texts: MC34063 - Stucks with too much parallel devices

texts:
I've a circuit schematic:

I power my circuit using only PWR+ and PWR- at 24V.
When my power supply powers only one circuit or two, in parallel mode, I don't have any problem.
When I attach more like 3 circuits, sometimes at power ON all this circuits doesn't goes on.

I've measured voltage on PWR+ and PWR- when they stucks and all of them have 4.8V between PWR+ and PWR-. I've removed FUSE, D3 and V4 but nothing. Also reduced 100uF to 2.2uF and nothing.

I've supposed that if the voltage is too slow to rise on this device, it may stuck at certain point with a voltage at 4.7V (and output at 2v).

How I can solve or made immune this device to this behavior?

Also I can't understand how this device reduce my Vin from 24v to 4.8v, since I've 24V on my power supply instrumentation.


texts: N-mosfet detects the proximity of my hand. Can it be useful?

texts: When the gate of an N-channel MOSFET is not connected, it allows current to pass from drain to source, and the amount of current depends on the distance between my hand (or a piece of metal touching my hand) and the MOSFET (or a wire connected to the gate). Are there any designs that take advantage of this?


texts: Trying to split the current output of an LED driver

texts: I am currently using an 8 channel LED driver wher I have set the outputs to produce 20mA of constant current. Problem is I have 11 LEDs to drive. So I have decided to connect two LEDs in paralelled to each output, and then finally on the 6th output connect a single LED. I have 100Ohm resistors in series with each of those parallel resistors, and my LEDs can handle up to 30mA of current. However I want all 11 LEDs to have the same brightness, more or less. How do I get that 11th LED that is alone to split its current in half? Can I put a resistor in parallel with that LED? if so how do I calculate the resistor value to get it as close to 50% as possible, or should I use dummy LEDs to put in parallel?


texts: Driving two parallel LEDs with PWM brightness control and a "LED selection" signal

texts:
I am working on a LED board for a flashlight powered by a 3.7 V battery. The flashlight have a dual light feature : both white and UV light are available.

Four signals are sent to this board by the motherboard : the VCC (3.7 V), GND, a "Led selection" signal (to switch between the UV LED and the White LED) and the PWM signal to control the brightness.

The control signals are provided by a PIC16F887, which is also powered by 3.7 V from the battery.

Here is the desired operation:

When the LED-selection signal is == 0, the white LED is lit / When
== 1, the UV LED is lit.
The PWM signal is common for both LEDs, so that when the current operating LED is switched, the duty cycle is applied to the other one without having to set it again.
Finally, the current is taken from the VCC, so the PWM is applied to a MOSFET that will allows the current to flow through the currently active LED at the desired frequency and with the desired duty cycle.

I also want to use as few components as possible to make the board compact (it must be fitted in a limited mechanical package: 39 mm x 23.5 mm)

Here is a picture of my actual circuit. I use three MOSFETs because the current drawn will be greater than 200 mA (at least for the white LED).

My questions are:

Is the actual circuit correct in its structure? I tried to simulate it in Tina and it seems like it is working as I want (I replaced the "LED selection" by a On/Off switch and the PWM by a clock).
I am not sure of the wiring of the PWM mosfet (Q1). Normally, the source should be wired to the GND as the transistor is N-channel. I don't really know if a P-channel mosfet would be better for this application. However, I've read that P-channel MOSFET are used if the signal voltage is of the same range as the power supply voltage (which is the case here) and to connect the source to the positive side of the load so I am considering to replace Q1 by a P-channel MOSFET. However, again, the simulation shows no problem on the operation of this circuit (which I doubt being accurate).
Should this board have its own power supply rectifiers so that the LED are fluently supplied? The wires between the motherboard and this one will not be longer than 5 cm so I suppose that it should not cause problems.


texts: I just bought an MCP23017 port expander and hooked it up to my an Arduino card. I used the sample code to turn on four LEDs when the program launches. Works great, except that after several minutes all the LEDs switch off and won't come back on until I actually power down the entire card and plug it back in (hitting reset won't cut it). I've checked and rechecked and everything else looks fine. Is it possible I've got a bad I2C chip?


texts: How to implement a flip-flop with synchronous and asyncronous reset?

texts:
The flip-flop of FPGA (at least those from Xilinx or the ECP5 family from Lattice) support both synchronous and  asynchronous reset (extract from the ECP5 datasheet :  "There is control logic to perform set/reset functions (programmable as synchronous / asynchronous)".

The only way I can think of is to have a sync DFF and an async one, and a mux for selecting the data from one or the other:

module DFF(output q, input d, clk, rst, is_rst_sync);
    reg q_from_async_dff;
    always @(posedge clk, posedge rst)
        if (rst)
            q_from_async_dff <= 1'b0;
        else
            q_from_async_dff <= d;

    reg q_from_sync_dff;
    always @(posedge clk)
        if (rst)
            q_from_sync_dff <= 1'b0;
        else
            q_from_sync_dff <= d;

    assign q <= is_rst_sync ? q_from_sync_dff : q_from_async_dff;
endmodule

But it seems unlikely to me that this is the solution used because of the surface waste.

How this kind of sorcery can be implemented efficiently in verilog?


texts: Charging a 4000mAh Li ion battery using multiple TP4056 ICs

texts:
As single TP4056 IC rated current is 1A,so I was thinking to connect multiple TP4056 ICs in parallel, such that enough current can be sourced to charge the li-ion battery(400mAh) connected.

Here is the schematic I was going through:

Will this circuit work well or does need any changes? And a schottky diode is being used at the input to maintain the supply voltage level at 5v, I'm guessing that it could be for that reason.

Is that 5.5v Schottky diode necessary? Can I avoid that instead?


texts:
I need a transistor as a switch. I need to power a motor with a 9 v battery and on or off the circuit using a 5v signal (from an arduino board). I don't which NPN transistor to choose. (I don't know how to use sandbox properly so there might be some mistakes in the diagram. )
I need a list of NPN transistors suitable for the job. (Sorry it 9v not 12 v). The current through the motor is about 0.75A.Thanks in advance!


texts: Selecting external RAM for an ARM static memory controller

texts:
So I'm going through the datasheet for a device by Atmel (AT91SAM) and it shows the followings:

  This SMC is capable of handling several types of external memory and
  peripheral devices, such as SRAM, PSRAM, PROM, EPROM, EEPROM, LCD
  Module, NOR Flash and NAND Flash.

So that's good as I can get SRAM from Digkey, however there are many types: .

Which one is the right one? Perhaps several? I remember doing these exercises in the university all the time in micro-computer class, but we never talked about which type of exact memory we're hooking up to the 8086 micro :)
I'll appreciate help clearing this up. BTW I see that the bus width is just 8bits so that will also help minimize the selection but the type is still needs determining.


texts: What kind of sensor can determine relative altitude with 50cm resolution?

texts:
I would like to know if you have any idea of what kind of sensor I need to be able to tell the relative position of an Arduino board with regard to another one. I only need to know if an Arduino is above or below another one.

Said differently, I have two Arduino boards and I want to know when one board (placed on an object) is below/above the other board (placed on another object) by about 50cm to 1 meter.

Update:
   @Andyaka and @OliGlaser : no ... I only need it to work when the two boards are 50cm to 1 meter away (bellow/above) from each other.

Here is the application I want to develop: each of the arduinos will be on a goat. And the idea is to know exactly when my male goat is on my female goat for mating.


texts: Automatic on and off bulb using CAPACITOR

texts:
Automatic ON and OFF BULB for specific time only.

Following are considered to achieve the project...

As 12 v is supplied, relay R1 is slowly activated and bulb B1 will glow for specific time T which is dependent on capacitor C. As C is fully charged after sometime, say 5v, it blocks current and hence B1 is off.
In the meantime, R2 is always activated as long as 12v is supplied. Now, as 12v is disconnected, the energy stored in capacitor C is discharged through 87a of relay R2 and B2 now glows for specific time T again.
In short, B1 glows for time T and off when capacitor C is full, and B2 glows for time T only when 12v source is disconnected.

Would like to hear any comments or suggestions to rectify my project in achieving the on and off bulb for specific time only. Thanks.


texts:
I have to design a multilayer Board (8 Layer). This is a part of 4 PCBs in a product with plastic enclosure. The high speed signal on PCB are Ethernet, USB2, LAN and UMTS integrated modem. Product dimension is 4" x 4" x 2" . I'm undecided between two stackup tipology EMC oriented (the product will be tested in laboratory for CE mark).

STACKUP (A)

Signal1
VCC
GND
Signal2
Signal3
VCC
GND
Signal4

Routing layer is formed by pairs signal1-signal2 or signal3-signal4.

High-speed signals are buried between planes, therefore the planes provide shielding to reduce the emissions.  In addition the board uses multiple ground planes, thus decreasing the ground impedance. But (this is my doubt) in this configuration is necessary a capacitor (VCC to GND) near the signal via, in order to provide an adjacent return path for the current.

So i want use this configuration

STACKUP (B)

Signal1
GND
Signal2
VCC
GND
Signal3
GND
Signal4

Routing layer is formed by pairs signal1-signal2 or signal3-signal4.
Here high speed signals have the same reference, but i have only one buried capacitors and I fear that the signals are poorly shielded.

How is critical the return current in Stackup A? I suppose that the best in my application is stackup (B).

Thanks and best regards.


texts: How does sonar locate an object in three dimensional space to output data for imaging?

texts:
I'm working on a small learning project where I want to connect sonar back to an android phone over bluetooth.  I'm working with an hc- sr04 that a friend gave to me and I'm trying to piece together how this would locate an object in the water.

I understand the basic concept, speed of sound, pulse emitted, calculate the time to find the distance.  What I'm lost on is how you can actually locate where the object is relative to the sensor.  If the only thing I know is the distance the object could be anywhere on a sphere on that radius within the viewing angle of the sonar.

Would I need multiple sensors to use triangulation?  Or are there sensors that can tell me more information about the echo?


texts:
I am trying to select a diode to prevent my circuit from being damaged by the collapsing magnetic field from the solenoid in my circuit. Solenoid power  will be switched off through the actuation of either a relay or darlington transistor which is controlled by an arduino.

Specifically, I am looking at this solenoid: https://www.amazon.com/uxcell-JF-1578B-Linear-Solenoid-Electromagnet/dp/B07DC95KRX

It's rated at 192W, 8A and 24V. My main question is will the current that the flyback diode experiences at shut off be 8A? If so, does this mean that I must use a flyback diode that has a higher rating such as a 10A capacity?

I have been looking at either purchasing a IN4007 Plastic Silicon rectifier or a MIC10A10 (10A, 1000V) general purpose plastic rectifier. I am having difficulty finding specs for voltage drops and resistances for the diodes. My thought is that they change given the temperature, but I haven't been able to find much information on them. I am hoping to come up with an equivalent circuit for when the power supply is switched off.

It would be nice to have fast switching and thus have been looking into Schottky diodes, but honestly, first I need to figure out the amperage and voltage requirements for the diode.

Edit: Specifications: The solenoid will act as an actuator for a flipper mechanism (similar to a pinball machine). Once the plunger has fully pulled down I would like it to rise back up quickly without holding. I am not sure how long this is just yet, as I do not know the mechanical dynamics of the motion yet (time to plunge).

Another hope is that I can use my arduino to specify a PWM. Any leads on controllers that will allow me to do this would be great. The game will have LEDs that will act as a "striking power meter," thus if the button is hit at a weak power, then the solenoid will not plunge.

Any help would be appreciated!


texts: Creating an electronic switch for controlling a headset's control button

texts:
Some background information

I have an Android based phone. The headset that came with it uses a TRRS connector. We normally have a button on the headset which when pressed, would allow you to play/pause or pick up calls.

You can read about how this works here: http://www.wisebread.com/build-a-cable-to-control-your-android-phone-while-you-drive

The sleeve of the TRRS and the ring next to it are normally open. The open circuit voltage that we get is around 2.5V (which the phone gives). When we press the button, these two connections essentially get shorted and we get a very small potential difference between these two pins. That's how the phone knows that the button was pressed.

My problem

Now, I want to control this button electronically using my microcontroller (MSP430). So, I decided to use an electronic switch.

My proposed circuit http://img832.imageshack.us/img832/2576/51364385.jpg

In the above switch, the 2.5V source on the left and the 33k resistor corresponding to it is my phone. The BJT is used for switching, and the 3.6 voltage source on the right is a high output from my micro-controller.

This is the circuit I had initially thought of (Of course, I'd add current limiting resistor in the base). The problem is, when the BJT is on, I get an expected drop of about 1.026V in the CE junction. So, the ground wire and the wire on the top are not exactly shorted, even though the BJT allows current to freely flow.

What I need

I'd like to short top write to ground electronically, just like a mechanical switch. However, is it possible to do it without using relays and other stuff. Or, people who already have knowledge working with headset buttons, can you provide me with another solution?

Something I haven't tried

A spare TRRS connector is hard to find here. So I haven't tested anything practically. SO, I'm not sure if the sleeve and the ring need to be voltage shorted, or just need to have current passing through them.

Thanks.


texts: Voltage drops on circuit powering a servo motor. Is there a solution?

texts:
I have a 5 Volts, 4 Amps power supply that gives power to a Raspberry Pi Zero W (120-230mA at 5.19V), and a servo motor with these specifications:

Operating Voltage Range (Volts DC)  4.8V ~ 6.0V
Current Draw at Idle                8 mA
No Load Operating Current Draw      240 mA
Stall Current Draw                  1,200 mA
Maximum Torque Range oz. / in.      42 ~ 49
Maximum Torque Range kg. / cm.      3.0 ~ 3.5

Sometimes it is able to perform its action, and some other times it stalls half-way with the voltage dropping in the 3.5 V - 4 V range. Even though my power supply should be good enough in theory, I thought that adding a 4 F (16 V) capacitor could alleviate the problem, but it does not seem to make any difference.

Do you think the voltage drops because I am using the servo to perform a task at the limit of its strength, or that the servo stalls because it does not have a good enough power source?

Unfortunately, I do not have any tool to measure the torque of the item the servo is rotating.

Servo Motor: Hitec 32085S HS-85MG Metal Gear Micro BB HS/HT Universal Servo

Please bear with me. I have some electronics notions, but I am no electrical engineer. If you think I posted this message in the wrong stack, please let me know. It just seemed the most appropriate one to me for this question.


texts: Onboard temp sensor for household thermostat - accurate enough?

texts: Many microcontrollers, such as the TI MSP 430 have an on board temperature sensor. If one is designing a typical smart thermostat for heating/air conditioning is this sufficiently accurate or would there be any practical advantage to using an alternative sensor?


texts: How to determine the power rating of an output LC filter

texts:
I am trying to design a Class-D Amplifier using the TPA3116D2 IC chip. Using the typical application circuit provided by the datasheet on Pg.26

Everything is going well with the support circuitry but what's getting me all stuck is the "OUTPUT LC FILTER" section.
I am not sure the power rating of what the components is suppose to be as its the ouput stage assuming a lot of current is going to be drawn.
Currently I have the amp setup to output a ~14.14VRms into a 4Ohm load, which should draw a ~3.54ARms
getting 50W out of it.
Does anyone know how to determine the power rating of the components mentioned?


texts: Which parts to trade out of a PWM for higher HP

texts:
My neighbor owns a scrap metal yard which he lets me pick over as needed. I have an assortment of DC motors from 4 250W 24V motors to a 2.5HP 90VDC from a treadmill. I am looking at building a go kart for myself and my kids to play with but need some help with the PWM controller.

It would be great if I could find a single design that would work for all standard DC motors (not brushless of course) and just vary the input voltage from 12-90V. My understanding is that I can run a 0.25HP motor on a 5HP controller, but not the other way around. Assuming the cost isn't significant to trade out some MOFSETs it would be great to have a single design to replicate as needed.

I have seen several sets of plans such as http://www.instructables.com/id/How-to-Make-an-Universal-DC-Motor-Speed-Controller/ that use a 555 timer, one that uses a 556 timer and so on. Now my thinking that that there are many components in the plans that would stay the same such as the potentiometer and timer since those won't have tons of amps flowing through them, but if I get larger MOFSETs, do I need to get larger capacitors and resistors?

I am not an EE, but I would imagine there will be a couple things to consider when trading an IRFZ46 (https://www.digikey.com/product-detail/en/infineon-technologies/IRFZ46NPBF/IRFZ46NPBF-ND/811998) for a beefier MOFSET such as:

https://www.digikey.com/product-detail/en/texas-instruments/CSD19532KTTT/296-43211-1-ND/5764599

Now I am hoping to not be building a 100HP controller like this guy: http://www.instructables.com/id/Homemade-100-HP-Motor-Controller-for-an-Electric-C/ since it cost him a few hundred, but I figured that with the plentiful nature of DC motors in my life, buying them retail would really add up.

The first link for the universal controller looks pretty simple, what do I need to do to be able to power a large HP motor with it?

In other news, my neighbor just bought a bunch of electric trains from the city which are getting scrapped which have about 250 300 amp hour lithium batteries weighing 156lbs each. I thought I might just throw that in behind the seat of the go kart. I figure if it puts out enough amps, I could convert the voltage from 12V to anything needed for the controller without needing to wire them in series.


texts: lower limit to lower feedback resistor value in a transimpedance amp?

texts:
The upper limit to the gain setting feedback resistor value in a transimpedance amp is dictated by op amp rail voltage but is there lower limiting factor for the value also?

I changed this feedback resistor value to a much lower value in an audio DAC with very high current output (~30mA), this reduced max gain to safe levels  as desired but caused caused severe distortion and I'd like to learn why.

Op amp is OPA1612, the recommended op amp in DAC's datasheet.

DAC is AK4499


texts: ESP8266 - free GPIOs for relay switching

texts:
I'm using a NodeMCU as shown below, to switch 4 relays using Micropython.

For that purpose I need 8 GPIOs (4 for relay and 4 for switch buttons).

For the first pair (UP/DOWN) I use pins D1, D2 - for output, and pins D3, D4 for buttons inputs.

The code seems to work OK, and quite simple. When I assigning 4 more GPIOs for the exact same purpose - I get an error , that I think concerned using other pins :D5, D6, D7, D8  - I'm guessing D7, and D8 are the ones causing the trouble ):

1) When using D7, D8 as an input - D8 is pulled low ( i guess in hardware) and not allow to use it as a switch.

2) When I'm using it as an output - I can rshell back in, and I have to erase flash of esp8266.

My question is - is there a way I can use ANY additional 2 digital pins for that purpose?


texts: Calculating Maximum execution rate of instructions

texts:
Im working on the following question:
Suppose an instruction can be carried out in 3 stages, the stages taking 3 ns, 7
ns, and 10 ns, respectively. (a) What is the maximum execution rate without
pipelining? (b) What speedup is possible with pipelining?

I have managed to get the following answers is it correct?
a) For a non-pipeline system these 3 stages can be carried out one after another.
Total time required is (3+7+10)ns=20 ns
Now to computer 100 instruction time required = 100*20=2000 ns

b) A very interesting feature of pipeline is that in pipeline all the stages have same length. In the given problem we have a stage, which takes 10 ns, which is largest. We will equate is value with the pipeline stages. So now each pipeline stage is of length 10 ns to execute. Now total latency time= 20*2 ns= 40 ns.
There is an overhead associated with this. Lets assume overhead is of 2 ns. So total time to execute one stage of pipeline is 22 ns. Speed up is (3+7+10)/10=2.0


texts:
I know this topic has already been brought up and I have been going through those posts but I still can't get my UART1 RX interrupt working. What I am trying to do is receive the NMEA string from my GPS module which I can see is being delivered to the UART RX pin after inspection with an oscilloscope.

These characters that I am receiving I want to then display on an LCD display which is a piece of the code that I already have running. What I don't understand is why an interrupt is not being triggered when characters are being sent to the UART1 port? I will attach my main() and ISR routine. Any help would be hugely appreciated.

main()
{
        InitApp();             //initialise ports
        intLCD();              //initialise LCD
        clrLCD();
        putsLCD("Initialising \n \t TCAS");
        INTEnableSystemMultiVectoredInt();
        //UART
        U1MODEbits.UARTEN = 1; //enable UART1
        U1MODEbits.PDSEL = 0;   //8 bits, no parity
        U1MODEbits.STSEL = 0; //1 stop bit used
        U1BRG = 1041; //set baud rate to 4800
        U1STAbits.URXISEL = 0; //interrupt flag bit is set when a character is received

        PORTSetPinsDigitalOut(IOPORT_F, BIT_5);                    //data transmitter
        PORTSetPinsDigitalIn(IOPORT_F, BIT_4);                     //data receiver

        //interrupts
        IEC0bits.U1RXIE = 1;   //enable interrupt
        U1STAbits.URXISEL = 0; //interrupt after character is received

        gpsINITIALISE();        //initialise GPS to receive data
        int check = 0;
        while(1)
        {                   //wait in here for uart interrupt
            if(check == 0)
            {
                sendMessages();  //send message to gps to recieve 0183 message
                check = 1;
            }
        }
}

void __ISR(_UART_1_VECTOR, ipl6) _U1RXInterrupt(void)
{
    putsLCD("interrupt \n \t triggered");
    if(U1STAbits.OERR == 1)
        U1STAbits.OERR = 0;

    if(U1STAbits.URXDA) //check if data is ready to be read
        {
            c = getcUART1();
            while(BusyUART1());
            if(c == '$') //c == $, hex=0x0024
            {
                count = 0;
            }

            if(count < 6)
            {
                dataTemp[count] = c;
                count++;
            }
            else if(count > 5 && count < 80)
            {
                if(dataTemp[4]=='G')
                    GGA[count]=c;
                else  //error

                count++;
            }
        }

    //parse GPS
    parseGPS();
        GPStest();              //function to test GPS
    IFS0bits.U1RXIF = 0; //clear RX interrupt flag
}


texts: Does layer order matter on multi layer PCB?

texts:
I have a 4 layer PCB with the following planes...

Connector (Top): Holds all traces going from connectors to components.
Signal
Ground: Coper filled completely.
Power (Bottom): Coper filled for +15V and traces for -15V

Does it matter if the bottom layer is the power layer and that the ground layer is adjacent to it on the 3rd layer?

Some notes about the design:

Uses +15V -15V
Signal is audio with some op amps.
Basically building simple audio mixer, nothing fancy.


texts: What could cause PIC GPIO pins to fail short to ground?

texts:
I have a PIC18F2420 in a design that has now had two instances of the Port C0 pin failing short to ground. The first instance, we literally finished some testing, and went home for the night. When we came back the next morning, the pin was dead. In that case, it worked for over a week. In the second instance, the pin sat idle for most of a day before failing. When I desolder the PIC, it measures about 1 Ohm, from C0 to the Vss pin.

The only peripheral that uses this pin is Timer 1. It is the oscillator output, and is disabled.

simulate this circuit – Schematic created using CircuitLab

The switching is happening very slowly, < 1 Hz. We measured 275 mV of overshoot on the high to low transition, but nothing significant going low to high. The overshoot is close to the absolute minimum, but is it enough to kill the pin? There is another pin with an identical configuration that is toggled much more often, and it has remained rock solid.


texts: LCD not powering up on a breadboard - is the wiring correct?

texts:
I'm trying to power on a LCD on a breadboard. For some reason, the LCD is not turning on (No backlight). Here's how I wired it and I'd like to know if I messed up on anything:

Datasheet: http://www.lcd-module.de/fileadmin/eng/pdf/doma/dip203-4e.pdf

I've checked the voltages on VDD (Pin 2) and LED Backlight (Pin 17) and they are getting 3.3V. Measuring voltage on VEE (Pin 3) gets about 2V, which I'm assuming is the voltage being dropped from the pot and internal resistor inside VEE.

Before connecting the LCD, I've also measured the current I'm driving on pin 17 using an ammeter on LED B/L+ (17) and it's at 33mA. The datasheet says the maximum current on LED Backlight pin is 45mA so I think I'm safe here. Connecting the LCD drops that current to 0.7mA though.

I haven't wired the data lines yet because I can't even get this LCD to power up.

The LCD was bought 2 days ago, so while not impossible, it's very unlikely this is defective.

Is there anything I've messed up in my wiring?


texts: Derivation of current gain and voltage gain for common base BJT

texts:
For a common base configuration BJT such as the one shown here:

How can I derive the voltage gain and current gain?


texts:
I want to make a new project with AT91SAM9260 in Atmel Studio 7 but it doesn't support the device.

My question is:

Did Atmel make a C library with this device to Atmel Studio 7? If no, what version does this device have ?


texts: How to calculate power balance of a given circuit

texts:
Problem:
I need to calculate a power balance, to check that i have found the correct currents.

I have found that:

\begin{cases}
I_{1}=-2.571 \\
I_{2}=-1.244 \\
I_{4}=1.755 \\
I_{6}=0.42
\end{cases}

The task is to calculate power balance and check it:

I do it using this formula:

$$R_{1} \cdot I_{1}^2+R_{2} \cdot I_{2}^2+R_{3} \cdot I_{2}^2+R_{4} \cdot I_{4}^2+R_{5} \cdot I_{general}^2+R_{6} \cdot I_{6}^2 = E \cdot I_{2}+U_{general}I_{general}$$

\$R_{1} \cdot I_{1}^2+R_{2} \cdot I_{2}^2+R_{3} \cdot I_{2}^2+R_{4} \cdot I_{4}^2+R_{5} \cdot I_{general}^2+R_{6} \cdot I_{6}^2\$ = 727 Watts

Update:

\$U_{general}=-R_{5} \cdot 3A+R_{2} \cdot I_{2}-8+R_{3} \cdot I_{2}+R_{1} \cdot I_{1}=0\$

\$U_{general} = 245.91 Volts\$

\$E \cdot I_{2}^2 = 12.38 Watt\$ and \$U_{general} \cdot 3=737 Watt\$

Sum of power of sources = \$737+12.38= 749.38\$

Consumed power = 727 Watts

Given 3% of inaccuracy, which is 22 Watts, I guess that I solved it right, didn't I?


texts: What is the name/type of this soldering iron tip?

texts:
I have a soldering iron station called Dibotech soldering station 60W which is a temperature controlled soldering station. You can set the temperature of the tip between 50-480 degrees Celsius.
The problem is I can not find the name of the tip to the pen. I contacted the sellers but they had no name for it.
I found 800L-T-B which looks similar but which I can't find the inside and outside measurements of it. Is these standard measurements?
Can I buy a new soldering pen with all the same functionalities and assume it will work? Or are not every soldering station compatible even if the contact is?
Here is image of the tip and it's measurements


texts: Why do people use AT commands in serial communication?

texts:
I need to know why people in embedded systems use AT commands?
When I have asked people say that it is a standard.

So my question is: What does "AT" means? Why do people keep saying it's a standard?


texts: Solid state relay not turning on motor as expected

texts:
I have a very simple control system for two homebrew pumps using a 12VDC control circuit and two (2) solid state relays (https://www.sparkfun.com/products/13015). Specs on the pumps can be found here, they are simple 115VAC motors.

Each relay controls a single outlet to which a pump is plugged in.

When the relay is off, the pump is off. When the relay is on and the pump is plugged in with the relay on, the pump will start. When the relay is turned on while the pump is plugged in, the pump will not start. Unplugging it and plugging it back in will start the pump.

ASCII circuit diagram:

+12VDC          +       ~
---- SW1 -----+           +----------------------
              |   RELAY   |                       HOUSE MAINS (120VAC)
--------------+           +--------- PUMP -------
+0VDC           -       ~

Am I using the wrong relay, or do I need to add a starter capacitor of some form to the pump side of the circuit?

Note: when I replace the pump with a 120V floor lamp, the lamp is controlled as expected, without having to unplug it and plug it back in after the relay is on.


texts: How to plot BER Vs SNR of a received signal

texts:
I am using USRP to transmit and received MIMO frames similar to Wi-Fi standard that I created on my own. After receiving the signal, it is processed as described in the standard.

While I plot the QPSK constellation points after frequency and phase correction, I have a plot (shown above) which is noisy. Now I want to plot (BER Vs SNR).  I know that we can calculate BER as: (Error Bits/Total No. of bits). But I am not sure how to calculate SNR from these complex symbols.

What I understand from online materials is that SNR is the noise variance that is estimated from around the constellation points (maybe some distance/deviation measurement form the true point. The question might be very silly, but I really appreciate anyone helps to understand how this is actually done. I am doing all the coding in python.


texts:
I would like to develop a laser range-finder board similar to Extech DT300. I would like to achieve a centimeter precision at 20 meters.

I don't know if devices such as DT300 use a "standard" time-of-flight approach (delta time between emission and reception) or a phase-shift time-of-flight approach (continuous emission, phase shift detection).

Question #1: Could ISL29501 achieve a similar precision? Datasheet is available here. The idea would be to use a laser emitter / receiver like here.

Question #2: Should I use another chip to drive the laser emitter / receiver in a "standard" time-of-flight approach as described above?


texts: Bulb replacement in a car 12V 60mA vs 14V 65mA

texts: The climate control in my car needs to have some  backing lighting bulbs replaced. Can I use a 14V 65mA bulb instead of the 12V 60mA bulb that is suggested by other people who have replaced these bulbs? Not sure but I believe the orginal burnt out bulb is a 12V 70mA. Anyone forsee any problems using the 14V bulb.  Thanks!


texts:
I'm building a RS485 network with rpi3 as master and a bunch of c51 mcu as slaves. After sending an address, the master waits for the slave to respond and then starts to send data. I'm using Pyserial on Pi and it does a good job.

This is the class part

class Rs485(serial.Serial):
def __init__(self,en_pin):
    serial.Serial.__init__(self, '/dev/ttyAMA0', baudrate=9600, write_timeout=3.0)
    self.en_pin = en_pin
    self.data_buf = 0
    self.parity =  serial.PARITY_SPACE
    self.init()
    self.timeout = 0.03

This is the part where read is called

def receive(self):
    ts.output(0, self.en_pin)
    data_buf = self.read()
    ts.output(1, self.en_pin)
    return data_buf

However, as I'm trying to enhance the transmission efficiency, I found that there is an unexpected delay after each time the serial.read is called. The ts.output lines are used to set max485 enable pin to receive mode and they cost almost no time. I have confirmed that the self.read line costs about 5.7ms.

My questions are:

Why the delay?
Any suggestions on how I could reduce the delay?

Thanks!


texts: We have a meteorological station (Made by the now-defunct Solar Millennium) next to our solar plant that has a faulty connector from its PV panel. It has a circular cross section and has a screw-in weatherproof housing. What is this connection called and where can I find one. Please see the enclosed photographs.


texts:
Receiver has noise figure 4 dB and ENBW 3.6 MHz. Used with antenna with noise temperature 200 K. Demodulator needs S/N of at least 13 dB.  What is the receiver sensitivity?  Give your answer in dBm, rounded to one decimal place.

Sensitivity = 10×log10(kTB)+NF+S⁄N

kTB = (1.38e-23)(210)(1) = 2.76e-21

Sensitivity = 10 x 10log10(2.76e-21) + 4 dB + 13 dB = -205.59 + 17 = -188.6 dBm

Is this correct?


texts: Why is my 220v - AC/DC 3.3v transformer cutting power when relay comes on?

texts:
Being super original I've made a DIY Thermostat with an ESP8266. Being a bit of a novice (I'm learning). I've run in to some sticky bits with my kit. For the most part it works fine, but when turning on a 3v Relay to make a connection between AC Live and the Boiler (To turn it on) do I run in to an issue... The power from the transformer just,.. goes and then recovers a split second later. But this causes the ESP8266 module (and relay) to lose power causing a reset.

This isnt the ESP8266 shutting off, I have a cheap oscilloscope and I've monitored the V+ line and I can see when the relay goes on occasionally the power fails from the transformer.

Circuit (A Battery symbolises 3.3v input, sorry):

simulate this circuit – Schematic created using CircuitLab

The transformer is very similar to this:

https://www.ebay.co.uk/i/182200000506?chn=ps&adgroupid=13585920426&rlsatarget=aud-295856144804%3Apla-142405595586&abcId=&adtype=pla&merchantid=113593976&poi=&googleloc=9045866&device=c&campaignid=207297426&crdt=0

The only thing I haven't tried is shutting off the WiFi every time there is a relay change, I've heard the current draw from both could be enough to cause a problem. Its annoying its intermittent, it used to be a lot worse. But its still far too regular. All help is much appreciated, Thanks in advance.


texts: What are the situations which can cause a resistor to permanently increase its resistance?

texts:
The resistance of a resistor in the HVDC circuit permanently increases.
Is it because of voltage or some other reasons?
Note that there are no short circuit cases seen in the system.


texts: Constant DC 12V, 2A from USB 3.0, SATA, Molex or other common PSU cable?

texts:
I'm in the process of trying to power a simple LED strip lights, spec 12V, 2A, through a PC rather than transformer. So far, I am debating the first stage.

After looking into USB 3.0, it can supply 1500MA, 12V which is sufficient, but will this remain constant under load through other devices?

Could a SATA or Molex PSU power line achieve this?

Perhaps there is another alternative, involving PC power outputs, thanks in advance!


texts:
I'm looking at the user guide for the MSP430x5xx family. It says there in section 9.1 that:

The RCCTL0 register is protected with a key. Only if the correct key is
written during a word write, the RCCTL0 register content can be modified.
Byte write accesses or write accesses with a wrong key are ignored.

And in section 9.3.1 that:

Field RCKEY: RAM controller key. Always read as 69h. Must be written as
5Ah, otherwise the RAMCTL write is ignored.

Can anyone explain to me what a strange protection if the password (code) 5Ah is known? For what purpose it was made?
Why RCKEY always read as 69h (not 5Ah)?


texts:
I’ve bought 2 x RN4871 and connect them to a MCU at first and FTD1232 3.3v in a second time.
My problem is, when I try to find these device on windows 7, I can’t find them. When I try to config then with « $$$ » command with promini 3.3v or FTD1232 : NOTHING !!
When I replace the RN4871 by a RN42, its working. No I’m wondering if there is a firmware inside these modules, I’m not sure of that or perhaps their are defects. 2 weeks on this problem.
here the circuit

Best Regards


texts: µC (Arduino) and Dealing with thermocouple noise

texts:
We've recently used an arduino along with a MAX31856 breakout board to measure some type-J Thermocouple temperature and then replicate it as a KTY xxx through a digital pot (MCP4261).

So all this people is communicating through SPI and it's all fine and dandy until we start the induction motor the thermocouple is mounted in (probably potted into the stator, don't know the exact position)... then everything goes berserk from the conducted EMI...

I think (quite obviously actually...) the thermocouple is not electrically in contact with the stator but as soon as we start running the motor even without load, the Arduino resets or just gives completely false readings (usually higher than real).

Now the question is : how should I deal with that?
I've already isolated the +12V Arduino supply through a DC/DC but it might also make a ground loop if the thermocouple is grounded somewhere...

Is my only option going through an optocoupled SPI and isolated supply to the MAX31856?

Thanks for the help!

Marc

In order to answer to some of the comments :

Yes the motor is run from an inverter taking its power from a battery pack (it's an EV application). This battery pack is isolated from the +12V supply through an isolated DC/DC and the arduino is yet again isolated through another 12V/12V isolated DC/DC (helped a lot with other EMI problems).
The arduino doesn't really reset anymore (since we isolated it's supply) but it gives wrong measurements. For example : we set a threshold above which a fan goes off and when we accelerate the motor, the fan briefly turns itself on from the EMI noise picked up by the thermocouple which gives a false high reading. Then when we let off the throttle, it just stops...
Powering the arduino from a battery gives the same results...
The thermocouple is not connected through a twisted pair from the motor terminals to the arduino but that is something we can change. The path inside the motor is not in our hands though...


texts: Most simple way to detect small voltage changes(~150mV)

texts:
I have one unit of museum cabinet detector that works on 18v. I want make simple security circuit with detector. I've figured out that two output ports on detector are normally contact(NC), but it'll shows ~150mV difference charge when it sensed something. So main alarm system get signal. I have only units and I need to control it with my circuit with battery.

I assume It is quite simple logic so I sorted out with arduino at the moment. (Analog input from the detector, digital output to latch up alarm circuit. Alarm rings whenever it get signals for 3 seconds.)

But I believe there must be much simpler way to build it by only electronic components. I tried to sense voltage changing of the detector with FET, Opto-coupler, relay but has failed. Probably my component's specification doesn't match well with the situation but also I am not sure if I approach proper way.

When activated voltage changes 0~150mv what would be best and cost efficient way to detect the signal so that alarm circuit could get it as input?

simulate this circuit – Schematic created using CircuitLab


texts: Brightness control with PWM dimming LED driver LM3406/06HV

texts:
I have an changing input voltage. I would like to feed it into LM3406 and have varying brightness from the Led. So I go through the datasheet.

However,the only information and characteristic of the IC I can understand is that the duty cycle of the output is Vout/Vin when PWM dimming is being applied. I dont know how to obtain desired Vout.

I am not familiar with LEDs. The datasheet tell me high power LEDs can be used. What is high power Led actually. I can find many types of LED on the street and I dont know the compatiblity of each one.

In my case , is it dim pin is not necessary to connect anything? I find that that pin is left open in input voltage comparator for PWM dimming.


texts: Will this work and what transistor do I use?

texts:
I posted this question in the Meta Stack Exchange but David Tweed said that the idea was flawed so any alternative circuit suggestion would be appreciated.

I have this Ikea lamp. It runs off 5V usb power however it draws 0.6A which according to this is more than the GPIO pins can supply. So I need to use a transistor but I don't know how to find one that will work.


texts: Using two regulators to create new ground: How do I calculate needed power?

texts:
I'm thinking of using two regulators to create a ±5 V power supply. I'd use a 10 V regulator and a 5 V regulator and use the 5 V regulator's output as ground for the circuit and 10 V regulator's ground as the -5 V.

Something like this:

What's confusing me in this setup is how do I calculate the power of the + 5 V regulator.

I guess that the load of the 10 V regulator would be the load of the whole circuit (including the 5 V regulator). Would the load on the 5 V regulator then be only the return current going into the GND pin?


texts:
I need to find the delay of a full adder. I searched for it but I couldnt find absolute information.

Sample delays : XOR - 8ns / AND - 2ns / OR - 2ns

What is the delay of this circuit?

My Solution

I think the delay is the maximum time.
For Full Adder : XOR + XOR = 16ns (max) Is it correct?
Another question is how can I find the delay of 4-bit adder?

Thanks in advance.


texts:
I am trying to learn altium.I just placed stm32f407vg microcontroller and one resistor these gives me error as in the picture :

(Failed to add the class and unknown pin error)
http://oi68.tinypic.com/28hzbeu.jpg


texts:
I have to use a linear actuator in my project and according to my need and availability I found this Linear actuator MEGAMAT2. This requires 24 V supply.

But I am unable to understand the pin configuration diagram provided by dealer

I think yellow, green and black are for moving forward and backward at full stroke speed and also red, white, blue are for controlling the speed of stroke. But I am still struggling with this pin diagram. Please help about this issue.


texts:
I'm trying to use this delay timer to control an exhaust fan. I have a 3 pin connection (with earthing wire) powering this fan and it works fine.

If I have to insert this delay timer module in between the fan and socket, what do I connect the earthing wire to ? Can I leave it connected to the fan's earthing wire directly (as it is now) and use the hot and neutral to connect to this module or should I be looking for another module supporting an earthing wire ?


texts: Driving blue LED with 3.3V using an op-amp

texts:
I'm trying to design a circuit that drives six LEDs - two red, two green, and two blue - off a 3.3V GPIO pin. Since the voltage drop on a blue LED is in that range, I'm attempting to step the voltage up with an LM318N and then drop it with a resistor. However, all the red and green ones are working when set up like this, but the blue ones are not.

Is this a reasonable setup to accomplish what I'm going for, or is there something wrong with the way I'm approaching this?


texts: I would like to understand how to connect the Hella Bistable Latching Relay https://www.delcity.net/store/Latching-Relays/p_818110.h_818111 The intended use is on a motorcycle to turn on and off an accessory by tapping a button which momentarily connects to ground. Each tap would sequentially turn on or turn off the accessory.


texts: How can I safely determine the output voltage and current of a transformer?

texts:
So I am building a Tesla coil with my partner for a senior design project.

We safely ripped out a transformer from a microwave oven. However, after a good amount of research, we were unable to find the maximum output values from the transformer. We know the input values, the standard 120 V and 60 Hz from a US outlet. We need to know the max/peak kV to figure out the capacitance we will need for our primary coil that we need to construct.

Here is what it looks like:


texts:
I am going to start a project in FPGA and "graphical screen" scaling. I am still in the "reading-the-material-phase".

Are there any differences between video-scaling and display(e.g. Windows Desktop)-scaling?
Video scaling is using Bi-linear,Bi-cubic etc. IEEE got a lot of articles related to hardware implementation of video-scaling. But I have not found anything related to display (desktop) scaling.
If I have multiple displays and want to share the same computer-desktop, but the displays are using different ports (VGA, HDMI, display-port) and the displays are of different size. What kind of scaling algorithm are they(Microsoft,Apple etc.) using as standard to adapt an application for each display/screen
When I want to resize a screen from e.g 720x480 —> 1280x720, what type of standard scaling algorithms are used?(bilinear, bi-cubic)


texts:
Is it OK to not connect the GND pins and at the end I fill the zone with copper pour?
When I run the DRC in KiCad everything looks good (all pads are connected.)


texts: Are there commonly used equations for short-term overpower of wirewound resistors?

texts:
If I have a wirewound resistor rated for 250 W that might need to dissipate, say, 400 W for several seconds, is there a commonly used equation for finding its temperature rise or time to failure under overpower conditions?

I have found equations for wire temperature rise in inductors and transformers, but nothing for wirewounds.


texts: Having trouble with deriving the state diagram for an exam problem

texts:
The Problem:
Derive the state diagram for a circuit that takes one input, A and gives out one output X, X is to be one, if and only if it detects a sequence "101" in A.

Understanding The problem:

if A=0001011011..

then X=00010010..

Now the first problem is how many states have I got?, for me its two, some of my colleagues argue that they are three.
the second question is how many bits do I need for each state, shouldn't they be three?
This isn't the whole problem, I should then use flip flops to implement it, but I'm stuck at the state diagram.


texts:
I am working on a project in which a very high negative voltage is required. I have the following equipment

DC power supply with max output voltage of 300V
Function generator with a maximum peak-to-peak voltage output of 20 Vp-p
An electric probe, which is essentially a wire

I would need to control the electric potential of the probe using a sinusoidal waveform. For example, the  waveform may have a frequency in the range of 30-50 Hz, a peak-to-peak voltage of about 150 Vp-p, and reach a DC offset of -300 V. It is important to reach voltages of about -350 V.

I was wondering if using a linear operational amplifier (op-amp) would be a doable way to create a waveform similar to the one described above.

Essentially, to use a function generator to create a signal (e.g., a sine wave of 30-50 Hz, DC offset of -20 V, peak-to-peak voltage of 20 Vp-p) and amplify the signal with an op-amp having a gain of 10. The output signal would have a same frequency, DC offset of -200 V, and peak-to-peak voltage of 200 Vp-p.

Is it possible to achieve those negative voltages with an op-amp?
If yes, are there off-the-shelf op-amp able to do so?

EDIT
The output current is 50 mA, at most.


texts: Hold-up time calculation with high capacity MLCCs

texts:
I am designing a linear voltage regulator for 5V (from 30V) at 10mA for a low cost application. Everything works out so far, but I need around 10ms hold-up time in case of an input voltage failure. All the hold-up energy has to be provided by the 5V output capacitor as I cannot use a decoupled input capacitor.

With the help of an LTSpice simulation model I found out that I need around 44μF to provide around 2.7V (which is sufficient) at the end of the 10ms interval. Of course, these results assume ideal capacitors and in this application electrolytic caps would be close enough to ideal.

However, I would prefer to use MLCCs to save a few cents but unfortunately these are not ideal. Their capacitance changes by a large amount if a voltage close to the rated voltage is applied. The measurements regarding this I have seen so far refer to the small signal capacitance under DC bias and I suspect that I cannot use this figures in this application. In fact, in this application there is some kind of DC bias that decreases in an interval of 10ms.

Does the capacitance "recover" during this decrease, even if there is no energy supplied externally?
Are there any guidelines how to calculate the discharge to obtain a hold-up time figure?


texts: Boost a HV power supply from +1250 V to +1500 V

texts:
I'm designing a base for a photomultiplier tube using a recycled HV power supply. The power supply is an EMCO C12. The base has a 14 pin socket (to connect to the PMT), the EMCO C12, a DAC to program the EMCO C12, a 5 pin ZH connector (DAC), a 2 pin PH connector (DC in), and a BNC connector (Signal). Below is a schematic.

My problem is that the gain of the PMT is simply not enough at the max voltage of the EMCO C12. If I could boost the voltage up just 250V then I could increase the gain almost 4 fold.

It's very important that the method used to boost the voltage maintains a very stable voltage output and be able to output . Also, it needs to introduce as little noise as possible to the output signal.

Any suggestions?


texts:
I've built a band pass filter to detect speed using a radar motion detector (IPM-165 http://nic.ath.cx/PDF/sensors/radar/CDM324-doppler/InnoSenT/InnoSenT_application_note_III_11_06.pdf).

Using PSpice I have simulated the circuit as well as building and testing on a breadboard. From the radar I receive values of approximately 5.4mV (Vamp) and 21.0143MHz.

There appears to be no AC voltage and therefore frequency after capacitor C1, is there any obvious reason for this that I am missing?

Any help would be greatly appreciated, I'm at a bit of a loss with it.


texts: How to reduce test cases for testing verilog circuits

texts: I have a verilog combinational circuit and I have written a testbench which uses a test vector containing 32,768 testcaes. At the moment I am performing exhaustive testing. How can I reduce the number of testcases while ensuring the circuit is properly tested.


texts: Splice high current charge source into USB cable?

texts:
Normal computer USB max current is much lower than needs of modern smartphone to charge while running, commonly needing ~2 amp chargers.

I want to be able to have my phone connected to my computer via usb for data purposes, but it maintain it charge.

Is it possible to do something like this to a usb cable, so instead of the 5v coming from computer, it comes from phone charger instead ?

simulate this circuit – Schematic created using CircuitLab


texts: Can rechargeable batteries with different mA values be used in the same device with good/normal results?

texts:
If I use the two AA batteries (shown below) in a digital camera (where two are needed) will I experience any odd behavior due to the difference in mAh, such as:

camera not working properly?
battery power being dissipated more quickly?

Can you think of any other adverse issues that I might experience?

Also, is mAh (milliAmpere hours)?
What is the h denoting?


texts: STM32F746 on Nucleo-F746ZG - difference between PWM1 and PWM2 signal names

texts:
I understand that each timer channel can be configured at either mode 1 or mode 2.
On the timer  signal names, I see "PWM1" or "PWM2."
I'm confused by this nomenclature.
Does it mean that this signal is already configured as one mode or the other?  If so, how is that impacted by the OCxM bits in the TIMx_CCMRx register?


texts: 1.5v solar cell to replace two D batteries

texts:
I just bought a very small aerator called "Metal Marine Bubble Box" that runs off a small DC motor. Not much torque needed. I tried reading the print on it and all I could read was 1.5v. This makes sense since it takes 2 D batteries which are 1.5v. With both batteries can run for 40 hours, but it can also run on 1 D battery for 20 hours. I know a D battery's current is about 25mA. I want to eliminate batteries.

I want to build a solar cell/panel that can run it instead of using batteries, or that also will charge the batteries while running it, or something like that.

I've seen someone create a small fan from a dollar tree/store solar garden light but couldn't tell exactly how they did it.

What do I need to build it (diodes, resistors, etc.)? I'm a noob and know nothing about circuits, voltage, current needed to run this tiny motor. I'm wondering if I have to perfectly match the voltage/current.


texts: What does the abbreviation IP in "System-on-Chip (SoC) infrastructure IP applications" stand for?

texts:
I'm looking at a Texas Instruments datasheet, and noticed the phrase:

"System-on-Chip (SoC) infrastructure IP applications"

and was just wondering what IP stands for.


texts:
I want to use a crystal as the base clock for a watch.
Most reference designs I could find use a 32.768 kHz crystal at 20 ppm (parts per million) precision.
According to my calculations, this leads to an error of max 52 seconds in a month.
After 6 months, that 5 minutes. I would like something better!

There are some solutions I could think of (better crystal, or compensate in SW), but I am surprised not to find any reference online.

Surely I am not the first person to try and address this problem. Do you have any suggestion as to how to deal with this, and possibly reference design?


texts: How does underdriving a powerful (eg. 50w, 100w) LED chip work?

texts:
My question concerns under driving an LED chip.

Unlike quality brand chips (Bridgelux, Cree), in my experience, under-driving non-brand ones make things more long lasting and favorable.

Using the potentiometer on my quality LED driver, I can lower or increase the Voltage to underdrive a typical 12v LED strip which comes with resistors etc.

My question:

How can I underdrive a powerful 50w or 100w LED chip?
Do I need to lower the voltage again, or is there any other way? (to run 50w chip on 35w, for example)


texts:
I'm attempting to program a Cortex M3 based microcontroller over SWD, more or less from first principles. I've written an SWD interface library and have it running on a second micro.

I've largely been following this blog post: http://markdingst.blogspot.ie/2014/03/programming-internal-sram-over-swd.html

As well as this SiLabs application note:
https://www.silabs.com/Support%20Documents/TechnicalDocs/AN0062.pdf

I can halt the core and read and write SRAM. I'm wondering how to obtain the bare-metal code that I can write to SRAM. Can I just take the .hex file the compiler outputs and write that to SRAM word by word starting at 0x20000000?

And if so, what core registers do I have to configure so that the new program in SRAM will run on reset? Will setting the PC to 0x20000000 be enough?

I appreciate all and any help! Thanks!


texts:
I'm trying to bias the following circuit to power an 8 ohm speaker with an 8Vptp output. The following are the calculations I've done to get this current setup but the output is only good up to 1Vptp before it starts to lose gain and get crossover distortion. What am I overlooking here?

Taking power output as 1W, V=sqrt(P*R)=sqrt(1*8)=2.82. sqrt(2)*2.82=3.99V so this should give me an 8Vptp output.

I=sqrt(P/R)=0.35A, sqrt(2)*0.35=0.5A

Taking hfe of 100 then Ib should be 5mA

12V-1.4 for the diode drop =10.6 and dividing by 2 to bias equally =5.3V

5.3V/5mA = 1060 ohms

Fixed design with transistor at correct orientation:

Actual output:

What can be done to eliminate this clipping in the practical circuit?


texts: More accuracy from analog multiplication?

texts: Let's say I want to detect a voltage signal that's guaranteed to be between 0V and 1V through an ADC whose upper range is 5V. I can hook the signal up to the ADC directly, but then I'll only be using 1/5th of the ADC range. Or, I can multiply the signal by 5 through an amplifier to have the signal extend to the entire ADC voltage range. Then, I would divide the signal by 5 (using software) to get the signal back to a number between 0 and 1. Would this latter approach offer better accuracy? Intuitively, I would think that extending the signal to match the entire ADC range would offer better accuracy, but I wonder if I'm just fooling myself.


texts: Microchip PIC Development with OTP Devices (12C672)

texts:
I have to work on a system that uses 12C672 PICs from Microchip.

These are one-time-programmable (OTP) devices. The board has been designed already without any in-circuit programming facility.

How do people normally develop with these? Are the ICE systems good enough and affordable, or is there always a flash alternative part that people use?

I am used to developing with flash AVR microcontrollers and just do in-circuit serial programming.

This PIC project will be a small production run of 100 or so units, so I am also interested in recommendation for a programmer to use.


texts: Why do bipolar electrolytic caps have a long and short lead?

texts:
Ok maybe not all, but the Nichicon UES series of bipolar "audio-grade" electrolytic through-hole caps have a short lead and a long lead..

Why?

The datasheet has nothing to say about it.
This fairly recent question: Orientation of "bipolar" capacitors on PCB
...seems somewhat related, and I did some searching and found a boatload of speculation but nothing that stuck. So far the only thing that seems likely to me is that perhaps the manufacturing process is built around the more common polarized electro with the uneven leads. Or that the reason is common knowledge and I am once again tragically out of the loop.


texts: 48VDC SLA charger from 12VDC supply design help

texts:
I am in the process of designing a 48 VDC (comprised of 4 x 12 VDC) lead-acid battery charger, with an input voltage of 12 VDC. 1W - 2W output is sufficient, and relatively high efficiency with low quiescent current are important.  I have looked at many of battery charger ICs and none that I have found can handle 48V output.  The image link below (sorry, my reputation is not high enough to post images) is a first pass at custom charger.  The pulse supply (V2) would be replaced with a small, low-power microcontroller that samples the voltage at the divider.  It could also have a thermistor to adjust the charging target voltage for temperature.

Based on my design criteria does this seem like a reasonable approach?  Perhaps there is a charger IC I missed, or maybe a commercial off the shelf charger I do not know about?

Any suggestions, including parts to consider or modifications to my boost converter would be greatly appreciated.

Thanks,
Sam

Simple boost-style 48V battery charger

Added:

Not sure if this is the correct way to add additional content.

450 W*hr is correct.  The internal battery pack is 28 D cell alkaline batteries in series.  We wish to use this internal battery back as an "emergency" backup battery.  This is useful if we get frayed wires, blown fuses, charger failures or a long streak of cloudy weather.  The internal pack and external supply (what I am designing) are diode protected so in any of the above "emergency" cases if our external supply drops below a certain voltage the internal pack will take over and merrily supply the ADCP for another 6-8 months.  This is the main reason for selecting 48V for our supply.  Yes, we may be capable of modifying the internal pack...  but getting permission is another story.

While I fully support the use of LiFePO4 (As an Engineer I think they rock in so many ways), SLA has proven very robust in the harsh marine environment and no one in the group other than myself and possibly one other are interested in trying a new battery technology.   Mostly the idea of spending $6k/day to replace a failed battery scares them.

Initially I designed a dual-phase 12V - 48V step up converter (kicad schematic and pcb files) and quickly discovered that this is perhaps infuriating instrument in existence.  Shortly before the ADCP collects its ensemble it basically shorts the power pins (it draws > 3A @ 48V for < 10 us).  I know it has to boost the voltage to several thousand volts for the transducer so I can only imagine that the ADCP opened a relay to its SMPS.  This transient current draw which is is more than 11 A from the main battery causes a large voltage spike ( ~ 7 - 8 volts above nominal) across the battery terminals.  This may be due to a poor design on my part (lack of shielding, no common-mode choke, etc?) but another engineer and myself tried tracking the problem down for several days to no avail.  I am not entirely convinced that what we were seeing was "real".  I think it may have been radiated from the wires from the battery to the regulator, inducing a voltage on the o-scope probe.  No idea really...  microcontrollers are really my areas of expertise, I am merely dabbling in power switching.  Honestly this problem highlights why I may want to use an isolated smps (forward of flyback).  Either way we will be moving the high current path much closer to the instrument this way...

Sorry for the long post, hopefully that clears up some design decisions.


texts:
In the circuit description they claim that one stage would have 12dB gain.
From what I learned is that in negative feedback operation the gain is 1+Rf/Rg=1+20/47=1.42=~1.5dB
Where is my mistake?

From:
http://publications.lib.chalmers.se/records/fulltext/218195/218195.pdf

Amplifier schematic is on page 60, description on page 30.


texts:
Is it safe to charge a battery 'BLP657' using a module charger 'TP4056'?
Specifications: BLP657
Type: Lithium battery
Rated Voltage: 3.85V
Charge Limited Voltage: 4.4V
Capacity: 3300mAh
Rechargeable: Yes

Specifications : TP4056
Charge module- Linear charging.
Current- 1A adjustable.
Charge precision- 1.5%.
Input voltage- 4.5V-5.5V.
Full charge voltage- 4.2V.
Led indicator- red is charging Green is full charged.
Input interface- micro USB.
Work temperature- -10° to +85°.
Inversed polarity- NO.
NOTE:

Ampere meter can only be connected to 5v input end of the module.
It is better that the charging current is 37% of the battery capacity. If you charge to the battery of 1000mAH, current of 400 is enough.
The connection wire should not be too thick.
Make sure the connect point is good.
If the input voltage is too high, like 5.2v, the current will be less than 1000mA, it is normal. It is protection function, auto-substract the charging cur


texts: What is the minimum value of voltage and current that HSPICE can measure?

texts:
I am using HSPICE for my simulations. I want to make sure HSPICE is measuring the minimum value of current and voltage correctly. What are those values?
How can I set them?


texts:
I am repairing a battery pack (see below) which has some old foil capacitor (100nF) between a sense Terminal and the negative (together with a NTC thermistor).

Can I replace the foil cap with a X7R ceramic cap?


texts:
I've been stuck on this problem for a couple of months now and haven't had much luck finding the exact information that I need. So, I'm currently working on a project to make a handheld raspberry pi, and utilizing small push buttons to communicate with the Pi as a USB device or via GPIO pins as a keyboard. I'm not too worried about the code to translate a signal to a keystroke, but I'm not entirely sure on how to actually connect an ATmega328 to the Pi. I've looked around online and see people using an entire Arduino board to do what I'd like, but it needs to be able to stay compact, so I plan to send the code to the ATmega328 and directly connect it within the circuit. I don't have much experience with building circuits that communicate with computers, so any help would be greatly appreciated.

Here's an idea of the kind of circuit that I'm looking for. I'm not entirely sure on the exact layout, but this is sort of a rough sketch to give an idea of what I'm trying to accomplish.


texts: Intuitive to get pole and zero points for lead compensator

texts:
The circuit below is a lead compensator. I can easily know exact the pole and zero of the network by deriving the transfer function. However, I am wondering if there is an intuitive method to get the pole and zero of the network (even approximation).
Thanks.


texts: Raspberry Pi B+ with relay: Lights change but relays don't click

texts:
I am using an 8 Relay module, bought from dx.com.
It has no instruction manual...

This board has 8 inputs (IN1,...,IN8) to control each relay, 1 VCC pin that requires 5V and 1 GND pin.

I connected the VCC to the 5V pin of the raspberry and the GND to the ground of the raspberry. After that I tested each relay by connecting them to a GPIO-pin as I saw other people doing it: video

But only 2 of the 8 relays seem to work fine. The indication lights of the other 6 do change, but the relays don't 'click'.

Is somebody experiencing the same problem, or does anybody know how to fix this?
Thanks in advance!


texts: Power Plane and Decoupling Capacitors Routing

texts:
Forgive me for my simplicity. I'm just a hobbyist and not an engineer by trade.

I am trying to make my first 4 layer PCB in Eagle and I have a question I cannot find the answer to regarding power planes and decoupling capacitors for ICs.

The PCB has an embedded Atmega328 operating at 16 Mhz and the power is +5V with a max current draw of 5A, but I don't expect rapid and big fluctuations as it is mostly just 1 or 2 LEDs turning on/off at a time. (If that matters.)

1. How should the power plane interact with the decoupling capacitors and the Vcc pins of my ICs?

When I first drew my power plane and labeled it to the +5V net, it made connections to all the vias on that net. And what I saw was that now my ICs are just straight connected to the power plane without being directly routed through the adjacent decoupling capacitors, like this:

I guess, I thought that the Vcc needed its own independent trace. And that the +5V for the Vcc would enter the trace at a single point, route past the 2 decoupling caps and to the Vcc pin, like this:

Instead, when I name the power plane to the +5V net, all three pins (Vcc for the IC, +5V side of C1, and +5V side of C4 are just all connected that would route the +5V past the decoupling caps to the Vcc pin. Is one way preferable over the other? Does it matter? The capacitors are still as close as possible to the Vcc pin of the IC. If they are all just connected to the common power plane, do they still function as intended or do they need to have the isolated trace that directs the current past the decoupling capacitors directly to the Vcc pin?

2. I'm only beginning to understand how ground loops work on a PCB. Do I need to be mindful of making a single point power distribution or does an arbitrarily poured power plane take care of this? Does it matter at 16Mhz? Will a power plane arbitrarily poured over the entire power plane layer work okay?


texts: Can a diode prevent backwards current flow from a constant current source?

texts: I'm trying to make a AA battery replacement battery for a vintage computer because its actual battery has gone bad. Its of the NiMH type and I'm pretty sure those are charged with a constant current. I want to make sure that my alkaline batteries don't get accidentally charged if the AC adapter were to be plugged in. Would a diode prevent the constant current charger from charging my AA batteries?


texts:
What is the current state of things when it comes to super capacitors and batteries? Are super caps anywhere near rivalling LiPo's in capacity?

I've often heard people talking about super caps as being a viable replacement for batteries, in that you can charge virtually instantly and recharge millions of times, but is this just a pipe dream?


texts: Parallel 18650 battery pack voltage not stepping-up with Boost converter. Why?

texts:
I'm new here and I hope this is the right place to ask!

I have assembled a 6P 18650 battery pack out using Samsung 25R cells, soldered altogether with Nickel strips, effectively giving me 3.7V 15Ah.

I want to increase the voltage, so I hooked it up to a "XL6009 boost converter" module and also on a "250W 10A boost converter" module, both of which would not allow me to go anywhere near or above 5V!

This has lead me scratching my head and pulling hair out, as I do not understand why this is happening. Both lower and higher end modules are not able to "do the job", leaving me very confused.
I was wondering if anyone might know why this is the case? And what would I have to do if I want to step-up to 7-10V??

Thanks and I look forward hearing back!

Do you think it's simply because the input voltage is too low??


texts: Pebble watch charging contacts worn out, options?

texts:
My pebble is getting harder and harder to charge, every time I need to clean the contacts, press hard and hope it charges, and once it does, hold it still..

I am wondering how I can improve the situation, is it possible to rebuild the contacts in any way? I was thinking I might place a bit of regular solder over the two contacts, but I am seeing a few places say thats a bad idea..


texts:
I want to make a simple ladder circuit to control the on and off of a light bulb using 2 switches, but I am going to manipulate one of the switches by means of a microcontroller, and also I don't want to use a relay because they wear out with time. I am trying with this circuit with optocouplers, a pnp transistor and triacs, as seen in the image, but it does not work well, also when I am simulating it in proteus 8.9 after a certain time it throws me these errors:
[SPICE] DELMIN increased to 8.88178e-016 due to lack of time precision
[SPICE] transient GMIN stepping at time = 6.54158
[SPICE] TRAN: Timestep too small; timestep = 1.11022e-016: trouble with node # $ IAC AMMETER # 0020_AVS1 # AB # branch.

I don't know what I'm doing wrong, I already tried it on a breadboard and it doesn't work either.
If someone can help me or suggest another circuit that works for what I need, I appreciate it a lot and forgive my English.


texts: Why do x amp rated consumer electronics often come with >> x A rated BS1363 fused plugs?

texts:
I often find that consumer electronics from reputable brands come with fused plugs that are rated significantly higher than the actual product.

I would have thought that the ideal fuse would be \$x+\epsilon\$ where \$x\$ is the product's expected maximum draw. Obviously, that's not practical, but frequently I find the fuses are larger than they 'have to be', that there's a standard size between what they shipped and \$x\$.

Is it just being cheap, using whatever's available (even if it's actually more expensive than the better choice, I suppose it may be 'cheaper' by availability)?

Surely the greater difference between the fuse and \$x\$ the less point there is in having it at all. Or is it more complex than I realise, should I prefer whatever was shipped over one closer in rating even if I happen to have it?


texts:
SITUATION:

Nodal Analysis is nothing more than applying KCL and is very powerful. I'm working on developing a more clearer perspective of two approaches in Nodal Analysis "GENERAL & FORMAT". Mesh Analysis is also quite powerful but my questions below are pertaining to Nodal Analysis.

The "General Approach" seems to be more extensive when it comes to factoring and simplifying equations into a form to later solve using simultaneous calculation. After studying the "Format Approach" I started to see a more clearer picture of what my equations were actually representing after the factoring and simplification steps. It was showing that the voltage at the node I was applying KCL too, was simply being multiplied by the sum of the conductance attached to that node.

QUESTION #1:
Among the many methods used in solving for unknown currents and unknown voltages would I be theoretically correct in saying that the "Format Approach" is effective in most cases? If not could you explain?

EXAMPLE #1:

I'm including an example here from my textbook to show the "Format Approach".

QUESTION #2:
How do I write the equation, "in the same format as the first example", that is used to solve the circuit below? Since the circuit below has 2 components that are shared, "12V Source & 10 ohm Resistor", I just can't figure out how to write the equation using the same approach as above.


texts: How separators prevent electrons from passing through

texts: Separators (polymers) in batteries keep electrons from passing through but they let ions through. How do they do that if electrons are smaller than ions? Can we imagine it as a kind of 3D wire mesh whose molecular configuration repel electrons?


texts: How does this controller detect both sides?

texts:
I've come across an old joystick, which I presume worked at the time (I have no way to tell, since it uses the old serial port). Naturally I got curious how it was made and opened it up.

The black part you see does not conduct electricity at all. There seems to be no wires connecting the top right part, so while the state in second image conducts the electricity I don't see how the state could be reported. The same story is with the back and forward control. I've thought that it might only support two states, but that makes a pretty bad joystick, so I figured it must detect the state somehow, despite there being no wires. How does it work?


texts: How to divide 50MHz down to 2Hz in VHDL on Xilinx FPGA

texts: I have a Xilinx FPGA board, with a 50MHz crystal. I need to divide that down to 2Hz in VHDL. How do I do this?


texts: Changing a homemade LED light (14V Battery Pack) to run off mains?

texts:
I've got a wee challenge on my hands. My ex-girlfriend gave me this light as a b-day present 3D printed. I've been told that the LED is a 10mm Ultrabrite LED.
See the picture attached for the battery pack at the bottom. How would I go about changing it from running off batteries, to running off the mains? She said her uncle who made it says I'll probably need a '14v power limiter'. Haven't touched a soldering iron since high-school; willing to do so.
Cheers for any input - its much appreciated.
Pictures Of Lamp


texts: What PIC microcontroller can interface with an ADXRS800 gyroscope with SPI output?

texts:
Straight to the point...

I planning to use an ADXRS800 gyroscope and its output is a 32bit SPI message, does this mean that it can only be interfaced with a 32bit PIC microcontroller, or could i use my 8 bit microcontroller.


texts: VHDL if generate in the preamble, is it possible?

texts:
Is it possible to generate different set of constants in a vhdl preamble using a kind of "if generate statement"?

For example I was trying:

library ieee;
use ieee.std_logic_1164.all;

entity my_entity is
   generic(flag : integer);
   port(x : in std_logic_vector(31 downto 0);
        y : out std_logic_vector(31 downto 0));
end entity my_entity;

architecture arch of my_entity is

   flag_true : if flag /= 0 generate
      constant K1 : integer := 32;
   end generate flag_true;

   flag_false : if flag = 0 generate
      constant K2 : integer 32;
   end generate flag_false;

begin

   flag_true_conc : if flag /= 0 generate
      y(K1 - 1 downto 0) <= not x(K1 - 1 downto 0);
   end generate flag_true_conc;

   flag_false_conc : if flag = 0 generate
      y(K2 - 1 downto 0) <= x(K2 - 2 downto 0) & x(K2 - 1);
   end generate flag_false_conc;

end architecture arch;

But when I run the ncvhdl for the syntax check it returns me loads of errors:

ncvhdl: 14.20-s029: (c) Copyright 1995-2016 Cadence Design Systems, Inc.
architecture arch of my_entity is
                                  |
ncvhdl_p: *E,EXPBEG (entity_test.vhd,10|34): expecting the reserved word 'BEGIN' [1.2].
      constant K1 : integer := 32;
                                   |
ncvhdl_p: *E,EXPBEG (entity_test.vhd,13|35): expecting the reserved word 'BEGIN' [9.7].
      constant K2 : integer 32;
                            |
ncvhdl_p: *E,EXPSMI (entity_test.vhd,17|28): expecting a semicolon (';') [4.3.1.1].
      constant K2 : integer 32;
                                |
ncvhdl_p: *E,EXPBEG (entity_test.vhd,17|32): expecting the reserved word 'BEGIN' [9.7].
   end generate flag_false;
                            |
ncvhdl_p: *E,EXPEND (entity_test.vhd,18|28): expecting the reserved word 'END' [1.2].

I don't think except for the if generate in the preamble I've done something weird.

Assuming I made you understand what I'm trying to achieve is it possible to do that?

(You have to imagine the situation where in the preamble I want to generate different set of constants based on some kind of flag or condition).


texts:
I am trying to use a transistor to drive a lamp from a Raspberry Pi (3B+) and I went after one that can be switched by the 3.3V logic.
I found the FQP50N06L to have a max Vgs threshold of 2.5V, so it should work (right?).
Here's the circuit I am using:

simulate this circuit – Schematic created using CircuitLab

The lamp is rated 0.75A @ 5V, so this setup should be working, but it's not. The lamp turns on if I use 5V at the gate and goes dim for 4.5V or so.

I would suspect I chose the FET poorly, but I'd appreciate someone else's input on the matter before going hunting yet again for another transistor and found out the circuit is wrong.

So what could be the problem here?

EDIT: Yes, I forgot the word "threshold" on "max Vgs threshold."


texts:
I need to measure a very small current at the high-side of a circuit. The high side is at 3000VDC. The measurement needs to ultimately be in the form of a signal with a peak of no more than 5V, so some isolation is required.

I am tinkering with a TI AMC1200, which is an isolation amplifier. The data sheet for the device is here http://www.ti.com/lit/ds/symlink/amc1200.pdf

My question is with regards to powering the amplifier. The data sheet specifies that the high and low side should be powered up to around 5v. So, can I just use 2 different 5V power supplies? I am confused, because the signal being measured will be across a sense resistor, so it will be floating up around 3000v.

Perhaps a diagram is in order...this is what I am trying to explain...

I have built a little test circuit, with 20V on the high side, and 2 separate power supplies as suggested above, but it doesn't do anything.

I know this is probably stupid, but I'm pretty new to this stuff.

Any help would be appreciated.

Thanks so much.


texts: Is anyone familiar with lock-in amplifiers and why we would use two input voltages with them?


texts: A relay that behaves like a simple one but doesn't continuously use power?

texts:
I'd like to find a simple way to switch the audio output of my Amazon Echo between its internal speakers and an external audio system. Fortunately, Amazon was gracious enough leave a little cavity at its base.

I was thinking of installing a switched phone connector and a DPDT relay such that the switch inside the phone connector controls the supply of power to the relay: plugging the jack into the connector switches the audio to the external speakers; unplugging it switches to internal.

I could quit here but it bothers me that the relay will likely be energized, consuming 140mW, for days or even weeks at a time.

An impulse relay comes close to solving this, except it transitions on an impulse, not a step. I'd rather not have to deal with the headache of building a differentiator, experimenting with pulse durations, rectifying the output, and fitting it all in a small space...

It seems like a relay that had this behavior built-in should exist, and actually be quite common, but I can't seem find it. Is there a simple way to accomplish this objective?


texts:
Why is the following circuit an adjustable current limiter? It looks like a adjustable current source to me.

EDIT: I know the difference between current limiters and current sources. Lets analyze the circuit the clear up some misunderstandings.

From the datasheet: "In operation, the LM150 develops a nominal 1.25V reference voltage, VREF, between the output and adjustment terminal.".

I think that R2 in combination with the diodes and jfet is used to superimpose a voltage on top of the adjust terminal so that the voltage over R1 decreases, which in turn limits the current that can flow through R1. This sets an upper limit for the current, but what happens if output current is less than current that we can draw? Since the difference between output and adjustment terminal is set to 1.25V and a voltage forced on top of the adjust terminal (and thus over R1), what is left to change to downregulate the current? The only thing I can come up with is that the excess current needs to be sinked, but where?


texts: Can a 1:1 transformer prevent the SMPS noise of one load from reaching other loads plugged into a mains outlet?

texts:
It's my understanding that a load which has a SMPS can put noise back onto the power cord, which could reach another component that's plugged into the same outlet.

Is it true that a 1:1 transformer can prevent SMPS noise of one load from polluting the power that goes to other loads?

If so, must that transformer have a floating-neutral secondary or can the secondary be grounded (to block this "backwash" noise) and must it be positioned between the mains and the offending load that has a SMPS or should it be positioned between the mains and the other load that you are trying to protect?

Thanks!


texts: Can a microcontroller work from an oscillator if it is expecting a crystal?

texts:
I'm designing a circuit that will accept and program various microcontrollers, e.g. Atmel's ATmega328P.

These microcontrollers usually have so-called "fuses" to configure their clock sources, and they generally offer the following options:

Internal oscillator
External crystal
External oscillator

My question is simple: If the microcontroller is configured to expect a crystal, will it work correctly if you instead provide it with an external oscillator?

For extra credit: What will happen if you give it a slower oscillator? Will it just perform more slowly?


texts: Output waveform of an SMD crystal oscillator

texts:
I am going to setup lwIP on STM32f107RCT6 with DP83848 PHY device. The green LED of RJ000002 magjack is turned on and solid and the orange one is blinking. However, I have not been successful to run ST ECHO TCP Server example on my own board. I started debugging from any point. Now correct function of HX0-36A 50.000 MHz (SMD crystal oscillator) is open to question for me. Its output waveform is:

(DC offset around 1.5V and VPP about 900mV)
Does it output correctly?
If it works fine why in its datasheet it is mentioned that:
Output Voltage:
VOH = 90% VDD Min  = 2.97V Min
VOL  = 10% VDD Max = 0.33V Max
The waveform of VDD voltage given at Pin 4 as power supply:

I edited my post based on Justme's answer:
With 10x mode and BW limit off the result is:

which is not matched with values provided in the datasheet (VOH = 2.97V).
This is my project (PDF file included).


texts: 24 Volt system with 2 outputs. Convert to 12 Volt Outputs

texts:
What would I need to add to set up to get 2 outputs at 12 volts.  Outputs are 0 and 1.  I would assume relays.
Signal Outputs.  For a 3 Position 12V Solinoid.
Micro 820 2080-LC20-20QWB


texts:
I want to run a 2G Modem HL6528RD. I provide it with 3.6 V, got from the following circuit :

I finally manage to make it work but the problem is that if R108 is mounted, the modem doesn’t work, (the modem's power supply drops by 1V due to current peaks of up to 2A and causes the modem to restart).

However, if I replace R108 by an inductor with high enough value (2.2uH for exemple), the voltage hardly changes when current peaks occur.

Could someone explain to me, what is causing this phenomenon?

Thanks for reading my question


texts: Single Phase Diode Bridge Rectifier - Inductive Smoothing Question

texts: So I don't understand how the answer is 2.124 volt-seconds when if you put the equation through a calculator it comes out as -0.174. Is there an additional mathematical step to do on the cosines in square brackets?


texts: Why does this buck boost with dual MOSFETs fails output at certain input voltages at light load?

texts:
Buck boost design
A buck boost converter for 11A 45V output and 33.0-55.0V input has been designed using the Webench Power Designer. The LM5176 based PCB design was adapted for dual MOSFETs (4 times 2 pieces) having the TI evaluation board SNVU547 in mind.
Wrong output at light loads
I measured at different input voltages in steps of 1.00V difference.
3.00A output = OK
No output errors were found at steps of 1.00V. Should I repeat with smaller steps?
1.0A output, output error at 46.00V input
It light loads of 1.00A the output is around 15 volts instead of 45 volts.
0.10A output, output error at 42.00, 43.00, 45.00 and 46.00V input
At even lighter loads of 0.100A the output voltage is around 32-40 VDC for 42, 43, 45, and 46 VDC input tests.
As soon as there is an issue, I do hear a "ticking" sound.
Single MOSFET = OK
I also have the same PCB populated with single (4 times 1) MOSFETs. That board has no issues. I even stepped that board in 0.1V steps over the full range and in 0.01V steps over the 46 to 42 VDC range without spotting any output issues at light 0.100A load.
What is the issue with the (design of the) dual MOSFET board?

Schematic

Evaluation board

Prototype
The prototype is a 6-layer 4Oz printed circuit, where board top and bottom sides of the dual MOSFET version do look like this:

BOM

Rvisns 1.98kΩ ERJ-6ENF1961V
Cboot1,Cboot2 100nF ESR=1mΩ C0603C104M3VACTU
Cbulk 68uF ESR=320mΩ EEV-FK1K680Q
Ccomp 39nF C0603C393K5RACTU
Ccomp2 750pF C0603C751J5GACTU
Ccs 47pF ESR=147mΩ 06035A470JAT2A
Cf 100nF 06035D104KAT2A
Cin1, Cin2 15uF ESR=40mΩ 100V 100SXV15M
Cin3…Cin14, Cout1…Cout15 4.7uF ESR=4.236mΩ 100V CGA6M3X7S2A475K200AB
Cout16…Cout18 33uF ESR=25mΩ 63V 63SXV33M
Cslope 1.2nF CL10C122JB8NNNC
Css 22nF C0G GCM21B5C1H223JA16L
Cvcc 1uF GRM188R61C105KA93D
Dboot1 10A 0.91V MBRD10200CT-13
Dboot2 20A 100V 0.455V STPS20M100SG-TR
Df 100V 1.0A 1.05V STPS1H100A
L1 10uH SER2915H-103KL
M1,M3 80V  BSC037N08NS5ATMA1
M2 150V 50A BSC190N15NS3GATMA1
M4 100V 5.3mΩ CSD19531Q5A
Rcomp 4.64kΩ ERJP03F4641V
Rcsg,Rcsp 100Ω
Rf 10Ω
Rfbb 20kΩ
Rfbt 1.1MΩ
Rpg 10kΩ
Rt 86.6kΩ
Ruvb 9.31kΩ
Ruvt 249kΩ
Rmode 93.1kΩ
Rsense1 62mΩ // Rsense2 5.1mΩ -> Rsense 4.7112mΩ


texts: how to measure the internal resistance of a voltmeter?

texts:
How to find out what is the internal resistance of a voltmeter? I imagine the higher the better - it'll have less influence on the measured circuit.

What is the approximate internal resistance of cheap DMM on the voltmeter setting? Do more expensive multimeters have better (higher) internal resistance? Is there a significant difference in internal resistance of the voltmeter between a Fluke and a 5$ DMM?

What is the best method to measure the internal resistance of a voltmeter?


texts: How a bad USB cable that doesn't follow the spec can damage the charger/hub?

texts:
In this review (that quickly received significant public attention), a Google engineer pointed out a flaw in the cable, that, according to him can be "potentially damaging the USB hub or charger".

From the same review, "a value of 56 kΩ ± 5% shall be used, in order to provide tolerance to IR drop on V BUS and GND in the cable assembly". Could someone shed some light on this and explain how a bad cable could actually damage a hub or charger and why the 10 kΩ resistor used in this particular cable does not suffice to prevent this?


texts:
I am not from an electrical background and this might sound silly.
What I am trying to do is create a hot wire cutter to cut thermocol(Styrofoam). The sugestions from internet is to use Nichrome but I cannot find one.

I have bunch of copper wire though. Can I heat the wire good enough to cut Styrofoam by shorting with 3 AA batteries ?


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Background:

I am using a shielded inductor in a switching power supply, and am investigating an EMI issue.

My hypothesis is that since the inductor is saturated, the magnetic field is no longer contained in the ferrite core, and the inductor becomes equivalent to an air core inductor. I know that air core inductors radiate their magnetic field much more than ferrite core inductors.

Question:

Once a ferrite core inductor saturates, does its magnetic field get radiated significantly more?


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I need to make a square wave -5 to +5 V at approx. 500 Hz - with small current. I have 0 (ground) and +5 V and a PWM (a Waspmote with a ATmega1281 microcontroller). I think it would be possible to make the square wave with a UART/RS232 chip - but I'm not sure.

It's important that the square wave is shifting between -5 and +5 volts. Any ideas?


texts: (VCA - VGA) Design of an amplifier controlled by a ramp

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I would like to design a circuit with an AOP which will have a variable gain controlled by a tension (a ramp). Could you help me and explain me the circuit please?

Thank you,

Farad


texts: current transformer behaving like voltage transformer

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I wrapped wire around a steel core, and then i put a cable that carries around 10A through the center. This should be a current transformer and should behave like a constant current source. The bigger the load in the secondary the bigger the voltage drop should be (with the current staying constant). And the more the turns of the secondary the less the current should be. But that is not what happened.

As i put bigger resistors in the secondary the current dropped along with the voltage drop. As i wrapped more turns around the core, there was a bigger current and a bigger voltage drop in the secondary.

This behavior is similar to a voltage transformer, isn't it? What is happening?


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I have designed the below circuit to automatically switch between a primary cell (3v) battery, and if available, an external DC power supply (~3.3v). Since the cell is a primary cell, it needs to be protected against trying to charge from the DC power supply.
I used a P-Channel MOSFET for the design, as I would like as little voltage drop as possible when the device is powered by the primary cell battery.
My theory of circuit operation is:
No Aux DC Power

Gate of the M1 (P Channel MOSFET) will be pulled nearly to 0V by R1 (47K pull-down). Technically between the R1, and voltage divider (R2 & R3), it should have ~31.33K pull-down to ground.
Voltage would flow (through the M1 body diode) from Drain to Source. This would give the source of M1 a voltage of around 1.8v (1.2V Forward voltage). With the Gate at ~0v, and Source at around 1.8V, M1 should become fully "ON", and create a low resistance flow from the Primary Battery to Vout. This would then provide 3V on the Source pin of M1, making -3V Gate-Source.

With Aux DC Power

When 3.3V is provided on Aux DC Pwr, the Gate pin of M1 will be around 3.3V, turning the FET to an "OFF" state. The voltage will then flow through D1 (schottky diode) to Vout.
In this mode, the current could still flow from the Primary Cell Battery to Vout if, the voltage after D1 is lower than the Voltage at Drain of M1 (after the body diode of M1).

simulate this circuit – Schematic created using CircuitLab
So I have production boards using this design, and all of my testings had been going well with this design. I recently started running into an issue, where D1 seems to fail, and cause "funky" results on Vout. For instance, 1 out of 20 boards will have the issue, and when I measure Voltage, I will get:

3.1V at Primary Cell Battery (Drain of M1)
2.6V at Vout (Source of M1)
2.6V at Gate of M1.
D1 appears to have failed, as I can replace it, and usually, the boards will start working as I expected them to once again.

Can I get some thoughts on what I may be doing wrong, that would be killing D1?


texts: Will this circuit for two Wiegand card readers allow them to talk to one control board?

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I'm working on designing a PCB to allow two Wiegand HID card readers to be connected to a single control board using digital isolation IC's and wanted to make sure the IC's and other components are adequate for the job and if there is anything else I may be missing.
Each card reader only uses four signals, CARD PRESENT, BEEPER, DATA0, and DATA1, which will get wired into two terminal blocks (J1 and J2). From here, the signals are connected to discrete inputs on the digital isolation IC's: an SI8640AB-B-IS1R for 4 of the signals and an SI8631BT-IS for the rest. The outputs on the IC's are then tied together so whichever input of a pair is triggered, a single output will be activated, ex: DATA1_A and DATA1_B are on inputs A1 and A2 and the corresponding outputs, B1 and B2 are tied together as DATA1 which gets sent to the controller.
The BEEPER signal coming back to the card readers is fed into two AND gates along with the CARD PRESENT signal which will route BEEPER to the correct reader being used.
(Click image below for larger version)

Original schematic PDF link via Sharepoint
Si86xx Data Sheet


texts: Rigid vs flex cable board to board connection

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I am working on a project, that has 2 separate PCBs in one enclosure, those PCBs should talk on 20 pins (GPIO). The entire system is prone to low to moderate vibrations. While there is no concern around PCBs themselves, I am rather concerned about the connection between them. I so far see 3 choices:

Rigid connection via IDC connectors 1.27mm pitch THT. This seems to be fairly cheap option, but considering vibrations, will require some additional mount points between PCBs to avoid disconnect due to slippage and also it will probably cause some strain on the connector solder joints.
Ribbon cable using IDC connectors. That seems to be middle ground on price, avoids strain on connector solder joints, but it is bulky and still would probably be prone to slippage?
FFC cable - seems to be most compact non-rigid solution, but rather expensive and I have no idea whether it is reliable in environment with vibrations.

I am so far inclined more towards option 2. But I don't know whether this is a good choice and whether I am missing some aspect that would result in unexpected failures.

I guess my questions are -- is the analysis of each option above correct? Is there any other option I overlooked?


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I'd like to know some general approaches to creating DIY connectors for a custom PCB or card. Mainly I'd like to know how to connect some flat SMD pads to standard jumpers that would connect to a breadboard or arduino header.

For example, here's the internals of a genuine PSX memory card:

It's worth noting that each pad is separated by 2.54mm (standard DIP header), although in 3 (non-standard spaced) distinct sections.

I've considered the following:

Probes (Some of the pads are too far from the edge of the PCB for this to work)
Hot glue DIP headers to the pads (Messy and unreliable connection)
Solder some cables to the pads (I don't want to leave any solder residue as I want the device to remain in original condition)
Alligator clips (too large)


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Can I connect this analog meter directly to 220VAC without any additional components?

And what is the meaning of writing on the right?