texts: Wiring a Crompton Parkinson single phase motor

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I have acquired an Elliott Progress No.1 pillar drill with a Crompton Parkinson motor. It must date from the 1960s.
The motor worked fine when I first acquired it. The rest of the drill was in a bad state, so I stripped and restored it and gave the motor a good clean. It's single phase with two windings, a centrifugal start switch, and a start capacitor. Once reassembled, I wired it back up the way it was when I dismantled it, and switched it on. The motor emitted a loud buzzing sound but did not move.

The bearings are good, there are no obstructions, and the spindle turns smoothly by hand. One thing I did notice was that with the power on the spindle locked – I couldn’t turn it in either direction until I cut the power.

I've spent weeks trying to get it to work, and have scoured the web for ideas. I found a few posts on various forums that described similar motors, but none quite the same. I've run out of options and hope someone with more knowledge may be able to help me. I'll describe the configuration as clearly as I can.

There are notches for six terminals on the connection plate inside the motor marked, from top to bottom, K, Z, AZ, S, A, T. K and S are empty.

Mains live was connected to T, neutral to A, earth to the earth
terminal. A wire runs from T to what I believe is an overload switch,
and from the switch to AZ.
From AZ, one wire runs to the centrifugal switch. On the other side
of the switch a wire runs into one of the windings. Another wire runs
from AZ into another of the windings.
Apart from mains neutral, two wires were connected to A, one running
to a capacitor, the other into one of the windings.
The other side of the capacitor was connected to Z. Another wire led
from Z to one of the windings.

I’ve tested the resistance of the windings, one is quite high (around 19 ohms), the other much lower (around 4 ohms). I presume the first is the start winding, the second the run winding.

The centrifugal switch seems ok, no missing, damaged or corroded parts or obstructions.

I replaced the original start capacitor with one of the same specification, but this makes no difference.

I’m 99.9% sure this is exactly how it was wired when I dismantled it for cleaning. I can’t work out what the problem is. Although my electrical knowledge is basic, I got the impression that the start capacitor is supposed to be placed before the centrifugal switch in the circuit to provide the start winding with additional torque. As it is, it seems to be placed between the two neutral terminals, A and Z. Much Googling later, I am none the wiser as to why this should be.

How do I get this motor working again?

UPDATE: one of the winding wires snapped while I was working on the motor and I lost the end. It's now beyond recovery unless I replace the windings, which I suspect would cost more than a new motor. Thanks everyone who helped!


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I've seen both of these in the PCB tab when editing the PCB board in Altium Designer.. what are the two?
I thought I new, but I have fully routed traces with signal lengths of 0 as well as signal and trace lengths that are totally different from each other.  As well as sometimes signal lengths go up and down with the trace lengths as I'm routing, but other times the signal lengths do not change...

What are these two things, how are they related, and how do I edit signal lengths? (I'm assuming I'm right in thinking trace lengths are determined by the physically routed length of the traces.  If not then please explain).

Thanks!


texts: Does the value of opamp input impedance have direct effect on the amount of noise measured in this scenario?

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Regarding noise added on a signal during transmission i.e. along the long wires between the source and the amplifier, Im wondering whether in a single ended system does the input impedance of the receiver/amplifier(not the gain) has any effect on the amount of noise at the output.

For example in a single ended system; a 1V DC signal source with an output impedance Rout is coupled to an opamp which has input impedance Rin and and gain of 1 as below:

The output then will become roughly(neglecting the voltage divider effect) 1V plus the noise picked up due to long non twisted wires along the way. The noise could be due to EMI or ground loop.

Now where Im stuck is: Is this noise’s magnitude have any relation with the value of Rin or it is only a function of Rout?


texts: Why is it not possible to measure voltage between one battery pole and mass/ground

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If a DC multimeter is attached to the plus pole of a battery and the other pin to ground. In my understanding there is a positive potential on the positive battery pole. And a zero potential at ground. Shouldn't the multimeter show the difference in potential between those two points of contact?

What is the difference between connecting the negative terminal of my multimeter to the negative terminal of the battery vs connecting it to earth ground?


texts: I am a quadriplegic. Would it be possible to power my ventilator humidifier with a battery?

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I am an absolute novice in regards to electrical engineering, and so I am hopeful your expertise can guide me in the right direction.  I know this is an unusual post for this forum, and so I thank you in advance for your consideration.

First, let me provide some context to my question.  I am a quadriplegic, and I use a ventilator to support my breathing.  The ventilator setup includes a humidifier to keep my lungs moist.  In my particular situation, I'm unable to be without humidification for any significant period of time.  I do use a heated wire with the humidifier which decreases condensation in the ventilator tubing.  Both the ventilator and humidifier are attached to my wheelchair, and each has its own power cords.  The ventilator also has its own battery component, but the humidifier does not.  As you might imagine, needing to be connected to a power outlet greatly limits my mobility.

Given all of that, I would love to be able to power my humidifier with some type of battery pack - although I don't know how or if it's possible.  With the advances in battery technology, I'd like to think it's possible.  My initial idea was to tie into the batteries that power my wheelchair, but the people who service my chair told me those batteries would be depleted quickly from the humidifier.

Here are the electrical specifications for the humidifier, along with a couple of other pictures:

So, I guess I have several questions.  Where would you begin if you needed to resolve this problem?  What capacity battery would I need in order to run the humidifier for several hours?  Is such a battery readily available or would it need to be designed specifically for this purpose?  Could the connection be grounded?  Is there any other issues that I might be overlooking?

I would be very grateful for any knowledge you could share with me.

Many thanks,
David


texts:
I have worked with PLCs in the past. Now, I'm working with devices called 'vital-logic controllers'. The vital logic controllers are similar to PLCs, but I'm wondering about a subtlety of how the ladder-logic is evaluated in PLCs compared to vital-logic controllers.

In PLCs, my understanding is that one 'tick' represents one pass through the equations; every gate is updated once with respect to its inputs. This does not  guarantee that the change-of-inputs has propagated to the outputs. Therefore, a PLC may require several system-ticks for the outputs to stabilize w.r.t. the inputs.

In contrast, I have been told that vital-logic controllers execute the ladder-logic repeatedly, within one system tick, in order to force the change-of-inputs to propogate all the way to the outputs in one tick.

So, my question is:

Am I correct PLC systems-ticks just update each gate once, and do not attempt to stabilize the equations?
Is my colleage correct that vital-logic controllers repeatedly execute their ladder-logic equations until the outputs have stabilized?

Update to answer comments.

1) Yes, by 'vital-logic' I am referring to railway signalling controllers where fail-safe operation must be guaranteed.

2) I have been unable to find a manual for a vital-logic controller covering this level of detail. I'll get in touch with the manufacturers.

3) By 'tick', I meant 'program scan'. I am basically asking if there is any difference between the program-scan operation in a PLC, compared to a vital-logic controller.


texts: Optical Communication Two Sources One Receiver

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I'm working on a project that requires me to wirelessly transmit analog information over a short range (few meters at maximum) to a receiving end from two transmitting ends. The tricky part is I can only use one receiver and I have to build these transmitter-receiver parts from scratch, meaning no microcontrollers or ready-made modules (like those 433MHz RF transceivers that I see commonly used).

I want to use IR or LASER LEDs for this purpose but am unsure how that would turn out. What kind of output would I observe from a photodiode if I were to shine two LASER beams on it simultaneously? For instance, if I were to drive the two LASER diodes with PWM and have a significant difference between their frequencies (5kHz and 100kHz for example), would I be able to filter the two transmitted signals using basic filters with corresponding center frequencies on the receiving end? I don't need extreme precision, as long as I can compare the amplitudes of my original signals on the receiving end I'm good.

I realize that with this kind of set-up the best method would be time division multiplexing but I'm unsure how to achieve that with analog circuitry.

Would you guys suggest any other method for this type of wireless communication? I don't think I have enough experience with electronics to build my own RF transceiver but if you have any tips on that it would also be appreciated. Thank you!


texts: Servo motor signal voltage vs "working" voltage

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I'm looking at a few servo motors (on Amazon.)
Typically the "Working Voltage" is 6-7.4V. I can supply that with a power supply but what can I do about the signal? Can I just feed it the 5V PWM from an Arduino? Sadly there's no other voltage mentioned on the listing; do they have to match, or be at least the minimum of the working voltage, in this case 6V?
I can't find the specification sheet for most of them outside Amazon; but I assume the question is more about my understanding of servos than this particular one.
Edit: Yes, they take a PWM signal; [ground, +, signal] sort of connector.


texts: ROV tether: will DC power supply interfere with the control signal?

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I'm designing a tethered underwater drone. I think I will use RS-485 for control.

I can either place batteries in the ROV itself or supply it with electricity via tether. In the latter case, will DC supply line create noise in the control wires? The ROV impedance is going to vary, as far as I understand this is going to cause short voltage drops in the supply line even if it's connected to a battery, isn't it?


texts:
I designed a PCB, but I'm unsure whether this topology correct or best one.
The circuit powered with Li-ion battery and the battery should charge over USB.
When USB has not been connected, Step up-down IC supply 3.3Volt to the board.
When USB has been connected, Li-ion charging and also supply power to the board.
Both charging and working of board could be possible at the same time. Is there any drawback?


texts: What are these types of logic diagrams called?

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They are not quite "logic circuits" because when I look that up I get mostly the ones with logic gates drawn, not the transistors and such like these.

Also if I wanted to find a book that would teach me specifically about transistors and understand these types of circuits specifically, not digital systems in general, what should I look for? Any recommendations?


texts: Setting DC-bias on LVDS receiver with internal 100ohm differential termination

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Here is the setup :

simulate this circuit – Schematic created using CircuitLab

RX channel is routed as 100ohm controlled impedance. FPGA input pins are LVDS IOs. I want to apply a DC bias of +1.2V at the FPGA. can I simply add 50ohm pull-ups to +1.2V on each of the differential lines? Thanks.


texts: Why would IO pins be tied to VCC or GND with 0 Ohm resistor on FPGA Dev Board?

texts:
I have a cheap Altera Cyclone II EP2C5T144C8 Dev Board and a few (4) of the IO/LVDS pins are shorted to VCC or GND as shown in the schematic segment below. The pins are also brought out to headers on the board.

The only things I can think of for why they are there are:

They are meant to be left non-populated (but were accidentally populated) for the user to add pull-up/pull-down resistors
They are somehow helping power the FPGA

Is there any reason a direct short to VCC/GND would be desirable for an IO pin on a Dev Board? Can I remove these resistors without negatively impacting the board's performance?


texts:
StackExchange

When I was getting help with my last circuit people gave me the advice to add some resistors. So I finally got this result.

The stats to the part are the following:

V1: 9V

V2: 5V

M1: RF-130 CH

U1: 4n35 Optoisolator

Q1: BC547 Transistor

I figured out that R3 should be about 70 Ohm due to the forward voltage of the U1 diode being 0.8V and the forward current being 60mA. With R = U/I this brings me to R = (5-0.8) / 0.06 ==> 70 Ohm
I just wanted to post this in order to make sure I didn't do any mistake here.

Now comes the harder part as I do not know exactly how to calculate the other resistors. I just wanted to ask if anyone could give me like a general idea where to start calculating all of the missing values.

Thanks for your help.


texts: How does the capacitor C1 provide filtering in this second order active low pass filter?

texts:
I am looking at this second order active filter:

I can see that the cap C2 provides a short to ground for HF signals; providing filtering, but could someone please tell me how the cap C1 provides any filtering?


texts:
I know how to calculate Noise figure of an amplifier on the paper but how can measure Noise figure of a LNA in real world?

Our lab doesn't have a fancy Noise figure meter but I can readily access to VNA, Spectrum analyzer and signal generator. As none of these instrument are perfect I'm wondering if it's possible to measure accurately NF of a DUT without having a noise source.


texts:
So I have a 270uF 350v capacitor that I am trying to charge.

The schematic shows a the right size for a 22uF, how do I know what size resistor i need to charge it?
What type of transistor do I need?
I'm assuming the voltage needs to match the capacitor in order to charge it to full capacity, correct? Short of simply buying a voltage booster is there a fairly simple way to charge this up using a 12V 2A DC power supply?

Why does it say 350wv instead of 350v?

Sorry for so many questions on my first post. I know these answers are out there somewhere but Google is not being very helpful right now.

Edit: added transformer schematic (I don't actually have the transformer/inductor to test so im I'm not 100% sure if it's correct) I believe it is a tecnically a pulse  transformer


texts: How do I define a tented via-in-pad in Eagle?

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How do I define a tented via-in-pad in a parts library in Eagle PCB? (Example of result here:)

Once I define the large pad underneath the QFN, I seem to be able to turn the soldermask on and off. However, once I turn the soldermask off, it seems impossible to just define little circular areas of soldermask (soldermask layer in Eagle is just tStop).


texts: Do power amplifiers that use a dynamic power supply operate in the active region, i.e. as a voltage controlled current source? or do they operate in the saturation region? and how do the current and voltage waveforms look like?


texts:
I'm repairing an ancient stereo multiplex decoder which has diodes in the signal path for mono/stereo switching.

For headroom reasons, I need plenty of Vf on these diodes, which are pulled up by a DC signal generated from the pilot tone. So I am wondering whether there is any linearity reason why I couldn't use a suitable LED. That would also give me some nice indicator lighting at the same time of course.


texts: Is this noise in current amplifier feedback because of my PCB design?

texts:
Problem
I am trying to design a 24V, 4A BLDC motor driver. Here is the PCB I have designed for it.
Discussion on this topic could be found here. In summary, open-loop works, but closed-loop is all over the place.
I was told that the current feedback is too noisy for the closed-loop mechanism to work. Also, I was given a reference current feedback reading.
Measurements
Here is my current feedback readings and below is the one for the reference board. These readings are transferred to my computer over UART with the help of Kinetis Motor Suite GUI. So, these are the readings of the ADC of the microcontroller which measures the output of the current sense resistor amplifier. More specifically CUR_A, CUR_B etc..

With no activity on gates, here is the voltage across R52, which is the Phase C current sense resistor. Scope is AC coupled and BW is limited to 20 MHz in this measurement. Scope probe ground lead has about 1 cm length:

This is the output of the OP-AMP, U6, pin 14. DC Coupled. Scope and probe BW is 200 MHz:

Zoomed of above, noticeable, steady ~56 MHz oscillation:

This is also the output of the OP-AMP, U6, pin 14. But AC Coupled. Scope and probe BW is 200 MHz:

Zoomed of above:

A New Observation

I have removed the feedback capacitor C39, which did not have much help with the oscillation, then, when the starred components are not populated, which are C28, R23, C29, R26, C34 and R36 from left to right, the above oscillation problem is solved. Not populating these components effectively prevents ADC_MID line from going to other OP-AMPs in the package. Why would this cause a problem?
PCB Layout
I am suspicious that my PCB design is problematic. Here are my schematics, layer drawings and gerbers. Could you notice a problem that would cause this?
Top Copper:

Bottom Copper:
Schematics in PDF: https://drive.google.com/file/d/0B1xsxA1iARHGNUlVR3YwOWxCQzA/view?usp=sharing
PCB layers in PDF:
https://drive.google.com/file/d/0B1xsxA1iARHGblBZZDRLd0hScWM/view?usp=sharing
Gerbers, zipped:
https://drive.google.com/file/d/0B1xsxA1iARHGU0w2a3ZQeUQ5bTA/view?usp=sharing


texts: Difference between ADUM6403 and ADUM6403ARIZ?

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I bought ADUM6403ARIZ and I am thinking how it might fit ADUM6403.
I am thinking the differences between the two chips

ADUM6403
ADUM6403ARIZ

ADUM6400ARIZ should be equivalent to ADUM6403, but not sure how equivalent is ADUM6403 to ADUM6403ARIZ.
Manual here.
There are also other endings CRIZ, CRWZ, ARWZ, ... about which I am not sure.

Can you use ADUM6403ARIZ in the place of ADUM6403?


texts: How can I prevent my soldering tip oxidising while I'm using it?

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I have a temperature-controlled soldering iron. When I use it above 250°C, the tip quickly dulls and won't take solder. By "quickly" I mean "within 20 seconds". I have to clean the tip with copper wool or a damp sponge literally between every joint.

I am using leaded solder, and I only solder at these higher temperatures when the wires/contacts are large and difficult to heat. Or when using desoldering wick, which amounts to the same thing.

Is my tip just of poor quality? I have tried different tips, but maybe they just all suck. Should I be using a more expensive tip?

EDIT: I'm using a MarkEthan SMD Rework Station, with generic Ebay tips, and "AlphaMetals 8-Sn60Pb40" leaded solder.


texts: I'm looking for equations on how to calculate output voltage of a simple power supply made of a step down transformer with Rs secondary resistance, a bridge rectifier and a capacitor with different loads.


texts: How to determine a system is stable using pole zero analysis?

texts:
To my knowledge, as long as the poles of the transfer function are in the left half plane, then the system is stable. It is because the time response can be written as "a*exp(-b*t)" where 'a' and 'b' are positive. Therefore, the system is stable.

However, I saw people stated on websites that "Also no zero is allow in the right half plane". Why?


texts: Creating positive and negative voltages from a battery

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I have a circuit that is usually powered by +9V and -9V (uses two 9 volt batteries), but I am trying to power this from a rechargeable 3.7 V battery. The circuit does not draw much power (can be powered down to about +2V and -2V), but it has op-amps that require both a negative, and positive swing (LF412).

I was wondering if it would be possible to create a dual supply from the battery, and if so, what the most efficient method would be to do this. I have a couple of ideas that i might try:

1.) Use a boost converter to step the voltage up, generate a pulse (555 timer), send it to a transformer, and use a center-tap to create the separate voltages, which can then be filtered.

2.) Follow the steps for idea 1, but instead of a 555, use a micro controller to generate a sin wave (DAC lookup table method), which can be amplified, send this to the transformer, as this would be more efficient for transferring the power.

I would really appreciate the help!!


texts: I need to create the following trace in Eagle but I can't work out how to make it go from one width to another across a set distance like below.


texts: How to make usb 3G modem signal stronger with aluminum foil antenna?

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I'm in an area with weak signal reception, but I'd like to make my 3G connection better at very low cost.

I heard using aluminum foil as reflecting surface and placing the modem in some way in front of it will enhance the signal. Is there a particular rule on how to place the modem and what form must aluminum surface have?

Illustrations are welcome.


texts: Intercepting signal between uC and LCD driver

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I'm trying to intercept the signals between an old Elan uC and a HT-1622 LCD driver using a PIC18F14K50. There are 3 lines that are connected to the IOs of the uC: CS, WR(write clk) and DATA. At first sight it looks pretty simple, I just soldered 3 cables between the inputs on the HT-1622 and RB4, RB5 and RB6 on the PIC, and then I configured the registers like this:

TRISB = 1;   // set all pins on port b as inputs
ANSELH = 0; // digital inputs
WPUB = 0;  // disable the pull-up resistor

The problem arises when the PIC is powered on, the LCD driver stops working as it should, and the signals I get on the PIC inputs aren't valid (they're always 1). Once I disconnect VCC on the PIC, the LCD Driver works again. So it seems I'm missing something, any thoughts?


texts:
I have been researching this question:
What is the pinout for an intel celeron N2930 soc?

But I cannot find it in the datasheet, or on google.

Thanks


texts:
I have put together the following circuit to drive some 12V pumps from a micro-controller using a ULN2003, but it has a few issues.

First issue is that the relays click in immediately. I want the relays to only kick in when signalling from micro.

The second issue is that when the motor comes on, it stays on. I think it is browning out everything and causing havoc. With the motor running I read 2-4V at the com pin of the ULN2003.

Does this schematic look correct? What would cause the motor to do that?


texts: TI TM4C1294 UART on Port C problem renders the board un-programmable

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In the aforementioned board, port C is 8 pins in which 0-3 are used for JTAG (So 4-7 should be GPIO available right?). I am using the following code:

#include <stdint.h>
#include <stdbool.h>
#include "inc/tm4c1294ncpdt.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"
#include "inc/hw_types.h"
#include "inc/hw_gpio.h"
#include "inc/hw_memmap.h"

int main(void)
{
    SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ | SYSCTL_OSC_MAIN | SYSCTL_USE_PLL | SYSCTL_CFG_VCO_480), 12000000);

    SYSCTL_RCGCUART_R = SYSCTL_RCGCUART_R3;
    while((SYSCTL_PRUART_R & SYSCTL_PRUART_R3) == 0);

    SYSCTL_RCGCGPIO_R = SYSCTL_RCGCGPIO_R0;
    while((SYSCTL_PRGPIO_R & SYSCTL_PRGPIO_R0) == 0);

    // HWREG(GPIO_PORTC_BASE+ GPIO_O_LOCK) = GPIO_LOCK_KEY;
    // HWREG(GPIO_PORTC_BASE + GPIO_O_CR) |= (GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3|GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6|GPIO_PIN_7);

    GPIO_PORTA_AHB_AFSEL_R = GPIO_PIN_4 | GPIO_PIN_5;
    GPIO_PORTA_AHB_PCTL_R  = 0x00110000;
    GPIO_PORTA_AHB_DEN_R   = GPIO_PIN_4 | GPIO_PIN_5;

    // UART3_LCRH_R &= ~UART_LCRH_FEN;
    UART3_IBRD_R  = 78;
    UART3_FBRD_R  = 8;
    UART3_LCRH_R |= UART_LCRH_WLEN_8;
    UART3_CC_R    = 0x0;
    // UART3_LCRH_R |= UART_LCRH_FEN;
    // UART3_CTL_R  |= UART_CTL_TXE | UART_CTL_UARTEN;
    UART3_CTL_R  |= UART_CTL_UARTEN;

    while(1)
    {
        while( (UART3_FR_R & 0x0020) != 0);
        UART3_DR_R = (char) 'a';
        SysCtlDelay(1000000);
    }
}

The code is configured to work with UART 3 (RCGCUART_R3) module which resides on port A (RCGCGPIO_R0) pins 4 & 5. Changing the configuration to UART 5 which resides on port C pins 6 & 7 will successfully download the binary to the board on the first time only, on the subsequent trials I always get "Unable to initialize target - 0". I still get the error after the first successful programming even after doing the Unlock Sequence

Trying to unlock port C even with port A is used in UART does not work. The previous code won't print the character 'a' when the unlock sequence is uncommented. Does the board see port C as one unit so I have to unlock the whole register? The schematic confirms that pins 0-3 are for JTAG while the rest are for GPIO.

Another question is the use of UART FIFO buffers. Correct if i'm wrong, the FIFO is a buffer used to receive/write data between the serial port and the memory. But what i'm not sure of it, when do I really need it and when I do not need it?

Another question, in general is it possible to detect that the UART port is connected? For example, detect an FTDI FT232 chip when it is connected to the appropriate pins.

Thank u very much!


texts: I am trying to use an Arduino Uno as a timer so that when current passes through an input pin it will only continue out of the output pin for a certain amount of time and then the current will stop flowing. Does anyone know how to achieve this and the code necessary? Any help is appreciated.


texts: Turn on one light in a series like a christmas tree light string

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If I have a string of lights in series, like a christmas tree string of lights, is it possible to turn on 1 of the lights with an intelligently regulated voltage from a raspberry pi. I have found a resource stating the fastest GPIO voltage regulation time to be in the 22 MHz range.

http://codeandlife.com/2012/07/03/benchmarking-raspberry-pi-gpio-speed/

Can I, with a combination of changing the input and output voltage of a raspberry pi, create a waveform that could light up a single light or even a discrete set of lights in that series?


texts: Is the error in a "5%" resistor consistent across measurements?

texts:
One of my projects involves a number of voltage dividers... but if I'm worried about precision (which I'm really not, but I want to understand how these things actually work) can I realistically use "standard grade" 5% resistors for these dividers and calibrate around the error?

What I'm really saying is that if a given resistor is "off" by 3.5% I don't really care... as long as it's always off by the same 3.5%.  But if from one measurement (voltage?  current?) to another it might be +2% one time and -3% another time, then I need to get higher quality components...


texts: 5A 12V Battery charger -> 12V Marine Battery -> Inverter -> Fridge for longer run-time?

texts:
I currently have a 12V Deep Cycle Marine Battery hooked up to a 1,000W (2,000W peak) Inverter, this should run my fridge no problem, however the runtime wouldn't be terribly long.
I also have a 700W propane generator (900W peak), I don't believe it can support the startup of the fridge, so my question is can I use the battery charger hooked up to the propane generator to provide additional run-time to the marine battery while it powers the fridge?
Thanks!


texts: Bit banging synchronous serial protocol on SAME70

texts: I am trying to implement synchronous Serial protocol with SAME70 using board SAME70-XPLD. For that I need to generate clock of 2MHz. For that I am using TC module running at MCK/8 = 18.75MHz (MCK set to 150MHz), configured in compare mode. At each compare interrupt I update data and clock lines. I am not getting accurate timing results, Please suggest if bit banging with 2MHz clock is even possible or I am just wasting time?


texts:
Eberhardt Rechtin and Richard Jaffe (both involved in NASAs DSN) published this paper (paywalled) on PLL-design and -performance back in 1955. It is referenced quite often, so I wanted to understand what makes a "Jaffe-Rechtin"-loop or -filter. I would have expected a wiki-article on a seemingly important concept after such a long time, but found ... nothing. Same for StackExchange.

From the abstract, I have the impression that a bandpass limiter in the loop is the distinctive element. Later JPL publications (this technical report f.e.) do mention bandpass limiting, but the term Jaffe-Rechtin-filter was apparently not formed in 1966.

On the other hand, I found some remarks in the IS-GPS redaction process (slide 2), that suggest that Jaffe-Rechtin-PLL is a vague term and needs clarification.

What do engineers mean when they speak about a Jaffe-Rechtin-PLL? What makes it special? Pointers to free publications are welcome if it would be lengthy to explain here.


texts: Inductor/Electromagnet used to lift up a magnet? Joules to Newtons or Joules to Gauss?

texts:
With interest in using an electromagnet to lift up a magnet.
I dove in. I will state general information. The set up is unknown but I'm interested in the physics/electrical engineering involved in calculating the amount of ______ needed to lift up a mass (magnet with magnetic strength x).
I reviewed "electromagnets". I see an inductor produces a magnetic field, a summation of the contributions of electrons and we get some equations.
Regarding inductors, Energy is .5LI². We can adjust the power/energy/magnetic flux in an inductor by varying the voltage/current/turns, etc.
Also since V = dϕ/dt, maybe we can integrate velocity to find the magnetic flux or something but idk if magnetic flux is relevant to lifting a magnet on the ground.
So I found a link to the an equation expressing the force between two magnets in Newtons homework and exercises - calculate force between two magnets - Physics Stack Exchange
I see magnetic force is measured in Gauss.
I've nearly finished relearning Classical Mechanics, so I'm thinking about using F = ma, and I'm not sure how the inductor/"electromagnet" ties into this nicely.
I don't know how to convert an inductors properties into Gauss, nor express it as a function of distance, and I think you guys can help!
I considered using F = kqq/R or some other attraction law, but still idk how to relate an inductor and it's Joules or other properties to "magnetic strength" I can use in a kinematics analysis.


texts: How to bypass current sensor (ACS712) default 2.5V voltage output in buck/boost converter PCB

texts:
I'm having a bit of trouble coming up with the most practical fix for my buck/boost converter PCB. To give a bit of an overview, I'm using a current sensor to read the current value through an inductor, that output is fed through an op-amp to amplify the signal, and then that is finally fed into comparators that controls a circuit to switch two MOSFETs on/off to maintain the inductor current between a min and max value.
In short, the circuit goes: current sense -> op-amp -> comparators -> MOSFET driver.
This worked well in simulations, however, on my PCB, the current sensor's default voltage output when it doesn't sense a current is 2.5V. Because of this extremely high voltage, the value goes right past the comparators and keeps one MOSFET on, without ever switching the other. The normal voltage values that the current sensor should output is between 0-500 mV. I only need to get past the initial default 2.5V on the output by pulling the line to GND briefly (to get the other MOSFET to turn on and allow current flow to the inductor) to get my circuit to start working.
I've brainstormed two ways to go about this, but I would love to get additional feedback.

Find a diode with a forward voltage greater than 500 mV, and solder it directly to the output of the current sensor. This way, whenever the voltage on the line goes above 500 mV (would never get this high during normal operation), the diode will short straight to GND.

Use an additional comparator on the current sense output that pulls the line low whenever it detects 2.5V at the output and 2.5V on the other input pin. Since my PCB has already been fabricated, I would need to run about 8 wires that connect to this IC all over the board. Not ideal, but I think it will get the job done.

What are your thoughts? Thanks for all your help. I've included a link to the part I'm using below.
https://www.digikey.com/en/products/detail/allegro-microsystems/ACS712ELCTR-05B-T/1284593


texts:
I want to know two things,how big does the phased array needs to be to form proper beam and what is the smallest area the beam can be focused.I learned little bit about lasers and with focal lense,the smallest spot that it can be focused is 1 wavelenght in theory,in practice about double.From loudspeaker theory I know that for driver to exhibit directional radiation it needs to be atleast 1 wavelenght big,significant beaming doesnt happen until the driver is 5 times the wavelenght.

But this isnt optics or acustics,how does this work for microwave phased array transmitters? I want to achieve small spot size,around 1cm and very low divergence,pencil like beam,but I also would like to use relatively lower frequencies like 2.4 GHz which have 12.5 cm wavelenght.If it was like speakers and lasers,smallest spot size would 12.5 cm,and the array would be too large,around 60 cm in diameter.

I know that dielectric materials slow down the speed of electric field,thus shortening the wavelenght without increasing frequency,is it possible to use this property to make small size array that is able to focus to spot size that is below 1 wavelenght in vacuum/air?


texts: newb to arduino, how to navigate the ESP8266 vs ESP32 examples and tutorials?

texts:
a big thanks to the many before me creating this space and solving many questions.

I've been learning ESP32 (currently using ESP-WROOM-32 board) while I've found tutorials specific to this board, also finding cool examples built for ESP8266 which are close but using different pins (this I can fix) and different imported libraries (which I'm struggling with).

What's the most complete ESP32 tutorial series you've found?

I'll also be working through similar examples on uno, raspberri pi, so I'm expecting to run into this issue in future. Just curious how others deal with the pedantics of different libraries for different hardware..

any pointers appreciated.


texts: MOSFET symbol with no arrow but circle instead?

texts:
In the linked application note, I have come across a symbol on page 5, of which a captured image is embedded below.

I have never seen this symbol before, but based on context I am assuming that it is two drain connected NMOS MOSFETs.

This MOSFET is being used to switch the 20V on or off just as a mechanical switch.

Is this so? If not what is it?


texts: inductance of a closely wound toroidal coil

texts:
"The qualification that the coil should be closely wound on the toroid is to minimize the linkage flux around the individual turns of wire"
what does it mean that "the linkage flux around the individual turns of wire"?


texts:
I am designing an RF transciever board. I have quite a few inductors in the RF section. But, I am a novice in RF circuits and hence am not so aware of the parameters of importance. My usage of inductors is for switching power circuits and I usually just check the DCR and the saturation current. Then based on the formula for inductance I select it.

But, when it comes to RF inductors, how do I select them ?
I have read that there are 2 more parameters viz - Q factor and SFR.
The Q factor , I understand is Q = Xl/Rl i.e - Impedance of the Inductance/Resistive component of Inductance.

Now, what is the SFR ? I find confusing definitions online. I would appreciate if anyone could point me to a tutorial on this please.

Also, how does the Q factor and SFR affect the performance of the circuit ?


texts:
I'm new here so I'm going to make is as simple as it can get..
How can I bias a Gilbert cell with bjt transistors like this one:

What methods can I use to bias the transistors? Is there any example schematic where they show how biasing resistance are put and calculated?

I've tried many methods but I got stuck, because I suck at dealing with transistors since uni days.. For instance, I could bias the diff amps with base resistance method, like this one:

but got stuck in biasing tail transistor since it's its collector is linked to the upper diffs emitters rather than +vcc like in this example:

I may have done my research in the wrong way, but I've looked in many articles, files etc even in different languages, but all I can find is basic gilbert cell theory and that's it, I managed to find only one practical example so far.

Please, I'm getting really desperate, I've been stuck with this for a very long time now, the place where I live, electronic devices are really limited, I can't find mixers in any shape or form, IC mixers, or even toroid to make a diode ring mixer since it's simpler. All I have is only 2N2222A transistors that could operate up to 300 MHz, so they're my only way. I appreciate any type of help, advice or information you can give me.


texts: Can a flip flop possibly work at over 800MHz?

texts:
As I know, the setup time is at least required time for data to become stable at the input of a FF before the sensitive clock edge. Hold time is the required time for data to remain stable after the clock edge.

Usually I use a clock from a 24MHz OSC, when I use a test board. But when I synthesize with the RTL to make a chip, I used to 88MHz to 120MHz. I think this is meaning that this board can work at almost 120MMz.

Then what if I want to make a chip with RTL that works at almost 800MHz frequency, then is this meaning that the Flip-Flop is working in 800MHz?

If yes, which fab companies support that frequency? Is this possible way?
Is this needed some unique process in a fab?


texts: MCP73871 Battery Under Voltage Protection

texts:
I want to use MCP73871.

Is there a battery under voltage protection in this charger IC?

or may I use a battery protection IC?

Answer for @Bimpelrekkie

I decide to use my power architecture as below.

I add DW01A for protection as your advice.

  My system has GE910QUAD gsm modem and ATmega328P MCU. My MCU works with 7.3728 MHz external crystal and 3v3 power supply. A timer is enabled LDO regulator within a time interval (15 min).

I think this architecture is true, what is your comment?


texts:
Could anyone give me a hint in analyzing the Twin-T Active Notch Filter?
I tried a delta-star transform, followed by nodal analysis, but ended up with conflicting equations. For an example, look at Figure 1 from the Texas Instruments application note "An audio circuit collection, part 2":

In the more general example I am studying, I remove C4/C5 and R6/R7 (and that Vcc) and treat the T passive components as matched conductances as follows:

R1 and R2 become Y1,
R3 becomes 2Y1,
C1 and C2 become Y2,
C3 becomes 2Y2,
R4 and R5 generic voltage divider with resistances R1 and R2


texts:
I have a Problem turning a MOSFET On/Off with my Arduino. I try to controll multiple mosfets to supply a high power Device with current. Now my issue is that the mosfet does not turn on.
Here is a basic sketch of the circuit for one MOSFET.

I use this mosfet

At this point, I am not sure if the 5V supply Voltage is enough to switch the MOSFET.
The max. VDD is 200V and 1A

I tried adding a Bleed Resistor at 10k Ohm but that didn't really change anything.

The Analyzer is my Supply and measures the Current/Voltage.

simulate this circuit – Schematic created using CircuitLab

The Analyzer is A B1500A

It can measure spot, sweep, sampling and pulse in the range of 0.1fA-1A or 0.5uV-200V


texts: ADC value changes with changing power supply

texts:
I'm measuring weight using hx711 ADC and load cell.
HX711  schmatic:

I use 12V 1A power supply and 6V/4Ah dry cell. Also I use MT3608 boost converter to increase battery voltage to 12V because battery voltage is not enough for voltage regulator (LM2576). LM2575 need at least 8 volt.
MT3608 boost converter schematic:

There is also a charger in the system for dry cell.

charger schematic:

When I disconnect the power supply, the ADC value drifts. It causes a 100 gram offset. Both power supply gives 12 volt but ADC values are changed if I start to use battery. What can be the reason? I'm sorry if this information is not enough.


texts:
I attached a image of ESP32's datasheet where it say to add a series 470 ohm resistor to Tx transmission line. I wonder is it talking about which line, what are the pins?

And why that specific value?

here Is the link to the ESP32 datasheet https://www.espressif.com/sites/default/files/documentation/ESP32_FAQs__EN.pdf


texts:
I was asked to first design a Gunn oscillator for a frequency of \$10GHz\$, feeding an  output line of impedance \$50ohm\$. I was told that the Gunn could be represented as a diode of impedance \$Z_D=-20+j60\$ ohm and was asked to connect it to a transmission line of impedance \$Z_c=100ohm\$. I managed to solve that and determine the necessary stub lengths etc. rendering oscillations possible using a Smith Chart.

I am now asked to implement this design for a Gunn oscillator on a dielectric bed using microstrips; moreover, to show the feeding DC network and the RF output so that optimal isolation between the DC and RF ports is attained. Is the third drawing in the attachment the one meeting the requirements? I'm not sure and would be thankful for some guidance.


texts: My company has a Philco Predicta television model H3407 as described here: Philco Predicta description. Will this TV still work with modern broadcasts?


texts:
I am trying to plot the bode diagram of a flyback converter on LTspice. This is the first time that I do this and before trying to plot my flyback converter, I would like to plot the bode diagramm of a flyback whose I know the answer in order to see if I am able to do it correctly. So I took an example from the book "Switch mode power supplies" (amazing book) written by Christophe Basso.
Here is the example:

I have some troubles to understand how the optocoupler is modelized. The parameters of the optocoupler model are the following :

CTR (CTR = 2)
Fp which is probably the frequency of the pole of the transfer function of its model (Fp = 6k)

As Christophe Basso wrote it in its book an optocoupler has a parasitic emitter collector capacitor. So I did the following model :

Nevertheless, It probably miss something ... as I do not get how to have a 1st order transfer function with a pole :
$$H_{opto}(s) = \frac{G_{0}}{1+\frac{s}{wp}}$$
Thank you very much and have a nice day !


texts: Based on the diagram on the datasheet, I don't see that the AC line voltage measurement circuit is reinforced isolation. Resistor dividers can't be reinforced isolation circuits as my understanding. Can anyone explain? Thanks in advance


texts: Two different widths / sizes of banana plugs on home audio receivers?

texts:
I am replacing an Onkyo TX-SR606 with an Onkyo TX-NR575. On the TX-SR606 unit, I used these "dual" banana plugs (see photo), a single unit with both positive and negative connections on it. Unfortunately, these "dual" banana plugs don't fit into the terminals on the new TX-NR575. Hence, I have to buy new, single banana plugs that aren't joined together.

Are there two different sizes / widths of "dual" banana plugs? I thought these things were more or less universal.


texts:
I have a radio transmitter (for my quadcopter) and I wanted to improve its range. So for now I removed its integrated antenna and I soldered a male sma connector so I can plug in any antenna I want. I was thinking to add one more antenna. Keep in mind that the transmitter has only one antenna. So adding a second antenna will be something like this:

simulate this circuit – Schematic created using CircuitLab

Basically the second antenna will be connected to the first one. I would like to know if adding the second antenna will be better, worse or simply the same.


texts: Raspberry Pi Super Capacitor On Battery Loss

texts:
I am looking to provide power to my raspberry Pi upon power loss from 5v power supply. It just needs to provide power long enough for the Pi to safely shutdown (with the setup I have, I am estimating around 5 seconds to cleanly shutdown, but if it takes longer than this I can always add more caps to cover the time).

The circuit is as follows:
The 5V battery/power supply source powers the Pi and charges the Caps through the 5v to 2.5V voltage regulator while plugged in. Upon battery being unplugged, the super caps then power the Pi through the boost converter, and a signal is sent to the Pi to shutdown immediately by the PNP transistor.

The super caps are 10F each, which should provide 8 seconds of usable power at 50% efficiency by my math.

2.7V Full
20F Capacity
2.0V Fully Drained
2000mw Average Draw from Pi
_
Joules = 20F * ((2.7V^2)/2) = 72.9 J
Unusable Joules = 20F * ((2.0V^2)/2) = 40 J
_
mW seconds = (72.9 J - 40 J) * 1000 = 32,900 mW seconds
_
Supply Time = (32,900mWs / 2,000mWs) * 50% (efficiency loss) = ~8 seconds

The PNP transistor should kick-in when the 5V power source drops off, thus sending a signal to the Pi on GP21 to shutdown immediately.

Assuming I can code this to shutdown fast enough, will this circuit work as I am expecting?

Thanks in advance for any help on this!

Note: The 3.3v is not used for anything in the sketch. My understanding is that the Pi is powered via 5V, not 3.3v.


texts: How long does ultrasonic rangefinder last

texts:
I've built a parking sensor in my garage that uses the HC-SR04 ultrasonic rangefinder and an arduino to measure how far the car is from the back wall.

The one thing that I'm worried about is if the sensor will continue to work for a long time.  When it senses an object, it senses distance 10 times per second and once there's a period of inactivity, I scale it down so that it senses distance once per second.  So it will be sensing once per second pretty much all the time, which is like 86000 per day, or 31 million times per year.  Anyone know if these sensors go bad over time or if they're rated for a certain number of senses?

Thanks for any advice!


texts: Altium - line spacing between the parameters in the schematic symbol

texts:
Does anybody know how to change the line spacing between the parameters in the schematic symbol without disabling the autoposition feature in Altium Designer? If I change the font (smaller) of the parameters, the line spacing is getting too big (see “Default”).

I want it to be like “Wanted” without moving every parameter on every component by hand.

Is this possible?

Another question is how to make sure that the parameters are shifted up if there are added more parameters to the schematic symbol. If I add two more parameters, it looks like in “More parameters”.

I want it to be like in “More parameters centered” as the first step and of course the answer to my first question would lead to the final solution “More parameters centered wanted”

The first question is my biggest problem and much more important than the second, because the schematic is getting too big because of those big line spacings.


texts: Designing a 4-bit Adder-Subtractor Circuit

texts:
I am designing a 4-bit adder-subtractor circuit using CMOS technology.

The instructions I was given for the design portion are as follows:

Given two 4-bit positive binary numbers A and B, you are to design an adder/subtractor circuit to compute (A+B) or (A-B), depending upon a mode input which controls the operation. You may use one’s or two’s compliment of B to perform subtraction. The result with the proper sign is to be displayed in un-complemented binary form.

My approach is to use four full-adders with a 4-bit input A, and a 4-bit input B whose bits may be XOR'd based on the mode chosen.
The mode will be decided by bit M in the circuit below.

For subtraction M = 1. 1 is chosen because M acts as the carry-in.
Therefore, all bits of B will be inverted and 1 will be added to the LSB to find the 2's complement.

For addition, M = 0. Therefore, carry-in is set to zero as desired.

The problem I am having is how to define the rules of the circuit.

If the inputs A and B are unsigned, the answer will give A - B if A >= B OR the 2's complement of (B-A) if A < B. In this case, I would have to compare the inputs to see which one is larger and in cases where B is larger than A, take the 2's complement of the answer to show the positive value and turn on a bit to show that it is negative.

If the inputs A and B are signed, the range of values I could use are from 0 - 7 and the result will give signed A - B as long as there is no overflow.

0101    5         0111 7

+1010  -6       + 1101 -3
________        __________

1111  -1         10100 -> 0100 : 4

The problem with using signed inputs and signed outputs are that the instructions ask for the answer to have the proper sign (indicated here by the MSB) but UNCOMPLEMENTED. My interpretation of uncomplemented is for the answer to be unsigned. I would have to therefore design a method, as in the case above to change 1111 (-1) to unsigned. Here is where I am stumped, as then the answer would have to appear as 10001. The MSB indicating it's negative and the other 4 bit's indicating the value.

Ideally, I would just have the answers be signed binary, but I am afraid I am overthinking the process to have the answers in uncomplemented binary. Any guidance is appreciated. A thought I had was to attach an XOR gate at each output: So, S1, S2, and S3 with the MSB (1 when negative) in order to invert the bits of the answer when negative and then adding 1 to that circuit. The problem with this idea is that the MSB can also be 1 when overflow occurs.

Thank you.


texts: Can not jump to Timer interrupt function in STM32F4 discoverty

texts:
I made a code to call Timer2 interrupt function like this :

timerx->TIMx_PSC    =42000;   // prescaler
timerx->TIMx_ARR    =2000;    // counting number
timerx->TIMx_CR1    |=0x90;   // auto reload, count down
timerx->TIMx_DIER   |=0x01;   // enable update interrupt
interruptsx->ISER[0]|= 1<<(TIMER2_INTERRUPT);   // enable timer_interrupt
TIMER2_INTERRUPT=28
timerx->TIMx_CR1    |=0x01;   // enable counter
timerx->TIMx_EGR    =0x01;    // update generation

and

void TIM2_IRQHandler(){
if(timer2->TIMx_SR & 0x1){
gpio_toggle_off(gpio_A,GPIO_Pin_1);
number_display(gpio_D,number0);
}
timer2->TIMx_SR=0x0;
}

The problem is : it doesn't jump to TIM2_IRQHandler(). How can I solve this problem?


texts: Hall sensor for slowly varying magnetic fields

texts:
I am trying to measure the change in the field of a permanent magnet (at about 50 mT) due to temperature fluctuations at room temperature (timescale ~ mins to hours). The sensor I am currently using is a A1326 linear hall effect sensor from Allegro (https://www.digikey.ch/de/datasheets/allegromicrosystemsllc/allegro-microsystems-llca132456datasheetashx). The sensor has an output of 2.5 V DC and varies between 0 V and 5 V. Currently I am limited by low frequency (1/f) noise coming from the Hall sensor. This is where my two questions come in:

Does this noise generally come from the Hall element itself or from the electronics (presumably amplifiers) present within the Hall sensor?
Would chopper-stabilization of the amplifier in the Hall sensor mitigate the 1/f noise? Such as found in this sensor from TI: http://www.ti.com/lit/ds/symlink/drv5053.pdf


texts: VHDL: Simulating Delay for ISE UNISIM components

texts:
I have extracted VHDL source of my design from Xilinx ISE.
It uses UNISIM library to model Look-Up Tables and Flip-Flops and other components.
When I simulate my VHDL design (a combinational circuit) using ModelSIM, there are no delays displayed in simulated WaveForms.
I want to know how can I add delay to elements of UNISIM library and then see its effect on MODELSIM simulation?


texts: Irrigation Valve (24VAC Solenoid) Multiplexing

texts:
I have a fairly extensive sprinkler system in which I have used all of the available wires.  I've added new landscaping that requires irrigation, but without available wires to use for the valve control, I need to come up with a creative solution (I don't want to dig another 100' of trench).  My control box has plenty of available zones, it's just a matter of moving the electrons out to the valves.  One thing working in my favor is that these systems only ever power one "zone" at a time.

There are some expensive solutions for multiplexing that use one wire pair (http://www.smarthome.com/3139/DuWa-8ZEXT-Irrigander-8-2-Pro-Irrigation-Sprinkler-System-Zone-Expander/p.aspx) but I think something simpler will work for me.

I want to make a little box that sits on the end of the existing pair of wires and toggles between two or more solenoids each time power is applied to the wire.  This will work since the solenoids are normally closed, and only stay open while power is applied.  I'll program the controller to hit the same zone twice (or more) to toggle the power to each solenoid in turn.

So, to the electronics question:  What do I need to think about to make this work.  I'm a rank amateur.  I think I need:

Some kind of "memory" to know which solenoid to turn on next
Relays to route the 24VAC to the right solenoid
Parasitic power for whatever logic is needed
Copious use of diodes to prevent magic smoke escaping

I'm doing well to get an MSP430 to light LEDs, so some tips on how to make this work would be very greatly appreciated.


texts: Does radiation level of an antenna depend on the antenna's parameters?

texts:
I am a newbie when it comes to the theory of telecommunication. I wonder whether radiation exposure may exceed recommended safety levels after changing the antenna only? I'm asking since I've seen people making their own antennas for various mobile devices, such as phone built-in bluetooth or wifi modules. An example can be found here:

https://dl.xda-developers.com/3/4/3/1/3/0/4/DSC06952.jpg?key=nOTc6qou05QQmaIKa6IgEg&ts=1508944630

I think it is possible in theory as a material that an antenna is made of as well as its dimensions may influence radiation resistance. Also, shape of an antenna influences gain, which may result in sending more energy in one direction. Is it something that should be considered in practice though when it comes to low power devices such as phone wifi, GSM or bluetooth modules, wifi routers that one uses at home etc.?


texts:
What is the second/lower 15 k-ohm resistor for?

I understand why there is a 12 k-Ohm resistor in the top, that's for the V-out. But why is there a 15 k-Ohm resistor in the lower right? Why would you need to make a voltage drop on the path back to the battery, isn't that just waste of energy?


texts: Why use DDR instead of increasing clock speed?

texts:
Why would you want to use DDR ram and read/write on every rising and falling edge of the clock instead of just doubling your clock speed and read/write on just one of either the rising or falling edge?

Are there pros and cons to each?


texts: Testing an induction motor with a VFD, difference in voltage and mechanical power vs electric power

texts:
I have question about a electro motor powered by a frequency regulator. It is the first time I did some test on a frequency regulator on school.

This are the parameters of the motor

The motor is connected in triangle.
The frequency regulator is from Schneider. I forgot to write down the specs.
But it's a special module for students. It has the schneider frequency regulator, leroy Somer asynchrone motor and a DC motor the can be used as generator to put some load on the asynchrone motor.
There is also some special software that came with test bench . With this software we can do test.

So the test I did:
I connected a constant load of 5Nm on the motor. After this I regulated the frequency from 10Hz to 50Hz. The following table gives the results of all signals measured.

Where f is the frequency, n the rotation speed, Tu the connected torque, Pm the mechanical power, U voltage output(internal voltage meter of the system, not so accurate), I current, Pe electric power, los. power loss = Pe-Pm , Um.rms is the same as U but with a more accurate voltage meter, Um.1h is the voltage of the first harmonic of the PWM signal, Im.rms current.

Now  there are 2 thinks that I don't understand:

the first question:
So when I compare  Um.rms and Um.1h, with other words the RMS value of the output and the first harmonic of the output there is a difference difference between them. I think this is because, the other harmonics also have a big influence on the RMS value. I read in an technical article (I can't post the article url because reputation isn't high enough yet.) that the 5th and 7th harmonic could have an amplitude of 10% - 40% of the fundamental harmonic. So I think that this is the reason that there is such a big difference between the RMS value of the output and the first harmonic of the output.  Is this true?

The second question:
When I compare  Pe and Pm there is a big difference between them. The motor efficiency is around 50%. Is this because it is powered by a frequency regulator, because the harmonics in the current and voltage? Or those it have another reason. I have no clue why this is. (I can't post the plot because reputation isn't high enough.)


texts: Speed difference between SRAM (Static RAM) and DDR3 RAM

texts:
This is more of a computing question, but only electronics geeks would know such things. Today's computers use multiple layers of memory in order to work with data quickly. Currently CPU speeds are anywhere from 10 times to 100 times faster than RAM memory. Therefore, CPUs are built with a small amount of very fast memory (Static RAM, or SRAM) which is usually from 10 KB to 10 MB in size. Data cached in this memory is the fastest to work with and DDR RAM is usually much slower (10-100 times).

Wikipedia says DDR3 RAM currently takes 5-10 ns per "cycle". What does this mean exactly, and how fast is SRAM in comparison? Also, for embedded projects utilizing FPGA's, how useful is SRAM and DDR3 and can either be omitted in favor of the other? (eg. No need of SRAM if DDR3 speeds are similar)


texts: One potentiometer supplying two effect units

texts:
How can i do this?

I want a simple expression pedal splitter where one expression pedal can be used to control two effects units. I don't want to setup a additional powersupply or digital potentiometers.

I had tried simply disconnection the supply on one effect unit and driving it with the voltage from the other unit.That worked ok for two 3.3volt units, or two 5 volt units.

However, now i have one effects unit uses 5volts and the other uses 3.3volts. I thought some Schottkey clipping diodes like in the schematic would do the trick, but it seems to be clipping at about 4 volts rather than 3.3v. Why would that be? Though I think there must be a limiting resistor for this constant current but a voltage drop cannot be allowed in this circuit else full modulation of an effect will not occur.

The 27K resistor is needed because this particular 3.3volt effect unit will not modulate with a simple varying supply on the tip of the control jack, but must also have a small load as would be expected if an expression pedal was connected to it. Most effects are not like that, but this one is.
Can this be done.

Also, it is not known whether someone might use two 5v units, two 3.3 volt units, or a 5v & 3.3v, and in any order.


texts: An error in using FIFO block in system generator

texts:
I have designed a circuit in System Generator. I want to put a FIFO at the output before out gateway as shown in the below picture

When I run it I face to the following error

I should connect the we and re pins to a clock, hence I set clock probe at their inputs. I do not know where is wrong. Can any one help me in driving these two input ports of FIFO?


texts: I am working on a DMM project and need sockets for standard probes. I don't even know what keywords to search for these. I could fallback and use banana sockets but it would be better if I could use the standard socket.


texts: Dependence of output voltages of an op-amp on rail voltages

texts:
I want to use an op-amp as an inverting amplifier to convert negative voltages to positive voltages,

simulate this circuit – Schematic created using CircuitLab

If my input varies from 0 to -5V and I want from 0 to +5V as output, is it Ok to connect V+ to 5V and V- to ground?
From what I know, the rail voltages just saturate the output between the V+ and V- values but I'm not sure about how it sources and sinks the functions internally.


texts:
I have a question about the input buffer of the PCM4202 ADC. On page 22 of the PCM4202 datasheet, they describe an input buffer. It's pretty standard with gain and filtering. However, the ADC requires the input to centered at +3V so it uses a COM pin on the op amp (OPA1632). However, this COM output from the PCM4202 needs to be buffered which makes sense. What doesn't make sense is why they use an OPA227, a high end expensive audio op amp. To me, that seems like a job for a ua741. Digging in to the OPA227 datasheet, I see a VERY low input offset voltage (+-5uV). Is this why they chose that op amp? What issues could arise if using a ua741 (since ua741s can have a high input offset voltage)?

Note that I have access to OPA2227s, which are 2 channel OPA227s with the same functionality excluding offset trim, and ua741s. However, I don't currently have the PCM4202 or the OPA1632.

Links are provided below of the datasheets:

http://www.ti.com.cn/cn/lit/ds/symlink/opa227.pdf
http://www.ti.com/lit/ds/symlink/pcm4202.pdf
http://www.ti.com/lit/ds/symlink/opa1632.pdf


texts:
I am trying to connect to an e-bike controller to reprogram it, and have to find the female counterpart to this connector for this purpose. Ideally, I want to find the part that will plug into this.
I've spent a couple of hours going through lists of connectors, but no luck so far.

Here is a photo showing the cable connector I have:

6 pins
external diameter ~8mm
internal diameter ~6mm
as shown on the photo, there is a flat part on the top side of the photo
the connection is made by pushing the other part in, no screwing or baionets
given that it is on an outdoor bicycle kit, I'd think it has a reasonable water-tightness rating.
it says "JULET" on the side of the connector (it's hard to see this on the photo)
the casing is somewhat flexible plastic material

Any tips would be great!


texts: How to implement and tune a LC band-stop filter?

texts:
I have designed a simple LC band stop filter with a center frequency of 433MHz. The schematic looks like:

The caps are NP0 0603 and the inductors are from the Coilcraft 0603HP series. The values shown don't give me a center frequency of exactly 433MHz but that's the best I could do with the values available. I figure that I'll need to tune the filter with a spectrum analyzer by substituting different values of capacitors to compensate for the parasitics.

Simulating the exact values yields something like this which isn't quite ideal:

My PCB layout looks like:

My assumption that I could simply tune this by substituting caps while looking at the response on the spectrum analyzer doesn't seem practical now. I was going to purchase several caps a tenth of a pF apart (ex: 4.5pF, 4.6pF, 4.7pF, 4.8pF, etc) from one another and simply substitute them in. However, I find that I have to buy a reel (and wait 14 weeks) to get the caps I want (0603). For instance, I can only get a 4pF, 4.7pF and a 5pF cap for the series element. Is this the way to tune the filter? If not, how else could it be done? What kind of response should I reasonably expect? Do you see anything wrong with my approach?


texts:
I'd like to know what type of cable this is. It looks very similar to the types used in phones and tablets and is for a camera. I need a replacement and would appreciate any help to locate the correct part.

Many thanks for your help.


texts:
I am working on a circuit design that has multiple IC's on it. My MCU requires 2.5-3.3 VDC for it's power. Another IC that I am using requires 5V for it's logic power. So what is the cheapest and simplest solution for powering both of these devices. I figure my options are:

A) Use two voltage regulators a 3.3 and a 5V.
B) Use just a 5V regulator and used diodes or something to drop the voltage down the an acceptable level for the PIC.
C) Maybe there is a dual voltage regulator out there?
D) Something else?


texts: SMT reel: taking a couple of parts off the reel

texts:
I have a couple of SMT parts that I ordered "digireels" for - i.e., essentially tapes wound around a spool, with some leader tape attached at the front. This is good for the pick and place machine - but what if I want to take off a couple of parts from the reel myself, for quick prototyping/debug? is there a best practice for manually dealing with such reels - for example - is taking parts off the front better or from the rear? Or anything I should be careful about, so that the pick and place process does not get affected due to my "tampering" with the reel?

Thanks.


texts: Optimal method to drive a pair of 10W 28V 0.35A LEDs using PWM for dimming

texts:
Using DC/DC boost converter is inevitable because the power supply will be 12V, so the voltage has to be stepped up to at least 28-30 volts.
The biggest aspect I am looking at is to have as few components as possible. Using just a single driver IC without any PWM external generation circuit would be an advantage. The chip would have to have PWM generation inside itself. I am trying not to use any microcontroller for PWM generation, but 555 timer or other IC wouldn't be too bad, however, as I've mentioned before, the goal is use a single IC chip. So the key question is what would be the recommended IC for this specific LED drive.


texts: How to cover vias with solder mask (solder resist) on Proteus

texts: I am using Proteus 8 and wish to cover all the vias with solder mask (solder resist). Could anyone please tell me how to do this?


texts:
I need to measure the switching frequency of an open collector output.
The waveform will be square shaped and the frequency range is specified as 0 to 5kHz.
First of all I don't want to count pulses because I want to determine the duty cycle as well. So here comes my problem:

For this task I explicitly need to use an ATMega16 without any external circuitry (except crystal)

I know there is a pretty simple way of determine frequency and duty cycle, and I already did use this technique: hook the signal to an interrupt, combine it with an asynchronous timer, do a little bit of math and done!

Now this works pretty well with the 16 Bit timer module but not so great with one of the 8 Bit timers since those overflow much faster.

Now I'm curious if I can determine the accuracy of this technique beforehand, e.g without testing it out.

I know the frequency reading will mostly depend on the timers frequency: the higher, the better. An 8 Bit timer running at @ 2MHz (prescaler 2 ; from 16MHz) should give me a basic 0.5us per LSB resolution which looks pretty good on paper.
Combined with a 16 Bit overflow register I theoretically could measure up to one second time period. But I know this won't work: updating the 16 Bit overflow register would take too much instructions in the ISR and effectively wreck my accuracy.
So is there any way of getting reasonable accuracy (+-5%) from a single 8 Bit timer module in the specified frequency range (0...5kHz)?


texts: Is there such a thing as a PWM expander like there is a GPIO expander

texts:
I found this MCP23008 and its a nice little DIP GPIO expander over I2C. Is there a chip like this for PWM outputs?

Specifically I want this PWM generator to be used for the inputs on several L298Ns.


texts: MCP3008/ADuM3154/ESP32 - Corrupted MISO Data Line

texts:
I have 3 MCP3008's being read by an ESP32 on the same bus isolated by an ADUM3154ARSZ. I was reading each pin on the MCP3008's about every 10ms. I seemed to have a lot of jitter and after averaging the values I found them to be way too low. I then tried just reading one of the inputs every second to see what was going on and it appeared to be missing almost every second result. (0 or very low value)

02:28:21.170 > 426
02:28:22.178 > 0
02:28:23.204 > 1
02:28:24.210 > 422
02:28:25.218 > 0
02:28:26.230 > 424
02:28:27.234 > 1
02:28:28.242 > 425
02:28:29.250 > 0
02:28:30.258 > 0
02:28:31.282 > 423
02:28:32.290 > 0
02:28:33.298 > 424
02:28:34.306 > 1
02:28:35.314 > 0
02:28:36.322 > 425

I hooked up my scope to the serial pins at the MCP3008 and I seem to be getting corruption/low voltage on the MISO data line between the MCP3008's and ADUM3154ARSZ. (See pictures below) I have stripped everything down to just reading one MCP3008 through the isolator. I added a 10k pullup on the MISO line thinking that the isolator wasn't pulling the line up hard enough, but did not seem to change anything. I added some different delays between pulling the ADUM3154ARSZ address lines low and starting the SPI transaction but it did not seem to help either. (Shouldn't matter as address 0 is both address lines low anyways) Changing up the time between reads does not seem to change the ratio of how many good readings vs bad readings there are.

Also, when zooming right out on my scope I see the MISO line getting pulled down up to 15ms after the initial read and then about 12ms and then 9ms and keeps going down till 0ms and goes back 15ms or so. (Not sure what this is but seems to be a repeatable pattern)

I am not sure why it's doing this and was hoping someone here could spot what I am doing wrong.

Thanks!

Schematic for reference: (L3V3 and LGND are supply for ESP32 and P3V3 are supply for MCP3008's)

Good Reading:

Bad Reading:

Another Bad Reading:


texts: Philips/Magnavox LCD TV Service UART / ComPair

texts:
I have a Magnavox 42MF438B/27 42" LCD TV.  The IR sensor (or something related) quit working after awhile, so we have been unable to use the remote.  Today, I was digging around behind the TV and noticed a "Serv U." port on the back with what looks to be a standard 1/8" jack.  I figured this was a serial port for firmware upgrades and what not.  Some quick googling revealed this assumption was correct... the manual calls it "Service UART".  So I am assuming it is a standard 1/8" TRS plug, one ground, one send, one receive.

My hope is that I can send it commands... volume up/down, power on/off, etc. over this port.  Trouble is, I can't find any specs.

Does anyone know what the voltage this serial port runs at?  I'd rather not fry it with RS232 levels if it is just 3.3V.  Then, any thoughts on what the pinout might be?  Or, any safe way to find out?

Finally, any thoughts on where I can find protocol spec?  I certainly have no problems poking around, but I'm hoping perhaps a Philips tech can help me out here a bit.

Thanks a ton!

Edit: I found another message board post where someone's manual says, "For use by authorized service personnel, for installers, integrators, do not connect RS232 without level shifter", so I think I am on the right track.  3.3V then I am guessing?  I think I have an old USB->cell phone cable around with the appropriate adapter.

Edit #2: I found a service manual!  It says their techs can connect with HyperTerminal... 38400 bps, 8/N/1.  It also says I can access "Customer Service Mode (CSM)" by keying in the code 123654.  For "Service Default Mode (SDM)", 062596menu or for DVB-T Service Mode, 062593menu.  For "Service Alignment Mode (SAM)", 0625961+ (osd/status).  That last character may be an "i", not sure.  Program display option code, 062598menu.  No specs on the port itself though, or what is in those modes.  Still digging...

Edit #3: Seems the service cable adapter kit is called ComPair, or possibly ComPair II.


texts:
simulate this circuit – Schematic created using CircuitLab

In analysing an ideal op-amp circuit I'm asked to state the input resistance seen by an input voltage.

Some of this may be irrelevant but a quick summary of the circuit:

Two unknown voltages, VinA and VinB are connected to the inverting and non-inverting inputs, respectively. Both have a 10k resistor between Vin and the input.
Vout feeds back to the inverting input, through another 10k resistor.
VinB, after the first 10k resistor, is connected in parallel to the non-inverting input (as stated) and another 10k resistor which continues to ground.

So, the question is what is the input resistance seen by VinB.

Is it

a) the two resistors in series (since no current flows to the input), i.e. 20k?

b) the resistance used in a voltage divider formula, i.e. 10k/10k+10k = 0.5?

c) something else I've overlooked?

Thanks in advance.

EDIT: Added the circuit diagram.


texts: what should be the Vbe voltage to turn on the pnp transistor and is it always necessary for the base to be negative or is it just that Base needs to be more negative than the Emitter by approx 0.7 volts.


texts: What device can I use to parallel 4 dry contact signals from 4 timer relays

texts: What device can I use to multiplex 4 dry contact signals from 4 timer relays to  actuate an isolation valve? In other words, any of the signals from the timer relay should be able to actuate the isolation valve, it could be more than one timer relay that is activate, but the isolation valve will see only one signal which it needs to actuate the valve.


texts: Verilog assigment and replication , What do the parenthesis do?

texts:
I am trying to understand the following Verilog code sample, so far I could say that if address == 0 then perform the bit-wise & with data_in or if it is 1 perform bit-wise & with data_dir. The thing here is that I am not sure if those parenthesis imply conditional and why it is using replication by 1 to convert vector to integer if this is the case. Thanks in advance.

  ....
module DE1_SoC_QSYS_i2c_sda (
                              // inputs:
                               address,
                               chipselect,
                               clk,
                               reset_n,
                               write_n,
                               writedata,

                              // outputs:
                               bidir_port,
                               readdata
                            )
;

  inout            bidir_port;
  output  [ 31: 0] readdata;
  input   [  1: 0] address;
  input            chipselect;
  input            clk;
  input            reset_n;
  input            write_n;
  input   [ 31: 0] writedata;

  wire             bidir_port;
  wire             clk_en;
  reg              data_dir;
  wire             data_in;
  reg              data_out;
  wire             read_mux_out;
  reg     [ 31: 0] readdata;
  assign clk_en = 1;
  //s1, which is an e_avalon_slave
  assign read_mux_out = ({1 {(address == 0)}} & data_in) |
    ({1 {(address == 1)}} & data_dir);

  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          readdata <= 0;
      else if (clk_en)
          readdata <= {32'b0 | read_mux_out};
    end

  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          data_out <= 0;
      else if (chipselect && ~write_n && (address == 0))
          data_out <= writedata;
    end

  assign bidir_port = data_dir ? data_out : 1'bZ;
  assign data_in = bidir_port;
  always @(posedge clk or negedge reset_n)
    begin
      if (reset_n == 0)
          data_dir <= 0;
      else if (chipselect && ~write_n && (address == 1))
          data_dir <= writedata;
    end

endmodule
  ....


texts: picking the right Vgs th based on VOH and VOL

texts:
My microcontroller has a VOH min of 2.4V and a VOL max of 0.4V.  How do I spec the right Vgs th for a transistor switch?

At first I thought, aim for the middle and go 1.5V.  But then I was thinking about needing to operate in saturation region and I'd be better off picking a lower Vgs th if I could.  Plenty of options at 0.7V and 1V.


texts: How the low pass filter works in this circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

Vi=input, Vo=output signal. The capacitors and resistors of the output terminal of the above circuit is supposed to act as low pass filter (i.e. attenuate all frequencies of the input signal greater than a particular frequency). The  only problem is that I can not understand how a low pass filter is obtained at the output in the above circuit.
The problem is that (as in my textbook) 'CU' is calculated as if it is in series with 'RC' and acting as that low pass filter. But 'CU' is parallel to 'RC'! Also 'CO' is calculated as if 'CO' is in series with 'RC' and acting as high pass filter when 'Vo' is considered as input. And thus it becomes very confusing. Please help me understand it.


texts: Snubber to protect a VO2223A optical triac switching 0.5A @24 vac?

texts: Is a snubber necessary to protect a VO2223A optical triac to occasionally control a valve that draws .5 amp @ 24 vac 60 hertz. What would be the R/C values if required?


texts: Can one use a current transformer of 1A for a 5A input

texts: Is it possible to use a current transformer that is rated secundary 1A for a 5A input circuit taking into account the scale (hence multiply the output *5) or would this cause problems?


texts:
I'm putting together a kind-of sort-of theremin (this one in particular http://www.popsci.com/diy/article/2008-04/build-pocket-theremin-cheap) and I'm looking to make a bit of a change to it.

What I would like to do is add in an output jack so I can connect to a small amplifier.  I have a 1W Marshall mini guitar amp to play around with.  My question is how big of a resistor should I be looking to put in series with the output jack?  From what I've been finding, guitars output around (1 * 10^-7A) and 100mV to 1V.  So if I wanted to drop the 9V of the theremin (which will end up being a bit less after all the circuitry and the volume knob) to around maybe .25V I think I'd be looking at...

\$R = \dfrac{V}{I} = \dfrac{.25V}{1\cdot10^{-7}A} = 2.5M\Omega \$

I really just need someone to confirm this for me and let me know if I'm proceeding properly here.  It's been a while since I've done any circuit analysis and I don't think nodal analysis would work here so I'm a bit in the dark.  I don't know if impedance matching is going to be an issue here either, so if someone could point me in the right direction for that as well, that would be great!


texts: Using Audio Cable to connect to computer

texts: I have a HB100 Microwave Sensor Module which I am going to use for an experiment, and I want to transfer the data it produces directly onto my computer. Since the output of the device is in the audio frequency range, I want to connect it using an audio cable. But how exactly do I do this and receive the data on my Windows 7 machine? Do I need additional programs?


texts: Controlling an Op-amp gain using an MCU && || DAC?

texts: I'm building a circuit that will generate various wave forms. The output from the circuit is fed to a summing amplified where positive or negative dc offset is being added. This signal should be attenuated or amplified according to what's written in code (this means no pots.). The control elements I currently have are the MCU with a few free GPIOs and a free channel on a bi-polar 14bit DAC. The solution should take in account the fact this design should be of high quality, so I am not sure using an LED+LDR combo or something like that is really an option as the control should be tight and repeatable.


texts:
I'm trying to build a simple temperature controller by using a thermistor and a potentiometer attached to a Schmidt trigger to control a relay.

I realize that I have some serious design flaws in this circuit:

The power dissipated through the thermistor is to large (discovered after nicking my finger).
The op-amp's output hits almost no resistance, leading to a short.

Iv'e tried solving this by adding more resistors, but I'm not sure how to proceed while keeping the op-amp's inputs away from the (one-sided) supply's  limits.

Any help apreciated.


texts: Looking for a quick and easy way to boost +5VDC to +24VDC

texts:
I am looking for a simple IC solution how to boost +5VDC to +24VDC 1A.   Requirements:

THT (the project is on a 2.54mm(0.1") experimental breadboard)
low-cost (this is a hobby project, so arround $5 for the whole converter system)
simple (fewest external elements)
has been around for a while (most recent chips are delivered to my country mainly by the Farnell, charging high transport prices).

Is this attainable? What are a part number or two, that I can toss in the local electronics shop and get the device working by the afternoon?


texts: Multiple charge controllers on the same solar panel

texts:
I have two 12v lead acid batteries on my boat. One at the front for the trolling motor (~80 AH) and 2 smaller batteries in parallel at the rear for electronics (~30-35 AH combined).

I want to put a solar panel on my garage, so I can hook the batteries up when I get back from the lake to recharge them and to keep them maintained. I only need a 30 or 50 watt panel to charge both battery banks, since I never use full capacity and usually have at least couple days between trips. Instead of buying 2 smaller panels, one for each battery bank, I was thinking about hooking up 2 charge controllers to the same solar panel.

The solar panel disconnect switch is required because the batteries should be connected to the charge controllers before the solar panel is connected. On my boat, I would add DC plugs for both batteries to connect the charge controllers.

I think this will work fine, but I have done a lot of searching and could not find any information about connecting multiple charge controllers to the same solar panel. I am aware they make dual battery charge controllers, but they don't look any better than the $10 units you can find on Amazon and they are more than double the price.

simulate this circuit – Schematic created using CircuitLab


texts: Can I amplify a thermocouple Signal with the GS8332-SR OP-Amp?

texts:
Theremocouples have a very small voltage of around 0.4mV/10C.
K Type Thermocouple Voltage Table

I want to amplify that signal so I can read it with an ADC on my Arduino Microcontroller. The Voltage would be GND to +5V. Will the GS8332 IC do the job?
GS8332-SR Datasheet

I am not sure because I don't see any CMVR data in there (first time reading OP-Amp Datasheets). The Offset Voltage is only 10uV so thats good. But could it be that there is more that I need to keep in mind?


texts: Make a Negated General Impedance Converter

texts:
A General Impedance Converter (GIC) looks like this:

Source: http://www.ee.nmt.edu/~wedeward/EE212L/SP15/ImpedanceConverters.html
Where
$$Z_{tot} = \frac{Z_1*Z_3*Z_5}{Z_2*Z_4}$$
But I need a circuit that gives me \$ \frac{1}{Z_{tot}}\$
How would I create a circuit that gives me \$ \frac{1}{Z_{tot}}\$ for Zin?
(Or something like \$ Z_{in} = \frac{Z_2*Z_4}{Z_1*Z_3*Z_5}\$)
The problem is if I put an inductor on this circuit, I can't select a series of impedance's Z_1 through Z_5 using only resistors and capacitors to end up with a combined impedance of 1.


texts:
I have copied a schematic from my school project, and the task is to simulate it in pspice then do it in real life using a oscilloscope and function generator. I can't even do the first step which is to simulate it. I don't know what to put in AF in and AF out and where to put the sinus power source. Also I don't know if the Vdc represents V+ like it does in my schematic :S

Can you guys please help me...


texts: Frequency response - finding transfer function

texts:
I have a this circuit:

I am asked to find |H(\$\omega\$)| in its simplest form.

I approached the problem by first recognizing that the first op am was a standard inverter. With that I basically rewrote the circuit so that the second op amp had a common input of -Vi.

Using a voltage divider for C1 and R6 I found the transfer function to be:

\$(2R_x/(R_x+Z_c)) = -(V_o -Vi)/V_i \$

assuming that I did that right which is probably not a good assumption, the questions asks choose R6 and C1 so \$ \angle H(2\pi*10^3) = -90^\circ \$

I'm not sure how to get the transfer function from a magnitude to an angle so I can sub 1K (a practical value for an op amp) in for R6 and solve for C1?

Any help with this homework assignment is appreciated.


texts: What would cause a voltage regulator to output much lower than its rated voltage?

texts:
I am building a 12v power supply based on this.

Main changes are use of two 2,200uF filter caps instead of one, and 7812 (12v) regulator instead of 7809.

Plugged it in the first time and the voltage regulator went up in smoke before I noticed and unplugged it.

Having now replaced it, it still gets very hot very quickly after being plugged in, but I can't see what I have done wrong with the wiring. Voltage straight off the rectifier is about 17v. With the rest of the circuit connected, voltage on pin 1 (input) of the regulator reads about 11v, and the output around 1v. Within a couple of seconds the regulator is too hot to touch.

First thought was that regulator pinout was wrong, but it is 7812 - pin 1 v(in), pin 2 ground, pin 3 v(out).

Any ideas what would cause behaviour like this?

This is a picture of my implementation:

The terminals 1 & 2 are the input rail, terminals 3, 4, 5 & 6 are output - the copper bar (and outer two terminals) is the negative rail. The regulator connects the three - Pin 1 in, pin 2 negative, pin 3 out.


texts: Why are there diodes going to D+ on this alternator/generator

texts:
Below is a schematic of an alternator/generator.  I understand the rectification going to B+, but I don't understand why there are 3 diodes going to D+.

The way I understand the setup, D+ measures the voltage at the battery, and the delta between that and the preset voltage in the regulator drives the field to increase/decrease the output of the generator.  I know why you need the diodes to charge the batteries, but why would you put the rectified current on the D+ sensor line.  Seems like that would defeat the purpose of the sensor.

Maybe I'm completely misreading the diagram, if so, please point out my error.


texts: When using Thevenin's Theorem, why is R_thev of resistors calculated in parallel, when original circuit had them in series?

texts:
Example circuit has a voltage source, and 3 resistors.

When constructing Thevenin equivalent circuit, the voltage source is replaced with a short, while R1 & R2 resistance is calculated as though they were in parallel, even though in original circuit they were in series.

Why?

When using Thevenin's theorem to calculate current and voltage of R3,

simulate this circuit – Schematic created using CircuitLab


texts: STM32F030 analogue input pin impedance (does value change during conversion period?)

texts:
The analogue input pin impedance for the STM32F030 is listed as around 50K in the datasheet. Does this value apply only during the conversion period, or would it be higher when the pin is configured as an analogue input pin but no conversion is taking place?

http://www.st.com/web/en/resource/technical/document/datasheet/DM00088500.pdf (see p. 64)


texts:
I have a resistor on a power supply for an amplifier.  It has failed and I am trying to find a replacement.

Can anyone point me in the right direction? I've only ever played with low voltage stuff and this is dealing with higher power and voltages thsn I am used to.

The capacitor beside it had also blown which I was able to replace (not in this picture.)


texts:
I was having a ton of trouble understanding oscillators, and I needed something to power a tank circuit at its resonant frequency.

I decided to just come up with something myself and this is what I arrived at.  I tested it and it seems to work great.

I know that there are many named oscillators and I wanted to know if anyone could tell me what other oscillators this might be similar to or how you might classify it.


texts: What symbol to use for a solid state relay in a schematic?

texts:
What symbol should I use to indicate a solid state relay in a schematic?

The internal schematic of the solid state relay is shown in the data sheet, but showing all of the internal components in the schematic is not necessary and would be more confusing than a single symbol.


texts: I'm hoping someone can help me identify this connector housing. It is 3-pin nylon and keyed by small squares in two corners. I've searched all through Mouser, Digikey, TE, etc and haven't found it.


texts:
I am planning on building an ~60V, ~50A, 18650 battery pack to power a 2 kW electric motor. I've called some electronics stores and it seems like I can get a decent amount of old laptop batteries for free. The obvious problem is that each cell is going to have different lifetimes, capacities, resistances etc. so ill need some way to balance them.

How can I make what is probably going to be the most hack battery ever, as reliable as possible? Should I buy a few BMS's and try and balance each individual cell? should I balance each parallel group? should I not even bother trying this and shell out money for real batteries?


texts: PID control achieves zero steady state error with step set points and disturbances?

texts:
How can I explain this with proper reasoning?

I'm also having doubt understanding why a proportional controller cannot eliminate SSE and how a PI controller eliminates it.


texts: How would a using a resistor and regulator together affect a circuit?

texts:
I'm having trouble understanding a concept.
Let's just say that I have a simple circuit made using a 15V power supply.
If I have a linear 7805 5V regulator connected along the circuit, and then add an 1000 ohm resistor to the board, how would the output voltage change?
Is there a way to calculate this?


texts: Why isn't this ribbon cable between two board-to-board connectors working?

texts:
I wanted to connect 2 boards that normally sit on top of each other so I could separate them.

To that end I got a 7x2 pin connector cable with the right (2mm) pitch (there was no M/F for that pitch so I got a F/F and a male header).

When I plug the cable at both ends it all fits, but when power is turned on it doesn't work. It looks like it's not connecting. What could be the reason?

UPDATE: It works now, with 2 cables and 2 headers. Thanks, folks!


texts: Kicking RJ11 cash drawer via PC's serial port

texts:
I have a Star CB2002LC-FN cash drawer. Normally, to kick it, it needs to be connected to the peripheral port of a receipt printer via RJ11/RJ12. The PC can then send a control signal to the receipt printer, which then in turn signals the cash drawer to kick. I believe this protocol is called DKD.

My objective is to mimic this behavior, but without the receipt printer and instead controlling it via our own software.

The solution I came up with was to use an RJ12 to Serial adapter to connect the drawer to PC and trying to trigger it by activating certain pins. I've tried several pin configurations based on different documents I've found online but have not been successful in getting any kind of response from the drawer.

The general idea seems to be that voltage should be provided to two of the pins. By then cutting the voltage to one of the pins the electromagnet (solenoid) should release. I've tried using the serial DTR and RTS pins as I can activate those individually. It might be a simple case of the PC's serial port not providing sufficient voltage.

There seem to be commercial products available that can do this, but I would prefer to DIY a solution if possible.

Is there any way I can accomplish my goal?


texts: Desoldering with cheap Hot Air Rework Station

texts: I bought a $50-$60 hot air rework station on ebay, im trying to learn micro soldering and when I try desoldering a random chip on a board, it wont come off, I seen youtube videos saying that when using 350 degrees temperature the chip should come off within 30sec, not working with me, not even after 2min. is the problem due to the cheap rework station? note: im also not using flux as atm don't have any.


texts:
I have a water fill level sensor which is capable to power a 3A single phase 230V motor.

However, I have a three phase water pump. Is there a generic "switch" / relay which "operates" on single phase but is capable to switch three phases?


texts: Unexpected indeterminate outputs from verilog conditional operator

texts:
I have the following combinatorial assignment in a verilog module:

assign ififo_di = fetching_pc ? { 5'h02, 3'h7, 16'h8000 } : decoded_insn;

where ififo_di is an output, fetching_pc is a local register and decoded_insn is an input (which, in all my testing so far, is always set to 24'h000000).

And have a clock-triggered action that sets fetching_pc for a single cycle in specific circumstances.  The same block also provides synchronous reset and sets up a monitor for debugging purposes:

always @(posedge clk)
begin
    fetching_pc <= !reset & next_task_ready;
    if (reset)
    begin
     // reset registers
     $display ("ifetch reset");
     $monitor ("active: %b, task_loaded: %b, fetching_pc: %b, ififo_di: %b", active, task_loaded, fetching_pc, ififo_di);

     active <= 0;
     task_loaded <= 0;
    end
end

The test bench code that triggers these actions is:

@(posedge clk);
reset = 1;
@(posedge clk);
reset = 0;
@(posedge clk) #10;

next_task_channel = 3;
next_task_thread = 0;
next_task_ready = 1;

@(posedge clk) #10;

// at this point the ififo_di output is checked and the test fails

At the time the next_task_ready input is set to 1, the reset input is 0, and the internal registers active and task_loaded are both verified as containing 0 (although task_loaded is changed to 1 in the same cycle -- but altering this so that this change doesn't take place gives identical results).

My expectation is that when this happens, ififo_di will change from 000000h to 178000h, however what really happens (testing in icarus verilog) is this:

ifetch reset
active: 0, task_loaded: 0, fetching_pc: 0, ififo_di: 000000000000000000000000
ifetch reset
active: 0, task_loaded: 0, fetching_pc: 0, ififo_di: 000000000000000000000000
active: 0, task_loaded: 0, fetching_pc: 1, ififo_di: 000x0xxxx000000000000000

Why would the output by changing the bits that need to change to x rather than to 1 as expected?  I would understand if fetching_pc were x, but it's clearly being shown in the monitor output as 1, so what's going on here?

(updated: Eliminated some unnecessary code so that I can provide the entire always block as tested, thus showing all potentially-relevant content of the module.)


texts: 4-20 ma analog output. circuit for increased resolution

texts:
I have a device that uses the 4-20ma outuput. I want to convert this to a range of 0 or 0.48V to 2.4V. So I decided to use a precision resistor of 120 ohm resistor.

My questions is how can I adjust my circuit in order to get the maximum resolution possible. I mean what would a good circuit that can catch the change from 6ma to 6.2ma or 6.4ma.

Maybe even a noise reduction add on my 120 ohm circuit to help me get better results?

any advice welcome.

EDIT:: I must have not explained well my situation and I am sorry for the misunderstanding.

I have an output of 4-20mA and I want to convert to the range of my adc 0-2.4V

so the best solution is a 120 ohm resistor that I use in order to have 4ma*120=0.48V minimum voltage at my adc and 20ma*120=2.4V maximum voltage at my adc.

My question is about the circuit. Now I use only the 120 ohm resistor connected at the 4-20ma output pins and then I connect my resistor to the adc.

how can I adjust my circuit, in order to catch the smallest change in milliamps possible? I mean that i want to catch even the smallest change for example 6.0ma to 6.2 ma. this change in the amps gives me an 0.2ma*120=24mV of change in my voltage. How can I adjust my circuit to make these kind of changes better visible to my adc.

this is why I spoke about noise reduction at my first post.

searching I found that if my output signal is slow i can add a 100nF capacitor parallel to the 120 Ohms resistor.

I am looking for something like this but to help the adc get better readings from the 120 ohms resistor.

hope i cleared things a bit, again any advice welcome.