texts: Using Titanium as antenna in implantable tracking system

texts:
I have some question regarding using titanium as antenna. I have to think about an implantable tracking system for animals. One of the requirements is that it should be as small as possible. Other requirements is that it should has good range and transmission power, while being super low power.

For this I am thinking of using CC430F5137 uC that has embedded radio (433MHz) and wake on radio capabilities. The design should also have accelerometer and temperature sensor as well. This components added together, will exceed the maximum length and diameter of the capsule I have in mind which is around 2(w) by 8(l) cm dimensions.

So basically it will be a battery and PCB inside some sort of bio safe capsule. This forces using an external antenna, basically a piece of wire that exits the capsule. Since the only metal I know that does not react with body is titanium, what would be your thoughts about this?

The length would be something around 8cm (considering 1/8 of wavelength)

Also it comes the problem of soldering the titanium on PCB which I believe it is not possible, unless I think of a socket that antenna goes in and fixes in place.

please let me know what you think.


texts: Need to understand AC current resistor/capacitor circuit

texts:
I'm very confused about capacitor & resistor in AC current circuits, I followed the equations but still confused, my question is will the voltage & current be decreased ?

If we applied an AC current 220v/60Hz on point A let's assume R = 1K  C = 100nF, What will voltage and current be on point B ?

Please if you don't mind to let me understand the result by running equations


texts: how can homeplug device send ethernet down mains wiring

texts:
AFAIK when you wire a patch cable out of 5e, you only need to wire two of the conductors correctly for it to function as a ethernet cablebut you won't get gigabit ethernet.

However Homeplug uses your mains wiring which clearly only has 2 connectors and a earth wire.

Does home plug use the line conductor and netural as a pair?


texts:
strong textDoes anyone know what kind of led driver i need for this strip ?? its not started flashing

https://ibb.co/prTq90P


texts: How to calculate discharge time of DC motor via flyback diode in H bridge

texts:
The setup is as follows:
DC Motor: Brushed DC Motor
PNP NPN standard H Bridge with 4 numbers of 1N4448 for flyback protection.
Stall current of the Motor: 200 mA (Stalling is expected)
Typical load current is 80 mA.
Motor cannot run freely unless driven.
DC resistance of Motor in OFF condition is 13 Ohms.
Voltage applied across Motor varies from 2.2 to 3 V depending on battery voltage.

How to calculate the time taken to discharge the current through the flyback diodes and DC motor when Motor is turned OFF suddenly?
The inductance of Motor Measured using Agilent LCR meter is about 8.12 mH.

Edit: Purpose of this is to have an idea on the delay to be introduced before driving the motor in other direction, if it makes sense


texts: Why is the motor phase current like this in six-step BLDC drive?

texts:
I am using the inverter circuit I posted before Inverter in this previous thread to drive a BLDC motor. However, the current waveforms have some strange shapes that I couldn't understand. Below is the Hall sensor signals and current waveforms.

I have confirmed that the six-step switching sequence is correct with respect to Hall signals. So my question is, why could the current peaks marked in yellow circles happen? How to eliminate them?

[Edit]

The current is measured using Tektronix TCPA300 current sensor and clamped at individual motor terminal wire. I also captured the Vgs for upper arm and lower arm and I couldn't see there is wrong ON status for either one.

Upper arm Vgs vs current

Lower arm Vgs vs current

I also tested another driver board which has only 6 MOSFETs in the inverter, the phenomenon is the same. The following picture is the motor terminal voltage Va vs. Ia. From this picture, it seems the lower side freewheeling diode was conducting when both upper and lower MOSFET was OFF. How could that happen?

[Edited again to answer @John Birckhead]

Here is the results showing the ground at MOSFET current path side and the gate driver side. However, from the results, I couldn't conclude that lower side MOSFETs were wrongly turned-on because of noise spikes on grounds because their amplitudes are only less than 1V.


texts:
I am trying to measure the temperature from four MCP9700AE temperature sensors (http://www.digikey.ca/product-detail/en/microchip-technology/MCP9700A-E-TO/MCP9700A-E-TO-ND/1212508) using an ATMega 2560 microcontroller. However I get different temperature readings depending on which 5V input on the board and which ground on the board I use. I measured the potential difference between the 5V inputs and grounds using a multi-meter and they are all the same. So I don't understand why the temperatures are different. Anyone have any ideas?

By the way I tested this using two different AT Mega 2560s and the results were the same.

So I hooked up a 10 DOF sensor that has a temperature sensor as well to the ATMega. (https://www.adafruit.com/product/1604)

This chip requires an SDA and SCL connection. Now all the temperature sensors give 21 C temperature reading. Not sure what this modification does as I didn't change anything for the MCP9700A.


texts: MIPS Assembly Memory Addressing "Pseudo Direct Addressing"

texts:
Could anyone explain how does Pseudo Direct Addressing work in MIPS?

I don't really get how does using the last 4 bits from the PC (Program Counter) fit into the picture?

Suppose I want to goto Address

0000 0000 0000 0000 0000 0000 0000 0100

And my PC looks like 0101 ...

Then I can't? Because I will need the last 4 bits to look like 0101 instead? So it will somewhat be relative to PC too?


texts:
In synchronised circuit, if output of first IC is connected to input of second, should I bother about setup delay or will it work just fine?

If not then what about longer chain? When will be an issue and can I just run circuit on slower clock and it will work again?


texts: Minimizing reflection coefficient of a low-pass filter

texts:
I'm trying to figure out (with not a lot of success) as to what I need to consider when I want to minimize reflection coefficient below a certain point. I'm trying to  design a low-pass shunt stub filter with reflection coefficient below -12 dB (and a given \$f_C\$, but that part is easy).

Here's an example of a fifth-order Chebyshev low-pass filter with ideal components.

The reflection coefficient will spike in two spots of the pass-band on Chebyshev's prototype filters like so:

I tried different orders of Chebyshev filters and I tried swapping the filter design to Buttersworth/Bessel, but they all had their own characteristic reflection coefficients that way exceeded the desired value (example, Bessel's reflection coefficient would be very big towards f=0 Hz and would decline somewhat fast, though it was still too high of a value from what I desired).

So I have a few things I'm pondering about it.

If my pass-band is whatever it is, do I usually have to care about the reflection coefficient at extremely border cases (just at the cut-off frequency or after it or at near-zero frequencies when the cut-off frequency is at GHz scale)

What things should I consider when I want to minimize reflection coefficient up to a point?

And if someone thinks that I've fundamentally approached the problem in a bad manner, that'd be great to know as well.


texts: Appendix C.3 Resistance marking of The Art of Electronics, third edition: Finding resistor values

texts:
I am currently studying The Art of Electronics, third edition, by Horowitz and Hill. Appendix C.3 Resistance marking says the following:

Leaded resistors are marked in one of two ways: (a) with  a set of four or five color bands, indicating resistance and  tolerance; or (b) with a 4-digit resistance code, followed by  a letter that indicates the tolerance. Surface-mount resistors  use either (a) a 3- or 4-digit resistance code, or, for the  smallest package sizes, (b) no marking at all!

I don't understand the description of C.1.: Am I supposed to be able to tell from the information given that "yellow-violet-orange-gold" is 47 \$ \text{k} \Omega \$ and "yellow-white-white-black-brown" is 499 \$ \Omega \$? I understand how the tolerances were found, but it isn't clear to me that the the information given in this section alone is sufficient to deduce these values.
I would greatly appreciate it if people would please take the time to clarify this.


texts: Saving the state of the LED on illuminated momentary button

texts:
I have three illuminated momentary buttons with a separate anode and cathode for the led.

 (source of image)

I want a circuit that illuminates the LED of the button that was most recently pushed.

My initial idea has been to use three SR Latches created using NOR gates. Connect the S or Q of each latch to the reset of the two other latches. But then this creates the opportunity for HIGH on both S and R which is disallowed. Right?

I imagine there are other ways to accomplish this without latches too. Any help is greatly appreciated.


texts: can't mix new and old batteries. how are people building battery packs out of old laptop batteries?

texts:
Why is it bad to mix new and old batteries?

Link about why you can't mix new and old batteries

yet this guy, who is an engineer is building battery packs out of cells he scavenged
https://www.youtube.com/watch?v=Z-VLdE6RxYQ

and also I can't add an extra cell to my ebike becuase my batteries are 4 month old (mine are sla though had 100 cycles on them)


texts: DC coupling - How can I reduce low frequency noise?

texts:
I'm using a precision 16-bit DAC (AD5689) to create DC bias current source, as indicated in the following picture and I'm detecting a high level of low frequency noise.

I represented L1 as an inductor for simplicity, but it is a filter with an high output inductance.  Vout is a signal DC (controlled by the DAC) + AC (from L1).
At the moment I removed the AC component so that I could analyze the noise. I connected Vout to a opamp chain with gain of ~19k compensating the DC offset. From the datasheet of the DAC, the integrated noise (0.1 10Hz) is 6uV. That would give an output noise of 0.114V at this gain (without any filtering). I simulated the circuit with the opamp chain and I get  76mV of output integrated noise (0.1Hz 100MHz).
Scoping the output from the opamp chain, I got the following picture:
(2V/div 1s/div)

I managed to track down the noise to Vout, since I probed the signals along the opamp chain and they are coherent. Given that the problem presents at low frequencies, I tried increasing C1 and C2 and adding a capacitor to the DAC output (300uF), but the noise level remained similar. I also resoldered the DAC just in case.
Is there a way to reduce this noise?
Eddit:
Shorting Vout to ground reduces the noise level as seen in the following picture. Unfortunately I used a probe to short Vout which may have introduced some noise.

Eddit2:
Simulation of current and voltage requirements @ DAC , C1, C2
DAC: V(n006) I(v1)
C1: V(n001) I(C1)
C2: V(n002) I(C2)


texts: Components to avoid using on an ultrasonic cleaner

texts:
What components populated on a PCB are not safe to clean in an ultrasonic cleaner?

It is not limited, but I specifically wonder below components if they are safe to use or some requires special attention (low temperature, low power, or what kind of attention is recommended):

MCU/ICs
SMD resistors
MLCC
SMD inductors
Aluminium electrolytic capacitor
Crystals
u.FL, SMA,.. type RF connectors
power transformer (e.g, flyback)
SMD transistors
Optocouplers
Choke
Fuse
SMD LEDs

I read that in some cases crystal oscillators may get damaged because of the ultrasonic power. What characteristic does it depend on? I have 24 MHz, 40 MHz, and 32.768 kHz crystals with 20 ppm tolerance. Does any of them sound on a risk group?


texts: Push-pull converter transformer calculation

texts:
every one,
I am an automation engineer, not an electrical, but I have some knowledge about electricity (I hope).
I am designing a power supply with input voltage of 3,1V and the output voltage of 175V (10mA max). I am using push-pull configuration like on the figure below.

This schematic requires custom transformer. I am pretty much limited with free space within enclosure. As a “real” engineer to make this power supply I first tried to brute force the problem. After few failed attempts I have a working prototype on the breadboard. I winded the transformer from an inductor. It functions approximately at 230 kHz (I know, 230 kHz and breadboard is complete nonsense and stupid). That is why probably I have so much lose and terrible energy conversion efficiency, as well as because the transistors are getting very hot(I believe they are running at their maximum).

In order to make everything properly this time I read a book “TRANSFORMER AND INDUCTOR DESIGN HANDBOOK Third Edition, Revised and Expanded “ by COLONEL WM. T. MCLYMAN. Link to the book Link to the book . If I understand correctly in order to decrease the size I should to increase frequency even more. So I decided to switch to MOSFETs. The schematics with MOSFETs looks as follows.

I have Si7940DP laying around, so I will using it. Also in order to increase energy conversion efficiency I want to wind a proper transformer. I have made calculations (version in google sheets with formulas) for that. Calculations have been made according to the chapter 7 from the book.

Can somebody verify my calculations and say to we that I am not dreaming or vice versa. That I can reach such frequency with MOSFETs and transformer  Also there are few sings that I do not understand completely, they are marked with red. There are:
1. How to choose “Operating flux density” and how it affects the design?
2. And how to choose “Magnetic material”, what Permeability (L - 900, R - 2300) suits better?

Hate and critics are welcome.
Let me know if additional information required.

Thanks for help,
Arttu


texts: Is my current transformer rated for 11kV Tranmission line?

texts:
I'm using a current transformer to measure current on HV transmission lines.
Except i'm finding it difficult to find a split core CT that will be rated for 11kV.

My CT that i'm looking at is the DP-58 1000-5A 5VA transformer
It has a maximum voltage 0.72/3kV.

CT Link

How do I know if will be safe on an 11kV line and does anyone else have any other recommendations?


texts: Connect a switching power supply to the EU grid

texts: I just bought a switching power supply which is supposed to be connected to the power grid using three connections (Neutral, Live and Ground). Unfortunately, all common cables can be plugged into outlets in any rotation, which means that I don't always know where Neutral or Live is. Does this imply that I can only hard-wire the power supply and that I can't use a standard cable?


texts:
I have a two strips of WS2815 neopixel LED lights (400 pixels per string) being driven by WeMos D1 minis with the WLED library to control them.

Since the two strips are on opposite sides of my porch, I purchased a 25' 18/4 solid wire to run the strip furthest away from the control box & power. However, when turning the pixels on they turn the appropriate color for a second and then the entire line starts to flash erratic colors. It isn't flickering or dimming so much as changing color randomly. If I reduce the amount of LEDs being controlled to 200 or less it seems to function fine (other than only half the string being used).

My first guess would have been voltage drop, but that doesn't seem consistent with the result being produced (I would have expected discoloration or dimming). This is my second cable (the first one being 22/4, thinking the gauge was too small I went with 18 on the new one), the new cable seems to be able to control more lights than the prior cable but not the whole strip.

From individual testing I'm positive that the power supply, controllers and LED strips are all good and in working order, so I'm left thinking it has something to do with the length of the cable.

Am I overlooking something? Could 25' be too long for a data/neutral wire? Would splicing in a single pixel halfway through do any good (acting as a signal repeater)?


texts: In the CB configuration, a signal is applied to the emitter to create an in-phase amplification at the collector. I am confused, however, on how exactly this happens. In the picture below, if the input signal raises the emitter voltage on the positive swing, it would mean that there is a larger voltage across the emitter resistor, which by Ohm's law entails a larger current and thus a larger voltage drop at the collector resistor. For an in-phase amplification to happen, there needs to be less current at the collector, which means I am failing to understand this configuration. Can anyone please help clear the fog?


texts: How to make this I2C OLED screen work? (probably SH1106)

texts:
I have just received this screen: link but unfortunately it's different then other showed in reviews. That's my version link

It's probably based on SH1106 but I can't make it work. I have tried few popular Arduino libraries but I can't get address of this screen from I2C scanner - it's not answering.

Anyone knows how to program it?


texts: I need a pre-amplifier for my sound card with high gain without noise

texts:
I'm trying to make a pre-amplifier for my PC microphone with high gain and low noise.
I tried a few circuits but they had a lot of noise and low gain.
How can I make a preamplifier with high gain and low noise?

Frequency range: up to 20kHz
Supply voltage: 5V

I tried this circuit:


texts: i read in a book that when we have for instance a NAND or NOR gate ,the processor doesn't lose energy because we do not have direct current transfer from Vdd to Vss so the processor does not consume energy (apart from some leakage currents). I didn't understand it so much ,so my question is, why we don't have?( if someone could be more specific)


texts: Why my Toroid Isolation Transformer has 112.3v to soil

texts:
I'm looking for a brand of Toroid isolation transformer with electrostatic shielding. There may be one brand which has this. Unless there is just none in the whole world? Is it not possible to put electrostatic shielding in any Toroid isolation transformer?

Original message (findings: It's a semi isolation transformer)

I bought a Hammond Isolation Transformer (dual 234v/117v primary and secondary) for isolating test projects from ground. But when I measured it from one of the output to the soil, it measures 112.3 volts. The other lead is near zero. I thought it was supposed to be isolated to ground.

Here's the model.

https://www.hammfg.com/electronics/transformers/power/1182.pdf

I chose the m117 model or 500va.

Here's the primary connection

Here's the secondary connection

Note all the 4 windings have no connection to each other initially (tested using continuity meter). Even after connecting them right. There is still no connection between primary and secondary (any of the wires), when not powered.

It's not an autotransformer which has connection between one of the leads of the primary and secondary. Unless a toroid autotransformer has no connections between the primary and secondary too?

So why does one of the leads reads 112.3 volts to the soil? Isn't it an isolation transformer?  But the primary and secondary windings are supposed to be separate which is what makes isolation transformer, isn't it. What do you think?

An autotransformer only has one winding. The Hammond 1182 toroid has 4 windings. So how could it still be an autotransformer??


texts: I have a toroidal ferrite core which has an outer diameter of 15 cm, inner diameter of 11 cm and height of 4 cm. I want to use it to make a transformer which takes in mains voltage (240V) and outputs high current (>50A) at any voltage (even half a volt will be okay). I will be using wire of 2.5 square millimeters for winding the primary and secondary of 10 square millimeters. How many turns of each do I need to make? Will this be safe? Is there anything else I need to know?


texts:
For the circuit below, what is the purpose of the 2 bias resistors.
They are said to detect breaking, what does it mean.


texts:
I have an Arduino project that

is powered from 12v/15A dc power source
needs to switch to battery power and still get 12v (dc power may start/stop at any time)
 recharge the battery when dc power restored (top-off or full recharge)
if battery dies, will still work from 12v main dc power (dead battery would just prevent it from powering off the battery)

I am thinking of using:

an 7.2v 1500mah NiMH battery-pack (weight doesn't matter, so its not worth the risk using LiIon/LiPo). 10 Cells in series.
BQ2002 - NiMH battery controller
MC34063A - boost converter to boost the 7.2v from the battery controller to 12v (I only need 12v500ma out)

Are there better battery controllers or boost converters to use?

How do I do #3 and #4?

At what rate would the battery be recharged? I want to limit this to 1amp

Will I also need a temperature sensor, at least if I only charge it at 1ah?

Do I need a voltage regulator, or is the output from the battery controller going to be stable enough for an Arduino?

I want to use existing ICs for as much as possible. I want to minimize how much I have to build, but I also can't use an Arduino shield.


texts: 100VAC between concrete floor and outlet ground

texts:
I have been tinkering as an enthusiastic hobbyist in my garage 'lab' for about a year. It's an old rented house in Sydney, Australia. Puzzled by several odd small shocks and confusion as to why my oscilloscope insists that my current project's circuit ground is somewhere around +2.4VDC, I thought to put a voltmeter across the garage floor slab and the wall outlet's earth/ground terminal.
According to my DVM there is 50Hz AC present between the floor surface and 'earth' measuring over 100VAC.
Mains AC here is 240V, 50Hz.
Similarly between the floor and the project on my wooden bench which is not connected to any appliance the DVM shows 40VAC.
Voltages measured between the floor and other metal items within reach (old Tektronix scopes) are in the region of 15 to 30VAC.
The floor is reinforced concrete direct on the ground and gets damp when it rains (as was the case when I made these measurements).
I plan to tabulate voltage measurements to see if these change (with weather, say), but this suggests to me that the house's earth wiring might be wholly fictitious!
Sanity check, please - I'm enthusiastic but not experienced and I don't mess with mains power. I'd like to understand what's happening though!


texts: Can't enter Programming Mode Atmel Studio

texts:
I have a custom board based on the ATmega328. I want to program it usign Atmel ICE Basic  ISP interface, to make sure that I'm connected to the target I've tried to read it ID, I get the following :

Since uC isn't programmed before, and I'm using only Atmel Stuff to that I don't know where the  problem is, and how may solve it.
the uC is not wired to anything beside the Pull-up resistor and the and a capacitor as followed :

any idea how may solve this ?
thanks in advance !
Update
uC schematic

the programer is connected to the SPI


texts:
I am building a flight computer for a sounding rocket. I want to include redundant power supplies - in other words: parallel DC-DC converters. What do I need to consider in order to do this? (is my approach doable: see schematic)

V+ on the input is connected to two 3S LIPO Batteries (also in parallel with ORing diodes).

Additionally: would you suggest using ORing FETs instead of just diodes? That would give me the possibility to disable a power supply that has "burned through" (output = input)


texts:
I am using MSP430 UART with DMA transfer for sending Modbus packets. As a master at the end of packer I need to change my RS 485 transceiver direction line for reception.
I am sending 10 bytes in packet and at the end of last byte sent I want to change direction line. But DMA interrupt occurs when byte count reaches to zero and not when last byte is transferred. Hence I change the line in DMA interrupt my last byte will not pass through transceiver.


texts: Forward Error Correction code, Reed Solomon, Turbo Code, Low-density parity-check

texts:
I am new to FEC (Forward Error Correction). Pointers highly appreciated.

I am experimenting software with configurable "error protections". Result improving as setting raise to 40%. Still not enough 'margin'. The software uses Reed Solomon inside.

Experiemntal data suggests, 'subjective performance' should be good at "60% to 200%".   Speed is no issue. We can afford adding extra bits to raise transmission success rate.

a) Does Reed Solomon code has good scalable improvement over high number of reduanant bits? I believe many FEC schemes use 30% extra bits and we need much more.

b) Should we try newer Turbo and Low-density parity-check codes. Which one has better proformance at high redundant rate (40% to 200% reduanant bit added)?

c) Where can I get experimental FEC software with high configurable redundant rate (40% to 200%)?

The channel cannot be fully modelled since some of the error sources are human / machine operation allowance, etc. It will be heavy on 'real-life' subjective tests.


texts: Can creepage distance be separated into more sections?

texts:
Can I count that the creepage distance of two separate circuits can be divided into two sections, while the inner conductive pad/track is isolated/floating?
Similarly, can I use two resistors (200V rating, 2mm creepage) in series to achieve the same as 400V rating and 4mm creepage resistor?


texts: How does AM radio passive signal boost antenna work?

texts:
When I was a child I saw advertisements for an AM signal booster which used no batteries or electricity and was simply placed near an AM receiver and a knob turned to tune it. The ads said things like "turns a tiny transistor [radio] into a tiger!"

The pictures showed a flat round box about one foot high with the knob in the center. I saw one built with a long piece of wire on an X-shaped frame about a foot high, connected to a tuning capacitor from an old radio. How can this device boost signal strength with no energy input?


texts: I am using a MOV for relay contact protection. I am switching a pump of current 12A @230V using relay. But I faced contact arcing problem so I added a MOV. I followed this guide for MOV selection as I am using their relays. But I found some strange effect of adding MOV. The pump won't start if MOV is added across relay contacts. Without MOV pump starts. I am using MOV of Elpro with rating of 440/20.


texts:
Is there a rough relationship between the current rating of a device, say a connector, and the duty cycle? For example, I assume a connector rated at a continuous 5 amps isn't necessarily going to be able to cope with 10 amps peak at 50% duty cycle?

Edit: E.g. an ignition coil with a primary resistance of 0.5 ohms would draw 24 amps at 12V. However, at 6000RPM, it's effectively a saw tooth with a 4ms duration. The RMS voltage of which is 6.2V so is that sufficient to calculate current requirements?


texts:
I have a F system and a input of this system is e x(n) = e^iπn/4 and output is y(n)=cos(πn/4)

So is the  F system is LTI or it would be ?

I try to using addivity and Homogeneity but I cant do it


texts: Getting started with electronics with minimal space?

texts:
I've wanted to get started working with breadboards and basic circuits, but I have very little space with which to work or to store any tools. The largest contiguous surface I have is a weak 2ft by 2ft pull-out wooden keyboard drawer on my desk. I might be able to manage something with that, but I don't know how I'd be able to safely store anything I work on or any of the equipment (wires, soldering iron, electronic parts, etc.).

Given a shortage of space, is there any way to still work with electronics?


texts: I recently came across with the catalogue where the wire sizes and their specifications are listed. In that, there was a specification "current carrying capacity - 2 wires single phase". What does this specification mean? I normally know the meaning of current carrying capacity but this what does this "2 wires single phase" exactly mean. Whether it says that one wire is connected to line and another to neutral in single phase so that two wires provide that specified current rating or it says two wires in line and two wires in neutral are to be connected to achieve that provided current rating?


texts: Switch that is physically closed, and electrically opened

texts:
Is there a switch which a user pushes/actuates to close, and which can be reopened with an electrical signal, and which does not consume power to stay closed or open? E.g. the user pushes the "Start" button, which closes the circuit and powers the device, then at the end of the device's cycle, it sends a signal to the switch to reset (open), cutting off its own power supply in the process. Is there a switch or component which does this, and if so, what is it called?

Optional bonus features:

User can manually re-open the switch (e.g. by pressing it again)
An electrical signal can also close the switch (e.g. a low-power microcontroller periodically turns on a higher-power device for, say, 30 seconds, then turns it back off)


texts: I don't understand how the graph of H(w) is used to find the equation for H(150) and H(200.)


texts:
How do I synchronize this system? The data valid at the input indicates when the data is valid at the input. Similarly the data out valid indicates when the output data is valid. Both data_in_valid and data_out_valid remain high for one clock cycle.

This is to be done without a FIFO.

What is required is I am writing data at 100 MHz and want to read it at 30 MHz at the output. The signal valid_in is respect of the input clock and valid_out is respect to output clk.

clkA and clkB are both inputs. Data_in and Data_out is 1 byte written and read respectively. It is required to write data at clkA when valid_in is high and read data at clkB when valid_out is high. What I had answered was with the use of 2 stage synchronizer (running at clkB) for both data_in and valid_in and the outputs of the synchronizers wold be valid_out and data_out respectively.


texts: How to determine the critical delay for a closed-loop system?

texts: Using the open-loop transfer function we can easily determine its Nyquist plot, and from it we can get the critical gain such that the system is stable. Now, let's consider a system with delay \$t_d\$. Then, the new transfer function will have the factor \$e^{-st_d}\$ . According to the theory, we can just "ignore" this delay and draw the Nyquist and from it we can deduct the maximum delay before the system gets unstable. How can we get that delay? Can we use the phase margin to know it?


texts: What Fuse rating to use in a power entry module?

texts:
I have a 12 V DC, 80 watts fan that is powered by an 8 Amps power supply. I would like to fuse the input power entry module (Corcom) 120 VAC. It seems that most fuses out there are rated for 250 Volts.

Can I use a 240 VAC fuse on a 120 VAC circuit.
What current rating should the fuse be?
Should I fuse the DC circuit as well?

The product is an indoor table-top small spray booth.


texts: Is Arduino ideal for making a HRNG (hardware random number generator)?

texts:
I'm putting together a design for a hardware random number generator that will utilize multiple sources of entropy (combined):

Ambient light
Ambient sound (and sound levels)
Ambient temp
Ambient humidity
Position of the device itself (upside down, tilted left, titled right, etc)
Other sources in the future, possibly even GPS data (marked possible because two users may be standing next to each other, hence possibly deterministic if you know them.)

My idea is to make an entropy pool 'recharger' that people can carry around with them during their day while it continues to write to a USB drive.

After a few hours, the user will have a nice ~4GB entropy pool that can be plugged in to a PC and used. I can't afford the really expensive QRNG's based on light or radioactive decay, so I'm trying to come up with something cheaper.

In your opinion, is Arduino the best choice for prototyping this? If not, what would you recommend?


texts:
I have a small magnetic buzzer which needs to be turned on and off at 10Hz speed via an attiny13a mcu io pin. Since the buzzer is a magnetic one I am using a 2N2222A BJT NPN transistor for the switching part according to what the datasheet suggested along with a 1N4148 diode as flyback just like the diagram suggests.

The diagram base resistor 180 ohm is given for a 3.3V output pin but my mcu will give 5V 40mA on it's pin so what resistor should I choose to substitute. Will a 330 ohm do the job?


texts: I was looking for some time to find a TDA2055 or LM3886 LTSpice, but I wasn't able to find any, so I was wondering is there a way to get TDA2050 (or other equivalent op amp) LTSpice Model for circuit simulation?


texts: Can I rebuild a cordless drill batt-pack with regular AA Ni-mh batteries?

texts:
I have an 18v "Task Force" cordless drill that I got in Homedepot for $20 about 5 years ago and it has served me well. (A lot better that what I would have expected for the price paid)

It is still kicking bat the battery pack has finally died on me.

I am not an engineer but I've done a few things in the soldering and repairing of electronics and I feel confident that I can tackle this one.

My problem is that I am in a budget and the original SC1.2V 1000mAh Ni-Cd run for at least $2.50 each and i need 15 of them so at the end I am spending more on the pack than on the drill itself.

My question is what happens if I buy 15 AA regular Ni-Mh rechargable batteries and adapt them to the plastic casing? I know is not gonna look nice with all the duct tape I would have to use but is there any technical no-no or risk about switching from SC Ni-CD to AA Ni-MH?

The original charger which I was hoping to use delivers 24v and 400mA

At at least $37.50 for the real deal I don't mind risking the drill...

Thanks!


texts:
Do I need a snubber circuit across the motor here?. I implemented the circuit and checked it working fine so far without a snubber circuit. what are the possible problems that may arise in this circuitry?
Motor Specs: 24v dc ,4kgcm,FLRPM:500,2A


texts:
I am working on the development of a dual pH and dual Pt100 sensor interface for a fish farm tank control system.

The tank is expected to have about 75m3 of water, a number of pumps, and feeding systems that are expected to inject noise.

The LMP91200 have been selected as pH sesnor amplifier. Since the distance between the two pH sensors is expected to be about 6-7m and since they are high  I am wondering if there is a need of isolation between the signal conditioning cirquits of the two sensors and isolation with the controller.

Any ideas/proposals for the best approach between the follwoing? Any other suggestion?  -


texts: How to choose correct value of inductor in a circuit

texts:
I have a PCB where SIM900 is used. As SIM900 needs at least 2amps of current during transmission burst so I have used LM2576 for its power. Below is its schematic:

In the circuit, I am using 200uH inductor. During a call, SIM900 stops suddenly and inductor is blown. This happens for the first time so I replaced it and again I tried and the same thing happened. Inductor starts heating up and then it get blown. What value of inductor should I use with this circuit.?


texts: Reed switch only triggers with scope probe connected

texts: I've run into a very odd problem. I've created the attached circuit, designed to cut power supply when a magnet is brought near the device. It works perfectly with the reed switch disconnected from the circuit. However, when everything is powered up, the reed switch doesn't react to the magnet at all unless I put an oscilloscope probe on pin 2 (NC) of the reed switch, at which point everything works as expected. Datasheet for the reed switch.


texts: ATmega - magnitude comparator for hardware PWM

texts: Does someone has an information how hardware PWMs of ATmega, etc.. compare registers with timer/counter value? Is there inside a true 8bit magnitude comparator for every channell or is there some simplified solution? Or am I totally out?


texts: Correct Ethernet Jack + Magnetics for 100Base-TX

texts:
I've been shopping around for Ethernet jacks for use in a personal project. The part specifically states that it's internal PHYs are 100BASE-TX/10BASE-T/Te IEEE 802.3

I understand the basic difference between 100Base-T and 100Base-TX, but I guess I don't understand why an Ethernet jack and/or the magnetics need to be spec'd for this. It's all getting clocked through the wire at ~125MHz, right?

Digikey seems to differentiate between -TX and -T. Mouser's parametric search doesn't mention anything like the connection speed and is very unhelpful, showing me stuff with and without magnetics.

The 100Base-TX jacks with mags seem to be more expensive than -T (on Digikey) so that leads me to believe some timing requirement of 100Base-TX require entirely different magnetics specs or something. But if it doesn't matter, I certainly don't want to spend $4 on a jack when I could spend only $1.60.

Any advice? I'd appreciate it!


texts: Why do we still use cable for a lot of forms of data transmission?

texts:
Like many people I'm often annoyed by ugly cable clutter, especially when it's long distance. In my opinion it would be ideal if cables could be eliminated altogether, so that you'd just have two corresponding plugs without the cable, which you plugin at either end and transmit their information wirelessly.

Maybe that would be a little futuristic for now, but what about transporting data over a wireless computer network (or two paired bluetooth transmitters)? That's perfectly possible, and all you'd need is a little box that can convert data to a format that can be transmitted over a wireless network, and a box that converts it back to the appropriate format at the other end. Over time this technology would surely be miniaturized until it fits in a plug. (you could use this for HDMI, audio or other information for example)

Why doesn't this technology exist already? Am I overlooking something, or are there some difficulties with it that have to be solved first?


texts: Can I use just plain GCC to compile program for Nucleo?

texts:
I have a ST Nucleo F446RE. It's an ARM board which provides quite an interesting interface for uploading programs - it presents itself as USB storage device and the program can be copied on it, which causes Nucleo to reset and launch the program.

As such, I'm kinda reluctant to even bother installing (yet another) development toolchain. I'd rather just use GCC compiler, some makefile for compiling and flashing and probably some required Nucleo header libraries.

Is there a way to setup lightweight environment like this for Nucleo? It's probably worth mentioning that I'm a newbie to emdedded development.


texts:
I want to build a custom connector to attach to the PICKIT3 serial pins. I have the black plastic bit and little metal bits (similar to the picture below), and wire.

Out of these components, I would like to build a connector with a small piece of wire sticking out for every hole from the black plastic bit.

What are the steps to assemble the connector? What tools I should use?


texts:
I'm starting with a small dev board using the STM32F103C8T6. The learning curve is steep and I'm trying to find some examples regarding peripherals.

I am using the Coocox IDE, the ARM GCC, and an ST-Link.

Is there any official code repo/docs for ARM GCC?


texts: Running a N channel MOSFET from 3.3V MCU

texts:
I am trying to run a low side switch with the 3.3V GPIO output of the Raspberry Pi (3.3v MCU), and for the particular transistor I’m using (IRF520) the 3.3V is barely enough to turn it on - is there some clever positive feedback I can use to force the transistor ‘very on’ when on and off when off?

How about this, I put the GPIO into high-impedance input mode to turn transistor on, and set output=0 to turn transistor off. Current into gpio pin when output=0 is 1.2mA which I suppose is ok. Is 12V after 10Kohms ok on a Raspberry Pi input pin?


texts: Understanding constant current source in amplifier stage

texts:
I am teaching myself electronics in my spare time and I am trying to look at circuits and understand how they work. I am currently studying amplification and transistor basics, and I have started analysing the audio amplfication circuit below.
In particular, I am trying to figure out how exactly the darlington pair Q7 and Q9 associated with Q5 work: this is all quite confusing to me at the moment. The circuit description reads: 'the predriver stage (Q7, Q9) is a Darlington connection the load of which employs a constant current source (D5, Q5), resulting in a high voltage gain.'
Am I correct with the following?

constant current source: Q5 acts as a constant current source for the darlington pair. As such, if there were an increase in current at the collector of Q5, the emitter-base forward bias of Q5 would reduce (from the higher voltage drop across the emitter resistor of Q5), and the resulting lower Ib would reduce Ic and Ie. D5 maintains forward bias between the emitter and the base.
Darlington pair: this darlington pair is configured as a common emitter amplifier with Q5 as its load. With an AC input signal at its base, the positive portion of the signal increases the forward bias of Q7 and Q9, which would increase the collector currents. Since current is constant, what happens here, a smaller Vce drop for Q9 as the collector of Q9 gets closer to -B2? If that is the case, assuming that with constant current the voltage drops across R31 and R29 should remain constant, is also Vc of Q5 getting closer to -B2? Am I correct to deduce that this is a phase-inverting configuration?

I would appreciate if you could help me clarify these questions.
Thanks.


texts:
I'm having trouble with my f_open. It won't create the file on the QSPI flash. I am able to mount and make a drive so the error confuses me. Error is FR_NO_FILESYSTEM. My LL Driver is similar to this github contribution:
https://github.com/greedyhao/stm32/blob/master/QSPI-FATFS/Src/user_diskio.c
Are there any suggestions to this problem? Thank you
QSPI Memory Chip:
/* Indirect Mode */
BSP_QSPI_Init_t init
init.InterfaceMode  = MT25TL01G_QPI_MODE;
init.TransferRate   = MT25TL01G_STR_TRANSFER;
init.DualFlashMode  = MT25TL01G_DUALFLASH_DISABLE;

if(BSP_QSPI_Init(0,&init) != BSP_ERROR_NONE)
{
Error_Handler();
}

UINT fnum;  /* Number of successful reads and writes of documents */
BYTE ReadBuffer[4096] = { 0 }; /* Read the buffer */
BYTE WriteBuffer[] = " Neo...I am a GOD in the Matrix! \r\n";

/* Gives a work area to the default drive */
retUSER = f_mount(&USERFatFS, "0:", 0);
if (FR_OK != retUSER) {
 /* FatFs Format Error */
  Error_Handler();
}

/* Format the default drive with default parameters */
retUSER = f_mkfs("0:", FM_ANY, 0, ReadBuffer, sizeof(ReadBuffer));
if (FR_OK != retUSER) {
 /* FatFs Format Error */
  Error_Handler();
}

/* Create a file as new */
retUSER = f_open(&USERFile, "0:FAT32_Test.txt", FA_CREATE_ALWAYS |
FA_WRITE);
if (FR_OK != retUSER) {
 /* FatFs Format Error */
 Error_Handler();
}
if (FR_OK == retUSER) {
 /* Sanity Check */
  for(;;){
     HAL_GPIO_TogglePin(LD7_GPIO_Port, LD7_Pin);
     HAL_Delay(500);
    }
 }


texts: Setting up SPI between a STM32F4-Discovery Board and a MCP4151 Digital Pot

texts:
I'm currently working on a project in which I'm trying to interface a MCP4151 Digital Potentiometer with the STM32F4-Discovery Board using the Mars Eclipse IDE. I have downloaded and included the STM32F4xx HAL but am struggling in getting all the pins and setting right.

From the STM32F407 datasheet (page 49) I was able to deduce that I want to use PA5 and PA7 as pins for SPI_SCK and SPI_MOSI. So I modified the code from this project to enable these pins:

void SPI_Init(){
   hspi1.Instance = SPI1;
   hspi1.Init.Mode = SPI_MODE_MASTER;
   hspi1.Init.Direction = SPI_DIRECTION_2LINES;
   hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
   hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
   hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
   hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
   hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
   hspi1.Init.NSS = SPI_NSS_SOFT;
   hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_2;

   HAL_SPI_Init(&hspi1);
   /* Peripheral clock enable */
   __SPI1_CLK_ENABLE();

   GPIO_InitTypeDef GPIO_InitStruct;
   /**SPI1 GPIO Configuration
   PA5 ------> SPI1_SCK
   PA7 ------> SPI1_MOSI
   */
   GPIO_InitStruct.Pin = GPIO_PIN_5 | GPIO_PIN_7;
   GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
   GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
   GPIO_InitStruct.Pull = GPIO_NOPULL;
   HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

   GPIO_InitStruct.Pin = GPIO_PIN_0;                //Chip Select
   GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
   GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
   GPIO_InitStruct.Pull = GPIO_PULLDOWN;
   HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

   __HAL_SPI_ENABLE(&hspi1);
}

With that I try to initialize the values on the potentiometer using:

void SPI_SendData(uint8_t* adress, uint8_t* data, uint16_t size, uint32_t timeout){

   HAL_GPIO_WritePin(GPIOC, GPIO_PIN_0, GPIO_PIN_SET);

   HAL_SPI_Transmit(&hspi1, adress, size, timeout);
   while(HAL_SPI_GetState(&hspi1) == HAL_SPI_STATE_BUSY);

   HAL_SPI_Transmit(&hspi1, data, size, timeout);
   while(HAL_SPI_GetState(&hspi1) == HAL_SPI_STATE_BUSY);

   HAL_GPIO_WritePin(GPIOC, GPIO_PIN_0, GPIO_PIN_RESET);
}

And then write:

void POT_Init(){
  uint8_t data = 0x00;
  SPI_SendData(&STATUS_REGISTER_ADDRESS, &data, 8, 100); //Set SREG bit 1 to 0. Device is NOT in shutdown.
  data = 0x0F;
  SPI_SendData(&TCON_BIT_REGISTER_ADDRESS, &data, 8, 100); //Connect Wiper 0
  data = 0x08;
  SPI_SendData(&WIPER_0_REGISTER_ADDRESS, &data, 8, 100);
}

Problem is, I'm probing SCK and SDI/PA5 and PA7 and am not seeing anything move across the line. The two devices are connected as below:

So why am I not seeing anything?
I'm assuming something is missing in my Init function but I can't put my finger on it and I'd appreciate a second look.


texts:
I've been trying to plan out a new project for a while. It's a wideband antenna anaylyzer for radio applications. I've figured out most of the details, but the most important part - the frequency source - has me stumped.

I'm trying to figure out the best way to cover the frequency range of ~1MHz to ~1GHz, which would cover pretty much all of the communications frequencies in use today.

I was originally planning on using a DDS chip like the AD9910, which is around $40 and about the most I want to spend on a single component. The problem with that chip is that even with a 1G reference clock it still goes downhill pretty quickly after 400MHz. Analog has more options, but price ramps up pretty steep after this chip.

The Si570 series from Silicon Labs was another idea I was tossing around, but the output of the 10M-1.4G chip is LVDS which is not easily converted to a sine wave without a lot of filtering.

A PLL was something I was tossing around, but I haven't done much research into them and it seems that most chip offerings are designed for higher microwave applications.

I know regardless of what I use I'll be including switchable filter banks to cover the entire range. I would love to hear input from some people who have more experience with RF design and see what you guys think I should be using to generate these frequencies. And by all means, feel free to tell me that what I'm doing is a very tall order.

And yes, I'm aware there are commercial options that I could buy instead of building an antenna analyzer myself, but where's the fun in that? This will be used for mostly amateur radio applications, so I'd love to homebrew something together.

UPDATE:

I'm now considering using the AD9910 coupled with a frequency multiplier of some kind to reach the desired range of 1 to 800 MHz. This could be the best option, if I can find a suitable chip for a reasonable price.

Thanks for the help.


texts: Match Digital Amplifier to Audio Speaker

texts:
I am working on a Raspberry pi audio project and need help creating the proper schematic.
I am given:

a amplifier detailed here
a vanilla audio speaker with 5 W rated input power and 4 ohm impedance

The 20W amplifier seems to be an overkill and I am not sure how to get started on building the circuitry. Any advice is appreciated


texts: Converting Pulse Sequence Inputs Into Separate Outputs

texts:
I'm trying to find the simplest way of accomplishing the following task:

Convert 3 different pulse input sequences into one of 3 different output lines

The image below explains the problem graphically.

We have 3 possible input pulse sequences on the input line

if pulse pattern 1 is received on the input line then output line 1 should go high (e.g. +5V) (and outputs 2 and 3 would be ground)
if pulse pattern 2 is received on the input line then output line 2 should go high (all others ground)
if pulse pattern 3 is received on the input line, then output line 3 should go high (all others ground).

Any thoughts / comments on the easiest way to accomplish this task would be greatly appreciated!

For example, I'm not sure if there is a specific Integrated Circuit chip that inherently can do this (e.g. some sort of Decoder)?  Or do I need to buy an Arduino microcontroller and write a program that listens for different pulse patters on the input line and then sets one of the output lines high when it detects one of the 3 possible pulse patterns?

Thank you for your help!

UPDATE (More Details) - We can differentiate the 3 different pulse patterns based on the duration of each. Let's say, for instance, that each pulse is 1ms high and 1ms low. So we know that an input pulse sequence is complete when the input line has been low for several milliseconds. Since these pulse patterns won't be coming in too frequently (probably 1 pulse input pattern every couple of minutes).  The output line should go high (e.g. +5V) for a few seconds after the incoming pulse sequence is determined.


texts:
What are the major differences between these two ICs 74LS47 and 7446N whose working is mostly the same ?
Both are used as BCD to 7 segment decoder driver


texts:
We got an example exercise in which we need to calculate the voltage and current in certain places of a circuit with a zener diode with different input voltages (ranging from -10v to 10v). Most of the exercise is just applying ohm's law but I can't figure out how they get the voltage over the diode (the blue number).

These are parts of the solution

The orange number is the voltage of the source (-1,05V in the first case and 6v in the second). The green numbers are calculated using ohm's law and the voltage over the diode. But how they get the blue number (which is the voltage over the diode) is a complete mystery to me :/

NOTE: English isn't my first language so I might get certain terms wrong.


texts:
I am working on a lab bench power supply capable of 30V at 5A. It is a linear PSU so therefore i will need 30VDC to feed into a regulator (5x LT3080 in parallel). I think that 1A is enough for the control circuit, so in order to deliver 5A at the output, the first "stage" of my power supply will be to convert 230VAC @ 50Hz down to 30V capable of delivering 6A with low ripple (1A for the control circuitry).

This is the circuit i have so far:

My theory is as follows,

The transformer lowers the mains voltage to 30V RMS
The diode bridge rectifies the 30V RMS to 42.4VDC with two big capacitors to filter the ripple.
The RC circuit, made from R1 and C1, filters the ripple with a cutoff frequency of around 0.3Hz. This voltage is then fed into the base of Q1 (which can deliver more current than the RC filter), which creates an emitter-follower capacitance multiplier.
The driving circuit for Q2 is inspired from the LM78xx simplified schematic. Q3 is added for increased current capability, and will turn on when a current of 133mA flows through R2 and R3 which will create a 1V voltage drop (base-emitter saturation voltage of Q3 is around 1V).
Q2 will be driven by the op amp such that it's inverting input will have the same value as the non-inverting. This should create 30V at the emitter of Q2.

R8 is just a potentiometer for calibration. The value of R5 and R8 should be 10k as the voltage divider will have an output voltage of 10V at an input of 30V. ZD1 is a 10V diode.

My question is if i have missed anything? Do you have any recommendations for the design?


texts: EN 300 328 CE radio certification with power limit

texts:
We have developed product for Malesia country, where we need local SIRIM certificate.

RF module we used in our product is 2.4Ghz wifi mesh, with max 30dbm (1 watt) output power capacity.

To get SIRIM we need to submit CE report of product to SIRIM. We have done EMC testing as per CE, but have some doubt in radio related testing as per EN 300 328.

Q1) at what power level we need to set in our radio to do this EN 300 328 testing. Do we need to set 100mW,500mw or 1W?

Q2) Malesia max limit is 500mW.  Do we need to set 500mW or is anything less than 500mw ok?

Q3) If we set 100mW and completed CE test and later in final product we can not go more than 100mW since Malesia have till 500mW.

Q4) EN 300 328 "maximum power test " say 20dBm (100mW is max,) then what does it mean we can not test a product more than 100mw if they has capacity more than 100mW.

Q5) If I test at 500mW then in EN 300 328 "maximum transmit test ' is it going to fail?

Please advise.
Below is the link of sample report of EN 300 328 taken from internet.
http://processors.wiki.ti.com/images/8/8c/ER3N2752_R01_EN300328_Texas_WG7835-B0.pdf


texts: Why can sticking fingers in an electric outlet kill you?

texts: I just wanted to learn some differences between volts, amps, ohms and so forth and came up with this question. If your skin has 100k ohms resistance and the outlet is 220v wouldn't the current flowing through your body be 0.0022 amps?


texts: Controlling a dc-motor by keeping electrical power input constant

texts:
I have seen dc-motors controlled by current control and rpm control. As I understand it, one could use a PWM for example to control the mean current of a motor while measuring it and therefore keeping the current approx. constant. If the current rises, the on time of the PWM would fall and the mean current I (to keep it constant) and mean voltage U would drop.

What would happen if instead, one where to control the electrical power? Meaning, keeping P=UIt_on/(t_on+t_off) constant by changing only t_on/t_off.

Imho, if the torque rises and therefore I rises, t_on would drop to a different point. The mechanical power would change, but what else would happen? Or rather, why does seemingly nobody do this? Are there some serious drawbacks I haven't figured out? Would it simply not work?

I'd appreciate some literature as an answer/comment too.


texts:
Correct me if Im wrong, a via is a hole that join two or more layers in a PCB.
I have a PCB design who has the pads to solder but I want solder only one side, do all my pads that are connected to my top and bottom layer are plated through holes? are they automatic connected together? this picture is for example a capacitor who has both layers connected, is a pad, do I have to solder both sides?


texts:
I attended a workshop on troubleshooting and we were asked to find the flaw in the given circuit. A guy pointed out to the organizer that R3 was short ckt and R2 was open ckt.

However I was pretty sure that R2 was short ckt and R3 was open ckt because same voltage is appearing, but didnt point out ( for which I lost a 1 minute clapping).

So who was correct (or no one ) ?

Thank you.


texts: How can I connect a USB keyboard to a DE1-SoC?

texts: I recently got a DE1-SoC development board from Intel and I wanted to use it to instantiate a computer design I created while following along the Nand2Tetris course on Coursera. Unfortunately, this design requires a keyboard to be connected to the board and I do not have PS2 keyboards (only USB ones) or USB to PS2 adapters. While I could go and get the required hardware, I think that PS2 keyboards are becoming outdated, so I want to be able to use my USB keyboard. The board has 2 USB ports and according to this document, they should be able to interface to the FPGA fabric. Unfortunately, this guide specifies only how to instantiate a USB OTG port and how to connect its clock to the top-level design. It does not specify how to access the data coming from the USB. I have searched for specific instructions online, but so far I have found nothing. Is there a way to, say, display the scan code of the key pressed on a USB keyboard on the board's LEDs?


texts:
I am studying this application circuit to design the biasing circuit.
I have understood the explanation up to a certain point, but I am stuck at the "Gate bias supply circuits" section.
It says that "When the ON/OFF switch is OFF condition, both the gate voltages VGS1 and VGS2 will be set to -4.5V. This is accomplished by pulling the adjust pin of the voltage regulator to ground through a 1kohm resistor (Flags FL2 or FL3 are driven low by the sequencing IC)."

As the switch position is in "OFF" state, the sequencer will hold the FLAG 2 and 3 to low.
When the switch is in "On" state, the sequencer will hold the FLAG 2 and 3 to high impedance open-drain state, then VGS1 and VGS2 are set by the potentiometer adjustments.
The LT3021 is a VLDO regulator and LT1497 is a current feedback amplifier. So using both these chips and based upon the FLAG signal from LM3880 VGS is either -4.35V or can be adjusted through 25K pot.
I am unable to understand the working flow between these chips.
Can somebody explain to me the same or provide some hints for me to proceed further?


texts: Is there a tip to using the reference node?

texts: Sometimes circuit analysis can get confusing as to which way currents go in and out of nodes , especially when there are many current / voltage sources. Is there a trick to see which way i should reference everything? I always see reference with respect to ground but I'm not too sure what that means. Here is an example from my professor, although im not too sure if he made a mistake on i2


texts: Help me interpret solenoid shopping info

texts:
I'm trying to get a cheap pull-type solenoid that can operate for at least ten seconds at a stretch to serve as an electronically-controlled ward in a lock (for a wooden box) I'm building.

I'm a novice and confused at my findings. Can anyone enlighten me?:

This model touts a stroke length of 0.05 inches. Does that really mean that the shaft only retracts 5 hundredths of an inch?

What's a "nominal" stroke? How is it different from a maximum stroke? (I'm looking at the table on this page.)

If max stroke is specified but nominal stroke is listed as n/a, does that mean that nominal stroke length is 0?

Lastly, any counsel on where to shop for the solenoid I need? I want a retraction of about 1/8 inch but could just as easily make use of 1/2 inch.

TMI: My shopping criteria:

cheap
small
>= 1/8" stroke length
DC
<= 12V


texts: Altium: Length match different parts of a line

texts:
I design a PCB using Altium with some length sensitive lines. They have up to 4 connection points. Is there a way to length match the individual parts of the line?
Lengthmatching the complete line is easy, but I need the connections in the middle to be at the same distance as well.


texts: Simple Detect Physical Touch - If object is up against the sensor/object

texts:
Definition: Physical touch, meaning the touching of a physical object. Not objectively human in nature, just anything touching / covering the sensor or switch.

The above line is included as every search result I could find, had to do with capacitive touch sensors and human-touch.

Instead, this is much simpler. The sensor would be placed at the bottom of the object, and we just need to detect if the object is set down against something. This could be a table, or anything really. I've researched many types of sensors, but most are far more sophisticated than what is actually required here. (Most measure distance, while we just want to know if the sensor is covered or not.) Due to this a switch may be preferred, however the durability of the switch is a concern especially if it's meant to stick out of the bottom of the object.


texts:
I have two questions related with the USB connections on a pcb:

1- Is it possible to connect D+ line between 2 devices and 1 host? something like SPI fashion where MISO and MOSI lines are shared between all slaves? Or like I2C where every node listens to the bus and replies only when the given address is called? The same with the D-.

2- I'm designing an embedded application with 2 devices, one of the is a USB-device and the other one is a USB-OTG. When the communication is between them, I believe there is no problem, the OTG behaves as a host and the second one as a device.
However, my question comes when I need to connect them (both as devices) to an external PC, is it possible to share the signal lines to the external PC, so I will have 3 devices connected on the line: uC USB-device, USB-OTG programmed as device and the PC USB-host.


texts: I am a novice / hobbyist and I have a project in mind that involves detecting where a laser is aimed at on a relatively large scale (300+ sensors). I've found circuits that would work on a small scale such as a phototransistor or a comparator IC to compare resistances, but I have absolutely no idea how to scale this up in a cost effective manor. This will be used to then output digital logic signals to a microprocessor. Any ideas?


texts: Voltage (and possible resistor) required for electromagnet

texts:
I have a small electromagnet which moves a lever (it's a part from a larger device). I'm not sure of the supply voltage but other parts of the device required 20V.

The resistance of the electromagnet is 53 ohms.

I tried low voltages and nothing happened, but the highest I can try at the moment, 12V, slightly moved the lever.

Is there a way to confirm the voltage required? If it is 20V, will a resistor be needed?

Thanks.


texts: I need a powersource based on locomotion (3V 20 mA)

texts:
Dunno whether this is the right place to ask this but i'll give it a try.

I want my bicycle light to be powered on the sideways motion of my bike. For this i would need a device which is also in 'automatic' watches like the seiko kinectic (they do not require battery but winded up by the motion of the wrist).

Does such a thing exist in electrical form (the watch version being mechanical)? And if so, would the power be large enough for a LED to burn?

Thank you!


texts: Why does Altera DE2-115 board GPIO expansion header contain 5V & 3.3V power but the IO standard has no 5V?

texts:
The altera DE2-115 board user manual section 4.8 page 47 describes the GPIO expansion header. It is clear that it has 3.3V and 5V power supply.

However, it later says that "The voltage level of the I/O pins on the expansion headers can be adjusted to 3.3V, 2.5V, 1.8V, or 1.5V using JP6 (The default value is 3.3V, see Figure 4-17)."

(1) I am confused, why is 5V power supply provided if no IO standard goes upto that? Also, why have IO standard down to 1.5V when power supply provided only goes downto 3.3V? Certainly an IC that takes 3.3V won't work with IO of 1.5V. Am I missing something here?

(2) Even though there are clamp diodes on these pins of the expansion header, is it ok to use a 5V IC that shall have VOH(max) of close of 5V?


texts: Is it possible to use internal pullups on SAMD21 when pins are configured for SERCOM (SPI) mode?

texts:
According to the datasheet screen clip shown below, the internal pull up/dn configured in the PORT registers is still supposed to work even when the pin is configured for use by the SERCOM/SPI peripheral.

When I step through the SERCOM SPI Slave initialization code snippet below, I can see the pin pulled up after gpio_set_pin_pull_mode(), but the pullup goes away as soon as gpio_set_pin_function() is called.  At this point, I can still pull up the pin with an external resistor.  The internal pullup comes back after the second gpio_set_pin_function() call returns the pin to GPIO mode.  SPI_LCC_CSL is the GPIO pin macro from Atmel START.
Is the documentation wrong, or is there something else that I need to do to keep the pullup enabled in SPI mode?
    gpio_set_pin_direction(SPI_LCC_CSL, GPIO_DIRECTION_IN);

    gpio_set_pin_pull_mode(SPI_LCC_CSL, GPIO_PULL_UP);

    // Internal pullup goes away ...
    gpio_set_pin_function(SPI_LCC_CSL, PINMUX_PA10D_SERCOM2_PAD2);

    // Internal pullup returns ...
    gpio_set_pin_function(SPI_LCC_CSL, GPIO_PIN_FUNCTION_OFF);


texts:
I have recently start using the M2S150 Development kit from Microsemi and have run into an issue when attempting to program the board (via Libero 12.1).
When running the "Run PROGRAM Action" command the log reports the following
Error: programmer 'E2005ASNAY' : device 'M2S150' : Executing action PROGRAM FAILED, EXIT -31, refer to FlashPro online help for details.
In the FlashPro User Guide it says that this could be because:

The certificate is corrupted
The user hasn't provide application code in the eNVM (or the code is invalid)
FAB_RESET_N is tied to ground

I can confirm that 2 & 3 are not being done because I have tied FAB_RESET_N high, and while I was initially trying to put application code in the eNVM when this error occurred, I attempted to program the board without putting application code and the error persisted.
I should note that I have been able to program this board before. In fact I currently have some very basic LED Blink code on the board and I am able to change the software portion via IAR. Additionally, I did find some information on retrieving the certificate via software, and have done that, but I'm not sure what they mean by "corrupted"
Would anyone know what is going on and how I could fix it?


texts: Inferring RAM ALTERA from vhdl of HDL CODER

texts:
I've generated vhdl from Simple port RAM and Dual port RAM in simulink and I tried to synthesize  with Quartus 14 and 16 on Arria V and 10. The option to allow RAM for any size is ON but I don't understand why it isn't recognized. Have you never seen this?

I also synthesized the Altera template with the same data and address and it's correctly recognized.
I used matlab 2016

Thank you to all


texts: Does this wiring pattern for a DB9 cable exist as a standard cable?

texts: I have a scientific instrument that uses a DB9 cable to connect to the standard RS232 port on a computer for communication. I've deconstructed one of the cables as I needed to make another one but I am wondering if this wiring pattern is a standard wiring variation seen with DB9 cables or if it is completely proprietary. I don't want to have to make these cables if I don't have to.


texts:
I can't work out what the issue with my setup to control a 2.5" hard drive BLDC motor is. I have a 3 pole 2.5" hard drive connected to the following drive circuit, but the motor isn't spinning.

simulate this circuit – Schematic created using CircuitLab

I'm using a current sinking shift register to drive the MOSFETs so they need to be pulled up by default.
The motor driver seems to be working correctly, the arduino code is simply

static uint8_t motorVectors[6] = { 0b100100, 0b100001, 0b001001, 0b011000,
0b010010, 0b000110};
int vectorPos;
void setup() {
  Serial.begin(9600);
  for(int x=2; x<8;x++){
    pinMode(x,OUTPUT);
  }
}

void loop() {
//AB
  digitalWrite(2, 0);
  digitalWrite(3, 0);
  digitalWrite(4, 1);
  digitalWrite(5, 1);
  digitalWrite(6, 1);
  digitalWrite(7, 0);
  Serial.println("AB");
  delay(10);

//AC
  digitalWrite(2, 0);
  digitalWrite(3, 0);
  digitalWrite(4, 1);
  digitalWrite(5, 0);
  digitalWrite(6, 1);
  digitalWrite(7, 1);
  Serial.println("AC");
  delay(10);

//BC
  digitalWrite(2, 1);
  digitalWrite(3, 0);
  digitalWrite(4, 0);
  digitalWrite(5, 0);
  digitalWrite(6, 1);
  digitalWrite(7, 1);
  Serial.println("BC");
  delay(10);

//BA
  digitalWrite(2, 1);
  digitalWrite(3, 1);
  digitalWrite(4, 0);
  digitalWrite(5, 0);
  digitalWrite(6, 1);
  digitalWrite(7, 0);
  Serial.println("BA");
  delay(10);

//CA
  digitalWrite(2, 1);
  digitalWrite(3, 1);
  digitalWrite(4, 1);
  digitalWrite(5, 0);
  digitalWrite(6, 0);
  digitalWrite(7, 0);
  Serial.println("CA");
  delay(10);

//CB
  digitalWrite(2, 1);
  digitalWrite(3, 0);
  digitalWrite(4, 1);
  digitalWrite(5, 1);
  digitalWrite(6, 0);
  digitalWrite(7, 0);
  Serial.println("CB");
  delay(10);
}

all seems to be working, I don't have an oscilloscope so I cant check the output waveforms over time but the output of the driver seems to be working correctly when I test each phase shown in the code.

I there anything glaringly wrong?

I have checked other answers and they seem to agree with the setup I have here.


texts:
From this answer:

The Fourier series:
\$ V_t = \dfrac{a_0}{2} +    \displaystyle \sum_{i=1}^{\infty}[a_i sin(i \omega_0 t) + b_i cos(i \omega_0 t) ]  \$

Why is the DC level written as \$\dfrac{a_0}{2}\$, and not \$a_0\$? stevenvh says it's convention, but there has to be an explanation. Where does it come from?


texts: What are reasons for NOT connecting exposed pad (EP/thermal pad) to ground?

texts:
For what reasons would a manufacturer suggest that the thermal pad should NOT be connected to ground?

See link and snippet from a Nordic datasheet.

https://www.nordicsemi.com/eng/nordic/download_resource/9404/1/76425885

Thanks in advance.


texts: Can I use a line multiplexer as a level shifter as well?

texts:
I have 40 x 5V inputs that I want to read using 3V GPIO pins on the beaglebone black. I am planning on using 5 multiplexers (such as the 74HC151 or 74HC251) that will be sharing the 3 select lines.

I'm not sure what the best strategy for level shifting would be:

Power the multiplexer with 3V VCC and hope it'll work with 5V inputs
Throw in a level shifter / buffer before each multiplexer, something like 74LV245.
Use a series resistor to limit current on each of the inputs since I just need unidirectional 5V->3V shifting (Yes, I know this won't change the voltage but perhaps it'll protect the multiplexer from the 5V signal by reducing current?)
Is there a different multiplexer I should be looking at that will be tolerant of the different voltages?

I'm really hoping I can do (1). The datasheet says input voltage should be between GND and VCC. How bad will it be to power it with 3V and leave the inputs 5V?

Thanks!


texts: How can I supply 5v voltage to circuit in a portable way?

texts:
I have made a circuit which needs 5v to operate, I want to give 5v supply to that in portable and compact way. I didn't find any battery with 5v specs. I managed to run it with 9v battery in combination with 7805 voltage regulator but that battery is too heavy, bulky and I don't want to waste 9v for getting 5v only. Please let me know most compact and efficient way of supplying 5v voltage to a circuit.

P.S. Can I use 3v coin cell to run that circuit. Is there any way to step up from 3v coin battery to 5v?


texts: Is it possible to find the voltage gain of the constant gain block of this control system?

texts:
I'm looking at the following circuit and I don't know how to find the gain of the constant gain block. The only information I'm given are the Bode plots (magnitude and phase) of the two transfer function blocks. I'm also given the phase margin of the closed loop system (which is 60 degrees).

Edit: The circuit actually looks like this. The problem is asking to find K1 since it is equal to Vi/Vt. To give more information, the system is for a DC-DC converter and I'm not given any information about Vi or Vt. I've thought about this for a while now - there's no way to find Vi or Vt right? If the only information I am given is the phase margin and the Bode plots of G1 and G2.


texts: Name of fabric insulator found inside motors

texts:
What is the name of the fabric sleeve insulator used for components (typically fuses) and solder joints found inside motor windings?

Can regular heat shrink tubing be used as a substitute?

Image by cwbenz. Retrieved from here.


texts:
I was trying to make an FM transmitter and, because I have no mic, I thought I could just use an Arduino (Uno) to generate some tones for testing. It turned out I never got a signal from the circuit but from the Arduino alone.
I'm connecting it to pin 9, battery- to GND, battery+ to Vin and no other connections. The transmitter circuit is gone.
I tested it with multiple antenna lengths. Every time, it produces a signal that can clearly be picked up by my radio on multiple different FM frequencies. I know this radio works, since it can receive multiple radio stations in my area.
How could this be happening?
Here is the code I'm producing the sound with. Both times, the same thing happens.
void setup() {
  pinMode(9,OUTPUT);
}

void loop() {
  while(millis()%1000<500){
  delayMicroseconds(1136);
  digitalWrite(9,HIGH);
  delayMicroseconds(1136);
  digitalWrite(9,LOW);
  }
  while(millis()%1000>=500){
  delayMicroseconds(757);
  digitalWrite(9,HIGH);
  delayMicroseconds(757);
  digitalWrite(9,LOW);
  }
}

void setup() {
  pinMode(9,OUTPUT);
}

void loop() {
  delay(500);
  tone(9,440);
  delay(500);
  tone(9,660);
}


texts: Build a Simple Serial PIC16F84A programmer

texts:
I decided to build My own PIC16F84A programmer,The Problem with 16F84A is the Voltage in MCLR pin (+13V). How we get this with a (-10v;+10v) Serial port. Yeah, There are alot of methods, but I choose the simple one. :=D

So I searched the net & I found this Simple one
http://www.eeweb.com/blog/extreme_circuits/simple-universal-pic-programmer.
Thankx Luke Weston for sharing.

Question 1 : I built the Circuit, but can't retrive the Vpp on the emitter of the BC337? is there a mistake ?

Question 2 : So i made the This circuit below to contorl the Vpp (+13v) with serial port signal (is two stage inverter), Is it correct ?

simulate this circuit – Schematic created using CircuitLab

If Signal from PC = -10v ===> Vpp = 0v
If Signal from PC = +10v ===> Vpp = +13v

first Modifications After Some Discussions:

simulate this circuit


texts:
I have been thinking about my design for a while but couldn't figure out a better way to deal with buffer overrun in multiple interrupts.

A dsPIC33EP chip is connected to a TFT display, a UART sensor, a micro-SD card and a UART camera. The baudrate of the UART sensor is 921600 and the camera (50k per pic) is 57600. The SD card sector write (512 bytes) time is a little bit less than 2ms. The screen (EVE FT800) takes 20ms to update.

The goal is to respond to the UART sensor (at least every 30ms) and update screen accordingly (update labels) and at the same time write pictures into the SD card.

To break down the task, I have successfully saved multiple pictures to the SD card using interrupts when only camera and SD card are running.

The interrupt routine:

volatile unsigned char buff[512];
volatile unsigned int ptr=0;
volatile unsigned char EOF=0;
volatile unsigned char buffReady=0;
void ISR(){
    static unsigned char temp;
    temp=UART_Read();
    buff[ptr++]=temp;
    if(ptr==512){ptr=0;buffReady=1;}
    if(...){EOF=1;}
}

While the program is stuck in a loop to check EOF flag

while(1){
   if(buffReady){SD_Write_Sector(buff);buffReady=0;}//write 512 bytes of image to SD card
   if(EOF){break;}//jump out if the image has been finished
}

My concern is, how do I incorporate the routines to update the screen while receiving data from the UART sensor? It looks like the buffReady flag must be checked constantly. Any delay between each check may lose couple bytes since they are overwritten with new bytes.

Since the picture size is around 50K and the baudrate is 57600, there will be six bytes coming from the camera every millisecond. If the screen introduces a 20ms delay in between, the picture will sure be corrupted.

I thought about using a larger buffer to store pictures but larger buffer needs more time to be written to the SD card.

How should I arrange update screen and write image to SD card?


texts:
While investigating the design of J-K Flip Flop, I cannot get my head around how toggle work. I know it only toggle as the clock goes from 0 to 1.

Here's my false understanding of how the toggle works.

Assume it's Q = 0, Q' = 1, and J = K = 1. Now the clock goes up, the detectors picks it up, and send an impulse.

The next state is Q = 1, Q' = 1, and that's nowhere near Q = 1, Q' = 0. Worse, as J = K = 1 and clock stays high so no impulse is sent, it actually oscillate between 00 and 11.

What's wrong with my understanding?

I'm simulating the one constructed by 4 NAND, and next state is determined by the following equations:

 Anext = not (Clock and J and Q')
 Bnext = not (Clock and K and Q )
 Qnext = not (  Q'  and A)
Q'next = not (  Q   and B)


texts: What do dotted outlines of components mean on circuit schematics?

texts:
Can anyone tell me what the blue dotted outlines of components represent in this schematic?
There are 4 diodes on the LOAD, AND, OR and XOR lines and a not gate on the STORE line. Are these components that were present in an earlier revision but have been removed?

Complete schematic:
https://cdn.hackaday.io/files/20781889094304/Schematics%202020-03-20.pdf


texts: should I open a solder mask over a high speed microstrip line in a PCB?

texts:
Top layer of the PCB, 50 Ohm microstrip line transmitting 650 MHz/1.3 Gbps (corrected: 1.3 GHz) rectangular pulses.

To keep good signal integrity, should I remove a solder mask ink over the top of my trace?


texts: How could I create a high-precision voltage with the atmega128?

texts:
In my solution i have to replace an 10 turn potentiometer ( 5 K Ohms ) with a digital circuit. the potentiometer is dividing a voltage between 4v to 21v. so it seems if i could generate a voltage between 4v to 21v with a Atmega8 or Atmega128 ( indeed it must meet high accuracy ) I'm done !
I have tried to use Digital potentiometer , but got in to 2 problems :

  1 - first they can not stand the current going throw the potentiometer
  :  (21-4)/5K = 3.4mA

  2 - they don't have the required accuracy
     (21-4)/256 = 66 mV ( but i need 0.5mV)

Is there any way i could do this?


texts:
I have some difficulties in understanding the difference between bandwidth and slew rate.
I got that we are talking about large or small signal but what if for example the input signal is a PWM one with a given frequency and a peak voltage which can be considered large signal? Which parameter do I have to look at in this case?


texts: Use Thermal Relief in High Current Traces?

texts:
I'm designing a SMPS PCB with a pretty high current goal (using it to power multiple servos). Using KiCAD, I decided to use solid fills on the pads of the high current areas, but by default thermal reliefs are enabled. This takes the large filled zone and necks it down to small areas.

I've read that with the right size soldering iron, this is no problem, but I was thinking of paying a little extra and just having the PCB fabricator assemble the board to save myself from SMD soldering, and then I can shrink some of the components.

Would a typical hobby/prototype PCB fabricator balk at having to assemble boards with solid filled zones connected to the pads?

Edit: I maybe wasn't clear enough, I am not concerned about hand soldering these large packages. I have other components that are much smaller, like 0603 and TSSOP packages, the board also has components on two sides. Instead of trying to solder it myself, I was thinking of paying the pcb Fab house to assemble the components as well. My question is will solid filled zones on these high current large traces affect the pcb assembly house if designed like in the second picture below? Will the components float/not align properly, or does the silkscreen alleviate that?


texts:
I'm doing a homework problem, and I think I've made some progress, but I'm starting to get confused and was wondering if somebody could help out with the next steps, the problem is below

So for part (a), I calculated the Thevenin equivalent circuit, getting \$V_{th} = 8 V\$ and \$R_{th} = 4k \Omega\$. Then I was a little confused with what to do for a DC LR series circuit, in terms of the impedence for the inductor. I said that since there's constant current flowing through the inductor, it acts as a short circuit, so I got \$i_L = 2mA\$. Is this the correct thinking?

(b)

For part (b), I am definitely stuck. First off, at \$t = \infty\$, I completed disregarded the left half of the circuit (I think I can do this right?), so now I only had to deal with the right side of the circuit. Using kirchoff's current law, I determined that $$7mA + i_L = i_2$$ $$i_2 = 4i_L$$ $$i_L = 2.33mA$$

Somehow I don't think I did this correctly, because I'm getting that the current is flowing the opposite way in which it flowed in the original circuit. Can somebody please help me out here and find where I'm going wrong? If you need more details, let me know! Thanks!


texts: Chaotic circuit for random number generation

texts: I know, there is an analogy between RLC circuits and harmonic oscillators. Now there is a physical system, called double pendulum which has chaotic motion. I'm just curious if it is possible to create a circuit, which behaves like a chaotic pendulum, and use it for hardware randomization?


texts: Can a charge-pump be 100% efficient, given ideal components?

texts:
A recent question about cyclically charging a capacitor reminded me of something I read once. As I remember, it demonstrated that it's impossible to construct a charge pump that is 100% efficient with ideal components, but it is possible to build a 100% efficient boost converter with an inductor if components are ideal.

Does this resonate (no pun intended) with anyone else? Any way to demonstrate or refute the truth of this?

To be clear: we are assuming we have ideal components. I realize no real circuit will be 100% efficient with real components. Diodes may have zero voltage drop. Transistors may be ideal switches that take no energy to change state. Wires may have zero resistance.


texts:
I am kinda new in power electronics and I have a task at hand that requires assistance.

I have an assignment to build a SMPS. My prof gave me a breakdown that once I rectify the Input from mains AC (230V rms), 50Hz to a DC (300V), I need to channel the output through a DC / AC Inverter. I have been searching the net for a pretty beginner level decent explanation on the principle of operation but I got confused along the way. I have come across the fundamentals of the SMPS Flyback Converter. Is that a better option to use instead?

Here is the block diagram from my prof

Rectify from Mains -> DC/AC Inverter -> Transformer -> Rectify -> 2 outputs , (12V, 5A),
Thanks in advance


texts:
I am trying to use MSP432 on chip 14 bit ADC to sense output from a current sensing op-amp.

I am getting a large reading error from my ADC compare to the multimeter reading.

Do I need to have a front end amplifier to buffer the input to ADC, or can I directly sense it?


texts: Reflow oven AC cable splicing insulation and thermocouple readings

texts:
I'm building a reflow oven. I know what I'm doing, I just want to verify my plans to make sure I'm not doing anything stupid before I start.

The idea is to have an arduino (powered externally) control a relay which is spliced into the neutral wire of an AC cable connected to a toaster. I chose to splice the neutral cable and not the live wire for obvious reasons (that way if you touch something exposed by accident, you're less likely to be shocked). Meanwhile I plan on putting all of the splicing under several layers of heatshrink, glue gun, and electrical tape, and then inside of a small plastic project box for extra protection.

I'm just mainly wondering if the insulation I'm using is safe enough.

Also, should the thermocouple be touching the metal grill that the pcb board to be soldered sits on? should it be in the air above the pcb board? I imagine the safest bet is to take a small pcb board that's not being soldered and attach the thermocouple to that one and then place it next to the pcb board being soldered (in order to best simulate the temperature on the actual cooking pcb board).

thanks for your help!

EDIT:

After getting several answers, I realized I made a huge mistake in trying the neutral wire. Thanks guys. I don't know what I was thinking. (I was so concerned about the insulation failing on the connection to the relay that I forgot that the heating elements weren't particularly isolated).

Also, I will definitely go with with a double-pole relay (well, I'll just get a second single-pole relay and connect their inputs together).


texts:
I have 10 x 1.2V Sanyo NiCd batteries. They are connected in series. I would like to charge them. The thing is, I don't have a charger. I looked up chargers and they are all quite expensive(I live in India). I would like to know what voltage AC to DC adapter should I get to charge them.

What are the risks involved in doing so?

Could you also suggest me some cheap ways of getting the batteries charged?


texts:
I need help with a project. I want to make a circuit to work as a night-time motion detector circuit that will power several LEDs. I bought:

1 LDR
some NPN transistors BC547 and 2N3904
some resistors 100kOhm
boost regulator 3V to 5V
PIR sensor

I connected the LDR to 2 NPN BC547 transistors and successfully tested it.
Then I connected the (-) from NPN transistor to the (-) of the PIR and the (+) of the PIR to (+) and the output of the PIR to a single led. It worked but the LED had a low output.

If I connect the PIR output to a 2N3904 transistor and after to the LED, the LED is brighter. But when I connect the current to the voltage booster and to all LEDs, the light is very low.

The problem is the 3.3V from the PIR output. I need 5V to work my LEDs. How can I establish this?

Update:
This is my PIR Sensor (mod edit: Pretty much a standard BISS0001 Design, no transistor on the output.)

My Power Supply Is 2 Batteries 3.7V 18650


texts: How to control 200 relays with micro controller?

texts:
I want to control 200 relays, I want to use AVR controller. Because I am out of pins,
I was thinking of connecting the micro controller (for routines and such things) to a FPGA and use the output of the FPGA for controlling the relay.

Is that a good idea or is there any other option which is simpler and more efficient to implement?


texts: Compilation and synthesis work both fine but the wave simulation seems stuck

texts:
The following code is an attempt to implement the responses given in this post, a program that takes in its entry a real number coded in 2's complement in a 16 bit std logic vector (the integer part starts from index 15 down to 6, i.e., 10 bits for the integral and 6 bit for the fractional part). At the output where are going to have the same real number represented in the IEEE 754 single precision format.
Here is a schematic summarizing the above

The VHDL code I used to try to implement the circuit is
entity fixed_to_float is
    Port ( fixed_input : in  STD_LOGIC_VECTOR (15 downto 0);
            float_out :out std_logic_vector(31 downto 0);
                j:out std_logic_vector(4 downto 0);
              clk:in std_logic);
end fixed_to_float;

architecture behavioral of fixed_to_float is

signal x:std_logic_vector(15 downto 0);
signal k:integer:=15;
signal i:integer;

signal sign:std_logic;
signal exponent:std_logic_vector(7 downto 0);
signal mantissa:std_logic_vector(22 downto 0):="00000000000000000000000";

  begin

process (clk) begin

  if fixed_input(15)='1' then
    x<= not (fixed_input)+1;
  else
  x<= fixed_input;
  end if;

  for i in 15 downto 0 loop

     if( x(i)='1') then
             k<=i;
             exit;
     end if;

 end loop;
      mantissa <=(others=>'0');
      mantissa(22 downto 22-k+1)<= x(k-1 downto 0);
end process;

j<=std_logic_vector(to_unsigned(k,5));

sign<= fixed_input(15);

exponent<= std_logic_vector(to_unsigned(127+k-6,8));

float_out <= sign & exponent & mantissa;

end architecture;

The code, first, locates the index of the first non-zero bit of the 2's complement of the input vector, \$x\$, going down from the 15th position. Everything that's after this index, named \$ k\$ in the code, i.e., everything from \$k\$ down to 0 in the input vector is the mantissa. And the exponent is how far \$ k\$ is from the bit at the 6th position, where the integer part starts. Both the compilation and the synthesis worked fine, no warnings whatsoever. When I tried to run a waveform simulation to try and test some values, the waveform window essentially gets stuck, it doesn't show anything and the simulation keeps running endlessly. Any hints as to why the simulation wouldn't work?
EDIT: The use of a for loop instead of a while has indeed solved the problem.  I ran a simple test bench to see how the code behaves, I've inputted "0000000001000000" , 1 in decimal; the output was "0 01111111 00000000100000000000000 ", both the sign bit and the exponent have the correct values, only the mantissa seems to be incorrect, it should be all zeros. I cannot really fathom why did this '1' appear in the mantissa, especially with regard to its position
EDIT2: Setting the mantissa's value to zero inside the process in conjunction with moving the assignment of the upper part of the mantissa (please see the edit) inside the process has solved the problem, I can't see why putting these two assignments inside the process, as opposed to outside, can have any effect on the output.


texts: Distinguishing between FIR and IIR filters from transform function

texts:
I was good at this but unfortunately I have forgot almost everything... So the question is what are the steps to tell if a transform function is for IIR or FIR filter:

$$H(z) = \frac{z^3+5z^2+3z+1}{10z^3}$$

Also how to tell it it has linear phase response?


texts: Is there a way to define enumeration for certain signals after simulation?

texts:
I have run some verilog simulations in questa simulator and while viewing the waveforms i see that it would have been easier for me to debug the signals had there been some enums defined for them (To look at strings instead of bit streams).

Is there a way i can add enum definition for signals without re-running the sims say for example using some do file or using a feature in simulator (If there exists a generic solution)


texts: Metal casing makes ultrasonic humidifier unstable

texts:
I have a prototype setup, where an ultrasonic humidifier is controlled from a microcontroller (Teensy 3.2) through a power MOSFET to humidify the air passing through a metal container partially filled with water in which the humidifier is submerged.
The humidifier itself is unbranded and I cannot find a datasheet, but it's identical to this one.
The humidifier has a metal "rod" going out from the housing and extends up above the membrane, and this rod has to be submerged in water for the humidifier to turn on.
My best guess is that the rod is one electrode in some kind of conductive level switch used to only excite the membrane, when it is fully submerged, to avoid damage. Near the membrane there is another metal "ring", which (maybe?) constitutes the other electrode of the switch.
The system was first tested in a plastic container, where everything worked as expected, but when moved to the metal enclosure (needed because of the water temperature) the humidifier turns on and off at irregular intervals even when fully submerged. This behaviour is easily replicated when moved between the containers.
I have included a simplified schematic of the setup here:

My best guess is that when placed in the metal container, some kind of leakage current influences the internal readout from the level sensor, making it unstable. I tried grounding the metal container properly which seemed to help a little (longer time between the humidifier turns off), but it did not solve the issue.
PSU1 and PSU2 are two separate switch mode power supplies operated from the same 230VAC power outlet.
Do I need some kind of galvanic isolation of the humidifier, or what would you suggest the next step should be?
Any help is much appreciated!


texts: How to find SMD transistors library for Altium Designer?

texts:
I am new in PCB design, so excuse me if this is a bad question!
I know the basic electronics and how to draw schematics in Altium. But about SMD parts, I am a little confused! How can I find SMD transistors, diodes, resistors, inductors and capacitors? Is there any specific library for them? If not, how should I find them?


texts: Cheapest way to build or buy a remote controlled sound maker?

texts: For my high school class's senior prank, we'd like to buy cheap prepaid cell phones (like these: http://bit.ly/VSqOk3), hide them in the ceiling tiles, and then call then randomly throughout the day. However this gets expensive quickly. Is there a cheaper way to build or buy something with similar functionality? It doesn't necessarily even need to be remote controlled if it could be programmed to go off at certain times.


texts: STM32F105 bootloader: jump address problem, bootloader loops

texts:
Problem: The bootloader loops.
I think there is a problem with the transfer address.
The entry point of the main program is at:

This is how the entry point to the main program looks like in the microcontroller memory (0x801F24D)

The address of the transition to the main program looks like this

Jump address to main program is not equal 0x801F24C (Reset_Handler main program has an address 0x801F24C)
Jump function code:
#define MAIN_PROGRAM_START_ADDRESS  0x08010000
void ExecMainFW(void)
    {
        uint32_t app_jump_address;
        typedef void(*pFunction)(void);
        pFunction Jump_To_Application;

         __disable_irq();

        app_jump_address = *( uint32_t*) (MAIN_PROGRAM_START_ADDRESS + 4);
        //app_jump_address &= ~(uint32_t)0x01;
        Jump_To_Application = (pFunction)app_jump_address;
        __set_MSP(*(volatile  uint32_t*) MAIN_PROGRAM_START_ADDRESS);
        Jump_To_Application();
        while(1){}
    }

If I run the code as shown above, the loader will loop. The controller seems to reload itself as soon as it calls the function Jump_To_Application().
If I uncomment the line app_jump_address &= ~(uint32_t)0x01;  I get the correct jump address 0x801F24C  but then the loader loops at HardFault_Handler().
I don't understand where is my mistake? help me please.
Main app settings:
/* Memories definition */
MEMORY
{
  RAM    (xrw)    : ORIGIN = 0x20000000,   LENGTH = 64K
  FLASH    (rx)    : ORIGIN = 0x8010000,   LENGTH = 64K
}

int main(void)
{
  /* USER CODE BEGIN 1 */
    __disable_irq();
    SCB->VTOR = MAIN_PROGRAM_START_ADDRESS;
    __enable_irq();
  /* USER CODE END 1 */
  //...
  while(1)
  {
    //...
  }
}

Oddly and I don't know why, but everything works if I remove this line __disable_irq();


texts:
I need to find the voltage on the diode, ie the potential difference between NODE1 and NODE2. I thought of using Thevenin or knits, would anyone know a better way to analyze this circuit?

simulate this circuit – Schematic created using CircuitLab


texts: Can anyone tell me how to make a simple electric shocking device (like a electric pen or hand buzzer style). I've seen people use piezoelectric elements from lighters (is that correct?) but I would like to know how to create one from scratch, and also what current and voltage is needed to give a small shock. Thanks, ell.


texts:
I did the magnetic calibration here on the LSM303DLHC for a field roughly 48 uT. The method seems to have worked in that the combined bias (b) values went from thousands to hundreds like the tutorial says they should

The readings are around 48uT indeed, but they vary by +/- 50% upon moving the sensor around. Is this the expected behaviour ?

From the comments:

Calibrated and tested in the same spot.
Was unable to obtain any better calibration values than those from the second run (meaning the first actual calibration run) - tried running the calibration program again and again but the combined bias (b) values from magneto12 software did not get any closer to 0 (neither did they stay the same).

LE

I have read today about elevation and bank angle effects (collectively called tilt) on the magnetometer's axial sensitivities. I'll be diving deeper into it. Don't know if that is my issue indeed

http://www.sensorsmag.com/components/compensating-for-tilt-hard-iron-and-soft-iron-effects

LE2

Nope, seems that tilt effect is used for correcting heading readings (yaw angle around the z axis) and after doing the correction the overall field magnitude does not change.
Just tried again calibrating it with some longer wires running from the Arduino to the module - same deal. Perhaps their accuracy is just not as good as their advertised precision is.


texts: I don’t know what smart thermostat to use with my high voltage

texts: I think I have 120v but not 100% sure, I don’t know what the wires do. I live in a condo with water cooling/heating furnace. Can someone help explain what the wiring means. Because I do not have a neutral wire so it makes it a little harder. I would be okay with adding a neutral but I have no idea how.


texts: 4-20mA current loop - transmit sensor reading

texts:
I am working on design loop current transmitter- to transmit reading value from thermocouple sensor using below design. I measured co-junction temperature using NTC instead of RTD.

During applying supply and connect load resister 500 ohms at Vloop-, the current flow 4-20mA when input is 0-100 degree. My co-junction reading start to increase from 25 degree to 27 degree.

My problem was when applying supply, BJT bc548 heats up when sensing current. It makes Co-junction temperature increases then my input temperature reading is not accurated.

I try to place NTC near input terminals and all the circuit is inside the small closed case. wherever I tried to place NTC, my co-junction reading still drifting from the heat of BC548.

I wonder Is there a away to reduce BJT heat during sensing the current?