texts: 555 timer one-shot 30 second light LED strip, TOTALLY CONFUSED!

texts:
I'm working on a personal project and I am at my absolute whits end here. I have a configurable N.O. or N.C. switch (nteinc Magnetic Alarm Reed Switch) so I'm not too concerned with which way I use it.

My goal is as follows:
When the two parts of the switch are separated from each other an LED strip turns on for 30 seconds and then turns off until the switch pieces are brought together again and then pulled apart again at which point it would then turn on for another 30 seconds...repeat indefinitely.

What I've tried:
I've calculated that I'll be using 1Mohm resistor and 22uF capacitor to generate a 24.2 second pulse (which is close enough to 30 for me right now). I've attempted to hook up the following circuits

http://electroschematics.com/wp-content/uploads/2010/11/555-timer-positive-trigger.jpg

http://forum.allaboutcircuits.com/attachments/ne555-power-on-one-shot-png.38684/

and a few more this system won't let me link to
but they do not perform as expected and either only turn on/off the led strip by the switch without the timer or they run indefinitely..

Power Supply: 12v worth of AA batteries
LED Strip: 9-12v (preferably closer to 12v)
LED Strip: 30mA

I'm not entirely sure what I'm missing here but I would greatly appreciate an education as well as reference circuit. I think this has to be very common because it's almost like an intrusion alarm where if the window is opened an alarm sounds for a period of time so I'm not sure why I'm unable to get this to behave the way I want to.

Thanks in advance! You'll be saving my sanity here, I've been at this all day.


texts: SIM908 GSM and GPS modules individual power control

texts:
I've been searching around google and even in manufacturer site for this information and found nothing relevant.
Is it possible to turn off GSM module and keep turned on the GPS? How can it be done?

This point is critical to my application since I need to keep GSM module OFF almost all the time and the GPS always ON.

edit:  Command manual and product page for Simcom SIM908.


texts:
I want a 90 degree rotate antenna for my SIM800L module.I couldn't find one so I hooked up a wifi antenna & it worked nicely.Does it matter for reliability?
Does it match with my sim800L module?

My GSM subscriber = 900Mhz-2100Mhz

Wifi Antenna Spec

This is a true 6dBi antennas
Gain: 6dBi
Radiation: Omni
Connector: RP-SMA
Frequency Range: 2.4 Ghz ~ 5.8 Ghz
Antenna length: extended 6.3 inches (16.1cm) and folded 5.4 inches (13.7cm)
Suitable for wireless LAN and WiFi router adapter
Compatible with all mini PCI card or most mini PCI-E card
Great for wireless router, access point repair or similar projects
Compliant with IEEE 802.11a, 802.11b, 802.11g, 802.11n wireless LANs.

https://www.ebay.com/itm/6dBi-WiFi-RP-SMA-2-4GHz-5GHz-Dual-Band-flat-Antenna-for-TL-WA5110G-USB-Adapter-/392535637250


texts:
The diagram of the cascode was taken from "the Art of electronics":

simulate this circuit – Schematic created using CircuitLab

The claim is that in this configuration they practically eliminate the Early effect in Q1, but for me this does not solve the overall problem, since they just pass the defect to Q2, which now will suffer from this effect. Moreover the compliance is slightly reduced.

The question is, why would this scheme be more stable against changes in the beta factor?


texts:
I have designed a circuit and it is working. However, I think it is too complicated and can be changed or simplified. I might be missing something. I am finding hard to create a 1 second delay.

A locomotive has to run, without attention, backwards and forwards along a length of track. At each end it is to stop for about a second before starting in the reverse direction. light dependent resistors (LDR) are used as sensors and they are under the track. The H-bridge has two logic inputs, X and Y, to control the polarity of the track; X high Y low makes the engine move in one direction, X low Y high makes it move the other way. X and Y in the same state disconnect the supply from the track and stops the engine.

I have access to:

4016 quad bilateral switch
4027 dual J-K master/slave flip-flop
4093 quad 2-input Schmitt NAND
4520 dual 4-bit up counter
4538 dual re-triggable monostable
DG211 and DG212  quad analogue switch
555 timer


texts: Implement a 3-input function using only two 2-input LUTs

texts:
This is my homework: "Given the function \$f(x_1, x_2,x_3) = \sum (2,3,4,6,7)\$ Show how it can be realized using two 2-input LUTs. Give the truth table implemented in each LUT."

At  the beginning it seems very simple, but this is a beast! I don't want you to solve it, but just show me a way to come up with a general formula to solve these kinds of LUT optimization problems.

I only know that an n-input LUT can be used to implement a \$ 2^n\$ input function, so in this case we have 3 inputs so we need a 3-input LUT. Meanwhile if we are forced to use 2-input LUT, then I can see that we can divide the function output values into two LUTs with \$x_1, x_2\$ as their inputs, and then put a MUX with \$x_3\$ as its selector to produce  the function \$f\$. But in this problem we are not allowed to use the MUX, but only two 2-input LUTs. How  can it be?!


texts: Can we apply voltage across 1 and 2 pins to control normally closed (N.C) and to pins 3 and 4 for normally open (N.O) at the same time in AQW610EAH ICs (pin diagram of that IC above)? Or only one N.C or N.O can be controlled at a time and the other will operate normally? I have read its datasheet and searched for operation, but I still have no idea. Any one that knows about this IC or something else similar please help!!


texts: Cyclone V SE use FPGA to add additional HPS RAM

texts:
As near as I can tell, the Cyclone V SE HPS HMC accesses up to 512Mo per chip select, limiting the CPU to 1Go of physical RAM.

I can't find documentation indicating if the HPS can be instructed (i.e. configure the MMU) to address another memory controller on the FPGA to access expanded RAM.  The documentation for Xilinx devices (UltraScale+ MPSoC) indicates 32Go maximum capacity plus additional via the FPGA fabric, indicating those devices can do such a thing.  I've seen no such thing for Intel's FPGA SoC.

If not, the only solution (for the Cyclone V SE) would be a DIMM controller on FPGA and an OS that treats that RAM as system memory, using the 1Go HPC RAM as a giant cache area.  Modern OSes already do this:  add a driver exposing your big RAM area as a block device and provision the entire device as swap (for S&G, use zswap to manage the swap area as compressed RAM and expand its effective capacity).

Just a curiosity.


texts:
Can I build a transistor through two diodes?

I am studying transistor and, from what I understand, a transistor it is two diodos, right?

I am thinking using two diode, just like this (see image), to make the place the transistor (e.g. BC548).

Someone already experience this?


texts: I designed a small circuit to drive LEDs with a classical constant current source (transistor and opamp). Then I realized, that a colleague using this circuit might do something wrong and tries to drive a super high current through the LEDs (SW problems we all now). The LEDs would die. To avoid this I want to limit the input signal (the voltage at the non-inverting input). What do you think about this protection circuitry?


texts: Motor driver / power supply selection issues

texts:
I'm planning on running two identical stepper motors controlled by arduino.
The specs are:

Bipolar RMS current - 3A

Bipolar RMS voltage - 3V

I plan on running them at very low (<60) RPM (the speed for max torque, according to the phone rep I spoke to from the manufacturer) and cannot sacrifice power, but can compromise speed.

The problem I'm having is that I can't find both a stepper motor driver and a power supply that operate at that Amp rating and also have a low enough voltage rating. After foraging around on here I stumbled across this helpful(ish) post:

Stepper driver 3.3V 3A

Unless I'm interpreting some of these comments incorrectly, it sounds like operating just below the voltage range of the driver isn't horrible. But other places I've read have said that using a motor below the driver specs can cause damage. Once I select the drivers I'm not too worried about finding a fitting power supply, but that's a bridge I'll have to cross after I decide the drivers I'll be using.

I'm obviously VERY new to the world of electronics and would really appreciate a push in the right direction

link to the motors: http://www.anaheimautomation.com/products/stepper/stepper-linear-actuator-item.php?sID=797&pt=i&tID=80&cID=52


texts: How do I identify and work with this thermistor

texts:
I've got a PTC thermistor, as pictured. It's being used to detect the output temperature in an in room eletrothermal storage (ETS) unit from Steffes.

One of them fell out. It's like some kind of rough material on the outside and I have no idea how they ever got it to adhere to the board in the first place. Also, the one that fell out is damaged a bit.

Anyway, how would I reattach it? What soldering technique was used to get the one on there on. BTW, I found something like them by the 2500 at digikey. It says "clamp on", maybe that's why the other one fell off, these are just held in by the tension on the wire? That doesn't seem right.

Also, how would I identify just what the specs of the thermistor are? I have some hints. The thermal fuses have two different ratings, the lowest of which is about 160°C and there is 250V going to the board (AC, home heater connection).


texts: Can I connect a mobile charger of output 5v 2amps to power a 3-6v dc mini motor pump of current intake 130-220mA?

texts: I wanted to power a 3-6v dc mini motor pump using mobile charger do I need to use a limiter to control the current since motor requires only 130-220mA and charger output is 2A


texts: How to get high current from 9 volt batteries

texts:
I am planning to make a solenoid.. Which should be so powerful as to lift up about 600N force.
I have thought about it, and I have a doubt. How can I get DC currents up to 20-30 A using a 9 V battery? Please suggest a way I can set them up in a way that would give enough current.

Another question, I thought about stepping up the voltage for a larger current. Would that work?


texts: Source synchronous vs Common clock methodology in Physical design

texts:
The common clock and source synchronous clock scheme is explained here:  http://referencedesigner.com/books/si/common-vs-source-sync.php.

Question is:
1) How is maximum frequency attained with source synchronous more than common clock mechanism ? As maximum frequency depends on data path which will remain constant for both clocking techniques.
We have the following equation for setup time of flip flop.
Tclk2q + Tcomb < Tperiod + Tskew -Tsetup
Thus:
Tperiod > Tclk2q + Tcomb -Tskew + Tsetup
From this we see Tperiod(1/Max_fequency) depends on Data delay (constant for common clock and source synchronous).

2) And if source synchronous is better than common clock mechanism then why don't we follow source synchronous clocking for all flops in the design? And instead of doing CTS why not just do source synchronous clocking for every flop in the design?


texts: Altium de-highlighting nets after using 'Find Similar Objects...' command

texts:
I can't work out why Altium is doing this, or how to undo it, or how to make it stop doing it.

It happens when I use the 'Find Similar Objects... ' option; all of objects that it hasn't found are faded out and I can no longer select them.

Anyone know how to fix this?

Additionally, if anyone knows how to change, en masse, the components' footprint library to 'Any' through the SCH inspector, that'd be really helpful too.


texts: Reduce 160 Volts AC to 100 - 110 Volts AC (EL Wire Tape) Help

texts:
I am trying to put EL Wire Tape in a project that I am working on.

I decided to go and build an inverter for 12VDC to 100VAC and that fell through. I couldn't find any guides that helped on EL Wire in computers and a lot of people used battery packs. So I was going to buy a battery pack and tear it apart. That didn't work either.

The molex connector on a computer is Yellow (+12VDC), Black (Ground), Black (Ground), Red (+5VDC). So either way I needed to get from 12VDC or 5VDC to 3VAC for the battery pack inverter.

So, I finally changed my plan to a 12VDC Inverter from Radio Shack. One end has a barrel plug for a wall adapter and the other is for the EL Wire. I am going to chop off the barrel end and solder it to a molex connector.

The other end is a problem... I got the EL Wire Tape and the Inverter from Radio Shack and EL Wire requires 100VAC and the Inverter puts out 160VAC 1W(Watt). That is confusing?

I know EL wire can be powered at higher current but it doesn't last as long. 180VAC will degrade it fast. I need to find a way to reduce 160VAC to 100VAC. Not sure what would be the best way to do this and the smallest way. Any help would be awesome. Update: Added Radio Shack Sku's.

39.3" (1m) White EL Tape (Radio Shack Sku 2760337)
12VDC INVERTER (Radio Shack Sku 2760341)


texts: How can a USB cable extender boost the signal without an external power source?

texts:
I've been searching online for a USB Cable extender for a rather long distance (let's say 10 meters). I'm familiar with the notion that the longer the cable, the weaker the signal might get, more noise, increase error rate, etc.

Usually, you solve this by putting an active element in the middle. In Ethernet connections is can be an active switch, a router, etc.

Now, I'm seeing this extenders that advertise no external power source is needed because they rely on an "ASIC chipset" that "buffers" the signal.

From what I know, it doesn't make any sense to claim that you can boost a signal without adding a power source. Also, buffering AFAIK could, at best, serve to some error-correcting algorithm or something.

So... what sorcery is this? :P

Thanks!


texts:
I'm tryng to select a Bulgin Buccanneer power connector, and the panel-mounted ones come in "Front Panel" and "Rear Panel" varieties. Why is there a distinction?

I'm struggling, because I need a connector to fit on a panel that's on the side...!


texts: Brushless motor back and high current and IC

texts:
I'm trying to replace the brain of my neato vacuum which is broken.

I've already repair a cleaning MOP but with this one I have a problem with the brushless motor which is throwing some party fun in the circuit.
First I was Using the onbord 5v regulator from the l298n module like this:

But when the brushless FAN motor start turning quickly, the Atmega start to hang.
I've tred to use a powerbank to power the IC and it was going well.

I've start to plug a regulator LM7805 on the battery power source, It was really better, but one time or two I have notice a little hang.

here is a video to explain:

How could I filter more the current for my IC?
Put others capcitors?

Maybe starting the wheels once the brushless motor speed is stabilized could be an idea? Could use some delay inside the IC before starting?


texts: Why are there different Ethernet PHY magnetic configurations?

texts:
I'm looking at pcb-mount Ethernet ports like these:

I'm seeing a few different configurations of the magnetics within the ports. On a single Wurth data sheet, there are 4:

Schematic 2 is the part we currently use, but is going obsolete. I found potential replacements which look more like Schematic 1.

What is the difference? Are there benefits to the different designs?


texts: Multiplexer to switch between many sets of 8 channels

texts:
I have many (up to 16) 8-channel "buses" (not digital, but analog) each with signals which I want to read with a single 8-channel analog-to-digital converter (ADC). I would switch between these ~16 buses at about 1 Hz and measure their 8 channels simultaneously with the ADC card. I'm trying to find an IC that might do something like this.

I know there are many single-channel and dual-channel multiplexer chips available, but I'm looking for one that can switch between sets of eight. Is there any hope that such an IC exists that can do this? I realise such a chip could have hundreds of pins. The alternative is to wire up 8 of these single- or 4 of these dual-channel multiplexers in parallel, which will likely require many board layers to avoid overlapping copper traces.


texts: How to drive four nixie tubes with arduino?(in-14/clock)

texts: I'm looking to build a nixie clock. I have looked online, I found some guides but many used expensive nixie clock kits or custom pcbs. I came across some threads about driving a single nixie tube with an arduino. Later I found this thread here on this site called "How to drive nixie tubes from Arduino". In the thread JIm Dearden solved the problem that the creator had like me he also had a problem/question about connecting multiple nixie tubes to one board. But if you want to connect 4 digits/nixie you would need 16 io pins. But the board only got 14? Jim also talked about adding 4 bit latches between the arduino and the 74141 driver. Avoiding the need to tie up the I/O lines or multiplex the display. What does he mean with that? How do you wire it? Is it another chip that you put between or how does it look? This is the picture that Jim Dearden posted in the thread that I want to follow. Thank you for you time :)


texts:
Is there a way to get one component per line in the bill of material ?
For example, currently I have two different designator who have same value and they share the same line. I would like to get one designator per line.

Anybody know how to make this ?

Currently I have my bill of material as below and as you can see this is a bit mess up. I don't know why Altium is displaying this way ? Why it doesn't separate them ?


texts:
First, a bit of background: I am just a hobbyist with electronics and have very little formal education in the area. I understand most terminology, but generally require a schematic for me to be able to create something of any decent complexity.

I am working on a personal project in which I have run into a bit of an issue.  I have a digital square wave that I need to transform into pulses. My guess is that there is something that can output a pulse on the rising edge, but I don't know what it would be called. Sorry if this has been asked a thousand times, or is something elementary.  I've tried searching all over and am not sure what something like this would be called. I want a circuit to transform a digital waveform that looks like this

____------____------_____

into one that looks like this

____|_________|__________

using common ICs and/or passive components that a hobbyist might have around.

Thanks.

edited to remove superfluous details

Edit:

Maybe I can rephrase the issue in another way, instead of shortening a pulse to some undefined short duration.  What I want is to divide a clock by 4096, such that every 4096 pulses, I can get a pulse of the same duration as the input clock.

i.e.

_-_-_-_ ... x4090 ... _-_-_-_-_

becomes

___________________________-___


texts: EEPROM or SD card storage for a general logger application?

texts: If you need to store data, let's say numbers (one byte each), and you need a capacity for at least 100,000 readings in a low power sensor (3.3 V and less than 20 mA in stand-by operation), will you go using an SD card storage type or a simple EEPROM chip and why?


texts:
simulate this circuit – Schematic created using CircuitLab

I have an AC wired fluorescent lamp (antique one,) and I am making it portable by removing the bulb inside it and wires.

I am going to replace it with LED which runs on DC power.
I have bought a 3V yellow SMD LED. I have also bought two 1.5V AA pencil cells and connected it to the LED. But it ran for only 1.2 hours. I want it to last for max 6-8 hours. I have a solution like I can use a 9V rechargeable cell and drop volt to 3V and make it run more but it will make my lamp bulky and it will not look good.

I have tried with alkaline AA cells (Duracell, two 1.5V) and it ran for 2.5 hours max.

Is there anything I can do to overcome this issue?

This is the 3 watt SMD yellow LED I am using:

Mobile battery I am using:

The switch I am using:

So how to create that constant current LED driver circuit without LM IC's and just with Res, cap, and diodes I have seen Most of the people using LM317 IC and creating circuit from 12V power supply or 9V to LEDs but that's now power supply source is so...


texts: How to make a circuit that generates 50mA current at +1.8v within 10ns rise time?

texts:
I am using Atmega328 MCU to control a SRAM IC and it is required to power up the IC using a source that can deliver 50mA current at +1.8v within 10ns rise time without any voltage drop. unfortunately my MCU can't provide this much current with such rising time. So I need an external circuit that can be controlled by my MCU which have these capabilities.

It's a PUF based SRAM IC, we fabricated it. It's not a commercial IC.

The idea is based on whenever we power the SRAM cell it will give us the initial bit stored in the SRAM, and this bit is always the same. This bit is different from one cell to another and is based on the fabrication variation. So we need a very fast source to power up the SRAM, if it's not fast enough we could get the wrong bit.


texts:
First of all, I'm a mechanical (robotics) engineer, so I do not know much about electric power systems.
I'm making a mobile robot that should have electrical motors and drive system.
The problem is that I have a 240V Li-ion Battery System only, and the Driver Input must be under 200V!
I can set the battery charging limits to 200V  but I want to use the full range of battery power.
So I'm trying to find a DC-DC converter that converts DC input voltage (of 230V) to output of 200V or 195V, with up to 60 A current.

Does anybody know about something like this?

Specifications:

the peak current   : 60A with 3sec
continuous current : 20A
the total power   : 13kW.


texts: How are integrated circuit photomasks fabricated with such high resolution?

texts:
I understand that photomasks / photoreticles are used for the fabrication of integrated circuits, CPUs, and such. I also have read that CAD software and languages like VHDL are used to describe the actual physical layout of the gates and their transistors.

However, none of the answers on this site (and others) seem to explain how the photomask itself is manufactured. Or in other words: how do you "print" the CAD models onto the photomasks? Considering the tiny size of modern electronics (my own CPU apparently uses 14nm lithography) how do we achieve the necessary resolution?

Do we start with a bigger photomask, and then project onto the smaller one, with some lens in-between? Or are there motors/mechanisms actually capable of moving at ~14nm precision, that print out the design? Or is it something else altogether?


texts: How to populate unused flash for an armv7a processor?

texts: I have a decision on how to fill unused memory in a flash device.  I've heard of populating with reset instructions as a safe way to handle rogue pointers, etc.  Is there a concept of an assembly reset instruction for armv7a processors?  Is there an industry standard on how I should fill the contents of this flash?  Default erased 0xFF values?


texts: what is the tempreture at which the thermal limit of an amplifier is reached

texts:
Introduction:

I am upgrading a "power amplifier" that a fellow engineer has designed , my job is to add thermal protection against failure in prolonged use (or operator miss use).

The package of the transistors used is To-247-3, the metal area is 140mm2 according to :infineon  the interface material (silicon pad , insulator and grease free) used has thermal impedance of 0.23°C-in2/W (@50 psi) , the thickness, conductivity and other parameters are provided in this table :

The tempreture sensor has a lug mount and will be screwed into the heatsink directly close to the transistor similar to this amplifier.

The power dissipated by each transistor is 5W , the maximum junction temperature is 175 degree Celsius and Rjunc/case is 0.29 degree / W.

I think we should keep the junction temperature below 150 to be a bit away from the absolute maximum.

Now for calculations :

140mm2 = 0.217 inch2 , so sil-pad resistance is 0.23/0.217= 1.05 degree C/ watt.
total resistance from junction to sink is 1.05+0.29= 1.34 .
delta T = 1.34*5w= 6.74 degree C . So the heat sink is allowed to reach 150-6.74= 143.25 degree Celsius ?!!

EDIT: due to comments and answers i would like to add the following , the transistos used are mosfets used switched 45 A in half bridge topology at 20khz from a decent gate driver to minimize switching losses , the conduction losses are : RxIxI = 0.0022 x 45 x45 = approximatly 5W .

Rds(on) MAX is found from this curve at 125 degree .

QUESTION: I feel the numbers are not adding up (because other parts on the pcb would be toasted if the case is at such a high tempreture) please correct my calculations and tell me what i am missing ? and state what is usually the case temperature at which the thermal limit is reached ??


texts: How to silence a 5V electrical beeper/buzzer

texts:
We have a simple circuit operated by 2 AAA batteries, it has a simple board inside with one of these 5V electrical beepers that makes sound every time it does something.

It looks exactly like the one in this page:
https://rcexplorer.se/product/5v-beeperbuzzer/

The problem is I want to silence it, maybe removing it would be enough but I don't want to do it without asking first because I don't know if it will break the device, maybe I have to replace it with something, or remove it leaving the circuit closed, I don't know what impact it can have.
Other solutions on how to make it more quiet even if it still beeps are also welcome, but I prefer complete silence.


texts:
I'm working on an android controlled input/output/gauges manager for cars based on a pic24 micro controller. I'm really not an electronics expert so I had someone working on the schematics but he has no time anymore.

I previously asked a question here about the outputs schematic that he designed: Mosfet as switch for high output current and it turns out the schematic was crap!

I've found automotive high side drivers for a fair price and I think these would do the job perfectly. I want 5 outputs to drive various loads (leds, solenoids, dc motors, etc) and turn them on/off from the pic micro controller.

So I've chosen a single channel driver (for bigger loads) and a 4 channels driver (supports 12A so I would think that equates to 3A per channel?).
http://www.st.com/content/ccc/resource/technical/document/datasheet/cd/1f/d3/43/b8/2d/48/0b/DM00157127.pdf/files/DM00157127.pdf/jcr:content/translations/en.DM00157127.pdf

Here is the schematic that I think would be ok for both drivers. Is 1w rating enough for the zener diode and is 1a enough for the ground diode? I think I can share them between the 2 drivers, is that correct?


texts: Preventing overcharge of a SLA battery in a solar electric fence charger

texts:
I recently purchased a solar electric fence energizer, specifically the Patriot PS5. After it had been sitting in the sun a while, I noticed the battery was making a "gurgling" noise, which according to my research means the battery is overcharging. Upon opening the unit, I noticed that there was no protection circuitry whatsoever between the solar panel and the battery.

The battery is a 4 V SLA battery, and the solar panel can reach up to 8 V on a sunny day with no load. The solar panel, battery, and the rest of the electronics for the energizer are all connected in parallel.

My question is, what is a simple way I can modify the circuit to prevent overcharging of the battery? Also, is the 3-step process recommended by Battery University necessary in this case, or will a simple voltage-based cutoff work?

I designed the circuit below for this purpose, but I'm not sure if it will work or not, and it seems somewhat over-complicated. It uses a diode-based voltage reference and an op-amp to determine if the battery voltage is above a certain level, and shuts off current flow to the battery if it is.

simulate this circuit – Schematic created using CircuitLab

I'm fairly new to this, so I'm sorry if the schematic is poorly laid out. Any feedback would be great. Thank you!


texts: Bootloader and Vector Table on STM32F051

texts:
I'm going through my company's code for a Bluetooth remote that uses a bootloader to download the main application over Bluetooth. The remote is pre-programmed with the bootloader application. Once the main application is loaded, the remote boots from the main application, unless there is a specific command to jump back to bootloader.

I'm new to bootloaders, so I've been trying to understand how it works. So far I'm quite confused. My main points of confusion are:

Why is there a need to remap the vector table in the main application? I've seen a post on this, but I'm still not satisfied with the answer. How does the remap enable differentiation of the ISRs between that of the bootloader and main app? I include here a snippet of the remapping portion of the code:

void remapMemToSRAM(void)
{
    uint32_t vecIndex = 0;
    __disable_irq();

    for(vecIndex = 0; vecIndex < 48; vecIndex++)
    {
        VectorTable[vecIndex] = *(volatile uint32_t*)(APPLICATION_START_ADDRESS + (vecIndex << 2));
    }

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

    SYSCFG_MemoryRemapConfig(SYSCFG_MemoryRemap_SRAM);

    __enable_irq();
}

APPLICATION_START_ADDRESS is defined as 0x08004000. What does that for loop do? What kind of data is in those memory locations from 0x08004000, and how does it get put there?

In the startup file, I see that reset handler branches to main after setting up the data in RAM etc. How does remapping the vector table enable the branching to go to different main()? I still don't see that.
Do the bootloader and main application need separate linker files?
Why must we remap the whole vector table? I understand the need for it for the reset vector, it needs an address to jump to upon power on or a reset. But for the other vectors shouldn't the stack be enough to tell if the caller is from the bootloader code or the main application?

I apologize if the questions are not clear, if they are let me know and I'll try my best to be clearer. I'm just very confused at this point.


texts:
I purchased a Dremel tool from the United States and using it in India. As always, the trouble is with the power inputs. A step down converter is simply too expensive for those power ratings (>2 Amps output), and hence I am trying to mode the circuitry which is driving the Dremel motor.

Here is the circuit diagram which I have been able to trace from the driver board!

I have searched online and could not find a way to control the firing of the Triac.The BR is a bridge rectifier and connects directly to the power plug.There is a diac in series with the 23ohm resistor.The space was so tight, I could not read the values of the capacitors.

My understanding is that as the cycle progresses, the voltage across the last branch on the left will trigger the triac into conduction.The variable potentiometer is what controls the speed of the DC motor which is in series to the bridge rectifier.

Which part of this circuit will need modifying so that it works with 230v input.The bridge rectifier is capable of handling 400 volts, the lowest voltage on the motor is 33 volts and the highest is 100 volts.
Component values not in the Diagram
Bridge Rectifier- KBPC604 Full wave Bridge Rectifier with 400V input limit
BTB06- 6A Triac
Capacitor series with 100 ohm resistor-2E104K 0.1uF 10%


texts:
I've read quite a lot of threads here about P-MOSFETS and how to drive them properly from IC but still have some questions.
Here's the schematic:

Some useful values from MOSFET datasheet
Vgs(th) -2..-4 V
Rds(on) ~0.07 Ohm
C ~1.5 nF

Schematic will be used to control a lot of common-anode RGB LEDs and current will be around 1A, so 60V/28A(max) MOSFET may be an overhead but that's what I got.
Can you please help me with the following
1. Will the schematic work as it is without NPN transistor controlling MOSFET gate?
2. Do I actually need current-limiting resistor to control Vgs or just the pull-up will do it?
3. Will MOSFET saturate on Vgs ~ -5V?
4. Will MOSFET close on Vgs ~ Vd - Vs = -1.7V?
5. How does the value of Pull-Up resistor affect how quickly I can switch MOSFET on/off (is 100Hz achievable?)


texts:
I have a few questions about modeling an RFI filter in LTspice with a triac-based dimmer circuit. I'm referencing the circuit described in Figure 11 in Triac Principles and Circuits -- Part 2 (Nuts & Volts Magazine), which uses an LC filter on the input.

When I run the simulation without the LC filter, the waveform looks like a "textbook" chopped triac output. When the filter is added, there are high-voltage spikes at the trigger points. If you zoom in on these spikes, the response is an underdamped oscillation, as one might expect.

According to another question posted here, Using LC filter instead of RC filter in mains powered circuits, input filters on dimmer circuits are designed to 1) reduce the 50/60 Hz harmonics that affect radio frequencies and 2) limit \$dI/dt\$ to avoid damaging the triac.

Reducing \$dI/dt\$ makes sense because the damped response with the LC filter is slower than the instantaneous change in the other circuit, even if the peak voltage and current is higher for a matter of microseconds. But what about the high-frequency radio interference?

The values for L (100 uH) and C (100 nF) correlate to a ~50 kHz resonant frequency per \$f=(2\pi{}\sqrt{LC})^{-1}\$. I've looked at many triac dimmer circuits and the LC values are very inconsistent. I have a Lutron dimmer right here that uses a 47nF/22uH configuration, which equates to about 157 kHz. Are there really that many harmonics of mains frequency that cause interference, and why such variation between designs?

Lastly, I'd like to see how the LC filter values affect high-frequency blocking. Are there ways of simulating RFI in this circuit with LTspice?

Thank you for the help!


texts: Converting single-ended line audio to differential, on single supply?

texts:
I built an audio amplifier based on TI's TAS5630 IC. This is a Class-D amp with multiple configurations. I'm using it as a 2-channel amp. The problem is that this configuration requires a differential input.
So I built this little circuit that seems to do the job:

The outputs are between C2/R6 and C3/R7.

Is it worth designing an opamp based circuit or is this "good enough"?


texts: Very high current very low voltage application

texts:
I'm not an electrical engineer. I have an unusual need and would like suggestions as to how to proceed. I have an application that needs very high currents at very low voltages. I'm trying to heat a thin strip of aluminum to temperatures near 100C quickly and then control the temperature. My calculations suggest about 150 to 200 amps at less than 0.1 volt. About the only idea I have is using a toroidal transformer with maybe 1000 turns and thick copper bar passing through the center of the toroid connected to the aluminum strip. I can use either AC or DC current and if AC, I'm not necessarily limited to 60hz.

Any and all good suggestions are welcome.


texts: Reading a Micron 29F32G08QAA NAND Flash IC

texts:
It would be nice if this was a shopping question - but it is 99%+ likely to be an electronic construction question :-(.

I wish to find the quickest / easiest / cheapest way to read a 4GB NAND Flash IC in a damaged USB memory stick. The onboard controller IC is dead.The Flash IC may also be dead but I will assume it isn't until it becomes otherwise obvious.

Reading it could involve

(1) Making a custom reader,

Maybe not a wholly silly idea as connections to Flash are fewish (8 data and a handful of controls.)

How likely it is that I could easily access the data if I did this I don't yet know. Obtaining a bit image is bearable worst case BUT I'd far far rather have something that "sees" the files system and files as was. Of course.

(2) soldering in a new controller IC

I do not yet know if these are in common use in other devices. Sample of 1 checked so far had 100% non-match. There may be an industry standard, part number irregardless, I know not (yet).

SK6211. QFP48. Outline description here and
 Datasheet here.

Or

(3) Removing the Micron 29F32G08QAA 32 mbit NAND Flash IC.
 Datasheet not yet located.

Markings VERY dim. Here is "enhanced photo image of markings".

SO

Does anyone have any suggestions how I might BEST read this memory with original format, or at all?

Any thoughts on source of 6211, commonality with other parts, ability to use "any old" NAND Flash reading IC  etc.

Any hints.

Background:

A good friend who had been warned about the need for data backup failed to heed the warnings as has "lost access" to an extremely valuable set of files stored on a USB memory stick. She is studying to be a teacher and the files are lesson plans and other material created over a long period of time.

The USB memory stick was physically severely damaged by being knocked sideways while plugged into a USB port. Apparently attempts were made to read it by pushing it together. When it got to me 3 of the 4 connections between PCB and connector were broken. I resoldered these, expecting there to be a good chance of restoring operation.

When plugged into a USB port the memory stick draws a large current (probably port limited) and the controller gets VERY VERY hot - I first discovered this by burning myself badly on the IC. The actual memory IC is on the opposite side of the PCB. It also appears to get hot BUT this may be due to the very large Wattage going into the controller IC. Desoldering will happen.

Part number corrected to 29F32G08QAA


texts: If a GPIO pin is not interrupt configurable as external interrupt, is it still possible by any chance to detect the button press on the pin without polling just like an interrupt?


texts: Why are DC power supply's AC source connections interchangeable?

texts: When we cut a power supply's DC output tips we need to be careful how we feed the circuit since one side is negative one side is positive. But why doesn't the same apply when we plug for example a laptop charge, mobile phone charger to a wall outlet? Is that because alternating current has no one sided direction? What about the rectifier's input after the transformer?  Or is there a preventing circuit inside?


texts: Multipath fading in mobile radio systems

texts:
Here is the problem that left me thinking:

"In a mobile radio system (e.g., cell phones), there is one type of degradation that can be modeled easily with sinusoids. This is the case of multipath fading caused by reflections of the radio wave interfering destructively at some locations.  Suppose that a transmitting tower sends a sinusoid signal, and a mobile user receives not one but two copies of the transmitted signal: a direct-path transmission and a reflected path signal (e.g. from a large building).

The received signal is the sum of the two copies, and since they travel different distances they have different time delays.  If the transmitted signal is s(t), then the received signal is
$$r(t)=s(t-t_1)+s(t-t_2)$$
In a mobile phone scenario, the distance between the mobile user and the transmitting tower is always changing.  Suppose that the direct-path distance is
$$d_1 = \sqrt{x^2+10^6}$$
where x is the position of a mobile user who is moving along the x axis.  Assume that the reflected-path distance is
$$d_2=\sqrt{(x-55)^2+10^6}+55$$
The amount of the delay (in seconds) can be computed for both propagation paths, using the fact that the time delay is the distance divided by the speed of light (3 x 10^8 m/s).

Assume that the transmitted signal is

$$s(t) = cos(300 \times 10^6\pi t) $$

The amplitude of the received signal is a measure of its strength.  Show that as the mobile user moves, it is possible to find position where the signal strength is zero.  Find one such location."

So, here's what I did:

The only thing needed from the received signal function is the amplitude, so I turn each direct and reflected signal into their phasor representation:

$$S_1 = e^{-jt_1}$$
$$S_2 = e^{-jt_2}$$

Then I sum the phasors:

$$S = S_1 + S_2 = e^{-jt_1} + e^{-jt_2} = cos(-t_1) + cos(-t_2) + j(sin(-t_1) + sin(-t_2))$$

Then the amplitude can be achieved this way:

$$A = \sqrt{(cos(t_1) + cos(t_2))^2+(sin(t_1) + sin(t_2))^2}$$

And make the amplitude equal to zero:

$$0 = \sqrt{(cos(t_1) + cos(t_2))^2+(sin(t_1) + sin(t_2))^2}$$

But when I try to solve for x (in which is obtained from t = d(x)/c) using Wolfram Alpha, I got no solution.  What am I doing wrong here?


texts: analog multiplier using log and antilog amplifier issue

texts:
I'm trying to build an analog multiplier that takes any two voltages and produces the product for them

This is the basic layout of the circuit:

can this layout do what I need?
  I know there is problem with the last stage, the last opamp should give me gain: k2, to get V1 * V2
but I don't know that the value of k2?


texts:
For a buck converter, I am trying to understand how the appropriate signal is sent to the PWM block to control the duty cycle of the FET. When the output voltage is equal to your reference voltage (15V in picture), the error is 0. So does that mean the PID controller somehow outputs a signal of 0.5357 assuming a 0V to 1V sawtooth signal to compare to for the comparator to generate the PWM?

Because with a buck converter: Vout = D*Vin, so Vout/Vin = 28V/15V = 0.5357 = D.


texts: Relay-Relay circuits: flywheel diode - yay or nay?

texts:
If you're going to control a relay with a transistor and will not include a flywheel diode, you're going to have a bad time, it's a known fact. But what about relay-relay circuits? I have mixed feelings about this:

When "driving" relay A is switching off another relay B, the inductive kickback of coil B would produce a spark in relay A contacts, thus, potentially reducing the overall life of relay A. So, we just include a flywheel diode on relay B and none on relay A. Well...what if A is also driven by another relay? (i.e. in a relay-based CPU? :))
So, if all relays have flywheel diodes, then we have a problem on "driving" or "controlling" relay A again: according to this article: http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C3264_AppNote&DocType=CS&DocLang=EN adding a flywheel diode would modify de-energizing profile of the coil, which modifies how the contact spring reacts to a switch off, which damages spring and reduces life of a relay.

Any comments? Drop them, use them, or use diode+zener? I think I may have to just make a pair of inverter loops (with and without diodes) and see which one dies first :)


texts:
Is the UV curable paint used for PCB etching the same UV curable paint used for making PCB solder masks? Some have different eBay descriptions but they're all in identical 100g black containers.

As far as I can tell, the only difference to making a solder mask is only doing the first development with sodium carbonate to remove the unexposed UV paint and then leaving the rest? (i.e. no ferric chloride / ammonium persulphate or sodium hydroxide)

Can I do multiple layers of solder masks? Can I use a second white solder mask over the top of the first green solder mask in place of silk screening to add the legend on?


texts:
We at my company, has a very strange issue regarding til MMA8451. We are experincing that our accelerometers data can be suddenly wrong over time.

We have approximately 250 devices out, running in the field, and we have about 10 devices which got this problem. What happens is that the sensor data:

Suddenly has a completely wrong offset (out of the min/max values, that the MMA should even be capable of).
Or has it's z-axis locked in a "fixed" value or fluctuating.

We see that a mechanical bump of the PCB/sensor can make it suddenly work again. That makes us think that the MMA chip has been damaged.

If we take a brand new MMA and solder onto a PCB which had the problem ealier, no problems exists. So it's happening over time. And when it has happend, it can recover or come back to normal again.

We do of course have a lot of software, checking that all communication is alright on the I2C etc. We interface with a STM32 microcontroller. When the problem occurs, all power offs, resetting the chip etc, has no influence of the wrong data.

Here I have some visualizations of how the data looks. First an all normal functioning MMA measurement: (x-axis = red, y-axis = green and z-axis = blue). All measurement are done with the device fixed horizontal in the z direction, and then turned around the z-axis.

The x axis of this graph is samples (100 hz sample rate). The y axis is the raw sensor value.

The following pictures shows malfunctioning MMA measurements:

And another:

As you see, the sensor works in some sense, as the x and y axis changes. But has an unrealistic offset. If we hit the device mechanically, the axis happens to be normal afterwards.

The z-axis can act like this, just fluctuating, or it can be locked in either 8192 (max) or -8191 (min).

We have done various ESD tests to debunk that as a reason for the malfunctioning devices. But that do not seems to be the problem.

We hope that NXP or some of you people, have some clever ideas about this issue, or have heard about this before?

NB. Same question is posted on the NXP closed forum without answers yet.


texts: Custom USB Gamepad Working But Not Detected In-Game

texts:
I've created a custom HID gamepad using an STM32L151C8T6 (probably irrelevant) and my computer recognizes the device using the gamepad tester application built into Windows 10.

I can verify the functionality by moving the joystick around and pushing a button and the application will display the joystick position and button indications. However, when I go to use this gamepad in a game, every game I try will not recognize it (not even Steam).
In order to rule out a couple of things I am posting what I believe to be important information:

USB Report Descriptor
     0x05, 0x01,     //USAGE_PAGE (Generic Desktop)
     0x09, 0x05,     //USAGE (Gamepad)
     0xA1, 0x01,     //COLLECTION (Application)
     0x09, 0x04,     // USAGE (Pointer)
     0xA1, 0x00,     // COLLECTION (Physical)
     0x09, 0x30,     // USAGE (X)
     0x09, 0x31,     // USAGE (Y)
     0x16, 0x01, 0x80,   // LOGICAL_MINIMUM (-32767)
     0x26, 0xFF, 0x7F,   // LOGICAL_MAXIMUM (32767)
     0x36, 0x01, 0x80,   // PHYSICAL_MINIMUM (-32767)
     0x46, 0xFF, 0x7F,   // PHYSICAL_MAXIMUM (32767)
     0x75, 0x10,     // REPORT_SIZE (16)
     0x95, 0x02,     // REPORT_COUNT (2)
     0x81, 0x02,     // INPUT (Data,Var,Abs)
     0xC0,           // END_COLLECTION
     0x05, 0x09,     // USAGE_PAGE (Button)
     0x19, 0x01,     // USAGE_MINIMUM (Button 1)
     0x29, 0x06,     // USAGE_MAXIMUM (Button 6)
     0x15, 0x00,     // LOGICAL_MINIMUM (0)
     0x25, 0x01,     // LOGICAL_MAXIMUM (1)
     0x75, 0x01,     // REPORT_SIZE (1)
     0x95, 0x06,     // REPORT_COUNT (6)
     0x81, 0x02,     // INPUT (Data,Var,Abs)
     0x95, 0x02,     // REPORT_COUNT (2)
     0x81, 0x03,     // INPUT (Constant,Var,Abs)
     0xC0    /*     END_COLLECTION                */

USB Configuration

I am hoping that there is a simple answer to my problem, such as Steam and games only recognizing certain controllers (i.e. Xbox 360, Xbox 1, PS4...).
Perhaps there is an application I could use to bridge my controller to a virtual gamepad that could be used as a workaround?
Perhaps my USB HID Report Descriptor is faulty in some way that prevents it from being used in-game?
I would be more than happy to share details with my project, please ask away. Thanks a million!
GitHub Repository: GMK-Lite
Edit: This is not a usage question. proof


texts:
My first post here, I have been playing with a DC motor and attempting to upgrade the original batteries from SLA to Lipo, the scenario is as below and i'm looking for some advice on what happened and some advice on a motor upgrade to avoid what happened to the original motor in the future, apologies for the long post...

So I had a DC motor (400 W) powered by a 12V SLA 33Ah battery, I have bought some 4s Lipo batteries (80Ah total) to replace the 12v SLA, the Lipos are lighter and have a much greater capacity but in turn deliver above the original 12V spec of the motor (16.8V full, 14.8V nominal).

I was hoping for a slight speed increase and an increase in duration, what I got was a massive speed increase and now a burnt out motor !

Originally the underwater dive scooter this setup was working in used to run for one hour at around 30 meters per minute covering approximately 1800 meters before the SLA battery.

When I took it for a dive with the new Lipo batteries it ran for 80 minutes covered 3600m at 45 meters per minute then the power dropped off rapidly. I assumed the batteries were low, took it home recharged and tried to dive again but the motor was severely under powered then stopped completely, on examination at home the coil has melted in places.

So my basic knowledge leads me to believe that the increased voltage of the Lipo batteries lead to an increase in the speed and an increase in current drawn which lead to more heat and the motor eventually burning out; firstly could someone confirm i'm thinking along the right lines here ?

Its an old Bosch motor which I don't have the specs for all I know was its 12V and 400 W.

Main question is this: I would like to replace the motor with a 24 V 750 W, one of these as they are used in other 24V dive scooters:

http://www.everything-ev.com/index.php?main_page=product_info&products_id=242

What are the likely consequences of supplying the 24V motor with the 4s 80Ah Lipo configuration and delivering between 13.2V (min.) to 16.8V (max.) to it, i'm expecting this will decrease its speed and power considerably but not sure what implications this might have on the current it draws if its designed for 24V supply.

Second option will be to rearrange the battery pack, so its 8s and delivering between 26.4V (min.) and 33.6V (max.) and put in a regulator limiting it to 24V to the motor.

Any thoughts on this much appreciated


texts: Understanding microcontroller ADC input pins (atmega328)

texts:
If I set up the ADC on the ATmega328 to read from a certain ADC pin, what state is the ADC pin put in to?

Since I don't explicitly enable any pull ups, is the pin floating/high voltage/low voltage?


texts: Improving throughput of a Bluetooth Low Energy Connection

texts:
Follow-Up question from Stackoverflow

I am trying to write a characteristic value repeatedly over a short amount of time. Different sources tell that rates between 200 and 305 kbit / s should be possible. However, I reach only ~36 kbit/s.

I am using an iPhone 4S to write the characteristic repeatedly. A development board with a CSR1000 BLE chip serves as the peripheral that accepts the writes. I am using writes without response to avoid acknowledgments on the attribute layer. See my question on Stackoverflow for further details.

A write to the 20 byte long characteristic value happens after every millisecond. Therefore, I am sending 160 kbit / s. Only ~36 kbit/s are actually received. The strange thing about it is, that, at the start of the session, everything works fine for a fraction of a second. Then, packets start to drop. However, most often, packs of four continuous write requests work fine before a varying number of packets is getting dropped again.

I have found a significant correlation between the throughput and the value of Conn_Interval. However, the iPhone 4S won't accept any lower Conn_Interval values than 0x0f. This is already lower than what Apple proposes within their hardware guidelines. When I comply to their values and use an interval minimum of 20ms, and an interval maximum of 40ms, the throughput decreases to ~15 kbit/s.

Conn_Interval = 0x000f = 18.75 ms
Conn_Latency  = 0x0000
Supervision_Timeout = 0x00fc

The "Modeling the Maximum Throughput of Bluetooth Low Energy in an Error-Prone Link" paper by Gomez et al. describes the influence of Conn_Interval and bit errors on the throughput. However, according to their analysis, there would be a relatively high amount of bit errors, if this would be the limiting problem source. The development board lies in close proximity to the iPhone 4S. Therefore, I guess that there exist other limiting factors.

What other parameters could have an influence on the throughput in Bluetooth Low Energy?
Why is the Conn_Interval such a big deal? If the interval is higher, shouldn't the individual connection events be filled with more packets, leading to a similar throughput?
Could a Bluetooth Sniffer / Analyzer help in detecting whether there are really so many bit errors? If yes, what analyzers would you recommend?


texts: What ESP32 UART Auto-Program Circuit Alternatives are there?

texts:
I am currently designing a board centered around the ESP32. I want to implement an auto-program circuit for convenience's sake, because I don't want to hold a boot button each time I want to program it.
My question is: Why is the below circuit that most ESPs use, designed the way it is? I am asking because this circuit fails to initiate the upload more often than I would like and I end up having to press the boot button. So I somehow think there is something with the design that causes this, as I had this problem with more than 1 ESP at different times.

Why not use something like this for instance? This is a thought experiment I made using the logic table and KV diagrams.
(1) EN = not(DTR) + RTS
(2) IO0 = not(RTS) + DTR
From this, I have developed this circuit:

So I know this can probably be done better, but maybe this will solve the reliability problem that I have. Or maybe I should use the relation I found on (1) and (2) to build the same circuit using OR-Gates. In any case, any thoughts on optimization or help on the matter would be appreciated.


texts: Why do so many logic ICs have output high voltages specified at 3V and 4.5V when they're primarily used at 3.3 and 5V?

texts: I've noticed this a lot, including this recent example. \$\text V_{OH}\$ is specified at 3V and 4.5V, for the maximum and a small output current. I assume this is to allow for 10% load regulation on the 3.3/5V, since those are common rail voltages. This doesn't really make sense. Why would the manufacturer assume some amount of load regulation rather than just specifying them at the voltages they're commonly used at? Making sure the load regulation won't effect logic levels is my job. Is there a historic reason for this, or is my assumption entirely wrong?


texts:
The formula of electric potential is $$V=\frac{kQ}{r}$$ and the voltage across two points is \$a\$ and \$b\$ that determines the work of the electric field on a charge \$q_1\$ from \$a\$ to \$b\$.

If, say, we have short wire and make a circuit with a power source, then there would be some voltage. Now if we use a long wire instead of short wire, isn't now the distance increased  between \$a\$ and \$b\$? So why does the voltage remain same if we consider the wire conductivity 100%? If we use the above formula then it means  that the voltage must decrease. So how does all this happen?


texts: Low cost and accurate Sensor technology for detecting objects at short distances (<5m)

texts:
I am interested in a project which aims to detect any object within short distances, at various directions. Hence, the sensor should be highly directional, fairly accurate and if possible, compact. Among the available ultrasound and IR sensors, which technology would be better and why?

The primary aim of this sensor is to assist a visually impaired person with moving around on his/her own.


texts: Film over an SMD LED to change its colour?

texts:
I require an RGB white + amber LED SMD chip. Unfortunately, it looks like nobody really makes such a thing except for one seller on Aliexpress. I tried purchasing a few of these only to find their definition of amber is more of a burgundy/red/orange hue.
So instead I'm considering a 5050 5in1 RGBW CCT chip and somehow modifying the warm white chip to produce a more true amber/golden yellow colour.
Is there a suitable film that I can stick over the warm light side of the chip to convert it into more of an amber light?

The purpose of these LEDs is to illuminate a light guide that's only big enough to accept one chip, two is not possible otherwise a separate amber chip would have been my solution.


texts: Car Battery + Car battery Charger = 12 V Bench Power Supply?

texts: So a bench power supply can be quite expensive, and something I already have laying around is a car battery and a car battery charger.  Is there any reason why a car battery + battery charger would not be a good bench power supply for stepper motors (given the need for straight 12V power, obviously the complexity increases when you must supply other voltages).  I'm looking at the setup with a scope and while it's a little noisy it's nothing out of the ordinary either.  I'm in the midst of testing out a RAMPS 1.4 unit with a megaduino and a single NEMA 17 motor.  While I'll probably scavenge an ATX unit soon, I was wondering if it was crazy to try such a setup with a car battery.  Furthermore, looking at the amps some of these car chargers put out, it seems worthy of looking into for vastly more powerful projects as well.


texts:
with 1000 rpm how much load it can move on 12v?
I want to no load of DC gear motor on 12v and 5v


texts: can NPN transistor be used when sinking current?

texts:
so to give a little bit of background, I want to experiment with led matrixes. I have multiple Arduino Nano boards, and have done small projects (9 LED bank with simple animations).

So I know that each pin can only supply a limited amount of current (perhaps 40mA).

So my test circuit of a 2*2 matrix has
P1, P2 for positive rows, and N1 and N2 for negative columns. All LEDs in row 1 have anodes wired together to P1, all cathodes in column 1 are wired together.  also resistors are hard wired to each LED.

Now I there's plenty of current with a small matrix but if I get 9*9 LEDs I would definitely run out of current both onboard and per pin/row.

I successfully used this schematic to wire in a 2n7000 mosfet (200mA max) to P1. http://www.learningaboutelectronics.com/images/N-channel-MOSFET-switch-circuit.png

My own circuit looks somewhat like this rather hard to understand ascii diagram

    P1--*---*--
    ....l...l..
    P2--*---*--
    ....l...l..
    ....N1..N2

The dashes are anode wiring, the l's are cathode wiring and the N/P 1/2 are the header wires. (I plan to expand this to 4*4*4 so I want to be able to turn them all on without worrying about current limitations)

To clarify I set P1 HIGH, and N1 LOW to get the top-left led lit. I want 1 transistor per P (for positive, anode) wire, and one per N (negative, cathode)

So here's my question. Do I have to buy a P-channel  mosfet in order to accomplish this? Or is there some way to do it with the 2n7000. (I bought 100pcs on eBay)

If I must buy P-channel transistors, can you provide a simple schematic and the equivalent to the 2n7000?

Thanks for reading and hopefully answering my post!


texts: Arduino smells burnt but works fine, what shall I do?

texts:
My Arduino Nano is on a stripboard which provides a convenient access to some pins. It is connected to two I2C devices. The power supply comes from the USB port. It worked yesterday.

Today I plugged it to one of the USB ports of my PC. The power LED lit up for a split second and then the LED went off. I could smell something had burnt. My USB ports are surge protected: if a device draws too much current the USB power supply should shut down.

I unplugged everything and tested in the following order:

All the USB ports of my computer work with other USB devices
The Arduino alone powers on
The Arduino can send serial data through USB
The Arduino powers on when connected to the stripboard
I can upload sketches to the Arduino
The Arduino can send data coming from the first I2C device through USB
The Arduino can send data coming from the second I2C device through USB
The Arduino can send data coming from both I2C devices at the same time through USB

The last test is exactly the same setup as when I experienced the issue. It now seems to work again. Visual inspection did not reveal any burnt component or tracks on the Arduino or the I2C devices. The smell seems to come from the Arduino.

Questions:

Can there be a smell without any actual damage?
What might have been the problem?
What tests I should run to check for hidden issues?

First question here, thanks for reading :)


texts: Help fix or ignore aliasing warning in gcc

texts:
I'm having a problem working with the TI/Stellaris EK-LM3S6965 demo board and associated software, specifically the OLED display driver.  My problem is not that it doesn't work, it's that it mostly works.  Except for this one section:

//
// Clear out the buffer used for sending bytes to the display.
//
*(unsigned long *)&g_pucBuffer[0] = 0;  //Line 438
*(unsigned long *)&g_pucBuffer[4] = 0;  //Line 439

which causes gcc to complain:

  rit128x96x4.c:438: warning:
  dereferencing type-punned pointer will
  break strict-aliasing rules.

The problem occurs because g_pucBuffer is declared as a character array:

//*****************************************************************************
//
// Buffer for storing sequences of command and data for the display.
//
//*****************************************************************************
static unsigned char g_pucBuffer[8];

but we're accessing it as a long (32-bit, 4 characters) and so clearing the array in 2 lines of code instead of 8.  The uC is a 32-bit processor, so it should do this in 2 cycles after setup. It actually uses 4 instructions, instead of the possible 1 store-multiple instruction in 2 cycles, but at this point I'm more than happy with the compiler's performance (It's a fairly new architecture, and the compiler's only a few months old).

But, when I write each byte sequentially to 0,

g_pucBuffer[0] = 0;
g_pucBuffer[1] = 0;
g_pucBuffer[2] = 0;
g_pucBuffer[3] = 0;
g_pucBuffer[4] = 0;
g_pucBuffer[5] = 0;
g_pucBuffer[6] = 0;
g_pucBuffer[7] = 0;

it does each write as a single instruction.  I know, it's 4 cycles, but I want to do this right, and I think I have a clever and safe piece of code.  It's more a personal issue now. I've got full optimization turned on, but it can't figure out that I really just want this 64 bits to be 0 as simply as possible.

However, what the warning wants me to do is access the variables as characters, because I'm crossing byte boundaries (Writing g_pucBuffer[0, 1, 2, and 3] in a single step).  I know that they're dword aligned, I know that the code works in the original, but I want the warning to go away.

How can I either cause gcc to ignore this specific cast/aliasing issue, or do it properly?


texts:
I want to ask something that I see in the circuit. As follows,

What is the purpose of using 2R resistor in this circuit?


texts: Confusion with applying incremental bandwidth to measure noise power spectral density

texts:
From a text, regarding the following paragraph about random noise:

Being not very informed on this topic, I don't understand what meant by the following statement:

  "If such a measurement is made over a specific incremental bandwidth
  Δf at a specific center frequency fk, the output noise
  voltage can be expressed in terms of..."

Does that mean a band-pass filter applied for each Δf? And is so will it be applied at the input or output? And how is this done by analog way in reality? Or is it more convenient to measure the entire signal and apply digital methods?


texts: XBee and ZigBee for long distance signal transmission

texts:
Extension to question: Zigbee communication outdoors at long distance ( around 1 - 1.5 km)

I was wanting to set up communication between controllers around the school campus, originally I plan to go for Zigbee, however, due to it's limit in transmission distance, I was not able to imply it to my project (My project requires a transmission distance of 1-1.5km).

However, recently I came across an article, which shows that XBee communication can go up to 10km ! And according to here(3), XBee is actually based on ZigBee. So question 1: is it true that XBee can go up to 10km transmission distance? would it be practical to use on ground? (altitude depended?)


texts: Not connected pins on microcontrollers: what are the advantages/disadvantages of internal pull-up versus tristate?

texts:
There are microcontrollers (for example all the ATmega chips as far as I know) that allow  ports to be set to "output", "input tristate" or "input internal pull-up resistor".

What are the advantages/disadvantages of either of those options in case of not connected pins? As I know, leaving them on output is the worst solution. The chips are shipped (I think) with all ports as input, tristate.

I'm asking specifically about the situation where those pins are not soldered anywhere. (or possibly soldered to ground, but the general case should be not soldered anywhere)


texts:
I am using TI's TCA9539 for some read and write I2C operation to control some signals on my test board (school project).
Per TI, the write operation comprises of the following,

"To write on the I2C bus, the master sends a START condition on the bus with the address of the slave, as well as the last bit (the R/W bit) set to 0, which signifies a write. After the slave sends the acknowledge bit, the master
then sends the register address of the register to which it wishes to write. The slave acknowledges again, letting the master know it is ready. After this, the master starts sending the register data to the slave until the master has sent all the data necessary (which is sometimes only a single byte), and the master terminates the transmission with a STOP condition."

However i am always getting a Nack from slave when i send the register address information to the slave.

Here is my sample code (very basic)

int Address = 0x74;
#define control_register 0x02 // command byte for Output Port 0
#define data_register_1 0xFF

void setup()
{
    byte ack;
    Wire.begin();
    Serial.begin(9600);
    while (!Serial);
    Wire.beginTransmission(Address);
    ack = Wire.endTransmission();
    if (ack == 0)
    {
        Wire.beginTransmission(control_register);
        Serial.print("Control Register is : ");
        byte bck = Wire.endTransmission();
        if (bck == 0) // since i dont get a nack, this portion of code doesnt execute
        {
            Wire.write(control_register);
            Wire.write(data_register_1);

        }

    }
}


texts: I am was repairing a micro switch on a PCB that controls a vent hood.  The PCB was connected with this connector.   When I tried to reconnect some of terminal pins broke off.  I have attached two images


texts: Write to File in Computer running IAR Workbench

texts:
I am currently writing and testing an embedded system in which I need to collect data from an accelerometer over a period of time.

I already have functions that can read the data at a point in time during the system's execution. At the moment, the way I was considering writing the data was through a series of printf statements; I know that IAR gives access to an I/O console where the output can be shown. What I was going to do then, was simply perform a series of printfs, ensure the data appears in the console, and after a round of testing, exit the program and copy+paste the data into a file.

This seems like kind of a hack, and I was wondering if it was possible to access the C Standard Libraries like fwrite to create/write a file on the computer IAR is running  and write to it. This way, I don't have to rely on printf statements and can then format the code as I write it to a file.


texts:
Let us consider the circuit above (R3 and R4 should actually be \$1\$ ohm each)

Using time-domain analysis, we reach that \$V_o=-6V_2\$.

Using laplace transforms (Block Diagrams), we would just have a negative transfer function.

What I cannot understand is this:

1) Intuitively, this system must oscillate since we are making a signal greater by a constant factor, returning it back, then multiplying again, so where did I go wrong in calculations?

2) Can we reach that this system oscillates algebraically without any intuition whatsoever?


texts: How do I calculate the gain of opamps in this circuit?

texts: I can calculate the gain of AD8656 but can not calculate the overall output gain of this circuit. What is the method of doing the calculation?


texts:
A common technique used in battery charging algorithms is Constant Current / Constant Voltage. That is to say, initially a battery is charged by applying a constant current (which I believe is what is commonly called 'fast-charge'), up to a sensed condition, and then Constant Voltage is applied (which I believe is what is commonly called 'trickle-charging').

I envision this working (at least logically) as having (1) a Constant Current Source circuit set to the fast charge current and (2) a Voltage Regulator set to the fully charged target voltage, and switching the positive terminal of the battery between these two circuits.

What is a useful electrical model (e.g. for simulation) for a discharged rechargable battery? If it matters, I'm most interested in Lithium cell chemistry (Lithium Polymer to be more specific).

UPDATE

In order to get some more concrete feedback on this question (maybe this should be a separate question?), what does a circuit that practically / realizably implements CC/CV charging actually look like? From there, if you were to want to simulate this circuit, in SPICE or CircuitLab.com or whatever, how would you actually model the battery in that circuit?


texts:
I am confused about inrush current for a relay. For example, if I had 12A as the inrush current due to a motor, if the contact rating of a relay is only 6A, does a new relay need to be chosen?

As in how do you know what the inrush current rating of relays is? Is there a thumb rule, does it typically not matter due to it only being for a few milliseconds?

Example for this relay: RV8H-L-D24, Datasheet: http://www.farnell.com/datasheets/1769354.pdf
How do you know what the inrush current rating is of that relay for 24Vdc?


texts:
I have been reading up on grounding and what is AGND and DGND i.e / analogue ground and digital ground respectively. Suppose , I have an ADC chip and a MCU in a PCB. Now, previously I would have a ground plane beneath them and split them into Analogue ground and digital ground. I have now realised that splitting the ground planes will be detrimental to my return path at higher frequencies of the signal.

So, the best way is to have a single ground plane or have 2 different ground plane which is connected by a ferrite bead. Then during layout remove this bead to have a thin connection between the 2 grounds.

But, this approach has an issue according to me, which might be wrong. Will this thin line not act as a sort of high impedance that blocks currents thereby making the 2 grounds at 2 different potentials ?


texts:
Some (electrolytic) capacitors I have in a kit have vents, some do not (not on the top, not on the bottom).

The vents are there to safely let the gas out instead of letting the capacitor shoot.

So why don't all the capacitors have these? If they would fail (you never know): aren't the vented capacitors safer to use?


texts: termination of a parallel wire differential transmission line as delay line on variable dielectric constant medium

texts:
Well this has quite a long title, lets explain the situation
I'm currently working on the design of a sensor to measure the dielectric permittivity of a liquid medium, the idea is to use a ring oscillator and a delay line (the mentioned transmission line)

problems arise however due to the transmission line effects, the bandwidth of the drivers is around 750mhz (the actual oscillation frequency should be around 70-150M) and the separation between the conductors in the line must be reasonably high so as the fields to propagate outside the pcb and actually change the propagation time, in turn changing the frequency of the oscillator

the problem in question is that the impedance of the given wave guide actually changes when the medium changes, so the termination will be only suitable for a given range of dielectric permittivity, then it will start bouncing significantly, that wouldn't be much of an issue except that if the signal bounces from the tx side into rx with enough strength it can flip the inverter and the frequency would not be linear with propagation time anymore

so the question would be, is there some way of terminating the line that somehow compensates for this?

and also what about the transition zone from narrow to wide wave guide? there is not enough space to make a long tapered adapter, what method do you suggest to minimize reflection there?


texts: How does buffering in the MCP79410 RTC work?

texts:
From the MCP79410 datasheet, p.16:

Doesn't this mean that the data is being buffered when I read the seconds register, then again when I read the minutes register, and so on? This would mean there's no buffering at all. I would expect data to be buffered e.g. when I read the seconds register and when I read the minutes register I would read from the buffer (which would remain unchanged).

Can somebody shed a light on this?


texts: Increasing input signal by 5V (Using 7805 voltage regulator)

texts:
I have an analog voltage input of 0-5V DC, and need a corresponding output of (IN + 5V) 5-10V.

My first thought is to use the +5V regulator to "step-up" the voltage directly, connecting the input to the ground of the regulator and using the regulator's output as my final output.

I have a +15V power rail that I'm using to power the 7805, but when I try to hook it up, the 7805 pulls its ground (the input) up to almost 10V. Is it bad form to use voltage regulators in series? I'm modeling my input using a variable PSU for now, so could it be a problem with current not allowed into the PSU?

UPDATE: The problem is definitely that the PSU will not accept back-current, as suggested in the answer by Oli Glaser below. I would love to use a voltage follower op-amp to buffer this current, but I don't know if I have/can obtain any op-amps that can survive that much current (I can't remember exactly how much, but I know I measured sink current in excess of 100mA when the regulator was connected directly to ground). Would a voltage follower transistor design be more robust in that way?


texts: Eagle Cad: Library package appears different when placed on pcb

texts:
￼I placed a device and package on the schematic and board. However, the package appears different on the pcb, and generates DRC 'dimension' errors. The package is a 3-pin sip, Allegro Micro Hall-effect bipolar switch.
The difference is the pads are much larger when the package appears on the brd screen in Eagle Cad, which doesn't leave enough space between pads.
I have been using Eagle Cad for a few years. Unfortunately, its only about once a year, so I hope the solution is obvious to some of you experts out there.
The drag and drop option for pictures didn't work, otherwise, I would have done included the pictures.


texts: can I parallel two TP4056 to charge 1 cell?

texts:
I have a 3600mah Li-ion battery and I want charge it at 2 Amps.
I want to use TP4056 module but its output current is 1 Amp max.
so I decided to use 2 module in parallel like I draw in photo
is that possible? Is there any problem?

this photo shows what i want to do


texts:
I have listed myself as an electrical engineering major, because I like building small electronics projects and physics. When I ask people the difference between Electrical engineering vs. Computer engineering vs. Computer science I get mixed answers. Especially which mostly deals with hardware, microprocessors, software, etc. When I decided to go into electrical engineering I assumed I would be doing what I already love; using electronics to make life easier, designing circuits with ICs, soldering, working with microcontrollers like Arduino and entering the DIY community. This website sort of got me appeals to being a electrical engineer:

  http://www.mastersportal.eu/articles/181/10-good-reasons-why-to-study-electrical-engineering.html

But it didn't answer a lot of my questions. I keep looking for a job description for what these three people do on a daily, monthly, and yearly basis. And the curriculum for each degree. I know what college your going to and the company you work for matters, but there must be some general things they do.

I want to know what I'm getting into. I don't want to change my mind 2 or 3 years into my college education or hate my job. If any of you have any experience in getting these degrees, having jobs in these fields, or websites that list what I've asked for I'd really appreciate it.

Again, main things that get confused in each major/job: hardware, microprocessors, software

ADDED LATER: My programming skills are limited to HTML and CSS that I just learned on my own. I'm taking a C++ course this upcoming semester but I don't think I'm going to get inspired because I hear the (only) professor offering it isn't a great teacher.


texts: Determine the z parameters of two port network

texts:
New to EE, and I was wondering if anyone could help me check what is wrong with my answer on this question.

$$\frac{V1-Vn}{4}+\frac{V2-Vn}{3}=\frac{Vn-4V1}{2}$$
$$Vn=\frac{-27}{13}V1-\frac{4}{13}V2  -(1)$$
$$I1+\frac{V2-Vn}{2}=\frac{Vn-4V1}{2}, I1=\frac{Vn-4V1}{2}-(\frac{V2-Vn}{2})   -(2)$$
$$I2+\frac{V1-Vn}{4}=\frac{Vn-4V1}{2}, I2=\frac{Vn-4V1}{2}-(\frac{V1-Vn}{4})   -(3)$$
Subbing equation 1 into 2 and 3, I got I1= -2V1+0.5V2, which does not correspond to -2 and -2/3.
Any idea why? Thanks
EDIT to response:
Hi there, thanks for your response.
Unfortunately, I don't quite get your explanation. From my notes:

It seems as though they wanted me to use nodal analysis to solve this problem, hence my workings as followed.
For example,

Hence I am still unclear/unsure of your suggested solution. Pardon for being a newbie at this just started my first-year course for EE.


texts: Making a Remote Control for My TV from Scratch

texts:
This might seem silly to many of you, but I lost my TV remote when I moved awhile back and instead of buying a universal remote for cheap, I want to make a remote for my TV from scratch myself. I'm talking about designing the pcb, soldering parts together, the whole shebang. I know nothing about electronics and thought it would be a great way to learn.

I just need some guidance on how to start or advice on whether this is even possible without having the original remote to decode the IR signals? Am I able to look up the IR codes for the receiver by looking up the model number of the TV? What components do I need and how do I organize them on the circuit board?

I know basic parts that I would need are an IR LED, transistors, push buttons, and a microcontroller. I'm not sure which specific transistors or microcontroller to use though or how to design the parts on the pcb. Pointing me in the direction of useful resources would definitely help. I've already read a few instructables and watched a few videos on making a remote, but none of them told me how to design one from scratch for a specific receiver without the original remote. Thanks in advance!


texts:
I've tried many times to read electronic schematics. I always struggle to understand how to read it in order to understand how the circuit works.
The most important problem I have is trying to figure out the purpose for all the different capacitors.
I know that I should split the circuit in different functional parts but I still have this kind of problem.
Would you please tell me how to read a schematic specially when capacitors are involved?
For instance this very basic schematic about a blinking LED.


texts: Sizing bootstrap capacitor for Power Mosfet driver chip

texts:
I read some questions on this form regarding bootstrap capacitor e.g.:
Bootstrap capacitor - Explanation
and this
Boost capacitor sizing, gate driver LM5106 used with N-MOSFET IPP075N15N3 G

the second one is a bit helpful but they are basing the cap size based on Qg but not showing any calculations. The mosfet I am using is IRF1405 and datasheet shows Qg:

The driver I am using is HIP4081. I read the application notes for the driver and on page 6 has a formula for Cbootstrap:

and at the end the formula boils down to this (we can ignore the marked term):

assuming bootstrap cap voltage difference is 1 **QRR** = 12.5nC. Then QBS = 260 + 12.5 =  272.5nC or 0.27uC.

should I go with 0.33 uC or 0.22 uC?


texts: Inverter Design - High Side MOSFET - Slow Switch Time

texts:
I've posted previously on a similar issue which can be found here

Overview:

My design is a 3 phase inverter with:

MOSFETS are STF10N60DM2
Gate Driver is 6EDL04N06PT

I'm using only a single high and low MOSFET for some testing.

The picture of my setup looks like:

The specifics of the setup are:

30VDC Bus Voltage (But the design is to be used at 310V)
10R Gate Resistors
820R Load Resistor
Vth of the MOSFETS are 4V
VCC to the driver is 16V
The coloured circles match the probe points on the scope capture.

The Objective:

The object of the test is to check the switching response of the MOSFETS. During the testing I found that the High side MOSFET appears to switch off, in that Vgs < Vth however there is still voltage on the phase terminal (to the load). This voltage decays over some 3uS.

What I'm trying to determine:

When the lower MOSFET is switched on there is still a significant voltage at the phase connection, this is equal to DCBus and at 310V creates quite a disturbance.
Where is the stored energy coming from after the upper MOSFET is off. I don't have any additional capacitors, other than a small 100nF ceramic as the bootstrap caps and some filtering on the VCC.

The scope capture is shown below:

Specifics of the capture:

D0 and D1 are the PWM 1H/L digital inputs into the driver
Yellow = Lower gate (I have to pulse this for the bootstrap caps)
Purple is the Upper Gate
Blue is the Phase Voltage
White is the math Vgs (Delta between Purple and Blue)

My Questions:

Can anyone please describe why the phase voltage / gate voltage takes so long to decay? Obviously the load resistor plays a part in the decay, but where is the energy coming from that has to be bled by the resistor?
Is it possible that because the phase connection is linked directly to the gate driver's VS pin, that there is some magic within the gate driver preventing the phase voltage to drop? I doubt this is the cause as there is no direct connection from the gate driver to DCBus after the upper MOSFET is off.
Is the upper MOSFET actually switched off? Even though the Vgs is about zero, and by all accounts the MOSFET SHOULD be off, I'm wondering if it actually is not properly switched off..

Thanks in advance!

Update 2018-10-22:

I've struggled to find almost anything on the web about this issue (specifically the transients that occur during switching). However I did find an Infineon application note

The image from the app note is appended below, and clearly shows the same conditions that I've encountered on page 10. It also shows the switching transients that I'm experiencing.


texts: What capability or features are needed to make a module programmable?

texts:
This is a noob question but I was looking at some modules just to realize not all of them have MCUs - meaning they can't be programmed considering MCUs have a flash memory where the programs are stored, and SRAM to store the data. Is this the main reason? Basically, how does one determine whether a module is programmable or not from a hardware architecture standpoint?

Those modules though contain peripherals (i.e SPI) over which they can be communicated with another the MCU. For the context, I'm referring to nRF24L01


texts: Ident of a 10 contact RJ45 style connector with 8 + 2 contacts

texts:
I'm trying to find a plug that will fit into this RJ45 style socket.

The top picture shows 8 contacts just as you would expect from a RJ45 8P8C style socket, in fact you can plug a standard ethernet LAN cable into this socket and it mates perfectly.

The bottom picture is the same socket but it shows two extra contacts. These pins carry a voltage supply to an encoder.

I'm trying to source a compatible plug with 8+2 contacts but cannot find a reference to one anywhere so I was wondering if anyone recognises it as a standard part number?

Note that this isn't a 10P10C connector.

I can buy a pre-made cable with this plug on one end and a circular M23 on the other but I would like to source the plug to make up my own cable.

Matt.


texts: How to find the apparent power absorbed by a three phases load?

texts:
Given a symmetric and balanced three-phases circuit, I would like to calculate the apparent power absorbed a three-phases delta load. I’m given the rms value of the line voltage applied to the load, which is 300V, and \$Z_\Delta = \sqrt{2}(1-j)\$. How can I find the apparent power absorbed by the three phases load?
I suppose the line voltage is equal to the phase voltage, so I calculate the power as \$P=\frac{V^2}{Z_\Delta}\$ and then I multiply it by 3, but I don’t think it’s right since the solution is \$135kVA\$


texts: Will an 0603 capacitor fit on an 0805 pad?

texts:
I am in a pinch and just submit my final board design to a pcb house. Unfortunately, I messed up the design and had an 0805 pad in a spot where a an 0603 should have been. I will be getting the boards in this Friday with a 2-day turn.

Can I get an 0603 to fit on the 0805 pad in a pinch? I know it's not ideal, I just need to know if it will work so I don't have to pay 25$ to overnight 50 cents worth of capacitors from mouser or digi-key.

I did a mock up on a scale printout and it looks VERY close like it should be fine.


texts: Help with semi-controlled full wave monophasic rectifier using MOC3011 and SCR

texts:
I'm trying to build a full wave semi-controlled rectifier with this circuit:

The zero's detection is working well and I am firing the TRIAC depending on the position of the potentiometer, the negative semi-cycle is doing what it must, it rectifies the voltage at a certain alpha angle.
However, the positive semi cycle has the same circuit and the same program for the zero detection and the firing is working well, but we obtain this at the SCR output:

I don't know if that behaviour is because the circuit should be different for both semi cycles or if the SCR nor the MOC are burnt, we have already tried to change the SCR and it does the same thing, any ideas on what can be wrong? I am using two MOC3011 and two SCR tyn612


texts:
I want to set LCD TFT 3.5 to Arduino UNO but it can not display graphics test.
I installed this ILI9486 driver, I think this is true.
Can you tell me if you need more information?


texts: Open circuit test of a single phase transformer

texts:
In open circuit test of a transrormer,
will the values of the parameters be different if we perform the test on the high voltage side and then we perform the test on the low voltage side ?


texts:
I have a DC motor with field winding rated to 180 V like these.
Will the winding work normally when fed with rectified (diode bridge) 220V AC voltage?
I assume that rectified current will be almost constant due to field winding inductance and it is like feeding the winding with average rectified voltage, that is about 200V. Is this assumption correct?
Otherwise where I am supposed to get this 180V from?


texts: What is "Input high voltage common mode range?"

texts:
I am using a MC100EP016A IC which is an 8-bit synchronous binary up counter.

According to the specifications of the IC, you could use either single ended or differential clock input for the counter.

For the differential input mode, the parameter specified is:

  Input high voltage common mode range

I do not understand what this represents. Can somebody help?

It says that the Input high voltage common mode range is min 2V and max 3.3 volts. What does this mean?


texts: Question about RLC circuit and struck in a problem, in the calculation getting current as infinity for the given values

texts: Question about RLC circuit and struck in a problem, attached the photo related in the calculation getting current as infinity for the given values.any idea how to move forward


texts:
An EL wire consume ~10mA/m, and need a 1800Hz, close to main voltage, sinusoid supply. (The noise is not a matter as the EL wire itself will cut off the frequency >2kHz).

for an installation I would like to power 1km of wire. Therefore I would need a 10A supply to power in order to do that.

What is the simpliest way to do such high-power sinusoid power supply ?
I thought of :

amplifying a low-power sinusoid signal.
using a H bridge controlled in a way it will get a noisy sinusoid.

I'm trying to see if it is easy to do, or if it would be cheaper to just buy a bunch of 5 to 10 meter EL wire driver...


texts: Need to alter a 3 V - 4.2 V output to a 1 V - 5 V input

texts:
I'm currently using a bargraph meter with a scale of 1 V - 5 V to read the voltage of a lithium cell. I run the cell between 3 V and 4.2 V, so although this works, I'm only utilising a small amount of the bargraph.
The meter itself is separately powered by a 12 V supply, so is just reading the battery, not also powered by it.
I'm looking for a solution that will allow me to convert the 3 V - 4.2 V range I'm reading from the battery to a 1 V - 5 V input to the meter in order to utilise the full range of the meter's bargraph.
Thank you all for any solutions in advance.


texts: How is the zero flag set in terms of hardware?

texts:
I'm angling this as a general question on the assumption that it doesn't differ significantly with architecture - at least at the level I'm asking.

I'm curious how - in terms of hardware, not the obvious 'result is zero' - the zero flag/status bit is set (or cleared for that matter).

It never really occurred to me before, but it seems a fairly intensive task, at least relative to say, a carry or overflow flag. Am I correct in thinking there's no way to know the result is zero, other than to check each bit?

Unless I'm missing something obvious, it seems that it must take 'a lot' (if that's sensible to say in \$\text{ns}\$) longer than determining the overflow, and the carry status of course is 'already there' as a consequence of the operation.

My question, really, is just how is it 'usually' implemented?


texts: Is it possible to convert a low frequency signal into a higher frequency signal?

texts:
I have a signal generator that has an adjustable frequency range that is below the required frequency that I need.

Is it possible to input a signal from my generator into a passive series RLC filter that will output the frequency that I want? I would like to do this using a low-pass filter.


texts:
I have an embedded device using an SD card.  Occasionally I see SD cards fail, and I need to understand the failure mode.

Are there tools, perhaps for specific manufacturers, that help me understand why the card is failing?  Whether it's a memory problem, a controller problem, electrical problem, etc?

We are using Sandisk in general, and aren't concerned about data recovery, but we do need to maximize lifetime and reduce failure, so understanding the reasons cards are failing in our application is important.


texts: Should I add a resistor to the RCA Outputs of my device?

texts:
Very simple question I just can't find any information about that is not someones opinion or "what their ears think sounds best"

When getting the Line output from my final Opamps to the RCA Jack, should I add some small resistors to its output? Is this actually beneficial like this?
If it is (or not), can anyone explain the reasoning behind this?

Thanks!

My schematic of the RCA Jack:


texts: Output Capacitor value calculation based on Transient response in Buck converter

texts:
In Buck design,

The output capacitor's initial value is calculated based on how much current transient buck will support.
Few equations took from appnotes.

from these equations,
for A given Vin(12V),Vout(0.925),Istep(12A @ 20A/us) and Cout(884uF) combination,
Vovershoot is large compared to Vundershoot.

from my understanding, Undershoot is occurred during Load increase which is
worse than Overshoot which is occurred during Load Unloading .

But as per equations Overshoot value is large compared to Overshoot value.

Is there any theoretical area behind this.


texts: Calculation of max possible current load from voltage multiplier connected to PSU 12V rail

texts: today I found in a box a PSU with two 12V rails each delivering 17A (Fortron SAGA II 400W) and decided to step-up the voltage so can feed the DPS5020-USB DC-DC converter (rated at 60V/20A max output). What's the proper way to calculate maximum current load allowed through the voltage multiplier, knowing that 12V rails have fluctuating 12 Volts (11.95 to 12.25V)


texts: How to check whether a component can work in strong magnetic fields?

texts:
I want to design my PCB to operate nicely even when we place it next to a neodymium magnet. How to check whether my component can work in such condition without shielding?

Edit: I haven't face any problem with my circuit when I place it next to a magnet, but people will start questioning about the stability and I have no idea how to proof it. The main component are NAND Flash memory, microcontroller, MEMS accelerometer, battery, wireless transceiver on the board.


texts: Using KCL, KVL and Ohm’s Law find I0 in the circuit in Fig.1.1

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I have spent more than 8 hours studying KCL and KVL and Ohm's law but I still can't solve this :
If anyone can help me understand how to find I0, Ix and 2Ix I will really appreciate it.


texts: Calibrating a multimeter without another multimeter

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I have a hand-me-down multimeter from my Mom made in the 80s. I don't have another meter that is good enough to be used as a calibration standard, however I do have a few reference chips and precision resistors. I hope I can calibrate that multimeter using those.

My 3.5-digit multimeter is a Zhenxing DT-890 made in the 80s. I have a few of each reference chips, ADR02B and ADR03B. I have an And I have a few 0.1% tolerance resistors. Are those reference chips good enough? To calibrate lower voltage ranges, is TLC5615 a good enough chip to use to divide the reference voltage down?

I am on a tight budget so this meter have to be kept in spec for a while, before I can save up for a used Keysight 34401A.


texts: Identify capacitors in Arduino Starter Kit

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I have a couple of components in the Arduino Starter Kit that I'm not able to find the specs for, this is a picture of them (ruler in cm for scale):

It's probably not possible to read the labels on them, so I'll write them down: The blue ones say

µ1J63
?1E6

Where the ? represents a celltower-like symbol.

And the orange ones say

101
Suntan *

The manual mentions that they are capacitors but doesn't say anything about them. The online starter kit page only mentions one capacitor type and that one wasn't even included.


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If I wind a coil around a hollow plastic tube and apply voltage it will create a magnet that is capable of pulling an iron based plunger into the tube. I imagine the plunger will stop in the magnetic field's center. What current fluctuations in the electromagnet can I expect, and where in axial relation to the the coil? In other words will the magnet's current change as the plunger position changes? Will it increase or decrease as the plunger moves towards the magnetic center? How big a change can I expect?

Thank You


texts: How much has the power density of electrical motors and generators changed in recent decades?

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I would like to know how much lighter (if at all) a matched combination of an electrical motor and generator with a given power output would be today, compared to a similarly powerful combination manufactured in the 1960s or 70s. In each case, the technological capabilities of the time should be exhausted. Money is a secondary concern.

While general trends would be the most helpful, if details are needed, they could be like this:

Since the generator would be purpose built for just this one motor, the type and voltage of the current between the two can be chosen freely
The rotational speed is different, maybe 40 000 RPM for the generator and 10 000 RPM for the motor
The mechanical power from the motor should be about 15 kW
While efficiency shouldn't be absolutely neglected, low weight is more important. I don't know what kind of efficiency I could reasonably expect.
For the sake of simplicity, let's say no superconduction


texts: I have measured a charge and discharge curve of a capacitor with resistor and I want to calculate the frequency of this signal (for a low pass filter). Am I on the right way if I calculate 1 divided by time constant for the signal frequency? Or should I use  fft?


texts: How to obtain Input voltage from ADC value

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I am using atmega328p for my project. I have to read my battery voltage and display it in my cloud. For that, i am using ADC. Now I am getting the ADC value for input voltage applied. But i need to convert the ADC to voltage.

When I go to datasheet, I observed the following equation

So to convert ADC, Vin=(ADC/1024)*Vref.

But When i searched the google I found another equation and it is

Vin=(ADC/1023)*Vref

Now I doubt that which equation is to use?

If we use 1024, ADC value will be 0001 when the input voltage is equal to 1LSB voltage(Vref/1024).

If we use 1023(second equation), ADC value will be 0000 when the input voltage is equal to 1LSB voltage (Vref/1024)


texts: Communication between a Computer and Microcomputers

texts: I am currently working on a project that require me to communicate between several Raspberry Pi's and a computer. I'll display data that sent by Raspberry Pi on that computer. Since I am using Raspberry Pi, I thought I can take advantage of using network layer protocols. Therefore, I concatenated almost thousand float numbers as a string and send it over Local Area Network using UDP protocol. At computer's side, I am parsing those float numbers from string and showing them as live data plots. This process is not for one time, it's working in a loop. I haven't seen any problems so far but my question is "Is there a way to make communication more relaible? What would you use for that?"