texts: Wiring Optical Encoder according to datasheet

texts:
I've had success wiring a mechanical CUI encoder according to their datasheet. Values are spot-on for a hardware debouncing and diagram simple to understand for me.

Nevertheless, I prefer for my application a better tactile feedback for the user, so I researched a bit, and it seems like Grayhill 62AG Series would fit perfectly.

Now, looking at their datasheet, I'm surprised how much the wiring changes from the CUI wiring. I suspect this is due to it being an optical encoder vs mechanical to the CUI (?).

Here is the datasheet extract :

What is the thing next to the two capacitors ?

What is the LED's purpose between +5V and GND ?

I actually have doubt whether this is the internal wiring of the encoder, or the recommended wiring for it...


texts:
Currently, I am doing some experiments with Single Photon Avalanche Diodes where I get output voltage of 0.9V. And I am trying to invert the output using a regular inverter(74HC04). But, the Inverter considering 0.9V input is LOW, thus, giving me the HIGH output.
Can I find any low voltage Inverter in the market that gives me LOW output when I give 0.9V as input? Also, please suggest an alternative to solve my problem.


texts: How are the neat sinc function shaped carriers produced in OFDM?

texts:
I am learning about OFDM and QAM.

Every explanation I have read illustrates how the separate carriers are sinc functions that are arranged to overlap in a nice orthogonal way so as to cancel out interference from neighbouring carriers.

The part I don't understand is how is it possible to generate these neat perfectly overlapping sinc functions,  when they contain constantly changing symbols. Each transition from 1 symbol to the next, in the time domain is a random change in phase and amplitude. This must correspond to a random change in the sideband pattern of the carrier in the frequency domain, and therefore disrupt the orthogonal arrangement.


texts:
I am finding it difficult to understand how exactly this works and would appreciate any help.

From my understanding:

The emitter base junction has to be in forward bias meaning that Vb is more positive than Ve ( ie Vb>Ve ?)

The base collector junction has to be in reverse bias hence Vc is more positive than Vb ( Vc>Vb ?)

From what I know current should go in from the emitter then through P-type and if it is thin enough it would reach the collector. Here the currents seem to be in opposite directions and I cant make much off it.

I understand the P-n junction theory between holes and electrons and how this can be seen as 2 back to back diodes however I am finding it difficult to analyse exactly how it works from the very start.

If we where to start straight from the begging where current flows from the cells how would it work?

I would appreciate the help. Many thanks.


texts: Very low power shunt regulator for signal clipping

texts:
I'm designing a very-low-power, i.e. less than 5 uA device, that requires external inputs. These inputs need to be protected against over-voltage. The allowed range is about -0.1 V to 3.0 V. If necessary, I can live with a top voltage that is limited at a value as low as 2.8 V and as high as 4.0 V, so at least there is some flexibility.

The whole device has a power source at a somewhat higher voltage and a step-down converter to a system voltage at 3.0 V, so I could in general just add a protection diode to that 3.0 V system voltage, accept that the limit is increased to at most 4 V and be done with it. Sadly, I can not limit the current through this diode to the point, where the device would just sink that, as the device itself only consumes about 5 uA and there may be up to 1 mA of current through that diode:

simulate this circuit – Schematic created using CircuitLab

So, instead I would prefer to have some other means to limit that voltage. The typical approach here is to use a Zener diode to ground, bypassing the system itself. Of course that also fails, as there are no Zener diodes with a sharp enough knee in that voltage range to ensure that there is voltage limitation above, say, 3.5 V and very low current consumption below 2.8 V, which is kind of required for this circuit to function. I also can not add a resistor divider before the input and then use a Zener diode with a higher Zener voltage, because that would create a pull-down which in conjunction with an additional pull-up, would greatly increase current consumption at the permissible resitance range.

So, the last solution I see is some more complex method of limiting the voltage. The approach I prefer is some sort of shunt regulation. I did not find any shunt regulators sufficiently low-power for my needs, like the ALD111933, which is a trimmed-threshold FET pair. With it, I could create a circuit like this:

simulate this circuit

Do you see a particular problem with this? There is no need to filter out extremely fast transients, another mechanism will take care about that.

Are there any alternatives? I thought about low-power operational amplifiers, but they have such low bandwidths, that even with the transient filter, they would be too slow.

Also, the only really acceptably trimmed FETs seem to be from that manufacturer. Are there others, that I just can not find?

Edit: I've kept the actual signal on the input hidden, sorry for that. The reason for it is, that it can be quite diverse. In general, it should be a digital or analog signal between 0 V and 2.8 V; analog signals at a bandwidth of less than 100 Hz, digital signals up to 10 kHz. There are no protection diodes in BUF1, which has an absolute maximum at to 4.3 V. In case of errors that may occur during normal operation, I have to expect voltages up to about 8 or 9 V. In case of severe errors, that should not occur, but would be nice to withstand, the voltage may rise to up to 30 V at the input. I can also scale R1 appropriately, selecting low-leakage diodes. BUF1 also has very low leakage current, so R1 would be around 200 kOhm.

Edit: Another small clarification: I'm not just interested in blocking transients. It may be necessary to allow a over-voltage to be applied over the duration of days until the fault can be fixed.


texts: JTAG cable and device interchangeability

texts: I see a lot of device specific JTAG cables such as AVR jtag or specific ARM JTAG.  Is there any such thing as a 'standard' JTAG cable that will work on multiple devices? I want something that will work with xilinx FPGAs, STM32s and AVR microcontrollers


texts:
In the N-port theory, it says that the total admittance matrix for the parallel connection of two 2-ports is the sum of individual admittance matrices "if it is possible to connect them in parallel".
\begin{equation}
\hat{Y}_\text{tot} = \hat{Y}_1 + \hat{Y}_2
\end{equation}

Is there an example of two 2-ports with well-defined admittance matrices that do not yield a total admittance matrix according to the above sum rule when connected in parallel?


texts: I was studying single phase rectifier circuit with RL load. There I found that they are using a freewheeling diode in parallel to the RL load. So is a freewheeling diode different from a power diode ? Or it is just the same with a little higher rating?


texts: Working of Comparator and LED Driver pin function?

texts:
I have this LED Driver - A80604
I need to generate 30V for my LED Driver String for generating 300mA.
My question 1 -
Both pins ADIM and PWM seem to perform the same function? Both typically take in PWM inputs and alter the LED Current through the LED Strings accordingly. Am I understanding it correctly? Or does the pins perform a different function al-together?
My question 2 -
There is a push-pull comparator circuit pins as shown below:

I am not sure why there is a comparator circuit. The cathode of the last LED in the LED String (LED_K1) is connected to the LED pin of the A80604 IC and also provided as the inverting input to the Comparator.
I am trying to understand how this circuit will work. But in order to understand the circuit working, I am not sure of what voltage will be present at the LED_K1 and what would be its duty cycle/frequency? Agreed that the duty cycle and frequency at LED_K1 would be according to my inputs (again not sure whether it would be according to my ADIM input or PWM input?)
The non-inverting input would always seem to have 6.8V since the voltage at U12V will always be between 8V and 16V.
Can someone help to understand this.


texts: Arduino Control 12V Lamp with Car Battery

texts: I'm working on a small project to control a lamp with car battery and I found this circuit on Internet. Now my car batter delivers 5 amperes and I would adapt this circuit to my needs. Is it possible? Can you help me? Thanks in advance ;)


texts:
Second this week... But was it easy I wouldn't be here...

A problem asked me to identify the diagrams from this picture:

The following are the correct answers, acording to the test developers.

a. The first diagram may represent the voltage over the load of a 4-wire Unbalanced Star.

b. The first diagram may represent the voltage over the load of a 3-wire Balanced Star.

c. The second diagram may represent the voltage over the load of a 3-wire Balanced Star.

d. The second diagram may represent the voltage over the load of an Unbalanced Delta

Again: all the above assertions are to be taken as true

I need help understanding these truths/assertions.

As far as I know, the line voltage is 30 degrees ahead of the phase voltage on a star connection (a neutral wire enforces this in case one of the impedances is not equal)

This knowledge matches the a. and b., but doesn't seem to my eyes to make sense for c.. How is the assertion c. possible ?

As far as I know, the line and phase voltages on deltas are equal, with No angle between them. But that wouldn't match assertion d. How is such assertion possible ?

Maybe the trick is in the distinction between load and source...

Who has the patience for this ? If I think any longer I lose my sanity

This is an adaptation of the actual question. The original is longer and not in english.
Here, question number 29:
https://arquivo.pciconcursos.com.br/provas/21572117/1fc8bd07ea0/tecnico_eletrotecnica.pdf

*I believe the D letter in the diagram is a typo


texts: Difference between junction points in old schematic

texts:
What's the difference between the black circle and the white one in this old schematic? Of course the black ones are junctions, but are the white circles a pin, or an input of some kind? I'm trying to redraw the circuit in KiCad but I can't find a way to express the "white" junction.

The attached picture is a Tone assembly of a vintage amplifier from the 70s.


texts:
I am missing libraries of certain ICs for use in Eagle. Can someone guide me to a source where I can find these IC libraries? I am asking this question to find out if there is any central repository where I can find most/all of the IC libraries.

Additional Information (if required):

Currently missing ICs are AD8318, ADL5542, and TLV3501
I am using Eagle v5.6.0 for Windows


texts: Active clamp forward converter (High side and lowside) with synchronous rectification

texts:
Please help me with the detailed description of Active clamp forward converter with synchronous rectification.I have   seen a lot of journals regarding this and   I am getting more confused when I read more        journals.

I need a simple but detailed explanation for the active clamp foward convertor.                Help me please and thanks in advance !


texts: Can you help me find the part number for this push button cap?

texts:
I've been searching high and low for the part number and manufacturer for this button cap. I've tried it out and it works perfectly for my project. Note: I do not want the button itself, as I've already found one that fits the "springiness" level that I need (Omrom B3F-5050, if you're curious -- they don't require as much force to press as others -- 1.27 N). Please note that these have a low-profile and slightly rounded/domed top (kind of shaped like a circular pill).

Here's an Amazon link for the cap I'm trying to find. I would like to be able to buy more of these, potentially in large quantities, but just the cap.

EDIT:
In order to make this question more useful for others, I'll reword it a bit: I'm looking for round, low-profile buttons to fit the Omron B3F-5050 push buttons. Any suggestions would be highly valued. I find that most button caps are tall, and sometimes folks need buttons that are lower-profile. The domed top is a "nice to have", but the low profile is most important.


texts:
I am trying to figure out how this DMA Initialization code is used to sample following 4 ADC channels and save data in 'adc_data'.

ADC1: channel 1 & channel 3.
ADC2: channel 2 & channel 4.

To me it looks like incomplete code as it is only initializing ADC1 but not ADC2. My MCU is STM32L476.

extern volatile uint32_t adc_data[];

  // DMA for ADC1
  RCC->AHB1ENR |= RCC_AHB1ENR_DMA1EN; // DMA1
  // Wait a bit
  nop(); nop(); nop(); nop(); nop(); nop();
  DMA1_Channel1->CPAR = (uint32_t)&(ADC123_COMMON->CDR);
  DMA1_Channel1->CMAR = (uint32_t)&adc_data;
  DMA1_Channel1->CNDTR = 2;
  DMA1_Channel1->CCR = DMA_CCR_MSIZE_1 | DMA_CCR_PSIZE_1 | DMA_CCR_MINC |
                       DMA_CCR_CIRC | DMA_CCR_TCIE | DMA_CCR_EN;


texts: Confusion with understanding output impedance on datasheet

texts:
I'm a little confused with a DAC datasheet and its output impedance spec. It says in the table that is has an output internal impedance of 100 ohms but then I look at the circuit application and it shows an output internal resistance of 50 ohms (circled in red). What am I missing?

DAC datasheet application information

DAC datasheet electrical characteristics


texts:
As a novice reading "Build Your Own Transistor Radios" by Ronald Quan I was kind of mystified by the author's statement that using "vector" board would be easier than using prototype boards, but the easiest is to use copper clad.

I could understand why you do not want to use prototype boards, since they have a lot of stray capacitance and I heard you do not want to use them for radio projects.

On the other hand I could not understand how copper clad could be easier, since I assume he meant I would need to etch and drill the board, which did not seem easy at all.

Then, I found on the web pictures of the author's own versions of the projects he did for the book. Here is a clip:

I do not get how this works. Do you just solder leads right to the board? In that case, isn't everything just shorting out? Also, when I try to solder stuff like this (big metal slabs) it soaks up so much heat I cannot get the solder to melt.

I assume the sea of copper has some kind of electrical shielding benefit, but do not know what that is.


texts:
I recently made a solar charger. The output energy  of solar cell is 2 Watts. The voltage is around 20 volts.
I used 7805 IC voltage regulator so i could get around 5V.
I used a female USB and connected it to solar panel adding leds to prevent the back flow of current .

Now my questions are :
Why do we use capacitors ?
--I believe we use capacitors for storing charge and what is the purpose of using it?

Why do we use resistors ?
--Resistor  consumes energy than why we are using it?

Is it a good to use 7095 IC Voltage regulator?-- is there better option ?

What about mAh ? Can it destroy the mobile cell? How much mAh do solar cell give?

Is it good to make solar cell mobile phone charger using that solar panel??

I learned to make such things from youtube and i am asking these queries that striked on my mind while watching it.


texts: Identification of antenna parameters for calculation

texts:
Sorry if my question may seem simple, but I discover the plans of an antenna (RECTANGULAR COIL WITH MULTILAYER) and I can not identify b and h on this given schema,

Where:
x = width of coil
y = length of coil
b = width of cross section
h = height (coil build up) of cross section

Here are the three possibilities that I see,
The first one that seems to me to be the good one:

The second that could be as valid:

and finally the thirteenth which could be valid too but in this one there would be no 'depth' or thickness so I doubt that it is the right one:

Do the circles in the rectangle of the section represent wires ?

Where are b and h ?

What is the direction of 'coil build-up' ?

Thank you for your help.


texts: In terms of object tracking, I'm working on making a small device/tag that uses bluetooth technology to keep track of objects but a friend told me about RFIDs which are supposedly cheaper and also works with NFC enabled phones. SO I'm wondering, I don't know much about the technical aspects of RFIDs, bluetooth also looks like a promising solution but can be quite costly. So keeping this in mind, what would you advice as the best approach? RFID? Bluetooth? Or something I never thought of?


texts: If you refer to Figure 14 of http://www.analog.com/media/en/technical-documentation/application-notes/EE-269.pdf.  There are 2 transformers on each data pair.  Can someone help explain how they work?  In particular, what's the purpose of the "horizontal" transformer on the right? Thanks.


texts: low pass filter design for accelerometer

texts:
I find the following code for a simple implementation of a low pass filter.

#define alpha 0.1

accelX = (acceleration.x * alpha) + (accelX * (1.0 - alpha));

I have been experimenting with the value for alpha. But I want to know how exactly we can find this value for accelerometer data (in Android). I understand that we would need the sampling rate and the cut off frequency. How can I find the cut off frequency for this kind of data(I guess this involves noise modelling and finding its frequency range? If so how should I do it? )


texts: I had some nema 17 style stepper motors from an old prusia i3 and tried to use them to automate my blinds but noticed that they weren't powerful enough for my blinds. I used a basic newton meter to check the amount of weight i need to apply to move the blinds and it's roughly 25-30newtons. My stepper motor looks like it can only pull around 15-20 newtons. Is there anything i can do to increase the torque of the stepper motor(i'm using a L293D motor shield on an uno)? And i was thinking about adding gears but wasn't sure about the best type or the needed ratio so it doesn't reliably skip any steps, speed isn't really important? Any advice you have would be really helpful, thanks!


texts: 125vdc Snubber Circuit for Relay Contacts - 125vdc, 3.2amp load

texts:
Does anyone know of a manufacturer that makes a prebuilt "ready-to-go" Off-the-shelf snubber circuit / Arc Suppressor that can be used to protect the contacts of my dinrail-mounted relay.  My load current that the relay is switching is 125vdc, 3.2amps.

The Snubber/Arc Suppressor would need to quench the arc that occurs when the contacts open up.

So far, I've only been able to locate a company in Colorado called Blue Point Engineering and from what I can tell, their unit is only suitable for AC circuits.

Please point me in the right direction.

Thanks in advance for your help.


texts:
Is this low pass filter (see the part marked in red below)?
If yes, why author used low pass filter in this place?


texts: What Gerber file extension is used to specify PCIe edge connector plating?

texts:
I am designing a PCB in Eagle using the mini PCIe card format and am not sure how to specify finger plating the board edge connector to the PCB fabricator. These plating regions are specified in Eagle at layer 33 tFinish for the top layer and 34 bFinish for the bottom layer.

My preferred fabricator is ITead Studio but I can't seem to ascertain from them what Gerber file extension is needed to specify edge connector plating. Of course this may simply mean they don't cater for such a requirement.

In order to gain a definitive response I thought I might add Gerber files for this purpose and see whether they reject them or not. What Gerber file extension (i.e. the top copper layer file extension is usually .GTL) is commonly used by other fabricators to specify edge connector plating?


texts:
I am quite new to this and am struggling to read through the data sheets of the Sparkfun 16 segment display, datasheet here.
I have managed to get all of the LEDs wired up through a LED driver, with 7v input and all pulling through a single resistor of 220 ohm.

As the short segments are one LED and the long ones are two, as soon as I switch on any of the short segments all the other ones are short circuited and switch off. Despite my best efforts I am unable to come up with a good solution to this, can anyone help?

--- Extra Information ---

LED Driver is the TLC5916IN datasheet here

The drivers are set up in a breadboard inside the pins of the LED display, so at the moment they are directly connected through the breadboard. If they need to be moved to accomodate extra resistors then that can be done, would just rather not if possible.


texts: 24bit or better ADC at 10V with at least 100ksps?

texts:
I have a signal from 0 to 10V dc.  I need to 24bit or better ADC that signal at 100ksps or greater.  I can't find ADCs that will do that, they either read at lower voltages or not as fast.  I have contemplated using a normal ADC with a MUX http://www.sparkfun.com/products/9907 and tune each section to a seperate voltage range, then scan till its in range and ADC the signal then.  I didn't want to have to manipulate the data that much.  Or use a 4 2.5V ADCs using relative ADC line references and scan 0 - 2.5, 2.5 - 5, 5 - 7.5 , and 7.5 - 10.  Then add them together in the end to get the total ADC.  I would like to do this on one chip or know a "good" way to do it.

Thanks for the help.


texts: Calculating the voltage generated by an 40KHZ Ultrasonic Tranceiver

texts:
In particular, this device: http://www.hexamite.com/hx40str.htm

Electrical Specifications HX40STR
----------------------------------------------
Parameters              Values      Units
Operating Frequency     40          kHz
Input Voltage           42 (max)    Volts (p-p)
Output (SPL) @20V       112         db
Receive (Sensitivity)   -60         db/V/Ubar
Impedance               300         ohm
Beam Angle              ±12         degrees
Bandwidth               1           kHz
Settling Time           5           mS
Temperature             -40 to 100  °C

Assuming the scenario that two trancievers are used, T1 as transmitter, T2 as receiver, 125mm apart. (Assuming no attenuation over distance.)

Output SPL at 20V => 112 db.

Converting pressure to uBar (because sensitivity is in uBar):
P = pressure in uBar

112 = 20 log (P/0.2e-3)

P = 0.2e-3 * 10 ^ (112/20)

P = 79.621 uBar

Input Sensitivity => -60 db V/uBar

S = Sensitivity in V/uBar

-60 = 20 log (S/1)

S = 10 ^ (-60/20)

S = 1e-3 V/uBar

Final Voltage V = P * S

V = 79.621 uBar * 1e-3 V/uBar
V = 0.0796721 V

However, looking at the graph "G3, Amplitude vs Excitation"

"Above: Continuous exitation voltage oscillating at 40Khz  is applied to T1. The T2 resulting amplitude is plotted above."

We see that the output voltage at 20V is 0.6V. This also excludes the attenuation over the space of 125mm, which I've calculated to decrease the output V to 0.079 V to ~0.075 V.

What am I missing in my generated voltage calculation?
Why is there a discrepancy?


texts: Source of 5v power on a typical motherboard

texts:
Forgive me for asking an interdisciplinary question.

I need to get more 5v power out of a desktop power supply to power a bunch of peripherals.

These supplies can go as high as 1600w but the power is mostly only 12v. For example, 1200w available to 12v rails but only 150w to the 5v.

I had this dumb idea. Can we get more 5v power out of motherboard?

Does it typically use something like a buck converter to feed the USB ports (internal and on the PICE) or are they wired to, and thus limited by, the PSU's 5v rails?


texts:
I have an inquiry about the circuit below:
When a high signal is continuously given to the transistor, it enables the optotriac with zero crossing. The optotriac enables the power triac, and the AC signal goes to the rectifier, and gets rectified. What is the DC rectified voltage?


texts: Does the bias amplifier of the RLD amplifier need to be connected to reference electrode of the measurement sensor?

texts:
I am using the MyoWare AT-04-001 muscle sensor and FSR400 force sensing resistor sensors with the ADS1299 amplifier and ADC and I need to improve the CMRR.
The datasheet mentions that an RC filter must be wired to the bias amplifier and connected to the reference electrode.
Does anyone have an idea how can I wire the MyoWare and FSR sensors to the ADS1299 because I don't have reference electrodes in my case?


texts: Cortex M0 or M3 serial interface to ARM7

texts:
I have worked on ARM7 controller (LPC2138) for my application. But now to add NFC module I am using LPC1227 controller along with NFC chip. ( Both dies in single package )

Now, if I want to communicate between these two controllers( Cortex M0/M3 and LPC2138 ), Is there any issue ( communication related ) if one will be higher end module ( either cortex-M0 or M3 )?

Both controllers will be interfaced with I2C or UART interface.

Thanks.


texts: What's the difference between linear and audio tapers, and why should I care?

texts:
I'm stocking up on a variety of potentiometers to keep on hand for my audio projects, and I'm trying to figure out what to buy.

The projects I'm working on seen to call for either linear & audio taper pots. I know the difference between linear and log, but where does audio taper fit into the mix?

Here's what I've researched so far:

No schematic or parts list has BOTH linear and audio.
Looking at the Bourns pot spec sheets, they seem to be using linear and audio taper synonymously, but they have different part numbers.
Sites like mouser and digikey often have, say, a 10k linear and a 10k log, but no 10k audio pot in a search. However, when I search on the Bourns part number for an audio taper, the part is described by mouser as linear taper.
A lot of audio forums I've been trolling talk about pots as either audio or
linear, but they don't appear to be synonymous in the discussions.

See why I'm confused?

So once and for all...can someone school me on the difference between linear and audio taper? I'm also interested to know how to decide which to choose for a particular application, and if they are different enough to have distinct uses, what types of interesting and unexpected results will I experience if I substitute one for the other?


texts: I have no idea where to connect my power leads to this electrical block on my saw motor, its a 220v single phase, the white wires are the capacitor.


texts:
How do you deal with version control of your schematics and pcb design?
So far, I did it by creating a bunch of copies and finally, I don't have the possibility to compare to schematics/pcb.
Could you recommend any technologies or useful tools?


texts:
I would really appreciate some help on this one. I am doing my bachelor's thesis/project which requires me to design and construct a DC-DC converter. I have been working on it for a couple of weeks now.

My main issue is justifying the selection of a specific converter topology. Simply put, I have read a lot about different topologies, been through a lot of literature, but I don't really feel much better off than when I started.

How do I select the appropriate topology for my project? What are the relevant pros and cons?

The requirements are as follows:

Up to 21 V at max 3 A in voltage mode
Up to 5 A into minimum 3 ohms, max 21 V in current mode
Input voltage in the range 26-105 V
210 mV output ripple
Can't use electrolytic capacitors

There are also some requirements for the control loop.

Here is my thought process:

I would prefer to avoid resonant converters as I don't want to open that can of worms. Furthermore, galvanic isolation would be good, but isn't necessarily a strict requirement.

For the flyback and forward topologies, I am a bit concerned about the ripple current in the input capacitor.

I am looking into the following topologies at the moment:

SEPIC
Flyback
Forward

I am open to considering other topologies.

Please ask if anything is unclear or you need any additional clarification.


texts: How to fix a RJ45 connector patina without poison or with common tool?

texts: The RJ45 connector from the wall of my house is rusted. The copper pins are covered by thick patina. The patina is so thick that it looks black. It definitely reduces communication quality so I would like to change it. The RJ45 cable goes into wall from living room and comes out from bedroom, so it is difficult to replace cable in wall. It is a male socket with patina from wall. The other end is a female socket. I think it is safe to assume the female socket is covered by patina too because they are the same old.The only option is to fix the connector. I think I have two option: remove patina by some chemical or make a new connector. I do a web search and find many accessible patina remover. But, they are used to clean art works or antiques, and not a single one lists component and I cannot even start to google if it is poisonous or not for my kid, so I give up. If you know any safe remover I will appreciate. The second way is to make a new one like this video. However, I don't have a RJ45 crimping plier. . The video doesn't show detail of crimping. If crimping only attaches connector to outer layer of cable surface, then theoretically it is possible to make a RJ45 connector without a crimping plier. I just need a glue to attach them. But, if the crimping tool is to push the copper pin into the eight tiny wires to connect, then I don't know how to do it without a crimping plier. And, in fact I don't know how it really works. These two are just my assumption. So, is the any way to fix a RJ45 connector without poison or with common home tools instead of a RJ45 crimping plier? In fact there is maybe still another way. I can cut the cable of a new RJ45 connector and weld it to the old cable. It just looks ugly ,maybe easy to break, and doesn't looks like a good idea.


texts: Why only half the peak voltage in my half wave rectifier?

texts:
I built a simple half wave rectifier using a center tap transformer and a 1N4007 diode.
I connected the 1N4007 diode to one of the live secondary wires of the transformer and measured the DC voltage across the diode and the neutral wire. It is just showing around 6 volts whereas my output AC voltage from the transformer is around 14 volts.
Also, the voltage drop across the diode is around 5 volts and not 0.7 volts.
I am a beginner in electronics and I can't figure out what's wrong.


texts: Base resistor value on 2n3904 used as a switch

texts:
I am well aware that similar questions has been asked and I have read a lot of them. I still need to ask this before I loose my mind :)

I want to, and have also managed to use a 2n3904 as a switch/button, where I use a digital pin connected to the base of the 2n3904 to "push" the button which is between the emitter and ground.

simulate this circuit – Schematic created using CircuitLab

I calculated a resistor value which works great. Using these formulas:

Ib = Ic / Hfe
Urb = Vcc - Vbe
And finally
Rb = Urb / Ib

BUT here is the thing, I realise that when measuring Ic I measured it to 0.113mA which I then used in the formula and forgot to divide by 1000 to get it in Amps, so my calculation was wrong but the circuit works. With an Rb around 1.2kOhms.

So I try to make it the riht way and use 0.000113 as Ic value instead. This gives me an Rb value in Mohms! And well, when adding a 1mohm resistor to the base the circuit does not work.

I just need to know what I am doing wrong. Hoping someone can tell me.
So the values I used for the formulas are:
Ic: 0.113mA (measured over the button I want to exchange)
Hfe: 60 from datasheet
Vcc: 5v as I run everything from the arduino.
Vbe: 0.65 min value from datasheet

Or am I using the wrong formulas even???


texts:
I am working on a 4x4x4 LED cube. I have connected all the negative terminals of LEDs in a horizontal layer to each other, and am using one Arduino pin per layer. I have connected all the LED positive terminals of a vertical column together and am controlling each column via a pin.

So, 16 pins used for columns and 4 pins used for horizontal layers. The pins are directly powering and sinking the LEDs.

From my calculations, I can turn on atmost 16 LEDs at one time before reaching current limits. So, if I want to light up all the layers simultaneously, without burning the board, how should I go about it ?


texts: I forgot a resistor on my PCB prototype - how do I add one in?

texts: I need to add a resistor into a data line on my project. The data line is a trace and carries low speed data. A through-hole resistor will be fine. The pins for both ends of the trace are exposed, but how do I add the resistor and remove the trace?


texts: Does this piece of code follow the required timing constraints?

texts:
I trying to interface with an stepper motor driver board (ST330-v3 - page 7)

Timing diagram from the datasheet:

The board need sequence of signals, which i tried create by this code. but aren't sure if the code follows  the timing required, or descriped in the data sheet.

Which is why i hoped that any of you guys could look through the code and see if the timing fits or not..

Here is the code:

.h file:

/* Class: stepper_motor
 * Info: contains the setup, and primary interface to control
 * the stepper motor
 *
 * stepper_motor(): constructor -  setup the connection to the control board
 * void step_pwm():  Moves the tilt - uses the bool to determine the direction.
 * bool alive_bool: Is either high (1) or low (0), used for the alive void.
 */

#ifndef stepper_motor_h
#define stepper_motor_h

#include "Arduino.h"
#include "pins_arduino.h"

#define step_pin  D0
#define dir_pin   D1
#define en_pin    D2

 class stepper_motor
{
  public:
    stepper_motor();
    void alive();
    void init_communication();
    void step_pwm();
  private:
    bool alive_bool;
    bool position_bool;
};

#endif

.cpp file

#include "stepper_motor.h"

stepper_motor::stepper_motor()
{
  pinMode(BUILTIN_LED,OUTPUT);
  pinMode(step_pin,OUTPUT);
  pinMode(dir_pin,OUTPUT);
  pinMode(en_pin,OUTPUT);

  alive_bool = true;
  position_bool = true;
}

void stepper_motor::alive()
{
  if(alive_bool == true)
  {
    digitalWrite(BUILTIN_LED,HIGH);
    alive_bool = false;
    delay(2000);
  }
  else if(alive_bool == false)
  {
    digitalWrite(BUILTIN_LED,LOW);
    alive_bool = true;
    delay(2000);
  }
}

void stepper_motor::init_communication()
{
  digitalWrite(step_pin, HIGH);
  digitalWrite(dir_pin,HIGH);
  digitalWrite(en_pin,LOW);

  delay(0.01); //t1

  digitalWrite(step_pin,HIGH);
  digitalWrite(dir_pin,HIGH);
  digitalWrite(en_pin,HIGH);

  delay(0.005); // t2

  digitalWrite(step_pin,HIGH);
  digitalWrite(dir_pin,LOW);
  digitalWrite(en_pin,HIGH);

  delay(0.005); //t4

  digitalWrite(step_pin,LOW);
  digitalWrite(dir_pin,LOW);
  digitalWrite(en_pin,HIGH);

  delay(0.0025); //t3

  digitalWrite(step_pin,HIGH);
  digitalWrite(dir_pin,LOW);
  digitalWrite(en_pin,HIGH);

  delay(0.0025);

  digitalWrite(step_pin,LOW);
  digitalWrite(dir_pin,LOW);
  digitalWrite(en_pin,HIGH);

  delay(0.0025);

  digitalWrite(step_pin,HIGH);
  digitalWrite(dir_pin,LOW);
  digitalWrite(en_pin,HIGH);

  delay(1000);

  digitalWrite(step_pin,HIGH);
  digitalWrite(dir_pin,HIGH);
  digitalWrite(en_pin,HIGH);

  delay(0.005);

  digitalWrite(step_pin,LOW);
  digitalWrite(dir_pin,HIGH);
  digitalWrite(en_pin,HIGH);

  delay(0.0025);

  digitalWrite(step_pin,HIGH);
  digitalWrite(dir_pin,HIGH);
  digitalWrite(en_pin,HIGH);

  delay(0.0025);

  digitalWrite(step_pin,LOW);
  digitalWrite(dir_pin,HIGH);
  digitalWrite(en_pin,HIGH);

  delay(0.0025);

  digitalWrite(step_pin,HIGH);
  digitalWrite(dir_pin,HIGH);
  digitalWrite(en_pin,HIGH);

}

The init_communication() is here in question.

Thanks in advance


texts: Re-building a Crock-pot controller - how are the heating elements powered?

texts:
After a few good years, my CrockPot gave up. It looks to me that there may be something wrong with electronics, and being and Arduino enthusiast, I thought I could re-build it. The symptoms are that the whole device switches on but whenever the actual program is set, it just switches itself off again (goes dark).

From what I can see there is one heating element and a temperature probe attached to the main body (white wire):

.. another view at the connections:

The main circuit board features connection of the temperature probe (NTC1) and a transistor to switch the heating element on/off, as well as all of the buttons, display and power processing components:

The markings on the main driver are can seen on a closeup here:
(probably this one: http://www.nxp.com/documents/data_sheet/BTA208X-600E.pdf)

Rear view of the circuit board:

Is my assumption correct that there is probably something wrong with the controller and the heating elements are most likely fine & can be reused?

My main hurdle is to understand exactly what the circuit may look like in this case and how much of it do I need to re-create for basic control. I am happy to design the control/arduino part but for exact understanding what are the requirements of the heating elements, that is where I need help!

Update

I've now also measured resistance between the red and black wire (heating element) - 250Ω.
The thermistor seems to be clocking at 13.8kΩ.


texts: Placing capacitors between opposite rails in an unregulated power supply

texts:
I am making an unregulated dual rail power supply for an audio chip amp from a center tapped step down transformer and bridge wave rectifier. There are capacitors between the ground and the positive, negative rails. Is there any problem with putting capacitors between the positive and the negative rails besides the above mentioned capacitors? If not what are some pros and cons.
I have never seen such implementation. I thought it would be beneficial as it would store more energy at higher voltage.


texts:
See edits at bottom:

I'm trying to design a network of circuits (see example below), in which a modular circuit (non-static, can be change, with high variability in current draw) is connected on any of several PCB positions, and while drawing power, can detect the position it is located.

Min Current: 0.1mA, Max Current: 600mA

Due to mechanical constraints, no additional connections (i.e. only PWR, GND) can be made between PCB position #, & modular circuit.

My idea is to PWM (100Hz, could be higher) the PWR line, and use a high-pass filter to eliminate lower freq's. Modular circuit will check for what freq removed.

Any other advice is also welcome,

*******in response to comment about not being clear:******

Maybe to simplify imagine using a Smartphone USB Charger, and connecting custom split cable to several PCB board (as many as 24), with battery connectors. Then modular circuits are attached to battery connectors and they need to know which position their in.

Based on suggestion by @WhatRoughBeat, i've added another possible schematic, of a voltage divider, instead of pulse train.

Please Note: in original question/schematic I made some error, the following have been corrected:
(1) schematic, Switched from low-pass to high pass of using low-pass filter;

(2) schematic, Switched from plain diodes, probably schottky

(3) added current max/min

(4) lower PWM from 1KHz to 100Hz, to help reduce EMI

(5) modified title


texts: How to solve this block diagram. I am only having difficulty with G3?


texts: Will an AC/24V DC-40A charger power a 24V/10-15A pump, regardless of battery bank (6) condition?

texts:
This relates to a boat, having a bank of 6 batteries (12V/250AH) in series, to produce 24V.  The battereis are 5 years old, regularly checked and maintained and dash monitored digital voltmeter consistently at 26V to 28V.

An AC to 24V DC/40A on board charger constantly on, with AC shore power.

The circuit being DC charger/24V battery bank/automatic bilge pumps, with no other DC draw.

Question: regardless of potential battery condition, in this circuit, should the 40A/DC charger continue to provide adequate power to operate the 24V/10-15A pump?


texts: What is the maximum and minimum of antenna gap of dipole antenna?

texts:
Consider the picture below is design of half wave length dipole antenna. I read some explanation that it is the best design to get the optimum transmit power. Or it is cut to 0.47Lamda to 0.48Lamda to get the optimum impedance (CMIIW).

But my concern here is, what is the minimum or maximum distance of the gap as in the picture? Gap between the two elements which the feeder line is connected?


texts: How to use supply voltage for a small circuit from a huge variable power supply?

texts:
I have a 300 watt solar panel whose voltage and current need to be monitored by installing a device there. There is no source of power supply that I can use for this monitoring device but the solar panel itself. How do I extract this small voltage from the panel?
Note that the solar panel is a variable source of energy. Hence, Just voltage divider won't work.
The panel produces voltage in the range of 0-40 V depending on sunlight. In absence of sunlight my circuit can switch off.


texts: Purpose of this Zener diode (reverse protection)

texts:
I have the below MOSFET circuit:

Zener diode - Datasheet
N-channel MOSFET - Datasheet
I want to understand what is the purpose of the Zener diode D5202 and at what conditions does the Zener diode come into action?


texts:
I'm looking for my old Fluke 23 service or calibration manual but all the Fluke 23 I find in a google search are the series II or series III. Mine is the oldest I guess, it has no series. Thanks.
UPDATE: Added pictures as requested. Left: With holder front, Middle:No holder front, Right: No holder back


texts: How do I decople a microcontroller with odd number of ground pins?

texts:
I'm building a DIP adapter board for MSP430FR5739 and I want to include the decoupling capacitors on the adapter board itself.

From what I can see, I'll need a capacitor on the analogue and digital ground pairs plus one on the Vcore pin whose other side I'd connect to DVSS.

This leaves me wondering what to do with pin number 38, the second AVSS pin.

What would be the best way to decouple it?


texts:
I'm currently trying to design a system that incorporates an ADP5092 which can use a supercapacitor as the storage element but I am also considering other similar PMIC chips so this is more for reference. In this application the load system will include a transmitter so there will occasionally be large short duration current draws at a maximum of around 130-140 mA for sub-millisecond durations.
In the ADP5092 datasheet there are reference designs which mention a specific 220mF supercap is rated at 5V and has low ESR (300 mΩ) and is fairly expensive.

My understanding is that the PMIC voltage into the storage element should be well regulated and for example if configured for 3.3V should output reliably at 3.3V to the storage element. Does this mean that a supercap voltage rating could be chosen for 3.3V + negative tolerance?
e.g. tolerance -20%, 80% --> minimum 1.2 * 3.3 = 3.96V+ rating

Is the ESR value important:

In general for a power storage supercapacitor?
For this application (intermittent high TX current draws)?

If the ESR is not important a larger variety of supercaps are available with prices up to 5x lower than the one used in the example could be used and lower voltage rating further increases the available options due to the generally low voltage of supercaps.


texts:
I'm a electronics newbie, and I'm making a project with 8 24v solenoids playing percussion quickly. I want to power these all with the same power source, so I'm being careful.

This is similar to power supply unit for Arduino/solenoid project but different in the fact that I am trying to sense-check what the manufacturers say about their products.

Some solenoids are spec'ed as having a draw of around 350mA:
http://www.adafruit.com/product/413

And others are spec'ed as having a draw of 2A:
http://www.amazon.com/0-7kg-Holding-Force-Solenoid-Electromagnet/dp/B009PMCSFO/ref=sr_1_4?s=industrial&ie=UTF8&qid=1431813437&sr=1-4&keywords=24v+2a+solenoid

Are these two options just different in terms of the power of the solenoid's movement (i.e. the 350mA will be considerably weaker than the 2A)? If I went for 8 x 2A 24V solenoids would a 20A 24V power source be enough to power everything  at its peak usage?

Thanks :)


texts:
Im trying to develop the PWM-Switch Model of a Cascaded-Buck-Boost.

First of all i want to extract the Large-Signal Transfer function for the Buck-Mode.

I'm working through the book "Switch-Mode Power Supplies_ SPICE Simulations and Practical Designs" from C. Basso (here: https://cbasso.pagesperso-orange.fr/Spice.htm)

and the APEC 2013 Seminar: https://cbasso.pagesperso-orange.fr/Downloads/PPTs/Chris%20Basso%20APEC%20seminar%202013.pdf

My problem is, i cant get the jump of the Topology from Slide 57 (in the Seminar) to Slide 61 (Maybe i think Slide 57 is the Buck, and 61 is Boost?)

But anyway, I have problem rearraging my Topology to see clearly what my next step is .. maybe someone can help me to get further:


texts:
I have an application which would involve having data lines connected to a microcontroller which would signal at lvttl (3.3v) levels and also take in 24v for a resistive load (~600mA). I have previously used a mechanical relay for this same application without any major issues. I'm in the process of switching the microcontroller on this to something more modern, more powerful, cost effective and much smaller in size and decided to switch out the mechanical relay with a Solid State Relay. This would provide much higher life for the product, help me with making the part smaller and at the same time make manufacturing easier as the pick and place can mount the SMD SSR not requiring me to hand solder these separately.

From the datasheet I'm using connection "C" as that would be more suitable for the load I'm planning.
My issue is: The application my board connects to has a common ground. The lvttl lines and the 24v input both share the same ground, how would I handle that if I'm using a G3VM-61E1 or something similar? It seems internally the logic is similar to an N-Channel style mosfet.

So how would I handle giving both my digital signals and HV supply a common ground in this case?
If this isn't the right place to ask this question, please feel free to point me in the right direction or any resource you think is more appropriate.
Thanks,


texts: SMPS Control - Comparator in Sinking or Sourcing Configuration

texts:
Tried something for fun: I modified a constant-current-output SMPS' feedback-control block which is in sinking configuration to sourcing configuration.
Here are the simplified schematics of the secondary side:
Before:

simulate this circuit – Schematic created using CircuitLab
After:

simulate this circuit
The circuit is not working in sourcing (latter) configuration. It works if I revert it back to the sinking (former) configuration.
Does it really make a difference? What can cause this "problem"? What may I have done wrong?


texts: Producing electricity from heat on a small scale?

texts:
Using a small solar panel like in the following picture we can produce around 0.935W of power with a peak voltage of 5.5V and current of 170mA under good sunny conditions

Does a similar type of small device exist which we can turn heat into small amounts of power like in the above?


texts: Why is conventional current still taught in school when it is unreal, given that real current flow is electron flow?

texts:
Conventional current as a concept is easily understood until the professor says what actually takes place is electron flow. Electron flow moves in the opposite direction as conventional current.

Why doesn't electrical engineering text books teach electron flow current since it reflects the actual situation more accurately?

I am sure I have missed out something. Can the more learned members here enlighten a confused person?


texts: How to detect which timer interrupt called callback when using ASF?

texts:
I have a general function, which gets passed among others a timer. It initializes the timer using common callback function:

void setup(config_t* config) {
    ...
    tc_enable(config.timer);
    tc_set_overflow_interrupt_callback(config.timer, common_callback);
    ...
}

That function might be called a few times with different configurations, timers included. In the interrupt callback I'd like to somehow identify which timer caused the callback.

void common_callback() {
    // Which timer called?
}

I did not find an asf tc_ function that would give me some kind of id.

I tried looking at TCXX.INTFLAGS, but the overflow flags seems to get reset by the asf code.
A hacky approach I could come up with is comparing the count register

Is there a simple way to do this using Atmel Software framework. I assume asf has an internal interrupt handler that does thing like reset the interrupt flags before calling the user defined callback. Another approach would be write similar tc_set_overflow_interrupt_callback-function that would keep some of that information.


texts: Interpretation of Time Domain simulation output

texts:
I have the following circuit and I want to know the voltage on each node and the current on each loop. I've run the Time Domain simulation (I'm not sure of the differences between this and Bias Point simulation) and I've got the following results:

However, I'm not sure about what figure points to what nodes and loops. Can you give me a hand?

Thanks


texts:
I want to filter out high frequency noise on my power line. At first, I was considering to use an LC filter on the line; but then, I learned about choke filters are used exactly for this purpose. However, I can't find anything specifically about choke inductors on Google since 'choke' word alone is common in the language and if I added the word 'inductor', I end up with inductor tutorials containing the word 'choke'.

The noise is superimposed on the mains voltage for some background reason. The voltage on the resistive load without any filtering is as expressed below.

$$
V_\text{LOAD} = 120\sqrt{2}\sin(2\pi60t) + 5\sin(2\pi50000t) \quad\text{Volts}.
$$

I want to design this choke filter myself by using a ferrite E-core which already exists in my inventory. I roughly know the basics for the transformer design. At the nominal working frequency, the primary side inductive reactance must be small enough to keep the magnetizing current small. I understand that my choke must behave as a voltage transformer at 50kHz by inducing a reverse voltage same in magnitude. I also understand that it should have negligible effect on the 60Hz line voltage.

But how? What are the critical design parameters that will make the choke allow the 60Hz signal while blocking the 50kHz one? I think the number of turns will be same, thus the winding self inductances will be the same as well. The winding inductances must be on of the critical parameters. What are the other parameters of design? Can you please shortly summarize me the design steps?

Also, I browsed some commercial products. They specify a saturation current limit. Why does a choke inductor saturate? I mean, the current flows through the windings in reverse direction which will create reversely flowing fluxes in the core and they will cancel out each other making the net flux zero technically. What causes the core saturation in choke inductors?


texts:
I have an assortment of T1 and T1¾ LEDs from sampler kits and beginner kits. The kits have sketchy documentation, with missing or inaccurate part numbers. I was able to track down datasheets for some of them, like the “WP7113HD” and the “L934LID.” For others, all I have is a description like “Violet Hi-Br Clear.” So I have several LEDs with a missing or questionable datasheet. It looks like they all of the LEDs expect 2mA, 10mA, or 20mA forward current, but I’m not sure which are which.

Another complication is that some of the datasheets are ambiguous about the intended forward current. For example, the WP7113ID datasheet specifies luminous intensity relative to IF=10mA, but most of the optical and electrical characteristics are given for IF=20mA. So even with the datasheet, I’m not sure whether that LED is supposed to be driven at 10mA or 20mA.

How should I choose a forward current for these LEDs? What will happen if I get it wrong and drive a 2mA LED at 10mA, or a 10mA LED at 20mA? I think they are all safe for up to 25–30mA, but I suspect that it’s not a good idea to overdrive them.


texts:
I am making an opensource automated wireless window blind controller.

It uses a motor to open and close standard metal blinds.

Below are links to the project documentation:

Full project page
Schematic

I have very little experience designing circuits.

This circuit features a continuous servo to open and close the blinds, limit switches to detect when the blinds are fully adjusted in either direction, a solar panel to charge, batteries, an optical sensor to detect room light levels.

The circuit should power the motor to move the blinds, charge the battery when it's not full, not overcharge the battery or charge too quickly so as to cause a fire, allow wireless control via the ESP8266, and detect ambient room light levels. And minimize cost for people wanting to make this. Maybe I could provide kits to give bulk discounts on materials...

Please tell me what is right/wrong with this circuit. I will purchase the parts soon but when I jump the gun and buy things, I am usually told I should have asked for advice before wasting my money. So here I am, please advise :) .

Edit:
Clarification of question- Will the battery charge? Did I wire the ESP8266 correctly? Is the ESP8266 a good choice for wireless communication? Or should I use a different module?

Additional details-
here is the ESP8266 seeedstudio.com/depot/WiFi-Serial-Transceiver-Module-w-ESP8266-p-1994.html?gclid=COCWyoLuscICFREpaQodznEA2g


texts: Using "oscillator" rather than crystal for MCU

texts:
I'm kinda new to this so the name is based on Digikey. I have a PIC24FV32KA304 and I want to put an external oscillator of 32mhz. I found out that an oscillator like this one is a bit cheaper than say, like this one.

This is the configuration I thought using a crystal :

My question is, if I want to use an oscillator rather than a crystal, how do I connect the output of it to pins 30 and 31 ?


texts:
I am developing a product that uses the Atmega328P (currently using Arduino nano as the development board). I would like to keep the software private, but also have the option to update it during the products life-cycle.

the way i am currently thinking is programing the 328P using ISP and locking the relevant fuse bits to prevent reading. I don't want to use the DIP version  (based on potential customer base feedback, it looks cheap and outdated WRT other forms like TQFP, unfortunately this is actually important enough to warrant a design change)  .

Can i use a TQFP with a mounting like this, and then have the user be able to take the chip out to replace it with one that has an updated software? or is this not feasible (is it stable enough inside a socket and not soldered to pcb, is it too difficult for normal person to swap, or the possibility of damaging the chips or putting it in wrong are high, these are my concerns.)?

Also, my plan is to use a potting compound for the PCB/case and have it go around the perimeter of the previously mentioned socket and about 3/4 of the socket height due, to the thermal/vibrations stresses in the environment.


texts: I'm embarrassed how many times I've used ordinary BJT transistors in circuits that clearly would have been better suited to a FET, and even better a MOSFET. This is because as a lifelong hobbyist, I have a huge stash of common BJTs, and sadly the days of well stocked "neighborhood" electronic store are long gone. Experimenting always requires ordering parts first. Now I understand MOSFETS well enough to pour over specs and parameters and make choices, but maybe someone with more experience could point me to a short list of "general use" enhancement mode P and N channel mosfets that are both inexpensive and readily available as both SMT and through hole parts, that I  basically couldn't go wrong ordering a supply of. I realize there are thousands of good choices, but if you consider that the old familiar (and cheap!) 2N2222 (NPN) and 2N2909 (PNP) BJTs have satisfied the bulk of my needs for simple switching or basic amplification apps for as long as I can remember, perhaps some parts will come to mind. I very seldom need to handle more that 500mA, and usually have low voltage and power requirements (15VDC, seldom more than 1W). Honestly most of my needs are for switching and about the only 'specialty" wishlist item I have is that the lowest "on resistance" would certainly be worth a few cents more. Suggestions welcome.


texts: Switches needed in an n-location multiway switching system

texts:
Wikipedia shows us we can construct a two location multiway switching system with two 3-way switches:

They also teach us how to perform three location multiway switching with two 3-way switches and one 4-way switch:

Is it possible to make a similar system (three locations, all able to switch the light in any situation) with only three 3-way switches?

What can be said in general about the switches needed to make an n-location multiway switching system?


texts: Why should one buy through digikey or element14?

texts:
I quite often find that digikey or element14 have quite expensive pricing for the parts, right now I'm looking for memory chips and compare it to ebay sellsers:

http://www.digikey.com/product-detail/en/W25Q80BVSSIG/W25Q80BVSSIG-ND/2202664

http://www.ebay.com/itm/10Pcs-W25Q80BVSSIG-SOP-8-SPI-W25Q80B-Original-SMD-FLASH-Memory-/181471914814?pt=LH_DefaultDomain_0&hash=item2a4091ab3e

And this is not the only case, I've seen ridiculously expensive(like double or triple price) chips on element14.

I understand that on ebay you can get counterfeit parts, but it is so rare, all parts I get are good ones. So the question is why should one use digikey or element14 sites? It is said everywhere that it's better to buy there, but why would I want to buy a chips for 4x price(above example)???
I'm not trying to be aggressive against these sites, just don't get the reason of buying there.


texts: Does anybody know what this electronic component is?

texts: I have an electronic component which has no letter or number on it. It has 2 legs and when you shake it there is something moving inside up and down. I am searching for it for hour still have no clue. Here is the photo I've just taken:


texts: Breaking out a few QFP footprint to a small connector

texts:
I have a PCB that has an realtek RTS5169 controller IC(QFP-48) on it. The IC itself is attached to USB data lines. I want to remove this controller and add another USB device to the PCB. Now I don't really know what is the best way to attach a flat connector to this footprint. Essentially I only need 4 wires of the entire footprint but since the PCB will be in a mobile device I'm not sure how to proceed. Is there some best practice kind of way to do this?
Any help is appreciated!


texts: Switching between 2 24V 30A power sources

texts:
I am trying to make a changeover switch. The current at full load which the switch needs to handle is 30A.
I looked into automotive relays, but I believe they are not rated for continuous use.
I also found out about shotcky diodes, but I believe they are not suited for my needs, here is why:

The two sources consist of:
One solar charger controller which will output battery voltage and eventually cut at 22V low voltage and 3 parallel 24V smps

If my understanding is correct, using shotcky diodes will work, but as soon as the battery bank will reach a value lower than the smps the power will be drawn from this. Also there will be some power loss, which I would like to avoid.

Instead I would like the system to be powered until the battery reaches 22V and only then it should switch to the smps. Once battery output will be again available from the controller, the system should switch back to battery.

I thought of using mosfets, but I don't want current to flow back trough the body diode to the controller or to the smps.

Any suggestions?


texts:
I have a cooked component that I believe to be a ZNR since it is labled JNR01J and is in series with a 125V T2A fuse. It is from an air conditioner PCB. It was cooked while using a portable generator (also cooked the cable box and 1 power strip).

I can't find any cross reference to this component. Any help would be greatly appreciated.


texts:
I have a component, which is added several times by a generate command:

Gen_RayMemory: for i in 0 to RayCount-1 generate
    Mem: RayMemory
    generic map(
        length_data => Data_length,
        length_ray => RayLength,
        direction => '1'
    )
    port map(
        clk => clk,
        i_start => i_user,
        i_data => i_data,
        i_store => Rays_save(i),
        i_invalid => Rays_invalid(i),

        r_rd => select_ray(i),
        r_data => data_out(i) --    <- Fix here (std_logic_vector)
    );
end generate Gen_RayMemory;

Lets have a look a the ports starting with r_ only. Always only one of the components is enable by the r_rd signal. The enabled component will put its data to r_data.

Is there a elegant way, to combine these outputs to a single data_out? They could be OR-ed or multiplexed by select_ray(i).


texts:
I've spent a decade or two noodling around with logic gates on paper and in various simulators. By this point I think I have a good understanding of how to use them to build things. Now I'm interested in actually building real electronics with this knowledge. In theory, theory and practice are the same. In practice...
Question: How to real, physical logic gates differ from their theoretical cousins? What do I need to watch out for?
From my research so far:

Real gates take a finite amount of time to respond to their inputs ("propogation delay").
The exact propogation delay is not guaranteed to be the same for all the gates in the circuit.
Each output can only drive some finite number of inputs ("fan out").
"Unconnected" ≠ "logic low". To get logic low, you have to actually connect to (−).
Unconnected inputs are catastrophically bad and will cause your soul to burn in agony for all eternity.
It is not possible to construct fast logic circuitry without a PhD in advanced electrical engineering and several billion dollars worth of specialist hardware.

Have I missed anything? What other traps await me?


texts: How much current does this stepper motor need?

texts:
I have a Astrosyn Miniangle Stepper motor that I just got and I need to know how much voltage and current I need to drive it. I am having trouble finding the specs online so I am trying to understand what the stuff written on the motor means. It says:

2.3 V/Phase
2.3 A/Phase
1 Ohm/Phase

Does this mean that It needs 2.3 volts and 2.3 Amps, and that the coils are giving 1 ohm of resistance?


texts: Which configuration is better for pulling down an NPN transistor's base?

texts:
I was discussing on pull down resistors with a colleague of mine. Here are the two configurations for transistor as a switch.

The input signal can either come from a microcontroller or an another digital output to drive a load, or from an analogue signal to give a buffered output from the collector of the transistor to the microcontroller.

On the left, with Q1, is my colleague's configuration. He states that:

A 10K resistor is needed directly in the base to prevent the Q1 from switching ON unintentionally. If the configuration on the right, with Q1, is used, then the resistance will be too weak to pull the base down.
R2 also protects \$V_{BE}\$ from over-voltage and give stability in case of temperature changes.
R1 protects from over-current to the Q1's base, and will be a bigger value resistor in case the voltage from "uC-out" is high (in example +24V). There is going to be a voltage divider formed, but that doesn't matter as the input voltage is high enough, already.

On the right, with Q2, is my configuration. I think that:

Since an NPN transistor's base is not a high impedance point like a MOSFET or a JFET, and the \$H_{FE}\$ of the transistor is less than 500, and at least 0.6V is needed to turn the transistor ON, a pull-down resistor is not critical, and in most cases is not even needed.
If a pull-down resistor is going to be put in the board, then the value of exact 10K is a myth. It depends on your power budget. A 12K would do fine as well as a 1K.
If the configuration on the left, with Q1, is used, then a voltage divider is created and may create problems if the input signal, that is used to switch the transistor ON, is low.

So, to clarify things, my questions are:

Is 10K pull-down resistor a rule-of-thumb that I should apply everytime? What are the things to consider when determining a pull-down resistor's value?
Is the pull-down resistor really needed in every application? In what cases the pull-down resistor is needed?
Which configuration would you prefer and why? If none, what would be a better configuration?


texts: Altium custom shield as component, allow other component to be inside

texts:
I'm creating a shield for arduino and to avoid recreating it in future, I created its base as component(both schematics and pcb) and only added arduino header pads in it. Everything is just working fine except in PCB designer when I put any other component inside the shield component, then both components gets green(error). Which is very correct behavior though. But I want other components to be inside as its a shield.

I even set shield component height to 15mm. But still error is not going away.

Edit (inserted 3D screenshot) :

How can I make shield component allow to have other component inside ?


texts:
This is my first question here and I am new to board level digital design(I have years of experience on programming development boards though).

So here is my question, what are the differences between different footprint surface mount RLC components? To be more clear, i quote some data from Wikipedia article below

For resistors it seems like only power rating is different for different footprints.

For example does it make any difference to use a 0402 or 0805 footprint 50ohm resistor as terminating resistor? Or as long as given spec data is same, does it matter to use a 0402 or 0805 470nF ceramic capacitor as decoupling capacitor? Why I ask this? Because I am
designing an FPGA board using some reference designs and I plan to make board assembly at home :) I want to use bigger components as a beginner.

0402 (1005 metric): 1.0 mm × 0.5 mm (0.039 in × 0.020 in). Typical power rating for resistors = 0.1 or 0.062 watt

0603 (1608 metric): 1.6 mm × 0.8 mm (0.063 in × 0.031 in). Typical power rating for resistors = 0.1 watt

0805 (2012 metric): 2.0 mm × 1.25 mm (0.079 in × 0.049 in). Typical power rating for resistors = 0.125 watt


texts: Calculation of inductance of rectangle coil

texts:
I'm currently working on a project about inductance. I want to calculate the inductance of a rectangle-shaped coil with a pitch different from zero. I tried this by applying the law of Biot-Savart. If i do this for one wire in a cartesians axis system i get a formula of the shape \$B=\int{\frac{(y-y_0)}{\sqrt{((x-x_0)^2+(y-y_0)^2)}^3}}\$ from 0 to \$x_0\$ or \$y_0\$. Which i can't integrate by hand or by numerical integration in matlab (singularity at \$y_0\$). If i write it out in polar coordinate system, i get \$B=constant*(\sin(\theta_2)-\sin(\theta_1))\$. But i can't figure out how to calculate the magnetic flux (phi=int{B dA}). And numerical integration has again some problems with the singularity close to the wire.

Has someone a better idea to calculate the inductance instead of using Biot-Savart? Or someone who knows how to integrate those integrands. Thanks a lot!


texts:
[![enter image description here][2]][2]I am trying to simulate a FIFO generated by the IP Catalog.

I chose for the FIFO implementation an independant clock BRAM with empty full almost empty almost full flags.

It is 7 bits wide and 16 bits deep.

I don't understand when I deassert the reset all the flags remain at '1' it means that FIFO is empty and full at the same time?

Then I assert the write enable to '1' and I write a couple of times the word '03' in the FIFO but it takes me 11 read clock cycle to finally read the word '03' and it reads it only twice, but I wrote the word more than two times.

And during the write and reading the empty and full flags don't make sense to me


texts: Role of resistors in SCLK-CS-DI-DOUT lines in SD card circuit

texts:
hope everyone is safe and well.
I want to design a microSD card circuit. I searched for a reference design I noticed that they add a resistors in series in SCLK-CS-DI-DOUT lines.Catalex-Micro-SD-Card-Module
My questions :

why they are adding this resistors?

How can I determine their values?


texts: Question about the power rating of a RF power amplifier

texts:
In HMC453ST89's datasheet, it gives the electrical specifications when Vs = +5V:

The max. output power is around 32.5dBm, about 1.6W. But for a 50 Ohm load, 1.6W means the peak voltage is about 12V. How is it possible with Vs = 5V?


texts: How to measure RSSI of bluetooth devices on PC

texts:
I'm a student in highschool doing research for a science project. I want to measure the RSSI of bluetooth devices on my Windows PC. I've searched on the internet for around 3 days but found no success.

The only method seems to be using a software called Bennett. However, it doesn't give me the signal strength. I contacted the company and they said Windows doesn't support such measurements. They told me to install Bluesoleil to run their software. However, Blueleil seemed to be not working on Windows10 and their website seemed quite sketchy.

I also heard that I could measure bluetooth signal strength on Mac OS. However, when I tried the same thing shown on online tutorial with my friend's mac, it didn't work. It seems like Apple removed the feature as time passed.

So I've thought about getting an Arduino and a HC-05 sensor and use some methods discussed on this website to get RSSI. But it would take some time to order the parts and get that thing working. I'm in a hurry as the deadline for my project is incoming, and I've got basically nothing done.


texts: I'm designing an audio equalizer with the option to relay switch between a solid state and transformer output path. I'm worried that the relay will cause an audible pop on the output as the relay switches. My thought is to use an additional relay that creates a resistive path to ground a moment before the output relay switches and remains active until the output switch becomes stable. I'm thinking for half second before and half second after. This needs to be accomplished with the Output Select DPDT switch. When the switch is activated the resistive shunt relay would need to activate half a second before the output relay switches and release half a second later. This process will occur each time the switch is pushed in or out. I will have 24 volts to activate the relays and the circuit. Does anyone have ideas


texts: Multiple nrf24l01, shared power, ripple/interference, DSO screenshot provided

texts:
I've got this circuit with 3x atmega328 & nrf24l01+ running off shared power supply, either 2x AA battery or 3v3 reg.

It acts as a repeater, and depending on the origin of the message and the destination it could be passed through all 3 radios on its way. And sometimes when I send signals through it, they don't get to their destination.

Generally at higher PA (power amplifier) settings it is less reliable, though I don't think its RF interference as I have tried them at varying distance from with each other with little change. Also if I run all 3 separate on their own batteries, I can have them as close as I can get, right next to each other and it works fine at max PA.

I think it is more power related. I have tried big electrolytic cap on power supply and 100nF on the module them self.

On my scope I have seen various interference pattern in the voltage supply, as pictured.

Generally I see patterns like this at same time message have trouble reaching their destination.

One radio/328 by itself is not a problem, it seems when they all run off the same supply each of their individual ripple is combined to make something that has effect.

I am hoping someone can look at the capture and recommend something?

*edit, added 2nd grab.

100N cap:

470uf cap:

2x470uF on each, scope on cap leg:


texts:
I've created 3 or gates in an electric circuit with transistors (bipolair npn). I've tested 3 OR gates. with no transistors, with 1 transistor (the same as no, but the output is going to a single transistors base), and with 2 transistors. I've checked the output with an LED. All OR gates give the right output. After that I've created 3 XOR gates, an NAND gate and an OR gate ging into an AND gate. Switch A goes into input 1 in the NAND and the OR and switch B goes into input 2 in the NAND and OR gate.
Only the XOR gate with the 2 transistor OR gate works but I have no idea why the others don't work. any help?

I'm using a breadboard with a 5V DC source with a max of 2.1A (phone charger)

circuit is here:

Solution: if A is true and B isn't, current can flow to a transistor of the nand gate.


texts: I'm struggling to decide if this capacitor is 150pF or 68pF (and in the latter case, what does the 151K stand for?)


texts: Op-amp and ideal diode problem: determine Vout as a function of Vin

texts:
"Determine and graph v OUT as a function of v IN for the circuit
shown in Figure 16.31. In doing so, model the diode as shown in Figure 16.29, and
assume that the Op Amp is ideal. Also, contrast the input-output behavior of the circuit
shown in Figure 16.31 with that of the half-wave rectifier studied in the chapter on
nonlinear analysis."

I'm confused what happens when the diode is off. Can someone explain?
here's the circuit:

thanks in advance.


texts:
Theoretical question: I was told by an auto mechanic friend that replacing a clockspring in the steering wheel of a car with concentric conductive rings (separate ring for each component powered such as horn, airbag, etc.) on the steering column-side and contacts on the wheel assembly-side (thus replicating what the CS does now) would not be feasible. He mentioned this is because of the resistance the copper (or whatever material used) would pose too large of an impedance to DC current for it to be used.

Is this true, and if so, why? I understand current flow, impedance, and so forth, but I'm having a hard time conceptualizing why it would be insufficient.

For those that are wondering, I'm not asking because I plan to do this, but rather I was trying to envision a simpler solution to a complex clockspring that could be used in this application.


texts: what's the fastest way for switches the high voltage?

texts:
i want to use relay for project that the electricity will turn on and off about five times per second ...
30 volt 5 ampere DC i think will work for the project , and the load is Resistive ...
is there any relay that can support that rate .. ?
i think the normal relay won't work but what's the solution ?
totaly what's the best way to switch the high voltage with highest speed and accurate ..?
it's too important for me to switch several times on or off in one second ...
anyone can help me please ??


texts: Thevenin equivalent with dependent source

texts:
Well, I'm trying to find the Thevenin equivalent of this circuit:

As you can see, the only current source is a dependent source. However, the control variable is in a wire where, if nothing is connected between A and B, is \$i_\Delta = 0\$ A, and that makes the source 0 A. However, if I connect an impedance \$Z\$ to the circuit, I will have current, and a Thevenin equivalent. I don't know how to solve this problem. I've bee searching here for a while, and I found this: Thévenin equivalent with a dependent source
. I can see how is solved that case. However, I still don't know how to apply that method to my circuit.

Any help about finding the Thevenin equivalent is appreciated n.n


texts: Why is this second order system difficult to control?

texts:
Why is system of the type

$$T = 1/(s^2 - 1)$$
Difficult to control using standard control methods?

When I look at frequency plots, it doesn't seem to give me any important information as to why this system would be difficult to control using classical methods

Can someone who knows control theory (especially the part about compensators or other classical control techniques) inform me as to why this system would be difficult to be controlled using classical frequency based methods?

http://link.springer.com/article/10.1007%2FBF00933284


texts:
As I'm a complete novice, I thought I'd start with something really simple: making a led blink. According to several websites, this is something everyone should be able to do... Hmmm... In my case, the LED doesn't do anything. It stays dark. Why?

This is the program I've written (on a Ubuntu 12.04 machine):

#define F_CPU 1000000UL

#include <avr/io.h>
#include <util/delay.h>

void sleep(int milliseconds)
{
while (milliseconds > 0)
{
    _delay_ms(1);
    milliseconds--;
}
}

int main()
{
// set lowest bit to output in DDRB register
DDRB |= 0x01;

while(1)
{
    // switch led on
    PORTB &= 0x01;
    sleep(500);

    // switch led off
    PORTB &= 0x00;
    sleep(500);
}

return 0;
}

Then I followed these steps:

Compiled my program:

avr-gcc -mmcu=atmega8 test-001-blinkingled.c -o test-001-blinkingled.o -Os
Hex

avr-objcopy -j .text -j .data -O ihex test-001-blinkingled.o test-001-blinkingled.hex
Uploaded to the microcontroller (using an AVRISPmkII):

sudo avrdude -p m8 -P usb -c avrispv2 -U flash:w:test-001-blinkingled.hex -F -v

with following result:

This is a picture of my very basic circuit:
(I use an old 9V adapter for power, so I used 2 resistors to regulate the voltage to 4.95V)

What am I doing wrong? If you see other strange or stupid things, please educate me!


texts: ISE: Force the compiler to accept long loops

texts:
At the moment ISE limits generate loops to 64. When I go above, it produces the error:

  Loop count limit exceeded. Condition is never false.

I found that the loop_iteration_limit option should be added to the corresponding project .xst file. However, when I add the line -loop_iteration_limit 10000 to the .xst file, and recompile, that line disappears.

How can I do long loops in Verilog with ISE? (The reason I want to do this is to instantiate many copies of an inverter to try to heat up my FPGA and test the power supply.)


texts: online band pass filter calculator confusion?

texts:
I am using a bandpass filter calculator online https://rf-tools.com/lc-filter/ , and for some reason it is calculating some capacitor values that are usually a polarized electrolytic capacitor like for example an 330 uF.
Can I use a electrolytic capacitor, or can I put multiple non polarized capacitors in parallel with each other to get the value that is needed?


texts: Different value of N Pulse signal with STM32 and PWM

texts:
Regarding my Post I put a counter in my interrupt, In the output I have a 1000Hz signal which it means I should have 1000 pulses in each second, but I get 100 pulses each second. what is my problem?
Prescale=7;Periode=7999;Pulse=3998;
void PWMControl(unsigned int Freq){
TIM_TimeBaseInitTypeDef     TimeStructureure;
TIM_OCInitTypeDef       TIMOCStructureure;

        TimeStructure.TIM_Prescaler=Prescale;
        TimeStructure.TIM_CounterMode=TIM_CounterMode_Up;
        TimeStructure.TIM_Period=Period;
        TimeStructure.TIM_ClockDivision=TIM_CKD_DIV1;
        TimeStructure.TIM_RepetitionCounter=0;
        TIM_TimeBaseInit(TIM4, &TimeStructure);
        TIM_Cmd(TIM4, ENABLE);

        TIMOCStructure.TIM_OCMode=TIM_OCMode_PWM2;
        TIMOCStructure.TIM_OutputState=TIM_OutputState_Enable;
        TIMOCStructure.TIM_OCPolarity=TIM_OCPolarity_Low;
        TIMOCStructure.TIM_Pulse=Pulse;
        TIM_OC1Init(TIM4, &TIMOCStructure);
        //TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);
        TIM_ITConfig(TIM4,TIM_IT_Update,ENABLE);
}


texts: Ion-selective electrode: high input impedance to measure the voltage

texts:
I read that an ion-selective electrode has an high impedance (\$100 \, M\Omega\$) and that it's necessary a high input impedance to measure the electrode voltage.

I'd like to understand the above sentence with a circuit. I tried to draw a circuit with a voltage source and two resistances (input resistance and load resistance):

for the Kirchhoff law:

$$E=(R_i+R_L) \, i$$

At this point it's difficult to me to understand why I need a high Ri.
Could you suggest me the right way please?

EDIT

I am studying a biosensor (https://ieeexplore.ieee.org/document/7576627/) and at page 947 there is the sentence: Ion-selective electrodes (ISEs) separate specific ions with a semi-permeable membrane between two electrodes, thereby
creating a potential difference (∼0.1–100 mV) proportional to
the amount of that ion concentration in the solution. However,
due to the nature of these sensors, their impedance is very high,
roughly on the order of 100 MΩ, necessitating high resolution
sampling of the electrode voltage with a high input impedance.

Thank you in advance.


texts: Transistor circuit to toggle motor on/off not working (Arduino)

texts:
I've been trying to create a simple transistor circuit with a 2N3904 that will toggle a geared DC motor on and off without drawing power from the arduino - I've followed the schematic seen in the 2nd image.

 (Breadboard view)

 (Schematic)

The circuit isn't behaving as I expect it to. For testing purposes, I've been feeding the 5V from the arduino into the base pin (before the resistor) to activate the 'switch' of the BJT. This only powers the motor when I have a low valued resistor at the base (~10ohms). When I use 1k resistor, the motor does not turn on. Also, I have used a digital pin set at high to attempt to power the base pin and toggle the motor on/off, but this does nothing, regardless of the value of the resistor.

Perhaps my circuit is incorrect? All I want the circuit to do is turn the motor on and off when I feed it a high signal from the arduino.

Notes: The red wire coming into the node at the top is from a 9V battery. The ground bus on the breadboard has both the arduino ground and battery ground connected to it.


texts:
I want to use MAX17498 in boost mode.

I have a problem setting the slope compensation. The slope (as I understand) is the gradient of the inductor's current ramp. The unit is [A/s] or [A/us]. However, the MAX17498's datasheet requires it as [mV/us] (S_E)

I guess that the MAX17498's current sensor characteristic missing to calculate this value.

How to calculate the slope resistor's value of MAX17498?


texts: Soft core Processors VS Hard core Processors

texts:
I am doing a study on FPGA interfacing with Microprocessor such as ARM9.

Came across the concept of Soft core and Hard core Processors in my study. May I know what is the comparison between these 2 type; similarity or differences in the implementation ?


texts: Rationale for operating the diode in the (reverse biased) breakdown region

texts:
For the circuits I've studied thus far involving diodes (which admittedly are not that many), they have been nominally used in the forward-bias mode. For example, the LED only lights up when it's operated in the forward-biased region, and is not designed for reverse bias, let alone the burn-out breakdown region.

However, I recently read about the Zener diode, and I found that this particular diode is predominantly used in the reverse-biased, breakdown region, with the following regulator circuit being a popular example:

Although this circuit works, why can we not achieve the same voltage regulation functionality by operating the diode in the forward-biased mode, like this:

This is I-V curve I am assuming for the diode:


texts: Offset of amplifier input voltage of shunt current amplifier

texts:
I'm trying to build a 20A E load and decided to use a 0.01Ohm shunt for the current measurements and set so I needed to amplify the shunt voltage by 10 using the "rail to rail" AD4522-2.
At 0A on RShunt I get 0.17V at the output and that doesn't change until after roughly 1A RShunt which is a dead band of 5% for me which I suppose is because of the rail limitations of the amplifier.
What is the common solution to offset up (add 0.2V to thrbop amp output) of the amplifier / shunt input so I will be able to measure the full current range of my shunt from 0-20A?
Note current sensing op amp U3 has 3.3V connected to VCC
Schematic below:

Also I'd love to hear improvement suggestions for the circuit.


texts: Can I replace a non-polarized electrolytic capacitor with a ceramic disc capacitor?

texts: I need to replace a non-polarized electrolytic with a ceramic disc capacitor, can I do that? If not, is there other ways to replace it?


texts: Connecting a photodiode in reverse bias to an oscilloscope

texts: The attached photo is a diagram I wrote years ago when I was connecting a photodiode in reverse bias to my oscilloscope. Is this correct? The battery is a 9 volt. The photodiode is a from Thorlabs. It is FDS100 silicon PIN with a 10ns rise time. I am looking to measure light pulses in the 20ns range. I am not an electrical engineer so please keep that in mind when responding. Any information or confirmation is greatly appreciated. Thanks


texts: In my Arduino project, a 3v 50RPM DC Motor starts to rotate an independent mechanical knob. When the mechanical knob reaches its zero point, it gets locked. How can I get this lock feedback so I can stop rotating the motor and avoid damage to the motor?


texts:
I am building a pcb where I will be switching a bunch of MOSFets which are optoisolated. My plan is to do this with optotransistors.

A typical circuit for a transistor controlled MOSFet, which I'm seeing online, is as follows:

simulate this circuit – Schematic created using CircuitLab

My concern about this circuit is that it seems to be inverting. When the input is high the MOSFet is turned off and vice versa.

Would the following circuit be a viable non-inverting replacement?

simulate this circuit

NOTE: Transistors showing second half of optoisolators


texts:
I want to amplify a voltage range (from 0.54 mV to 42 mV) in below circuit which the gain of the Op Amp is 10x, so the Vout will be (5.4 mV : 0.42 V) ..

and this Vout will be a Vin again in another non-inverting Op Amp to be amplified 10x so the final Vout will be (54 mV : 4.2 V)

Question
What's the Vdd that must be supplied to the Op Amps in both amplifying stages to get these Vouts --the Supply has to be 2.5 volts only--?


texts: Can I share a 3-phase motor branch with a small single phase load?

texts:
I have a 15hp 3-phase motor on a 50A 120/208 wye circuit.  I also have a small 1A dc motor with controller and some monitoring circuits - this  secondary system needs 24vdc and 1.5A altogether.  I have an ac-dc converter that's rated up to 240VAC and about 1A input current to provide the DC power.

Is it safe to wire the converter with the incoming 3-phase for the motor?  I figure since the starter coil is using L1/L2 I can connect the ac-dc unit to L2/L3 and have a balance on the 3 legs.  The motor runs for a max of about 1hr continuously, it's fla is 39A.  Most of it's operation is for short durations - about 10min at a time.
If this is acceptable are there any extra precautions other than fusing the secondary unit?  Also, in case the large starting current cuts the DC power, what would be a good solution to avoid the voltage dips besides a large capacitor?


texts: BLDC motor drive: Requires an external push to start rotating

texts:
I am trying to drive a 23-pole pair(i.e. 46 poles) BLDC motor using an LV8139 pre-drive, the output of which is fed to drive the 3 half bridge MOSFETs. I managed to connect the correct phase sequence(out of the 6) between the motor and driver.

The pre-drive IC basically provides a hardware solution for 120 degree and 180-degree commutation(sine wave). It requires a DC control signal to vary the speed of the motor, which I am doing via a potentiometer.
Here is the link of the datasheet for the same

https://www.onsemi.com/pub/Collateral/LV8139JA-D.PDF .

Now there is literally zero material on the internet about this chip but I am able to use it to drive the motor. I do have a few problems though:

1.) Mostly I need to give a physical push (by hand) to the motor before it starts to rotate normally. I feel that this is an issue of the hall sequence. But once the external push is given, the motor starts normally.

2.) The specification says that motor will rotate in 120 degree mode till a certain speed and then it will jump to 180 degree sine wave. However I don't see any such transition i.e. the commutation is 120 degree always.

I searched about the first issue on the internet and found some suggestions to add a high value capacitance across the power supply to provide sufficient initial current, but the issue persists.
Any suggestions are appreciated. Thanks & Regards


texts: Synchronous buck converter - MOSFET selection

texts:
I am relatively new in the design of DC/DC converters and have some difficulties with the selection of the switching MOSFETs for my design. To be completely honest, I am trying to find out if the already selected MOSFET (DMN3010LSS from DIODES Inc. and as second source the SM4832NSK from sinopower) by another designer is OK or I need to substitute it.

The specifications are:

Vin = 12V
Vout = 1V
Iout = 12A
PWM controller: MIC2102
switching frequency: 437kHz
inductor value between 1.5uH and 3.3uH
(the last two are design choices)

My biggest problem right now is how to calculate the maximum current that will flow through the transistor and the maximum power losses. Naturally, I studied the datasheet of the controller, but I have the feeling that somehow some information are missing.

Regarding the MOSFET power loss, so far I have understood that it consists of two parts, the conducting power and the switching power loss. The conducting power for the high side is given by:

$$P_{cond,\ HS} = I_{out}^2\ \times\ R_{{DS}_{on},\ max}\ \times\ \left (\frac {V_{out}}{V_{in}} \right )$$

and for the low-side by:

$$P_{cond,\ LS} = I_{out}^2\ \times\ R_{{DS}_{on},\ max}\ \times\ \left ( 1 \ -\ \frac {V_{out}}{V_{in}} \right )$$

Is that correct? The MIC2102 data sheet is pretty crappy in this point: I suppose Eq.9 is incomplete; the duty cycle is completely missing!

Then, the switching power losses for the low side are negligible and can be ignored, as far as almost everyone says.

For the switching power losses of the high side MOSFET I tried to follow the information in the MIC2102 data sheet, but I was completely confused. Obviously one has to use Eq.12, where the switching transition time is given by Eq.11 (they say they have assumed that the turn-on and turn-off times are equal, which I haven't found anywhere else, but anyway). If we are to follow Eq.11, what is the difference between Vin and VHSD? To my understanding they are totally the same! Any idea?

Assuming that we finally compute the total power losses, how do I select an appropriate MOSFET?

Another topic is then: When selecting the MOSFET, what about the IDS current? How to choose the max IDS current that the MOSFET can accept?


texts: Physical wiring architecture for a CAN Bus

texts:
I want to wire a CAN bus for multiple motors(BLDC) in robotic arm. I am building out my motor such that they have a controller and a CAN transciever built in. There will be upto 6 motors with the total length of the bus bieng around 1 to 1.5 meter.

What kind of physical architecture is best suited for this kind of application?

Should I daisy chain them or should I use a T connector and drop off a connection for every motor or is there an option better than both? Considering I will have around 6 drop off points.

My main requirements are reliability of data, atleast 256kbps of speed on the CAN Bus, and also, the whole system with the motors will be moving and could be exposed to noise from the motor power line.


texts: If it is more efficient to have high voltage, low current power lines,  why aren't homes and appliances adapted to accept high voltage and low current (and remove the need for transformers)?


texts: How to Generate Light in the 10,000K Spectrum?

texts:
I need to generate a lot of light with the same spectrum as the sun - 10,000 Kelvin (10000K). I have searched around for hours, however all full spectrum lights available are either 5500K or 6500K - but I need 10000K..

For reference I've searched Amazon for hours but I found nothing. I searched other places and the only such bulbs I found where for cars or fish tanks.

Therefore, I'm interested in learning what technology is available to generate this kind of light spectrum?

I am not asking for specific product recommendations but rather the general category of such products. For example, one person recommended a metal-halide discharge lamp.

Are there any other options?


texts:
Firstly, I'm not sure if sensitivity is the correct term, if anyone has a better suggestion please feel free to edit the title

So I have a motor and I want to measure the current output which I'm doing via a low ohm resistor in series. The voltage across this resistor then goes through an op-amp and finally through an A/D. I then take this digital value and plot it on a graph in real time.

The motor moves back and forwards along a rail, the problem I have found is that some rails I've bought have had burrs/defects and I have to resort to grinding every rail I buy. So I want to measure the motor current so as to look for which rails are ok and which ones need grinding as the motor should draw more current when passing over the burrs/defects.

The current circuit I have works great, however the extra current drawn when passing over the defect parts of the rail doesn't deviate too much from the standard current draw. This means that when I plot it on a graph in real time it's hard to discern where the defect parts of the rail actually are.

What I want to do is to increase the sensitivity(?) of the op-amp. So that there is a greater deviation on the output voltage. I would just increase the gain but the problem I have then is hitting the rails of my op-amp.

simulate this circuit – Schematic created using CircuitLab

What are some other ways to increase my input to output ratio?
The only idea I've had is to decrease the sense resistor value and use a higher gain.

Some values incase you need them:

Motor Voltage:  5V
Motor Current:  600mA
Sense Resistor: 0.27R


texts: My DC motor slows down and stops while using an L298N motor driver with an Arduino Uno

texts:
Whenever I run a program for running the DC motor, the motor suddenly slows down and finally stops, I don't know why it happens.
I use an L298N motor driver, an Arduino Uno, and a 9V battery for motor and separate power for the Arduino.
code:
int In3 = 7;
int In4 = 8;
int ENB = 5;
int SPEED = 250;
void setup(){
  pinMode(In3,OUTPUT);
  pinMode(In4,OUTPUT);
  pinMode(ENB, OUTPUT);
}
void loop(){
  analogWrite(ENB, 255);
  digitalWrite(In3, HIGH);
  digitalWrite(In4, LOW);

}

I am following this circuit:

Is something wrong with my code or is it a hardware problem?


texts: Which STM32 microcontroller has the most PWM channels?

texts:
I need a MCU with a minimum of 32 PWM outputs and at least 1 analog input. Are there any STM32 MCU which satisfies the requirements?

I thought of multiplexing 16 PWM channels to 32 channels, but I would rather not as it would increase the size/cost. Are there any other suggested alternatives? The frequency doesn't matter that much as long as they're higher than few kHz.


texts:
I understand what this circuit does but I can't find a reason for adding the 10K Resistors connected to the base of both Q1 and Q2.

Is it okay if I replace them by shorts?

Would the stability of the circuit be affected if we replace them by shorts?


texts:
What's a good circuit to use to generate a square wave? The exact waveform isn't too important - I just want to get a piezo buzzer cranking at 150 kHz. I also want efficiency and adjustable amplitude.

(Motivation: I want to vaporize some oil in order to burn it. I choose 150 kHz after the Glade Wisp as hacked in Make.)

The simplest I found was this one consisting of a capacitor, 3 resistors and an op amp a comparator. Is this design a good way to go?

Assuming so, according to the same page, it has a period of

\$T = 2RC ln \dfrac{1+L}{1-L}\$ where \$L = \dfrac{R1}{R1+R2}\$

Choosing R1 = R2 gives L = 1/2, giving (1+L)/(1-L) = approximately e, giving the simpler

T = 2RC

I'm in the woods here, but I'll suppose that R1 = R2 = R is a good choice.

The T I want is 1/150kHz; thus RC = 3.33e-6

Another abitrary choice presents itself. Say, a 100 ohm resistor and a 0.033 uF capacitor? Is this choice important? Is choice of op amp important?

Sorry for the long question, but if someone who knows what they're doing could walk with me here, I'd surely appreciate it.


texts: How to confirm if diode bridge is faulty

texts:
How could I confirm if the faulty component in my circuit is the diode bridge (marked as B) in the attached image?
If I set my polimeter to AC and measure LN in point A I get the correct 220v, but there is no voltage between the diode AC inputs, so this makes me think that maybe some other component is faulty.
Any ideas on how to confirm the faulty component in the attached image circuit?


texts: What's the purpose of the inductor in this microphone biasing schematic?

texts:
I'm just wondering what's the purpose of the inductor in this microphone biasing schematic?

Could it be that I have very low input signal from the microphone because of missing L1? Bias generator derives it's power from 3.3V LDO. The microphone I use with this is:

Sensitivity:-30dB+/-2dB
Frequency Range: 50Hz-20KHz
Output Impedance: ≤2.2 kΩ SNR: >58dB
Standard Operation Voltage: 4.5V Operation Voltage: 1.0V-10V.DC