texts: Can someone explain how this RFI filter works?

texts:
This is an RFI filter from a 12V automotive DC motor.  This motor design is over 20 years old and currently in "service" production.  We just learned that the capacitor we're using is now in short supply and we need a replacement.  Unfortunately, we can't find a comparable capacitor that also satisfies our mechanical dimension constraints.

We're starting to look at possibly using a smaller capacitor that will still satisfy our noise requirements.  It's been a very long time since I've had to think about a filter.

Can someone please give me a generic understanding of this filter?
I know the capacitor is acting as a low-pass filter, but why the two inductors?
If we were to replace the 2.2uF with a 1.0uF, what affect will it have (again, just looking for a relative understanding).  I assume it will affect the cut-off frequency and/or attenuation?

Some additional info:

Capacitor:  2.2uF, 63V, polyester film
Inductors:  2.2uH, 10kHz, 15.5 turn
Motor:  12VDC, brushed, 2 pole, 8 com


texts: OpAmp based constant current source/sink produces high peak current when load voltage is pulsed

texts:
I'm trying to build an OpAmp based high constant current source/sink based on the analog devices application note 968.

In the first step I designed it for maximum of 1A, but later up to 10A is planed. The load with 1mOhm is just an example for very high load that should be restricted by this circuit.

Everything works as expected as long as the load voltage isn't pulsed (or even turned on once) in some way. In my example I added a load voltage source VL with 50Hz pulsed 20V to demonstrate this. To be precise: In case of a constant current source VL is the voltage source the circuit will provide to the load. In case of a current sink, VL is the voltage source the user will provide to sink into this circuit.

What happens is, that there is a large unrestricted peak current flowing through RL for about 20µs. After another 20µs the current stabilizes to the expected set current.

I tried to change C1 in various ways. Choosing too small values causes the OpAmp to swing like in following example. The lower C1 the larger are the swing peaks.

I played with various OpAmps and mosfets types but there were no real change. Is there a way to prevent this high peak current in some way? What could I change? Is this peak current really a problem since it's time is really small?


texts: How to adjust output current on a buck converter?

texts:
I 'm planing to use a zinc–carbon 9 V battery to power up:

the circuit that battery belongs to
BeagleBoard-xM

I 'm thinking of using a breadboard, in order to power up both circuits. Beagleboard-xM's electrical specification is 5 V, >1.5 A. For this reason, I plan to use a buck converter to get this voltage. (e.g. LM2596S-ADJ). As I can see, there is a potentiometer in order to adjust the desirable output voltage.

My questions are:

Except 9 to 5 V convertion, how can I adjust about 3 A output current?
How voltage drop of the buttery that will occur over time, affects output voltage and current?


texts:
I will be using the TMP117 in a design I'm working on, and was a bit curious to what the difference is between the different Lead/Ball finishes listed in the datasheet?

There's a choice between NIPDAU and SAC396, and I havent been able to find much information on the advantages/disadvantages betweent the two. As far as I've gathered sofar it relates mostly to the shelf life of the components, but I'm not sure about that.


texts:
I am using the MPLAB Code Configurator for serial communication via a UART. My clock setting for system is FRC oscillator set to 8 MHz with PLL enabled (4x multiplier) to make a 32 MHz clock.
I am confused on which clock source and baud rate to set up for the UART. The clock sources are FRC, PB and SYSCLOCK.


texts:
I'm working on a object detection robot project.I'm using open cv software to detect objects.
My question is how can i take open cv outputs(x-y coordinates) to servo motor.and how can i interface computer ports using open cv.


texts: Is it feasible to synthesise sound with analog circuitry these days?

texts:
A friend of mine who is a layman in terms of electronics asked me to teach him how to synthesise audio with some analog circuit and how to build it. For some reason it has to be analog. Probably because that's so cool these days. I don't really get this.

The problem is that I'm not into discrete electronics either.

I concluded that there are many circuits that can produce oscillating signals and thus sound. The astable multivibrator came to my mind. However, for audio the signal cannot be just periodic. It is necessary to produce the desired shape like sine, triangle, rectangle, etc. without overtones (or at least as few as possible)

In theory for example, a simple \$RLC\$ circuit can produce a nice decaying waveform of a single frequency. But in the real world, a component is part of an electrical network that influences its behaviour.

The answer I gave was "Just use a microcontroller."
However, I received the the answer that programming is "very complicated". I have a feeling that behind this lies the fallacy that designing analog oscillators is an "easy task".

Am I on the right track that it doesn't make too much sense to create audio with analog circuits these days? I found this upvoted answer from Olin, which supports my reasoning. I don't want to be the downer and due to my own lack of experience I might be on the wrong track entirely. Maybe there are simple ways to create oscillators for audio synthesis with analog components?


texts:
I have a question regarding the SOA graph and a low Vds voltage (below 100mV), I will get to the questions below but needed to layout some information first.
I am looking at a International Rectifier part IRLMS6802PbF, RDS(on) data from datasheet shown below

So assuming I have a 1A current flowing and the Vgs voltage is a stable -4.5VDC, as I understand Vds should be in the region of 50mV, which would result in a point off to the left of the SOA graph shown below

The red dot provides an approximate position based on assumed Vds.
What I am trying to understand based on the assumed position on the SOA graph is this will also be outside the RDS(on) limit line for the graph.
So is this an impossible situation?
or will the Vds be higher?
or Does the RD(on) line go horizontal once it exits to the left on the SOA graph?


texts:
I’m currently working on a project where I am utilizing PWM on an Arduino to control a solenoid proportionally. I am designing a device that will play the piano. I would like it to mimic hand movements as close as possible and PWM is my best chance at that.

I currently have a circuit in mind where I utilize 3 pins from the Arduino and have them daisy chained through 3 shift registers for a total of 24 outputs. I am having issues find an appropriate mosfet that can handle the PWM action. The solenoids are rated at 12v and 1amp. From what I found this circuit is pretty simple but from the other projects I have seen they are not utilizing PWM pins and are just turning the solenoids on and off with out the varing touch.

I am sorting through data sheets and I feel like the 5v coming from the Arduino wouldn’t be enough if the duty cycle was too low, as it would drop the voltage below the threshold.

I am sorry for not being more up on this, I’m a Mechanical Engineer, this Electrical Engineering stuff is black magic :). I linked a picture hopefully. It’s just a rough idea I had in fritzing so nothing is labeled but it should be semi ok to follow.

Thanks for any help you may be able to give.


texts: Read-only for some masters but read-write for other?

texts:
Is it possible that a memory/memory region be read-only for some masters/chip components but read-write for others?

It is kind of vague question, but from a conceptual point view would this be possible?

Thank you


texts:
I am using the TLV221 opamp for differential to single ended output with unity gain of 1.
In simulation, we didn't get the expected output.  The output of the AMC1301 isolation amplifier is 1.98V so the output of the TLV2221 should be 1.98V but here it shows only 0.98V.
What is the problem here? Can anyone explain it?


texts:
I have 4 pairs of "LED + LDR" sensor. I need to be able to switch each of them on/off independently and take reading from the LDRs. To connect all of them to the microcontroller board, I would need 4 output pins for the LEDs, 4 output pins for the LDRs and 4 input pins for the LDRs. The output pins (also the power supply for the components) turn the LEDs and LDRs on/off while the input pins measure the current/voltage from the LDRs. My microcontroller board has only 12 input/output pins, how do I minimize the pins usage? I know the LDRs can be connected to a single input pin via a multiplexer but how do I connect the output pins to the components?
A schematic diagram would be very convenient. Thanks.


texts: How can I convert from voltage TDR into impedance TDR

texts:
Based on the circuit below I have built the voltage based TDR diagram.
Then I went to the ADS TDR simulation and constructed by the manual the circuit below.
In the ADS circuit they say that IMPEDANCE=V/I=V/(delta(V)/R)=V*R/Voltage_drop_over_R
I can't see the logic of  this formula.
Why does measuring impedance on the left side of the transmission line over time means its the impedance at some location in the transmission line?


texts: So, I'm a little fuzzy on vacuum tube designs, but I am under the impression that some use the filament directly as the cathode, while some use the filament to heat a plate which is the cathode. Since the filament is what burns out on a vacuum tube (I am aware of sputtering, but that failure takes longer to happen), why aren't tubes built with an external, replaceable filament? Furthermore, why do filaments actually burn out as often as they do? Toasters, for example, seem to have a very long lifetime, and their filaments are in air.


texts:
I'm testing a circuit with a NE5532 op-amp in buffer configuration and I think I've somehow broken something.

These op-amps need 5V and -5V as power input. The 5V voltage is easy to obtain, but the -5V is hard to obtain without having a proper bench power source. I've ordered some ICL7660s to get -5V from the 5V power rail in my circuit, but they are not arriving on time, so I've hooked up some AA batteries and I'm able to obtain -5.2V in theop-amp Vcc- pin. The positive voltage Vcc+ ended up between 4.8V and 5V. There's a difference of about 0.2V. Can this be problematic?

My first attempt succeeded, but the proto board was so messy I decided to start a new circuit in another protoboard. And now this very same chip no longer works. The output, which should be a square wave about 40mV peak to peak, centered at 0V, is suddenly 4.5V DC.

Do these things get easily damaged? I might have applied 5V and nothing in Vcc- for about a second, or even floating Vcc+ and -5V in Vcc-.


texts:
I have heard many people talk about using a charge pump circuit instead of a bootstrap approach when supplying MOSFET gate drivers with a biasing level for the high side. I have yet to see anyone show what that would actually look like. I have already looked at 100% duty cycle drivers from Analog Devices with built in charge pumps. They are FAR too expensive and they don’t care to provide any useful information in their functional diagrams about how they are wired. My application absolutely must remain on indefinitely.

Here is the IR2101, a common gate driver for MOSFET transistors I have used before. Notice the bootstrap circuitry. I want to design a charge pump that operates up to the full 600v, all the way down to 15ish volts. I am tired of solutions that only work for one exact supply voltage or else they would become ineffective or exceed the Vgs rating of the MOSFET. I don’t want any extra ics, preferably just a few discrete components.

My biggest issue is exceeding the rating of the FET while the source is floating. My application has no guarantee that the low side MOSFET will ever come on at all. This means it would be best to float the charge pump off of the source, switching the oscillating capacitor terminals between the source and ground, just like a bootstrap circuit, only without using the main switching FETs. I do not know how to do this with transistor switches; switching between Vcc and GND would be easy.


texts: Is there a RF viewer like a thermo camera?

texts:
So I know thermo cameras are sold.  Police/Fire use them all the time.  You point your little hand held black box at a bush and you can see if there is a creature living in there or at a burn zone and see where the hot spots are.

Is there a device that will do the same for RF signals?  VHF up to 2.4GHz
I was thinking it would be a great aid in locating RF noise in a sensitive environment.


texts: Problems with uln2803 darlington transistor array

texts:
I am using a few ULN2803's to control LED's. The pin connections and circuit that I am using are shown in the figures below.

When a HIGH signal is sent to any of the inputs of the transistor array, all of the LED's switch on, whereas only the one receiving the 5V signal is supposed to be switching to ground.

When there is no HIGH signal to any of the inputs, all LED's are off.

Is there something obvious that I am missing? What would the solution be?

simulate this circuit – Schematic created using CircuitLab

ULN2803 Datasheet


texts: A High Voltage AC or a High Voltage DC which is more dangerous for human?

texts:
Not going too High Potential.

Say a 200V supply.

If somebody accidentally touches the bare terminals of supply,
for which case ( AC or DC ), the effect on the person will be more
dangerous.

And in which particular case more precaution should be taken ?


texts: Design for test - What the different ways in which this is done

texts:
I know that when we are designing digital circuits we may add porition to it that helps in testing it. This may go beyond merely boundary scan test. What resource can I can use to understand this methodology and where can I find examples of it?

I know that this question shall be marked as too broad. I just need a few examples anyway.


texts: why do resonant inductive coupling circuit operate at high frequencies?

texts: Just as the title says. Whenever I read a research paper on wireless power transfer via resonant inductive coupling the authors just mention frequencies that range in the kHz and Mhz range, but none of them explain why high frequencies must be used.


texts: Solar panel to battery, dc to dc converter question

texts: I need to design an MPPT and the converter that uses it. the thing is: the Solar panel has a max voltage of 40V and the battery that is going to be charged is around 100V, the most easy thing would be to use a Boost converter, but from what i understand, an MPPT changes the duty cycle of the dc-dc converter according to de current and voltage of the panel, so it couldn't produce a stable output voltage to charge the battery, my idea would be to use a buck converter for the MPPT and boost the output of the buck with a boost converter, each converter with independent duty cycles, is this a bad idea?, why?, what would be a better solution? and if it's the correct route, should i put a capacitor between the 2 converters as an energy reservoir?


texts: Reading the configuration array of a MAX7000 PLD

texts:
Well, I have a little problem in my hands, I need to clone an Altera Max EPM7128ELC84, luckily the PLD comes in a socketable PLCC84 package and has a JTAG interface.

Now my question: what approach should I take? this can be done?

I have:

A generic JTAG-USB adapter
The means to make a socket with the cables attacehd to the JTAG
The datasheet
A little experience programming FPGAs

Thanks in advance


texts: Is there a generic transistor symbol that is not specific to the transistor type?

texts:
Many schematic symbols exist for transistors (such as the examples shown below), but each seems to be specific to the transistor structure and polarity.
Is there any suitable symbol that would represent a transistor of any structure (rather than specifying it as a BJT or a FET), for applications in which the specific transistor structure is not important?
BJT NPN:

JFET N-channel:


texts: Cheapest way to communicate with a Fez Panda II (or Arduino board)?

texts:
I have an application where I will have 30 Fez Panda II boards connected together. They will be spread out over an area of about 100' x 150'.

I prefer TCP/IP communciation, but adding a FEZ Connect Shield adds the cost of $35/each and I was hoping to have something less expensive.

I would gladly even utilize the built in USB cable, if only a way to connect them all to a computer over that long distance.


texts: So I am wanting to make a custom LED scrolling message display. Basically I have a surface I am going to mount 32 LED's to and then have them controlled by an Arduino. What kind of hardware would I need and what would you suggest for a power source, I want to go as light and compact as possible.


texts: What happens when we connect battery to a circuit?

texts:
Example setup:

I have a piece if metal and I have 12v battery. When battery is connected to the metal current flows through the metal.

So, my question is, does electrons from battery move through out the entire circuit?
If yes, what is velocity of electrons.

What I imagine when there is a current flowing through a circuit:

I imagine a bunch of electrons leaving negative terminal of battery and these electrons travel through the circuit and reach the positive terminal of the battery and how fast the electrons travel decides the value of current.

Is this correct? I'm confused.


texts: What are ways of isolating/splitting one DC power source

texts:
I'm building a 6S Lithium Ion battery pack with a nominal voltage of 22.2v. The pack will be enclosed so taking the batteries out to charge them is not practical; therefore, I'll need to add the charging circuit to the pack. Ideally, I'd have 6 TP4056 modules charging each li-ion cell and wired like this:

However, that is not possible with these modules as IN- and B- shorted together by design. Wiring it like that would short the batteries.

To avoid this, I'd have to have isolated power supplies for each module. 6 individual wall wart 5v power supplies would do the trick, but that is clumsy.

Ideally, then, I want to power 6 TP4056 boards with one 5v source.

Is it possible to "split" that 5v power source into 6 isolated 5v sources? I read somewhere that capacitors can be made to isolate DC sources, but I don't see any sources on the web backing that up.
Is there any better way to retain a 6S configuration yet be able to safely charge each cell? Obviously there are BMS's, but I do not have any stores that cell them near here. There are, of course, these ebay things but they do not have any datasheets.

6 DC-DC converters are not an option for me. I have literally scoured the internet today and am tearing my hair out over this issue. Would diodes work anywhere?


texts:
I've created a circuit on my breadboard including multiple shift registers and a teensy 2.0++.

My program takes inputs from the shift regs and converts them into MIDI messages. Using my teensy in MIDI mode, my project works just fine.

I'm now moving all this to a permanent solution using an ATMEGA328P. I used my teensy as a programer and then as serial-to-USB-bridge. The project works well this way too, and the midi messages are received and interpreted correctly by my DAW.

When all the stuff is moved to the casing and screwed together, I want to use MIDI-over-USB instead of using regular MIDI connectors.

So my question is this: How do I extend my circuit to be compatible with USB HID and send the serial data via USB-MIDI?

Ideally I'd like to have an architecture with exchangeable I/O Boards:

My main controller outputs the MIDI commands via a 31250 baud serial bus. This signal could then be sent to:

A USB-board that sends the MIDI via USB
A standard MIDI-board
Or even an ethernet-board to add network support.

Would that be worth the effort?
How could that be done?


texts: Why is the bunny-ears TV antenna normally connected to 300 ohm twin lead?

texts:
The bunny-ears antenna is similar to a dipole, which has an impedance of ~75 ohm.

Why are the elements of such antennas connected directly to 300 ohm ladder line? Wouldn't that cause mismatch losses (even with the other end going into a balun)?


texts:
I'm having a LM358 opAmp with the following Schematic, as I'm not from Electrical background, can you please help me determining it's gain. I just want to find out it's gain.

simulate this circuit – Schematic created using CircuitLab

I think it is R5/R4=4.7/1=4.7?


texts:
A floating DC voltage output sensor will be powered locally and the signal will be sent outdoors 200 meters far away to a data acquisition board. I didn't receive the sensor yet and don't have the datasheet. But my question will be about something else.

For such long transmission I was first thinking to use a differential line driver at the sensor output or convert the voltage signal to current and send it as current or send as digital ect ect.

But I can use a differential ended input data-acquisition board has the following architecture:

Omitting the voltage divider effect, if I use this module and data acquisition as in below diagram would that be a adequate to eliminate common mode noise issues or capacitive coupling noise issues?Or still a differential line driver or current conversion is needed?

to be updated soon...


texts: Unusual or Strange Behavior: uint8_t in for loop in avr MCU

texts:
I am learning programming MCU with c

I am using atmel studio 7, averdude, USBasp and Atmega16a

this is my code

#define F_CPU 1000000
#include <avr/io.h>
#include <util/delay.h>

int main(void) {

DDRA = 0xff;
DDRC = 0xff;

while (1) {
    for (uint8_t i = 8; i >= 0; i--) {
        PORTA = (1 << i);
        _delay_ms(100);
    }

    PORTC = 1;
    _delay_ms(1500);
}

return (0);
}

the for loop never finished and when it reaches i=0 the first LED in PORTA stays on for about 14 seconds and turn off after that for about the same time and after that the for loop starts again without reaching

PORTC =1;
_delay_ms(1500);

when I use int instead of uint8_t it works fine

can someone explain why is this happening ?


texts: How does this current sensor work (with only half magnetic core)?

texts:
I have been working for sometime with current sensors (current sensor goes all around the conductor to get a voltage reference corresponding to the amperage), however I just found this little device that claims to be patented (I couldn't find the patent).

It has come to my attention that the system measures current just as a current sensor (sensor around the conductor), and it measures voltage with the "little plated pins", in order to provide relevant information, apparent power, power factor, current, etc...

The datasheet claims that it has been patented (it does not provide patent number) according to what I know, the current sensor shouldn't work as intended since it does not close the loop so the readings should not be accurate, and yet the device claims a 2% accuracy.

I have also been looking for any articles about what kind of device or technology is behind this device to verify its accuracy however I haven't found anything about it nor about current sensing techniques involving incomplete magnetic cores.

I'm clueless about what's going on here so I have come here to ask (hopefully I can get a lead); what am I missing here?


texts: Use Arduino for switch a 12v powered remote control

texts: I've a remote control powered by a 12v battery. I need to switch a button using arduino, can I use directly the digital pin without any relay or transistor? Thanks in advance


texts: Frequency response of a parallel RC filter (smoothing capacitor in rectifier circuit)

texts:
I understand qualitatively and electrically how a smoothing capacitor works in the case of a diode-based full-bridge rectifier but what I am not too certain of is how to describe it in terms of its frequency response, since the capacitor is in parallel with the load resistor.

It makes sense for this parallel RC circuit to act as a low-pass filter to remove the harmonics and fundamental frequency of the rectified AC signal to preserve only the DC component.  But all analyses of RC-based lowpass filters are series-based circuits, with the frequency response based on voltage gain Vout/Vin. i.e. \$H(\omega)=\frac{1}{1+j\omega RC}   \$

simulate this circuit – Schematic created using CircuitLab

However, for the parallel RC circuit, this voltage gain is unity since the voltage across the R and C is the same.

simulate this circuit

So how does one find the frequency response of smoothing capacitor in parallel with the load resistor and show that it is a lowpass response?

My guess is that we are modelling the current gain, i.e. treating the diode rectifier circuit as a current source, so that we can transform the current source in parallel with load resistor (Norton equivalent) into a voltage source in series with the load resistor (Thevenin equivalent), which makes it into the conventional series RC circuit.

simulate this circuit

Does that look reasonable? Or is there is better way of calculating the lowpass response of the smoothing capacitor?


texts: I am designing an DC to AC converter operating at 10MHz. Its a low power converter and the input current is under 2A. What PCB trace width should I use and can someone give me a guideline on how to select the PCB trace width based on the frequency.


texts:
If the speed of the motor speed depends on the duty cycle how frequent should that   pulse be passed to the motor.  I know that there is some minimum frequency such as 33Hz but I am not sure, and I am not also sure about the maximum frequency?

I dont have any particular servo in mind, more sort of how they work in general.  A good example  could be the SG90.


texts: how bits are still synchronized in asynchronous transmission?

texts:
I was reading a textbook which syas:
In asynchronous transmission, we send 1 start bit (0) at the beginning and 1 or more
stop bits (1s) at the end of each byte. There may be a gap between bytes.Asynchronous here means “asynchronous at the byte level,” but the bits are still synchronized; their durations are the same.

I am a little bit confused here, what does bits are still synchronized mean? how does bits gets synchronized and whom those bits gets synchronized to?


texts: Reducing the Number of Logic Gates in a NOR-driven 7 Segment Display

texts:
I have been given a prompt to design a 7 segment display using NOR gates. My understanding of the prompt (8.R) is:

Design an excess-2 code converter to drive a 7 segment display. Design the display using two, three, and four input NOR gates and inverters. Any solution that uses 16 gates and inverters or fewer (not counting the four inverters for the inputs) is acceptable.

Using K-Maps, I have derived seven POS equations that I converted to NOR gates through double inversion.

Segment
POS Equations
NOR Gate Implementation

1
(A + B + D')(B' + C' + D)
[(A + B + D')' + (B' + C' + D)']'

2
(A' + C + D)(B' + C' + D')
[(A' + C + D)' + (B' + C' + D')']'

3
(A + C + D)
[(A + C + D)']'

4
(A + B + D')(A' + C + D')(B' + C' + D)
[(A + B + D')' + (A' + C + D')' + (B' + C' + D)']'

5
(D')(A' + C' + D)
[D + (A' + C' + D)']'

6
(A + C + D)(C + D')(A + B + D')
[(A + C + D)' + (C + D')' + (A + B + D')']'

7
(A + B)(A' + C + D')
[(A + B)' + (A' + C + D')']'

To reduce the number of gates, some are reused. These gates are (A + B + D')', (B + C + D')', and (B' + C' + D)'.
Afterward, my logic diagram looks like this:

The Problem
Counting up the logic gates on my diagram (excluding the inverters from the inputs A through D), I count 17 gates. This does not satisfy the requirements of the prompt. Therefore, I am thinking I messed up somewhere along the way, either in:

Deriving POS gates from my K-Maps
Reusing shared gates

I'm lost as to what I could improve to reduce my gate count by one. Any ideas?


texts:
Is is possible to use a 4V supercap (say ESR = 100 Ohm), to charge an X5R ceramic capacitor (assume also 4V)?

I think this is possible, so my second question: is there a way to calculate/estimate how long it will take to charge the MLCC?


texts:
I'm trying to find a good and practical current sensor and I found this: Si8519
http://www.silabs.com/Support%20Documents/TechnicalDocs/Si85xx.pdf

My idea is monitor AC Mains current, so this Si8519 works up to 20A.

After read the pdf document I have no idea how to wire this stuff to a Raspberry Pi.
I have searched on google, but still no results, does anyone know about this chips?? Not even a single example found on the internet.

I'm using 20pin chip with legs. Also I saw very IIN and IOUT on the chip, don't know how to use it and I don't want to blow up the chip.

Can someone help me understanding how to wire this stuff?


texts: Transformer voltage rating vs open-circuit voltage: what's the typical load assumed for the voltage rating?

texts:
This appears to have been asked in some way before (at Transformer: loaded vs open-circuited vs short-circuited) but both the question and the answers there are rather vague to me, so I'll try to be more explicit.

As anyone who was toyed a small transformer might have noticed, the output/secondary voltage in "open circuit" (actually seeing the megaohm-level resistance of the DMM/voltmeter as load) can be much higher than when the transformer is under significant load. For example, I get 8V on a "5V" transformer (it's built on an EI-30 core, so you get an idea of its approximate power rating; somewhere around 3VA). So, my question is: what's the load typically used to rate the voltage "faceplate" output of such transformers? (I assume this might be mentioned somewhere in IEC and/or US transformer standards, if you know more precisely please let us know).


texts: Would twisting 3 wires together be as effective (or close) to a twisted pair?

texts:
Would twisting 3 wires together like a twisted pair would be as effective as an ordinary twisted pair? Or at least a definite improvement to not twisting them at all?

simulate this circuit – Schematic created using CircuitLab
I need to measure the current of each load and I can only do it near the voltage source. Although I plan to use an ethernet UTP cable of which I can just use another wire for a second ground. I am curious if a 3 wire twisted cable is as effective as the twisted pair or it might be not as effective but close.
Intuitively speaking it should still work because the EMI would still cancel out assuming the wires are twisted properly.


texts: 2,4GHz antennas are compatible with 5GHz connection?

texts:
I have a laptop that I would want to upgrade the wireless device with a new one that operates at 5GHz, and my question is if the antennas used for 5GHz connections are the same as for the 2.4GHz, or I'll have to change antennas with new ones.
Thank you very much!

EDIT
I'm refering to change first the wireless card from my laptop. My idea is to buy a mini PCI-e version of BCM94360HMB, named "AzureWave AW-CB160H", to update my older Realtek RTL8723BE.
Like KalleMP said, I found that my laptop was distributed with dual bands adapters.
I supose that my question is already answered, basically I want to know if the antennas for 2,4GHz and 5GHz bands are the same or not.
Thanks for everyone!


texts: altera FPGA acting like OR gate when programed as AND gate

texts:
I'm new to altera fpga , I've bought development board based on EP4CE6E22 cyclon IV and tryed to program it with basic program in quartus environment

module my_and(a,b,c);
input a,b;
output c;
assign c = a & b;
endmodule

I've loaded pin assignment from files that came with the board and programmed it with some chinese jtag blaster.

but when i tryed to push one or the other or both (attached to a,b signals)button - the led turned on , and went off when released (like OR GATE)

so i tryed to program it as OR GATE gate and the board started acting like AND GATE

am i doing somthing wrong?


texts: Any better alternative to produce PCB than UV etching

texts:
I hope this is an appropriate question to ask it here.

I work for a small start up company that has a limited budget. We have UV box, etching tank, etc from manufacturer like Mega UK.

Our problem is that it is too problematic to manufacture a PCB that includes an IC that has a tiny distance between its pins. For example,  80 pin MCU that has 0.2mm spacing between pins, or thin traces (e.g., 0.25mm) are really really problematic. The layouts are printed fine with a dark ink, the UV source is even, and PCB that we use are good quality, printed side is closer to the copper, etc.  but, it still requires too much attempt to produce a board correctly. It is usually overwhelming to deal with it.

We use a Chinese manufacturing house that accepts small quantity and do not charge tooling cost etc. which is good for prototyping. But, it is still not cheap (30USD DHL freight + duty cost + PCBs + cost of cross-border payment) and takes too long to receive the boards (5 working days for manufacturing + 3 days for delivery) for a PCB that is not mature enough. It is an often case for me to produce a PCB multiple time to fix some errors or optimize it. So, we cannot afford the time to order it from abroad.

I think it is better to go for an alternative way to produce a PCB in house that will save a lot time. This method should be easy to produce a PCB that has tiny pitch sizes. Do you know any method that would be less problematic than a UV etching and not too expensive to hurt our budget.

I have seen some modified CNCs that route and mill PCBs according to the uploaded gerber files, and looks impressive with the accuracy. However, they are what I see on the web and has never seen it real life. Also, the prices that I have seen are expensive (£2000). Do you have any experience on such CNC devices and could tell me if there is any issue to use them (life time, accuracy, calibration, etc.) or suggest me such CNC that would not be less costly than £2000 and have a fine accuracy.


texts: Help with an Arduino-based PC "Ambilight" setup

texts:
I have been trying to follow this guide to make a PC ambilight setup.

I am having trouble finding a good power supply (bought an unsafe one from eBay). I have 65 LEDs, so according to that video (and this link) I need a 5V 4A DC power supply and associated barrel connector.

First question, because these are PC/arduino-controlled LED strips with an external power source, it's not clear what the LEDs will do when the PC is off. Would it be also possible to include an in-line switch between the power supply and the LEDs?

Second question, an even better improvement, but possibly the most tricky (?) - this LED strip is going to be replacing a lamp. Could I have the LED strip output a single colour (warm-white) that isn't controlled by the PC when desired?

I was hoping to have a 3-way switch setup:

Off
Warm-white "lamp mode"
PC ambilight

Here is a photograph of the back of my monitor with the LED strips on showing where the Arduino will sit and the ideal location of the switch.


texts: Does a thyristor experience loss if it is switched at zero volts?

texts:
I have developed a circuit that uses a capacitor's voltage to reverse bias a thyristor.

The voltage to reverse bias it is only about 10% of its off-state blocking voltage.  I am confused how I would calculate the losses of the thyristor in simulation.

Would I find the turn-on/off energies at the specified di/dt for the turn off, and then scale that by the blocking voltage (which, at the moment of switching, is only 10% its maximum?)


texts:
I am using the following circuit for two purposes:

As a voltage divider, to reduce DC sensor output to a range suitable for my ADC.
As a lowpass filter, to remove high frequency noise from the signal.

It works great, but my choice of component values has largely been a matter of trial and error, so I have a few questions:

What is this type of circuit called? Is it a low-pass filter, a voltage divider or both?
What is the equation for \$f_c\$ (cutoff frequency) for this circuit and how is it derived?
What is the output impedance \$Z_{out}\$ of the circuit in terms of \$R_1\$, \$R_2\$ and \$C_1\$?
If the design requires a specific \$f_c\$, \$Z_{out}\$ and DC \$\frac{V_{out}}{V_{in}}\$, is it possible to derive simple equations for \$R_1\$, \$R_2\$ and \$C_1\$ in terms of these?


texts: Contradiction while solving circuit problem!

texts:
Translation: Find the supplied power from the 4V Source using meshes method

I proposed five equations related with the circuit but I only find contradiction cause I find Rv value fixed. I suspect there should be voltage drops in current sources but I am not sure I think I am doing something conceptually wrong.

Here my calcuations

I skipped some steps but I hope you can follow me.

I am currently getting I2=I3 = 0 which makes the first two equations to fix Rv. By my understanding it is a contradiction.

Note: .5Nk is a name for the resistor value (proportional to N), I have just called it Rv.


texts: How to apply passive PFC on low side of transformer in power supply?

texts:
I have a low power power supply, built with a 60Hz 120v/12v 0.3A transformer. It will have an ordinary diode bridge and capacitor filter. What I want to achieve is reduction of current/magnetic field spikes caused by power factor effects.

I read about PFC, but can only see examples with parts on "mains" side of transformer. I dont want to mess with mains, so I decided to put PFC after secondary winding.

What parts, configuration and values are needed to achieve good low voltage PFC for very low noise power supply?


texts: Why bolted short circuit current in Arc Flash calculations much lower

texts:
Given single phase 240/120 transformers with 75 kVA rating and 2% impedance

computing using the infinite bus short cut method

75,000 / 240 / 0.02 = 15625 amp

or the long cut (with derivation) method

kVA = 75,000
Voltage = 240 V
The impedance of a load that would draw 75 kVA is 2402 / 75000 = 0.768 ohms.
Transformer impedance = 0.02 x 0.768 = 0.01536
Short circuit current = 240 / 0.01536 = 15625 amp

Now consider 20 feet of wire has resistance of about 0.002 (from an online wire impedance calc). To add them together one, one uses this

\$Total\ impedance = \sqrt {0.002^2 + 0.01536^2}= 0.01549 \ \text{A} \$.

Bolted short circuit current 20 feet away AWG 1 is 240 / 0.01549= 15494 A.

The difference with adding 20 feet of AWG 1 wire is decrease of only 1% of the short circuit current.

Now consider the Arc Flash fault calculation method here.

You can try it in excel spreadsheet (here).

Input the same data.

With terminal short circuit current of 15625 A.

The short circuit current 20 feet away AWG 1 is much lower 11595 A.

Why is it much lower?

Did the arc flash method somehow give the 20 feet conductor an inductive value, but it's not part of the transformer winding.

Let's go to the Arc Flash Calculation method formulas:

at 1Ø Line-to-Neutral (L-N) Faults

f = [2 x L x I (l-l)] /[ C x n x E (l-l)]

$$ f = \frac {2 L I_{l-l}}{ C n E_{l-l}} $$

Where:

L = length (feet) of conductor to the fault.
C = constant from Table 4 of “C” values for conductors and
Table 5 of “C” values for busway.
n = Number of conductors per phase (adjusts C value for
parallel runs)
I = Available short-circuit current in amperes at beginning
of circuit.
E = Voltage of circuit.

(How did they determine C where  the bolted short circuit current is much lower using this method but high when directly computing for it. Also how did they drive f?).

Then you get \$ M = \frac{1}{1+f} \$

And multiply the transformer terminal short circuit current by M.

The result is much lower bolted short circuit current 20 feet away (AWG 1) about 25% less compare to the ballpark computations. Why? Where is the hidden impedance in the wire. Instead of 0.002, it becomes higher like 0.010, how?


texts:
I am trying to observe a wave on my oscilloscope (with a CRT display). I can see a point on the screen tracing out the waveform, but the wave does not stay on the screen for me to say. This wave is very slow (only 1 Hz). Could that be the problem?
I have linked a video of what I see below:
https://drive.google.com/file/d/1jHj5FqOF1nYCibUaxG_4Qu_OmAZMekKa/view?usp=sharing


texts: Scr triggering design, shuld i use four pulses for each SCR ot two for each pair of the SCR?

texts:
I have used a TRIAC and an MOC3021 opto-coupler connected to a PIC16F887A to simulate a a full wave rectifier.
I am now to design the same using an SCR h-Bridge.
My question is, in order to trigger the SCRs, do i need 4 separate triggers for each SCR? or could i use two trigger pulses, one for each pair of the SCRs?
I would appreciate any advice. am fairly new to the field.
Thanks.
The following is the layout of the circuit.
Specs:220VAC, 60 Hz.
Load 1Kohms.
These were provided by my senior supervisor.


texts: Lead acid battery charger and fuel gauge?

texts:
Can someone recommend me a lead acid battery charger and monitoring circuit? I've found such circuits for lithium batteries, but not for lead acid.

Alternatively, I could use two circuits, one for charging and one for monitoring, but I would like to know if there is a solution with one circuit performing both functions.


texts: High Power Battery System: Variable Input DC Voltage to Fixed AC Output Voltage

texts:
We are a team of students trying to build a battery system which would recreate wall socket conditions with up to 2 kW output.

Some of the main challenges are basically to have the battery's variable output voltage fixed at a certain value, let's say 24 V DC and then converted to 230 V AC.

In order to get a fixed voltage output at the battery (24 V), is the best option to use an isolated DC-DC converter? The problem is that with the powers involved (2 kW), we really are struggling to find off-the-shelf converters that would safely do the job. I guess we could get multiple smaller ones and connect them in parallel but then weight and volume become significant, is there any other method or is an Isolated DC-DC really the best solution?

The next step is to then convert this 24 V 2 kW output to 230 V AC, I guess here we have no choice but to find a suitable DC-AC converter or are there any other methods we could use?


texts: Asymetrical square wave or rectangle wave amp op

texts:
I need to find a circuit that produces a rectangle wave(picture below) and that only uses one capacitor(0.01 micro Farad), 1 amp op with a single supply line(Vsat+ = +10V and Vsat- = 0) and how ever many resistors is needed. I can only use these elements.

This is what I have done till now:

For that, I want to use an relaxation oscillator because it produces a square wave but the problem is that because Vsat- is equal to zero, the capacitor won't discharge to 0 and I have researched a lot on the topic and can't find anything.

Your help would be greatly appreciated and sorry for my English it's not my first language.


texts: Two identical DC power supplies in parallel for redundancy?

texts:
I'm trying to design a power backup system for my saltwater aquarium. In short, the system will be powered by a 12VDC power supply while the mains power is on. On power failure, the system will automatically switch to a battery source until the mains comes back on. At this point, it will switch back to the 12VDC power supply. I believe I have all that worked out, no issues.

The only thing I'm stuck on is the 12VDC power supply that runs the system under normal conditions. If this power supply fails, the system will detect this as a power failure and switch to the battery bank. The batteries will eventually run out because they're meant for short term life support, not for indefinite running. At this point, it seems like the greatest weakness in the system is the 12VDC power supply that runs the system during normal operation.

So, my question: would it be safe to wire two identical 12VDC power supplies in parallel for redundancy purposes only? Note, I am NOT trying to gain additional capacity from this configuration, only redundancy. One power supply could very easily handle the entire load. The power supplies in question will be 12V 40A, and the consumption of the system tops out around 300W.

Thanks in advance for any help regarding this.


texts: Data flip flop - I don't understand its purpose

texts:
The data flip flop can delay operation based on the time of the cycle of the clock.
If the clock's cycle is fast, the DFF is useless because it's like an instant change.
Is it possible to change the cycle speed of the clock?
If yes, so for which purpose I would want to change something now -> and let it change only T time after?
I understand that DFF is used in computer RAMs for saving data, but I don't really understand how it saves data because:
If the clock cycle is really fast, it's like an instant result, so I don't need the clock,
If the clock cycle is slow, I don't want it in the RAM because I need an immediate change to the data.
Basically, I'd like clarification about DFF generally and its connection to RAM registers :)


texts:
In an ideal flyback diode selection, one would seek a diode which has
  very large peak forward current capacity (to handle voltage transients
  without burning out the diode), low forward voltage drop, and a
  reverse breakdown voltage suited to the inductor's power supply.
  from Wikipedia

I'm confused. Shouldn't the forward voltage drop of the diode be higher so that energy can be dissipated in fewer cycles.


texts: Saving user input as an array and recalling it later

texts:
I am currently working with an Arduino Mega and a SainSmart LCD and I have gotten most of my project to work except for a problem I am currently having.

On my LCD screen, I have various buttons, and these buttons in my code, correlate with an array. Thus, when a user presses the button, the array stores that value.

I have created a one line array that contains 12 int values. The following is where I am getting stuck:

I would like to save the array and be able to recall it as needed.

I have created a page where there are "saved programs" and there are buttons that coordinate the order of how the arrays were saved.

I would like to be able to save the arrays and then when I press the button, the arrays can be called on and the task performed.


texts: What is the maximum slaves supported by SPI and how it is limited?

texts:
I was learning the basics of SPI-communication. It was came to following section and I was bit confused to understand the sentence.

What is the meaning of " each slave in the chain will act as the master for the following slave ". Can anyone elaborate it ? And what is the possible maximum slaves supported by SPI and what factors limits it?


texts:
In a balun I have, (model 50-7725 from CPC, datasheet -> http://www.farnell.com/datasheets/2365902.pdf?_ga=2.142463986.1590159842.1535980880-667311346.1535980880)

It shows the Balun as:

What is the see through circle on the signal line, to the left, which connects to ground, mean?


texts:
I wonder if the circuit below is correct. What I need to do is: When SW1 is open, the LED is off and there is no connection between the battery and the 5v source. When SW1 closes the LED turns on and then the battery starts to be charged by the source through the short between collector and transistor emitter. Is correct? Is there a better way to do this?

simulate this circuit – Schematic created using CircuitLab


texts: What is the best and cheapest load to test a variable frequency drive at full load?

texts:
what is the best and cheapest load to test a variable frequency drive (1 HP VFD) at full load?

Maybe a centrifugal pump ?

Thanks in advance


texts: PIC18 not working when wiring 30pf capacitors of cristal resonator to ground

texts:
I'm using pic18 with external oscillator 16MHZ 16M HZ HC-49S Crystal Oscillator with two 30PF capacitors

configuration OSC = HS

using breadboard, when wiring the capacitors to ground the pic stop working, but when letting them in open circuit (just wire one side to PIC, other side stay open) the PIC work again.

but when removing the capacitors from the circuit, the PIC also not working

what explanation for this


texts:
There have been previous versions of this question that were closed since "there is no reason to create a one-off actual thumb drive", however, I have a very specific idea for a USB flash drive in mind.

I am getting married next year and I'm thinking of the save-the-dates in the form of a USB dongle. This would actually be a PCB with a USB plug that, when plugged in, flashes a few LEDs on the PCB and contains a multimedia file announcing the wedding date.

I figure I'll use a small microcontroller to control the LEDs. That part is easy and well within my skillset. I probably need a NAND chip and a controller for the flash drive part. Has anyone ever done this before? Any guidance would be appreciated, even just suggesting ICs to use, or a schematic to read over.


texts: Single power feed for two lamps plus a spark core microcontroller

texts:
I'm starting a project where I want to control two lamps which are currently powered from mains electricity using a Wifi-capable microcontroller (spark core) and a relay.

I want the result to be as neat as possible so I wanted to use only one source of power for the whole arrangement, this would mean wiring up the two lamps together and also taking a 5 volt feed from that same power source.

I'm coming at this from the programming world, so have a little microcontroller experience but I'm not sure how I would wire up the rest of the arrangement, can anyone illustrate how I might achieve this?


texts: function of GND pin in voltage regulators

texts: In a voltage regulator what is the function of the GND pin?I thought it was to create a reference voltage for the input/output but I have seen it being fed from the output of the voltage regulator through a voltage dividers so now I am not sure.


texts: Power loss in an RC circuit with very low resistance

texts: I read at some point that an RC circuit with extremely low resistance might end up not being more efficient than one with higher resistance because the voltage change will be so fast that the capacitor will act like an antenna?  Does this occur if the time constant is so low that metal the length of the capacitor would be able to act as an antenna at that frequency?


texts: Ground mesh under the capacitive touch pad

texts:
I am going replicate a circuit basing from adafruit AT42QT10xx, I will be using the AT42QT1010 variant.

The touch pad is the blue pad bottom layer, but there is this mesh on the top layer after i traced it, is connected to ground.

What is the purpose of this mesh? Does it have to be a mesh? Will filling it with a ground plane be better? Will placing the components directly above the pad okay too?

My hypothesis is it to prevent "touches" from the bottom, I do not own one of these modules so i unfortunately cant test it.


texts: How do I derate paralleled diodes with negative temperature coeffecients?

texts:
In my application, my load current is 1.4 amps, and for reasons of cost, availability, and recovery time, I want to use this particular 1 amp diode. Like many diodes, this one has a negative temperature coefficient; the hotter they get, the lower their voltage drop for a fixed current. This means that if you parallel two diodes, they are not guaranteed to share current well; one device will take more current than the other, heating it up more, causing it to take even more current.

How can I estimate how many 1-amp diodes are needed in parallel to carry 1.4 amps?


texts:
I'm sorry for such a simple question, but I'm pretty much brand new to this stuff.

I want to wire up in parrallel and plug in 3 little fans to a USB for power, however, these 3 fans are 12 volt .12 Amp fans and I was wondering if I'm going to be drawing too much power through that USB port that it might "burn out" so to say, or ruin it in any sort of way.

I know that USB only does 5 volts and I know the fans won't operate at full capacity this way but that isn't much of an issue for me, I don't really care that they aren't as fast as they should be.

Thanks for your help in advance.


texts: Explain why the NodeMCU auto-program circuit would be useful

texts:
I'm looking at the NodeMCU "auto-program" circuit but could not understand why it is there at all.

From my point of view, this circuit enables open-collector outputs, but makes programming dependent on the time between switching the DTR and RTS pins being smaller than the ESP goes from reset to sampling the GPIO0 level.

Another reason I could imagine was to avoid invalid startup/connection resets, but I can't see why proper pulling couldn't fix this.

Is there any reasoning I couldn't see from my analysis? Why isn't DTR/CTS connected directly with one transistor on each line? Why controlling each line directly (and thus allowing to switch GPIO0 low before resetting without glitches) wouldn't be better?

EDIT: while the question is about the same structure shown in Is this a flip-flop?, I understand it's function and know it's not a flip-flop (no need to redraw it). What I'd like to do is know why was it chosen instead of a much simpler open collector configuration like the one below, specially since this one doesn't generate a glitch in the transition between the two programming states (from reset to/from GPIO0=0).


texts:
I have this circuit where I'm supposed to find the current I. I know I'll find it by (V3-V4)/R10. I have done the nodal analysis, however, my teacher says that I have done my nodal analysis incorrectly, but I can't figure out what the problem is. I already have all the values for the resistors, current source, and voltage source, and the resistor between V5 and V4 is called R7, I just forgot to label it.
Maybe someone has an idea of what I have missed in the nodal analysis.


texts: Reduce 50 Hz noise from robot-mower charger

texts:
I just bought a robot-lawnmower (Husqvarna Automower 105), which is working perfectly.

But the charging station is making a loud 50 Hz noise all the time, even without the robot charging.
I have uploaded a video with the noise here: https://streamable.com/dd35mh

Any suggestions on what I could do to fix this? Would adding a ferrite bead have any effect? Would appreciate any tips on what could help. I haaaate trafo-noise. :p


texts: I need to keep one of my input signal of my mixer intact

texts:
I'm currently working on an audio circuit.

I'm using a simple mixer to mix two audio signals together. It works well enough for now.

Here is the circuit :

simulate this circuit – Schematic created using CircuitLab

Yet, I would like to be able to have an unmodified version of my in1 signal.

Maybe this is because I'm a newbie, but am I wrong to consider that this circuit makes it impossible to keep my in1 signal intact?
Do I need to split it before mixing it or use a more complex mixer?
Is there an easy way to do that?


texts: Are these two Li ion chargers equivalent, despite their stated spec?

texts:
Not being game enough to DIY it  (as suggested in some answers to this question) I've bought a 240V charger for my beard trimmer. Despite the singular "240V" listed on the label, the person at the other end of the Wahl support line insisted that it will work on 110V in the US with only a pin adapter, but the original charger (rated for 120V, left) would not work here in Australia on 240V.

I find it quite surprising that the 240V charger would in fact be "world compatible" and not labelled as such. Is it inherent in the nature of switching power supplies that one rated for 240V will work when presented with 120V but the converse would not be true? What are the odds of the magic smoke leaking out if I plugged the one rated for 120V into a 240V socket via a pin adapter?


texts: Is it possible to reduce the resistance of a voltage source (coil)? If yes, how can I do that?

texts:
First, I should inform you that I am a mechanical engineer, so this is an adventure to me. What can sound as basic to you, is like a new discovery for me.

Second, I would like to introduce you the context I am going to use this:
I have set up an experiment in which I have a beam with a fixed end and a free end. The free end has a magnet coupled, which moves inside a coil, in order to transfer energy from my mechanical domain (beam) to an electrical circuit.

Due to my experimental restrictions, I can't attach the coil to the beam and build a proper magnet circuit around it, so in order to improve my electromechanical coupling I have built a coil with 27k turns (using AWG 34), which gave me a 3.3 KOhms resistance and 10.8 H inductance.

Since I am investigating the damping provided by the electrical domain to my beam, I don't care about the inductance, but the internal resistance of my coil is an issue. Finally I come to my electronics question: is it possible to reduce the resistance of a voltage source (coil)? If yes, how can I do that?

I have tried building a Negative Impedance Converter (NIC) so I could achieve a static negative resistance. Apparently, this NIC only works to improve the impedance of current sources, but it is not practical to use it to improve the impedance of voltage sources. I have studied a bit of Norton's theorem to get my equivalent current source and I have tested it with the INIC, but the results were just equivalent to having my coil short circuited, which means the equivalent resistance was the internal resistance (Rs) of my coil (or near it).

So is it even possible to reduce my coil's internal resistance without changing it, just using electronics? I have seen there are another options like gyrators, but I would not like to lose more time to just discover it won't work.

Hopefully you will be able to help me and if you think I should improve my question just ask for more details.

Thanks!


texts: How can I generate a noisy environment to test my PCB?

texts:
I am developing a PCB project but i want to use the PCB in noisy environments (which usually contains 7.5-45 kW multiple motors with frequency inverters and also ignition transformers). I made some basic test and test circuits passed them but I want to create a really noisy environment in order to test my PCB under conditions which are more noisy than the real environment. How can i generate this noisy environment?

I thought that some big coil with a high frequency square wave (square wave because frequency domain of it contains more harmonics (am I right?))  generator can produce instantly changing magnetic field and it can induce voltage drop between my traces. But I couldn't be sure that it is enough.

Actually, I want to learn what is noise and what types of noise there are. And I want to test my PCB's vulnerability to noisy environments by learning step by step EM theory. I also want to learn mathematics beyond this but my first purpose creating a noisy environment (whatever it means, i don't really know) and then understand how these things work.


texts: This is a diode for a 9500-HBE Dock. I can not seem to be able to identify it.  It's connected to the DC jack. Thanks for your help.


texts:
I would like to buy either a 17-way one of these plugs (see pictures) or a 12 way and a 4 way (the socket has a set of pins that aren't used so there's 4 double pins, then a gap, then 12 double pins).

Currently I'm using single female to male 2.54mm breadboard jumper wire. The female sockets fit on the pins perfectly.

This socket fits one of the plugs but I need a 17 way one (or 12 and 4 way) for another plug but I don't know what these are called in order to Google them and find one for sale.

Also, a secondary question, what do I need in order to wire this type of socket up? Is it possible to use the inners of the breadboard jumper cables (by pulling them out of the small plastic housing) or, if not, can I buy the 'pins' for this type of plug ready made or would I need to invest in some form of crimping tool?

Thanks for any help you can give me.


texts:
I tinker with AVR, 6502 and z80 designs, just muck around really, nothing overly serious. But as a result I had a thought of an idea for a new chip.

Specifically a SoC built around a z80 core. But who would I talk to too even see if what I'm thinking is feasible? And if it is who would I talk to too, to get a price estimate to have the thing designed into a chip? Would the cost of doing something like this be prohibitively expensive?


texts: Finding the fourier series coefficients of the signal $$1+\sin (\omega_0 t) + \cos (\omega_0 t) + \cos (2\omega_0 t + \pi / 4) $$

texts:
I have come across this question that asks to find Fourier series coefficients of the following signal. $$1+\sin (\omega_0 t) + \cos (\omega_0 t) + \cos (2\omega_0 t + \pi / 4) $$

In my intuition, the signal is already in Fourier series form, and the question asks just to find the trigonometric Fourier coefficients.

I started breaking down the original signal and rearranging, which gives:
$$1+\cos(\omega_0 t) + \frac{1}{\sqrt 2}\cos (2\omega_0 t) + \sin(\omega_0 t) - \frac{1}{\sqrt 2}\sin(2\omega_0 t)$$

While figuring out the pattern in the signal, the coefficient of cosine term is always 1, while the coefficient of sine term alternates in sign. So, in more general terms,
$$1+\sum_{n=1}^{2}{(\frac{1}{\sqrt 2})^{n-1}.\cos(n\omega_0 t) + (-\frac{1}{\sqrt 2})^{n-1}\sin(n\omega_0 t)}$$

With an analogy to the trigonometric Fourier series, the coefficients are found out to be $$a_0 = 1, a_n = (\frac{1}{\sqrt 2})^{n-1}, b_n=(-\frac{1}{\sqrt 2})^{n-1}$$

Is this what am I required to do when asked to find the Fourier coefficients? Or should I take that signal and then follow the whole procedure of finding a0, an and bn using the Euler's coefficient formula?


texts: Relay sla-05vdc-sl-c is not working on arduino uno and nano

texts:
At first time, trying to check this relay modules (I got 2 the same) they both worked nice - no problem.

But now I am going tu build the temperature controller for old fridge (it is working constantly). I got the problem: both LEDs (red indicates relay being ON and green - indicates POWER ON) are working, but there is no connection between NC and COM.

Does not matter HIGH or LOW jumper position.

At first tests I wasn't used any resistors, and everything was fine. Voltage between DC+ and DC- are about 4.7 V. Between DC- and IN - about 4.5V.

At first I was sinking about not enough current form Arduino NANO with miniUSB, but the same result.

So, I have this schematic (have tryied some pins - doesn't affect anything.

simulate this circuit – Schematic created using CircuitLab

I have tested using this code:

int testpin = 7;

void setup() {
  pinMode(testpin, OUTPUT);// initialize the pin as an output
}

void loop() {
  digitalWrite(testpin, HIGH);//turn on
  delay(5000);// wait for 5000 milliseconds (five seconds)
  digitalWrite(testpin, LOW);//turn off
  delay(5000);//wait five seconds
}

So, have I burned my relays?
If I use 4 1,5 batteries to check it working - it cannot damage anything?

How exactly wire this relay?

Should I try to use solid-state relay (and how to manage it working)?


texts: How do I connect a PIC microcontroller to a computer?

texts: I am still a beginner, middle school student, and I recently started taking interest in Arduino, Raspberry Pie, etc. Now I want to play around with the PIC microcontroller, but I can't find a way to start since I can't find an online source for learning. I want to know how to make it execute programs, because I want to play around with LEDs. Can anyone help me? Also, can you give me a link to a place where I can learn online, please?


texts:
I am new to this and I would like to ask for advice on FM receivers.

I want to create a very low powered (mass produced) item that has a super bright LED, battery and then related circuitry(for FM).

The item must switch on/off the RGB LED (in different states) at different frequencies that are broadcasted from a central FM transmitter.

So, I want to have ten different items (little plastic RGB boxes) that operate at ten different frequencies, so that I can use ten different transmitters to control the ten different items' switches.

Is it possible to send a digital signal (ie on or off) via FM?
Do you think I will be able to make a very small, low powered unit?
Any advice will be greatly appreciated!


texts: What kind of hardware implements Fourier transform?

texts:
I looked around online but I found nothing relevant. It is very difficult for an electronic device to decompose a signal in different frequencies.

How this is done at the bare metal level?

Any suggested source or comment will be very helpful


texts: How do I create a 1-bit full adder that outputs a 2-bit sum?

texts:
I am trying to build a 1-bit full adder that outputs a 2-bit sum.
I know that the standard 1-bit FA outputs a 1-bit sum and a carry bit, but I was wondering how can I modify the FA such that the carry bit output is discarded and the only output is a 2-bit sum.


texts: Digital Circuit Simulation Electric VLSI/LTSpice: .VEC command

texts:
I'm designing a series of arithmetic circuits for a Digital Design class. I must use Electric VLSI for layout and LTSpice from simulation.
Since I'm builnd circuits with a lot of inputs (up to 64 for the 32x32 multiplier) I'm trying to automate the simulation process, I wish to:

Generate a list of input vector using Matlab
Import the as a .vec file
Evaluate the average power consumption

Is there a tutorial/resource on this? The best I could find are

HSPICE command reference
HSPICE User Guide: Simulation and Analysis

And even ther the only example I could find reads:

Since the 1st and 2nd commands are options I tried to launch the simulation only by adding the .trans command, the .vec one and my model file for devices, but no luck. I'm missing something.

I think I understood how to write a .vec file, but not how to embed it into an actual simulation.

For a simple full-adder I'd use:

How to set up the Spice command to execute the digital simulation given this input? Is there a better reference/place I can look for?

Best regards,
Andrea


texts: What does this extra notation mean when writing a sum of products expression from a truth table?

texts:
So I am practicing for an exam in digital electronics. I am doing some exercises on writing expressions from truth tables, and I came across a description for the columns that should be true and false in the truth table I have never seen before.

It is the + d(0,4) part in the end that I don't know what it means. How does it apply when I write the truth table? I have googled for quite some time and I cannot find it.

This is what it looks like:

So my task was to write a truth table and then a sum of products expression from it. I'm confused and don't know if the d(0,4) in the end mean that columns 0 and 4 also should be true.


texts: What is the ideal way to handle data pins D+ and D- on a USB power adapter to be compatible with fast charging on devices?

texts: I have found that many USB wall chargers use a resistive voltage divider to set the D+ and D- pins to a specific voltage, usually between 2 and 3 volts.  Other USB wall chargers short the D+ and D- pins together with no connection to anything else.  From my experience some devices will not accept a charge rate above 500mA on the chargers using the voltage dividers, but will charge up to their max input on a charger with the data pins shorted. I have read things that suggest the opposite may be true as well, but have been unable to verify this. I am hoping to figure out which method provides the best compatibility with all USB devices.


texts:
I have this problem in a book and I've did good through the entire problem until I had to calculate current gain. I've been stuck for the past 30 minutes. The formula I get is different from the one in the book and I'm wondering why. This is probably some simple mathematical thing and I'll probably end up embarrassing myself but I just don't know why I get different current gain. I can't continue if I don't understand this.

What I get is that the second term in current gain (circled red on the picture) is reverse, that is numerator and denominator are reverse. I just need an explanation for that term in the book.


texts: The circuit is made of a variable resistor of 10kΩ value and two fixed resistors R1 and R2 .The output voltage V0 should be variable from 2V to 9V, i have to calculate the values of the two fixed resistors R1 and R2. I don't know how to start.


texts: Generating a current between 0 - 250 mA for a load up to 40 ohms

texts: I'm trying to use a howland current source to generate stable current for a load which is =<40 ohms. The load does not need to be connected to groud. I can work with a DAC to supply the Vin (V3 in the figure), which would help me control the load current, however, I'd like to limit the voltage used as input to 12V if possible.


texts: Do stepper motors fail if not allowed to rotate?

texts: I have a rudimentary understanding of the operation of a stepper motor. I have a situation in which a stepper motor will try and rotate something; but if the bar is already in the stop position the motor will still get the pulse to rotate. From a top level point of view I don't mind about this, but I'm concerned that repeated operation like this could damage the motor. Is there any reference that I can check against for this type of problem?


texts: Can I generate following voltage waveform with single PWM FET?

texts:
I am designing power supply which must output following voltages at a maximum of 1.5 A stepped down from a 24 V DC supply.

24 V
13-15 V
0-5 V

Waveform for one of the inputs requires following timing diagram.

PWM seemed intuitively like the easiest solution as single 24 V source can be used to generate all the needed voltage levels.

My trouble is finding the adequate component to do the switching. Components I found by browsing for integrated packages on the TI website so far either can't handle the voltage or switching frequency is too slow.

This transistor though seems like it may be just right.

NDT3055L

Its features include voltage up to 60 V, current up to 4 A and 110 ns for single wave.

Assuming I follow design below is it possible for me to obtain the voltage values I desire?

Additionally can PWM be applied in such way that 24 V signal is on for 800us and the drops to 5 V?

Issue I see possibly arising is PWM being an averaged value over a period of time from where it's generated and unable to respond to quick changes such as those desired by that timing diagram.


texts: Question about diode strings in high voltage applications

texts:
Background:

My ancient Telequipment D43 oscilloscope exploded last week.  One of the paper and oil capacitors blew its guts all over the place.  Fortunately, it didn't catch fire like the last time it exploded twenty years ago.

Replacing the exploded cap didn't fix it, and after a couple of days carefully trouble shooting it with a multimeter, I came to the conclusion that the high voltage supply (3.2KV) for the CRT wasn't working.  After replacing the diodes in the voltage doubler circuit (I had some spare K8/50 diodes from a pile of spare D43 parts laying around,) things still didn't work.  After much fiddling, I decided the spare diodes were toast as well.

To get to the point, I ended up building diode strings out of 1N4007 diodes to replace the diodes in the voltage doubler.  The scope is working again.  Yay!

Question:

Now to the actual question:
Since replacing the diodes with my 1N4007 strings, I have been told that reverse leakage can be a problem, and that I need to put resistors in parallel with the diodes to prevent them from blowing up and killing the capacitor again.

I've been unsuccessful in finding out how to calculate the needed values and how to estimate the needed voltage ratings for the resistors.

Could someone tell me how to calculate the needed values and voltage ratings for the resistors?

Alternatively, is there a diode type better suited for this that doesn't require the resistors?  Some reading I've done suggested that "more modern diodes" are not susceptible to problems with reverse leakage in high voltage use.  They didn't name any specific type, though, so I don't know what to look for.

simulate this circuit – Schematic created using CircuitLab

In case it helps, here's the schematic of the EHT section of the D43:

MR403 and MR405 were bad.  C403 was the capacitor that exploded.  These parts are to the right of the transformer, about the middle of the page, and are connected to the 1200V tap on the transformer.

Using Dwayne Reid's answer, I come up with the following:

Assumptions:

1N4007 diodes from Vishay  Not the ones I have, but this is just an example to be sure I've got things right.
Operating temperature up to 100 degrees C - the old D43 gets HOT.
10 Diodes in series - needed to get the maximum voltage down to something typical resistors can handle.  Mouser shows 1/4Watt carbon composition resistors up to 350 V.
3200Volt output from the voltage doubler

10 Diodes for 3200 volts leaves each diode with a reverse voltage of 320 to handle.  That's 32% of the rated maximum, so from the Vishay 1N4007 datasheet, I find I can expect a reverse leakage of 2 to 3 µA.  Call it 3µA.

10 Times the expected leakage is 30µA.

R=E/I, so at 320 V that gives me a resistor value of 10.7MOhm

P=EI, so 320V*30µA= 0.0096 Watts.  Pretty much any resistor (except maybe SMDs) can handle this amount of power.

So, for each K8/50 I want to replace with 1N4007 diodes, I need 10 each  Vishay 1N4007 and 10 each 10MOhm resistors rated for 350V.


texts: help me to understand ANSEL register in PIC

texts:
in new to PIC,this is bit confusing.

For switch ,usart we should clear ANSEL regsiter to make as digital IO so then only we can read 0 or 1 from that pin?,

data sheet says if we set particular pin as analog input and when read those pin it will return 0, So what is the need of ANSEL and when to enable

if im totally wrong please forgive and exlain me thanks


texts:
I got this board I need to connect to. The 3 connectors are about 5mm long all together. I can see bigger pins/connectors online but not this small. I did solder but it takes time to do so for every device.
Is there a way to connect easily to them other than soldering?


texts: What are shunts, as related to their use in current sensing in microcontrollers?

texts: Within the manual for the I/O module I'm using (a Loytec LIOB-153) there are wiring diagrams to aid in wiring up your sensors and other inputs/outputs. There are two wiring diagrams for the purpose of showing you how to wire up 4-20mA transmitters as an input. The first wiring diagram describes the input as having an internal shunt. The second wiring diagram tells you that there are other inputs where you must supply your own 249 ohm shunt. What is the purpose of these resistor shunts?


texts: How to call AT command on XBee from Arduino

texts:
I am trying to set the SM (sleep mode) register on the XBee radio. These registers can be set with so called AT Commands, listed from pg. 28 in the XBee/XBee Pro Product Manual.

This can be done using the X-CTU desktop application, either by typing the AT commands in the built-in terminal or by editing the values in a list and then click "Write".

But is it possible to modify these registers on the fly from a sketch running on the Fio?


texts: Troubleshooting a Triac Motor Control Circuit

texts:
I have a Xytronic 988 soldering station. It has a regular soldering iron on the left and an iron with a vacuum pump on the right. It has served me well over the years and one day when I was swapping irons I accidentally attempted to plug in an iron into the wrong plug and I heard a pop and the station stopped working. Even thought the power was off there was AC at the handle plug and I shorted something. I pulled it apart and found a transistor blown apart. I figured it would be an easy fix.... One month, twenty plus dollars in parts and many changes of components it is still not working correctly.

The problem is on the right side, the handle with the solder vacuum pump. When you press the button on the handle the pump turns on and runs and when you let the button go, the pump will run for a few seconds, like it should and then there will be a big surge in current and sometimes it will blow the fuse on the Xytronic. This big surge shouldn't be there. Everything else is working as it should.

I looked into this circuit and it is using a zero crossing triac in a six pin DIP. A MOC 3041 this triggers the triac a BTA12 600C. It has a coil, two .1uf caps? or protection devices. A few resistors in this part of the circuit. I check them all out of circuit and they seem to check OK. It is kind of typical of AC triac motor circuit. I tried to upload the schematic but I am having problems with the cookies on this site and it won't let me do it because it things this is my first question. What looks simple, and just might be has me perplexed. What would cause this big surge of current when the motor stops?
Thank you,
Russ

This is the schematic from the motor part of the circuit board.  The load goes to a small AC motor 110V. It isn't 240V,as marked in the picture. it is all 110.  I took a schematic I found on the web and changed a few parts in paint shop to get it match what I had. It seems like I see this type of circuit in a number of places. The .1uF are square plastic film or some kind of protection caps.  Thanks again, Russ


texts: How I could use a 2v LED to indicate line continuity on a 220VAC line

texts:
I have a 2v-2.5v DC LED and I want to use it to indicate if the line fuse is working.

ON fuse is ok

OFF fuse blown up

What is the proper way to connect it since obviously a direct connection would fry it instantly (and using a dedicated AC-DC adapter just for a led would be crazy)?


texts: How is Transformer's Current Rating calculated

texts:
First of all, I am not an Electronics guy originally. I love to spend time with Electronics. May be this is a basic question. But I am struggling to find the answer on internet.

I am from India and I often see that locally manufactured step-down Transformers are not sold with Volt-Ampere ratings. Instead they specifically mention following parameters:

Input Voltage
Output Voltage
Max Output Current

Well, I know how to calculate VA from those params :) But my question is how do they control/determine what is the max allowed output current? I am assuming that following is the principle

Assume,
V1=220VAC
V2=12VDC

Since, V1/V2 = I2/I1 = N1/N2

N1/N2 = 18.333

N1=3666.6, N2=200 [Less turns on Primary/Secondary = Higher Current Output]

N1=9166.5, N2=500 [More turns on Primary/Secondary = Lower Current Output]

Is this understanding correct? If yes, then my last question is, how does this theory influences the gauge of the primary and secondary wires?


texts: How do I supply a short but high power pulse (higher voltage and current) from a low power source?

texts:
I'd like to be able to throw a relay and solenoid from an AVR.

For this project, I'll occasionally need 12-36V for maybe 250ms.  I found someone having done something very similar using the following circuit:

My (somewhat weak) understanding of capacitors leads me to believe that a sufficiently large capacitor charged with a 5V source at low current might be able to put out a lot of current at 5V, but won't necessarily be able to put out higher voltage.


texts: Can I replace a power adapter of 1.5A with one of 1A?

texts:
I have a Western Digital external hard drive that uses a power adapter to 12v and 1.5A, and it stopped working. I tried it with a tester and doesn't output any current at all.
Can I replace it with other adapter that is 1A? would that ruin the disk? would this work?

edit: The disk is a Western Digital 1TB ( model WDBACW0010HBK-01 )
http://wdc.com/en/products/products.aspx?id=240
http://wdc.com/global/products/specs/?driveID=886

It doesn't seem to show anything about current requirements here.


texts: Are SPI slave select lines hardware enhanced?

texts:
I have a question regarding SPI communications. I feel like I have a good understanding fundamentally of how SPI works. However, I'm often confused when implementing the slave select line of SPI.

Is the slave select line on a microcontroller, in general, enhanced via hardware? That is, is there anything different between a slave select output and an output controlling an LED? Do microcontrollers allow certain I/O to be toggled faster when used for SPI?


texts: Solving diode circuit with iteration - why doesn't it work?

texts:
We are given the information that the forward voltage drop of the diode \$V_D\$ is 0.7 V @ 1 mA.
Applying KVL, we get: \$-V_{DD} + R \cdot I_D + V_D = 0\$

We know that \$I_D = I_S \cdot e^{\frac{V_D}{V_T}}\$. Plugging in \$V_D = 0.7\text{ V}, I_D= 1 \text{mA}, V_T= 25 \text{mV}\$, we find that \$I_S = 6.9144 \cdot 10^{-16} \text{A}\$.

Rearranging the 1st equation, we have \$V_D = V_{DD} - R \cdot I_D = 5 - 10\text{k} × 6.9144 \cdot 10^{-16} × e^{\frac{VD}{0.025}}\$.

According to my understanding, we can solve this by iteration. We pick a value of \$V_D\$, say 0.7 V, plug it in the RHS of the last equation and we should end up with a better approximation. Repeat until we are satisfied with the result. However this does not work and I end up with a garbage value.

Anyone knows why?

simulate this circuit – Schematic created using CircuitLab


texts: When they talk about the "cell" in cellular communication, they often refer to the shape of hexagon. If I am correct, this is probably the coverage area of the transmission base tower. SHouldn't be circular shape instead?


texts: How to issue the SLEEP command in Attiny

texts:
I want to put an Attiny13 to sleep. In short chapter 7 of the datasheet says you have to do the following:
    set sleep mode
    sleep enable (set SE bit)
    issue SLEEP command

Generally this is done with aid of the 'sleep.h' library and then translates to

set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sleep_enable();
sleep_cpu();

If I dont want to use the sleep.h library, the sleep mode and sleep enable are easy to set via 3 bits (SM[1:0] and SE)  but how do I issue the SLEEP command?
If I look how the sleep.h library actually does it, it is defined as __asm__ __volatile__ ( "sleep" "\n\t" :: );
That seems odd, do i really have to issue the word 'sleep' somewhere in a program to get the attiny to sleep? Cant I just set a register somewhere?
The Sleep.h library seems like a lot of overhead if i just want to put a chip to sleep


texts: What is the cylinder on this wire? Is it some kind of adapter or transformer? What purpose does it serve? Why couldn’t it be incorporated into the primary adapter that plugs into the wall at the other end?


texts: Parasitic power and an LTC490 as DMX (RS485) bus repeater

texts:
I'm in the process of building a DMX bus repeater for a light control installation using the LTC490 bus driver in this configuration:

Now, this works well when using an external power supply (5V DC), but I was thinking if it would be possible to harvest some power using the DMX+ line of the input to power the rest of the device.

Two questions:

Is this advisable or even possible?
How should I do it?


texts:
I wanted to ask you a quick wiring question - I need to run a wire to my new thermostat from the furnace - I have a spare telephone cable in the wall that has 4 22 gauge wires. I'll be running about 30ft and require 24v to power the system (drawing about 0.5 amps) The 4 wires are are independent insulated as well as being in cased in a blue phone cable.

My question is - would you know if 22 gauge wire will suffice? If not would using all 4 wires act as a higher gauge wire? I am trying to get around running a new wire.

update:
Thank you gents.   Turns out as I opened the wall to retrieve the 22 gauge wire found a 18 gauge that was already fished to my furnace room. Better to be lucky than right.  Thank you again


texts: Guitar signal input to Arduino UNO ADC - alternative part for TL972 op-amp

texts:
I'm trying to make a guitar pedal with atmega328 in Arduino but I've had trouble with input stage.
I found this circuit from electrosmash.com, but I can't find the TL972.
Are there any replacement for TL972?
Can I use TL082 for that circuit?
Or any circuit for guitar signal input stage to ADC.
I'm an IT student so I only know a little about electronic.
Thank you so much.


texts: Can a power adapter give out hazardous voltage

texts:
In an application, I use an industrial AC-DC power adapter, the meanwell GST160A15.
The power adapter gives 15V@144W maximum power.
I carefully read the datasheet, and it states that the power adapter has overvoltage protection, 105 ~ 135% of output voltage.
My question is, in case of fault, can the power adapter give out an hazardous voltage? With hazardous I refer standard convention for wet locations, 70V DC or 33 V r.m.s and 46.7 V peak


texts: Putting LED near incadescent light source on lava lamp

texts:
I am currently trying to modify a traditional lava lamp, to change the colour of light it emits, by placing an LED strip somewhere around the body, so it also lights the inside of the lamp.
My lava lamp is powered by a 25 watt incandescent lightbulb, which, as you may imagine generates quite a lot of heat. My question is, what is the maximum temperature my LED strip can take, whithout it seriously impacting longevity (I would like it to work for at least 2-3 years).
Is it even possible to do this?


texts: JTAG not erase entire flash memory in code composer studio with MSP-FET

texts:
I am using MSP430F2619 for storing device specific parameters in internal Flash memory using flash write routines.

while debugging using JTAG MSP-FET I found that my flash is getting written during debug session. But when I reload the program next time using JTAG previously written flash memory segments are erased by debugger.

Is it possible to set JTAG such that it will not overwrite this segment of program memory?

I am using code composer studio 6.


texts: Case to heatsink thermal resistance with multiple MOSFETs

texts:
I have 3 paralleled MOSFETs which will be attached to a single heatsink.

I am trying to calculate maximum possible power dissipation and required heatsink thermal resistance Rsa(sink-ambient).

I start from the general equation:

Rja(junction-ambient) = Rjc(junction-case) + Rcs(case-sink) + Rsa(sink-ambient).
Rsa = Rja - Rjc - Rcs
Rsa = (Tj-Ta)/Pd - Rjc - Rcs

Ta is ambient temperature and is choosen to be 45 °C due to forced air cooling and enclosed device.

Tj is arbitrarily choosen to be 150 °C with 25 °C headroom (Tjmax = 175 °C) which should be enough? Or should I go for more headroom?

Rcs includes resistance of thermal compound and insulating pad.

And here is where I have some doubts. Since all MOSFETs will be attached to the same heatsink how do I calculate Rsa?

Lets say that power dissipation of each MOSFET will be 20W thus 60W in total. Do I plug 60W into the above equation and multiply Rjc and Rcs by 3 (as their values are for single MOSFET)?

Or do I plug in 20W, calculate Rsa for single MOSFET but divide final result by 3 (due to 3 MOSFETs)?

The latter method seems more "right" to me, dont know why tho...


texts: How do I determine whether a switch can handle the power/current in a circuit?

texts:
I have a switch that has "3A 250VAC" and "5A 125VAC" printed on it, which I imagine are ratings of what the switch can handle, but my understanding that 3A at 250V would be 750W and that 5A at 125V would be 625W so I'm confused about how the ratings correlate. If current or power alone are not sufficient to describe the capability then how would one determine whether any given values are within the acceptable range? In the ratings given there's an inverse correlation between the current and power so it seems conceivable that it can handle more current at a lower power, but that doesn't seem specific enough provide the power handling at a given amperage or to communicate the absolute limits for voltage/current/power.
To give a concrete example, I have a guitar speaker cabinet that contains 2 8-ohm speakers wired in series and I want to add a switch to toggle the speakers between series and parallel. The most powerful amplifier I would use to power the speakers says it makes 120W, but it's never turned up to more than half power so I'm assuming 120W is a safe estimate of the max power the switch would see. Into the 16-ohm load when the speakers are in series 120W would be "2.74A ~44VAC" which is less than the smallest of each value in the provided ratings so I assume it's okay. Into the 4-ohm load however 120W would be "5.5A ~22VAC" which is a higher current than the highest rating on the switch. Assuming the higher-current-at-lower-power thing is true I'm tempted to think 5.5 is a little more than 5 and 22 is a lot less than 125, but hardly seems like a reliable formula.
I've tried googling things like "understanding electrical ratings", "understanding wattage and current ratings", "how do I know if a switch can handle the power/current in a circuit" but I just finding explanations of what wattage/amperage/voltage are, their relationships to each other, analogies about water pressure, etc. I also tried searching for switches with various ratings and I found ones that were rated by wattage instead of A/VAC but nothing sufficient to answer my question.
Thanks


texts: Question about pressurization and introducing air into a small chamber

texts:
This is probably very easy to answer, but I'm working on a project where I need to heat a chamber (insulated Styrofoam container), and my option to heat it is essentially a hair dryer, as a heat gun outputs too much and would melt it since I do not have access to a variable temp heat gun.

My question is that if I have a hair dryer blowing hot air into the box, I likely need some sort of escape vent or area for air to be removed so that it does not become too pressurized, correct? I first thought about completely sealing it so the hot air doesn't escape but I'm guessing that wouldn't be a good choice if there is no place for the air to escape.

Also, sorry if this isn't the correct place to ask this but I hope it's an easy question :)


texts: How to interpret these antenna radiation patterns?

texts:
The datasheet for this chip antenna shows a couple of radiation plots, but I don't know how they correspond to the physical orientation of the antenna.

I want to orient the antenna so that the nice, omnidirectional "co-pol H-Plane" is parallel to the ground.  For example, say I placed the device on a table in a room.  I don't care how well it radiates above or below the table, but I want to be able to walk in a circle around it and always get consistent signal strength.

Are the angles (\$\theta\$ and \$\phi\$) standardized?  I've seen other datasheets (for different antennas) that show the corresponding orientation, but I'm stuck with using this one.

In other words: Should I orient the antenna "side-to-side", or "up-and-down"? :)

Thanks.


texts: the transistor for increasing current output of linear voltage regulator

texts:
based on a suggested circuit from the datasheet, supplied current of LM7805 voltage regulator can be increased.
I can't source that BD536 pnp transistor or any equivalent listed on some websites.
What parameters I should consider when searching for an transistor to use instead of the suggested BD536 ? (hfe, Ic, Vce-sat, Vceo ...)
I need to supply around 0.9A, which is just about the max current 7805 can supply. I'm trying to make the circuit above to avoid over-heating. can this transistor addition reduce the heat produced by the regulator when high currents are required ?


texts: Why don't stepper motors ring indefinitely?

texts:
I don't have much of a EM background but I have used stepper motors for things. What's not clear to me is why don't stepper motors ring indefinitely?
Excluding physical friction, what actually causes a stepper motor to stop at a given location? It's clear how the acceleration takes place to the next position - there is an induced magnetic field which forces the motor turn.
But once that acceleration has taken place and the shaft reaches the next step location, significant momentum has been built up and the shaft is traveling at a certain rotational velocity. This will result in the motor over shooting the step location - while it's clear the magnetic field will attempt to accelerate the shaft in the other direction once over-shoot occurs, it seems energy is simply being added to the system producing a harmonic oscillator whose magnitude will continue to increase instead of decrease.
Could someone explain what mechanism is causing energy to leave the system?
If it was frictionless, would oscillation be indefinite?


texts: Amplitude modulated wave weird display in oscilloscope

texts:
In my lab experiment (http://www.ele.uri.edu/courses/ele436/labs/expA2.pdf), My amplitude modulated wave is not displaying the vertical lines-the high frequency waves of carrier
(as shown in accompanied figure).

top- message signal; bottom = modulated wave(here overmodulated)

top- message signal;bottom = modulated wave(here m<1)

 What could be the possible reason for it. Has flickering display of oscilloscope caused the problem?. How it can be corrected?


texts: Does GPS module need a wireless service? do I have to pay a service to get my gps module working?

texts:
Hi I'm new in the GPS world, I'm looking for a GPS module to track X amount of object the question is do I have to pay any service (cellular, data,etc) to get my gps working?
I'm sorry for the dumby question but I'm new here

thanks


texts: Amplifying particular range of analog signal

texts:
I am working on an a project where I need to get the reading of  an analog transducer via Arduino's 10 bit ADC.
The problem is, the range of the signal is such that the 10 bit ADC value is moving from 200-500 (1V-2.5V) on a scale of 0-1023(0V-5V).

My question is, is there something I could do to magnify the analog signal part such that the signal varies from 0-1023 instead of 200-500 so that I can get much better resolution?
I know I can use a better resolution ADC but I want to use the full range of  10 bit ADC of Arduino.


texts: Maximum resistor values for transistor inverter (NOT gate)

texts:
I have my circuit configured this way because I'll be hooking up my 8051 microcontroller GPIO pin to the point where three resistors (R2, R3, and R4) intersect, and the microcontroller only outputs my choice of high-impedance and ground, never VCC. The 500K was included in this circuit because I was simulating that the micro was producing a high-impedance output.

Other than 500K, what would be the absolute maximum resistor values I can use for R1, R2, and R3? The target device needs at least 3.5V input for a logic high and less than 3V for logic low.

Is my logic sort-of right if I did the following math?:

 Target voltage wanted for logic high (3.5V)
 divided by
 Target device leakage current
 Then
 Result divided by sum of Result + R1 times 5V = Target voltage?

I ask because I'll be running this circuit off of a regulated 5V source which is powered by batteries.


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I am developing a redesign of a current PCB which uses the attached circuit in order to evaluate the temperature using a PTC thermistor (which is R3 in the given image). The circuit is connected to three ADC/GPIO pins of a microcontroller.

I have looked through a few application notes, but I haven't found this type of PTC evaluation circuit. Can anyone tell me how this circuit would work and what the advantage of this circuit would be?
What alternative PTC circuits would you recommend for a temperature sensing application? I would like to keep the PTC as the sensing element, however I am unsure how I would get a temperture-compensated, high-accuracy PTC circuit.

simulate this circuit – Schematic created using CircuitLab


texts: Tube Guitar amp Input Transformer Removal

texts:
for a few weeks I've been trying to remove the input transformer from my little 60's Magnatone amp. The schematic indicates a 1:3 step up input transformer, but from reading elsewhere on the internet it seems that it is in fact a 1:1. Whenever the amp is run at the same time as other certain devices in my home e.g. laptop charger, washing machine, it picks up some severe hum (particularly with the washing machine). It sounds a bit like an arc welder. This makes the amp practically unplayable when these appliances are running. I'm certain this hum is being picked up by the input transformer.

Here is the schematic for the amp. The transformer in question is T2. http://www.magnatoneamps.com/schematics/magnatone_401_412.pdf

I have tried bypassing the transformer, connecting a wire from the 10k resistor on the low gain input to the volume pot (and disconnecting from the transformer, which results in greatly increased hum (louder than the guitar) and reduced guitar volume. Connecting a jumper around the 220k resistor and .047 capacitor, to the volume pot ground lug results in a short which shuts off the house's circuit breaker. I cannot see why this occurs as there is no AC or DC voltage between these.

Interestingly, I discovered the heater of the 20EZ7 is wired in reverse compared to the schematic (pin 2 connects to V2 heater, while pin 1 is used as the common return for nearby components e.g. V1 cathode, volume pot ground, 220k resistor and .047 capacitor. I'm not sure if this is relevant to the problem.

Any help here would be much appreciated. I'm completely stumped and out of ideas here. If you need any further information or clarification, just ask. I can also provide photos of the wiring if necessary  I would like to think I'm not completely inept in the workings of tube amps, as I'm currently building a 5F6a Bassman.

Thankyou in advance

EDIT: My amp is run through an isolated 240-110v step down transformer, so the transformer is not needed for isolation. Also, I've added a 3 prong power cord and grounded the chassis

Further information: I replaced the 50uf filter caps a few weeks ago. Another thing, the hum reduces and cuts off when I turn off the volume pot, so the source of the hum must be before the volume pot