texts: Suggestions on how to control a 1000W DC motor

texts:
I would like to find out the best solution to safely control two 1000W DC brushed motors by using a atmega328p.
In particular, the DC motors are rated: 1000W, 50A, 24V, 2400 RPM.

I have a radio transmitter system which has a receiver able to provide two types of outputs:

PWM in current mode (12V, 2A max)

or/and

PWM in voltage mode (0-5V, 200 mA)

Each output on the receiver is triggered by a proportional stick on the transmitter.

I was thinking to use the PWM output in voltage mode as input for two analog atmega328p inputs and then use these values to control two PWM outputs on the atmega.

The problem is:

what is the best solution to control and switch the high current?

How to control each motor in both directions?

I also would like to set a maximum current limit (for example, 100A) for safety reasons.

Should I use 100A-rated contactors, for example?

May be, relays are too slow..

Thank you for all your suggestions!


texts: Comparing inductances from LCR measurements and FEMM simulations of a simple transformer

texts:
I am trying to compare the results from a simple transformer using two identical Wurth Elektronik inductors (Reference 760308102308, datasheet attached). I measured the inductance with an LCR while doing an open circuit and then a short circuit test. I got 5.6uH for the open circuit and 3.7uH for the short circuit test.
Pictures from the set up are shown below.

In addition, I also measure the inductance of these two configurations that I found in another post. The Mutual Inductance found combining the two measurements was 3.77 uH which seems to match the short circuit value and L1 = L2 = 5.22 uH which match with the value found in the previous open-circuit test.

I wanted to compare these results from the measurements with a Finite Element Method Magnetics (FEMM42) but when I do the problem and run the simulation the results don't match, and it seems that they are switch. Open Circuit Inductance is 3.7uH and short circuit 6.7uH. I used a current of 1A to simplify the calculations and below you can see the simulation problem and the results I got. I don't know if I am missing something or if I am assuming the wrong conditions or making a mistake in my calculations. I already double-check them and it seems that I cannot connect the LCR Measurements with the results in the simulation
I hope someone can help me understand what I am missing or what I am doing wrong.
All the best, and Thank you for your attention


texts: I am currently reading my text, for my electromagnetics course, and we are discussing guided waves. The text casually mentions the term "guided modes", and never really defines what that means.


texts:
Update: This question is based on a wrong assumption, the problem has now been fixed.  The problem was an incorrect register setting in the RTC.  However the answers given regarding load capacitance for crystal oscillators may have value to people in general situations.

I have a prototype PCB of my own design.  It was originally designed to use an ST brand "M41T81S" real time clock chip with a cheapo 12.5 pF watch crystal.  Timing accuracy is not important (+/- 5 seconds per day drift is fine).

I have swapped out the old RTC and I'm now using a Microship brand "MCP7940N" instead, which is a pin-for-pin match for the original and has fully compatible voltages.  The new chip works fine as far as the I2C communications goes.  I can program the registers and read them out without problems.

The original design does not include load capacitors as the old chip didn't need them, it kept reliable time and didn't miss any clock pulses.

However the new chip does appear to have stricter requirements for the oscillator circuit and only sporadically responds to the crystal's signal (perhaps 1 in a million pulses is registered).  Most of the time it does not "keep the time" at all.  It effectively cannot see the crystal signal.

The scope reads a clean and stable 400mv p-p sine wave on the XTAL1 pin with the new RTC.  I'm guessing this isn't suitable for the new chip, the datasheets for the xtal and new RTC do not specify the waveforms produced or required.

I admit that the new chip's datasheet says that "12.5 pF crystals are not recommended".  Fair enough, my own stupid fault for buying these parts without properly checking for compatibility.  Doesn't really matter in the long run.

Question:

Given that I've already made a dog's dinner of this prototype, is there a way that I can hack something together in the short term in order to get this new RTC to operate with the unsuitable 12.5 pF crystal and lack of load caps?  It's only a prototype and definitely needs a re-spin of the layout for several other reasons besides this problem.

I figured I should change the crystal to a 6-9 pF as stated in the datasheet for the RTC but that still leaves me with nowhere to put the load caps.  I've never had to mess much with crystal circuits before and could use some advice about just bodging this prototype to get this "proof of concept" board to function.

(If this turns out to be impossible then I still have the option of running the RTC from an external signal such as a microcontroller outputting a square wave, so all is not lost.  I'm mainly asking this question out of curiosity rather than necessity)

Datasheets:

Crystal: http://www.farnell.com/datasheets/9024.pdf?_ga=1.115641094.1422151987.1489565541
Old RTC chip: http://www.farnell.com/datasheets/1690409.pdf?_ga=1.178012581.1422151987.1489565541
New RTC chip: http://www.farnell.com/datasheets/2129560.pdf?_ga=1.178012581.1422151987.1489565541


texts: I am trying to solder a continuous line with a non-lead soldering wire but I ended like this. Now it's not conducting but there is no gaps between anywhere. How can I fix this?


texts:
I built a H bridge circuit and I'm struggling with the analysis part.
Below is the H bridge circuit I built .A brief description of the circuit:  V1 and V2 both send inverse PWM signals and U1 and U2 are both optocoupler where U3,U4,U5,U6 are MOSFET and the circuit is being powered by a 7.2 voltage supply.

The issues I'm having is how can i run a DC sweep to investigate the minimum Dc operating point especially when the battery is low.
How can i run a AC sweep of the input source.


texts: What's the simplest way to dim LEDs for tail lights?

texts:
I'm building tail lights for an old car. They're going to be as simple as possible, high intensity LEDs and resistors to bring down the ~5.5 volts the car supplies to about 2.2.

The car originally used a dual filament bulb, a dim filament for running lights and a bright one for brake lights. I want to use the same LEDs for both brake and running lights, with all of the LEDs being activated at all times. Dim when just running and bright when you hit the brakes.

The car just runs two +5.5 volt wires to the bulb and they share a common ground.

What's the simplest workable solution?


texts: Voltage on coaxial line - calculation process

texts:
Compute the voltage on the end of coaxial line (\$Z_0=75~\Omega\$, \$l=100~m\$,\$\tau=5~ns/m\$) at time \$t=1.6~\mu s\$ after connecting the line to voltage source (\$U_0=6~V\$,\$R_i=0~\Omega\$), if line is ended by resistor \$150~\Omega\$.

Found this example in older test. I have no idea how the schema should look like, nor what \$\tau\$ is and how does it affect the computation. Does anybody understand what is needed to do? I don't know result.


texts:
A little bit of context:
I'm doing a project for my physics class where I could choose the topic, and I chose to do phases in sound and noise cancellation (wavelengths and frequencies). Essentially, I'm measuring the distance between two out of phase speakers and how that affects the consistency of noise cancellation when playing a single tone. My only problem is that my speakers are currently in phase (as speakers normally are) and I need them to be out of phase in order for my experiments to actually work. I've read that it has something to do with the wiring of the speakers. Also, the speakers that I'm using are a pair of HP 2.0 Compact Speakers that connect to computers through a USB 3.0 and a standard audio jack.

What's the easiest way to get my speakers to be out of phase? Is wiring involved as many others have said?


texts: Adding an amplifier to a speaker-level audio output

texts: My ham radio has a speaker output rated at 2W, 8 ohms.  I want to increase the power to feed a 30W speaker, which is also 8 ohms.  How can I connect an amplifier to this speaker output?  The amp I'm looking at now is a Kinter MA-170.  Its output is good, at 18W, 4-16 ohms.  But the input impedance is 47K ohms, and I don't know if it can handle the speaker-level output. There is no line-level output available on this radio.


texts: I would like to ask let's say I'm biasing the input of an op amp by using a simple voltage divider DC with an input Ac voltage which is placed with a capacitor. The output seems to be amplified but only the Ac signal is amplified. Why is that so? Shouldn't DC biased voltage be amplified together?


texts: Why two resistors(R5 and R9) are required at the gate side of IGBT Q3? According to me they are used as potential divider, but can any one tell why it is needed over there? In datasheet it is clear that voltage at pin 13 of L6386D can be varied from -3 to Vboot-18.


texts:
I would like to build a system which could capture an analogue waveform data in real time. For the basic data acquisition system I can use an ADC to digitise an analogue waveform and store this in a memory buffer.

However, when I have to read the data out of the memory, I can no longer write data in. This will give me a break in my data acquisition.

What I would like is some memory which would allow one location to be read whilst reading from another. I understand this probably doesn't exist, but I am sure real time data capture does.

So how do they do it?

Do they use two memory chips, and write to one whilst reading from the other with some VERY careful timing controlling the switch over?


texts:
I am want to design a remote control. All I need is the appropriate IR LED and the Receiver to use, that will yield optimal performance. i need real practical experience here.

What is the best receiver to use. Photo diode or a Photo transistor.
As regards the distance. This remote control ought to work like that if the Indoor AC,radio or TV sets, where at a distance of about 10-12 Feet maximum. Also I am considering a good reception angle for the receiver.

I have know about the modulation method, which I believe is the best. So how do I possibly go about it.

Circuits diagrams, components data sheets, and detailed analysis will be greatly appriciated.

Thank you all.


texts: How do I figure out max continuous discharging current of a battery?

texts:
Looking into ordering a battery for a prototype I'm working on. The power rating for my product requires 4610.6mah to power it for 1 hour and I'm looking for a battery that can support its run-time for up to 10 hours. so 46000mah-50000mah would be ideal.

Upon messaging 1 of the manufacturers they asked me "What is the max continuous discharging current of the battery you need?" This was based on LI-ION batteries and not LiPo.

With me being a newbie to battery ordering can anyone provide me with an explanation as how I can find out the max continuous discharging current for a battery that is say 50000mah?


texts: Trying to understand inductance while driving a laser module

texts:
I have a simple circuit working where I drive a laser module with a mosfet(2SK4017Q), a 10K resistor (gate-source) applying 3.3V on the mosfet gate. Mosfet drain is connected to laser module GND, and 5V applied to laser module Vcc. Laser specifications are: output: 5-10mw, working voltage: 4.5-4.8vdc, working current: 40mA. Microcontroller is a Teensy 3.5.

I wanted to miniaturize this but now I believe I have made a mistake choosing some wrong smd mosfet (2N7002). I say "now", because I have made this circuit to work once, but could not reproduce it again (...) In this thread I am trying to understand what's happening next - see picture.

I have removed the 10K resistor from its place (as shown) so gate is floating (when microcontroller is not sending any signal). Any value of resistor I tried until here produced just very pale light, and forward voltage on laser module terminal was about less than 2V.

Inductance (I hope this is the proper term) happens when I hold a (conductive metallic) screwdriver on the laser module trim pot (picture), and simultaneously another screwdriver on the mosfet gate, laser module light gets vivid again and circuit seems to work as expect. I am not sure how to start to fix it.


texts: Why output is high even though trigger pin is high in Proteus simulation of IC555?

texts:
In the below attached circuit of IC NE555 Proteus 8.0 simulation, TRIGGER pin (Pin 2)is set at Vcc. So why the output is high? It should be low since voltage at TRIGGER pin (Pin 2) is more than 1/3 of Vcc.

Please let me now if there is anything wrong in the circuit or is it a problem in the simulator?


texts: Can we conclude from Friis formula that high frequency mean more loss.

texts: I am trying to understand the Friis transmission formula: https://en.wikipedia.org/wiki/Friis_transmission_equation From the equation in terms of directivity can we conclude that higher the frequency higher the loss and less energy will receive in the receiving antenna. I assuming this as it is proportional to square of wavelength.


texts: Back EMF of an inductor in a DC circuit?

texts:
Will an inductor in a DC circuit act as a voltage source and oppose the applied current creating the magnetic field? Or is it because of the steady state direct current there is no change in I there is no back EMF opposing the power supply?

simulate this circuit – Schematic created using CircuitLab

Source:

I'm confused, going from 0A to xA wouldn't that be a change? Creating a growing magnetic field...?


texts: ARM MCUs in hobbyist-friendly packages (DIP, SOIC)

texts:
UPD Please do not answer or comment it anymore, the question is too broad and not valid. Since I asked it I get used to using STM32 chips with handmade PCBs (so it's rather an issue of improving etching skills).

This surely was asked several times, but I see the information is generally outdated.

I wonder what ARM chips now exist in DIP or SOIC packages so that I can use them in either bread-board or fast hand-drawn pcb-prototype. E.g. with distance between pins no less than 1mm.

As for DIP's, there seems to be only two famous: LPC1114 (28 pins) and LPC810 (8 pins)

With SOIC situation looks bit better, I've found so far LCP1110, LPC1112 in 20-pin packages (which cost almost the same price as my favorite ATMega8L) and could be programmed via UART which is quite convenient.

Surprisingly Atmel have several ATSAM9... and ATSAM10... in SOIC-14 and SOIC-20 - regretfully I have no experience with them yet. Probably I'll try soon.

If you are acquainted with any other (excluding tiny evaluation boards), could you please help me extend this small list?


texts: How do floating voltages affects circuits/systems?

texts:
I was at a talk recently regarding robustness testing. It was separated into parts: Uncontrolled and Controlled.

Uncontrolled involved applying high floating voltages to various pins and logging the results. The circuit in question was an ADC  that operated at +/- 20V, and 40V floating voltages were applied at the analog IN pins.

I'm aware that the floating voltage is not referenced to the ground of the ADC circuit, but in what way would would it affect the circuit, and why the need for two tests (controlled test voltages were referenced to circuit ground)?


texts: Correct calibration of reflection (S11) measurement

texts:
Following situation (apologies for my potential stupidity, I am very new to RF): I am doing a reflection/S11 measurement using a cut-off piece of coaxial cable (no stub, just a straight cut).
The idea is to get the reflection response of a circuit to be touched/approached with said cable ("the probe"). Now, my first approach was to do a measurement of the S11 coming from the probe without any sample, so just using air as termination and then to subtract it from whatever I get when attaching the probe to the sample. But this obviously does not take into account that there are standing waves (and plenty thereof) in the piece of cable I am using as a probe which behave differently with the different termination that is the sample and thus will show up in my measurement and look bad. They occur at more frequencies than the fairly broadband behaviour of the circuit, but they still don't look good.
Is there a way, ideally by calculation, to eliminate the influence of these standing waves / the probe?


texts:
I'm developing an STM32-based device, one of whose functions is to periodically monitor the main power 12V battery voltage.

I created a simple switching circuit with a voltage divider. I have added a pull-down resistor (R7) to the MOSFET gate, to make sure the switch is always off. On the PCB, I placed these components on the 'dirty' ground corner, near the 12V source (and the switching DC-DC converter). It has a ground plane which connects with the MCU's ground plane at single point.

So the question is: Will switching the VBAT_SENSE_EN pin to low by the MCU, cause a ground loop to the 'dirty' ground? Will this effect be significant? Or should I eliminate R7 and use the internal MCU pull-down?


texts:
I have got a 6 wire stepper motor. It's a chinese one (OKI KFL42LL) with Black, Brown, Orange, Yellow, White and Grey wire on it. Its specs are 8.7ohm and 7.5 degrees/step.

I went through a lot of tutorials to figure out the coils of stepper motor. Most tutorials say that 3 wires form a coil and we should get 2 different coils by measuring resistance of the coils.

Going through the tutorials I understand that one set will have A, B and a centre tap. Resistance between A to B will be maximum and centre tap will make it half. The other coil will have an infinite resistance w.r.t. to the first coil.

In the stepper motor I have, all the pins are internally connected and the resistance between all the poles is appx 18 ohm and with centre tap is appx. 9 ohm. I am unable to figure out the coils in correct way, can anyone please help me with some other way to work on it?

Let me know if any other information is needed. Thanks in advance.

P.S: The white and grey are centre tap as their resistance is 0 ohm and they show 9 ohm when connected with others. By programming and permutations I got to know that Yellow and orange is one coil; black and brown other coil. Checked the same with other stepper motor. But would still like to know the way to find it out.


texts: Do LCD's or Plasmas have a circuit for each pixel or they are lit in an array fashion?

texts:
I'm trying to understand how LCD's display a picture.
I've read articles and papers, but sometimes I get contradicting information.
Some say that each pixel ( actually a sub-pixel ) have their own circuit, meaning that at any one time that sub-pixel can be lit or dimmed / or shut without affecting the others.

Some others say that there's a grid ( for example on a 300 x 300 ) screen, assuming the LCD subpixel matrix scheme uses an RGB/RGB/RGB one, there are 900 wires going from the top of the screen to the bottom, and 300 going from one side to the other. If that's the real case, saying that the screen has wiring for each sub-pixel is wrong. Say that I want to light the first sub-pixel, but not the second on the first row, and light the second sub-pixel but not the first on the second row

*-
-*

In an LCD, to shade/"block the back-light" of the second pixel on the first row I would have to power the second wire that goes from top to bottom and the wire that goes side to side through the first row. You get the wiring's for the other pixel. You may have noticed that you end up powering all the wires, therefore all the 4 sub-pixels end up dark.

Again if that's the case it means the only 1 row at a time can be displayed, and the monitor displays them so quickly the they eye interprets as a single image.

I am very confused, please tell me how they actually work, I might have everything completely wrong. Thanks


texts: A Bluetooth device that will send data to a mobile phone

texts:
I want to make a device which will send a data to a mobile phone which is connected using Bluetooth.

Here is the thing: http://www.youtube.com/watch?v=g0qARDGJj1w.

I want something like this. The problem is I have no electrical background. But I have theoretical knowledge as I had a few electrical subjects in college.

The problem is: I don't understand what should I Google, precisely. Just throw me in the best direction so I don't get lost and don't waste time. Give me a basic idea or something that will motivate me.

I don't want the exact thing shown in video. I just want following thing to happen at least:

The user pushes a button, read what that button is for (say it is for the letter 'A'), then the mobile phone will show the letter 'A' in some app, e.g. notes.

Here I am considering data could be sent over Bluetooth, and the mobile phone is an Android device.


texts: I want to control an analogue synthesizer with CV from my audio interface outputs. i have tested with a multimeter and the output seems to be DC coupled with this i mean that when i send a DC offset it remains steady there are no capacitors at the output to filter the DC offset. Also the output after some tests seems to work allright. But i ask here to further understand. How to identify if my output can carry DC signals without geting damaged? is this a specification of the interface or this can be tested electrically?


texts: Lower supply voltage LED status indication

texts: I have implemented the circuit as shown in attached image for 2.1V status LED indication. But after turning OFF VCC_2V(=+2.1V) while VCC_5V(=+5V) ON condition, LED is not turning OFF immediately. Can anyone please correct the circuit implementation?


texts: How to use 3.3 V FTDI Serial Cable with LeMaker Hikey 620 which has 1.8v UART signals

texts:
I have FTD Serial Cable TTL-232R-3V3 which operates on 3.3V.
https://ftdi-uk.shop/collections/usb-cables-ttl/products/ttl-232r-3v3-2mm

I was trying to use it on my Hikey LeMaker for an hour with no success. Then I realised that the signal levels are different which might be the reason that I was not able to establish a serial connection.
On LeMAKER Hikey, user guide, UART3 uses 1.8V signals and hence its perhaps not compatible with my FTDI Serial cable which operates on 3.3V

Is there a way/hack so that I can use this 3.3 V cable on hikey? I am not good in electronics, so cosider me noob. Can I take use of 1.8 V from Hikey Board or can I use a similar trick like this one :
https://discuss.96boards.org/t/1-8v-uart-ttl-to-usb-diy-for-around-5-for-ce-boards/1911

Or can we use bi-directional logic converter here, something like this : https://robu.in/product/level-converter-4-channel/?


texts: I have designed a model reference adaptive controller for which I have obtained the step response for different values of adaptation gain. I have attached the output graph obtained. Can anyone please tell me why there is a gap between the model output and the actual output of the system


texts: Commonly used standard for telephone wires

texts: What type of wires are commonly used as indoor phone lines? I'm curious to know what is their bandwidth compared to my CAT5 cable that I use with DSL modem.


texts: How to interface with an H-bridge IC (L298N) using a single PWM pin

texts:
I would like to know if it's advisable to control an H-bridge IC (L298N) using a single PWM pin?

Let me explain: By driving ENB pin High and by feeding complementary PWM (achieved by using a simple NPN transistor inverter circuit to invert PWM signal from Arduino) to IN1 and IN2, the dc motor connected to OUT1 and OUT2 is working (circuit schematic shown below).

In this setup, I am only using a single PWM: a duty cycle of 0% is maximum speed in one direction, a duty cycle of 100% is maximum speed in the other direction and a duty cycle of 50% stops the motor.

Apart from having a reduced resolution, everything seems to work. However all the tutorials online advise to use 3 pins to control L298N, with the PWM pin connected to ENB (for example this Tutorial). Why is this so? Is it not advisable to do what I did, using a single PWM pin?


texts: Temperature dependence of the energy bandgap and Simulink way

texts:
I know the equation about the temperature change of band energy

but Simulink must find another way to define it like below.

dEg=-2.677 10^-4
I can't find a single reference about that equation. I hope someone in here know it.


texts: What microcontrollers are suitable for a keypad

texts:
I'm a beginner in electrical engineering but I'm into mechanical keyboards and I want to build a keypad (1 row, 6 cols).
I recently wrote a macro for a keyboard (ATmega32U4 microcontroller) using the QMK Firmware and I'd like to restart from there.

What microcontroller should I use to build this keypad and what resources or open-source projects should I look at to get there?
I prefer the AVR family since I'm more familiar with but any advice is helpful at this point!

Thank you.


texts: How to output Fiducials to Pick&Place but exclude them from BOM in Altium?

texts:
In Altium, the (not so) obvious way was to set the Fiducial component type to "Standard (No BOM)", but this also prevents them from showing up in the Pick&Place output.

I could set the type so "Standard" and manually add a filter in the BOM each time, but that is far from ideal. The filter does not support using a negative mask (like: "hide all where designator contains FD*) and its cumbersome.
The preferred way would be if the behavior is tied to the Fiducial component itself.

Does the typical manufacturer actually care if Fiducials appear in the P&P data or not? (the last one cried at me for not having them in the P&P data). But isn't the same extra step required if you have a panelized design with "extra" Fiducials on the panel which have no reference coordinate with respect to the board?

Am I missing some easy way to achieve it?
How do you do it?


texts:
In my design, I have a +3.3 V SMPS that provides power to digital circuits (microcontroller, EEPROM, etc.). The microcontroller allows applying a 100 Hz PWM signal with variable duty cycle and with an amplitude of +24 V to a resistive load. This is done with the following circuit:

Where:

HEATER_PWM is a 100 Hz PWM signal with an amplitude of +3.3 V coming from the microcontroller.
HEATER_A and HEATER_B are the connections to the resistive load.
HEATER_ISENSE+ is the voltage signal used for current sensing.

+3.3 V power supply

+24 V power supply

This is the plot of the +24 V power supply when the PWM is activated.

Issue

When the 100 Hz PWM is enabled (and only when it is enabled), the +3.3 V power supply produces an audible noise which seems to be at the PWM frequency. I suspect that this is due to the power inductor "vibrating" at 100 Hz.

I tried to increase the value of R116 to 100 kOhm without any effect.

How could I get rid of this acoustic noise?


texts: Trying to find an electronic single-pole multiple-throw switch

texts:
I am trying to find an electronic component that does the following.
The electronic component is basically a switch, that can switch to many different wires, based on a given input. This input can be a digital binary number or an analog input. This is used for a very low current application.  I am an electronics beginner and I am not sure if such a component exists.


texts: Power MB102 from a USB port in the computer

texts:
Just bought a MCU ESP-01 which requires maximum 3.3V and uses at peak 200mA. So to power my projects, I also acquired a breadboard power supply (MB102) which can output 5V and 3.3V simultaneously. It's powered by a 6.5 to 12V power source, either through a USB connector or the other connector (which I don't know the name).

The problem is that the MB102 requires an input source of at least 6.5V and I don't have any power supply to feed it. So my question is: Will it be enough to power the MB102 using a USB male-to-male cable connected to my computer USB port? I will only be using the 3.3V option.


texts: Advice for low voltage electrolysis system please

texts:
I want to setup a simple electrolysis system with an energy source, two cables, a graphite anode and a steel cathode submerged in sea water. A low voltage of exactly 1.23 V needs to be applied over a couple of weeks with as few interruptions as possible.

I only have rudimentary knowledge about electronics. Some help would be greatly appreciated!

The wall sockets at my place deliver 230 V and an AA battery about 1.5 V. How could I reduce the voltage to the required 1.23 V? And what would be the most secure and reliable energy source, keeping in mind that the system stays connected over a couple of weeks?

What hardware should I get for the system? Does the diameter of the cables play a role or is any size fit for the job?

Any help is welcome! Thanks.

Edit (10 Oct. 2018):

Edit (13 Oct. 2018):


texts: Z80 Instructions with accumulator as both operands?

texts:
Currently I am reading up on some documentation on the Zilog Z80 instruction set.  There are a few instructions that has one operand that involves the Accumulator, which is denoted as an 'A' in the data sheet, and another operand that takes any of the registers within the CPU.  For the purposes of asking this question, I will only focus on the "ADD A, r" instruction.

As taken from one of the Zilog Z80 datasheets, this is what is presented on the instruction:

As seen from the possible registers that can be chosen, register 'A' is one of them.

Register 'A' is also the Accumulator as given here:

My question is, how is it possible to put both operands as the Accumulator?  One thing I should also clarify is that there are other instructions that have this same kind of situation.


texts:
I have a question, my book says that for the system in this picture:

If the system has G(s)*H(s) with a module of 1 (0dB) and a phase of -180°, the system is in Simple Stability, so it is like in this picture:

So if we apply a disturbance, the disturbance will not make the output grown too much, since the new point of stability will be translated not far from the old point of stability, but now I have 2 questions:

How is it possible that the output will not go to infinite? I mean we have \$ \frac{G(s)}{1-1} = \frac{G(s)}{0}=\infty \$, so the system will be blown up, but my book said that the system will be stabilized to a point near the old point of stability.[Note that we have -1, because module 1 and -180° mean a signal of -1 (The - is added by the 180° phase)].
Let's assume that we have a stable system, \$W(s)\$, so with a module of for example -100(-40dB) and a phase of -180°, if a disturbance is applied,for example 1V (I know that in reality this will be impossible) the disturbance will become a disturbance of -1V, and when it go in the feedback node since in the node there is a -, we will obtain a positive feedback that will destroy the system, how is it possible that this system is stable?


texts: Is a capacitor a high-pass filter or a band-pass filter?

texts:
This has been bugging me for a while now... Does a single capacitor, on its own, behave as a high-pass filter or a band-pass filter?

In a crystal radio set, you use a single capacitor as the tuning element, to select which radio frequency the radio will receive. This strongly implies that a capacitor is a band-pass filter.

But reading Wikipedia, it is suggested that a capacitor is actually a 1-pole high-pass filter.

Well, obviously it can't be both. So which is it?

(Bonus points for anybody who can point to an actual frequency response curve.)


texts: How to communicate with Keithley devices on linux (without NI VISA)?

texts:
Keithley devices let you read/write commands/data over GPIB (examples). LabView has dedicated blocks (VIs) for this purpose, and other wrappers such as PyVISA use the commercial VISA drivers by NI.

Is there another way to communicate over GPIB with Keithley devices without NI VISA?


texts: Op-Amp Input Offset Voltage Affect Dynamic Range?

texts:
In an audio system, with an AC coupled signal into an op-amp with unity or low gain,
does input offset voltage reduce usable dynamic range?
For example, if a TL071 has an offset voltage of 1mV, and my average AC audio signal is 10mV, are quiet parts of the signal effectively lost?
Google has been unclear, but it seems reasonable to me that any AC signal within the offset voltage band would be nulled out.


texts: Are there any electrical components which may keep electricity inside them after the device is turned off?

texts: Is there any electrical component where electricity may remain after a device is turned off?


texts: "Capacitor" for regulating AC line voltage?

texts:
I have an issue with my air conditioner. When it clicks on, the lights in my apartment dim for half a second.

If this was a car audio system, I would just wire some large caps up to the battery to smooth out those current spikes.

However, this is an AC circuit and a cap won't work here. So what's the equivalent?

What can I install on my circuit to help smooth out these spikes and prevent that annoying voltage sag?

Changing the wiring of my house etc is not an option, I need to fix this myself, so please don't suggest that.


texts: How realistic is the famous "Bill sux" picture of a chip internals artwork?

texts:
There's an urban legend that some version of Intel Pentium chip had "Bill sux" caption somewhere on the circuit. The legend is accompanied with this picture:

Now let's assume for a moment that the legend is in fact true.

How realistic is the picture? Specifically why are all the elements of the same color? Why don't traces differ in color from the surroundings?


texts: 18650 battery pack with "dead" cells, other cells still usable?

texts:
I have an 18650 battery pack (12p20s so 240cells) with 2 parallel groups which recently "died" (voltage is 0v or very close to 0v (0.09v for one of the packs 0.0v for other parallel group). All other parallel groups in the pack are approximately 3.6-3.7V. The (dead) cells most likely died because I discharged/charged the cells without using a BMS for a long time (since my bms had broken and I was too ignorant to replace it right away).
I am quite sure the cells were never over-discharged (<2.5v) since the total pack voltage remained above 65v (3.25 average). However, I am sure the cells were badly overcharged for many charge cycles (seeing as when I decided to replace my BMS with a working variant eventually, some of the cells were already 4.2V when the total pack voltage was approx 78v. So I'm quite sure that killed them...
My question now is: Should I even consider re-using cells from this pack for building a new battery pack? Or should I replace all cells?
Does testing the cells for capacity and internal resistance give a good indication of how much the cell was overcharged/overdischarged/overheated? Or is there no real way to measure the 'health' of these cells properly? How much of a negative effect does overcharging and discharging have on capacity and internal resistance?
Thank you very much for any input, it is greatly appreciated


texts: How to create a simple audioplayer-device for a single soundeffect

texts:
How can you create an audio player device which can play a single sound effect when a button is pressed?

A button and the speaker should not be the problem, but the tricky part is, what I have to do with the circuit board, where to save the sound effect and all that stuff.

To power it, I'd use a 9V battery or multiple AA's or are there any other suggestions?


texts:
I designed a board with a microcontroller (Atmega328), 3 relays and a RS485 transceiver. The relays control SMPS LED drivers (Meanwell LPF series). The system consists of 10 boards, each one controlling 3 drivers, for a total of 30 drivers. These boards are the slaves, while a PC running linux, with a USB-RS485 dongle, acts as the master.

I don't have any problems with comms (Modbus RTU at 9600bps) as long as the power supplies are disconnected or the relays are turned off. Immediately after SMPSs are powered on, noise appears on the bus (and stays), completely killing communications. The noise is seen as a huge amount of random data on the python script manning the communications. If I disconnect the drivers, comms are reestablished. If only a few drivers are powered on (less than 10), no problems are observed. Connecting more and more drivers begins to add noise. Between 10-15 SMPSs the bus becomes unreliable, more than 15 drivers, bus becomes unusable.

I implemented this design (same board, but with HLG series drivers) in other installations, with up to 60 drivers, with no problems. I can't find in the driver's datasheet any substantial differences.

My questions are:

Can a faulty/very unregulated electrical grid be the culprit of this behavior? (this control system is implemented in farms, where a poor quality electrical grid is common)
Does Total Harmonic Distortion play a role in this?
The bus connects to the dongle using only A and B, the third connection (shield) is not used. Should the GND plane of all boards be connected to this pin?
Any ideas on how to solve the problem? (without changing the LED drivers, not even sure if this solves the problem)


texts: Does shorting this branch disable these resistors?

texts: When I short the branch across the nodes connection R15 and R10 will they be disable, and I only need to calculate R6||R6||R24 + R2?


texts:
i want to limit the current through a MOSFET (high side) as simple as possible.
The MOSFET will switch 600V and approx. 150mA for 1-2 seconds.
The focus really lies on simplicity.
I know that i can control the drain-souce current through gate voltage.
But is this reliable?


texts:
I have an application where we use RS485 to communicate messages to a series of LED Displays on the bus. Our first version of the board seemed to work fine with no problems, however we have made a new revision that is using a different RS485 Transceiver and now some displays do not receive their messages reliably. However not all displays on the bus are being affected. Only one or two are being affected. We never had to use any biasing resistors or terminating resistors with the first version so I can't see that as the problem for this case. The only thing I can see that might be causing the problem is the change in RS485 Transceiver that was used.

The first 485 Transceiver we used was a ST485C, however, the new board is using a SN65HVD485E 485 transceiver. Is it possible that the change in chip has caused a difference in performance? I know there is only one way to find out, but I just wanted to know if this was a reasonable causation?

We also use Cat5 UTP cable and use the following pin configuration. This is T568a standard.

RS485 B
RS485 B
RS485 A
GND
GND
RS485 A
VCC
VCC

I know that the above wiring doesn't follow RS485 standard wiring, but it worked with the last Revision and I can't see how this could be the reason for the current problems.


texts: Why should I use a pull up/down resistor for a GPIO output pin?

texts:
I know there are lots of similar questions and read them, but I need a simpler and clearer answer.

I understand why and how to use a pull up/down resistor when using a button (GPIO input). But while configuring a GPIO pin which will be connected to an LED, what is the use of these settings?

I tried no pull-up and pull-down and pull-up for example, but I could not see a difference in the implementation.

I am using STM32F407-DISC.


texts:
I'm following instructions from Charles Platt's "Make" and trying to mount PUT oscillator. Strangely, it blinks only once when I switch on the DC current, no oscillation was observed. I have tried different combinations of resistors, changed capacitor from 1 uF to 300 uF, voltage source from 6V to 9 V, however, there is no any significant change in behaviour of my oscillator.
Here is the schema:

And here is my plate with all data measured by multimeter:

Please, can anybody tell me what is my mistake?


texts: Gradually increase the voltage to fade in LED

texts: I understand how to fade out the LED with capacitor, but I don't seem to understand how to 'fade in' the LED. Can I also do it with capacitor or do I need to use resistor? because if I put a resistor, the led never fades in, just gets weaker. Thanks


texts: Theoretical: Would it be possible to have a worldwide AC standard at 55hz

texts:
The question comes from a discussion I had years ago with a keyboard player who had perfect pitch.  His problem came from the fact that he lived in a very small appartment in an old building and he had to play at a very quiet level.  So quiet that he could hear the 60hz humm (we are in north america) coming from electric appliances and that would bug him a lot.
He thought about it a lot and he realized that the electricity itself was actually out of tune.  Since most modern occidental music is based the reference not of A=440Hz, if you go 3 octaves below that, you get to 55Hz.  But AC around the world is either 60Hz or 50Hz.
When he made that calculation, he declared that 55Hz would be a very convenient and musical average if there is ever a worldwide standard.

So here is the question.  Is there a reason for 50 or 60 Hz?  Or it might as well be 55Hz?


texts: Can computer speakers emit ultrasound? What is the maximum frequency that computer speakers can produce?


texts: Monitor goes to sleep immediately after reboot

texts:
After booting my BeagleBord (Original Rev C5), Monitor shows the ubuntu login screen and everything seems fine. but after few seconds the monitor goes blank and displays "Going to sleep".
Why does this happen? and how can I prevent this?

Note: I am using a VGA cable and a HDMI/VGA converter to connect Monitor with the Board


texts: Are there any modern tradeoffs that come with designing more efficient DC-DC switching power converters?

texts:
Are there common metrics that usually degrade (ex. ramp time, line/load regulation, low-load efficiency) when pursuing more efficient designs, especially for isolated converters?

If you saw a new isolated high-power DC-DC converter advertising 99% efficiency, what performance factors would you be skeptical about?

(sorry if this is too broad again, still getting used to what scope I should write my questions at, and I have a lot of questions I'd like to ask.)


texts: Binding LM4871 audio amp output to another circuitry with ground referenced input

texts:
I using LM4871 as a audio pre-amp in my device. If I let the output to earphones or external speakers then it works great. If I want to loop LM4871 output (pin 5 and 8) back to one of the local audio inputs then I have a problem. LM4871 output is not referenced to ground (looked with oscilloscope), but my other inputs are. How should I solve that?
Here's the LM4871 application circuit I'm using:

[ http://www.ti.com/lit/ds/symlink/lm4871.pdf ]


texts:
I'm trying to do a current controlled resistor, but I dont know how to use .param, .subckt or .func to make it.

How can i do a current dependent resistor on LTSpice?
ps.: This is what shows up about the error
]2
ps2.: the new netlist


texts:
I have a wireless sensor circuit with a microcontroller and a 2.4 GHz transceiver module, some integrated sensors with I²C interface, a UART port and the necessary discrete components.

This board is designed for scavenging power from a solar (PV) panel, with a LiPo battery and a shunt charger. This allows the sensor to be self powered and be operating for an indefinite time, requiring the least possible maintenance.

I'd like to explore the possible faults that can occur in a system like this, and that can be due to aging, violation of environmental specs (temperature, humidity and so on) or wrong maintenance (not design issues/bugs), in order to maximize its operation lifetime.

The environment in which the sensor node operates is a building, sticked to the ceiling or the walls. So extreme temperatures or rain are not considered.

What I came up with are some faults that I try to summarize:

Component broken -> open\short circuit
Sensor faulty -> wrong output values (but how wrong?)
Defecting isolation due to dust\water -> increased leakage
Temperature out of range -> ???

How can I estimate how the sensor node is going to fail, and why?


texts: Why don't SSDs use the +12V rail for programming/erasing?

texts:
According to the wiki page on flash memory, flash chips have built-in charge pumps to step up the 1.8v supply to a higher voltage to program/erase the cells. This wastes a lot of power and is apprarently a common failure mode. The wiki page mentions the idea of using a single shared boost converter for chips with a separate Vpp pin, but apparently this is not very common anymore. Besides, this still seems like only a half-solution; I recall reading that this voltage is on the order of 5-10 volts, a voltage range that is abundantly available on PCs.

For SATA SSDs, one could use the 12V rail if available, and fall back to a boost converter drawing power from the 5V rail; for standard PCI-e cards, there's a guaranteed 12V supply available. (m.2 appears to only have a 3.3v supply, which begs the question of why, given what appear to be obvious advantages of higher voltage supplies for flash)

I understand single power supply is convenient, but surely a couple more layers would be worth it for the efficiency and performance(?) benefits. And economies of scale doesn't seem like a good explanation, given there is a pretty large market for high-performance flash.

So, why are single-power-supply flash chips so ubiquitous?


texts: Converting Christmas Village from DC to AC

texts:
So this was the year we bought a AC-powered O-gauge Lionel train and a battery-operated village to add to our Christmas tree decor. The problem, the village eats batteries like a kid eats cookies.

Here is the setup:

3 village houses running on (3) AA batteries each [1.5V * 3 = 4.5V each house]—batteries last the longest here, two houses have 1 LEDs, the church has 2 LEDs.
1 village skating rink that also plays music and goes through batteries faster (3) AA batteries [4.5V]. There are 2 bright LEDs, 2 lamp LEDs, and 16-17 LEDs that blink to the music.
2 street lamp posts running on (1) 3.5V CR2450 button lithium battery [3.5V each lamp). The box calls it 3V—these batteries go fast too.

The bulbs are not designed to be replaced and there is no such indication of the watts or mA consumption.

The options as I see it are to buy a AC-to-DC power adapter for each of the two circuits above—3.5V circuit/adapter and 4.5V circuit/adapter. I have found for example, an AC adapter with a DC output of 3.5VDC@400mA. I have no idea if that would work for the lamp circuit and if done in parallel to keep volts the same at 3.5, does that 400mA become 800mA and what that means to the bulb that is currently running on 3.5V@650mAh. I guess what I need to learn is what rating that bulb could be on a unit where a bulb is not designed to be replaced or its mA use documented.

The other option of course is to create a custom circuit board and get my hands dirty in the details—I have 10.5 months so I'm open to it. I would imagine a single AC input split into two circuits that are individually transformed. I would love to have a setup on a board where I had screw terminals, one for each circuit to add each unit (house or lamp) to the board. Are there kits for this?

I greatly appreciate any thoughts, directions, and/or lessons.

UPDATE #1
The current in mA for each device is as follows:

2 Street Lamps draw 10mA@3V each (each one has 3 small LEDs)
2 Houses draw 35-40mA@4.5V each (each with 1 LED)
1 Church draws 40-50mA@4.5V (2 LEDs)
1 Skating Rink draws between 10-240mA@4.5V (16-17 LEDs, 2 constant, the rest flashing, plus plays music)

Total per circuit:

20mA@3V
85-330mA@4.5V

UPDATE #2
With confidence gained from suggestions here, I've cracked open each unit.

The lamp posts with 3 tiny LEDs in each, have a 51Ω±5% inline resistor.
The houses have no resistors (1 LED in each house).
The church (with 2 LEDs) has 2 lines to the positive battery post, one without a resister, the other with a 220Ω±5% inline resistor—my guess is this is going to an LED in the tower and dropping the power/brightness a bit for the small space to equalize the appearance of the 2 lights.
The skating rink has no in-line resistors, but a printed circuit board and speaker.


texts: How to switch both AC and DC voltage to a load

texts:
I have a load, an electrode basically acting as a very tiny capacitance, that I want to supply a voltage or bring to ground. The voltage can be either DC, up to about mains voltage, or AC into low KHz frequencies. I'm trying to switch this voltage supply on or off digitally using a microcontroller.

What components or circuit will let me do all of this? I don't believe I can use normal relays, because there is going to be more than one electrode, the footprint of the circuit has to be rather small, and the electrodes will be switched rather frequently. I just recently learned about a number of devices that will only help me switch either AC or DC but are not capable of both, so I'm looking for any tools or techniques I'm not aware of yet.

Edit: As for the electrode current, if the switch is DPST between the hot line and ground, then I expect it to be 1 mA or less, since the electrode is basically a capacitor on the order of 10 pF with a very large resistance. If the electrode cannot directly be grounded by the switch, then it needs some way to bleed off any charge, so another medium resistor might need to be added to accomplish this and the current would be slightly higher. The purpose of the electrode is just to bring the surface just above the electrode + a dielectric layer to a given voltage, there will never be real current draw.

The switching rate might be something like 0.5 Hz sustained for half a minute, or it might be even more for a longer period, but I can't be absolutely sure.


texts:
I have been working on design for which I have a reference schematic. I came across the following crystal setup:

I've always seen crystals being connected to two pins on an MCU, like XIN and XOUT with its corresponding capacitors to make up for the required load capacitance.
In the reference design, the crystal is connected only to the XIN pin—in fact, there is no XOUT pin. At the beginning I thought it was an active oscillator but it is indeed a simple crystal.
How does this work? Does it have to do with series/parallel resonance of the crystal?
Thanks


texts: Is there a way to Divide two 8 bit number in PIC 18fXXX assembly language not C?

texts:
I Can easily do the division in C of PIC micro controller.
But is there a way to divide two number stored in two 8 bit registers.
For example look at this code.
I have to do it in PIC assembly for 8 bit Microcontrollers.

ORG 0H
R1 EQU 0X06
R2 EQU 0X07

MOVLW D'64'
MOVWF R1
MOVLW D'8'
MOVWF R2

; We want to Do R1/R2 We can assume that R1>R2 and we don't need Decimal Values
;SUGGESTIONS?

END


texts:
I attached the question as well as my design, I don't know why it does not work( I get no output on simulation).
could you have a look at it and comment on it?
Thanks


texts: Understanding Mosfet simulation and initial conditions in Spice

texts:
Here is a simple circuit with a P mosfet. I got a strange behavior when powering a circuit, so I isolated this part to understand it.

Circuit is powered at t = 3s (I've used a pulse input voltage source to simulate it). Here is a zoom on power on :

blue plot : input voltage
green plot : PMOS gate voltage
red plot : output voltage

As we can see, when circuit is powered on, during a transient phase of some µs, PMOS is closed.
How can we explain that? Are some initial conditions missing in LTSpice simulation?


texts:
I've been given a bench grinder (rated for 150W @ 230V), which uses a (psc motor?), just an induction motor with start/run capacitor/winding (it has no centrifugal switch whatsoever).

I always wanted to use an atmega to make a 3 phase inverter for motor control, but the high voltages and currents involved at mains have always set me back.

So I thought that being useless as a grinder, because it bogs down as you try to sharpen anything (besides that I already have one three times as powerful), I could try rewinding it for 12 volts three-phase and use a pc power-supply to play around with it.

That way I'd save the mains-filtering and rectification part of the inverter, and yet have 5 volt supply for the micro out of the box.

However, been looking for a while on the internet and found nothing related, so just wanted to ask, would it be worth the effort?

I still have to count motor's number of poles to check it can be three-phase, but the fact nobody has ever done this before leads me to ask.

Cheers!


texts: Matching speaker specifications with bluetooth audio board specifications

texts:
As the title states, I am having trouble interpreting the specifications for a Bluetooth audio board I have to determine what kinds of speakers I need, or if I need an amplifier circuit between my speaker and my bluetooth audio board.

For reference, the specifications of the Bluetooth audio board I used are here, and the specifications of the speaker that I am using are here.

I'm assuming that the important specifications for the audio board are the sensitivity and the frequency range, and that the only important specifications for the speaker are the resistance and the power rating. But like I said, I have no idea how to find out if they are "right" for each other.


texts:
On rare occasions, my ATMega169PA resets with MCUSR=0. What can cause this?

I have multiple units (> 500) running the same code and on rare occasions 1 or 2 units will reset with MCUSR=0.


texts: 3-phase motor (hi-hp) fails on start, insulation was > 500 megohms. WHY?

texts:
This is a common situation in industry where the 3-phase motor has a resistive reactance fault (as small as 1% unbalance) PRIOR to start. Insulation has been subject to excessive heating but meets IEEE std. for safe operation. The trip occurs as reverse torque is generated due to current unbalance. Overload relays protect & function as designed.

Upon resetting the "ground fault" - insulation appears in safe range. At start, current is in excess of the "norm" in the effected phase (with the reactance fault). Current exceeds the 7-25X fla (dependent on motor design) and insulation fails! I have utilized this analysis on 3-17,500hp motors with a 95-100% success rate at predicting a pending motor insulation failure!


texts:
I'm going to assemble a prototype PCB which have components on both sides. I have access to a reflow oven with profiling control, solder paste and stencils (from OSH-Park)
In the reflow process for the second side, I expect that small components will stick to the board even in the melting temperature, as mentioned in this answer.
But I'm worried about a big component that I used on the board. SEDC-10-63+ is a 3cmx2cmx1cm coupler with weight of 7.3g. I have two of them exactly packed back to back on the layout. Because of the exposed pad at the bottom of package I cannot use a heat gun nor the hand soldering iron to solder the part. My question is that does the bottom part will fall off because of it's size or I will going to get a successful soldering and I shouldn't be concerned so much.

Non-Acceptable Answer
I know that I can use a low-temperature solder paste like this one, or using SMD Epoxy Adhesive but I'm more interested in hearing the limitation of simple reflow process about what packages can and what can't soldered using this method (with exactly dimensions and weight they have successfully/unsuccessfully assembled)
Thanks


texts: What happens in an 8085 if HOLD, READY, and RESET requests are received at the same time?

texts:
What happens if an 8085 microprocessor 8085 is executing a program and it gets a request from the Ready, Hold and Reset pins at the same time?
How will microprocessor respond?


texts:
I need to build a scale that is not attached to any computer. The goal is to weigh a dustbin and show the weight value on a small LCD screen. The weight I want to measure is approximately 10 kg, but I have to do the tare of the weight of the dustbin to weigh only the contents. The price of the equipment has to be cheap. I tried to look for an online solution and the only solution I found was with an Arduino. The problem is that the Arduino is connected and powered by USB to the computer and I can not use computer. How could I build the balance cheaply? Is there any way to run the program on Arduino without having to always connect it to the computer and feed it by stack for example?

Example with Arduino:


texts: Brightness when using 3.7v battery for powering 6 LEDs rated at 5v in a series

texts:
I am using 6 LEDs in a series (APA102C spec) these specifically powered by some atmega chip, and am having trouble finding a sufficiently small battery that will allow me to run the LEDs at maximum brightness.

My current working design is here, based on adding 3 E90 batteries in the square block as pictured below:

quite ugly, and does not fit the form factor of the rest of the device.

My question is what is the minimum voltage I can use to get the greatest brightness out of my 6 LEDs, and, how much worse off (in terms of brightness) would I be with a 3.7v? (the 3.7v are very small, which makes them attractive for my project). Also, what is the minimum mAh count I can target to get the LEDs to run oh, say, 30 minutes?

Suggestions as to which batteries may be a good fit in my "ring" would be further appreciated as well!

Thank you!


texts: Isn't there a Voltage drop across a resistor?

texts:
I've been reading this Wikipedia - Electrical Load topic and there is a section which is confusing me... So what you do is go to the "A more technical approach" section in this topic and then read the 4th line which starts with "With no load (open-circuited terminals)...".

Now the line says that "With no load (open-circuited terminals), all of Vs falls across the output; the output voltage is Vs." But how? Isn't there be a voltage drop across the resistor Rs? If not, why not?


texts: Is this design of a charge amplifier for a piezoelectric sensor correct?

texts:
This is the specifications that must be met: "Design a charge amplifier for a piezoelectric sensor that has 500 pF capacitance. It should pass frequencies from 0.05 to 100 Hz so that it can detect carotid pulses, and it should not drift into saturation."
This is the values that I was able to solve:

The resulting circuit looks like this:

I based it on a circuit I saw on the internet but I'm not sure. Was I able to do it correctly?


texts: Combining ±% with ±dB in measurement uncertainty

texts:
Firstly apologies if this is not the correct place to post this but wasn't sure which site would be good to ask regarding about measurement uncertainty calculation.

I am trying to calculate the combined measurement uncertainty, however the uncertainties I want to combine are using different scales:

Carrier level uncertainty: ±0.5dB (logarithmic)

Modulation uncertainty: ±5% (linear)

Converting either from one format to another will not give me a simple ±value in the other format

What is the best way to combine these uncertainties


texts: What will be the current i(0) in this problem?

texts:
I am doing b) and I am just wondering whether i(0) will be v_in(0)/R. Do I use 5 V or 2 V or is it 0?

Thanks.


texts: Turn on 12v car amplifier with ATX POWER_GOOD?

texts:
Does anyone know how to turn on a 12v subwoofer amplifier, using the ATX power supply control wire for POWER_GOOD?

I am using an Azza model PSAZ-1000A14S, 1000 watt, single 12v rail, computer power supply so that a car subwoofer can be used indoors for parties. This already works great just using a manual toggle switch on the amplifer.

The power supply: http://www.newegg.com/Product/Product.aspx?Item=N82E16817517008

Amplifier wiring: https://www.youtube.com/watch?v=NtKoavsVoVg

Opened the PSU and desoldered all unnecessary power wires for +5v, +3.3v, -12v, +5vsb, the 5/3.3v grounds, and miscellaneous ATX power plug wires. Combined the remaining +12v and Ground wires into two wire bundles, covered each with cable wrap from the original power supply cable groups, zip-tied the wrap ends, and soldered the +12v / Ground into an Anderson Power Products SB 175A disconnect plug with a propane torch.

For the box with the two LEDs, I am passing to it POWER_ON, POWER_GOOD, a +5v wire, a +12v wire, and a Ground wire.

Using at a dance: https://www.youtube.com/watch?v=vr0WfQz5G3w

But I don't want the amp to be direct connected with no control. If the manual power switch is left on, and the amp tries to fully power up before the PSU is ready, then the PSU internal protection may crowbar itself, due to it assuming there's a dead short as it turns on.

I would like the PSU to turn on the amplifier automatically using the POWER_GOOD output. I think the add-on car amplifier expects a 12v signal from the stereo system, but don't know that for certain.

I already tried buying a tiny 5v relay (SRD-5VDC-SL-C) and directly connecting POWER_GOOD to it, to supply 12v to the amplifier power-on circuit, but there's not enough current from POWER_GOOD to activate the relay. It can directly light a LED however, as shown in the first video.


texts: Skew angle in 3-phase AC induction outer rotor motor

texts:
I am working on a motor like the above stated.
I have 3-phase winding on a 24 slot stator.
I am now designing the rotor part.
What skew angle should i use for a very smooth rotational torque?
Is there a specific number of slots to be made on the rotor for my application?
What kind of metal is preferable: copper or aluminum?
Thank you for your input...


texts: Buck Converter Control Scheme- Why isn't just a comparator not enough?

texts:
I am supposed to come up with some control schemes for the converter before understanding the standard PWM control scheme.

Isn't it just enough if the output of the converter is compared with a fixed reference voltage to drive the output to required voltage level? Although I'm not sure there is a lot more to it, this seems to work pretty well.

I've tried simulating this circuit with L,C and R values from an example.

Schematic:

The required output voltage is 6V. S2 is a voltage controlled switch, controlled by the output of comparator.

V2(green) is the output of comparator and V1(red) is the output of buck converter.


texts:
The story for this signal is the following. I've bought an NAD C 356BEE amplifier with an integrated MDC DAC module. It has optical and USB input. The optical is OK, but if I connect the DAC to my PC with USB, then it makes clicking/popping noise at specified times. The click frequency is somehow related to the signal sample rate. For example at 96 kHz it pops in every 2.5 seconds, but at 48 kHz it pops at 30 seconds.

I've played a sine wave, and I've recorded the noise and zoomed in to the waveform. It's a very short signal, about 0.008 seconds. Do you have any idea what it could be?

The amplitude of the noise signal is much higher than the test signal. The length of the noise signal is random (but very short, you hear just a click), but the waveform is always the same for the same test signal.

Different test frequencies cause different error signals. It seems like the error signal is some transformation of the original.


texts: How to add a capacitor and switch correctly to piezoelectric circuit?

texts:
Am a hobbyist beginner with no prior electrical engineering knowledge (though can follow a basic circuit), so please bear that in mind when giving your valued advice! am following an instructable to build a piezoelectric circuit project.

The instructions say that the piezo elements generate AC and not DC so a bridge rectifier made of four diodes needs to be added, since the piezo elements will cancel each other's output if these diodes are not included.

6 piezo elements and 1 bridge rectifier is called for per piezo element to prevent this, however only one bridge rectifier is shown for 3 piezo elements in the instructions.

So far, I've followed the circuit below with 3 piezo elements and one bridge rectifier:

However, I'm aware that another 5 bridge rectifiers to be added (the other 3 piezo elements are underneath the white board I think). I'm looking for the following:

1) Can anyone describe the circuit diagram I should follow to include the additional 5 bridge rectifiers? here's the current circuit

I realize that each bridge rectifier should be connected on the silver wire connecting the piezos in the jpg, but then does that mean I need to connect all six wires from the rectifiers back to the - and + of the battery?

2) Can anyone describe/explain how to connect the circuit diagram with the rectifiers, capacitor + switch

3) An idea of what type of capacitor is best to use here (maybe a ceramic capacitor that can handle 100V, as it should be x3 the potential highest output which is around 27V? but may be incorrect)

Thanks for your help


texts:
Please explain  how the bootstrapping circuit help in driving both the mosfets connected to IR2101 driver.Please explain this by taking an example of any voltage so that I can understand easily.Explain how the capacitor charging and discharging during this procedure and the use of diode and resistor connected.
It will be really helpful for me if someone explain this


texts: 1-Wire DS2480B overvoltage and ESD protection

texts:
I'm designing a series of 1-Wire components for my SmartHome Bus and use the DS2480B as Busmaster. Because the cable I run around the house has 3 wires (24V, 1-Wire, GND), I'd like to protect the DS2480B from overvoltage caused by accidentally short-circuiting the 24V and DQ lines. If possible, the design should also protect the Busmaster from ESD.

Note that I don't use 12V EEPROM programming, so the Voltage on the 1W line should never exceed 5V during normal operation. The DS2480B has an absolute max rating of 14V on the 1W line.

This is the original circuit proposed by Maxim to RC-Filter the 1W line and to protect the DS2480B from ESD:

I think I cannot use the DS9503 because it requires that both GND and 1W go through the package. Because I have additional components further down the bus that draw several 100mA of current (from 24V) and the DS9503 has a max current through package of 80mA rating, I can't loop GND through the DS9503.

So I came up with the following designs:

Use a Polyfuse in Series with the Resistor (reduce the resistor so that resistor + R_Fuse =~ 62) and add a Zener-Diode between the DS2480B and the Resistor.

If 24V is connected to the 1W line, the Zener will short-circuit the excess voltage to GND and letting the fuse trip.
Problems/Questions:

Is this feasible?
What kind of Zener and Fuse would I need to use so the Zener survives the hit, and the Fuse adds a reliable, low resistante during normal operation?

Same as 1., but add a P-Type Mosfet between the Fuse and the Resistor.

Now, the Mosfet would short-circuit the 24V to GND, causing the fuse to trip faster and taking off load from the resistor and the Zener. However, the Mosfet has to take the hit this time. However, even the smallest Mosfets can take 0.8A continuous and 5A pulsed max currents, so they should be okay.
Use a Polyzen-Fuse such as TE ZEN056V075A48LS.

Problems/Questions:

During normal operation, the current would flow from V_OUT to V_IN through the package. Is this an issue?

Which design would you recommend, or what kind of dimensions for the components would you use?
Additionally: How do I protect all the components from ESD? Can I still use the DS9503 and just connect one of the GND pins (and if so, which)? or both?

Of course, if you have better ideas, I'm all ears.

Thanks a lot in advance!


texts:
I downloaded the datasheet for this MOSFET, but can't find where it labels the pinout anywhere. Has anyone used these before? I got them for cheap from Amazon, and I'm hoping to control some DC lights with them from an Arduino.

Here's the datasheet: IRL7833

From what I know, these are actually quite old, dating back to the mid 1990's. But I'm thinking that they should work fine. One thing that also confuses me is the max. gate threshold voltage, which is 2.3V. I'm a newbie to electronics, but is that saying the maximum voltage I can output to the gate is 2.3V?


texts: What is the unit for resonant frequency? where \$\omega_0 = \frac{1}{\sqrt{LC}}\$? Is it just \$HF^{-1}\$?


texts: Drive 230Vac load (bulb,fan etc) using microcontroller (3.3V or 5V)

texts:
i want to drive the the lights and fan used in home(230Vac/50Hz) using digital circuitry.
so kindly suggest me the best one.
1. using micro-controller i want to actuate the loads like Bulb,incandescent lights and also their dimmer action
2.drive fan and also control its speed.

Basically i have done it using the flow as shown
microcontroller to opto-coupler to transistor(BC547B) to relay.
but i came to know that the relay switching efficiency is poor due to which fluctuations in switching of Lights and bulb is observed.
so kindly suggest me some more sofisticated circuit to drive the loads as i want to design this circuit and implement in my home.


texts: Can I use the 12V line of a computer PSU to power my circuits?

texts: Or is there any issues I should be wary of? I need at least 7A on a 12V line, but I've found that a computer PSUs are significantly cheaper.


texts: Reducing 16.5VDC battery output to the range of 13.8VDC +- 15% without introducing noise for 15 Amp load

texts:
The title pretty much says it all. The (up to) 15A load is a ham radio, which is the reason for the 'no noise' constraint. Maybe a tiny bit of noise is OK? I don't know how I could tell.

To save you the calculation, 13.8VDC +- 15% = 11.73VDC to 15.87VDC

Of course I've thought about a buck/boost DC to DC converter, but I hear those are too noisy. Is there some kind of signal cleaner I could drop in after the converter?

What about a voltage divider? Could that work?

LM7812 seems like a possibility, but won't I be seeing huge losses? Not to mention I'd probably need 10 of them in parallel.

Thanks for your help!


texts: What is the difference between a static and non-static expression in vhdl?

texts:
suppose if I have two signal declarations as follows

signal x:std_logic_vector(1 downto 0) := (others => '0');
signal y:std_logic_vector(1 downto 0);

does that mean x is static and y is non-static?

Also does a vhdl function call fall into the category of a non-static expression?


texts: Bit-Structured Registers for Embedded Hardware

texts:
So I've designed a piece of hardware that has an Atmega168pa microcontroller communicating with an external IC over an SPI bus.  The external device has a few registers, with hardware mapped bits.

I'm looking for a way to easily manipulate this structured-bit data in the Atmega.  The first obvious solution is a bit-field, but I haven't had much success.

Goal is to try to map this into 3 bytes so that I can:
A) Access the data simply, e.g. n_reg.b_counter = 230
B) Write this structured data byte by byte with an spi_write(uint_8t) type function.  Obviously this would have to iterate through the three bytes, maybe with some kind of index.

What I've tried thus far:

struct PLL_N_REG
{
    uint32_t control_bits : 2;
    uint32_t a_counter : 5;
    uint32_t reserved : 1;
    uint32_t b_counter : 13;
    uint32_t cp_gain : 1;
    uint32_t div_by_2 : 1;
    uint32_t div_by_sel : 1;
};

struct PLL_N_REG n_reg;
n_reg.div_by_sel = 1;
n_reg.b_counter = 230;
n_reg.control_bits = 2;

This fulfills objective A as it's easy to access, but I don't know how I'd easily grab each byte in order to send to the spi_write(uint8_t) function.

I've tried doing something similar with hardware projects in the past but have ended up using work-arounds.  I'd like a method I can apply easily to any hardware I need to implement.  All of the other examples I've found have been for mapping microcontroller-internal hardware registers.

Thanks a lot in advance!


texts: SMPS circuit components need some explaination

texts:
I am pretty new to SMPS circuits. I understand there's a bleeder resistor, a flyback diode circuit to power the transistorized osc circuit. I guess that the current around the MOSFET will be like a pulse train.
Q1: What is the role of R1, D1 & C1? Is it a buck converter? Does D1 ensures biasing to R1 is not disturbed?
Q2: What role does R2 play? Restrict current to the MOSFET and biasing?
Q3: Does C2 block the biased DC voltage from entering the fly-back circuit?


texts: Powering an LED from RF (cellphone signals)

texts:
How can we design a cellphone detector similar to the one shown in the YouTube video, provided we set the following restrictions:

purely passive, (no external sources like battery)
power should come from RF signals from the cellphone

Notice that the brightness of the LED must be high. What components/diodes will we need and is there any schematics you could point out?

PS: based from the comments, they use RF diodes but didn't indicate any part numbers. Also, somebody tried it using RF diode/microwave diode but they failed to make the LED light up as brightly as in the posted video.


texts:
Suppose I've a circuit that is affected by EMI noises that have a freq. less than 80khz and noises above 2ghz. I want to cut off this noise freq. before they reach my ICs. The circuit is powered by 5 different voltage regulator on the same pcb with a single power supply from a battery.

In the first case I want to filter freq. less than 80Khz so I realize an LC filter with 3.3uH L and a 1uF C.

My problem is, where I need to place this filter?

A single filter between BatteryVcc and all voltage regulator is ok?
A filter for each voltage regulator Vin?
A filter for each voltage regulator Vout?
In the last two cases that will rise a lot my BOM. Is necessary?

Another question I have:

Since I have decoupling capacitors before my final connections, placing a filter before them, will change my C in my LC filter(more Cap in parallel)?

About 2Ghz noise:

Should I use a ferrite bead?
A ferrite bead between BatteryVcc and voltage regulators will create me problems whereas some voltage regulators power MCUs?
There's alternatives to void ferrite bead use?


texts:
In my electrical engineering lecture we analyse such circuits with given Resistances \$R_i\$ and given \$U_{q1}\$ and \$U_{q2}\$ ( see example below ), and we try to find the current intensity \$I_{i}\$ at each point.
We use a long way to find them using matrices (Elimination using Gauss process, matrice transformation, Kirchhoff laws... (see 2nd picture)) + one error can cost errors everywhere.

The problem is that I can't even check if my answers are correct when doing a exercise. Is there any tool on internet that calculates such things?

Can you recommend any more secure and quicker way to analyse it?

Thank you in advance.


texts: Why does a wound-rotor induction motor produce a higher starting torque?

texts:
I know that with a wound-rotor we can add external resistance and in this way reduce starting current but doesn't a lower current mean a lower torque?

I'm guessing that an additional resistance causes more things to happen and that's why the torque is greate, for example a smaller counter-emf.


texts: Moving a magnet through coils wound in the opposite direction

texts: Suppose I want to harvest kinetic energy by moving a magnet back and forth through a coil assembly. Faraday flashlights work by this principle, but to my knowledge those usually only have one coil. Could this design be improved by taking two coils wound in opposite directions from one another, wiring them in series, placing the magnet near the midpoint of the coils, and restricting the magnet's position to stay near that point? Or would mutual inductance from the coils cancel out the harvested energy?


texts: Need help improving the Caller ID FSK demodulation circuit

texts:
I have a project for which I need to be able to read Caller ID from the telephone line.

I found MT88E43B chip that does FSK demodulation. They have an application circuit in their datasheet (specifically page 15, Figure 11).

I have assembled it using the values for 5V power supply and increased speech immunity (C=0.1μF, R3=825K, R2=226K, R1=430K, R4=34K).

The circuit works great when connected directly to the VoIP device at the house, it can decode the Caller ID and I can successfully get it in the microcontroller for further processing.

However, if I connect it to the house wiring when the VoIP device is wired through the patch panel, it reads gibberish from the line.
I did the testing and found out that a regular telephone, or even a modem, can easily read and decode the Caller ID signal when connected to the same outlet, while this circuit can't.

I did some measurements, and of course there is a lot of noice on the line in range from ~200 Hz to ~5 Khz that runs on top of 60 Hz.
I guess I'm missing some sort of a filter before the circuit, or it needs some input adjustments.

At this point I tried using a ferrite choke and a DSL filter with no help. Currently my best idea is to use 2 parallel LC bandpass filters for 1200 and 2200 Hz respectively, and I'm looking at 2nd order Butterworth because of its simplicity.

It's a hobby project, and I don't have enough knowledge to figure it out on my own, so I would highly appreciate any advice!

Here's the schematic I'm talking about:


texts: Computing the voltage across a parallel LC component at resonance?

texts:
Problem

For the circuit illustrated below, I am trying to compute the sinusoidal voltage across resistor \$R_{1}\$ when the parallel LC component is in resonance:

I setup my problem with the following information:

My voltage source produces signal: \$V = 8\times sin(\omega t)\$
My voltage across \$R_{1}\$ is going to be a voltage divider: \$V_{R} = V \times \frac{Z_{R}}{Z_{R} + (Z_{C} + Z_{L})}\$

The Circuit

Reasoning

At resonance, I know that my angular frequency will be: \$\omega_{0} = \frac{1}{\sqrt{LC}}\$.

This should remove the impedance component for the parallel LC part of my circuit. I show that now:

$$V_{R} = V \times \frac{R}{R + \biggl(\frac{1}{j \bigl (\omega C - \frac{1}{\omega L} \bigr )}\biggr)} = V \times \frac{R}{R - j\biggl(\frac{1}{\bigl(\omega C - \frac{1}{\omega L}\bigr)}\biggr)} = V \times \frac{R}{R - j(\frac{1}{0})}$$

This results in an undefined solution though. However, I also know:

If there is no impedance, then the resistor is the only component of the circuit providing resistance
Thus the voltage is simply determined by the resistor.
In which case won't the voltage across the resistor simply be the same as the voltage produced by the source?

What confuses me is trying to reconcile these two explanations I have been given. I am confused as to why I cannot obtain something like \$V_{R} = V\$, assuming that is indeed the correct measurement for the voltage across \$R_{1}\$.


texts: Phase difference between voltage source's voltage and current

texts:
I tested a simple circuit with AC voltage source and, when I probed the source input for voltage and current, I was surprised to find that they were 180 degrees out of phase.

I tested in the LTSpice simulator.

Is it normally like that in real world or something to do with the simulator or my circuit?

and the wave generated is


texts: Measuring voltage across a resistor using a micro controller

texts: I want to measure voltage across a resistor using the ADC of a PIC micro controller. But my problem is that both ends of the resistor are above GND and may be above 5V. But the difference is always =<5V. I need a circuit which operates at 5V, because i can use only a 5V supply in my design.


texts: How are air-core inductors typically constructed?

texts:
I'm considering learning to build air-core inductors for power applications.

For example, I presently want a .5-1 mH choke capable of handling 50 amps for two seconds. Winding my own air-core seems like it might be a cost-effective solution, but I'm not clear on how large coils like that would be physically constructed and held together.

I've used cable ties before, but that's a cheap and quick solution, not something I'd want to use for production, especially in any sort of high-vibration environment.

Is there a standard way such things are typically built?

Edit: these chokes are intended for use in ~600 VAC systems, so the insulation is going to have to have some pretty high withstand ratings.


texts: Why do mobiles phones have non removable batteries at all?

texts:
Doesn't a removable battery have a lot of advantages over a non removable battery?
In case the phone drops in water/the battery gets faulty due to whatever reason, we can always change the removable batteries and voila, problem solved!

why do manufacturers produce phones with non removable batteries at all? is there some significant benefits of having a non removable battery over a removable one?


texts:
Why is it that surface mount (SMT) PTC fuses can only be used on DC lines but through-hole PTC fuses can be used for both AC and DC?

This came from a cautionary note on one of Bel Fuse's PTC application note documents.

Page 3:

I've also seen Littelfuse documents that specify the working voltage as VDC instead of VAC/VDC.

The only time I've seen reference to AC PTCs is with these THD parts from Bel Fuse: https://belfuse.com/resources/0ZRE%20Sep2016.pdf


texts: Impedance Matching using Transmission line

texts:
Hi! I was looking at this research paper for Energy Harvesting through Rectanna and I stuck with this thing. The author, first, calculated the Rzin of the rectifier circuit. He had a source resistance of 50 ohms. Then he calculated the length and width of the transmission line which he was using for impedance matching.
My question is how he calculated this? is there any formula or relation for finding these parameters? In the paper, there is nothing mentioned about this. Please let me know if anybody has knowledge about this. Thank you.


texts: Help with a full bridge three phase rectifier powered floor

texts:
I originally posed a question here asking about solutions to power a small rover 24/7 from a powered floor.

It seems the best solution is a full bridge three phase rectifier circuit.

I have a few questions about this:

What zener diodes should I use for such power (and I'm presuming they are all the same, just different directions)
Any suggestions for the component to use for brushes under the rover?


texts:
I am beginning to learn AC circuits and am trying to analyze the following RLC circuit:

I want to find the real-time voltage across the resistor. I believe I will do this by finding the current with I = V_p / Z then use that current to find the voltage on the resistor. I'm not sure how to calculate Z in a parallel circuit. Would I do Z = (1/(Z_R + Z_C) + 1/Z_L)^-1 as I would with resistors in parallel?


texts: Looking for a pin-compatible to LT1013DID rail-to-rail in/out op-amp

texts:
I have designed a circuit using LT1013DID (SOIC 8 footprint) op-amp and while Spice simulation worked, I forgot about input common-mode voltage limit (which it seems is not simulated) and thus need an in/out rail to rail op-amp which LT1013DID isn't (it is out rail-to-rail only) as my real-life circuit/PCB does not work near power supply voltages.
LT1013DID has a specific footprint where pin 1 is A-IN and not A-OUT.

I am wondering if anyone is aware of any other op-amps with such footprint layout that I could use as a replacement?
So requirements are: 2 channel SOIC 8 in/out rail-to-rail op-amp with a single supply of more than ~17V that is pin-compatible with LT1013DID


texts: Just wanting to ask if there's a way that an old computer could be like a microcontroller. In the sence that it has a range of pins (standard, PWM and analogue), both input and out put could be emulated by the operating system.


texts: How can I find the equivalent resistance, Rxy, of the two NMOS transistors in Figure 5.25 in Razavi's "Design of Analog CMOS Integrated Circuits"?

texts: While calculating the gain (\$-G_mR_{out}\$) of the differential pair (with active current mirror), in order to find \$R_{out}\$, how is Razavi able to substitute M1 and M2 with \$R_{xy}=2r_{01,2}\$?


texts: Amplify current from a 4-20 mA temperature controller to drive a Peltier module

texts:
I have a temperature controller (Chino DB1000) which has a PID output of 4-20 mA. With this, I want to control the current going to a Peltier thermoelectric module (15V, 6A).

I am doing this via an ON-OFF circuit with a DC solid state relay, a 15 VDC power supply, and a temperature controller for SSR. But I don't want to keep doing this since the ON-OFF is not good for the thermal control or for the Peltier itself.

Is there any simple circuit to convert the 4-20 mA from controller to a regulated current to the Peltier? The 4-20 mA are not the sensor signal, but the processed PID control signal from the controller

After searching similar questions, I think that the answer might be towards PWM or MOSFETs.

Thanks a lot!


texts:
I have a EFM8 Sleepy Bee chip (EFM8SB20F32G-B-QFP32 specifically).  I would like to connect USB for programing etc. and I assume I connect the Data+ to pin 7(P2.7 / C2D) and Data- to pin 6(RSTb / C2CK).
Is this correct?  If not any information is greatly appreciated.


texts: How do I2C modules select between more than 2 slave addresses?

texts:
I am using the TMP112 I2C temperature sensor and noticed that you can choose between 4 slave addresses by connecting the A0 pin to V+, GND, SCL, or SDA.

How does the sensor tell between SCL, SDA, and V+?

It makes sense that V+ and GND can set the LSB of the slave address, but I am curious as to how the other two connections work.

Here's the link to the datasheet: http://www.ti.com/lit/ds/symlink/tmp112.pdf

I am using this sensor in an undergraduate senior project and am just curious about how this works. The answer won't affect my use of the sensor; I am just curious.

Thanks

Side note: this is my first question on StackExchange so any feedback on improving my questions is appreciated.


texts: How to implement autocorrelation (matched filter) in hardware?

texts: I have an understanding of how to implement autocorrelation via the means of software, but after an extensive search on the internet I could not find how to implement it with hardware/electronics. In some places, it was suggested to use a correlator.


texts: Create a differential Op Amp Subtractor With Single Supply?

texts:
Is it possible to create a subtractor op amp circuit using a single supply? For example, if I am using a non-inverting op amp to buffer a DC signal, how can I offset this voltage by 1V?

My voltage supply to my op amp is 3.3v (V+) and GND (V-).


texts: Verilog SPI module functioning in unpredicted ways

texts:
I am currently trying to implement a simple SPI Master module in Verilog using Quartus Prime Lite V15.1.0 Build 185 for compilation and Simulation Waveform Editor as my simulation tool. The module has been designed to ideally work in such a way that you load an 8-bit value onto a bus, toggle a 'transmit' bit telling the module to send out the value, and finally the module replies by toggling a 'done' bit to notify the host module that the byte was sent out. The SPI module doesn't control CS lines, as it is assumed these will be controlled by the master module.

//CPOL 0, CPHA 0 RIC60 SPI Master module

module SPI (
output reg MOSI,                        // Map to external I/O pin that will act as MOSI for the spi interface
output wire SCLK,                   // Map to external I/O pin that will act as SCLK for the spi interface
output wire DATAEN,                 // Map to external I/O pin that will act as DATAEN for the spi interface

input wire [7:0] inData,// Data to be sent over SPI

input wire CLK,                     // System clock
input wire datCLK,                  // Clock to be used for SPI
input wire transmit,            // Trigger for when to send out SPI command
output reg done,                        // signal to trigger finished SPI comm
input wire reset);                  // System reset input

    reg _moduleActive, _moduleActiveQue;
    reg [7:0] _inData_INT;
    reg [7:0] _countDown;
    wire _shiftData;

    reg _DCLK2, _DCLK3;
    wire _DCLK_FALL, _DCLK_RISE;

    reg _Transmit2, _Transmit3;
    wire _Transmit_FALL, _Transmit_RISE;

//Initialize
    initial begin
        _moduleActive = 0;
        _moduleActiveQue = 0;
        //_countDown[7:0] = 8'b01001100;
        MOSI = 0;
    end

//SPI Clock catch edges
    always@(posedge CLK)
   begin
      _DCLK2 <= datCLK;
   end

   assign _DCLK_FALL = (_DCLK2)&(~datCLK);
   assign _DCLK_RISE = (~_DCLK2)&(datCLK);

//Transmit catch edges
    always@(posedge CLK)
   begin
      _Transmit2 <= transmit;
   end

   assign _Transmit_RISE = (!_Transmit2)&(transmit);

//que module start at next rising edge of SPI clock
    always @ (posedge CLK) begin
        if (_Transmit_RISE) begin
            _moduleActiveQue = 1;
        end else if (_moduleActive) begin
            _moduleActiveQue = 0;
        end
    end
//put module into 'active' state
    always @ (posedge CLK) begin
        if (_moduleActiveQue && _DCLK_FALL) begin
            _moduleActive = 1;
        end else if (_countDown == 0) begin
            _moduleActive = 0;
        end
    end
//set SPI clock
    assign SCLK = datCLK && _moduleActive;

//clock out data
    always @ (posedge CLK) begin
        if (_moduleActiveQue && _DCLK_FALL) begin
            _inData_INT = inData;
            _countDown = 8'b10101010;
        end else if (_moduleActive && _DCLK_RISE) begin
            MOSI <= _inData_INT[7];
            _inData_INT <= _inData_INT << 1;
            _countDown <= _countDown << 1;
        end
    end
    endmodule

The module works using a 'counter' comprised of a value stuffed with 1's, and bitshifts on each clock until it equates to 0. Currently this counter bus, denounced _countDown, is what is proving to provide the biggest headache. When the above code is simulates it produces the waveforms as seen in the waveform window below.

The least significant bit of _countDown seems to be stuck at high impedance and it does not count down as I would expect form the given code. Also as you may have noticed, in the 'initial begin' block the initialization of _countDown has been commented out. If this line of code is uncommented I find that _countDown always stays in a state of high impedance. I am relatively unexperienced with Verilog (which may show itself in the code) so any pointers would be highly appreciated.


texts:
I'm new here, as I'm slowly drifting from mechanics and programming into more electronics stuff.
The question I have, is if anyone could possibly point me in the right direction, as all of my searches have failed me so far (I might need more coffee, but hey ;-)
The issue: I have a 555 timer in astable mode wired up, of which the output pin 3 triggers an NPN transistor to another 555 timer in astable mode. The circuit is basically working: the first 555 ensures that the second 555 turns on and off at the timing set by the resistors and the capacitor. The second 555 reacts as it should, and blinks a led (for testing) on and off with its own timing settings. So far so good.
However, there is one thing I cannot explain: The timing of the second 555 should be to turn the led on for 7.6 seconds (approx) and off for 0.6 seconds (approx). This works fine =from the second cycle onwards=. During the first cycle just after powering on, the led lights for about 11 seconds, instead of 7.6 seconds. This behavior is the same, whatever changes I make to the timing through changing the resistors on pin 6/7/8 and the capacitor on pin 6, meaning that during the first cycle after power-up, the led stays on too long, and the off-time for the led is also too long.
I'm using a breadboard power supply that supplies 5V to the board from a 9V power adapter plugged into a regular 230V AC power socket.
What I've tried:

changing resistor values to verify that the timing changes => yep, no problem
changing capacitor values to verify timing changes => yep, no problem
tying and untying pin 5 (control) to ground with a cap => no change
tying pin 4 (reset) to V+ with a resistor (10K or 100K) => no change

I've posted the schematic, maybe I'm just missing something obvious?
What happens at startup of the circuit that I'm not seeing/understanding?
Is it to do with the fact that I'm using electrolytic caps on pin 6 maybe?
Would love to hear what I've overlooked :-)
Regards,
Paul


texts: Arduino + transistor to switch PC fan on/off

texts:
I have:

an Arduino UNO
a 12V PC fan with 1.68W rating (140ma).
2n3904 transistor
12V 500ma power supply to connect to Vin.

What I would like to do is to simply use a digital output pin on the Arduino to turn the fan on and off (no need to PWM). What resistor should I use at the base of the transistor and in series with the fan if I want to switch the fan on and off using this transistor?

Without the transistor I see that a 100-ohm resistor seems to power the fan nicely, but in conjunction with the transistor and 100-ohm it doesn't run. My guess is that is might be due to lack of proper current management on my part of the base of the transistor and that I'll need to take into consideration the current gain.


texts: Lionel Model Train Transformers: Request for explanations of how things inside work

texts:
Lionel is a company that makes model railroad sets and parts. I have some of their "O-gauge" products and want to learn more about how the transformers work.

Above is a schematic of the transformer by a train enthusiast. No schematics are available from Lionel.

The transformers are actually 'controllers', as they do more than just transform the voltage. They also provide three different "activation" buttons:

1) Direction - a button press switches the locomotive's direction with each button press, Forward to Neutral to Reverse to Neutral to Reverse, etc.

2) Bell - a button press turns the bell sound ON. A second press turns the bell OFF. This happens because a button press "adds DC current to the output" which "changes the shape of the AC sine wave". (from sine wave shape to 'shark-fin' shape)

3) Whistle - momentary switch that makes the whistle sound while the button is pressed down. This also happens because a button press "adds DC current to the output" which "changes the shape of the AC sine wave". But this sine wave mod is different from button (2)s sine wave change.

I am not interested in the electronic function of the (1) direction control. The direction is also controlled by reducing voltage to 0 via the voltage control handle. The button seems to be redundant control of voltage supply, and it's probably just a momentary kill switch. In any event, that's not what I'm keen to learn about.

What I am really curious about is what the other buttons do electronically and electrically.

I already know that pressing either (2) or (3) adds DC current to an AC signal. Or at least that's what I think I know from what I can Google about it. And that DC current overlaid on the AC current is what distorts the AC sine wave.

It is somehow the shape of the sine wave that activates the sounds, or DC on the tracks that activates the sounds, or some combination of the two. I have read much that is unclear or seems contradictory out in Google-land.

I also have read that when the sound control buttons are pressed, the 18v AC gets some 'boost' somehow to allow for consistent delivery of power to the locomotive's motor (thus not causing the locomotive to slow down every time you sound the whistle).

But I don't really understand what's happening here... It's all done via a processor on a chip on the circuit board inside the transformer and I am WAY past my limits of comprehension.

So...

Can someone please give me a step-by-step explanation of what actually happens as you press (2) or (3)?

An explanation comprehendible by someone with only very limited knowledge of electronics?

Thanks.


texts: Measuring the resonant frequency of a crystal

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I am trying to measure the frequency of crystals in my box. I have a signal generator set to output a sine wave at 5V p/p. The output is applied to the crystal and then the other lead of the crystal is fed to the oscilloscope. The ground of the signal generator and the oscilloscope are connected together.
I changing the frequency of the signal generator around the rated frequency of the crystal. I was hoping to see large amplification at the resonant frequency. Instead I am seeing nearly the same wave amplitude at all frequencies.
My signal generator is capable of generating frequency accurate up to two digits after the decimal.
Are all my crystals bad somehow?


texts: Beginner questions about wiring power for solenoid valve

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Thanks in advance for any help/advice. I am in the US and attempting to use a solenoid on a CO2 line.

I have a Burkert 0201 solenoid (6V, DC, 4W) as pictured here. It has a molded-in power cord with brown, blue and green/yellow leads with a forked connector. I am unable to open the housing.

Questions:

I have a spare solenoid DIN connector, can I/do I need to use this for my solenoid to work properly? I don't see how I would connect it as there are no DIN prongs on the solenoid.
How do I wire this to a plug so I can connect a timer to switch the solenoid on/off? What items would I need to buy?

I've always had in interest in EE but always hesitate to experiment with these type of things.


texts: replacing a transformer with one of slightly more voltage

texts: I have some audio subwoofer amplifiers that require a 96v center tap 5 amp transformer for a non-regulated supply (Cerwin Vega Sub 150). I can source 90vct 4.4 amp $57 and 100vct 5 amp $51 transformers, a difference from 400VA to 500VA. Of course I want mass quantities of power, so is 100vct too risky? I see that I need to look at the transistors and try to identify them and get the specs.


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I'm using this Mitsubishi RF amplifer in a portable device. The Mitsubishi amp operates well between 7V - 9V.

But I have to interface with a power source that gives 1.5V, and stepping 1.5V up to 7V seems like a huge waste.

Are there any RF amps for a 400 MHz signal that operate closer to 1.5V? Or are there any super efficient step up regulators?