texts: Which component can control the heat of a hot plate?

texts:
About this kind of hot plate I was told, quote:

  That's very bad because potentiometer needs to emit power which is sufficient part of all heater consumption. In this case we cannot use potentiometer.

But surely there's a way to control it as it's done in hot plates for cooking etc.


texts: Why high voltage from TV flyback shocks you without the need to complete a circuit?

texts: Assuming the TV is plugged into an isolation transformer (although I think there is already a small transformer onboard), then ground is not part of the secondary side. Yet, high voltage from flyback still wants to arc to earth (or just about anything), through human body as a medium.


texts:
I am trying to construct a simple low-pass filter for the following scenario:  A high-voltage DC signal with lots of noise.  I looked at Wikipedia's article on a simple passive low-pass filter.  I understand how the capacitor "looks like a short" to high-frequency signals and open for DC.  What I don't understand is the role of the resistor.  I read what Wikipedia has to say, but am not quite grasping how the resistor influences the "time for the capacitor to charge up".  I vaguely grasp the idea of resonant RC circuits, but don't really understand the relevance of that principle in this context.  Any insight would be greatly appreciated.

Thanks in advance,
Brian


texts: Selecting the right microcontrollers for this project (Arduino based)

texts:
I'm thinking about buying some Arduino development kits to migrate from my actual development platform (picaxe) to Arduino. I want to buy just what I need to develop my next project, but taking in consideration that I am a total ignorant of the Arduino capabilities I have some issues trying to decide what to buy. So I decided to explain you what I want to do and what I think I need (in terms of hardware) hoping to have some feedbacks.

Ok the idea is simple, over the serial cable my computer (or USBtoserial) I will send some commands to my Arduino Uno board: these commands are composed of several bits (defined in my own protocol); anyway, after my Arduino has received this commands it will take some actions, at the moment the only action that matters is to send a word to other Arduinos connected to a communication bus (need to decide if I2C, serial or TTL). This word is composed of 1000 bits, the firsts 8 bits are just the header (containing the address of the chip that will receive the data) and rest is just data (the actual length of this word is always fixed to 1000 bits).

So in summary this is what I will do:

For example, from the PC, I send the command over the serial cable: 110110111010101010011…….01101.
This goes to  the Arduino board who resend it to the communication bus where all the other micro controllers are always listening to the bus, they will read the first 8 bits and compares them to their own address: if it matches the micro controller address (stored in a variable), it will store the next bits on memory (if the power goes off I don’t need to save the informations, so it could be a volatile memory).

After that the micro will be waiting for a future command that will eventually tell him to output the data bits over an output pin. All the micro will only save one word of 1000 minus 8 bits at the time, so the memory is fixed for just 9992 bits.

I'm having problems to decide which small microcontroller to use, which communication protocol to use and some issues with the software. Taking is consideration that the distance between the first micro and the last one could be up to 7 meters I think that I2C is not the way to go, serial will be great but that means that I will need a serial to ttl converter on each micro (take in consideration that they could be up to 128 micros) so that can make the project to go out of my budget, TTL will be great but I never tried a communication via TLL over 7 meters, what do you think? I think a good cable will not drop so much voltage in 7 meters, also the speed I thinking to use is max 19200bits/s.

About the micros, my biggest concern is to choose the cheapest alternative because they will only receive data in one pin (serial data) saved in a volatile memory, and then output that data at a fixed rate over an output pin (to light up and off a led for example). I saw on internet that you could program the ATtiny with the arduino board, is this chip capable of doing what I need? Do I need an external memory to store the data? Or I can save it on a variable? (what memory you suggest?)

And my final question is about software, when I was using PicAxe, a very simple development kit for microcontrollers when I need to store a word over a serial input I just make this:

serin serpin,N2400,(27),seraddr, b4,b5

Where serin is the command to begin the serial acquisition, serpin is the number of the input pin I want to use and b4 and b5 are four bits variables so using they two I have a 8 bits word. The PicAxe platform is fixed with 10 4 bits vars (b0,b1…….b9) so it will be imposible to store a 1000 bits word without passing the information to an external memory. With the Attiny I can store that amount of data on a program var? What is the maximum I can store? At the point do you still think the attiny is the way to go?

Thanks so much for any feedback and suggestion!


texts:
I am in the process of building an electric generator for the first time, and I have found out most of what I need to do, except the following things.

Can I have 2 rows of magnets linked together side by side spinning around the stator?

a. If possible does this change the recommended size of the inner diameter of my coil? (I read it's suppose to be about the width of my magnet)

This is the type of generator i'm building. >https://www.youtube.com/watch?v=yuKKrVlilVk
Right at the beginning the video shows a rotor with 1 row of magnets going around it. I am wondering if I can add another row of magnets side by side going around the wheel.

So the wheel would look like this.

+-+-+-+-+-+-+-+-+-
-+-+-+-+-+-+-+-+-+

I am wondering if a positive and negative going across the wire at the same time would like cancel each other out or something.


texts: How efficient are lab bench power supplies? (affected by output voltage?)

texts:
As how I understand it, there are two ways of converting DC. One is by using a voltage regulator (zener diode, feedback combination etc), and the other is by using a buck boost converter. Firstly, if there are other methods, please tell me!

How do lab bench power supplies work? I've heard that buck-boost supplies are noisy (for precise lab requirements) and I know that voltage regulators basically drop the remaining voltage as wasted energy.

Now to my question: I have only seen a single transformer in any lab supply, so obviously the output voltage of it is fixed. If say the bench supply's max voltage output is 24V, then I'm assuming the output of the transformer would be ~24+V.

If this is going (after AC-DC conversion) to a voltage regulator, and say I pick 1V fixed o/p voltage and connect the bench supply to a load that draws 1A current. If I understand it correctly) the lab supply will waste at least (P=VI=[24-1]*1) 23W and have an efficiency of just 4%.

Is this true? If so, the heat output would increase dramatically as selected output voltage    is lowered (and current increased). So much energy would be wasted? Not to mention heat sinking etc.

What am I missing? Is there a better way? Or is this a necessary sacrifice for getting a precise power supply?


texts: Why are motor poles oriented radially rather than tangentially?

texts:
I wonder why motor poles aren't oriented tangential to the circumference of rotation of the motor (for brushless DC motors).  It seems like radially oriented motor poles would be less efficient when the rotor is swinging past that pole.
This is what I picture:


texts:
I’m trying to create a multimeter, I’ll be mainly using a 16 bit ADC (ADS1115), an ESP8266 on Node MCU, I’ll use the MCU to communicate with a phone app to switch between different multimeter modes, i.e. NOT using a physical switch, however I encountered some issues trying to implement the voltage measurement functionality.

For current measurement, I’ll be using a current sensor module, specifically (ACS712), with the ADC to measure currents.

For Voltage Measurement:

I’ll be using a decoder to switch between different scales (1V, 10V, 50V, 100V, 200V)

My approach is to use switches and voltage divider as shown in the image below:

The input voltage (The one I will be measuring will be applied at 1 ) then I’ll basically use high-side driver switching transistors combination for switching, and then take the output voltages summed up from all the different scales(except the 1V scale, the 1V scale will be directly fed to the ADC) then added up to a summing amplifier then to the ADC input pin then I’ll do the required calculations to obtain the true voltage.

Notice: I’m not using the correct resistor values, I’m still constructing it, the intermediate op-amps are for buffering, and the final op-amp is to sum.

However, I have noticed an issue:

When applying a high voltage reading, the voltage around the OFF transistors will be the same reading (causing the transistors to burn due to excessive voltage applied), making this circuit unreliable practically for switching, I don’t know if I can find a transistor that can bear application of 200V.

I took another approach for voltage measurement, -not much different though-, I’ll be using only 1 switch and voltage divider for all scales and the output then will be fed directly to the ADC, but here comes another issue:

As of my understanding, the ADC (http://www.ram-e-shop.com/ds/ic/ADS1115.pdf
) won’t be able to detect low voltages <2V, the output from a decoder will be around 5V, and according to datasheet of the ADC the maximum ratings of Analog to input ground maximum ratings range between VDD -0.3 V and VDD + 0.3V where VDD is the applied voltage, please look into the datasheet for more info.

Making me unable to use it for low voltage readings (the 1V scale).

So my question is how to be able to overcome the issues mentioned above, is there any better approach to implement the voltage measurement rather than decoding and switching?

My main issue is to find a reliable switch that would handle high voltage applications.

I also tried to think of a different approach using an analog multiplexing IC (http://www.ram-e-shop.com/ds/74xx/744051.pdf
)

To switch between the different voltage scales, but the output of the IC is limited by the input voltage of the IC, i.e. due to limitation can’t obtain much voltage from its output.

Finally, any help is appreciated.

Thanks in advance!


texts: Is there a convention as to placing a resistor before or after an LED?

texts:
We know that it makes no difference whether a resistor is placed "before" or "after" an LED in a circuit.

Changing the resistor to be in front or behind an LED doesn't affect brightness?
Does the resistor have to be before or after the component
Should Resistor be before or after an LED series

Is there a commonly used convention that encourages one or the other?


texts: PCM CCM Converter using SIMetrix/SIMPLIS

texts:
I have built the attached file which is a peak current mode buck converter on SIMetrix/SIMPLIS software but I cannot simulate due to some errors that I could not troubleshoot. Please can anyone resolve the problem to me?

Here is the link to download my file:

https://drive.google.com/open?id=14U9AxbnpqrWlDvse91k5KQVtTGo5skSz


texts: Do I really need to solder headers to a shield? Or can I just plug it into my Arduino?

texts:
I recently purchased an MP3 Player Shield for my Arduino. I bought a couple of headers to run through the shield's holes down to my arduino. Is this TRULY necessary (for testing purposes)? Or could I just plug it in and down to the Arduino.

By "plug it in and down to the Arduino," I mean running the stack headers through the shield's pinholes and down into the female pins of the arduino" without any soldering.


texts:
so my question is regarding the diode used across the relay coil.
My A level textbook (the section from the textbook is given below) says that its purpose is to protect the op-amp from a back emf induced when the current in the coil is switched off. But this explanation is not adequate enough for me. I don't understand how this will protect the om-amp.

My problems are:

1)I don't understand, how the emf is induced in the relay coil when the current is switched off.
2)I can't visualize how the current will be moving in the flyback diode when the current in the coil is switched off.
3)I don't understand how the diode will protect the op-amp, given that the first diode will stop any current from flowing back to the op-amp.

Please explain in layman terms. My qualification is just UK Cambridge international A level physics. Hence I don't understand the other complicated explanations given about flyback diode in this site.

thank you very much!


texts: Drain Li-Ion battery by connecting USB +5V and GND

texts:
I have a sportswatch which can be connected to a PC via USB for downloading the training information, upgrading the firmware, etc. I have used those features for a year on weekly basis, but since today, kernel does not register the watch and Linux ring-buffer logs following if I connect the watch:

[772682.440095] usb 1-3.1: new full-speed USB device number 36 using ehci_hcd
[772682.848050] usb 1-3.1: device not accepting address 36, error -32
[772682.920092] usb 1-3.1: new full-speed USB device number 37 using ehci_hcd
[772683.328030] usb 1-3.1: device not accepting address 37, error -32
[772683.400094] usb 1-3.1: new full-speed USB device number 38 using ehci_hcd
[772683.472094] usb 1-3.1: device descriptor read/64, error -32
[772683.648094] usb 1-3.1: device descriptor read/64, error -32
[772683.824096] usb 1-3.1: new full-speed USB device number 39 using ehci_hcd
[772683.896093] usb 1-3.1: device descriptor read/64, error -32
[772684.072094] usb 1-3.1: device descriptor read/64, error -32
[772684.176098] hub 1-3:1.0: unable to enumerate USB device on port 1

I have tried with different computers and reset the watch to factory state, but this has not helped. As a last resort, I would try to drain the battery of the watch. As seen on the picture below:

..it uses TA type screws in a deep sockets and I do not have a screwdriver for those, i.e. I can not simply remove the battery. In addition, during normal operations, the watch will go to some sort of standby mode in case the battery is very low and it could stay there at least for days.

Has anyone drained Li-Ion battery by connecting the USB +5V and GND through a resistor? Is there a risk that Li-Ion battery will get so drained that later it will not start charging anymore?


texts:
Does anyone know the equation that relates current to voltage for a specific tunnel diode(can be any tunnel diode)?

I know these are old tech but I can't seem to find a relationship anywhere, all the info on tunnel diodes seems to be about the quantum mechanics involved.


texts:
I have designed a custom level translator using SN74LVC1T45. I have placed chips on top and bottom to reduce the board size and because of this, I have used vias for the input and outputs for the bottom chip.

So is it okay to use vias in input and output path?

The board operating frequency is 10Hz to 20Mhz.


texts: How to calculate the current of a MCU and CAN BUS circuit?

texts:
I have a circuit which uses a STM32F205RGY MCU, and two SN65HVD230 CAN Bus transceivers, one 20mA LED with a 100Ω resistor and a USB port.

The MCU will run a 24MHz crystal.

Each CAN Bus Transceiver will run at 1Mbps

The USB is standard speed.

The circuit is 3v3 and the working input voltage is 8-30v.

I'm struggling to work out what current my regulator needs to supply. Due to size constraints I will probably use a LDO regulator.

I have a similar circuit built but with 4 LEDs, and a STM32F105 and that uses 0.04A-0.1A with no data on the CAN Bus as I have no CAN analyser at my current location, this seems awfully low though.

What current can I expect my circuit to use? Will a 300mA LDO be ok?


texts:
Last week we had very cold weather; and as a result there were lots of frosted pipes (iron and plastic). I spent a lot of time defrosting metal pipes with a torch, but could not do the same with plastic ones.

Could a practical gadget be made to thaw the ice trapped inside metal/plastic pipes based on induction? What would a blueprint of such look like?


texts: How do I choose the power rating of resistors in audio power amplifier?

texts:
I read a bit about audio power amplifiers and struggle to understand the power rating of the emitter (i.e. current sharing) resistors in power amplifiers.

I refer to this project.

[EDIT: schematics and BOM below: all credits and copyright go to buildaudioamps. com)]

According to the BOM, the resistors R31-R34 are chosen to have a 5W rating (wirewound type).
I have done some simple Spice simulation and I see that at the maximum (reasonably usable) input voltage, the power dissipation across a single emitter resistor is only about 500mW, which is to be expected because of their low value.

Somehow I have the feeling, that the guy has an idea of what he is doing.

Can anybody tell me a reason for the chosen power rating?

Schematic:

BOM:


texts: So I'm designing an FPGA based device, it has two clock sources, one is 48 and other is 64 MHz and I need to implement a detector if one of them (or both) is not present and light a warning LED. How this could be done? All circuits I found require at least one working clock but what if both clocks have failed?


texts: What does "1.2 psrms integrated jitter" mean? What is "psrm" as a unit for jitter? and how is it calculated? and does a unit interval differ from circuit to circuit?


texts: Trying to understand behavior of p-FET in lipo charger circuit

texts:
I am building a lipo charging circuit based on Microchip's AN1149: http://ww1.microchip.com/downloads/en/AppNotes/01149c.pdf. It seems to have all the functionality that I need to build a circuit that can charge a lipo while also powering the main circuit.

The part that I am trying to understand is the p-FET that switches between battery source and USB source for the system load. This corresponds to figures 6 and 7:

The following are my questions:

Is this rationale for figure 6 correct: Vd = 4.2V (lipo), Vg = 5V, Vs = 5V -> Vgs = 0V so FET is off, body diode is reverse biased so no current flows through the FET.
Is this rationale for figure 7 correct: Vd = 4.2V (lipo), Vg = 0V, since anode of D1 = 0V, body diode of FET conducts, so Vs = 3.2V (assume 1V forward voltage). Once body diode starts conducting, Vgs = 0-3.2V = -3.2V -> Q1 turns on (logic level FET), and eventually settles at Vgs = -4.2V since the body diode will be bypassed by the conducting FET.
I would like to use this circuit to drive some tiny DC motors, probably pulling a maximum of 2A (only off the lipo, external power unplugged). If my rationale for #2 is correct, will the system load see a voltage of 4.2V (minus losses in the drain-source resistance), or does the forward voltage drop of the body diode come into play? Minus the drain-source resistance, is there any difference between the state in figure 7 (external power unplugged, running off battery) and directly powering the load off the lipo battery (no charging circuit)?
I found part Si4497DY (sorry, not enough reputation to post another datasheet link). It is logic level, has very low Rds, and can easily handle the current I'm using. It seems like it'd be reasonable for Q1, but I don't really have any experience hooking up a p-FET in this manner. Is there anything that I'm overlooking here?

Thanks!


texts: How could I replace the lamp on a regular projector for a LED lamp?

texts:
I have a 1080p projector and I want to change the regular 230w lamp for a LED lamp that uses less energy and lasts longer.

How complex would this be? LED projectors with these specs are ridicously expensive, but only a few unknown brands offer them. Some have design issues and overheat or break.

I don't know why most companies don't offer these, maybe the money is in spare bulbs which can be as much as half what a new projector costs.


texts: Need a device to calculate the FFT more than 100 times per second (my scope is maxed out at 10hz)

texts:
I'm writing some Python code which retrieves the FFT data that is generated in my Rigol DS1102E oscilloscope via its USB connection.

My trouble is that no matter what time scale I set, I get no more than 10 FFT results per second.

Are there any fast USB devices which can produce results more frequently? I was hoping to achieve at least 100 FFTs per second.

Currently my scope generates 512 bins, and my input waveforms range from 100hz to 10,000hz.

I was thinking of using a soundcard for this but was actually hoping to find a "co-processor DSP" device and let it do all the work independently of the device which Python is running on.

Due to python not being very fast and the fact that I may want to monitor multiple inputs at once, It would be difficult to use the soundcard for live FFT visualization (especially on something like a Raspberry PI)

Thanks!!


texts: Qi charging multiple devices with single transmitter

texts:
I am looking for a Qi charging compliant transmitter and have found kits from different manufacturers like ST/TI/Microchip. These kits have one receiver and are tuned to work together.

How can I build a transmitter (chip+coil) such that I can transmit power to multiple lower power devices with one transmitter? I haven't been able to get much information on how that can be done.

For example, to use a 15W transmitter to power four 3W receivers. Can the transmitter communicate with all devices under the Qi protocol? Will this boil down to designing the coil appropriately or there needs to be support from the transmitter chip as well?


texts: Theory for 3-bit full adder and calculations with un-/signed integers

texts:
With the following scheme, I built myself a 3-bit full adder. What I'm wondering is, and I couldn't figure this out myself, does the adder calculate with signed or unsigned values?

Is the range for the 3-bit adder between (-4) and 3, or is it between 0 and 7?
Alternatively, is it whatever. As in, can I choose whether I want the binary number 111 to represent (-1) or if I want it to represent 7?

The adder of course can make both addition and subtraction. The scheme I took came from here. The site has a scheme with overflow and subtraction/addition added to the scheme.

The site claims: "When is the result negative? When its most-significant bit is 1. " But I'm still not sure if that must be the ABSOLUTE truth. I'm thinking the range (-4) and 3 is necessary to calculate with subtraction. Am I correct?

Answer to my problem. The main reason we use 2s complement is in fact the advantage that we can display unsigned and signed integers on the same circuitry.


texts:
I built an oscilliscope with ARM and internal ADC (Atmel), but my signal is very thick (noisy). It looks like this link, but sometimes worse!

Could the ADC be outputting noisy values?
What could be some possible reasons?
What are steps I can take to resolve this issue?

I should also mention that the maximum frequency is 25kHz.

Can a special capacitor resolve this problem?

Also, I would appreciate suggestions on how to chose a DAC and optimal frequencies.

Thanks in advance.


texts: Help identify this IC (voltage regulator?)

texts: While reversing an old made in Russia power supply I had found these ICs. Here I am attach the circuit I had drawn and the components. The VCC and other power symbols are my assumptions. 16-pin SOIC is 26A14, maybe a transistor array?


texts: How to power up BeagleBoard-xM using batteries?

texts:
I 'm looking for a battery solution to power up BeagleBoard-xM. Until now, I used a 5 V, 3.2 A AC/DC power supply adapter (2.1 mm barrel plug).

I 'm thinking of using a 4 x 1.2 NiMH AA battery pack (or NiCd). This way voltage will be 4.8 V, that is the minimum -xM's electrical specification for input voltage DC. If this is not a proper solution, please let me know.

My question is:

How can I determine amperage to be 2 A or greater? As far as I know, the board will only take the current it needs when attached to the battery, but low amperage may be the reason of features misfunction.

Any help, or even different solution, would be appreciated.


texts: representation of electrical circuits (paper)

texts:
I'm looking for an old paper about a format for representation of electrical circuits using text, similar to some of the current netlist formats. Here is what I remember:

it was written by Richard Stallman and (Gerald Sussman or Hal Abelson) from MIT;
circa 1970 (with big error margin);
it focused in writing software that solves electrical circuits in Lisp;
it was likely typed using a teletype;
it describes a simple yet effective language for representing analog electrical circuits.

I searched but cannot find it in my bookmarks and google. Does anyone knows any information about this?


texts: Is it necessary to integrate the output voltage of Rogowski Coils, but not the output voltage of current transformers?

texts: I have researched how Rogowski Coils works, and I have seen the integrator circuit at the output of the coil, I have seen the waveforms, done the math, I know that it's necessary to integrate the signal. However, current transformers are magnetics core with the coil around them, and I haven't seen any circuits after the coil or anything like it, they work on the same principle, so am I missing something? Is the integral of the output voltage necessary when I'm using a current transformer to get the current waveform of a conductor? Thanks in advance


texts: Converting a digital incremental encoder to an analogue voltage

texts:
Is there a way to convert the output of an incremental encoder (50% duty cycle) to an analogue voltage using analogue components? This is because the interface that I'm using doesn't handle a large enough sample rate to accurately determine the shaft angle with just using interrupts directly from the encoder. (Any other possible solutions are greatly appreciated)

P.S. using a potentiometer attached to the shaft is not a solution.


texts: Capacitor negative voltage in flip flop circuit

texts:
I'm trying to understand the basic flip/flop circuit as explained here : http://www.electronics-tutorials.ws/waveforms/astable.html

I'm having some trouble understanding how the capacitors work in the circuit, especially the negative voltage shown on my meter. I've highlighted the pieces of text that confuse me and the questions I'm trying to answer.

I'm a bit puzzled by the following piece of text:

The instant that transistor, TR1 switches "ON", plate "A" of the capacitor immediately falls to 0.6 volts.

The way I understood it

If a transistor is turned OFF, it's base is < 0,6V and its collector will be high (reaching Vcc).
If a transistor is turned ON, it's base is at around 0,6V, and its collector will be close to 0V. (on my demo circuit it is reading 0,08V).

Now, coming back to the quoted text. If TR1 switches on, why would plate "A" of the capacitor C1 fall to 0,6V ? Why doesn't it fall to 0V ?

I would imagine that the C2 plate connected to the TR1 base would fall to 0,6V, but not the plate A of C1.

Another thing I found puzzling was :

This fall of voltage on plate "A" causes an equal and instantaneous fall in voltage on plate "B" therefore plate "B" of the capacitor C1 is pulled down to -5.4v (a reverse charge) and this negative voltage turns transistor TR2 hard "OFF". One unstable state.

OK, so before, when TR1 was off, I can imagine plate A being close to Vcc (as it is connected to the collector of the transistor that is turned off), and plate B being 0,6V (as it is connected to the base of the transistor that is turned on).

So when TR1 turns on, the collector voltage of TR1 will drop, as will the voltage on plate A.

So how am I suppose to read this negative voltage on the capacitor ?

plate A drops from 6V -> 0,6V   (a 5,4V drop)
plate B also needs to drop 5,4V ? from 0V to -5,4V ?

I understand that this negative voltage will cause TR2 off.

Capacitor C1 now begins to charge in the opposite direction via resistor R3 which is also connected to the +6 volts supply rail, Vcc, thus the case of transistor TR2 is moving upwards in a positive direction towards Vcc

So here I guess we're talking about C1 charging from -5,4V to 0,6V (the point that turns TR2 back on). If somebody could point me to an article / explanation that explains how I should interpret this negative voltage that would be great.

I guess I'm having trouble with

the negative voltage.
the charging (in different directions ?) / discharging of the caps.
the fact that plate A of C1 drops to 0,6V.


texts: How to control a buck-boost converter circuit from a microcontroller?

texts:
I'm reading about buck-boost DC-DC converters lately and one thing is still not very clear for me. Most of the converter ICs that I've seen have a feedback loop input pin. For example LTC3780 requires a voltage divider, on the typical application it's created with R1 and R2 resistors (on the left):

As far as I know the only way to adjust such a circuit from a microcontroller is to use a digital potentiometer. The problem is, digital potentiometers that I found are either quite expensive or have a huge tolerance, like 20 or 30%.

Is there any better way to adjust the output voltage of such converters? And if not, are there any other types of ICs that allow easier control from a microcontroller?


texts: How to reliably switch a DC analog signal that can vary from 10mV to 12V, and 1mA to 100mA

texts:
Preface: I'm a Controls Engineer, not an EE.

I currently have a system that tests resistance through a Device Under Test using voltage drop. I am using 12 Phoneix Contact PLC-RSC relays to alter the test circuit to perform various tests. I have had some periodic false failures and bizarre test values. I believe I have isolated this problem to inconsistent contact resistance in the relays. I also previously replaced one relay that was reading consistently high across the contacts (around 1 Ohm).

So to my question, is there a type of transistor/SSR/MOSFET etc that can switch a voltage this low and a voltage range this wide (10mV - 12V), and a current this low 1mA to 100mA?

I have been googling for a while but I am really not sure what terms to be searching for.


texts: Spring Loaded Contacts in vibrating Environment

texts:
I need to create a high current (~2A) connection between multiple closely stacked PCBs. Signal connections are made using a 0.5mm pitch, 4mm stack height mezzantine connector with a individual pin current rating of only 300mA. Using this connector to carry the 2A and associated ground would consume a lot of pins.

Therefore I am looking for alternative connectors that are both stackable and have higher current rating. I am considering spring contacts (both of pogo-type and simple metal latches) but wonder how well those will function when the PCB is subject to vibrations. Can someone share his/her experience? Note that those contacts should carry power, not signals.


texts: Bus and self powered device using FTDI FT230X

texts:
I'm trying to wire up my first device using an FTDI USB to Serial converter. FTDI recommends not mixing bus and self powered designs. But they also mention that it's possible in the documentation. My current design will be mostly self powered but will connect to a PC for data dumps and charging (200mA). It will be powered from a single cell LiPo and has some protection circuitry to prevent over discharging.

What I suspect might be a problem is USB suspend mode, which states that if no data is transferred for a set period the USB device should reduce power. Since most of my design operates from 3V, I want the FT230X to interface from this level as well. VBAT is guaranteed to always be 3.3V - 4.2V. Below is what I have so far, the idea was that configuring CBUS3 as a keep_awake that would prevent it from going to sleep (as I understand it), this would cause it to always be active though, even when self powered:

So my question is this, how do I implemented a bus and self powered device that can drain 200mA from the host for charging even when no data is being transferred?


texts:
I recently made a board for the TPA3004D2 Class-D Amplifier Chip.  It has a fairly large thermal pad on the bottom for heat dissipation.  I used an existing TQFP-48 library in Eagle that had a thermal pad which I resized (my first mistake).  I then put a 4x4 grid of vias connecting the thermal pad to the bottom ground plane, as recommended in the datasheet.  Anyways, I got the boards yesterday and this is what they look like:

As you can see from the picture, the 4 vias in the center of the top-layer grid got grouped together which is good.  But for some reason, the thermal pad that was supposed to be there never got fully "etched" out, and the copper is actually under the purple, thus reducing the surface area that the thermal pad will contact the vias with.  So what are my options for soldering this?  I was thinking about going in from the bottom and soldering through each via, thus giving me maximum area and heat transfer.  Thoughts?


texts:
I've a TLF80511TF 5V LDO regulator, which I think gets a bit hot. At least it gets much hotter than I expected an LDO to get. Perhaps this is normal, it is certainly within the absolute maximum of 150C. On powering up the chip rapidly goes up from 23C room temp to about 60C on the plastic surface to about 80C on the ground tab and stays there.

The datasheet does have a Dropout Voltage Vdr versus Junction Temperature Tj (TLF80511TFV50), but I'm not sure I understand that chart exactly:

I feed the LDO 24V and it takes in about 150mA, now this is on the display of an uncalibrated bench voltage supply, so it may be a bit more or less. It's powering an Arduino Pro Mini + 5 other chips (TJA1051, MCP2515 and three PCF8575's which at the moment are kinda idle, they're connected but aren't programmed to do much at this time, most chips only take a few mA). I don't know how much mA the board takes, not sure how to measure this on a PCB..


texts:
I'm not sure if this was asked already, but I could not find it when I searched.
We're learning about source transformations, and while reading my textbook I came across this:

and in the following example they go on to say that if you encounter this situation, you can just remove the resistor that's in parallel (for the voltage source) or series (for the current source). This makes absolutely no sense to me.

For example, for the voltage source with resistor in parallel, won't the current be different once the parallel resistor is removed? And if not, then at the least wouldn't the power delivered by the voltage source have to be much greater to keep the current the same with the parallel resistor as without it?

I doubt the book is wrong, so what am I missing here?


texts: Behaviour of Voltage on Base in a fixed BIAS Common Emitter Amplifier

texts:
I'm having some trouble understanding the behaviour of the basic common emitter fixed bias amplifier.  I've been looking at this for awhile now and I'm starting to think there is a foundational problem with my understanding.

I understand that I need at least 0.7V applied to the base to turn on the base emitter junction, and also that I want to choose R1 so the base current biases the transistor in the middle of it's load line.

My confusion starts when I inject a signal to be amplified.  The signal will be superimposed on the bias, however wouldn't that super imposed signal now be varying slightly above and below 0.7V thus turning the transistor off and on, creating a very distorted output signal?

I've tried to think this through and I suspect the  current in R1 must start to vary slightly in relation to the input signal?

Another possibility is that I know the base emitter junction doesn't exactly turn off at 0.7V but it does become nonlinear.  Would that mean the outputted signal is distored on the negative part of the input signal?

Is this correct?

simulate this circuit – Schematic created using CircuitLab


texts: What type of relay should i use to control a water pump (with a raspberry pi)?

texts:
I've got a straightforward question: I'm wanting to control a pump (120V     AC) with my Pi. I tried using a Cyrdom SSR (info) but I now realize it is for resistive loads only. Is there a relay rated for motors          I can directly control with GPIO pins on the Pi that will work with my pump? Anything else to know before wiring it up?

Pump info:

HP: 1/200
Voltage: 115V
Current: 1.1A
Wattage: 70W

The pump will be turning on for 1-5 seconds every few minutes (reliability is important).

Thank you!


texts: How to control the gain of more than one TDA2030/2050 IC with a single potentiometer?

texts:
I am on a project of making a music system which will be able to output 6 speakers. I want to control the gain of each six TDA2030/50 ICs with a single potentiometer.
Here is a schematic example of 2 ICs controlling with a single potentiometer, I have tried but does not seem to work correctly.

simulate this circuit – Schematic created using CircuitLab
When I tried this schematic, I get music sound but also with music, it offers some free noises.
Now some of you may think that this might be the answer I am looking for but, unfortunately, the answer schematic given here is not understandable to me as a beginner, and I don't want to use another TDA IC to generate a static voltage or something like that which may create difficulties for me to understand. I only want to use either BJTs (2N2222A) or MOSFETs (IRFZ44N), so if anyone here has a solution for me, please do me a favor by sharing it with a proper understandable schematic and pointing my mistakes respectively for a beginner like me.
Please avoid suggesting any kinds of ICs for performing this action till there are other ways left.


texts:
What is the difference when you send/receive data via Linux serial device file like ttyS3 and when you directly read/write from/to UART FIFO buffers? What situation is more safe and better?

How device file ttyS and UART FIFO buffers are connected, how do they communicate?

Will Linux have a problem if we directly read/write from FIFO buffers, instead of using drivers made for that purpose?


texts:
I found this "MG8Q6ES42 - N CHANNEL IGBT" power switching control motor hybrid integrated circuit between some old motor application circuit boards. Although I found datasheet for it, I didn't found any test circuits or something alike (usually datasheets contain something like that).

Anyone knows how could I test it just to check if it is still operational for motor application circuits or other?

I haven't had any experience with motor control ICs until now, and I think it is wasteful to throw it away, especially since it price isn't so low either.

Here is the equivalent circuit diagram:


texts: Which interface to choose SPI MIPI or Parallel?

texts:
I'm trying to connect the AR sensor module (AR0331) with the IMX6 processor and the problem is the camera uses a HiSPI & parallel line. Similarly, there is MI-PI (CSI) and Parallel line in the IMX6.
Which interface will work best if i want to get the best of the camera....
Parallel???
OR
Serial??
and i want to use it for image processing so i want to make use of the camera to the fullest..


texts: Why is the voltage gain in the simulator so different from the expected gain?

texts:
simulate this circuit – Schematic created using CircuitLab
I was watching this youtube video for an explanation of voltage gain.
Just for verification, is the formula for voltage gain also applicable for circuit below or there is some limitation to it? I was using a simulator and found the gain only is  140. For an input signal of 10mv(peak), the output was only 1.4V(peak.)
I got the following parameters from the simulator:
$$I_b=0.291mA,I_c=47.33mA,\beta=163,r_e'=0.52ohm,\beta*r_e'=85.56ohm$$
The coupling capacitor I calculated as below
$$C=\frac{1}{2*\pi*(R_2||\beta*r_e')}=3.79x10^-6 farad$$
My voltage gain (the node between R1 and collector terminal of Q1) should be \$A=\frac{R1}{r_e}= 476\$. Since the emitter is grounded, it can be treated as if the emitter is connected to a load resistance of 0, just like the equation in the video at 1:31.
$$A=\frac{r_c}{r_e'+R_E}$$


texts: How to detect impending user touch before it happens?

texts:
I would like to detect an impending human touch on my microcontroller (I use an ESP32) - before it happens and setoff some kind of beeper (nasty humans, yees... touching electronics when you know you shouldn't). TL;TR: How can I reliably detect the presence of a finger within 0-3cm of my device?
Conditions

it should allow for omnidirectional sensing of 'hand' distance (<3cm would be sufficient)
the device size should ideally remain as small as possible (e.g. size of arduino nano)
should be implementable/interface-able with an arduino-like microcontroller and provide a readout of the range

Here are the methods I could come up with to go about solving this problem practically with some pro's and con's (mostly the latter):

sound based: Several ultrasonic sensors (e.g. the hc-sr04) mounted. This would probably have some 'holes' in detection even if one sensor per cardinal direction is mounted. Sensors also tend to be somewhat large.
electromagnetic frequency/light based (sorted by typical wavelength band):

laser-based: not omnidirectional.
IR based: might be affected by daylight
far IR based: common sensors don't seem to be optimally suited for short distances, and usually they are quite large (this may also be just due to the Freznel lens, but this would allow omnidirectional sensing to my understanding)
microwave or 'radar' based: might be optimal, but common, affordable sensors seem to have issues for
omnidirectional sensing (e.g. RCWL-0516). Also seem to have issues with short range detection.

capacitive: seems to work well for certain kinds of applications (like the musical instrument theremin). Apparently needs to be calibrated a lot though (imagine chip lying on a metal surface, or you taking your shoes off - apparently this varies signal strength greatly and could lead to false positives - i.e. chip beeping for no reason) - and apparently requires an antenna.

Questions:

Are there any known methods that I have not discovered (see list above, that I will update), or any ideas that my imagination and googling skills seemed to have lacked to come up with?
Is there any recommended method, from an theoretical engineering principle side (and feasibility/practicality side) to do this? I.e. would you recommend any method listed above for this problem?
currently, I would tend towards a capacitive sensor for this approach - however I seem to be lacking some kind of integrated circuit (IC) that would allow me to do this easily. This, old article a bit more, but it's unclear how much calibration is needed and how well this would work. Then another question remains, can this be optimized using the ESP32 (or any other) touch sensors?


texts: Sprinkler controller: Can one field zone wire be 'doubled' and used on two controller zones?

texts:
Is it possible to hook up the same sprinkler field zone wire into two different controller zone slots?

I just bought a replacement sprinkler controller believing it had the same multiple watering options as the timer it replaced.  It doesn't.  I don't want to hassle returning and replacing it right now. Eventually I will get one that does what I want, but for now I was wondering if I can make use of the empty zones on the controller to have more watering options.

It's a rainbird SST 6-zone.  I have two control wires, each in their own slot, and three zone wires, one each in slots 1,2,3.  Slots 4,5,6 are empty.  All working correctly.

What I'd like to do is send the zone 1 field wire to both slot 1 and slot 4, the zone 2 field wire to slot 2 and slot 5, and the zone 3 field wire to slot 3 and slot 6?  If I can do this, then I can program 1,2,3 for morning waterings and 4,5,6 for night waterings, something the controller can't do for me now because the max hours interval to second watering is 12 hours and it isn't enough.

The controller states it will not water more than one zone at a time no matter the settings, so I think I'm OK that the controller will not try to open the same valves from two different zones.

Is this even possible?  Is this a really stupid idea?


texts:
I'm trying to build a high-side current sensing circuit with a differential op-amp which can be seen below:

The LT1006 is actually an LM358 IRL(I know it's a peanut op-amp, but it's what I have available). Anyways, according to this setup, I should have unity gain. 5V/101.1 OHM = 49.4mA. So the shunt has 49.4mA * 1.1 OHM = 54mV across it, and therefore the LM358 should output around the same voltage, but it doesn't. I've made sure the resistors are very matched and also tried using 100k resistors. I've also experimented with different power rail voltages and even tried setups that would give a gain of 5, 10, and 20, and I still can't get the op-amp to output the expected voltage. What am I doing wrong? I've read the datasheet and I'm pretty sure I am within spec of the common mode input range.
Thanks.


texts: Electret Microphone cannot recognize human voice

texts:
I'm trying to transfer sound from an electret microphone to my speaker.

I'm copying a simple circuit from the Internet with 5V source from USB and a 1Kohm resistor. However, because I don't have a capacitor here, I removed it from the circuit.

The output is connected directly to the speaker. After finishing it, I tested my project by saying some words into the electret microphone. It can reproduce my voice when I bring my mouth very close to the microphone and talk 'uuuuuuuuu' 'aaaaaaaaaaa'. It can record my breath when I blow to it. But it cannot reproduce any other sound around me or 'real human voice' as a working microphone. What am I doing wrong in my project?


texts: MOSFET with high pulse current characteristics and low current average, small package

texts:
I need a MOSFET N CHANNEL for charging and discharging a capacitive load (several IGBTs). The current is really high for a very short time and then equal to 0. I currently use a MOSFET with high pulse drain 24A (I have no information about the length of the pulse) and an average current equal to 8A. The package is DPAK which is very big in my application. I would like to reduce this package. I do not know if it possible physically to have a smaller package with a lower average current and the same pulse current? There is proabably a link between the package and the maximum pulse current? If anyone can explain it physically it would be great :) (I do not ask to find me a MOSFET, I just want a general explanation)

EDIT

I encircled in red an area on the SOA graph. As Andy Aka and Neil_UK said, there is a relation between the time pulse length and the maximum current drain. The more the pulse length is, the lower the maxmimum current is. Does it mean that if my pulse is shorter than 100 µs, I could make flowing into the MOSFET a higher current? It seems that the overall is related to the maximal power dissipation as there is a graphic between the pulse length and the thermal impedance.
Thank you very much,
Have a nice day!


texts: I have this timer circuit. Push and release vs push and hold give me different times

texts:
I have a timer circuit which I slightly modified from the one in this link

I have an image below of what my circuit looks like.

My problem is this: When I push my start button and immediately let go, the circuit gives me 14 minutes like I want. When I push and hold my start button for a few seconds and then release, I get something much longer than 14 minutes.

I believe it has something to do with the capacitor taking some time to fully charge but there is only wire resistance and the current limitation of the power supply (1.3 Amps). I don't know how to account for this. Ideally I want to push the button and get it to fully charge. If I hold it for a few seconds, I don't want it to affect the time more than a few seconds at best.

Thank you.


texts:
I am building a power supply using LM78×× voltage regulators.
The circuit works as expected with no load but when I connect the circuit to external connectors, LM7812 on circuit starts getting very hot.

My inference:
The metal in the connector is acting as ground and forming a short thereby making current maximum and LM7812 hot.

•Is my inference correct ?

•If yes , how can this be solved ?


texts: SharkX6 Flight Controller USB data connection cable

texts:
I have a SharkX6 flight controller (FC) that I am using in a quadcopter that I am building. The flight controller came with a broken (the fried IC is to the left of the '100' component) power distribution board (see attached image). This board besides providing +5V to the FC (via a voltage regulator circuit) and power to the ESCs, also provides a USB circuit for connecting the flight controller to the PC via a MicroUSB port. The USB circuit in the power distribution board takes 4 USB lines (VCC/5V, DATA+, DATA- and GND) and outputs two lines marked U+ and U- that go to the FC USB pins. The USB circuit is shown with the blue arrow in the picture. On the right of the board BLACK is VCC, WHITE is D+, RED is D- and ORANGE is GND.

The power distribution board picture is here:

Using a (borrowed) working power distribution board, when connected to the PC I verified that my FC is correctly recognized by the PC, so the FC USB connection port works. The problem I have is that I have to somehow create a cable or circuit to replicate this function because the power distribution board is not available for sale and I would like to be able to connect my FC to my computer and change it's parameters.

My question is: is there some ready-made or easy to understand and build circuit that would allow me to connect the FC to the PC? I have tried pulling up the D+ line to 3.33V by using the VCC line through a voltage divider without success; the computer does recognize that a USB device is connected but it fails with an unknown descriptor and I get the familiar Windows message for malfunctioning device.


texts: What is the transconductance value of a given bjt?

texts: In a BJT transistor Vbe is 0.7V and reverse saturation current is 10-15 A. What is transconductance value ?


texts:
First, let me premise this question with the fact that I'm not well versed in electricity.

Here's the problem:
I am trying to power a UPS with an inverter and two deep-cycle batteries run in parallel. Connected to the UPS are a laptop, router, RFID reader and printer. When everything is turned on, the UPS repeatedly (every two seconds exactly) kicks on and off. We've tried different inverters and the same thing continues to happen. The UPS' red "building fault" light illuminates as well. Can someone help me understand what we're doing wrong?

My best illustration of the configuration:


texts: Confusion with relating thermal resistance temperature, and electrical power and heat sinking

texts:
What is meant by the following?:

  In general, a device with a thermal resistance θ equal to 100°C/W will
  exhibit a temperature differential of 100°C for a power dissipation of
  1 W, as measured between two reference points.

I don't quite understand the relation between the dissipated power and temperature rise. What should be the way of thinking here?

The device datasheet has both max voltage current and power ratings; and it also has the max junction temperature given. How to relate those and what to do is a bit vague for me.


texts: I had draw a DAC by using an adder circuit.Can i know why there is spikes on the graph generated?


texts: Fly back converter- No output voltage at secondary winding

texts:
IC controller datasheet

From my preliminary examination, I found that the VDD is fluctuating from 12 to 5v, My inference from the datasheet is that the High voltage current source is helping till it reaches VDD(start) and turns off to let the bias voltage take over, but that's not happening, so it resets, and reinitiates the startup sequence and is in a loop. I'm getting roughly around 300V at the bulk caps after Full bridge rectifier and zero volts at the secondary. Kindly note this is a TI generated schematic. The PWM signals will drive the power Mosfet only when VDD Is at 14.7v. The symbol used in Altium's library for that transformer shows the dot placed wrongly. The transformer used was constructed according to Ti's design report.
If someone could help me out on this one it would be greatly appreciated.


texts: How to correctly isolate sense lines, and drivers, and coax cables, and noisy environments

texts:
I am having problems figuring out the best way to isolate sense lines, filter noise, and avoid ground loops. Here is the situation:

Sense multiple points on a DUT board (extremely noisy environment).
Drive the sense signals along ~50ft of 50ohm coax.
Measure the signals with Scope(s). Using standard BNC input, differential probes are not an option.

I am using a single ended Hi-Speed buffer LH0063 (very high slew-rate and very high input impedance),
click here for datasheet
I have to use this part. I cannot swap it for a different signal driver. The driver(s) can go unstable. If there are ground loops or multiple drivers not correctly decoupled or driver lines to close to sense lines, the output will oscillate.
Here are 3 scenarios I came up with. I don't know which is best or if I should do a combination, or what changes I should make. Any feedback would be helpful.

ALL TRANSMISSION LINES ARE 50ohm BNC cables

SENSE SIGNALS ARE IN ~10MHz frequency range

Scenario 1

Scenario 2

Scenario 3


texts:
I am new to encoders in general and I am thinking about using a magnetic encoder in a personal project were I will need to make my own servo, and thus get an absolute position reading (instead of the relative reading provided by an optica encoder) from the magnetic encoder.
Are there any pitfalls one should know?
How should I know how many resolution (in degrees) a sensor may have? Is it just about its bits output or there are more hidden problems, like the magnet's properties?

(I know people usually ask for help in this site, and general questions get voted down, but I honestly think this is very helpful so people may avoid wasting time and money in ideas they didnt have the proper knowledge to pursue)


texts:
I'm using this circuit to amplify a geophone's signals but I'm having trouble understanding exactly how the  circuit's op-amp stages work. I'd appreciate any explanation. I'd also like to know if and, hopefully, how it can be (better?) re-implemented with an in-amp, say like the AD623.

EDIT:

I'm hoping to be able to detect footsteps within a few meters radius eventually after the geophone has been buried. But I'm only after re-design mostly because the AD623 is what I have at the moment and not necessarily because the current circuit has issues. Only standard op-amp I have for now is the LM2904, not quite what is needed for such sensitivity, I think. If re-design isn't feasible, I'm okay with simply understanding how the circuit works.


texts: How do I identify identify if a resistor is 300 or 1k?

texts:
I got an Arduino-compatible board from this indiegogo campaign and the kits come with 10 330-resistors and 10 1k-resistors, but I don't know how do I identify which resistor is which. The board forums from the campaign's authors are broken (try to register/login), then I cannot ask there.

The resistors have color patterns printed, but I don't know what they mean.


texts: Leakage inductance is function of the air gap

texts:
I would like to know why leakage inductance is function of the air gap transformer. How does it influence the leakage flux ? What is the relation between them ?

Thank you very much :)


texts: Why is it difficult to lower the overdrive voltage (Vgs-Vt)?

texts:
To save power consumption of switching devices in MOSFETs, the supply voltage (Vdd) should be lower. But, the lower the threshold voltage, because of the Boltzmann tyranny, the bigger the leakage current. Therefore, impossible to reduce Vt more.

But why not lower the overdrive voltage? Why is that difficult? I tried to find the reason for it, but I couldn't. Can someone help to understand this?


texts: How can I protect this 48VDC device from overvoltage?

texts:
I'm powering this isolated DC/DC converter from a power supply that is a nominal 48V, but could potentially reach a maximum voltage of 56V. The datasheet for the converter says that the absolute maximum is 54V. How can I protect this chip from the potential 2V's above it's maximum?

This regulator is being used to power an isolated MOSFET gate driver.


texts:
Due to some electrical issues in my locality, the supply voltage of 230V was unfortunately reduced to 110V. When I connected the 5V charger (Input: 100-240V AC; 50/60Hz; 0.2A & Output: 5V 800mA) to my mobile phone, it indicating charging.

How will my phone charge during 110V and what about its charging output voltage and current at this low supply voltage(110V) situation?

Can the charger pull its required 800mA for charging at this situation?


texts:
I have a pair of motors and the datasheet says that typical peak effective current is 177mA, max rated current is 218mA, typical no load is 53mA.

Now thats all fine but it also says typical start current 1230mA.

My question is how important is this number...

If 1230mA cant be supplied does that mean the motor will not start? Or just start slower?

Im looking at a H bridge IC and its maximum output current per bridge is 1A. Does this mean the motor will not start at all (or slower?) also would it burn out the chip? Or because its only a start current and not an average current the sudden spike above 1A will not affect the chip (just aslong as its not above 1A for too long?)

The motor is 12V


texts: Calculating Base Resistor for Darlington Pair

texts:
So I know lots of people have asked this question but the more answers/threads I read the more confused I get because people explain it so differently.

My confusion is why do I have to even use the hFE Current Gain in any part of my calculation for the base resistor value?

My thought process is since Vbe is 1.4V (0.7*2 transistors) and my arduino output is 5V then lets say "I choose" to have Ib be 2mA then by ohms law R=(5-1.4)/2mA=1.8K ohms.

Does this thought process not work? The purpose of the resistor is to limit current to the transistor, well if I decide to limit it to 2mA then I have all my parameters to choose R without having to use hFE at all.


texts: Adding of frequency divider causes no output VHDL

texts:
I'm trying to get the output from this code. The output is not showing after adding the frequency divider. Before the frequency divider, the code worked well and display the output.

This is my code

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity ASM_combine is
port(clk,rst, A, B,DOOR: in std_logic;
    Z:buffer std_logic_vector(1 downto 0);
    out1,out2,out3:out std_logic_vector(0 to 6));
end ASM_combine;

architecture structure of ASM_combine is
component divide_by_25M is
port( clk: in std_logic;
clk_out: out std_logic);
end component;

component ASM is
port(clk, rst, A, B,DOOR: in std_logic;
    Z:buffer std_logic_vector(1 downto 0));
end component;

component bcd_7segment
port( BCD:in std_logic_vector(1 downto 0);
 decoder_out: out std_logic_vector(0 to 6));
end component;

component bcd_7segment2
port( BCD:in std_logic_vector(1 downto 0);
decoder_out: out std_logic_vector(0 to 6));
end component;

component bcd_7segment3
port( BCD:in std_logic_vector(1 downto 0);
decoder_out: out std_logic_vector(0 to 6));
end component;

signal c: std_logic;

begin
U0:divide_by_25M port map (clk=>clk, clk_out=>c);
U1: ASM port map(clk=>c, rst=>rst, A=>A, B=>B,DOOR=>DOOR, Z=>Z);
U2: bcd_7segment port map(BCD(0)=>Z(0),BCD(1)=>Z(1),decoder_out=>out1);
U3: bcd_7segment2 port map(BCD(0)=>Z(0),BCD(1)=>Z(1),decoder_out=>out2);
U4: bcd_7segment3 port map(BCD(0)=>Z(0),BCD(1)=>Z(1),decoder_out=>out3);
end structure;

Testbench:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity ASM_combine_tb is
end ASM_combine_tb;

architecture behave of ASM_combine_tb is
component ASM_combine
port(clk,rst, A, B,DOOR: in std_logic;
    Z:buffer std_logic_vector(1 downto 0);
    out1,out2,out3:out std_logic_vector(0 to 6));
end component;

signal clk: std_logic :='0';
signal rst : std_logic:='1';
signal A,B,DOOR: std_logic:='0';
signal out1,out2,out3: std_logic_vector(0 to 6);
signal Z: std_logic_vector(1 downto 0);
constant clk_period: time := 200ns;

begin
uut: ASM_combine port map
(clk=>clk,rst=>rst,A=>A,B=>B,DOOR=>DOOR,Z=>Z,
out1=>out1,out2=>out2,out3=>out3);

clk_process:process
begin
clk<='0';
wait for clk_period/2;
clk<='1';
wait for clk_period/2;
end process;

-- Stimulus process
stimulus: process
begin
rst<='0' after 100 ns;
DOOR<='1' after 1800 ns;

A<='1';
B<='0';
wait until rising_edge(clk); wait for 1 ps;
A<='1';
B<='0';
wait until rising_edge(clk); wait for 1 ps;
A<='0';
B<='0';
wait until rising_edge(clk); wait for 1 ps;
A<='1';
B<='0';
wait until rising_edge(clk); wait for 1 ps;
A<='1';
B<='1';
wait until rising_edge(clk); wait for 1 ps;
end process;
end behave;


texts: Why is the naming meaning of Compound DC Motors?

texts: Why is the Cumulative Compound DC Motor called Cumulative and why is the Differential called Differential?


texts: Exchange instruction of 8085 microprocessor

texts: How XCHG instruction is executed by 8085 microprocessor ? By default XCHG instruction takes place between DE pair and HL pair. Suppose let us assume contents of DE pair is replaced by the contents of HL pair, then how contents of HL pair are replaced by the contents of DE pair, because it is already replaced by contents of  HL pair. How this is possible ?


texts: Why can the effective number of bits be a non-integer? What does this physically represent?

texts:
The effective number of bits (ENOB) describes the "real" resolution of an ADC.
I paid no attention to it when I was first taking the class but now when I think about it I cant really make sense of it that the result can be something like 6.8 bits. I can't really make sense of what 6.8 bits physically represent.
I would appreciate it if someone could expain why the ENOB isn't rounded down.
For instance why isn't ENOB = 6.8 = 6 bits? How would you interpret a rational ENOB in a real scnerio?


texts: Are there removable/soluble potting compounds that are moisture-proof yet removable without damaging electronic components? I've been able to plunge-mill potted devices to get near enough to components or test points to take measurements. A potting compound that is soluble in some sort of solvent would make failure analysis and rework easier.


texts: Is there a way to reduce the size of an mbed-os project?

texts: Every time I create a new mbed-os project, (mbed new ...) I end up with a 1GB folder. This seems a tad bit excessive. How can I reuse the mbed-os folder so that every call to mbed new just uses the same repo?


texts: Schmitt trigger with 741 op-amp not behaving as in simulation

texts:
I am implementing a Schmitt trigger using the circuit shown below. This circuit consists of one LM741 op-amp, which acts as an asymmetrical Schmitt trigger with a single power supply. According to this calculator, choosing a 5 V supply and 1 k-ohm resistors for R1, R2, and RFB should result in a lower threshold of 1.66 V and an upper threshold of 3.33 V.

I first simulated this Schmitt trigger in LTspice with an ideal op-amp (universal op-amp 2). A circuit diagram is shown below.

This resulted in the ideal behavior in which the output saturates to positive or negative rail (ground) when the input falls below the lower threshold or rises above the upper threshold, respectively:

I next replaced the ideal op-amp with an LM741 (what I am using in practice) and re-ran the simulation. I got the LTspice model for the 741 from TI's website. The circuit diagram is shown below:

Upon running the simulation, I find that the op-amp is not able to saturate all the way up to the positive rail or down to the negative rail:

I next built the device on a breadboard and measured the output voltage when input was either grounded (0 V) or tied to the +5 V supply. A figure showing my circuit is shown below. The green wire on the left is tied to ground, the green wire on the right is tied to +5 V, the red wire is the input, and the blue wire is the output.

When I measure the output voltage with an oscilloscope, I find that when the input is grounded, the output is +4.5 V and when the input is tied to +5 V, the output is 2 V.

Questions:

Where does the non-ideality in the 741 op amp come from? What causes both the second simulation and the real circuit to deviate from the ideal op-amp in the first simulation?
Is it possible to make the 741 behave more like an ideal op-amp? Or are there other op-amps I could consider using that have similar specifications for output current that behave more like the ideal op-amp (part numbers would be great)?
Why doesn't the simulated result for the 741 match the experimental result?

Edit: Upon seeing @Felthry's comment, I simulated the same circuit but with an LM358 instead of LM741 using the model found here. My circuit and result are shown below:


texts: Pull-Down / Pull-Up Resistor value for minimum current leakage

texts:
I'm using a step-up converter (MT3608) to convert 3.3V to 5V Output. However, because I don't need the 5V all the time and my device is battery powered, I want to turn off the MT3608 IC through its EN pin (LOW = Off, HIGH = On).

Two questions:

Do I need a pull-down resistor from EN to GND to ensure that the converter doesn't "accidentally" turn on?
Here are some characteristics for the MT3608's EN pin:

What value should the pull-down resistor have to ensure reliability and minimum current draw while the converter is powered off?

I'm also using a logic level converter consisting out of a transistor (BSS138) to convert a 5V logic signal to 3.3V. Here I'm using 3 pull-ups (2 to 3.3V, one to 5V) for which I have the same question as above (best resistor value for minimum current consumption whilst maintaining reliability)

Thanks!


texts: What is the name of this electronic component

texts: I'm trying to attach certain components to my prototype board. However they have short pins, so it is hard to wire-wrap to them. Someone showed me something that you can insert the pins into to make them longer. They come in strips which can be divided. He called it something that sounded like "borgstrip", but that's not what it is. What is it called?


texts:
I would like to formulate how much load can carry for the magnetic actuator used in RC airplanes. Example photo:

It consists of a coil and a magnet. And works according to lorentz force principle.
The torque exerted by the magnetic field on the magnet is directly dependent on the strength of the magnet, the number of turns on the coil, and the current through the coil. So to increase or decrease the torque, we need to either get a better or worse magnet, wind more or less turns, or increase or decrease the current.  How can formulate it? Like
Torque = current x magnet property x turn of coil
2 N.cm = 0.1mA x ? x 340 turns  (numbers are only example,not real)


texts: Very confused regarding parallel resistors limiting current

texts:
I'm an electronics noob trying to understand this Arduino circuit below.

Having very cursory knowledge of electronics, I'm extremely confused by this statement I took from the Arduino Knock example:

  Additionally, connect a 1-megohm resistor in parallel to the Piezo element to limit the voltage and current produced by the piezo and to protect the analog input.

You can see the diagram they provide below.

My question is this: How does a resitor in parallel to the piezo limit the current it outputs? I thought that in order to limit the current from a power source (like a battery) you connect the resistors in series?

Some of my confusion also stems from playing around with a circuit simulator, which seems to support my (apparently incorrect) hypothesis i.e. resistors in parallel don't limit the current. See below a screenshot I took from the simulation in question:

Any help would be hugely appreciated. Thank you!


texts: Question on Profiling sample time on arduino atmega328

texts:
I am implementing a PID controller on the Arduino, I transformed my transfer function from the S domain to the Z domain and I require the sample time in seconds. This is how long it takes to get a sample from a position sensor.

This is my question:

I measured the execution time of the entire function with the millis() command. The is the time of the function execution 349uS. which is roughly 2865 samples per second. But the actual command overhead of AnalogRead() is 100uS so would my "true" sample time be 449us?

Thanks !


texts: Why is the capacitor short-circuited in this example?

texts:
Please forgive me if anything wrong in my question. I am a school student.

I have following circuit diagram:

simulate this circuit – Schematic created using CircuitLab

There are three capacitors with equal capacitance \$C\$. As they are in series combination, the total capacitance should be \$C/3\$.

But my teacher said that the second capacitor (C2) is short circuited, so the output will be \$C/2\$.

My question is: why is C2 termed as short-circuited in this diagram?

I asked him again on why C2 is short circuited, but he said me that I should search about it. Unfortunately, I couldn't find anything helpful on google.


texts: Am I following the procedure to set the sensitivity in Try Mode for the A1362 Hall-Effect sensor correctly?

texts:
I am following Figure 5  pg. 18 of this data sheet: Vp(HIGH), Vp(MID), Vp(HIGH), followed by 0-255 Vp(MID) pulses that increase the sensitivity each time Vp(MID) is applied.

However, when I bring the north and south poles of a strong fridge magnet close to the hall effect sensor I always get approximately 4.5668 volts for North and 0.3012 volts for South, no matter how many Vp(MID) pulses I send to VOUT pin.

The circuit I am using is here:

https://www.circuitlab.com/circuit/x22u47/hall-effect-sensitivity-offset-programming2/

You may get a little confused about the 27V (Vp(HIGH)), 15V (Vp(MID)), and 3V (Vp(LOW)).  Basically I have a single 30 Volts power supply that I am dialing up and down to get the high,mid, low voltage pulses needed to program the sensor.

For example, I set the power supply to 27 volts and connect it to hall-effect's VOUT pin.  Then I unplug the jumper wire connecting to VOUT, dial down to 15 Volts, and plug the jumper wire back in. Unplug jumper wire, dial back up to 27 volts, plugin jumper wire into VOUT pin again. The voltmeter attached to VOUT pin gives me correct voltage readings when I plug the jumper wire into VOUT.

But this still does not explain why my north and south pole readings do not change significantly even though I have sent up to 30 Vp(MID) pulses after the initial Vp(HIGH)-Vp(MID)-Vp(HIGH) pulses.

I would greatly appreciate it if someone could point me in the right direction.

If you look at Figure 5 on pg. 18, you will see they send out a Vp(HIGH), then it drops down to Vp(LOW).  Then it goes up to Vp(MID), then back down to Vp(LOW).

The way I am doing it, instead of dropping down to Vp(LOW), the voltmeter reads 2.0V when the jumper wire is unplugged, which is the "Pre-Programming Quiescent Voltage Output" as shown on pg.4 of the data sheet under "Pre-Programming Target".

So I don't specifically send out a Vp(LOW) pulse, but 2.0 volts is technically less than the 5.5 volts required for Vp(LOW) as shown on pg. 15 of the data sheet.

So I am quite confused about why the hall-effect sensor's sensitivity is not changing despite following Figure 5 exactly as shown.


texts: DC12V motor with arduino+esp8266 with one power

texts:
now i have some problem ,i want to use relay to control motor off,
but when i turn on the power motor run and it will reset my esp8266,
i have already add a diodes(1N4007) between my motor but it still can't fix the problem,cuz the space,so i only can use one power.
it's frustrat me few days hope someone can give me some suggest or sketch .
thanks all.


texts: How to convert this combination into simple series and parallel?

texts: In this problem we are not using delta wye method. But I don’t know how they converted this combination into simple series and parallel combination. Help :(


texts:
I am trying to understand compensation using TPS40200 datasheet, the flow is given in Page 26 to 30 of the document.

This sentence is bit is irrelevant in Page 29, because Kfbfeedback gain is already calculated previously as 11.4dB the only remaining factor is error amplifier gain

 - And later error amplifier gain including feedback is calculated using this formula

How is this derived or seen? Is this closed loop gain which is desired to be 7.9dB?


texts: I have a 11.1V li po battery (3S). I wanted to drain it fast so I could test a charger circuitry. How can I do that fast. Unfortunately, I do not have high current consuming loads which can drain a batt and then I do the test.


texts: Change output depending on State in VHDL

texts:
My output has to be high if my state is either F or H, i've written this:

z <= '1' WHEN y = (F OR H) ELSE '0' ;

But this doesn't work. I've also tried writing it like:

IF y = F THEN
    z <= '1' ;
ELSIF y = H THEN
    z <= '1' ;
ELSE
    z <= '0';
END IF ;

But now get Error 10500 in Quartus 2 so whats wrong with my syntax or is there a better way to write it?


texts: Would shooting laser or UV light at an inverter make it permanently slower?

texts:
I'm studying the topic of cloning electronic circuits for my research. And I have a scenario as the following:

Chip A has two ring oscillators (RO1a and RO2a). And RO1a is faster than RO2a.
Chip B has two ring oscillators (RO1b and RO2b). And RO1b is slower than RO2b.
Now, if I want to clone chip A using chip B, I must somehow make RO1b becoming faster than RO2b.

One way I can think of is to shoot laser or UV light at the inverters of RO2b for a long time (of course, not too long because it will burn the inverters so bad that they will become nonfunctional). My reason for this approach is that laser can induce extreme heat. And if we subject the inverters to high temperature for a long period of time, it will age the transistors much quicker (I believe this is called aging effect in electronic circuits). As the inverters age, they will become slower. However, I am not an expert in semiconductor physics to really say with certainty that this approach will actually work. Can someone (who has studied a great deal of semiconductor physics) confirm to me that this approach will work or won't work? Can you also give me some references to justify your answer?


texts:
Why are two diode drops assumed when sizing a transformer in an unregulated power supply with a bridge rectifier since there's only 1 diode between each transformer terminal and load? See for example p123 and p142 of Learning the Art of Electronics:
"Tranformer voltage: This is just the peak value of Vout plus the two diode drops imposed by the bridge rectifier..."


texts: How to calculate the gain for a load cell to be used with instrumentation amp?

texts:
I was hoping someone can give me a step by step process for calculating the gain of my load cell.Here is the datasheet to it LoadCell datasheet.
I also plan on using the INA125p instrumentation amplifier.
Here is the datasheet to it <INA125p Datasheet

Kind Regards


texts: Changing amperage without changing voltage

texts:
I know this has been covered before but I don't see an answer for what I want to do.
Using a 12 volt car battery I want to power up a wound coil to produce a magnetic field.  I would like  to have a steady current as I plan on using a pulse generator to produce a frequency in the 300 to 900 Hz range.
I have a trigger circuit that will take the pulsed 12 volt source directly to the coil.
At least I think it will.
If I just hook the battery to the coil I believe I would be creating a dead short.   So I want to limit the amperage draw without inducing an unwanted frequency.
Is this possible?


texts: Can two different power factors cos(fi) be added together?

texts:
Image of the problem (I need to calculate the overall power for these 4 elements):

Results given:

My main problem is that I'm unsure whether I can add cosfi1 + cosfi2=cosfi. I calculated them both, one for RC and the second for RL.

Here is my overall (exhaustive) attempt on this problem (please correct if you think something is wrong).
Data given:
$$R_1=20\Omega;R_2=3\Omega;L=12.73*10^{-3}H;C=212.2*10^{-6} F; f=50Hz, U_{R1}=40V$$

Solution:
$$X_L=2\pi fL=4\Omega$$
$$X_C=(2\pi fC)^{-1}=15\Omega$$
$$Z_1=\sqrt {R_1^2+X_C^2}=25\Omega$$
$$Z_2=\sqrt {R_1^2+X_L^2}=5\Omega$$
$$I_1=\frac{U_{R1}}{R_1}=2A$$
$$cos_1\phi=\frac{R_1}{Z_1}=0.8$$
$$cos_2\phi=\frac{R_2}{Z_2}=0.6$$
$$U_{XC}=I1*X_C=30V$$
$$U_1=\sqrt {U_{R1}^2+U_{XC}^2}=50V$$
$$U_1=U_2=50V \quad (see \quad image)$$

$$I_2=\frac{U_2}{R_2+X_L}=7.14$$

And now calculating total I with total U being 50V

$$I=\sqrt {I_1^2+I_2^2}=7.41A $$
$$ P=U*I*(cos_1\phi+cos_2\phi)= 50*7.14*(0.8+0.6)=499.8W$$

I get 500 W, which is not listed in the results. Can anyone pinpoint my error?

EDIT:
Tnx to Spehro Pefhany (answer below) I've found my answer:
$$I_2=\frac{U}{Z_2}=\frac{50}{5}=10A$$
$$P_1=I^2*R_1=4*20=80W$$
$$P_2=I^2*R_2=100*3=300W$$

$$P=P_1+P_2=380W \quad answer: \quad c)$$


texts:
I have an amplifier model circuit where I've determined the load (speaker) voltage (using its peak power output and its resistance) and measured the open-circuit voltage.

How can I work out the Thevenin resistance?

I am familiar with finding Rth when condensing a standard linear circuit but struggle to work backwards.

Any help or suggestions are much appreciated.


texts: Can I connect three wires using a screw terminal?

texts:
I often use screw terminals like the below for semi-temporary setups (e.g. in the lab)

However, I often need to connect three wires together, so what I've been ending up doing is squashing two wires into one side of the connector and one into the otherside. But this doesn't seem like the best way to do it - what should I be doing here?


texts: What's the difference between CPLD and an FPGA?

texts: What's the difference between a CPLD and an FPGA?


texts:
I know this has something to do with finding the poles on the plane of this function. However, I don't really understand it.

I am making the following assumptions:

\$ V_{IN} = IZ \$

\$ H(s) = \frac{I_{IN}}{V_{IN}} = \frac{1}{Z} \$

\$ H(s) = \frac{s+a}{s-(a-1)} \$

When does the pole become stable?
And WHAT are poles?

Thanks!


texts:
I am confused on how to find the output resistance of transistor amplifiers in general, but more specifically when it's a combination of different resistances.

Here's an example (concrete) of the source follower (from Sedra Smith 6th ed.):

Could someone give me a purely analytical solution on how they came to the conclusion the output resistance \$ R_o \$ is \$ \frac{1}{g_m} \parallel r_o \$ in the small-signal model?

Beside, what is the general method to get the output resistance? Do we cancel \$ v_{sig} \$? Do we replace the output terminal with a voltage source \$ V_o \$ and calculate the thevenin resistance \$ \frac{V_o}{i_{o}} \$ ? I'm not sure exactly what sources we keep and what we cancel, etc.

Thanks


texts: What is the current through this parallel circuit?

texts:
I'm trying to solve the attached circuit for I1 and I2. I think I1 is just 5A but I'm not so sure about I2, I think it might be just 10/5=2A but I'm not sure if the voltage in the top right part is still equal to 10V or not.

I'm new to electronics, thanks in advance!


texts: Determine transfer function from circuit

texts:
I'm studying my first year of electrical engineering and I am stuck with understanding how to determine transfer functions from different circuits.

As of right now I'm trying to determine \$\omega_1\$ and\$\ A\$ in the following transfer function. \$\ H(\omega)=\frac{A}{1+j\frac{\omega}{\omega_1}}\$

The circuit to be analyzed is this one:

I tried solving it with the complex \$j\omega\$ method but there is something that i don't really understand.

My unfinished solution:


texts: Are capacitive display(s) capable of measuring what fraction of a finger is touched?

texts:
I'm really curious to get an answer for this question. Since I don't know the functioning of a capacitive display and Google didn't help me on this issue, I landed here. :)

Are capacitive displays used in most modern phones capable of measuring relative fraction of the finger being touched? For example, if I touch the screen and then apply pressure gently, will the system be able to make out the increase in the surface area of contact?


texts: I have a button that when push turns on a little light (light blinks; like a counter) - is there an easy way to hijack this signal so that my windows box can also detect if the button is pushed?  I have access to RS232 port and USB; I can also read from the RS232 port.  I don't really care what signal it sends so long as there is something that I can record once a button is pushed.


texts:
1)What are the rating for these kind of presets?
  I need the maximum current they can withstand without any harm, (Imax).
  [data need for a 100k preset]

2)I'm hoping to use this kind of voltage divider method to set reference voltages to a     voltage comparator circuit. Because ref voltage should be able to adjust. Is there any good method to set reference voltages rather than this?


texts: Altium 21.1.1 - Disable component clearance

texts:
I'm royally confused!
I have Altium 20.x.x on one PC. I do a PCB design on this PC and I have no issues. I port that same project to Altium 21.1.1 and suddenly I have major clearance issues when I go to design the PCB. Certain components can be placed next to each other while others have an incredibly large clearance requirement.
I've ported my settings from one Altium to the other, and vice versac, and it doesn't make a difference. I've played with all sorts of settings in the preferences and nothing has changed this. I've created a constraints file and set the horizontal clearance to zero. I've attached a picture of an example. I then just started a new project in Altium 21.1.1 and used different components but when I go to design the PCB layout I have the same issue.


texts:
I have this rotary encoder and I am not quite sure how to debounce the internal push button switch (shown in the SW02 diagram).

Any help would be appreciated, I'm a noob with this stuff.

EDIT
I would like to implement a hardware debounce

My primary problem is that I need to have my VCC on pin 5 and my ground on pin 3 in order to have my LEDs also work. And I don't know how to make the debounce work properly with that setup.


texts:
We are trying to have a moving IR receiver pickup a specific IR-led for a range of IR-LEDs.

The options we're looking at :

Send and unique pwm signal from each different led, the moving object
knows then at which led it is by receiving the id
light up each subsquent led exactly once at a timebased interval, the
moving object and ledstrip are synced in time so that we know ata
given point in time at which led the moving object is

Questions we have about these two methods:

is it possible have a ledstrip of reasonable length which would be
able to produce these patterns
is there anything that can drive this ledstrip for both methods
what would be the max length we can have for such a ledstrip
which type of IR Leds should we use to transmit to a length of up to
7meters
what kind of IR receiver is best suited for this


texts: Measuring ripple voltage using on-board components. Is it possible?

texts:
I am designing a circuit with a very sensitive analog part. In order to eliminate SMPS noise from a regular power supply, the device has its own non-SMPS power supply followed by an ultra low noise linear regulator (LT3042). However even after this, the device still sees some noise coming from mains socket if a noisy equipment is connected on the adjacent socket.

Usually, simply choosing a socket on a different wall, or moving the equipment power cables apart, significantly reduces noise. I see this as free noise reduction over and above what can be done in the circuit.

I would like to have some mechanism in the device that can inform the user about noise on the line. I don't need exact ripple voltage measurements just something good enough to tell that cable arrangement B is better than cable arrangement A. This would allow the user to try different sockets and choose one that has the least noise.

Alternatively, the device can simply have a noise threshold below which a "Power Good" indication will be provided to the user.

Just FYI, this is for an industrial application and the position of the device or its wiring won't change very often. If during operation the noise level rises above threshold, say due to some other equipment connected nearby, the device can notify the master via RS485.


texts: I am currently reading Malvino's book as my text book. As stated in the picture "At low frequency (maybe DC) this impedance is purely resistive and defined as ....", I am not  able to understand how did they derive the formula, also, is there any intuitive "feeling" for the base impedance? let me ask the question more precisely,first, do they mean the base impedance (maybe dynamic) as the impedance at the base "material" as shown in the picture below?


texts: Calculation MOSFET max current needed for PCB + pulldown calculation?

texts:
I would like to know if there is a calculation that allows me to look up at how much current my PCB would draw in the worse-case scenario if all my MOSFETs would have to change at the same time. In the PCB I use  11 IRLL014 in a SOT223, and 4 IRF3704 in TO 220.
https://www.mouser.de/datasheet/2/427/sihll014-1768836.pdf
http://www.irf.com/product-info/datasheets/data/irf3704.pdf
It would be fine if you say what I have to look at in the datasheets.
Another thing is to recalculate the pull-down resistors, what I would need to look at as they are right now with 10K they don't work right.

on the GAIN there are SSR and 12V,
SOURCE is gnd
GATE comes from the ESP32(ttl)
On the Load Side there are either
https://store.brewpi.com/featured/3-phase-solid-state-relay-ssr-20a
https://store.brewpi.com/featured/ssr-40a
https://store.brewpi.com/featured/td5-24v-pwm-brewing-pump
As you can see there is already a 10k Ohm pull down but it seems that this one doesn't work as the fet doesn't turn off all the time or delayed. Should I just put in a 100k/1k and check if it works or is there a way to calculate it?
Thanks !


texts: Can you identify the Xbox 360 battery pack connector?

texts:
This is the contact used on the Xbox 360 battery pack.  Is it a custom part that was made for Microsoft or is it an off-the-shelf part?

If it is a custom part is there anyway I can replicate it short of sending it off to China?


texts: what do dots, dashes, caps on wires indicate?

texts: I found these 5 wires with markings on them attached to an electronic device's control panel. Does each marking signify a function? If so what are they?


texts: Why do people try to avoid stub in a pcb? Can we foresee the stub in schematic level?

texts:
Please excuse me for this generic question. But all I know is via stub is the un-used part of a through-hole via? And I have seen schematic notes like "Place X close to Y to avoid stubs" .

How can we forsee the stub at schematic stage? Wouldn't a stub be known only during placement and routing?
What are the issues with having a stub in the signal/current path?


texts:
I have a circuit that develops an 800Hz square wave of 5 volts and about 200mA (it's a buzzer oscillator) when energized, I want to detect this square wave and turn on another 5v circuit with a separate power source (an audio playback IC) when the square wave is present, and then turn it off when the square wave is absent. I could do this with an arduino and interrupts, but is there a way to do it in analog? I'm looking for the lowest component count (cost) and complexity possible... if I just run the 800hz signal through a capacitor can I use the smoothed output to switch a transistor? I really just need to get a "hi" output while the square wave is present, and "low" when absent. I can trigger the target device either by switching its power or using a ttl signal.

This seems like it should be a very basic question, but I'm very much a novice...


texts: Relationship between Electrostatic Force and Circuit Layout / Dimensions

texts: Super basic question, but I'm struggling to figure out how to word this: In the usual scenario, current in an electrical circuit is induced by some voltage differential (maybe this last term is redundant).  The voltage is based on the various electrostatic forces, which are represented as a field.  The field doesn't have to stay within the boundaries of the circuit's wire (since it's a field), whereas typically, the current does (I know there are exceptions in cases of high voltage).  Does that mean that the layout of the circuit (ie how close the components/wire are placed from each other) could affect it's ability to operate as expected?  For example, could you reduce a working circuit to a really small size and find that two different wires are really close together, causing some sort of interaction based on the comingling electrostatic fields?  Could this effect inhibit the circuit's proper operation?  (Maybe you could inadvertently create something like a primitive capacitor?)  Is there a limit to how big/spread out you could make a given circuit?


texts: High voltage to low voltage in ps/nanosecond time (Zener/opamp?)

texts:
So I have a signal that goes from 0 to ~800volts in 30ns. I would like to use this signal to trigger a camera (input impedance of 50ohm) which takes a max of 10 volts and requires the rise time to be 1ns for this 10 volts.
I tried a 10 volt zener diode which works... but delays the signal a lot (not sure why) so I get 10 volts in 8ns instead of 1ns. [People said zeners are made for DC and not so much for high frequencies, so maybe thats why]

I then thought of using attenuators to make the signal go from 0 to 10 volts (instead of 800V) in 30ns then use an opamp as a comparator with a 10volt DC battery connected to +Vs and Ref, Vin-, -Vs connected to the negative side of the battery. (and ofc the main signal going to Vin+)
Since different opamps got different operating frequencies and slew rates I got this one:  THS3491IDDAT
Which got a  320 MHz operating frequency and  8 kV/us slew rate

However, I was getting weird results that I wasnt able to understand and shortly after multiple legs of the op amp broke, so I wasn't able to capture the output signal

Here is the input signal which is attenuated using 38dB (div 80) [time scale is 10ns/div and voltage scale is 10v/div

Was I doing something wrong? or is there an easier circuit to use? Any recommendation for other opamps that are easy to handle? (this one was tiny)

The source is a Rogowski coil with a resistance of 4ohm and inductance of 1.4e-7 H. (1 turn coil).

Thanks in advance.


texts:
As far as I understand, the 8051 microcontroller is able to read a pin

(1) by reading the actual pin, assuming the nFET is in cutoff (so a logic 1 is written before reading the pin)

(2) by reading the corresponding latch

Now is it true to assume that reading the latch only makes sense when using the pin as an output? And what are the advantages of reading the latch (which is used in e.g. read-write-modify instructions) instead of the actual pin?


texts: Potentiometer on max. resistance at lowest setting (off)

texts:
first question ever here:

I'm struggling with a 10K log potentiometer in an EQ. When at lowest CCW setting it's the same value as on full CW pos.

Is this typical when a pot goes bad or is that fixable?

update:

Thanks for the advice! I'll change the pot and maybe have a look at the wiper when I have it unsoldered.

update:

When measured 1 between the wiper and one of the end terminals the resistance varies gradually (log), but after it goes down to 0 at CCW position it sometimes jumps to the max. value:
Which in this case is our Pultec EQ and results in full boost.3
We have a lot of people using our gear, so maybe someone just forced it and broke it.


texts: Understanding of torque constant and efficiency of a permanent magnet motor from datasheet

texts:
I am trying to understand the efficiency of the following permanent magnet synchronous motor Motor Datasheet (note we are using the medium voltage model), and its relationship with the input voltages and currents. The application is an electric racecar.

I made the following graph from the data given in the sheet. The blue line is directly taken from the datasheet graph, and the red line is generated from the torque constant on the first page of the datasheet. I understand that the difference between these lines is due to magnetic saturation of the motor.

The graph on the right is what I understood to be the efficiency (the graph data / the ideal torque). At 120Nm of torque (~300A) the efficiency appears to be 75%. However, when looking at the datasheet's efficiency map, the efficiency at 120Nm could be as high as 94%.

Given the following equations, that does not make sense, unless the voltage vs rotational frequency graph curves in the opposite direction, enough to compensate.

Pin = Vin * Iin
Pout = Wm(Vin) * Tq(Iin)
Efficiency = Pout / Pin = torqueEfficiency * speedEfficiency

Additionally, I was wondering how the efficiency could be mathematically defined as a function of the input harmonics (we are wondering how to determine the ideal switching frequency of our inverter).

Am I fundamentally misunderstanding electric machines?


texts: Can vibrations of quite an appreciable amplitude affect the clock signal of a crystal oscillator?

texts: I'm very curious to know as I was told that these crystals are electro-mechanical transducers. So theoretically any excess mechanical vibration should result in an error, right?


texts: FTDI and ST LINK devices together to STM32

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I have an STM32 board (blue pill) that I am programming with the Arduino IDE.
I couldn't program it using an FTDI adapter because I couldn't make the Arduino IDE communicate trough the USART for uploading codes, so I am using a ST LINK V2 to program the STM32.
On the other hand, once the program is on the STM32 I can use the FTDI to communicate to the STM32 via the USART using the COM ports.
So, I am planning to use the FTDI when running and the ST LINK adapter when uploading codes.
My question (before I short circuit something doing it):
Can I connect the two devices to the STM32 and leave them connected to the host PC with power ON? That way the only thing I have to do is selecting one for programming and the other one when running. The STM32 is never connected directly to the PC. See picture.


texts: Power pin used as power in and power out

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This is my first post here... I hope I will do everything correctly.

I need to use a pin as power in and power out, switching it when needed. In particular, I want to use a USB micro B (5 pin) and use the ID pin as power in-out selector like an OTG cable does.

I need a power out when the ID is floating (NC) and power in when ID is connected to ground.

It can be done with an SPDT relay, but I don't have enough space to place it! So I need to realize the SPDT circuit over the main pcb.

To be more clear, I'm using the USB connector as a hardware connection only! No D+ or D-communications. It's useful that the battery charger will always be connected and the boost will power the load only when ID is tied to ground.

Specs:

Voltage: 5V
Current: 1A


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While designing converter I got to the point of calculating secondary coil. Most guides have these equations for it:

Wait a second, didn't I calculate Nps already at the very beginning? Yes, I did! And I've used it extensively throughout the process.

Nevertheless, I use these formulas and get a different Nps. I thought I am going crazy, until I noticed tiny detail: I did not use (1-Dmax) in the beginning. Instead, I used (0.8-Dmax) to leave 20% dead time before CCM boundary.

Question: Is the above equation for reflected voltage applicable in DCM? Or should I just use the Nps that I already have?

This tiny change unfortunately resolves into 30% in coil turns, the difference that does not fit on the core.

UPDATE:

In the equations and text:
Vr - voltage reflected to primary when the switch is off
Vin(min) - minimum input voltage
Vo - output voltage
Vf - forward voltage drop on rectifier
Dmax - maximum duty cycle
Nps - primary-to-secondary turns ratio


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I tried SAM-BA monitor for atmel at91samxxxx chips

I'm working with non-atmel board using at91sam7s128 , I tried the monitor program with board option : at91sam7s128 and noboard but neither of them works they are not responding ?!

My computer recognized the chip and I tried the board on both windows xp and linux :

In linux I have this when I put in terminal lsusb :

Bus 005 Device 008: ID 03eb:6124 Atmel Corp. at91sam SAMBA bootloader

and in windows I installed the driver and board is recognized in serial port category .

So if my computer recognize the chip and SAM-BA therefor do every thing must be ok ?

I also tried SAM_I_AM ,it successfully open a communication with my board using 'open command' but when I give a command like 'info usb' it gives me 'Error: SAM-BA not responding'

in my board I used some estimate value , in specific :

I used 31 ohm resistors instead of 27 ohm for DP-DM .
I used 12pf capacitors instead of 15pf for DP-DM .
I used 1.47k resistor in pll RC loop instead of 1.5k .which maybe
sounds good as what the pll calculator says .
and I used 12pf load capacitors instead of 10pf load capacitors for 18.432MH crystal .

and this schematic shows all parts related to usb in my board :

is there any thing could help me to indicate the problem ?  also I have some fears about FDN360P maybe it is slow in switching , but datasheet didn't said any things on how fast pulling up will be .


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How many  prime Implicants are there, 2 or 3?
F(w,x,y,z)=Σ(5,7,8,10)+d(9,11,13,15)

I am confused if red block will be counted as Prime Impicant or not?