texts: What is wrong with this PIC pin change detection?

texts:
I have two PIC18F4620 connected via SPI + Slave Select + additional IRQ line. Both controllers are driven from the same crystal oscillator using the same clock settings. The master sends one byte and then waits until the slave toggles that additional IRQ line. The duration of the toggling is 4 instruction cycles. All the edges look good on the scope and SPI communication works properly, except for the detection of the toggling (while(!PORTBbits.RB1);).

This is my SPI sending code:

    while (spi_out_msg_buffer.write_cursor > spi_out_msg_buffer.read_cursor)
    {
        DisableInterrupts;
        SSPBUF = spi_out_msg_buffer.data[spi_out_msg_buffer.read_cursor];
        LATBbits.LATB0 = 1;
        while(!PORTBbits.RB1); // wait for toggle on IRQ line
        LATBbits.LATB0 = 0;
        EnableInterrupts;
        spi_out_msg_buffer.read_cursor++;
    }

The while(!PORTBbits.RB1); is translated into two instructions:

BTFSS PORTB, 1, ACCESS
BRA 0x188

I insterted that B0 line for debugging purposes, you can see it at the very bottom of this timing diagram:

You can see the toggling of the IRQ line (second from the bottom) and how it goes undetected, because the B0 debugging line stays high. When I stop the execution via ICD it hangs inside the while.
It is worth to mention that it usually works for a few bytes and then stops, as you can see here:

I measured that the pulse is actually 4 instruction cycles (= 16 PLL cycles = 4 clock cycles) long:

I think that should be sufficient for the pulse to be detected. Even if the first BTFSS misses it because the port is sampled at the beginning of the instruction cycle, then the second one should get it:

10 MHz -> PLL -> 40 MHz -> 10 M instructions per second -> 100 ns per instruction.

Shouldn't that be long enough to exit the while?


texts: Combining AC and DC components in same Spectra/Molex Microfit connector

texts:
I am making a control unit. It will interfaced with AC devices like fan, pump, light along with one DC device, namely, a Solenoid lock.

All the devices will be placed outside of the control unit.
I am planning to use 8x2 microfit connector as the interface between the control unit's PCB and the deivces.

Just wanted to know, if its a good idea to have all the above devices interfacing with the PCB via one microfit connector.

Or, should I use separate connectors for AC devices and the DC device.

Power supply and the PCB designing is all set, just wanted some guidance for the above.


texts: 9v AC 2000mA power adaptor for a 9v AC 1000mA device

texts:
Possible Duplicate:
  Choosing power supply, how to get the voltage and current ratings?

I need to replace a 9v AC 1000mA adapter for a 9v AC 1000mA device but all I've been able to find is a 9v AC 2000mA adapter.

Will this work or will it fry my device?


texts: H bridge heating issue when driving BLDC

texts:
Hi I have been trying to create a custom Brushless DC motor driver circuit using P type and N type transistors (known as H bridge).

This is the circuit I designed and prototyped on the breadboard.
Im using and gates to control the PWM of the H bridge.

Im using IRFZ48N (P channel) and IRF4905 (N channel) as mosfets
Im feeding it with 24V DC.
Im using an Arduino mega to feed it with 62khz signal and gate
states. The software makes sure that pin going low comes before pin
going High (so that it doesn't conduct both N and P at same time.

The IRFZ48N mosfet in the middle down sequence (Next to the Q3) gets overheated

Currently I dont have any oscilloscope so can't do any measurements wave wise, but I have couple of multimeters with 2 point presicion if that helps to measure.

The circuit seems right to me even though it gets heated. Any help would be appriciated


texts: I have a .asc PADS file that defines the footprint for a part I am using. Is there any way I can use this file with Eagle so that I don't have to make the package from scratch?


texts:
Before someone suggests a shaft-mounted Hall effect sensor and an LM2917 I should explain that on a diesel fire-fighting water pump there is neither alternator tach pulse nor access to the driveshaft, which  goes directly from the engine into the pump.

Although I'm piloting this on my home water pump, there are other applications for this solution, not least of which is as a no-wire tach sensor for use in cabin-mount vehicle telemetry systems. I was trying to avoid making disparaging public comments about the apparent inability of my employer's installers to find a tach pulse behind the dash, but I think Peter Bennet's otherwise reasonable comment deserves an answer.

I'm interested in using a microphone or similar transducer that measures vibration in the 0 < f < 1kHz range.

As pointed out by Andy, RPM != Hz. The single cylinder diesel waterpump fires once for every two revolutions of the crank, so running at 3000RPM the frequency of detonation is only 25Hz. This point gave me considerable pause. However, engines do not produce a pure tone. Firstly, the entire engine block functions as a bell. If I remember my bell theory that should produce at least five tones of reasonable power (it starts off pretty loud!). Secondly, the exhaust baffle works by inducing a complicated series of reflections with deliberate refraction. The resultant wave has many times the frequency of the base harmonic. To get a reliable answer I'll have to use a spectrum analyser. Happily there's one at work and while I don't really know how to use it, I have colleagues who do. This should prove interesting.

My first experiment was a Jaycar kit that provides life-support for an LM2917. It worked well for detecting a frequency threshold, but what I want to do now is convert the dominant frequency to a voltage.

FFT is not a load I care to place on an embedded CPU that's already busy, but if there is a spectrum analyser on a chip, that would be superb so long as it isn't thirsty or ridiculously expensive.

Investigation of the aforementioned LM2917 reveals that it can be configured as a frequency to voltage converter, which is exactly what is required as the input for an ARM SoC.

Broadly speaking (if I've understood the docs correctly) it's a charge-pump arrangement inside the LM2917 with some op-amp cleverness to produce an output voltage linearly correlated with frequency.

Figure 33 of the app notes in the TI documentation for the LM 2917 is titled "Frequency to Voltage Converter with 2-pole Butterworth Filter to Reduce Ripple" which is pretty much exactly what I wanted. The output is linearly scaled from Gnd to Vcc with the range governed by the drain-to-ground resistance on pin 3, so now I guess the question has mutated into...

What's involved in using a microphone to supply f(in) of an LM2917?

A little digging reveals that an electret microphone is an assembly with a capacitor where the distance between the plates changes according to air pressure and the tiny change in C is converted to a signal by an embedded op-amp. You have to supply power, and the output voltage range is determined by the supply voltage.

The problem to which Andy alluded is that these frequencies are so low that signal integration won't work so well. My whole strategy really depends on being right about the harmonics. Stay tuned (sorry, couldn't resist it).


texts: relation between battery and motor parameters

texts: I have a motor with the following specifications: 24V,10A, 250W.  If I run the motor using battery of 35Ah, for about 5 seconds, What will be the power consumed by the motor ?


texts: hump on rectified signal and inconsistency on gate signal

texts:
Following is the image of my circuit, I am working at the moment. This is not my own circuit but I am trying to understand and work on it.

Following is the signal I am getting at Gate2. What could cause one gate signal fine and another gate signal worse. The Gate 1 signal is pasted at the very end ( sorry for disorder).

Following is the signal I am getting at B'. I do not understand why I am getting bit of noise in between two half waves. This is same at A' also. When I enlarge the image, I get big hump ( Smaller than AC signal). What could cause this? This is the signal immediately after rectification from diode.

Following is the signal I am getting at Gate1.

I am getting half output from the my system. I am guessing this might be because of the turning of only one gate. Could there be any reasons why one gate can go faulty. I replaced the TRIACS and TRIAC Driver already, but did not help.
The vertical glitch lines on each half waveforms on third image, is that because of firing angle? or will any component cause this? I guess the reason being firing angle because this vertical line moves left and right when I decrease and increase the output.
Any help will be highly appreciated.

so this is the rest of the picture. I hope I have included everything.


texts:
What is the mechanism by which Triodes in audio tube amps generate harmonic distortion?

It is my understanding that the distortion is generated by means of electron bunching. That is, when the grid voltage swings negative and is larger than the cathode voltage, it blocks off electron flow from the cathode to the anode plate and creates a cloud of electrons with non-uniform density. When the negative grid voltage falls to 0, this cloud of electrons moves forward to the anode in the form of a bunched wave which adds harmonics to the signal. Or when there is a capacitor connected to the anode lead by means of a T-junction that can cause the anode voltage to swing negative, repelling the oncoming free electrons emitted by the cathode and creating a "space charge" between the anode and the grid with nonuniform density due to velocity modulation. Is this correct? If not please explain why.


texts: What's the difference between 74LS00 "gates" and 74LS37 "buffers"?

texts:
The TI 74LS00 is "quadruple 2-input positive-NAND gates" and the 74LS37 is "quadruple 2-input positive-NAND buffers."

The pinouts are identical. The LCCC package is documented exactly the same for both and, though the DIP package pinouts are labeled slightly differently (pins 9/10 are labeled  "3B/3A" on the 74LS00 and "3A/3B" on the 74LS37), this this should make no difference in actual operation since there's no difference between the two inputs of a NAND gate.

The switching speeds may be slightly slower for the 74LS37; 12/24 ns typ/max versus 9 or 10/15 ns typ/max for the 74LS00, but I don't know if this might be simply because I'm looking at (the data sheet for) an older part for the 74LS37.

The input current draw seems the same for both.

The major difference appears to be the current capacity of the outputs; the 74LS00 sources up to 0.4 mA when high and sinks up to 8 mA when low; the 74LS37 sources up to 1.2 mA when high (3x) and sinks up to 48 mA (6x) when low.

Is this output current capacity the difference between this 74LS00 "gate" and 74LS37 "buffer"? According to the Wikipedia description of a "digital buffer" a buffer would offer better input characteristics, which don't seem to be different here. (Almost all of the other parts labeled "buffer" have open-collector or tri-state inputs.)


texts: Is three-stage lead acid battery charging possible with PWM solar charger?

texts:
I have studied lead acid battery charging methods from the website http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery. In which they mention three stages of charging:

My question:  I already made a PWM solar charger unit using the P-MOSTFET IRF4905, in which I can control the PWM duty cycle and can be reduce the current, but when reducing the current the voltage applied to the battery will also be reduced, then how can I implement these three stage of charging by use of PWM? i.e. constant current mode ok, but how can we apply top charging?


texts: Is it possible to get ST-LINK's virtual COM port working without launching any program in Ubuntu?

texts:
I did some development on a Nucleo-64 board (specifically the NUCLEO-F303RE with the STM32F303RE microcontroller) and used OpenOCD and GDB with target remote :3333 to flash my code (with load) onto my microcontroller.

During this time, I used the ST-LINK's virtual COM port on my Linux machine (Ubuntu 16.04 (Xenial Xerus)) to talk with the microcontroller's USART. Now I would like to just use the virtual COM port to talk the microcontroller without needing to start OpenOCD or GDB.

I was surprised to discover that this doesn't just work. The symptoms are that my device doesn't receive bytes send by the host nor vice-versa. (I detect bytes arriving at the target device by blinking an LED.) Therefore, it seems that the state of the ST-LINK microcontroller, or perhaps the Linux kernel on my host machine, is somehow changed by the process of connecting via OpenOCD and flashing the program.

My main question is: Is it possible to get to this virtual COM port working state on my Ubuntu 16.04 machine without launching OpenOCD or GDB? Ideally, I would not need to use any additional program, but perhaps just change some configuration setting.

My second question is: Why is this happening? Is the ST-LINK device itself changing modes here?

And my third question: Why is the following happening and what can I do about it? Sometimes, even after successful flashing, the target microcontroller can send bytes successfully, but is unable to receive them. Furthermore, I think one of my boards is neither able to send or receive bytes using this method although the firmware seems to upload just fine.

On MacOS 10.12.1, my target microcontroller is immediately connected and accessible as desired (with no further command running or firmware flashing) via the virtual COM port at, e.g. /dev/tty.usbmodem1423. Therefore, I now suspect the issue is with the Linux kernel side and the driver that creates /dev/ttyACM0.


texts:
I need to have a dimensio for a component however i could not be sure about it. I need "x" distance that i mentioned below.

This is the datasheet drawings;

In my opinion it should be x=1.3 mm Can you say your consideration? Thank you.


texts:
Estimate the bandwidth required to transmit 1Mbits/s of data using a modulation scheme which comprises 32 different frequencies and 2 amplitude levels

Yes, this is a homework question that ive been trying to do. What i have so far is the following:

I think 32 frequencies implies that i have 32 symbols, and therefore i have 64 bits, i saw somewhere that the number of bits is always 2*(number of symbols).

bps = 1Mbps = baud*bpb from here

=>baud = 1Mbps/64 = 15625

and i also saw somewhere that Band Width = 2*baud = 31250Hz

Is this correct?

-Thanks.


texts: What are some techniques to troubleshoot a second order sigma delta loop?

texts:
I have designed a slightly modified second order (3-bit) multi-bit incremental sigma delta modulator (IDSM) in simulink (system level). The SNR that I get is 45dB, which is not as expected. But ideally with 3-bit IDSM, we should get 78 dB. So, I wanted to troubleshoot why my designed second order system is not behaving as it should.

For copyright reasons, I could not share the exact designed architecture. But the architecture is similar to the model shown below:

(I use the fine ADC as 2nd order sigma delta). The reason that I compared with (3-bit) multi-bit incremental sigma delta modulator is that I have 3-bit coarse ADC.

I would like to know any other way (other than SNR) to verify/troubleshoot why we would not get a second order behavior?

1-noise shaped output spectrum (which i could not for Incremental architecture, but I have posted a question in DSP forum for this - https://dsp.stackexchange.com/questions/54548/how-to-plot-noise-shaped-spectrum-of-first-order-incremental-sigma-delta-adcs-o)

I guess that this is a control system loop and is there any other way to troubleshoot like - Impulse response or any other way?

Thank you.


texts: SP4T slider switch on two states at the same time

texts: I have a SP4T slider switch, where common is connected to the power rail and each pin is connected to a led and resistor. The problem is, if I position the switch between two terminals, the leds of both terminals light up. Is this a sign of a bad switch? Even if it is, are there any way to prevent two leds lighting up at the same time with this switch?


texts: What happens if power sources are connected in violation of ideal circuit theory?

texts:
My circuits knowledge is (mostly) limited to ideal circuit theory, where:

An ideal voltage source maintains a prescribed voltage regardless of
current flowing though its terminals
An ideal current source maintains a prescribed current regardless of
voltage across its terminals

The below circuits are not permissible according to ideal circuit theory, but obviously they could be connected as shown.  Im trying to gain a better sense of what happens in real (physical) circuits when connected improperly.

simulate this circuit – Schematic created using CircuitLab

In reality, what happens if power sources are connected in violation of ideal circuit theory?

I expect the answer depends on specific power sources and their internal circuitry - a power source might fail, or regulate mismatched current/voltage, etc.  Still, is there a predictable outcome to this type of problem and how is that outcome determined?


texts:
I have an ATmega328P that seems to be fried. It was in an Arduino board (Freakduino-chibi, specifically) and working when it suddenly stopped responding at all.

Investigation showed that the fault followed the chip from board to board.

Using a BusPirate, I tried to access the chip via avrdude and the ICSP header on the Arduino. No dice: avrdude failed to initialize the chip. Using the same board and a different 328P, avrdude was successful.

Any thoughts on how to possibly resurrect the broken chip?


texts:
Atmel AVR1916: USB DFU Boot Loader for XMEGA  application note reports that for the ATxmegaxxxA1U the pin for starting the programming is PF10, but the devices has no such pin, as shown in the datasheet.

On the web the problem is highlighted here and here but no answer is given.

In particular, the last link reports that PF0 did not work.Code for other devices have a match between the ISP_PORT_PINCTRL and ISP_PORT_PIN   (5 and 5, 3 and 3, ...)
but A1U seems not to.

00068 #if XMEGA_A1U
00069 # define ISP_PORT_DIR      PORTF_DIR
00070 # define ISP_PORT_PINCTRL  PORTF_PIN5CTRL
00071 # define ISP_PORT_IN       PORTF_IN
00072 # define ISP_PORT_PIN      0
00073 #elif (XMEGA_A3U || XMEGA_A3BU)
00074 # define ISP_PORT_DIR      PORTE_DIR
00075 # define ISP_PORT_PINCTRL  PORTE_PIN5CTRL
00076 # define ISP_PORT_IN       PORTE_IN
00077 # define ISP_PORT_PIN      5
00078 #elif XMEGA_A4U
00079 # define ISP_PORT_DIR      PORTC_DIR
00080 # define ISP_PORT_PINCTRL  PORTC_PIN3CTRL
00081 # define ISP_PORT_IN       PORTC_IN
00082 # define ISP_PORT_PIN      3
00083 #elif XMEGA_B
00084 # define ISP_PORT_DIR      PORTC_DIR
00085 # define ISP_PORT_PINCTRL  PORTC_PIN6CTRL
00086 # define ISP_PORT_IN       PORTC_IN
00087 # define ISP_PORT_PIN      6
00088 #else
00089 # error Unknow AVR Xmega part
00090 #endif


texts: LTspice "could not open library file" for a third party amplifier

texts:
I'm trying to use INA129 in LTspice. So first in TI's page I go to Tools & software and under the model download the file called: INA129 PSpice Model (Rev. B).zip

In this zip file there are files with extension .OLB, .DSN, .opj and .LIB. There is nothing with .cir or .MOD extension.

I changed the INA129.LIB name to INA129.MOD. Then I made an 8-pin symbol for the amplifier and associated the net list to each pin due to the following line in the LIB file:

The file includes the netlist:

  .SUBCKT INA129          1   2   3   4   5   8   9  10

And below is how I set the amplifier attributes:

To test the setup I use the following directive and schematic:

But I keep getting the error:

Could not open library file "INA129 .MOD"

What could be the issue here? I found this question so far but has nothing to do with my case.

edit:


texts: PIC24 Primary Oscillator XT_PLL frequency is off by 3 percent

texts:
I am using a PIC24. After solving the issue with the PLL (PIC24 PLL module is always out of lock) I am struggling with large variation in the system frequency. I wrote a small code that is used to measure the system frequency using internal LPRC timer. The primary oscillator FOSC is 8 MHZ and with PLL its pushed to 32 MHz. The FCY is FOSC/2 (16MHZ). My code is reading an FCY of 15.522 MHz which is 3 percent off the actual expected frequency. As a result I am not able to connect my PC to the UART running at 38400 bps for debugging.

I think my computer's serial port is not able to tolerate such high a drift in the baud rate and hence causing a serial port framing error. Please suggest a way to improve my frequency.

Here is my uartInit function

#define  peripheralPinSelectUnLock() do { OSCCON = 0x46; OSCCON = 0x57; OSCCONbits.IOLOCK = 0; } while(0)
#define  peripheralPinSelectLock()   do { OSCCON = 0x46; OSCCON = 0x57; OSCCONbits.IOLOCK = 1; } while(0)
#define UART1_BAUD_RATE              (38400ul)

uint32_t ui32Fcy=16000000;
unsigned long int baudRateDivider = ((ui32Fcy/(4*UART1_BAUD_RATE))-1);

peripheralPinSelectUnLock();   // PPS Unlock
PPSInput(PPS_U1RX, PPS_RP30);  // RF2/RP30 as U1RX
PPSOutput(PPS_RP16, PPS_U1TX); // RF3/RP16 as U1TX
TRISFbits.TRISF2 = 1;          // RF2/RP30 is set for input (RX)
TRISFbits.TRISF3 = 0;          // RF3/RP16 is set for output (TX)
peripheralPinSelectLock();     // PPS Lock

U1BRG = baudRateDivider; // Divides to UART_BAUD_RATE
U1MODEbits.UARTEN = 1;   // UART2 is Enabled
U1MODEbits.ABAUD = 0;    // auto baud is disabled
U1MODEbits.BRGH = 1;     // Low baud rate ?
U1STAbits.UTXEN = 1;
IFS0bits.U1RXIF = 0;      // clear interrupt flag of rx
IEC0bits.U1RXIE = 1;
IPC2bits.U1RXIP = 7;      // enable rx recieved  data interrupt

The value of U1BRG (watch variable) is 103 for a baudrate of 38400.
Thanks for any help.


texts: How can I model a Diode in a Bond Graph?

texts:
I'm trying to analyze the following circuit and turn it into a bond graph so I can derive the state space equations from it. I'm getting stuck figuring out how to convert the diodes for the rectifier into bond graph elements.

Ignore the values for the circuit elements, the circuit drawing software I used automatically applies them and won't let me turn them off.

This is what I've gotten converted from the circuit into the bond graph so far. I feel like I've messed up a little somewhere, but I'm unsure exactly where as well. I'm hoping that figuring out how to convert diodes will help me to figure out how to fix that. I just realized I mislabeled the voltage source as SF instead of SE.


texts: How is a differentiator op-amp current possible?

texts:
I have been reading about op amps and came across this description of a differentiator variant using a capacitor.

The author explains that current can go through the capacitor when there is changing voltage, but I struggle to understand how the capacitor does not block the DC voltage source. Could anybody explain how there can be current in this situation?
Full link to article


texts:
There is this socket for a light bulb, and it says LED only.

Why is it like that?

Is it just for power limitation (not to exceed power,) because LEDs take less power, or is there another reason?


texts: GSM noise from a 2-layer PCB with SIM800C

texts:
I've designed a 2-layer PCB that contains a 12-5V buck converter (P2576L-50 - a Clone of the LM2576), 3.3 (AP1117-33) and 4V (MIC29302WU) shunt regulators, an STM32 micro and a SIM800C GSM module.

The board has 4 connections to another board, where it takes its power and ground from as well as 1 input and 1 output. The problem I'm having is that I get GSM noise transferred into a speaker that's connected to the other board, so clearly there's an EMC layout issue. I've tried to keep the bottom ground plane as solid as possible in order to minimise any EMC issues. I also put vias near the ground pins of the ICs to allow returns currents to return through the bottom ground plane.

Can anyone point out where the layout problems are? I'm interested in learning where the problem areas are.

Here are the top and bottom views:

TOP:

BOTTOM:


texts: Is it possible to use i2c accelerator to multiplexer input?

texts:
I have 10ft long wire cabled i2c 4 buses (for 8 sensors, sensor are not in the same place each has 2 i2c addresses),

I try to use i2c multiplexer PCA9548A with an i2c accelerator Ltc4311,

i2c accelerator will be placed in between Arduino and the i2c multiplexer input side, the output side of the multiplexer will connector 4 separate i2c buses where each end has 2 sensors

I cannot use CAN bus, also bigger circuits like i2c extenders

Is there any other way to handle this with a minimum number of components?

What are the other possible issues can occur?

I haven't selected a cable yet.

edited

I2C 400kHz


texts: how to fix output voltage of an NMOS switch with changing load characteristic?

texts:
In an NMOS low side switch the output voltage at drain depends on the operating point decided from the Id-Vds curve and load line.

According to my understanding, for a low side switch with Vds around 0, we need to keep the operating point in triode region. This can be achieved by keeping Vgs-Vt>0 and relatively high load resistance to keep the NMOS in triode region. I hope this is correct?

Further, for my application, I am using NMOS switch for providing ground voltage to a memristor which is connected between Vdd and Drain terminal whose resistance changes during the ON cycle. This leads to a shift in Drain voltage as the memristor is being programmed for desired resistance. The shift is undesired as i need a constant voltage across memristor during this ON cycle.

The shift is seen from the following SPICE simulation(Vx1-).

So my final question is, How can i make a low side switch for this application which will provide a constant Vds with changing load resistance?


texts: Why does the opamp output voltage saturate?

texts:
simulate this circuit – Schematic created using CircuitLab
Vout = Vin (1 + R2/R1)  According to this positive feedback topology   - made an error here, it's Vout = Vin(-R2/R1) (edit)
Now I read in a tutorial - http://www.electronics-tutorials.ws/systems/feedback-systems.html  , that

If the input voltage Vin is positive, the op-amp amplifies this positive signal and the output becomes more positive. Some of this output voltage is returned back to the input by the feedback network.
Thus the input voltage becomes more positive, causing an even larger output voltage and so on. Eventually the output becomes saturated at its positive supply rail.

How does this happen? Shouldn't Vout be constant at a particular value, because we aren't changing Vin or the resisitors right? Shouldn't the equation Vout= Vin ( 1 +r2/r1) always hold? Error Vout = Vin(-R2/R1) (edit)
So how is the Vout increasing iteratively?


texts: PIC12F617 Device ID read when debugging but not when programming

texts:
First time using a PIC12F (I've used PIC16, PIC18, DSPIC24F, DSPIC30F and DSPIC33F in the past).

Made a very simple pcb (see sch below), but I'm having problems programming it with an ICD3.  Didn't know, but these need a special header for debugging using ICD3 (don't have), but from what I understand it should be possible to program it without it (maybe not?).

When I try to debug, telling MPLAB that the header is there (but isn't), it detects the correct Device ID (1360), but complains that it is not what was expected (because it expects the header).  But the point is that it COULD READ the Device ID.

But, when selecting the ICD3 as programmer (as opposed to Debugger), it reads 0's as Device ID, so it can't continue.

Any thoughts on why it is not reading the Device ID when in programming mode?

By the way, I don't use the stock RJ11 connector because it's too big, but I've used this smaller Molex successfully on tens of different custom pcbs with other Microchip microcontrollers.

UPDATE:

Not being able to read the Device ID is still a mystery, but it turns out that it can be ignored and the device will program just fine.  The fact that the program can be verified and that it will read the device id with ICD3 as debugger makes me doubt the signal integrity hypothesis.  I tried the 100 ohm resistor very close to the chip's ICSPDAT/PGD pin, and also a small cap right after (well, just a scope probe), without change in the results.

To really solve this I'll have to capture the PGD-PGC-VPP exchange and analyze it.  If I do it I'll post the results here.


texts: Sending debug information from MSP430 to CCS Console

texts:
I am debugging some code written for the MSP430F2132, which has very little flash memory available for the program. In order to debug properly, I must send information out to a terminal so that it can be stored and viewed at a later time. Normally I would use printf or a similar command (putchar, perhaps) and have it linked to the CCS 6.1 console. However, due to the lack of program memory on the micro, I am unable to use these functions. I also do not have the option of modifying the board to make use of a built-in UART channel on the micro. I am connected to the micro using the MSP-FET430UIF USB debug interface, which supposedly implements a back-channel UART interface but I think this requires special connections to the target that I do not have. Do I have any options that use very little memory that would allow me to store debug information? I just need to send two long ints each cycle.

EDIT:

Upon further inspection (the design was not originally mine), I notice that the "special connections to the target" required for the MSP-FET430UIF (simply to the UCA0RXD and UCA0TXD pins on the target micro) do exist, but the signals are converted to RS-485 using transceivers on the interface board (a test fixture) and the target board. Perhaps I can use the FET430UIF backchannel UART after all, though I have yet to find good instructions on how to do that. If anyone here has experience doing this and will be able to offer guidance, it would be very helpful.


texts: Flyback diodes issues and pull-in & hold current issues in this Relay circuit

texts:
Although this may be a basic question but I'm still struggling with it. In this schematic, two zener diodes D1 and D2 are connected back-to back across relay coil L1. The BVds = -30V for Q1. Can I use 15V(Vz = 15V) zeners for D1 and D2 instead of 5.1 V zeners? Will the relay coil or contacts can get damaged during turn-off of relay?  If required, I'm using this relay (5V DC Standard Coil).

Also, to reduce steady state current consumption of relay coil, I wanna use the RC ckt shown aside in schematic. As soon as Q1 turns-on, uncharged capacitor temporarily appears as a dead short, causing maximum current to flow through the relay coil and closing the relay contacts without chatter.
As the capacitor charges, however, both the voltage across and the current through the relay coil decline. The circuit reaches steady state when the capacitor has charged to the point that all the current through the relay coil is moving through R1. The contacts will still remain closed until the drive voltage is removed.

Which is the best place to put this RC ckt - section marked 'A' or 'B' in schematic. Will it make any difference? Section-B seems to me the best choice, as when Q1 turns-off, capacitor C1 can discharge via R1 through ground. How will C1 discharge when instead I place RC ckt at section-A? Am I missing something here?
Does putting this RC ckt has any side-effects? Any better solution?

Please correct me if I'm wrong or missing something?

UPDATE1 on 2012-07-09 :

Say in above schematic I have 6V DC Standard coil(see datasheet above), 48.5 ohm relay. And take C1 = 10uF say. Assume that R1C1 ckt is placed at section-A in schematic above. The power supply is at +5V.

For a Drop of 3V(Hold-on voltage) across relay coil, the current must be 62mA approx. through coil.
So drop across R1 at steady state is 2V.
For a current of 62mA through relay coil at steady state, R1 must be 32.33 ohm.

And charge on C1 is 2V x 10uF = 20uC, at steady state.

Now in this data sheet, the operate time is given to be 15ms worst case.
From above data we have RC = 48.5ohm x 10uF = 0.485 ms. So, as soon as Q1 is turned on, the C1  will be almost fully charged in 2.425 ms.

Now how do I know that this duration of 2.425 ms is sufficient for relay to make its contacts close?

Similarly, as soon as Q1 is turned-off, due to back emf generated and clamped to 3.3V by zener D2(Vz = 3.3V) plus diode D1 drop of 0.7V, the voltage across C1 will be  -2V + (-3.3V - 0.7V) = -2V. But charge on C1 is still 20uC. Since capacitance is constant, so charge must decrease as voltage across C1 decreased from +2V to -2V instantly after turning off Q1.
Isn't it violation of Q = CV?

At this point, the current that is flowing through relay coil due to back emf will be 62mA in same direction as was before turning-off Q1.

Will this 62mA current will charge or discharge the C1? The voltage across C1 is 6V as soon as Q1 is turned off right?
I didn't get how currents will flow b/w  R1, C1, D1, D2 and relay coil as soon as Q1 is turned-off.

Can someone throw light on these issues?

UPDATE2 on 2012-07-14 :

"Current in an inductor will not change instantaneously" - While there is a flyback diode D1(Say, D1 is not zener but a small-signal or a schottky diode, and zener D2 is removed in the schematic above), as soon as Q1 is turned-off, will there not even be a current spike(not even for few usecs)?

I'm asking this becoz, if there is a current spike then the amount of current that will flow during this spike(say > 500mA in this case) might damage the flyback diode if I had selected a diode with max peak forward current rating of around 200mA or so only.

62mA is the amount of current that is flowing through the relay coil when Q1 is on. So, will the current through relay coil never exceed 62mA - not even for a moment(say for some usecs) after Q1 is turned off?


texts: I am fairly new to electronics and I recently made an inductive charger that transfers 18 volts over a couple mm from 120 volts. The problem I am having is that while the voltage transfer is good, the current transfer is minimal. I tried putting the voltage through a step down transformer to increase the current, but this got rid of the voltage as while as the current. Is there any way to increase the current?


texts:
Title might seems confusing but I want to connect two seperate transistors' outputs - bridging them.

Main question: Would there be a short circut if I connect +V(voltage from another transistor output) to transistor output (Emiter if NPN, Collector is PNP)?
I didn't have such a problem with briding relays but now Im confused.
Thanks in advance


texts: first time here. Today, I was looking on my motherboard/graphics card and I noticed tiny little pin width points of solder with nothing soldered to them. The distance between most of them are just right for a small rectangular capacitor or resistor, but I can't seem to think of why the manufacturers would put the solder there yet not do anything with it. Just curious, thanks.


texts:
DC current through a very long wire losses its first current, because the wire work as a resistor.

This is the biggest problem when using DC appliances in solar home systems, because there is a very long distance between the battery bank and the load.

So, I consider distributing the batteries through the wire, for example if the wire is 60 meters  long and we have 3 batteries, I will put one battery in each 20 meters.

Is the diagram below correct? Will it have effect on battery charging process?
Are there other solutions for this problem?


texts: Can adding power storing capacitors burn up an adapter?

texts:
I have been working on a circuit board for an Arduino project.  It contains an LCD screen, linear regulators and several relays.  In an attempt to remove voltage spikes and dips, I have added several capacitors with several different values all around the circuits.  I may have over done it.

I am wondering if having lots of capacitance on my power lines will cause an unsafe draw of power from my transformer when I turn it on?  How can I prevent this?  Also, will having lots of capacitance cause problems for the Arduino and the LCD circuit at start-up (because of a lack of power availability at first)?

I am powering an:

One Arduino Mega
One 32 character LCD screen
Two 9 volt to 5 volt linear regulators
16 relays
Two large 8 segment LED displays
About 20 LED strip segments

with a 2 amp, 9 volt power supply.

Near the power supply: 100 uF and 10 uF
Near the Arduino Mega: 100 uF and 10 uF
Near both linear regulators: 10 uF and 1 uF on both sides
Near Relay power lines: 1 uF and a zener diode
Near LCD Power lines: 1 nF and 100 nF
Near all 9 digital in/out lines: 100 pF and a zener diode
Near all 20 switches: 100 nF

Total is getting close to 300 uF


texts: How would you wire small computer to run on both batteries and AC power?

texts:
I'm trying to use a motherboard (Mac mini 2018 model) for a project that will require it to be able to run off batteries. The project is essentially building a custom laptop using the Mac mini mobo and power supply internally with an mxm GPU board for upgrade able graphics in the future.

How would I wire up the batteries with the power supply in order to be able to hit swap between AC and DC power and also keep the batteries charged when plugged into the wall? I could either use the power supply from the external GPU or the power supply from the Mac mini I think.

External GPU I’m considering is the Sonnet Breakaway Puck.  Max power from the included power supply is 160W or 220W depending on which model I buy and it marketed at being able to power itself and a laptop connected via USB-C so maybe this is enough for both Mac mini power and GPU power?


texts:
I’m doing a 16 rows & 48 column LED matrix design. The attachment shows only one row & some columns.

I’m scanning rows @ 1/16th rate. Designed for 4mA average current to the LEDs. I’m doing a 5V design (PIC & shift registers working on 5V), but For LEDs I can increase supply more than 5V.

My LEDs are bit dim.When I increase the LED supply voltage to 6.5V then the brightness improves.But I'm not sure is that voltage is too much for LEDs.

I use 3V LEDs.I need to make imrovements in my deisign.What modifications needs to do to make a brighter display?


texts: SDCC generates invalid programs for PIC 16f628a

texts:
I've been learning how to code for PIC 16f628A and I wrote a very simple code to turn on a LED, which is connected to RB0, and keep it on. My original intention was to use SDCC and GPUTILS to compile the projects. However, it seems that SDCC or GPUTILS are generating invalid hex files, since the program doesn't act as expected whenever I upload it to the chip, the LED keeps off during all the program execution. A similar code compiled with CSC's compiler runs without any problem. Also, I got no success in executing a simple program compiled with GPASM. It's noteworthy that GPSIM executes all those programs perfectly and shows the pins are working as expected. I'm using K150 as programmer. I don't know what is going on with SDCC and GPUTILS.

#include "pic16f628a.h"
//#include "tsmtypes.h"
//#include "tsmpic.h"

#include <stdint.h>

//CONFIG:__config (_CP_OFF & _LVP_OFF & _BOREN_OFF & _MCLRE_ON & _WDT_OFF & _PWRTE_ON & _INTOSC_OSC_NOCLKOUT)

uint16_t __at 0x2007  __CONFIG = _CP_OFF & _LVP_OFF & _BOREN_OFF & _MCLRE_ON & _WDT_OFF & _PWRTE_ON & _INTOSC_OSC_NOCLKOUT;

#define CLOCK_8MHZ 0
#define CLOCK_4MHZ 1

void main(void)
{
    //SCS = 1;

    TRISA = 0x00;
    TRISB = 0x00;

#ifdef __16f628a    // Only compile this section for PIC16f628a
    CMCON = 0x07;   /** Disable comparators.  NEEDED FOR NORMAL PORTA
         *  BEHAVIOR ON PIC16f628a!          */
#endif

    // Loop forever.
    while(1) {
        RB0 = 1;
    }
}


texts: Cost reduction by eliminating vias from PCB design

texts:
I am designing a small (30mmX20mm) and not complicated two layer PCB. It is possible to do the design without using vias.

Is it possible to determine how much can I save approximately by eliminating vias from design?
Is it worth it?


texts: Protect PC817 Optocoupler Anode from High Voltage

texts:
Voltage at IN3 will vary from 10V to 28V, How can I protect the optocoupler from getting damaged due to high voltage.

What is the maximum voltage and Minimum voltage should be given at anode (Pin 1) to sense LOW properly on GPIO.

Is there any external pull up needed at Pin 4 connected to GPIO of MCU.?

EDIT :

I am doing few calculations based on the comments, let me know if they are right

First of all the Optocoupler forward voltage is 1.2V and the maximum forward current for LED is 60mA.

The value for resistor R13 should be

We will take LED current as 10mA

R = (Vin - Vf)/I

R = (12-1.2)/0.01

R = 1080 ohm ~ 1K resistance

If Voltage is increased upto 28V,

I = (28-1.2)/1000
  = 26mA

This is well below the maximum LED current i.e 60mA. So there should be no issue with the high voltage and the 1K resistor is fine.

Now coming to collector load resistor value which is not mentioned in the image,

in data sheet the Vce saturation voltage is 0.1~0.2V

if Load Resistor is 10K
Ic = (Vcc-Vce)/R
  = (5-0.1)/10000
  = 0.49 mA

This value is also well below the maximum collector current which is 50mA.

So I think based on above calculation, Input resistor of 1K will work fine and collector Load resistor has to be added of value 10K.

Comments?


texts:
I am trying to communicate with a Nokia 1202 LCD with my Arduino using SPI.

The LCD using the STE2007 Controller. As per the datasheet here @ page 12, you find that the min time for SCLK is 250ns => 4MHz and no maximum value listed. So what i understand is that this driver can communicate using SPI with SCLK being max. of 4MHz.

Since my arduino board is running at 16MHz, and I will be using the 'spi' library this is what I think i should do:

set bits SPR0 and SPR1 in the SPCR register to set the spi clock speed @ 4MHz
do spi.begin()
execute spi commands as normal

Is this correct ?

Something like ...

void setup()
{
  pinMode(SPI_SS, OUTPUT);
  pinMode(SPI_DC_SEL, OUTPUT);
  SPI.begin();
  SPI.setBitOrder(MSBFIRST);
  //set spi register to set SCLK @ 4Mhz
  //SPI2X = SPR1 = SPR0 = 0
  SPCR &= ~(1<<SPR1);
  SPCR &= ~(1<<SPR0);
  SPSR &= ~(1<<SPIX2);
}


texts: How do I draw a transistor with a circle at the base?

texts: I've seen schematic diagrams with transistors that have a little circle right where the gate connects with the rest of the transistor. From the context it seems like the behavior is that the resistance between the source and drain goes way down if the gate voltage is LOW, not high. Does such a transistor exist? If it does, how can I create a schematic diagram with it, using the tools on this forum? I couldn't find a transistor with such a circle among the items I can choose from.


texts: Why does inverter synchronization with the grid take 5 minutes?

texts:
We had some solar panels & an inverter installed recently. Every time the inverter is turned on (after maintenance or with the first light of the day) it has to synchronize its generation phase with the grid, and it is easy to understand.

But why does it take around 5 minutes? When I asked the guy installing it, he said "it is some sort of standard, every inverter takes around 5 minutes to sync" and had no idea about the reason.

The inverter has 60 changes per second to sync with the grid. Sometimes it might be needed to observe the grid but still, 5 minutes is too much time and missed opportunities to synchronize:

60 Hz x 60 seconds x 5 minutes = 18,000 cycles

Am I missing something?

My inverter is Delta SOLIVIA Solar Inverter 3.8 TL.


texts: Relationship between base-emitter voltage, base current and collector current

texts:
I'm reading Sedra's Microelectronics book and I can't understand the following:

We can get a relationship between \$I_b\$ and \$V_{BE}\$ (DC):

$$I_B=\frac{V_{BB}}{R_B}-\frac{1}{R_B}V_{BE}$$

This tell us that \$I_B\$ and \$V_{BE}\$ are inversely proportional, but how can this be if:

$$I_C=I_S\exp(V_{BE}/V_T)$$ and $$I_C=\beta I_B$$

I simulated a circuit with this exact configuration and it shows that \$I_B\propto V_{BE}\$ which is what I expected. Snipping of the oscilloscope's graph. Levels and magnitudes are adjusted just to fit the image, but clearly they are proportional.

What am I missing? Thanks...


texts: Build A Two Port Write and Two Port Read Register File with 4 Registers

texts:
I am facing problem in my current task. I need to build a 2-port write and 2-port read register file with 4 registers. I am able to do the 2-port read part but I could not do the 2-port write part. How do I use two 2-4 decoders and two data lines to write 2 registers at the same time?

Thanks in advance.


texts: positive voltage from non-inverting amplifier is cut off

texts:
I'm experimenting with simulations in Kicad and have weird behaving output voltage and input current. R2 is being tuned in the simulation window to 2k. I'm using TL082 as the subcircuit for the opamp.

why is the voltage being cut off? Why is the input current in spikes?


texts: Question about Design of Isolated Output of Laptop Charger

texts:
Let's say one has a typical HP 19.5V Laptop charger, and consider the isolated output DC end. There is an metal outer-pin and inner-pin (which is difficult to touch with fingers). My theoretical understanding is that the outer-pin would have a potential of 0V and inner-pin has 19.5V, relative to ground?

As an aside, would the presence of a grounding-pin affect these?


texts:
Which ARM MCU family is better for beginners?

I mean which family:

Is straightforward and easier to learn
Has more/better learning and development resources available
Has bigger and better community
[Has FLOSS learning and development software/hardware available]

Update:

Do starting with Cortex-M4 is good idea? (because of ARMv7, Harvard mem arch etc)

between NXP, ST and TI Cortex-M4 based MCUs which is better for start?  (based on requirements above)


texts: How do I secure the connection to this battery (CR1616)?

texts:
I'm replacing the batter in a Game Boy Advance game cartridge.

(Don't mind the bad solder job; the iron isn't handling well.)

I've gotten it to work, but the battery is held down with very little force; so I don't have much confidence in the actual connection between the bottom pad and the positive-side of the battery. I feel like one bad shake and the battery might (even if momentarily) disconnect on the bottom side.

I tried shaping the bottom pad using some small pliers, but that clearly wasn't enough. Does anyone else have any ideas on how to make a more solid connection on the bottom side?

I have electrical tape, pliers, soldering iron, and even some solder tabs.

Here's a different angle, in case it helps:

Here, the pad and battery only touch at a single point. It's slightly better when there is pressure pushing the battery down.

NOTE: If anyone feels this belongs in a different site, please feel free to move it.


texts: Capacitive sensing between two copper plates

texts: Is it possible to detect touch event and its position coordinates between two copper plates spaced apart by approximately 6-7 centimeters? The space between plates have to be transparent.


texts: BLDC motor information to build an E-bike

texts:
I'm planning to build a light e-bike kit and want to use a super-efficient BLDC inrunner RC motor.

Many people seems to build e-bikes around AstroFlight 3210 2kW motor, because it is the most efficient motor on the market. However I'm not in for a monster, but a smaller 250-300W motor is good for me, so I have been thinking about using Astro 819M-9T.
https://www.astroflight.com/819m-9t-astro-19-brushless-motor-details.html

I will use a high reduction gearbox, so don't think about the RPM to wheel for now, I have a solution for that.

My problem is I don't now anything about RC motors or ECS  and I don't even understand how to read the specification for this motor. They only specify maximum power/amps etc. and I need to now nominal values for it. Also there is no torque rating for it, only a description of what size of prop and weight of models.

Questions:

What will the nominal values be for this motor?
What torque does it have and approximately how will the torque curve look?
Suggestion of other motors that would be good for this?
Would it be better to have a BLDC with sensor?


texts: OrCAD PCB Designer File Export to PDF (Gerber)

texts:
i want to export this PCB circuit to PDF exacty as it is (above image), but when i click on file -> export -> PDF, its shows exacty the window on the left "Allegro PDF Publisher", then i click on film creation, and the window on the right pop up, i custumized the domain to SMBOTTOM, to show only the pin soldermask bottom, pin/bottom, etch/bottom and board geometry outline all with black color, exacty as the first image, but the PDF exported (last image) is different than the first image (like i want).

My question is how do i export the first image to PDF exacty as it is ?


texts: How do I wire up this 4 wire 120v AC motor and capacitor

texts:
Little back story, I harvested this motor out of an electric pressure washer. I had to cut off a couple metal tangs on the motor and in the process took the motor apart and lost my wiring diagram.

Here is the motor

And here too

So I was hoping someone could help me figure out the wiring for my motor. the wire colours on the motor are white and black and the wire colours on the cap are white and black aswell.

Your guidance would be much appreciated.


texts: Do I need to worry about EMI/RFI/etc. for 110V and 12/5V electronics in the same electric panel?

texts:
I am building an electric panel (steel) which will house automation equipment in my home. The box is 20x20x10 inches and will include the following (all attached via DIN rail):

12v and 5v switched power supplies
GFCI breaker
Arduino
8 channel Arduino relay

The following sensors which will be connected to the panel via XLR ports and then Arduino via terminal DIN blocks:

Thermocouples (x3)
Solenoids (x2)
Motorized ball valves (x2)
Pressure transducers (x2)
110v outlets driven by relay board and arduino digital pins (2-4x)

Overall...

Is EMI/RFI/other noise something I need to be concerned about in this setup where 110v and lower voltage (12/5/3.3v) equipment is connected?
If so, how can I best partition the panel box from HV (110v) vs. LV (<12v)?
Will plastic cable raceways suffice or do I need metal raceways (maybe this is overkill)?


texts: How to provide power to a device that needs 3 different input voltages?

texts:
I have a device with 3 different modules that require different input voltages: 2 V, 5 V, and 30 V. The 2 V supply needs to be electrically isolated from the others. What would be the simplest way to provide the 3 different voltages?

I've been considering using 3 different AC/DC switching power supplies or somehow using a single power supply and splitting the output voltage. I'm having trouble finding inexpensive (less than $100) power supplies that can output 2 V or 30 V which leads me to think that most people must be doing something more customized when they need these voltages. According to the specs of my device, the ripple for each of these voltages should be less than 200 mV. The maximum current for the modules doesn't need to be more than 1 A.

Edit: There is no sequencing requirement for the different voltages. The typical currents are as follows: 1 A (for 2 V), 0.2 A (for 5 V), and 0.01 A (for 30 V). The specific device is a single photon counting module (SPCM-AQ4C Excelitas). Since this is for sensitive measurements, the power supplies should be well-regulated and low-noise. Also, the device will be using mains supply not battery.


texts: Testing strategies for testing a Scheduler

texts:
We have developed an in-house Scheduler which is based on Rate-monotonic scheduling.
We have 6 tasks (5 actual tasks and 1 idle task). Our scheduler works on 1msec timer interrupt. Before sending it out in the real world, We want to test it thoroughly.

What are the best and/or commonly used strategies for testing a Scheduler?

One thing we performed was added functions which require very high processing time in each task and checked whether scheduler still switches on the given deadline or not. But I feel this is not enough to gain confidence.


texts: AVX M830120 SMD GPS antenna problems - cannot get GPS fix on a prototype board, strange S11 measurements

texts:
I’m struggling with AVX M830120 SMD GPS antenna in my project. I have used it in prototype board, did PCB layout more or less according to datasheet, and couldn’t get GPS fix no matter what I tried. I have soldered U.fl socket in place of this antenna, connected external ceramic patch antenna to my prototype board, and it works without any problems - I get GPS fix right away.
To rule out some design errors on my prototype board, i made test PCB with AVX M830120 antenna, microstrip feed line, and U.fl socket only, trying to exactly follow suggested PCB layout (solder patches are home made vias to ground plane on the other side of the PCB):

External ceramic patch antenna test setup:

Then i made S11 SVWR and S21 gain measurements with Nano VNA V2, comparing results from external ceramic patch antenna, and from my AVX antenna test PCB.
S21 for external ceramic patch antenna

S21 for AVX M830120 test PCB

S11 SVWR for external ceramic patch antenna looks more or less as it should (it reaches value of 1 at expected GPS signal frequencies, has strange, sudden change of characteristic just in the middle of GPS band, but i can still get GPS fix with it!), but S11 SWVR for AVX one is completely unexpected, and it looks like it reflects a lot of signal back to the source, and doesn’t even resemble expected characteristic at 1.575 Ghz.
S11 for external ceramic patch antenna

S11 for AVX M830120 test PCB

One maybe important thing is, that AVX antenna has this unique design, where feed line should also be connected to the ground:
AVX antenna layout suggestion from data sheet:

My questions (i'm definitely not an RF expert, as you can probably see from this post):

What can cause this strange S11 results from AVX antenna? Can it be that this specific antenna design (feed shorted to ground) makes it somehow impossible to do proper S11 measurement?

How this strange discrepancy between S11 and S21 for AVX antenna is possible? I would expect that if S11 looks like this, then S21 also should not resemble anything proper?

Can you use S11 at all to investigate parameters of receiving only antenna (as GPS one)?

Any ideas why this mediocre ceramic patch antenna works ok, and AVX one basically does not work at all? What mistakes i'm making here?


texts:
I'm designing a level converter PCB using a LVPECL driver (ADCMP573) and a LVPECL-to-LVTTL translator (SY89323L).

I'm reading a document about LVPECL termination schemes and there's something unclear to me. As shown in the internal schematic of an LVPECL driver, the output impedance of the driver is zero.

Meanwhile in the following schematic of the industrial standard LVPECL termination, the output impedance (Zo) is 50 ohms.

Do I need to use resistors to match the Zo values?


texts: What is the relationship between the PWM duty cycle input and the angular displacement and RPM of a DC motor?

texts: If possible, could someone point me to some resources explaining these relationships? It would also be helpful if the resource discusses non-linearities such as dead-zones in terms PWM duty cycle vs. angular displacement for example.


texts: an fm antenna plug I've never seen before

texts: I just acquired a Sony STR DN1080 AVR, and the FM plug on it is not coaxial or anything else I've seen before. Does anyone know what it's called and if an adaptor to a standard coaxial F connector is available? (see photo):


texts:
I have an Atmega88P (default 1 MHz clock) and I'm trying to have a LED blink and to regulate the luminosity of another one using the potentiometer. For the first LED I used TIMER/COUNTER0 in CTC mode and it works. For the second one, I used the TIMER/COUNTER2 to create a PWM wave with the fast PWM mode, wich also works just fine. The problem comes when I try to change de duty cycle of the PWM wave with the value obtained from the ADC conversion of the potentiometer.
I've used a multimeter to check if the potenciometer works and it does, but every time I upload the code the LED just stays at a constant luminosity.
#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdint.h>
#include <stdbool.h>

#define BLINK_LED_PIN PD4
#define INSTENSITY_LED_PIN PD3

#define LED_TOGGLE_TIME 500 //ms
#define TIMER0_CYCLE_TIME 10 //ms
#define MAX_LED_BLINK_CNT (LED_TOGGLE_TIME / TIMER0_CYCLE_TIME)

volatile uint16_t led_blink_cnt = 0;
uint8_t adc_value = 0;

// Called every 10 ms
ISR(TIMER0_COMPA_vect) {

    // Blink LED every 50 cycles (1 Hz)
    if (++led_blink_cnt >= MAX_LED_BLINK_CNT) {

        PORTD ^= (1 << BLINK_LED_PIN);
        led_blink_cnt = 0;

    }
}

// Check if the ADC is occupied converting
bool is_adc_converting() {
    return (bool) (ADCSRA & (1 << ADSC));
}

// Setup for the Timer/Counter 0 (1 ms)
void setup_timer0() {
    // CTC Mode
    TCCR0A &= ~(1 << WGM00);
    TCCR0A |= (1 << WGM01);
    TCCR0B &= ~(1 << WGM02);

    // Normal port operation
    TCCR0A &= ~((1 << COM0A0) | (1 << COM0A1));

    // Prescaler (64)
    TCCR0B |= (1 << CS00) | (1 << CS01);
    TCCR0B &= ~(1 << CS02);

    // Compare value
    OCR0A = 155;

    // Enable interrupts
    TIMSK0 |= (1 << OCIE0A);
}

// Setup for the Timer/Counter 2 (PWM)
void setup_timer2() {
    // Fast PWM Mode
    TCCR2A |= (1 << WGM20) | (1 << WGM21);
    TCCR2B &= ~(1 << WGM22);

    // Clear OC2B on Compare Match, set OC2B at BOTTOM, (non-inverting mode).
    TCCR2A &= ~(1 << COM2B0);
    TCCR2A |= (1 << COM2B1);

    // Prescaler (No prescaling)
    TCCR2B |= (1 << CS20);
    TCCR2B &= ~((1 << CS21) | (1 << CS22));

    //Compare value
    OCR2B = 0;  // Arbitrary initial value
}

// Setup for the ADC
void setup_adc() {
    // Set ADC as ADC0
    ADMUX &= ~((1 << MUX0) | (1 << MUX1) | (1 << MUX2) | (1 << MUX3));

    // AREF
    ADMUX &= ~((1 << REFS1) | (1 << REFS0));

    // Left adjust the result
    ADMUX |= (1 << ADLAR);

    // Enable ADC
    ADCSRA |= (1 << ADEN);

    // Set the division factor to 16
    ADCSRA &= ~((1 << ADPS1) | (1 << ADPS0));
    ADCSRA |= (1 << ADPS2);

}

void setup_ports() {
    // Set PD4 and PD3 as outputs
    DDRD |= (1 << BLINK_LED_PIN);
    DDRD |= (1 << INSTENSITY_LED_PIN);

    // Turn off the led
    PORTD &= ~(1 << BLINK_LED_PIN);

    // Set PC0 as input
    DDRC &= ~(1 << PC0);

}

// Runs once when the program starts
void setup() {
    cli();

    setup_timer0();
    setup_timer2();
    setup_adc();
    setup_ports();

    sei();  // Start timers/counters
}

// Runs every frame
void loop() {
    ADCSRA |= (1<<ADSC);
    while(ADCSRA & (1<<ADSC));

    adc_value = ADCH;

    OCR2B = adc_value;

}

int main() {

    setup();
    while (true)
        loop();

    return 0;
}

I think the problem is in the ADC setup. I've tried plenty of other setups such as free running mode, with an ISR, ...


texts: LTC3780 for charging batteries (backflow protection)

texts:
I have very little experience with these type of things and I couldn't find the answer anywhere else. I want to use LTC3780 module with ATX PSU to primarily charge batteries (deep cycle battery and maybe lead acid batteries).

In the description it says that it does not have backflow protection. I assume if I were to charge batteries and then disconnect module from the input voltage, battery would kill the module? To prevent this I should use Schottky diode.

There are diodes like 20SQ045 which are rated at 45 V 20 A and would be more than enough, but in the description it says to use diodes in series? Can someone help me and tell me what diodes should I use? Do I really have to use more than 1? I am aware that more powerful diodes have a higher current leakage but how much is too much?


texts: Is it possible to use a membrane keyboard chip in another membrane keyboard?

texts: I have a membrane keyboard that has stopped working. I would like to fix it using the chip of another older keyboard. Is it possible?


texts:
Output result of the circuit

I have connected the circuit in hardware, but how come the output is like this?


texts: Simple spark gap for ignition - Looks correct?

texts:
I was wanting to build a simple fireworks igniter (single line, 1m cable to actual firework)

Here is my current circuit design:

I suppose after the switch is pushed, it will send 9+9 (18V) to the transformer, and for a short time causing an 180 or so volt spike.

It will then store and discharge in to the electrodes (a few mm apart I guess)

Do you see any major issues with the design? Will small spark gaps like this actually spark with that voltage?


texts: Which method or component is best to regulate 42 to 3.3 V?

texts:
I am using a 36 V battey pack (10s 2.5 A each cell 3.6V.) Its maximum voltage is 42 V. I am using a STM32 microcontroller whose input is 3.3 V.

I am designing a PCB in which the power supply is drawn from the battery pack (42 V.) I would like to power the STM32 microcontroller from the battery pack power supply.

I would like to regulate 42 to 3.3 V so that I can power my STM32 microcontroller.

Which method is best to convert it either using regulator or buck converter based on the pcb designing?

Battery Specification: 10s1p

Battery pack nominal voltage: 36 V
Battery pack maximum voltage: 42 V
Battery pack current: 2500 mAh

Microcontroller specfication: STM32F401RCT6

Supply voltage: 3.3 to 3.6 V
Supply current: 100 to 160 mA

Which method or component is best to regulate 42 V so that I can power my microcontroller with 3.3 V?


texts: Please don't use odd horizontal lines to drive LCD for both odd and even fields simultaneously?

texts:
Here's a datasheet for a small TFT LCD panel. http://www.yc-dz.com/productimages/05334956.pdf

On page 7 (9th page of the PDF) there's a tabulated spec for tV, "Horizontal lines per field" (Min: 256, Typ: 262, Max: 268) puzzlingly given in units tH, which is the horizontal start pulse signal period - I can only assume this means that there are 256 to 268 lines per field, and that given each scan line has a duration tH, tV is the duration to complete all horizontal lines in the field. My real question is on the referenced note:

  Note 2: Please don't use odd horizontal lines to drive LCD panel for both odd and even fields simultaneously.

What ever could that mean I wonder. Is it a warning that I can only use an odd number of lines every other frame? Is it some sort of caution against interlacing frames?


texts:
As a follow up to this question: How to sample audio at Nyquist frequency with MSP430F5438?

What type of circuit would I use to generate something that a microcontroller could use to determine the max frequency of an input? I was thinking it would preferably provide a voltage that is lineally related to the frequency.

The information provided by the frequency detector could then be used by the microcontroller to know what frequency it needed to be sampled at.

Is there any ICs that do this? or any circuit that will do this?


texts: Build custom capacitor and measure charge

texts:
My goal is to charge small metal ball/cylinder (steel ball - roughly 1 cm in diameter) to the maximum possible capacity.

One way to do it is to build a custom capacitor with metal ball being one of the electrodes.

I am curious how can I measure charge on this ball? The only thing that comes to my mind is to monitor current while charging and take into account resistance. Are there simpler ways to accomplish it?


texts:
I am not able to find any breadboard headers for this particular usb asp connector

Here

They do exist because I've seen then at school, but I can't seem to find them online. I bought breakable male male pins, but they are too short to fit in the board. I also bought a black header for it on ebay, but it is also too short for the breadboard, only good for soldering.


texts: Calculate pull-up resistor for phototransistors

texts:
I have made a sensor which uses six IR phototransistors, three per sensor block, opposite it is a matched IR diode(940nm). This is in turn connected to a MCU.

The function of the circuit is an airrifle chronograph, the circuit generates a signal when a pellet passes over one of the sets of three transistors, thus breaking the circuit giving a pulse. Look at the first image on the linked page here.

Problem

Firstly the device is detecting an object with a 4.7mm cross section passing between sensors, the original application used an audio port and the internal amplifier and some pull ups to create a pulse for each crossing of the sensor. When I added a external pull-up and measured the voltage, only a small change was visible. This yielded results such as \$ 0.4v < VOut < 0.9v\$, which obviously will not be picked up by an interrupt. I concluded that I would need to use a compartor to give a clean signal for the input to the MCU, this would be a standard circuit with hysteresis non-inverting.

Question: How do I calculate the needed pull-up resistor to give me a voltage range of 1.5 - 3V from a 5V supply with 6 phototransistors(linked above). This will be feed into the comparator circuit.

I know that transistors can be simplified to equivalent resistors but I do not know how to determine them for a phototransistor, I am assuming one can do this so as to find a pull-up.

Edit

The datasheet for the IR led.

Here is a snapshot of the wave form from the audio port and software used to read the signal:

Each spike is a break of a three set sensor of the six.


texts: Why does this zener diode fix the voltage to the LEDs?

texts:
I am just getting started working with small electronics.  I have soldered together a few kits and recently converted a car stereo into a home stereo.  With all of this soldering, I found this schematic for a soldering fan/lamp that is made out of a computer fan and two LEDs.

from Instructables

In the description that goes along with the instructions, they explain that the zener diode allows for the LEDs to receive a fixed voltage.  I looked up zener diode and saw that it was a diode that allowed for current to flow in the opposite direction if the voltage was high enough.  I am having a hard time understanding how being able to switch the direction of the current fixes the voltage?


texts: Convert 4.11 (integer.fraction) to float32

texts:
Im getting a value from a register (SRCx_RATIO) from a SHARC DSP, the datasheet says:

I'm using the following code to convert the value:

 // Convert the sample rate ratio to a float from 4.11 format.
   int_part = (((src_reg  >> 14) & BIT_0) * TWO_POW_3) +
              (((src_reg  >> 13) & BIT_0) * TWO_POW_2) +
              (((src_reg  >> 12) & BIT_0) * TWO_POW_1) +
              (((src_reg  >> 11) & BIT_0) * TWO_POW_0);

   frac_part = (((src_reg  >> 10) & BIT_0) * TWO_POW_MINUS1) +
               (((src_reg  >>  9) & BIT_0) * TWO_POW_MINUS2) +
               (((src_reg  >>  8) & BIT_0) * TWO_POW_MINUS3) +
               (((src_reg  >>  7) & BIT_0) * TWO_POW_MINUS4) +
               (((src_reg  >>  6) & BIT_0) * TWO_POW_MINUS5) +
               (((src_reg  >>  5) & BIT_0) * TWO_POW_MINUS6) +
               (((src_reg  >>  4) & BIT_0) * TWO_POW_MINUS7) +
               (((src_reg  >>  3) & BIT_0) * TWO_POW_MINUS8) +
               (((src_reg  >>  2) & BIT_0) * TWO_POW_MINUS9) +
               (((src_reg  >>  1) & BIT_0) * TWO_POW_MINUS10) +
                ((src_reg         & BIT_0) * TWO_POW_MINUS11);

   // Return the value to be used.
   *ratio = (int_part + frac_part);

The defines are:

// Power of 2 converstion used with 4.11 to float conversion.
#define TWO_POW_0       1.0F         // (2^0)
#define TWO_POW_1       2.0F         // (2^1)
#define TWO_POW_2       4.0F         // (2^2)
#define TWO_POW_3       8.0F         // (2^3)
#define TWO_POW_MINUS1  0.5F         // (2^-1)
#define TWO_POW_MINUS2  0.25F        // (2^-2)
#define TWO_POW_MINUS3  0.125F       // (2^-3)
#define TWO_POW_MINUS4  0.0625F      // (2^-4)
#define TWO_POW_MINUS5  0.03125      // (2^-5)
#define TWO_POW_MINUS6  0.015625F    // (2^-6)
#define TWO_POW_MINUS7  0.0078125F   // (2^-7)
#define TWO_POW_MINUS8  0.00390625F  // (2^-8)
#define TWO_POW_MINUS9  0.001953125F // (2^-9)
#define TWO_POW_MINUS10 0.000976563F // (2^-10)
#define TWO_POW_MINUS11 0.000488281F // (2^-11)

#define BIT_0  (1 << 0)

Anyone knows a better way to get this value?


texts: current limiter for TIA, reducing the problem of distortion in over limit input

texts:
Problem:

my photo diode recieves pulses of width 10ns-150ns and repeating at rate of 1Hz-50KHz

the current from photo diode depending on incident light can go from 10nA-100mA, so i have two photo diodes to cover the dynamic range, what i want to do is limit the current from a photo diode to 5mA lets say in one channel

Approach Followed:

in search i found some thing similar to my need here

the patent claims:
in the picture the current sources 30 and 38 are the maximum current at which the TIA saturates, as soon as the TIA saturates, the schottky bridge isolates the TIA from source,

i have less idea whether the patent circuit can work for pulsating current, but when i tried the results did not show any difference

if you think this is not the right circuit for my application, kindly let me know if any other approach i can follow to put my TIA away from excess current than saturation,

EDIT: with constructive comments i have changed the FET to p-channel which worked like charm, but i am not very clear of

how to select the schottky diode and also the pJFET for much better response

if you see below schematic i have given a trail of pJFET of all available with LTspice, and same with schottky

Result after change in type of FET to PJFET, you can clearly see the input current being more than current sources

How to realize 30 and 38 on practical circuit ?, how can i create stable dc current sources ?

EDIT:

How to realize 30 and 38 on practical circuit ?, how can i create stable dc current sources ?

Work Done:

for realizing these current sources i have chosen a 2 terminal programmable current source from LT, which solved the problem to an extent, but few problems still exist

Modified Design:

Results with 10uA pulsating input:

Results with 100mA pulsating input:

further work:

even though the excess current is limited i want the waveform not to distort, kindly point out flaws in the design

PS: an unclear but similar question present here


texts:
The book Practical Electronics by Scherz and Monk states (3rd ed., p 48):

  A ground bus, or bus bar found in breadboards... serves as an adequate substitute for a single point ground.

Is this statement correct?


texts: Weird failure: Loud Sweep Tone on SMPS, ideas?

texts:
my brother has an old mac computer that didnt work, so he asked me to fix it, its one of those macs from the early 90s, a Macintosh Classic II.

So i opened it up and i found electrolyte all over the power supply, some of the secondary caps leaked it, i also discovered that the MOSFET was burned up, the shotky diodes looked "warmed" because even the part number wiped out, but they tested ok, i tested every other component with my multimeter and the rest tested ok (besides mosfet and fuse).

I replaced every electrolytic with low ESR caps, including the main reservoir cap, and i also replaced the MOSFET, the mosfet wasnt exactly the same part IRFBC40A (original) vs IRFBC40APBF (replacement) but i compared both datasheets and they seem to be the same thing on paper.

Anyway, after replacing those parts (electrolytics and MOSFET) the powersupply lid up, the computer turns on, the OS loads and it seems to be working properly, however theres a very loud tone that appears to come from somewhere between the FET and the transformer, i cant exactly tell which one is vibrating since both parts are very close together.

This tone starts at a very very high frequency, im guessing above the human hearing threshold (say 25KHz), and starts sweeping down slowly, first you can barely hear it, but as the frequency decreases, you can hear it very loud, the tone is always sweeping down, i can compare it to the sound of a piezoelectric buzzer on old computers, i havent actually waited for it to end, i've turned it off when the sound is around 1KHz, but the sound is so intimidating that i can imagine the SMPS completely melting down at some point.

Could it be that the transformer's primary is not completely dead, but somehow damaged? or that the electrolyte somehow leaked into the transformer?, could it also be that the MOSFET may not be the correct one?

Any ideas of what might be the culprit? like i said the PSU works but its unbearable to hear that tone.

Thanks!


texts:
I'm trying to build a laser engraver/cnc router with Arduino Uno, CNC Shield v3, A4988 step motor drivers. I'm newbie about electronics and Arduino so sorry if I'm asking non-sense things.

I've installed GRBL 1.1 on Arduino Uno, connected A4988 drivers and two stepper motors (link to datasheet below). I used LM317 power supply for powering CNC shield. I haven't done any setting with A4988's trimpot.

When I try to send commands with Universal Gcode Sender, step motors turning well for single-axis movements. For example when I command to move it on X-axis, it seems it works well.

Here my questions are;

1- When one motor steps, the other motor also starts to work and vibrates without turning. Is this normal behaviour? Does CNC shield makes it "ready" as receives GRBL commands?

2- When I click on "return home" on GRBL controller software, step motor turns for several times and then stops and I guess skips (doesn't turn shaft) with a weird sound. What can be the reason for that? Does it means LM317 doesn't supply enough current? (I set it to 12V) Also A4988 doesn't heat at all, I suppose it should, can it be related?

3- Sometimes motor vibrates too much even for single-axis movement. Can it be also related to not enough current from power supply?

and also I'm thinking about connecting TTL/PWM laser diode with 12V/2.5A specifications, should I also consider this when calculating enough power supply? Or shouldn't I connect it to CNC shield, what is the best practice about this?

I'm thinking about buying 24V/5A power supply. For two step motors (0.4A * 2) and 2.5A laser I suppose I need 3.3A and as step motors are 12V and they will act better with higher voltage, I will buy 24V. Is this correct calculation or should I consider some other things?

My stepper motors' specifications:

https://www.omc-stepperonline.com/download/17HS13-0404S1.pdf

A4988 step motor driver specifications:

https://www.pololu.com/file/0J450/a4988_DMOS_microstepping_driver_with_translator.pdf

CNC Shield v3 technical data and instructions:

http://www.zyltech.com/arduino-cnc-shield-instructions/

The laser module I would like to connect:

https://www.banggood.com/EleksMaker-FB03-2500-2500mW-Blue-Laser-Module-2_54-3P-TTLPWM-Modulation-for-DIY-Laser-Engraver-p-1266171.html?rmmds=detail-left-hotproducts__2&cur_warehouse=CN


texts: How to connect PCU to Stepper driver (NEMA 23)

texts:
I have bought a stepper motor, NEMA 23 (Bipolar, 4 wires, 23HS30-2804S-PG15)
I also have PCU 350W 48V 7.3A 115/230V (S-350-48)
I also have stepper driver (DM556T, Digital Stepper Driver 1.8~5.6A 20-50VDC)

(I hope it fits together..)
I want to connect it together, but:
DMT556T has connections named: V+ and GND
PCU looks like this:

My confusion is like an output is (I think marked) V+ and V- , ground is where I connect it from the wall and it doesn't look marked like an output.
So how should I connect these together?
I was googling like crazy and found two:

a) Some people connected V+ to V+ and V- to GROUND and driver
b) Some additionally connected on PCU from "a loop" from GROUND to V- (so ground on PCU has input from wall and at the same time is connected back on PCU on V-)

I saw so many videos and saw these approaches I believe - but none of them explained why and when it is applicable and what drives this decision?


texts: Effects of multiple voltage sources in a transformer

texts:
What happens to inductor di/dt when you have multiple MMF sources such as the schematic of a coupled buck converter below? Specifically when D>0.5 so M1 and M2 are overlapping.

What I would expect is :

M1 turns on, increasing core B field in "positive" direction.
M2 turns on, creating an opposing H field
The opposing H field cancels the increase in B or dB/dt
No dB/dt means no back EMF at L1/L2 terminals, which I thought was the effect slowing down di/dt in the first place.
Assuming ideal components, di/dt goes to infinite.

Now obviously this does not happen, or converters such as these would not be effective. Hopefully somebody can correct my understanding.

=== UPDATE ==

A helpful comment was mentioning how higher duty cycles were dependent on leakage inductance, and attached a document explaining these issues. However the paper itself contradict this (page 20), stating that the higher coupling factor, the higher performance.

Borrowed figure 1.25 from the white paper.

Citation P.Wong:

  "From Figure 1.25, the stronger the coupling, the better the
  performance of the multiphase coupled-inductor buck converter"

So I still feel unclear about how physically this technique works.


texts: Cordless vacumn charger rating calculation

texts:
I got a cordless vacuum whose charger got damaged and I found a "close enough" replacement. What could be the new charging performance that I can expect or how can I do a calculation to determine the charging duration?

Original charger rating:
22V
500ma
5 hours

Replacement charger rating:
18V
2000ma
?? hours


texts: Can one communicate with smartphones only in a directional cone?

texts:
I'm thinking about a device that can communicate with a phone. Think of it as simply something that will tell an app "1" if it communicates with it, otherwise the app will remain "0."

But what I want is for it to, for example, be able to be placed on a table, and it facing a certain way. If two people are sitting opposite each other on the table and the device is pointing towards one of them, it will tell the person it is pointing towards "1" but the other person, who is "outside of the cone" would not get a "1" because of that and his app would stay at "0." The person it is facing towards could move to the side a few feet and no longer receive a "1" because he moved out of the "cone."

I know there are directional antennae, but that seems to be more about increasing the signal strength.

Specifically it would only need to cover a few square feet.

I guess bluetooth is really the way you would communicate with an iphone/android. Is this possible to work with bluetooth?


texts:
This is the first time in my life I need to try "Modbus RTU", and as a master I need a RS485 to USB converter which will establish connection to the PC.

I have found some converters in the market which stress and mention their product is Modbus compatible such as this one.

On the other hand there are many other RS485 to USB converters which does not mention Modbus at all.

Below is my basic plan:

I found a converter for this purpose, but its data-sheet does not include a word about Modbus. Isn't Modbus a protocol and the converter itself a physical layer? What is being meant here by saying "Modbus compatible"? Most importantly, how can I know whether this converter supports Modbus RTU or not?


texts:
I have an STM32G031K8 Nucleo development board and was thinking about interfacing it's GPIO with an old BCD-to-Seven-Segment Decoder integrated circuit (SN74LS47N). This is a 5V part... and while I know that the GPIO pins are "5V tolerant", I don't know whether it is safe for these parts to be connected under power up/power down sequences when the microcontroller may be off while the IC is powered.
The IC input pins has this input circuit that has an internal pullup to 5V with some additional Schottky diodes to protect the IC. If the IC is powered and the microcontroller is not, will the microcontroller be damaged? The STM32G031K8 datasheet says the GPIO pins can only withstand, at worst, a voltage of Vdd + 4.0... but then again there is very little current available to drive into the pin.


texts: AC Voltage: Wild Reading: phase-neutral & neutral-ground (240V/120V)

texts:
I'm getting some unexpected readings when testing a circuit for my wall mounted AC&heat. I'm on standard USA 120V/240V split-phase/three-wire AC power; the specific circuit is 240V.

here's a picture of my wiring terminal:

United States Wiring

When comparing black(phase 1) to red(phase 2) I get the expected 240V. When I compare black or red to ground, I get the expected 120V. When I compare red or black to white(neutral) the value jumps around and does not settle within any recognizable/readable range. It also jumps around the same way when comparing neutral to ground. Why is this? I am using a basic digital multimeter(Mastech MS8268).

I want to wire in some extra fans with a fan speed controller, for a filter-box I am building. The controller is only rated to 120V. So I was thinking I would wire it between phase 1 and neutral, although after getting my readings, I am concerned. Is there a problem? Do I need to use a different circuit? I assume the unit was installed correctly, and it has been running fine, although it gets clogged with dust...


texts: Can I use an AC rated momentary switch as a PC power button?

texts:
I was looking to make a custom button to power my PC (I needed something which was a bit more custom than the traditional push buttons for PCs (it's not important)) and I came across these: https://www.amazon.co.uk/dp/B0825JMH6F/
I can see they're momentary switches and (I'll be attaching headers to the end of the wires so they go on the motherboard) but the description says, "AC 250V 3A", and since I'm not really an expert, I just want to find out what this really means. As in, if I bought these would they "blow up" the computer, or are they perfectly safe to use and I'm overthinking things?


texts: Do pcb manufacturers solder components as well?

texts: Let's say I have all the Gerber files generated in Eagle and I send them to a manufacturer. Do pcb manufacturers like 4pcb or seeedstudio usually solder your components as well or do they just send you the pcb only and you will have to order and solder parts yourself? If the former how do you send them the parts info? If the latter are there any manufacturers that also assemble your components?


texts: I built a variable state VCF from Ray Wilson's book on analog synths. It works well except the resonance: turning it up should yield oscillation, instead it just doubles the gain of the output signal (but doesn't change the waveform). The wiring is correct, the only things is my circuit runs on 0-9V (4.5V virtual ground) instead of -9 - 9V. Any ideas how can I get that resonance working correctly? The said part is R16 and R17. Please disregard the red arrow on the pic.


texts: Drawing power from only one phase of a 3 phase alternator

texts:
Note: I am busy learning about 3 phase alternators. A lot of my understanding is theory so I'm running through scenario's for better understanding.

Scenario:

Lets say we have a 2KW-220V-50Hz 3 phase alternator with 3 live wires and no ground. The voltage between phases are 220V.

We decide that we want to power a 180W induction bench motor and 3x100W light bulbs (480W load) from one of the phases of the alternator.

We know that the 2KW alternator is 80% efficient, So we should be able to safely draw 1600Watts from the combined phases and 533W maximum per phase.

My questions are:

Are 3 phase alternators tolerant of drawing power from only one phase ?
Will drawing from one phase cause the alternator to vibrate more ?
Could drawing from one phase cause the alternator to wear out faster ?


texts:
I was wondering what would be the voltage of the node which is connected to 1K and 4K resistors? sometimes I think I need to add up the two voltage sources( 13-2=11V) but I wonder maybe it is just 13V . can you give me some insights please? I am really carious to know when can we add up and when we cannot? what if the polarity of 2V source was the other way around? ( I think then that would 13+2=15V).

The main goal is to find V0
here is what I have tried so far. I would appreciate your comments on that.


texts: Is my heat sink calculation for the LM317 correct?

texts:
Using the formula PowerDissipated = (Vin - Vout) * Iout where:
Vin = 12 V
Vout = 2 V
Iout = 450 mA
Power dissipated = (12 - 2) x 0.45 = 4.5 W
And heat sink value = (MaxTemp - AmbientTemp) / Power dissipated
Power Dissipated = 4.5 W
MaxTemp = 60
AmbientTemp = 20
Heat sink value = (60 - 20) / 4.5 = 8.88
So I need a heat sink value less than 8.88 °C/W - is that correct?
I'm using a linear regulator LM317 by the way


texts:
I'm trying to learn electronics and right now I'm reading the book The Art of Electronics.

I'm stuck on this chapter 2 on figure 2.10B.

In particular I'm simply confused with the lingo like "pulling"  collector to the ground, R3 "hold off" Q3, what does the author really mean? If it is some sort of quantity like voltage or current, why doesn't the author just say something like "voltage/current increases/decreases to X"?
What is "sinks the current"?
The part where it says "make sure you understand why?" well, no kidding I don't understand... :( I've understood about NPN and PNP thing, like for example to get into saturation mode Vb > Ve and Vb > Vc (NPN) and stuff like that, but I still didn't get how R3 keeps Q3 off when Q2 is off?
Well, I used the SPICE simulator, the result is exactly as the book says, but
I don't understand why. Many book reviews seems to state the book is great for beginners, but it just skims through so fast on the foundations part.

Here is the text:

  Figure 2.10B shows how to do that: NPN switch Q2 accepts the “logic-level” input of 0 V or +3 V, pulling its collector load to ground accordingly.
  When Q2 is cut off, R3 holds Q3 off; when Q2 is saturated
  (by a +3 V input), R2 sinks base current from Q3 to bring it
  into saturation.
  The “divider” formed by R2 R3 may be confusing: R3's
  job is to keep Q3 off when Q2 is off; and when Q2 pulls
  its collector low, most of its collector current comes from
  Q3's base (because only ∼0.6 mA of the 4.4 mA collector
  current comes from R3 – make sure you understand why).
  That is, R3 does not have much effect on Q3's saturation.
  Another way to say it is that the divider would sit at about
  +11.6 V (rather than +14.4 V), were it not for Q3's base–
  emitter diode, which consequently gets most of Q2's collector current. In any case, the value of R3 is not critical and could be made larger; the tradeoff is slower turn-off of Q3, owing to capacitive effects.


texts: LTSpice Level 2 Simulation CMOS follower

texts:
I'm trying to make a level 2 simulation of a voltage buffer made by a CMOS circuit:

Buffer http://www.ele.uri.edu/images/Gif/buff_tran.gif

For this, I have been told to use level 2 CNM25 technology Spice models for the transistors, and I have been given the models:

.model NEWPMOS PMOS (LEVEL=2 TOX = 380E-10    VTO = -1.139  NSUB = 1.355E16 UO = 212.7 UCRIT = 1E4      UEXP = .1159  NFS = 662.4E9   WD = .4268E-6 DELTA = 1.824    RS = 134.9    LD = .8101E-6   XJ = 2.783E-9 VMAX = 120.3E3   NEFF = .06665 CJ = 3.816E-4   MJ = .3499 CJSW = 7.384E-10 MJSW = .3916  PB = .56)

.model NEWNMOS NMOS (LEVEL=2 TOX = 380E-10    VTO = .9418    NSUB = 2.639E16 UO = 648.2 UCRIT = 1E4      UEXP = .06857  NFS = 710.8E9   WD = .4086E-6 DELTA = 2.2      RS = 93.77     LD = .9132E-6   XJ = .0824E-6 VMAX = 59.62E3   NEFF = 1.479   CJ = 3.495E-4   MJ = .3950 CJSW = 5.952E-10 MJSW = .2941   PB = .65)

When I simulate the circuit, the output signal has rising peaks at the edges when the input signal goes from high to low and from low to high:

When I zoom in into the peaks, they are really weird and have a 400mV amplitude which I don't know where it comes from.

Is this suppose to happen or is there something wrong with the models? or, if it is correct, why does these peaks occur?


texts: What is an acceptable power dissipation in automotive wiring?

texts:
I am trying to figure out what a reasonable power dissipation would be in a 12V automotive wiring harness to determine my wire gauges.

Is there any automotive standard that specifies what voltage drop/power dissipation is reasonable?

Regarding fusing, how much power can a wire dissipate safely before it starts to become a hazard?


texts: Soldering smallest SMD components such as 0402 with Microscope?

texts: I need to use as small components as possible but I need to do everything by hand. My plan is to use OSH Park for the production of the board. The answers did not focus on whether they used microscope or not. Now suppose you have a microscope. What is the maximum limit you can solder by hand? Are there some components that are only meant for machines? In using as small components as possible what kind of things should I consider?


texts: I have a 5V TTL which is basically a trigger output that I want to give to an FPGA I/O pin which takes 1.5V, 10mA. What's the best way to do it and what's a quick way to do it ? I was able to look up techniques on converting from 5V to 3.3V but not many on 5V to 1.5V.


texts:
I have a device (XT107) that requires a SIM card. It takes a SIM card that have cobber plate (not sure what to call that) that supports all 8 curcuits on the device.

When speaking with people, some say it's a 2G SIM card, but I doubt that since some of my friends have a HTC Desire which uses this kind of card.

Mini sim card - 4 pins - (8 circuit):

Mini sim card - 3 pins - (6 circuit):

What are the differences between these two cards above? I'm really lost here. I need that one with 4 pins(8 circuit), but when speaking with the mobile phone companies' tech support, they are totally lost.

Update

I have added the real names for the simcard to the above, but still maintain the original question with names etc.


texts:
could someone please help me to identify what is long white SMD with JR marking? I am trying to draw a schematics for better understandig how ethernet and PoE on this device is implemented.

It has near zero resistance and i could not google anything with JR marking witch would have this shape.
Board function is Ethernet input overvoltage protection and PoE voltage extracting.

My best guess is that it is fuse but it is quite big one.

And i don't understand why there would be two of those - one is connected to +48V supply over ethernet and one is 0V. Both lines are separated from chassis grounding


texts: Passive low-pass filtering question for a transducer output

texts:
I'm having ringing-noise from a pressure transducer analog output.
Here is the only information about the instrument:
http://www.trescal.be/pdf/PPC500_GB_SI.pdf

Let me briefly explain the device and the issue:

This device has an internal analog to digital conversion at some stage and outputs that information on its display. The output from digital data displayed on the screen can be sent via RS-232 directly or as an analog output which is created using digital to analog  conversion. The both RS-232 and analogue output sends the averaged voltages from the transducer at a rate of around three times per second.

For some reason I have to use the analog output. I record the readings from the analog output by a data-acquisition device which has 1GigaOhm input impedance. The DAQ device has many analog inputs and one of the analog inputs comes from this pressure transducer via a BNC cable which is between 10 up-to 15 meters long. All the analog inputs share the same ground and only at this transducer's channel I'm observing  ringing-like noise. Same noise is observed if I hook the BNC up to an oscilloscope.

Below is an example of the transducer's analog signal in question. It shows the signal in time series for 60 seconds which is sampled at  8000 Hertz and plotted in LTspice:

Here below if I zoom the signal, please see the three steps of discrete voltage sent by the transducer’s analog output per second:

It seems like there is no reconstruction filter on the output of the transducer’s DAC. But actually it doesn’t matter in my case. What bothers is mostly those crazy jumps/ringings on the edges which sometimes exceeds one volt.
And here below I'm directly zooming to the crazy ringing-edge and by using LTspice's cursors I find out that the ringing-noise is around 1kHz:

So I decided to use a RC passive low-pass filter but only checked in LTspice and the simulation results are below (V1 is the output from the traducer; C1 and R2 represents the low-pass filter; R1 is the input impedance of the data acquisition channel; green plot shows after filtering):

And for a better comparison before(blue) and after the filter(green) here:

  Here are my concerns and questions:

1-) I found the solution by filtering. It seems to me the loading is
negligible due to the huge input impedance of the DAQ channel here. So do you agree in this case to use these R2 C1 values are optimum for a passive low-pass filter to eliminate 1kHz?

2-) Do you think this passive filter enough here? Is active filter necessary(I haven’t built any yet)?

3-) What could be the reason for this ringing? Could it be length of
BNC or inductive effect? (It seems like we have an DAC outputting 3Hz discrete signal sent via a BNC coax cable)


texts: How can I increase battery charge from 590mA to 900mA with BC1.2

texts:
I have a 5v battery connected to a mobile device on the VBUS and GND which is charging at 590mA. I would like to increase this to 900mA with BC1.2

The Data+ and Data- are currently shorted otherwise there is no charge, my questions are:
Does BC1.2 increase the charge by sending power through the Data+ line ?
Is is possible to modify the cabling in the photo to reach a charge of 900mA ?


texts: PIC16 I2C interrupt does not occur if serial port enabled

texts:
I'm using a PIC16F1825 mid range PIC and I've used it with a UART and SPI for a good while without issues. When I added code to handle I2C (instead of SPI - it's either one or the other on this PIC) I ran into problems with not receiving the I2C interrupt - thus SCL would remain stretched forever.

After some considerable debugging I figured out that removing the code that activated the serial port fixed the issue - the I2C ISR gets called and acts normally.

All I'm doing in the serial init is setting SPBRG and then:

 bcf         TXSTA, SYNC             ; Async (default)
 bsf         RCSTA, SPEN             ; Active serial port

 bsf         TXSTA, TXEN             ; Enable TX
 bsf         RCSTA, CREN             ; Enable RX

That it. No interrupts are enabled (I just set the flag on transmit)

I've searched the docs and the errata and find no hint that enabling the serial port would mangle I2C functionality like this. Is this my misunderstanding or there an actual silicon bug here?


texts: Moore's law: relationship between transistor count on an integrated circuit and minimum feature size

texts:
I'm doing a project about Moore's law, looking at physical limits of the technology / materials we're using (photolithography for example), the limit you'll come to is the minimum feature size.

For this project I also have to establish a model, I've done so in mathematica, but since we're following Moore's law it's a pretty simplistic model that just doubles the transistor count of a base year every two years.

My question is: is there a strong relationship / conversion (possibly from data) between minimum feature size and the transistor count on an integrated circuit?


texts: What is the cause of the error/unexpected outcome in water temperature control heating system circuit?

texts:
Here is the circuit with components I built as shown over here. The title of the circuit is water temperature controlled system. The function of this system is to control the heating while sensing the temperature, but due to safety purposes, I used a red LED to represent as the heating element. The op-amp act as a comparator to compare the voltages of the NTC thermistor,VA and the potentiometer at preset resistance,VB as shown in the diagram.

The resistance of the NTC thermistor is 2kohm when the water temperature is 50˚C, so I set the potentiometer 2k so that when the water temp. is approximately below 50˚C, the LEDs will up; when temp. is above 50˚C, the LEDs won't light up. To do this experiment, I used hot water around 52˚C and I started recording the data until it cools down to lower than 50˚C, to see if the outcome is expected or not.

The expected outcome is that when the water temp. is approximately below 50˚C, there will be a positive voltage difference between VA and VB (VA>VB), the op-amp will turn on and both green and red LEDs will light up to show that the transistor and relay are turned on and so is the heating element (represented by red LED).LEDs won't light up when VA=VB,and VA less than VB

Here is the problem.
The actual outcome I observed is not expected:

In 50.7˚C, VA=4.25V, VB=4.54V, No LEDs light up. but there is voltage difference

In 50.6˚C, VA=4.25V, VB=4.58V, ONLY green lights up (unexpected outcome).

In 49.3˚C, VA=4.25V, VB=4.71, then BOTH red and green start to light up

Both LEDs only light up when the voltage difference is a bit larger which is 0.46V. Why does the red LED light is a few degree Celsius delayed from the green LED? Is it the cause of hysteresis in the op-amp?

*In the diagram,the orientation of the green LED is wrong, the positive terminal should connect to relay.


texts: Why does arcing occur on helicopter power-line repair

texts:
I saw this video, where a guy did power line inspection from a helicopter, which is isolated from ground. When he held out a "magic wand," a small amount of arcing came off of the power line to the helicopter.

This got me confused, though, because I thought since he was isolated from ground, the power would not want to go anywhere.

The helicopter simply has no relationship to ground.

So, why does the Magic Wand arc to the helicopter?