texts: Comparator: Noisy sine to square wave, how much phase noise?

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In a circuit a comparator is used to convert a sinusoidal signal to a square wave. The input signal however is not a clean sine wave, but has some noise added to it.

The comparator is supposed to be ideal and has a hysteresis which is much larger than the noise signal, thus there is no ringing at the zero crossings of the sine wave.

Yet due to the noise on the input signal, the comparator switches slightly earlier or later as it would for a clean sine wave, hence the produced square wave has some phase noise.

The plot below illustrates this behavior: the blue curve is the noisy input sine wave and the yellow curve is the square wave generated by the comparator. The red lines show the positive and negative hysteresis threshold values.

Given the spectral density of the noise on the input signal, how can I calculate the phase noise of the square wave?

I would like to do a proper analysis on this, but could not find any resources on the topic yet. Any help is much appreciated!

CLARIFICATION: I would like to analyze the phase noise produced by the given circuit and am NOT asking on how the reduce the noise!


texts: Wiring LEDs in parallel with 5-pin LED on/off switch

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simulate this circuit – Schematic created using CircuitLab

I'm creating a costume with some lights and am trying to run 10 LEDS and an on/off button with an LED from a 9V battery (so 11 LEDs in total). Due to the fact that it needs to be from a 9V for portability, I've opted to run the 10 individual LEDs in parallels of 2 each, with 100 Ω resistors at the front of each set, and then a 270 Ω resistor at the end of the series in front of the LED button. (Not gonna lie, I had to use the ledcalc website to guide me on how to wire them all up. I'm a novice when it comes to this sort of thing!)

I would prefer to have the switch at the opposite end of the circuit as the battery, since in the costume the battery pack will be at the top, the lines of 2 leds will be stacked down the middle, and then the button will be at the bottom. But I also know that I can make the wires as long or as short as needed in order to physically place everything where it needs to go so that's not as important. :)

My confusion/question comes from how to incorporate the on/off LED button into the circuit. I want the light to be off if the circuit isn't powered, but to come on when it is, but I can't have the LED part of the button accidentally complete the circuit. The details on the button say that the LED and the switch are separated, so they can be controlled independently, but I'm not not sure how to physically solder the wires correctly to make it work.

LED switch

Does anyone have insight into this 5-prong switch and could guide me on which prongs to attach to which? Thank you!

[edit] Added a schematic for visuals!


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I have a solar electric system from many years ago.  The setup runs on 400 to 480VDC from a string of solar panels.

I have a unit that converts 250 to 600VDC to 48VDC for charging lead acid batteries.

I was thinking of stringing a bunch of the inexpensive 12.8VDC $30 LiFePo4 batteries into a 4 kWh energy store.

Everyone including the manufacturer Miady tells me not to parallel the batteries.  So series it is.

Could some one point me in the right direction for building a charger for this setup?  To maximize battery life Miady says to stay under 0.2C charge rate.  This would be around 960watts in the setup I am envisioning.  So 400 or so VDC at 2 Amps.

I have around 400VDC at 7 Amps to work with.  What would be appropriate to regulate the current so the battery bank charge is limited to a particular current?  I am thinking along the lines of a switch mode regulator.

In addition to regulating the current, I would probably need a voltage cut off as LiFePo4 do not need a float voltage.

More or less the process would be: cut out, wait till VDC around 400 and then charge batteries at up to 0.2C (around 2amps) and then cut out later when the voltage reaches a certain level on the battery side.

Some people may feel I need to shunt the excess power somewhere.  With solar electric panels you can just not draw off the power and nothing bad happens.


texts:
Potentiometers are renowned for wearing out (at least in my experience); the little wiper eventually just wears its contact and nolonger has a firm electrical connection. For an audio device, this can manifest as a crackle when changing volume. The wear isn't necessarily even and there may be positions that have worse contact than others. I've noticed it be worse usually near the upper limit (full volume; full brightness; etc.), but the wear distribution can probably mostly be attributed to how the device has been used.
    Having a component with such friction seems like a very bad idea to me (and evidently it is) and I often wonder whether there are commercially available designs that do not have a sliding contact (excluding digital potentiometers[1]), and whether they're economical. I envision that one such wiperless design would be based on ball-bearings or epicyclic gears, with at least one of the balls or planet gears being conductive, the rest being insulative, and the tracks in which they roll, or the annulus or star/sun gear, having the resistive gradient element(s). But is anything like this currently available?

Note 1: It should behave similarly to an ordinary passive potentiometer. Digital potentiometers require a power supply and draw power so, as I understand, are not necessarily drop-in replacements (a 3-pin digital potentiometer would require that the end pins double-up as the power supply, which isn't always the case). I'm specifically interested in knowing whether such components as wiperless passive potentiometers exist which in their simplest form have 3 pins where the sum of the resistances between pins 1 and 2 and between pins 2 and 3 is intended to be constant (i.e. a 2-pin variable resistor is not by itself a potentiometer).


texts: Difference between General purpose PCIe signals and PCI Express Graphics (PEG)

texts: What is the difference between General purpose PCIe signals and PCI Express Graphics (PEG) in standard COM modules (type-6) ?


texts:
I am trying to run a 100W 32V Led with a DC-DC boost converter from a 6 volt battery, and I want to make it so it will shut off when the battery voltage gets low. So I am using a TIP122 transistor with the collector connected to the ground input to the Boost converter, The emitter connected to the battery ground, and the base connected to a 5.6V zener diode. The LED takes 3.3A, but even with a base current of 60mA, the transistor is only supplying 600mA.

Am I doing something wrong?

simulate this circuit – Schematic created using CircuitLab


texts: Potentiometer getting burned out while connected between motor and 5V 2A ac adaptor

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I have an old trimmer with damaged battery. I know it is more economical and reliable to buy a new one rather than repairing it, but I find it interesting to play with electronics/electricals. I want to run it from a 5V 2A mobile charger (it was running on a 1.2V rechargeable cell earlier).
I tried my own voltage divider using resistors but the trimmer motor didn't move and resistors work like heating coils. When I directly connected the motor to the power supply (5V 2A) the motor worked rigorously. I know it will burn if I use it longer. Then I tried a potentiometer (22 kΩ) to find it works at first but also end up with fire and smoke. What did i do wrong (or did I do anything right)?


texts: Please explain the purpose of following circuit

texts:
This is the excerpt from the 2VCO synthesizer unit.
Someone, please, can explain me what is this strange arrangement with VCO2 Out jack through the switch inside of it? I understand that when the Jack is inserted I have clear VCO2 voice output. But when the jack is out, the switch inside of it shorts to 6/10. What is the purpose of it?
Big big thanks is advance.


texts: How to make the the voltage higher after a logic gate

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In my circuit a have a 2 switches that connects to a logical gate and the output of gate will go to a relay but after the logic gate the voltage got lower to mili voltage and not enough voltage for the relay to work, they say that I must use capacitor but it only last for a second and I want my relay to work in indefinitely by the result of the two switches of the logic gate.
Anyone have an idea or hint to solve my problem?

here's a picture of my circuit design


texts: Communication protocol analysis via microcontroller board

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I have an idea for my master's thesis.
I want to make a communication protocol analyzer and monitor the data on a PC via software I coded.
For the first stage, I need a kind of data acquisition system like below:

The communications bus I am interested in has 2 MBps bitrate, and Manchester coding (±5V differential voltage.)
I have no experience in high speed communication signal processing. What do you suggest for this task? Should I use some kind of ADC/transceiver or process the data directly via microcontroller with high sampling rate? In that case, is there any microcontroller you could propose with high msps?
By the way, writing ADC may cause misunderstanding. Scope of my evaluation is Manchester-high, Manchester-low and non-data (means no 1 or 0.)


texts:
I am trying to switch a IRL520N logic-level MOSFET using a 0-5V PWM signal from my microcontroller (PyCom FiPy).

I tested just the MOSFET with a 10 Ohm series gate resistor and my load is a 9-15V brushless DC pump (TD-3LS from this manufacturer). I had my load rail at +12V and a power supply driving the gate at around 2.3V-4V. The pump ran just fine.

Then I hooked it up to a function generator to test the PWM signal at the gate. I tested a variety of amplitudes (0-5V, 0-10V), frequencies (500mHz to 5kHz), and duty cycles (0-100%). None of them turned on the MOSFET and ran the pump.

I've attached a schematic of the final pump drive circuit that this MOSFET will be going into and the original designer said that he got it to work with a PWM signal of 5V, 2.4kHz, and 0-100%, so I'm not sure why I can't even get the MOSFET to work on it's own (note: I've also tested this circuit with a variety of PWM signals and steady drive voltages, and could not get it to switch on the pump).

C35: UFW1H470MED1TD
L2: 1536Y
Pump DCR: 9kOhm

EDIT: I was able to get the pump running off the IRL520N MOSFET. It needs to run for a few seconds at 100% duty cycle first before switching to a pulse (duty cycle was 50-75% at a frequency of 500 Hz from the Arduino). However, still not able to get it running with the driver circuit below, so open to any suggestions about what could be wrong with that. I thought maybe I wasn't giving enough time for the capacitor to charge up so I ran the pump at 100% duty for 20s before switching to the PWM, but still nothing.


texts:
I am building this basic linear power supply as I am new to constructing one from scratch. I know the dangers of AC voltage and transformers. I would like to know the purpose of the round inductors on some power supplies and if you would recommend any in this circuit and where and what size?

https://www.popsci.com/diy/article/2009-12/build-simple-dc-power-supply

Thank you everyone. I will not include the inductors as they are not needed and I will use a smaller transformer of the proper rating.


texts: Which part of some LED TV screens acts as two gratings crossed at non-straight angle?

texts:
Some modern LED TVs display the following diffraction pattern (photos taken from this question):

In my answer to another question about the origin of this pattern I explained that this should be due to two diffraction gratings crossed at a non-straight angle, since the inverse Fourier transform of an idealized reproduction of the pattern (rotated by 90°, see the answer in the link above for the pattern) looks like this:

But if we look at a close-up, we'll see a simple square grid of pixels, so we can't easily see the crossed gratings:

I've now gone to a electronics shop and found several such screens, so I can now name exact models and provide more close-ups. One of them is LG 49LK5400. Here's what its pattern looks like, with an image, so that the lit pixels are also visible. Note that the photo is a good representation of what the human naked eye sees (up to compression artifacts). Click for full resolution.

Another screen with a very prominent cross (in addition to some other patterns) is that of HP Spectre 13-af006ur. It has much smaller pixels, so I couldn't resolve them.

My guess is that this effect might be caused by the arrangement of the conductors powering the pixels. Or it may be the pattern from one of the layers of light spreading system of backlight.

But I may be wrong, so I thought it's better to ask experts: what is the actual part of the LCD screen which results in this type of crossed-gratings-like behavior?


texts: How to solder a wire to a massive copper busbar

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I need to solder a wire (tinned coper) to a massive copper busbar, I tried two approaches but to no avail.

I tried heating up the busbar with a heat plate to 300 °F (150 °C) and then tried to solder the wire to the busbar a) with a soldering iron or b) with a heat fan but it didn't work: The solder (we use SAC) doesn't melt properly (it doens'ntbecome fluid, only some small balls are formed) and the copper in the busbar started to change color, which I gather is oxidation in the copper.

Do you guys have any idea how to accomplish this?


texts: Charging Li-Poly Battery with Small solar panel

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I have Li-poly battery that is 4.2V 2000mAh with a protection circuit.

I have solar panel that is 5V 250mA.

The aim is to charge the battery to maintain a fully charged battery, so it really preforms as a top up charger.So if the battery is completely low the first step would be to use a Li-poly charger to charge the battery and then use the solar panel.

I would like to know if there is a disadvantage of my setup as my tests have found it to be the most efficient way.

Setup
I have not used a li-poly charge IC, as i have found they require a minimum voltage and when the sun is low this would mean no charge at all as the current draw from battery would completely drop the input voltage, as my panel size is very small.I feel as my current charge is very low, as it is below 300mA, i can get away with this setup, but if i had a much larger solar panel i would need a dedicated charger IC.

But what i have done is the following:

1)I have connected my solar panel via a diode and load switch to the battery.
2) Using a ADC and voltage divider circuit(via 2nd load switch) i am continuously monitoring the voltage so that once it reaches 4V i would switch off the charging process. This is done using a micro controller.

I have noticed even when the sun is low and therefore the solar panel is producing only few mA, the battery still get some charge. The current draw on battery never effects input voltage by dropping it to low as , as the voltage drop on solar cell never drop below the battery voltage.Where as with a Li-poly IC i have noticed, that there would be no charge in these conditions.

Ay disadvantage of this setup? As it seems to be working well.


texts: Eagle: use device in schematic, but hide it on board

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How can I hide a device on a board, but still use it in the schematic?

For example, I want to have relays in my schematic which are on an other board, to make the schematic more understandable.


texts: How to connect pins with ratsnest connection after netlist transfer in Proteus ARES

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I have a schematic file in Proteus-ISIS. I transferred into the ARES, after defining board edge and placing components, I placed 1x5 connector (CON5_1X5_U_FCI). But I could not connect pins of the  1x5 connector with the other part of the design which was transferred from the ISIS by ratsnest connection..

In this circuit I could not connect 4.pin of the 1x5 connector to the 13. pin of mcu. When I clicked to 13. pin of mcu the green line (ratsnest line) disappears. How can I handle this situation? By the way this circuit is set up for only demonstration. I tried this with Proteus 7 and 8.0.

The error message is: "Cannot add manual connection here!"


texts: How would you design an electromagnet for maximum force when you have a fixed power available?

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There are number of variables like current, wire dia, number of turns, dia and length of electromagnet. The distance at which force is applied is constant

The distance is nearly 12 inches. Power is nearly 88.4 KW. The electromagnet should be not more than a few meters at max. Weight is not much of an issue. Calculation is not needed just need an idea on how to select the optimum values of variables. The formula I am using is
F=(mu)(n*I)^2/2g^2 mu= permeability

The project is about use of regenerative braking to charge electomagnets to attract the rails. This force is being utilised to avoid derailment during train emergency braking. Just a college project in analysis not any research.


texts: I-V curve of resistor in special condition

texts: What will happen to the i-v curve of a resistor when we apply more power than its nominal power? for example applying 30v to 100ohm resistor which nominal power is 0.5w.


texts: What is the difference between residual phase noise and absolute phase noise?

texts: Studying the characteristics of an oscillator with a phase noise analyzer, but I don't quite understand the difference between absolute and residual noise. Any help would be greatly appreciated


texts: Is it possible to build or purchase a DC to DC converter with high power inputs and outputs?

texts: I am currently working on a project that involves connecting a 24 V battery system to an electric motor I purchased. Ideally I would like to run the electric motor at 48 V and around 400 A for maximum torque output. When I look online for off the shelf DC to DC boost converters I'm seeing that many products are maxed out at currents around 5 A. Are there any suggestions for where I can find an efficient boost converter that can operate at high power inputs and outputs?


texts: overvoltage and transient protection for ADC pin

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I'm building an industrial circuit, and want to use 0-10V and 4-20mA sensors in this circuit.
I want to protect my ESP32 MCU(NodeMcu board) from transients and high voltages.
I design this circuit and have questions:

Is this circuit works good for my purpose?
which component is necessary and Which one is optional(schottky diodes,100nf capacitor,polyfuse)?
NodeMcu does not have any Analog ground ,does it matter?
whats your opinion on this circuit?

It's not a precision system, but I want to protect it in a good way.


texts:
I'm trying to replace the tip on my soldering iron. I got it a few years ago and quickly destroyed the tip. The problem is the iron is generic, and I cannot find any markings to identify the correct tip size. Here are a photo and some measurements.

They look alot like this set, but appear to be too short.

Here is a photo of the station:

Here is a more detailed photo of the pen. The hollow shaft goes through the entire tip.


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I'd like to use MX-05V 433MHz receiver together with a Raspberry Pi.
The MX-05V operates on 5V, but the Raspberry Pi's inputs only allow 3.3V.

So i need to shift the RX data output level from 5V to 3.3V.
Would a simple voltage divider (e.g. with R1=200 and R2=100 Ohm) work?

Edit: Would it be possible to use a transistor like below?


texts: Why can't I test the transistor part of an optocoupler using my multi-meter?

texts:
I attempting to test if my PC111 opto-coupler is working properly (pulled from a PSU).

I wanted to use my multimeter first (so the device not connected to anything), setting the multimeter in the diode test mode.
Testing pin 1 and 2 (the LED) was fine. I saw the voltage on 1 end and OL on the other.
I assumed that the output transistor could also be testing this way as the base pin is also exposed,
I thought base -> emitter and base -> collector would show a voltage drop (like with a regular NPN transistor).
However this was not the case and always shows OL (I tried it with another opto-coupler also).
I then tried both opto-couplers in a simple circuit with an LED (hooking up 5V through 2K resistor) to turn on the LED using the transitor and that worked fine.
Someone also told me that I should check for continuity between emitter and collector when the optocoupler is activated but also that doesn't work.
So why can't I test the transistor using my multimeter that way (diode test and continuity) ?
I tried it with a second opto-coupler (pulled from a working PSU). A CNY17GF-2. Exact same thing. Multimeter diode test on transistor pins fails, simple circuit to turn on LED via opto-coupler does work.
I then bought a brand new CNY17 (same pin layout as the previous 2 opto-couplers), and there the multimeter diode test on transistor pins does work.


texts: LED brake lights - detecting voltage drop?

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I am trying to light up some LEDs on my Rustler VXL RC car only when braking/reversing.
I found out that on my receiver I have three wires: black(-), red(+), white(+). The one that interests me is the white (signal wire). This wire tells the speed controller to either turn the motor clockwise or anticlockwise.

White wire voltage is as follows.
- no throttle: 0.55V
- full throttle forward: 0.71V
- full throttle reverse: 0.39V

So, when I brake/reverse the voltage drops from 0.55V to some value but no less than 0.39V.

How can I design a system to catch that voltage drop and activate a switch to light up the LED?
What parts would I need to buy?
And, what's the difficulty level for this?

Thanks


texts: What factors affect the no-load current of a transformer

texts:
I am currently performing the open circuit test on a transformer at my school to separate the hysteresis loss and the eddy current loss. Thus, I am changing the frequency of the AC current while keeping the flux constant by changing the applied voltage accordingly.

However, the current reading on my multimeter kept fluctuating badly. So, I wanted to know what is supposed to happen in theory and if the no load current is supposed to change when changing the frequency while keeping the flux constant.

Some more context:

The equipment my school has is not great right now. Actually its pretty terrible. The signal generator I am currently using can only give out 5V maximum, and the transformer I have is a dissectible transformer with no specifications. Due to the tiny voltage, the current reading is also pretty tiny too. Like I have to use microamps or milliamps on the multimeter to measure the current. When I said my multimeter fluctuates badly, let me just describe what it does:

Current at 35Hz: Around 3.5mA

Current at 40Hz: Around 3.2mA and it just keeps going up and down constantly

The current going down at 40Hz has screwed up my experiment as that means the power loss due to iron core losses decreased when frequency increased. However, the power loss due to iron core losses is supposed to increase with frequency when the flux is kept constant.

How do I find the no load current on a transformer?


texts: Do I need to maintain source of a signal till it reaches the destination?

texts: If I send a signal through a wire having delay of 10ms, then should I need to maintain the source of the signal till it reaches the destination or can I change after, say, 2ms and send the next signal. The 1st signal reaches destination at 10ms and 2nd signal reaches destination at 12ms.


texts: How a little extra current can affect a motor

texts: I want to run a 12V, 19 watts DC motor. Which should use 1.5amp of current. Now, I have a 12v DC, 2 amp power supply adapter. How it will affect the motor in the long term. Will it burn the motor for this little extra current?


texts: What are the specific scenarios that an isolation transformer is useful for avoiding?

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I have a home workbench and do minor refurb work with old turntables and monitors (CRT) etc. That implies potential exposure to high voltages (mains or above) at power supply capacitors, etc. I have seen many recommend that having a 1:1 isolation transformer on the bench is a critical safety measure.

There are a few questions floating around about this here. I understand that by doing this you're no longer connecting to earth ground directly, but I'm perhaps less well educated on the principles of electrical engineering and trying to understand which specific "I touched this component, at this time" scenarios are improved by using the isolation transformer, and which ones are not.

It sounds like there's some sense that you could in theory poke at various components while the device is powered on and as long as you only touched in single places and didn't accidentally bridge circuits you would be safe, but this doesn't sound intuitive to me. I mean, I'm in danger normally of shocks towards ground even with shoes on, aren't I?

Does any of this matter if the device is powered off? (E.g. as a large cap discharges)

Links or other pointers welcome, of course. Thanks.


texts: Creating gerber layer for glue screen creation

texts:
We are trying to get away from using a glue dotter. Instead we would like to use our screener to apply the glue to the board. The gerber files we get from our customers have the layer for the pads which we send to our board houses to get a screen for applying soldering paste.

The gerber files do not have a layer that would represent what we would need to create a screen for applying glue. How is this typically handled? Is there functionality in Engineering software that can automate the creation of this layer? Or is it typically done manually?


texts: How to power small solenoid with a 3.7V lithium battery pack

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I've got a small 1.5V 2W pull-type spring-loaded solenoid I'm trying to fire with a 3.7V (45mAh at 1C) lithium pack for about 0.5 sec.  I am able to get it to work using a (1.5A max) voltage source at 3V, but the battery can't discharge the rated solenoid current (667mA at 3V) into the solenoid from the battery pack, it pretty much kills the pack instantly because it is trying to draw too much.  I've tried charging a large electrolytic 470uF capacitor so that the current isn't drawn all at once from the battery, but it fires too weak I think because it can't supply enough current either.

Is there any way to do this given the circuit constraints?


texts: PIC32 Peripheral Pin Select for Digital Output

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I'm using a PIC32MX250F128B for a project to drive several digital outputs; I need to control the digital output for about 13-14 pins. (using the code below).

These pins work: RA0, RA1, RB0, RB1, RB2, RB3, RB10, RB11, RB13, RB14, RB15
These pins do not: RA2, RA3, RA4, RB4, RB5, RB7, RB8, RB9

By "not work" I mean there is not output voltage at all, just a disconnected state (whereas the "working" pins successfully toggle high to low). My theory for why the pins aren't working is that the pins require an extra peripheral register selection of some kind to configure them to function as General I/O pins. I'm not sure if that's correct, but googling and testing hasn't turned up any results, and the datasheet has not been very helpful.

void main() {
  mPORTBClearBits(BIT_4 | BIT_5 | BIT_7 | BIT_8 | BIT_9);
  mPORTBSetPinsDigitalOut(BIT_4 | BIT_5 | BIT_7 | BIT_8 | BIT_9);
  mPORTAClearBits(BIT_2 | BIT_3 | BIT_4);
  mPORTASetPinsDigitalOut(BIT_2 | BIT_3 | BIT_4);

  while(1) {
    mPORTBToggleBits(BIT_4 | BIT_5 | BIT_7 | BIT_8 | BIT_9);
    mPORTAToggleBits(BIT_2 | BIT_3 | BIT_4);
  }
}

My config bits are set to the standard values (I can post the entire main.c file if necessary. EDIT: see below). Why is this subset of pins giving me so much trouble?

EDIT: here are my config bits

#pragma config FNOSC = FRCDIV           // Oscillator Selection Bits (Fast RC Osc w/Div-by-N (FRCDIV))
#pragma config FSOSCEN = ON             // Secondary Oscillator Enable (Enabled)
#pragma config IESO = ON                // Internal/External Switch Over (Enabled)
#pragma config POSCMOD = HS             // Primary Oscillator Configuration (HS osc mode)
#pragma config OSCIOFNC = ON            // CLKO Output Signal Active on the OSCO Pin (Enabled)
#pragma config FPBDIV = DIV_1           // Peripheral Clock Divisor (Pb_Clk is Sys_Clk/1)
#pragma config FCKSM = CSDCMD           // Clock Switching and Monitor Selection (Clock Switch Disable, FSCM Disabled)
#pragma config WDTPS = PS1048576        // Watchdog Timer Postscaler (1:1048576)
#pragma config WINDIS = OFF             // Watchdog Timer Window Enable (Watchdog Timer is in Non-Window Mode)
#pragma config FWDTEN = ON              // Watchdog Timer Enable (WDT Enabled)
#pragma config FWDTWINSZ = WINSZ_25     // Watchdog Timer Window Size (Window Size is 25%)
// DEVCFG0
#pragma config JTAGEN = ON              // JTAG Enable (JTAG Port Enabled)
#pragma config ICESEL = ICS_PGx1        // ICE/ICD Comm Channel Select (Communicate on PGEC1/PGED1)
#pragma config PWP = OFF                // Program Flash Write Protect (Disable)
#pragma config BWP = OFF                // Boot Flash Write Protect bit (Protection Disabled)
#pragma config CP = OFF


texts:
I am making my first battery charger for ni-mh and ni-cd batteries that i use.

I have 9 battery slots :

1x : 9v ni-mh or ni-cd battery

4x : AA 1.2v batteries for ni-mh or ni-cd batteries

4x : AAA 1.2v batteries for ni-mh or ni-cd batteries

as from this link :
Reduce voltage to many lower output with resistors
and from other circuits and search around the net i understand how it needs to be done to one battery.

But how needs to be done to many as for my needs i need some help.

I havent connect them yet parallel or one by one or serial or whatever it needs.
I just have a stable input from a ac to dc transformer that gives me 12volt - 2 amperes

what i want is learn how to do this, if i cant charge them all at once at least to be able to charge as much as i can with a simple way of resistors and diodes.
I even have 78L05 that outputs 5v - 100/150 mah stable or mt1117 stable 3.3 volt output and 1 amp or adjustable.
Ofcourse the only thing needed is a led to each battery when plugged in to indicate that is connected and charging. (ofcourse if i want the led to go off when fully charged i need some q1 transistor etc etc that i personally dont want to complicate things to much).

I need help to understand which is the best way to charge as many as possible with low mah of about 150 - 300 mah or even splitted by its types and use an appropiate mah for each type.

------------------------------------- UPDATE -------------------------------------

I am updating this post and maby someone could help
i have this circuit for my 4xAAA 1.2V batteries and i need to charge them
at a stable current of 150 mah - 160 mah
I use the 78L05 regulator that provides 100mA stable and 5V output.
More infos about 78L05 here : http://213.114.137.49/info/regulator.htm

Can anyone tell me if this circuit is working correct cause i dont have the
appropiate test equipment for the moment and the online circuit creations are not so helpfull at my knowledge.
Any kind of help or correction would be nice


texts: Strange oscillation in buck converter (AP3431)

texts:
I am having a lot of trouble getting AP3431 to work reliably. The converter works properly for about 30 seconds, and then oscillations begin, with brief periods of normal function.

Here is how it is hooked up:

I am testing this converter with a custom made constant current sink:

And here's what the physical construction looks like:

For the first 30 seconds, everything is good. Vin = 5V, Vout=2.5V, FB = 0.79V:

Then the oscillations begin, and they are accompanied by a high-pitched buzz either from the converter, or the inductor:

Here's a short video that demonstrates the whole malfunction cycle and the high-pitched buzz:
https://www.youtube.com/watch?v=48_JTKHtnE4

A few further observations:

Using a different load leads to the same oscillations eventually.
Using no load at all, also eventually malfunctions! Here's an example with no load. You can see that the converter operates properly for brief periods of a few seconds, but mostly Vout is at Vcc:

After the oscillations begin, restarting the converter does not fix the problem. It seems that unplugging and waiting for about a minute is what returns the converter to a working state for a short while.
Nothing gets hot, or even warm.
I've been having very similar problems with other converters as well. See these posts:

Help understanding switching voltage regulator (OKR-T/1.5-W12-C)

How to troubleshoot a boost converter (ADP1613)?

I have changed quite a few things since my initial attempts described in the 2 posts linked above:

I selected a better inductor, which has it's specs tested at 1MHz (switching frequency of the buck converter).
I mounted everything, except the FB voltage divider resistors on the breakout PCB
I have used a different breadboard, just to rule out a board defect
I've used a different converter
I was much more rigorous with calculating the inductor value
I used different power sources

Despite all these steps, I am still having the same stability issues.

What could I possibly be missing?

Any advise would be appreciated.

EDIT 1: Is there any significance to the fact that the period of the oscillation is about 600us, and if we just look at the voltage rise part, it's more like 475us. The Soft Start time is listed as 450us typical. It's in the same range, at least. I wonder if the regulator is repeatedly shutting down and entering soft start for some reason?

EDIT 2: In accordance with many suggestions here, I have soldered the divider resistors directly onto the PCB, and I think it became a little more stable. Still started oscillating sooner or later though, depending on load current.

Then I connected everything with direct wire connections. The only stuff
still connected to the breadboard was Vin and GND. However, by now
something else happened and the chip started heating like crazy, even
with no load. I suspect it might be damaged - it is still regulating,
but goes to > 60C within the first 30 seconds.

I changed too many things at once, so I think I need to start over.
Unfortunately I am out of boards, so I'll need to make another. I may as well redesign it. I'll try the following:

Put the resistors on the PCB
Widen high current traces
Put capacitors closer to the IC
Shorten the track to the inductor

Please let me know if I am missing anything in this list!

EDIT 3:
Does this look like a reasonable design?


texts:
What is the functioning of a sense amplifier?
Does it take 2 inputs and calculate which is higher or lower, then output a signal?

I have come across this in S RAM


texts:
I am a beginner. I want to purchase a variable AC power source for my personal lab, and I am having a lot of difficulties getting a good variac in my region whose shipping cost is not 5 times the price of the device.

However, I noticed that variable motor speed controls basically work the same way, they vary output voltage, and my question is can I buy a motor speed control and have it do the same things as a variac?

What are the fundamental differences between the two?


texts: Passive RC network with voltage gain greater than unity?

texts:
I'm a EE student who recently purchased the classic Art of Electronics (new 3e). I was reading the first few chapters when I was referred to appendix J in the book depicting a SPICE tutorial but also with a circuit containing only resistors and capacitors (no inductors!) claiming to have a voltage transfer function greater than unity.

simulate this circuit – Schematic created using CircuitLab

Could someone kindly explain to me how this circuit operates such that V_out is greater than V_in? If it is a common circuit, what name does it have? The peak, according to the textbook, is at 1.096kHz with a voltage gain of 1.142. All the simulators I have tried agree with this result, and at least according to the textbook an actual circuit probed with an oscilloscope had the same behavior.


texts: Bode Plots - Absolute Value of Complex Function in Magnitude calculation

texts:
I'm struggling with one step in the magnitude calculation during manual Bode plotting. Specifically during the step of applying the absolute value to \$s = jw\$, what is the reasoning for why you can so nonchalantly disregard any imaginary terms that occur? Obviously I must have misunderstood something, but the examples I've seen skip this step without further explanation.

Where exactly in the calculations below do I go wrong?

$$
G(s) = \frac{1}{s+1}\\
|G(jw)|_{dB} = 20\lg\left(\sqrt{\left(\frac{1}{jw+1}\right)^2}\right)  \\
= 20\lg\left(\sqrt{\left(\frac{1^2}{j^2w^2+2jw+1^2}\right)}\right) = 20\lg\left(\sqrt{\left(\frac{1}{-w^2+2jw+1}\right)}\right) \\
= 10(\lg\left(1\right)-\lg\left(-w^2+2jw+1\right))
$$


texts: Need help determining values of passive components for SGL8022W

texts:
I'm trying to create a touch sensitive LED dimming circuit with a SGL8022W (Datasheet). The LED I'm using will be powered with 3.3 V and 420mA via USB (5V).

My questions are:

How do I determine the values of the passive components? The chip can output 500mA as is, do I even need to change them?
Do I need a Schottky diode on the 5V input to prevent reverse current?
The value of C3 dictates the sensitivity of the touch surface. The touch surface will be operating through ABS. How do I determine the value of C3?


texts: Building an inverter to charge various devices

texts:
With all the power outages being caused by Hurricane Irene, I thought it might be useful to have an inverter that I could charge my cell phone with.  Plug in battery power on one end, cell phone on the other.  I've poked around a bit and found this schematic:

http://project-circuit.blogspot.com/2009/11/dc-to-ac-inverter.html

So a few questions...

First, would this work?
Second, would this damage my phone or whatever device I charged with it (a 3DS for example)?
Third, how fast would this drain say, a 9V battery?  Is it even feasible to do this?

EDIT: I've just been notified it sounds like I'm trying to build a charger.  This is not the case, I'm shooting for a power source that I can plug chargers into.  Also, I just realized, is this outputting 120V or 120V RMS?

And I'm sure it's obvious, but just in case, I'll be building this thing myself..because well..I like building things!


texts: Can a piezoelectric inverter for CCFL work for similar sized neon tubes?

texts: I've done some backlight work for instrument displays using CCFLs and designing custom drivers (12 Vdc to ~1000 Vac) so I have some experience with these designs.  Recently a friend of mine was interested in doing some custom neon controllers for small diameter, short length tubes ( < 1m).  Are the electrical characteristics for neon similar for CCFL?  Has anyone experimented with modifying piezoelectric inverters to drive neon lamps?


texts: IC 555 timer to provide oscillation for high amp electromagnet

texts:
I am using a self-built electromagnet in my project that consumes 9.0 amps at supplied voltage of 12 VDC. I don't mind even if amps goes high. The power supply I am using can provide up to 30 amps. I have to experiment with providing an oscillating power supply to electromagnet.

I want to use IC 555 timer for that purpose. But IC 555 timers that I searched appear to have output 200 mA. Is there any 555 timer that provides high current what I need OR is it possible to use same 555 timer with some external equipment for that. Any sources or tutorial for that will also be very helpful.


texts:
I'm working on a project that requires an ATSAMC21 microcontroller. I've got a reasonably good setup; air reflow system, USB microscope, ESD mat... the works.

I soldered the chip on the board using solder paste and I wanted to test to make sure the connections were good. When using my multimeter to do a continuity test, I keep getting a short between two non-adjacent pins. The pins are both SPI pins, and there are no other components on the board. The solder looks really good, so I'm kind of out of ideas. The chip itself could be damaged, but what are the odds that the two pins that happen to be damaged are two non-adjacent ones that I actually need (there are 100 pins on this microcontroller). I am measuring the short on all unpopulated pads that these pins are connected to. The weirdest thing is that the pin between them is not shorted to either of them. I also checked an unpopulated board, and these pins are not short on it. Does anyone have any ideas about what this could be?


texts: Where can I find an ic at home relevant to my project?

texts:
I am fairly new to electronics but I have a decent understanding of how basic components work. I want to start building my own audio equipment as fun projects and for actual use in my home studio (going for very unique sounds).

Unfortunately, I do not have access to a credit card and there are practically no decent electronics shops in my country that can provide the variety of parts that I require. I am also university student so I am broke :D. This means I have to salvage old equipment and reuse various components.

Right now I am trying to build an audio amplifier to power four 8 ohm speakers (2 tweets and 2 subs). Where is the most likely place that I can find an ic for my amp at home (aside from other amplifiers)?

Side note: I have one very old car amp, but the components that "looked" like ics don't yield many results on google, and I am really not sure if I can just supplant say an lm3886 chip for any random chip that I found lying around. The component's model is la3607. Also, could someone please tell me if there is a definite way to determine that a particular component IS an ic and what purposes it can be used for without google?


texts: The expression I came up with this circuit is A'B + A'CD + C, would the output change to AB' + AC'D' + C' since it is inverted? I'm assuming the D input compliments and cancels out? What would the logical expression actually be? I am confused about the inverter on the output.


texts: Does a battery push and pull or only push?

texts:
I've seen many analogies comparing a battery to a pump. The negative terminal pushes electrons into the wire which causes a chain reaction of the electrons in front of it moving forward, a lot like a pump.

Does the positive terminal do the opposite? Can it be likened to a vacuum that sucks electrons while the negative terminal pushes them?

Or is the positive more like a passive sink that just absorbs electrons?


texts: Voltage problem in printed circuit with switches

texts:
I've got a simple circuit consisting of a 74157 MUX, whose entries come from switches. These entries have also 10k pull-up resistors, so when the switches are open (default), inputs are at 5V. When pressed, inputs are at 0V.

However, one of the inputs (the one connected to R2 pull-up resistor) is having 0.8V when open instead of the correct value of 5V. I've checked and replaced the resistor but the problem remains.

Any hint of what should I check to find out what's wrong?

UPDATE: The problem seemed to be S2 switch pads. I brushed them with solvent, and now, the circuit is working OK. What I'd like to know is why the voltage was 0.8V instead of 0 assuming there was some kind of short in S2. Thanks!

Here's a simplified schematic (only 2 switches represented) of the affected parts:

And here, a real photograph:


texts:
I'm designing a Buck boost LED driver using the ZXLD1370 IC. the circuit works but as one engineer said ("its easy to design a circuit but difficult to get it to pass EMC).
This is where my problem is. I am testing to the EN60945 standard.
according to the standard, the limit is 50 dBu from 150 kHz.

When doing a conducted test, the peak is at the switching frequency. I added a Common mode choke and Pi-filter to get it to 47 dBu, but I want to get it down to approx. 44 dBu so that there is enough room for proper EMC testing. I am attaching my filter design and EMC reading for your information.

I believe this is common mode noise. How would I go about to choose a suitable choke? Right now, I'm using a WE-SL5 (744272471) choke.
am I right in thinking that because of the switcher frequency (350 kHz-500 kHz)

My question is: Do I need to choose a choke that has a high impedance at this frequency range?

simulate this circuit – Schematic created using CircuitLab


texts: Max frequency that can be measured with Arduino Atmega2560

texts:
For the school project I must measure frequency with Arduino Atmega2560 (or some other microcontroller). The idea is to have timer interrupt set to 1 second and external square signal (frequency) connected to pin interrupt. Each interrupt on pin increment counter for 1. Every second (timer interrupt) the frequency is calculated and counter is reset to 0. The frequency I must measure vary from 2-11 kHz. Can this be done?

regards


texts: Power requirements, and feasibility for a short high power bursts (very fast heating application)

texts:
I would like some help to evaluate the electrical feasibility of a system to heat 35 gram of thermoplastic material (for active stiffness control) in 50 ms, by about 100 degrees Celsius.

The material will be for example a thermoplastic polymer such as poly carbonate, or a composite. The idea is to have some sort of resistive wires integrated in the material for the heating process, similar as done in [1]. But please do not worry about the material part to much.

From a rough calculation i get that the required energy is:

1200 [J/kg°C]*0.035 [kg]*100[°C]=4000[J]

to heat it in 50 ms, the power required would be approximately:

4000[J]/0.050[s]=80 000 W or 80kW.

At this point i would like to know if this is roughly feasible or not from an power and current point of view with a battery set or supper capacitors of a "typical" electric car? What type of Power Draws for short peaks are feasible with capacitors, and batteries which are typically available in electric cars?
What is the approximate range? Do i need to go down a factor of 10, or can i go up a factor of 10?

[1] Tridech, Charnwit, et al. "High performance composites with active stiffness control." ACS applied materials & interfaces 5.18 (2013): 9111-9119.


texts: Can I use a power strip with max 250v to a 120v power outlet without a converter?

texts:
I'm going to move to Canada from EU. From my research, most people said that if someone from US moves to EU, they'll need a power converter otherwise it might fry the thing.

My question is, if I use a power strip from EU (max 250v) to the 120v power outlet, would I need a power converter? And if I plugged things on the strip with 100-240v and some other plugs (probably the same or 200v), would it work or do I need a new power strip?

Thank you!


texts: How does a poorly designed SMPS affect another device

texts:
I have seen many examples including my own that sometimes SMPS sharp high switching freq. interfere with another device which is connected to the same mains system.

Can someone explain it in a pictorial manner in a simple way how is that happening? How does the switch finds a route all the way to the other device's electronics.


texts: Same serial command, different serial replies

texts:
I have a device (a traffic counter) that communicate with my computer throught Serial Port.

To extract data from this device, I use a specific software. I'm also using a Serial Port Monitor to check what is written  on the serial port and what is the serial answer.

So for example if in the software provided with the counter I click on "get power consumption information" my serial monitor capture the following result:

[30/08/2018 18:29:28] Written data (COM4)
    3f                                                ?
[30/08/2018 18:29:28] Read data (COM4)
    3f 20 33 63 20 28 30 38 3a 33 35 20 30 39 2d 30   ? 3c (08:35 09-0
    37 2d 32 30 31 38 20 29 20 2b 28 4d 3d 35 2e 36   7-2018 ) +(M=5.6
    38 56 2c 20 52 3d 35 2e 33 37 56 29 0d 0a 35 62   8V, R=5.37V)..5b
    ...

Then if I send by myself the same Serial command (so ? or 3f in hexadecimal), I obtain the exact same result. Great.

Now I try to extract the stored data. So I click on "extract the stored data" and my serial monitor capture the following result:

[30/08/2018 18:42:46] Written data (COM4)
    72 30 35 64                                       r05d
[30/08/2018 18:42:46] Read data (COM4)
    64 20 02 f4 01 b8 5f aa 81 00 ca 39 2b 4b b8 28   d .ô.¸_ª.Ê9+K¸(
    dc 98 77 2c 59 ad 19 f6 5b 34 9c c7 31 5e 1f 1e   Ü˜w,Y.ö[4œÇ1^..
    68 5f c8 8e 7b 32 4f ed 10 60 51 d2 a1 5b 33 62   h_ÈŽ{2Oí.`QÒ¡[3b
    ...

But this time if I send by myself the same Serial command, the result is totally different !

[30/08/2018 18:41:01] Written data (COM4)
    72 30 35 64                                       r05d
[30/08/2018 18:41:01] Read data (COM4)
    72 20 30 35                                       r 05

Why the same serial command give me two differents answers ?

If I can get the same answer it will be easy to recreate the file created by the software... but I need the same answer.


texts: Removing noise from TDA2007A Audio amplifier circuit

texts:
I have built an audio amplifier circuit like the test circuit in this TDA2007A datasheet
I am going to use this circuit with Raspberry Pi 3B+ and going to feed sound via 3.5mm of Raspberry Pi to this circuit.

I am using 2x3W 4Ohms speakers at the output of pin7 of the circuit (using like a mono.) I have not created another part of the circuit of pin1,9 and 2.

I have connected everything perfectly on the zero PCB and made it run but lots of noise is there on playing anything. So how can I remove those noises?

EDIT

Hi, I have tried the solution of potentiometer it worked a little bit. The sound which is coming out still has noise. If I set the potentiometer at which the noise is not produced the output sound is very low on that. If I increase the sound with the noise I can't hear anything at all.

Here's what the noise sounds like.


texts: Triggering 12v Relay with HC-SR501 PIR sensor

texts:
I have a SRD-12VDC-SL-C relay with this configuration:
https://robu.in/product/1-roadchannel-relay-module-light-coupling-12v/
And I want to trigger it with PIR Motion Sensor Detector Module HC-SR501
https://robu.in/product/pir-motion-sensor-detector-module-hc-sr501/
The problem with direct connection to PIR is, when I connect PIR with 12v DC the Relay remains always ON, i.e. trigger from PIR does not switch it off.
And when I connect it via 5V supply the Relay remains always OFF. The trigger output of PIR is 3.3V how can I rectify this problem? by adding some resistor/FETs, or something else.
Edit:
The voltage at Relay-In(Green) is 10.5V and the relay is OFF it need to go below 9V in order to switch the Relay ON. When I connect it to PIR trigger it goes down to 2.7V (Thus Switching ON the relay, below 9V). And when the PIR trigger of 3.3V comes it goes up to 7.2V but because it is still below 9V) Relay does not switch.


texts:
Please see attached Question & Answer screenshot. I have managed to answer up to part 4 of the questions however in part 5, after countless working out and re-evaluating my approach, I still can't seem to understand how K=4/27 from the gain criterion? Also I'm having trouble understanding how the time-constant is found? Please can you help me

Thanks


texts: Setting up internal oscillator PIC12F1822

texts:
I am trying to set up the internal oscillator on my PIC to oscillate at 16MHz and am trying to test if it's working correctly by blinking an LED. As I understand it, each command takes 4 clock cycles to execute, and I have two statements in my while loop. I increment of my counter and have if statement to check if the counter has reached 4000000 yet. If it has reached it, then it toggles the LED and resets the counter.

If both the increment and if statement take 4 clock cycles to execute, that means that the LED should roughly toggle once every 2 seconds as it should take roughly 32000000 clock cycles for i to equal 4000000. However my LED is only toggling once every 20 seconds. Could someone please tell me what am I doing wrong/What do I not understand?

// PIC12F1822 Configuration Bit Settings

// 'C' source line config statements

// CONFIG1
#pragma config FOSC = INTOSC // Oscillator Selection (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE = OFF // Watchdog Timer Enable (WDT disabled)
#pragma config PWRTE = OFF // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = OFF // MCLR Pin Function Select (MCLR/VPP pin function is digital input)
#pragma config CP = OFF // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config CPD = OFF // Data Memory Code Protection (Data memory code protection is disabled)
#pragma config BOREN = OFF // Brown-out Reset Enable (Brown-out Reset disabled)
#pragma config CLKOUTEN = OFF // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO = ON // Internal/External Switchover (Internal/External Switchover mode is enabled)
#pragma config FCMEN = ON // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is enabled)

// CONFIG2
#pragma config WRT = OFF // Flash Memory Self-Write Protection (Write protection off)
#pragma config PLLEN = ON // PLL Enable (4x PLL enabled)
#pragma config STVREN = ON // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LVP = ON // Low-Voltage Programming Enable (Low-voltage programming enabled)

// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

#include <xc.h>

#include <stdio.h>
#include <stdlib.h>

/*
 *
 */
int main(int argc, char** argv) {
    OSCCONbits.SCS=0b11;//needs to be 1x for high frequency oscillator
    OSCCONbits.IRCF = 0b1111; //sets to 16MHz
    unsigned long i=0x0;
    TRISA=0X00; //portA as an output
    PORTA=0X00; //LED off
    while (1)
    {
        i++;//increment counter
        if (i>4000000) //is time to toggle?
        {
            i=0; //reset counter
            PORTA=~PORTA; //toggle LED
        }

    }
        return (EXIT_SUCCESS);
}


texts: Opamp filter cutoff frequency not as expected at higher frequencies

texts:
I'm still working on learning Butterworth filters.  So far this weekend I went back to school, read about Lapace transforms, poles and zeros, Saleen key design, and finally back to Butterworth filters again.  I've been working on understanding this TI app note:

http://www.ti.com/lit/an/sloa049b/sloa049b.pdf

I followed the math for their example in section 10 and then spiced it and I saw the -3dB was 1Khz like it says.  So then I tried to design the same filter with a cutoff of 5Mhz, but instead of -3dB down it was around -6dB down.   Then I tried to build a 5Khz filter to check my math and this one was -3dB at 5Khz.   I'm using a TI OPA355, and was looking through the datasheet but all the charts make me think it's good to at least 200Mhz.

Obviously I'm doing something wrong but I'm not sure what, I suspect it has to do with the performance of the opamp, and something I don't know to look for or calculate from the datasheet?

Here's my circuit:


texts: Is current the same coming out of an IC as it was going in?

texts:
(source: fatcow.com)
This is my first diagram so keep that in mind.  I've come up with this circuit because
I've got some 74** series ICs and I want to be able to make them work.  This example is
a simple AND gate with the 7409 IC.
Obviously, if the circuit works, the LED should glow but only if both switches are on.
What I don't know is what the current will be when it gets to the LED.
The reason I'm not sure is what happens to the current when it is output from pin 3?
R1, and R2 slow down the current so that it can safely enter pins 1 and 2.  But is the
470 ohm resistor required to protect the LED?


texts: Master SW (bit-bang) I2C with Interrupts?

texts:
I've written a set of "bit-bang" software routines for the PIC18F2620 device. These routines work well for reading and writing 24LC256 EEPROM and DS1307 RTCC devices for the most part.
(I wrote this set of routines after spending a hair-tearing week trying to get C18 HW I2C to consistently work).

I am now writing verification (V&V) tests for this set of routines and am experiencing intermittent failures when writing longer sequences of data to the 24LC256 (> 40 bytes). My system has a 2mSec timer running (TIMER0) high priority, and a USART receive interrupt on low priority. I am beginning to suspect that the TIMER0 interrupt is leaving a Master-write sequence hanging too long during an interrupt, and the slave 24LC256 is giving up. Since there is no such thing as clock stretching for the master I believe I may have to start disabling interrupts during Master I2C transactions (from I2C_Start through I2C_Stop). I am leary of writing code where an interrupt is disabled in one routine and with hopes that it will always be properly re-enabled in another routine. (kind of a malloc/free situation).

Before adding these enable-disable interrupt changes I want to ask if others in this forum have had to deal with similar situations, and how they were handled.


texts: BJT astable multivibrator generate triangle wave

texts:
In this circuit there is a bjt astable multivibrator. It generates a square wave. And according to the description, at the output of the opamp it generates a triangle wave from this square wave.

I've tried to implement this circuit in LTSpice.

When I simulate output of the first circuit (astable multivibrator) looks fine.

But if you look at the output of the opamp there are some glitches rather than triangle wave.

What might be wrong with this circuit here.

Edit :

I changed the value of R6 resistor to 1000000 ohms but still output of the opamp doesn't look like a triangle wave.

Edit2 :
After playing around with potentiometer values,I should be able to see a waveform which looks like triangle at the output of opamp.

But if I increase the simulation time from 100 milli seconds to 700 milli seconds I see DC 15 volts at the output of op amp. I don't know why this happens.


texts:
It's my first time doing this kind of task, so I'm a little unsecure if my method is right.

Heres my setup and what I`ve done so far.

I`m using a PCAN USB (Peak System) + PCAN View tracing a J1939 Network using extended identifiers.
The application has no numerical indication about the bus load, only status like bus ok, heavy bus... So I decided to convert the trace record into a CSV and then analyzing it with Python.

Once I had it converted, I was interested in get 4 fields of information: message ID, data size (how many data bytes in that message), how many times that message was sent, and the message itself.

Cycletime was calculated as the total recording time divided by how many times that message was sent.

Message Size was calculated considering:

Start of Frame - 1 bit

Identifier A - 11 bits

Identifier B - 18 bits

Substitute Remote Request - 1 bit

ID Extension Bit - 1

Remote Transmission Request - 1

Reserved Bits - 2

Data Length Code - 4

Data Field - 0-64 bits

Cyclic Redundance Check - 15

CRC Delimiter - 1

ACK Slot - 1

ACK Delimiter - 1

End of Frame - 7

________________________________TOTAL (considering a 8 byte message): 128bits
Load was calculated as 128bits*1000/cycletime

% of Bandwidth was calculated as Load/250000

Am I Missing Something?

Is there another method that's more accurate?


texts: Synchronous Up/Down counter which shows given sequence simultaneously on 5 x 7-segment displays

texts:
I was given a project to design a Synchronous Up/Down counter which displays my sequence (2,1,0,6,5) on 5 x 7-segment displays simultaneously. I started first by designing the Up/Down counter and simulating it. I used both Multisim and Crocodile Clips to simulate my design and it works fine.

The problem comes when I need to display the entire sequence on the 7-segment displays. I used a 5-bit ring counter using D flip-flops with a BJT transistor and 10k Ohm resistors to do this but the sequence doesn't display correctly on either of the two programs. On Crocodile Clips only the '1' in the sequence displays and Multisim shows all the numbers but very incorrectly.

I'm not sure what to do to fix this problem. If anyone can help I'd be very grateful. The main problem I'm facing is that I cannot get the sequence to display. The full sequence doesn't show on all the 7-segment displays simultaneously like I need it to, instead it still shows the sequence as it counts from 2,1,0,6,5 up and down. In Multisim I cannot get the numbers to display correctly and in Crocodile Clips there is only one number that displays.

Here's all my work so far:

Counter Equation:

Multisim Design:

Crocodile Clips Design:

Link to Crocodile Clips file: Here

Link to Multisim file : Here


texts: What will the output voltage be of an audio usb converter/dac

texts:
Lately I've started designing an audio amplifier with usb input. After searching I found about T.I. and their usb audio interface-codecs.

I am going to talk specifically about the PCM2900C, even thought all of them seem to have a similar dac.

In the datasheet it is stated that the output voltage of this dac is 0.6*Vcccl Vpp with 0.5*Vcccl V center voltage. So how these values affect the outputted ac signal?
For example if I were to use 3.3V for Vcccl, then with respect to AGNDC what will the Vout voltage be:

If the connected computer is not outputting any audio.
The min and max voltages when the computer is outputting audio.

Also I am wondering how and if these voltages are affected if I were to add coupling capacitors in series with the Vout pin and the load/speaker/amp.

(I am reffering to the "typical circuit connection" design as demonstrated in the datasheet of the PCM2900C)


texts: What style of socket can I use for thin leads?

texts:
Preamble

This is not a shopping question in the usual sense, because I'm not looking for specific product recommendations. I'm looking for advice on what category or style of connector is best-suited to this particular task.

Requirements

I have a relatively large module, a
RAC03-05SGA,
that I want to be replaceable and non-soldered. As indicated in the datasheet, there are 5 pins at 200mil pitch, but they're in an irregular pattern - two pairs far apart from one another, and one pin far apart from the pairs. The pins are 0.6mm wide and 3.5mm long.

I'm interested in getting three socket modules to accept pins 1-2, 4-5, and 3 (with the second socket beside 3 empty). Ideally, I'd also like fairly good retention force similar to that achievable by screw tightening.

Options so far

I looked at top-entry two-pin terminal blocks with screw retention to a leaf spring. These hit a lot of good points - great retention force and solid design. Unfortunately, I doubt that they're going to work, because there's almost always a significant gap between the wire entry point and the leaf spring action, so they probably wouldn't be able to grab much of the leads that are only 3.5mm long. See for example this profile view from the OSTTB 5.08mm pitch series; entry from the bottom left.

I looked at top-entry rectangular header sockets with interior finger clip. These are simple, cheap and abundant, but seem to have poor withdrawal force (typically less than 2 N). Also, they don't seem to have enough interior space for the leads, with a little over 2mm. (I could snip the leads to make them fit, but I'm not in love with that idea.) See for example the Preci-Dip 801 or 310 series. Finally, it's doubtful that these are well-suited to round leads; they seem designed for rectangular pins.

I found an odd-ball product filed under IC sockets, though it doesn't look like an IC socket - you can get single-pin solderless press-fit "IC sockets" that have 150mil (3.8mm) of interior space; see for example the 346 series from Mill-Max:

The size of pin seems appropriate - 0.6mm is 23.6mil, which is within the 25mil pin width indicated by the spec. However, it doesn't give any data on retention.

Promising but difficult-to-find is a device somewhat similar to a terminal block - a right-angle barrier strip with screwed captive plate, such as the TE 4DB-R108. The pitch is technically wrong, but the gaps are big enough that the leads might fit:

What style of socket would work best here?


texts: Powering 100W amplifier with 12V rails from ATX power supply

texts:
I've got some old speakers that I'm planning to power using this 2x50W amplifier(link)(I'm open to suggestions of a better quality to price amp). To power the amp I was thinking of using an old ATX 400W Power supply(link) and connecting the four 12V wires.

My calculations:
100W(power requirement)/12V(supply) = 8.3A(being drawn from the psu)

Therefore, if the psu uses 20AWG wire(with about 5A ampacity):
4(wires) * 5A = 20A(maximum usage)

Would this be enough of an amperage gap to prevent wires from overheating, or does this design pose a large fire hazard?

Thanks for the help.


texts:
I read a lot about MOSFET protection and built this scheme.

simulate this circuit – Schematic created using CircuitLab

I was thinking that gate and DS are protected enough but experience showed that I was wrong. I made 3 PCB's and all blowed. Motor during continous work takes 20A but I'm sure that overcurrent or power loss wasn't reason why MOSFET blown.

1. Why it doesn't work?

Now I know that D2 should be between R2 and SW1 but what else could cause damages?

2. How can I make it possible most failure-free?

I've seen scheme where between drain and gate was added bidirectional TVS diode but whether it is better solution than unidirectional TVS diode between source and drain?


texts: To get a spark plug to fire I read that it requires approximately 12,000 Volts. If I have an ac generator giving a RMS Voltage of about 10 Volts (pretty small) what do I need to do to get the spark plug to fire? I was thinking about possibly adding a step up transformer but unsure whether or not that would even be possible. So what is typically done with an ac circuit to get enough voltage to allow the spark plug to fire? I would like the spark plug be able to fire periodically like an engine.


texts: Is it safe to provide 3.3V to 1.8V I/O supply voltage?

texts:
I want to connect a single board computer to a TFT display. The TFT has two power lines:

I have a 3.3V supply from the SBC.

Is it safe to use it for both power inputs (VCI and IOVCC)?
Can I just connect directly from the SBC to these power lines?
Or do I really need to lower the I/O voltage to 1.8?

This is just a prototype for personal use, not for a product.


texts: Techniques for accurate 5.5 Vdc active voltage clamp

texts:
We are currently using TI ISOW7841 Digital Isolation modules /w built-in isolated 5 Vdc DC-DC converter Datasheet.  We are having rare failures.  Failure shows up as the module running much hotter than normal.  The module appears to continue to work correctly for some time before failing completely.

Because we have had only 3 failures so far, it is hard to pinpoint the cause.  However, I suspect that the input DC supply line (5 Vdc) is having transients that exceed the module's maximum allowable input voltage of 6.0 Vdc.

The 5 Vdc supply normally comes from a -48V POE (Power Over Ethernet) DC-DC converter module (AG9905MT from Silvertel Datasheet).  There is also a connector for an external 5 Vdc supply for when POE is not available.

I want to add an accurate clamp device or circuit that will not allow the 5V rail to exceed about 5.75 Vdc.  I am not aware of any such devices on the market.  Accordingly, I probably have to build this myself.

It needs to be fast - response time better than 1us or faster.

It needs to be accurate - the margin between voltage okay and too high is quite small.

It needs to be small - PCB layout is already done and there is not much room left to allow the PCB to fit in the enclosure.

Obviously, big-ass Zener diodes or Tranzorbs are out, simply because they are not sufficiently accurate.

I'm currently thinking about using the ubiquitous TL431 driving a low-gate-threshold-voltage (TrenchFET) P-channel MOSFET but would appreciate other opinions.  In particular, I don't think that the TL431 is fast enough.

If anyone can suggest devices that already do this function, I would gladly explore those first.  Other circuit approaches also appreciated.

{Edit}

I've since become aware of devices with tradename of Polyzen (From Littlefuse).  I'm currently looking at the version rated at 5.8 Vdc Datasheet.

That said: I'm still asking for opinions and alternative options.


texts: Global Array Size Affects Clock Frequency Only On Linux (avr-gcc)

texts:
I am having the most peculiar problem. When the size of a global array changes, it alters the clock frequency of the ATmega164a. This is on Linux. When compiled on Windows, this problem doesn't occur (irrespective of whether the .hex file is actually programmed onto the ATmega164a in Windows or Linux aka I don't suspect avrdude is contributing to this problem). I even ran on Linux the exact commands run by AVR Studio to build the target, and still encountered this problem.

The CLKDIV8 fuse is not set, and the Internal RC fuse is set, so the ATmega164a should be running at 8MHz nominal.

This is the minimum working example of the code that runs correctly:

#include <avr/io.h>
uint8_t bytes[6];
int main(void){
    DDRB = (1<<PB5);

    while(1){
        PORTB |= (1<<PB5);
        PORTB &= ~(1<<PB5);
    }
}

An oscilloscope shows the resulting pulse is 250ns wide (2 cycles).

However, increasing the global array size by one results in odd behavioral.

#include <avr/io.h>
uint8_t bytes[7];
int main(void){
    DDRB = (1<<PB5);

    while(1){
        PORTB |= (1<<PB5);
        PORTB &= ~(1<<PB5);
    }
}

An oscilloscope shows this pulse width as 444ns, and the time between pulses increases in the same ratio which indicates the clock frequency has decreased.

I have no clue where to go from here. It took me a very long time just to narrow it down to this minimum working example. I have pasted my Makefile to pastebin.

EDIT

Here are the listing files for the two cases.
bytes[6]: pastebin
bytes[7]: pastebin

I have verified with a 16bit timer that the clock frequency is indeed decreasing by the factor previously quoted (250ns -> 444ns).


texts: How to use BSIM3v3 capacitance for hand calculation?

texts:
As you all probably know, capacitances in BSIM3v3 are just the partial derivatives of the terminal charges with respect to the terminal voltages. They are not physical two terminal capacitors.

Cij = dQi/dVj.

For a MOSFET, we have Cgs, Cgd, Csg, Cgg,...

Because they are not physical two plates capacitor, how do you convert these capacitances to physical value for hand calculation?

For example, Cgs as formula above is not the total equivalent capacitance between Gate and Source.
How do you calculate total real Cgs?
Also, how do you use these partial derivatives for hand calculation?


texts:
I have a new 2 kW inverter connected to my 12 V lessure battery. As soon as I had plugged a 1 kW appliance into it it blew. Pic shows a component that looks like it's melted. I'm very limited with electronics knowledge, can anyone guess why this could be happening. This is the second inverter to blow in the first try.

Many thanks.


texts: Return path magnetic field on hall effect current sensor

texts:
We would like to use a toroid core and hall effect sensor shown in the figure below for measuring current in an Electric Vehicle from a battery pack.

Questions are:

Would placing the wire carrying the return current next to the toroid affect the sensing?
Would the effect of the return path wire be removed if a PCB with an almost continuous copper plane be placed in between the toroid and the return path wire?


texts: Optimum volt not returning on lead acid battery when load is put on the battery

texts:
My Tractor battery (110ah) 12V when I put it on backup check, when the load is put on the battery of discharging 400watt bulb, the battery doesn't reach back to 12v after load, it stays around 11.80 to 11.90.
please tell


texts: How should DC motor brush capacitors be sized?

texts:
I have seen capacitors placed near the brush connectors on DC motors.

What are these for?
How should they be sized?
Do they affect PWM behavior?


texts: Does using only NAND/NOR gates increase circuit delay?

texts:
I remember learning in school that one can construct any logical circuit from solely NAND or NOR gates.

First of all, I am wondering if this is how it's actually done: i.e. when Intel makes a CPU, do they build all the registers, etc. using NAND/NOR gates, or do they have some other fancier way of doing things?

Secondly, I'm wondering if constructing everything in this manner increases propagation delay compared to a circuit made using AND/OR/NOT gates as well.

I know that when using PMOS/NMOS configurations to build gates, an AND or an OR comes out as 2 stages as opposed to a NAND or a NOR which are both only 1.  Since I know you can make an AND from 2 cascaded NANDs and an OR from 2 cascaded NORs, it seems as though propagation delay would not increase as long as manufacturers were using both NANDs and NORs.

Does anybody have any insight on all this, especially as to what is really done on manufactured ICs?


texts: I am planning to build a system that can track and present for me a path for the route a Bee or a Wasp has flown. What I am looking for is the tiny device can be placed on the back of an insect. Does such a device exist? If so what is it called?


texts:
I am designing a Reverse Polarity Protection circuit for a project by using an n-channel MOSFET. A basic schematic is shown here. I've added an RC filter so that the voltage on the Gate pin changes slowly. This is done because I need the circuit to be able to conduct under a reverse polarity condition for a short period of time, but only if the MOSFET is already on at the time that the reverse polarity condition occurs. This means that if no voltage is applied (the battery is disconnected) and then the battery becomes connected in reverse, then the circuit should not conduct at all.

I have tested this circuit and it works properly, using a 100K-ohm resistor in series with the Gate and a 0.1uF capacitor in parallel with the Gate-Source pins of the MOSFET.

Moving forward, I'd like to use only one component for the RC circuit. I believe that this can be done using a larger resistor and utilizing the intrinsic Gate-Source Capacitance of the NMOS. But, my concern and my question here is the following:

Is there reason to keep the resistance on the Gate pin low?
I have had a hard time finding info on this, but in Stephen Collings answer to the following question he mentions that if the resistor is too large, we can run into "noise immunity issues." How can I slow down the switch time of a MOSFET?

Can anyone point me toward more info on this, or advise me on how to set the limit for resistance values? A limit on the resistance will force me to try finding an NMOS with a high enough Gate-Source capacitance.

Thanks for the help.


texts:
I have 2 channels that I want to switch between every 15 sec.
so I guess I need a switch that switches channels by logical pulse ( lm555 I guess?)
which ic/ circuit would be the best?
Accuracy of the switch doesn't matter much ( 1/2 sec delay wont hurt anyone)
the channels will have up to 200ma of current  - 9V of voltage.


texts: What is the origin of the "r" in resistance measurements?

texts:
In a post to the diyaudio forums, www.diyaudio.com/forums 67232, I see terminology that are likely to be measurements of resistance: "0r1", "1r0", and "10r".  I am thinking the "r" there means a decimal point.  If that is true, then is this some standard used in the electronics industry, and if so, what is the name of the standard and/or URL's to descriptions of that standard?

In case that forum ever disappears, below I quote that post's content.

  now we know what you are trying to measure to, tell us what the probe
  to probe resistance reading and also the probe vias winding to probe
  resistance reading is. That way we and you can compare the extra
  resistance as the likely winding resistance. <=0r1 indicates a big fat
  secondary capable of many amperes. 1r0 indicates a big fat primary
  capable of many hundreds of VA. 10r starts to show current
  limitations.


texts: Can I use one voltage divider to bias multiple points in circuit?

texts:
I have 4 nodes in my circuit that require virtual ground of half the power supply voltage. 2 of the nodes are just offset for input signal and other 2 are for op-amp biasing to virtual ground.

Can I use one voltage divider to provide offset for all these nodes? This would greatly reduce BOM and save PCB area(eliminating 6 resistors and some capacitors), but I am not sure if this can't cause some kind of issues?

There was similar question, but it was talking about one IC, in my circuit I have two separate input connections and two op-amps(though they are in same package).

Also maybe a better question would be in more generic form - can one use single voltage divider to bias several points(no matter how many) to virtual ground? I understand that in some circuits the resistance on the output of voltage divider will basically make no sense, but if I for example have 16 op amps that need to be biased - will it work?


texts:
I'm running an audio signal into an ADC on a teensy 3.1. The teensy then detects the first several harmonics of the signal. I had this project working on a breadboard for a good while and finally got around to putting it on some PCB. Since putting it on the PCB, the signals harmonics are detected properly only from ~1kHz to 2kHz (the program should work from 20hz to 2kHz).

The signal just runs from an audio jack to the ADC pin. I've blindly experimented with different values of termination resistors by touching leads to the exposed solder but haven't come up with anything too good.

The signal is originating from some synthesizer modules - a VCO patched to some modules which attenuate it and add an offset to condition it for the ADC. (I intend to house these signal conditioning things on-board in a future revision.)

When the signal is sourced from a waveform generator its harmonics are detected perfectly so the problem must be something to do with the VCO signal source.

Why is the signal only detectable over the range of 1000-2000Hz?

Is the problem diagnosable from the information given?

Is this a case where I must consider the output impedance of the source?
If so, is there a way to design the input to the ADC so that it works with any source, no matter its output impedance? (opamp buffer?)

Are there standard practices for designing ADC input paths?


texts: Low priced universal USB ARM JTAG that works with a broad range of devices and SDK's?

texts:
Can someone recommend a reliable USB JTAG programmer/debugger for ARM processors, mostly Cortex-M3/M4, from a variety of manufactures like ST, TI, Atmel, and NXP, that will work with Keil, IAR, etc. (And Visual Studio's .Net Micro Framework, although I don't know anything at all about that.) Perhaps even Eclipse and on a Linux OS, although this isn't very important.

I would like to get something that will not break as it gets passed around the office, and can handle a semi-professional work load over the next year or two. $200 at the most, however less than $100 would be nice. I have a bunch of old, crummy kit type units, but it's time I pickup something a bit more professional.


texts: Signal integrity at 40 MHz with parallel signals

texts:
I have to design a board with an 8 bit parallel port that carries 40 MHz signals. It is not possible to wire them very short and in parallel (I am sure the wires will be about 7 cm long), so I have to wire them separatelly in pairs of 2 or 3 wires together because my microcontroller doesn't have all the port pins together (TQFP44 package).

Is any signal integrity considerations at this frequency ? I use Altium and can make trace lenght equal but this wires are not alone and maybe can affect other wires such as UART, TIMER inputs, etc. Moreover signals are not differential so I don't know what problems can it cause.

EDIT:

It is my microcontroller:

I need to use the 8-bit low side or 8-bit high side of PORTB (16 bits) or PORTC (16 bits) to connect it to an 8-bit buffer. As you can see pins are not consecutive so I will have to wire the traces whit more lenght (I have been say that at 40MHz lenght is not a problem yet) but I don't know how it can affect to other traces and how can I prevent high frequency problems like EMI.


texts: Modified Nodal Analysis for Diode , Approach?

texts:
I was learning to implement MNA(SPICE) and I am quite stuck near diodes . I read through a couple of sources and they instruct using Newton-Raphson to basically find the intersection of the load line and the diode IV curve iteratively .MNA for the circuit below proceeds as follows

$$\begin{bmatrix}1/R&-1/R&0&1\\-1/R&2/R+G&-G&0\\0&-G&G+1/R&0\\1&0&0&0\end{bmatrix}\begin{bmatrix}V1\\V2\\V3\\I1\end{bmatrix}=\begin{bmatrix}0\\-Ieq\\Ieq\\Vs\end{bmatrix}$$

Where \$Ieq\$ and \$G\$ are the current source and conductance of the diode companion model respectively .I'm lost at how to proceed further . I can't seem to understand where Newton-Raphson fits in here?


texts:
I am working on a project using an STM32F4 nucleo board and a MLX90621 device.
I have a problem regarding the communication between the two using the HAL I2C library.

The EEPROM has two devices inside, an EEPROM and the IR thermal device itself.
Using the HAL library with the I2C implementation, I can read the EEPROM perfectly but I cannot read the device itself. I checked with the oscilloscope and the device does not acknowledge when I want to read it. What might be the cause?

I will attach some oscilloscope capture images below and how should they look from the datasheet.
Reading whole frame:

Lack of acknowledge:


texts: How to quantify the health of an electronic appliance according to its power consumption?

texts: Is there any ways to quantify the health of an electronic appliance according to its power consumption?


texts: Detecting Zero Crossing of Mains (Sine and Square Wave)

texts:
I need to design a circuit that can measure and output pulses for a MCU at zero crossing of 220VAC waveforms. The application requires that that both square wave waveforms and sine-waves should work. The square waves are important due to circuits being powered off cheap UPSes here.

I am familiar with the simple 'AC input' opto-isolators + resistors approach. That has worked very well for sine waves but in a square wave, the waveform crosses the zero point much more quickly and my circuit has very little time to react, it seems. Here's the circuit:

Based on this circuit I thought that slowing down the square-wave might work. So I designed a low-pass filter in addiion to replacing R1 and R2 with some capacitors to reduce power loss. Resultant circuit:

I don't quite remember the values for the LPF so the values in the schematic are just a guess. Note that this circuit does work as the square-wave is basically slowed down. It does have some phase shift but as long as that's constant, I'll just program it out into the MCU. I hope capacitor tolerances won't bother that too much.

My question is: is there a better way? The circuit has a switch mode power supply so no traditional transformer where I could have done zero-cross detection with a comparator - I do require isolation here. I'm also OK with the idea of a dedicated transformer provided it's very small and is able to pass the sine and the square wave.


texts: Why are resistors necessary in the following circuit?

texts:
simulate this circuit – Schematic created using CircuitLab
The circuit is taken from the schematic of a SONOFF of the ITEAD house.
If a gate of a MOSFET behaves like an open circuit, why are resistors needed?
Applying 3.3V from GPIO12 directly to the gate of the MOSFET should work correctly and barely circulate current through the gate of the MOSFET.


texts:
I have the schematic of Arduino DUE for EAGLE software, I found a part I dont know what means for Altium Software.

Can somebody tell me what is it "ETH" ? A header??

Arduino Due schematic

I found this schematic Altium on Internet

DUE Altium


texts: Switch a Transistor ON/OFF with Txd Line From USB2SER Adapter (CH340)?[Resolved]

texts:
Note/Update:
The Problem was The Use of an extension cable (RS232 Null Modem Without Handshaking).So, The RxD & TxD are inverted.it means if you want to measure TxD voltage You should Get it from The Pin 2.

I have an USB2Ser Adapter (CH340), and want to use the TxD line to control an 13V voltage On/Off. (The pins RTS,DTR already occupied.So, really stuck only with TxD).

After some tests i found that the Txd Pin change state between (0V & 0.42V) (logical 1 & logical 0). So, We have Two states 0V & 0.42V.
0V ------> Transistor is OFF. is OK.
0.42V ---> Transistor is ON. is it possible ??

UPDATE :
DataSheet : http://www.seeedstudio.com/wiki/images/7/7c/CH340DS1_EN.PDF (from @WhatRoughBeast)
TTL levels of My Adapter are : 0V & 3.5V
  RTS, DTR lines : logical 0 = 3.5V , logical 1 = 0V . So, are normal. it's OK.

To test the TxD line i used a BREAK command to make it at logical_zero (3.5V), but when sending a BREAK (Pyserial.sendBreak(Time)) i got a 0.42V on TxD, and as the guys said is abnormal.
i think that My adapter doesn't support the BREAK fucntion.
And When Transmitting 00 on TXD Line I got : 0.2V not normal ... WTF !!!.

I used AccessPort software http://www.usconverters.com/downloads/tools/AccessPort136.zip  to test the Adapter in loopback mode (TxD to RxD), And Transmitting Some Words, the Test is passed !! what i send, i get it in the Receive window. it means that My Adapter is O.K !!!


texts: Why in some instruction the order of register is different between machine code and assemble code for MIPS?

texts:
For example in assemble code we have /add rd rs rt/ but in machine code we have /opcode rs rt rd/, where the destination register is at last position. Why MIPS arrange their code like this ?
I know in machine code the rd is put at last position because some instruction does not have it, so why they don't write assemble code like add rs rt rd ?


texts: Move silkscreen text from component on EAGLE CAD

texts:
How can I move a silk text from a component? I cant use the button move to the text and when I click smash nothing happend. I need to move the number 8 inside the board

Edit1

I try to smash but when I press it, a new text appear and this I can delete it, but I cant move the numbers or delete them, how can I modify the footprint? or erase the numbers and add it manually?
(you see the opcion unsmash because I already smash it)

Edit2

I did it! Thanks all! I could modify the footprint going to library, then selecting the library, then package :)


texts: Connecting a 3.5mm audio jack to a 12V DC power cable

texts:
My old Sky+ box had a 9V RF output that powered my 2 way satellite distribution amplifier directly in the loft. It allowed me to watch TV in two more bedrooms upstairs.

Recently I had the Sky+ box upgraded and the 9V output is now too weak to provide the same service.

The 2 way amp (http://www.philex.com/catalogue/product/?id=901&cat=1069) has an external DC port so I can power it from the mains, but of course the adapter did not come with it in the first place. Here's a pic:

I rang them this afternoon and they informed me they don't even sell the adapter anymore! Anyway I thought it shouldn't be too difficult in sourcing a 12V DC adapter for this device until I saw the connection on it.

It looks (and I'm 99.9% sure I've seen this written somewhere else online) that the device takes a 3.5mm audio plug! Not a normal power barrel.

I'm handy enough with soldering but I'm just not sure if what I think I can do is acceptable...

Can I take an old 12V DC adapter I have lying around here, and snip off the power tip at the end, strip back the wire and solder it to one of the many many 3.5 audio jacks I have here currently connected to various cables?

How do I check I get the polarity correct? Is there an easier way? Am I missing anything?

Thank you.


texts: Splitting mains power into multiple relay-switched circuits

texts:
Summary Introduction

My goal is to split a 1-gang mains power extension lead into three, have my Raspberry Pi plugged into one of the outputs, and have the Pi able to switch the other two outputs using relays.

Background

I want to use my Raspberry Pi to switch on and off two mains-powered appliances using solid-state relays.  I've found this useful video which demonstrates the concept on a mains-powered lamp.

The video suggests cutting the lamp's power cord and wiring that up to the relay, but I don't want to cut the cords for my appliances.  I am, though, happy to use an extension lead and cut that instead.  However, I don't want to have to buy and cut an extension lead for each appliance; nor do I want to have to plug three things (the two appliances and the Pi) into my wall socket individually, for neatness' sake.

So I thought maybe I can make a 3-gang extension cord and have the Pi run off one output and attach the relays to the other two.

The Plan

My idea is to get myself a nice long 1-gang extension chord and two spare extension chord sockets, so I'd have something like this (please excuse my crude illustrations!):

I would then cut the extension cord say 3m from the plug end and cut two more times to give myself two pieces of headless chord, like so:

Now I can wire those loose bits of cord into the spare sockets.  Furthermore, I could cut those cords again to insert the relays, giving me this:

The final piece of the plan would be to join all those loose ends in a junction box.

The Question

Sorry it's taken so long to get here, but here is the question (well, two actually):

Is this plan feasible?  And if so, what's the best (i.e., safest) way of connecting those loose ends?  I thought of using a junction box and I've Googled endlessly but can't seem to find anything that takes one input and allows multiple outputs.  The closest thing I can see is this but I think the cord might be too thick for it.

Also, I'm a little concerned that shoving three wires under one screw in the terminal block of a junction box might be insecure and lead to them coming loose.

Any advice and suggestions are most welcome!


texts: Maximum Gain For Chopper Stabilized Instrumentation Amp (MCP6N11)

texts:
I am using a Microchip MCP6N11 chopper stabilized instrumentation amplifier to amplify the signal from a MPX2300DT1 Wheatstone bridge pressure sensor.  My schematic is attached.  As shown the gain is 170.  To get enough signal I need to increase it to at least 800.

According to the datasheet this may require too high a value of feedback resistor. In the datasheet there is a formula for the maximum feedback resistor:

I'm not sure what values to use for fGBWP and CG.

Can I safely get a gain of 800 to 1000 out of this type of instrumentation amplifier or should I add a second stage of amplification?  Frequency response only needs to go up to about 10,000 Hz.

This is my schematic:


texts: What is best to use for a desktop computer, 2 prong or 3 prong power plugs?

texts:
We purchased a second hand NEC desktop computer and just lately we had a long beep problem that occurred. I figured it might be the RAM, so I disassembled the system unit and cleaned the RAM. However, there is an instance when I plugged it all in again and experienced some electric shocks on the case.
Everywhere I touched has this electricity so I immediately shut it down. I know static electricity might affect the motherboard that's why I am quite worried. I checked the plugs and found out that it was 3 prong plug but the ground is missing. I am not sure if the previous owner just cut it down or it just had a space available to input ground (not sure if this is a thing though).
I am thinking of buying a 3 prong plug and replace it but I am not sure if that would be safe. I am aware that every unit is designed specifically whether it needs to be grounded or not. That is why every single one of them comes with a different plug type.
Would replacing the plug a good idea and will prevent future instance of this issue?
Can someone enlighten me more about this?
Any help would be appreciated. Thanks in advance.


texts:
I have a 3D printer. Its control board gets too hot - it works but it get too hot.

I want that the current of the hotend flows through a MOSFET
source ->mosfet (using ramps output as signal)->hotend
 to the hotend and not form the
source ->ramps->hotend.

I discovered that if I touch the ground of the source and the ground of the hotend control board output it automatically turns on without command, so I had to use some isolator.

I built the following circuit; I use a 4N35 for isolating the hotend controlboard output, and then use a PNP transistor to connect the gate from the MOSFET to the 12 V rail. I put 2 diodes to step down the voltage to 10 V. I want to use an IRF740N.

I don't know if my circuit is wrong or if it's my circuit simulator that is wrong because the MOSFET is always on.

In theory the pnp transistor should be open if no voltage is aplied in the base, so the mosfet will be off, but in my circuit simulator its always on, and i dont know why, i dont know if my circuit is bad or my simulator has a bug.

I build this circuit

i replace the diodes becouse the hotend is controlled by pid, so needed a faster diodes.

So i choose to divide the current with resistor

after building the circuit i realize that the circuit simulator was wrong, i am using livewire 1.14.
The circuit actualy work as intended.

But after conected it in to the ramps dosent work, but stand alone with a led and a power supply works fine.

I research a litte and discover that the heat come from the 5v regultor from the arduino board.

The reason of the heat wasen't the mosfet or the hotend, it was the graphics lcd that draws too mach current of the arduino regulator.

The solution is to remove one diode of the ramps and feed external 5v in a pin, so the regulator it's dosent need it.
 but i dont know why when i pluged the second circuit it dosent work, for somebody who knows the ramps 1.4 board maybe can solve the problem

I consider my problem solved,and learned a lot about mosfet in the experince, thanks a lot to those that really wants to help people and are very humble


texts: Experimentally measuring the gain of an amplifier with noise

texts:
Normally rms value and the mean value of a perfect DC voltage is same.

So lets say I want to measure the gain of an amplifier.

I first apply an offset Vin_off to the inputs, then I measure Vout_off.

Then I apply Vin to the inputs, then I measure Vout.

So I calculate the gain as:

\$G_{dB} = 20 \ \log_{10}([Vo_{mean} - Vo_{off-mean}]\ /  [Vi_{mean}-Vi_{off-mean}])\$

Basically I measure the gain by calculating the ratio of the change in output voltage to the change on input voltage.

But as you see I use mean values..

What if the input and output signals also have some noise on them?

Should the mean values or instead rms values be used as:?

\$G_{dB} = 20 \ \log_{10}([Vo_{rms}-Vo_{off-rms}]/[Vi_{rms}-Vi_{off-rms}])\$


texts: Trouble understanding thevenin's model from AoE Lab

texts:
I am using the AoE lab book to teach myself electronics. I am on the voltage divider section, and I am confused at their simplified explanation. I'd like to explain it a different way, but I am not sure how to understand the open circuit voltage.

For the following circuit:

simulate this circuit – Schematic created using CircuitLab

Calculating Vout is simple:

$$V_{out} = V_{in}\frac{R2}{R1 + R2}$$
$$V_{out} = 30\frac{10000}{20000} = 15V$$

Now we introduce a load into the circuit:

simulate this circuit

My approach to solving this myself was to turn the original circuit into a black box and imagine we are looking at it from the perspective of the output.

From reading, the short circuit current here will be

$$I_{sc} = \frac{V}{R} = \frac{15}{10000} = .0015A$$

The first of my questions is - why does only the first resistor matter for calculating the short circuit voltage? Shouldn't both resistors be...resisting in the circuit? Intuitively, is this because we are bypassing R2 via a short circuit and the voltage will just (for lack of a better term) ignore the resistor and follow the path of least resistance (ground)?

After this I need to derive the open circuit voltage. I am having trouble figuring out how to view the circuit in a way that makes this make sense. If I disconnect the load, the open circuit voltage would be the original Vout, would it not?

Basically, I am trying to derive the math that makes treating R1 and R2 in parallel make sense. I understand the thevenin resistance will be this value, and the thevenin voltage is equal to vout (15V) in this case. The explanations in the lab book, while helpful, sort of handwaved through this part (they began to talk about switching voltages and grounds to show which resistor matters) and I'd appreciate any help in understanding this section. I feel like it is critical to understanding circuit impedance (the next section) and I would like to fully understand it before moving on.

Thank you!


texts: Connector Identification; How to Case Mount

texts:
I have these connectors and need to case-mount the female part of the pair.  I've been trying to find out their mfg/part no so that I can look at the spec to figure out how to mount it.  No luck.  The drawing below is my best attempt to show the identifying mark that is on the male connector.  The pictures are of the connector set.  Supposedly the female connector will case-mount, but having looked at if for a few hours, I am stumped.  If anyone has an example to share, that would be a wonderful thing.

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