texts: Power Supply Selection for PWM Controled Landscape Lighting

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I'm planning to build a multi-zone outdoor lighting system, controlled by an Arduino.  This will be a 12v DC system, and use purchased 12v DC landscape lighting.

I plan to control each 'zone' with a simple MOSFET switch and use the Arduio's PWM outputs to enable independent dimming of the zones - one PWM output per zone.

My question is about power supply selection.  Ideally, I'd like to get a single power supply rated to handle all of the lights in the system, say 120W.  However, I am unsure how to select a power supply that will allow for PWM dimming on the 12v side of the circuit.

I am currently looking at : http://ca.mouser.com/ProductDetail/Mean-Well/HLG-120H-12/?qs=3IPTn0w%2f0t%252bZhU8K7VADrQ%3d%3d

can you help me determine how to tell if a power supply is suitable for the purpose I've described?

the other option is to use several smaller 'dimmable' power supplies (one per zone) and run the PWM signal directly into them.

Thanks,

Adam


texts:
In my study book of radio frequency engineering is a question, which is pretty odd in my opinion.

Calculate the electrical field of a cathode ray for the cases r < d and r > d. There are two following conditions.

Velocity as a function of radius
$$ v_z =v_0 \cdot [1 - (\frac{r}{d})^3]$$
Charge density
$$ \rho = \rho_0 \cdot [ 1 + (\frac{r}{d})^2]$$

Can anyone tell my how to get to this conditions? There are no other mentions about them in this book. I tried to calculate the E-field with $$E = \frac{\rho}{2 \cdot \pi \cdot \epsilon \cdot r}$$ but i cannot figure out, how to get a proper solution.

PS: I don't know which radius and what's meant with d. I hoped one of you can help me, maybe there's a known similar example.


texts: Why is there a difference in the voltage drop across the same resistor when using an oscilloscope and a multimeter?

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I am measuring the voltage drop across a 1 ohm resistor within a circuit with an oscilloscope and a multimeter.

The impedance of the oscilloscope is 1M ohm and the impedance of the multimeter is 10M ohm.

I am reading approx 5mV when using the multimeter and approx 2mV with the oscilloscope.

Which of these two values would be most accurate, if any and if not, how would I go about ensuring the voltage drop measured across the resistor is accurate?

Edit -

Accuracy of equipment:

Oscilloscope

[3%×(|reading|+|offset|)+1%×|offset|+0.2div+2mV], ≤100mV/div

Multimeter

1.0% + 3 counts

Settings used:

Oscilloscope

10mV / div

Multimeter

mV setting with resolution of 0.1mV


texts: Help Understanding a PCB Circuit from Cordless Hot Glue Gun

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I'm trying to understand the circuit in this PCB taken from a cordless hot glue gun. Battery voltage is 18-19v. I've been able to identify most of the components but not all. And most importantly I would like to understand what the circuit is doing.

What I Think I Know about the Circuit

Q1 Fairchild 4486 TrenchMosfet

Pin 1 is Gate (top left)
Pin 2,3,4, are Source
Pin 5,6,7,8 are Drain (entire right side)

R1 31 Ohm
R2, R3, R4 1 Ohm
R5 20 Mega Ohm

The main ic is a Fairchild Semiconductor 30V P-Channel PowerTrench MOSFET

This circuit sits between the battery and heating element. I think it just makes sure the drain on the battery isn't too fast and that it isn't shorted. Please correct me or confirm my theory.

I'd like help to identify the unknown components then understand what the circuit is doing. My ultimate goal, if possible, is to control the heating element on/off with an Arduino or similar control circuit to maintain a specific temperature via a thermister added near the heating element.


texts: Conceptual confusion about voltage multiplier circuits

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I can do circuit analysis of the half-wave series multiplier (also called Villard or Greinacher cascade or Cockcroft-Walton multiplier) and see that it works, but I have several conceptual confusions about it stemming from how it is almost universally explained: each stage is a clamper that shifts the waveform up by the peak voltage, whose output is sent to a filtered half-wave rectifier (i.e. a peak detector) to produce a smooth doubled output DC voltage. It is explained that if we want to produce a V\$_{out}\$ = NV\$_{in}\$, that we string together N of these stages.

For clarity I've separated the following three confusions but I think they are just helping to explain the same central question.

1) My first confusion is that if we wish to ultimately produce smooth DC output, it would make the most sense to save N-1 diodes by only doing the smoothing after the voltage multiplication. And yet most online resources describe the smoothing as being somehow integral to the operation of each stage, without explaining why. This is particularly confusing because if the output waveform really were smoothed to a constant DC voltage at each stage, then the polarity would not change for the next stage and it would therefore be unable to do its job!

2) My second confusion is related to the first: why can't we therefore just get rid of the rectifier in each stage and just string together clampers (and save any smoothing to the end)? The reason this is particularly confusing is that both circuits are actually the same circuit, that is, a daisy chain of 2N clampers (swapping polarity for each added clamper), is the same circuit as a daisy chain of N (clamper + filtered rectifier).

3) My third confusion is that if I really were to understand the multiplier as a chain of clampers and filters in series, then I would expect V\$_{out}\$ to be between the two "rails" rather than between a ground placed next to V\$_{in}\$ before the first stage, and the output of the last stage (as in this diagram).

Again, I can successfully do circuit analysis on the multiplier circuit, but I've found all of the common conceptual descriptions to be very confusing.


texts:
I need to charge a 1000uF 400V capacitor bank off of a 7V LiPo battery within roughly 5 seconds, and have the circuit be as small and light weight as possible. With a constant voltage supply and a resistor to limit the current, the peak current when the capacitors are discharged is around 200mA, and with a constant current power supply the peak current is around 100mA. The constant current supply would also make other parts of my circuit easier, so I would like to have the power supply current limited if possible.

The flyback converter seems like the best topology so far, but how does the flyback compare to other topologies like cascaded boost and boost with autotransformer converters for this kind of voltage?

Would constant current flyback controllers like the UCC28700 and LT3798 work for this? All the ones I can find seem to be designed for stepping down voltages from rectified AC power to a low voltage DC, and I'm not sure if it is possible to run the the opposite way.

There are a few other questions on here about high voltage supplies, but they're all limited to current levels in the uA, so I'd appreciate some direction.


texts: Recreating a missing wireless keyboard dongle with NRF24L01

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I have found an old Logitech Wireless Keyboard (specifically, the MK250 model), which was originally sold with a separated "standard" 2.4Ghz receiver dongle (Not 'Unifying', as written here). I assume that the keyboard itself has a corresponding 2.4Ghz transmitter inside.

My goal is to recreate a receiver which will communicate with that specific keyboard properly from one side, and with the computer's USB from the other side, just as the original dongle did. This is what I had in mind in order to achieve it:

Sniff 2.4Ghz communication from the keyboard using NRF24L01. Not sure how to do that; perhaps scanning all NRF's channels for some communication? Should I expect 802.11 interference from wireless routers around?
After I could determine the RF coming out of the keyboard, next step would be to reverse the protocol in use. Not sure how to go here either; I guess that it would be some sort of trial and error...
Use some MCU or similar to relay keyboard information as HID over USB.

Does this seem the right direction here?
Any advise about the sniffing/reversing part?
Is it too ambitious/can't be done?


texts:
I am working with the book "Build Your Own Transistor Radios" by Ronald Quan in which he has a lot of AM projects. I am having a hard time figuring out what I need to buy from his specifications. For example, he has the item L1 Antenna Coil, 470 mH primary 23 mH secondary which I assume means I need to buy two axial inductors, a 470 and 23. But there are a lot of possible parameters: tolerance, max DC, max current, self-resident frequency, whether it is shielded, etc. How do I know what to get?

Also, sometimes he talks about a "wrapped" inductor. For example, antenna coil 470 mH with 1 turn wrapped. What does that mean? If you go to Mouser you do not find anything with this description. Another example is antenna coil, 600 mH to 680 mH, 10 to 20 turns for secondary winding.


texts:
When I had Raspberry Pi I used to control the GPIO (pins) from a Java application using the Pi4J library.

Is there any library to control the GPIO (pins) on the PcDuino using the Java language?


texts: Relationship between frequency and current

texts:
Hello I have a simple question, I was reading in my Airplane Maintence book that in AC motors are frequency sensitive (I understand that) frequency changes can cause speed changes of the armature.  But what I don't understand is this line: "Some components can overheat if the frequency drops and the current increases" I understand more current overheating, I don't understand how lower frequency would increase current.

Edit:  Again thanks for those answers to my above question, but I guess another question I have on this train of thought(confusion) is with inductive reactance, where it opposes current at higher freq, yet dosen't use power or convert it into heat, where does it go?


texts:
I'm pretty new to electronics, so be forgiving.
I bought this electronics kit (basically in order to get my new ESP8266 working), and got a 74HC595 chip with it, so I read a little bit about shift registers, and now I want to experience with it. I managed to got it working with the ESP8266, i.e., to have the ESP8266 use shiftOut function to set the shift register values.
But I was wondering if there's a way to work with it manually, i.e. to set 1's and 0's in the shift register manually.
What I tried to do is to for e.g. connect the pin 14 (data) to power, and then connect for a moment pin 11 (clock) to power. As far as I understand, this should set a 1 to the shift register, shifting all the rest of the bits one position down.
As you might guess, this is not working as I expected. Can someone tell me why?
PS
I would be glad if someone could clarify what is the duty of the pins:

Pin 10 - MR
Pin 13 - OE


texts:
The answer given in my workbook to the above problem is A.

The things I was able to point out

secondary c-phase current = 300A and other secondary phase currents = 0A since the entire current flows through the fault.
Total kVA of primary = 1.732 * 33kV * IL and primary kVA = secondary kVA
i1 = (IL/3) and i2 = 0

I am confused on how to calculate secondary kVA

and why it wouldn't be {(33kV/1.732) * 300A} + 0 + 0 ?


texts:
I'm a novice when it comes to electronics, so please bear with me. :) I have this idea of a Internet connected hight adjustable desk that keeps tracks of it's "modes". With other words: I would like to know when the desk is adjusted from sitting to standing and vice versa.

This is my plan:

Some kind of sensor connected to a Raspberry Pi through GPIO.
Simple daemon that reads the input from the sensor and determines if the desk is adjusted for sitting or standing.
The daemon logs everything to a database.
A web app that presents the data in some nifty way.

My only problem is the sensor. I have no idea of how I should determine the state of the desk. Any ideas?

The desk is an IKEA Galant with adjustable legs. Sorry about the Swedish on that page.


texts:
Is there a way to use the TX/RX on the STM32F030 Discovery board?
The User's manual says "reserved", but since the Cortex M0 doesn't have an ITM, I'm looking for another way to get data out of this board (I need to measure PWM & Duty Cycle for a bit, then prototype away)...

Does the TX/RX do anything on this board or do I have to get another USB->Serial adapter and wire it in?


texts:
I have assembled an audio amplifier, starting from a cheap tpa3116d2 circuit board. It is powered up by using another cheap step-up circuit to reach 14V (manufacturer suggested 24V).
I wanted to dissipate any potential heat by adding a (oversized) vent to the circuit.
Both the amplifier + step-up are supplied by a 12v PSU from an old desktop pc.
To feel safe that this setup wouldn't burn my house, I had decided to add a fuse on the +12V line between the PSU and the vent+stepup circuit, on a small prototype PCB. I had placed it the closest I could to the 12v connector.
I had some 250V rated glass fuses, I had found (by trial and error) that the 0.5A glass fuse does its job (the 0.25A fused as soon as I have turned on the amplifier), and it has protected the speakers from a overcurrent spike by opening the circuit (the amplifier does not turn on properly when the volume is set to high on boot).
Do I have to worry about the fact that the glass fuses are 250V and not 12v rated? Are there any factors to take into account when considering fuses?


texts: Voltage buffer output not similar to input

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I am having trouble interfacing with MIC6211 op-amp. I have it configured as voltage follower (buffer):

VIN changes from 5 V to 20 V. The op-amp output is high impedance (100% sure, even disconnected the load). My problem is that around VIN = 9V and going down, the op-amp stops following the voltage provided at pin 3. The voltage at pin 3 keeps dropping but the output (pin 4 and 1) does not. Going further down the voltage is so low that it cannot provide sufficient level for the op-amp to operate so the output drops as well.

Removing the op-amp from the circuit and shorcuting pins 3 and 1 provides proper operation of the circuit. This op-amp was only suppose to buffer the voltage divider voltage in case any load occured at PVOL.

What could be the case? Looking at the datasheet of the device this conditions should be fine, I should be able to buffer the voltage from 4 V to 32 V.
I would appreciate all help.


texts: How does a cascode current mirror maintain equal Vds of the bottom transistors?

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A basic current mirror is shown below:

The load and reference current relationship is affected by channel length modulation:

In order to cancel the effects of channel length modulation, vds1 and vds2 need to be  equal. A cascode current mirror is needed to make this happen, but how? The book I'm using is by Razavi..

Vn = Vgs3 + Vds2
Then, in order to make Vds1=Vds2, vn must satisfy:
Vn = Vgs3 + Vds1   or
Vn  = Vgs3 + Vgs1
But from the circuit:
Vn=Vgs0 + Vgs1 !!!
How are Vgs0 and Vgs3 equal?


texts: Question about Synthesizable For loop and Generate

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I am using the Verilog language and Zedboard as a target board.

As far as I know, the for loop can be synthesized, and the synthesis tool translates the for loop as a sequence of duplicated instructions like the loop unrolling.

For example,

for ( i = 0; i < 4; i=i+1) begin
  mem[i] = i;
end

will be translated to
mem[0] = 0;
mem[1] = 1;
mem[2] = 2;
mem[3] = 3;

Therefore, as far as I know, the for loop can be used if the resource is available to infer the multiple but same purposed gates.

However, it seems that the generate in Verilog can be used to, not only imply the multiple instances, but also the multiple instructions same as the for loop.

I understand the generate can only imply the multiple instances of the module and the for loop cannot be used for that purpose.

Then what is the difference between the generate + for loop and just for loop? I think both works like the loop unrolling though. Is there any noticeable difference? If there is no difference, which one is preferable coding style to induce loop-unrolling?


texts:
I'm thinking about building a basic AC mains voltage detector. I'd like for it to be both protected and isolated, so I have a zener TVS and an optoisolator.

R1 and R3 are chosen so that between them, the expected peak voltage is equal to the standoff of the TVS.

Since it's a double-diode isolator there's no need for a rectifier bridge. After the optoisolator is a basic RC LPF and a Schmitt trigger. R2 and C1 will have to be fine-tuned so that on every cycle, the voltage creeps up to the inverter's high input voltage (minus some safe tolerance).

Is this safe? Is the concept sound?


texts:
How is it possible to use op amps on a supply of (+3v), for example: mp3 player and other battery operated devices?
What type of op amps do we use in low voltage applications?
How is it possible they have such a big output voltage in relation to the supply voltage?

This is my first time dealing with op amps in low voltage applications. I'm grateful for any kind of feedback.


texts: How much weight can a motor take before it can't run?

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I bought these 50:1 gear motors for a project robot I'm building for this YouTube walkthrough series with a couple of Arduino's, two other servo motors, a motor controller and various hardware.

The photo below shows where the motors are placed on the sides near the bottom...

My question is, without testing and getting everything done, how do I determine the weight these motors can handle with these wheels? Is there some formula that will help me get a general idea of the max weight these diameter of wheels can hold on the motors mentioned above?


texts: How to efficiently trigger QC and convert it to constant 5V and a peak of 5A?

texts:
Introduction

For a university project I started working on RGB LED Shutter glasses, which are based on the idea of a kickstarter by Macetech. However, these glasses miss some features I was looking for and therefore seemed a good idea to improve upon. Also, they are pretty expensive and most components were given by my university so I was very glad my idea was chosen for the project. That said, our project goal was pretty simple: reverse engineer these glasses and make them react to sound.

However, during the project I stumbled on some pretty cool other use cases for these glasses and therefore decided to develop it further in my free time. However, our prototype is very rough. The LED's are on a pcb which is taped on some 3d glasses and a four threaded wire is connecting the LED pcb to the microcontroller. Not quite nice looking...

Since I want to use these glasses for myself (and wearing them at festivals), I want to make them look more professional. So I'm planning to create a 3D design which is bulkier than normal glasses but doesn't look stupidly big. This means all my electronics (except power) must fit in a small case in the glasses itself. For that, the legs of the glasses seem the best idea, especially if only one leg is used. This volume is approx. 4x6x1 cm.

The electrical components for in the glasses' legs are:

Wemos D1 mini pro
3 buttons and a pull down resistor for each button
Small microphone (max4465)
Connector for power (located at the end of the legs of the glasses, so not in the said dimensions)
Power delivery circuit (constant 5V, max 5A)

The Problem

Therefore I'm looking for a way to get quite a lot of power to these glasses. The WS2812B I'm using has a max current of 60mA per LED, of which I have 72 which accounts for 4.32A. Normally these leds function on 5V, but they also seem to do fine on a bit less (li-ion voltage of 3.7-4.2V). So in the worst case they can suck 21.6W. Later on, I'm also planning on increasing to more leds while still maintaining the same surface. So for that I will be using the sk6812 mini, which I'm able to squeeze 100 leds on a new verion of the pcb. This will account for 50mA per led, which is at peak 25W.

Since I like to reuse the whole power design, I'm looking for a way to get constant 5V, max 5A. The way which seemed the most ideal to me was using a powerbank which has quick charge. To trigger this I could use a qc trigger board (as suggested here) and then step the voltage down to the desired 5V 5A. However these two boards are pretty large and certainly won't fit in my glasses.

I also found it's pretty simple to trigger qc, but since I don't want to waste power pulling a constant 12V doesn't seem like a good idea.

Last thing was that I saw a usb c qc trigger board on aliexpress, but these boards are very expensive.

The question

So I'm interested, how I can efficiently pull power from a QC power bank and step it down to a constant 5V and a max 5A, while maintaining a small size?

TLDR

I'm looking for a small circuit which can trigger QC and convert it to a constant 5V and a peak of 5A. How can I achieve this? Also, other options are welcome as well.

Bonus info

Earlier on, I said that I wanted more features from my LED glasses and will tell here more about that.

My glasses are currently able to display approx. 30 cool presets, but I have quite a lot of others in the making. Some of these presets have quite a lot of customizability, like setting a color (or on some a palette), showing different forms or reacting to sound or not. I also can show text and adress a certain letter with a color. And last but not least, it sort of works with ARTNET (recieves data, atm doesn't tell it's an ARTNET device). Also, I like to make an app which can control a certain preset and configure all the different options of it.


texts: Single master I2C with multiple target devices

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I have a one I2C master with 14 I2C target devices connected on the bus.
I want to clarify the order of things that happen on the I2C bus.
Let say the master send an ADDRESS. All the target devices will hear, then target A will respond with ACK since the address matched.
Then master will detect that it got an ACK and send some bytes. Let's say the master sends bytes X, Y, and Z onto I2C bus.
Is it possible, during the sending of bytes X, Y, and Z, that if byte X, Y, or Z matched one of the other target device addresses then that target would respond it?
For example, byte Y coincidentally matched the target B address, then during the transmit of byte Y, target B also responds with ACK, even though we expect only target A to hear it?


texts: Effects of continous slow charge on a battery?

texts:
If you connect a solar panel to a phone battery, but the solar panel provides about 1/4 (or 25%) of charge (mA) compared to the battery's original charger. Will this slow power charge the battery (albeit at a very slow rate)?

If so, what would be side effects of the battery being left on this slow charge all day every day?

EDIT: This question is for charging the battery separately from the phone and so extra precautions as highlighted below are needed to control V and mA, etc.

I want to charge the battery while it's still in the phone. Solution is also below in the answers and comments.


texts: In automotive electronics ECUs, why is an external EPROM IC often used instead of the MCU's internal EPROM?

texts:
I am a bachelor of vehicle engineering.
It's easy to see many Automotive class MCU own interior EPROM,for example S9S08DZ,S9S12XS and some PIC 8-lead chips.
But,I have seem many Automotive electronics ECU use a EPROM IC(for example M95320).
Why they don't use MCU internal EPROM directly?
Is it because of lifetime?
I know some PICF12 8-lead watchdog MCU own interior EPROM,they won't lose power.(Beacuse they are watchdog MCU)


texts: How to generate high voltage with inductor

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I was tinkering with old camera circuits and I am amazed to find these can generate 400 V with 1.5 V battery. So how can I make such a circuit to generate and store high voltage?

I searched about these circuits in internet but results are people trying to avoid inductor backfire rather than store it.

I have 400 V 100 uF capacitors and inductor wire but I don't know how to discharge the inductor fast enough to create high voltage.


texts: trouble getting the amplification of this circuit(microphone amp)

texts: I am having trouble getting the amplification of the circuit ,though I( believe it is R8/R6.Am I right?


texts: Protecting a comparator in a tension measurement device

texts:
I am building a device to measure the tension of a conducting wire using an Arduino.

The basic circuit concept consists of two stages:

The wire is placed in a strong magnetic field. Then the Arduino send a 2 seconds saw-tooth pulse going up to 24V through the wire which cause it to vibrate in its fundamental frequency ranging around 60-200 Hz.
Since the wire is now vibrating in a magnetic field, it produces an induced AC EMF with the same vibration frequency. The voltage on the wire is amplified using a comparator which sends a square wave back to the Arduino where the frequency is measured. Calculating the tension from the fundamental frequency is then very simple to do.

A more detailed schematic:

simulate this circuit – Schematic created using CircuitLab

I am looking for a way to protect the 5V comparator from the 24V pulse going through the wire that will not affect my ability to measure the induced voltage later on.

An Ideal solution would be a way to switch the system from the "pulse stage" to the "measure stage", each time disconnecting the unnecessary part of the circuit. I was thinking of achieving that using a MOSFET switch but got it all messed up. I did manage to pull it off with a mechanical relay disconnecting the comparator but I  rather find a different solution.

Note that this is an individual device that will not be mass produced, so a solution does not have to be cost efficient.

This is my first circuit I ever design and my first time asking for help on StackExchange so if there is anything unclear please tell and I'll be happy to explain some more.


texts: I am wondering how people manage signals in the high frequency range (77+GHz). How do people connect a differential Tx radar signal and sample it on a Spectrum Analyzer? Articles and books would be very helpful. I understand pcb patch antennas are more common in this frequency range but i need to find more information on it.


texts: Expected breaker temperature on a 208V 30A circuit with continuous 80% load

texts:
I have several cabinets of servers in a datacenter and each of these cabinets is on a dedicated 208V 30A circuit. The load on each of these circuits is 24A and one circuit is slightly higher (~24.6A).

Recently, a datacenter technician (not an electrician) got in touch with me and said that my breakers in the panel were hot and that I should reduce the load on the circuits.

He took measurements using an infrared gun on three circuits. He said that the temperature was 117F for two of them and 110F for the other. He said that the maximum temp should be 104F. The ambient temperature in the room is roughly 72F.

A couple questions:

Is it normal that my breaker temps are reaching 117F on a circuit that's at 80% load or slightly higher?
Is the max temp for a breaker really only 104F? If humans and sensitive electronics can handle 104F, then surely a breaker could handle much higher temperatures...

I understand that it's impossible to give an exact answer to these questions when I'm unable to provide specifics on the breaker panel -- I'm just trying to get a general idea of what's 'reasonable' before I start pushing back on this request.


texts:
I'm doing a project and I have a PCB which needs surface mount components attaching to it. One component has already been attached, and I have some 138deg solder paste in a syringe.

This is possibly going to sound very stupid, but is it feasible to use my kitchen oven or a similar household device to heat up the solder? This is just a one off for me and I am not planning on doing any surface mount soldering in future, and I do not have easy access to a proper reflow oven.

All the components will be mounted on one side if that's an issue.


texts: Simple buck circuit reducing 240V AC to around 5V at 300mA

texts:
I work with a lot of ESP8266 microcontrollers, and often need to power them from 240V AC mains. This generally involves either a wall-wart or a dedicated isolated module such as the HLK-PM03.
However, it occurred to me that - in situations where isolation from the mains supply is not a requirement - I could maybe use a simple buck circuit.¹
I came up with this circuit:

The resulting 6V-or-so could then be passed through an LDO to produce a stable 3.3V supply.
Assuming I use a 250V-rated triac to chop the mains supply into pieces, is there any good reason this circuit wouldn't work and/or be unsafe?²
In addition, would I need to use an inductor and capacitor rated for 250V? Under normal circumstances, they would spend most of their time seeing low voltage.

¹ I toyed with the idea of capacitive droppers, but the current requirements of the ESP8266 are too high for that to be feasible.
² I am well aware of the importance of isolation, thank you. This is for use in situations where mains-referenced power is not a concern.


texts: Apply Thévenin equiv. on this diode problem?

texts:
I'm wondering if I'm thinking right when wanting to use the Thévenin equiv. on this diode problem?
I'm thinking that in order for me to calculate \$I_D\$ then I have to "open circuit" the diode?
Am I thinking wrong?


texts: 2 nos Peltier connection... Series or parallel

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I'd like to build a mini AC using two Tec1 12706 Peltier modules. If I use two of them, should they be connected in series or parallel?

Can I use a 12VDC power supply that outputs 2A and takes 220VAC as input? Also, how do I assemble two of these Peltier modules?


texts: Using MIL-DTL-38999 circular connector for Ethernet applications

texts:
A MIL-DTL-38999 connector based on insert arrangement has a different service rating (M, N, I and II). Service rating of M shows a suggested operating voltage of 500VDC (pin to pin and pin to shell).

Does that mean that this connector cannot be used for Ethernet (10, 100, 1000 Base-T) as isolation of 2250VDC for 60s is required to meet the IEEE802.3 Standard between frame ground (shell) and MDI pins (A+/-, B+/-, C+/-, D+/-)?

Most decent density 38999 pin insert arrangements are service rating M and a lot of products in the market use M rated insert for Ethernet. I wonder how they meet this requirement.


texts:
I am trying to recreate this D-Latch using only logic gates:

So far I have this for the latch:

What am I missing here?  There should only be one input of c and an output of A1, so I tried connecting the inverter directly to the output of A1 since there is no input of D allowed.  But something is still wrong, because the D input isn't connected directly to the output in that picture but how can I show this using only logic gates and not directly having D as input?? Thank you!


texts:
I was studying the function of this simple relaxation oscillator based on a single transistor, 2N4401. The schematic looks like this:

From 2N4401 datasheet, the collector-emitter breakdown voltage is 40V. My question is, how does then the above oscillator work? In the given schematic, the voltage on the +ve plat of 3300uF cap would never reach the required breakdown voltage so the transistor can fully conduct.


texts: Mbed cli speech commands on STM32F469I Discovery board example not working

texts:
I am trying to deploy the tensorflow lite speech commands example using mbed cli on the STM32F469I Discovery board as instructed in the following link:
https://developer.arm.com/solutions/machine-learning-on-arm/developer-material/how-to-guides/build-arm-cortex-m-voice-assistant-with-google-tensorflow-lite/single-page
I manage to compile the example using the target name of the board and then copy the binary file to the board as instructed. The board LED LD5 and LD6 flash as I suppose it should. But then, I am not sure how to check if the program is working, as I do not observe any response from the board after the program is flashed.
I tried to connect my terminal to the board’s serial output, but was unsuccessful. The example in the provided link used the 'screen' command to acheive this. However, I do not see any serial output using that command. Please let me know how to establish serial communication with the board. I use a USB to UART cable to connect to the board, so I’m looking to establish the connection using this. Note that the example in the provided link uses the STM32F7 board, so I do not know screen is only compatible for that board.
Please let me know how I can run this program on this board and verify it is running correctly. As i mentioned, I connected the board to my PC using a USB to UART cable
I am using mbed cli on my Linux terminal:
mbed cli version: 1.10.4
Global GCC Arm path: GCC_ARM_PATH=home/taiman/gcc-arm-none-eabi-9-2020-q2-update/bin
Local config:
TARGET=disco_f469ni
TOOLCHAIN=GCC_ARM
Your help would be very much appreciated.


texts: Can anyone explain the difference between these two forms of PID controllers?

texts: Usually, when people talk about PID controller, I think of the "parallel form" of PID controllers, I know how it is derived (we just need to add all 3 three P I D controllers together). This is the first time I have ever seen the "series form" of PID controller (being second year engineering student). Can you tell me how it's derived and how it's drawn in a diagram? Thanks.


texts: Using dedicated power supplies versus using pulse transformers?

texts:
In our current design of our single-phase NPC T-type converter, we are using four dedicated (and expensive) power supplies (actually, DC-DC converters, since we have incoming 48V, and the converters step that down to 12V). Upon running a simulation, I have found that I can use much cheaper pulse transformers... So I would be powering four MOSFET drivers in parallel from the output of the converter, and the output of these (Vb and Vs) would be wired to each of the four primary sides of the pulse transformers.  The secondary sides would be wired to the V_gs of the four MOSFETs.

How would this method compare to using four dedicated power supplies, instead of one oversized one?

Thanks a lot.

EDIT: Many are asking for schematics.  This is kind of difficult since I am using new simulation software (PSIM) and I haven't mastered it to the point of making easily readable schematics.  I made a very simplified one to illustrate what I am trying to say.  Only the gate signal for the low-side MOSFET is shown.

simulate this circuit – Schematic created using CircuitLab

EDIT#2:
I am reading through a .pdf, and the following is a proposed circuit that can be used so that pulse transformers can be implemented... Would this circuit work if correct component values are chosen?


texts: What are the uses for a water soluble IC socket?

texts:
I recently stumbled across water soluble IC sockets after being given a bag of them. While they do dissolve successfully from the board, I can't seem to come up for a valid explanation for why anyone would ever want to specifically spec out water soluble IC sockets for their project. What are their intended purpose(s)?

For reference, it does appear Digi-Key sells one model of these however the page and reference sheet provide no clues as to its intended use.


texts: Transistor Level Shifting in Buck-Boost Converter

texts:
Ive been reading some of the LT application notes on Jim William's Analog Circuit Design book, and there's something I don't quite understand. I'm attaching a scan of the circuit in question.

The LT1070 has its ground pin at -12V, and Q1 is forcing a current of around 1mA through the 1.24k resistor, this produces a 1.24V drop through that resistor, which corresponds to the 1.24V reference inside the FB pin (the error amplifier).

Ok I understand that, what I don't understand is why use the transistor in the first place? Why not just use a simple resistive voltage divider? whats the advantage of using Q1 rather than a simple resistive voltage divider?


texts: Will a 3D printed ESD dissipative housing prevent spark travelling through air hole to PCB?

texts:
I have little clearance between my PCB and the air holes of its plastic housing, meaning an air discharge is able to conduct to the PCB through the hole. If I make the housing out of an ESD dissipative material will the spark discharge to this first as the ESD gun approaches, or will the housing's resistance be too high?
I am considering dissipative plastics such as ABS-ESD7


texts: What drawbacks to bucking, then boosting the same current?

texts:
Are there any real negative drawbacks - outside of the double drop of efficiency - of DC-DC boosting a power line that was already DC-DC bucked?

I'm building a modular system, serially linked through contact points. Most modules need 5V and low amps, but a couple need 12V and 1A. I'm intending to use a 12V power supply as the main source, but would like a battery option.

The most straightforward option is to have dual power rails, one 5V and one 12V, and let each module just draw from whichever rail works for it. This means I would only have to implement the boost/buck converter once, in the controller. But it would mean having to use six contact points (12+, 12-, 5+, 5-, and two data lines) on the sides of each module, which cost significantly more than the four-contact strips I'm looking at. (I also just want to reduce complexity with the connection)

I could also just run one 12V line down to each module, but this would mean implementing a buck converter in each 5V module, so again not very economical. In the case of a user opting for the battery pack, this would also require a boost converter in the battery pack to provide the 12V rail.

So I could also just run a 5V line down the modules. I buck the 12V power supply once in the controller, or just let the 3 or 4 AA battery pack run straight through. This would mean including a boost converter in the modules that need the extra voltage. This works out economically because it's a relatively small number of modules that need this. But does it work out electrically?

There are two possible issues I can see -- first is my title question. This would mean bucking 12V to 5V, then later boosting 5V back to 12V. I'm not worried about the loss of efficiency. But are there any other concerns?

Second is, would the batteries be able to handle boosting from 3.6 (3 * 1.2 rechargeable) - 6.0 (4 * 1.5 alkaline) volts to 12V with a 1A draw? The vast majority of the time my 12V module will draw 1A in very small pulses. 1-5 pulses lasting 10-50ms each, with 3-15 second pause between them. Fairly low overall power. But every now and then the user will need to trigger a routine that will pull the 12V/1A for 30s at a go, perhaps multiple times. Assuming an ideal boost converter, 12V/1A would pull 6V at 2A, so I've got to assume it could be even larger with real world components. Can AA batteries handle that? (another option: this routine is not the primary function, so I could possibly just tell the user they can't do that with a battery pack)

Thanks for any advice. I'm new to this field but having fun learning. :)


texts:
OK, this is really annoying me.

I have an old bedside radio/alarm clock that's been fine for a couple of decades, and which still works perfectly well at night. Its crude FM antenna is a simple strand of PVC-insulated wire dangling from the back of it, with a plastic lump on the end about 1cm long and 4mm diameter which might or might not contain any components moulded in. Recently in the mornings (only), the audio has been seriously compromised by crackly interference.

It seems to make no difference how I arrange the wire antenna, but I get perfect reception whenever I hold the lump on the end of it, and back to crackles when I let go.

Any suggestions as to what's going on, and/or what I might clip on the end of that piece of wire to approximate an adult human being and suppress the interference?


texts: How to calculate using mesh method when there's a current source and a resistor between two meshes

texts:
I'm trying to get the current in the 3 ohm resistor using mesh analysis. Forget about thevenin's theorem here.

However, what I know is that if there's a current source between two meshes then we do the supermesh analysis. But in this case there is a resistor and a current source in between the two meshes, which means we can't do the supermesh.

Here's the circuit:

So how do I get the current throught the 3 ohm resistor using the mesh method in this case?

I'm not asking for the final answer but how do I move on when a current source and a resistor are between 2 meshes ? Should the 3 ohm resistor take all the value of the current source(which means that the value of the current through the 3 ohm resistor is 5A)? Any help will be much appreciated :)


texts: TLC59116F (i2c led driver) everything seems ok but LED doesn't work

texts:
I'm trying the LED driver TLC59116F with an arduino UNO R3. This IC is a i2c controllable LED driver with PWM and 16 outputs. The registers seem all loaded fine, here's a print of their contents:

0:11
1:0
2:C8
3:C8
4:C8
5:C8
6:C8
7:C8
8:C8
9:C8
A:C8
B:C8
C:C8
D:C8
E:C8
F:C8
10:C8
11:C8
12:FF
13:FF
14:FF
15:FF
16:FF
17:FF
18:D2
19:D4
1A:D8
1B:D0

As you can see, all outputs are on C8 (200) which should be high brightness.. and all LED are active I think (the FF registers). I have attached an LED to OUT0 like this:

simulate this circuit – Schematic created using CircuitLab

If I attach the led to GND instead of OUT0 it (of course) works fine. The IC talks fine on i2c therefore it shouldn't be burnt.. The IC power comes directly from the arduino 5v, which is in turn powered by the USB connection.


texts: Why there is no brushless field wound DC motor

texts:
One classification of DC motor separate them into Brushed and Brushless, and then the brushed are further broke down into series wound, shunt wound or externally wound. Brushless motors, on the other hand, are permanent magnet.

I dont understand why we cant have brushless shunt wound motor, for instance. Why brushed motors always dont have permanent magnet.

It seems that certain combinations simply dont exist.


texts: Direction of electron flow in semiconductors

texts:
This picture shows how the electrical current actually flows in Silicon material. So current obviously flows from the negative pole of voltage source to the positive. What about holes? Are they moving in reverse direction? Are they even moving in any direction? Do electrons moving from negative to positive pole fill up the holes to move forward?

I have read a few articles about this process but I still have some basic questions. I would be very tankful if anyone would share their knowledge here. Thanks :D


texts: What is the effect of aliasing in discrete time controller?

texts:
Suppose we have a controller whose TF is $$ G(s) = \frac{1}{(s^2+1)} $$ This yields two marginally stable poles at \$ s = \pm  j \$

Now let's discretize the controller through z transform, after which we obtain an expression that looks similar to

$$ \frac{z-1}{(z-e^{-jT})(z-e^{jT})} $$

So our poles in the Z domain are \$ z = e^{\pm jT} \$

Let's vary our T, for \$T = \frac{\pi}{2}\$, we have z = -/+ j, exactly as our continuous time controller.

But for \$T = \pi\$, we see that both of the poles of z are at - 1.

What is the effect of this aliasing from continuous time controller to discrete time controller? i.e. what happens to the output this for this case

What are used to prevent aliasing?


texts:
I have a problem to get to an conclusion with the VS- or CC-balance.

I know that the voltage over an inductor in an switched topology behaves in an stationary state like this:

So the voltage-average over one period is equal to zero.
It follows that the current-average over one period is constant.

How do i get to that conclusion? (I have the same question for the CC-balance for the behavior of the current and voltage of the capacitance)


texts: miniDIN - style connector with many pins

texts: I'm looking for circular connector with size of mini din with so many pins as possible. I'm building embeddable controller for Roomba vacuum cleaner robot, and I want to led as many pins as possible from microcontroller through this connector.


texts:
I am trying to make a circuit for my newly installed DRL (Day running lights), what I am trying to do is have the DRL run all the time, turn off when using high beam, dimmed when headlights are on.

I bought two 5 pins relays and attempted to make a circuit for that purpose, here is an image of what I have done so far (excuse my drawing, I have no idea how to make proper diagrams, I am a systems engineer and I work as a mechanic and electrician for my first project car on my spare time)

DRL (Day) = Day Running Lights running normal
DRL (Night) = Day Running Lights are dimmed
HL= Headlights
HB= High Beam
ACC= Accessories/(+)

I have connected the ground and the (+) to the battery and a small 12v light to the ground and to (DRL (Day)), the light was working fine, I have connected (HB) to ACC in order to activate the first relay and it worked fine by cutting the power to the second relay. The problem was with the second relay, when I connected (HL) to ACC both (DRL (Day)) and (DRL (Night)) stopped working, what was supposed to happen is to switch the power from (DRL (Day)) to (DRL (Night)).

The diagram is exactly what I have done to the relays, same pin locations and same connections. This is my first time to work on relays so excuse me if the problem is too obvious.

Side question: If I want to dim the 12v DRL by 50%, how can I find the required resistor?

EDIT: The diagram on the relays is exactly the same in the picture I have attached.


texts: Why would a digipot require the voltages on its terminals to be between ground and VCC?

texts:
I'm not sure if other digipots are like this, but with the MCP4151, which I'm using, the datasheet says that the "Resistor Terminal Input Voltage Range (Terminals A, B and W)" has a min voltage of Vss and max of Vdd.

I was skeptical about that since internally it's just a resistor ladder, but when I fed an audio signal through it slightly outside of Vss and Vdd, there was a bunch of staticky noise not present when I use a mechanical pot instead. I don't understand why it matters what the input voltage is as long as it doesn't melt the internal resistors.


texts:
So I'm just starting to get into soldering, and being a noob, I got the most el cheapo solder kit you could possibly get.

Now the problem is that the soldering iron isn't very hot. So with lead-free solder, it takes some convincing and pressing the solder onto the iron for a few seconds before the solder melts.

This is fine if I don't have my fan (regular desk fan) on - I could solder quite normally. However, the fumes smell horrible, and apparently they are bad for you. But when I turn my fan on, the solder won't melt. Or it would melt after 2 minutes with me pressing down the soldering iron and overheating everything on the board, but instantly freeze as long as it it's not directly in touch with the soldering iron. I even got solder wire stuck firmly onto a circuit board because it froze so quickly.

It seems like the fan is cooling down the solder, which is strange since it's not a super powerful fan or anything. Is there a way to prevent this? Or do I need to get one of those special fume extractor fans?


texts: Bypassing input capacitor with a microcontroller

texts:
I am designing an amplifier stage and I would like to be able to switch between AC or DC input coupling. How do I achieve this with a microcontroller?

I was thinking about using a relay, but it seems like an overkill for such an easy task.


texts: Simulating High-Side N-Channel Bootstrapping in LTspice

texts:
I'm working on understanding bootstrapping, so I copied the schematic used in this YouTube tutorial in LTspice. However, my simulation doesn't appear to yield the results that I would expect from a properly bootstrapped circuit. While the gate-source voltage appears to be properly switching between zero and (approximately) twelve volts, the load doesn't have twelve volts across it, which is kind of the point, as I understand it...

I noticed that the content creator said repeatedly in the comments that this circuit is not intended for high-frequency switching, so I made the switch toggle very infrequently (once per second), but this didn't appear to fix the problem. I also added a gate-source capacitance to model the internal capacitance of the transistor and made sure that the bootstrap cap was ten times this value in accordance with rules of thumb, but this didn't help.
At this point, I can't tell if the problem is my implementation of the schematic or my simulation parameters (.tran 4). Does anyone have any ideas?


texts:
The scenario went like this: I used to run this amp with +-20v DC, and it seemed to work fine except for a little bit of clipping. Now, I changed my mind to make it work with bigger voltage!!!
I've increased the voltage to +-50V DC. After powering the amp, a nice smell got out but it was working!!!
Now I didn't cut the power to experiment what actually happens. Funny isn't it?
Anyway, so, after playing the amp for around a minute things got out of control with a little burst!!

Therefore I've opened the amp and found that the supply decoupling caps got fired along with a few small transistors and one Output transistor from one channel only!!! My amp got 4 channels!!!

So, I took out the burned parts and replaced only the decoupling caps. Problem arised when I powered it after replacing the damaged parts. The divider resistors in the diagram (marked red) are getting hot and funny smell is coming again. Now, these resistors have been changed when I opened the amp because they got burned out too.

I've checked all the components connected to that divider network but failed to find any visual fault.

What can cause the resistors getting too hot?

Any suggestions would be greatly appreciated!!!

I've just replaced the 220 Ohms resistors with 1.2k.
Still it's getting hot!!!

I think 1.2k won't hurt according to the formula!!


texts: Why is distribution voltage 480V but equipment is usually only rated for 460V?

texts: In the US, distribution voltage is usually 480V. However, most industrial equipment is only rated for 460V. Why is this the case?


texts: Ultrasound project - voltage/current, pulse width

texts:
I need help with my ultrasound project.

My plan is to generate -170 V powering voltage with MAX1847 DC/DC from 5 V. Excite the transducer (2,25 MHz, 50 ohms at resonant freq) with square wave (pulse excitation) with this pulser circuit:

The transducer is Olympus V305-SU-F, they don´t provide datasheet.
I want to use one pulse per work cycle with repetition of few hertz.

I have following questions:

a) How to select pulse width?

My thoughts: Here is said, that "a square wave pulse must be tuned to the frequency of the transducer", so -> 2,25 MHz -> T = 1/f -> 440 ns pulse width?

What if it will be shorter/longer. I can think only about transfered power loss.

b) What is the relationship between voltage and current?
   When I apply -170 V at resonant frequency with 50 ohm from Ohms law I get 3.4 amps (like is said in my another question on this side here ) Correct?

How does this work with square wave excitation?
   Can I lower the current with input resistor without losing the possibility of sensing the returning echo?
   This seems tricky for me, because I can´t get so huge current from MAX1847 and through TC6320. Any thoughts how to solve this?

My confusion come from this:
All ultrasound pulsers that I have found cant handle 3.4 A. Most of them generate pulses around +- 100V. With common transducer impedance of 50 ohms the current is still to high :/

P.S. For others interested in this topic, I have found great book: Piezoelectric_Transducers_and_Applications link on PDF file


texts: The meaning and role of the phase in antenna measurements with VNA

texts:
VNA measurements of an antenna return Z, RL, Xs, Rs... and also phase. I usually check Z=50 and Xs=0 to reach the max Return Loss and the lowest SWR 1.0:1, without having care of phase values.

However I noticed that in some cases even if Z and Xs are 50 snd 0 the SWR is high (even 6:1... 10:1) becouse of a particular high value of phase.

What's the best value of phase I have to reach for a perfect matching?

Do I need to have always care of the phase like Z and Xs?


texts:
I'm building a distortion pedal and I was wondering which tapers to use for which potentiometers in the tone control section. I normally design my own circuits, but I'm going by someone else's schematic this time. While I'm very familiar with simple RC filters and use them all the time, I don't quite know how this network works.

I'm guessing that the BASS pot should have an audio taper because it seems like it's effectively a normal, first-order RC high-pass filter, which would have a cutoff frequency of 1/(2πRC). I also think that maybe the TREB pot should be linear, because it seems like it's mixing signals between nodes A and B. I have no idea what taper MID should use.

What tapers should I use for each pot? How can I determine which tapers to use for similar networks in the future? What is each pot doing? I know I have a lot of questions, but I very much want to learn.


texts:
Hi i am a electrical engineering student first year since we study only microcontrollers and processors I have decided to learn more about fpga (I have a little experience with spartan 3e vhdl) . My goal is to be able to perperform video processing on a video stream and detect ,track multiples objects . I have 4 months periode . For the fpga I think basys3 board from digilent will do fine ( 1800 kb of ram 90 dsp. Vivado ) ?
The problem I don't know where to begin ? What I should study ? Ho im gonna feed the video to the fpga ? any help would be great thanks


texts:
I am struggling to find out the Value of Ie and Ib here.

Ic I have taken to be Vcc/10k. If this is correct I could use Ic/alpha = Ie . I would like to know if this is the case but seems to easy to be the case?

Usually we would have Re to stabilise the heating effect and Ie would just be

Vb-0.7/Re.

I would appreciate the help.

The reason I am doing this is to try and find the Range of values for Vout based on different gain Values of beta.


texts: Arduino Every Nano with 3.7V Li-Po - Reading voltage

texts: I have Arduino Every Nano and 3.7V Li-Po battery (Akyga LP903759). I want to read the current voltage of a battery using analog pin. If I use a 50 kOhm and 200 kOhm resistor (in voltage divider) I'll get 2.96V on the output. In Arduino datasheet I see than typical resistance which works with this microcontroller is 40 Ohm (Min-20 Ohm, Max-60 Ohm). Could I damage Arduino using this resistor and giving almost 3V to analog pin? Do you know how to get properly values of resistors to read battery level with this Li-Po battery?


texts: Why does more bandwidth guarantee high bit rate?

texts:
The definition of bandwidth is frequency range and it seems to be correct to say that higher bandwidth guarantees higher data rate.

However, i do not understand why it does.

Data rate depends on modulation scheme and nowdays QAM, which is combination of ASK and PSK, is most widely used scheme.

I have understood that FSK needs more frequency so it needs more bandwidth but I do not understand why ASK and PSK need more bandwidth. (If QAM did not need more bandwidth, QAM could be used in small bandwidth and it would mean that bandwidth has nothing to do with data rate.)

As i understand, ASK does not need more bandwidth. If transmission power in transmitter is bigger, the amplitude of wave will be bigger. In that sense, ASK can be achieved by transmission power control.

Furthermore, PSK will be constructed if signal is delayed. As I know, the angle of phase is decided by delay of wave (timewise.)

If what I explained is correct, why does high bandwidth guarantee high data rate?


texts: A Motor That Only Runs One Rotation (Or For A Certain Amount Of Time)

texts: I'm certainly no kind of expert when it comes to electrical engineering, so any help is appreciated. For a project I'm working on I need some sort of small motor (smaller the better) to spin a wheel one revolution and then stop. I feel like the easiest way to do this would be to have a timed motor that starts at the press of a switch and then stops after a second or two, similar to the motor in an automatic soap dispenser. Is there an easy way of doing this? Thanks!


texts: I need help identifying two passive SMD components from [ GoPro Hero+ ]

texts:
[

This is the bottom side of the GoPro PCB. I marked the components I need identifying. I assume they are either capacitors and/or resistors, but I need confirmation.


texts: Using 6x58W fluorescent lamps instead of 6x55W, what could possibly go wrong?

texts:
I'm planning to buy a fluorescent photography lighting head, but the manufacturer specified it uses 6x55W lamps, but I want to use Philips Graphica 58W lamps. 3 watts more per lamp, doesn't look like a big increase over the limit, but could it damage the lamps so they will burn out quicker? Or this is within some safe range?
Maybe it's a duplicate, but I haven't got any luck with Google, and the lighting head is not that cheap, it's $300, and I need two of them, so no way I'm going to test it out myself, without knowing if it will work.


texts: Confusion between Voltage gain & Voltage gain in decibels (dB)

texts:
The definition of voltage gain is \$V_{\text{out}}/V_{\text{in}}\$.

However, I read some articles about the gain in decibels, and I have a confusion now.

Here is an article about it: https://en.wikipedia.org/wiki/Gain#Voltage_gain

Here, I understand the definition of Power gain in decibels, which is $$ \text{Gain} = 10 \log \left( {P_{\text{out}} \over P_{\text{in}}} \right)\text{ dB} $$

However, I can't understand why Voltage gain in decibels is $$ 20 \log \left( {V_{\text{out}} \over V_{\text{in}}} \right)\text{ dB} $$

If \$ 20 \log \left( {V_{\text{out}} \over V_{\text{in}}} \right)\text{ dB} \$ is derived from $$ 10 \log {\left( {V_{\text{out}}^2 \over R_{\text{out}}}\right) \over \left({V_{\text{in}}^2 \over R_{\text{in}}}\right) }\text{ dB} $$ then this is the power gain, not the voltage gain, isn't it? However, the Wikipedia says it is a formula for the Voltage gain in decibels. I thought the voltage gain in decibels would be \$ 10 \log \left( {V_{\text{out}} \over V_{\text{in}}} \right)\text{ dB} \$. Actually, the example section in that linked page uses voltage gain \$ V_{\text{out}} \over V_{\text{in}} \$.

Why did \$V^2/R\$ suddenly come out from the voltage gain in decibels?


texts: Perfect AC sinusoidal wave dimmer with PWM from micro-controller

texts:
I am designing a circuit for controlling speed of a AC fan using Arduino UNO, this is how the circuit looks like .
In this circuit the waveform generated for load is not perfectly sinusoidal,what i want is to generate a perfect sine wave with low voltage , that some thing looks like the below circuit:-

Supply voltage available is 5v. Please help me with the approach or circuit that can be used to achieve this.
REF of Imageshttp://tahmidmc.blogspot.com/


texts: Issues encountered when adding DC adapter to light powered by battery

texts:
I have an LED light bar powered by 6 AA batteries connected in series. There is also an RF control unit to turn the light on/off. The light eats through the batteries rather quickly thus I decided to experiment attaching a DC adapter to the light.

Due to the way the batteries are connected, I assumed that the light takes 9V to power, so to test my theory I grabbed a used 9V cell and it worked perfectly - even responds to the RF remote.

I then grabbed several DC adapters that output 9V with varying current and then began testing to see which one will work. First I tried one with 200mA and the lights turn on, but does not respond to the remote control. I then upped the current to 300mA with same result, but when I tried it with 600mA I heard the dreadful "buzz" as soon as I connected the circuit (did not even turn on the switch). As expected, I fried the RF receiver module in the light - yet the light still works. Even going back to the 9V battery does not allow the light to be operated by the RF remote.

So now I'm trying to find out what happened. If I have the voltage correct, shouldn't the worse that could happen is under-powering the light due to insufficient current? I'm assuming that even if I increased the current, there shouldn't be a problem since the resistors in the circuit should be limiting the current so there shouldn't be a risk of burning something out. The only thing I can come up with is that the adapter was putting out way more than 9V to fry the RF receiver circuit. Are there other possibilities about what could've went wrong?


texts: Are there any micro-controllers produced by companies based in the UK?

texts:
The closest I've got is a company called FTDI which produces USB ASICs.

Are there any micro controllers manufactured by or built for uk-based companies? If they do indeed exist, can you tell me how they compare with their better known counterparts? (PICs for example)


texts: Power Factor Correction Circuit (LED lighting)

texts:
I've been researching how to design power factor correction into an agricultural LED lighting system. My client requires at least a 0.95 power factor. I'm planning to use PWM controlled buck converters (e.g. TI LM3404 or similar) to supply constant current to the LEDs.

In my research one simple thing I've turned up is a Valley Fill circuit.

My questions are:

I could use some help understanding the design process behind component selection for the six components C1, C2, R1, D1, D2, and D3.
The Wikipedia page seems to indicate that it's a mediocre power factor correction circuit (total harmonic distortion of ~35%), what should I be looking into given a requirement of at least 0.95 power factor?
This is in reference to an LED lighting project I'm working on. Should I have a PFC circuit in place per LED driver? Where do these types of circuits belong in the topology of a lighting system.


texts: How to optimise wire gauge selection for electromagnetic applications?

texts:
Disclaimer: Hobbyist "maker" with limited experience and no relevant education. Please considerate and answer in detail. Feel free to skip to "Question".
Context
I have an intention to build a simple solenoid for no other reason but my own interest. A basic review of theory brought me to the equation B = μIN/L whereby B = Field Strength,μ = Magnetic Permeability, I = Current, N = Coil Turns and L = Coil Length. For what ever reason my first observation was that there was surely an optimisation to be solved in the selection of wire gauge since an increased wire cross-section would increase your available Current Capacity (I) but decrease the Coil Turns (N) along a constant length. I then stopped short of attempting any calculation since I being proportional to the cross section area of a wire (in terms of Ampacity) and N being a first order relation, it seemed logic that the "bigger the wire the better, turns don't matter that much"... this can't be right. What further confused me was to investigate the current draw of commercial BLDC motors, of whatever size, and note that their amperage was surely beyond what would usually be carried on the wire gauges used for stators. Something to do with the AC driving? I sit confused.
Question

What is the optimal design approach for selecting wire gauge for electromagnetic coils of a given length and diameter?
What factors are most import to consider?
Are there conventions or standards I should know about?


texts:
I solder about once or twice a week, and I use leaded, rosin-core solder from RadioShack(bought it before they went under). I do notice that their are flux fumes rising from the board when I solder something on, and I am aware that they can cause some short-term and long-term health effects determined by the frequency of inhalation.

My Question: Is a simple fan enough to blow the fumes away from my nose or should I invest money in a soldering fume extractor?


texts: Will inout ports used only as in or out be optimized?

texts: I am writing a VHDL design in Xilinx Vivado. I received an example code for an FMC card where all the ports are designated as inout. If I use an inout port only as in or out in the rest of my architecture, will Vivado optimize the port to the appropriate type during synthesis? Or will it stay an inout port?


texts: how to shifted phases in PWM with PIC18F4431

texts:
I am trying to design a driver for a BLDC motor.

I have managed to generate 6 PWM signals with the PIC18F4431.

But I don't know how I can shifted the phases.

I attach my code and the image of the PWM signals.

void pwm_inicialitze(void)
{
  PORTB=0x00;
  TRISBbits.TRISB0=0;
  TRISBbits.TRISB1=0;
  TRISBbits.TRISB2=0;
  TRISBbits.TRISB3=0;
  TRISBbits.TRISB5=0;
  TRISBbits.TRISB4=0;

  INTCON=0XC0;
  IPR3bits.PTIP=1;
  PIE3bits.PTIE=1;
  PIR3bits.PTIF=0;

  SEVTCMPL=0X00;
  SEVTCMPH=0X00;
  DTCON=8;
  FLTCONFIG=0X00;
  OVDCOND=0XFF;
  OVDCONS=0X00;

  PTMRL=0X00;
  PTMRH=0X00;
  PTCON0=0X00;
  PTCON1=0X80;
  PWMCON0=0X50;
  PWMCON1=0X01;
  PTPERL=124;
  PTPERH=0;

  PDC0L=60;
  PDC0H=0;
  PDC1L=60;
  PDC1H=0;
  PDC2L=60;
  PDC2H=0;
  PDC3L=60;
  PDC3H=0;

  ADCON0=0x00;
}

void main(void)
{
   ANSEL0=0X00;
   ANSEL1=0X00;
   pwm_inicialitze();
   while(1);
}


texts: How to power 2 15.2v 57.2 watts peltier plates

texts: I am building a custom peltier cooler out of aluminum insulated with styrofoam I currently have 2 tec-12706 peltier plates and 2 PC fans what would be a adequate power supply for this setup?


texts: How to export component layout in KiCad?

texts:
I want to export a PDF from KiCad that shows how the components are distributed in a board I designed, with no tracks at all. I want something like this.

How could I do that?


texts:
I bought an Eval kit for an RFID module. The reader detects the card included in the kit just fine, but it can't find a separately bought, completely blank RFID tag.
The reader is 13.56MHz and supports ISO 14443B.
The Tag is 13.56MHz and ISO 14443B.

The RFID reader is the DLP-RFID2-EDK
https://www.dlpdesign.com/rf/dlp-rfid2-ds-v114.pdf

The Tag in question is
https://www.digikey.com/product-detail/en/microchip-technology/AT88RF04C-MVA1/1611-AT88RF04C-MVA1CT-ND/6831584

http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-8672S-CryptoRF-AT88RF04C-Datasheet-Summary.pdf

http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-5276-CryptoRF-AT88SC0808CRF-1616CRF-3216CRF-6416CRF-AT88RF04C-Datasheet.pdf

The software is a TI demo GUI called TRF7970A_GUI_WIN7_11_2013

Is there a special initiation process for new tags? or does it have anything to do with the security features of that specific tag?

EDIT:
from http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-8672S-CryptoRF-AT88RF04C-Datasheet-Summary.pdf Section 2 Communications
"The IC includes an integrated tuning capacitor, enabling it to operate with only the addition of a single external coil antenna."

Does that mean these tags need you to solder on an antenna?


texts: Best way to control heater coil in portable application

texts: I have a resistance wire (kanthal) that is about 2 ohms; with a power source of 3.5V. I'm trying to figure out the most efficient and portable way to control the coil; I'm toying with a mosfet right now, but It gets almost as hot as the coil itself! What would be the most efficient, cost effective, and space saving way to go here?


texts: Why does differential signaling send complementary signals instead of just pairing the input and ground voltage?

texts:
I'm very new to EE, so please excuse me if this question is bad or has an obvious answer. After reading an overview of differential signalling, it left me wondering:

Why does differential signalling use "complementary" signals for D+ and D- instead of simply making D+ the input voltage and D- the "ground" voltage (or whatever the reference voltage is)? In other words, instead of:

D+ = +½ V_SIGNAL
D- = -½ V_SIGNAL

(as this site states is the case for differential signalling), why not simply make the signal pair as follows:

D+ = V_SIGNAL
D- = V_GROUND

External interference would still affect both wires the same, and the receiver could still do V_SIGNAL = (D+) - (D-) to remove common-mode interference and recover the original signal.

Update: This graphic I made should help clarify what I'm asking - Why is the DS sent as "complement" signals (like on the left) instead of sending the orignal signal "as is" and ground reference (like on the right)? Would external interference not be "induced" into the ground wire in the same way?


texts: Can a DC motor be of specification 320Watts, 3A, 24 V?

texts:
The above is the specifications of a wheelchair DC motor I'm trying to use as my hobby project.

My question is how can a motor of 320 Watt and 24 V DC be of 3.0 A max rating when the current should be around 13 A?


texts: Removing PCB from complex pattern of soldered-in thru-hole posts?

texts:
I have a PCB mounted to a chassis with 16 feedthrus, the feedthrus posts are soldered to plated thru-holes in the PCB.  I would like to remove the PCB from the chassis, the problem is that I am unable to remove 100% of the solder from the plated thru-holes and I am unable to simultaneous heat all 16 points to try and remove the board while the solder is hot.  The 16 posts are arranged in two identical groups of 8 with an identical outline.

I've tried to remove the solder from the thru-holes using solder wick and a vacuum solder-removal gun but a little solder is always left, this is probably due to the sizing of the holes which are only slightly bigger than the feedthru pin, 22 and 18 mils respectively.

One idea is to make a custom soldering iron tip that exactly matches the hole pattern so that all 16 holes can be heated simultaneously, then the board can be removed while the solder is liquid.  I've never made a custom soldering tip before so this method has some inherent risks from the unknowns.

Any other suggestions for removing the PCB?  Also, heating the whole assembly above 150°C is not desirable due to sensitive components that are mounted to the chassis on the other side.


texts: SN65HVD3x (RS485 Driver) - Termination resistor

texts:
I want to use the SN65HVD31DR to connect two microcontrollers together. The connecting cable has an impedance of Z0 = 80Ω. According to the data sheet it is recommended to terminate the connection cable on both sides. So there would be two 80Ω resistors connected in parallel which would effectively make a parallel resistance of 40Ω. According to the datasheet the differential load resistance RL must not be less than 54Ω.

So is it right that I am not allowed to terminate the connection line with two 80Ω resistors and I have to use a cable with a higher impedance so I can use higher termination resistors? Or do I misunderstand something?


texts:
I am working on an ASIC design and need to use different clock sources for a digital block in different operating modes.

Can I safely use clock gating in combination with an OR gate to generate the clock as in the following diagram?

If that is ok, what constraints do the clk_enable signals need (i.e. glitch-free, non-overlapping, timing with relation to the respective clk, ...)?

Note that the clock gates are using a D-latch which is transparent when the respective clk is LOW.


texts: How to 'average' a sine wave of RMS values?

texts:
Lock-in amplifiers (Stanford Research Systems 830) display sine wave signals in RMS values SR830 Manual (page 3-3). One can use the internal buffer to rapidly measure a signal, storing up to 16000 points with a measurement rate of 512Hz. These points are RMS values of the original signal, if I'm not mistaken, and often slowly oscillate (due to a small frequency component not completely filtered out by the low pass filter). How does one 'average' these buffered points?

I'm not sure it makes sense to calculate the RMS value of a wave build up from RMS values, but taking the simple average of this wave also feels incorrect.

Thanks in advance!


texts: Multiple Voltage (230VAC & 110VAC) panel indication

texts:
I am looking at driving an LED panel indicator from either 230VAC or 120VAC to inform an operator that a hazardous voltage is present. I want this indicator to operate with minimal additional electronics (i.e. not converting to a lower DC voltage through a SMPS) so that it is a direct representation of the mains voltage. Most indicators are designed to operate at a single voltage level and if you undervolt them (i.e. buy a 230VAC indicator and put 110VAC into it) they are sometimes too dim to be usable. They would also not look great on the panel as I would end up with various brightness levels depending on what mains voltage is applied (I will have some 24VDC indicators also on the panel too).

Would Zener diode clamping be a suitable? Using an online calculator http://www.petervis.com/electronics%20guides/calculators/zener/zener.html for a quick estimate (assuming 10mA panel indicator, 9.4mA Iz, 100VL and 230VS) my diode would have to dissipate 1W and the resistor 1.35W which would mean they could get quite hot. Is there is a more efficient way of doing this?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm working on a high speed ADC/DAC board. I saw some reference designs for the device, there are matching series resistors connected between output digital pins & controller.

Though, resistor network's value is given in the schematic. I'm curious to know, How do you calculate What resistors to be used for impedance matching.

What parameters of the input pins should be taken into account. Is there any formula for calculating the same ?


texts:
I have a machine (a machine with seven three-phase motors) with this information on its nameplate:

  3 Phases

  400 V, 50 Hz

  100 A, 40 kW

I am wondering:

Is 100 A for all three phases or only for one phase?
What does it mean by 400V? Line to line voltage? Or the phase one?
Is 40 kW the maximum power consumption? Or I should consider the reactive power and provide a larger power source such as 50 kVA? Also is it for all phases?
What size of wire should I choose?

Edited:
5. How was the power, 40 kW, calculated? 400V x 100A = 40kW? So what about P = sqrt(3) * VL * IL?

Environment: My machine has 7 three-phase motors. Local electricity line: 220V, 50Hz, each phase.


texts: To "ground fill"or not to "ground fill"?

texts:
I have been reading up on the EMI issues in Electromagnetic Compatibility
Engineering by Henry Ott. (wonderful book btw).

One of the topics "PCB Layout and Stackup" (aka Ch 16) there is section about ground fill (16.3.6).
Basically what it states, that to minimize the "return current path" filling the areas between connector pads with ground fill should be done. Quite understandable, however in the same section at the end it states "Although often used with analog circuits on double-sided boards, copper fill is not recommended for high-speed digital circuits, because it can cause impedance discontinuities, which can lead to possible functional problems.".
That last part confused me a bit, since I would expect that for high frequency signals (that try and follow the signal trace) a longer path would be decremental.
Can anyone explain why this remark is made?


texts:
I have built the following AM radio circuit :

I was able to pick several radio stations. I fixed the variable capacitor so that I can only hear the 1230 kHz station which I identified from the FCC call letter. I connected the antenna directly to my oscilloscope and obtained the following FFT:
This shows all the stations received by the antenna.
However, I connected my oscilloscope between the diode and the variable capacitor in reference to the circuit ground and obtained the FFT:

How is it possible that the largest peak was not attenuated while small peaks surrounding the station I hear were attenuated even though I can't hear the largest peak frequency? and why is the voltage increased?


texts: If I have 5% 100k resistors but wanted 1% precision, can I use 4 of them in series parallel to improve on the 5% precision?

texts:
I made an error on ordering and am receiving a shipment of 5% 100K resistors when I wanted 1%.

This is for a voltage divider circuit.

Would it help improve the precision if I put two each in parallel then put them in series to achieve the 100K?

Or would the extra parts be worse for the circuit than simply using a DMM to find the most accurate one and use that?

Please excuse me if this sounds like a dumb question.  The order was wrong.  It is a simple case of the computer doing what I told it to do instead of what I wanted.  (Old joke, I know).

Thanks in advance for your answer(s).


texts: How does the collector emitter relationship work with a transistor?

texts:
So,

I'm not understanding how NPN transistors really work in this scenario.  In this image, I
have highlighted what I understand to be the collector and emmiter.  My understanding is
that power flows from the collector, TO the emitter right?

In this example, the base either turns the circuit on or off.  I get that the circuit is
open when the transistor isn't being fed positive power.  But, why is the emitter running
to ground?  Shouldn't it be the other way, collecting and emitting to the LED?


texts: Which ground (digital or analog) measurement components should be connected to?

texts:
Good day,
I want to measure current and voltage of switching power supply that is on board together with ATMEL AT32UC3L microcontroller.
I think I understand how to measure - using resistor divider to lower voltage so it does not exceed ADVREF, and to use current monitor IC that will convert current across shunt resistor into proportional voltage.
What I don't understand is how to connect resistor divider and current monitor grounds. Should they be connected to analog or digital ground?
If I connect them to analog ground, will I not introduce noise to it?
If I connect them to digital ground, will I have correct values as AD[x] inputs measure against AGND?
Or there might be other solutions?
Thanx for advice.


texts: Mathematical model for differential signals and relation with reality

texts:
i have a question and i hope is not that strange.
i spend some time asking myself how people came out with the mathematical model for differential signals and why is this better in this way?!

to be clear i'm asking about this model:
vcm = (v1+v2)/2 and vdiff = v1 - v2!

i can understand why the equation for vdiff, that is obvious, but what about vcm?

in the simplest cases vcm is an offset voltage that is the same for both signals v1 and v2. and now i get why is this common and how the equation for vcm works. but what about signals that have on their common mode also noise and they also have different offset voltage?

how the equation works now and why is this still useful?


texts:
Exppresion for saturation current in GaN based diodes
$$J_{s1}=e[\sqrt\frac{D_n}{\tau_n}\frac{n_i^2}{N_D}+\sqrt\frac{D_p}{\tau_p}\frac{n_i^2}{N_A}]$$
For the simplicity, parameters:
\$e=10^{-19}, N_D=N_A=10^{16},n_i=10^{-10},D_n=25,D_p=5,\tau_n=\tau_p=10^{-9}\$
at room temperature (T = 300K) i get value ~ \$10^{-50}A/cm^2\$ (too low?), is this the right way to calculate saturation current or am i missing something ?

sorry for my bad english, and thanks in advance


texts: In = 3.7V / Out = 5.2V @ 2A Switching Regulator

texts:
I'm setting up a Step-Up Boost circuit for my main board using the MT3608 CI. It will be powered by a 18650 3.7v battery and need to output 5.2v @ 2A.

Reading the datasheet ( http://prom-electric.ru/media/MT3608.pdf ) of MT3608 I saw that it regulates its output through R1, R2 and the Schottky diode.

I wonder if R1 and R2 are correct and what is the value of my diode to get 5.2v output?

My Schematic:


texts: Op-Amp comparator output not reaching 0V

texts:
I am using a UA741CP opamp IC as a simple opamp voltage comparator.

I initially supplied it with 5V and tested the circuit as shown but even though I give voltage less than inverting input to non-inverting input I am getting 1.8 V or near not 0 V as output.

I hope someone knows the answer.

Regards,


texts: Why does large inductance have a constant current through it?

texts: I wanted to know, if an inductor is large, why would the current through it be constant? If an inductor is large, it means that it would be an open at moderate frequencies, and at DC the inductor is a short anyway, so how does any of that explain the constant current? Does it have something to do with the fact that the current cannot change instantaneously in an inductor? If that's the case, what does the size of the inductor have to do with that particular observation (current cannot change instantaneously)? I've attached an image of the problem. Thank you.


texts: Soldering CPUs/GPUs/FPGAs - temperature issue

texts:
I am thinking about making my own FPGA board and soldering using reflow. The tutorials I've read all say the process requires temperatures in excess of 220 °F. However, at least according to this datasheet, FPGAs have "max operating temperatures" below 200 °F. How does one then solder an FPGA?

EDIT: I have a new question in response to the answer given. Why would the max operating temperature differ from the max soldering temperature?


texts: Would like some help with Logic Gates, Trying to use two inputs to create three outputs

texts: I'm totally lost and I've got no idea what to search to help find this. Basically I have two inputs [A,B] Where A represents the number 1 and B represents the number 2. I'm trying to make it so when 1 is "on" It turns on a little LED, and when two is "on" it turns a seperate LED on. I've got that, but I want to add an AND gate to make it so when both are on it turns a new LED on and the other two turn off. I've tried using a XOR gate & and gate but it can't differentiate the two signals, [1,2] Hopefully I can finally understand this. I'm currently using Logism to make it easy to see and understand. Thanks.


texts:
There is  a  Bluetooth model in MATLAB  that can be accessed  using this command :

commbluetoothfduplex

Here its Link :
https://www.mathworks.com/help/comm/examples/bluetooth-full-duplex-voice-and-data-transmission.html

Also it is shown in the below figure :

The model can display PSD of the recieved signal before detection which is shown below :

As we can see the range extends from 0 till 40 MHz , but it is supposed that the Bluetooth uses the ISM band 2.4 GHz ? So please someone explain this received PSD. Thanks in advance


texts: What charger for a 13s10p Li-ion battery pack?

texts:
I plan to make a battery pack for my vehicle, 13s10p Li-ion battery. It gives me 30Ah.

If one battery can be charged at 1A, can I charge 10 batteries in parallel at 10A?

For now I have a 2A charger and the calculations come out to me that I will be charging the entire package for 15 hours and I would like it to charge as fast as possible - of course within safety limits.

Update:

Here are the specifications of the Samsung INR18650-30Q cell I want to use:

Nominal discharge capacity: 3000mAh

Charge: 1.50A, 4.20V,CCCV 150mA cut-off

Discharge: 0.2C, 2.5V discharge cut-off

Nominal Voltage: 3.6V

Standard Charge: CCCV, 1.50A, 4.20 ± 0.05 V, 150mA cut-off

Rapid Charge: CCCV, 4A, 4.20 ± 0.05 V, 100mA cut-off

Charging time: Standard charge : 180min / 150mA cut-off / Rapid charge: 70min (at 25℃) / 100mA cut-of

Max. continuous discharge (Continuous): 15A(at 25℃), 60% at 250 cycle

Discharge cut-off voltage: 2.5V

Cell weight: 48.0g max

Cell dimension: Height : 64.85 ± 0.15mm / Diameter : 18.33 ± 0.07mm

Operating temperature (surface temperature): Charge : 0 to 50℃

Storage Temperature: 1.5 year -30~25℃(1*) / 3 months -30~45℃(1*) / 1 month -30~60℃(1*)

And datasheet:

https://drive.google.com/file/d/1rVakjo344K7ZV_1GL6SCfT8tnT-cgtVM/view


texts: Using an oscilloscope to test SMPS controller IC signals

texts:
So I have a simple 2 stage SMPS, boost then buck, using ST's L6563 and L6599. I want to measure the gate drive and other signal components on the ICs. However, whenever I connect the Oscilloscope ground alligator clip to the common ground, my fuse blows. I'm not sure what the problem is, the simplest explanation would of course be that its causing a large inrush current, but I'd like to know how that makes sense, if that is the case. I tested with the oscilloscope powered off and just connecting the pins as well, but same result.

Without the oscilloscope clip, the fuse doesn't blow, but I'm not able to troubleshoot the reason why the 6599 is driving wrongly. Using a multimeter, I can get some voltage values but that isn't entirely helpful. Thank you.


texts: STM32L0: Fast processing of an analog sinusoidal signal

texts:
I have an embedded system based on a STM32 ARM Cortex M0+ microcontroller (STM32L051K6) and want to use it to convert an analog sinusoidal input signal into a digital pulse signal and do some SW calculations on the number of pulses (for additional digital busses, like I2C).
For the application, it is very important to count every pulse without any loss and forward each pulse with a minimal delay of not more than few tens of microseconds to a digital output pin. One other limitation is the power consumption, and this was one reason for choosing this MCU and operating it only at 4 MHz.

My first approach was to use the ADC with DMA for the input signal to empower a discrimination with a lower and upper threshold, in order to be as flexible as possible for the future, since later in the field, in terms of amplitude (300mV-5V) and frequency (0.5Hz-20kHz) the input signal can vary widely. In other words, it should act as a dynamically programmable Schmitt-Trigger:

For this, I used the STM32 HAL library. It worked seamless, but quite too slow for my application, the delay between one input and output pulse is significant over 100us and with a quite wide jitter...
I also had the idea to use an external circuit to trigger a comparator input of the MCU, but I wanted to evaluate the performance of all available possibilities first, before changing the PCB layout.

What are your impressions of my approach?
Does anyone know a better/more performant solution with this kind of MCU?


texts: Why is my signal stronger in the positive than in the negative when i use 2n3819?

texts:
simulate this circuit – Schematic created using CircuitLab

In the above circuit I have created a JFET amplifier for small signal purposes. When I run tests on the circuit, i get this weird event where my signal is stronger in the positive than in the negative by at least 40mV. Is this in any way common to happen with an amplifier or should it be a cause for concern before i build the circuit?
And is this circuit a proper one to boost a guitar signal back to where it should be, around 100mV?


texts: Best way to Step down 6V DC or 9V DC for 3.3V DC operation

texts:
I am basing on TIs TPS62745DSSR.
I have the circuit above and I want to use two CR2032 coin cell batteries to power VCC_IN. I have made this circuit based on info collected from the internet. My load is maximum 300mA.
I unsure on:

What does the MOSFET (CJ2301) do in this case? Does it just smooth out the input voltage? Why would this be needed when I am using batteries anyway?
In every other buck "step-down" design I have seen a diode. Why would I not need one in this case?  Should I add one?
I am leaning towards making the C3 4.7uF capacitor a tantalum instead of ceramic. Does this make sense in this setup?


texts: Phone charging Lipo battery power bank with 5V regulator overnight charging deep discharge

texts:
I was looking to implement a solar charging circuitry to charge a 6000mah battery which will act as a power bank to my LED/MCU loads as well as a smart device load. I found issues with my design when my battery would go into a deep discharge since I leave my phone plugged into my power bank overnight. I was wondering if there is anything I can implement just before my USB type-A female plug in the schematic found below that would prevent my device from pulling charge from the power bank when it reaches full charge and disconnect.

This is the 5 V regulator portion which will also supply the other MCU/LED loads, so the 5v needs to be on at all times for these loads while the USB should stop supplying current to the device when it senses that it is fully charged.
Would a MOSFET configuration be sufficient and is there a way for the system to determine when the smart device has reached full charge??
Thank you
EDIT: The schematic of the overall project is attached below


texts:
Does a multi-conductor DC clamp meter exist? Possibly using hall effect sensors in a specific orientation?

I typically work with 24-28V DC solenoids valves & pressure transducers with 2 and 4-conductor configurations, respectively. The solenoid valves can have 50'+ of insulated 2-conductor SJOOW cable from where they are actuated using solid state relays to the valves themselves. Accessing the solid state relays can be a pain and actually fitting a clamp meter around the + excitation line is difficult. I'm trying to figure out a tool to easily measure if a DC circuit is powered or not. Ideally, this tool would be in a clamp meter configuration, where I can wrap it around any 2-conductor DC cable and be given some sort of audible confirmation that a load is present and even a rough current draw estimate (does not need to be accurate).

I know what I'm asking for seems impossible but I've referenced this previous forum several times now in regards to AC circuits and it gives me hope.
Can single clamp measure total current from 3 wires?

An even more ideal feature would be if this clamp meter could also work on a 4-wire pressure transducer (+ Excitation, - Excitation, + Analog, - Analog). However I don't know how the hall sensors could be aligned for this application. Especially if the cable is shielded twisted 2-pair which we typically use (sounds even more impossible).

Any input is appreciated!


texts:
If voltage is the same across each resistor in a parallel circuit,  what's the point of resistors if there's 4 of them in a ciruit with 50volts, it won't affect the voltage.

I also noticed that when more resistance is added into a parallel circuit, it actually gets decreased instead of increasing. Please someone explain why that is.


texts: Hi, so I'm a bit confused with this solution (though I'm not sure if it is correct). Why is the R in the solution 8 when the magnitude of the impedance is 10. Is this because the resistance is only the real part of the impedance? But why is the I equal to 10 in the equation not 10 cos(-37) when using P=I^2R? Last question is power dissipated equivalent to active power(real portion of apparent power)?


texts:
I had a matching technique described to me by a professional broadcast engineer. Here's the problem: you have a vertical antenna with a low resonant impedance1, let's say \$38\Omega\$, but you need a better match to a \$50\Omega\$ feedline.

Solution: put a coil between the base of the aerial and ground. Then, you feed off a tap in the coil:

(image source: G3TSO on QSL.net)

How could this work? I can understand how adding a shunt inductor could improve the match if the antenna presents a capacitive load. But, why feed off a tap in the middle of the coil? If it's working as an autotransformer, wouldn't it be making the antenna impedance appear to be less to the feedline (the opposite of what we are trying to accomplish)? Also, if the antenna is already resonant, wouldn't the addition of shunt inductance make the match worse? Or is this why the feed is off a tap? Please help me understand how this works.

1: in my particular case, the impedance is even lower (I measure \$14\Omega\$) due to shortening of the antenna.


texts: Simple audio equalizer design: One filter is sending all the other signals to ground

texts:
I’m designing and building an audio equalizer with active frequency filters for my school project and I thought the base design was completely functional until I decided to simulate it on Proteus VSM.

Turns out the circuit output doesn’t correlate with I was expecting. Analysing the circuit cautiously I found out that any potentiometer affects all the other filters and sends all their signals to ground (Or that’s what it looks like).

Circuit schematic:

Explanation:

Proteus VSM Screenshots (Blue signal is Output):

98% (Signal displays)

28% (Signal disappears)

I don’t know if the base design I'm following is wrong or the simulation is showing a mistaken output. Any advice or suggestion will be appreciated. Thanks


texts: What kind of power supply is best for IoT application?

texts:
I am trying to make some IoT devices to fit in wall outlet. There is an issue with power supply. I have to feed my circuits from 220V outlet and there is a limitation in size.
I tried to use some HLK modules, but those are big and expensive.
I think IoT devices use some kind of transformerless power supplies (am I right?) but I have voltage drop problem with them.
What kind of power supply is recommended to power my 5V/500mA circuits from 200V AC?

(My English is poor so please excuse me for my bad grammar!)


texts: What are these character sequences in connection with DTMF and a modem (telephony)?

texts:
I have a telephone, with which I dial a modem (analog, no ISDN) in order to send DTMF tones. If basically works, I receive something!

For each key I press on the telephone I get a string like follows (e.g. key 4 pressed):

<DLE>/<DLE>4<DLE>4<DLE>~

DLE is ASCII 16(dec), and I found out that those different parts seem to have the following meaning:

<DLE>/    # DTMF start
<DLE>4    # key I pressed
<DLE>4    # same key again ???
<DLE>~    # DTMF stop

I searched the web for a document specifying this format, but did not find any hint except the link.

Can anyone point out to a proper documentation? Is this format correct? What about the repitition of the actual character, is it correct too? What about having it three times?


texts: How can I preventing sparks from a plasma tube arcing onto electromagnet

texts:
I'm building a very small version of this it's a Plasma tube with an electromagnet (the two red coils) wrapped around the tube see link or image below.

I want to send AC and DC Signals into the electromagnetic coil wrapped around the plasma tube using an audio receiver, DC power supply, and an amp (I want to see how different signals effect the plasma).  The problem I have is arcing, how can I prevent the arcs created by the plasma tube from interacting with my electromagnetic coils wrapped around the tube?  (I don't want the arc travelling down and frying my receiver which is powering the electromagnet).

What I'm using is a Tesla Violet ray wand (see image below) also here's link to a video of one being taken apart along with a circuit explained.  I'm using this as the plasma tube and high voltage source and wrapping wire around the little plasma tube and sending the ac/dc signal into the coil. How can I prevent the arcs created by the plasma tube from interacting with my electromagnetic coils around the tube?  (I don't want the arc travelling down and frying my receiver).

The kit looks something like this Link.
Video of it being taken apart Link.


texts: Does "POLY-MET" unambiguously describe a capacitor type?

texts:
I have a BOM where one of the capacitors is described as .33UF 250V 10% POLY-MET.

I did a search on the term "poly-met" and found a Cornell Dubilier device with that particular designation. It's a metallized polypropylene capacitor, which makes sense of the nickname.

But I'm wondering, couldn't it also mean a metallized polyethylene or poly-other-ene construction as well? Is it a conventional nickname applied to in particular to metallized polypropylene or perhaps the -ene that's used doesn't matter that much for most applications? (In this case its used for high-frequency bypass on a transformer secondary before a bridge rectifier.)


texts: 220v hot glue gun with Great Britain plug to be used in USA

texts: I was mistakenly sent a 220v hot glue gun with a Great Britain plug . The plug also has a 5 amp fuse within it. Can this be used in the USA with just an adapter, or does it also need a converter/transformer?