texts:
I am using a PIC16F18877 to control some LEDs on a control panel.  The whole project is rather huge, involving multiple processors communicating via SPI. This particular processor is controlling 88 LEDs in an 11 x 8 matrix arrangement.  Pins RA0-RA7 and RE0-RE2 are providing the 11 (cathode) lines via ULN2803 transistor arrays, data for the LEDs is on Port D.
I want to add simple PWM brightness controls to the LEDs, during the refresh cycles, so I want to use a timer (TMR2) as a one shot timer, feeding this into CCP5 to produce a PWM signal which can be routed to ports A and E, via PPS.
The timer interrupt service routine will then output the data for the appropriate 'column' in the matrix, and start the timer for PWM control.  On the next interrupt, a new column, data and PWM output pin can be selected, the timer re-started, and the process repeats ad nauseum, producing the correct display.
However, I am really struggling to get TMR2 to work in one-shot mode.  As a free running timer, it counts.  As a one-shot it does absolutely nothing.
This is my timer 2 initialization code:
START
CALL  Init_TMR2
Main_Loop        ;Just a dummy empty loop for testing Timer2
NOP
NOP
NOP
GOTO Main_Loop

Init_TMR2
    Banksel TMR2
    MOVLW 0xFF
    MOVWF T2PR
    MOVLW 0x40      ;Prescale 16:1
    MOVWF T2CON
    MOVLW 0x01      ;Fosc/4 clock selection
    MOVWF T2CLKCON
    MOVLW 0x08      ;One shot mode, software controlled
    MOVWF T2HLT
    CLRF  T2RST     ;No external reset required - will be done in ISR

    BSF   T2CON.ON  ;Start the timer

    RETURN

Checking this in the MPLAB simulator / single stepping and checking TMR2, if I set T2HLT to zero i.e. free running, the timer counts, but with Mode 8 (one shot) it doesn't.
What have I missed?


texts:
I was wondering about free software for modelling RF communications, such as creating a transponder equipment line up, changing equipment parameters etc and modelling performances like BER, S/N, Phase Noise, IQ Imbalances etc...

I know of SystemVue and ADS by Keysight... Are there free alternatives out there? Maybe python libraries? Is GNURadio any good?

I did a search but there was recommendations for RF circuits only.


texts: Turning OFF the grill when the espresso maker is ON

texts:
These are the variables to this problem:
We have two 120 volt appliances:
- an espresso machine (draws 8 amps)
- and a grill (draws 12 amps).

The grill is ON all the time (it actually stops heating when it's at the right temp, but let's consider it ON all the time).

The espresso machine is ON at random times.

I need to turn OFF the grill when the espresso machine goes ON (basically when anything is drawing from the 'espresso' outlet) -> (Can't exceed 13 amps at any given time on this circuit).

The grill's heating element is turned ON by a relay until the temperature is reached.
The 12 volt relay coil is switched ON by a transistor that is itself switched ON by a 5 volt signal going into a 4.6K resistor then to the base (so 1mA at the base).

Current sensing of the espresso machine is accomplished by a split-core transformer that clamps around the live wire. This is actually a (cheap but fairly accurate) clamp meter.
Now, inside this 9 volt clamp meter, I found the op-amp (lm358) that amplifies the tiny signal from the 'clamp'.
If the meter reads 0 amps, the voltage at the 'output' pin of the op-amp is 6.30 volts.
When the meter reads 8.5 amps (that's the espresso turned on), the voltage at that pin is 6.50 volts.
If the meter reads 12 amps, that voltage climbs to 6.70 volts. So I can use this signal for something.

Now, this is the part where I get confused.
What's the best/easiest way to insert a 'switch', obviously/probably a transistor, somewhere in the relay's coil switching circuit?

Would it be better to pull the 5 volt 'on' signal to ground to turn OFF the transistor that drives the relay (maybe not a good idea, I don't know what actually produces the 5 volt signal, maybe doesn't like to be shorted to ground?)

Or would it be better to insert a transistor in the 12 volt line that would be 'ON' all the time, and then turned OFF when the signal from the clamp meter comes in?

Before all that though, I need to figure out even this simple thing: how can I have the transistor be off when the clamp meter's signal is 6.30 volts, and then have it on if the voltage is any higher than that? Making 6.30 volts the 'threshold' voltage so to speak?

I was convinced this whole thing was going to be trivial when I started thinking about it, but now I realize it is not. I am still convinced the answer is fairly simple!

Can anybody chime in with some great ideas? Maybe another approach altogether?
Oh yeah, and the goal is to keep it simple and hopefully not have to order components. I have all the resistor values and a bunch of general purpose transistors, diodes and the like.


texts: If this element is unidirectional or bidirectional ? (see the image)

texts: Below the I-V characteristics of two elements .Is these elements are  unidirectional or bidirectional ?


texts: Is it better to keep LiOn battery charge on the lows or the highs for battery lifespan?

texts:
I know that neither keeping battery full or discharged is good for battery life, but I want to know a basic answer: which one of the two bad alternatives is better? Full or empty.

This is given that self discharge bellow 0% is not an issue as I would plug the devise in after it's off for some time.

I have a bad habit of either keeping my phone battery full (by constantly looking for charger) or having it almost empty (by charging when it's dead for 10min and then going after business). So  I want to know which of the two habits will wear my phone battery faster? Keeping constantly charged to near 100, or barely charged.

Thanks.


texts:
Why are transformers cores made of iron and not nickel, when the relative permeability is higher for nickel?
The permeability of nickel being 600 and the one of iron being 200.


texts: Basic circuit to keep LED either on or off depending on night/day

texts:
How can I have a LED either on or off (not in between) depending on night or day with basic electronics? I have created the circuit below, but it only shines and in darkness it dims.

The photo-resistor is about 3kΩ when light shines and about 1MΩ when dark.

I want my LED to shine at night and be off at day.

What is the simplest way I can achieve this?


texts: SainSmart 5V 4 Channel Relay momentary switch

texts:
I am wanting to hook this relay up here:

(source: sainsonic.com)

What I am wanting it to be hooked to (output) is the PWR and reset switch on a PC motherboard to act as a momentary switch:

(source: hardwarezone.com)

I am also wanting to hook one of those relays up to the 5v USB power so that I can turn off a USB product when I put the relay on high (which does not connect anything to the USB out).

So I am thinking it would be hooked up like so:

http://www.june3rdsoftware.com/relayArduino.jpg

And here is the schematic:

(source: sainsmart.com)

Let me know if this is correct!


texts:
I bought a musical birthday card with a small circuit in it hooked up to a piezo speaker. I took the circuit out and realize that it was ridiculously simple (from what I can see). So I was thinking if there is anything I can do to change the song it came in with ? (I was thinking checking each contact point with an oscilloscope when it runs but I don't have an oscilloscope)

I do suspect that the song is recorded in the white blob in the middle of the circuit, so any tips on breaking it open?

EDIT: This whole post and idea will be abandoned as there should be no possible way for me to hack a musical birthday card. Thanks to everyone who answered.


texts: OP Amp as audio preamp - am I doing it right?

texts:
I have a design that uses an ATXMega32E5 for two audio sources. In one case, a timer output square wave (3.3v logic) goes through a low-pass filter to make beeps, and in the other case, a DAC channel outputs 8 kHz audio samples (0-3.3v). Each goes into a 20k pot, the output of which goes into an LM4871, and into an 8Ω speaker.

The audio sounds fine, but the levels are way too low - like hold the speaker next to your ear.

I tried cranking up the LM4871 gain a little, but you're not really supposed to do that, and 3 dB of gain from the reference design didn't really make much of a difference I could hear.

I'm thinking the correct thing to do is stick an op amp (inverting configuration with half-vcc virtual ground) gain stage in.

Audio isn't really my strong suit. Can someone look over the proposed design and tell me what's wrong with it? :)

The original circuit just connects the R8/R13 output directly to C23. Everything between those two points is the addition I'm thinking of.

Note that during the test, AUDEN is high - with AUDEN low, there's no audio at all (which is the whole point of that line).

P.s. The differential output on the speaker leads (with the speaker attached) is around 2v P-P. Is it perhaps just that this speaker sucks?


texts:
When I programming SPI flash via SPARTAN 6 by Platform Cable USB II all FPGA pins (or almost) are HIGH state. Is it possible to change pins state to floating? Thanx.
Does anybody know How I can change the temporary core ( designed for program SPI flash via FPGA) or change any parameters for it? Needed Cores - xc6slx9_spi.cor, xc6slx16_spi.cor
There is solution for xc6slx45 - look xc6slx45_float.zip


texts: Common voltage when use a battery powered DMM to measure a voltage

texts: I'm a little confused by the common-mode voltage in this situation: Assume you use a DMM to measure a signal generator's output voltage, the signal generator is grounded, apprently the DMM is not. If the DMM use a differential input front, then what's the common-mode voltage the DMM see? I've never seen the internal of a DMM, so can someone explain me, how DMM handle this?


texts:
Hi Am looking for to design timer circuit for run Exhaust fan

My requirement is
three phase 1 HP motor, 440 V ac, 50 Hz supply
On time ; 4 Min
Off time: 1 min
so i need this cycle continuously. meant to say once the motor power on it has to run for 4 min and 1 min it has to stop then(4 ON + 1 OFF=5 min) 6 min it will run for another 4 min. so anyone kindly advise me how to design timer circuit for my Application.


texts: Schematic for N64 controller to PC adapter confusing

texts:
I'm working on this currently.

I'm a bit confused as to how this tutorial expects me to connect it to the controller. It just shows the controller plug with the three holes. How exactly do I connect the wire into that? It says the left hole is a ground wire. The bottom wire, is that referring to the middle? Is the wire to the left referring to the left hole?

Sorry for all the questions. Probably the last for now on this.


texts: Temperature sensor for solar dryer heat control

texts:
I am designing a control system that runs a fan and electric heater based on the temperature measured inside of a hybrid electrical/solar dryer (for fruits and vegetables).

Temperatures inside could vary between 0 and 200 degrees (very, very roughly).

What kind of sensor would you suggest using for this kind of application?


texts: Pull-up resistors needed for quasi-bidirectional push-pull PCF8575/PCF8574(A)

texts:
I wonder if I need pull-up resistors when using the PCF8575 I/O extender.

It's not directly mentioned in the datasheet (http://www.ti.com/lit/ds/symlink/pcf8575.pdf). The datasheet does remark that the I/O ports are quasi-bidirectional push-pull design, but I'm not sure if that says anything about internal pull-ups.

The PCF8575 is connected to ACPL-247 opto-couplers for input (collector/emittor side) and NCV8402D mosfets for output.


texts: Question about the basic differences between a MOSFET and a FET

texts:
I'm still new to all this stuff, but I'm slowly trying to understand. I'm getting most of my information from "Getting Started in Electronics" (Forrest Mimm's book)

Okay, so MOSFETs allow current to pass through the source and drain if positive current is flowing through the base. Am I correct?

FETs do the same thing, but it's when a negative current is applied to the base. Is this correct? (It showed a chart with negative current flowing to the base, basically stopping any current from the source to the drain.)

First of all: Negative current going to the base. How would you set this up?

Also, I don't really understand how a bipolar transistor differs from these other two? Is it just that a bipolar transistor is the same as a MOSFET, but only has an OFF and an ON, rather than a OFF, "some", and "full current"?
Sorry, I'm a HUGE newbie at this stuff, but I'm just trying to "get it".

Also, I'm not really sure what a Transistor Amplifier does, or what purpose it serves.


texts:
The light would shine down towards the board instead of up and away from it.

This would be useful where for example the board is being used as some sort of capacitative touch pad with LED indicators. The designer would either drill a hole through the board, or maybe even just have a gap in the solder mask and copper underneath and let the light diffuse through the glass fibers.

I've tried searching and can't seem to find any documentation suggesting this exists; is this because it doesn't or because I'm bad at searching?


texts:
I am trying to design an amplifier that will amplify input audio signal by about 2x when input peak voltage is below 500mV. If above it should act as a unity gain amplifier.

I've designed below circuit and tested it on breadboard. It seems to work as described above but when OA2 is active (its output is grounded) there seems to be voltage induced on M1 and M2 gates. It gets cliped to about +-600mV (probably by Q1 and Q2?) so MOSFETs arent turning on (which is correct).

simulate this circuit – Schematic created using CircuitLab

Yellow waveform is audio output and blue is M1 and M2 gates. What is causing voltage on M1 and M2 gates? Is it possible that 1kHz signal is getting induced with more than 1V peak-peak amplitude?

How can I get rid of this? I've tried ground M1 and M2 gates with 10kOhm with no success. Is it because of breadboard?


texts:
i'm trying to understand how Bruno putzey in
Globally Modulated Self-Oscillating Amplifier with Improved Linearity
in section 4.2 Analysis comes to the equation in presented in (2), see snapshot below.
I've tried to do common fourieseri of a square, wave but i do not get the same answear, it annoys me very hard!

I wish someone could help me understand how to come to the same answear?

More information:
I've tried to calculate the rectangulare fourier series,but I still do not come to the same result as in the article, but I think I'm getting closer.

Se link to calculations in comments (due to not enough reputation)


texts: Why Does Relative Magnitude of AC Current Waveform Decrease Based on Phase Ange?

texts:
Background
First off, I apologize if this is comparatively basic theory.  My primary profession is firmware and I only do electronics as a hobby.
I am attempting to design a power supply for a ~450W resistive heating element.  The circuit is pretty basic and uses a microcontroller, optoisolator and a triac to control the load.  This is working as expected but, now, I am attempting to read the current.  This is done using an external sensing IC (ACS71020) which is giving strange results.  This question, however, is not about the ACS (it will get its own question once I understand the general question asked here).
The Setup
In an attempt to understand how current flows through this device I have created the following (simplified) test setup:

simulate this circuit – Schematic created using CircuitLab
Where:

XFMR1 is a 1:166 current transformer
SCOPE is my oscilloscope (Siglent SDS1104X-E)
DMM is a Fluke 77 for additional data
TRIG is the optoisolated trigger signal from the MCU

The Problem
It seems like the amplitude of the current waveform is progressively more attenuated as the firing angle is reduced.  Consider the following graphs taken from my oscilloscope at different firing angles (as measured as a percentage of total output power).  Note that the yellow trace is the unmolested line voltage and the pink (purple?) trace is the measurement from the current transformer.

10%:
50%:
70%:
90%:
100%:

Notice how the current waveform begins to diminish (relatively) as the power is increased.  In each of the waveforms above the scale is held constant.
Questions

What causes this behavior and is it expected?
My DMM measures a linear increase in RMS current; in order for this to be true shouldn't the waveform NOT diminish?
How does this not violate Ohm's law given that my controller already accounts for the area under the curve (eg. 30% power is 30% of the area under the curve; not 30% the distance from the zero cross point)?

Edit 1:
The load resistor was calculated by following this guide.

First, I calculated the max p-p secondary current: 5A max * 1.414 = 7.07A p-p * 1/166 = 0.0429A.
Then, I chose 4V RMS as max voltage based on the datasheet for the current transformer I had on hand.  This was converted to p-p: 4 * 1.414 = 5.656V
Next, Rload = V/I = 5.656 / 0.0429 = 132.8 Ohms.
The closest standard resistor I had handy was 110 Ohms.  Feeding this back in: Vmax = 0.0429 * 110 = 4.685 * 0.707 = 3.312V.  This is less than the 4VRMS max for the transformer so I should be good.

Edit 2:
For the DMM, below are the readings I get at various power outputs on the bulb:

As you can see, it is quite linear, which I would expect since my controller handles the integral for the area under the curve which corresponds to a given power.
Is this linear assumption incorrect?


texts: Microphone voltage on a 3,5mm PC microphone/headphone jack

texts:
I bought one of those cheap cup-anemometers that you can stick into the 3.5mm headphone jack of an iPhone or Android device. I'm assuming it is some sort of pulse generator and that the app uses an audio library of some sort to count and time the pulses. I want to hook the thing up to an oscilloscope and see what it outputs so that I can eventually hook it up to a Raspberry PI or C.H.I.P board computer. Since I don't want to fry the thing and I'm not really very good with electronics I figured it might be a good idea to ask what the microphone output voltage of, say, an iPhone is?

I'm assuming that all I have to do is simply connect N Volts to the 'Mic' part of the 3,5mm jack on the anemometer and connect the 'Ground' section of the 3,5mm jack to Ground on the scope and then observe the output with an oscilloscope?

So N=?


texts:
I'm trying to induce Quality factor of RLC circuit.

In series, I did it with Frequency responce
$$ H(s) = R/(R+sL+1/sC) = (something)/(s^2+2sw_0\zeta+w_0^2)$$
And
$$Q=1/2\zeta$$
But I can't find how to induce it in parallel.


texts: SIM868 breakout board does not accept GNSS/GPS AT commands

texts:
I bought SIM868 breakout board with GNSS support. https://www.aliexpress.com/item/33013782111.html

However, I can’t get coordinates using standard at-command AT+CGNSPWR=1, AT+CGNSTST=1, etc. I get “+CME ERROR: unknown” all the time.
I tried commands for GPS also, in case if seller was not exact.
Does anybody know how to get location with this kind of module?
PS. There are also extra UART pins for GNSS. As far as I know, there is is an alternative way to work with GNSS, however It will make to remove two resistors, what I don’t want to do.


texts: Passing VHDL string generic with spaces via Modelsim command line

texts:
Given the following code:

entity foo is
  generic
  (
    VAL : string
  );
end entity foo;

architecture behav of foo is
begin
end architecture behav;

How can I set VAL via the command line using Modelsim, if VAL contains spaces.  For example, there's no problem doing something like this:

entity tb is
end entity tb;

architecture behav of tb is
begin
  foo_inst : entity work.foo
  generic map
  (
    STRING_VAL => "a b c d"
  );
end architecture behav;

But if I want to do something like:

vsim -c work.foo -gVAL="a b c d"

I get:

# ** Warning: (vsim-3351) Invalid value "a b c d" for generic "VAL".  Not using this value.

I've tried several variants:

  vsim -c work.foo -gVAL="a\ b\ c\ d"
  vsim -c work.foo -gVAL='a\ b\ c\ d'
  vsim -c work.foo -gVAL='a b c d'
  vsim -c work.foo -gVAL={a b c d}
  vsim -c work.foo -gVAL="{a b c d}"
  vsim -c work.foo -gVAL={"a b c d"}

I'm using Modelsim 10.7c on Linux and Windows, and it fails with the same error on both.


texts: How to make a proportional current output on a constant current driver with PWM dimming

texts:
I'm making a constant current LED driver out of 2 2N2222 transistors and a couple of resistors. Works great. I added a PWM signal to the input so I could dim the LED, also works great.
The problem is, I'm using this LED driver for a video camera, as the shutter speed is very fast(Like 1/100000) the PWM dimming is not usable, as the camera flickers.
Is that possible to make the LED current proportional to the PWM duty cycle, and not like on/off, like a low pass filter but for the current :)
Here is my circuit:

Here is my LED current:

I'm using a single 5050 LED package with 3 diodes in it, 20mA each LED. I need to set the brightness and leave it. Eventually, I need to change it after some time, but not often.


texts:
I want to drive a DFB laser in a type-2, 14-pin butterfly package. The manufacturer has provided limited information on how to bias the laser diode and could not get any information on the reference or test circuit.

The laser diode's anode is connected to the case ground. I need to DC bias the cathode with a voltage of 2V at a maximum of 200mA current using a constant current source to drive the laser without damaging it. And, I do not want to monitor its output with the internal photo diode. I just want to bias the laser diode.

I have been researching for some circuits, they are either using LM317 or very complex circuits using integrated ICs with additional controls and functionalities.

I am looking for a very simple circuit to bias my laser. Please help!

Datasheet: http://ao-inc.com/images/uploads/products/01-05-1347_DFB-XXX-BF-XX-CW-FX-HX-N347_REV_001.pdf


texts: Why is this Op Amp generating a 12kHz signal?

texts:
I'm a bit of a noob, but am trying to manually build an IR receiver circuit from a photo diode and a few other parts (the circuit im trying to reproduce is shown @ http://online.physics.uiuc.edu/courses/phys405/P405_Projects/Fall2005/Nabil_IR_Remote_Control_Demodulation.pdf on page 2).

I haven't received all the parts yet, but I figured as I have the op amp and the photo diode I would try just putting the inverting amplifier stage (ie up to point A) together to see if I could see any output from a tv remote on my crappy usb oscilloscope. At some point I noticed a weird 12kHz almost square wave coming from the circuit, even with the photo diode disconnected (circuit diagram shown below).

I was wondering if anyone would be able to shed any light on what's going on? As you can see from the diagram is a very simple circuit, consisting of only a few resistors and an LF356N Op Amp.

Thanks for reading :)

EDIT: It's worth mentioning that I get the same effect with a load resistor across Vo (was using 10M Ohms).


texts: Can I turn a device on and off using an antenna and tuner? Do I need to amply the signal?

texts:
I would like to use a radio receiver to turn a device on and off.

The idea is that when the signal is received, the device is turned on, and when the signal stops, the device turns off.

I want to use an antenna and a tuner to receive the radio signal.

I am assuming these components are all that is needed to receive the signal, and that amplification of the signal is not necessary - is this correct? If the device is turned on by detecting the presence of the signal, and turned off by detecting its absence, is it necessary to process the signal (i.e. amplify, demodulate) once detected?

As long as the signal is received, will it matter how strong/weak it is?


texts: Don't have a momentary switch, what else can I use?

texts:
Hi everyone and apologies if this is a really dumb question.

I'm following this to control the GPIO on a raspberry PI:

I bought a starter kit which has 2 mini push buttons, but I've no idea if they can be used?

If not there's nowhere round here I can buy a switch so it'll be a day or two, is there any way to DIY a suitable switch?

Any help would be great and sorry about the question. You're probably sick of raspberry pi questions but I have no one to ask.


texts:
My application requires to connect through Bluetooth reliably. I have an issue is that the receiver is not always in line of sight and when not, I experiment connection drop.

I would like to have 2 antennas in 2 different direction. The chipset is CSR 8635. Is that even possible to have dual antenna?


texts:
My goal is to have a rechargeable battery pack that outputs 5V 10amps.

approach: I think I could get a 2 cell 18650 battery management board,  (so that I may recharge the batteries and make them safer to use) passing the positive output from the bms of ~6.6V through a linear voltage regulator. The voltage regulator has an output voltage of 5V and up to 5 amps.

would it be possible to have 3 packs (the 2cell bms board) and take the output from the three linear voltage regulators, each 5V ~5amps, and wire them together to achieve 5V ~15 amps?


texts: Is it advisable to stay stick to Arduino IDE?

texts: Is it better to move to AVR studio (or any other better alternative?) over the Arduino IDE. Feel like it's so simple and childish. I need to know the experts idea and choice..


texts: How to save and reuse outputs of different steps of synthesis in Design Compiler?

texts:
Is it possible to save outputs of different steps of synthesis in Design Compiler and load them later? For example, is it possible to do analyze, save the output of that, and use the saved output during next session in order to save some time and continue where I left off? Is the same thing possible for other commands such as elaborate, etc.?

If yes, how?


texts: Good idea to control LCD contrast using a microcontroller?

texts:
In a commercial product, would it be a good idea to control LCD contrast using a microcontroller?

The LCD is to be installed in a vehicle and is to withstand temperature changes. I am concerned if the temperature changes would cause the LCD to be become unreadable.

The microcontroller i am using to control LCD does not have a DAC so I will be using a digital pot or external DAC.


texts:
I bought a mixed bag of ceramic capacitors from Maplin and I'm struggling to identify most of them. I'm a bit of an electronics newb, but I understood that a capacitor usually has 3 numbers on and sometimes a letter at the end of the numbers.  The third number indicates the amount of zeros you add to the first two to get the value in pF.  Am I correct?

Well with that in mind, I introduce you to:

The first one is a bit blurry, but it seems to have 8P2 printed on it.  Next has n51 with Sy below it.  The 3rd and 5th ones have a horizontal line under the number, and what might be a number one, or a corresponding vertical line, can't decide which it is.  The 4th one seems a bit more clear now that I can see the writing more clearly in the picture - I assume this is 180pF?  Finally the last one has 82 on it, is this simply 82pF?

Is there a way to test the capacitance at all?  I have countless smaller ones with either blurry text, or nothing written on.


texts: How can I communicate between micro-controller and PC without the use of RS232/USB Adapter?

texts:
I use an NXP micro-controller, P89V51RD2, and use a RS232 to USB converter to program it. I'd like to communicate with the computer to send data but without using the RS232 adapter and convert serial data from micro-controller to USB compatible form without the RS232 element.

Current stituation :

  uC(serial) --> MAX232 --> RS232/USB adapter --> PC(USB)

Required stituation:

  uC(serial) --> [some small circuit] --> PC(USB)

What can I do so that the new circuit is small enough to be burned on a PCB with the controller and directly interfaced with a USB?


texts:
I would like to know if there is a way to program a PIC for the first time (write in Flash) through an FPGA card.

The PIC is already soldered to the FPGA and I can't remove it. No bootloader exists on the PIC. Thus I need to program it in USART / SPI / I2C  mode with a bootloader so that it can receive data from the FPGA.

I know that normally I have to unsolder it, connect it to a hardware programmer like PICKit and program it with a software on the computer like MPLAB, but I cannot afford that.

I can generate the bootloader with MPLAB, which is a .hex file, but how can I transfer it to the FPGA and then to the PIC through the FPGA pins?

PIC used is Microchip PIC12F1822.


texts:
I seem to struggle with the notations and concepts used in signals & systems.

The book states, given that x2(t) = x1(t-T), x2(2t-5) is equal to x1(2t-5-T).

This might be a dumb question, but why wouldn't x2(2t-5) be x1(2t-5-2T)?


texts: Need advice on new device regulatory requirements

texts: I have designed a product (device) that runs on 12 VDC (similar to a laptop). It is AC powered using a (table top), detachable switching power supply 100 VAC to 240 VAC, 50-60 Hz, again exactly like a laptop PC. The external Power supply with cord is already among many others, UL, CSA, CE  approved. Do I need to get any more regulatory approvals on the device? If not, can I tag the device with these approvals as self certified.


texts:
Is it possible to swap wires in data bus between CPU and DDR3 x16 memory for routing optimization?

So, for data lines depends on the correct order?

For example connect DQ0 on CPU to DQ1 on memory and DQ1 on CPU to DQ0 on memory.

Personally I think that this is possible, but I'm not sure.

(About address wires it is clear that they cannot be swapped, because address bus is used also as command)


texts:
I just encounter the notion of trip-off current and timing in an electrical document. This document is not available online but i'll try to describe it hereafter.

simulate this circuit – Schematic created using CircuitLab

(schema from the documentation)

According to the documentation, the mosfet can drive 2A nominal with a 2.4A trip-off current and a trip-off timing of 10ms. Does it mean that the drive 2A at anytime and 2.4A for a period of 10ms? Once this delay elapse, the control switch off the mosfet to not damage the load?


texts: Light-emitting diode luminous intensity at sub-mA currents

texts:
I am trying to find a graph or table that relates the light intensity (either relative, absolute, or total luminous flux) of a light-emitting diode at the low range of drive currents - below 1 mA and ideally down to nA and pA levels.

Most, if not all, datasheets from manufacturers tend to specify output brightness down to 1 mA, but not lower (as usually, it is not application-relevant). I've made an honest effort to parse the literature available to me, but have failed to find a reference for light output over a broader range of currents.

Alternatively, I'm also looking for some first-pass approximation for the relationship of current and light output. At higher currents, the common assumption is a linear dependency. I doubt linearity is maintained at much lower currents, but I am interested in what the curve would be and if it is monotonic and how it can be expressed mathematically.

(N.B. I hesitate whether to ask this at physics.stackexchange.com or here. Hopefully someone with overlapping expertise can chime in!)


texts:
I want to simulate PTC thermistor in Proteus, but I need this informations.

Thermal Contact Res. (°C/W)

Thermal Res. to Ambient (°C/W)

Time constant (s)

full datasheet:
http://www.farnell.com/datasheets/2050662.pdf?_ga=2.261979140.845161386.1546173081-1474740581.1524733191
How can I reach variable values in 1,2 and 3 from datasheet?


texts: How to route audio between different "groups" of speakers

texts:
The title for this question might not make a lot of sense, and for that I apologize.
I am currently working on setting up electronics inside a school bus to RV conversion I've been working on. For the head unit, I'll be using a Raspberry Pi, which will be the source of audio. I want to have two "groups" of speakers - one for sound inside the bus and another for outside. My end goal is to be able to a) use only the inside speaker group, b) use only the outside speaker group, or c) use both speaker groups at the same time.
What I am imagining is having some sort of buttons/switch setup between the amplifier and speaker groups that will allow me to specify what groups will be receiving the audio signal. Based on my searching, the first things that really sticks out to me a 1-2-both battery switch used to charge either one, another, or both batteries off of a single alternator. Obviously that's not correct for this application, but it's at least a start.
Very much looking forward to any and all suggestions, I'm pretty open to anything. Thank you!


texts: Inverter not showing the right output in HSPICE

texts:
This is the code snippet apart from the usual headers in the rest of the file:

.param VDD=0.88
.param VSS=0
.param out_capa_load = 0.1f
.param inputv=VDD

XINV in VDD VNW VPW VSS out  INV_X1B_A9TL_C35
Cload out VSS out_capa_load
vin in 0 VDD
*.ic V(in) = VDD

.print v(out)

vVDD VDD 0  VDD
vVSS VSS 0  0
VVNW VNW 0  VDD
VVPW VPW 0  0

.tran 100 1000

.end

If I execute this code I get the output voltage around 271m at time = 1000. But if I replace "vin in 0 VDD" with "vin in 0 0" I get v(out) as 250m at time =1000. The inverter model is a standard one and there is no issue there. What could be the problem?


texts: Using an optocoupler to drive a pulse counter

texts:
I am trying to design a circuit to measure the RPM of a small internal combustion engine.
The ignition on the engine is a simple magneto style ignition. These ignitions are switched off by grounding a wire. When not grounded, the wire carries a signal that pulses once per revolution from 0V to up to 270V. The pulse length is typically 5 micro seconds.
Because the engine drives a remote controlled vehicle, it is important to isolate the ignition from the rest of the electronics, to reduce RF noise. Thus, I was thinking about using an optocoupler to take the pulse as input, with a suitable resistor in series to limit the current. On the output side, I am thinking about connecting the source to a pull-down resistor, and the drain to +Vcc of the Arduino.
The idea is to turn the input pulse (the yellow curve in the below image) into a square wave, and that is why I am thinking about a MOSFET-based optocoupler. The source would be connected to an input pin on the Arduino, programmed to work as a pulse counter (I have that part already done).  The square wave does not have to have the same width of the pulse. In fact, I would like the square wave to overlap the portion of the pulse above 50V.
So my question is: What is the best optocoupler to use, and what is the best way to apply the 50V threshold?

Figure 1: The yellow pulse is the one that is fed to the optocoupler. Note that here it is inverted


texts: driving low side of a mosfet bridge with 3.3V

texts:
I'm trying to drive a the low side of a n-channel half bridge with a 3.3V signal that is not enough to switch the MOSFET I think (sometimes it does switch and sometimes it doesn't).

I did this: http://upverter.com/nraynaud/9737d290ff152f76/half-bridge/
The high part comes from another circuit, but I built the low side on my own so I'd like some review.
The 22k resistor is a pull-up because adding the circuitry complements the inputs, making everything closed when there is no inputs.

Thanks for your advice.


texts: Controller for a DC motor for moving 18 cm constantly

texts:
I am working on designing a micro mouse that solves a maze. The objective is to reach the centre of the maze. The mouse needs to move one block distance at a time, which is 18 m. Currently, I am using a position control which calculates the error in distance and converts that into PWM value. So, as the error gets lower, the PWM decreases. Below is the code for it:

if( distanceRight < 60 || distanceLeft < 60)    // Encoder Pulses from the left and the right wheel
        {
            //Finding the error and converting into fraction values to be used as PWM
            errorRight = (60.0 - distanceRight)/60;
            errorLeft = (60.0 - distanceLeft)/60;

            PWM_RightWheel = (errorRight);
            PWM_LeftWheel = (errorLeft);

            distanceRight = abs(encoder1.getPulses());
            distanceLeft = abs(encoder2.getPulses());
        }

But, here is the problem. Sometimes the mouse overshoots due to its inertia. The encoder that I am using to measure the distance has a max of 48 state changes for one revolution. Considering the radius of the wheel, this gives me the ability to measure 0.25cm distances accurately.

What kind of controller can I use to reduce the problem of overshoot? This overshoot problem also occurs when I use the encoders to calculate distance while turning right or left. Again, in both the cases, sometimes I have the problem of overshoot.

Do I need to use a PID controller? If yes then how can I find the transfer function for the motion of the wheel and implement it in code?


texts: Compute spatial integral using analog computing

texts:
Let me start by saying that I am not an electrical engineer but a mathematician, who just started to dive into the world of analog computing using for the moment Simulink to simulate an analog computer virtually.

Consider the first-order differential equation

$$
\frac{dy(t)}{dt} = c - Fy(t), \quad y(0)=y_0
$$

with explicitly given constant \$c\$. The coefficient \$F\$ is given implicitly by the following integral

$$
c=\int_a^b f(x) dx,
$$
where \$f(x)\$ is a computable function that depends the spatial coordinate \$x\$ (but not on \$t\$) and the integration bounds \$a < b\$ are fixed.

I already know how to compute the above differential equations with analog computers using integrators given that \$c\$ and \$F\$ are known constants. Assume that I am not really interested in the transient behaviour of the differential equation but in the steady-state solution

$$
y(t)=c/F.
$$

My question is, how can I perform the integration of \$f(x)\$ in the finite bounds \$a<b\$ on a (virtual) analog computer?


texts: What does 1/8 watt power rating for resistors actually mean

texts: I know resistors have a maximum power rating in watts. But if my pack says 1/8 watt does that mean 0.125 watts max, or does it mean 1 watt up to a maximum of 8 watts?


texts: P-Channel Enhancement MOSFET strange behaviour

texts:
I am using GPIO pins to control the switch.  If OE of the 74LVC1G126 line driver is enabled, I like to switch the VBUS on by setting A to low and VBUS off by setting A to high.

The DMG2305UX is a P-Channel Enhancement MOSFET.  Gate Threshold Voltage is -0.5 min and -0.9 max.

When Source Voltage (VCC) is 5.09V, Gate Voltage is 5.08V, I would expect there is no voltage on VBUS unless I enable the line driver and set A to low.  But there is voltage around 4.43V on the VBUS when OE is disabled.

74LVC1G126 Function Table:

I come from a programming background and do not have much experience with electronics.

Am I designing the circuit correctly?


texts: Understanding Ac coupling in this circuit

texts: I'm simulating the circuit below in LTspice and there's something I don't get regarding C3 and C4. Suppose the input signal is a 32 uArms 60Hz current as shown. This value multiplied by the burden resistor gives (32uA * 1.91k) = 61.12 mVrms. However, in the simulation if I measure the voltage at the burden resistor, I get about 30mVrms signal. What is the effect of C3 and C4 that is causing the input signal to be reduced?


texts: Circuit changing the color of an led with a button?

texts:
I'm trying to make a circuit WITHOUT the use of any IC's or micro controllers. I'm basing it so far off of the circuit in the picture. Im planning on adding a flip flop circuit to it to make it the light stay on when you touch it.

The issue I'm having though is that this circuit would only light the led in one color. I have a 4 pin led and my end goal is to have the circuit able to switch between each color every time you touch the "button".

Ive been stumped on this for days. There has to be a way to wire this up manually so I don't have to use an IC or a micro controller right?


texts: Magnetometer- there is no low current feature?

texts:
I have gone over all magnetometers available, most of them using I2C, and connected to some MCU, and i couldn't find even one with interrupt.

That means the processor cant go to sleep, and always has to listen to what is going on, there is no interrupt on change option in any of them.

Is there something special about them that none of them have an interrupt when a threshold is met?

LSM303
MAG3110
HMC5883L

How can you build battery operated devices that sense motion when you always have to listen?

Accelerometers (that can't detect slow movement) always have some interrupt, but magnetometers do not .

Any help/replacement about this issue would be helpful.


texts: Is it safe to touch one terminal of a floating 20kV 1A PSU?

texts: Yes, I know - stupid question, Darwin Award time... but, could someone get away with touching only one terminal of the floating PSU and not be seriously inconvenienced?


texts: LM 56 temperature trip point resistor selection

texts:
I'm having a hard time grasping on how to calculate the values for resistors R1 R2 and R3 in the typical application diagram pg.2 in the data sheet. Could some one break down the calculation steps down for me? Maybe ELI 5? I need OUT 1 triggering at 2 deg c and OUT 2 at 40 deg c.

http://www.ti.com/lit/ds/symlink/lm56.pdf


texts:
I came across this page on building your own current source.

What are current sources used for in real-world applications?  The only places I've seen them used are textbooks.

Do you have any suggestions for some fun weekend projects involving a current source?


texts: Is it possible that a new transistor is not good even if a current runs through it?

texts:
I just got an NTE121 replacement transistor for an old 2N2148 that was in a guitar amp.  It was the only part I replaced and now I have no sound coming from the speaker.  I checked every component on the board with a multimeter and did not find any dead spots, including the new transistor.  Is it possible that a new transistor could be dead out of the box?  I have really only ever dealt with capacitors before.

Thanks


texts: Single Supply AC Gain Opamp With Unity DC Gain

texts:
I'm trying to build a AC amplifier that will amplify an input signal of around 0.4Vptp @ 160kHz to around 1.7Vptp. I'm also attempting to do this with a single supply (3.3V) opamp. I built the circuit depicted below.

simulate this circuit – Schematic created using CircuitLab

After building and testing this circuit I ran into some very weird behavior.

The voltage at the non inverting is suppose to be around 1.65V but during measurement it was around 0.5V. My first assumption was possible the input bias current was causing this. After checking the datasheet the bias current is only 0.5pA and with a 2M resistor that should only cause a change of around 2uV.
Despite the weird bias I was able to get some scope measurements (note: yellow trace is at the non inverting pin of the opamp and the blue trace is at the output:

Over time the output started to clip and eventually the output became flat (over a periods of a few minutes)

Once the output had flat lined I noticed the current being pulled by the opamp was around 50mA!!

I was hoping for some direction on this issue. I have no idea where to start.


texts:
This is my first time posting on this forum, so please bear with me. I'm trying to design a 'logic converter' to convert a signal from one logic standard to another, and vice-versa. The first logic standard is the Nuclear Instrumentation Module fast logic standard (NIM logic), whose logic voltages are 0 volts when low and -0.8 volts when high, and it remains high for only 10 nanoseconds. The other logic standard is the TTL standard, 3.3 V when high and 0 V when low. The inputs can also be seen as 50 Ohm line outputs depending on the direction. In terms of power supplies available, the module that will power this circuit has +6, 0 (GND), and -6 volts to work with.

I'm trying to start off by converting the NIM logic to TTL logic. My thought was that I can first boost the NIM logic signal to something higher, and then use that larger voltage to activate a switch to provide the 3.3 V output as needed. For example, I boost the input so it reaches 0 V and -1.8 V, which then activates a PMOS switch to provide a 3.3 V signal accordingly. The issue is that with such a small input voltage, it's not enough to activate a PMOS (specifically the ALD 1107), so I thought I had to use BJTs to get the fast switching necessary. I tried simulating it with a current switch (emitter coupled), but it doesn't seem to reach the appropriate low logic level needed.

simulate this circuit – Schematic created using CircuitLab

The circuit shown is what I have so far, and I'm simulating it through LTspice. I have very little experience designing circuits like this, and I'm not sure what else I can do to approach this problem. The time to switch is in nanoseconds, and I'm not even sure if my choice of BJTs is appropriate for the time needed. Power isn't a problem right now; I'm just trying to see what I can do to get it working. Are there any other kinds of circuits that would be helpful to look at given the goals?


texts:
What is the right way for measure Phase angle?

for use in non harmornic and harmonic situaltion (for meter).

asin (Q).
acos (P/S)
measure time delay between V and I at zero crossing.
acos{Total PF/[1/((1+THDi^2)(1+THDv^2))]}
other way?

where >>
Q = Reactive power average 4000sample

P = Active power average 4000sample

S1 = V1*I1

V1 = fundamental Voltage

I1 = fundamental Current

Total PF = Total power factor = P/S

I'm so confuse what the phase angle should calculate?
It is displacement angle or displacement + distortion angle?


texts: What is the "input" being fed into a Delta-Sigma Modulator in a Fractional-N PLL? Are bits needed for a specific resolution at the input or output?

texts:
I'm doing some reading into Fractional-N PLL design and I have a bit of conceptual confusion regarding a delta-sigma modulator used to toggle the modulus of a divider. If you're trying for a certain fractional frequency division, you want a the output to average at a specific value to, on average, divide by some non-integer value. This output is the input put through a Delta-Sigma modulator; if this average should be constant, shouldn't the input be constant?
In diagrams I often see the PLL Feedback fed into the delta-sigma modulator at some point, "fdivided" as seen in the example below.

Is "fdivided" in this case meant to be the frequency the DSM is oversampling by? (So if f_ref is 1MHz and fdivided is 1MHz, if the DSM's oversampling rate (OSR) is 8, then the sampling rate is 8MHz)?
When it's said a specific number of bits is needed for resolution on a divider, that's referring to the bits in the input, correct? So for a DC input, that is how precise that DC value can be (-0.5 and 0.5, or -.3, -.1, .1, .3, something of the like)? Textbooks I've read sometimes don't distinct if the bits needed is at the input (the "DC" value) or the output (i.e. the bits of the Quantizer, also related to the amount of moduli on the frequency divider).
Sorry these questions are a bit scattered, I'm just slightly confused conceptually on how some things have been phrased in various papers or textbooks.


texts:
I am adapting a design using a PIC32MX (which is actually working) to put an extra add-on. The add-on is a fingerprint reader which communicates via UART. Regarding that I have the USB pins exposed in my design, I found a way to connect a ftdi 3.3V (https://www.sparkfun.com/products/9716) between UART and USB.
I am planning to connect my VCC ( 3.3V in my design , which I believe it can give me more than 200 mA) to the VUSB red wire cable. The other pins are straight forward.

So my questions from now are:

The purpose of the VBUS pin on the PIC32mx is to recognize if there's any device plugged or not, right? Is there any problem if I leave it not connected?
Do I need to connect the VBUSON pin to somewhere? I am already using for something else (the pin is shared/not dedicated).


texts:
I am trying to interface a TI c6678 8 core DSP evaluation board to a USB camera.  The TI chip / board does not have USB, it has 1 SPI, 1 UART, 1 PCIe (2 lanes), and SRIO.  The eval board only has an AMC connector, but there is an add on that breaks out the PCIe to a male edge card connector.  I also have a USB -> PCIe bridge evaluation board (TUSB7320) that has a male PCIe edge card connector.  I need to connect these together so I can interface the USB camera to the c6678.

I started out trying to find a direct female -> female PCIe connector, without any luck.  Next I soldered up some jumper wires between the edge connectors.  Besides the obvious issues of impedance matching and length matching, noise, etc, this approach will not work because the c6678 EVM does not support generating a PCIe reference clock, although it does support acting as a Root Complex.  I now have a PCIe reference clock IC that I am trying to get working on a protoboard without any significant luck.  The 100 MHz clock signal is absurdly noisy with a ton of jitter on my scope (not surprising).

I am now out of options for trying to prototype something with what I have.  I have not been successful at finding a PCIe backplane that connects two slots together, the ones I have found go from each female slot to a PCIe switch and then out to a system board connector.

My options at this point seem to be

Find an off the shelf backplane that connects slot to slot directly AND has a reference clock generator on it. (backplane may be the wrong word for this)
Design a simple PCB with 2 female PCIe connectors and a reference clock generator on it.

I have been unsuccessful in accomplishing #1, so I am now moving on to #2.  Since I have no capability to prototype the design, I am very nervous about the PCB I design functioning properly.  I have Altium and can match the trace lengths, what are some other considerations I should take into account when routing this PCB?

Datasheet links: TI c6678 EVM TUSB 7320 EVM


texts: MOSFET package with lower thermal resistance than D2PAK

texts:
As far as PCB surface mount MOSFET packages go, does D2PAK generally have the lowest thermal (junction to ambient) resistance? Are there other packages with lower \$R_{jc}\$?

This question is based on this document:

PACKAGE THERMAL RESISTANCE TABLE from Linear


texts: best choice of a stepper motor to lift a 3kg load

texts: first time working with a motor.am designing an egg incubator and need a stepper motor to tilt the egg tray at 45 degree occasionally.there are two egg trays each is attached to the incubator wall and is free to rotate.the two trays are connected together such that they move together.the weight of the egg trays with eggs is 3kg. i am to use a stepper motor to push and pull the tray up and down. which stepper motor is best to lift a 3kg load? my question


texts:
In the Patterson & Hennessy book,

This is for these 4 instructions, if I need to implement instructions like andi, addi, ori, j, etc, do I add on to this table? Or do I do something else?

UPDATE

If I do add on, I think the hard part is the ALUOp. There are only 2 bits, I think I need the below operations. And I added what my idea of an implementation. Whats the correct MIPS implementation tho?

instr    ALUOp
--------+------
AND      0000
OR       0001
add      0100
sub      0101
slt      0111
funct    1xxx

Where the MSB (bit 3) is a "see funct" bit (R-Type instructions). bit 2 will be "use ALU" bit. Then the last 2 is the operation bits. I saw various implementations, where there are more instructions like NOR, XOR, shift etc. Is there no standard or most commonly used standard?


texts: How can I design a 8 to 3 priority encoder using 4 to 2 priority encoders?

texts:
This is what I've done so far and I really don't understand how to continue. The V variable is for verification

[EDIT]

it works for Y2 and Y0, but it doesn't work for Y1


texts: What is the green/red drag line in Altium?

texts: When I drag a component in Altium there is always a line (sometimes it's red, sometimes it's green) connected in the center of the part and pointing to some place in the PCB. I always wonder what is this line for anyways?


texts:
A 1.4 A shunt DC motor, with brushes, in a home made pottery wheel from 1970s runs slightly erratically.
In general I am well impressed with it as the motor choice is appropriate for the application, being low speed and even running under varying load. The speed controller circuit board is also home made but I think the fault may be simple to correct (not sure as I am amateur.)
In the attached circuit diagram there are two bridge rectifiers with connections "x and xx" to field windings and "A and AA" to armature.
The field winding rectifier is about 10mm diameter "S1-60" and the armature rectifier is grey square with 400 V printed on it. So this looks as if the circuit controls armature current, but would it be better if the winding current was controlled? If so can I swap the  motor wires between rectifiers? Would the rectifiers still be appropriate?
Notes
33 kΩ resistor may be 22 kΩ, 0.1 μF components look like Mullard capacitors - I have not used symbol and value may be wrong.


texts: Reactive Power in grid side converter for Doubly fed induction generator

texts: Does the grid side converter in a DFIG absorb/provide reactive power or is it reactive neutral? Also, what can we say about reactive power exchange in the rotor side converter?


texts: What components are necessary for an FPGA?

texts:
I've worked on an FPGA dev board, (The DE0), but never designed an application using the chip alone. On the board I have, there's alot of components, and I'm not sure which ones are necessary for designing a standalone circuit.

I know that the EPC4S is important, because it holds the .pof, and I would want a USB controller, but there's about 20 other chips on there. Can anyone explain what the bare minimum an FPGA would require if ignoring the different connectors and peripherals?


texts:
I am using a shunt to measure the current on a 12V system on a boat. Most currents are very low (under 4 A) but when using the starter the peak current reach peaks of 250 A.
I've sized the shunt to 50 A to ensure sufficient precision on the measurements (there is a 1% error, if a 300 A shunt would be used, that would show potentially 3 additional A). However there is the risk of overheating when using the starter.
I was thinking of installing some sort of thermal protection, where the shunt would be bypassed if it reaches a certain temperature. I've tried looking for some sort thermal automatic resetting fuse or switch but do not find anything that could accept so much current.
Do you have any suggestion?
Thank you very much


texts: Why is this Arduino RF Receiver changing value back and forth so much?

texts:
So I have a 315Mhz receiver hooked up to an Arduino, and constantly printing the value of the A0 Analog in pin over to the Serial Plotter that is built in to the Arduino software.

This is the graph. You can see at the end there is some data from another 315mhz transmitter.

My question is, why is there so much noise when something is happening? Is this normal? Maybe a bad receiver chip?


texts:
Background: I designed a simple board a while ago using a ATMEGA328 and a ESP8266. The idea is that the ATMEGA deals with sensor data and the ESP8266 deal with the whole online bit.

I did a initial run of 20 prototypes when a client of mine showed interest in the board and data I was collecting. This board consisted out of 1 PIR sensor, 1 Sound sensor, DHT11 for temp, MQ135 for air quality and also a RGB led which helps me debug without the need to connect to serial etc.

Initially I had JST 2.54mm connectors on the board for connecting the sensors to the board. See this pack of connectors at DFRobot to get an idea of what I was using. The idea was for 20 units to crimp a header to one end stick it into the header on the PCB and then solder the three wires onto the sensors/led and viola all done. Sounded simple but soldering 20 PIR sensors, 20 LEDs, 20, MQ135 with three wires each led to a whole new level of respect for workers at FOXCON!!! On the plus side I now have a level 1 soldering badge.

Here is a picture of a my test model I am working with to give you an idea of how it looks. Sorry my cell phone camera is obviously dying at the moment so pic not great quality. NOTE: Dupont connected to JST at the moment is FOR TESTING ONLY!

So now the client wants 100 of these boards and I am having cramps in my hands just thinking about it. I was thinking of using just normal PCB header pins on the pcb and then using Dupont breadboard wires between the PCB and the PIR Sensor, LED etc. This will require a lot less soldering and since these devices are going to be mounted in air conditioned offices on a rather stable surface vibration will be kept to a minimum.

Essentially I tested replacing the JST with simple headers and using Dupont connectors and it works pretty well. The Dupont female points grab those PIR pins pretty damned tight and I have been unable to shake it loose(trying to simulate vigorous usage of the sensor which wont really happen in normal use).

Since I am limited in experience  I need some guidance from the Jedi and Sith master on this site.

Is using Dupont connectors even advisable for production usage?
Alternatives to using either the JST or Dupont? I would rather solder prototypes than focussing on soldering production models.
Would a PCB manufacturing house be able to help me with the soldering of the sensors? If not is there other assembly houses that could help?

From my research it seems there is no real standard and using what works seems like a logical and viable alternative. Just trying to get some feedback from more experienced engineers and makers.


texts: How a P-Channel Mosfet works with a pull-up resistor

texts: I have been desperately trying for days to troubleshoot this h-bridge I build so I'm trying to completely understand it first. What I don't understand is how R1 and R2 in the below image operate. Is the V+ powering both the source pins of the P-Channel MOSFET's and their gate pins and also the drain of both N-Channel MOSFET's Q9 and Q10? How and when do the resistors R1 and R2 come into play?


texts:
I'm working on a small project to power a magnetic lock that deactivates when a series of switches are turned on. I've re-designed my circuit based on help from another post, but isn't supplying the correct voltage to the magnet. Any ideas?

simulate this circuit – Schematic created using CircuitLab

EDIT: Here's an updated circuit that takes into account the recommended changes


texts: Circuit analysis using Mesh current method

texts:
I want to find voltage across 3k resistor using Loop/Mesh analysis.
answer in SPICE = 4.0135

My Solution :

$$ 8=2(I_2)+1.5(I_2-I_3)+3(I_1-I_3) $$
$$ 0=3(I_3-I_1)+1.5(I_3-I_2)+10(I_3) $$
$$ I_1-I_2=0.5 $$
Hence :
$$I_1=1.5980 \\
I_2=0.5304   \\
I_3=4.7973$$
Voltage  at  3K $$3(I_3-I_1)=9.5979 $$
Which is wrong answer .
Correct answer is 4.0135V
Where am i wrong ?


texts: How do 100mA ELCBs provide human protection?

texts:
Usually we use 30mA rated ELCBs in our homes. This is for our own protection against leakage current. But in instances where you have a 100mA or 250mA 3 pole ELCB used in industry, an earth leakage of about 60mA would shock you before the ELCB trips. So how are humans protected in this case?

Any information would be appreciated.


texts:
I have for some days worked with an RTL inverter and an totem pole drive to drive a high voltage MOSFET. And I am happy with the result except for one thing the rise time on the inverter output (from ON to OFF). Here I have to choose between large power consumption or large dV/dt. And in the application for which this is to be used I do not have the possibility of high power consumption bur I still need a large dV/dt output. I have tried to come up with a circuit that bypasses R1 and releases charge from Vcc to Aout, but has not succeeded does anyone have a suggestion?.
In the simulation is three run with 1k, 5k and 10k, as seen the 1k gives the best result highest dV/dt.


texts: Above the barrier voltage does a pn junction behave ohmically?

texts: I understand that below the barrier voltage no current flows, and once the required voltage is met the current rises exponentially, in accordance with the ideal diode equation. However at voltages above this region (~1.0-1.5v for a silicon diode) it appears that here is a linear relationship between V and I. Is this correct? [Edit: for a real diode]


texts: Differentiating Equation containing modulo operation

texts:
(DC motor Single Loop setup)

I have the equation for flux containing mod operation of the angle as an independent variable.

the graph:

The textbook then directly derives the derivative of flux for the calculation of emf as follows:

My question is, where did the mod go after differentiation?


texts: What is a SRF? (This is used in AC power distribution system with isolation transformer)

texts:
Following image shows a block diagram of a AC power system. What is that SRF equipment comes with the isolation transformer?

What SRF means and what it does?


texts: How to use a relay to "lift" 12v ground of a two 12v battery system

texts:
First off, sorry about the long title as I don't know a better brief of my situation.

Project:

I am converting a bus into a trailer to be pulled by a semi truck 5th wheel style.

The bus has it's own electrical systems that I don't want to take away, but i need to control the stop lights, etc from the semi truck when it is attached. The semi truck by design of course can power lights on a trailer so I will be using it in this way to control the lights on the bus.

I want to have a bypass switch. If the bus is powered on by the master disconnect switch, then I need it to lift the ground from the semi truck power feed...thus turning off the control of the lights from the truck battery

Concept:

Here is what i think will work using a 5 pin relay. Your input will greatly help me.

Explanation:

I'm thinking to tap the bus positive, post master disconnect switch, to feed relay point 86. 85 goes to the bus ground. This same ground is where 87a, via 30 allows the semi truck to complete the circuit to control the lights.

Application:

When the bus master disconnect switch is switched off (normal usual operation), the ground from the truck connects to the bus allowing the truck system to control the bus lights.

When the bus master disconnect is switched on (rare but to operate the bus systems independent from the truck), the ground from the truck should "lift". This will assure that both battery systems are not powering the same circuit.

Is this a good way to do it even though I'm only working with 12v on either side of the relay? Am I missing something?


texts: How to implement an ON/OFF switch in a simple digital circuit?

texts:
I'm trying to find a way to implement a simple ON/OFF switch, alongside a START/STOP switch in a simple digital circuit. Here's an example simulation of what I did:

As you can see, I have some undefined states in the fourth case, when the circuit is off, but its functionality is started. What would be ideal in this case is, when the on/off switch is on (not pushed), the start/stop switch can change states independently, but when the on/off switch is off (pressed down), the start/stop switch goes down with it. What would be a good way to implement this in the digital domain?

The circuit is a simple digital dice. When it is started, the LEDs change states between numbers 1-6 quickly, and when it is stopped, the LEDs stop at one of the states. The on/off switch, however, turns off the LEDs and IC that drives them.

Edit: This is the IC that is controlled by ON/OFF switch:


texts: This SR latch built with 180nm CMOS does not work in ltspice. How do I fix its behavior and parameters?

texts:
EDIT: I copied over the latch from another larger model that had Vdd defined, but missed it when copying over the design. However, after adding in Vdd, I still run into this confusing issue where the R seems to trigger Q and not S.

I used these 180nm mosfets to build this SR latch:

I used the nmos4 and pmos4 and added a spice directive with the models. I sized the nmos as L = .18um and W = .5u and the PMOS as L= .18u and W=1u (to get more symmetrical rise fall time, though Im not sure by what factor exactly I would need to scale the width):

However, even though I followed a regular schematic for an SR latch it does not work. When the S and R are triggered it seems that R triggers Q and not S.  Then again, not all the parameters are recognized by ltspice and Im not sure how to get around that other than by using another transistor. Is there a way to make this current design work? Also, any chance someone could let me know if the warnings I am seeing are a clear need to fix a particular thing in the circuit?

[


texts: Vacuum Tube Tesla Coil (VTTC) schematic interpretation

texts:
I'm quite new to the Tesla Coil stuff and I want to build a VTTC form a GU-81 tube. I'm using schematics from this Instructable.

I don't want to make anything I don't understand and although I understand basic Tesla Coil working principles there are some questions left unanswered. After asking on Instructables page and not receiving a response I decided to ask here.

There are some questions about the design I really need to know the answer for.

  You need something that limits the amaount of current floating through the tube grid and the feedback coil. It doesn't really matter if you use a high wattage resistor or a light bulb. The most important thing is that the calculations are correct ! All calculations for the GU-81 pentode  R= V(Anode voltage)/(4*I(Anode current)) =5900V/(4*0.6A)  =2458 Ohm  --> Use at least a 2,5kOhm resistor! (at least 130W)  W= (V(Grid Voltage)/R)*V(Grid Voltage) = (600V/2458Ohm)*600V = 162W  --> Use definitly not more than a 160W light blub (I use 100W)

There is no clear information what bulb shall I use (What voltage should it be for, The bulb in the picture is way too small for a 100W)

What is the purpose of the 700pF 12.5KV capacitor? Can I use a 1000pF 15KV cap instead ?

3.What is the purpose of the 4.7nF 6KV cap in the filament transformer output? Does it have to do with the fact that the tube is heated directly?

Should I use a separate grounding rod for the Coil and if yes, to which part of the circuit should I connect it? (I have RCD breakers so any current flowing to ground will trip them)

5.One more thing. Will I die if i touch the sparks (I mean secondary, not the primary circuit. The primary part of the coil would kill me instantly)

I'm sorry if any one of my questions cannot be answered, I just want to be sure before building a device that is so dangerous.


texts: Why do MOSFET drivers need so much current?

texts:
I'm using a MOSFET driver to drive a 6 MOSFET H-bridge, with a 40V supply. At 25 KHz, the driver gets very hot, almost too hot to touch. The MOSFETs have a gate charge of 350 nC. Why does it take so much current to switch the MOSFETs? If the average switching current can be calculated with QxF (gate charge times frequency, which yields 9 mA), why does the driver become so warm? Does the power dissipation in the driver depend on the peak current or the average current? It seems that the average current should be the same regardless of the gate resistor, because the same charge needs to be delivered at the same frequency.

I'm using an Allegro A4935 MOSFET driver and IRFS7530TRL7PP MOSFETs.
Here is the schematic:


texts: Thermal paste residue very difficult to clean

texts:
I'm trying to remove thermal paste residue from the die of my Radeon GPU with q-tips and isopropanol. The CPU was fine, but the GPU is extremely stubborn. It looks worn and dirty regardless of how much I try to clean it. Like I said, the CPU looks sparkling right now.

Should I be worried or should I just make sure there's no thermal paste left and go ahead and apply the new stuff even if it looks a bit rugged?


texts: Best way to amplify 3.3V square wave at 1MHz to 10V square wave at 1MHz

texts:
I am trying to build a bus transmitter complying to 1553 standards.  Its input is a 3.3V square wave at 1MHz (CMOS data) and it has to be amplified to 10V or higher at the same frequency. The load will be a center tapped isolation transformer whose primary side inductance is around 5mH.

My current implementation involves an LT1210 current feedback amplifier which is able to amplify square wave but the catch is high current drawn from the sources (500mA) which leads to high power consumption as the datasheet suggests.

Following is my setup:

Right now to the left of the 10 ohm resistor I get 8.5V peak to peak.

What I need to know is if I am on the right track here. Are there any other operational amplifiers available that could amplify large square wave signal and use less current at the same time, or are there any modifications that I could make on my circuit to draw less current and achieve same levels of voltage? (I clearly don't seem to need 500mA.)

P.S. This is a part of a project which is a 1553 bus transceiver analog front end. HI-1579 chip is very close to what I am intending to build.


texts: How to fix a broken sub connection and wire?

texts:
The wire connecting to my sub has snapped off, and it brought the metal connector piece with it.

I don't want to buy a new sub, but it looks like this is going to be hard to repair. Anyone have advice for me?

The sub:

The broken part:

Demonstrating how it is supposed to look:

The sub wire is broken too:


texts:
I have problem getting the output resistance of this current mirror.
How should I draw the small signal circuit and derive the output resistance equation?


texts:
I am building a HID USB device (via Microchip PIC MCU) with a MIDI interface, which is functioning as intended (sending midi to the host). My intent is to make it usable by a DAW (such as Reaper), and to ensure precise and accurate timing, I believe I need to implement MIDI timestamps. My questions:

Is implementing MIDI timestamps going to dramatically improve the precision and accuracy of recorded midi notes without degrading real-time performance?
Do MIDI timestamps need to be implemented by the MCU, or is that handled inherently by the driver?
Where can I find documentation on implementing timestamps if applicable? (Google appears to not be helping in this case)


texts: What am I doing wrong with this dummy battery for my camera?

texts:
Im trying to make a camera battery grip for a Canon M50 that uses LPE12 batteries. They output 7.2V.
I'm using this PCB to try and convert 3.7V coming from a 18650 battery to the appropriate level:

I was able to get the correct voltage but it is still not working:

EDIT: I did some more tests and it turns out that the original coupler supplies the dummy battery 8V 1Amp if plugged in to a USB power bank and the same on a wallwart charger. When I remove the 18650 battery from the circuit and power the pcb through its microb usb charging port I do manage to get 8V 0.9Amp which is close enough i would suppose. When I plug it into the camera, the voltage did drop to 5V indicating that it's not able to sustain power. Which I was slightly expecting because of Dave's observation that my pcb didnt have the proper electrolytic capacitors to sustain the power. But it all seems to go batshit once I put the battery back on the circuit. I couldn't seem to measure the output Amp of the board because it seems to go over the scale. I even tried to limit the current by adding a 8ohm resistor to try and limit the circuit to 1Amp but all it does is make the resistor go hot.


texts: 5.5" portable CRT television with several black lines

texts:
I have this monochromatic chinese television largely manufactured in the past decade,
marketed under several brands (Coby, Curtis, Precision, etc). This one in particular have a external AC DC converter of 1.6A and 12v and AV out. His cover is  like this one but silver.

In this photo as you can see, it shows several horizontal black lines along the image vertically expanded. I already opened it to clean (had small cockroaches living in with his feces). This photo was taken while plugged in with a alternative smaller and lighter ac dc adapter (1.5 a 12v). The original power adapter seems to be faulty, because in addition of this lines the screen becomes unstable, as if closing.

I wonder if someone could give me a answer or clue about this problem. Thanks.


texts: How to Test Allen Bradley PLC Analog Output Scaling?

texts:
I have an Allen Bradley ControlLogix 11756-L72S PLC with a 1734-OE2V 2-Point Analog Output card connected to a SMC pressure regulator that takes a 0-10 V input signal to set the pressure setpoint.

I want to test that the loop is scaled correctly. I'm thinking that I'll enter the setpoint at the HMI and verify the voltage at the input. So with a setpoint of zero (0) psig I would expect 0 V at the input and with a setpoint of 75 psig I would expect 10 V the input, which would then be configured at the device to correspond to 75 psig.

Is this a good way to test analog output scaling? Is there anything I'm missing?


texts: What is the reason for my 74LS08 Quad AND gates' weird behavior?

texts:
I have a simple circuit that consists of three binary counters that are 74LS161 in cascade, three 74LS08 AND Gates and a Flip Flop.
The AND Gates connected to the output of the counters recognize when a certain number is reached and set or reset the Flip Flop.
What I noticed with the oscilloscope is that the output's wave is correct when I put the AND Gates in a certain order, but it is incorrect and random when I switch the AND chips.
All components are brand new. What I don't understand is that if one of them was broken, the output should not be right in any case.


texts:
I was reading Hayt Kemmerly Engineering Circuit Analysis Book,(I tried others, but this is the most comprehensible to me.), And I came across this circuit. I understand the first two, but I don't understand how, in the 3rd circuit (c), there is negative voltage through the resistor \$R_3\$ , while the current through it from \$+\$ to \$-\$ is positive \$7A\$. I don't understand how resistors can supply voltage. My guess is this is only a mathematical model, not real.
Edit: The Answers are shuffled in this book.
Edit 2: It looks like this book is not in the public domain, as I originally thought. However, I am not removing this image because it falls under fair use.


texts:
How would I wire a light-emitting device (not necessarily an LED) in the following schematic to indicate the input (High to run) is high? Would it be in parallel with R4? Before or after R3?

Thanks, Russell McMahon, for making the schematic for me.


texts: Simplest AC-DC: charging capacitor at needed AC input voltage

texts:
To implement a simple AC mains input circuit to charge a capacitor with low voltage DC I think that it should be possible to connect the output capacitor to the AC line through a diode, and a transistor which will disconnect the capacitor from AC line after the input AC sine will go higher than some certain voltage (Uthr on the picture). So the power will be consumed from the input AC line only within narrow periods of time when the AC voltage is higher than the current capacitor voltage and lower than some certain limitation (let's say 30 Volts):

After this "rectifier" an LM7805 or similar IC can be used to stabilize the output voltage.

I suspect that this schematic can be useful in application not demanding for power, efficiency, input to output isolation and power correction factor. However it could be extremely cheap and simple.

If this was already been realized, how can I search for related products (switch driver schematic, special purpose ICs, switches...)?

UPDATE 1

I have to say sorry to many of downvoters for my poor English. This was a struggle for me to put my idea into English words.


texts: How to find out the output of state machine if not listed

texts: I'm studying Moore and Mealy machines, everything works fine, until I found a Moore machine where output was not listed.I know that outputs of Moore machines depend of present state, but how can I figure out the output in my case? If u ask me about the output of below machine, I'd say is '100'. But why is '100' and not '000' or '010' ?


texts: What do you call it when you add energy to an inductor?

texts:
When you add energy to a capacitor, you say that you are "charging it".  (This is kind of a misnomer, since the total amount of charge in the capacitor is the same, but whatever.)

But what do you call it when you put current through an inductor, and it ________es up and forms a magnetic field?

Edit: Actually, using "charge" for a capacitor is not a misnomer, as shown below and in 'charge' etymology, though it leads to confusion, with people mistakenly thinking that capacitors store electric charge, when in actuality, the charge of energy just moves the electric charge from one plate to the other.


texts: On several PC motherboards, I've noticed some solder blobs on traces and vias. What's the deal with that? Are they some kind of test points? If so, how are they used?


texts:
I'm trying to add an USB keyboard to an old 8-bit Amstrad CPC 464 home computer, like is done here.

To make a brief summary:

The keyboard is designed as a matrix with 10 lines and 8 bits per line, where each bit indicates the state of a key.

The scan of the keys must be done in sw by polling. The process, described here in detail, consists on the the CPU configuring the PPI (Programmable Peripheral Interface), first to output the keyboard line to scan on lanes C0-C7 and, second, to read the results from the A0-A7 lanes, which are connected to the PSG (Programmable Sound Generator) which also acts as a keyboard interface.

Here is an excerpt of the schematic with the involved parts:

The problem I'm facing is with the 74LS145 decoder. The original keyboard works well, so there's nothing broken. I'd expect to see the polling on the decoder input lines and the outputs changing accordingly, one output activating at a time indicating the selected keyboard line. All of that regardless of any key been pressed on the actual keyboard. But, although I see that the polling is done and the ABCD input lines change, the output ones are always L as long as I do not press any key. It's like the decoder would only be enabled if a key is pressed, but I don't see any enable pin on the decoder.

How can it be? The behavior of the decoder is simple, it just reacts to its inputs selecting one of the outputs. I don't see how output can depend on anything more than that...


texts: Are there any single logic gates which are just individual components?

texts:
As the question says, I need a NOT gate for a simple Bi-Colour LED circuit.
I do not want to use an IC with 6 or 7 integrated as I am only going to use 1, so it's just a waste.

So, do individual logic gates exist?

Do they have a specific name?

Note: Just so you know, I'm not looking for shopping advice. I just need to know if a component exists or not. Thanks!


texts: What is the internal structure difference between diode can take current and another one can take more current than the first one?


texts: 8-Bit stereo audio R-2R DAC, is this a right way to do it?

texts:
I am new to electrical engineering and the first project I would like to do is making a digital to analog audioconverter. I've found out that a good way to do this is to use an R-2R structure for the conversion.

I'd like to challenge myself and start from scratch with the digital part of the circuit, besides the fact that I can't really find any solutions on the web to help building it. I've got a circuit simulation program and started designing, while searching the web for all different kinds of electronics you might use for it.

Now I think I might be somewhere in the neighbourhood of understanding the principle of a DAC, but it would be helpful if someone experienced could help me check if I do in fact get it. Is this a right place to ask for that?

If so, here's the circuit I've designed:

I have used a shift register with output latch for each channel and linked Q7S from one to the other to feed the data. Is it right that audio files alternate left and right channel, or vice versa, in blocks? e.g. in an 8-bit file: 0010 0111 for left following 0010 0110 for right?

The shift registers I've used here are 74HC595s. When shifting-in bits non of the pins will be (momentarily) be active. When the latch [STCP pin] is triggered the bits get transferred from the shift register into the storage register, where they will directly output their value to the corresponding pins and stay active until the next 16 bits are allowed in.

Then there is the crystal, for which I've used a square wave signal to imitate one with the right oscillating frequency: 24,576MHz. It feeds the counter in which the frequency gets divided to output the frequencies my DAC needs. In this case the sample frequency has to be 192.000kHz and therefore the frequency at which the data is shifted in has to be 3.02MHz (192.000 x 16 bit). The 192.000kHz clock speed is used to trigger STCP.

The next thing I want to do is to figure out how to load data from a source (Raspberry for example) through maybe I2C into a buffer in the DAC and from there clock the bits out into the circuit you see here.

If you think I am or I am not on the right way, it would be very helpful to let me know.

Thanks!
Rogier

By the way, I forgot to mention that the DAC I would like to build is at least 24-bit per channel at 96kHZ. It just takes up a lot of space on this threat and shouldn't be difficult to add them afterwards. It's the same principle.


texts:
This is my first question here; if  its    not good enough, please let me know. Thanks

For underground cables, we can choose "concentric neutral cable" or "tape shielded cable".

For the first one, it contains 1/3rd sized neutral or full size neutral.
According to the following website:

http://peguru.com/2012/12/power-cable-neutral-and-system-grounding/

1/3rd sized neutral is used for three phase supply.
full sized neutral is used for single phase supply.

What is the difference of the structure between them?

Sorry, I do not see a full explanation on website as far as I can find.


texts: Narrowing the beam of an ultrasonic sensor

texts:
I need to measure the distance to a solid or liquid in a round tank about 2 feet wide and 5 feet deep using a sensor that can output PWM and run at 3.3 or 5 volts.
After testing, I've found that the HC-SR04 has too wide a beam to measure accurately at all distances within the tank, from what I assume is echos off the walls. I've found a MaxBotics sensor that works but is too expensive to use when making multiple sensing units.
Do you guys know of any cheap sensors that may be able to fulfill these requirements or a way to narrow the beam of the HC-SR04? It seems like an "exponential horn" on the sensor is one way to narrow the beam, but I can't find any resources on the dimensions of such a horn.


texts:
I am connecting 7 solar cells, the data or info shown below -

simulate this circuit – Schematic created using CircuitLab

The above schematic is how I am rigging up my solar cells. There are 7 cells in series. I am assuming each gives out 2.740V(Voc). So 7 in series = 19.18V.
I am making 2 different panels (each with 7 cells). They are connected in parallel to increase the amperage to the batteries via an MPPT charger. max current drawn is 0.5Amps per panel.

Now, my doubt can be stated in 2 phases -

1) Imagine there is full light incident on panel A and not so full on panel B. So, panel A gives out 0.5Amp, while panel B gives out a lower ampere, right ?

2) Panel A , suppose gives the max of 19.18V. So, in Node 1 we get approx that value. Panel B,due to lesser incident light , gives approx 15V,at node 2. What will be the voltage at node 3 ? Will any current be even drawn via node 2 ? because the cathode of D9 will be at higher voltage than anode of D9, so current will be forced in or rather the D9 will be reverse biased, thereby blocking any current from panel B.

Hope my reasoning and logic is correct. If this is so, any panel, connected in parallel will work only if same light is incident on all of them, which is a stupid thing, right ?


texts: Fast, long linear motion (about 60 cm/ 23 inches)

texts:
I'm currently researching a way to build a punch imitation (for boxing training) and for this i need a simple, fast (if it can be configurable great) and long linear motion which can handle a resistance (if the punch land on someone's face).

The things that I found which are similar to what I'm looking for are: solenoid (which, from what I heard have limitation when it comes to size) and a linear actuator (which is kind of slow from what I saw in couple of videos).

I'm really inexperienced when it comes to physics and hardware, so I need some kind of advice on what tools to research (mechanic parts and hardware) and for what to look for in general. Any help will be appreciated!


texts:
I need advice here.

One of my mid term hobby projects is to build an instruction set emulator of popular ISAs (e.g. ARM7) on a FPGA device. A lot of people have done this before.

My requirements are specific. I am looking for a development platform with SoC reference project and onboard peripheral support. Idea is to focus only on the CPU while the rest of the stuff comes from a reference project. It should be possible to compile and download an application in C into onboard volatile memory such as SDRAM have the soft core execute it.

What could be a possible development platform?


texts: Can I cut a circuit board and will it still work?

texts: I have a pc usb and front panel audio circuit board, and I only plan on using the audio connectors. Can I cut off the USB ports part of the board and still have functional audio ports? The usb does not connect to the audio connectors on the board.


texts: Is there a safe way to operate any type of a tesla coil on a functioning modern car (moving road vehicle)?

texts:
(Updated with clarifications)
Could a tesla coil be safely built, installed and operated on an active road vehicle which is driving a regular city street? Let's say we want the discharges to be 20-30cm long in the longest direction. Could that tesla coil be actively operating for long periods of time on that car while it is moving, or would this inevitably damage some parts of the car or immediate surroundings (like other cars or electric equipment around that) around it? If it could be switched on/off, then perhaps it would be enough to only make sure it doesn't damage the car itself, while turning it off when too close to other cars or objects.
If there is a safe way to operate it, does that way entail building some kind of electrical cage around the tesla coil? Or would that not help? Or is not even required? Would it need to be a bipolar TC since those don't require ground connection?
How would you even approach this question, what would be hypothetical damage to the car if it was not in fact safe? For the types of the damage that it could cause, is there a way to diagnose, monitor and prevent it? For example if the problem is RF frequency interference, is there a way to shield the electronics from it, or monitor it with some sensor to make sure it is within a certain range?
Several people have asked what the "intend application/usage case is". The usage is to use the tesla coil as a show, for coolness factor. (But are they really ever used for anything else at all? Maybe scientific experiments?) The regular operating environment would be normal city streets.


texts: Modelling transistor V_be and bulk resistance

texts:
I'd like to calculate algebraically the DC behaviour of various bipolar transistor circuits that used matched pairs or quads (exponential converters, current mirrors etc.), taking into account the imperfect matching between transistors and deviations from exponential behaviour. The aim of this is to see when cheap matched pairs (e.g. DMMT3904W) will suffice for a particular application, and when precision parts (e.g. SSM2212) are required.

Two of the parameters specified for the above parts are the offset voltage and bulk resistance (\$r_{be}\$). In the context of an Ebers-Moll model, where the emitter current is given by
$$I_e = I_s (e^{V_{be}/V_t} - 1)$$
how should I model these parameters?

Should I model the offset voltage just by specifying a different \$I_s\$ for each transistor in the pair?
As I understand it the bulk resistance is effectively a resistance in series with the base-emitter diode - but is the voltage drop across this resistor equal to \$r_{be}I_b\$ or \$r_{be}I_e\$?


texts:
My lack of knowledge makes me see this as contradictory, but:

I've read that mosfets are better (especially for logic gates) over BJT, because they don't consume power, don't require so much voltage (or current?), react quicker and such.

However, I also read that if the voltage on the gate is below 10V, they will act like resistors and generate lots of heat. So it makes me feel that both gate and drain-source voltage must almost be equal, for a 12V battery ?

Finally, I also read that mosfet can have noise at the gate, so if it was for a CPU, wouldn't that be a huge problem ?

Thanks!


texts: How does a CD-ROM rotor know when to stop the moving plate?

texts:
I need to make a mechanism with a RaspberryPi like in CD-ROMs, so I can easily move a plate from the minimum position (CD-Rom closed)  to maximum (CD-ROM open). I have a DC motor (from CD-ROM) and I can only tell it to turn around a given angle. I've also tried using the CD-ROM itself, but it is far to big.
How can I determine if the plate reached minimum or maximum? Or maybe I can modify the CD-ROM to make the mechanism smaller (I have a lot of them so I can experiment)?


texts: How do I get the transfer function from this step response?

texts: I have the following step response of a closed loop system. Using the calculations below, I tried to calculate the transfer function. I am trying to get the same response in Matlab. However, I seem not get it right. Can someone please tell me what I am doing wrong? My result in Matlab as well is given below.


texts: solar panel: how much energy has been charged?

texts:
first time here and still learning.

I have just ordered a 100W solar panel with these specs:

V:21.61V
I:5.73A

I am aware that to calculate the power output i can multiply V x I.

However the sun is not always shining and the panel is not mounted on a sun tracking system, thus sometimes the solar panel will output more than other times. The questions is: is there a way (like a digital device) to read how much energy (or power) has been produced by the panel at the end of the day?

I plan to connect the panel to a 12V car battery and then keep an LED light turned on for about 14-16 hours per day.


texts: Given an Op Amp where the output voltage is fed back into the negative terminal, why is the gain one?

texts: Apparently, the gain of this Op Amp is one, but I can't see how I could figure that out. Can someone help?


texts:
I'm working with a device that reads and writes to an eeprom via I2C.  It automatically uses a starting address at the bottom (beginning) and I cannot change this.  But this device uses a fairly small amount of space compared to common eeproms these days.  I would like to introduce a system of alternate options("presets", "programs" or "spaces" if you will) using a hardware switch.

Is there a shift register type of device that can cause the addressing of the eeprom to shift up by a specified amount such that the master device will think it is reading from address 0 but is actually reading from a much higher address (a different address space of the eeprom that does not overlap)?  I would need this shifting to be controlled by my hardware switch and I want at least 5 different "address spaces" to be possible.  If I understand correctly, this is kind of the opposite of an I2C mux.

Update:
To help clarify the question (although Duskwuff understood and provided a useful suggestion):  The main device reads initialization data from an eeprom when it starts up. Very simple setup.  It just starts reading at 0. I wanted to create a system of startup presets for this device such that a multiple position switch of some sort would allow the user to select which startup preset would be active.
But I was hoping to do this without using a separate micro-controller and/or multiple eeprom chips.  The question was about whether there is an obscure (or not so obscure) chip on the market that can "translate" the address of the read (or write) 'I2C transaction' in order to map them to a different space in a single eeprom.  Board space is one consideration for why I was looking for such a thing.  It appears that the answer is "no".  Although if I can find a micro with enough internal memory I might be able to use it as a one chip solution (as mentioned in the other aswer and commments). So far, I haven't found a suitable micro but the project is back-burnered anyway.


texts: Why is there a 5V linear regulator on this USB ATTiny85 dev board?

texts:
This dev board. 78M05G regulator, attiny85 MCU.

Similar (ON MC78Mx05) regulators' dropout voltage is listed at 2V0. USB voltage is specified at 5V0 (+0V25)(-0V55). The ATTiny85 can take 2V7 to 5V5, though for some variants the 4V45 low end of the USB spec straddles a speed grade.
By my understanding you're operating in undefined territory if you are below the sum of output voltage and dropout voltage, which would be 7V here. So why the linear regulator? Alternatively, what am I missing?


texts: How are most ALUs built, and is it possible to 'build your own'?

texts:
I've been REALLY really trying to learn about the very low level of computers. I've been looking at a lot of homebrew pages and it's quite a lot to take in. I took classes in electronic engineering in college, but we didn't really go into super depth on the subject (it was computer science, so most of it was in fact algorithms and such).

Anyway, how are/were most ALUs built? I realize that's not the only part of a computer, but still it's an important part.

And could you sort of build your own ALU just using logic gates (for learning purposes)? I understand this probably sounds stupid to those more knowledgeable, but I'm just trying to understand. (Heck, even a simple adder would be a neat project.) If so, how would this be done? Are there any hardware examples? (I've looked around Google, but I can't find anything that kind of has a step-by-step guide explaining things).


texts:
I have decided to implement a FIFO buffer in verilog (for fun). Here is my primary prototype you can say :

It will consist of a register bank or memory.
Each register will be of size N and there will be M such registers / shift registers.
The registers support serial write and serial read only ie serial-in serial-out topology.
Two registers 'read' and 'write' will be used which act as enable signals.
A register 'writeLoc' is used which tells where data was last written to. Its size should be M. It is decremented with each write.
A register 'readLoc' is used which tells where data was last read from. Its size should be M. It is incremented with each read.
If readloc = writeloc,

if last operation was read, then buffer is empty.
if last operation was write, then buffer is full.

A register 'lastOp' is used to signify last operation. It is set whenever last write was sucessful. It is reset whenever last read was sucessful.
A register 'isEmpty' is used to signify that buffer is empty. It is set whenever buffer is empty.
A register 'isFull' is used to signify that buffer is full. It is set whenever buffer is full.
Experimental feature 1 : A register 'lock' can be used to prevent reading data while writing and vice versa. 'lock' is                            set whenever 'write' is set ie whenever data is being written. 'lock' is reset whenever no data is being written. The reader can read from buffer when 'lock' is reset. Likewise, the writer can write to buffer whenever lock is set.

However I have a few concerns :

1) Firstly, have I left out some critical component ? And is there some flaw so far ? Keep in mind it is meant to be a simple design, with 'essential' functionality.

2) My first concern is whether buffer full and empty conditions are correct or not. I have tried my best, but I'm not sure.

3) Can isEmpty and isFull registers be dispensed with ?

4) At the receiver end, the data can come any time. I feel that if I implement the lock feature, then if at the time when data is coming and lock is held by reader, data will be lost. On the other hand, lock is also necessary to prevent reading while writing and vice versa. Can you point me in the right direction as to how to overcome this problem ?

(Apologies if this question does not belong here. Please be kind enough to suggest appropriate place).


texts:
I am new to electricity & electronics, and I'm interested in using this "On-Off-On-Off" pushbutton in a project. I want to just make sure that I understand how its intended to be wired:

In that diagram above, it looks like I'm supposed to wire the middle pin to power/PWR. It also looks like I'm supposed to wire both the left and right pins to other (independent) "left" and "right" circuits, and eventually wire them both back to ground/GND.

If that's correct, then I believe what will happen is:

I push the button for the 1st time, and it will route power from the middle pin to the left-most pin (thus providing power to whatever circuit that leads to).
Then I push the button a 2nd time, and the switch turns off (no power to either left- or right-circuits).
I push the button for the 3rd time, and it will route power from the middle pin to the right-most pin (thus providing power to whatever circuit that leads to).
Finally, I push the button a 4th time, and again the switch turns off (no power to either left- or right-circuits).
This pattern repeats indefinitely

Is my understanding of the wiring and behavior here correct, or am I way off base?