texts: Is it possible to design a linear voltage regulator which delivers constant current but adjustable output voltage?

texts:
Is it possible to deliver a linear voltage regulator with the following specficiations:

input reference voltage is from 0.8V to 1.4V
output voltage has to follow the input reference voltage, it is the voltage connected to the load
deliver about 1mA to the load regardless of the output voltage, that is, when the output voltage changes from 0.8V to 1.4V, the output current has to be constant at 1mA.

In my understanding, if the loading is unchanged, say fixed at 6 ohm, then increasing the output voltage will cause an increase in output current as well. So how to make the output current constant at 1mA?


texts: Why are the ADC and DMM readings different?

texts:
While doing an experiment we reached a conclusion which we wrote down as the DMM and the ADC reading being different.

Now after doing some research It does confuse me as a DMM does contain an ADC of it's own. Can someone explain the reason of such?

Our ADC is very simple : An attenuator (voltage divider) connected to an ADC chip.

One of the reasons I can assume is having some inaccuracies in the attenuator but when I asked our prof he told me that there are TWO reasons in fact. Can someone kindly clarify?


texts: Which voltage should I use to calculate Amps when running an inverter on a 12v system

texts:
I want to run a coolbox in my campervan that has a 12v leisure battery.

The given wattage is 35w

It would be plugged into an inverter that provides 230v and has roughly 85% efficiency

How should I calculate the amp usage so I can judge the amount of time I can run the fridge from my battery?

a) (35W/230V)*/0.85 giving 0.18 Amps

b) (35W/12V)*/0.85 givig 3.4 Amps

c) ???


texts: Where might I find a prefabricated enclosure for a PCB?

texts:
I'm working on a small electronics project that includes a micro-controller and a few extra items soldered down to a PCB. This project will need to be contained in a nice chassis/enclosure that can be permanently mounted somewhere.

Unfortunately I don't know the terminology required to search for an enclosure online. What kind of terminology do I need to use in order to find what I'm looking for? A shortlist of reputable websites would be an added bonus.


texts: What are buffer and latches in microprocessor?

texts: I would like a description that clarifies the concepts of what buffers and latches are and the difference between them. I'm asking for buffers and latches in respect to the 8086 microprocessor.


texts: capturing 12-bits raw bayer data using STM32F429 MCU

texts:
The datasheet of the STM32F429 MCU says that the MCU's DCMI supports parallel digital image data with 14-bit bit depth. But at the same time it says that you can capture raw bayer data only in 8-bit. Does it mean you can't take 12-bit raw bayer data from image sensors?

I'm confused, because the document AN4658 shows that STM32F429's DCMI is capable of taking 8/10, 12, 14 bits progressive video (monochrome or raw bayer).


texts: I need help for soldering. Is this good flux for use on PCB/Electronics?

texts:
this is a specific question to a product for soldering.

I am a newbie to soldering so be kind.
To be honest I was trying to learn soldering and watched videos and read some.
But in germany there seems to be an unwritten law to make finding the right soldering stuff as hard as possible (also confusing)
It is called soldering paste which someone else in IRC thought is something else but after he showed me what soldering paste is , some grey material for stencil , I can assure you it is not. This stuff is orange like flux should be I guess.

So I got me some tools and materials and one of them is these:

http://www.conrad.com/ce/en/product/588206/Solder-paste-Stannol-165018-Content-50-g-F-SW-26

If you go to the download sections you can see Datasheets.
Edit : It says "Activated resin mixture with petrolatum"

Now my question is can I use this on electronics? I want to solder on PCB, some pins to a microsd adapter for example.

This material is orange and I did not test it yet.

Here is a pic of it:

Also if you can tell me if that soldering tin (Sn60Pb39Cu1 with flux) is good (for my purposes)?
You can search on Conrad.com for it just enter this in search : 812803
I can not post anymore links thx to this restriction..

tl dr :
Is this good flux for electronics soldering?
Is this soldering tin good for electronics soldering?
Also if any tips, tell me.

Thanks for your read :)


texts:
I know that this is a 4:1 MUX, but what does the little line across the w1 w2 selection line mean?

You know, the little black line that has a "2" next to it.

Has it something to do with "array" or something?


texts:
I am doing a project using a PIC18F25K80 to stream live audio through ZigBee. I used the PIC audio development board (Microchip) as my reference circuit. In this circuit the in-built ADC of the PIC is used for Analog-to-Digital conversion and in-built PWM is used for Digital-to-Analog conversion.

In this circuit, sampling rate is 8kHz, ADC resolution is 10-bit and PWM frequency is 25kHz. The circuit is affected by severe noise while in playback and the signal strength is very low. How can I  solve this issue?


texts: Build a voltage-controlled voltage source out of discrete components

texts:
I'm in a bit of a pickle. I need to build a voltage-controlled voltage source, but I don't have any opamps (or time to order them). I have been working for several hours trying to simulate a circuit in LTSpice that will do the job, with no luck. (BJTs were never intuitive to me, and it's been a while since my circuits class!)

I would really appreciate it if you guys could help me out, and hopefully the next poor schmuck who comes across this type of problem will too.

I need to turn a 0-5V DC signal into a 0-15V (not-necessarily-high-current) source.  Here's what I have to play with:

all the 1/4 watt resistors one could want
a bag of 2N4401 NPN BJTs
a bag of 2N4403 PNP BJTs
several nameless 60V 30A n-channel MOSFETs
various capacitors
24V, 15V, and 5V power rails (avoiding the 15V would be nice, but not nessecary)


texts: Effect of "wrong" driver with slightly long RS-485 stubs

texts:
I have a planned 250 kbit/sec, single-pair, 36-metre RS-485 installation where it is advantageous for wiring purposes if the stub lengths can be a little longer than optimal.  There is a single almost-always transmitter and three almost-always receivers.  "Almost always" means during normal operation, but during monthly maintenance visits, the receivers will transmit for a few seconds.  (It's DMX-512 lighting control with very occasional RDM.)  It is controlling underwater lighting for architectural purposes, so the downside consequence of data corruption would be merely aesthetic.

RS-485 is clearly designed to be used with the shortest stub lengths practical.  However, it's an engineering question about how the stub length affects signal quality and what to do if other matters require longer stubs.

The following is from Texas Instruments "AN-1057 Ten Ways to Bulletproof RS-485 Interfaces"

  Although the discussion of configurations and the section on stubs advises minimizing stub length to avoid transmission-line problems, the application may not permit minimizing stub length. Another approach is to increase the driver's transition time to permit longer stubs without transmission-line effects. If you use the DS36C280, long stubs can branch off the main cable. This arrangement keeps the main cable short, whereas looping the cable back and forth to reach inconveniently located nodes would greatly increase the main cable length. Besides allowing longer stubs, the slower edge rates generate lower emissions. Thus, this transceiver is also useful for applications that severely limit emitted noise.

The cable is custom high-quality unshielded 0.34 mm2 conductor twisted pair (approx 22 AWG) with 1.0 mm2 24 VDC in the same sheath.  The installation is about 1 metre under water.

What is the effect of a driver with 10 ns rise time versus one with 1.2 μs rise time?

My understanding is that rise/fall time is limited to 30% of bit time and that various rules-of-thumb put the stub length at the 10% to 25% propagation distance of the rise time.  (Using various TI and Maxim application notes.)

Our desired driver is something like that Maxim 3430 which is slew-rate limited suitable for 250 kbit/sec (datasheet), but we might be forced to use equipment with Maxim 3485 (datasheet); alternatively Analog Devices 2582 with 15 ns when we would prefer 2587 with 200-1100 ns (datasheet).

What effect might this have?  Should we do something special if we have the "wrong" driver?

My calculations

Data rate is 250 kbit/sec
Bit time therefore 4 μsec
Max rise/fall  time therefore 1.2 μsec (30% of bit time)
At 0.6 c signal velocity this is 216 m
25 % of that is 54 m

Simplified diagram:

            22m     14 m
    t-T-+--------+-------R-t
        | 6 m    | 6 m
        R        R

 T transmitter, R receiver, t termination, m is metres

Given my total length is 36 m and my stubs are 6 m, I believe this suggests it will work reliably.  Am I misguided?

Many thanks for suggestions and advice.


texts: Capacitor bank with variable speed motor

texts:
I have a set of three pumps (power ~100 kW) with variable speed AC motors and I would like to know the best option(s) to reduce the cost of reactive energy.

For instance, would it make sense to install a capacitor bank in the electrical cabinet?


texts: Invert ground vs. open "signal" - relay?

texts:
first post here.

I'm trying to design a circuit to invert a ground/open input signal. I.e., output is grounded when the input is open, and vice versa.

I have a feeling this can be accomplished with a relay - but could be mistaken.

Specifically, this is to resolve an issue in my car's instrument cluster - I've upgraded to a nicer cluster, and everything works, except that the ABS light functions backwards - i.e., on when it should be off, and off when it should be on. I've confirmed this behavior by comparing the results of various tests between the two clusters.

As far as I know, the ABS computer controls the light by grounding a particular wire (I know which wire it is). With this wire cut, I now have an "ABS side" and a "lamp side". In order to reverse the behavior, I was considering the following circuit:

85: 12V from ignition
86: ABS side (states are either open or grounded)
87: N/C
87A: Lamp side
30: Ground

If I have understood correctly, this would mean when the ABS side is open, the lamp side is grounded, but when the ABS side is grounded, the lamp side will go open.

Is this correct?

simulate this circuit – Schematic created using CircuitLab


texts: Voltage divider resistor sizing to minimise voltage variance

texts:
I've got the following circuit design simulated in SPICE, this is a copy of the EmonPi circuit design (https://github.com/openenergymonitor/emonpi/tree/master/hardware/emonpi/emonpi_V1_6).
I've got a current transducer (CT) input, which, with a 22 Ohm burden should give me a max AC current of 150 Pk-Pk (-75 -> 75A).
There's a voltage divider adding a DC offset to one side of the burden resistor, so that a negative current can be read as a positive voltage.
Now the problem is that the voltage divider producing the DC offset is not perfect and the DC bias seems to shift sinusoidally, causing the AIN to go over my max ADC voltage (3V3).
Obviously, when I reduce the value of the resistors in the voltage divider, the DC bias sinusoid's amplitude reduces. But reducing the value of the resistors also increases the passive current draw.
I don't know how to phrase this question, so searching hasn't been any help. But can you point out any design guides, or best practises for minimising the voltage divider variance.
Also bonus Q, is this effect due to the divider's impedance?
Find the circuit design below

and the SPICE simulation (red is the voltage divider output)


texts:
Can someone suggest me circuit to detect the earth  to neutral voltage. I would like to trip relay coil using microcontroller if earth to neutral voltage exceeds 3v.

There are device RCB and RCBO which serve for over current protection in these case. If i would like to achieve using PIC or arduino microcontroller how can be done. Please let me know simple circuit or application to get started.


texts:
edit
-added pin 9 as output in setup and now HIGH/LOW code works.
-When the pump is set to LOW it turns on, when it goes HIGH it is disabled. So when I plug the arduino in, by default the pump turns on before it reads any code. Is there anyway to set a pin to HIGH (by default) so that it doesn't pump when plugged in?
...I talked with the manufacture again, and it seems like they sell another model that doesn't pump when it's low... so for now, they suggested putting an on/off switch between the red wire and 5V pin.

end of edit

I'm trying to control a 5V piezo pump (micro pump) with my Arduino uno, but I'm having some difficulty getting it to work properly. This is the pump I'm using.

I'm not sure if I should be using a separate power supply to run the pump, or if I can get away with using the 5V pin from the arduino. The pump uses 0.05-0.25W... so at 5 V, it should have a max current draw of 50mA. Would a resistor be enough to protect the arduino and run the pump (I'm using a 470 ohm resistor, not sure if it should be more of less)? The pump has a red wire(5V), black wire (grd), and a yellow wire (PWM control).

This is the code I'm using (trying to turn the pump on then off)... the code worked when I left the yellow wire unattached and sent the black wire through an N-Channel MOSFET... but it pumped very slowly. When I hook up the pump like the picture below, it runs loud for a second, then slightly less loud for a second and repeats... (it just pumps then sputters)

The manufacture told me I need to program PWM with certain duty ratio per 1 second period and that the pump is set to operate at a default frequency of 50Hz.

void loop() {
tone(9, 50, 1000);  // 9=PWM pin, 50 = freq (Hz), 1000 = hold freq. for 1 sec.
delay(1000);

noTone;             //turn pump off
delay(1000);
}

I also tried this to no avail (assuming that it would run at the default 50Hz when set HIGH/LOW)

void setup{
      pinMode(9,OUTPUT);}

void loop() {
      digitalWrite(9,HIGH);
     delay(1000);
      digitalWrite(9,LOW);
     delay(1000);}

Any help in getting this to work would be greatly appreciated. Thanks!


texts: How to choose resistors for a multiple resistor voltage divider circuit?

texts: I am trying to create a voltage divider circuit to off offsset two BJT input voltage is for a push pull amplifier configuration, and I am having trouble choosing the proper resistor values for my circuit. My source voltage is 12V Vcc and I need to create something like below. I know the basic theory behind voltage divider but I’m having trouble making it. Also, the solution has unlimited solutions so what are the best range of resistors to use? I will be powering an 8 ohm speaker with my amplifier. Thank you kindly.


texts: Capacitance vs. Frequency Graph of ceramic capacitors

texts:
I'm looking at ceramic capacitors on TDK and I see this graph

Does this mean above several hundred kiloHertz - or wherever the graph stops - that the capacitor no longer functions probably ?


texts: How to avoid NPN leakage current turning on a PNP darlington has high level switch for automotive electrics

texts:
I'm new to this forum; I have searched around but can't quite get the answer I need. I am building a kit car and using an Arduino to run all of the electronics. For my power output I am using TIP125 PNP Darlingtons, which are switched by the Arduino using an NPN transisitor:

I'm worried that the gain of the PNP and NPN combined will be so high that leakage currents through the NPN maybe enough to turn on the darlington.  How do I work out if this is possible and what could I do to reduce the risk? On another post I saw mention of a pullup resistor for the darlington, but I think they have these built in. I wasn't sure how to work out if these are sufficient.


texts:
Can you explain schematic of IC UC3842/5?
First of all here general schematic:

What I can't understand is lower left corner and pins number 2(VFB), 1(COMP) and 3(CURRENT SENSE). What I understand is that signal of 2.5V and VFB compare in ERROR AMP.(so it isnt comparator? is it amplifier? or it is equal in this case). Then second  what for they put two diodes?
Third, How does current sense comparator work? Why at one pin signal is inverted? so what stabilizer do? if over 1v then always 1v and then it is inverted and go to -1V or 0V?

For example, VFB is 3V, then output of ERROR AMP is high, then if voltage of current sense is lower than 1V the output of CURRENT SENSE COMPARATOR  is low? Am I right?

And I'm absolutely cannot understand this schematic. If comparator has high output then what is role of COMP signal?And what is current source here doing?


texts: Are electrodes mostly homogeneous or are there variations by usage, such as EEG vs EKG/ECG?

texts:
Are electrodes mostly homogeneous or are there variations by usage? My main usage is EEG. I have some interests in other areas and see similar electrodes sold for less money when marketed for different purposes.

I imagine there are differences in precision? Is that accurate or

Sorry for the basic question.

I've been experimenting with the use of electrodes for EEG and I'm trying to understand if these expensive EEG electrodes ordered from the EEG development board makers are "special" in some way that I'm not aware of - such as if different hardware designs detect different ranges of electrical activity - or if all electrodes styled for use on humans result in essentially the same data and just perhaps vary by accuracy?

Are there common metrics or features used to rate or distinguish electrodes by purpose?

Stated differently, my question is essentially what factors to consider when selecting an electrode for human use, such as EEG, ECG/EKG, EMG, etc.


texts:
I've just put together my first busk converter with a LMR16006Y-Q1.
http://www.ti.com/lit/ds/symlink/lmr16006y-q1.pdf

Here is what it looks like on the scope.
The Pink signal is unloaded, the other is with a 90 ohm load. It seems noisy to me. I think I need to make some changes. But I'd like to get input from someone else.

I'm using a 6.8uH coil, 2.2uF cap on the input a 15uF cap on the output (ignore the second output cap in the schematic)
The schematic is here:

It's laid out on a PCB almost exactly like this, with the only difference being that the Feedback is tapped straight into the inductor output pad rather than stretching all the way to the output after the cap. I'm not sure if that will really mak a difference. :


texts: LTspice .TRAN UIC simulations with initial conditions as .IC directives

texts:
Starting from this question a doubt arises about the use of (global) .IC directives for 'branch currents' in LTspice (or maybe just SPICE)
Consider the .TRAN card with UIC flag. From some test done it seems to me possibly .IC directives set for inductor currents (e.g. .IC I(L1)=10) are actually not employed as initial conditions.
Is anyone aware of this? Thanks

Edit: Based on the comments received I add another screenshot for the simulation of the same circuit this time with the L1 inductor initial current set at device level (per-instance)

As you can see the result is different. This time it seems device-level condition for I(L1) is actually taken in in account. Thus for the .TRAN simulation with UIC flag it seems the global .IC directive for 'node voltages' alone is actually taken in account (to work out the voltage initial conditions for capacitors)
My question was to confirm this behavior. Thanks


texts: Why do n-type materials have a smaller conduction energy band?

texts:
I looked at "Why does a p-type conduction band have higher energy then n-type conduction band in a p-n junction?" and am still confused.

From the image above we can see that the conduction band on the p-type part of the material is at a higher energy. Why is that?
In my head, the p-type region is electron deficient because we doped it with an element from group III. This means it should have lower energy right?
Applying the logic, the n-type region has extra electrons because we doped it with an element from group V, so shouldn't the conduction band be at a higher energy?
I then thought that maybe for electrons in the p-type region, we'd need more energy to excite the electron into the conduction band. But this energy would still be $$E_c - E_v$$ which is the same in both regions...


texts:
I am trying to make an amplifier with an opamp, using a single supply.
I found lots of ressources online. This response was very informative and I tried to simulate this circuit.

Let's say that I have +/-0.5V signal, and I want to amplify to +/-1V. This is what I did:

(simulation)

This seems to work, but why isn't the signal AC-coupled?

After trying different things I found out that adding a 1k resistor to the ground after the last capacitor seems to fix it, but I can't really understant why. Is it the right way to do it? Why 1k?

Also, I heard somewhere that rail-to-rail opamps were preferable for these kinds of designs (single supply amp). I only got TL072, would this work? I assume that it would be a problem if I used a very low power supply (like 5V) for my opamp but should be OK with a 12V supply, am I wrong?

Thank you!


texts: Why do the satellite manufacturing companies themselves make their crystals?

texts:
Yesterday, I saw this documentary: How To Build A Satellite (look at these intervals: 27:29 - 30:16) and after seeing it, I had a question but I couldn't find any answer for it. My question is this:

Why do the satellite manufacturing companies themselves make their crystals (or crystal oscillators)?

For example, there are so many crystals and crystal oscillators available at Digikey, but they don't want to use any of those. Why?


texts: Is a solid state relay with over 1 MHz driving frequency physically possible?

texts:
I could only find one question semi-relatable to mine on SE, but I have a more demanding application in mind. I have designed a 32 stage 40 VAC -> 1000 VDC Cockroft-Walton voltage multiplier which I plan to drive with the 2.6 VAC clock from my MCU. To get my SMD capacitor sizes submillimeter, I have to run the clock at over 3 MHz...
My plan was to use a LT8410 to boost my battery's 3 VDC to 40 VDC and switch that w/ the clock through an optocoupled solid state relay:

I went with this topology bc I read somewhere that SSRs "have fast switching speeds which can range from 1 to 100 nanoseconds" but the smallest \$t_{\text{ON}}\$ (Turn-ON time) I've found was 500 ns & I need less than 50 ns to obtain an acceptable square wave at 3 MHz.
So is it even possible for an SSR to switch this fast or should I have went with a different topology to deliver the 1000 V?


texts: IR remote output signal without IR Led and TSOP

texts:
I have IR receiver module based on AVR + TSOP, it gets IR signal from remote and passes it to RF tranceiver.

Now I want to make some improvements and try to connect output (IR Led pins) of IR remote directly to AVR bypassing TSOP to pass it's signal to RF.

Is it identical to use remote IR output as TSOP out to decode signal without "airing" it?


texts:
There is a  transformer with \$600V/120V\$, and the impedance in the high voltage side is \$52-30j Ω\$, and there is a loading, which impedance is \$0.8∠10°Ω\$, connected with the low voltage side. Now when the \$V_2=120∠0°V\$, what is the value of the current in the primary side??
My thinking
\$V=IZ,\$ so \$I_1=\frac{V_1}{Z_1}\$, that is, current in the primary side \$I_1=\frac{600}{52-30j}=\frac{600}{60∠\theta }=10∠-\theta A\$
Solution
Current in the secondary side \$I_2=\frac{V_2}{Z_2}=\frac{120∠0°}{0.8∠10°}=150∠-10°A\$,
so current in the primary side \$I_1=I_2 \times \frac{N_2}{N_1}=I_2 \times \frac{V_2}{V_1}=150∠-10° \times \frac{120}{600}=30∠-10°A\$
The solution just use \$I=\frac{V}{z}\$ to calculate the current in the secondary side,\$I_2\$, then use the ratio between voltage and current to calculate the  current in the primary side, \$I_1\$.
However, we have the voltage and impedance in the primary side, why don't  we just use \$I_1=\frac{V_1}{Z_1}\$ to calculate the current in the  primary side?Why will we get the wrong answer if we use \$I_1=\frac{V_1}{Z_1}\$ to calculate \$I_1\$ directly?


texts: BJT amplifier negative feedback question

texts:
This is a BJT amplifier we have learned

I read from the book that the feedback type of it is voltage series negative feedback.
I have 2 questions :

If this is a negative feedback circuit how can we compute its open loop voltage gain?
Is this thing(learn how to analyse bjt/mos negative feedback)important?


texts: Is there a sensor for counting the number of cards in a flipping scorecard?

texts:
I have a stack of cards and want to know how many cards are in the stack at any given time.  Any thoughts on how I might be able to do this?  Would it be possible for me to put a tag on every card and then use some type of sensor below the cards which could count the tags above it?
The cards are suspended from rings like this:

While there was a prior question that was similar, it does not appear there were any answers that came out of that question.


texts: Are these PCB , and if so can it be repaired?

texts:
I'm very new to soldering, and I think I have irreversibly damaged the circuit I was trying to fix.

The joints are pretty burnt, but I read that in some cases you can scrape the carbon off and get a workable joint. I'd very much like to know if I can save my circuit by doing so to these joints.

Thanks.


texts: How can I know an electronic device has been passed FCC test?


texts: LC Low Pass Output Filters for Inverters

texts: I need an output filter for UPS inverter. I am using 9.6kHz PWM  and 60Hz frequency. Can anyone help me with the right filter as I am new with filter design?


texts:
I want to hook up a 9v battery to a laser diode(linked to the ones I will get), but have seen laser drivers scattered across the internet and vaguely have heard of them. Do I need one to use the laser?
The laser will not be constantly on for very long, just whenever I'm pressing a limit switch in short bursts. I checked out this question which recommended a driver, but since I'm only using one, do I need a driver?


texts:
I really need a hand here. I am trying to control an IN-19B nixie tube with an Arduino UNO. I am using a 170v power supply with a 20K resistor on the anode and the k155id1 driver IC. I have got things working fine (cycling through characters) with the small problem that after about 10-60 seconds I will hear a small click/pop noise and multiple characters on the nixie light up, some still cycling but with other digits that are turned on obscuring them. I assume this noise is the nixie driver blowing and causing some cathodes to short to ground. I have checked the voltage I am supplying the chip with from my arduino (5V) and the placement of all jumper cables and everything seems to be wired correctly. I've also tried running the chip at a lower 3.3v in case I was somehow killing it overvolting it or something. (I know this is a bit stupid because the IC definitely runs at 5v but I was desperate at this point)

I would be eternally grateful if someone could shed some light on this situation. The graveyard of drivers on my desk is growing :(. I have contacted the eBay seller that supplied me with the drivers and they are equally confused. Below you should find the schematic I am using, relevant data sheets and an image of my setup. (I am aware the name of the driver on the schematic and in my circuit are different but from what I saw online the name is the only difference between the two)

I am hoping to use theses tubes in a project for my art A Level so you really would be saving my life if you helped. Thank you. :)

]5

Update:

The problem appears to be solved after re positioning and replacing the resistor on the breadboard all is functioning correctly.

Thank you everyone for your help and very well spotted. I'll make sure to learn from mistakes like this and hope this informs others that see this.

Update 2:

Slightly worrying development. The chip I tried after the fix just did the same thing. This time it took an hour instead of 10 seconds which is definitely an improvement but still sub optimal.

Update 3:

Through sheer incompetence I misunderstood the instructions about the resistor. I believe this should work. Really sorry about that everyone. I remember thinking the pink tinge to the cathode was odd. Assumed it was just variation in tubes but with the colour difference after re positioning the resistor it was obviously a cry for help. Thank you everyone again apologies for my incompetence I will also make sure to learn from this.


texts:
Can anyone help me identify this circuit symbol, it's on the data sheet for the AS3310 VC ADSR IC. It's connected to logic gates so I'm assuming it has something to do with logic level signals.

Thanks in advance


texts:
After having a UART echo working on my nucleo F446ze, I am trying to get UART interrupts working.
I thought all I had to do is :

set the priority for the UART3 interrupt
enable the USART3_IRQn
implement the weak functions (USART3_IRQHandler, and HAL_UART_RxCpltCallback)

But no data is being received, the interrupt callback never fires.
Main.cpp :
extern "C" {
    #include "stm32f4xx_hal.h"
    #include "stm32f446xx.h"
}

static UART_HandleTypeDef s_UARTHandle;
static bool uart2HasReceivedData;

static uint32_t start;

void ConfigureLedGpio()
{
    __GPIOB_CLK_ENABLE();

    GPIO_InitTypeDef gpioLed;
    gpioLed.Pin = GPIO_PIN_0 | GPIO_PIN_7 | GPIO_PIN_14 | GPIO_PIN_8;
    gpioLed.Mode = GPIO_MODE_OUTPUT_PP;
    gpioLed.Pull = GPIO_PULLUP;
    gpioLed.Speed = GPIO_SPEED_HIGH;
    HAL_GPIO_Init(GPIOB, &gpioLed);
}

void ConfigureUart3Gpio()
{
    __GPIOD_CLK_ENABLE();

    GPIO_InitTypeDef gpioUart;
    gpioUart.Pin = GPIO_PIN_8 | GPIO_PIN_9;
    gpioUart.Mode = GPIO_MODE_AF_PP;
    gpioUart.Alternate = GPIO_AF7_USART3;
    gpioUart.Speed = GPIO_SPEED_LOW;
    gpioUart.Pull = GPIO_PULLUP;
    HAL_GPIO_Init(GPIOD, &gpioUart);
}

void ConfigureUart3()
{
    __HAL_RCC_USART3_CLK_ENABLE();

    s_UARTHandle.Instance        = USART3;
    s_UARTHandle.Init.BaudRate   = 115200;
    s_UARTHandle.Init.WordLength = UART_WORDLENGTH_8B;
    s_UARTHandle.Init.StopBits   = UART_STOPBITS_1;
    s_UARTHandle.Init.Parity     = UART_PARITY_NONE;
    s_UARTHandle.Init.HwFlowCtl  = UART_HWCONTROL_NONE;
    s_UARTHandle.Init.Mode       = UART_MODE_TX_RX;

    HAL_UART_Init(&s_UARTHandle);

    // Give USART3 interrupt priority and enable it
    HAL_NVIC_SetPriority(USART3_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(USART3_IRQn);
}

int main()
{
    HAL_Init();

    ConfigureLedGpio();
    ConfigureUart3Gpio();
    ConfigureUart3();

    uint8_t receivedByte = 0;

    start = HAL_GetTick();

    // Trigger the hall that I am expecting data
    HAL_UART_Receive_IT(&s_UARTHandle, &receivedByte, 1);

    while(1)
    {
        // Blink LED: Easy check to keep track that the program is still running
        if (HAL_GetTick() - start > 100)
        {
            GPIOB->ODR ^= GPIO_PIN_0;
            start = HAL_GetTick();
        }

        if(uart2HasReceivedData)
        {
            uart2HasReceivedData = false;

            /**
             * Blocking read/write, this works, so I think proof that the configuration for gpio and uart are correct (?)
             *
             * HAL_UART_Receive(&s_UARTHandle, &receivedByte, sizeof(uint8_t), HAL_MAX_DELAY);
             * HAL_UART_Transmit(&s_UARTHandle, &receivedByte, sizeof(uint8_t), HAL_MAX_DELAY);
             */

            // Trigger HAL that I am expecting data again
            HAL_UART_Receive_IT(&s_UARTHandle, &receivedByte, 1);
        }
    }
}

/**
 * Below the C interupt handlers
 * Must be implemented, otherwise the weak implementation will go into infinte loop and hang up the app
 * Must delcare as extern "C" otherwise cpp linker won't match it with weak defined function (which results
 * in the same behavior, infinite loop -> app hung up)
 */

extern "C" void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandle) {
    uart2HasReceivedData = true;
    GPIOB->ODR ^= GPIO_PIN_0 | GPIO_PIN_7 | GPIO_PIN_14;
}

extern "C" void USART3_IRQHandler()
{
    HAL_UART_IRQHandler(&s_UARTHandle);
    GPIOB->ODR ^= GPIO_PIN_0 | GPIO_PIN_7 | GPIO_PIN_14;
}

extern "C" void SysTick_Handler(void)
{
    HAL_IncTick();
    HAL_SYSTICK_IRQHandler();
}

What am I still doing wrong?


texts:
Ive currently analysised a circuit and gotten a function
$$(R2 + R1R2Cs)/(R1+R2+sR1R2C)$$
But i need to somehow transform this into the form of $$ H(s) = K * (s+z)/(s+p)$$
where z is a zero and p is a pole.
My circuit has a resistor and capacitor in parallel and another resistor on it own
My working so far is that $$H(s) = Z2/(Z2+Z1)$$
$$Z2 = R2$$
$$Z1 = C1||R1$$
In s domain capacitor is $$1/sC1$$
$$Z1 = 1/(1/R1 + 1/(1/sC1))$$ $$1/((1+sC1R1)/R1)$$
We get: $$Z1 = (1+R1sC1)/R1$$
$$H(s) = R2/[R2 + (1+R1sC1)/R1]$$
Simplifying we get:
$$(R2 + R1R2Cs)/(R1+R2+sR1R2C)$$


texts: Controlling DC motor with H-Bridge motor driver and a relay

texts:
I am trying to build a smart car.
I have 4 DC motors with tires. They are yellow 3-6V hobby project motors. I have two L298 H-Bridge boards and 1 relay.
I connected two of motors to one H-Bridge and other two to the other H-Bridge. I want to control it with my Raspberry but the power sources should be different because of the motors' current so I am using 12V battery for the motors. I also want to use one relay to control its power with the Raspberry to switch. My relay is FL-3FF-S-Z 5VDC single relay (10A-250VAC/30VDC, 12A-125VAC/28VDC.)
Can my relay support the current for 4 DC motors?
10A is written on my relay however I dont know if it can reach to 10A with my 12V battery.
When my motors are loaded, how can I calculate the maximum current if it is working with my relays threshold?
Edit:

Here is my motor
Here is my relay
Here is my H-Bridge


texts: Do LED and photodiode rise times matter for time-of-flight (TOF) measurement?

texts:
Do I need small rise times of an LED and a photodiode/APD when considering time-of-flight measurement? Given I know rise time of both diodes I am always able to count time of flight by subtracting those times from the final measurement, right?

A sub-question: does a photodiode need a pulse that is longer than its rise time for the pulse to be detected at all?


texts: Steps to calculate the band profile of a complex semiconductor heterostructure

texts:
I am an EE undergraduate with a lot of interest in semiconductors. I took an introductory semiconductors course which was helpful but left me with some holes in my understanding, as the course (rightfully) assumed that the EE students had not yet had quantum or solid state physics. As I dig deeper into the topic, I find many papers that will give a complex layer structure (not exactly complex, just a "stack" of parameters) and then show the conduction band profile of the device, which is probably calculated using some simulator.

I have looked at many, many books to find the steps involved in calculating such a thing given a layer structure, but most explain the pn junction, metal metal junction, and then a heterojunction, and stop there without showing any concrete examples. What I have learned is that there is both a classical (I'm assuming extending the junction problem and electrostatics)  and quantum way ("introducing new long-wavelength boundary conditions")

I am simply interested in the steps a simulator would go through, classically or otherwise, to take a stack of semiconductor layers and spit out a conduction band profile. Answers like "it iteratively solves such and such equation" is fine/what I'm looking for, or a direct reference that will explain to me what I am looking for is also great, as I have been searching hard for a clear answer.

As a bonus, I am mostly interested in III-V materials, how all of this relates to quantum wells, wires, and dots. I also understand the complexity behind this, things like strain and lattice matching and the electrostatics involved, and would also appreciate knowing under what assumptions your answer applies to.

Thank you!


texts: How can I make the dimensioning of a temperature monitoring circuit?

texts:
I need to design a circuit to measure temperatures in the range 15-40 degrees C (this will later be the basis for a regulator of a peltier-element for a fridge).
I tried a circuit using the bandgap-reference of 2 transistors, but it did not work. Now I would like to use a circuit with a transistor used as a diode. I could only come up with a transistor (with B and C connected together), in series with a resistor (for a supply voltage of 12 V I will choose a resistor of 11.3...12 k). But I think this circuit is too simple.
I also found this circuit, but I don't know how to make the dimensioning of the components.


texts: Connecting RS232 output of Lattice XP2 Brevia Kit to PC USB (virtual COM port over USB) using a FTDI RS232RL based board

texts:
I have a Lattice Brevia XP2 Kit (the older one that came out in 2010/2011, and the not the newer version 2). The only PC connectivity it has is through serial (rs232). I have anetbook that does not have the rs232 port, but I regularly use a Sanguino via virtual COM port over USB.  I use a FTDI breakout board for this.

I am trying to use this FTDI board to also communciate with the XP2 kit. For this, I have wired the rs232 null modem cable supplied in the XP2 kit to the FTDI board via temporary connections using jumper cables. Here is a pic (apologies for the quality) and the wiring diagram is below it.

RS232 pin assignments on the XP2 Brevia kit:

Wiring diagram:

When I analyze this using the Advanced Serial Port Monitor utility, I see no errors and can send data without errors. I am supposed to see some headers from the Brevia XP2 board but I see nothing (no errors too).

What am I doing wrong?

Rgds,
Sushrut.


texts:
Three capacitors (of value 600uF) are connected in series together and connected to an AC voltage source. Capacitors will be damaged if they are subjected to any fast changes in the current passing through them (i.e., they are sensitive to high di/dt). How can the capacitors be protected versus the fast changes in the current passing through them?

I think, adding an inductor to the circuit solves this problem? But how it is going to solve it? I am not quite sure. Can anyone out there help me in this? Many thanks.


texts:
I am interested in 3g signal repeater and decided to design one. I am planning to just buy 2 antennas and design the amplifier circuit only.

my questions are:
Should I care much about the antennas?
some resources about the design.

I mean to build something like that 3g signal repeater on ebay

Thanks in advance.


texts: Cut off a circuit whitest charging a battery

texts:
I have a simple (analog) photosensitive circuit designed to turn on at night. My question relates to charging it. I need an easy, preferably cheap method to disable everything in the circuit whilst it is connected to the charger. A Manual switch will not work since it will be fully autonomous.

To simplify, when connected to the charger, the only load seen is the cell/battery (the rest of the circuit is cut off from any current). When disconnected from the charger, the photosensitive circuit becomes operational.

I am fairly new at this kind of thing, so the more simple the explanation the better.

Thanks!


texts: Would a square piece of copper have a similar maximum current rating as a copper wire?

texts:
If I have a 3mm x 3mm x 3mm piece of copper that conducts a DC current, is there a way to determine its maximum safe current?
I looked into here,
and found information for copper wires, shown below.
From the chart, a diameter of 3.264 mm corresponds to an area of around 8.36 \$mm^2\$ (area = \$ \pi [d/2]^2\$),
while the copper piece has a cross sectional area of 9 \$mm^2\$.
Would I be able to take its cross sectional area and assume similar fusing current limit for a square copper piece?


texts: Finding Thevenin equivalent circuit and using that circuit when terminals inside circuit

texts:
Sorry for the bad title, but I'm trying to get the Thevenin equivalent circuit and then use that circuit to calculate a current i. The problem I'm having is I'm not sure what to get the open circuit voltage with the terminals in this arrangement. Here's my circuit and the work I've done:

So I know these equations: $$V_{oc}=V_{th}\;\;\;,\;\;I_{sc}=I_N\;\;\;,\;\;R_{th}=R_{N}={V_{oc}\over I_{sc}}$$
So to start, I will find $$I_N$$
Here's the circuit for it:

Using the supermesh:
$$-20+15i_1+5i_1=0\;\;\;\;\;\;\;\;I_{sc}=i_1=1A$$

Now I get stuck. I've tried finding R Thevenin and R open circuit but with both of those, I come to equations that have more unknowns than equations and thus can't solve them. What could I do? If I do the open circuit way should I omit the 6 ohm resistor and use KCL?

(just noticed that there is a schematic editor, but anyway, that current source is controlled, sorry for the confusion)

I'm not sure where to go from here and would really appreciate some help. Thank you.


texts: Why doesn't my computer USB port break when I plug in a 2A device?

texts:
For typical AC to DC power adapters, I understand that the device draws the current it needs from the adapter.  If it pulls more than the adapter can supply, this can cause overheating and lead to breaking the adapter.

Following this... I am always charging my phone or tablet on 1A USB chargers or in normal PC USB ports, yet I have never experienced a broken USB port resulting from this.

My question is:

Do USB ports or devices typically have a mechanism to regulate current to avoid overloading ports?

I'm mostly thinking in the context of devices which charge via USB.


texts: I want to cool some electronics with peltier elements in order to increase their potential working temperature compared to the surroundings. Unfortunately the surface where these elements are distributing heat is smaller than the peltier element surface. Now I was wondering if that influences the maximum power the peltier element can "heatsink". If the surface of the device is half the surface of the element, is the maximum power being able to transported with a given $\Delta T$ half the potential maximum power of the element? Or is it still the same?


texts:
I tried to design a common emitter amplifier for the first time, for an audio amplifier; however the gain is not as I expected. I don't understand why voltage changes when I measure the voltage from the right or left of the capacitor c2. My question is what kind of effect C2 has on the circuit? So I can change it in a way that my gain is not lost. Below graph red is the output voltage I get when I measured voltage at the leftside of C2 (Vc) and green is Vr3. (R3 is 1K which is not seen on schematics)
Thank you.


texts: Does the power factor of a balanced 3 phase system is 1?

texts:
One of my friend told me about that the power factor of a 3 phase balanced system is 1. I don't get any book reference for it. Is it true?

If true, then why? If I assume the 3 loads are equal 4+j3 ohm in the balanced system. Then there should a phase difference between the current and voltages.
Can anyone plz explain?


texts:
I have a question involving a couple problems in the following PDF: http://www.engr.colostate.edu/ECE103/FA13/homeworks/Homework6%20FA2013.pdf

For convenience, I'll also post them below.

As far as I understood, an inverting op amp would take the input voltage and multiply it by -(Ro/R1). So for instance, in #1 the output voltage would be 2 volts, correct?

However, what is the input voltage I am to multiply by in the case of #2, where the positive terminal is linked to a 5 volt power supply? Is it still 10 volts (v1) or is it now 5 volts (or something else)?

Problems:


texts:
I need to find a PID controller for a 12V 1hp DC motor.

I am currently building a tachometer for velocity feedback.

My question is if anyone can suggest PID control hardware and software that is good for this type of motor?

I was thinking about using this driver from Pololu with an Arduino microcontroller but I am not sure if this is a robust enough solution. Also I dont believe that this can handle the current from the motor. Still doing calculations on that.

I will need to program a routine for the motor to run through. It will speed up, slow down, and change direction over time. Actually I will be using two motors but I figured it would be hard to find a dual motor PID controller. Any suggestion would be greatly appreciated.


texts:
I am using Saleae logic analyzer to reverse a console port. Saleae is able to successfully decode the signal (asynchronous serial) after performing an "invert" operation on the received signals.

I am trying to figure out how this transform(invert) works in order to write a custom program to interface with the console port. The protocol is asynchronous serial with a baud rate of 9600, one stop bit and no parity.

invert(0x35) = 0x4E ("N")
invert(0x17) = 0x65 ("e")
invert(0x11) = 0x74 ("t")

Is this a standard inversion algorithm for asynchronous serial communication? Am a beginner in this field and hence a bit confused.


texts: How to add manufacturer and supplier part numbers to components in Eagle?

texts:
I recently switched to Eagle for my board designs. Because most components I use are not in the predefined libraries, I've made a "Managed Library" myself. When making the BOM list (using a predefined ULP from Eagle), I really miss the manufacturer and supplier part numbers (eg. Farnell or DigiKey numbers). It would be nice if I can add them to my "Managed Library" in such a way that the BOM ULP from Eagle outputs them accordingly in the BOM list.

Can anyone help me out on this?


texts: Replacing two 16.5V transformers with one

texts:
I'm an enthusiast so please be gentle! I have a transformer question and can't find a similar previously asked question.

I have an ADT/Honeywell security/smoke system. We experienced a utility generated power surge which burned up at least 7 transformers and caps in the house including HVAC, doorbell, freezer, oven AND the ADT security system transformers, Models XF-1620 and 1321. The 1620 outputs 16.5V/20VA and the 1321 outputs 16.5V/25VA/. I want to replace with one transformer outputting 16.5V/45VA. I think it is just that simple. Am I missing something? I am NOW in the hunt for a whole-house surge protector strategy as well.


texts: using citric acid alcohol solution to clean rusted terminals

texts:
I used to clean old computer sockets and terminals with citric acid solution in alcohol. It worked fine for long time, but for the tiny connectors of DIMM Ram sockets it works for a very short time before the disconnection problem appear again.
What solution do you have for this problem?
There should be a chemical that can clean oxide from metal and create a conductor protection layer.


texts:
I bought a dph3205 module and I see that it has 2 inputs (2+ and 2-). What will be the point for this?

What it will happen if I connect both inputs from different sources?

Thanks


texts: Want a Second Look Do all of these Capacitors Need to be Changed?

texts: I pulled apart my monitor to check the capacitors and I think almost all of them need to be replaced but there are a couple I am not sure about


texts: Why do Arduino shield kit designers "consume" pins they don't use?

texts:
I've done 5 or so Arduino projects now and am at the point where I think I'm outgrowing the whole pre-packaged platform/shield arrangement.  It was great for lowering the barrier to entry of getting into microcontroller projects, and for quickly getting projects off the ground, but I'm really seeing the cost and implementation tradeoffs impacting me more and more these days.

One question that has been bugging me is, why do shield designers and manufacturers leave so little room for other circuit elements in their design?  Who really does a project that is literally just an arduino and a shield?  Doesn't everyone hook up other inputs and outputs to fully realize the vision behind their project?

If a shield only needs and uses 5 or so pins, why not omit the headers for the other ones, or better yet provide some blank through holes/pads connected to the unused underlying arduino pins for the user to utilize as they see fit?

I know some shields do this to some extent.  The Speakjet/voice shield from Sparkfun for example has a relatively large open prototyping section.

It seems like shield designers almost go out of their way to make it more difficult than it needs to be to tap into the pins their design doesn't use, by calling for headers that seem to only serve as a mechanical connection to the arduino, surfacing with a tiny soldered nub you can tack a wire onto but can't make a solid mechanical connection?  Or am I missing something basic in my soldering/construction skills?  Is there a better way to utilize pins a shield doesn't need?

I know about stackable headers...but wouldn't it be better to provide a more directly solder-friendly set of through holes for tapping into the unused pins?

Again, maybe this is just reflective of where I'm at with my relationship with arduino right now...ready to get off the yellow brick road of arduino + shield = solution and into using the arduino strictly as a dev and prototype platform.


texts: Simple Constant Current Circuit Acting Strange on Occasion

texts:
I have a simple constant current source driven by a DAC.  Very low frequency, less than 100 Hz changes on the input.

I have had trouble once in a while when the transistor either fails or temporarily stops working correctly.  I thought I had a bad batch of 2n2222a transistors, so I substituted that part with a 2n4401, and it seems better.  It's very difficult to find the conditions where it fails.  The load, in some cases, might be slightly inductive.

It struck me that perhaps I'm getting an oscillation sometimes, but I can't seem to see that, or a failure, when I have a scope connected.

Anybody have an idea of what might be going on?  I'd love to find the problem and hopefully make a change with adding a component (board is pretty full, but I could fit one more on there).  If it is an oscillation, would fitting a lower bandwidth op-amp help?

If the load is at the max (10 ohms) it's pushing the current limit of the transistor, but the issue doesn't appear to be happening near full load.

Thanks for any thoughts anyone might have.

New input after first two responses:  I appreciate your thoughts thus far.  Actually, the load isn't as bad as it would seem.  When the load is less than about 90 ohms, the power to the load is typically 5v, maybe a max of 8 volts, rather than 12 volts.  The OpAmp power rails are 5v/gnd.  The DAC can go up to about 2.6 v, so current won't exceed about 500 mA.

Sorry about the small graphic, I converted the schematic to a PDF, then copied the part of interest and converted it to a jpg - ended up with low resolution.


texts: Controlling multiple servos and servo driver through Blynk

texts:
I'm working on a project to control multiple servos using a servo driver, through sliders on Blynk.

I'm using:
ESP8266 WeMos D1R2 microcontroller (wifi connected)
Adafruit PCA9685 Servo Driver
Blynk v0.5.3 on iOS

Blynk connects to WeMos through Wifi, and WeMos is connected to the servo driver through the SDA and SCL pins, which should then drive the servos. I'm having trouble with the transmission between WeMos and the driver, however. The code i am using is the servo code from the Blynk website. I would think the servo.attach() command has to be changed to something to transmit i2c? Not sure about how to change the output data to a suitable one for the servo driver, please help! Thank you!


texts: Details on PCB layout for microcontroller

texts:
Update: the follow-up question shows my take on the resulting PCB layout.

I'm laying out my first board with a uC (I've got a reasonable amount of experience in using and programming embedded systems, but this is the first time I'm doing the PCB layout), an STM32F103, this will be a mixed-signal board using both the internal DACs of the STM and some external DACs via SPI, and I'm a bit confused about the grounding.

The answers to these questions:

Decoupling caps, PCB layout
Competing PCB Crystal layout recommendations
Mixed signal PCB layout for PSoC

clearly state that I should have a local ground plane for the uC, connected to the global ground at exactly one point, and a local power net, connected to the global power near that same point. So this is what I'm doing. My 4 layer stack is then:

local GND plane + signals, uC, it's 100nF decoupling caps, and the crystal
global GND, unbroken except for vias. In accordance to sources such as Henry Ott, the ground plane is unsplit, with the digital and analog sections physically separated.
power, a 3.3V plane under the IC, thick traces for the 3.3V external DACs, thicker traces for distributing the \$\pm15\$ volts in the analog section.
signal + 1uF decoupling caps

Further away on the board the analog components and signals are on the top and bottom layers.

So the questions:

should I break the global ground under the uC, or is it good to have the full ground plane under the local one?
Power plane: I'm intending to have a power plane only under the uC and use vias to bring the power to the decoupling caps and therefore the uC on the top layer, as I can't really use one much elsewhere. The external DAC's should be star distributed, so I have separate tracks for them, and the rest of the board is \$\pm15\$ volts.  Does this sound ok?
I'm using both the ADC and DAC of the uC, and generating a reference voltage in the analog section of the board, which I bring to the Vref+ pin of the uC with a track on the power plane. Where should I connect the Vref- pin: local ground, global ground, or make a separate track on the power plane connecting it to the global ground in the analog section, where the ground should be quiet? Maybe near to where the reference voltage is generated? Note that on the STM32 the Vref- is distinct from the analog ground VSSA pin (which I suppose goes to the local GND plane?).

Any other comments on the design here are of course welcome too!


texts:
I'm not exactly a novice to electronics, but my problem is closely related, and I still feel like a complete newbie at those times.

I have no problem sourcing parts for new projects. Part of that is knowing a suppliers stock, and if my favorite two or three don't have them, I'll look to my semi-favorite suppliers. Usually, they have datasheets for their devices linked right in their web shops, so finding datasheets for those parts is no problem at all.

However, when trying to identify components (especially on older devices), I feel like running against walls.

Here's an example: I found a socketed IC with the label "IAM E3318" in a standard DIP package. I have no idea what this thing is, let alone found a datasheet for it. All I can deduce, is the manufacturer's short name is "IAM", and the part number is E3318.

However, this happens to me on many devices, especially older ones. Is there any standard method of seeking info about obscure parts like this, other than googling for hours?
Some datasheet aggregaters like Alldatasheet, sometimes give a positive result, only to link me to a completely other, unrelated part. Other times, I get a seemingly positive result, when clicking on the PDF symbol: "DATASHEET NOT AVAILABLE". This goes on and on, and is furiously frustrating.

What should I do? How should I go about looking for datasheets?


texts:
So I'm looking at the circuit below and a little confused by it.

How are there two current sources facing opposite directions? What does this even mean and how can it be a valid circuit, since current can only travel one direction?


texts: What are all the components used in this sketch?

texts:
I am trying my hand at electronics.  Here's the sketch of a device I'd like to build that I found online.  It's for a coil gun.  I just don't know enough to understand the full sketch.

I've been researching this for several days now.  I'm hoping someone on here can help me.

I've determined I need the following.  What am I missing?

switch
2 1M ohms resistors
1 microF Capacitor
1 electromagnetic coil
1 NPN transistor


texts: How much power can electrical noise (EMI) produce?

texts:
I have a 5-meter-long wire connected to an ESP8266 input. The wire is connected to a regular wall-mounted switch and goes through my room's wall and is adjacent to mains power lines.

As you would expect there is significant noise on the input of the microcontroller. I intend to use an optocoupler to eliminate the noise, but I was wondering if this noise can also turn on the LED in the optocoupler.

Can electrical noise create enough voltage and current to turn on an LED? Say it's a regular IR LED with a 1K resistor in series.

I'm asking since even after putting the optocoupler in the circuit I still could read false LOW/HIGH triggers on the input.

(I have done my research about input signal noise and know that I should use twisted shielded wire, filters, etc. but my question here is specifically about the amount of power that I can expect from EMI noise created in a 5m wire in a household environment)


texts:
I'm trying to understand the exponential converter in the MFOS VCO.  Here is a link to the complete MFOS Noise Box synth schematic.
http://musicfromouterspace.com/analogsynth_new/NOISETOASTER/NOISETOASTER.php
However I tried to isolate just the exponential converter of the VCO here.

https://www.circuitlab.com/circuit/8emjqv7bj65n/mfos-exponential-converter/ (warning, when simulated, this circuit does not work.  I'm new to circuitlab so I'm not sure why)

Is this what going?  The input (at node in) coming from the VCO mixer goes through an inverting opAmp (not shown), so represents a negative DC voltage at the base of transistor Q1.  The - input of OpAmp OA1 is positive but near ground because + input is at ground.  This drive the output of the OpAmp very negative.  This turns on both PNP transistors.  Because current is exponentially related to voltage across a transistor, the output is an exponentially related negative current.  ?

(Bonus question, why doesn't the circuitlab simulation work?)


texts:
I would be grateful for assistance in identifying an old motor from Matsushita Electric Industrial Co. Ltd.  I have been unable to find a datasheet for the motor. An image of the partially disassembled motor is included below.  I am able to take more specific pictures if requested and directed.  The text reads:

IB30-16.5

4P 30W

220V 50Hz 3.5uF

240V 50Hz 2.8uF

The cylindrical case has an outer diameter of 90mm and height of 110mm.

I assume this is a single-phase four-pole motor.  I would be grateful for guidance in determining whether the capacitances listed are for start capacitors or run capacitors, and which of the three wires - white, brown, black - is which.

I have measured resistances and inductances.  The resistances were measured directly with a multimeter.  The inductances were measured by driving a square wave through the windings in series with a known resistance of 270R, and measuring the RL time constant from the captured waveform.  The results were as follows:

white to brown: 210R 127mH

white to black: 94R 87mH

brown to black: 120R 94mH

In calculating inductance via the resistance and time constant, I summed the 270R and winding resistance and multiplied by the time difference between the peak of the waveform and 0.37x that peak with respect to the waveform's minimum value.

I believe that the winding with the largest inductance is the main winding.  I also believe that the winding with the highest resistance tends to be the auxiliary winding, but this makes the results contradictary.  However, I could understand a lower resistance for the auxiliary if it is substantially shorter.

I hope my inexpert research can help an expert to answer my questions on capacitors and winding identification.  I would also welcome any corrections, especially if I am way off base!

Thanks for considering my question.


texts:
I haven't done any hardware work in a lot of years, but I've run up against an oddity.  I'm doing some retro-stuff with a Z80 from scratch and I'm finding that the chip is heating up pretty fast; so much so, that it is causing the ship to crash.

This means that either a) I've wired something wrongly and I can't see it or b) these chips get really hot with slow clocks (??? which sounds absolutely crazy to me).

I have included a photo below.  Note that there are 10pf ceramic capacitors on the VCC pins to ground that are not in the photo.

Currently, D0-D7 are pulled to ground, A0-A9 are run through an LED light bar, through appropriate resistors, M1 is tapped with an LED and resistor, MREQ is also tapped through an LED/resistor, RESET, BUSRQ, WAIT are pulled high, as are INT and NMI.

If I clock it at 5 hz or so it will count upwards of 0xAF in the address lines, sometimes higher.  If I clock it faster (around 50 hz), it will get as far as around 0x5F and then crash.  If I add some heat dissipation to the top of the chip, it will count longer, so it's definitely heat.

Another possibility that occurs to me is that the Z80 likely isn't designed to source current to 12 LEDs at the same time... Could that be my issue?  Ought I add buffers in here?

Can anyone read or see anything obviously incorrect here that would be leading to heat?


texts: UART - getting gibberish data from MAX232 with PIC16F877A mcu

texts:
I have created a serial communication between my laptop and 16F877A mcu. I have used MAX232EPE IC as level converter also. According to my code If I send a character to the MCU, MCU will return a String related to the character.

Now, what's happening is, when I am sending a character, MCU is getting it properly, because corresponding LED is getting turned on but what MCU is return as String is complete gibberish.

    // Configuration Byte
#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF         // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3/PGM pin has PGM function; low-voltage programming enabled)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

#define _XTAL_FREQ 20000000

void main() {
  //Initialize USART with baud rate 9600
  USARTInit(9600);
  TRISB = 0;

  PORTBbits.RB0 = 0;    //pin 33-Green
  int green_led = 0;

  PORTBbits.RB2 = 0;    //pin 35 - Red
  int red_led = 0;

  PORTBbits.RB4 = 0;    //pin 37 - Blue
  int blue_led = 0;

  PORTBbits.RB5 = 0;    //pin 38 - Yellow
  int yellow_led = 0;

  USARTWriteLine("Connected");

  while(1) {
      uint8_t n = USARTDataAvailable();

      if(n != 0) {
          char data = USARTReadData();

      if(data == 'G'){
          if(green_led == 0){
              PORTBbits.RB0 = 1;
              green_led = 1;
              USARTWriteLine("Green LED turned on");
          }else{
              PORTBbits.RB0 = 0;
              green_led = 0;
              USARTWriteLine("Green LED turned off");
          }
      }else if(data == 'R'){
          if(red_led == 0){
              PORTBbits.RB2 = 1;
              red_led = 1;
              USARTWriteLine("Red LED turned on");
          }else{
              PORTBbits.RB2 = 0;
              red_led = 0;
              USARTWriteLine("Red LED turned off");
          }
      }else if(data == 'B'){
          if(blue_led == 0){
              PORTBbits.RB4 = 1;
              blue_led = 1;
              USARTWriteLine("Blue LED turned on");
          }else{
              PORTBbits.RB4 = 0;
              blue_led = 0;
              USARTWriteLine("Blue LED turned off");
          }
      }else if(data == 'Y'){
          if(yellow_led == 0){
              PORTBbits.RB5 = 1;
              yellow_led = 1;
              USARTWriteLine("Yellow LED turned on");
          }else{
              PORTBbits.RB5 = 0;
              yellow_led = 0;
              USARTWriteLine("Yellow LED turned off");
          }
      }else{
          USARTWriteChar(13);
          USARTWriteChar(10);
          USARTWriteString("Invalid command : ");
          USARTWriteChar(data);
          USARTWriteChar(13);
          USARTWriteChar(10);
      }
          n = 0;
          USARTFlushBuffer();
      }
  }
}

When I am sending "G", I am receiving "��g����wf�}w��]w���" where I should receive "Green LED turned on", both are 19 character in length

If anyone can help me, it will be really great.


texts: Boost regulator current draw seems excessive

texts:
Recently I obtained this setup-regulator module (archive link) from Ali Express for a 3.3V project to be powered by two 1.5V AA alkaline batteries.
The seller had this to say about the module:

Input voltage 0.8 ~ 3.3V,output 3.3V
Maximum output current: 500 MA,
Start Voltage 0.8V, Output Current 10MA
INPUT 1-1.5V,     OUTPUT 3.3V 50-110MA;
INPUT 1.5-2V,      OUTPUT 3.3V 110-160MA;
INPUT 2-3V,         OUTPUT 3.3V 160-400MA;
INPUT above 3V,  OUTPUT 3.3V 400-500MA;
DC-DC Boost module working frequency 150KHZ. efficiency is normal 85% .
2.54mm pin pitch, Arduiuo Breadboard friendly.
Excluding Pin Size 11mm x 10.5mm x 7.5mm(Very small)
Weight : about 1.2g( Very light)

The seller does not specify the regulator used. I can read the numbers 2108A 1515/33 off the chip.

Based on the wave symbol I expect it to be the ME2108A of the DC/DC Step up Converter ME2108 Series (archive). The characteristics seem to match, as do the example circuits.
My application draws about 75mA when on, and about 100uA in sleep mode, which would seem to be in-spec. However, upon connecting everything I found out it was drawing significantly more current than I was expecting, even with the device in sleep mode. To troubleshoot the issue, I made a minimal linear test circuit.

simulate this circuit – Schematic created using CircuitLab
Here M1 is the regulator module mentioned in the listing above. The diode D1 drops the voltage just a bit, so it's clearly under the desired 3.3V. The regulator should boost the voltage to 3.3V, which when passed through a 47R resistor should result in about 70 mA of current, which is similar to the draw of my project. Between the lower input voltage (I measure about 2.65V) and the regulator effciency (which is advertised as 85%), I would expect to see about 100mA going into the regulator. Instead I measure over 230mA going through R_sense.
The second graph on page 8 of the datasheet suggests that for an output current of 70mA and an input voltage of 2.65V, I should be seeing an efficiency of between 85% (@3V) and 77% (@1.5V). Instead I'm seeing about half that.
What's going on here?


texts: Other than direct radiation, how can RF interference transfer between stacked PCBs?

texts:
I have VHF aviation radio consisting of 3 boards stacked upon each other: digital, receiver and transmitter, the digital is on ‘top’ with receiver in the middle, there is thick shielding between the transmitter and receiver.

The digital uses a reference TCXO at 30MHz, when the boards are laid next to each other on a butterfly board I get good sensitivity. When stacked the sensitivity drops

I’m seeing a lot of harmonics of 30MHz near the connector between digital and receiver, and on some other parts of the board including on some power tracks, however no problem when on the butterfly board. But these don’t seem to travel to the receiver directly on the connector since no problem on the butterfly board. I’ve not found any surface track loops so far, and shielding different areas of the digital doesn’t seem to do anything

When I filter my signal generator to remove its own harmonics the problem goes, seems like mixing of these and the 30MHz harmonics down to my IF or RF and blocking, and these harmonics must be getting to the receiver

BUT since  shielding different parts of the digital and the connector has no effect and connecting the boards side by side stops the problem...I’m stumped. I have the problem of reducing the harmonic levels but I first need to find out how they are getting onto the receiver. Removing the standoffs between the digital and receiver has no effect,
Using a case on or around the digital and receiver doesn’t effect it


texts: Issue with driving Brushless Motor with a MOSFET Driver

texts:
So I have been given a circuit which supposedly works. The circuit was the the one shown but with a 10k resistor where the scribbles are.

Q17 is an IRLM6344TRPbF N-chanel MOSFET and Q16 is a ZXMP6A17G P-channel MOSFET

This didn't work at first until I removed the scribbled out resistor. After I managed to get it to actually change the output voltage dependant on the PWM signal that is applied, I encountered a weird problem.

The problem was that there was a weird correlation between the PWM duty cycle and the output voltage. When the duty cycle is between 0-30% the output voltage is ranging from 0-11 V and then increasing the duty cycle from 30% to 100% slightly increases the voltage until an output voltage of 11.8 V is achieved.

Can anyone explain why that is the case or what I am misunderstanding/doing wrong?


texts: Calculating base resistor value using voltage

texts:
I'm pretty new to electronics so my question is I think a relatively simple one.

On transistor datasheets, the base-emitter voltage is typically around 6V, which means that voltage across this connection should not exceed 6V, right?
When you calculate the value of the resistor connected to the base, you assume a 0.7V drop across the transistor (because this is saturation voltage), and the rest of the voltage is dropped across the resistor. You use this voltage, along with the current you want going through the base, to calculate the resistor value. But why are we assuming only 0.7V dropped across the transistor if it can have up to 6V dropped? And if it can drop more than 0.7V, then how can we calculate the resistor value?

Thanks in advance.


texts: Protection of Energy Meter from 35KV spark

texts:
I have been building a prototype of an energy meter for a project. One of the aims of the project is to make sure the energy meter can withstand a 35KV Spark applied to it.

I was wondering how this could be implemented..

Is is the merely the casing/enclosure of the energy meter that is required to provide this insulation? I realized that this can't be all since during the test, the spark is also applied to the input and output terminals of the meter.

What do the input and output sides of the circuit of the meter need to have to protect it from damage? And as a beginner, I'd be grateful if somebody could explain to me the purpose of this requirement. Thank you in advance.


texts:
simulate this circuit – Schematic created using CircuitLab

I am a newbie and this may not be a tough one. I am using Arduino UNO and trying to find the unknown resistance with the above schematic.

But when no input is connected the ADC pin it gives a random reading and when I connect an input it directly shows 1023 as analog reading. What is the problem here ? And also if I get proper ADC reading, can the unknown resistance value will be properly found with the above voltage divider? The voltage is measured between the ADC pin and Gnd pin. Is that OK?

I would be doing it like: \$ \large V_{R1} = VCC \times \frac{R_1}{R_1 + R_2} \$ and then finding out \$ \large R_2 \$


texts: Drawing TL094 Quad Comparator in Schematic

texts: Quick question on drawing schematics, when you are drawing a quad comparator into a schematic (such as the TL094), do you use the comparator symbol four times with the IC label by it or do you use the IC symbol with the power, inputs and outputs labeled? Does it matter or is it all just a matter of preference?


texts: How can I derive an approximate equation for the forward voltage drop of a particular component?

texts:
I have a situation where I have ADC value for a battery voltage and I am trying to re-create and display the actual battery voltage. Fairly straight forward situation but there is a diode drop in there that complicates things. The ADC values are taken after the diode and I am trying to display the actual battery voltage. I know the current through the diode at the time of the reading so my plan was to calculate Vf and add it to the reading.

The specific diode I am using is SSA34-E3/61T. It has a graph of the forward voltage as a function of current. My initial thought was to take a few values from this graph, drop it into excel, fit a logarithmic trendline to it and use the equation for that line to calculate the offset as a function of current. However, that trendline doesn't match very well as current surpasses 500mA or so. Any thoughts as to how I might calculate this with some accuracy?


texts: Equipment operating on negative voltage instead of positive voltage

texts:
Why do some devices, Carrier grade base stations for WISPs and cell towers for example, operate on a -48v system instead of a +48v system?

A few of our higher end devices operate on a -48v system instead of a +48v system. Why would these companies choose to operate these devices on a negative polarity? are there benefits to this? and to power these devices does your power supply need to specify that it can operate this way?


texts:
I am using SPI with an Arduino Uno for a few different things. My project's buttons are all running through a 74HC165 shift register to the Arduino's MISO. Unfortunately, the 165 has no 0E. As such, it seems that the 165's  output is constantly on even though it's slave select is off. This is interfering with the MISO of other SPI devices I am using at the same time.  I need a way of turning the 165's output off (ie linked to slave select).

Is it possible to use an n-MOSFET to control the data flow from the 165's output to the Arduino's MISO? Or do I need to use an IC like the 74HC125?

Thank you very much in advance!


texts: effective diameter vs overall diameter of multi-strand wire?

texts:
Is effective diameter the outer overall diameter of a 7-strand earth wire, (about 2.1 mm), or the copper-only diameter based on 7 x 1 mm strands. (2.645751 mm) ?
(Refer to answer on multi-strand wire inductance).


texts: How much current can I pass through an HCT4067?

texts:
I want to use this 16-channel analog multiplexer/demultiplexer (Datasheet: 4067) to pass the output current of a stimulation circuit through different channels. The output current is a square wave with a maximum of 3mA and 20KHz. I looked through the datasheet and I can't find a maximum current.

Does this mean I can pass whatever current form I want through the 16 outputs? Should I treat this IC simply as a few ideal switches?

Also, I assume the maximum output voltage would be the supply voltage. Am I right?

If there is anything important that I haven't taken into consideration, I'd appreciate it if you point it out.

EDIT: I need to both source and sink current, with voltage varying from -3V to 3V. I'm not sure if this IC works with double supply. Should I switch to another IC?
Can I pass the current in both directions?


texts:
As most people here know, by using 4 bits, we are able to count from 0 to 15 (0123456789ABCDEF in hexadecimal). But if we were to only count up to 9, we would still be using 4 bits, and the digits from A through F would be wasted.

However, Wikipedia's QR-Code page states that using only numerical digits from 0 to 9 uses 3⅓ bits per character, which is correct from a statistical stand point.
And yet a third of a bit is not a physical object, and sending a number from 0 to 9 uses at least 4 bits to my knowledge.

Is there any way to use the wasted combinations to effectively send a character with fractions of bits?

OK, let me give an example: The two digits "27" must be sent. With normal coding techniques, the bits sent would be 00100111. We could then imagine a system that would replace the digit '2' by the digit 'E' or 'F', depending on the next bit; in this case the next bit is 0, so the '2' is replaced by 'E'. The resulting bit-string would then be 11010111. On the other hand if the digits "28" must be sent, the first bit after the '2' is a 1, so it is replaced by the digit 'F' instead, yielding the string 11111000.

In both case, an economy of 1 bit has been effected, because one nibble was used for two different characters. In other word, three and a half bits are used on each character.


texts: Can a SMPS transition between 2 unsynchronised AC power sources

texts:
can a SMPS handle an instantanous transition between the grid AC and the inverter AC? even if the waveforms are unsinchronised?
with a simple 3Pole 2Throw changeover switch
also happy to use a latching relay as this can be automated for aditional functionality
some context for loads, mostly things like lcd computer monitors @ 40W,  sterio amplifier @30W , laptops @ 90W , Desktops @ 100w
i would be concerned though about doing it with the desktop PC, as this is the only sensitive device listed. i'll research whether UPS's synchronise AC waveforms.
Thanks


texts: Is it possible to map pre defined data sets in PDO Mapping of CANOpen protocol

texts:
I've been trying to learn about CANOpen protocol and create a slave device accordingly.
I understand that PDO mapping can be either static, or fully dynamic (according to CIA-301).
My coding skills and hardware doesn't have the strength to hold a fully dynamic structure.
My question is: is it possible to make pre defined data sets and map them as message blocks?
For example, like sets of data below:
package 1 : A,B,C,D
package 2 : E,B,F,G
package 2 : A,X,
etc.
if it's possible what is the correct way to put them in to object dictionary?


texts: I have studied the  diode model which treats diode like elements with constant voltage drop and depending on the bias of the diode the voltage drop varies. Now I'm starting to learn about the correct model, the diode has a variable voltage drop depending on the voltage, resistance.If I have a diode in series with a resistor how do I find the current through the diode so according to the IV curve I will be able to find the voltage and how does the resistor affect it?


texts: What potentiometer should I use for this phono pre-amp?

texts:
Please consider this DIY phono pre-amp.

The text states, that resistors R9 and R22 may be exchanged for potentiometers for gain control.

Since the circuit uses 1.2kΩ resistors for R9 and R22, I was wondering what kind of potentiometer I'd need. I was thinking of a logarithmic 10kΩ pot. However I'm not sure. In case there's a formula for computing this kind of resistance, please let me know.

The arrow "-VA" at IC1 (pin 4) should connect to the "-VA" point above C2, right? Likewise on the right channel.


texts: Determining power and resistor values for a zener voltage regulator

texts:
Above is a zener diode circuit used for voltage regulation.

In Art or Electronics textbook theres a following exercise about choosing the right zener:

Always Vz = Vout and 10mA is the zener current wanted;

so R = (Vin(max) - Vz) / 10mA = (25 - 10) / 10mA = 1.5k Ohm.

and for Pz = ( Vin(max) - Vout) / R - Iout(min) ) * Vz

Pz = ( (25 - 10) / 1.5k - 0mA ) * 10 = 100mW

But actually if we can use Pz = Vz * Iz

Pz = 10V * 10mA = 100mW

I found different answers to this question in different forums. Am I doing something wrong here?


texts: DIY DC Blocking Capacitor for oscilloscope

texts:
I'm studying switching converters and want a bench setup that will allow me to reliably observe the various voltage waveforms (output, inductor, switch) on my oscilloscope.

I discovered pretty quickly that just hooking up my 10x probe with witches hat and ground pigtail wasn't going to work very well, picking up large inductive spikes and hiding the rest of the action in noise:

This image is from the Analog Devices app note here on measuring switching regulator output ripple which is pretty much exactly the sort of thing I'm trying to do. The results I get are quite similar.

That app note advises a setup like this, which I'd like to build up:

The basic idea is a length of \$50\Omega\$ coax soldered directly to the output capacitor (SMD in this case), fed through a DC Blocking Capacitor (the tubular aluminum coupling on scope input 2), and using the built-in \$50\Omega\$ input impedance of the scope.

My scope (Rigol DS1054Z) doesn't have a \$50\Omega\$ option, but I have a feed-through terminator that accomplishes the same thing.

What I don't have is a DC Blocking Capacitor fitting.

So I was wondering. How hard could it be to put together at least a fairly usable one?

So my main question is how to size the capacitor and what type/dielectric would be suitable? I'm happy to order the right type and wait, but would also like to slap in the closest thing I have on hand that would work just to get a feel. The effective bandwidth would optimally be something like 10kHz to 100MHz.

I'm kind of supposing I would use an axial capacitor, solder it inline with the coax center conductor, shrink wrap that, then use some copper foil to wrap it and solder the coax braid to that, then shrink wrap the whole thing, maybe after wrapping some 2 liter Coke bottle plastic around it for mechanical strength.

If SMD caps were going to do the trick I could use a small bit of veroboard in roughly the same sort of way.

Anybody got any pointers on the capacitor selection or construction approach that might help me out?


texts: Programming Arduino AVR MCU with Atmel ICE

texts:
I have a question about programming Arduino with Atmel ICE. I am aware that the Arduino UNO has a ISP connection for ISP programming. If i'm not mistaken I should be able to plug in the ICE and program the Arduino UNO when I choose the method of programming to "Atmel-ICE"?
Another reason why I ask his is because I have made a PCB but I believe I may have made a mistake around the RESET pin. I am trying to program the attiny2313A with Ardunio code but am having trouble.
I have programmed this MCU though Atmel studio and can confirm I can program the chip though ISP with Atmel studio but NOT Arduino. I have also broke out the RX and TX pins to try and program with FTDI chip but I have not but a capacitor in series with the RESET line.
If possible I would really like to program with ISP. I have got the ATting files for programing for the following link on github: ATting2313 Arduino Files  (Look at ReadMe)
Any help would be great, I'm really stuck.


texts: R-L Transients Storage Phase: "Inductors" Help?

texts: The below expression is for finding the induced voltage across the coil (inductor) at a certain Time Interval. Furthermore, the additional expressions are to find the induced voltage at 1T and 5T. I would like to know if I'm doing this correct.


texts: Can I use an LED lighting power supply to power wifi devices?

texts:
I am wondering about the suitability of a power supply designed for LED lighting strips, to use as a replacement for some 24 V DC switch mode power bricks that came with some wifi network equipment.

The reason I'm tempted to use an LED lighting PSU for this application, is that it seems quite difficult to purchase a general purpose, outdoor weatherproof (rated IP67) DC power supply, in Australia at least, for a reasonable price.

I wish to power two wifi devices, with a maximum power draw of 4 W and 7 W respectively and wire them in parallel to a single PSU. The associated data sheet says that they accept anywhere between 8 and 30 V DC, using passive Power over Ethernet. These devices feature a small router, attached to an antenna.

I thought perhaps a "contant voltage" PSU such as the EVWP12/30 sold by Domus Lighting might be suitable. Output specs: 12V DC ± 0.5V, Low Voltage output: 30W DC, Tolerance: 10%, Output Current: 2.5A. Input voltage will be 240V AC.

My hesitation is about whether these PSUs modulate their output waveform using PWM (even though they're described as "DC"), in a manner suitable for LED lighting strips, but perhaps not for other equipment. Do you know if they will be suitable?


texts: What use is a pull-up/pull-down with a push-pull output?

texts:
For at least some STM32F4 MCUs, push-pull + pull-up/pull-down is a valid GPIO configuration, but what would you ever use it for, and why? I assume there's some saner reason than "I just really felt I needed that juicy extra 100µA of wasted current per pin"...

The configuration is listed in section 8.3 of the reference manual, on page 269:


texts: Solving for the Voltage Gain in Cascaded Two-Stage Amplifier

texts:
First, I drew the cascaded small signal equivalent circuit (unilateral hybrid pi transformation) for Figure 3 as:

After drawing the cascaded small signal equivalent circuit (unilateral hybrid pi transformation) of Figure 3, I determined that the output resistance \$R_o=R_{C2}\$ and the input resistance \$R_i=R_{B1}+r_{\pi}\$. Meanwhile, to find the voltage gain \$A_v=\frac{V_o}{V_i}=-G_mR_o\$, I first had to find an expression for the transconductance \$G_m\$. I began by writing an expression for the output current \$i_o=-g_mV_{EB2}\$. I needed to express \$V_{EB2}\$ in terms of \$V_i\$ and I did so using the following circuit analysis equations:

1) \$g_mV_{BE1}-\frac{V_{EB2}}{r_{\pi}}+\frac{V_{C1}}{R_{C1}}=0\$

2) \$\frac{r_{\pi}}{R_{B2}+r_{\pi}}V_{C1}=V_{EB2}\$

3) \$V_{BE1}=\frac{r_{\pi}}{r_{\pi}+R_{B1}}V_i\$

Eventually, \$V_{EB2}=-g_m(\frac{r_{\pi}}{r_{\pi}+R_{B1}}V_i)(\frac{r_{\pi}R_{C1}}{R_{B2}+r_{\pi}-R_{C1}})\$.

Plugging this into \$i_o=-g_mV_{EB2}\$ and solving for \$\frac{i_o}{v_i}=G_m\$, \$G_m={g_m}^2\frac{{r_{\pi}}^2R_{C1}}{(r_{pi}+R_{B1})(R_{B2}+r_{\pi}-R_{C1})}\$ so that \$A_V=-G_mR_o=-\frac{{g_m}^2{r_{\pi}}^2R_{C1}R_{C2}}{(r_{pi}+R_{B1})(R_{B2}+r_{\pi}-R_{C1})}\$ where \$r_{\pi}=\frac{\beta}{g_m}=\frac{100}{0.01{\Omega}^{-1}}=10000\Omega\$. My problem is that the denominator factor \$(R_{B2}+r_{\pi}-R_{C1})=30000\Omega+10000\Omega-40000\Omega=0\Omega\$ so that the gain \$A_v\$ becomes negative infinity. Is there something wrong in my process? Any help please?


texts: Mosfet, resistance between drain and source in circuit

texts:
in this circuit:

simulate this circuit – Schematic created using CircuitLab

is it possible to measure resistance between drain and source if no motor(inductance) is connected or do the diode/capacitor falsify results?

assuming the gate still carries a charge after being connected to a power supply, do i need to connect it to a power supply ground to get rid of the charge or just shorten source and gate?
can there be a charge at all or will R1 (1MOhm) take care of that?


texts:
Why here  http://www.talkingelectronics.com/projects/MOSFET/MOSFET.html they say that push-pull configuration with high-side transistor as PMOS and lowside as NMOS is incorrect?

I have found many sources which state that that configuration (PN) is correct like STM32F0 reference manual,GPIO section

Also the simulator shows both configurations (PN and NP) seem to work

How it is correct?


texts: How to design a LIFT simulator using FSM(Finite State Machine)

texts:
I want to design a LIFT with the help of Finite state machine.

There are four floors. So I took them as 0, 1,2,3 and correspondingly the states.
The 0,1,2,3 buttons are present inside the lift. If some one presses them accordingly it changes from one state(floor) to another.

But they are also UP, DOWN arrows present outside the lift on each floor.
  No DOWN arrow in 0th floor and no UP arrow in 3rd floor

I am not getting how to incorporate them into the design.
With only four states 0,1,2,3 and say a person pressed the button 3 inside the lift from 1st floor, we are sending it state 3 directly. Now if in 2nd floor someone presses the UP arrow, the the lift should stop at the 2nd floor before going directly to 3rd floor, which I am missing.

May be taking UP, DOWN signals as asynchronous may help. But they are 6 such signals. So it is posing me into trouble.

Can some one help me. A state diagram helps me further.


texts:
I'm working on some home networking and automation projects, and am trying to reproduce the circuitry in one of my remotes so that I can connect it to a microcontroller without rendering the remote unusable.  The remote circuit has two inductors in it, one of which is a variable (see the pictures below).  I'm not very knowledgable on inductors, so how do I identify the appropriate components to duplicate the circuit?  I know I can use the colors on the fixed inductor (If read it correctly, it's 1.1 µH ± 10%?), but how do I choose the right core to use?  I'm not sure what to do with the variable one, though.

Fixed Inductor:

Variable Inductor:


texts: Placing an RLC input filter at the input of a buck

texts:
Since bucks have current spikes at the input side, it's best to use an input filter as you get better noise reduction than using an output filter (afaik).

Using a regulator IC however, that is, one you don't know about the transfer function as the IC is like a black box somewhat, I wonder how would somebody design a filter for it and still meet correct stability.

I'd like to place a RLC 2nd order (flat butterworth response with cutoff around 4kHz) using the AOZ1284PI IC

This is to step down 5V to 4V.

My question basically is... how can I insure the buck will be stable with this input filter? Should I worry or are most bucks "stable enough" to support an input filter?

Thanks


texts: Getting started with an LPC1313 Microcontroller

texts:
I recently purchased this microcontroller along with an FTDI TTL-232R-3V3 cable. I want to program a blinking lights hello world application onto the microcontroller. I was told that I might be able to do this with flash magic. How could I do this?

Any help would be much appreciated as I am very new to this!


texts:
I help maintain an old beaten down LED sign on the side of a highway.

Right it has a program running on Win98 to generate the image that should be on the sign (FLASH animation, temperature, etc), and drive a PCI IO card which in turn drives the sign logic. I'd like to (be able to) replace the control package of the sign with something less painful.

A different sign we're working on has a DVI input to a control board. The control board takes a specific portion of the video and sends it off to the sign. I like this scheme because it makes it easier to change out the computer if it breaks, and allows a lot of freedom in terms of what software/hardware can be used- so long as a PC has a DVI port, it can drive the sign.

Core Question: How can I go from 'video input' to a copy of what is on the screen for consumption by digital logic?

The one thing I've come up with so far is using a TFP401A, and feeding that into an FPGA where a lot of accompanying logic would sit.

Does that seem reasonable? Is there a better way? At least one concern is that I don't have any experience with high frequency design- I'm not certain how much care needs to be taken on the traces between DVI connector and receiver, as well as from receiver to FPGA.

EDIT:

Few added details:

The sign is low resolution (47x127 image, 24x64 sign)
It displays animation (refresh rate > 10Hz)
I'd prefer something without dependence on software on the PC (suggests taking a video signal of some format)
This is 80% learning experience- while the goal is a practical replacement system, I would like to end with the knowledge of how this can be done.


texts: LPC1343 Firmware Loading - Change drive label

texts: I have a system that is using the built-in firmware loading facility of the LPC1343.  When the flash drive is mounted, the disk is always labeled "CRP_DISABLED". Is there a way to change the label of the drive to something else?


texts: Synthesizing Error while designing 4-bit ALU in Verilog

texts:
I'm trying to design a 4-bit ALU which does the following functions:

I've written the below Verilog code and the simulation is working fine without any errors.
`timescale 1ns / 1ps

module alu_4_bit(

    input M,
    input S1,
     input S0,
     input C0,
    input [3:0] A,
    input [3:0] B,
    output reg[3:0] F,
    output reg Cout
    );

reg Cout_temp; // Internal Variable //

always @(*)

    begin

                        case({M,S1,S0,C0})

                            /* Logical Operations */

                            4'b0000,4'b0001,4'b000x : assign F = A & B;
                            4'b0010,4'b0011,4'b001x : assign F = A | B;
                            4'b0100,4'b0101,4'b010x : assign F = A ^ B;
                            4'b0110,4'b0111,4'b011x : assign F = ~(A ^ B);

                            /*Arithmetic Operations*/

                            4'b1000 : assign {Cout,F} = {4'b000,A};
                            4'b1001 : assign {Cout,F} = A+1;
                            4'b1010 : assign {Cout,F} = A+B;
                            4'b1011 : assign {Cout,F} = A+B+1;

            /* When there's negation of any one data entry, Cout also gets negated */

                            4'b1101 :
                            begin
                            assign {Cout_temp,F} = A+(~B)+1;
                            assign Cout = ~ Cout_temp;
                            end

                            4'b1111 :
                            begin
                            assign {Cout_temp,F} = (~A)+B+1;
                            assign Cout = ~ Cout_temp;
                            end

                            4'b1100 :
                            begin
                            assign {Cout_temp,F} = A+(~B);
                            assign Cout = ~ Cout_temp;
                            end

                            4'b1110 :
                            begin
                            assign {Cout_temp,F} = (~A)+B;
                            assign Cout = ~ Cout_temp;
                            end

                            default : assign {Cout,F} = 5'b00000;

                        endcase

    end

endmodule

But when I'm trying to synthesize the project and View the Technology/RTL Schematics, I'm encountering the following error:

Can anyone point out where the mistake is and help me rectify it?


texts:
I'm a beginner in electronics. I am trying to use an optocupler (p621) to switch 12v supply to 5v for digital input.

Here is the fritzing diagram

So from the 12v supply I am using 1 1k resistor into the opto P621. So the LED turns on when the button pressed. Then in theory the 5v from arduino connects to pin 2 as a digital input.

Its working fine without much trouble. But even without Optos LED power, the Opto conducts 5v from arduino to the pin..
I've no idea what happens here.

I checked in serial monitor and it says high for that pin randomnly..

So does opto conducts without led voltage or something else wrong in my circuit??

Schematic View


texts: I don't have any experience with star delta starters but on doing some research I concluded that 2 push buttons(NO and NC) are required to turn on or off the system. I have a pump which is star delta controlled, turns on when I push green NO button and turns off when I push red NC button. Now I want to control this via Arduino rather than manually pressing buttons. What I thought so far is to replace push buttons with relay(NO with NO and NC with NC respectively) and control those relays with Arduino. But I've seen many systems of star delta connection where motor turns on or off with just a normal on/off switch i.e. no separate push buttons. That will be more feasible to control via Arduino since only one relay is required. But I nowhere found a way to replace 2 push button circuit with normal on/off switch. Please help out.


texts: How to represent Negative real numbers in Fixed Point representation

texts:
I find this module for the addition of two Fixed Point Numbers.
Manual for using this Module:
https://opencores.org/project,verilog_fixed_point_math_library,manual

How to add -1.5 (or any negative real number) to 0.5(any real number)??

My problem is that: I know how to represent positive numbers in fixed point representation. But I don't know how to represent -1.5(or any negative real number), but I tried taking 2's complement of 1.5 and given as input, but it is not giving proper output.

Edit: I tried, what Wouter and entrepreneur said, but that too not working.

Edit: Added Testbench of module.

module qadd(
input [N-1:0] a,
input [N-1:0] b,
output [N-1:0] c
);

//Parameterized values
parameter Q = 15;
parameter N = 32;

reg [N-1:0] res;

assign c = res;

always @(a,b)
begin
//both negative
if(a[N-1] == 1 && b[N-1] == 1) begin
    //sign
    res[N-1] = 1;
    //whole
    res[N-2:0] = a[N-2:0] + b[N-2:0];
end
//both positive
else if(a[N-1] == 0 && b[N-1] == 0) begin
    //sign
    res[N-1] = 0;
    //whole
    res[N-2:0] = a[N-2:0] + b[N-2:0];
end
//subtract a-b
else if(a[N-1] == 0 && b[N-1] == 1) begin
    //sign
    if(a[N-2:0] > b[N-2:0])
        res[N-1] = 1;
    else
        res[N-1] = 0;
    //whole
    res[N-2:0] = a[N-2:0] - b[N-2:0];
end
//subtract b-a
else begin
    //sign
    if(a[N-2:0] < b[N-2:0])
        res[N-1] = 1;
    else
        res[N-1] = 0;
    //whole
    res[N-2:0] = b[N-2:0] - a[N-2:0];
end
end

endmodule

//Test Bench

module qadd_tf;

// Inputs
reg [32:0] a;
reg [32:0] b;

// Outputs
wire [32:0] c;

// Instantiate the Unit Under Test (UUT)
qadd #(16,33) uut (a, b, c);

initial begin
    // Initialize Inputs

    b[32]=1;
    b[31:16]= 16'b00000000_00000001;
    b[15:0] = 16'b10000000_00000000;
    a[32]=0;
    a[31:16]= 16'b00000000_00000000;
    a[15:0] = 16'b10000000_00000000;

    #100;

    #100;
end

endmodule