if the divider is not in there at all. I set the MUX bit for activating the divider correctly - tride both settings etc...but to no avail. Hardware set-up: both control ports are tied to GND, the serial communication lines are tied to 5V via 3.9kOhm, and I have 0.1 and 0.01uF between GND and Vcc. The serial lines are connected to the Arduino's analog ports 4 and 5, and I am using the wire library. I think the fact that I can set the prescaler shows that the I2C is not the issue...any tips would be appreciated! Thanks!


texts: ESP8266 (esp-07) powered by battery(s) for at least 1 year

texts:
Hey all I am trying to see how long I can possibly have a ESP8266 ESP-07 operate with only 1 or 2 of the Lithium-ion Battery 18650 Cell which claims to have 2600mAh.
I am making a window alarm sensor and I'm looking to incorporate a window reed switch in order to check its status via the ESP8266 and if it's opened (meaning the window is not closed) then send something via WiFi to a REST service. Likewise, if the reed switch is not opened (meaning the window is fully shut) then sleep.
The flow with only ESP-07 would look something like this:

1: Power up for the first time.
2: Send Date/Time, window closed or opened, etc.. via ESP-07 WiFi to the REST service.
3: Have the ESP-07 go into deep sleep mode.
4: Wake up from sleep after 1 minute.
5: Check window reed switch.
5: If reed switch is open then send REST service via ESP-07 WiFi.
7: Goes back into deep sleep mode.
8: Loop back to #4.

The flow with ESP-07 & ATTiny85 would look something like this:

1: Power up ESP-07/ATTiny85 for the first time.
2: Send Date/Time, window closed or opened, etc.. via ESP-07 WiFi to the REST service.
3: Have the ESP-07 go into deep sleep mode.
4: Have ATTiny85 check every 30 seconds for window reed switch status.
5: If reed switch is open then send REST service via ESP-07 WiFi.
6: ESP-07 goes back into deep sleep mode.
7: Loop back to #4.

It would seem that using the ESP8266 along side an ATTiny85 would make it last longer since I could check the status of the reed switch via the ATTiny85 and if it sees the window closed then pause and check it again in 1 minute. If the ATTiny85 does see the reed switch opened then start up the ESP8266 and send the info via WiFi then go back into deep sleep. However, I am not sure how this would be on the battery side of things - if it would be less or same or more.
I'm looking to see how long 1 and/or 2 of the lithium-ion batteries would last (in days) with using just the ESP-07 and also using both the ESP-07 and the ATTiny85 as explained above.
I've done some googling and found a few websites that show how to put the ESP-07 into deep sleep mode but really wouldn't say how long it would take with my setup above. Most were using standard AA or AAA batteries.
The overall goal is: Have the window alarm power last at least 1 year.
The items:

Datasheets:
Lithium Ion Battery 18650 Cell
ATTiny85
Window Reed Switch (Generic) or Mouser (Generic)
ESP8266 ESP-07
The battery ESP-07 consumption chart I found:


texts: Prepreg thickness: ECAD specs vs. fabrication result

texts:
I have a question concerning the thickness of the prepreg layers in a PCB. If I understand correctly, the prepreg layers are used for "gluing" together the core(s) and copper foil layers.
According to this answer the thickness of the prepreg varies with the height of the etched boards either side of it. From this I deduce that the copper on the etched core will "enter" the prepreg layer, or, equivalently, the prepreg will "yield" where copper features are present (see snapshot below). Does this mean that the final thickness of the prepreg layer will be reduced by the thickness of the copper layer(s) which "enters" it?
To give a concrete example, imagine the following 4-layer Stackup:

Image source: Olimex Quiz Answer – PCB Layers stackup
Assume that the ECAD specs for the Stackup are:

TOP: 35 um
Prepreg: 100 um
GND1: 35 um
Core: 1200 um
GND2: 35 um
Prepreg: 100 um
Bottom: 35 um

According to the picture above, the copper of GND1 will "enter" the top prepreg layer. This means that, if initially the prepreg's thickness was 100um, after gluing it should be 65um. Is this a correct assumption, or does the stackup information in an ECAD file refer to the final product of the PCB manufacturing process?
In other words, if I give the above specs to a PCB manufacturer, will he use a 135um-thick prepreg to compensate for the copper's thickness, or will he use a 100um-thick prepreg, whence the final prepreg thickness will be 65um?


texts:
My question is probably pretty easy to answer for you smart people. But basically I'm building a Segway clone using an Arduino, two Jaguar speed controllers, and two 24 volt batteries (wired in parallel). I want to power my Arduino from the 24 volt batteries and am just wondering if I need any additional circuits to step down the voltage/current, stabilize/condition the power, or anything else that may need to be done before the Arduino can use the power.

I'm fairly new to basic electronic circuits and am more of a programmer. Can someone help me with my question?

Thanks!


texts: How is resistance in brushless motor ESC calculated by the manufacturers?

texts:
In hobby market (rc planes, cars, robots) one of the parameters manufacturers of the brushless motor ESC specify is resistance. ESC in this case means "electronic speed controller" and is a device used for commutation and speed control of the electric engine.

Is there a standard (written or informal) how this parameter is characterized? If yes how it is done?


texts: Feedback on a simple motion activated motor circuit

texts:
I have been working on a motion activated motor which uses a PIR sensor to detect the motion. The idea is when PIR detects user in front of it motor should start running and when the user moves away motor should stop.

Rev 3:

Rev 2:

The above circuit is the changes I have made in Rev 1 after valuable suggestions from Micheal. I have also added corresponding calculations for deciding the component value used in the above circuit.

I need to generate 1 sec time delay from PIR detecting motion and activation of motor. So

RC = 1 sec

Fixating the value of C as 10uF

R = 1 / 10 x 10^-6 R = 100k So the R1 value is 100k

Looking at capacitor charging curve a capacitor will charge 63% of applied voltage at time period T which is 1 sec. The output voltage of PIR sensor is 3.3v so 63% of 3.3 is 2.1v.

The voltage divider setup R3 and R2 values were chosen to give reference voltage as 2.1v . Did I make my calculations correct for what I intended to achieve ? I have also replaced the darlington transistor with N channel power MOSFET to drive the motor.

Rev 1:

In the above circuit PIR sensor is used to detect humans. And I have used a RC circuit R1 and C1 to introduce some time delay in order to avoid false triggering. The load current of motor is 1A and I have used darlington transistor TIP122 to drive this motor.

The Vbe of TIP122 is about 2.5v as per the datasheet. And I wanted the delay from RC to be about 1sec. So it will take 1.5RC for capacitor to reach 2.6v across its terminal and at that instant transistor will get activated and drives the motor. So I have fixed the R1 value to be 67k and C1 value to be 10uF.

So my question is:
Have I done the calculations right?  Will my circuit work as intended?

If not any thoughts to achieve what was intended?


texts: How to start 220/380V 3 phases induction motor by star-delta method with 3 phases 380V power source?

texts:
I would like to ask a question about how to start 220/380V 3 phases induction motor by star-delta method with 3phases 380V power source.
Practically I think that it is impossible to be able to do it without step-down transformer by convert the power source from 380V to 220V.
But, my boss tell me that I need to be able to makes it happen without using transformer.
So, is there any suggestion to solve this problem? I just start working so any help will be appreciated. Thanks


texts:
Is it possible to execute a sequential command from Eagle's input line? I want to do something like this:

name 1,2,3,4,5,6,7,8,9,10,...,100

so that I can avoid clicking hundreds of times and just click 100 times to name these massive IO systems. I'm finding that clicking a net and then naming it is just awfully slow. If there's no way to do the above, how can I connect many, many pins to each other quickly?


texts: Voltage and amperage requirements for resistance heating of glass

texts:
I am planning to introduce electric heating/boosting in my glass melting furnace.
The present temperature of the glass is around 1200 deg C and I need to raise it up to 1300 deg C. I am trying to get the design for a scott transformer of 10kVA, thyristor control panel for the job. 2 molybednum electrodes will be inserted into the hot glass and the control panel will supply the electrodes with the required voltage and amperage for heating of glass to the required temperature. I understand that the resistivity of glass starts falling with the rise in glass temperature and since the resistivity of molten glass is low, it might need low voltage and high amperage at the electrodes to heat up the glass.
The total glass pull/production is 100 kgs per hour.

My question is :
1. Can anyone help me in deciding the  voltage range and amperage range required for efficient heating of the glass from 1200 - 1300 deg C?
2. Will the distance between the electrodes have an effect on the efficiency of heating?


texts:
I've decided to try and make a Solar Powered MintyBoost. I've drawn up a very rough version of a schematic:

As you can see, I plan to use a solar cell to charge a set of 2 D batteries (in series), using a Diode to prevent the batteries from discharging through the PV module. The batteries are then used to power the MintyBoost circuit, and thus charge my device. Is this a sound design?

I was planning on using for of these cells in parallel to provide 4.5 V and max 320mA. However, this would take a long time to charge 2 10,000 mAh batteries (a long time being ~62.5 hrs). Can anyone suggest a better solution for the solar panel? I haven't been able to find many ~4V panels that can provide much current. Would it be a problem to use a module that provides more than 5V, seeing as how the LT1302 is meant to operate with an input voltage below 5V (though the datasheet says up to 10V)? Or would the batteries be forcing that node to 2.4V?


texts:
I am using TPS61021 boost converter IC to increase input voltage from 1.2V to 3.3V. I have designed the boost converter from the application called TI WEBENCH.

Input Voltage: 1.2V

Output Voltage: 3.3V

Min current: 300mA

The PCB that I have designed, is measuring 3.3V, but the efficiency is pathetic. It is well below 25%. In the BOM, TI WEBENCH software recommends using 10UF 10V capacitor, but I am using 10uF 6.3V. I am not able to understand why efficiency is so low? Datasheet for Inductor.

Below in the tabular format I have written current values that I have measured from multimeter.

Fig.1 Measurement of current at different load resistance.

Fig.2 TI WEBENCH application output

Fig.3 Schematic design of Boost converter


texts: Does a rated 5V, 2.1/1A charger provide a constant current?

texts:
I use power banks often to charge my iPhone. The default charger is a 5V/1A charger (which I assume provides constant current).

However, the power bank has 2 output ports - able to provide 5V=1A and 5V=2.1A - Does this mean it provides constant current or does it mean that the device will extract the current upto that maximum?


texts: earphone microphone out put voltage range

texts:
I want to send a signal through the 3.5mm jack(microphone port) to an android mobile and process the signal using android mobile application I created.

But I don't know the voltage range the microphone port can sustain. Please help me.


texts:
For a yearly running event at our university we have developed a lap counting system relying on Bluetooth-chips passing by small embedded computers. The chips are these. To power them, we use 4 AA batteries.

Last year, we devised a solution which involved cutting open a single AA battery holder, gluing it to a small plastic rail to hold four batteries, soldering this to our chip, and glued it on the plastic rail. During the event we soon realized this was a bad idea, as we had to deal with a large amount of running batons failing due to the plastic rail being broken, the connections breaking off or the batteries not making a good contact with the holder anymore.

It didn't help our weak design that on such a event batons are not handled with care, they are thrown, fall on the hard ground and get shaken around terribly. (You can read a full report here.)

This year we want to learn from our mistakes and produce an improved version of the relay baton. We were wondering on some design decisions to be made: what precautions should we take to build a robust holder for our battery and chip that can withstand extensive shaking? Are we better off looking for one battery of the right voltage instead of four AA's? Are battery holders with integrated springs a good or a bad idea? Ideas for putting (and keeping) it all together?

I'm not sure if this is the right place to ask but we could use some advice on this subject from people with a bit more practical technical knowledge.

EDIT: We're thinking about using battery holders like these. Would they still require additional enhancements to provide a steady power supply when being swung around? Being dropped is not that big of a problem, detection quickly recovers when power is restored.


texts:
A mosfet can be considered as a transconductance amplifier with unity gain frequency gm/(Cgs + Cgd).

The unity gain frequency is defined as the frequency where the current gain is one. What I am confused is why should we care about this frequency? What is so special about it?

Also because mosfet is a transconductance device meaning that it receives an input voltage and gives out a current.

So why do we focus on current gain Iout/Iin instead of Iout/Vin?

Thank you.


texts: 8259A End of Interrupt (EOI) signal question

texts:
In the x86 architecture, when a hardware interrupt's ISR finishes you need to tell the 8259A chip that it is done and you send an EOI signal to the chip. After that you can return from the ISR using an IRET instruction.

question:
Is there any reason why the IRET instruction isn't hardwired to automatically send an EOI signal to the 8259A? Wouldn't that save some processing?


texts: Buried zener voltage reference: noise vs temperature

texts:
Buried Zener voltage references like LTZ1000A are known for their low-noise. High stability of reference voltage is often improved by temperature stabilization at somewhat elevated temperature.
I wonder, does it impact noise performance? Is there any benefit in lowering operating temperature to room temperature/0/-20/-40°C with the goal of reduced noise, assuming that absolute precision of output voltage is less important than noise?


texts: Why is this ground and resistor connected here after the switches?

texts:
I had recently asked a quiestion here: Will this circuit for quiz buzzers work? and I got this answer.

I am trying to understand the circuit and I have understood most of it but there is only one part that I am not able to understand.

I don't understand electronics in theory properly so can you explain in simple english why this ground and resistor have been connected?


texts: Calculating current through multiple capacitors in parallel

texts: I have a capacitor bank with 4 units in parallel and I'm trying to figure out the worst case scenario of current sharing at turn initial turn on. If 3 of the capacitors have the maximum ESR and one is say half the maximum ESR, how do I calculate the maximum current of the low ESR unit?


texts: 512 channel LED strip controller over RJ45 (TCP or UDP based commands)

texts:
How would you make the following?

I'm looking for a 512 channel LED strip (varying size) dimmer, controlled over TCP/IP or UDP.

My dream board has:

512 individual channels @ 12V
Each channel capable of sinking up to 0.3A (ideally 0.5A max)
Overall average current per channel 0.2A (80->100A max total is more than adequate, won't always use the full 512 channels)
Predetermined fade time between on/off states, around 0.5 seconds
IDC connectors or screw terminal plugs in groups of ~16
RJ45 cat5e interface to control over network
The ability to send simple commands over TCP or UDP in a form like ".c,s;" (where c is channel number and s is state to switch to 1/0, on/off)
Decent latency times (i.e. unnoticeable delay when lighting all channels at once)
Industrial format (i.e. DIN rail mountable, insulated)

I've tried building and buying various systems. I developed an mbed/MM5451 board with high channel count (144) but low current rating. Tried working with PCA9685 chips, couldn't wrap my head round the functionality. Tried shift registers and darlington arrays with arduino, though scaling this up was problematic. Seen plenty of 3rd party solutions, non of which adequate. Most successful solution to date was daisy chaining specialist DMX boards, with an arduino intermediate and a Raspberry pi as a command server.

After a year of tinkering, I truly hope someone can point me in the ultimate direction. I usually end up compromising over current vs channel count with inadequate solutions to the same problem. Certainly not an electrical engineer, would appreciate an experienced opinion.

Ideas?

And is DMX suitable considering I have no need to vary brightness (besides the fading between states)?


texts: Can I get help with measuring particle charge using oscilloscope?

texts:
How can one measure particle charge using oscilloscope and op amp integrator circuit along with a capacitor and faraday cup. I am unable to figure out how to approach. I have the circuit ready but when I test the faraday cup by touching a separate charged capacitor, the oscilloscope doesn't show any visible change in voltage. How can I use all these components to get a particle charge. My plan is to drop the particles in the faraday cup and get the output voltage change from oscilloscope. Then calculate the charge with the help of rated capacitor. Also, I don't have any electrometer.

Can I get help with measuring particle charge using oscilloscope ?.
Also, how will the voltage waveform look like when oscilloscope detects any voltage ?

I have attached the circuit, maybe you can have a look into it. What I am doing is charging any capacitor (not included in the circuit) with one end grounded (from dc power supply) and then touching the faraday cup. The oscilloscope is not responding to the touch.

Also, when I am turning ON the power for OP-AMP, then even without applying anything to cup, I am getting a voltage at the output. Is this normal ?... Tell me anything in the circuit which needs to be changed or tell me the step by step procedure which can be used for particle charge measurement using the scope.

Thanks


texts:
I bought a few bc417 serial bluetooth modules which have pins that look like this:

Is there a standard name for this kind of pin?  I believe I can treat them like any other SMD pin, but I'm curious what the dents are for.  Are they intended for a header pin to go there somehow?  Just keeping your iron from slipping?  Something else?  What's the recommend way to attach these to a board?


texts:
It is said that the input impedance of a buffer must be high enough so that it can isolate its input voltage and carry it to its output for driving purposes.
What I do not understand is why we treat all the independent sources as shorts while calculating input impedance. I know that input impedance is the impedance seen by input voltage present at buffers input.
There is, however, a huge difference between treating independent sources as shorts while calculating input impedance, and not doing so. Someone on this website said you can try finding input impedance without treating independent sources as shorts and get the same result as if you did.
I do not believe that. Can you enlighten me on the use of input impedance and the logic behind its calculation?
Input impedance found by treating sources as shorts cannot be used as an impedance replicate of a circuit connected to some other circuit which we try to solve without writing lots of node equations and therefore has no practical use. Also I looked at posts regarding it on this website and none answered my question.


texts: Apparent inconsistency of MOSFET power rating in datasheet: SOA v. max power

texts:
I am trying to use an IPP114N03L G (datasheet).

I calculated the maximum power it could handle as follows:

From the first two pages of the datasheet:
Rthjc = 3.9K/W
Tj(max) = 175C

Assuming I can keep the case under 50C, max. power dissipation should be:
(175 - 50) / 3.9 = 32W

So 1A at 30V should be about the maximum.

Now looking at the Safe Operating Area graph on page 4, at 30V it says ~150mA max. and that is with Tc at only 25C.

Why do these figures disagree?

In practice, I have killed two of these devices now, the last one was at around 20V 200mA, so it seems the first calculation is wrong. The case was cool.


texts: Calculations for current transformer and output voltage

texts:
I'm trying to understand differences in my simulation (LTSpice) of a current transformer from calculations of the output voltage and current. In LTSpice with a 600ohm resistor across the secondaries; I get 18V and 30mA pk-pk. Obviously Im not taking into account all the factors and losses? How do I calculate the value of the resistor on the output for a given voltage? R = Vs/Is?
Current Transformer Spec
Source:
Current    = 10A pk-pk.
Freq       = 50Hz

Primary:
Turns      = 10
Inductance = 200uH
Resistance = 0.2 ohms

Secondary:
Turns      = 300
Inductance = 180mH
Resistance = 12 ohms

Verify Turns to Inductance:
Np / Ns = SQRT(Lp/Ls)
0.0333  = 0.0333

Calculate Voltage and Current:
Np/Ns = Vp/Vs = Is/Ip

Vp = Ip * Rp
Vp = 10 * 0.2 = 2Vpk-pk   <-- Verified as 2V pk pk in LTSpice.

Calculations:
Is = Ip * (Np / Ns)
Is = 10 * (10 / 300) = 333mA   <-- 30mA pk-pk in LTSpice
Vs = Vp / (Np / Ns) = 2 / (10 / 300) = 60V <-- 18V pk-pk in LTSpice

(unfortunately I cant added LTSpice pics due to an error)


texts: How do Wi-Fi controlled light switches feed themselves?

texts:
There are smart light switches in the market that are Wi-Fi controlled like Plumlife (formerly ube) and Belkin WeMo. I wonder how they control the electricity that they operate on.

When I unplug my old fashioned light switch, I see that there are two wires. I believe that they work in this way.

But in smart switches, there must be some inner circuit that contains a relay inside of the smart light switch. If current goes through that circuit, that means smart light switch is closed too; therefore bulb is on all the time.

How do these products run on and control the same electric wire. If there is an external power source that feeds smart light switch like a fellow stackexchanger mentions in this question , I understand. But there is not. So what I ask is how is it possible to feed a circuit that controls it's own electricity.


texts: What is the significance of numbers (2,3) mentioned in SOT23?

texts: Small outline transistor (SOT) packages have certain numbers which tell the package size, for example, SOT23 or SOT323. But what is the meaning of suffix 23 or 323?


texts:
I have been trying to grok the common base amplifier, and put together a few examples, but there is something that I do not get at all.  I have the setup below.  Things are working more or less as expected, but I measured the resistance of the bias divider, and even though I have a \$50k\$ and a \$100k\$ resistor, I measure \$\sim 33k\$ across both parts of the bias divider.  Why does this happen?

I suspect that \$R_2\$, \$R_4\$, and the BE junction make up one part of a divider somehow and \$R_1\$, \$R_3\$, and the BC junction make up the other.  Am I on the right track?  How can I calculate these results reliably?

I should mention (since it's probably nearing finals time for students) that I am not a student.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to understand how to configurate CAN filter. STM32F4 MCU is used. Idea is to catch only dedicated messages, for example messages with ID from 0x100 to 0x190. I understand that each CAN peripheral can take one of 14 filter banks. Filter bank 0 is currently be used. Filter is configurated in mask mode (CAN peripheral receive messages which have a certain ID range), 32 bit scale (which means that register F0R1 and F0R2 represent respectively Id and Mask register, in datasheet these register are defined as CAN TX mailbox identifier register (CAN_TIxR) (x=0..2)), FIFO0 is used for received data. CAN with Standard Frame Format (11-bit ID). Here is filter config:
sFilterConfig.FilterBank = 0;
sFilterConfig.FilterMode = CAN_FILTERMODE_IDMASK;
sFilterConfig.FilterScale = CAN_FILTERSCALE_32BIT;
sFilterConfig.FilterIdHigh = 0x0000;
sFilterConfig.FilterIdLow = 0;
sFilterConfig.FilterMaskIdHigh = 0xC000;
sFilterConfig.FilterMaskIdLow = 0;
sFilterConfig.FilterFIFOAssignment = CAN_RX_FIFO0;
sFilterConfig.FilterActivation = ENABLE;
sFilterConfig.SlaveStartFilterBank = 14;

My problem is how to quickly calculate the values of the ID and Mask registers to get messages within certain limits, is there any formula? After lot of attempts I found some values for ID and Mask registers.

TxHeader.StdId = (0x100 - 0x17F) <--->  FilterIdHigh = 0x100 << 5, FilterMaskIdHigh = 0xF000
TxHeader.StdId = (0x0 - 0x1FF) <--->  FilterIdHigh = 0x0000, FilterMaskIdHigh = 0xC000

Does someone have idea how to fast calculate values for registers?


texts:
In closed magnetic circuit, How many turns are when a conductor winded around a square mild steel core with permeability (Ur=2410)?

The outer length is 20 cm and inner length is 16 cm. The current measured is 1.482 A. Length of the coil is 10 cm

Any Hint where to begin?


texts: Theory: Can power cables induce AC voltage in human body?

texts:
In a demo video (which I unfortunately can't share) a man makes the following setup:

Multimeter on 200 V AC settings with one pin in the ground socket of a conventional mains power socket.

Right hand holding the other pin

Left hand free to hover over or touch a conventional extension cord (insulated) which is connected to a device with the mains power on.

Then he varies a few things and observes measurements:

Wearing shoes: hovering left hand over the extension cord gives 2~3 V readout. Gripping the cord gives 10 V readout.

Barefoot: hovering left hand over the extension cord gives 0.5 V readout. Gripping the cord gives 3 V readout.

I've been working on an idea for why this happens and I'll propose it here. The point of the question is to understand the theory by either getting your thoughts on my proposal, or your own proposal.
So my thoughts are as follows:
Wearing shoes

Left hand and cable are acting as two plates of a capacitor.
The human body is not a perfect conductor, therefore there is time for charge to "pool up" in the left hand in a 50 Hz cycle. Therefore when measuring the right hand relative to ground, we see an AC voltage readout.
To explain what I mean, I've modelled the human as 3 charge reservoirs interconnected by resistors. The middle reservoir is the body, the left reservoir is the left hand, the right reservoir is the right hand.
I also show the flow of charge with a double ended arrow (indicating that it's AC, but slow at 50 Hz)

Barefoot

Now there is a larger reservoir to draw from, that is the floor. So the main current flow is between the left hand and feet.
Therefore less charge from the right hand reservoir is needed to equilibriate.
Therefore the readout is lower.
Perhaps the current induced is larger than in the case where he is wearing shoes?


texts:
Voltage gain CE & CC from AC
Can you tell me please if I am true in calculation of gain of this circuit?
Assumption: gm is known and beta=inf, Early VA=inf => gbe=0, gce=0.

Here the Matlab code :
clear
clc
syms gm gs g1 g2 g3 g4 vo v3 v1 vi
a(1)=(v3-vo)*gm==0;
a(2)=gm*v1==v3*g4;
a(3)=(vi-(-v1))*gs==-v1*(g1+g2);
v=solve(a,vo,v3,v1)
av=v.vo/vi

Thanks!

Voltage gain CE & CC from AC without capacitor to R3
What about this equation ?

Here the Matlab code with only 3 equations about the first stage because the 2nd gives av=1 :
clearvars
syms gm gs g1 g2 g3 g4 vo v3 vi va ve
v1=ve-va;
a(1)=gm*v1==v3*g4;
a(2)=ve*g3+gm*v1==0;
a(3)=(vi-va)*gs==va*(g1+g2);
v=solve(a,v3,ve,va);
avWithoutC2=v.v3/vi

Thank You very much !


texts: What is the simplest and safest way to automatically make/break a ground to neutral bond in a mobile AC system?

texts:
I have an inverter/charger unit, with features I want, that is not typically used in an RV. It (unfortunately) does not automatically make/break a ground to neutral bond. I would like to automatically do this anytime shore power is connected to the RV. (As required by electrical codes).
I experimented with a 2 NO 2NC electro-mechanical relay with the coil connected to incoming 120V shore power. For the test, I ran a ground to neutral bond through one of the NC contacts, so that when shore power was not present, the bond was made. This appeared to work. When energized, the bond was broken, when de-energized the bond was restored.
But the coil could fail someday, and the manufacturer said it should fail in its normal state, not its energized state. I understand that is not a certainty, and therefore will deal with that issue separately. But for those reasons I also tested having shore power run through one of the NO contacts. That way if it the device fails and the ground to neutral bond is not broken, power is also not passed through to house loads.
When testing this, the coil began bouncing and no power was passed through the contacts. I called the manufacturer who stated that you can not power an EM coil with the same source that you're running through the contacts. The coil and and contacts are normally isolated, but by using the same source for both, you've now effectively created a jumper between them, which results in constant vibration/bounce, much like old AC doorbells use.
That being the case, in a chassis fault scenario where ground becomes hot, the coil would again be connected to the same source as one of the contacts, so it appears a contactor like this can not be used for this application.
I am therefore exploring alternatives. One option may be solid state relays, but does anyone know for certain if they will have this same issue? I see many for sale on Amazon boasting "switch the fan on when you turn the lights off," and other similar statements suggesting the SSR input and output can be connected to the same source with no issues. Is this correct?
Please note, I appreciate words of caution, and I am being careful. I am testing everything with full protective gear on a bench.
Here is the system's wiring diagram, but I had not yet drawn a diagram for the contactor that I was planning to use to make/break the ground to neutral bond It's the large yellow box with text on the lower right. (update: separate drawing is now included). I originally tested with the coil powered from 1 leg of the 120V utility hot (the one that will always be powered when using either single phase 120V hookups or when using split phase 120/240V hookups), and that same leg went through the contactors NO contact and then connected to the AC breakers in the diagram. That way if the coil's NC contact failed to break the ground to neutral bond when on shore power, no power would even reach the breakers, and I'd know to replace the contactor. But this didn't work in bench tests and manufacturer says it won't ever.

Update: I've added a drawing. Please understand my diagram skills are still limited, and I was trying to draw the device using the only available objects in EasyEDA's library. I also wanted the orientation to match the Contactor's diagram and my wiring. EasyEDA does not indicate when a wire jumps over another, so near R2 you'll see I tried to make the typical jump shape, but if there is no red node, then it means there is no connection. Please also note the Vehicle Chassis Ground to Neutral connection via R1 and R2 is mandatory code for RV power when not running on shore/main utility power. There is no debate over this. Where I have a circuit breaker and load drawn below, that is where the incoming power arrives at the AC Switchgear pictured above, then out to loads. But I included a simple CB and load below to complete the drawing.

Here is also a drawing of the front of the Contactor. You'll note its 4 pole, but I couldn't find a 4 pole in EasyEDA, so I used the next best thing.


texts: Why is the graph plotted by |V0| in lvdt characteristics graph

texts: In the transfer characteristics of an LVDT , why is the modulus of voltage taken and not just the voltage. In both cases we can see linear range so, what is the advantage of taking mod V.


texts: Detecting AC pump motor running (from the outside)

texts:
My heating system at home uses a couple of Grundfos pumps to circulate warm water. They are controlled by my heating system and as far as I can tell, running on 220V AC.

I would like to track when these pumps are running. Is there a sensor that could detect this? I don't want to connect something to my heating system, so the sensor should detect the running pump "externally".


texts: Use old battery pack charger as DC power supply?

texts:
I have an old charger for NiCd battery packs. It is labeled with:

  Input: 230 V~, 50/60 Hz, 33 W
  Output: 4.8 - 12 V DC, 1.4 A

I opened it and found a transformer and two circuit boards. I made a schematic of the first board (unfortunately I could not find out the exact names/values of some components):

I wonder how I can change this board to use it as a DC power supply, how I can adjust the voltage and what maximum current it can deliver. In addition I would like to understand how this circuit works.

The second board has two ICs on it: HCF4060BE and LM324N. In addition, there are a 2N3906 transistor, some capacitors and lots of resistors and Z-diodes. I suspect that this board is not needed when using the first one as DC power supply?


texts: Voltage drops after connecting two batteries in parallel

texts:
I have two batteries 12V GEL 130Ah, each charged to 14.4V. After connecting them together in parallel, the voltage drops gradually and equalizes at 12.99V. (I use 10mm^2 short cables to connect them together so I wouldnt expect much of a drop at the cable.)

I would expect voltage to stay the same. Why does the voltage drop occur? Does it mean that the battery bank is somehow faulty?


texts:
I want to find how long a capacitor takes to discharge from 12 volts to 2 volts using Qucs. I can use a voltmeter to measure the voltage across it when it charges up, but I cannot turn the power source off during simulation.

Suggestions? Thanks


texts:
I'm looking for an SPST analog switch (or alternative device) capable of handling >=150mA (5VDC) across its switch, controllable by a logic-high signal. I've been looking on digikey, and haven't had much luck finding anything capable of handling more than 25mA (it's also been tough as there doesn't seem to be a way to filter by current/power rating).

Thank you very much for your help!

EDIT:
Thank you all for the help and suggestions!

Umar: No, I meant capable of handling at least 150mA

mkeith: I'm actually rethinking my design, so I won't bother posting my very rough draft schematic

Alex Hajnal: I hhd tried that on Digikey but with no success, thanks for the mouser suggestion!

Transistor: Yea I realize my typo, that's what happens when I try to do stuff quickly late at night ;)


texts: Voltage dropping capacitor doesn't drop the voltage?

texts:
I am going to make a transformerless power supply.
Here I am using a 105J 400V polyester capacitor to drop the voltage.
I connected the capacitor and AC main in series, but when I measure the voltage across the capacitor using a multimeter, it shows same as 220 to 230V AC and no voltage drop there.
What can I do for that? Has the capacitor gone mad?


texts: HC-05 Bluetooth module not responding to certain commands

texts:
I've got a problem with my HC-05 BT module. I'm talking to it from my PC via USB/UART converter. When it's in slave mode I can link it with another device, send data using module's and converter's virtual COM ports. But some AT commands seems to be not working. For example, I can't check the module's name. Inquiring also does not work. Here is a sample "chat" I'm having with HC-05:

AT
OK
AT+VERSION
+VERSION:2.0-20100601
OK
AT+UART
+UART:38400,0,0
OK
AT+UART=115200,0,0
OK
AT+UART
+UART:115200,0,0
OK
AT+NAME //No respond to this command
AT+NAME=HC-05
OK
AT+CLASS //No respond
AT+ROLE
+ROLE:0
OK
AT+ROLE=1
OK
AT+INQM
+INQM:1,1,48
OK
AT+STATE
+STATE:PAIRABLE
OK
AT+INQ //My phone has BT and visibility on, so I can test this It didn's find any devices, no "OK" message is shown neither
AT+INQC //About 5 minutes later, I want to cancel inquiring, no respond to this command too
AT+STATE
+STATE:INQUIRING
OK

When I turn the power off and on, it's still inquiring, the only way to stop it is to change it back to slave. Am I doing something in the wrong way? Or my module is simply broken? I'll just mention that it's new, I've unpacked it like 2 days ago.
Anyway, thanks in advance


texts: Does Inductor saturation current play an effect in SMPS design?

texts: I am currently designing a DC-DC Buck power supply and now that I have chosen values for all my resistors and capacitors, I am looking for actual components. I was wondering if the saturation current of the inductor is an important parameter and whether I should scale it to my desired Iout or to some other parameter?


texts: MOS differential amplifier question please help

texts:
A MOS differential amplifier with IT = 0.4 mA is shown in the figure. Assume γ1 = γ2 = 0 , λ1 = λ2 = 0, RD1 = RD2 = 2.5KΩ, VT0 = 0.7 V, μnCox = 100 μA/V^2 ,
(W/L)1 = 24 and (W/L)2 = 26.

(a)Estimate the value of the input differential signal Vid = VGS1 - VGS2 , that causes differential output voltage equal to zero.

(b)Estimate the value of the input differential signal Vid = VGS1 - VGS2 , that causes ID1 = 0.7IT.

(c)Estimate the common mode gain of the circuit, if the channel length modulation parameter of the transistor realizing IT is 0.05V^-1.

(d)Estimate the CMRR if RD1 = 2.5KΩ and RD2 = 2.6KΩ.


texts:
We use laplace transform to convert time domain differential equation to frequency domain algebric equation. Due to this the equations become easier to solve.

But I am not able to analyse the s-domain like we are able to do with time domain. So I want to know the significance of s-domain and how do we analyse it.


texts:
I'm about to build a pid heating controller with a 1kW heater and a solid state relay.

The ESP8266 can go down to 1Hz pwm frequency.

So hopefully I can vary the number of active cycles per second, but turning it on and off every second.

Would it create more wear and heat on the solid state relay, or should I do manual pwm over say 10 seconds?

Any concerns about switching noise can be discarded, it is only to be heard by the tomatos at night, and I don't think they mind.

Edit: The specs say it is indeed a zero-crossing SSR, with a voltage drop of 1V. 1Kw at 230V gives approx 5A, I wonder if a heatsink is required for the 5W. It is only temporary for around a week, and will be lying on a concrete slab.

edit2
The ESP8266 appearently can't do 1Hz pwm; I have to go manually. However, the relay does seem to be able to do quite fast (i.e. a few cycles) switching.

Follow-up:
Using a pulse cycle of approximately 3 seconds, a proportional regulation of 1C responding to 0 to 100%, adding a factor for compensating for loss to outside of "tent" to greenhouse, and an part of integrating the error, I got the air temperature inside of ±0.04C, measured with a BME280 sensor. Most impressive.

(The tent was a tomato-incubator, a 6m² plastic tent inside a larger greenhouse, the purpose to keep the temperature higher than 10°C at night)


texts:
Is there a model to describe the behaviour of a power transformer?
Ideally in regard to several physical quantities. Is there something, even something basic?

add-on: I'm not looking for an electric circuit but for a mathematical description how a transformer behaves in dependency on oil temperatures, hot spot temperature, gas analysis, bushing monitoring, voltage loads and currents and what is left.


texts: Multichannel RF transmitter design for 315MHz and 433MHz

texts:
first time designing RF, so pardon my ignorance.
I want to design a ASK/OOK transmitter board operating on both 315Mhz and 433MHz ISM band frequencies. I have a MCU onboard that generates the data to be sent.
I am hoping to use "data-in RF-out" transmitter IC like MICRF112 along with passive components and crystal.

Is there a way to use a single transmitter IC and have the RF-out switched between the 315MHz and 433Mhz RF arms. I think it may not be possible as the crystal that goes along with each frequency is different.

What would be the recommendation to minimize the BOM here - as most of the non-RF components are identical between the two transmitters?
Thanks!


texts: Characersitics of a traveling wave on a half wave dipole antenna

texts:
For a center fed dipole antenna when operated at resonance, the AC electric potential applied at the feed point results in traveling waves of AC current which emanate from the feed point out towards the two ends of the antenna. When the traveling waves reach the ends of the antenna they are reflected back towards the feed point where they arrive in phase with the applied AC wave form. At the feed point then the voltage and current are said to be in phase, there is zero reactance in the AC impedance presented at the feed point, and the antenna is resonant.
I am very confused about the relationship between the applied AC electric potential, the traveling wave of movement of charge, and the amplitude and phase in time and space of the current and voltage at the feed point and at each point on the antenna.
I have searched endlessly on the internet and have found it astonishingly difficult to find information on this subject.
I am not looking a for picture such as this :
https://en.wikipedia.org/wiki/Dipole_antenna#/media/File:Dipole_antenna_standing_waves_animation_461x217x150ms.gif
The explanation given in Wikipedia doesn't come close to answering my questions.
Can anyone please either explain to me without using extensive math the exact details of the traveling wave mentioned, in terms of phase in space and time and the exact relationship between the traveling wave of movement of charges, instantaneous current, voltage and phase in time and space with respect to each other and to the feed point, or point me in the right direction where i can find an explanation ?


texts: Rauch section: determining output voltage when we have a constant input

texts:
I was asked to determine the output voltage for a constant input of the following Rauch section

(note that the input is on the left and the output is on the right)

This is looking too easy, that's why I'm questioning myself. If we put a constant input the capacitors behave as open-circuits. Therefore the mesh containing the input voltage is decoupled from the circuit. Therefore everything on the left of \$R_7\$ can be ignored. Now \$R_7\$ is the only thing connected to one of the op amp inputs. That means the current through \$R_7\$ is zero, and we can replace it with a short-circuit.
Therefore we can use KVL equations and determine the output voltage

$$V_{\text{out}}=R_9 I$$
$$12=(R_8+R_9)I$$

And that means that \$V_{\text{out}}=6\text{V}\$.
Is this correct? It seems correct but I feel that I'm missing something. I know that in my analysis I'm only using the "ideal op amp" model, but I guess that's what we're supposed to do.


texts:
I am using an LTC2945IMS to monitor power in a design I am working on. It uses i2c to communicate with a MCU and must be isolated. The chip has two separate pins for the data line (SDAI and SDAO) for input and output data. This is to make isolation easier. Below are some isolation circuits from their app note.

I already had an optoisolator in my circuit so I wanted to re-use the part here to avoid adding a line item. However since it is not inverting like the one in the app note I had to wire it a bit different (in order to combine the two data lines into SDA). My implimentation is below.. But I'm not sure if it is equivalent to what they were doing. Do you think this will work or am I missing something? Thanks!


texts:
Hi!

I got a simple problem. My objective is to measure voltage and power factor of a 16V AC through a differential ADC (ADS1115) that measures voltage difference between 2 channels. I only managed to measure current accurately through a CT.

In the positive cycle of the the circuit shown, the voltage across the 1k resistor is 1.45Vp which is measurable. In the negative cycle, the voltage across the resistor will be -14.54V which will burn the ADC.

Hence, how do I modify this circuit to achieve a safe voltage measurement? I will need to detect the waveform at point 0V in order to compare it to the current then measure power factor. I thought of connecting A2 to the ground of the DC supply instead of the nuetral, but I was not sure if that's the right approach.

Sorry i'm a beginner. Any input/ advice will be highly appreciated.


texts:
I'm in the process of creating my first 433mhz RF transmitter with a PT2622 encoder & SAW Resonator.  I included a portion of my schematic below that shows my PT2622.

Does my schematic look correct or am I completely off?

This circuit is causing me a lot of headaches! I can't seem to find any examples online of one being used with a PT2622.  The PT2622 datasheet shows an example circuit (below)...but they use an LC circuit rather than a SAW...What could I "take out" of this example and replace with a SAW?


texts: Why AM is preferred over FM in long distance communication?

texts: In almost all long distance communication AM is preferred over FM. Do type of modulation has anything to do with this or it is just depending on transmitting frequency?


texts: STM32 - Slave timer with the same clock as the master timer?

texts:
I try to synchronize timer1 and timer2 on an STM32F4 uC. So far, I could slave the timer1 in update mode, such that the clock is always updated when timer2 has an overrun, but for my application i need timer1 and timer2 to always have the same CNT value. How can I achieve that?
I'm starting both timers with:
  HAL_TIM_Base_Start(&htim2);
  HAL_TIM_Base_Start(&htim1);

I'm using CubeMX for the settings and my current settings for the timers are:
  /**
  * @brief TIM1 Initialization Function
  * @param None
  * @retval None
  */
static void MX_TIM1_Init(void)
{

  /* USER CODE BEGIN TIM1_Init 0 */

  /* USER CODE END TIM1_Init 0 */

  TIM_SlaveConfigTypeDef sSlaveConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};

  /* USER CODE BEGIN TIM1_Init 1 */

  /* USER CODE END TIM1_Init 1 */
  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 9;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 5000;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }
  sSlaveConfig.SlaveMode = TIM_SLAVEMODE_EXTERNAL1;
  sSlaveConfig.InputTrigger = TIM_TS_ITR1;
  if (HAL_TIM_SlaveConfigSynchro(&htim1, &sSlaveConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_ENABLE;
  sMasterConfig.MasterOutputTrigger2 = TIM_TRGO2_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_ENABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM1_Init 2 */

  /* USER CODE END TIM1_Init 2 */

}

/**
  * @brief TIM2 Initialization Function
  * @param None
  * @retval None
  */
static void MX_TIM2_Init(void)
{

  /* USER CODE BEGIN TIM2_Init 0 */

  /* USER CODE END TIM2_Init 0 */

  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};

  /* USER CODE BEGIN TIM2_Init 1 */

  /* USER CODE END TIM2_Init 1 */
  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 9;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 5000;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
    Error_Handler();
  }
  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_ENABLE;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_ENABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM2_Init 2 */

  /* USER CODE END TIM2_Init 2 */

}


texts: Replacing left logical shifts with other instructions in MIPS

texts: So let's say that we have two registers $s0 and $s1. Register $s0 can take values from 0 to 31 and is used to show how many bits register $s1 will be shifted left. How can i do this without using sll or srl. I know that left logical shift by n bits is the same as multiplying with 2^n. This exercise gives a hint that this can be done with 4 instructions only. Both registers are 32-bit.


texts: How to implement Ad Hoc on Radio Frequency node?

texts:
i want to implement RF based network as indicated in below figure

Node is Basically Radio Frequency Transceiver i.e Si4432 interfaced with C8051 Micro controller . These nodes are simply Act as a Transceiver's .

Simple Concept behind the Project is that data packet from Tx node is transmitted to reach Rx node but due to the more distance repeater's added between Tx and Rx node .

So if i want to increase distance then i have to add repeater node
into the network and i want to add this node using add hoc   concept
so i want some valuable suggestion , study material regarding this ,
and do i need to implement routing protocol for this ?

and sorry for my poor English    !!!!


texts:
I'm working on a brushed dc motor driver and I have to monitor the current. so I use ACHS-7121 current sensor. This sensor convert +-10A into 0V to +5V and have +2.5V in zero current.

Now I want to shift this to 0v to 10v without including the current direction. It means that the sensor shows that 0V to +2.5V means the current is negative and +2.5V to +5V the current is positive. But I want the op-amp map the values that include negative current (0V to +2.5V) on positive values and ignore the current direction.
\$ V_O = |V_I -2.5| \times 4 \$

I found difference amplifiers such as AD8276 but I'm not sure about that if it works for me or not if I use single positive supply.
Can anyone suggest another solution or confirm that AD8276 works fine?


texts: I ordered a few of these! , turns out they are a lot smaller then I planned (they are the size of a small ant). I was wondering if anyone knew where,if, I can find larger, preferably dime sized prototyping multiplexers? Or some piece of equipment that does a similar job.


texts: During a fault, how does current flow through the earth wire when the earth wire has no return path? Doesn't the earth wire in earth grounding terminate at a copper plate located deep underground, making the current flow unidirectional with no return path?


texts: How do I extend the output (high) time of my circuit (retriggerable)?

texts:
I need help with the design of a timer delay circuit for the output of a sensor circuit which can keep the output HIGH for an adjustable time range (about 1 to 10 min), after the digital output of the sensor circuit goes LOW.
Also, the timer should be restarted automatically if the output of the sensor circuit goes HIGH again in the middle of the timer operation.

I saw many different power off delay timer circuits which used the 555 IC, for example, this circuit, but I can't find a resettable timer circuit.

More details: in my case the sensor circuit is a temperature circuit with a LM35 sensor and after it triggered on adjusted temperature, the output went HIGH  (12V) and if the temperature suddenly drops below the trigger point, the output will go LOW as well(it contains hysteresis). I need a time delay after the output of the temperature circuit in order to keep the output HIGH for the adjusted time range, and, if the output of the sensor circuit goes HIGH again, the timer interval's must be restarted and it must wait  until the signal goes LOW again(like in the motion sensors's delay circuit which id active while it's sensing motion)

-I know it is easy to do it with a microcontroller but I still need to learn   more programming .
-It's not possible for me to learn programming at the moment ,so maybe a retriggerable monostable is what I want ?

Below is diagram of the temp. sensor:

simulate this circuit – Schematic created using CircuitLab

schematic according to RoyC answer:

simulate this circuit


texts: PIC16F18855 runs at half the clock frequency when I turn it off and on too quickly

texts:
I have a board that has a PIC16F18855 running at 8MHz from an external crystal. Most of the time it works fine, but if it gets rapidly power cycled it will restart at 4MHz. The main symptoms of this are things such as the UART baud rate and the PWM frequency dropping by half.

More specifically, if I flick the power switch on and off in less than ~2 seconds, it will run at the lower frequency. Longer and it works properly. When I program the board, it restarts at 4MHz, meaning I have to physically turn it off and on before it will work. If I short the MCLR pin to ground, the behavior is inconsistent - sometimes it will start at 4MHz and but usually it will start at 8MHz.

I have also had one instance where it was taking substantially longer, where turning it on within 10 minutes of turning it off made it start at 4MHz. I'm not sure if the problem is related, but I'm not able to reproduce that error at the moment.

From probing the OSC2/CLKOUT pin, I can see that the crystal itself is still running at 8MHz. With the probes I have I can't probe the OSC1 pin without it resetting the micro.

EDIT 1:

When the board is running at 8MHz, its OSCCONx registers are:

OSCCON1: 0x70
OSCCON2: 0x70
OSCCON3: 0x10

and when its running at 4MHz they are:

OSCCON1: 0x70
OSCCON2: 0x60
OSCCON3: 0x00

So it's running off the HF internal oscillator. Will look at this a little closer. Knowing this I may be able to come up with a work around, but I'd rather figure out the cause of the problem.

OSCFRQ = 0x02, which is the setting for 4MHz, so this is definitely whats happening. Terrible workaround would be to set the OSCFRQ register to the 8MHz setting, so it works the same either way, but then I lose the precision of the crystal. That may not ruin everything, but I have some timing sensitive things so I prefer to use the crystal if I can.


texts: Troubleshooting component failures in a metal box (that's next to an air band radio transmitter)?

texts:
I have a little project that's been experiencing component failures, and I'm having trouble figuring out what to do about it. I think the issue is ESD but that's just a guess. Also I'm a total noob so, whatever's happening, the root cause is definitely that I did something dumb, but hey, "experience is a series of non-fatal mistakes."
I've got an SBC and a few breakout boards in an aluminum enclosure with rubber feet. The breakout boards are a segmented LED backpack, an LCD character display, a differential I2C driver, and a LoRa radio. Power comes from a two-prong DC wall wart into a plastic barrel jack; from there a buck converter/switching regulator produces 5V.
There's an environmental detail that may or may not be important: the box is sitting on top of an air band (VHF, AM) radio transmitter—a fixed unit, not a mobile/handheld—connected to an antenna outside.
The first failures I had were the differential I2C driver getting fried. This happened twice. On a lark I added a connection from the case to ground at the barrel jack, along with a diode to make sure transients go to the wall wart and not to the ground pin on the buck converter, which is also connected to the jack. I haven't had any issues with I2C chips dying since doing that. (I'm not sure if this setup makes sense. Power kind of scares me, and like I said, this was a lark. But it seems to have worked?)
Now I've got a problem with the LoRa radio. It went very suddenly from working fine to completely unresponsive, and I suspect it's the same thing that was killing the I2C chips. It's connected to an antenna on the outside of the case, and the connector is a metal through-hole type. In other words, there's an electrical connection between the connector and the case. I don't know if that was the right thing to do either; you can add RF to the list of things that scare me.
In any event, I'm wondering if maybe whatever was zapping the I2C chips has now gotten the LoRa radio through the antenna connector. Before I start futzing with things and buying more parts though I'd really like to nail down exactly what's going on here, and clean up any blunders I've made along the way.
Does anything stick out to you experienced folks that might be the cause of these failures?
[Edited to add:]


texts: How to measure small AC currents from mains?

texts:
I want to measure AC current from the mains connected to an isolated source - such as a single 10 watt bulb. The standard multimeter measures the current only in DC, so I needed a device that provides AC current measurement (though, I am trying to avoid buying an expensive multimeter.)
I looked at many current transformers such as this:

However, these have a range of 30A measurement capacity, whereas the currents I am looking at will be very small (in a few mA.)
Are there any alternative solutions that I can build?


texts: I am working on a project and trying to figure out the appropriate circuit protection scheme. We have 2 AC/DC battery chargers that will be housed in a single enclosure, being powered off 220VAC. Meanwell DBU-3200. The spec sheet says AC current typical 17A, inrush current typical 55A. I'm not familiar with best practices here, but it seems like a breaker at the line input to feed these devices would make sense. But what value? Should it be a single breaker? Or 1 upstream breaker and then 2 individual downstream breakers? I'm assuming any breaker used should be 2-pole? Any thoughts or suggestions would be helpful!


texts: Can I run a 2xAAA battery device on a 5 volt USB device without the motor burning out?

texts: Just wondering and I don't want to waste parts if it will just burn out if I have it plugged in too long.


texts: Van with Solar power but no auxillary battery and only on sunny days. Do I need switches and isolators?

texts:
I have a 2018 Ram Promaster city cargo van with OEM 12v 70AH 120RC Sealed Led acid battery and a 160a alternator.

Sitting on top of the battery I have a 1200 Watt pure sine 110v inverter connected with 2 gauge wires and then have a 12 gauge run to the back of the van. I also have a single 12 gauge line running from the batteries hot to the middle of the van that gives in an always on 5v USB source.

To date, my power needs in the van are minimal. when I need 110v, it's for very short periods of time (15 minutes or less) to run 500-800w appliances & tools and when I do I am usually parked with the engine running.

When I've slept in the van overnight I run a 1a 5v fan from 10pm to 6am.
My battery has never been below 10v, but I do plan to install a 10v low voltage disconnect to the 12v hot line to be safe. My inverter already has a 10v low voltage disconnect.

However.. In the future, I would like to install a 200 Watt 18v 6a (max) solar flexible solar panel on my roof. It might be overkill, but the 32w x 42l size fits perfectly and will block a lot of sun and help with mid day interior temps. As I ponder how to benefit from this free power, NOTE: I am NOT looking to install or sleep with batteries in the passenger area. I would like to install a ceiling vent rated at 12v 3a when on high (specially a Max Air 14x14 fan 12v 900CFM fan). While I think I can easily run the fan overnight on low (12v 1a) and have no issues starting the van, I would like to run the fan on high (12v 3a) when the sun is strong during the day. Again, I have no plan to drain my 12v battery like a deep cycle. And finally, as I anticipate having more power than I need during the middle of the day even with a 12v 3a fan running, I would like to freeze the content of small 50w 12v freezer (Alpicool C15) during the day (9am-9pm) and then keep it off and closed overnight. I would anticipate interior ambient temps to range from 90F midday to 80F night. The ultimate goal being to keep the van cooler during midday and keep Milk and Cheese from going bad for a week.  In a pinch I can always find some ice if need be.

So my  questions...

(1) How can I connect the solar panels 20a charge controller (200W 18v 6a panel)to my battery so as not to impact/interfere my cars charging system and visa-versa? do need a switch or isolator? I am presuming my charge controller will have some protections like a reverse diode for night fall leak back.

(2) If later on I want to upgrade my battery to a new dual purpose 12v 100AH 200RC 830CCA battery will my 160a alternator be okay with having to work harder to recover for longer periods of time? Again, I do not anticipate ever draining my battery like a deep cycle battery. I will tell you I have experience with another automotive 160a alternator and a 90AH/140RC battery (running 2 amps overnight) that would get close to 10v many times and never had any issues.

(3) also wondering about Charge controllers that have an output ports. Are their controllers with output ports that can be regulated to 12v? how are they different from connecting directly to the battery? I might not be understanding schematics, but seems like there are controllers that offer Low Voltage cutoff and hours of operations from those ports.. is that right?