texts: Difference between SVM and sinusoidal PWM in BLDC

texts:
In this answer Answer to question regarding difference between 6-step and FOC, the author said:

"Likewise if you have gone to the effort to implement a FOC you might as well implement a SVM block to maximise the utilisation of your DClink voltage (sinusoidal PWM is only 50%, SVM is 86%)".

What i fail to understand is, how is SVM different from sinusoidal PWM. I thought SVM is just sinusoidal PWM on all 3 phases.

What is the difference between SVM and sinusoidal PWM when used with BLDC motors , and how does SVM utilise the DCLink voltage better?


texts:
I'm currently in the middle of my 3rd year university project and am trying to convert the STM Discovery board into a data-logger.
I've already found this site, which demo's how to make a GPS data-logger and should be a good springboard for me.

My question is twofold:

1) Is the STM's USB port capable of 15Megabits per second (15Mbps) data transfer?

2) I've read that there is a physical limit to the size of the USB stick that the STM can read, but have not found any reliable source for this. Does this limit exist, and if so, what is it?

To clarify, the data being transferred are raw AC voltages from numerous sensors, along with the type of sensor, time of reading, and a counter value. 7 sensors are audio and sampled at 100kHz (max frequency of interest is 40kHz), 144 sensors are sampled at 3125Hz, and a further 100 sensors are sampled at 391Hz. All 16 ADC pins are in use, along with SPI2.

Thanks in advance.

Edit: Here is the full calculated aggregate of the data being transferred:

(12bits * 100kHz * 7sensors) + (12bits * 3125Hz * 144sensors) + (12bits * 390.625Hz * 32sensors) + (16bits * 390.625Hz * 63sensors) = 14343750bits per second ~= 15Mbps


texts: CMOS Schmitt Trigger: contradictionary information

texts:
Weste and Harris in "CMOS VLSI Design" describe the CMOS trigger as follows:

Let's call the transistors in the first columns from bottom to top M1,M2; M4,M6 and the transistors in the second column M3 and M5.

Note that M3 and M5 are indicated as weak, implying that their sizes are smaller than the other transistors.

On the other hand, Jacob Baker in CMOS Circuit Design, Layout, and Simulation it is implied that the same transistors must be much larger for having hysteresis. For example, in example 18.1. he derives W1=10u, W3=22.5u, W6=20u, W5=26u; W2 and W4 larger than the other transistors.

Which version is now correct?


texts: Questions about the battery management circuit of Beaglebone Blue

texts:
I'm currently trying to build a battery charging circuit and decided to reverse engineer the battery management circuit of BeagleBone Blue to understand how it works. Some of my questions are pretty basic/shallow, so please bear with me.

1) The circuit is using a MP2615 for charging 2S Lipo/Li-ion batteries.

As I go through the datasheet, I wonder what happens if you try to charge a over-discharged (unhealthy) lipo/li-ion battery (lets say 1V per cell).

1.1.Q) Will MP2615 still try to charge it in trickle charge mode even the cells are at 1V (I couldn't find anything related in the datasheet with the minimum necessary battery voltage to start charging)?

1.2.Q) It says that Recharge Threshold at Vbatt is 3.0-4.0 V/Cell. Does this mean that it will not charge the batteries at 4.00-4.20 V/Cell? So you cannot charge a slightly discharged battery unless it is below 4.00 V?

2) The circuit has a S8261 for extra protection.

And the model they are using is S-8261AAJMD-G2JT2x which has an overdischarge voltage protection at 2.50 V/Cell.

2.1.Q) As I know that a healthy cutoff voltage for a Li-ion/Lipo is around 3.00-3.30V. So it is not a wise idea to use the batteries until the protection kicks in (2.5 V/Cell)? Why is undervoltage limit so low in BeagleBone Blue board?

Source: https://github.com/beagleboard/beaglebone-blue


texts: The datasheet mentions some Advanced Hardware Features which gets executed by the Digital Motion Processor. I'd like to use the Android Orientation motion-based function and send the orientation with SPI to the microcontroller. However I can't seem to find the registers in the MPU9250 I need to enable this. I've looked through both the datasheet and register map.


texts: Why Do The Wires Inside a Headphone Cable Touch? Can't Wires Not Touch?

texts:
If you cut open the wire of a pair of headphones, say Apple Earbuds, there are a whole bunch of different cables inside that look (more or less) uninsulated.

My understanding of Electronics is that if two uninsulated wires touch, then the circuit will not work. So how come my headphones work fine?


texts:
This one has 3 loops. I need to assign a direction (e.g clockwise), form 3 equations and solve simultaneously. But I can't seem to do this question.
There's no voltage source on the third loop. Any help?


texts: Current sensing in buck converter - current sensing resistor or hall effect

texts:
I designed a simple buck converter working with voltage up to 15V and current up to 8A. It works great, but I would like to add current sensing now. I don't need anything that's super accurate and fast (I use feedback loop in Arduino, so it's slow anyway), so I'm looking for a relatively simple solution.

I came across a current sensing amplifier MAX4080, which looks like something I could use. The problem is that the datasheet says that it works with input voltage from 4.5V to 76V. I'm not sure if that also applies to a voltage of my output.

In theory this amplifier measures voltage drop on the current sensing resistor, so it's not dependent on voltage (to some extent), but maybe I'm missing something?

An alternative would be to use Hall effect sensor like ACS711, but I'm not sure which solution is better for a buck converter.


texts: AC 20V to DC 5V converter with zener diode question

texts:
I have this AC 20V to DC 5V converter with zener diode circuit. It works as expected if there is no load connected. As soon as I connect the load, in this case LED diode with 20mA consumption, the 5V output is reduced to 1.9V only and LED lights only with low light. I tried to calculate various R1 values from 120Ohm to 3K, but i never can reach output voltage higher then 2.2V. I also tried to reduce and even remove R2, but there was no significant change. Without load output gives 5.1V. Zener current is calculated for 20mA without load.

Can someone point me what can be the problem?

20V AC source is 10Amps strong source, so it can be excluded as source of the problem.


texts:
It's been ages since I had to design something electrical so please don't laugh if this is stupid idea but I would like to power ESP32 with super capacitors, just for 30 sec or so so it can finish the sketch even if the power is cut off suddenly. Except I have no idea if this would work as intended.

I made a schematic here:

The problem is I'm not sure how long it could power the ESP32 in this config if I put 4x 0.47 F caps in parallel (would that even work?).

Am I missing something, i.e. over charging protection - is that needed? If by some miracle this works, how can I discharge the capacitors once the ESP32 finishes and shuts itself off?


texts: I'm just getting into FPGAs, and if I understand correctly, you are connecting logic gates together using code. So if I design a CPU in Verilog, it should connect some logic gates together and work, but how do I know how fast my DIY CPU can run? What does it depend on?


texts: Convert 0-5 V input signal to 0-100% PWM

texts:
I am attempting to speed control two aftermarket DC brushed fuel pumps in an automobile.  The OEM pump control works in the following manner:

When driving conditions demand a decrease in fuel supply, the fuel
pump control module (FPCM) reduces the supply voltage to the fuel
pump. When driving conditions demand an increase in fuel supply
(during engine start, low engine coolant temperature or high load),
the supply voltage to the fuel pump is increased.

To effect this, the factory ECU spends a low current 0-5 V signal to the OEM fuel pump control module.  The OEM logic is very simple and drives the pumps at three speeds which will call low, medium, and high. This translates into roughly 8.5 V, 10 V, or 14 V (battery voltage).

With an aftermarket ECU, all my fuel pump control issues are easily solved. But I am trying to do this using the factory ECU to speed control the pumps, but not drive them. I will be bypassing the factory Fuel Pump Control Module because it can't safely support this load.  I am also trying to greatly simplify the wiring of installing these aftermarket pumps.

I will be driving the fuel pumps using a high current MOSFET Sink Source Driver made by Racegrade. It contains qty4 10 amp outputs that can only be switched to the low side and are all PWM capable. Each pump will be driven by TWO 10 amp channels and pump draws a maximum of 15 amps at it's peak pressure.

Now here is my question:

I need a module or solution that would take the 0-5V pump control from the factory ECU, and then convert that to a 0-100 low side PWM signal. The SSD's output is activated when the control wire is pulled down to 0V.

Here is a wiring diagram of the SSD:

Thank you an advance for any input you guys can provide.  I am not an electrical engineer but I am very interested in circuits and vehicle control systems.


texts: Is it ok charge a 4S1P(16.8v) 18650 with 24v@0.5A?

texts:
I have the vacuum cleaner Ilife V7s pro. And I opened the battery pack, it was a 4S1P batteries: 18650 2600mah.

However the charger adapter output is: 24v 0.5.

With my little knowledge, 24v will be: 24 / 4 batteries = 6v instead of a maximum of 4.2v for each cell, isn't it wrong, bad or dangerous?

The pack has a PCM with it. Does pcm reduce a higher voltage to what it needs?

This is the model of Vacuum cleaner:

https://www.ebay.com/itm/ILIFE-V7s-PLUS-Robotic-Vacuum-Cleaner-Robot-Dry-Wet-Cleaning-Brand-New/392658291952?hash=item5b6c420cf0:g:WPMAAOSwQF5eLsDY

And this is the adapter charger:

https://www.ebay.com/itm/Vacuum-Cleaner-Adapter-Charger-For-ILife-V7s-pro-V7-V7s-EU-24V-0-5A/323950604868?hash=item4b6cf5f244:g:WrEAAOSw12Nc21lV

Thanks a lot.


texts: How to run a car radiator with a PC 450w SMPS?

texts:
I have a car radiator fan which when measured with a multimeter on a 12v car battery draws 4.7a. I've been trying to run it off an old PC SMPS which is rated at 450W with max amperage of 18a at 12v.
The smps doesn't start when i connect the fan to the power supply while the smps fan starts running when there is no load. What would be the problem? Can adding a capacitor make the  radiator fan start working - if yes, what values should the capacitors be? What is the right solution to get it working?
Thanks in advance for the answers. Please help.


texts: Transistor Based LED Switching Circuit Design

texts:
I was going over a schematic for a component I was using, and it uses a transistor to switch on an LED. For the most part the schematic makes sense, however I'm not quite clear on the necessity of the cap going from collector to ground. Could anyone provide some insight into this?

The component in question is for Sparkfun's  AT42QT1010 breakout. Here is the full schematic to perhaps add some further context.


texts: MIPS assembly instruction to machine code in hex

texts:
I am doing some practice problems involving MIPS assembly instructions and machine code(in hex). I am doing a problem but am uncertain if it is correct. This is the problem, and what I did:

addi $8, $9, -150

It is an I-type instruction, so I write it accordingly.

opcode: 001000
rs: 01001
rt: 01000
immediate: 1111111101101010

The answer I came up with is: OX2128FF6A

If anyone can check it and let me know if I have done it incorrectly or if you can offer any help/advice, I'd appreciate it. Thank you.


texts: Fiducial marks: Do they need to be a pad or is it okay if I use the top silk layer?

texts:
I have been advised by a more experienced engineer to integrate fiducial marks on my designs for P&P automatic assembly referencing, but he didn't say how to do it exactly.
I googled it, and I see that most designs use pads for this purpose.
Why can't I just draw a circle on the top silk layer instead of a pad?


texts:
I have a project in mind using an RGB LED (here: http://amzn.com/B007RO9X82).

I would like it to be powered by USB.  Since the LED is rated at 3.0-3.6V, I understand I'd need a resistor.  What resistor would I need and would it throw much/any heat in this situation?  The feed wiring and resistor would be enclosed in a hole drilled in a wood plaque...don't want to create a fire hazard.

USB Power specs from WikiPedia: [5.00±0.25 V (pre-3.0); 5.00+0.25-0.55 V (USB 3.0) Max. current 0.5-0.9 A (general)] what resistor would I need?  I assume if I sized the resistor for standard USB and it were to be plugged into a charge port (5A), that would cause trouble, correct?


texts: In an exam today I was asked to design 2 circuits that would keep an output turned on for 10 minutes. I used a 555 Timer and a PIC, but neither are the best solution if the time delay needs to increase. So what other options are there for creating long time delays, many hours/days of timing to a few milliseconds accuracy(1000's of a second)?


texts: Three phase to Single phase current calculation

texts:
I have a three phase 380V system using 16A MCCB. Phase to Neutral is 220V. I want to install a single phase elevator that has the following specs: Voltage = 220V. Power = 3700Watt. If I calculate the current requirement with the following formula: I = P/V I get 16.81A (3700W/220V). I called the sales to reconfirm and they told me that the required current to operate the elevator is 25A. Now, since I am taking the power from a three phase system, will it provide enough power for the elevator? Can someone please teach me how to calculate the current conversion from 3P to 1P?

UPDATE #1: Thank you for the responses so far. However, if we put in the variables in rapidtables, it gives me just 7A (W=3700, V Type = Line to neutral, V=220, pf=0.8). Please note that my three phase source is 380V and I am using one of the three line to neutral to get 220V for the elevator.


texts: Does through-hole mounting have an advantage over surface mounting in sub-zero temperatures?

texts:
I am working on a device that I want to work outdoors far up north (e.g. on a farm), maybe down to -40C. I read a lot about through-hole circuit boards being more resistant to environmental stress than surface mounts, including heat, but no mentions of cold. I am guessing that

because of the larger distance between parts they would be more resistant to condensate that might form and also
because through-hole parts have "legs" or pins, those act like springs when the board expands-contracts during the temperature fluctuations

Are those valid guesses? Are there any other advantages/disadvantages I am missing?

SM is cheaper than THM so I am trying to make a list of pros and cons before I decide whether to choose one or the other.


texts:
I working on a home (rather room) automation system using a Raspberry Pi as 'brain' and an Arduino as sensor board.

I find it quite difficult to come up with a solution to reliably track if a person is currently inside the room or not (to trigger the lights).

Here are my current ideas and what I think about them:

PIR: only for movement detection, probably can't see when I'm sitting at my desk: would need to wave to the sensor every once in a while.
Door counter: not reliable if someone decides to turn on his heels.
camera: too difficult to program reliably.
IR thermo array: probably the most reliable, but expensive for high resolution, not sure if something about 4x16 would be enough.  [Edit] I have found that the Panasonic Grid Eye 8x8 thermopile sensor (~30$)  is advertised by Panasonic themselves as that it could span a whole room and indicate the position of a person in the room. Even though I think that this won't work for the entire room, it will surely be enough to get a nice movement vector in the area of the door if someone enters or leaves the room (if the sensor is faced more to the door instead into the whole room).
microwave sensor: haven't really found information about sensitivity in comparison to PIR.

Does anybody have some more ideas or thoughts on the ones listed above?


texts: Conversion h-parameters from common emitter to common base (request source to verify)

texts:
I calculated the \$h_{ob}\$ parameter from h-parameters of a common emitter transistor:

$$h_{ob}=\frac {h_{oe}} {h_{ie}h_{oe}+\left(1-h_{re}\right)\left(1+h_{fe}\right)}$$

How could I verify the result? Someone knows a source which has a conversion table? Online there are only conversion in the special case \$h_{re}=h_{ie}=0\$.

Thank you for your time.


texts:
I was reading these slides about crosstalk between transmission lines. At page 6 there is this circuital model to describe the effect of mutual coupling between these two lines:

My doubt is: why \$I_{Cm}\$ goes in both directions while \$I_{Lm}\$ not? And what is the definitions of both directions? They seems equivalent for me (look for instance at the line at right: it is identical in both directions, since it is in both cases loaded with an impedance equal to \$Z_0\$).


texts:
I have collected a burst signal from a radio device using an RTL-SDR and gnuradio and demodulated the FSK, but am having trouble deciphering what the line code is.

Signal is at 151.3MHz

Here is the signal in inspectrum

Here is the signal zoomed in

You can download the raw captured burst. I am viewing it using inspectrum. Also available is the demoded signal

I'm expecting around 12 bytes, after the preamble, that are transmitted from a sensor (that is from a third party).


texts:
In the beginning I would just like to mention I don't have too much experience with electronics and English isn't my native language.

I would like to use a BTS7960 module with Arduino data sheet.
Driving a 18v motor from cordless Dewalt Dcd785 drill and the only power supply witch is accessible for me is 24v 20A like this
Is BTS7960 got a step down module or 24v will burn the motor?

Thanks in advance


texts: Help me implement the crossroad traffic lights using multiplexers 4/1?

texts:
I came across this problem and it has a solution and everything, but I don't understand it. Here's the illustration:

So, the picture shows a crossroad which has sensors along the higher-priority DC road and the lower-priority AB road. They detect if there's a car on any of them. If there is a car in any of those roads, the sensor output is 1, otherwise it's 0. The crossroad is operated by a traffic light which functions like this:

1) W/E state of the traffic light is green if:

both C and D roads are busy
C or D is busy and neither A and B is busy
no cars on the crossroad

2) N/S state of the traffic light is green if:

both roads A and B are busy and neither D or C is busy
A or B is busy and neither D or C is busy
Implement the circuit for controlling the traffic light using only MUX 4/1 multiplexers if the inputs of the circuit are the outputs of the sensor and outputs of the circuit are states of the traffic light (1-green state, 0-red state).

Solution:

The part I don't understand are the information inputs of the multiplexers. What do they represent? Please explain in detail.


texts: Block Diagram Simplification and Routh-Hurwitz

texts:
I'm trying to solve an exercise of block diagrams and Routh-Hurwitz, but I stuck in the simplification part. Could you help me?

Reduce to an equivalent single block:

For what values of K the system will be stable?

It's my first time trying to solve this, so I'm sorry if this is a "too easy question".

My effort:

I initially simplified the block diagram to this:

Then this:

Anyone can confirm if I'm right?


texts:
I'm trying to find resistance table for Ni 500 and Ni 200. I found tables for Ni 1000, Ni 100, NiFe 604 and NiFe 507.7. But I wasn't able to find resistance to temperature table for Ni 500 and Ni 200. Could you please give me these tables? Or is it possible to convert Ni 1000 resistance values to Ni 500 and Ni 200. For example is it valid :

(Resistance of Ni 500) * 2 : find this value from table of Ni 1000


texts: Capture and transmit NTSC with ESP32? (w/video decoder chip)

texts:
Is it possible to use a video decoder (ie. MAX9526) with an ESP32 to capture an NTSC composite video signal and then transmit over a web service?
Can anybody give me any advice or information?


texts: Why are there so many names for electronic components in eagle cad?

texts:
I was searching for a diode to add in my schematic diagram in eagle cad, and when I typed diode there were too many results. There were different codes for each diode.
Do they all function differently?
I have posted a photo of results below.


texts:
Looking at various ARA prototype pictures I noticed they all seem to feature pluggable connectors.

Sadly I could not find out which ones.
Can anyone make heads or tails of this picture?


texts:
I always see an rgb led ran with 3 resistors, for example a 20ma led on 5v power uses 150ohm's for red due to it's lower voltage but only 100ohms for green and blue. I am running 6 shift registers off of a microcontroller via spi. I have 16 common anode LED's. all of the anode's on the led's share the same source. my question is could I potentially limit the current going to all the anode's and then only have the red cathode's use an additional resistor?

i.e

          g on led no resistance- 1-|--------|-16 -vcc
          b on led no resistance- 2-|        |-15 -50 ohm resistor to R on (rgbled)
50 ohm resistor to R on (rgbled)- 3-|  74    |-14 -serial in from MCU or prev. register
          g on led no resistance- 4-|  HC    |-13 -NA
          b on led no resistance- 5-|  595   |-12 -latch to mcu & next register
50 ohm resistor to R on (rgbled)- 6-|        |-11 -MCU clock and clock on next register
          g on led no resistance- 7-|        |-10 -Master to 5v high for inactive
                             gnd- 8-|________|-9  -to pin 14 on next register
_____________________
|____________________|_R____ 50 ohm resistor to pin 15
|____________________|_+____ shared 5v with 100 ohm's resistance
|______RGB LED_______|_G____ pin 1 no resistance
|____________________|_B____ pin 2 no resistance
|____________________|


texts: According to this figure how do I get equation 4


texts: Effect of resistor on the attached circuit

texts: I have a circuit board that I am trying to repair. I have identified that the following components are bad. ICS801 and RS816 (0.65 ohm resistor +- 5%). I could replace ICS801 but could find an exact replacement for RS816. I am curious about the effect a lower (0.62 ohm) or a higher (0.68 ohm) resistor might have on the operation of the circuit.


texts: characterize internal capacitor of optocoupler

texts:
I am reading article Using an automated Excel® spreadsheet to compensate a flyback converter operated in current-mode by Christophe Basso, Tomas Petrek/David Sabatié.
In page 12, they explained how we can measure the opto's capacitor on the bench (see fig below).
but it is not clear to me why we have to change the Vbias to have 2,5V at VFB! is it related to Vref?
and why the select the Cdc equal to 10 uF?
generally, what are the rules to calculate them)


texts:
I'm trying to understand & design a circuit using two IR2184 half bridge drivers and some n channel mosfets to create a full H-bridge to control a motor.

Reading the datasheet for the IR2184 it mentions that there is a shutdown state. One of the pins on the IC is also marked shutdown and from the logic diagram appears to have an internal pullup resistor.

I assume therefore that in order to bring the IC from it's shutdown state to an active state I have to pull that pin to ground.

What I'm not sure about though is what does shutdown mean for the IC? Is it simply that regardless of the input both high and low outputs will remain low and therefore both mosfet gates will be closed?


texts:
I have (a chinese clone of) a Wemos D1 mini board, which uses the ESP8266 microprocessor. Since the ESP8266 has a 3.3V operating voltage, it includes a low dropout regulator for the USB 5V. According to the Wemos D1 mini schematic, it uses the RT9013 LDO .

According to the (RT9013 schematic), it has an operating voltage of 2.2V to 5.5V. This I do not understand, I thought the LDO could only drop to a lower voltage?

Also, it has a dropout of 250mV at 500mA, which I thought meant that there must be at least 3.55V. With that in mind, what's the best amount of AAA batteries I can use in series to power it?

I assume non-rechargeable batteries have an operating voltage of around 1.5V, which would mean that I would need three AAA batteries (4.5V). I've also read that the lowest the battery gets is 1.2V or so, which would mean that the total voltage would only be 3.6 V. This is still above the 3.55V minimum, so should it be OK?


texts: Make a button to control both AC and 12V DC light

texts:
I want to make a button which control both ac and dc light
When button is on
If there is Electricity
Then AC bulb will be on
Else
DC bulb will be on
And if button is off both ac ane dc bulbs should be off


texts: Finding the schematic of a black box with unknown impedances

texts:
I'm struggling with trying to understand a piece of homework in Electrical Engineering that I'm really trying to solve on my own but now I'm basically stuck.

The assignment is to find the schematic for the black box given below:

The black box can contain either 2 or 3 components according to the assignment. All impedances are unknown. The assignment is to explain how one would measure and analyze the circuit in order to understand which components are present and what their values are.

It's also given in the assignment that the system is a first order system which consists of RLC components in some combination (as I interpret it this would mean that it's an RL or RC circuit, so only 2 components then I suppose?). But I have no idea where to go from here... The main problem is that I'm lacking resources that I can further study for this also. Any help is much appreciated.


texts: How to find the output and input impedance of an amplifier

texts:
For example:

Vcc -> GND

capacitors -> wires

NPNs -> hi and current source

The schematic above becomes:

How can you find the output and the input impedance?

The answer in this case should be(output impedance):

I guess hi1=hi2 since it's the same transistor


texts: Step down from USB (5 V) to 4.3 V for battery dummy

texts:
I have a camera for which I bought a dummy battery to connect it with power bank or other power source. Original battery is 3.6 V Li-ion so I need around 4.3 V but the USB (from powerbanks) is 5.1 V usually.

What I can do to step down to 4.3 V without loosing much energy in the middle to not discharge battery quickly? I found the buck module MP1584 but in the datasheet there is Vin-Vout > 1.8 V so it won't fit right? Is there anything else I can do, or can I use a 5 V without destroying my camera?


texts: What did I do wrong with this switching voltage regulator circuit (LM2574)?

texts:
I'm new to the electronics world. I've been trying to build a switching voltage regulator circuit using the LM2574N-5G (datasheet) IC. I'm trying to switch 9V (from a 9V battery) to around 5V. I've tried to implement the circuit that the datasheet suggests, which looks like this:

Notice the red box I superimposed on the schematic. The manufacturer suggests a resistance of 3.1Kohms for R2 to achieve an output of 5V. I went ahead and used 2Kohms for R2 to try and get a voltage between 3.3V and 5.0V.

Here's my attempt to implement this circuit:

I connected two LEDs in series as a load at the output, and they immediately burnt up. I quickly unplugged the battery and checked to see if the battery or any of the other components were hot - they weren't.

After removing the LEDs, and with no load on the supposed "regulated" output, I then measured the voltage between the output and ground, and I measured 7.40V! I swapped R2 with some different value resistors and measured the voltage each time. Here is what I found:

R2      - Voltage
22 ohm  - 5.01v
200 ohm - 5.24v
510 ohm - 5.61v
1k ohm  - 6.20v
2k ohm  - 7.40v

Nothing was running hot during these measurements. Am I missing something obvious or critical? How am I meant to interpret this data? I wouldn't be surprised if my problem can be attributed to a silly mistake on my part - I have no intuition for this sort of thing. Thanks for any input.


texts: What design should I use to clean up this pulse wave?

texts:
I'm using common voltage controlled oscillator IC - AS3340.
It has some problem with pulse wave output on higher frequencies. The bottom of falling edge looses sharpness the higher I go.
This is how it looks at the limits of audible threshold:

I need some advice on cleaning up this signal so I would get nice and crisp pulse shape all the way.
This is my schematic. I'm measuring it at the PULSE_OUT node, without attaching the amplifier circuit.


texts: I'm on Mac OS X and have a license for IntelliJ Ultimate. Is it at all possible to use IntelliJ as an IDE for Arduino projects?


texts: I have been looking for a simple ac dimmer circuit to use with my arduino and/or raspberry pi. I have used the TLC 5940 PWM Driver before just to control LEDs and I wanted to adapt this to controlling strings of xmas lights. Since I am just beginning with electronics, I don't wanna blow my face off by doing it wrong. Do you have any suggestions for anything that is not only compact but cost effective???


texts: Question regarding 74HC574 (question very difficult to word)

texts:
Basically, I have a question regarding the timing of the 74HC574 octal latch.  According to the timing diagram, the data pins must be set for so many nanoseconds before the latch pin (rising edge triggered) is pulsed or else the data may not be retained as it should be.

Because the Z80 cannot change the states of its data pins (in which case I could set the data pins with one command, then pulse the latch pin afterwards) this leads me to believe I will have to purchase a parallel IO chip for the Z80 (which I don't want to have to do as that is yet another chip I'll have to add to the motherboard, making it even larger and/or more crammed for space).

BUT, I'm wondering if the I/O address decoding logic will create enough of a delay, as AND gate ICs will create a very small delay (in the nanosecond range as well). The data bus will be directly connected to the 74HC574 and therefore will change the data pins instantly, but the signal which will pulse the data latch pin will have to go through a few AND gates of glue logic which might create enough of a delay that the data pins will be set long enough before the latch pin is pulsed.

I apologize for not being specific in the title, although if you read this you probably agree that my specific question takes a paragraph to explain.


texts:
I'm trying to understand this temperature sensor circuit I came across on a room Air-Conditioner controller (Want to build one myself).

The sensor is an NTC type thermistor (15k at 25 deg C). What I collect is that the NTC along with R2 form a voltage divider, the output of which is fed into the ADC input of the microcontroller.

What are C1 and C2 for? Do they form RC filters along with the thermistor? If that is the case, then the cut-off frequencies are 106.1Hz and 1.06Hz? These appear to be very low.
What is R3 for? Is it limiting the current? If ADC input pins are high impedance, why limit the current?
Do R3 and C3 form another RC filter? Then again the cutoff frequency is 3.386kHz. And there's nothing apparently operating at that frequency on the board. (The micro controller is connected to a 4Mhz external crystal and the board is powered by 230V/50Hz mains).

Thanks.


texts: Connecting cell phone and computer audio through TRS and TRRS 3.5 mm audio jacks

texts:
I am trying to connect the computer audio output to the cell phone audio input and vice versa. There are two connection designs because I need to be able to connect both to a desktop and a laptop which feature different audio interfaces.

Regarding the connection I have several questions:

Are the pins correctly connected?
Will the signal levels work as is or should I amplify/attenuate them?
Can I only connect one channel and make away with the mixer? Obviously whatever comes out the other channel will be lost, but I am interested in knowing if it is safe to directly connect the audio output of one channel to mic/line in.
Can you think of a way of mixing the audio channels with only passive components or removing the mixer in any other way?
The desktop has both mic in (pink color) and line in (light blue color). Which of these inputs is better suited for my application? What do I need to do differently if I connect to one or the other?

Many thanks in advance.


texts: LTC 1060 switched capacitor filter in mode 3: why this output forms:

texts:
So I'm simulating a switched capacitor filter using LTC in mode 3. Here is my schematics:

Now I'm performing a transient analysis with a 3V sinusoidal voltage with frequency 1.4 kHz and a 3V square wave with frequency 250 Hz. However I don't understand my results. The sinusoidal one is way off, while the square wave is while more acceptable I don't get what is going wrong. Can someone please help me understand this?
My results:


texts: Which component/s determine the maximum voltage of an ESC?

texts:
Which component/s determine the maximum voltage of an ESC ?
( max esc voltage is 50v (12s * 4.2 ))
Does this limitation is due to vgs of mosfet, which i think is +- 25v , if yes why they choose 50v instead of 25v


texts:
We all have seen experiments where an electric arc is created. Sometimes arcs of four inches are created with pretty rudimentary devices.
When two electrodes are brought close together, a spark flashes. Then the arc is created an the experimenter moves the electrodes further apart.
My question is about the distance between two electrodes. What exactly should the distance be for a spark to flash? How is it related to the voltage?


texts: Termination of a convolutional encoder vs. state register reset

texts:
Usually, when designing a convolutional encoder for a transmitter, some sort of termination mechanism is applied to drive the encoder back to its zero-state after a message was transmitted. This is often done by appending a tail sequence to the transmitted message, e.g. a certain number (n) of zeros in case of a convolutional encoder without feedback. This way it takes n clock cylces to return the encoder to the all zero sate.
On the other hand, e.g. when implementing a convolutional encoder in HDL, this reset to the zero state could also be achieved by simply resetting all (shift)registers of the encoder. That way the zero state could be reached after only one clock cycle.
In the literature I never saw anyone mention the second method and was wondering what is the reason for terminating a convolutional encoder with a tail sequence instead of simply resetting the state registers?

EDIT: If the convolutional encoder contains feedback, additional circuitry is required to calculate an adequate termination tail to drive the encoder back to zero(a system of linear equations must be solved). So why would anyone trade the 'simple' reset solution for a solution consuming more hardware and time?
(My specific case concerns LDPC convolutional codes, which can have deep encoder memory, so the time required for terminating the code is not negligible.)


texts: Can the directory/path on the schematics be disabled for the print in LTspice?

texts:
When you print preview from LTspice schematics the program automatically adds path/directory of the file to the bottom of the pdf.

Not really a question directly related to an electrical engineering topic but I thought someone might have information about this. I've been searching to disable it but couldn't find a way. I don't even know whether it is possible to disable this.

Basically if you are using LTspice open one of your schematic go to File and select Print Preview and look at the bottom, it will show where your file is on the pdf. Can we disable this so that we don't reveal the directory?


texts: Understanding extra thermocouple voltage between computer and machinery

texts:
I developed my own circuit board which reads temperature from a thermocouple.  This board also plugs into a computer via USB and my software communicates with the firmware on the board.  It's fairly simple.

This is being used to record temperature readings from coffee roasters (here is an example).  Sometimes, a voltage develops between the roaster and computer.  What happens is that this voltage can be transmitted through the TC wire to the circuitry and throw off the temperature reading (since TCs work on the principle that the potential changes between the two wires as a function of temperature).  I've gotten around this by using ungrounded thermocouples exclusively, which isolate the actual TC wires from the outside world.

However, I'd really like to understand why this happens.  I'm not an EE genius...I prototyped this board on an Arduino and paid a real EE to build and program the actual circuit.  I'm simply confused about what is going on exactly, and how I can be sure to eliminate any stray potentials which can interfere with the temperature readings.


texts: How do I calculate the thermal resistance of aluminum flat stock

texts:
It's common for a lot of power circuits to bolt to a piece of aluminum flat stock. How large does the stock need to be?

Say that I'm mounting a tip122. The worst case condition is for it to have a 24V drop at 3A and a 50% duty cycle. So it is dissipating  36W.

Looking at the datasheet, at 35W, the max case temp is ~80C. Assume a 25deg ambient temperature.

Temp drop = 35W * Tr = 55 delta or 1.57C/W for the plate.

So how much surface area do I need to achieve that?

Did I approach it correctly?


texts:
What is the IEC 60617 schematic symbol for jumper and test point?

I have tried to find it in the official standards but it seems not to be defined explicitly.


texts: Multiple Minimal Expression for a given logical function

texts:
My professor said that there can be logical functions with multiple minimal sum expressions. However, I am unable to find any such example.
Can anyone please give an example of a logical function with multiple minimal expressions?


texts: Wiring up a computer fan to a normal outlet, without using a computer PSU

texts:
Ive got a Rack that is getting abit hot and i would like to cool using fans. Ive checked out units made by Mid Atlantic c.£300 which are really expensive, but have also come across places selling fan rack mounting panels for normal pc fans for about £10 and can hold 3 fans, and then a normal pc fan is about £6 each so i thought id give that a try first.

My question is how to power them up, as i understand a pc fan has a molex connection on it, as its meant to be used with a computer PSU, but in this application is there a way i could wire this so that it would work with a vis some sort of transformer ?

Power supply wise im in the UK.


texts: Is there a benefit to charging a supercapacitor in parallel and then discharging in series?

texts: I'm interesting in building a hand crank charger for a 12V supercapacitor bank. I'll need multiple supercaps in series to hit 12V but to my novice understanding, it seems more efficient to charge in parallel and then switch to series for discharge. I get more capacitance and my resistance should be lower. Therefore reducing the crank torque of the hand crank. I'm looking for someone who knows way more than me to tell me if I'm wrong. Thanks!


texts: Why does a transformer for halogen bulbs burn when bulbs are too strong?

texts:
If I have a transformer for 4x20W but I use halogen bulbs let's say 4x60W, why does the transformer burn then? I always thought that the bulbs are only as strong as the transformer gives, but it's the other way around. The transformer tries to give 4x60W and burns after short time.
Why is this so? I'd like to understand the physical background. Is this because the current density becomes too high or something like that?


texts:
I'm making a ESC for my BLDC motor. I used a STM32 (to generate my PWM), 3 IR2101 mosfet drivers (https://www.infineon.com/dgdl/ir2101.pdf?fileId=5546d462533600a4015355c7a755166c) and 6 mosfets to control the differents phases of the motor.
My schematic:

I generate my phase with a PWM on the High side and a GPO on le Low side.
HIGH side of my PWM (phase A,B and C)

PHASE A (going below 0V!)

The signal seems correct but when I connect my motor we can see that the BEMF is backward compared to a good BEMF.
PHASE A B C

BEMF A B C

I try to change the frequency of the PWM, change the duty cycle or the delay between each phase but nothing change (and sometime it's worse...). Do you have an idea why ?
My STM run at 8MHz.
PWM frequency : 900Hz with a duty cycle of 5%.
During this test my motor consumes 12V / 0.8 A.
EDIT
I don't know why my BEMF is reversed compared to a good one.

Below you can see my phase C (yellow), the virtual ground of my motor (light blue), the mathematical operation Phase C - Virtual ground (dark blue) and the output of my LM339 (pink).

I saw multiples subject about this problem on Stack exchange but each time the answer isn't clear. (enter link description here).
I guess that my PWM and BEMF aren't 'in phase'.. I need some explanations.


texts: What are the equations/values for Rayleigh Fading, path loss and log-normal shadowing?

texts:
I am to use the following equation as part of a model for a wireless communications network:

I would like to know the specific parts of the eqautions:

"k" - is this the Boltzmann constant?

"v" - I have read that the minimum value of this can be 2, but how do I calculate it or what is the formula for it?

"xi" (zero-mean log-normal shadowing) - how do I calculate this/what is the formula for this? (could it be the Friis equation?)

"F" the equation just says that this corresponds to Rayleigh fading but it isn't clear what this means.

This part of a model is taken from the following paper: http://thesai.org/Downloads/Volume9No1/Paper_55-An_Energy_Efficient_User_Centric_Approach.pdf


texts: Using an undersized LiPo/Li-ion charger for large pack of 18650 batteries

texts:
I'm looking at using a stock Sparkfun LiPo/Li-ion Battery Babysitter to charge an array of four 18650 Li-ion rechargeable batteries (Panasonic) in parallel, keeping the pack voltage at 3.7V. I chose the charger because it has excellent monitoring and control on-board. I read the data sheet for the Texas Instruments charge controller and it had the needed protection for the unprotected batteries (under-voltage, over-voltage), with the over-current protection provided by a simple fast-blow fuse.

The only issue is that the charger only runs at 1.5A max current. Considering that the battery array is capable of taking more than four times that rate, is there going to be an issue charging so slowly? I've seen Sparkfun recommend this charger for their 3.7V LiPo pack that uses three 18650 batteries, so I figured it would be fine and just charge very (very) slowly. If it's necessary, I suppose I could wire up two chargers and split the batteries between them, but I don't mind the slow charging rate if it won't hurt the batteries.


texts:
I'm a total newbie at this, but I have a photoresistor set up so that it controls the shorting on an audio circuit. When light is on, it shorts and cuts the sound. When it is dark, it closes and allows the circuit to run normally. How can I reverse this so that light will make the sensor close the short, thus allowing sound to run through?

More simply, I just want the photoresistor to open with darkness, and cause more resistance with increasing light. Sorry for being so layman about it, but like I said, I'm very new at this. Thanks for any help.


texts: Why does AC input have a parallel resistor and capacitor?

texts:
Well, I am trying figure out a situation with images and a circuit diagram.

I am checking all part looks normal, but if I insert this board on a machine the resistor is exploding and one leg of resistor is breaking off.

Actually I don’t understand why a resistor and capacitor was inserted parallel to the input of the AC power supply. Additionally, the resistor is exploding, but the fuse is solid yet.

simulate this circuit – Schematic created using CircuitLab

New schematic as a JPEG image:

For the circuit, I didn't find a varistor symbol, so I use an adjustable resistance symbol in circuit instead
Resistance: 470 kilohm


texts: Please help me identify the SMD component

texts:
I have two nVIDIA Quadro P5000 GPUs. This component got damaged in one of the GPU while I was removing it from the PC. Please help me to identify this SMD component so that I could purchase and solder onto the other GPU.
Thank you


texts:
one last question like that. I have the LM1496. The datasheet says that the maximum input voltage is 5V.
DATASHEET
The question is why is this true? What determines these 5V limit?
Thank you!


texts:
I want to install some smart switches in an older home without ground wires.

I'd also prefer not having to purchase a "Smart Hub" as they seem to be going away and not necessary.

Note, I use Google, no Apple if that makes a difference.

Other than running a ground back to the panel (too expensive) is there a way to make this work?

I realize the smart switch must have some power to stay On so it can respond to Wi-Fi, etc.

Thank you,


texts:
I have ACS712ELCTR-20A-T and I have connected it with the 5 Volt/10A converter.

Vout in the schematic diagram above, is connected to CURRENT in the diagram below:

I want to measure the output of the IC (in pin 7), but there is no change in the output of the IC (pin 7) W.R.T load. As per datasheet, Vout will change 100mV/A but I am getting 100mV all the time when increasing or decreasing the load.

Please suggest how to resolve this issue.


texts: Inverting amplifier vs noninverting voltage amplifier

texts:
A big advantage that noninverting voltage amplifier has over the
  inverter is a much greater input resistance. As a result, this
  amplifier will readily amplify the voltage from a source that has a
  large output resistance. In contrast, if an inverter is used, almost
  all the source voltage will be lost across the large output resistance
  of the source, as should be apparent from voltage division.

From textbook: "Schaum's- Basic circuit analysis"

How those facts ( like noninverting voltage amplifier has  greater input resistance) can be viewed ( through which equation), because the voltage gain doesn't seems to hold the answer?


texts: Why this selected area is bigger than the component area?

texts:
I am new to Altium, this is my first board development. My question is why the selection area is bigger than the component area, How to remove it{because I can't able to place another component near to them}?
Note: I used Ultra Librarian to download Component Library.
Thank You


texts: capacitor power supply for 1 Amp output current

texts:
I'm trying to make a fairly small AC(220V) to DC convertor to power microcontrollers and some actuators. It needs to output a current of 1 amp to the load. I tried looking at using transformers, but all the ones I could find that are rated for 1 Amp output current are too big for my design. So I changed my design to be a capacitor power supply. I'm thinking of using the circuit provided in this website: http://www.circuitsgallery.com/2012/07/transformer-less-ac-to-dc-capacitor-power-supply-circuit2.html

But this one only supports around 150mA, It seems that if I change the X rated capacitor to 11uF from 2.2, I can get an output current of 1 Amp. Does this seem feasible. I am fairly new to electrical design, any help would be very appreciated!


texts: Why is the output from my photodiode not linearly related to laser power?

texts:
I have some basic understanding of electronics but am having trouble optimizing our setup for laser intensity measurements.

Currently, we are using a Thorlabs photodiode PDA100A with 50Ω terminators connected to a Thorlabs 10kHz lowpass filter. The filter is then connected to our NI BNC-2110 connector (I would add more links to products but apparently I need 10 rep to post more than 2 links) on a analog input channel using differential terminal setup. We are reading the voltage using a NI PCI 6122 DAQ board. We are sampling at the max sample rate and using a trigger to determine which sample to read from the card.

The problem is, the relationship is non linear. We can double our laser power without doubling the voltage read on the DAQ card. The photodiode uses a transimpedance amplifier which we have set so that there is no gain. We are not reaching anywhere near the saturation limit of the photodiode - our measurements are more around 2-3V.

My question is at what point in our set up can you imagine nonlinearity taking over? I am skeptical of the low pass filter but that's partially because I don't know enough of the response voltages to understand how they would affect the data. Let me know if you have any suggestions.

Thanks in advance!


texts: How does a receiving antenna generate current/voltage?

texts: I have see on many websites people explaining how antennas radiates energy. But I am failed to find an explanation on how a receiver (i.e. receiving antenna) generates current/voltage? Can anyone explain?


texts: Measure current ripple over shunt, legit?

texts:
I'm thinking of using a calibrated shunt and then measure the current ripple by measuring the voltage over the shunt, with an oscilloscope.

I'm assuming a differential probe would be the best choice to go by.

The thing I want to achieve with measuring this way instead of my other option current probe is a wider bandwidth and to measure faster rise and fall times or the current.

However I'm a bit unsure about the Pros and cons of doing so? compared to a current probe.


texts:
I've been trying to program a word of flash memory on my STM32F030F4, but for some reason whenever I power it off and on again, the memory location has defaulted to '0xFFFFFFFF' again. Am I missing something here? is there something else I need to be doing to stop it clearing the memory on reboot?

Here's the code I'm using.

#define BRIGHTNESS_MEM 0x08003000

void FlashWrite(int data)
{

if(HAL_FLASH_Unlock()!=HAL_OK)
    ErrorHandler(FLASH_ERROR);

FLASH_PageErase(BRIGHTNESS_MEM);
FLASH->CR = 0;

if(HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, BRIGHTNESS_MEM, data) != HAL_OK)
    ErrorHandler(FLASH_ERROR);

HAL_FLASH_Lock();

}

I know it's writing the memory because after a write I can use the ST-link utility to inspect that memory location.

The steps taken when powering on to read the memory location:

int *mem = (int *)BRIGHTNESS_MEM;

// Load last brightness level
setBrightness(*mem);

I know it can read from that fine because I've tested writing to the memory and then checking that location for the data.


texts: Can someone help me fix this water level controller?

texts:
A, B and C are the prongs that stick into the water at 1/4, half and full respectively. D is used to provide the current to switch on each of the prongs as the come in contact with the water.

That all works fine but when the motor part is introduced it does not work as it should. When the water level is at A this is meant to be turn on the motor by turning on Q1 which should allow sufficient voltage to turn on the IRF3205 MOSFET. When C is turned on this should allow the power in the MOSFET to discharge and turn it off. But none of this happens, instead, D1 and D2 light up suggesting that something has gone wrong. Could someone please help?

Update:

I have added in the resistors and the BJTs are still BC635 and the MOSFET is still an IRF3205

Update 3:

I have changed where the base is connected and I think this would work @transistor


texts: Smaller alternative to RJ45 Ethernet connector

texts:
I am trying to minimize space usage for an enclosure that holds 48 boards with a RJ45 connector for Ethernet communication on each board. The boards work well with 10BASE-T (2 pairs) connection to a 48 port 10/100 Ethernet switch, faster is not really needed.

I am thinking of replacing the RJ45 with a much smaller connector, or with simple gold fingers and have an edge connector going on top - in best case even a backplane that connects to multiple boards at the same time (other end would still be 48 port Ethernet switch though for the time being).

Would this work or do you have other recommendations?

(objective is shaving off the height of the stacked boards, keep noise at minimum, and avoid connecting one by one if possible)


texts: Why the voltage is assumed zero Confusing

texts:
The question asks to solve for I and V.

Why the voltage is assumed to be zero?
Here is the solution

How did he arrive that V = 0 volts.
If he says it’s 2 volts would it be wrong? Why?
I am confused.
This example is from microelectronic circuits by sedra smith sixth edition page#182.
Just confused how is V = 0 volts


texts: Using an earth bonding plug for grounding server rack enclosure

texts:
I have a 18U server rack enclosure in my 4th storey home and want to connect the metal frame to electrical earth. The rails are already bonded to the frame with 2 wires by the manufacturer.

My wall sockets are 3 pin plugs with earth, live and neutral wiring. Would it be safe to use something like an Earth Bonding Plug for grounding the enclosure frame?


texts: When to not use electrolytic caps at the input of flyback converter?

texts: This reference design does not use bulk capacitors at the rectifier output. It uses small ceramic capacitors. On the bright side, I like it because it eliminates the reliability issues of electrolytic caps with time. But the ripple should be big. How do I decide if I can get away with no using bulk input capacitors and if my circuit can tolerate the high ripple? Can flyback design like this inherently tolerate it?


texts: Multiple nearby ICs require capacitor on power supply, do I need them all?

texts:
I am designing a circuit that has a voltage regulator supplying several ICs. The voltage regulator, sensor, and communication module all recommend capacitors from VDD to Ground (1µF, 100nF and 100nF respectively).
My understanding is that these capacitors will all be in parallel. If these devices are all within a few mm of each other, can I roll all the capacitors into one (1.2µF) capacitor from VDD to ground?


texts: What quiescent current draw of my circuit would be acceptable for a 100mAh battery?

texts:
The microcontroller and several sensors of my circuit draw 10µA in sleep mode. I am using a 100mAh lithium polymer battery. Is this quiescent current acceptable? Should I install a physical switch to shut down the device completely?

Should I install a p channel MOSFET on the voltage rail of my sensors to reduce the quiescent current down to 3µA?


texts: Is there a functional difference between square, round and octagonal via pads?

texts:
The reason why these different shapes exist is probably historical, but I'm interested whether there's any reason today to not only use a single kind of via.

The ones with round pads are the most effective in terms of area, so those are the ones I usually use.

Is there any scenario in which a via with an octagonal or square pad could be a better choice, even if it's just for routing purposes? Or are there maybe some PCB manufacturers only able to make certain shapes of pads?


texts: How do I calculate the resistor value for this circuit? Will this circuit allow buzzer to work?

texts:
I have a circuit that uses an LED and a simple buzzer.

I've created a basic circuit (below) and used a speaker to represent the buzzer.

I know two things about the buzzer :

Rated Voltage: 12V; Range of Voltage: 3-24V
Rated Current: 15mA at 12VDC

I'm not sure if that means max current but I'll just assume it does.

I use Ohm's law to calculate 3V / .015 = 200 Ohms and I place a 200 Ohm resistor in the circuit and I'm lucky enough because the LED will illuminate with that current.  But I have a couple of questions.

Voltage Drop of LED

But that is probably incorrect, because the voltage drop of the LED is approx 2V, right?  I probably need to calculate 1V / 0.15 and use a 60 Ohm resistor (or something close).

Would the buzzer work since it requires min of 3V and the LED drops the voltage by 2V?
I thought that voltage is variable within a circuit, but current is the same throughout?

Can you help me understand the steps I would take to calculate the proper resistor for this circuit and if it is possible to power both the LED and buzzer from the 3V power source?

simulate this circuit – Schematic created using CircuitLab


texts:
From the Wikipedia article Metastability in electronics:

  Metastability in electronics is the
  ability of a digital electronic system
  to persist for an unbounded time in an
  unstable equilibrium or metastable
  state. In metastable states, the
  circuit may be unable to settle into a
  stable '0' or '1' logic level within
  the time required for proper circuit
  operation. As a result, the circuit
  can act in unpredictable ways, and may
  lead to a system failure.

That seems to be a good definition, but what does it mean in an application?

From an electronics designer's standpoint, what are some examples of when this might occur and where should this type of failure be of concern?

Is there a more pragmatic or applied definition - something in more specific terms?


texts: Actual procedure used to establish a MW link budget in telecom?

texts:
If it possible can someone share with me the actual procedure used  (Not the theoretical steps in book !) like in Huawei or others telecom vendor to establish a Microwave Link between to sites

Like the Software tool they use and actual parameters.

Thank you all


texts: Does the resistor values used for opamp circuits come from the equations?

texts:
I've the following circuit:

I used the LM741 as the opamp. The input resistance is \$2\cdot10^6\space\Omega\$, the output resistance is \$75\space\Omega\$ and the voltage gain is \$2\cdot10^5\$.

  Question: I choose values for the resistors \$R_{in}\$ and \$R_f\$ that are between \$10\space k\Omega\$ and \$100\space k\Omega\$. But how does that range follow from the input resistance and output resistance equations?

My work: from this page (slides 31/32/33) I found that the equations are:

$$R_{input}\approx R_{in}+\frac{R_f+75}{1+2\cdot10^5}\to\infty_{ideal}\tag1$$
$$R_{output}\approx\frac{75}{2\cdot10^5}\cdot\frac{R_{in}+R_f}{R_{in}}\to0_{ideal}\tag2$$

  Now, I don't see how the values follow.


texts: How can I wire a RFID antenna to a Raspberry Pi?

texts:
I try to connect this RFID antenna with a Raspberry Pi 4B:

What does TX1 and TX2 stands for?
How can I make this antenna work like this RFID module I am using from a starter kit, which can be seen in this picture:

A GPIO extension shield is available for this task if it makes things easier for wiring up.


texts: How to interpret different socket tester results with and without power strip?

texts:
I bought a socket tester (this one) in order to check the power sockets in the house I rent. Half of them seem to be correct and the other half is marked as "LIVE/NEU REVERSE" which is not that good, as far as I understand.
One of those "LIVE/NEU REVERSE" sockets has a power strip plugged into it. It's a new power strip with ground connections and I've decided to check its sockets with the same device, just out of curiosity. To my surprise, the device marked all of the power strip sockets as correct.
What does it mean? Is it possible that power strip detects "LIVE/NEU REVERSE" state and corrects it automatically? If so, does it really fix the problem and make this socket safe to use?
UPDATE: I tried it with "correct" socket and now the power strip is marked as "LIVE/NEU REVERSE".


texts:
I am trying to design the usual remote-controlled relay board for mains usage (I live in Europe, so that means 230VAC). I need to tackle the usual problem of the switching of the relays hanging/resetting the microcontroller. As far as I know, there are two ways to prevent this:

Use galvanically-isolated power supplies for the logic and the relays.
Use a suitable snubber circuit on the relays.

I would like to avoid #1 for a matter of size and cost and focus on #2. As far as I understand, the snubber circuit should be tailored to the load the relay will drive, but I would like to come up with the most generic circuit that will work in most cases. This is what I have so far:

I put this together based on various circuits and various SO questions/replies I came across and hopefully the relay control part is correct. Here goes the actual question:

Is the snubber circuit (R1, C1, RV1) correct, both in placement of the components and values? Will it be appropriate for a wide range of loads, such as, for instance:
- A fan
- A heating device
- A refrigerator
- A water pump
- A printer
?

The above items are just what popped up in my mind right now, but you should get the idea. Feel free to add any examples of what might/might not work. Basically I would like to build this thing and then connect whatever I need to it, without worrying of it possibly affecting the logic part of the circuit.

My knowledge in this area is basically zero, so please excuse me if my question sounds unreasonable. Thanks in advance.


texts: What is a typical diode's ideality factor?

texts:
Some background, for anyone unfamiliar: The Shockley diode equation is

\$I_D=I_S·(e^{\frac{V_D}{n·V_T}}-1)\$

with the quantity \$n\$ called the ideality factor, a number between 1 and 2. Ideal diodes have an ideality factor of 1, while real diodes do not. (And, to my understanding, the ideality factor of real diodes can depend strongly on temperature and diode current.)

My question is this: What is a typical ideality factor for commercially-available pn diodes at room temperature? In what range can one expect the ideality factor to be? Will it be different for Schottky diodes?

The impression I got from my semiconductor devices class is that it's close to 2 for low currents, shifts nearer to 1 for moderate currents, and goes back to 2 at very high currents; is this correct? Are there more precise numbers available anywhere?


texts: understanding electrical motor and force

texts:
I am looking to drive an electrical motor to power a cart with some substantial weight.
I want to power this with as simple a method as possible but want to maximise the force for it.
I have several 18650 cells I can use for the main power source and the intended motor runs on 12v dc from a scooter.
I would like to try and increase the output force of the motor whole decreasing the drain on the actual cells, to this end I was thinking that driving it with circuit similar to what is inside a dispisable camera which charges a 2000volt capacitor from a 1.5 volt battery,but am unsure how the magic works to do this.

would a capacitor from a microwave which is apx 9000uf at 2000v be able to work for this?
what aditional parts would I need to add in the circuit?
as the existing wiring gets quite hot as is I fear overheating the motor and burning it up,could  such a method reduce the heat caused by this or would it make matters worse?
would I be able to make the system easier by using instead the microwave oven transformer with some sort of pwm or other transistor run by an 18650 setup?


texts:
I am working on RGB light strips. I have created the circuit that includes at Atmega 328P processor. See attached image.

I have question about applying dual power supply.

If using only 5V supply, I could feed the Atmega chip directly and also the led strip (addressable that uses 5V supply).

Using only 12V supply, it will feed different led strip (non addressable) that runs on 12V source. Also it will feed power to +5V regulator. At its output, it will feed 5V to the processor.

Now the question is... If connecting two power source ( to drive two different strips at the same time), as in the diagram, is it safe to run as in this circuit? I haven't tested with dual power yet.
Note:  +5V source is also connected to the output of regulator.


texts:
I have an Arduino Uno, using a MAX7219 to control a 8x8 Bi-color led matrix.

The problem however, is that upon activating a 5th led in the matrix, the unit "dies", in lack of a better word. I can activate any arbitrary combination of 4 leds, but upon the activation of a fifth, the matrix flashes promptly and goes blank.

What kind of problem does this sound like? Improper resistor value? Grounding or inadequate power?

UPDATE: Upon disconnecting the wire grounding the breadboard to the Arduino, all the desired leds are lighting up in my expected pattern, except with a low-intensity brightness.

UPDATE 2: Fritzing didn't have a resembling matrix model, and I'm not doing this by hand now. I have wired (to my understanding) like in this schematic, with both the 5V and RSet coming from the MAX7219 onto the power line of the breadboard, RSet via a 10k resistor.

Here are two pictures of the current setup: 1, 2.
2 ground wires as per the MAX7219 Datasheet, DIG0-7 on columns, SEGDP-G on rows, RSet to 5V via 10k resistor and normal 5V.

I am obviously new to this and I don't mean to ask stupid questions so please be patient.

Are there any logical flaws in these pictures?


texts: Using Supercapacitors with Motors - DC/DC converter?

texts:
We are an inter-university team working on a pod project. So far, team members have decided to concentrate on four DC motors for acceleration. Each of these motors requires 400A at startup before the pod speeds up and current draw lowers. This makes a total 1600A consumption at the start. Also, the motors work at 100V.

Looking at this enormous figure, I began to doubt would batteries handle such a power draw. Instead, I decided to look into the use of supercapacitors and make a hybrid system. I thought this would be more suitable because many supercapacitors can handle 1600A, and after the capacitors discharge, the battery could be used. However, the capacitor I am looking at provides only 48V. When I consider other capacitors above 100V, I can never find a perfect one, and so I must regulate the voltage.

My question is: how can I effectively regulate the capacitor's voltage to 100V and run the motors? I was thinking of a DC/DC converter, but I could not find any which could handle 1000A or more. I am relatively new to using DC/DC converters as well and I don't know if I'm missing a simpler solution. Perhaps the entire idea is unrealistic, given the high current?

So far I have based my figures on this particular supercapacitor:
http://www.maxwell.com/images/documents/48V_ds_DuraBlue_3000685_4.pdf

Thank you in advance.


texts:
The circuit below is a radio transmitter circuit of a typical RC car. The circuit makes use of IC TX2 encoder.

The output of IC ("SO" pin) is a series of pulses at low speed (84 Hz). This signal will be modulated by a crystal, onto an RF carrier (27 MHz) in order to be transmitted. Transmission is at 27 MHz.

Is it safe to assume that modulation is AM (as frequency remains the same)? Does circuit indicates the type of modulation? I know that part of the transmitter circuit is the modulator circuit, but I can't find which part is exactly.

Any help would be appreciated.


texts: No response from AVR microprocessor while programming

texts:
I've been attempting to program a few different micro-controllers using nothing but an FTDI 5V TTL cable and self-written software to bitbang the needed pins on the chips. Until now I had success only with my AT89S52 chips but I have a similar problem with the rest. The rest being an ATmega8, ATtiny13 and even a PIC16F84A.

None of these chips seems to respond on the appropriate pins (MISO, SDO, etc) while programming. These pins seems to always be in an high-impedance state and doesn't get pulled either HIGH or LOW.

I've checked this with a simple LED "logic probe", my Arduino as a Logic Analyzer, oscilloscope. There's just no response from these chips.
I even tried programming from the Arduino with simple sketches (SPI or bitbang) with exactly the same effect.

Is there something I'm missing or obviously doing wrong?
For all micro-controllers I've connected the pins directly to the FTDI cable's wires (or Arduino's pins) and in case HV programming is required I used the following circuit (which seems to work just fine when I'm measuring with my multimeter):

simulate this circuit – Schematic created using CircuitLab


texts: converting data sent into audio signal using microcontroller that suits the application

texts:
i want to convert text or some numeric data got into speech to make it audible for the listener how do i make it?
Like example :
Say the temp detected at some far place for some process is some "x" data this data got wirelessly near the operator room must be converted into audible voice how do i do this?
Which microcontroller can i use. I have arduino due.


texts: My question is, what if I want to charge my iphone that uses 5volts via USB, however what if I had a powersupply that could deliver 5volts upto 10amps, if I used this to charge my phone would it ruin the phone? I thought that the phone only draws what it needs from the powersupply to charge it. Or would I be best to buy a charger to be used to charge my phone? Are phone chargers smart and turn off when phone is charged?


texts:
I'm a little confused about the transformer "leakage inductance" for days. Per this text book, it gives a schematic view of fluxes flow in the transformer:

It's apparent that the two leakage flux will create separate inductance on each side. And it give s equivalent circuit:

You see, there are two separate inductance on each side, that is, the primary leakage inductance and the secondary leakage inductance.

And we reflect all the load at secondary to the primary side, then get

All are easy to understand, there are two "leakage inductance", though you can reflect them to the same side, but in physics, there indeed are two "leakage inductanes".

But in the app note from a leakage inductance tester, it says

  Leakage inductance is an inductive component present in a transformer
  that results from the imperfect magnetic linking of one winding to
  another. Any magnetic flux that does not link the primary winding to
  the secondary winding acts as inductive impedance in series with the
  primary, therefore this “leakage inductance” is shown on a schematic
  diagram as an additional inductance before the primary of an ideal
  transformer.

And it gives,

Apparently, there is only one "leakage inductance" at one side in the figure above.

Which one this inductance conrrespond to in the text book above? The primary one only or the primary one add the reflected secondary one?
When it measure the "leakage inductance", it short the secondary. I wonder if it can short the secondary leakage out as below (Note: The R2 can't be shorted, it should always exist at the left side of the red line). If it can, then the measured leakage inductance from primary side will contain only the primary leakage; if it can NOT, then it will get the primary inductance added with the reflected secondary leakage, right?


texts:
I am building an RC aircraft, 10kg weight range.
It is supposed to perform long flights (20km+), so reliability is my main concern, mainly on servos controlling Flight control surfaces.

How reliability is maintained on RC planes?

I am afraid if any flight control surface servo would be jammed while manouvering, crash would be quite horrible :-)


texts: How it's possible to determine the output frequency of STM32 without oscilloscope?

texts:
I am implementing a frequency meter on my STM32F4, but to do that I need to know exact frequency of the timer fed on GPIO pin.

Is it somehow possible to determine that without using external frequency meter or oscilloscope?


texts: Can someone please explain how windowed watchdog timer is different from the normal watchdog timer? When is windowed watchdog timer prefferred over normal watchdog timer?


texts: Implement a Boolean function using an 8x1 deMUX

texts:
Using a 1x8 deMUX with an AND gate, create F(x,y,z) where F has minterms at 1,3 and 5

This is the solution I came up with:

I'm pretty sure this solution works, but it doesn't quite fit the specifications. Can anyone help me do this with only one AND gate?

EDIT

Here is my function table


texts: 802.3at PoE power splitter design - how to pass the actual Ethernet signal along

texts:
I'm researching the design of a PoE splitter. I understand the actual 802.3at portion of things, and have some confidence in being able to get the 48 VDC out (TPS2378).

The question I have is... I've got the center tapped 1:1 transformers on the incoming pairs. That's fine. But what do I do with the secondaries of the transformers such that I can just connect up to an RJ45 intended to be the jack for the target device?

Is it just simply wiring the secondaries to the output jack?


texts: How to read potentiometer value in existing circuit

texts:
I built a circuit for heater controller and it works fine.

I want to read poentiometer R3 values with microcontroller Arduino. I am not sure if I am doing correct way, but I connected Arduino analog pin to potentiometer wiper pin and Arduino GND to circuit GND (heater circuit and microcontroler have separate power sources.) I got values in range 500-1000, but somewhere in  between of pot turning values drops to 20-40.

I know that we can read potentiometer values when we connect side pins to power and wiper pin to microcontroller analog pin.  But how can I read the potentiometer when the wiper is already connected to +5V?

I am using the following code:

void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin 0:
  int sensorValue = analogRead(A0);
  // print out the value you read:
  Serial.println(sensorValue);
  delay(1);        // delay in between reads for stability
}

enter code here


texts: I am trying to import the 2N3904 NMOS transistor in LTSpice but the program is not allowing me. I have pasted the model name in the spice schematic as shown below. The error message is : "cannot find 2n3904". Please let me know how I can fix this problem. Thanks.


texts:
i'm building a shot counter circuit for my airsoft gun controlled by an ATtiny26L MCU, where the shots are detected by an infrared diode + phototransistor couple. The PT outputs positive signal when it's triggered by the IR LED, which goes into a PNP transistor to invert the signal and then I have an electrolytic 1uF cap to lengthen the pulse, a 100k pull down resistor (initially there was a 1k), and a 1k resistor to regulate the output current to lenthen the cap's output:

The circuit works flawlessly when I block the IR diody by hand or drop a BB through the detector. However if I shoot a BB through it doesn't detect it.

The shot BBs trigger the detector for around 70 microseconds and if i'm correct there shouldn't be any trouble with a such big cap as 1uF lengthening the pulse, but maybe i'm doing something wrong? Or perhaps the phototransistor won't get triggered in such small time?

Also my MCU runs at 1MHz.

I'm glad to hear any tips.


texts:
So the question is short, how do i connect a single switch to a circuit that has a dual power supply (+/-) connected to it?
Or do i have to use an special kind of switch?


texts: Is the Verilog real data type synthesisable for a generic Xilinx FPGA? If not, what alternatives do I have for real number manipulation in synthesisable Verilog?


texts: Will the data throughput decrease if the transmitter and receiver are in motion?

texts:
What I'm thinking of is a 2 way communication (voice communication) between two systems which are in motion. (like 100 km/h difference)
Will the data transmission and reception be disturbed, by how much?

Is this present in modern transreceivers?

I'm not fixed on a particular frequency. In that case, what difference will it make for a 400 MHz vs a 2.4 GHz carrier on data throughput?

Background:
I read something about Doppler shift. How much noise will be induced due to this effect?

I found 2 questions similar in the same forum (not same questions but talking about similar communication stuff). I'll add the links once I get my hands on my PC.


texts: Delay and Stablity in Negative Feedback Systems: Confusion-2

texts:
This question is in reference to my earlier question:
Delay and Stablity in Negative Feedback Systems: Confusion
In that question I wanted to ask why the second order system is always stable. But I could not understand the issue well from the answers. So I am asking in a more definite way what doubt I have.
Delay block is ideal
When a step input is applied to the system with, say, ideal delay, the output would began to rise and after the specified delay Td (which is delay of the 'delay' block shown below in the figure) the sensed input would began to rise with the output. This is shown in the figure below, where the red curve shows the output, the blue curve is the sensed voltage which would be subtracted from the input (here the delay Td is shown to be 5s) and the black dotted line represents input step (Although, the figure is shown for speed but similar analogy can be drawn for voltages as well). Clearly, if this delay is too large then the error voltage (which is the difference between the input and the sensed voltage and is the input to the integrator) would remain high and the output of the integrator would continue to rise resulting in large overshoot. This should cause instability in the system. Is this correct?

Delay Block is RC system
If this delay block is a first-order RC system (so the overall system is second order now) and if the product R*C is very large, again the blue curve would rise very slowly causing the error to remain large and the red curve, which is the output of the integrator, would again have a large overshoot above the input step. Shouldn't this again cause the system to become unstable?
In other words, for large product of R*C there should be large overshoot. But is the system still stable? If so, why?


texts: AVR Timer not operating as quickly when changing number of PINs being turned on/off

texts:
I am following the tutorial on AVR freaks on Timers written by @Dean Camera. His code says:

#include <avr/io.h>

int main (void)
{
   DDRB |= (1 << 0); // Set LED as output

   // TODO: Set up timer at Fcpu/64

   for (;;)
   {
      // Check timer value in if statement, true when count matches 1 second
      if (TCNT1 >= 15624)
      {
         PORTB ^= (1 << 0); // Toggle the LED

         TCNT1 = 0; // Reset timer value
      }
   }
}

This flashes one LED. I edited the code to turn on and off all pins on PORTB but my code "runs slower", with the LEDs appearing less bright. My code:

#include <avr/io.h>

int main(){
    DDRB= 0xFF;

    TCCR1B |= (1<<CS10) | (1 << CS11);

    PORTB = 0xFF;
for (;;) {
    if(TCNT1 >= 15624){
        PORTB = 0x00;
        TCNT1 = 0;
    } else {
        PORTB = 0xFF;
    }
    }
}

Can someone explain why this is happening? Also is there a better way to turn on/off the pins this is the only way I could think of. I am just running this on a STK500 with a mega 16L.


texts: Increasing current in an Arduino circuit?

texts:
I'm trying to power a small electromagnet using my Arduino Uno, but when I use the 5V pin, the current flow is not enough and the electromagnet ends up being a lot weaker than it is with a regular 1.5V AA battery. I thought it was a resistor issue at first but even using a potentiometer to completely drop resistance does not solve the problem.

Would using a transistor or a relay help in this case? Do you have any recommendations on which one I should use? Is there anything else I would need to ensure there's enough current flowing?


texts: Power origin and power planes placement on PCB

texts:
Although there are many similar questions to this one, I wish to get your attention to this specific board layout.
The main power on the board will be 5V, and one of the layers is dedicated for this. However, the board will be connected to a 12V power, so I am using an LDO to drop the voltage to 5V. Keeping in mind current flows, the ideal placement of the LDO would, probably, be at the center of the board, however, I placed it on the top left (see the bottom plane layout).

Is this acceptable placement or there is a better way in this case? Maybe I should route a fat trace in the power/ground planes to the center of the board, so all the currents spread/return from/into the center like on the figure below? Should the ground from the 12V connector and ground LDO pin originate from the same point, or it's ok to connect them to ground plane at different points?

Is it useful (in my case) to have some ground plane islands on the top and bottom signal planes in addition to the separate ground plane layer, or should I limit the top copper plane to only certain areas? My biggest concern is bypass caps and GND pins connection. I did try to place the components so the negative pins go outward and connect to the larger top GND plane areas. However, would it not be better to place via right next to the GND pins so they connect directly to the GND plane layer?

Speaking of GND via: I tried to place them close to several ground pins at once to make a local GND 'star' connections. Again, would it be better to use more GND via at each GND pin, or that is unnecessary? Does it considerably increase the manufacturing price?

I also tried to spread additional GND via equally spaced across the entire board area. Is it a good practice? How is the efficiency vs. manufacturing price?

Should I make a small split in the GND plane layer somewhere between the ADC and a SN74 buffer? So to say I separated digital and analog grounds?

Please, comment on how I could improve my current PCB layout.

Additional info:

Planes: Signal, GND, Power, Signal
Main power: 5V and additional small LDOs (3.3V, 1.8V) designated with the letter V.
Sampling: 10MHz, oscillator 40MHz.
To the left: CPLD, small uC.
Center: linear imager.
To the right: OpAmp, Diff Amp, ADC, SN74 buffer (bottom to top).
Buffer gates designated with the letter G.
I will remove small unconnected islands of copper at last.

This is a combined image of TOP and BOTTOM planes:


texts:
i am renovating a house and the electrician has installed all new wiring ,circuit switches, outlets etc...  so now the electric company has asked if i want 1 or 3 phase.  I told them 3 phase and already paid for that but now i am worried that the wiring already done might be incompatible with 3 phase.  excuse my ignorance but i never could really understand how electricity works.
my old system was on a 5 amp meter and it was a given that i would change the meter to 15 amps--so the new wiring is up to spec--   can someone guide me a little on this.  by the way this is in northern thailand


texts: Can a computer use shift registers as memory?

texts: An 8 bit shift register stores a byte of information. Would it be possible (in principle) to create a computer that uses shift registers for memory instead of HDD technology?


texts:
I am in the planning stages of a project for my new son/daughter, who will be arriving in December. The project involves using muscle wire to make bug or bird slowly flap it's wings. The form will be made of fabric or foam.

Has anyone ever worked with muscle wire, and have some advice or warnings or painful lessons you learned that you could pass on?

My plan is to use a micro to energize the muscle wire (through transistors if the current draw is too great). This will cause the muscle wire to retract, pulling on the fabric wing and make the wing look like it's flapping.

This may not be the correct forum for such a question, but I'll ask anyway and hope for a favourable response. There is a lot of collective experience and knowledge among the users here, so I'm hoping to access some of that.

EDIT:
Thanks for all the suggestions. Lots to think about.

I should have mentioned this was going to be a mobile. You know, the kind that spin around above the babies crib? So my thought was muscle wire for low weight and silent movement. However some very good considerations have been made.


texts: Can we use the Halbach array configuration in an electromagnet?

texts:
I tried asking this question in several forums but didn't find any answers as i expected. It's very hard to find information about halbach array in google, especially in the electromagnetic field.

We know that Halbach array works well with a permanent magnet by giving a strong magnetic field in one side and weak on the other side.

I'm thinking to design solenoid in halbach arrangement to give a strong magnetic field in one side and weak in the other. We know that solenoid behave similarly to permanent magnet. My question what happens when we give alternative current or pulsed dc to solenoid coil? Will the direction change in magnetic field? I know pulsed dc doesn't change in magnetic field? Will this be a problem to achieve halbach array? kindly advise.


texts:
I need to find a replacement part for a burnt IC.
It is placed between a MCU and some exposed IO.
It was burned by applying 12V as input when 3V3 was the absolute maximum rating in the datasheet of the device.

I suspect that this IC is a kind of TVS or some protective device. By the way, it worked: the MCU is still alive after the 12V story. But the unknown IC is toasted...

It is ~4mm x ~1.6mm

Here is a picture of that IC (another one that is not toasted. The toasted one has literally blown up):

We can clearly read :
842
2HC

Does anyone know what it is ?


texts: How to use a signal from one function generator to gate another signal from another function generator?

texts:
I have 2 function generators with me and each is outputting its own signal. The first one is a 100kHz square signal and the second one is a 10MHz sine signal. What I want to do is use the first signal as a gate signal to gate the second signal.

What should happen is that when the square signal goes up, the sine signal is then produced as a burst for x-amount of periods and then the sine signal will stop when the square signal goes down.

How can I go about accomplishing this? Thank you!

PS: I am using the SIGLENT SDG5162


texts: theoretic modification to railgun base components

texts: I just began researching rail guns and want to build one myself had a few ideas but the actual barrel gave me an idea I wasn't sure of. Can you construct a coil that produces an electromagnetic field using fiber optic wire and if so would it be more efficient than a copper coil? I'm considering 100v 33300uf aluminum capacitors and have yet to look into diodes. Teaching myself the basics and principles as I go.


texts: Estimated voltage, amperage and phase count of this MASSIVE busbar system?

texts:
Any guesses as to the likely voltage, amperage, and phase count running on this massive 3-conductor copper busbar system?

Found in an old factory. Decommissioned long ago, so I can't just poke it with multimeter. :)


texts: How can a signal backfeed and create a crosstalk in a passive summation circuit?

texts:
...a passive summation circuit can be a simple way to
  combine signals but one disadvantage is that the summed signal will
  backfeed into each of the sources.  This could be an issue if you
  wanted to use the source unmixed as well as combined - you would get
  crosstalk.

  The amount of crosstalk will depend upon the impedance of the source
  and a low enough output impedance this wouldn't be noticed. (from Designing voltage summer without op-amp)

Can anyone explain this further? How can a signal backfeed?


texts:
My Task

I'm working on an extra work question our teacher assigned us from the book. Design a combinatorial circuit that compares two 4-bit unsigned numbers A and B to see whether B is greater than A. The circuit has one output X, so that X = 1 if A < B and X = 0 if A = B or A > B.

My Ideas

I had 2 ideas, but neither are very good. 1 was to get 2's complement version of A(positive) and B(negative). I could then add them together and if we had a negative, it would be obvious that B is greater than A. The leading bit would be 1 so I would just negate the leading bit and have that be my output. Else it would output 1. This is almost a solution, but I don't think it would work if we had A = B because then the leading bit would be 0 but we would have an output of 1 which would indicate A>B when in fact A = B.

My second idea was to split each number into 4 bits, and compare the bits of each number and find out that way. This would require a 256 row truth table though, and I'd rather just not answer the question than write that out.

Neither of my approaches really seem feasible(I don't even feel as though they accomplish the task). Can anyone suggest a hint as to what would be a good approach or idea to accomplish this task? (Not looking for a full out solution, just something to get me started)


texts:
I have a power transformer that I am trying to figure out if it works or not. It has the following listed on the input side

1  |
2  |
3  |
4  |
5  |  240v
6  |  230v
7  |  220v
8  |  210v
9  |  0v
10 |
11 |
12 |

I am in the UK and use 240 mains, I have a mains cable with an inline fuse. How should I wire the input up?


texts:
I'm working on an ultrasonic transducer driver circuit, originally designed by Lindsay Wilson, and I'm currently seeing spikes at the switching junction. I'm running out of things to troubleshoot, so I'm taking a very good look at my N-Channel MOSFET orientation.

I am using STP13NK60Z N-Channel MOSFETs.

According to the documentation listed above, for the TO-220 package the pin layout is as follows:

Gate
Drain
Source

The relevant part of the driver circuit shows the MOSFETs like this:

Looking at "Figure 1." The internal diode "points" from Source (Pin 3) to Drain (Pin 2). (So far so good.)

Looking at the Circuit Schematic for the driver the top MOSFET, Q1, appears to show the internal diode pointing from Drain (Pin 2) to Source (Pin 3).

Now, my questions are:

Am I interpreting this correctly?
Does it matter if pins two and three are reversed in practice?

Thanks for any help.


texts: This metal oxide resistor is first in line after mains

texts:
This resistor reads yellow purple gold gold white:

It is the first component after Mains L in, in parallel with the choke, safety X capacitor, etc.

It reads yellow violet gold gap gold white. I cannot identify the bands with online calculators. What could it be?

In the picture of the components the device is lower right, and it is marked  for ZNR1. Under the big capacitor is the four-diode bridge. The card is a Netgear wall wart.


texts: Unsigned 32-bit multiply in AVR assembly

texts:
How do I perform a multiplication by 2 of the unsigned 32-bit quantity in registers r18:r19:r20:r21 where r18 is the most significant byte?

My answer is this: rol r18; rol r19; rol r20; rol r21.

My thought process is that since this is an unsigned number, we can exclude the use of ASL as there is no carry out in MSB. But I didn't get it right; may I know which part is wrong?


texts:
In the timing report of a synthesis with Synopsys VCS, a warning states:

  Warning: Design contains 8 high-fanout nets. A fanout number of 1000 will be used for delay calculations involving these nets. (TIM-134)

How can I find the offending nets? Is there any report that I can use to find these high-fanout nets?

Crossposted at https://stackoverflow.com/questions/31285594/how-to-find-high-fanout-nets-in-vcs?noredirect=1#comment50563432_31285594


texts: Implementing a CAN protocol layer in software

texts:
Background

I'm developing a project which will require the modest microcontroller specs of:

8 12-bit, 10kHz ADCs
1kB of RAM
48-QFN or smaller footprint
20kbps daisy-chainable noise-resistant and error-correcting communication protocol

Signal processing requirements are fairly low, and most can be exported to the master processor in the system.  The first three specs are easy to meet, and can be done for less than $2 in quantity.  However, communication will be happening in a very electrically noisy environment, so noise-vulnerable networks like LIN and I2C are out. An additional argument against LIN is that I'd like to run the whole thing at 5V or 3.3V, and LIN transceivers require 12V, and so would require an extra regulator or wire per sensor board. I initially chose CAN for this task.  However, CAN controllers add considerable cost, and I'm curious if this can be done in software.

CAN Physical Layer

The CAN specification defines the Data Link and Physical layers of the OSI network reference model.  Many inexpensive 8-pin ICs, such as the NXP TJA1040/50, Maxim MAX3058/59, Microchip MCP2551, and TI SN65HVD1050 exist to implement the physical layer.  Implementing the physical layer with D/A converters or op-amps would be difficult, if not impossible, so these ICs are well worth the $1 or so that they cost.

CAN Data Link/Protocol Layer

For the Data Link layer, some microcontrollers add CAN protocol modules onto the basic UART, I2C, and SPI communications layers.  However, these are significantly more expensive than the basic chips.

Investigation of cost of CAN protocol modules

To substantiate this claim, here are a few popular micros in CAN and non-CAN versions, from the :

ATmega16 - ATMEGA16M1 (with CAN): $3.87, ATMEGA168A (no CAN): $3.23
dsPIC - DSPIC33FJ64MC802 (with CAN): $6.14, DSPIC33FJ64GP202 (no CAN): $5.48
PIC18 - PIC18F2480 (with CAN): $6.80, PIC18F24J10 (no CAN): $2.10
Cortex-M3 - STM32F103C4T6A (with CAN): $6.50, STM32F100C4T6B (no CAN): $2.73

To be fair, I only compared microcontrollers with equivalent memory sizes, however, many of the non-CAN versions are available with smaller memory sizes for less. External CAN controllers, like the Microchip MCP2515, are almost $2, so it's obviously more cost-effective to have the CAN integrated into the microcontroller if you have the option.

Interestingly, the ATmega part is by far the cheapest CAN-equipped part in Digikey's inventory.

Function of CAN protocol layer

The CAN module found in the dsPIC microcontrollers does the following:

  The CAN bus module consists of a protocol engine and message
  buffering/control. The CAN protocol engine handles all functions for
  receiving and transmitting messages on the CAN bus. Messages are
  transmitted by first loading the appropriate data registers. Status
  and errors can be checked by reading the appropriate registers. Any
  message detected on the CAN bus is checked for errors and then matched
  against filters to see if it should be received and stored in one of
  the receive registers.

This seems fairly doable in software.

The Question

Can a software protocol layer be used implement the CAN specification with only an inexpensive UART-equipped microcontroller and a CAN transceiver?  If so, do any open-source implementations exist?

Alternatively, can CAN transceivers be used with UARTs to implement a custom protocol?  I'm OK with a single-master topology; I understand that arbitration can be hard to get right in a custom protocol.


texts:
Far field zone of a single antenna can be determined by using the equation below.
$$R>\dfrac{2D^2}{\lambda}$$
Where D is the biggest dimension of the antenna.
This equaiton is suitable for single antenna. But what if there are more antennas than one?
How can we determine rayleigh distance, far-field distance, of an array antenna?
For example, how can I determine far-field distance of an two element (aperture type antennas) linear array antenna as shown below?


texts:
Me and my friend are preparing a senior design project on home automation. I have several things in my mind such as controlling drapes, lights, fans with an IOS application.

We started everything from scratch and came up with a great NTC controlled fan and etched it on a PCB as follows (I can't post more than 2 images unfortunately)

However, here's our bottleneck . Although this circuit works perfectly fine and dandy, this is kind of not we want. We want a user to control the fan, which made us realized this circuit is a total waste because it is independent of the user, turns up the fan when the temperature goes high not when the user wants it to turn up. What we really want to implement is using something that can be controlled with a phone and works as a switch.

How do you think we can do this? We have this in mind :

We are writing an IOS app with Xcode and we use ESP8266 Wifi module to bridge our phone to a web server which makes the connection between the phone and system. Do you think we can go from here? If so, what should we do to make this system work ?


texts: Is a half-wave rectifier particularly hard on a transformer?

texts: In the book Practical Electronics for Inventors, 3rd Ed., the authors recommend against using half-wave rectifiers because they're inefficient and cause "...the core to become polarized and to saturate in one direction." (Page 395.) Is this a valid concern and what are the risks for a long running half-wave rectifier power supply?


texts: Using 3 Channel Video Switcher Module with Arduino

texts:
Hey all I am wondering how to go about switch from camera 1, 2 or 3 using this 3 Channel Video Switcher Module on ebay here.

Since there's only V+, V- and signal for the "switch" it looks to take a PWM but I am not quite sure if that's correct or not. If correct then how would I (in code) send that out for each camera to change?

UPDATE

Well I've tried the following code:

int LED_pin = 9; // must be one of 3, 5, 6, 9, 10 or 11 for PWM

void setup() {
  pinMode(LED_pin, OUTPUT); // Initialize pin for output
}

void loop() {
  int dtwait = 1000; // Pause interval, milliseconds
  int V1=20, V2=220, V3=120; // 8-bit output values for PWM duty cycle
  analogWrite(LED_pin, V1);
  delay(dtwait);
  analogWrite(LED_pin, V2);
  delay(dtwait);
  analogWrite(LED_pin, V3);
  delay(dtwait);
}

and just to test it I hooked up 2 green LEDs to digital pin 9 and I can confirm it does light the led's in 3 stages. From bright, medium and then dim-ish.

So I went ahead and powered up the FPV by hooking it up like so:

One looks like it says P15V 331QE BZ10

While the other side has one that maybe says STC 15F104E F-4V938.A

What could I be doing incorrectly?